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A phagocyte-specific Irf8 gene enhancer establishes early conventional dendritic cell commitment
(2011)
Haematopoietic development is a complex process that is strictly hierarchically organized. Here, the phagocyte lineages are a very heterogeneous cell compartment with specialized functions in innate immunity and induction of adaptive immune responses. Their generation from a common precursor must be tightly controlled. Interference within lineage formation programs for example by mutation or change in expression levels of transcription factors (TF) is causative to leukaemia. However, the molecular mechanisms driving specification into distinct phagocytes remain poorly understood. In the present study I identify the transcription factor Interferon Regulatory Factor 8 (IRF8) as the specification factor of dendritic cell (DC) commitment in early phagocyte precursors. Employing an IRF8 reporter mouse, I showed the distinct Irf8 expression in haematopoietic lineage diversification and isolated a novel bone marrow resident progenitor which selectively differentiates into CD8α+ conventional dendritic cells (cDCs) in vivo. This progenitor strictly depends on Irf8 expression to properly establish its transcriptional DC program while suppressing a lineage-inappropriate neutrophile program. Moreover, I demonstrated that Irf8 expression during this cDC commitment-step depends on a newly discovered myeloid-specific cis-enhancer which is controlled by the haematopoietic transcription factors PU.1 and RUNX1. Interference with their binding leads to abrogation of Irf8 expression, subsequently to disturbed cell fate decisions, demonstrating the importance of these factors for proper phagocyte cell development. Collectively, these data delineate a transcriptional program establishing cDC fate choice with IRF8 in its center.
A systems biological approach towards the molecular basis of heterosis in Arabidopsis thaliana
(2011)
Heterosis is defined as the superiority in performance of heterozygous genotypes compared to their corresponding genetically different homozygous parents. This phenomenon is already known since the beginning of the last century and it has been widely used in plant breeding, but the underlying genetic and molecular mechanisms are not well understood. In this work, a systems biological approach based on molecular network structures is proposed to contribute to the understanding of heterosis. Hybrids are likely to contain additional regulatory possibilities compared to their homozygous parents and, therefore, they may be able to correctly respond to a higher number of environmental challenges, which leads to a higher adaptability and, thus, the heterosis phenomenon. In the network hypothesis for heterosis, presented in this work, more regulatory interactions are expected in the molecular networks of the hybrids compared to the homozygous parents. Partial correlations were used to assess this difference in the global interaction structure of regulatory networks between the hybrids and the homozygous genotypes. This network hypothesis for heterosis was tested on metabolite profiles as well as gene expression data of the two parental Arabidopsis thaliana accessions C24 and Col-0 and their reciprocal crosses. These plants are known to show a heterosis effect in their biomass phenotype. The hypothesis was confirmed for mid-parent and best-parent heterosis for either hybrid of our experimental metabolite as well as gene expression data. It was shown that this result is influenced by the used cutoffs during the analyses. Too strict filtering resulted in sets of metabolites and genes for which the network hypothesis for heterosis does not hold true for either hybrid regarding mid-parent as well as best-parent heterosis. In an over-representation analysis, the genes that show the largest heterosis effects according to our network hypothesis were compared to genes of heterotic quantitative trait loci (QTL) regions. Separately for either hybrid regarding mid-parent as well as best-parent heterosis, a significantly larger overlap between the resulting gene lists of the two different approaches towards biomass heterosis was detected than expected by chance. This suggests that each heterotic QTL region contains many genes influencing biomass heterosis in the early development of Arabidopsis thaliana. Furthermore, this integrative analysis led to a confinement and an increased confidence in the group of candidate genes for biomass heterosis in Arabidopsis thaliana identified by both approaches.
This Thesis puts its focus on the physics of neutron stars and its description with methods of numerical relativity. In the first step, a new numerical framework the Whisky2D code will be developed, which solves the relativistic equations of hydrodynamics in axisymmetry. Therefore we consider an improved formulation of the conserved form of these equations. The second part will use the new code to investigate the critical behaviour of two colliding neutron stars. Considering the analogy to phase transitions in statistical physics, we will investigate the evolution of the entropy of the neutron stars during the whole process. A better understanding of the evolution of thermodynamical quantities, like the entropy in critical process, should provide deeper understanding of thermodynamics in relativity. More specifically, we have written the Whisky2D code, which solves the general-relativistic hydrodynamics equations in a flux-conservative form and in cylindrical coordinates. This of course brings in 1/r singular terms, where r is the radial cylindrical coordinate, which must be dealt with appropriately. In the above-referenced works, the flux operator is expanded and the 1/r terms, not containing derivatives, are moved to the right-hand-side of the equation (the source term), so that the left hand side assumes a form identical to the one of the three-dimensional (3D) Cartesian formulation. We call this the standard formulation. Another possibility is not to split the flux operator and to redefine the conserved variables, via a multiplication by r. We call this the new formulation. The new equations are solved with the same methods as in the Cartesian case. From a mathematical point of view, one would not expect differences between the two ways of writing the differential operator, but, of course, a difference is present at the numerical level. Our tests show that the new formulation yields results with a global truncation error which is one or more orders of magnitude smaller than those of alternative and commonly used formulations. The second part of the Thesis uses the new code for investigations of critical phenomena in general relativity. In particular, we consider the head-on-collision of two neutron stars in a region of the parameter space where two final states a new stable neutron star or a black hole, lay close to each other. In 1993, Choptuik considered one-parameter families of solutions, S[P], of the Einstein-Klein-Gordon equations for a massless scalar field in spherical symmetry, such that for every P > P⋆, S[P] contains a black hole and for every P < P⋆, S[P] is a solution not containing singularities. He studied numerically the behavior of S[P] as P → P⋆ and found that the critical solution, S[P⋆], is universal, in the sense that it is approached by all nearly-critical solutions regardless of the particular family of initial data considered. All these phenomena have the common property that, as P approaches P⋆, S[P] approaches a universal solution S[P⋆] and that all the physical quantities of S[P] depend only on |P − P⋆|. The first study of critical phenomena concerning the head-on collision of NSs was carried out by Jin and Suen in 2007. In particular, they considered a series of families of equal-mass NSs, modeled with an ideal-gas EOS, boosted towards each other and varied the mass of the stars, their separation, velocity and the polytropic index in the EOS. In this way they could observe a critical phenomenon of type I near the threshold of black-hole formation, with the putative solution being a nonlinearly oscillating star. In a successive work, they performed similar simulations but considering the head-on collision of Gaussian distributions of matter. Also in this case they found the appearance of type-I critical behaviour, but also performed a perturbative analysis of the initial distributions of matter and of the merged object. Because of the considerable difference found in the eigenfrequencies in the two cases, they concluded that the critical solution does not represent a system near equilibrium and in particular not a perturbed Tolmann-Oppenheimer-Volkoff (TOV) solution. In this Thesis we study the dynamics of the head-on collision of two equal-mass NSs using a setup which is as similar as possible to the one considered above. While we confirm that the merged object exhibits a type-I critical behaviour, we also argue against the conclusion that the critical solution cannot be described in terms of equilibrium solution. Indeed, we show that, in analogy with what is found in, the critical solution is effectively a perturbed unstable solution of the TOV equations. Our analysis also considers fine-structure of the scaling relation of type-I critical phenomena and we show that it exhibits oscillations in a similar way to the one studied in the context of scalar-field critical collapse.
"Kinderwelt ist Bewegungswelt" (Schmidt, 1997, S. 156, zitiert nach Schmidt, Hartmann-Tews & Brettschneider, 2003, S. 31). Das kindliche Bewegungsverhalten hat sich bereits im Grundschulalter verändert, so dass sich Bewegungsaktivitäten von Kindern erheblich unterscheiden und keineswegs mehr verallgemeinert werden können. Richtet man den Fokus auf die Frage „Wie bewegt sind unsere Kinder?“ so scheint diese von den Medien bereits beantwortet zu sein, da dort von ansteigendem Bewegungsmangel der heutigen Kinder gegenüber früheren Generationen berichtet wird. Wenn es in den Diskussionen um den Gesundheitszustand unserer Kinder geht, nimmt die körperlich-sportliche Aktivität eine entscheidende Rolle ein. Bewegungsmangel ist hierbei ein zentraler Begriff der in der Öffentlichkeit diskutiert wird. Bei der Betrachtung der einzelnen Studien fällt auf, dass deutliche Defizite in der Messung der körperlich-sportlichen Aktivität bestehen. Zentraler Kritikpunkt in den meisten Studien ist die subjektive Erfassung der körperlich-sportlichen Aktivität. Ein Großteil bisheriger Untersuchungen zum Bewegungsverhalten basiert auf Beobachtungen, Befragungen oder Bewegungstagebüchern. Diese liefern ausschließlich zum Teil subjektive Einschätzungen der Kinder oder Eltern über die tatsächliche Bewegungszeit und -intensität. Das objektive Erfassen der Aktivität bzw. Inaktivität ist zwar seit einigen Jahren zentraler Gegenstand vieler Studien, dennoch gilt es, dieses noch sachkundiger zu lösen, um subjektive und objektive Daten zu vergleichen. Um dem Bewegungsmangel der heutigen Kinder entgegenzuwirken, sind empirisch abgesicherte Erkenntnisse über die Bedingungsfaktoren und die Folgen des veränderten Bewegungsverhaltens dringend nötig. Die Quer- und Längsschnittuntersuchung umfasst die Bereiche Anthropometrie, die Erfassung der körperlich-sportlichen Aktivität und die Herzfrequenzmessung über 24h. Für die Studie konnten 106 Jungen und Mädchen im Zeitraum von Januar 2007 bis April 2009 rekrutiert und überprüft werden. Die physiologischen Parameter wurden mit Hilfe des ACTIHEART-Messsytems aufgezeichnet und berechnet. Die Ergebnisse zur körperlich-sportlichen Aktivität wurden in die Untersuchungsabschnitte Schulzeit gesamt, Pause, Sportunterricht, Nachmittag und 24h unterteilt. Durch das Messsystem werden die Bewegungsaktivität und die Herzfrequenz synchron aufgezeichnet. Das System nimmt die Beschleunigungswerte des Körpers auf und speichert sie im frei wählbaren Zeitintervall, Short oder Long Term, in Form von „activity counts“ ab. Das Messsytem berechnet weiterhin die Intensität körperlicher Aktivität.
Algorithmic Trading
(2011)
Die Elektronisierung der Finanzmärkte ist in den letzten Jahren weit vorangeschritten. Praktisch jede Börse verfügt über ein elektronisches Handelssystem. In diesem Kontext beschreibt der Begriff Algorithmic Trading ein Phänomen, bei dem Computerprogramme den Menschen im Wertpapierhandel ersetzen. Sie helfen dabei Investmententscheidungen zu treffen oder Transaktionen durchzuführen. Algorithmic Trading selbst ist dabei nur eine unter vielen Innovationen, welche die Entwicklung des Börsenhandels geprägt haben. Hier sind z.B. die Erfindung der Telegraphie, des Telefons, des FAX oder der elektronische Wertpapierabwicklung zu nennen. Die Frage ist heute nicht mehr, ob Computerprogramme im Börsenhandel eingesetzt werden. Sondern die Frage ist, wo die Grenze zwischen vollautomatischem Börsenhandel (durch Computer) und manuellem Börsenhandel (von Menschen) verläuft. Bei der Erforschung von Algorithmic Trading wird die Wissenschaft mit dem Problem konfrontiert, dass keinerlei Informationen über diese Computerprogramme zugänglich sind. Die Idee dieser Dissertation bestand darin, dieses Problem zu umgehen und Informationen über Algorithmic Trading indirekt aus der Analyse von (Fonds-)Renditen zu extrahieren. Johannes Gomolka untersucht daher die Forschungsfrage, ob sich Aussagen über computergesteuerten Wertpapierhandel (kurz: Algorithmic Trading) aus der Analyse von (Fonds-)Renditen ziehen lassen. Zur Beantwortung dieser Forschungsfrage formuliert der Autor eine neue Definition von Algorithmic Trading und unterscheidet mit Buy-Side und Sell-Side Algorithmic Trading zwei grundlegende Funktionen der Computerprogramme (die Entscheidungs- und die Transaktionsunterstützung). Für seine empirische Untersuchung greift Gomolka auf das Multifaktorenmodell zur Style-Analyse von Fung und Hsieh (1997) zurück. Mit Hilfe dieses Modells ist es möglich, die Zeitreihen von Fondsrenditen in interpretierbare Grundbestandteile zu zerlegen und den einzelnen Regressionsfaktoren eine inhaltliche Bedeutung zuzuordnen. Die Ergebnisse dieser Dissertation zeigen, dass man mit Hilfe der Style-Analyse Aussagen über Algorithmic Trading aus der Analyse von (Fonds-)Renditen machen kann. Die Aussagen sind jedoch keiner technischen Natur, sondern auf die Analyse von Handelsstrategien (Investment-Styles) begrenzt.
In this work new fluorinated and non-fluorinated mono- and bifunctional trithiocarbonates of the structure Z-C(=S)-S-R and Z-C(=S)-S-R-S-C(=S)-Z were synthesized for the use as chain transfer agents (CTAs) in the RAFT-process. All newly synthesized CTAs were tested for their efficiency to moderate the free radical polymerization process by polymerizing styrene (M3). Besides characterization of the homopolymers by GPC measurements, end- group analysis of the synthesized block copolymers via 1H-, 19F-NMR, and in some cases also UV-vis spectroscopy, were performed attaching suitable fluorinated moieties to the Z- and/or R-groups of the CTAs. Symmetric triblock copolymers of type BAB and non-symmetric fluorine end- capped polymers were accessible using the RAFT process in just two or one polymerization step. In particular, the RAFT-process enabled the controlled polymerization of hydrophilic monomers such as N-isopropylacrylamide (NIPAM) (M1) as well as N-acryloylpyrrolidine (NAP) (M2) for the A-blocks and of the hydrophobic monomers styrene (M3), 2-fluorostyrene (M4), 3-fluorostyrene (M5), 4-fluorostyrene (M6) and 2,3,4,5,6-pentafluorostyrene (M7) for the B-blocks. The properties of the BAB-triblock copolymers were investigated in dilute, concentrated and highly concentrated aqueous solutions using DLS, turbidimetry, 1H- and 19F-NMR, rheology, determination of the CMC, foam height- and surface tension measurements and microscopy. Furthermore, their ability to stabilize emulsions and microemulsions and the wetting behaviour of their aqueous solutions on different substrates was investigated. The behaviour of the fluorine end-functionalized polymers to form micelles was studied applying DLS measurements in diluted organic solution. All investigated BAB-triblock copolymers were able to form micelles and show surface activity at room temperature in dilute aqueous solution. The aqueous solutions displayed moderate foam formation. With different types and concentrations of oils, the formation of emulsions could be detected using a light microscope. A boosting effect in microemulsions could not be found adding BAB-triblock copolymers. At elevated polymer concentrations, the formation of hydrogels was proved applying rheology measurements.
The present thesis introduces an iterative expert-based Bayesian approach for assessing greenhouse gas (GHG) emissions from the 2030 German new vehicle fleet and quantifying the impacts of their main drivers. A first set of expert interviews has been carried out in order to identify technologies which may help to lower car GHG emissions and to quantify their emission reduction potentials. Moreover, experts were asked for their probability assessments that the different technologies will be widely adopted, as well as for important prerequisites that could foster or hamper their adoption. Drawing on the results of these expert interviews, a Bayesian Belief Network has been built which explicitly models three vehicle types: Internal Combustion Engine Vehicles (which include mild and full Hybrid Electric Vehicles), Plug-In Hybrid Electric Vehicles, and Battery Electric Vehicles. The conditional dependencies of twelve central variables within the BBN - battery energy, fuel and electricity consumption, relative costs, and sales shares of the vehicle types - have been quantified by experts from German car manufacturers in a second series of interviews. For each of the seven second-round interviews, an expert's individually specified BBN results. The BBN have been run for different hypothetical 2030 scenarios which differ, e.g., in regard to battery development, regulation, and fuel and electricity GHG intensities. The present thesis delivers results both in regard to the subject of the investigation and in regard to its method. On the subject level, it has been found that the different experts expect 2030 German new car fleet emission to be at 50 to 65% of 2008 new fleet emissions under the baseline scenario. They can be further reduced to 40 to 50% of the emissions of the 2008 fleet though a combination of a higher share of renewables in the electricity mix, a larger share of biofuels in the fuel mix, and a stricter regulation of car CO$_2$ emissions in the European Union. Technically, 2030 German new car fleet GHG emissions can be reduced to a minimum of 18 to 44% of 2008 emissions, a development which can not be triggered by any combination of measures modeled in the BBN alone but needs further commitment. Out of a wealth of existing BBN, few have been specified by individual experts through elicitation, and to my knowledge, none of them has been employed for analyzing perspectives for the future. On the level of methods, this work shows that expert-based BBN are a valuable tool for making experts' expectations for the future explicit and amenable to the analysis of different hypothetical scenarios. BBN can also be employed for quantifying the impacts of main drivers. They have been demonstrated to be a valuable tool for iterative stakeholder-based science approaches.
Corvino, Corvino and Schoen, Chruściel and Delay have shown the existence of a large class of asymptotically flat vacuum initial data for Einstein's field equations which are static or stationary in a neighborhood of space-like infinity, yet quite general in the interior. The proof relies on some abstract, non-constructive arguments which makes it difficult to calculate such data numerically by using similar arguments. A quasilinear elliptic system of equations is presented of which we expect that it can be used to construct vacuum initial data which are asymptotically flat, time-reflection symmetric, and asymptotic to static data up to a prescribed order at space-like infinity. A perturbation argument is used to show the existence of solutions. It is valid when the order at which the solutions approach staticity is restricted to a certain range. Difficulties appear when trying to improve this result to show the existence of solutions that are asymptotically static at higher order. The problems arise from the lack of surjectivity of a certain operator. Some tensor decompositions in asymptotically flat manifolds exhibit some of the difficulties encountered above. The Helmholtz decomposition, which plays a role in the preparation of initial data for the Maxwell equations, is discussed as a model problem. A method to circumvent the difficulties that arise when fast decay rates are required is discussed. This is done in a way that opens the possibility to perform numerical computations. The insights from the analysis of the Helmholtz decomposition are applied to the York decomposition, which is related to that part of the quasilinear system which gives rise to the difficulties. For this decomposition analogous results are obtained. It turns out, however, that in this case the presence of symmetries of the underlying metric leads to certain complications. The question, whether the results obtained so far can be used again to show by a perturbation argument the existence of vacuum initial data which approach static solutions at infinity at any given order, thus remains open. The answer requires further analysis and perhaps new methods.
Most of the microelectronic circuits fabricated today are synchronous, i.e. they are driven by one or several clock signals. Synchronous circuit design faces several fundamental challenges such as high-speed clock distribution, integration of multiple cores operating at different clock rates, reduction of power consumption and dealing with voltage, temperature, manufacturing and runtime variations. Asynchronous or clockless design plays a key role in alleviating these challenges, however the design and test of asynchronous circuits is much more difficult in comparison to their synchronous counterparts. A driving force for a widespread use of asynchronous technology is the availability of mature EDA (Electronic Design Automation) tools which provide an entire automated design flow starting from an HDL (Hardware Description Language) specification yielding the final circuit layout. Even though there was much progress in developing such EDA tools for asynchronous circuit design during the last two decades, the maturity level as well as the acceptance of them is still not comparable with tools for synchronous circuit design. In particular, logic synthesis (which implies the application of Boolean minimisation techniques) for the entire system's control path can significantly improve the efficiency of the resulting asynchronous implementation, e.g. in terms of chip area and performance. However, logic synthesis, in particular for asynchronous circuits, suffers from complexity problems. Signal Transitions Graphs (STGs) are labelled Petri nets which are a widely used to specify the interface behaviour of speed independent (SI) circuits - a robust subclass of asynchronous circuits. STG decomposition is a promising approach to tackle complexity problems like state space explosion in logic synthesis of SI circuits. The (structural) decomposition of STGs is guided by a partition of the output signals and generates a usually much smaller component STG for each partition member, i.e. a component STG with a much smaller state space than the initial specification. However, decomposition can result in component STGs that in isolation have so-called irreducible CSC conflicts (i.e. these components are not SI synthesisable anymore) even if the specification has none of them. A new approach is presented to avoid such conflicts by introducing internal communication between the components. So far, STG decompositions are guided by the finest output partitions, i.e. one output per component. However, this might not yield optimal circuit implementations. Efficient heuristics are presented to determine coarser partitions leading to improved circuits in terms of chip area. For the new algorithms correctness proofs are given and their implementations are incorporated into the decomposition tool DESIJ. The presented techniques are successfully applied to some benchmarks - including 'real-life' specifications arising in the context of control resynthesis - which delivered promising results.
Business Process Management (BPM) emerged as a means to control, analyse, and optimise business operations. Conceptual models are of central importance for BPM. Most prominently, process models define the behaviour that is performed to achieve a business value. In essence, a process model is a mapping of properties of the original business process to the model, created for a purpose. Different modelling purposes, therefore, result in different models of a business process. Against this background, the misalignment of process models often observed in the field of BPM is no surprise. Even if the same business scenario is considered, models created for strategic decision making differ in content significantly from models created for process automation. Despite their differences, process models that refer to the same business process should be consistent, i.e., free of contradictions. Apparently, there is a trade-off between strictness of a notion of consistency and appropriateness of process models serving different purposes. Existing work on consistency analysis builds upon behaviour equivalences and hierarchical refinements between process models. Hence, these approaches are computationally hard and do not offer the flexibility to gradually relax consistency requirements towards a certain setting. This thesis presents a framework for the analysis of behaviour consistency that takes a fundamentally different approach. As a first step, an alignment between corresponding elements of related process models is constructed. Then, this thesis conducts behavioural analysis grounded on a relational abstraction of the behaviour of a process model, its behavioural profile. Different variants of these profiles are proposed, along with efficient computation techniques for a broad class of process models. Using behavioural profiles, consistency of an alignment between process models is judged by different notions and measures. The consistency measures are also adjusted to assess conformance of process logs that capture the observed execution of a process. Further, this thesis proposes various complementary techniques to support consistency management. It elaborates on how to implement consistent change propagation between process models, addresses the exploration of behavioural commonalities and differences, and proposes a model synthesis for behavioural profiles.
Besteuerung von Unternehmensgewinnen im Licht des Konzepts der konsumorientierten Einkommensteuer
(2011)
Die Dissertation widmet sich dem Problem der fiskalischen Konsequenzen der konsumorientierten Steuern, die die unternehmerischen Gewinne unabhängig von der Rechtsform belasten. Im empirischen Teil der Arbeit wird der Untersuchungsgegenstand auf die zinsbereinigte Gewinnsteuer (allowance for corporate equity) eingegrenzt. Die Untersuchung beruht auf theoretischen Überlegungen sowie einer eigenen Simulationsanalyse. Den Schwerpunkt bilden dabei zwei Kategorien, zwischen denen ein kausaler Zusammenhang vorliegt: die Gestaltung der Bemessungsgrundlage einerseits und die Erfüllung der Fiskalfunktion andererseits. Das Hauptziel der Arbeit ist es, die fiskalischen Konsequenzen einer nach dem Konzept der Konsumorientierung modifizierten Bemessungsgrundlage der Gewinnsteuern zu überprüfen. Die Abschätzung der fiskalischen Konsequenzen wird aufgrund der vier folgenden Bereiche vorgenommen: (1) theoretische Konzepte der konsumorientierten Einkommensteuer, (2) bisherige Umsetzungen der Konzepte der konsumorientierten Gewinnsteuer, (3) bisherige Untersuchungen der konsumorientierten Gewinnsteuer, (4) eine eigene Simulation der fiskalischen Konsequenzen der konsumorientierten Gewinnsteuer. Um das Hauptziel der Arbeit zu erreichen, werden acht in Form von Teilfragen ausformulierte Untersuchungsprobleme gelöst. Sie betreffen sowohl die theoretischen Ausführungen, als auch die empirische Untersuchung. Dabei entsprechen sie den einzelnen Untersuchungsschritten, die in den aufeinander folgenden Kapiteln der Arbeit durchgeführt werden. Anhand der Analyse der bisherigen wissenschaftlichen Erkenntnisse und der praktischen Umsetzungen des Konzepts der konsumorientierten Steuern wurde die folgende Haupthypothese aufgestellt: Der Ausfall des Steueraufkommens, der ein direkter Effekt der Gestaltung der Bemessungsgrundlage nach dem Konzept der Konsumorientierung ist, schließt die Fiskalfunktion der Gewinnsteuern nicht aus. Das Verfahren, das eine Verifizierung der Haupthypothese zum Ziel hat, erfolgt durch eine Untersuchung von drei Teilhypothesen: der Hypothese über die Nullsteuer, der Hypothese über den differenzierten Aufkommensausfall und der Hypothese über die Konzentration der Steuerschuld. In der Dissertation werden empirische Daten aus drei Quellen benutzt. Sie umfassen einen Teil der in Polen in den Jahren 2004-2008 tätigen Unternehmen und ermöglichen es, eine Simulationsanalyse des Aufkommensausfalls durchzuführen. Diese bedient sich der Methodik der Mikro- und Gruppensimulation, was in den bisherigen Untersuchungen zur Unternehmensbesteuerung ein eher selten anzutreffender Ansatz ist. Die gewonnenen Ergebnisse zeigen, dass die Steuereinnahmen aus der Einkommensteuer und der Körperschaftsteuer durch die Modifizierung der Bemessungsgrundlage deutlich reduziert werden. Die relativ große fiskalische Bedeutung der beiden Steuern bleibt jedoch erhalten und der Ausfall des Steueraufkommens, der direkt nach der Einführung einer konsumorientierten Steuerreform eintreten würde, wäre der „Preis“ für eine bessere, weniger verzerrende Bemessungsgrundlage. Die Dissertation liefert Ergebnisse, die für die Gestaltung der Steuerpolitik in Polen wie auch in anderen Ländern relevant sind. Dies scheint insbesondere im Kontext des häufig diskutierten Umbaus des Systems der Einkommen- und Gewinnbesteuerung bedeutsam. Darüber hinaus bildet die Arbeit einen Ausgangspunkt für weitere, vertiefte Untersuchungen zu den möglichen Gestaltungsformen der Einkommen- und Gewinnsteuern wie auch zu deren Folgen. Die Methode der Steuersimulation kann weiterentwickelt werden und in anderen Analysen der potenziellen Konsequenzen von Steuerreformen Anwendung finden.
Business process models are used within a range of organizational initiatives, where every stakeholder has a unique perspective on a process and demands the respective model. As a consequence, multiple process models capturing the very same business process coexist. Keeping such models in sync is a challenge within an ever changing business environment: once a process is changed, all its models have to be updated. Due to a large number of models and their complex relations, model maintenance becomes error-prone and expensive. Against this background, business process model abstraction emerged as an operation reducing the number of stored process models and facilitating model management. Business process model abstraction is an operation preserving essential process properties and leaving out insignificant details in order to retain information relevant for a particular purpose. Process model abstraction has been addressed by several researchers. The focus of their studies has been on particular use cases and model transformations supporting these use cases. This thesis systematically approaches the problem of business process model abstraction shaping the outcome into a framework. We investigate the current industry demand in abstraction summarizing it in a catalog of business process model abstraction use cases. The thesis focuses on one prominent use case where the user demands a model with coarse-grained activities and overall process ordering constraints. We develop model transformations that support this use case starting with the transformations based on process model structure analysis. Further, abstraction methods considering the semantics of process model elements are investigated. First, we suggest how semantically related activities can be discovered in process models-a barely researched challenge. The thesis validates the designed abstraction methods against sets of industrial process models and discusses the method implementation aspects. Second, we develop a novel model transformation, which combined with the related activity discovery allows flexible non-hierarchical abstraction. In this way this thesis advocates novel model transformations that facilitate business process model management and provides the foundations for innovative tool support.
The Casimir-Polder interaction between a single neutral atom and a nearby surface, arising from the (quantum and thermal) fluctuations of the electromagnetic field, is a cornerstone of cavity quantum electrodynamics (cQED), and theoretically well established. Recently, Bose-Einstein condensates (BECs) of ultracold atoms have been used to test the predictions of cQED. The purpose of the present thesis is to upgrade single-atom cQED with the many-body theory needed to describe trapped atomic BECs. Tools and methods are developed in a second-quantized picture that treats atom and photon fields on the same footing. We formulate a diagrammatic expansion using correlation functions for both the electromagnetic field and the atomic system. The formalism is applied to investigate, for BECs trapped near surfaces, dispersion interactions of the van der Waals-Casimir-Polder type, and the Bosonic stimulation in spontaneous decay of excited atomic states. We also discuss a phononic Casimir effect, which arises from the quantum fluctuations in an interacting BEC.
Non-mycorrhizal fungal endophytes are able to colonize internally roots without causing visible disease symptoms establishing neutral or mutualistic associations with plants. These fungi known as non-clavicipitaceous endophytes have a broad host range of monocot and eudicot plants and are highly diverse. Some of them promote plant growth and confer increased abiotic-stress tolerance and disease resistance. According to such possible effects on host plants, it was aimed to isolate and to characterize native fungal root endophytes from tomato (Lycopersicon esculentum Mill.) and to analyze their effects on plant development, plant resistance and fruit yield and quality together with the model endophyte Piriformospora indica. Fifty one new fungal strains were isolated from desinfected tomato roots of four different crop sites in Colombia. These isolates were roughly characterized and fourteen potential endophytes were further analyzed concerning their taxonomy, their root colonization capacity and their impact on plant growth. Sequencing of the ITS region from the ribosomal RNA gene cluster and in-depth morphological characterisation revealed that they correspond to different phylogenetic groups among the phylum Ascomycota. Nine different morphotypes were described including six dark septate endophytes (DSE) that did not correspond to the Phialocephala group. Detailed confocal microscopy analysis showed various colonization patterns of the endophytes inside the roots ranging from epidermal penetration to hyphal growth through the cortex. Tomato pot experiments under glass house conditions showed that they differentially affect plant growth depending on colonization time and inoculum concentration. Three new isolates (two unknown fungal endophyte DSE48, DSE49 and one identified as Leptodontidium orchidicola) with neutral or positiv effects were selected and tested in several experiments for their influence on vegetative growth, fruit yield and quality and their ability to diminish the impact of the pathogen Verticillium dahliae on tomato plants. Although plant growth promotion by all three fungi was observed in young plants, vegetative growth parameters were not affected after 22 weeks of cultivation except a reproducible increase of root diameter by the endophyte DSE49. Additionally, L. orchidicola increased biomass and glucose content of tomato fruits, but only at an early date of harvest and at a certain level of root colonization. Concerning bioprotective effects, the endophytes DSE49 and L. orchidicola decreased significantly disease symptoms caused by the pathogen V. dahliae, but only at a low dosis of the pathogen. In order to analyze, if the model root endophytic fungus Piriformospora indica could be suitable for application in production systems, its impact on tomato was evaluated. Similarly to the new fungal isolates, significant differences for vegetative growth parameters were only observable in young plants and, but protection against V. dahliae could be seen in one experiment also at high dosage of the pathogen. As the DSE L. orchidicola, P. indica increased the number and biomass of marketable tomatoes only at the beginning of fruit setting, but this did not lead to a significant higher total yield. If the effects on growth are due to a better nutrition of the plant with mineral element was analyzed in barley in comparison to the arbuscular mycorrhizal fungus Glomus mosseae. While the mycorrhizal fungus increased nitrogen and phosphate uptake of the plant, no such effect was observed for P. indica. In summary this work shows that many different fungal endophytes can be also isolated from roots of crops and, that these isolates can have positive effects on early plant development. This does, however, not lead to an increase in total yield or in improvement of fruit quality of tomatoes under greenhouse conditions.
The present thesis was born and evolved within the RAdial Velocity Experiment (RAVE) with the goal of measuring chemical abundances from the RAVE spectra and exploit them to investigate the chemical gradients along the plane of the Galaxy to provide constraints on possible Galactic formation scenarios. RAVE is a large spectroscopic survey which aims to observe spectroscopically ~10^6 stars by the end of 2012 and measures their radial velocities, atmospheric parameters and chemical abundances. The project makes use of the UK Schmidt telescope at Australian Astronomical Observatory (AAO) in Siding Spring, Australia, equipped with the multiobject spectrograph 6dF. To date, RAVE collected and measured more than 450,000 spectra. The precision of the chemical abundance estimations depends on the reliability of the atomic and atmosphere parameters adopted (in particular the oscillator strengths of the absorption lines and the effective temperature, gravity, and metallicity of the stars measured). Therefore we first identified 604 absorption lines in the RAVE wavelength range and refined their oscillator strengths with an inverse spectral analysis. Then, we improved the RAVE stellar parameters by modifying the RAVE pipeline and the spectral library the pipeline rely on. The modifications removed some systematic errors in stellar parameters discovered during this work. To obtain chemical abundances, we developed two different processing pipelines. Both of them perform chemical abundances measurements by assuming stellar atmospheres in Local Thermodynamic Equilibrium (LTE). The first one determines elements abundances from equivalent widths of absorption lines. Since this pipeline showed poor sensibility on abundances relative to iron, it has been superseded. The second one exploits the chi^2 minimization technique between observed and model spectra. Thanks to its precision, it has been adopted for the creation of the RAVE chemical catalogue. This pipeline provides abundances with uncertains of about ~0.2dex for spectra with signal-to-noise ratio S/N>40 and ~0.3dex for spectra with 20>S/N>40. For this work, the pipeline measured chemical abundances up to 7 elements for 217,358 RAVE stars. With these data we investigated the chemical gradients along the Galactic radius of the Milky Way. We found that stars with low vertical velocities |W| (which stay close to the Galactic plane) show an iron abundance gradient in agreement with previous works (~-0.07$ dex kpc^-1) whereas stars with larger |W| which are able to reach larger heights above the Galactic plane, show progressively flatter gradients. The gradients of the other elements follow the same trend. This suggests that an efficient radial mixing acts in the Galaxy or that the thick disk formed from homogeneous interstellar matter. In particular, we found hundreds of stars which can be kinetically classified as thick disk stars exhibiting a chemical composition typical of the thin disk. A few stars of this kind have already been detected by other authors, and their origin is still not clear. One possibility is that they are thin disk stars kinematically heated, and then underwent an efficient radial mixing process which blurred (and so flattened) the gradient. Alternatively they may be a transition population" which represents an evolutionary bridge between thin and thick disk. Our analysis shows that the two explanations are not mutually exclusive. Future follow-up high resolution spectroscopic observations will clarify their role in the Galactic disk evolution.
In the living cell, the organization of the complex internal structure relies to a large extent on molecular motors. Molecular motors are proteins that are able to convert chemical energy from the hydrolysis of adenosine triphosphate (ATP) into mechanical work. Being about 10 to 100 nanometers in size, the molecules act on a length scale, for which thermal collisions have a considerable impact onto their motion. In this way, they constitute paradigmatic examples of thermodynamic machines out of equilibrium. This study develops a theoretical description for the energy conversion by the molecular motor myosin V, using many different aspects of theoretical physics. Myosin V has been studied extensively in both bulk and single molecule experiments. Its stepping velocity has been characterized as a function of external control parameters such as nucleotide concentration and applied forces. In addition, numerous kinetic rates involved in the enzymatic reaction of the molecule have been determined. For forces that exceed the stall force of the motor, myosin V exhibits a 'ratcheting' behaviour: For loads in the direction of forward stepping, the velocity depends on the concentration of ATP, while for backward loads there is no such influence. Based on the chemical states of the motor, we construct a general network theory that incorporates experimental observations about the stepping behaviour of myosin V. The motor's motion is captured through the network description supplemented by a Markov process to describe the motor dynamics. This approach has the advantage of directly addressing the chemical kinetics of the molecule, and treating the mechanical and chemical processes on equal grounds. We utilize constraints arising from nonequilibrium thermodynamics to determine motor parameters and demonstrate that the motor behaviour is governed by several chemomechanical motor cycles. In addition, we investigate the functional dependence of stepping rates on force by deducing the motor's response to external loads via an appropriate Fokker-Planck equation. For substall forces, the dominant pathway of the motor network is profoundly different from the one for superstall forces, which leads to a stepping behaviour that is in agreement with the experimental observations. The extension of our analysis to Markov processes with absorbing boundaries allows for the calculation of the motor's dwell time distributions. These reveal aspects of the coordination of the motor's heads and contain direct information about the backsteps of the motor. Our theory provides a unified description for the myosin V motor as studied in single motor experiments.
The complete consumption of the oceanic domain of a tectonic plate by subduction into the upper mantle results in continent subduction, although continental crust is typically of lower density than the upper mantle. Thus, the sites of former oceanic domains (named suture zones) are generally decorated with stratigraphic sequences deposited along continental passive margins that were metamorphosed under low-grade, high-pressure conditions, i.e., low temperature/depth ratios (< 15°C/km) with respect to geothermal gradients in tectonically stable regions. Throughout the Mesozoic and Cenozoic (i.e., since ca. 250 Ma), the Mediterranean realm was shaped by the closure of the Tethyan Ocean, which likely consisted in numerous oceanic domains and microcontinents. However, the exact number and position of Tethyan oceans and continents (i.e., the Tethyan palaeogeography) remains debated. This is particularly the case of Western and Central Anatolia, where a continental fragment was accreted to the southern composite margin of the Eurasia sometime between the Late Cretaceous and the early Cenozoic. The most frontal part of this microcontinent experienced subduction-related metamorphism around 85-80 Ma, and collision-related metamorphism affected more external parts around 35 Ma. This unsually-long period between subduction- and collision-related metamorphisms (ca. 50 Ma) in units ascribed to the same continental edge constitutes a crucial issue to address in order to unravel how Anatolia was assembled. The Afyon Zone is a tectono-sedimentary unit exposed south and structurally below the front high-pressure belt. It is composed of a Mesozoic sedimentary sequence deposited on top of a Precambrian to Palaeozoic continental substratum, which can be traced from Northwestern to southern Central Anatolia, along a possible Tethyan suture. Whereas the Afyon Zone was defined as a low-pressure metamorphic unit, high-pressure minerals (mainly Fe-Mg-carpholite in metasediments) were recently reported from its central part. These findings shattered previous conceptions on the tectono-metamorphic evolution of the Afyon Zone in particular, and of the entire region in general, and shed light on the necessity to revise the regional extent of subduction-related metamorphism by re-inspecting the petrology of poorly-studied metasediments. In this purpose, I re-evaluated the metamorphic evolution of the entire Afyon Zone starting from field observations. Low-grade, high-pressure mineral assemblages (Fe-Mg-carpholite and glaucophane) are reported throughout the unit. Well-preserved carpholite-chloritoid assemblages are useful to improve our understanding of mineral relations and transitions in the FeO-MgO-Al2O3-SiO2-H2O system during rocks’ travel down to depth (prograde metamorphism). Inspection of petrographic textures, minute variations in mineral composition and Mg-Fe distribution among carpholite-chloritoid assemblages documents multistage mineral growth, accompanied by a progressive enrichment in Mg, and strong element partitioning. Using an updated database of mineral thermodynamic properties, I modelled the pressure and temperature conditions that are consistent with textural and chemical observations. Carpholite-bearing assemblages in the Afyon Zone account for a temperature increase from 280 to 380°C between 0.9 and 1.1 GPa (equivalent to a depth of 30-35 km). In order to further constrain regional geodynamics, first radiometric ages were determined in close association with pressure-temperature estimates for the Afyon Zone, as well as two other tectono-sedimentary units from the same continental passive margin (the Ören and Kurudere-Nebiler Units from SW Anatolia). For age determination, I employed 40Ar-39Ar geochronology on white mica in carpholite-bearing rocks. For thermobarometry, a multi-equilibrium approach was used based on quartz-chlorite-mica and quartz-chlorite-chloritoid associations formed at the expense of carpholite-bearing assemblages, i.e., during the exhumation from the subduction zone. This combination allows deciphering the significance of the calculated radiometric ages in terms of metamorphic conditions. Results show that the Afyon Zone and the Ören Unit represent a latest Cretaceous high-pressure metamorphic belt, and the Kurudere-Nebiler Unit was affected by subduction-related metamorphism around 45 Ma and cooled down after collision-related metamorphism around 26 Ma. The results provided in the present thesis and from the literature allow better understanding continental amalgamation in Western Anatolia. It is shown that at least two distinct oceanic branches, whereas only one was previously considered, have closed during continuous north-dipping subduction between 92 and 45 Ma. Between 85-80 and 70-65 Ma, a narrow continental domain (including the Afyon Zone) was buried into a subduction zone within the northern oceanic strand. Parts of the subducted continent crust were exhumed while the upper oceanic plate was transported southwards. Subduction of underlying lithosphere persisted, leading to the closure of the southern oceanic branch and to subduct the front of a second continental domain (including the Kurudere-Nebiler Unit). This followed by a continental collisional stage characterized by the cease of subduction, crustal thicknening and the detachment of the subducting oceanic slab from the accreted continent lithosphere. The present study supports that in the late Mesozoic the East Mediterranean realm had a complex tectonic configuration similar to present Southeast Asia or the Caribbean, with multiple, coexisting oceanic basins, microcontinents and subduction zones.
Complete protection against flood risks by structural measures is impossible. Therefore flood prediction is important for flood risk management. Good explanatory power of flood models requires a meaningful representation of bio-physical processes. Therefore great interest exists to improve the process representation. Progress in hydrological process understanding is achieved through a learning cycle including critical assessment of an existing model for a given catchment as a first step. The assessment will highlight deficiencies of the model, from which useful additional data requirements are derived, giving a guideline for new measurements. These new measurements may in turn lead to improved process concepts. The improved process concepts are finally summarized in an updated hydrological model. In this thesis I demonstrate such a learning cycle, focusing on the advancement of model evaluation methods and more cost effective measurements. For a successful model evaluation, I propose that three questions should be answered: 1) when is a model reproducing observations in a satisfactory way? 2) If model results deviate, of what nature is the difference? And 3) what are most likely the relevant model components affecting these differences? To answer the first two questions, I developed a new method to assess the temporal dynamics of model performance (or TIGER - TIme series of Grouped Errors). This method is powerful in highlighting recurrent patterns of insufficient model behaviour for long simulation periods. I answered the third question with the analysis of the temporal dynamics of parameter sensitivity (TEDPAS). For calculating TEDPAS, an efficient method for sensitivity analysis is necessary. I used such an efficient method called Fourier Amplitude Sensitivity Test, which has a smart sampling scheme. Combining the two methods TIGER and TEDPAS provided a powerful tool for model assessment. With WaSiM-ETH applied to the Weisseritz catchment as a case study, I found insufficient process descriptions for the snow dynamics and for the recession during dry periods in late summer and fall. Focusing on snow dynamics, reasons for poor model performance can either be a poor representation of snow processes in the model, or poor data on snow cover, or both. To obtain an improved data set on snow cover, time series of snow height and temperatures were collected with a cost efficient method based on temperature measurements on multiple levels at each location. An algorithm was developed to simultaneously estimate snow height and cold content from these measurements. Both, snow height and cold content are relevant quantities for spring flood forecasting. Spatial variability was observed at the local and the catchment scale with an adjusted sampling design. At the local scale, samples were collected on two perpendicular transects of 60 m length and analysed with geostatistical methods. The range determined from fitted theoretical variograms was within the range of the sampling design for 80% of the plots. No patterns were found, that would explain the random variability and spatial correlation at the local scale. At the watershed scale, locations of the extensive field campaign were selected according to a stratified sample design to capture the combined effects of elevation, aspect and land use. The snow height is mainly affected by the plot elevation. The expected influence of aspect and land use was not observed. To better understand the deficiencies of the snow module in WaSiM-ETH, the same approach, a simple degree day model was checked for its capability to reproduce the data. The degree day model was capable to explain the temporal variability for plots with a continuous snow pack over the entire snow season, if parameters were estimated for single plots. However, processes described in the simple model are not sufficient to represent multiple accumulation-melt-cycles, as observed for the lower catchment. Thus, the combined spatio-temporal variability at the watershed scale is not captured by the model. Further tests on improved concepts for the representation of snow dynamics at the Weißeritz are required. From the data I suggest to include at least rain on snow and redistribution by wind as additional processes to better describe spatio-temporal variability. Alternatively an energy balance snow model could be tested. Overall, the proposed learning cycle is a useful framework for targeted model improvement. The advanced model diagnostics is valuable to identify model deficiencies and to guide field measurements. The additional data collected throughout this work helps to get a deepened understanding of the processes in the Weisseritz catchment.
The Arctic is a particularly sensitive area with respect to climate change due to the high surface albedo of snow and ice and the extreme radiative conditions. Clouds and aerosols as parts of the Arctic atmosphere play an important role in the radiation budget, which is, as yet, poorly quantified and understood. The LIDAR (Light Detection And Ranging) measurements presented in this PhD thesis contribute with continuous altitude resolved aerosol profiles to the understanding of occurrence and characteristics of aerosol layers above Ny-Ålesund, Spitsbergen. The attention was turned to the analysis of periods with high aerosol load. As the Arctic spring troposphere exhibits maximum aerosol optical depths (AODs) each year, March and April of both the years 2007 and 2009 were analyzed. Furthermore, stratospheric aerosol layers of volcanic origin were analyzed for several months, subsequently to the eruptions of the Kasatochi and Sarychev volcanoes in summer 2008 and 2009, respectively. The Koldewey Aerosol Raman LIDAR (KARL) is an instrument for the active remote sensing of atmospheric parameters using pulsed laser radiation. It is operated at the AWIPEV research base and was fundamentally upgraded within the framework of this PhD project. It is now equipped with a new telescope mirror and new detection optics, which facilitate atmospheric profiling from 450m above sea level up to the mid-stratosphere. KARL provides highly resolved profiles of the scattering characteristics of aerosol and cloud particles (backscattering, extinction and depolarization) as well as water vapor profiles within the lower troposphere. Combination of KARL data with data from other instruments on site, namely radiosondes, sun photometer, Micro Pulse LIDAR, and tethersonde system, resulted in a comprehensive data set of scattering phenomena in the Arctic atmosphere. The two spring periods March and April 2007 and 2009 were at first analyzed based on meteorological parameters, like local temperature and relative humidity profiles as well as large scale pressure patterns and air mass origin regions. Here, it was not possible to find a clear correlation between enhanced AOD and air mass origin. However, in a comparison of two cloud free periods in March 2007 and April 2009, large AOD values in 2009 coincided with air mass transport through the central Arctic. This suggests the occurrence of aerosol transformation processes during the aerosol transport to Ny-Ålesund. Measurements on 4 April 2009 revealed maximum AOD values of up to 0.12 and aerosol size distributions changing with altitude. This and other performed case studies suggest the differentiation between three aerosol event types and their origin: Vertically limited aerosol layers in dry air, highly variable hygroscopic boundary layer aerosols and enhanced aerosol load across wide portions of the troposphere. For the spring period 2007, the available KARL data were statistically analyzed using a characterization scheme, which is based on optical characteristics of the scattering particles. The scheme was validated using several case studies. Volcanic eruptions in the northern hemisphere in August 2008 and June 2009 arose the opportunity to analyze volcanic aerosol layers within the stratosphere. The rate of stratospheric AOD change was similar within both years with maximum values above 0.1 about three to five weeks after the respective eruption. In both years, the stratospheric AOD persisted at higher rates than usual until the measurements were stopped in late September due to technical reasons. In 2008, up to three aerosol layers were detected, the layer structure in 2009 was characterized by up to six distinct and thin layers which smeared out to one broad layer after about two months. The lowermost aerosol layer was continuously detected at the tropopause altitude. Three case studies were performed, all revealed rather large indices of refraction of m = (1.53–1.55) - 0.02i, suggesting the presence of an absorbing carbonaceous component. The particle radius, derived with inversion calculations, was also similar in both years with values ranging from 0.16 to 0.19 μm. However, in 2009, a second mode in the size distribution was detected at about 0.5 μm. The long term measurements with the Koldewey Aerosol Raman LIDAR in Ny-Ålesund provide the opportunity to study Arctic aerosols in the troposphere and the stratosphere not only in case studies but on longer time scales. In this PhD thesis, both, tropospheric aerosols in the Arctic spring and stratospheric aerosols following volcanic eruptions have been described qualitatively and quantitatively. Case studies and comparative studies with data of other instruments on site allowed for the analysis of microphysical aerosol characteristics and their temporal evolution.
Der Begriff Gesundheit wurde von der WHO definiert als „nicht nur die Abwesenheit von Krankheit, sondern, positiv als Naturrecht formuliert, vollständiges körperliches, seelisches und soziales Wohlbefinden“. Deswegen hat die WHO mit dem Gesundheitsministerium in Syrien das Programm „Gesunde Dörfer“ seit 1996 gestaltet. Es zielt darauf, den wirtschaftlichen, sozialen und gesundheitlichen Zustand der Landbevölkerung zu verbessern, insbesondere soll es den großen Unterschied zwischen Stadt und Land vermindern. Das Projekt stellt sich die Aufgabe, den Einfluss des Programms auf Wirtschafts- und Gesundheitsparameter im Vergleich mit anderen Kontrolledörfern zu analysieren. Hierzu werden Umfragedaten in Syrien ausgewertet. Die Auswertung der Befragung in der vorliegenden Arbeit zeigte, dass das Programm seine Ziele bezüglich der Verbesserung der Gesundheits- und Lebensqualität erreicht Erfolgreich war das Programm „Gesunde Dörfer“ auch, mit Ausnahme der nördlichen und östlichen Region, in der Verringerung der Anzahl arbeitender Kinder, in der Förderung der Frauen eine Beschäftigung aufzunehmen bzw. ein Studium zu absolvieren sowie in der Reduzierung der Analphabetenrate.
Bei der Entdeckung der Glutathionperoxidase-2 (GPx2) wurde zunächst davon ausgegangen, dass die Funktion dieses Enzyms im Kryptengrund des Colons einzig in der Reduktion von H2O2 besteht. Im Laufe der weiteren Erforschung zeigte sich, dass GPx2 auch in verschiedenen Tumorgeweben vermehrt exprimiert wird. Dabei wird diskutiert, ob die Wirkung von GPx2 im Tumor eher als pro- oder als antikarzinogen einzustufen ist. Mehrere Experimente in vitro und in vivo zeigten antiinflammatorische Eigenschaften der GPx2. Aufgrund dieser Befunde wird derzeit über weitere Funktionen der GPx2 spekuliert. In dieser Arbeit wurde die physiologische Funktion von GPx2 näher erforscht, dazu wurden Wildtyp- und GPx2-Knockout-Mäuse in Hinblick auf Veränderungen der Enzymexpression und der Colonmorphologie untersucht. Es wurden drei verschiedene Selendiäten verfüttert: selenarmes, selenadäquates und selensupplementiertes Futter. Unter physiologischen Bedingungen ist am Kryptengrund des Colons, innerhalb der proliferierenden Zone, die Mitoserate am höchsten. Der Großteil der apoptotischen Zellen ist hingegen an der Kryptenspitze vorzufinden. Durch den Knockout von GPx2 kam es zu einer signifikanten Erhöhung der Apoptoserate am Kryptengrund. Dabei war der größte Effekt auf selenarmem Futter zu verzeichnen. Hierbei wurde sogar eine Veränderung der Colonmorphologie dokumentiert, da die Verschiebung der Proliferationszone in Richtung Kryptenspitze eine Verlängerung der Krypten nach sich zog. Im Wildtyp wurden keine Apoptosen im Kryptengrund detektiert. GPx1 wird unter physiologischen Bedingungen im Gegensatz zur GPx2 in der Kryptenspitze exprimiert und ist im Selenmangel nicht mehr detektierbar. Der Knockout von GPx2 erhöhte die GPx1-Expression im Kryptengrund auf allen drei Selendiäten. Diese Überexpression von GPx1 am Kryptengrund soll vermutlich den Verlust von GPx2 an dieser Stelle kompensieren. Da jedoch dort die massive Apoptoserate detektiert wurde, kann die GPx1 nicht die komplette Funktion von GPx2 kompensieren. Diese Ergebnisse deuten darauf hin, dass die Funktion von GPx2 nicht nur in der Reduktion von H2O2 liegt. Vielmehr kann eine Rolle bei der Aufrechterhaltung der Homöostase von Zellen postuliert werden. Ein weiterer Bestandteil dieser Arbeit war die Klärung der Frage, welchen Einfluss GPx2 auf die entzündungsassoziierte Colonkarzinogenese ausübt. In dem hierfür verwendeten AOM/DSS-Model wird der karzinogene Prozess durch Entzündung vorangetrieben. Es erfolgte sowohl im Wildtyp als auch im GPx2-Knockout zum einen die Bewertung des Entzündungsstatus des Colons und zum anderen wurde die Anzahl von ACF und Tumoren verglichen. Das Colon im GPx2-Knockout war wesentlich stärker entzündet als im Wildtyp. Diese Ergebnisse bestätigen die für die GPx2 postulierte antiinflammatorische Funktion. Normalerweise führt eine Erhöhung der Mitoseanzahl zur Regeneration des entzündeten Gewebes. Jedoch beeinflusst der Verlust von GPx2 vermutlich den Ablauf der Entzündung, indem beispielsweise die Regeneration des Gewebes durch die enorm hohe Apoptoserate am Kryptengrund verlangsamt wird. Des Weiteren hatten sich im GPx2-Knockout tendenziell mehr Tumore entwickelt. Somit korrelierte die Entzündung des Colons mit der Entwicklung von Tumoren. Der Verlust von GPx2 begünstigte vermutlich sowohl die Tumorinitiation als auch die Tumorprogression. Allerdings stimulierte die Expression von GPx2 ebenfalls das Tumorwachstum. Es kann geschlussfolgert werden, dass eine adäquate GPx2-Expression vor Entzündung schützt und somit das Risiko für Colonkrebs senkt. Ob GPx2 aber insgesamt pro- oder antikarzinogen wirkt, hängt vermutlich vom Stadium des Colonkarzinogenese ab.
Das vorliegende Buch vergleicht Strategien biologischer Systeme mit militärischen Strategien. Die zentrale Fragestellung ist dabei darauf gerichtet, ob es neben systemischen Gemeinsamkeiten auch gemeinsame oder ähnliche Strukturmuster und ähnliche Prozessabläufe beispielsweise sowohl im biologischen Abwehrmechanismus des Immunsystems und bei Insektenstaaten als auch bei Prozessen im Militär gibt. Vor diesem Hintergrund klaffen in der Theorie der Strategie, speziell in den Militärwissenschaften Lücken, denn der Systemansatz wird nicht konsequent beachtet, wie in diesem Buch mehrfach nachgewiesen ist. Von einem allgemeinen Verständnis der Strategie als bewusstem planerischem Vorgehen ist Abstand zu nehmen. Ausgehend von der Methode der Analogie und des Vergleichs wird im theoretischen Teil dieses Buches die Allgemeine Systemtheorie erläutert. Dabei werden der Begriff der Strategie ebenso wie die Begriffe Struktur und Prozess und Ansätze aus der Kriegsphilosophie von Clausewitz untersucht. Den Ausgangspunkt und schließlich auch wieder den Endpunkt der Überlegungen bilden neben dem notwendigen weiten Verständnis von Strategie, vor allem der Begriff der Organisation, ihrer Umwelt und der in diesem Zusammenhang bestehenden Wechselwirkung. Sowohl die Wechselwirkung von Umwelt und System als auch ihre Abhängigkeit durch strukturelle Kopplung werden beschrieben. Das Zusammenspiel und die daraus entstehende Komplexität der fünf Komponenten der Wahrnehmung, der Information und der Führung im Zusammenhang der Komponenten von Raum und Zeit in einem sozialen System lassen die klassische Ziel-Mittel-Zweck-Beziehung Clausewitz´scher Strategiedefinition verkürzt erscheinen. Anhand eines kurzen Rekurses der Methoden der Sozialen Netzwerkanalyse (SNA) wird der breite und tiefgehende Analyserahmen der Messung und Transparenzerreichung in Organisationen vorgestellt. Die SNA wird als Ausprägung der Netzwerk- und Graphentheorie, in die Allgemeine Systemtheorie integriert. Sie bildet eine zukunftsweisende Methode der Untersuchung von Netzwerken wie etwa dem Internet (Facebook, Xing etc.). Der aufgezeigte Theorierahmen bildet dabei zugleich eine Methode für den Systemvergleich und kann als Vorgehensmodell künftiger Strategieentwicklung genutzt werden. Der anschließende Systemvergleich wird mit mehreren Beispielen durchgeführt. Ausgehend von der Zelle als Grundeinheit werden Strukturen und Prozesse des Immunsystems mit solchen in militärischen Strukturen, weil sie im Lauf der Evolution enorme Leistungen in Reaktion, Anpassung und Optimierung vollbracht haben. Der Vergleich geht der Frage nach, ob in diesen Bereichen der Strategie und Organisation systemische Grundregeln existieren. Das Beispiel der Wechselwirkung zwischen Parasit und Wirt zeigt, dass jeder Fortschritt und Sieg angesichts der Systemeinbettung von Strategie nur relativ wirken kann. Die Analogie zwischen Viren und Bakterien sowie die Entwicklung des Begriffs der sozialen Mimikry führen zu einem erweiterten Verständnis der Strategie von Terroristen in sozialen Systemen. Verdeutlicht wird das Grundschema des Täuschens und Eindringens in Systeme sowie die Beeinflussung und Umsteuerung von Prozessen und Strukturen in einem System durch Kommunikation und Implementation von Codes. Am Beispiel des Immunsystems und der Bildung verschiedener Kommunikations- und Steuerungsmechanismen von Zellsystemen sowie Beispielen von Schwarmbildung und der Organisation sozialer Insekten werden eine Vielzahl heuristischer Hinweise für neue Ansätze für die Organisation von Streitkräften und ihrer Steuerung gefunden. Neben der Erarbeitung eines grundlegenden Strategiebegriffs anhand von Wahrnehmung und Selektion als Grundprozess der Erzeugung von Strategie wird eine differenzierte Betrachtung von Begriffen wie Redundanz und Robustheit sowie eine relativierende Sichtweise von Risiko, Gefahr und Schaden gewonnen. Der Vergleich mit dem Immunsystems zeigt einfache Beispiele der Informationsspeicherung und -übertragung, die zudem Bypassfähigkeiten sowie dezentrale Eskalations- und Deeskalationsprinzipien veranschaulichen. Dies eröffnet in Analogie dieser Prinzipien einen weiten Raum Sicherheitsarchitekturen zu überdenken und neu zu strukturieren. Zudem kann die räumliche Ausbreitung von Information und Kräften als ein gemeinsames Grundproblem der Entwicklung und Wirksamkeit von Strategien sowohl in der Natur, als auch im Militär identifiziert werden. Die Betrachtung zeigt zudem wie Zellen mit fehlgeleiteten Prozessen und Strukturen umgehen. Die Analogie deutet auf das Erfordernis einer Veränderung im Umgang mit Fehlern und ihrer Rückführ- und Umkehrbarkeit im weitesten Sinne. Das Buch eröffnet überdies ein neues Verständnis von Staat, Gewaltenteilung und Institutionen in einem sozialen System. Die Ergebnisse sind auch auf andere Forschungsbereiche, Organisationen und unterschiedlichste soziale Systeme übertragbar. Es eröffnet sich ein breites Anwendungsspektrum für künftige strategische Untersuchungen.
Supermassive black holes are a fundamental component of the universe in general and of galaxies in particular. Almost every massive galaxy harbours a supermassive black hole (SMBH) in its center. Furthermore, there is a close connection between the growth of the SMBH and the evolution of its host galaxy, manifested in the relationship between the mass of the black hole and various properties of the galaxy's spheroid component, like its stellar velocity dispersion, luminosity or mass. Understanding this relationship and the growth of SMBHs is essential for our picture of galaxy formation and evolution. In this thesis, I make several contributions to improve our knowledge on the census of SMBHs and on the coevolution of black holes and galaxies. The first route I follow on this road is to obtain a complete census of the black hole population and its properties. Here, I focus particularly on active black holes, observable as Active Galactic Nuclei (AGN) or quasars. These are found in large surveys of the sky. In this thesis, I use one of these surveys, the Hamburg/ESO survey (HES), to study the AGN population in the local volume (z~0). The demographics of AGN are traditionally represented by the AGN luminosity function, the distribution function of AGN at a given luminosity. I determined the local (z<0.3) optical luminosity function of so-called type 1 AGN, based on the broad band B_J magnitudes and AGN broad Halpha emission line luminosities, free of contamination from the host galaxy. I combined this result with fainter data from the Sloan Digital Sky Survey (SDSS) and constructed the best current optical AGN luminosity function at z~0. The comparison of the luminosity function with higher redshifts supports the current notion of 'AGN downsizing', i.e. the space density of the most luminous AGN peaks at higher redshifts and the space density of less luminous AGN peaks at lower redshifts. However, the AGN luminosity function does not reveal the full picture of active black hole demographics. This requires knowledge of the physical quantities, foremost the black hole mass and the accretion rate of the black hole, and the respective distribution functions, the active black hole mass function and the Eddington ratio distribution function. I developed a method for an unbiased estimate of these two distribution functions, employing a maximum likelihood technique and fully account for the selection function. I used this method to determine the active black hole mass function and the Eddington ratio distribution function for the local universe from the HES. I found a wide intrinsic distribution of black hole accretion rates and black hole masses. The comparison of the local active black hole mass function with the local total black hole mass function reveals evidence for 'AGN downsizing', in the sense that in the local universe the most massive black holes are in a less active stage then lower mass black holes. The second route I follow is a study of redshift evolution in the black hole-galaxy relations. While theoretical models can in general explain the existence of these relations, their redshift evolution puts strong constraints on these models. Observational studies on the black hole-galaxy relations naturally suffer from selection effects. These can potentially bias the conclusions inferred from the observations, if they are not taken into account. I investigated the issue of selection effects on type 1 AGN samples in detail and discuss various sources of bias, e.g. an AGN luminosity bias, an active fraction bias and an AGN evolution bias. If the selection function of the observational sample and the underlying distribution functions are known, it is possible to correct for this bias. I present a fitting method to obtain an unbiased estimate of the intrinsic black hole-galaxy relations from samples that are affected by selection effects. Third, I try to improve our census of dormant black holes and the determination of their masses. One of the most important techniques to determine the black hole mass in quiescent galaxies is via stellar dynamical modeling. This method employs photometric and kinematic observations of the galaxy and infers the gravitational potential from the stellar orbits. This method can reveal the presence of the black hole and give its mass, if the sphere of the black hole's gravitational influence is spatially resolved. However, usually the presence of a dark matter halo is ignored in the dynamical modeling, potentially causing a bias on the determined black hole mass. I ran dynamical models for a sample of 12 galaxies, including a dark matter halo. For galaxies for which the black hole's sphere of influence is not well resolved, I found that the black hole mass is systematically underestimated when the dark matter halo is ignored, while there is almost no effect for galaxies with well resolved sphere of influence.
Im Rahmen einer prospektiven Längsschnittuntersuchung wurde der Berufseinstieg von ÄrztInnen (N = 185) als normatives kritisches Lebensereignis untersucht. Dazu wurden sie insgesamt drei Mal im Abstand von jeweils sechs Monaten im ersten Jahr nach ihrem Studiumsabschluss befragt (T1: in den ersten zwei Wochen nach dem Staatsexamen, T2: kurzzeitig nach dem Berufseinstieg, T3: im Schnitt 9.5 Monate nach dem Berufseinstieg). Die Ergebnisse zeigten zunächst, dass unlängst examinierte Jung-ÄrztInnen, die sich vergleichsweise schlechter auf den Beruf durch das Studium vorbereitet fühlten, ihren bevorstehenden Berufseinstieg negativer bewerteten und schon vor diesem beanspruchter waren. Die Bewertung des Berufseinstiegs vermittelte dabei den Zusammenhang zwischen einer schlechten Vorbereitung und der Beanspruchung. Arbeitsspezifische Copingfunktionalität wiederum pufferte den Zusammenhang zwischen einer schlechten Vorbereitung und der Bewertung des Berufseinstiegs. Das Problem einer als schlecht empfundenen Vorbereitung verdeutlichte sich in der Längsschnittanalyse – sie sagte eine höhere Beanspruchung zum zweiten Messzeitpunkt, d.h. nach dem Berufseinstieg, vorher. In der Untersuchung der Beanspruchungsentwicklung über die drei Messzeitpunkte hinweg fanden sich nur wenige Veränderungen. Es ließ sich zwar eine deutliche Zunahme der mittleren Depressivitäts-Ausprägungen über den Berufseinstieg hinweg herausstellen (T1-T2); auf anderen Beanspruchungsindikatoren zeigte sich jedoch kein direkter Effekt des Arbeitsbeginns bzw. fand sich auch keine Adaptation der Jung-ÄrztInnen an ihre neue Situation im Sinne einer sich verringernden Beanspruchung im weiteren Verlauf (T2-T3). In der Erklärung interindividueller Unterschiede in der Beanspruchung im Untersuchungszeitraum zeigte sich, dass die sich mit dem Berufseinstieg einstellende Arbeitsbelastung zum zweiten und dritten Messzeitpunkt erwartungsgemäß positiv mit Beanspruchung assoziiert war. Die Arbeitsbelastungs-Beanspruchungs-Beziehung bestand jedoch nur im Querschnitt; in der Längsschnittanalyse fand sich kein Effekt der T2-Arbeitsbelastung auf die T3-Beanspruchung. Ausgangsunterschiede in psychischen Ressourcen wirkten einerseits direkt auf die Beanspruchung zu T2, zum Teil moderierten sie aber auch den Zusammenhang zwischen der Arbeitsbelastung und Beanspruchung: Eine höhere Resilienz und die Wahrnehmung sozialer Unterstützung sagten eine geringere Beanspruchung nach dem Berufseinstieg vorher. Jung-ÄrztInnen, die sich durch eine stärkere Arbeitsbelastung auszeichneten, aber über ein funktionaleres Bewältigungsverhalten im Arbeitskontext verfügten, waren kurzzeitig nach dem Berufseinstieg weniger beansprucht als stark arbeitsbelastete Jung-ÄrztInnen mit weniger funktionalem Coping. Verringerungen in den psychischen Ressourcen über den Berufseinstieg hinweg wirkten sich direkt, d.h. per se ungünstig auf die Beanspruchung zum dritten Messzeitpunkt aus. Zudem interagierten sie mit der zu diesem Zeitpunkt bestehenden Arbeitsbelastung in Vorhersage der Beanspruchung. Stärker arbeitsbelastete Jung-ÄrztInnen, deren Copingfunktionalität und Wahrnehmung sozialer Unterstützung vom ersten zum dritten Messzeitpunkt abgenommen hatte, waren am Ende des Untersuchungszeitraums am stärksten beansprucht. Hinsichtlich der Auswirkungen des Berufseinstiegs auf die Persönlichkeit der Jung-ÄrztInnen fanden sich ungünstige Veränderungen: Sowohl die Ausprägungen psychischer Ressourcen (Widerstandsfähigkeit, Wahrnehmung sozialer Unterstützung hinsichtlich der Arbeitstätigkeit) als auch die der Big Five-Faktoren nahmen im Mittel ab. Interindividuelle Unterschiede in den Veränderungen ließen sich auf die Beanspruchung kurzzeitig nach dem Berufseinstieg (T2) bzw. auf deren Entwicklung in den Folgemonaten (T2-T3) zurückführen: Jene Jung-ÄrztInnen, die vergleichsweise stark beansprucht auf den Berufseinstieg reagiert hatten bzw. deren Beanspruchung im weiteren Verlauf zunahm, zeigten entsprechend ungünstige Veränderungen. Die Ergebnisse zusammengefasst verdeutlicht sich folgende Problematik: Jung-ÄrztInnen, die weniger gut, d.h. persönlichkeitsbasiert geschützt den Berufseinstieg absolvieren, reagieren stärker beansprucht und sind dann auch diejenigen, deren Persönlichkeit sich in den ersten Arbeitsmonaten ungünstig verändert. Jung-ÄrztInnen mit geringen psychischen Ressourcen sind folglich nicht nur besonders vulnerabel für die Entwicklung von Beanspruchung angesichts belastender Arbeitsbedingungen, sondern ihre vergleichsweise hohe Beanspruchung bedingt eine weitere Verringerung des Schutz- und Pufferpotenzials ihrer Persönlichkeit. Es kommt zu einer ungünstigen Akzentuierung der ohnehin schon vergleichsweise ressourcenschwachen Persönlichkeit, welche die Vulnerabilität für zukünftige Beanspruchung erhöht. Aus den Ergebnissen lässt sich ein Unterstützungsbedarf junger ÄrztInnen in der sensiblen und wegweisenden Berufseinstiegsphase ableiten. Neben einer Verbesserung ihrer Arbeitsbedingungen stellen eine rechtzeitige Sensibilisierung junger ÄrztInnen für den Arbeitsbelastungs-Beanspruchungs-Zusammenhang, ihre regelmäßige Supervision sowie vor allem aber auch kompetenzorientiertes und ressourcenstärkendes Feedback von den Mentoren und Vorgesetzten die Grundlage dafür dar, dass die Jung-MedizinerInnen selbst gesund bleiben und sie die ärztliche Tätigkeit trotz ihres wohl stets hohen Belastungspotenzials als erfüllend und zufriedenstellend erleben.
After the collapse of the Soviet Union the former member states have started the transformation process. The transformation process from planned to market economy includes not only the adaptation of the economy to the new market rules but also the profound social and political transformation. For this reason such processes present huge challenges to affected societies. The transformational recession in Georgia was significantly enhanced by the civil war and by ethnic conflicts in Abkhazia and South Ossetia. During the ethnic conflicts and civil war the business and technical infrastructure were damaged and most of them were completely destroyed. Poverty and political instability were predominated. The trade relations with the member countries of Council of Mutual Economic Assistance (Comecon) were aborted. Moreover, the conflict in South Ossetia hampered the power supply from Russia and a conflict in Abkhazia, the production and trade with tea and citruses, which were major trade commodities at that time. In the beginning of 90-ies, Georgian government with the assistance of international organizations, such as International Monetary Fund and World Bank started to elaborate political and economical reforms. The reforms included several aspects, such as the transfer of public assets to private through privatization, the liberalization of domestic market and trade and the creation of market-oriented institutions. Because of lack in implementation neither economical nor political transformation has been achieved. For instance, by the begin of market oriented reforms the awareness of policy makers about the importance of entrepreneurship, in particular small and medium ones for the economy was low. The absence of previous experience prevented the elaboration of appropriate policy instruments and methods for the development of competitive market economy. The stimulation of private sector has been generally neglected. This had a severe affect on political, social and economical problems, which still hampers the development of middle class in Georgia. The presented research indicates that productive entrepreneurship is a driving force of an economy. The entrepreneurial activities on the one hand facilitate the resource allocation and on the other through the development of new products and services urge the competition. Furthermore, they contribute to technological improvements through innovation, create jobs and thus boost the economic and social development of a particular region or country. However, it is important that the legal and institutional framework is appropriately settled. Unlike mature market economies, Georgia is not characterized by well-developed sector of small and medium sized businesses. Most existing SMEs are operating in local markets and predominantly in the shadow economy. It is also noteworthy that small business in Georgia belongs to so called “mom and pop” rather than to innovative, growth oriented businesses. They are mostly engaged in trade and craft. In addition of poor performance, the business activity of SMEs is very centralized. The vast majority of them are operating in the capital Tbilisi. The poor performance of small and medium businesses in Georgia and their negligence by the market forces is among others due to the armed conflicts and state failure. As in the beginning of transformation process, down to the present day, the state fails to provide necessary conditions, such as rule of law, the protection of property rights and competition, transparent and uncorrupted public administration. The result is the weak middle class. The weak middle class by itself has a negative impact on economic development and democratization process in Georgia.
Does it have to be trees? : Data-driven dependency parsing with incomplete and noisy training data
(2011)
We present a novel approach to training data-driven dependency parsers on incomplete annotations. Our parsers are simple modifications of two well-known dependency parsers, the transition-based Malt parser and the graph-based MST parser. While previous work on parsing with incomplete data has typically couched the task in frameworks of unsupervised or semi-supervised machine learning, we essentially treat it as a supervised problem. In particular, we propose what we call agnostic parsers which hide all fragmentation in the training data from their supervised components. We present experimental results with training data that was obtained by means of annotation projection. Annotation projection is a resource-lean technique which allows us to transfer annotations from one language to another within a parallel corpus. However, the output tends to be noisy and incomplete due to cross-lingual non-parallelism and error-prone word alignments. This makes the projected annotations a suitable test bed for our fragment parsers. Our results show that (i) dependency parsers trained on large amounts of projected annotations achieve higher accuracy than the direct projections, and that (ii) our agnostic fragment parsers perform roughly on a par with the original parsers which are trained only on strictly filtered, complete trees. Finally, (iii) when our fragment parsers are trained on artificially fragmented but otherwise gold standard dependencies, the performance loss is moderate even with up to 50% of all edges removed.
Dryland vulnerability : typical patterns and dynamics in support of vulnerability reduction efforts
(2011)
The pronounced constraints on ecosystem functioning and human livelihoods in drylands are frequently exacerbated by natural and socio-economic stresses, including weather extremes and inequitable trade conditions. Therefore, a better understanding of the relation between these stresses and the socio-ecological systems is important for advancing dryland development. The concept of vulnerability as applied in this dissertation describes this relation as encompassing the exposure to climate, market and other stresses as well as the sensitivity of the systems to these stresses and their capacity to adapt. With regard to the interest in improving environmental and living conditions in drylands, this dissertation aims at a meaningful generalisation of heterogeneous vulnerability situations. A pattern recognition approach based on clustering revealed typical vulnerability-creating mechanisms at global and local scales. One study presents the first analysis of dryland vulnerability with global coverage at a sub-national resolution. The cluster analysis resulted in seven typical patterns of vulnerability according to quantitative indication of poverty, water stress, soil degradation, natural agro-constraints and isolation. Independent case studies served to validate the identified patterns and to prove the transferability of vulnerability-reducing approaches. Due to their worldwide coverage, the global results allow the evaluation of a specific system’s vulnerability in its wider context, even in poorly-documented areas. Moreover, climate vulnerability of smallholders was investigated with regard to their food security in the Peruvian Altiplano. Four typical groups of households were identified in this local dryland context using indicators for harvest failure risk, agricultural resources, education and non-agricultural income. An elaborate validation relying on independently acquired information demonstrated the clear correlation between weather-related damages and the identified clusters. It also showed that household-specific causes of vulnerability were consistent with the mechanisms implied by the corresponding patterns. The synthesis of the local study provides valuable insights into the tailoring of interventions that reflect the heterogeneity within the social group of smallholders. The conditions necessary to identify typical vulnerability patterns were summarised in five methodological steps. They aim to motivate and to facilitate the application of the selected pattern recognition approach in future vulnerability analyses. The five steps outline the elicitation of relevant cause-effect hypotheses and the quantitative indication of mechanisms as well as an evaluation of robustness, a validation and a ranking of the identified patterns. The precise definition of the hypotheses is essential to appropriately quantify the basic processes as well as to consistently interpret, validate and rank the clusters. In particular, the five steps reflect scale-dependent opportunities, such as the outcome-oriented aspect of validation in the local study. Furthermore, the clusters identified in Northeast Brazil were assessed in the light of important endogenous processes in the smallholder systems which dominate this region. In order to capture these processes, a qualitative dynamic model was developed using generalised rules of labour allocation, yield extraction, budget constitution and the dynamics of natural and technological resources. The model resulted in a cyclic trajectory encompassing four states with differing degree of criticality. The joint assessment revealed aggravating conditions in major parts of the study region due to the overuse of natural resources and the potential for impoverishment. The changes in vulnerability-creating mechanisms identified in Northeast Brazil are well-suited to informing local adjustments to large-scale intervention programmes, such as “Avança Brasil”. Overall, the categorisation of a limited number of typical patterns and dynamics presents an efficient approach to improving our understanding of dryland vulnerability. Appropriate decision-making for sustainable dryland development through vulnerability reduction can be significantly enhanced by pattern-specific entry points combined with insights into changing hotspots of vulnerability and the transferability of successful adaptation strategies.
Die öffentliche Verwaltung setzt seit mehreren Jahren E-Government-Anwendungssysteme ein, um ihre Verwaltungsprozesse intensiver mit moderner Informationstechnik zu unterstützen. Da die öffentliche Verwaltung in ihrem Handeln in besonderem Maße an Recht und Gesetz gebunden ist verstärkt und verbreitet sich der Zusammenhang zwischen den Gesetzen und Rechtsvorschriften einerseits und der zur Aufgabenunterstützung eingesetzten Informationstechnik andererseits. Aus Sicht der Softwaretechnik handelt es sich bei diesem Zusammenhang um eine spezielle Form der Verfolgbarkeit von Anforderungen (engl. Traceability), die so genannte Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (Pre-Requirements Specification Traceability, kurz Pre-RS Traceability), da sie Aspekte betrifft, die relevant sind, bevor die Anforderungen in eine Spezifikation eingeflossen sind (Ursprünge von Anforderungen). Der Ansatz dieser Arbeit leistet einen Beitrag zur Verfolgbarkeit im Vorfeld der Anforderungsspezifikation von E-Government-Anwendungssystemen. Er kombiniert dazu aktuelle Entwicklungen und Standards (insbesondere des World Wide Web Consortium und der Object Management Group) aus den Bereichen Verfolgbarkeit von Anforderungen, Semantic Web, Ontologiesprachen und modellgetriebener Softwareentwicklung. Der Lösungsansatz umfasst eine spezielle Ontologie des Verwaltungshandeln, die mit den Techniken, Methoden und Werkzeugen des Semantic Web eingesetzt wird, um in Texten von Rechtsvorschriften relevante Ursprünge von Anforderungen durch Annotationen mit einer definierten Semantik zu versehen. Darauf aufbauend wird das Ontology Definition Metamodel (ODM) verwendet, um die Annotationen als spezielle Individuen einer Ontologie auf Elemente der Unified Modeling Language (UML) abzubilden. Dadurch entsteht ein neuer Modelltyp Pre-Requirements Model (PRM), der das Vorfeld der Anforderungsspezifikation formalisiert. Modelle diesen Typs können auch verwendet werden, um Aspekte zu formalisieren die sich nicht oder nicht vollständig aus dem Text der Rechtsvorschrift ergeben. Weiterhin bietet das Modell die Möglichkeit zum Anschluss an die modellgetriebene Softwareentwicklung. In der Arbeit wird deshalb eine Erweiterung der Model Driven Architecture (MDA) vorgeschlagen. Zusätzlich zu den etablierten Modelltypen Computation Independent Model (CIM), Platform Independent Model (PIM) und Platform Specific Model (PSM) könnte der Einsatz des PRM Vorteile für die Verfolgbarkeit bringen. Wird die MDA mit dem PRM auf das Vorfeld der Anforderungsspezifikation ausgeweitet, kann eine Transformation des PRM in ein CIM als initiale Anforderungsspezifikation erfolgen, indem der MOF Query View Transformation Standard (QVT) eingesetzt wird. Als Teil des QVT-Standards ist die Aufzeichnung von Verfolgbarkeitsinformationen bei Modelltransformationen verbindlich. Um die semantische Lücke zwischen PRM und CIM zu überbrücken, erfolgt analog zum Einsatz des Plattformmodells (PM) in der PIM nach PSM Transformation der Einsatz spezieller Hilfsmodelle. Es kommen dafür die im Projekt "E-LoGo" an der Universität Potsdam entwickelten Referenzmodelle zum Einsatz. Durch die Aufzeichnung der Abbildung annotierter Textelemente auf Elemente im PRM und der Transformation der Elemente des PRM in Elemente des CIM kann durchgängige Verfolgbarkeit im Vorfeld der Anforderungsspezifikation erreicht werden. Der Ansatz basiert auf einer so genannten Verfolgbarkeitsdokumentation in Form verlinkter Hypertextdokumente, die mittels XSL-Stylesheet erzeugt wurden und eine Verbindung zur graphischen Darstellung des Diagramms (z. B. Anwendungsfall-, Klassendiagramm der UML) haben. Der Ansatz unterstützt die horizontale Verfolgbarkeit zwischen Elementen unterschiedlicher Modelle vorwärts- und rückwärtsgerichtet umfassend. Er bietet außerdem vertikale Verfolgbarkeit, die Elemente des gleichen Modells und verschiedener Modellversionen in Beziehung setzt. Über den offensichtlichen Nutzen einer durchgängigen Verfolgbarkeit im Vorfeld der Anforderungsspezifikation (z. B. Analyse der Auswirkungen einer Gesetzesänderung, Berücksichtigung des vollständigen Kontextes einer Anforderung bei ihrer Priorisierung) hinausgehend, bietet diese Arbeit eine erste Ansatzmöglichkeit für eine Feedback-Schleife im Prozess der Gesetzgebung. Stehen beispielsweise mehrere gleichwertige Gestaltungsoptionen eines Gesetzes zur Auswahl, können die Auswirkungen jeder Option analysiert und der Aufwand ihrer Umsetzung in E-Government-Anwendungen als Auswahlkriterium berücksichtigt werden. Die am 16. März 2011 in Kraft getretene Änderung des NKRG schreibt eine solche Analyse des so genannten „Erfüllungsaufwands“ für Teilbereiche des Verwaltungshandelns bereits heute verbindlich vor. Für diese Analyse kann die vorliegende Arbeit einen Ansatz bieten, um zu fundierten Aussagen über den Änderungsaufwand eingesetzter E-Government-Anwendungssysteme zu kommen.
Die Natur unterliegt ständigen Veränderungen und befindet sich nur vermeintlich in einem Gleichgewicht. Umweltparameter wie Temperatur, Luftfeuchtigkeit oder Sonneneinstrahlung schwanken auf einer Zeitskala von Sekunden bis Jahrmillionen und beinhalten teils beträchtliche Unterschiede. Mit diesen Umweltveränderungen müssen sich Arten als Teil eines Ökosystems auseinandersetzen. Für Ökologen ist interessant, wie sich individuelle Reaktionen auf die Umweltveränderungen im dynamischen Verhalten einer ganzen Population bemerkbar machen und ob deren Verhalten vorhersagbar ist. Der Demografie einer Population kommt hierbei eine entscheidende Rolle zu, da sie das Resultat von Wachstums- und Sterbeprozessen darstellt. Eben jene Prozesse werden von der Umwelt maßgeblich beeinflusst. Doch wie genau beeinflussen Umweltveränderungen das Verhalten ganzer Populationen? Wie sieht das vorübergehende, transiente Verhalten aus? Als Resultat von Umwelteinflüssen bilden sich in Populationen sogenannte Kohorten, hinsichtlich der Zahl an Individuen überproportional stark vertretene Alters- oder Größenklassen. Sterben z.B. aufgrund eines außergewöhnlich harten Winters, die alten und jungen Individuen einer Population, so besteht diese anschließend hauptsächlich aus Individuen mittleren Alters. Sie wurde sozusagen synchronisiert. Eine solche Populationen neigt zu regelmäßigen Schwankungen (Oszillationen) in ihrer Dichte, da die sich abwechselnden Phasen der individuellen Entwicklung und der Reproduktion nun von einem Großteil der Individuen synchron durchschritten werden. D.h., mal wächst die Population und mal nimmt sie entsprechend der Sterblichkeit ab. In Experimenten mit Phytoplankton-Populationen konnte ich zeigen, dass dieses oszillierende Verhalten mit dem in der Physik gebräuchlichen Konzept der Synchronisation beschrieben werden kann. Synchrones Verhalten ist eines der verbreitetsten Phänomene in der Natur und kann z.B. in synchron schwingenden Brücken, als auch bei der Erzeugung von Lasern oder in Form von rhythmischem Applaus auf einem Konzert beobachtet werden. Wie stark die Schwankungen sind, hängt dabei sowohl von der Stärke der Umweltveränderung als auch vom demografischen Zustand der Population vor der Veränderung ab. Zwei Populationen, die sich in verschiedenen Habitaten aufhalten, können zwar gleich stark von einer Umweltveränderung beeinflusst werden. Die Reaktionen im anschließenden Verhalten können jedoch äußerst unterschiedlich ausfallen, wenn sich die Populationen zuvor in stark unterschiedlichen demografischen Zuständen befanden. Darüber hinaus treten bestimmte, für das Verhalten einer Population relevante Mechanismen überhaupt erst in Erscheinung, wenn sich die Umweltbedingungen ändern. So fiel in Experimenten beispielsweise die Populationsdichte um rund 50 Prozent ab nachdem sich die Ressourcenverfügbarkeit verdoppelte. Der Grund für dieses gegenintuitive Verhalten konnte mit der erhöhten Aufnahme von Ressourcen erklärt werden. Damit verbessert eine Algenzelle zwar die eigene Konstitution, jedoch verzögert sich dadurch die auch die Reproduktion und die Populationsdichte nimmt gemäß ihrer Verluste bzw. Sterblichkeit ab. Zwei oder mehr räumlich getrennte Populationen können darüber hinaus durch Umwelteinflüsse synchronisiert werden. Dies wird als Moran-Effekt bezeichnet. Angenommen auf zwei weit voneinander entfernten Inseln lebt jeweils eine Population. Zwischen beiden findet kein Austausch statt – und doch zeigt sich beim Vergleich ihrer Zeitreihen eine große Ähnlichkeit. Das überregionale Klima synchronisiert hierbei die lokalen Umwelteinflüsse. Diese wiederum bestimmen das Verhalten der jeweiligen Population. Der Moran-Effekt besagt nun, dass die Ähnlichkeit zwischen den Populationen jener zwischen den Umwelteinflüssen entspricht, oder geringer ist. Meine Ergebnisse bestätigen dies und zeigen darüber hinaus, dass sich die Populationen sogar ähnlicher sein können als die Umwelteinflüsse, wenn man von unterschiedlich stark schwankenden Einflüssen ausgeht.
Motivation | Societal and economic needs of East Africa rely entirely on the availability of water, which is governed by the regular onset and retreat of the rainy seasons. Fluctuations in the amounts of rainfall has tremendous impact causing widespread famine, disease outbreaks and human migrations. Efforts towards high resolution forecasting of seasonal precipitation and hydrological systems are therefore needed, which requires high frequency short to long-term analyses of available climate data that I am going to present in this doctoral thesis by three different studies. 15,000 years - Suguta Valley | The main study of this thesis concentrated on the understanding of humidity changes within the last African Humid Period (AHP, 14.8-5.5 ka BP). The nature and causes of intensity variations of the West-African (WAM) and Indian Summer monsoons (ISM) during the AHP, especially their exact influence on regional climate relative to each other, is currently intensely debated. Here, I present a high-resolution multiproxy lake-level record spanning the AHP from the remote Suguta Valley in the northern Kenya Rift, located between the WAM and ISM domains. The presently desiccated valley was during the AHP filled by a 300 m deep and 2200 km2 large palaeo-lake due to an increase in precipitation of only 26%. The record explains the synchronous onset of large lakes in the East African Rift System (EARS) with the longitudinal shift of the Congo Air Boundary (CAB) over the East African and Ethiopian Plateaus, as the direct consequence of an enhanced atmospheric pressure gradient between East-Africa and India due to a precessional-forced northern hemisphere insolation maximum. Pronounced, and abrupt lake level fluctuations during the generally wet AHP are explained by small-scale solar irradiation changes weakening this pressure gradient atmospheric moisture availability preventing the CAB from reaching the study area. Instead, the termination of the AHP occurred, in a non-linear manner due to a change towards an equatorial insolation maximum ca. 6.5 ka ago extending the AHP over Ethiopia and West-Africa. 200 years - Lake Naivasha | The second part of the thesis focused on the analysis of a 200 year-old sediment core from Lake Naivasha in the Central Kenya Rift, one of the very few present freshwater lakes in East Africa. The results revealed and confirmed, that the appliance of proxy records for palaeo-climate reconstruction for the last 100 years within a time of increasing industrialisation and therefore human impact to the proxy-record containing sites are broadly limited. Since the middle of the 20th century, intense anthropogenic activity around Lake Naivasha has led to cultural eutrophication, which has overprinted the influence of natural climate variation to the lake usually inferred from proxy records such as diatoms, transfer-functions, geochemical and sedimentological analysis as used in this study. The results clarify the need for proxy records from remote unsettled areas to contribute with pristine data sets to current debates about anthropologic induced global warming since the past 100 years. 14 years - East African Rift | In order to avoid human influenced data sets and validate spatial and temporal heterogeneities of proxy-records from East Africa, the third part of the thesis therefore concentrated on the most recent past 14 years (1996-2010) detecting climate variability by using remotely sensed rainfall data. The advancement in the spatial coverage and temporal resolutions of rainfall data allow a better understanding of influencing climate mechanisms and help to better interpret proxy-records from the EARS in order to reconstruct past climate conditions. The study focuses on the dynamics of intraseasonal rainfall distribution within catchments of eleven lake basins in the EARS that are often used for palaeo-climate studies. We discovered that rainfall in adjacent basins exhibits high complexities in the magnitudes of intraseasonal variability, biennial to triennial precipitation patterns and even are not necessarily correlated often showing opposite trends. The variability among the watersheds is driven by the complex interaction of topography, in particular the shape, length and elevation of the catchment and its relative location to the East African Rift System and predominant influence of the ITCZ or CAB, whose locations and intensities are dependent on the strength of low pressure cells over India, SST variations in the Atlantic, Pacific or Indian Ocean, QBO phases and the 11-year solar cycle. Among all seasons we observed, January-September is the season of highest and most complex rainfall variability, especially for the East African Plateau basins, most likely due to the irregular penetration and sensitivity of the CAB.
The impact of global warming on human water resources is attracting increasing attention. No other region in this world is so strongly affected by changes in water supply than the tropics. Especially in Africa, the availability and access to water is more crucial to existence (basic livelihoods and economic growth) than anywhere else on Earth. In East Africa, rainfall is mainly influenced by the migration of the Inter-Tropical Convergence Zone (ITCZ) and by the El Niño Southern Oscillation (ENSO) with more rain and floods during El Niño and severe droughts during La Niña. The forecasting of East African rainfall in a warming world requires a better understanding of the response of ENSO-driven variability to mean climate. Unfortunately, existing meteorological data sets are too short or incomplete to establish a precise evaluation of future climate. From Lake Challa near Mount Kilimanjaro, we report records from a laminated lake sediment core spanning the last 25,000 years. Analyzing a monthly cleared sediment trap confirms the annual origin of the laminations and demonstrates that the varve-thicknesses are strongly linked to the duration and strength of the windy season. Given the modern control of seasonal ITCZ location on wind and rain in this region and the inverse relation between the two, thicker varves represent windier and thus drier years. El Niño (La Niña) events are associated with wetter (drier) conditions in east Africa and decreased (increased) surface wind speeds. Based on this fact, the thickness of the varves can be used as a tool to reconstruct a) annual rainfall b) wind season strength, and c) ENSO variability. Within this thesis, I found evidence for centennialscale changes in ENSO-related rainfall variability during the last three millennia, abrupt changes in variability during the Medieval Climate Anomaly and the Little Ice Age, and an overall reduction in East African rainfall and its variability during the Last Glacial period. Climate model simulations support forward extrapolation from these lake-sediment data, indicating that a future Indian Ocean warming will enhance East Africa’s hydrological cycle and its interannual variability in rainfall. Furthermore, I compared geochemical analyses from the sediment trap samples with a broad range of limnological, meteorological, and geological parameters to characterize the impact of sedimentation processes from the in-situ rocks to the deposited sediments. As a result an excellent calibration for existing μXRF data from Lake Challa over the entire 25,000 year long profile was provided. The climate development during the last 25,000 years as reconstructed from the Lake Challa sediments is in good agreement with other studies and highlights the complex interactions between long-term orbital forcing, atmosphere, ocean and land surface conditions. My findings help to understand how abrupt climate changes occur and how these changes correlate with climate changes elsewhere on Earth.
Salty taste has evolved to maintain electrolyte homeostasis, serving as a detector for salt containing food. In rodents, salty taste involves at least two transduction mechanisms. One is sensitive to the drug amiloride and specific for Na+, involving epithelial sodium channel (ENaC). A second rodent transduction pathway, which is triggered by various cations, is amiloride insensitive and not almost understood to date. Studies in primates showed amiloride-sensitive as well as amiloride-insensitive gustatory responses to NaCl, implying a role of both salt taste transduction pathways in humans. However, sensory studies in humans point to largely amiloride-insensitive sodium taste perception. An involvement of ENaC in human sodium taste perception was not shown, so far. In this study, ENaC subunit protein and mRNA could be localized to human taste bud cells (TBC). Thus, basolateral αβγ-ENaC ion channels are likely in TBC of circumvallate papillae, possibly mediating basolateral sodium entry. Similarly, basolateral βγ-ENaC might play a role in fungiform TBC. Strikingly, δ-ENaC subunit was confined to taste bud pores of both papillae, likely mediating gustatory sodium entry in TBC, either apical or paracellular via tight junctions. However, regional separation of δ-ENaC and βγ-ENaC in fungiform and circumvallate TBC indicate the presence of unknown interaction partner necessary to assemble into functional ion channels. However, screening of a macaque taste tissue cDNA library did neither reveal polypeptides assembling into a functional cation channel by interaction with δ-ENaC or βγ-ENaC nor ENaC independent salt taste receptor candidates. Thus, ENaC subunits are likely involved in human taste transduction, while exact composition and identity of an amiloride (in)sensitive salt taste receptors remain unclear. Localization of δ-ENaC in human taste pores strongly suggests a role in human taste transduction. In contrast, δ-ENaC is classified as pseudogene Scnn1d in mouse. However, no experimental detected sequences are annotated, while evidences for parts of Scnn1d derived mRNAs exist. In order to elucidate if Scnn1d is possibly involved in rodent salt taste perception, Scnn1d was evaluated in this study to clarify if Scnn1d is a gene or a transcribed pseudogene in mice. Comparative mapping of human SCNN1D to mouse chromosome 4 revealed complete Scnn1d sequence as well as its pseudogenization by Mus specific endogenous retroviruses. Moreover, tissue specific transcription of unitary Scnn1d pseudogene was found in mouse vallate papillae, kidney and testis and led to identification of nine Scnn1d transcripts. In vitro translation experiments showed that Scnn1d transcripts are coding competent for short polypeptides, possibly present in vivo. However, no sodium channel like function or sodium channel modulating activity was evident for Scnn1d transcripts and/or derived polypeptides. Thus, an involvement of mouse δ-ENaC in sodium taste transduction is unlikely and points to species specific differences in salt taste transduction mechanisms.
Bildverarbeitungsanwendungen stellen besondere Ansprüche an das ausführende Rechensystem. Einerseits ist eine hohe Rechenleistung erforderlich. Andererseits ist eine hohe Flexibilität von Vorteil, da die Entwicklung tendentiell ein experimenteller und interaktiver Prozess ist. Für neue Anwendungen tendieren Entwickler dazu, eine Rechenarchitektur zu wählen, die sie gut kennen, anstatt eine Architektur einzusetzen, die am besten zur Anwendung passt. Bildverarbeitungsalgorithmen sind inhärent parallel, doch herkömmliche bildverarbeitende eingebettete Systeme basieren meist auf sequentiell arbeitenden Prozessoren. Im Gegensatz zu dieser "Unstimmigkeit" können hocheffiziente Systeme aus einer gezielten Synergie aus Software- und Hardwarekomponenten aufgebaut werden. Die Konstruktion solcher System ist jedoch komplex und viele Lösungen, wie zum Beispiel grobgranulare Architekturen oder anwendungsspezifische Programmiersprachen, sind oft zu akademisch für einen Einsatz in der Wirtschaft. Die vorliegende Arbeit soll ein Beitrag dazu leisten, die Komplexität von Hardware-Software-Systemen zu reduzieren und damit die Entwicklung hochperformanter on-Chip-Systeme im Bereich Bildverarbeitung zu vereinfachen und wirtschaftlicher zu machen. Dabei wurde Wert darauf gelegt, den Aufwand für Einarbeitung, Entwicklung als auch Erweiterungen gering zu halten. Es wurde ein Entwurfsfluss konzipiert und umgesetzt, welcher es dem Softwareentwickler ermöglicht, Berechnungen durch Hardwarekomponenten zu beschleunigen und das zu Grunde liegende eingebettete System komplett zu prototypisieren. Hierbei werden komplexe Bildverarbeitungsanwendungen betrachtet, welche ein Betriebssystem erfordern, wie zum Beispiel verteilte Kamerasensornetzwerke. Die eingesetzte Software basiert auf Linux und der Bildverarbeitungsbibliothek OpenCV. Die Verteilung der Berechnungen auf Software- und Hardwarekomponenten und die daraus resultierende Ablaufplanung und Generierung der Rechenarchitektur erfolgt automatisch. Mittels einer auf der Antwortmengenprogrammierung basierten Entwurfsraumexploration ergeben sich Vorteile bei der Modellierung und Erweiterung. Die Systemsoftware wird mit OpenEmbedded/Bitbake synthetisiert und die erzeugten on-Chip-Architekturen auf FPGAs realisiert.
Die Wahrnehmung von Geschmacksempfindungen beruht auf dem Zusammenspiel verschiedener Sinneseindrücke wie Schmecken, Riechen und Tasten. Diese Komplexität der gustatorischen Wahrnehmung erschwert die Beantwortung der Frage wie Geschmacksinformationen vom Mund ins Gehirn weitergeleitet, prozessiert und kodiert werden. Die Analysen zur neuronalen Prozessierung von Geschmacksinformationen erfolgten zumeist mit Bitterstimuli am Mausmodell. Zwar ist bekannt, dass das Genom der Maus für 35 funktionelle Bitterrezeptoren kodiert, jedoch war nur für zwei unter ihnen ein Ligand ermittelt worden. Um eine bessere Grundlage für tierexperimentelle Arbeiten zu schaffen, wurden 16 der 35 Bitterrezeptoren der Maus heterolog in HEK293T-Zellen exprimiert und in Calcium-Imaging-Experimenten funktionell charakterisiert. Die Daten belegen, dass das Funktionsspektrum der Bitterrezeptoren der Maus im Vergleich zum Menschen enger ist und widerlegen damit die Aussage, dass humane und murine orthologe Rezeptoren durch das gleiche Ligandenspektrum angesprochen werden. Die Interpretation von tierexperimentellen Daten und die Übertragbarkeit auf den Menschen werden folglich nicht nur durch die Komplexität des Geschmacks, sondern auch durch Speziesunterschiede verkompliziert. Die Komplexität des Geschmacks beruht u. a. auf der Tatsache, dass Geschmacksstoffe selten isoliert auftreten und daher eine Vielzahl an Informationen kodiert werden muss. Um solche geschmacksstoffassoziierten Stimuli in der Analyse der gustatorischen Kommunikationsbahnen auszuschließen, sollten Opsine, die durch Licht spezifischer Wellenlänge angeregt werden können, für die selektive Ersetzung von Geschmacksrezeptoren genutzt werden. Um die Funktionalität dieser angestrebten Knockout-Knockin-Modelle zu evaluieren, die eine Kopplung von Opsinen mit dem geschmacksspezifischen G-Protein Gustducin voraussetzte, wurden Oozyten vom Krallenfrosch Xenopus laevis mit dem Zwei-Elektroden-Spannungsklemm-Verfahren hinsichtlich dieser Interaktion analysiert. Der positiven Bewertung dieser Kopplung folgte die Erzeugung von drei Mauslinien, die in der kodierenden Region eines spezifischen Geschmacksrezeptors (Tas1r1, Tas1r2, Tas2r114) Photorezeptoren exprimierten. Durch RT-PCR-, In-situ-Hybridisierungs- und immunhistochemische Experimente konnte der erfolgreiche Knockout der Rezeptorgene und der Knockin der Opsine belegt werden. Der Nachweis der Funktionalität der Opsine im gustatorischen System wird Gegenstand zukünftiger Analysen sein. Bei erfolgreichem Beleg der Lichtempfindlichkeit von Geschmacksrezeptorzellen dieser Mausmodelle wäre ein System geschaffen, dass es ermöglichen würde, gustatorische neuronale Netzwerke und Hirnareale zu identifizieren, die auf einen reinen geschmacks- und qualitätsspezifischen Stimulus zurückzuführen wären.
Public debate about energy relations between the EU and Russia is distorted. These distortions present considerable obstacles to the development of true partnership. At the core of the conflict is a struggle for resource rents between energy producing, energy consuming and transit countries. Supposed secondary aspects, however, are also of great importance. They comprise of geopolitics, market access, economic development and state sovereignty. The European Union, having engaged in energy market liberalisation, faces a widening gap between declining domestic resources and continuously growing energy demand. Diverse interests inside the EU prevent the definition of a coherent and respected energy policy. Russia, for its part, is no longer willing to subsidise its neighbouring economies by cheap energy exports. The Russian government engages in assertive policies pursuing Russian interests. In so far, it opts for a different globalisation approach, refusing the role of mere energy exporter. In view of the intensifying struggle for global resources, Russia, with its large energy potential, appears to be a very favourable option for European energy supplies, if not the best one. However, several outcomes of the strategic game between the two partners can be imagined. Engaging in non-cooperative strategies will in the end leave all stakeholders worse-off. The European Union should therefore concentrate on securing its partnership with Russia instead of damaging it. Stable cooperation would need the acceptance that the partner may pursue his own goals, which might be different from one’s own interests. The question is, how can a sustainable compromise be found? This thesis finds that a mix of continued dialogue, a tit for tat approach bolstered by an international institutional framework and increased integration efforts appears as a preferable solution.
Mathematical modeling of biological phenomena has experienced increasing interest since new high-throughput technologies give access to growing amounts of molecular data. These modeling approaches are especially able to test hypotheses which are not yet experimentally accessible or guide an experimental setup. One particular attempt investigates the evolutionary dynamics responsible for today's composition of organisms. Computer simulations either propose an evolutionary mechanism and thus reproduce a recent finding or rebuild an evolutionary process in order to learn about its mechanism. The quest for evolutionary fingerprints in metabolic and gene-coexpression networks is the central topic of this cumulative thesis based on four published articles. An understanding of the actual origin of life will probably remain an insoluble problem. However, one can argue that after a first simple metabolism has evolved, the further evolution of metabolism occurred in parallel with the evolution of the sequences of the catalyzing enzymes. Indications of such a coevolution can be found when correlating the change in sequence between two enzymes with their distance on the metabolic network which is obtained from the KEGG database. We observe that there exists a small but significant correlation primarily on nearest neighbors. This indicates that enzymes catalyzing subsequent reactions tend to be descended from the same precursor. Since this correlation is relatively small one can at least assume that, if new enzymes are no "genetic children" of the previous enzymes, they certainly be descended from any of the already existing ones. Following this hypothesis, we introduce a model of enzyme-pathway coevolution. By iteratively adding enzymes, this model explores the metabolic network in a manner similar to diffusion. With implementation of an Gillespie-like algorithm we are able to introduce a tunable parameter that controls the weight of sequence similarity when choosing a new enzyme. Furthermore, this method also defines a time difference between successive evolutionary innovations in terms of a new enzyme. Overall, these simulations generate putative time-courses of the evolutionary walk on the metabolic network. By a time-series analysis, we find that the acquisition of new enzymes appears in bursts which are pronounced when the influence of the sequence similarity is higher. This behavior strongly resembles punctuated equilibrium which denotes the observation that new species tend to appear in bursts as well rather than in a gradual manner. Thus, our model helps to establish a better understanding of punctuated equilibrium giving a potential description at molecular level. From the time-courses we also extract a tentative order of new enzymes, metabolites, and even organisms. The consistence of this order with previous findings provides evidence for the validity of our approach. While the sequence of a gene is actually subject to mutations, its expression profile might also indirectly change through the evolutionary events in the cellular interplay. Gene coexpression data is simply accessible by microarray experiments and commonly illustrated using coexpression networks where genes are nodes and get linked once they show a significant coexpression. Since the large number of genes makes an illustration of the entire coexpression network difficult, clustering helps to show the network on a metalevel. Various clustering techniques already exist. However, we introduce a novel one which maintains control of the cluster sizes and thus assures proper visual inspection. An application of the method on Arabidopsis thaliana reveals that genes causing a severe phenotype often show a functional uniqueness in their network vicinity. This leads to 20 genes of so far unknown phenotype which are however suggested to be essential for plant growth. Of these, six indeed provoke such a severe phenotype, shown by mutant analysis. By an inspection of the degree distribution of the A.thaliana coexpression network, we identified two characteristics. The distribution deviates from the frequently observed power-law by a sharp truncation which follows after an over-representation of highly connected nodes. For a better understanding, we developed an evolutionary model which mimics the growth of a coexpression network by gene duplication which underlies a strong selection criterion, and slight mutational changes in the expression profile. Despite the simplicity of our assumption, we can reproduce the observed properties in A.thaliana as well as in E.coli and S.cerevisiae. The over-representation of high-degree nodes could be identified with mutually well connected genes of similar functional families: zinc fingers (PF00096), flagella, and ribosomes respectively. In conclusion, these four manuscripts demonstrate the usefulness of mathematical models and statistical tools as a source of new biological insight. While the clustering approach of gene coexpression data leads to the phenotypic characterization of so far unknown genes and thus supports genome annotation, our model approaches offer explanations for observed properties of the coexpression network and furthermore substantiate punctuated equilibrium as an evolutionary process by a deeper understanding of an underlying molecular mechanism.
Die Progressive Supranukleäre Blickparese (PSP) ist eine sporadisch auftretende neurodegenerative Erkrankung im Rahmen der atypischen Parkinson-Syndrome (APS), die im frühen Verlauf häufig mit dem Idiopathischen Parkinson-Syndrom (IPS) verwechselt wird. Dabei ist die Dysarthrie als eine erworbene, zentral bedingte sprechmotorische Störung ein häufiges und früh auftretendes Symptom bei PSP. Bislang spricht man von einer eher unspezifischen „gemischten“ Dysarthrie aus hypokinetischen, spastischen und auch ataktischen Komponenten. Im Rahmen einer explorativen Querschnittsstudie am „Fachkrankenhaus für Bewegungsstörungen und Parkinson“ Beelitz-Heilstätten in Kooperation mit der „Entwicklungsgruppe Klinische Neuropsychologie“ München (EKN) sowie der „Interdisziplinären Ambulanz für Bewegungsstörungen“ am Klinikum München-Großhadern wurden 50 Patienten dahingehend untersucht, ob sich für die Progressive Supranukleäre Blickparese (PSP) eine spezielle, frühzeitig zu diagnostizierende und differentialdiagnostisch relevante Dysarthrie beschreiben ließe. In diesem Zusammenhang soll geklärt werden, ob es sich um phänotypische Ausprägungen im Rahmen eines Störungsspektrums handelt oder ob sich differenzierbare Subtypen der Krankheit, insbesondere ein „klassischer“ PSP-Typ (PSP-RS) und ein „atypischer“ PSP-Typ (PSP-P), auch im Bereich der Dysarthrie zeigen. Im Rahmen der Untersuchungen wurde der Schweregrad der Erkrankung mittels der „PSP-sensitiven Ratingskala (PSPRS)“ gemessen. Die Dysarthriediagnostik erfolgte anhand der „Bogenhausener Dysarthrieskalen (BoDyS)“ zur Beschreibung der Art und Ausprägung der Dysarthrie bei PSP. Die Verständlichkeit wurde mithilfe des „Münchner Verständlichkeits-Profils (MVP)" sowie eines weiteren Transkriptionsverfahrens ermittelt, wobei Ausschnitte aus den Tests zum Lesen und Nachsprechen der BoDyS zugrunde lagen. Weiterhin erfolgte eine Einschätzung der Natürlichkeit des Sprechens. Die Ergebnisse hinsichtlich des Einflusses von Natürlichkeit und Verständlichkeit des Sprechens auf den Schweregrad der Dysarthrie zeigten, dass dieser modalitätenübergreifend mit beiden Schweregradaspekten korreliert, wenngleich es offenbar die Natürlichkeit des Sprechens ist, die bei PSP bereits frühzeitig beeinträchtigt ist und somit als das entscheidende differentialdiagnostische Kriterium zur Differenzierung zwischen beiden PSP-Subtypen zu beurteilen ist, möglicherweise auch gegenüber anderen Parkinson-Syndromen. Anhand statistisch valider Ergebnisse konnten spezifische Störungsmerkmale der Dysarthrie extrahiert werden, die eine signifikante Trennung von PSP-RS und PSP-P ermöglichen: eine leise und behaucht-heisere Stimme sowie ein verlangsamtes Sprechtempo und Hypernasalität. Damit können für die hier fokussierten Subtypen der PSP zwei unterschiedliche Dysarthrietypen postuliert werden. Danach wird dem Subtyp PSP-RS eine spastisch betonte Dysarthrie mit ausgeprägter Verlangsamung des Sprechtempos zugeordnet, dem Subtyp PSP-P hingegen eine hypokinetische Dysarthrie mit behaucht-heiserer Hypophonie. Desweiteren konnte ein „Dysarthrie-Schwellenwert“ als Zusatzkriterium für eine zeitliche Differenzierung beider PSP-Subtypen ermittelt werden. Anhand der Daten zeigte sich die Dysarthrie bei dem Subtyp PSP-RS gleich zu Beginn der Erkrankung, jedoch spätestens 24 Monate danach. Hingegen konnte die Dysarthrie beim Subtyp PSP-P frühestens 24 Monate nach Erkrankungsbeginn festgestellt werden. Die Daten dieser Studie verdeutlichen, dass der Frage nach einer subtypenspezifischen Ausprägung der Dysarthrie bei PSP eine Längsschnittsstudie folgen sollte, um die ermittelten Ergebnisse zu konsolidieren.
In this thesis chemical reactions under hydrothermal conditions were explored, whereby emphasis was put on green chemistry. Water at high temperature and pressure acts as a benign solvent. Motivation to work under hydrothermal conditions was well-founded in the tunability of physicochemical properties with temperature, e.g. of dielectric constant, density or ion product, which often resulted in surprising reactivity. Another cornerstone was the implementation of the principles of green chemistry. Besides the use of water as solvent, this included the employment of a sustainable feedstock and the sensible use of resources by minimizing waste and harmful intermediates and additives. To evaluate the feasibility of hydrothermal conditions for chemical synthesis, exemplary reactions were performed. These were carried out in a continuous flow reactor, allowing for precise control of reaction conditions and kinetics measurements. In most experiments a temperature of 200 °C in combination with a pressure of 100 bar was chosen. In some cases the temperature was even raised to 300 °C. Water in this subcritical range can also be found in nature at hydrothermal vents on the ocean floor. On the primitive earth, environments with such conditions were however present in larger numbers. Therefore we tested whether biologically important carbohydrates could be formed at high temperature from the simple, probably prebiotic precursor formaldehyde. Indeed, this formose reaction could be carried out successfully, although the yield was lower compared to the counterpart reaction under ambient conditions. However, striking differences regarding selectivity and necessary catalysts were observed. At moderate temperatures bases and catalytically active cations like Ca2+ are necessary and the main products are hexoses and pentoses, which accumulate due to their higher stability. In contrast, in high-temperature water no catalyst was necessary but a slightly alkaline solution was sufficient. Hexoses were only formed in negligible amounts, whereas pentoses and the shorter carbohydrates accounted for the major fraction. Amongst the pentoses there was some preference for the formation of ribose. Even deoxy sugars could be detected in traces. The observation that catalysts can be avoided was successfully transferred to another reaction. In a green chemistry approach platform chemicals must be produced from sustainable resources. Carbohydrates can for instance be employed as a basis. They can be transformed to levulinic acid and formic acid, which can both react via a transfer hydrogenation to the green solvent and biofuel gamma-valerolactone. This second reaction usually requires catalysis by Ru or Pd, which are neither sustainable nor low-priced. Under hydrothermal conditions these heavy metals could be avoided and replaced by cheap salts, taking advantage of the temperature dependence of the acid dissociation constant. Simple sulfate was recognized as a temperature switchable base. With this additive high yield could be achieved by simultaneous prevention of waste. In contrast to conventional bases, which create salt upon neutralization, a temperature switchable base becomes neutral again when cooled down and thus can be reused. This adds another sustainable feature to the high atom economy of the presented hydrothermal synthesis. In a last study complex decomposition pathways of biomass were investigated. Gas chromatography in conjunction with mass spectroscopy has proven to be a powerful tool for the identification of unknowns. It was observed that several acids were formed when carbohydrates were treated with bases at high temperature. This procedure was also applied to digest wood. Afterwards it was possible to fermentate the solution and a good yield of methane was obtained. This has to be regarded in the light of the fact that wood practically cannot be used as a feedstock in a biogas factory. Thus the hydrothermal pretreatment is an efficient means to employ such materials as well. Also the reaction network of the hydrothermal decomposition of glycine was investigated using isotope-labeled compounds as comparison for the unambiguous identification of unknowns. This refined analysis allowed the identification of several new molecules and pathways, not yet described in literature. In summary several advantages could be taken from synthesis in high-temperature water. Many catalysts, absolutely necessary under ambient conditions, could either be completely avoided or replaced by cheap, sustainable alternatives. In this respect water is not only a green solvent, but helps to prevent waste and preserves resources.
Regulation of gene transcription plays a major role in mediating cellular responses and physiological behavior in all known organisms. The finding that similar genes are often regulated in a similar manner (co-regulated or "co-expressed") has directed several "guilt-by-association" approaches in order to reverse-engineer the cellular transcriptional networks using gene expression data as a compass. This kind of studies has been considerably assisted in the recent years by the development of high-throughput transcript measurement platforms, specifically gene microarrays and next-generation sequencing. In this thesis, I describe several approaches for improving the extraction and interpretation of the information contained in microarray based gene expression data, through four steps: (1) microarray platform design, (2) microarray data normalization, (3) gene network reverse engineering based on expression data and (4) experimental validation of expression-based guilt-by-association inferences. In the first part test case is shown aimed at the generation of a microarray for Thellungiella salsuginea, a salt and drought resistant close relative to the model plant Arabidopsis thaliana; the transcripts of this organism are generated on the combination of publicly available ESTs and newly generated ad-hoc next-generation sequencing data. Since the design of a microarray platform requires the availability of highly reliable and non-redundant transcript models, these issues are addressed consecutively, proposing several different technical solutions. In the second part I describe how inter-array correlation artifacts are generated by the common microarray normalization methods RMA and GCRMA, together with the technical and mathematical characteristics underlying the problem. A solution is proposed in the form of a novel normalization method, called tRMA. The third part of the thesis deals with the field of expression-based gene network reverse engineering. It is shown how different centrality measures in reverse engineered gene networks can be used to distinguish specific classes of genes, in particular essential genes in Arabidopsis thaliana, and how the use of conditional correlation can add a layer of understanding over the information flow processes underlying transcript regulation. Furthermore, several network reverse engineering approaches are compared, with a particular focus on the LASSO, a linear regression derivative rarely applied before in global gene network reconstruction, despite its theoretical advantages in robustness and interpretability over more standard methods. The performance of LASSO is assessed through several in silico analyses dealing with the reliability of the inferred gene networks. In the final part, LASSO and other reverse engineering methods are used to experimentally identify novel genes involved in two independent scenarios: the seed coat mucilage pathway in Arabidopsis thaliana and the hypoxic tuber development in Solanum tuberosum. In both cases an interesting method complementarity is shown, which strongly suggests a general use of hybrid approaches for transcript expression-based inferences. In conclusion, this work has helped to improve our understanding of gene transcription regulation through a better interpretation of high-throughput expression data. Part of the network reverse engineering methods described in this thesis have been included in a tool (CorTo) for gene network reverse engineering and annotated visualization from custom transcription datasets.
Um Extremereignisse in der Dynamik des indischen Sommermonsuns (ISM) in der geologischen Vergangenheit zu identifizieren, schlage ich einen neuartigen Ansatz basierend auf der Quantifikation von Fluktuationen in einem nichtlinearen Ähnlichkeitsmaß vor. Dieser reagiert empfindlich auf Zeitabschnitte mit deutlichen Veränderungen in der dynamischen Komplexität kurzer Zeitreihen. Ein mathematischer Zusammenhang zwischen dem neuen Maß und dynamischen Invarianten des zugrundeliegenden Systems wie fraktalen Dimensionen und Lyapunovexponenten wird analytisch hergeleitet. Weiterhin entwickle ich einen statistischen Test zur Schätzung der Signifikanz der so identifizierten dynamischen Übergänge. Die Stärken der Methode werden durch die Aufdeckung von Bifurkationsstrukturen in paradigmatischen Modellsystemen nachgewiesen, wobei im Vergleich zu den traditionellen Lyapunovexponenten eine Identifikation komplexerer dynamischer Übergänge möglich ist. Wir wenden die neu entwickelte Methode zur Analyse realer Messdaten an, um ausgeprägte dynamische Veränderungen auf Zeitskalen von Jahrtausenden in Klimaproxydaten des südasiatischen Sommermonsunsystems während des Pleistozäns aufzuspüren. Dabei zeigt sich, dass viele dieser Übergänge durch den externen Einfluss der veränderlichen Sonneneinstrahlung, sowie durch dem Klimasystem interne Einflussfaktoren auf das Monsunsystem (Eiszeitzyklen der nördlichen Hemisphäre und Einsatz der tropischenWalkerzirkulation) induziert werden. Trotz seiner Anwendbarkeit auf allgemeine Zeitreihen ist der diskutierte Ansatz besonders zur Untersuchung von kurzen Paläoklimazeitreihen geeignet. Die während des ISM über dem indischen Subkontinent fallenden Niederschläge treten, bedingt durch die zugrundeliegende Dynamik der atmosphärischen Zirkulation und topographische Einflüsse, in äußerst komplexen, raumzeitlichen Mustern auf. Ich stelle eine detaillierte Analyse der Sommermonsunniederschläge über der indischen Halbinsel vor, die auf Ereignissynchronisation (ES) beruht, einem Maß für die nichtlineare Korrelation von Punktprozessen wie Niederschlagsereignissen. Mit hierarchischen Clusteringalgorithmen identifiziere ich zunächst Regionen mit besonders kohärenten oder homogenen Monsunniederschlägen. Dabei können auch die Zeitverzögerungsmuster von Regenereignissen rekonstruiert werden. Darüber hinaus führe ich weitere Analysen auf Basis der Theorie komplexer Netzwerke durch. Diese Studien ermöglichen wertvolle Einsichten in räumliche Organisation, Skalen und Strukturen von starken Niederschlagsereignissen oberhalb der 90% und 94% Perzentilen während des ISM (Juni bis September). Weiterhin untersuche ich den Einfluss von verschiedenen, kritischen synoptischen Systemen der Atmosphäre sowie der steilen Topographie des Himalayas auf diese Niederschlagsmuster. Die vorgestellte Methode ist nicht nur geeignet, die Struktur extremer Niederschlagsereignisse zu visualisieren, sondern kann darüber hinaus über der Region atmosphärische Transportwege von Wasserdampf und Feuchtigkeitssenken auf dekadischen Skalen identifizieren.Weiterhin wird ein einfaches, auf komplexen Netzwerken basierendes Verfahren zur Entschlüsselung der räumlichen Feinstruktur und Zeitentwicklung von Monsunniederschlagsextremen während der vergangenen 60 Jahre vorgestellt.
During reading oculomotor processes guide the eyes over the text. The visual information recorded is accessed, evaluated and processed. Only by retrieving the meaning of a word from the long-term memory, as well as through the connection and storage of the information about each individual word, is it possible to access the semantic meaning of a sentence. Therefore memory, and here in particular working memory, plays a pivotal role in the basic processes of reading. The following dissertation investigates to what extent different demands on memory and memory capacity have an effect on eye movement behavior while reading. The frequently used paradigm of the reading span task, in which test subjects read and evaluate individual sentences, was used for the experimental review of the research questions. The results speak for the fact that working memory processes have a direct effect on various eye movement measurements. Thus a high working memory load, for example, reduced the perceptual span while reading. The lower the individual working memory capacity of the reader was, the stronger was the influence of the working memory load on the processing of the sentence.
This work addresses issues in the automatic preprocessing of historical German input text for use by conventional natural language processing techniques. Conventional techniques cannot adequately account for historical input text due to conventional tools' reliance on a fixed application-specific lexicon keyed by contemporary orthographic surface form on the one hand, and the lack of consistent orthographic conventions in historical input text on the other. Historical spelling variation is treated here as an error-correction problem or "canonicalization" task: an attempt to automatically assign each (historical) input word a unique extant canonical cognate, thus allowing direct application-specific processing (tagging, parsing, etc.) of the returned canonical forms without need for any additional application-specific modifications. In the course of the work, various methods for automatic canonicalization are investigated and empirically evaluated, including conflation by phonetic identity, conflation by lemma instantiation heuristics, canonicalization by weighted finite-state rewrite cascade, and token-wise disambiguation by a dynamic Hidden Markov Model.
Human-induced alterations of the environment are causing biotic changes worldwide, including the extinction of species and a mixing of once disparate floras and faunas. One type of biological communities that is expected to be particularly affected by environmental alterations are herb layer plant communities of fragmented forests such as those in the west European lowlands. However, our knowledge about current changes in species diversity and composition in these communities is limited due to a lack of adequate long-term studies. In this thesis, I resurveyed the herb layer communities of ancient forest patches in the Weser-Elbe region (NW Germany) after two decades using 175 semi-permanent plots. The general objectives were (i) to quantify changes in plant species diversity considering also between-community (β) and functional diversity, (ii) to determine shifts in species composition in terms of species’ niche breadth and functional traits and (iii) to find indications on the most likely environmental drivers for the observed changes. These objectives were pursued with four independent research papers (Chapters 1-4) whose results were brought together in a General Discussion. Alpha diversity (species richness) increased by almost four species on average, whereas β diversity tended to decrease (Chapter 1). The latter is interpreted as a beginning floristic homogenization. The observed changes were primarily the result of a spread of native habitat generalists that are able to tolerate broad pH and moisture ranges. The changes in α and β diversity were only significant when species abundances were neglected (Chapters 1 and 2), demonstrating that the diversity changes resulted mainly from gains and losses of low-abundance species. This study is one of the first studies in temperate Europe that demonstrates floristic homogenization of forest plant communities at a larger than local scale. The diversity changes found at the taxonomic level did not result in similar changes at the functional level (Chapter 2). The likely reason is that these communities are functionally “buffered”. Single communities involve most of the functional diversity of the regional pool, i.e., they are already functionally rich, while they are functionally redundant among each other, i.e., they are already homogeneous. Independent of taxonomic homogenization, the abundance of 30 species decreased significantly (Chapter 4). These species included 12 ancient forest species (i.e., species closely tied to forest patches with a habitat continuity > 200 years) and seven species listed on the Red List of endangered plant species in NW Germany. If these decreases continue over the next decades, local extinctions may result. This biotic impoverishment would seriously conflict with regional conservation goals. Community assembly mechanisms changed at the local level particularly at sites that experienced disturbance by forest management activities between the sampling periods (Chapter 3). Disturbance altered community assembly mechanisms in two ways: (i) it relaxed environmental filters and allowed the coexistence of different reproduction strategies, as reflected by a higher diversity of reproductive traits at the time of the resurvey, and (ii) it enhanced light availability and tightened competitive filters. These limited the functional diversity with respect to canopy height and selected for taller species. Thirty-one winner and 30 loser species, which had significantly increased or decreased in abundance, respectively, were characterized by various functional traits and ecological performances to find indications on the most likely environmental drivers for the observed floristic changes (Chapter 4). Winner species had higher seed longevity, flowered later in the season and had more often an oceanic distribution compared to loser species. Loser species tended to have a higher specific leaf area, to be more susceptible to deer browsing and to have a performance optimum at higher soil pH values compared to winner species. Multiple logistic regression analyses indicated that disturbances due to forest management interventions were the primary cause of the species shifts. As one of the first European resurvey studies, this study provides indications that an enhanced browsing pressure due to increased deer densities and increasingly warmer winters are important drivers. The study failed to demonstrate that eutrophication and acidification due to atmospheric deposition substantially drive herb layer changes. The restriction of the sample to the most base-rich sites in the region is discussed as a likely reason. Furthermore, the decline of several ancient forest species is discussed as an indication that the forest patches are still paying off their “extinction debt”, i.e., exhibit a delayed response to forest fragmentation.
Aggregation of the Amyloid β (Aβ) peptide to amyloid fibrils is associated with the outbreak of Alzheimer’s disease. Early aggregation intermediates in form of soluble oligomers are of special interest as they are believed to be the major toxic components in the process. These oligomers are of disordered and transient nature. Therefore, their detailed molecular structure is difficult to access experimentally and often remains unknown. In the present work extensive, fully atomistic replica exchange molecular dynamics simulations were performed to study the preaggregated, monomer states and early aggregation intermediates (dimers, trimers) of Aβ(25-35) and Aβ(10-35)-NH2 in aqueous solution. The folding and aggregation of Aβ(25-35) were studied at neutral pH and 293 K. Aβ(25-35) monomers mainly adopt β-hairpin conformations characterized by a β-turn formed by residues G29 and A30, and a β-sheet between residues N27–K28 and I31–I32 in equilibrium with coiled conformations. The β-hairpin conformations served as initial configurations to model spontaneous aggregation of Aβ(25-35). As expected, within the Aβ(25-35) dimer and trimer ensembles many different poorly populated conformations appear. Nevertheless, we were able to distinguish between disordered and fibril-like oligomers. Whereas disordered oligomers are rather compact with few intermolecular hydrogen bonds (HBs), fibril-like oligomers are characterized by the formation of large intermolecular β-sheets. In most of the fibril-like dimers and trimers individual peptides are fully extended forming in- or out-of-register antiparallel β-sheets. A small amount of fibril-like trimers contained V-shaped peptides forming parallel β-sheets. The dimensions of extended and V-shaped oligomers correspond well to the diameters of two distinct morphologies found for Aβ(25-35) fibrils. The transition from disordered to fibril-like Aβ(25-35) dimers is unfavorable but driven by energy. The lower energy of fibril-like dimers arises from favorable intermolecular HBs and other electrostatic interactions which compete with a loss in entropy. Approximately 25 % of the entropic cost correspond to configurational entropy. The rest relates to solvent entropy, presumably caused by hydrophobic and electrostatic effects. In contrast to the transition towards fibril-like dimers the first step of aggregation is driven by entropy. Here, we compared structural and thermodynamic properties of the individual monomer, dimer and trimer ensembles to gain qualitative information about the aggregation process. The β-hairpin conformation observed for monomers is successively dissolved in dimer and trimer ensembles while instead intermolecular β-sheets are formed. As expected upon aggregation the configurational entropy decreases. Additionally, the solvent accessible surface area (SASA), especially the hydrophobic SASA, decreases yielding a favorable solvation free energy which overcompensates the loss in configurational entropy. In summary, the hydrophobic effect, possibly combined with electrostatic effects, yields an increase in solvent entropy which is believed to be one major driving force towards aggregation. Spontaneous folding of the Aβ(10-35)-NH2 monomer was modeled using two force fields, GROMOS96 43a1 and OPLS/AA, and compared to primary NMR data collected at pH 5.6 and 283 K taken from the literature. Unexpectedly, the two force fields yielded significantly different main conformations. Comparison between experimental and calculated nuclear Overhauser effect (NOE) distances is not sufficient to distinguish between the different force fields. Additionally, the comparison with scalar coupling constants suggest that the chosen protonation in both simulations corresponds to a pH lower than in the experiment. Based on this analysis we were unable to determine which force field yields a better description of this system. Dimerization of Aβ(10-35)-NH2 was studied at neutral pH and 300 K. Dimer conformations arrange in many distinct, poorly populated and rather complex alignments or interlocking patterns which are rather stabilized by side chain interactions than by specific intermolecular hydrogen bonds. Similar to Aβ(25-35) dimers, transition towards β-sheet-rich, fibril-like Aβ(10-35) dimers is driven by energy competing with a loss in entropy. Here, transition is mediated by favorable peptide-solvent and solvent-solvent interactions mainly arising from electrostatic interactions.
Functional analyses of microtubule and centrosome-associated proteins in Dictyostelium discoideum
(2011)
Understanding the role of microtubule-associated proteins is the key to understand the complex mechanisms regulating microtubule dynamics. This study employs the model system Dictyostelium discoideum to elucidate the role of the microtubule-associated protein TACC (Transforming acidic coiled-coil) in promoting microtubule growth and stability. Dictyostelium TACC was localized at the centrosome throughout the entire cell cycle. The protein was also detected at microtubule plus ends, however, unexpectedly only during interphase but not during mitosis. The same cell cycle-dependent localization pattern was observed for CP224, the Dictyostelium XMAP215 homologue. These ubiquitous MAPs have been found to interact with TACC proteins directly and are known to act as microtubule polymerases and nucleators. This work shows for the first time in vivo that both a TACC and XMAP215 family protein can differentially localize to microtubule plus ends during interphase and mitosis. RNAi knockdown mutants revealed that TACC promotes microtubule growth during interphase and is essential for proper formation of astral microtubules in mitosis. In many organisms, impaired microtubule stability upon TACC depletion was explained by the failure to efficiently recruit the TACC-binding XMAP215 protein to centrosomes or spindle poles. By contrast, fluorescence recovery after photobleaching (FRAP) analyses conducted in this study demonstrate that in Dictyostelium recruitment of CP224 to centrosomes or spindle poles is not perturbed in the absence of TACC. Instead, CP224 could no longer be detected at the tips of microtubules in TACC mutant cells. This finding demonstrates for the first time in vivo that a TACC protein is essential for the association of an XMAP215 protein with microtubule plus ends. The GFP-TACC strains generated in this work also turned out to be a valuable tool to study the unusual microtubule dynamics in Dictyostelium. Here, microtubules exhibit a high degree of lateral bending movements but, in contrast most other organisms, they do not obviously undergo any growth or shrinkage events during interphase. Despite of that they are affected by microtubuledepolymerizing drugs such as thiabendazole or nocodazol which are thought to act solely on dynamic microtubules. Employing 5D-fluorescence live cell microscopy and FRAP analyses this study suggests Dictyostelium microtubules to be dynamic only in the periphery, while they are stable at the centrosome. In the recent years, the identification of yet unknown components of the Dictyostelium centrosome has made tremendous progress. A proteomic approach previously conducted by our group disclosed several uncharacterized candidate proteins, which remained to be verified as genuine centrosomal components. The second part of this study focuses on the investigation of three such candidate proteins, Cenp68, CP103 and the putative spindle assembly checkpoint protein Mad1. While a GFP-CP103 fusion protein could clearly be localized to isolated centrosomes that are free of microtubules, Cenp68 and Mad1 were found to associate with the centromeres and kinetochores, respectively. The investigation of Cenp68 included the generation of a polyclonal anti-Cenp68 antibody, the screening for interacting proteins and the generation of knockout mutants which, however, did not display any obvious phenotype. Yet, Cenp68 has turned out as a very useful marker to study centromere dynamics during the entire cell cycle. During mitosis, GFP-Mad1 localization strongly resembled the behavior of other Mad1 proteins, suggesting the existence of a yet uncharacterized spindle assembly checkpoint in Dictyostelium.
Im Rahmen eines explorativen Vergleichsuntersuchungsplans wurde untersucht, inwieweit sich die durch biologische Faktoren bedingte unterschiedliche Lebenserfahrung sowie die Sozialisationsbedingungen in der psychosexuellen Entwicklung bei hetero-, homo- und postoperativen transsexuellen Männern (N = 191) auf die Integration der Geschlechterstereotypen in die kognitiven (Selbst-, Fremdwahrnehmung), emotionalen (Selbst- und Fremdbewertung) und verhaltensmäßigen Aspekte (Normen der geschlechtsspezifischen Verhaltens) der Geschlechtsidentität auswirken und ob sich Identifikationsmuster der Entwicklung des geschlechtlichen Selbstkonzepts ableiten lassen. Die Messung der kognitiven Aspekte des geschlechtlichen Selbstkonzepts (Maskulinität und Femininität) erfolgte mittels der GERO-Skala von Brengelmann und Hendrich (1990). Zur Erfassung der emotionalen Aspekte und Identifikationsmuster der Entwicklung des geschlechtlichen Selbstkonzepts wurden die Werte für die Variablen Maskulinität und Femininität zuerst mittels der computergesteuerten Methodik IDEXMONO und IDEXIDIO, die auf der Identitätsstrukturanalyse (Identity Structure Analysis) von Weinreich (2003) basiert, aufgearbeitet und weiter interferenzstatistisch ausgewertet. Weiterhin wurden der Fragebogen zur Messung normativer Geschlechtsrollenorientierung (NGRO) von Athenstaedt (2000) sowie ein ad hoc entworfener demographischer Fragebogen eingesetzt. Die Ergebnisse zeigen, dass der Verlauf der psychosexuellen Entwicklung einen starken Einfluss auf die Integration der Geschlechterstereotypen in die geschlechtliche Selbst- und Fremdwahrnehmung hat. Im kognitiven Bereich, bezogen auf die persönliche Identität (Grad der Selbstzuschreibung männlicher und weiblicher Merkmale), stellt die Maskulinität eine stabile und erstrebenswerte Variable zur Herausbildung des geschlechtlichen Selbstkonzepts bei allen Gruppen dar. Die Femininität trägt am meisten zur Differenzierung zwischen den Hetero-, Homo- und Transsexuellen bei. Sie wird, je nach der Entwicklungsphase, unterschiedlich in das geschlechtliche Selbstkonzept integriert. Hinsichtlich der sozialen Identität (Zugehörigkeitsgefühl) lassen sich die Gruppen bezüglich der wahrgenommenen Ähnlichkeiten sowohl mit männlichen als auch weiblichen Personen, je nach der Entwicklungsphase, unterscheiden. Die soziale Wahrnehmung von Männern und Frauen (Fremdwahrnehmung), ist bei Transsexuellen traditioneller als die der Hetero- und Homosexuellen. Bei der Selbst- und Fremdbewertung ergaben sich keine signifikanten Unterschiede. Bei der Internalisierung der sozialen Normen des geschlechtsspezifischen Verhaltens zeigt sich, dass Heterosexuelle der Ausübung der Geschlechterrollen gegenüber egalitärer eingestellt sind als Trans- und Homosexuelle. Bei den Sozialisationsfaktoren ist hervorzuheben, dass generell weibliche Identifikationspersonen einen stärkeren Einfluss auf die Herausbildung des geschlechtlichen Selbstkonzeptes hatten als männliche Identifikationspersonen. Es scheint jedoch, dass Homosexuelle bei der Entwicklung ihres geschlechtlichen Selbstkonzepts stärker unter dem Einfluss der Frauen stehen als die anderen zwei erforschten Gruppen. Zur Beantwortung der Frage, welche selbstkonzeptbezogenen Variablen und Entwicklungsfaktoren die größte statistische Bedeutung für die Trennung und Prädiktion der einzelnen untersuchten Gruppen haben, wurde eine Diskriminanzanalyse berechnet. Die größte diskriminatorische Bedeutung besitzen die Variablen „Stereotypische Wahrnehmung der männlichen Personen“ und „Ego-Involvement mit weiblichen Personen“ für die Diskriminanzfunktion 1 (Trennung der Transsexuellen von Hetero- und Homosexuellen) und die Variablen „Empathische Identifikation mit männlichen Personen in der Vergangenheit“ und „Zuwachs an empathischer Identifikation mit weiblichen Personen“ für die Diskriminanzfunktion 2 (Trennung der Hetero- von Homosexuellen).
Die vorliegende Arbeit beschäftigt sich mit der Synthese und Charakterisierung mesoporöser monolithischer Silica und deren Hybridmaterialien mit Ionischen Flüssigkeiten (ILs, ionic liquids). Zur Synthese der Silicaproben wurde ein Sol-Gel-Verfahren, ausgehend von einer Präkursorverbindung wie Tetramethylorthosilicat angewendet. Der Katalysator mit der geringsten Basizität führte zum Material mit der kleinsten Porengröße und der größten spezifischen Oberfläche. Eine Kombination von porösen Silica mit ILs führt zur Materialklasse der Silica-Ionogele. Diese Hybridmaterialien verbinden die Eigenschaften eines porösen Festkörpers mit denen einer IL (Leitfähigkeit, weites elektrochemisches Fenster, gute thermische Stabilität) und bieten vielfältige Einsatzmöglichkeiten z.B. in der Katalyse- Solar- und Sensortechnik. Um diese Materialien für ihren Verwendungszweck zu optimieren, bedarf es deren umfassenden Charakterisierung. Daher wurde in der vorliegenden Arbeit das thermische Verhalten von Silica-Ionogelen unter Verwendung verschiedener 1-Ethyl-3-methylimidazolium [Emim]-basierter ILs untersucht. Interessanterweise zeigen die untersuchten ILs deutliche Änderungen in ihrem thermischen Verhalten, wenn diese in porösen Materialien eingeschlossen werden (Confinement). Während sich die untersuchten reinen ILs durch klar unterscheidbare Phasenübergänge auszeichnen, konnten für die entsprechenden Hybridmaterialien deutlich schwächer ausgeprägte Übergänge beobachtet werden. Einzelne Phasenübergänge wurden unterdrückt (Glas- und Kristallisationsübergänge), während z.B. Schmelzübergänge in verbreiterten Temperaturbereichen, zum Teil als einzeln getrennte Schmelzpeaks beobachtet wurden. Diese Untersuchungen belegen deutliche Eigenschaftsänderungen der ILs in eingeschränkten Geometrien. Über Festkörper-NMR-Spektroskopie konnte außerdem gezeigt werden, daß die ILs in den mesoporösen Silicamaterialien eine unerwartet hohe Mobilität aufweisen. Die ILs können als quasi-flüssig bezeichnet werden und zeigen die nach bestem Wissen höchste Mobilität, die bisher für vergleichbare Hybridmaterialien beobachtet wurde. Durch Verwendung von funktionalisierten Präkursoren, sowie der Wahl der Reaktionsbedingungen, kann die Oberfläche der Silicamaterialien chemisch funktionalisiert werden und damit die Materialeigenschaften in der gewünschten Weise beeinflußt werden. In der vorliegenden Arbeit wurde der Einfluß der Oberflächenfunktionalität auf das thermische Verhalten hin untersucht. Dazu wurden zwei verschiedene Möglichkeiten der Funktionalisierung angewendet und miteinander verglichen. Bei der in-situ-Funktionalisierung wird die chemische Funktionalität während der Sol-Gel-Synthese über ein entsprechend funktionalisiertes Silan mit in das Silicamaterial einkondensiert. Eine postsynthetische Funktionalisierung erfolgt durch Reaktion der Endgruppen eines Silicamaterials mit geeigneten Reaktionspartnern. Um den Einfluß der physikalischen Eigenschaften der Probe auf die Reaktion zu untersuchen, wurden pulverisierte und monolithische Silicamaterialien miteinander verglichen. Im letzten Teil der Arbeit wurde die Vielfältigkeit, mit der Silicamaterialien postsynthetisch funktionalisiert werden können demonstriert. Durch die Kenntnis von Struktur-Eigenschaftsbeziehungen können die Eigenschaften von Silica-Ionogelen durch die geeignete Kombination von fester und mobiler Phase in der gewünschten Weise verändert werden. Die vorliegende Arbeit soll einen Beitrag zur Untersuchung dieser Beziehungen leisten, um das Potential dieser interessanten Materialien für Anwendungen nutzen zu können.
The lakes of the East African Rift System (EARS) have been intensively studied to better understand the influence of climate change on hydrological systems. The exceptional sensitivity of these rift lakes, however, is both a challenge and an opportunity when trying to reconstruct past climate changes from changes in the hydrological budget of lake basins on timescales 100 to 104 years. On one hand, differences in basin geometrics (shape, area, volume, depth), catchment rainfall distributions and varying erosion-deposition rates complicate regional interpretation of paleoclimate information from lacustrine sediment proxies. On the other hand, the sensitivity of rift lakes often provides paleoclimate records of excellent quality characterized by a high signal-to-noise ratio. This study aims at better understanding of the climate-proxy generating process in rift lakes by parameterizing the geomorphological and hydroclimatic conditions of a particular site providing a step towards the establishment of regional calibrations of transfer functions for climate reconstructions. The knowledge of the sensitivity of a lake basin to climate change furthermore is crucial for a better assessment of the probability of catastrophic changes in the future, which bear risks for landscapes, ecosystems, and organisms of all sorts, including humans. Part 1 of this thesis explores the effect of the morphology and the effective moisture of a lake catchment. The availability of digital elevation models (DEM) and gridded climate data sets facilitates the comparison of the morphological and hydroclimatic conditions of rift lakes. I used the hypsometric integral (HI) calculated from Shuttle Radar Topography Mission (SRTM) data to describe the morphology of ten lake basins in Kenya and Ethiopia. The aridity index (AI) describing the difference in the precipitation/evaporation balance within a catchment was used to compare the hydroclimatic of these basins. Correlating HI and AI with published Holocene lake-level variations revealed that lakes responding sensitively to relatively moderate climate change are typically graben shaped and characterized by a HI between 0.23-0.30, and relatively humid conditions with AI >1. These amplifier lakes, a term first introduced but not fully parameterized by Alayne Street-Perrott in the early 80s, are unexceptionally located in the crest of the Kenyan and Ethiopian domes. The non-amplifier lakes in the EARS either have lower HI 0.13-0.22 and higher AI (>1) or higher HI (0.31-0.37) and low AI (<1), reflecting pan-shaped morphologies with more arid hydroclimatic conditions. Part 2 of this work addresses the third important factor to be considered when using lake-level and proxy records to unravel past climate changes in the EARS: interbasin connectivity and groundwater flow through faulted and porous subsurface lithologies in a rift setting. First, I have compiled the available hydrogeological data including lithology, resistivity and water-well data for the adjacent Naivasha and Elmenteita-Nakuru basins in the Central Kenya Rift. Using this subsurface information and established records of lake-level decline at the last wet-dry climate transitions, i.e., the termination of the African Humid Period (AHP, 15 to 5 kyr BP), I used a linear decay model to estimate typical groundwater flow between the two basins. The results suggest a delayed response of the groundwater levels of ca. 5 kyrs if no recharge of groundwater occurs during the wet-dry transition, whereas the lag is 2-2.7 kyrs only using the modern recharge of ca. 0.52 m/yr. The estimated total groundwater flow from higher Lake Naivasha (1,880 m a.s.l. during the AHP) to Nakuru-Elmenteita (1,770 m) was 40 cubic kilometers. The unexpectedly large volume, more than half of the volume of the paleo-Lake Naivasha during the Early Holocene, emphasizes the importance of groundwater in hydrological modeling of paleo-lakes in rifts. Moreover, the subsurface connectivity of rift lakes also causes a significant lag time to the system introducing a nonlinear component to the system that has to be considered while interpreting paleo-lake records. Part 3 of this thesis investigated the modern intraseasonal precipitation variability within eleven lake basins discussed in the first section of the study excluding Lake Victoria and including Lake Tana. Remotely sensed rainfall estimates (RFE) from FEWS NET for 1996-2010, are used for the, March April May (MAM) July August September (JAS), October November (ON) and December January February (DJF). The seasonal precipitation are averaged and correlated with the prevailing regional and local climatic mechanisms. Results show high variability with Biennial to Triennial precipitation patterns. The spatial distribution of precipitation in JAS are linked to the onset and strength of the Congo Air Boundary (CAB) and Indian Summer Monsoon (ISM) dynamics. while in ON they are related to the strength of Positive ENSO and IOD phases This study describes the influence of graben morphologies, extreme climate constrasts within catchments and basins connectivity through faults and porous lithologies on rift lakes. Hence, it shows the importance of a careful characterization of a rift lake by these parameters prior to concluding from lake-level and proxy records to climate changes. Furthermore, this study highlights the exceptional sensitivity of rift lakes to relatively moderate climate change and its consequences for water availability to the biosphere including humans.
The needs for sustainable energy generation, but also a sustainable chemistry display the basic motivation of the current thesis. By different single investigated cases, which are all related to the element carbon, the work can be devided into two major topics. At first, the sustainable synthesis of “useful” carbon materials employing the process of hydrothermal carbonisation (HC) is described. In the second part, the synthesis of heteroatom - containing carbon materials for electrochemical and fuel cell applications employing ionic liquid precursors is presented. On base of a thorough review of the literature on hydrothermolysis and hydrothermal carbonisation of sugars in addition to the chemistry of hydroxymethylfurfural, mechanistic considerations of the formation of hydrothermal carbon are proposed. On the base of these reaction schemes, the mineral borax, is introduced as an additive for the hydrothermal carbonisation of glucose. It was found to be a highly active catalyst, resulting in decreased reaction times and increased carbon yields. The chemical impact of borax, in the following is exploited for the modification of the micro- and nanostructure of hydrothermal carbon. From the borax - mediated aggregation of those primary species, widely applicable, low density, pure hydrothermal carbon aerogels with high porosities and specific surface areas are produced. To conclude the first section of the thesis, a short series of experiments is carried out, for the purpose of demonstrating the applicability of the HC model to “real” biowaste i.e. watermelon waste as feedstock for the production of useful materials. In part two cyano - containing ionic liquids are employed as precursors for the synthesis of high - performance, heteroatom - containing carbon materials. By varying the ionic liquid precursor and the carbonisation conditions, it was possible to design highly active non - metal electrocatalyst for the reduction of oxygen. In the direct reduction of oxygen to water (like used in polymer electrolyte fuel cells), compared to commercial platinum catalysts, astonishing activities are observed. In another example the selective and very cost efficient electrochemical synthesis of hydrogen peroxide is presented. In a last example the synthesis of graphitic boron carbon nitrides from the ionic liquid 1 - Ethyl - 3 - methylimidazolium - tetracyanoborate is investigated in detail. Due to the employment of unreactive salts as a new tool to generate high surface area these materials were first time shown to be another class of non - precious metal oxygen reduction electrocatalyst.
Genetic variation is crucial for the long-term survival of the species as it provides the potential for adaptive responses to environmental changes such as emerging diseases. The Major Histocompatibility Complex (MHC) is a gene family that plays a central role in the vertebrate’s immune system by triggering the adaptive immune response after exposure to pathogens. MHC genes have become highly suitable molecular markers of adaptive significance. They synthesize two primary cell surface molecules namely MHC class I and class II that recognize short fragments of proteins derived respectively from intracellular (e.g. viruses) and extracellular (e.g. bacteria, protozoa, arthropods) origins and present them to immune cells. High levels of MHC polymorphism frequently observed in natural populations are interpreted as an adaptation to detect and present a wide array of rapidly evolving pathogens. This variation appears to be largely maintained by positive selection driven mainly by pathogenic selective pressures. For my doctoral research I focused on MHC I and II variation in free-ranging cheetahs (Acinonyx jubatus) and leopards (Panthera pardus) on Namibian farmlands. Both felid species are sympatric thus subject to similar pathogenic pressures but differ in their evolutionary and demographic histories. The main aims were to investigate 1) the extent and patterns of MHC variation at the population level in both felids, 2) the association between levels of MHC variation and disease resistance in free-ranging cheetahs, and 3) the role of selection at different time scales in shaping MHC variation in both felids. Cheetahs and leopards represent the largest free-ranging carnivores in Namibia. They concentrate in unprotected areas on privately owned farmlands where domestic and other wild animals also occur and the risk of pathogen transmission is increased. Thus, knowledge on adaptive genetic variation involved in disease resistance may be pertinent to both felid species’ conservation. The cheetah has been used as a classic example in conservation genetics textbooks due to overall low levels of genetic variation. Reduced variation at MHC genes has been associated with high susceptibility to infectious diseases in cheetahs. However, increased disease susceptibility has only been observed in captive cheetahs whereas recent studies in free-ranging Namibian cheetahs revealed a good health status. This raised the question whether the diversity at MHC I and II genes in free-ranging cheetahs is higher than previously reported. In this study, a total of 10 MHC I alleles and four MHC II alleles were observed in 149 individuals throughout Namibia. All alleles but one likely belong to functional MHC genes as their expression was confirmed. The observed alleles belong to four MHC I and three MHC II genes in the species as revealed by phylogenetic analyses. Signatures of historical positive selection acting on specific sites that interact directly with pathogen-derived proteins were detected in both MHC classes. Furthermore, a high genetic differentiation at MHC I was observed between Namibian cheetahs from east-central and north-central regions known to differ substantially in exposure to feline-specific viral pathogens. This suggests that the patterns of MHC I variation in the current population mirrors different pathogenic selective pressure imposed by viruses. Cheetahs showed low levels of MHC diversity compared with other mammalian species including felids, but this does not seem to influence the current immunocompetence of free-ranging cheetahs in Namibia and contradicts the previous conclusion that the cheetah is a paradigm species of disease susceptibility. However, it cannot be ruled out that the low MHC variation might limit a prosperous immunocompetence in the case of an emerging disease scenario because none of the remaining alleles might be able to recognize a novel pathogen. In contrast to cheetahs, leopards occur in most parts of Africa being perhaps the most abundant big cat in the continent. Leopards seem to have escaped from large-scale declines due to epizootics in the past in contrast to some free-ranging large carnivore populations in Africa that have been afflicted by epizootics. Currently, no information about the MHC sequence variation and constitution in African leopards exists. In this study, I characterized genetic variation at MHC I and MHC II genes in free-ranging leopards from Namibia. A total of six MHC I and six MHC II sequences were detected in 25 individuals from the east-central region. The maximum number of sequences observed per individual suggests that they likely correspond to at least three MHC I and three MHC II genes. Hallmarks of MHC evolution were confirmed such as historical positive selection, recombination and trans-species polymorphism. The low MHC variation detected in Namibian leopards is not conclusive and further research is required to assess the extent of MHC variation in different areas of its geographic range. Results from this thesis will contribute to better understanding the evolutionary significance of MHC and conservation implications in free-ranging felids. Translocation of wildlife is an increasingly used management tool for conservation purposes that should be conducted carefully as it may affect the ability of the translocated animals to cope with different pathogenic selective pressures.
Species respond to environmental change by dynamically adjusting their geographical ranges. Robust predictions of these changes are prerequisites to inform dynamic and sustainable conservation strategies. Correlative species distribution models (SDMs) relate species’ occurrence records to prevailing environmental factors to describe the environmental niche. They have been widely applied in global change context as they have comparably low data requirements and allow for rapid assessments of potential future species’ distributions. However, due to their static nature, transient responses to environmental change are essentially ignored in SDMs. Furthermore, neither dispersal nor demographic processes and biotic interactions are explicitly incorporated. Therefore, it has often been suggested to link statistical and mechanistic modelling approaches in order to make more realistic predictions of species’ distributions for scenarios of environmental change. In this thesis, I present two different ways of such linkage. (i) Mechanistic modelling can act as virtual playground for testing statistical models and allows extensive exploration of specific questions. I promote this ‘virtual ecologist’ approach as a powerful evaluation framework for testing sampling protocols, analyses and modelling tools. Also, I employ such an approach to systematically assess the effects of transient dynamics and ecological properties and processes on the prediction accuracy of SDMs for climate change projections. That way, relevant mechanisms are identified that shape the species’ response to altered environmental conditions and which should hence be considered when trying to project species’ distribution through time. (ii) I supplement SDM projections of potential future habitat for black grouse in Switzerland with an individual-based population model. By explicitly considering complex interactions between habitat availability and demographic processes, this allows for a more direct assessment of expected population response to environmental change and associated extinction risks. However, predictions were highly variable across simulations emphasising the need for principal evaluation tools like sensitivity analysis to assess uncertainty and robustness in dynamic range predictions. Furthermore, I identify data coverage of the environmental niche as a likely cause for contrasted range predictions between SDM algorithms. SDMs may fail to make reliable predictions for truncated and edge niches, meaning that portions of the niche are not represented in the data or niche edges coincide with data limits. Overall, my thesis contributes to an improved understanding of uncertainty factors in predictions of range dynamics and presents ways how to deal with these. Finally I provide preliminary guidelines for predictive modelling of dynamic species’ response to environmental change, identify key challenges for future research and discuss emerging developments.
It is well documented that transcriptionally coordinated genes tend to be functionally related, and that such relationships may be conserved across different species, and even kingdoms. (Ihmels et al., 2004). Such relationships was initially utilized to reveal functional gene modules in yeast and mammals (Ihmels et al., 2004), and to explore orthologous gene functions between different species and kingdoms (Stuart et al., 2003; Bergmann et al., 2004). Model organisms, such as Arabidopsis, are readily used in basic research due to resource availability and relative speed of data acquisition. A major goal is to transfer the acquired knowledge from these model organisms to species that are of greater importance to our society. However, due to large gene families in plants, the identification of functional equivalents of well characterized Arabidopsis genes in other plants is a non-trivial task, which often returns erroneous or inconclusive results. In this thesis, concepts of utilizing co-expression networks to help infer (i) gene function, (ii) organization of biological processes and (iii) knowledge transfer between species are introduced. An often overlooked fact by bioinformaticians is that a bioinformatic method is as useful as its accessibility. Therefore, majority of the work presented in this thesis was directed on developing freely available, user-friendly web-tools accessible for any biologist.
The past climate in central Asia, and especially on the Tibetan Plateau (TP), is of great importance for an understanding of global climate processes and for predicting the future climate. As a major influence on the climate in this region, the Asian Summer Monsoon (ASM) and its evolutionary history are of vital importance for accurate predictions. However, neither the evolutionary pattern of the summer monsoon nor the driving mechanisms behind it are yet clearly understood. For this research, I first synthesized previously published Late Glacial to Holocene climatic records from monsoonal central Asia in order to extract the general climate signals and the associated summer monsoon intensities. New climate and vegetation sequences were then established using improved quantitative methods, focusing on fossil pollen records recovered from Tibetan lakes and also incorporating new modern datasets. The pollen-vegetation and vegetation-climate relationships on the TP were also evaluated in order to achieve a better understanding of fossil pollen records. The synthesis of previously published moisture-related palaeoclimate records in monsoonal central Asia revealed generally different temporal patterns for the two monsoonal subsystems, i.e. the Indian Summer Monsoon (ISM) and East Asian Summer Monsoon (EASM). The ISM appears to have experienced maximum wet conditions during the early Holocene, while many records from the area affected by the EASM indicate relatively dry conditions at that time, particularly in north-central China where the maximum moisture levels occurred during the middle Holocene. A detailed consideration of possible driving factors affecting the summer monsoon, including summer solar insolation and sea surface temperatures, revealed that the ISM was primarily driven by variations in northern hemisphere solar insolation, and that the EASM may have been constrained by the ISM resulting in asynchronous patterns of evolution for these two subsystems. This hypothesis is further supported by modern monsoon indices estimated using the NCEP/NCAR Reanalysis data from the last 50 years, which indicate a significant negative correlation between the two summer monsoon subsystems. By analogy with the early Holocene, intensification of the ISM during coming decades could lead to increased aridification elsewhere as a result of the asynchronous nature of the monsoon subsystems, as can already be observed in the meteorological data from the last 15 years. A quantitative climate reconstruction using fossil pollen records was achieved through analysis of sediment core recovered from Lake Donggi Cona (in the north-eastern part of the TP) which has been dated back to the Last Glacial Maximum (LGM). A new data-set of modern pollen collected from large lakes in arid to semi-arid regions of central Asia is also presented herein. The concept of "pollen source area" was introduced to modern climate calibration based on pollen from large lakes, and was applied to the fossil pollen sequence from Lake Donggi Cona. Extremely dry conditions were found to have dominated the LGM, and a subsequent gradually increasing trend in moisture during the Late Glacial period was terminated by an abrupt reversion to a dry phase that lasted for about 1000 years and coincided with the first Heinrich Event of the northern Atlantic region. Subsequent periods corresponding to the warm Bølling-Allerød period and the Younger Dryas cold event were followed by moist conditions during the early Holocene, with annual precipitation of up to about 400 mm. A slightly drier trend after 9 cal ka BP was then followed by a second wet phase during the middle Holocene that lasted until 4.5 cal ka BP. Relatively steady conditions with only slight fluctuations then dominated the late Holocene, resulting in the present climatic conditions. In order to investigate the relationship between vegetation and climate, temporal variations in the possible driving factors for vegetation change on the northern TP were examined using a high resolution late Holocene pollen record from Lake Kusai. Moving-window Redundancy Analyses (RDAs) were used to evaluate the correlations between pollen assemblages and individual sedimentary proxies. These analyses have revealed frequent fluctuations in the relative abundances of alpine steppe and alpine desert components, and in particular a decrease in the total vegetation cover at around 1500 cal a BP. The climate was found to have had an important influence on vegetation changes when conditions were relatively wet and stable. However, after the 1500 cal a BP threshold in vegetation cover was crossed the vegetation appears to have been affected more by extreme events such as dust storms or fluvial erosion than by the general climatic trends. In addition, pollen spectra over the last 600 years have been revealed by Procrustes analysis to be significantly different from those recovered from older samples, which is attributed to an increased human impact that resulted in unprecedented changes to the composition of the vegetation. Theoretical models that have been developed and widely applied to the European area (i.e. the Extended R-Value (ERV) model and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model) have been applied to the high alpine TP ecosystems in order to investigate the pollen-vegetation relationships, as well as for quantitative reconstructions of vegetation abundance. The modern pollen–vegetation relationships for four common pollen species on the TP have been investigated using Poaceae as the reference taxa. The ERV Submodel 2 yielded relatively high PPEs for the steppe and desert taxa (Artemisia Chenopodiaceae), and low PPEs for the Cyperaceae that are characteristic of the alpine Kobresia meadows. The plant abundances on the central and north-eastern TP were quantified by applying these PPEs to four post-Late Glacial fossil pollen sequences. The reconstructed vegetation assemblages for the four pollen sequences always yielded smaller compositional species turnovers than suggested by the pollen spectra, indicating that the strength of the previously-reported vegetation changes may therefore have been overestimated. In summary, the key findings of this thesis are that (a) the two ASM subsystems show asynchronous patterns during both the Holocene and modern time periods, (b) fossil pollen records from large lakes reflect regional signals for which the pollen source areas need to be taken into account, (c) climate is not always the main driver for vegetation change, and (d) previously reported vegetation changes on the TP may have been overestimated because they ignored inter-species variations in pollen productivity.
Sediment records of three European lakes were investigated in order to reconstruct the regional climate development during the Lateglacial and Holocene, to investigate the response of local ecosystems to climatic fluctuations and human impact and to relate regional peculiarities of past climate development to climatic changes on a larger spatial scale. The Lake Hańcza (NE Poland) sediment record was studied with a focus on reconstructing the early Holocene climate development and identifying possible differences to Western Europe. Following the initial Holocene climatic improvement, a further climatic improvement occurred between 10 000 and 9000 cal. a BP. Apparently, relatively cold and dry climate conditions persisted in NE Poland during the first ca. 1500 years of the Holocene, most likely due to a specific regional atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the remaining Scandinavian Ice Sheet (SIS) might have blocked the eastward propagation of warm and moist Westerlies and thus attenuated the early Holocene climatic amelioration in this region until the final decay of the SIS, a pattern different from climate development in Western Europe. The Lateglacial sediment record of Lake Mondsee (Upper Austria) was investigated in order to study the regional climate development and the environmental response to rapid climatic fluctuations. While the temperature rise and environmental response at the onset of the Holocene took place quasi-synchronously, major leads and lags in proxy responses characterize the onset of the Lateglacial Interstadial. In particular, the spread of coniferous woodlands and the reduction of detrital flux lagged the initial Lateglacial warming by ca. 500–750 years. Major cooling at the onset of the Younger Dryas took place synchronously with a change in vegetation, while the increase of detrital matter flux was delayed by about 150–300 years. Complex proxy responses are also detected for short-term Lateglacial climatic fluctuations. In summary, periods of abrupt climatic changes are characterized by complex and temporally variable proxy responses, mainly controlled by ecosystem inertia and the environmental preconditions. A second study on the Lake Mondsee sediment record focused on two small-scale climate deteriorations around 8200 and 9100 cal. a BP, which have been triggered by freshwater discharges to the North Atlantic, causing a shutdown of the Atlantic meridional overturning circulation (MOC). Combining microscopic varve counting and AMS 14C dating yielded a precise duration estimate (ca. 150 years) and absolute dating of the 8.2 ka cold event, both being in good agreement with results from other palaeoclimate records. Moreover, a sudden temperature overshoot after the 8.2 ka cold event was identified, also seen in other proxy records around the North Atlantic. This was most likely caused by enhanced resumption of the MOC, which also initiated substantial shifts of oceanic and atmospheric front systems. Although there is also evidence from other proxy records for pronounced recovery of the MOC and atmospheric circulation changes after the 9.1 ka cold event, no temperature overshoot is seen in the Lake Mondsee record, indicating the complex behaviour of the global climate system. The Holocene sediment record of Lake Iseo (northern Italy) was studied to shed light on regional earthquake activity and the influence of climate variability and anthropogenic impact on catchment erosion and detrital flux into the lake. Frequent small-scale detrital layers within the sediments reflect allochthonous sediment supply by extreme surface runoff events. During the early to mid-Holocene, increased detrital flux coincides with periods of cold and wet climate conditions, thus apparently being mainly controlled by climate variability. In contrast, intervals of high detrital flux during the late Holocene partly also correlate with phases of increased human impact, reflecting the complex influences on catchment erosion processes. Five large-scale event layers within the sediments, which are composed of mass-wasting deposits and turbidites, are supposed to have been triggered by strong local earthquakes. While the uppermost of these event layers is assigned to a documented adjacent earthquake in AD 1222, the four other layers are supposed to be related to previously undocumented prehistorical earthquakes.
Eumelanin ist ein Fluorophor mit teilweise recht ungewöhnlichen spektralen Eigenschaften. Unter anderem konnten in früheren Veröffentlichungen Unterschiede zwischen dem 1- und 2-photonen-angeregtem Fluoreszenzspektrum beobachtet werden, weshalb im nichtlinearen Anregungsfall ein schrittweiser Anregungsprozess vermutet wurde. Um diese und weitere optische Eigenschaften des Eumelanins besser zu verstehen, wurden in der vorliegenden Arbeit vielfältige messmethodische Ansätze der linearen und nichtlinearen Optik an synthetischem Eumelanin in 0,1M NaOH verfolgt. Aus den Ergebnissen wurde ein Modell abgeleitet, welches die beobachteten photonischen Eigenschaften konsistent beschreibt. In diesem kaskadierten Zustandsmodell (Kaskaden-Modell) wird die aufgenommene Photonenenergie schrittweise von Anregungszuständen hoher Übergangsenergien zu Anregungszuständen niedrigerer Übergangsenergien transferiert. Messungen der transienten Absorption ergaben dominante Anteile mit kurzen Lebensdauern im ps-Bereich und ließen damit auf eine hohe Relaxationsgeschwindigkeit entlang der Kaskade schließen. Durch Untersuchung der nichtlinear angeregten Fluoreszenz von verschieden großen Eumelanin-Aggregaten konnte gezeigt werden, dass Unterschiede zwischen dem linear und nichtlinear angeregten Fluoreszenzspektrum nicht nur durch einen schrittweisen Anregungsprozess bei nichtlinearer Anregung sondern auch durch Unterschiede in den Verhältnissen der Quantenausbeuten zwischen kleinen und großen Aggregaten beim Wechsel von linearer zu nichtlinearer Anregung begründet sein können. Durch Bestimmung des Anregungswirkungsquerschnitts und der Anregungspulsdauer-Abhängigkeit der nichtlinear angeregten Fluoreszenz von Eumelanin konnte jedoch ein schrittweiser 2-Photonen-Anregungsprozess über einen Zwischenzustand mit Lebendsdauern im ps-Bereich nachgewiesen werden.
Darmkrebs ist die zweithäufigste malignombedingte Todesursache in den westlichen Industrieländern. Durch eine frühzeitige Diagnose besteht jedoch eine hohe Chance auf Heilung. Der Goldstandard zur Darmkrebsfrüherkennung ist gegenwärtig die Koloskopie. Eine Darmspiegelung ist jedoch invasiv und mit Unannehmlichkeiten für den Patienten verbunden. Die Akzeptanz in der Bevölkerung ist daher gering. Ziel des BMBF- Projektes „Entwicklung eines nichtinvasiven Nachweissystems zur Früherkennung von humanem Darmkrebs“, in dessen Rahmen diese Arbeit entstand, ist die Bereitstellung eines nichtinvasiven Nachweisverfahrens zur Darmkrebsfrüherkennung. Der Nachweis soll über die Detektion von aus neoplastischen Zellen stammender DNA in Stuhl erfolgen. Die Entartung dieser Zellen beruht auf Veränderungen im Erbgut, welches unter anderem Mutationen sind. Im ersten Teil des BMBF-Projektes wurde ein Set von Mutationen zusammengestellt, welches eine hohe Sensitivität für Vorstufen von Darmkrebs aufweist. Ziel dieser Arbeit war es, eine Nachweismethode für die zuvor identifizierten Punktmutationen zu entwickeln. Das Nachweisverfahren musste dabei unempfindlich gegen einen hohen Hintergrund nichtmutierter DNA sein, da im Stuhl geringe Mengen DNA aus neoplastischen Zellen bei einem hohen Hintergrund von DNA aus gesunden Zellen vorliegen. Hierzu wurden Plasmidmodellsysteme für die aus dem Marker-Set stammenden Genfragmente BRAF und dessen Mutante V600E, CTNNB1 und T41I, T41A, S45P und K-ras G12C hergestellt. Mit Hilfe dieser Plasmidmodellsysteme wurde dann das Nachweissystem entwickelt. Der entscheidende Schritt für die Detektion von Punktmutationen bei hohem Wildtypüberschuss ist eine vorhergehende Anreicherung. In der vorliegenden Arbeit wurde dazu die Methode der LNA-clamp-PCR (locked nucleic acid) etabliert. Die Bewertung der erzielten Anreicherung erfolgte über das relative Detektionslimit. Zur Bestimmung des Detektionslimits wurde die Schmelzkurvenanalyse von Hybridisierungssonden eingesetzt; diese wurde im Rahmen dieser Arbeit für die drei oben genannten Genfragmente und ihre Mutanten entwickelt. Die LNA-clamp-PCR wird in Anwesenheit eines LNA-Blockers durchgeführt. Das Nukleotidanalogon LNA weist im Vergleich zu DNA eine erhöhte Affinität zu komplementären DNA-Strängen auf. Gleichzeitig kommt es bei Anwesenheit einer Basenfehlpaarung zu einer größeren Destabilisierung der Bindung. Als Blocker werden kurze LNA-DNA-Hybridoligonukleotide eingesetzt, die den mutierten Sequenzbereich überspannen und selbst der Wildtypsequenz entsprechen. Durch Bindung an die Wildtypsequenz wird deren Amplifikation während der PCR verhindert (clamp = arretieren, festklemmen). Der Blocker selbst wird dabei nicht verlängert. Der Blocker bindet unter optimalen Bedingungen jedoch nicht an die mutierte Sequenz. Die Mutante wird daher ungehindert amplifiziert und somit gegenüber dem Wildtyp-Fragment angereichert. Die Position des Blockers kann im Bindungsbereich eines der Primer sein und hier dessen Hybridisierung an dem Wildtyp-Fragment verhindern oder zwischen den beiden Primern liegen und so die Synthese durch die Polymerase inhibieren. Die Anwendbarkeit beider Systeme wurde in dieser Arbeit gezeigt. Die LNA-clamp-PCR mit Primerblocker wurde für BRAF etabliert. Es wurde ein Detektionslimit von mindestens 1:100 erzielt. Die LNA-clamp-PCR mit Amplifikationsblocker wurde erfolgreich für BRAF, K-ras und CTNNB1: T41I, T41A mit einem Detektionslimit von 1:1000 bis 1:10 000 entwickelt. In Stuhlproben liegt DNA aus neoplastischen Zellen nach Literaturangaben zu einem Anteil von 1% bis 0,1% vor. Die LNA-clamp-PCR weist also mit Amplifikationsblockern ein ausreichend hohes Detektionslimit für die Analyse von Stuhlproben auf. Durch die erfolgreiche Etablierung der Methode auf drei verschiedenen Genfragmenten und vier unterschiedlichen Punktmutationen konnte deren universelle Einsetzbarkeit gezeigt werden. Für die Ausweitung der LNA-clamp-PCR auf die übrigen Mutationen des Marker-Sets wurden Richtlinien ausgearbeitet und die Blockereffizienz als Kennzahl eingeführt. Die LNA-clamp-PCR ist ein schnelles, kostengünstiges Verfahren, welches einen geringen Arbeitsaufwand erfordert und wenig fehleranfällig ist. Sie ist somit ein geeignetes Anreicherungsverfahren für Punktmutationen in einem diagnostischen System zur Darmkrebsfrüherkennung. Darüber hinaus kann die LNA-clamp-PCR auch in anderen Bereichen, in denen die Detektion von Punktmutationen in einem hohen Wildtyphintergrund erforderlich ist, eingesetzt werden.
Plant growth and survival depend on photosynthesis in the leaves. This involves the uptake of carbon dioxide from the atmosphere and the simultaneous capture of light energy to produce organic molecules, which enter metabolism and are converted to many other compounds which then serve as building blocks for biomass growth. Leaves are organs specialised for photosynthetic carbon dioxide fixation. The function of leaves involves many trade-offs which must be optimised in order to achieve effective use of resources and maximum photosynthesis. It is known that the morphology of leaves adjusts to the growth environment of plants and this is important for optimising their function for photosynthesis. However, it is unclear how this adjustment is regulated. The general aim of the work presented in this thesis is to understand how leaf growth and morphology are regulated in the model species Arabidopsis thaliana. Special attention was dedicated to the possibility that there might be internal metabolic signals within the plant which affect the growth and development of leaves. In order to investigate this question, leaf growth and development must be considered beyond the level of the single organ and in the context of the whole plant because leaves do not grow autonomously but depend on resources and regulatory influences delivered by the rest of the plant. Due to the complexity of this question, three complementary approaches were taken. In the first and most specific approach it was asked whether a proposed down-stream component of sucrose signalling, trehalose-6-phosphate (Tre-6-P), might influence leaf development and growth. To investigate this question, transgenic Arabidopsis lines with perturbed levels of Tre-6-P were generated using the constitutive 35S promoter to express bacterial enzymes involved in trehalose metabolism. These experiments also led to an unanticipated project concerning a possible role for Tre-6-P in stomatal function, which is another very important function in leaves. In a second and more general approach it was investigated whether changes in sugar levels in plants affect the morphogenesis of leaves in response to light. For this, a series of metabolic mutants impaired in central metabolism were grown in one light environment and their leaf morphology was analysed. In a third and even more general approach the natural variation in leaf and rosette morphological traits was investigated in a panel of wild Arabidopsis accessions with the aim of understanding how leaf morphology affects leaf function and whole plant growth and how different traits relate to each other. The analysis included measurements of leaf morphological traits as well as the number of leaves in the plant to put leaf morphology in a whole plant context. The variance in plant growth could not be explained by variation in photosynthetic rates and only to a small degree by variation in rates of dark respiration. There were four key axes of variation in rosette and leaf morphology – leaf area growth, leaf thickness, cell expansion and leaf number. These four processes were integrated in the context of whole plant growth by models that employed a multiple linear regression approach. This then led to a theoretical approach in which a simple allometric mathematical model was constructed, linking leaf number, leaf size and plant growth rate together in a whole plant context in Arabidopsis.
Service-oriented Architectures (SOA) facilitate the provision and orchestration of business services to enable a faster adoption to changing business demands. Web Services provide a technical foundation to implement this paradigm on the basis of XML-messaging. However, the enhanced flexibility of message-based systems comes along with new threats and risks. To face these issues, a variety of security mechanisms and approaches is supported by the Web Service specifications. The usage of these security mechanisms and protocols is configured by stating security requirements in security policies. However, security policy languages for SOA are complex and difficult to create due to the expressiveness of these languages. To facilitate and simplify the creation of security policies, this thesis presents a model-driven approach that enables the generation of complex security policies on the basis of simple security intentions. SOA architects can specify these intentions in system design models and are not required to deal with complex technical security concepts. The approach introduced in this thesis enables the enhancement of any system design modelling languages – for example FMC or BPMN – with security modelling elements. The syntax, semantics, and notion of these elements is defined by our security modelling language SecureSOA. The metamodel of this language provides extension points to enable the integration into system design modelling languages. In particular, this thesis demonstrates the enhancement of FMC block diagrams with SecureSOA. To enable the model-driven generation of security policies, a domain-independent policy model is introduced in this thesis. This model provides an abstraction layer for security policies. Mappings are used to perform the transformation from our model to security policy languages. However, expert knowledge is required to generate instances of this model on the basis of simple security intentions. Appropriate security mechanisms, protocols and options must be chosen and combined to fulfil these security intentions. In this thesis, a formalised system of security patterns is used to represent this knowledge and to enable an automated transformation process. Moreover, a domain-specific language is introduced to state security patterns in an accessible way. On the basis of this language, a system of security configuration patterns is provided to transform security intentions related to data protection and identity management. The formal semantics of the security pattern language enable the verification of the transformation process introduced in this thesis and prove the correctness of the pattern application. Finally, our SOA Security LAB is presented that demonstrates the application of our model-driven approach to facilitate a dynamic creation, configuration, and execution of secure Web Service-based composed applications.
Biology has made great progress in identifying and measuring the building blocks of life. The availability of high-throughput methods in molecular biology has dramatically accelerated the growth of biological knowledge for various organisms. The advancements in genomic, proteomic and metabolomic technologies allow for constructing complex models of biological systems. An increasing number of biological repositories is available on the web, incorporating thousands of biochemical reactions and genetic regulations. Systems Biology is a recent research trend in life science, which fosters a systemic view on biology. In Systems Biology one is interested in integrating the knowledge from all these different sources into models that capture the interaction of these entities. By studying these models one wants to understand the emerging properties of the whole system, such as robustness. However, both measurements as well as biological networks are prone to considerable incompleteness, heterogeneity and mutual inconsistency, which makes it highly non-trivial to draw biologically meaningful conclusions in an automated way. Therefore, we want to promote Answer Set Programming (ASP) as a tool for discrete modeling in Systems Biology. ASP is a declarative problem solving paradigm, in which a problem is encoded as a logic program such that its answer sets represent solutions to the problem. ASP has intrinsic features to cope with incompleteness, offers a rich modeling language and highly efficient solving technology. We present ASP solutions, for the analysis of genetic regulatory networks, determining consistency with observed measurements and identifying minimal causes for inconsistency. We extend this approach for computing minimal repairs on model and data that restore consistency. This method allows for predicting unobserved data even in case of inconsistency. Further, we present an ASP approach to metabolic network expansion. This approach exploits the easy characterization of reachability in ASP and its various reasoning methods, to explore the biosynthetic capabilities of metabolic reaction networks and generate hypotheses for extending the network. Finally, we present the BioASP library, a Python library which encapsulates our ASP solutions into the imperative programming paradigm. The library allows for an easy integration of ASP solution into system rich environments, as they exist in Systems Biology.
The Greenland Ice Sheet (GIS) contains enough water volume to raise global sea level by over 7 meters. It is a relic of past glacial climates that could be strongly affected by a warming world. Several studies have been performed to investigate the sensitivity of the ice sheet to changes in climate, but large uncertainties in its long-term response still exist. In this thesis, a new approach has been developed and applied to modeling the GIS response to climate change. The advantages compared to previous approaches are (i) that it can be applied over a wide range of climatic scenarios (both in the deep past and the future), (ii) that it includes the relevant feedback processes between the climate and the ice sheet and (iii) that it is highly computationally efficient, allowing simulations over very long timescales. The new regional energy-moisture balance model (REMBO) has been developed to model the climate and surface mass balance over Greenland and it represents an improvement compared to conventional approaches in modeling present-day conditions. Furthermore, the evolution of the GIS has been simulated over the last glacial cycle using an ensemble of model versions. The model performance has been validated against field observations of the present-day climate and surface mass balance, as well as paleo information from ice cores. The GIS contribution to sea level rise during the last interglacial is estimated to be between 0.5-4.1 m, consistent with previous estimates. The ensemble of model versions has been constrained to those that are consistent with the data, and a range of valid parameter values has been defined, allowing quantification of the uncertainty and sensitivity of the modeling approach. Using the constrained model ensemble, the sensitivity of the GIS to long-term climate change was investigated. It was found that the GIS exhibits hysteresis behavior (i.e., it is multi-stable under certain conditions), and that a temperature threshold exists above which the ice sheet transitions to an essentially ice-free state. The threshold in the global temperature is estimated to be in the range of 1.3-2.3°C above preindustrial conditions, significantly lower than previously believed. The timescale of total melt scales non-linearly with the overshoot above the temperature threshold, such that a 2°C anomaly causes the ice sheet to melt in ca. 50,000 years, but an anomaly of 6°C will melt the ice sheet in less than 4,000 years. The meltback of the ice sheet was found to become irreversible after a fraction of the ice sheet is already lost – but this level of irreversibility also depends on the temperature anomaly.
Within this work, three physicochemical methods for the hydrophobization of initially hydrophilic solid particles are investigated. The modified particles are then used for the stabilization of oil-in-water (o/w) emulsions. For all introduced methods electrostatic interactions between strongly or weakly charged groups in the system are es-sential. (i) Short chain alkylammonium bromides (C4 – C12) adsorb on oppositely charged solid particles. Macroscopic contact angle measurements of water droplets under air and hexane on flat silica surfaces in dependency of the surface charge density and alkylchain-length allow the calculation of the surface energy and give insights into the emulsification properties of solid particles modified with alkyltrimethylammonium bromides. The measure-ments show an increase of the contact angle with increasing surface charge density, due to the enhanced adsorp-tion of the oppositely charged alkylammonium bromides. Contact angles are higher for longer alkylchain lengths. The surface energy calculations show that in particular the surface-hexane or surface-air interfacial en-ergy is being lowered upon alkylammonium adsorption, while a significant increase of the surface-water interfa-cial energy occurs only at long alkyl chain lengths and high surface charge densities. (ii) The thickness and the charge density of an adsorbed weak polyelectrolyte layer (e.g. PMAA, PAH) influence the wettability of nanoparticles (e.g. alumina, silica, see Scheme 1(b)). Furthermore, the isoelectric point and the pH range of colloidal stability of particle-polyelectrolyte composites depend on the thickness of the weak polye-lectrolyte layer. Silica nanoparticles with adsorbed PAH and alumina nanoparticles with adsorbed PMAA be-come interfacially active and thus able to stabilize o/w emulsions when the degree of dissociation of the polye-lectrolyte layer is below 80 %. The average droplet size after emulsification of dodecane in water depends on the thickness and the degree of dissociation of the adsorbed PE-layer. The visualization of the particle-stabilized o/w emulsions by cryogenic SEM shows that for colloidally stable alumina-PMAA composites the oil-water interface is covered with a closely packed monolayer of particles, while for the colloidally unstable case closely packed aggregated particles deposit on the interface. (iii) By emulsifying a mixture of the corrosion inhibitor 8-hydroxyquinoline (8-HQ) and styrene with silica nanoparticles a highly stable o/w emulsion can be obtained in a narrow pH window. The amphoteric character of 8-HQ enables a pH dependent electrostatic interaction with silica nanoparticles, which can render them interfa-cially active. Depending on the concentration and the degree of dissociation of 8-HQ the adsorption onto silica results from electrostatic or aromatic interactions between 8-HQ and the particle-surface. At intermediate amounts of adsorbed 8-HQ the oil wettability of the particles becomes sufficient for stabilizing o/w emulsions. Cryogenic SEM visualization shows that the particles arrange then in a closely packed shell consisting of partly of aggregated domains on the droplet interface. For further increasing amounts of adsorbed 8-HQ the oil wet-tability is reduced again and the particles ability to stabilize emulsions decreases. By the addition of hexadecane to the oil phase the size of the droplets can be reduced down to 200 nm by in-creasing the silica mass fraction. Subsequent polymerization produces corrosion inhibitor filled (20 wt-%) poly-styrene-silica composite particles. The measurement of the release of 8-hydroxyquinoline shows a rapid increase of 8-hydroxyquinoline in a stirred aqueous solution indicating the release of the total content in less than 5 min-utes. The method is extended for the encapsulation of other organic corrosion inhibitors. The silica-polymer-inhibitor composite particles are then dispersed in a water based alkyd emulsion, and the dispersion is used to coat flat aluminium substrates. After drying and cross-linking the polmer-film Confocal Laser Scanning Micros-copy is employed revealing a homogeneous distribution of the particles in the film. Electrochemical Impedance Spectroscopy in aqueous electrolyte solutions shows that films with aggregated particle domains degrade with time and don’t provide long-term corrosion protection of the substrate. However, films with highly dispersed particles have high barrier properties for corrosive species. The comparison of films containing silica-polystyrene composite particles with and without 8-hydroxyquinoline shows higher electrochemical impedances when the inhibitor is present in the film. By applying the Scanning Vibrating Electrode Technique the localized corrosion rate in the fractured area of scratched polymer films containing the silica-polymer-inhibitor composite particles is studied. Electrochemical corrosion cannot be suppressed but the rate is lowered when inhibitor filled composite particles are present in the film. By depositing six polyelectrolyte layers on particle stabilized emulsion droplets their surface morphology changes significantly as shown by SEM visualization. When the oil wettability of the outer polyelectrolyte layer increases, the polyelectrolyte coated droplets can act as emulsion stabilizers themselves by attaching onto bigger oil droplets in a closely packed arrangement. In the presence of 3 mM LaCl3 8-HQ hydrophobized silica particles aggregate strongly on the oil-water inter-face. The application of an ultrasonic field can remove two dimensional shell-compartments from the droplet surface, which are then found in the aqueous bulk phase. Their size ranges up to 1/4th of the spherical particle shell.
Lamine bilden zusammen mit laminassoziierten Proteinen die nukleäre Lamina. Diese ist notwendig für die mechanische Stabilität von Zellen, die Organisation des Chromatins, der Genexpression, dem Fortgang des Zellzyklus und der Zellmigration. Die vielfältigen Funktionen der Lamine werden durch die Pathogenese von Laminopathien belegt. Zu diesen Erkrankungen, welche ihre Ursache in Mutationen innerhalb der laminkodierenden Gene, oder der Gene laminassoziierter bzw. laminprozessierender Proteine haben, zählen unter anderem das „Hutchinson-Gilford Progerie Syndrom“, die „Emery-Dreifuss“ Muskeldystrophie und die dilatierte Kardiomyopathie. Trotz der fundamentalen Bedeutung der Lamine, wurden diese bisher nur in Metazoen und nicht in einzelligen Organismen detektiert. Der amöbide Organismus Dictyostelium discoideum ist ein haploider Eukaryot, der häufig als Modellorganismus in den verschiedensten Bereichen der Zellbiologie eingesetzt wird. Mit der Entdeckung von NE81, einem Protein das mit der inneren Kernhülle von Dictyostelium discoideum assoziiert ist, wurde erstmals ein Protein identifiziert, dass man aufgrund seiner Eigenschaften als laminähnliches Protein in einem niederen Eukaryoten bezeichnen kann. Diese Merkmale umfassen die Existenz lamintypischer Sequenzen, wie die CDK1-Phosphorylierungsstelle, direkt gefolgt von einer zentralen „Rod“-Domäne, sowie eine typische NLS und die hoch konservierte CaaX-Box. Für die Etablierung des NE81 als „primitives“ Lamin, wurden im Rahmen dieser Arbeit verschiedene Experimente durchgeführt, die strukturelle und funktionelle Gemeinsamkeiten zu den Laminen in anderen Organismen aufzeigen konnten. Die Herstellung eines polyklonalen Antikörpers ermöglichte die Verifizierung der subzellulären Lokalisation des NE81 durch Elektronenmikroskopie und gab Einblicke in das Verhalten des endogenen Proteins innerhalb des Zellzyklus. Mit der Generierung von NE81-Nullmutanten konnte demonstriert werden, dass NE81 eine wichtige Rolle bei der nukleären Integrität und der Chromatinorganisation von Zellen spielt. Des Weiteren führte die Expression von zwei CaaX-Box deletierten NE81 - Varianten dazu, den Einfluss des Proteins auf die mechanische Stabilität der Zellen nachweisen zu können. Auch die Bedeutung der hochkonservierten CaaX-Box für die Lokalisation des Proteins wurde durch die erhaltenen Ergebnisse deutlich. Mit der Durchführung von FRAP-Experimente konnte außerdem die strukturgebende Funktion von NE81 innerhalb des Zellkerns bekräftigt werden. Zusätzlich wurde im Rahmen dieser Arbeit damit begonnen, den Einfluss der Isoprenylcysteincarboxylmethyltransferase auf die Lokalisation des Proteins aufzuklären. Die Entdeckung eines laminähnlichen Proteins in einem einzelligen Organismus, der an der Schwelle zu den Metazoen steht, ist für die evolutionäre Betrachtung der Entwicklung der sozialen Amöbe und für die Erforschung der molekularen Basis von Laminopathien in einem einfachen Modellorganismus sehr interessant. Die Arbeit mit Dictyostelium discoideum könnte daher Wege aufzeigen, dass Studium der Laminopathien am Tiermodell drastisch zu reduzieren. In den letzten Jahren hat die Erforschung unbekannter Bestandteile des Centrosoms in Dictyostelium discoideum große Fortschritte gemacht. Eine zu diesem Zwecke von unserer Arbeitsgruppe durchgeführte Proteomstudie, führte zur Identifizierung weiterer, potentiell centrosomaler Kandidatenproteine. Der zweite Teil dieser Arbeit beschäftigt sich mit der Charakterisierung eines solchen Kandidatenproteins, dem CP75. Es konnte gezeigt werden, dass CP75 einen echten, centrosomalen Bestandteil darstellt, der mikrotubuli-unabhängig mit der Core Struktur des Zellorganells assoziiert ist. Weiterhin wurde deutlich, dass die Lokalisation am Centrosom in Abhängigkeit vom Zellzyklus erfolgt und CP75 vermutlich mit CP39, einem weiteren centrosomalen Core Protein, interagiert.
Nanoporous carbon materials are widely used in industry as adsorbents or catalyst supports, whilst becoming increasingly critical to the developing fields of energy storage / generation or separation technologies. In this thesis, the combined use of carbohydrate hydrothermal carbonisation (HTC) and templating strategies is demonstrated as an efficient route to nanostructured carbonaceous materials. HTC is an aqueous-phase, low-temperature (e.g. 130 – 200 °C) carbonisation, which proceeds via dehydration / poly-condensation of carbon precursors (e.g. carbohydrates and their derivatives), allowing facile access to highly functional carbonaceous materials. Whilst possessing utile, modifiable surface functional groups (e.g. -OH and -C=O-containing moieties), materials synthesised via HTC typically present limited accessible surface area or pore volume. Therefore, this thesis focuses on the development of fabrication routes to HTC materials which present enhanced textural properties and well-defined porosity. In the first discussed synthesis, a combined hard templating / HTC route was investigated using a range of sacrificial inorganic templates (e.g. mesoporous silica beads and macroporous alumina membranes (AAO)). Via pore impregnation of mesoporous silica beads with a biomass-derived carbon source (e.g. 2-furaldehyde) and subsequent HTC at 180 oC, an inorganic / carbonaceous hybrid material was produced. Removal of the template component by acid etching revealed the replication of the silica into mesoporous carbonaceous spheres (particle size ~ 5 μm), representing the inverse morphological structure of the original inorganic body. Surface analysis (e.g. FTIR) indicated a material decorated with hydrophilic (oxygenated) functional groups. Further thermal treatment at increasingly elevated temperatures (e.g. at 350, 550, 750 oC) under inert atmosphere allowed manipulation of functionalities from polar hydrophilic to increasingly non-polar / hydrophobic structural motifs (e.g. extension of the aromatic / pseudo-graphitic nature), thus demonstrating a process capable of simultaneous control of nanostructure and surface / bulk chemistry. As an extension of this approach, carbonaceous tubular nanostructures with controlled surface functionality were synthesised by the nanocasting of uniform, linear macropores of an AAO template (~ 200 nm). In this example, material porosity could be controlled, showing increasingly microporous tube wall features as post carbonisation temperature increased. Additionally, by taking advantage of modifiable surface groups, the introduction of useful polymeric moieties (i.e. grafting of thermoresponsive poly(N-isopropylacrylamide)) was also demonstrated, potentially enabling application of these interesting tubular structures in the fields of biotechnology (e.g. enzyme immobilization) and medicine (e.g. as drug micro-containers). Complimentary to these hard templating routes, a combined HTC / soft templating route for the direct synthesis of ordered porous carbonaceous materials was also developed. After selection of structural directing agents and optimisation of synthesis composition, the F127 triblock copolymer (i.e. ethylene oxide (EO)106 propylene oxide (PO)70 ethylene oxide (EO)106) / D-Fructose system was extensively studied. D-Fructose was found to be a useful carbon precursor as the HTC process could be performed at 130 oC, thus allowing access to stable micellular phase. Thermolytic template removal from the synthesised ordered copolymer / carbon composite yielded functional cuboctahedron single crystalline-like particles (~ 5 μm) with well ordered pore structure of a near perfect cubic Im3m symmetry. N2 sorption analysis revealed a predominantly microporous carbonaceous material (i.e. Type I isotherm, SBET = 257 m2g-1, 79 % microporosity) possessing a pore size of ca. 0.9 nm. The addition of a simple pore swelling additive (e.g. trimethylbenzene (TMB)) to this system was found to direct pore size into the mesopore size domain (i.e. Type IV isotherm, SBET = 116 m2g-1, 60 % mesoporosity) generating pore size of ca. 4 nm. It is proposed that in both cases as HTC proceeds to generate a polyfuran-like network, the organised block copolymer micellular phase is essentially “templated”, either via hydrogen bonding between hydrophilic poly(EO) moiety and the carbohydrate or via hydrophobic interaction between hydrophobic poly(PO) moiety and forming polyfuran-like network, whilst the additive TMB presumably interact with poly(PO) moieties, thus swelling the hydrophobic region expanding the micelle template size further into the mesopore range.
Poröse Sol-Gel-Materialien finden in vielen Bereichen Anwendung bzw. sind Gegenstand der aktuellen Forschung. Zu diesen Bereichen zählen sowohl klassische Anwendungen, wie z. B. die Verwendung als Katalysator, Molekularsieb oder Trockenmittel, als auch nichtklassische Anwendungen, wie z. B. der Einsatz als Kontrastmittel in der Magnet-Resonanz-Tomographie oder in Form von dünnen Zeolithfilmen als Isolatoren in Mikrochips. Auch für den Einsatz in der Photonik werden poröse Materialien in Betracht gezogen, wie die Entwicklung des Zeolith-Farbstoff-Lasers zeigt. Mikroporöse Zeolithe können generell über einfache Ionenaustauschreaktionen mit Lanthanoidionen in lumineszente Materialien umgewandelt werden. Neben der Erzeugung eines lumineszenten Materials, dessen Lumineszenzeigenschaften charakterisiert werden müssen, bietet die Nutzung von Lanthanoidionen die Möglichkeit diese Ionen als Sonde zur Charakterisierung der Ion-Wirt-Wechselwirkungen zu funktionalisieren, was z. B. in Bezug auf die Anwendung als Katalysator von großer Bedeutung ist. Dabei werden die einzigartigen Lumineszenzeigenschaften der Lanthanoidionen, in diesem Fall von Europium(III) und Terbium(III), genutzt. In dieser Arbeit wurden Lanthanoid-dotierte mikroporöse Zeolithe, mikroporös-mesoporöse Hybridmaterialien und mesoporöse Silikate hinsichtlich ihrer Lumineszenzeigenschaften und ihrer Wechselwirkung des Wirtsmaterials mit den Lanthanoidionen mittels zeitaufgelöster Lumineszenzspektroskopie untersucht. Zeitaufgelöste Emissionsspektren (TRES) liefern dabei sowohl Informationen in der Wellenlängen- als auch in der Zeitdomäne. Erstmalig wurden die TRES mittels einer umfangreichen Auswertemethodik behandelt. Neben der Anpassung des Abklingverhaltens mit einer diskreten Zahl von Exponentialfunktionen, wurden unterstützend auch Abklingzeitverteilungsanalysen durchgeführt. Zeitaufgelöste flächennormierte Emissionsspektren (TRANES), eine Erweiterung der normalen TRES, konnten erstmals zur Bestimmung der Zahl der emittierenden Lanthanoidspezies in porösen Materialien genutzt werden. Durch die Berechnung der Decayassoziierten Spektren (DAS) konnten den Lanthanoidspezies die entsprechenden Lumineszenzspektren zugeordnet werden. Zusätzlich konnte, speziell im Fall der Europium-Lumineszenz, durch Kombination von zeitlicher und spektraler Information das zeitabhängige Asymmetrieverhältnis R und die spektrale Evolution des 5D0-7F0-Übergangs mit der Zeit t untersucht und somit wesentliche Informationen über die Verteilung der Europiumionen im Wirtsmaterial erhalten werden. Über die Abklingzeit und das Asymmetrieverhältnis R konnten Rückschlüsse auf die Zahl der OH-Oszillatoren in der ersten Koordinationssphäre und die Symmetrie der Koordinationsumgebung gezogen werden. Für die mikroporösen und mikroporös-mesoporösen Materialien wurden verschiedene Lanthanoidspezies, im Regelfall zwei, gefunden, welche entsprechend der beschriebenen Methoden charakterisiert wurden. Diese Lanthanoidspezies konnten Positionen in den Materialien zugeordnet werden, die sich im tief Inneren des Porensystems oder auf bzw. nahe der äußeren Oberfläche oder in den Mesoporen befinden. Erstere Spezies ist aufgrund ihrer Position im Material gut vor Feuchtigkeitseinflüssen geschützt, was sich deutlich in entsprechend langen Lumineszenzabklingzeiten äußert. Zusätzlich ist diese Europiumspezies durch unsymmetrische Koordinationsumgebung charakterisiert, was auf einen signifikanten Anteil an Koordination der Lanthanoidionen durch die Sauerstoffatome im Wirtsgitter zurückzuführen ist. Ionen, die sich nahe oder auf der äußeren Oberfläche befinden, sind dagegen für Feuchtigkeit zugänglicher, was in kürzeren Lumineszenzabklingzeiten und einer symmetrischeren Koordinationsumgebung resultiert. Der Anteil von Wassermolekülen in der ersten Koordinationssphäre ist hier deutlich größer, als bei den Ionen, die sich tiefer im Porensystem befinden und entspricht in vielen Fällen der Koordinationszahl eines vollständig hydratisierten Lanthanoidions. Auch der Einfluss von Oberflächenmodifikationen auf die Speziesverteilung und das Verhalten der Materialien gegenüber Feuchtigkeit wurde untersucht. Dabei gelang es den Einfluss der Feuchtigkeit auf die Lumineszenzeigenschaften und die Speziesverteilung durch die Oberflächenmodifikation zu verringern und die Lumineszenzeigenschaften teilweise zu konservieren. Im Fall der mesoporösen Silikamonolithe wurde auch eine heterogene Verteilung der Lanthanoidionen im Porensystem gefunden. Hier wechselwirkt ein Teil der Ionen mit der Porenwand, während sich die restlichen Ionen in der wäßrigen Phase innerhalb des Porensystems aufhalten. Das Aufbringen von Oberflächenmodifikationen führte zu einer Wechselwirkung der Ionen mit diesen Oberflächenmodifikationen, was sich in Abhängigkeit von der Oberflächenbeladung in den enstprechenden Lumineszenzeigenschaften niederschlug.
Magnetische Nanopartikel bieten ein großes Potential, da sie einerseits die Eigenschaften ihrer Bulk-Materialien besitzen und anderseits, auf Grund ihrer Größe, über komplett unterschiedliche magnetische Eigenschaften verfügen können; Superparamagnetismus ist eine dieser Eigenschaften. Die meisten etablierten Anwendungen magnetischer Nanopartikel basieren heutzutage auf Eisenoxiden. Diese bieten gute magnetische Eigenschaften, sind chemisch relativ stabil, ungiftig und lassen sich auf vielen Synthesewegen relativ einfach herstellen. Die magnetischen Eigenschaften der Eisenoxide sind materialabhängig aber begrenzt, weshalb nach anderen Verbindungen mit besseren Eigenschaften gesucht werden muss. Eisencarbid (Fe3C) kann eine dieser Verbindungen sein. Dieses besitzt vergleichbare positive Eigenschaften wie Eisenoxid, jedoch viel bessere magnetische Eigenschaften, speziell eine höhere Sättigungsmagnetisierung. Bis jetzt wurde Fe3C hauptsächlich in Gasphasenabscheidungsprozessen synthetisiert oder als Nebenprodukt bei der Synthese von Kohlenstoffstrukturen gefunden. Eine Methode, mit der gezielt Fe3C-Nanopartikel und andere Metallcarbide synthetisiert werden können, ist die „Harnstoff-Glas-Route“. Neben den Metallcarbiden können mit dieser Methode auch die entsprechenden Metallnitride synthetisiert werden, was die breite Anwendbarkeit der Methode unterstreicht. Die „Harnstoff-Glas-Route“ ist eine Kombination eines Sol-Gel-Prozesses mit einer anschließenden carbothermalen Reduktion/Nitridierung bei höheren Temperaturen. Sie bietet den Vorteil einer einfachen und schnellen Synthese verschiedener Metallcarbide/nitride. Der Schwerpunkt in dieser Arbeit lag auf der Synthese von Eisencarbiden/nitriden, aber auch Nickel und Kobalt wurden betrachtet. Durch die Variation der Syntheseparameter konnten verschiedene Eisencarbid/nitrid Nanostrukturen synthetisiert werden. Fe3C-Nanopartikel im Größenbereich von d = 5 – 10 nm konnten, durch die Verwendung von Eisenchlorid, hergestellt werden. Die Nanopartikel weisen durch ihre geringe Größe superparamagnetische Eigenschaften auf und besitzen, im Vergleich zu Eisenoxid Nanopartikeln im gleichen Größenbereich, eine höhere Sättigungsmagnetisierung. Diese konnten in fortführenden Experimenten erfolgreich in ionischen Flüssigkeiten und durch ein Polymer-Coating, im wässrigen Medium, dispergiert werden. Desweiteren wurde durch ein Templatieren mit kolloidalem Silika eine mesoporöse Fe3C-Nanostruktur hergestellt. Diese konnte erfolgreich in der katalytischen Spaltung von Ammoniak getestet werden. Mit der Verwendung von Eisenacetylacetonat konnten neben Fe3C-Nanopartikeln, nur durch Variation der Reaktionsparameter, auch Fe7C3- und Fe3N-Nanopartikel synthetisiert werden. Speziell für die Fe3C-Nanopartikel konnte die Sättigungsmagnetisierung, im Vergleich zu den mit Eisenchlorid synthetisierten Nanopartikeln, nochmals erhöht werden. Versuche mit Nickelacetat führten zu Nickelnitrid (Ni3N) Nanokristallen. Eine zusätzliche metallische Nickelphase führte zu einer Selbstorganisation der Partikel in Scheiben-ähnliche Überstrukturen. Mittels Kobaltacetat konnten, in Sphären aggregierte, metallische Kobalt Nanopartikel synthetisiert werden. Kobaltcarbid/nitrid war mit den gegebenen Syntheseparametern nicht zugänglich.
Von der Natur geschaffene Polymere faszinieren Polymerforscher durch ihre spezielle auf eine bestimmte Aufgabe ausgerichtete Funktionalität. Diese ergibt sich aus ihrer Bausteinabfolge uber die Ausbildung von Uberstrukturen. Dazu zählen zum Beispiel Proteine (Eiweiße), aus deren Gestalt sich wichtige Eigenschaften ergeben. Diese Struktureigenschaftsbeziehung gilt ebenso für funktionelle synthetische Makromoleküle. Demzufolge kann die Kontrolle der Monomersequenz in Polymeren bedeutend für die resultierende Form des Polymermoleküls sein. Obwohl die Synthese von synthetischen Polymeren mit der Komplexität und der Größe von Proteinen in absehbarer Zeit wahrscheinlich nicht gelingen wird, können wir von der Natur lernen, um neuartige Polymermaterialien mit definierten Strukturen (Sequenzen) zu synthetisieren. Deshalb ist die Entwicklung neuer und besserer Techniken zur Strukturkontrolle von großem Interesse für die Synthese von Makromolekülen, die perfekt auf ihre Funktion zugeschnitten sind. Im Gegensatz zu der Anzahl fortgeschrittener Synthesestrategien zum Design aus- gefallener Polymerarchitekturen – wie zum Beispiel Sterne oder baumartige Polymere (Dendrimere) – gibt es vergleichsweise wenig Ansätze zur echten Sequenzkontrolle in synthetischen Polymeren. Diese Arbeit stellt zwei unterschiedliche Techniken vor, mit denen die Monomersequenz innerhalb eines Polymers kontrolliert werden kann. Gerade bei den großtechnisch bedeutsamen radikalischen Polymerisationen ist die Sequenzkontrolle schwierig, weil die chemischen Bausteine (Monomere) sehr reaktiv sind. Im ersten Teil dieser Arbeit werden die Eigenschaften zweier Monomere (Styrol und N-substituiertes Maleinimid) geschickt ausgenutzt, um in eine Styrolkette definierte und lokal scharf abgegrenzte Funktionssequenzen einzubauen. Uber eine kontrollierte radikalische Polymerisationsmethode (ATRP) wurden in einer Ein-Topf-Synthese über das N-substituierte Maleinimid chemische Funktionen an einer beliebigen Stelle der Polystyrolkette eingebaut. Es gelang ebenfalls, vier unterschiedliche Funktionen in einer vorgegebenen Sequenz in die Polymerkette einzubauen. Diese Technik wurde an zwanzig verschiedenen N-substituierten Maleinimiden getestet, die meisten konnten erfolgreich in die Polymerkette integriert werden. In dem zweiten in dieser Arbeit vorgestellten Ansatz zur Sequenzkontrolle, wurde der schrittweise Aufbau eines Oligomers aus hydrophoben und hydrophilen Segmenten (ω-Alkin-Carbonsäure bzw. α-Amin-ω-Azid-Oligoethylenglycol) an einem löslichen Polymerträger durchgeführt. Das Oligomer konnte durch die geschickte Auswahl der Verknüpfungsreaktionen ohne Schutzgruppenstrategie synthetisiert werden. Der lösliche Polymerträger aus Polystyrol wurde mittels ATRP selbst synthetisiert. Dazu wurde ein Startreagenz (Initiator) entwickelt, das in der Mitte einen säurelabilen Linker, auf der einen Seite die initiierende Einheit und auf der anderen die Ankergruppe für die Anbindung des ersten Segments trägt. Der lösliche Polymerträger ermöglichte einerseits die schrittweise Synthese in Lösung. Andererseits konnten überschüssige Reagenzien und Nebenprodukte zwischen den Reaktionsschritten durch Fällung in einem Nicht-Lösungsmittel einfach abgetrennt werden. Der Linker ermöglichte die Abtrennung des Oligomers aus jeweils drei hydrophoben und hydrophilen Einheiten nach der Synthese.
The inspiral and merger of two black holes is among the most exciting and extreme events in our universe. Being one of the loudest sources of gravitational waves, they provide a unique dynamical probe of strong-field general relativity and a fertile ground for the observation of fundamental physics. While the detection of gravitational waves alone will allow us to observe our universe through an entirely new window, combining the information obtained from both gravitational wave and electro-magnetic observations will allow us to gain even greater insight in some of the most exciting astrophysical phenomena. In addition, binary black-hole mergers serve as an intriguing tool to study the geometry of space-time itself. In this dissertation we study the merger process of binary black-holes in a variety of conditions. Our results show that asymmetries in the curvature distribution on the common apparent horizon are correlated to the linear momentum acquired by the merger remnant. We propose useful tools for the analysis of black holes in the dynamical and isolated horizon frameworks and shed light on how the final merger of apparent horizons proceeds after a common horizon has already formed. We connect mathematical theorems with data obtained from numerical simulations and provide a first glimpse on the behavior of these surfaces in situations not accessible to analytical tools. We study electro-magnetic counterparts of super-massive binary black-hole mergers with fully 3D general relativistic simulations of binary black-holes immersed both in a uniform magnetic field in vacuum and in a tenuous plasma. We find that while a direct detection of merger signatures with current electro-magnetic telescopes is unlikely, secondary emission, either by altering the accretion rate of the circumbinary disk or by synchrotron radiation from accelerated charges, may be detectable. We propose a novel approach to measure the electro-magnetic radiation in these simulations and find a non-collimated emission that dominates over the collimated one appearing in the form of dual jets associated with each of the black holes. Finally, we provide an optimized gravitational wave detection pipeline using phenomenological waveforms for signals from compact binary coalescence and show that by including spin effects in the waveform templates, the detection efficiency is drastically improved as well as the bias on recovered source parameters reduced. On the whole, this disseration provides evidence that a multi-messenger approach to binary black-hole merger observations provides an exciting prospect to understand these sources and, ultimately, our universe.
Conventional energy sources are diminishing and non-renewable, take million years to form and cause environmental degradation. In the 21st century, we have to aim at achieving sustainable, environmentally friendly and cheap energy supply by employing renewable energy technologies associated with portable energy storage devices. Lithium-ion batteries can repeatedly generate clean energy from stored materials and convert reversely electric into chemical energy. The performance of lithium-ion batteries depends intimately on the properties of their materials. Presently used battery electrodes are expensive to be produced; they offer limited energy storage possibility and are unsafe to be used in larger dimensions restraining the diversity of application, especially in hybrid electric vehicles (HEVs) and electric vehicles (EVs). This thesis presents a major progress in the development of LiFePO4 as a cathode material for lithium-ion batteries. Using simple procedure, a completely novel morphology has been synthesized (mesocrystals of LiFePO4) and excellent electrochemical behavior was recorded (nanostructured LiFePO4). The newly developed reactions for synthesis of LiFePO4 are single-step processes and are taking place in an autoclave at significantly lower temperature (200 deg. C) compared to the conventional solid-state method (multi-step and up to 800 deg. C). The use of inexpensive environmentally benign precursors offers a green manufacturing approach for a large scale production. These newly developed experimental procedures can also be extended to other phospho-olivine materials, such as LiCoPO4 and LiMnPO4. The material with the best electrochemical behavior (nanostructured LiFePO4 with carbon coating) was able to delive a stable 94% of the theoretically known capacity.
The transcriptional regulation of the cellular mechanisms involves many different components and different levels of control which together contribute to fine tune the response of cells to different environmental stimuli. In some responses, diverse signaling pathways can be controlled simultaneously. One of the most important cellular processes that seem to possess multiple levels of regulation is photosynthesis. A model organism for studying photosynthesis-related processes is the unicellular green algae Chlamydomonas reinhardtii, due to advantages related to culturing, genetic manipulation and availability of genome sequence. In the present study, we were interested in understanding the regulatory mechanisms underlying photosynthesis-related processes. To achieve this goal different molecular approaches were followed. In order to indentify protein transcriptional regulators we optimized a method for isolation of nuclei and performed nuclear proteome analysis using shotgun proteomics. This analysis permitted us to improve the genome annotation previously published and to discover conserved and enriched protein motifs among the nuclear proteins. In another approach, a quantitative RT-PCR platform was established for the analysis of gene expression of predicted transcription factor (TF) and other transcriptional regulator (TR) coding genes by transcript profiling. The gene expression profiles for more than one hundred genes were monitored in time series experiments under conditions of changes in light intensity (200 µE m-2 s-1 to 700 µE m-2 s-1), and changes in concentration of carbon dioxide (5% CO2 to 0.04% CO2). The results indicate that many TF and TR genes are regulated in both environmental conditions and groups of co-regulated genes were found. Our findings also suggest that some genes can be common intermediates of light and carbon responsive regulatory pathways. These approaches together gave us new insights about the regulation of photosynthesis and revealed new candidate regulatory genes, helping to decipher the gene regulatory networks in Chlamydomonas. Further experimental studies are necessary to clarify the function of the candidate regulatory genes and to elucidate how cells coordinately regulate the assimilation of carbon and light responses.
Ein neuentwickeltes azobenzenhaltiges Material, das auf einem supramolekularen Konzept basiert, wird bezüglich seiner Strukturbildung während einer holografischen Belichtung bei 488 nm untersucht. Im Mittelpunkt stehen dabei eindimensionale, sinusförmige Reliefs mit Periodizitäten kleiner 500 nm. Es wird gezeigt, wie der Grad der Vernetzung der photosensitiven Schicht die Strukturbildung in diesem Größenbereich beeinflusst. Zur Maximierung der Strukturtiefe werden gezielt Prozessparameter der Belichtung sowie Materialparameter variiert. Unter Standardbedingungen und moderaten Belichtungsintensitäten von ca. 200 mW/cm² bilden sich innerhalb weniger Minuten bei einer Periode von 400 nm Strukturtiefen von bis zu 80nm aus. Durch die Beeinflussung von Materialparametern, wie Oberflächenspannung und Viskosität, wird die maximale Strukturtiefe auf 160nm verdoppelt. Durch Mehrfachbelichtungen wird auch die Bildung von zweidimensionalen Gittern untersucht. Die Originalstrukturen werden in einem Abformverfahren kopiert und in Schichten von unter UV-Licht aushärtenden Polymeren übertragen. Durch das Abformen kommt es zu einer geringfügigen Verschlechterung der Oberflächenqualität sowie Abnahme der Strukturtiefe. Dieser Verlust wird durch eine Verringerung der Prozesstemperatur verringert. Mithilfe kopierter Oberflächengitter werden organische Distributed Feedback-(DFB)-Laser zweiter Ordnung hergestellt, um den Einfluss von Gitterparametern auf die Emissionseigenschaften dieser Laser zu untersuchen. Dazu erfolgt zunächst die Charakterisierung der optischen Verstärkungseigenschaften ausgewählter organischer Emittermaterialien mittels der Variablen Strichlängenmethode. Das mit dem Laserfarbstoff Pyrromthen567 (PM567) dotierte Polystyrol (PS) zeigt dabei trotz konzentrationsbedingter geringer Absorption eine vergleichsweise geringe Gewinnschwelle von 50µJ/cm² bei ca. 575 nm. Das aktive Gast-Wirt-System der konjugierten Polymere MEH-PPV und F8BT* weist eine hohe Absorption und eine kleine Gewinnschwelle von 2,5 µJ/cm² bei 630 nm auf. Dieses Verhalten spiegelt sich auch in den Emissionseigenschaften der damit hergestellten DFB-Laser wieder. Die Dicke der aktiven Schichten liegen im Bereich hunderter Nanometer und wird so eingestellt, dass sich nur die transversalen Grundmoden im Wellenleiter ausbreiten können. Die Gitterperiode sind so gewählt, dass ein Lichtmode im Verstärkungsbereich des Emittermaterials liegt. Die Emissionslinien der Laser sind mit FWHM-Werten von bis zu 0,3 nm spektral sehr schmalbandig und weisen auf eine sehr gute Gitterqualität hin. Die Untersuchungen liefern minimale Laserschwellen und maximale differentielle Effizienzen von 4,0µJ/cm² und 8,4% für MEH-PPV in F8BT* (bei ca. 640nm) sowie 80 µJ/cm² und 0,9% für PM567 in PS (bei ca. 575 nm). Die Vergrößerung der Strukturtiefe von 40nm auf 80nm in mit MEH-PPV dotierten F8BT*-Lasern zu einem deutlichen Anstieg der ausgekoppelten Energie sowie der differentiellen Effizienz und einem geringen Absinken der Laserschwelle. Dies ist ein Resultat der erhöhten Kopplung von Lasermode und Gitter. Die Emission von DFB-Lasern mit zweidimensionalen Oberflächengittern zeigen eine Verringerung der Divergenz aber kein Einfluss auf die Laserschwelle. Abschließend erfolgt eine Vermessung der Photostabilität von DFB-Lasern unter verschiedenen Bedingungen. Das Einbringen eines konjugierten Polymers in eine aktive Matrix sowie der Betrieb in einer Stickstoffatmosphäre führen dabei zu einer Erhöhung der Lebensdauer auf über eine Million Pulse. Durch die Kombination von Oberflächengittern in PDMS-Filmen mit elektroaktiven Substraten wird eine elektrisch steuerbare Deformation des Beugungsgitters erreicht und auf einen DFB-Laser übertragen. Die spannungsinduzierte Verformung wird zunächst in Beugungsexperimenten charakterisiert und ein optimaler Arbeitspunkt bestimmt. Mit den beiden Elastomeren SEBS12 und VHB4910 werden in den Gittern maximale Periodenänderungen von 1,3% bzw. 3,4% bei einer Steuerspannung von 2 kV erreicht. Der Unterschied resultiert aus den verschiedenen Elastizitätsmoduln der Materialien. Übertragen auf DFB-Laser resultiert eine Variation der Gitterperiode senkrecht zu den Gitterlinien in einer kontinuierlichen Verschiebung der Emissionswellenlänge. Mit einem Spannungssignal von 3,25 kV wird die schmalbandige Emission eines elastischen DFB-Lasers kontinuierlich um fast 50nm von 604 nm zu 557 nm hin verschoben. Aus dem Deformationsverhalten sowohl der reinen Beugungsgitter als auch der Laser werden Rückschlüsse auf die Elastizität der verwendeten Materialien gezogen und erlauben Verbesserungen der Bauteile.
AM symbiosis has a positive influence on plant P-nutrition and growth, but little is known about the molecular mechanism of the symbiosis adaptation to different phosphate conditions. The recently described induction of several pri-miR399 transcripts in mycorrhizal shoots and subsequent accumulation of mature miR399 in mycorrhizal roots indicates that local PHO2 expression must be controlled during symbiosis, presumably in order to sustain AM symbiosis development, in spite of locally increased Pi-concentration. A reverse genetic approach used in this study demonstrated that PHO2 and thus the PHR1-miR399-PHO2 signaling pathway, is involved in certain stages of progressive root colonization. In addition, a transcriptomic approach using a split-root system provided a comprehensive insight into the systemic transcriptional changes in mycorrhizal roots and shoots of M. truncatula in response to high phosphate conditions. With regard to the transcriptional responses of the root system, the results indicate that, although the colonization is drastically reduced, AM symbiosis is still functional at high Pi concentrations and might still be beneficial to the plant. Additionally, the data suggest that a specific root-borne mycorrhizal signal systemically induces protein synthesis, amino acid metabolism and photosynthesis at low Pi conditions, which is abolished at high Pi conditions. MiRNAs, such as miR399, are involved in long-distance signaling and are therefore potential systemic signals involved in AM symbiosis. A deep-sequencing approach identified 243 novel miRNAs in the root tissue of M. truncatula. Read-count analysis, qRT-PCR measurements and in situ hybridizations clearly indicated a regulation of miR5229a/b, miR5204, miR160f*, miR160c, miR169 and miR169d*/l*/m*/e.2* during arbuscular mycorrhizal symbiosis. Moreover, miR5204* represses a GRAS TF, which is specifically transcribed in mycorrhizal roots. Since miR5204* is induced by high Pi it might represent a further Pi status-mediating signal beside miR399. This study provides additional evidence that MtNsp2, a key regulator of symbiosis-signaling, is regulated and presumably spatially restricted by miR171h cleavage. In summary, a repression of mycorrhizal root colonization at high phosphate status is most likely due to a repression of the phosphate starvation responses and the loss of beneficial responses in mycorrhizal shoots. These findings provide a new basis for investigating the regulatory network leading to cellular reprogramming during interaction between plants, arbuscular mycorrhizal fungi and different phosphate conditions.
Das Hauptziel dieser Arbeit ist das Verständnis der molekularen Kristallisation, sowohl mit als auch ohne polymere Additive, als einen mehrstufigen Prozess. Dieser beinhaltet eine transiente flüssig-flüssig Phasentrennung, die Nukleation von Nanokristallen in der dichten flüssigen Precursor-Phase so wie eine anschließende nanokristalline Selbstorganisation. Die Arbeit beginnt mit Untersuchungen an einem quaternären Modelsystem bestehend aus DL-Glutamat (Glu), Polyethylenimin (PEI), Wasser und Ethanol. Das Phasendiagramm dieses quaternären Systems wird durch Variation der Glu/PEI w/w und Wasser/EtOH v/v Verhältnisse bestimmt, wobei Präzpitat aus polymerinduzierten flüssigen Precursor, Koazervate oder homogene Mischungen erhalten werden Das thermodynamisch stabile Koazervat kann als Referenz für das Verständnis von flüssigen Precursorn angesehen werden, welche in der Natur metastabil und transient sind. Der mehrstufige Mechanismus der Glu-Präzipitation mit PEI als Additiv wird dann mittels Neutronen Kleinwinkelstreuung untersucht. Dies zeigt, dass die ursprünglich gebildeten flüssigen Precursor noch vor der Nukleation von Nanokristallen einen Wechsel von Wachstum und Koaleszenz durchlaufen. Die Ergebnisse aus optischer- und Eletronenmikroskopie zeigen, dass sowohl die flüssigen Precursor Superstrukturen ausbilden als auch, dass die Nukleation von Nanoplättchen in jedem einzelnen Precursor Tropfen von statten geht. Dies geschieht noch bevor sich die Nanoplättchen selbst in einer radialen Orientierung ausrichten. Diese Studie liefert die Kinetik der Präzipitation von organischen Stoffen in Gegenwart von polymeren Additiven. Eine ähnliche Vorgehensweise wie für die Herstellung von Mikrokügelchen kann für die Darstellung von gemusterten Filmen angewandt werden. Die homogene Nukleation von Nanopartikeln (NPs) findet während der Verdampfung einer quarternären DL-Lys·HCl-Polyacrylsäure-Wasser-Ethanol Dispersion auf einer hydrophilen Oberfläche statt. Die darauffolgende vollständige Verdampfung löst die Mesokristallisation eines kontinuierlichen sphärolithischen dünnen Films aus, welcher sich wiederum in einen mesokristallinen dünnen Film umwandelt. Mesokristalline Filme mit 4 Hierarchiestufen bzw. auch periodische Filme werden durch die Verdampfung der Mikrokügelchen-Dispersion erhalten. Die Ergebnisse zeigen, dass die Verdampfung eine einfache aber effektive Methode zur Herstellung von verschieden gemusterten hierarchischen Filmen darstellt. Nicht-klassische Kristallisation wird auch in der Abwesenheit von polymeren Additiven beobachtet. Wir verfolgen mittels Rasterkraftmikroskop (AFM) die Nukleation und das Wachstum einer neuen molekularen Schicht auf wachsenden DL-Glu·H2O Kristallen aus übersättigter Mutterlauge. Die Bildung einer neuen molekularen Schicht verläuft durch die Anlagerung von amorphen Nanopartikeln. Das Schrumpfen der NPs zusammen mit der strukturellen Änderung von dreidimensionalen NPs zu 2D Schichten wird während dieses Relaxationsprozesses beobachtet. Schließlich kommt es zu der Ausbildung einer neuen molekularen Schicht. Die Bildung einer molekularen Schicht durch die Anlagerung von Nanopartikeln aus der Lösung und die darauffolgende Relaxation liefert ein abweichendes Bild zu der bisher gängigen klassischen Theorie des Kristallwachstums.
Actin-based directional motility is important for embryonic development, wound healing, immune responses, and development of tissues. Actin and myosin are essential players in this process that can be subdivided into protrusion, adhesion, and traction. Protrusion is the forward movement of the membrane at the leading edge of the cell. Adhesion is required to enable movement along a substrate, and traction finally leads to the forward movement of the entire cell body, including its organelles. While actin polymerization is the main driving force in cell protrusions, myosin motors lead to the contraction of the cell body. The goal of this work was to study the regulatory mechanisms of the motile machinery by selecting a representative key player for each stage of the signaling process: the regulation of Arp2/3 activity by WASP (actin system), the role of cGMP in myosin II assembly (myosin system), and the influence of phosphoinositide signaling (upstream receptor pathway). The model organism chosen for this work was the social ameba Dictyostelium discoideum, due to the well-established knowledge of its cytoskeletal machinery, the easy handling, and the high motility of its vegetative and starvation developed cells. First, I focused on the dynamics of the actin cytoskeleton by modulating the activity of one of its key players, the Arp2/3 complex. This was achieved using the carbazole derivative Wiskostatin, an inhibitor of the Arp2/3 activator WASP. Cells treated with Wiskostatin adopted a round shape, with no of few pseudopodia. With the help of a microfluidic cell squeezer device, I could show that Wiskostatin treated cells display a reduced mechanical stability, comparable to cells treated with the actin disrupting agent Latrunculin A. Furthermore, the WASP inhibited cells adhere stronger to a surface and show a reduced motility and chemotactic performance. However, the overall F-actin content in the cells was not changed. Confocal microscopy and TIRF microscopy imaging showed that the cells maintained an intact actin cortex. Localized dynamic patches of increased actin polymerization were observed that, however, did not lead to membrane deformation. This indicated that the mechanisms of actin-driven force generation were impaired in Wiskostatin treated cells. It is concluded that in these cells, an altered architecture of the cortical network leads to a reduced overall stiffness of the cell, which is insufficient to support the force generation required for membrane deformation and pseudopod formation. Second, the role of cGMP in myosin II dynamics was investigated. Cyclic GMP is known to regulate the association of myosin II with the cytoskeleton. In Dictyostelium, intracellular cGMP levels increase when cells are exposed to chemoattractants, but also in response to osmotic stress. To study the influence of cyclic GMP on actin and myosin II dynamics, I used the laser-induced photoactivation of a DMACM-caged-Br-cGMP to locally release cGMP inside the cell. My results show that cGMP directly activates the myosin II machinery, but is also able to induce an actin response independently of cAMP receptor activation and signaling. The actin response was observed in both vegetative and developed cells. Possible explanations include cGMP-induced actin polymerization through VASP (vasodilator-stimulated phosphoprotein) or through binding of cGMP to cyclic nucleotide-dependent kinases. Finally, I investigated the role of phosphoinositide signaling using the Polyphosphoinositide-Binding Peptide (PBP10) that binds preferentially to PIP2. Phosphoinositides can recruit actin-binding proteins to defined subcellular sites and alter their activity. Neutrophils, as well as developed Dictyostelium cells produce PIP3 in the plasma membrane at their leading edge in response to an external chemotactic gradient. Although not essential for chemotaxis, phosphoinositides are proposed to act as an internal compass in the cell. When treated with the peptide PBP10, cells became round, with fewer or no pseudopods. PH-CRAC translocation to the membrane still occurs, even at low cAMP stimuli, but cell motility (random and directional) was reduced. My data revealed that the decrease in the pool of available PIP2 in the cell is sufficient to impair cell motility, but enough PIP2 remains so that PIP3 is formed in response to chemoattractant stimuli. My data thus highlights how sensitive cell motility and morphology are to changes in the phosphoinositide signaling. In summary, I have analyzed representative regulatory mechanisms that govern key parts of the motile machinery and characterized their impact on cellular properties including mechanical stability, adhesion and chemotaxis.
Cognitive psychology is traditionally interested in the interaction of perception, cognition, and behavioral control. Investigating eye movements in reading constitutes a field of research in which the processes and interactions of these subsystems can be studied in a well-defined environment. Thereby, the following questions are pursued: How much information is visually perceived during a fixation, how is processing achieved and temporally coordinated from visual letter encoding to final sentence comprehension, and how do such processes reflect on behavior such as the control of the eyes’ movements during reading. Various theoretical models have been proposed to account for the specific eye-movement behavior in reading (for a review see Reichle, Rayner, & Pollatsek, 2003). Some models are based on the idea of shifting attention serially from one word to the next within the sentence whereas others propose distributed attention allocating processing resources to more than one word at a time. As attention is assumed to drive word recognition processes one major difference between these models is that word processing must either occur in strict serial order, or that word processing is achieved in parallel. In spite of this crucial difference in the time course of word processing, both model classes perform well on explaining many of the benchmark effects in reading. In fact, there seems to be not much empirical evidence that challenges the models to a point at which their basic assumptions could be falsified. One issue often perceived as being decisive in the debate on serial and parallel word processing is how not-yet-fixated words to the right of fixation affect eye movements. Specifically, evidence is discussed as to what spatial extent such parafoveal words are previewed and how this influences current and subsequent word processing. Four experiments investigated parafoveal processing close to the spatial limits of the perceptual span. The present work aims to go beyond mere existence proofs of previewing words at such spatial distances. Introducing a manipulation that dissociates the sources of long-range preview effects, benefits and costs of parafoveal processing can be investigated in a single analysis and the differing impact is tracked across a three-word target region. In addition, the same manipulation evaluates the role of oculomotor error as the cause of non-local distributed effects. In this respect, the results contribute to a better understanding of the time course of word processing inside the perceptual span and attention allocation during reading.
Answer Set Programming (ASP) is an emerging paradigm for declarative programming, in which a computational problem is specified by a logic program such that particular models, called answer sets, match solutions. ASP faces a growing range of applications, demanding for high-performance tools able to solve complex problems. ASP integrates ideas from a variety of neighboring fields. In particular, automated techniques to search for answer sets are inspired by Boolean Satisfiability (SAT) solving approaches. While the latter have firm proof-theoretic foundations, ASP lacks formal frameworks for characterizing and comparing solving methods. Furthermore, sophisticated search patterns of modern SAT solvers, successfully applied in areas like, e.g., model checking and verification, are not yet established in ASP solving. We address these deficiencies by, for one, providing proof-theoretic frameworks that allow for characterizing, comparing, and analyzing approaches to answer set computation. For another, we devise modern ASP solving algorithms that integrate and extend state-of-the-art techniques for Boolean constraint solving. We thus contribute to the understanding of existing ASP solving approaches and their interconnections as well as to their enhancement by incorporating sophisticated search patterns. The central idea of our approach is to identify atomic as well as composite constituents of a propositional logic program with Boolean variables. This enables us to describe fundamental inference steps, and to selectively combine them in proof-theoretic characterizations of various ASP solving methods. In particular, we show that different concepts of case analyses applied by existing ASP solvers implicate mutual exponential separations regarding their best-case complexities. We also develop a generic proof-theoretic framework amenable to language extensions, and we point out that exponential separations can likewise be obtained due to case analyses on them. We further exploit fundamental inference steps to derive Boolean constraints characterizing answer sets. They enable the conception of ASP solving algorithms including search patterns of modern SAT solvers, while also allowing for direct technology transfers between the areas of ASP and SAT solving. Beyond the search for one answer set of a logic program, we address the enumeration of answer sets and their projections to a subvocabulary, respectively. The algorithms we develop enable repetition-free enumeration in polynomial space without being intrusive, i.e., they do not necessitate any modifications of computations before an answer set is found. Our approach to ASP solving is implemented in clasp, a state-of-the-art Boolean constraint solver that has successfully participated in recent solver competitions. Although we do here not address the implementation techniques of clasp or all of its features, we present the principles of its success in the context of ASP solving.
Die vorliegende Arbeit beschäftigt sich mit der Fragestellung, ob die Frühgeburtlichkeit eine Auswirkung auf den Spracherwerb im ersten Lebensjahr hat. Insbesondere wurde der Frage nachgegangen, ob sich die Verarbeitung der rhythmisch-prosodischen Eigenschaften von Sprache im ersten Lebensjahr und deren weitere Ausnutzung für die Entwicklung des Lexikons bei sehr untergewichtigen Deutsch lernenden Frühgeborenen im Vergleich zu Reifgeborenen unterscheidet. Die besondere Spracherwerbssituation Frühgeborener liefert weitere Erkenntnisse bezüglich der Frage, inwieweit der frühe Spracherwerb durch prädeterminierte reifungsbedingte Mechanismen und Abläufe bestimmt wird und inwieweit dessen Verlauf und die relevanten Erwerbsmechanismen durch individuelle erfahrungsabhängige Faktoren beeinflusst werden. Damit liefern die Ergebnisse auch einen weiteren Beitrag zur Nature-Nurture-Diskussion.
The modeling and evaluation calculus FMC-QE, the Fundamental Modeling Concepts for Quanti-tative Evaluation [1], extends the Fundamental Modeling Concepts (FMC) for performance modeling and prediction. In this new methodology, the hierarchical service requests are in the main focus, because they are the origin of every service provisioning process. Similar to physics, these service requests are a tuple of value and unit, which enables hierarchical service request transformations at the hierarchical borders and therefore the hierarchical modeling. Through reducing the model complexity of the models by decomposing the system in different hierarchical views, the distinction between operational and control states and the calculation of the performance values on the assumption of the steady state, FMC-QE has a scalable applica-bility on complex systems. According to FMC, the system is modeled in a 3-dimensional hierarchical representation space, where system performance parameters are described in three arbitrarily fine-grained hierarchi-cal bipartite diagrams. The hierarchical service request structures are modeled in Entity Relationship Diagrams. The static server structures, divided into logical and real servers, are de-scribed as Block Diagrams. The dynamic behavior and the control structures are specified as Petri Nets, more precisely Colored Time Augmented Petri Nets. From the structures and pa-rameters of the performance model, a hierarchical set of equations is derived. The calculation of the performance values is done on the assumption of stationary processes and is based on fundamental laws of the performance analysis: Little's Law and the Forced Traffic Flow Law. Little's Law is used within the different hierarchical levels (horizontal) and the Forced Traffic Flow Law is the key to the dependencies among the hierarchical levels (vertical). This calculation is suitable for complex models and allows a fast (re-)calculation of different performance scenarios in order to support development and configuration decisions. Within the Research Group Zorn at the Hasso Plattner Institute, the work is embedded in a broader research in the development of FMC-QE. While this work is concentrated on the theoretical background, description and definition of the methodology as well as the extension and validation of the applicability, other topics are in the development of an FMC-QE modeling and evaluation tool and the usage of FMC-QE in the design of an adaptive transport layer in order to fulfill Quality of Service and Service Level Agreements in volatile service based environments. This thesis contains a state-of-the-art, the description of FMC-QE as well as extensions of FMC-QE in representative general models and case studies. In the state-of-the-art part of the thesis in chapter 2, an overview on existing Queueing Theory and Time Augmented Petri Net models and other quantitative modeling and evaluation languages and methodologies is given. Also other hierarchical quantitative modeling frameworks will be considered. The description of FMC-QE in chapter 3 consists of a summary of the foundations of FMC-QE, basic definitions, the graphical notations, the FMC-QE Calculus and the modeling of open queueing networks as an introductory example. The extensions of FMC-QE in chapter 4 consist of the integration of the summation method in order to support the handling of closed networks and the modeling of multiclass and semaphore scenarios. Furthermore, FMC-QE is compared to other performance modeling and evaluation approaches. In the case study part in chapter 5, proof-of-concept examples, like the modeling of a service based search portal, a service based SAP NetWeaver application and the Axis2 Web service framework will be provided. Finally, conclusions are given by a summary of contributions and an outlook on future work in chapter 6. [1] Werner Zorn. FMC-QE - A New Approach in Quantitative Modeling. In Hamid R. Arabnia, editor, Procee-dings of the International Conference on Modeling, Simulation and Visualization Methods (MSV 2007) within WorldComp ’07, pages 280 – 287, Las Vegas, NV, USA, June 2007. CSREA Press. ISBN 1-60132-029-9.
Spatial and temporal temperature and moisture patterns across the Tibetan Plateau are very complex. The onset and magnitude of the Holocene climate optimum in the Asian monsoon realm, in particular, is a subject of considerable debate as this time period is often used as an analogue for recent global warming. In the light of contradictory inferences regarding past climate and environmental change on the Tibetan Plateau, I have attempted to explain mismatches in the timing and magnitude of change. Therefore, I analysed the temporal variation of fossil pollen and diatom spectra and the geochemical record from palaeo-ecological records covering different time scales (late Quaternary and the last 200 years) from two core regions in the NE and SE Tibetan Plateau. For interpretation purposes I combined my data with other available palaeo-ecological data to set up corresponding aquatic and terrestrial proxy data sets of two lake pairs and two sets of sites. I focused on the direct comparison of proxies representing lacustrine response to climate signals (e.g., diatoms, ostracods, geochemical record) and proxies representing changes in the terrestrial environment (i.e., terrestrial pollen), in order to asses whether the lake and its catchments respond at similar times and magnitudes to environmental changes. Therefore, I introduced the established numerical technique procrustes rotation as a new approach in palaeoecology to quantitatively compare raw data of any two sedimentary records of interest in order to assess their degree of concordance. Focusing on the late Quaternary, sediment cores from two lakes (Kuhai Lake 35.3°N; 99.2°E; 4150 m asl; and Koucha Lake 34.0°N; 97.2°E; 4540 m asl) on the semi-arid northeastern Tibetan Plateau were analysed to identify post-glacial vegetation and environmental changes, and to investigate the responses of lake ecosystems to such changes. Based on the pollen record, five major vegetation and climate changes could be identified: (1) A shift from alpine desert to alpine steppe indicates a change from cold, dry conditions to warmer and more moist conditions at 14.8 cal. ka BP, (2) alpine steppe with tundra elements points to conditions of higher effective moisture and a stepwise warming climate at 13.6 cal. ka BP, (3) the appearance of high-alpine meadow vegetation indicates a further change towards increased moisture, but with colder temperatures, at 7.0 cal. ka BP, (4) the reoccurrence of alpine steppe with desert elements suggests a return to a significantly colder and drier phase at 6.3 cal. ka BP, and (5) the establishment of alpine steppe-meadow vegetation indicates a change back to relatively moist conditions at 2.2 cal. ka BP. To place the reconstructed climate inferences from the NE Tibetan Plateau into the context of Holocene moisture evolution across the Tibetan Plateau, I applied a five-scale moisture index and average link clustering to all available continuous pollen and non-pollen palaeoclimate records from the Tibetan Plateau, in an attempt to detect coherent regional and temporal patterns of moisture evolution on the Plateau. However, no common temporal or spatial pattern of moisture evolution during the Holocene could be detected, which can be assigned to the complex responses of different proxies to environmental changes in an already very heterogeneous mountain landscape, where minor differences in elevation can result in marked variations in microenvironments. Focusing on the past 200 years, I analysed the sedimentary records (LC6 Lake 29.5°N, 94.3°E, 4132 m asl; and Wuxu Lake 29.9°N, 101.1°E, 3705 m asl) from the southeastern Tibetan Plateau. I found that despite presumed significant temperature increases over that period, pollen and diatom records from the SE Tibetan Plateau reveal only very subtle changes throughout their profiles. The compositional species turnover investigated over the last 200 years appears relatively low in comparison to the species reorganisations during the Holocene. The results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem. Forest clearances and reforestation have not caused forest decline in our study area, but a conversion of natural forests to semi-natural secondary forests. The results from the numerical proxy comparison of the two sets of two pairs of Tibetan lakes indicate that the use of different proxies and the work with palaeo-ecological records from different lake types can cause deviant stories of inferred change. Irrespective of the timescale (Holocene or last 200 years) or region (SE or NE Tibetan Plateau) analysed, the agreement in terms of the direction, timing, and magnitude of change between the corresponding terrestrial data sets is generally better than the match between the corresponding lacustrine data sets, suggesting that lacustrine proxies may partly be influenced by in-lake or local catchment processes whereas the terrestrial proxy reflects a more regional climatic signal. The current disaccord on coherent temporal and spatial climate patterns on the Tibetan Plateau can partly be ascribed to the complexity of proxy response and lake systems on the Tibetan Plateau. Therefore, a multi-proxy, multi-site approach is important in order to gain a reliable climate interpretation for the complex mountain landscape of the Tibetan Plateau.
Resolute readings of later Wittgenstein and the challenge of avoiding hierarchies in philosophy
(2011)
This dissertation addresses the question: How did later Wittgenstein aim to achieve his goal of putting forward a way of dissolving philosophical problems which centered on asking ourselves what we mean by our words – yet which did not entail any claims about the essence of language and meaning? This question is discussed with reference to “resolute” readings of Wittgenstein. I discuss the readings of James Conant, Oskari Kuusela, and Martin Gustafsson. I follow Oskari Kuusela’s claim that in order to fully appreciate how later Wittgenstein meant to achieve his goal, we need to clearly see how he aimed to do away with hierarchies in philosophy: Not only is the dissolution of philosophical problems via the method of clarifying the grammar of expressions to be taken as independent from any theses about what meaning must be – but furthermore, it is to be taken as independent from the dissolution of any particular problem via this method. As Kuusela stresses, this also holds for the problems involving rule-following and meaning: the clarification of the grammar of “rule” and “meaning” has no foundational status – it is nothing on which the method of clarifying the grammar of expressions as such were meant to in any way rely on. The lead question of this dissertation then is: What does it mean to come to see that the method of dissolving philosophical problems by asking “How is this word actually used?” does not in any way rely on the results of our having investigated the grammar of the particular concepts “rule” and “meaning”? What is the relation of such results – results such as “To follow a rule, [...], to obey an order, [...] are customs (uses, institutions)” or “The meaning of a word is its use in the language” – to this method? From this vantage point, I concern myself with two aspects of the readings of Gustafsson and Kuusela. In Gustafsson, I concern myself with his idea that the dissolution of philosophical problems in general “relies on” the very agreement which – during the dissolution of the rule-following problem – comes out as a presupposition for our talk of “meaning” in terms of rules. In Kuusela, I concern myself with his idea that Wittgenstein, in adopting a way of philosophical clarification which investigates the actual use of expressions, is following the model of “meaning as use” – which model he had previously introduced in order to perspicuously present an aspect of the actual use of the word “meaning”. This dissertation aims to show how these two aspects of Gustafsson’s and Kuusela’s readings still fail to live up to the vision of Wittgenstein as a philosopher who aimed to do away with any hierarchies in philosophy. I base this conclusion on a detailed analysis of which of the occasions where Wittgenstein invokes the notions of “use” and “application” (as also “agreement”) have to do with the dissolution of a specific problem only, and which have to do with the dissolution of philosophical problems in general. I discuss Wittgenstein’s remarks on rule-following, showing how in the dissolution of the rule-following paradox, notions such as “use”, “application”, and “practice” figure on two distinct logical levels. I then discuss an example of what happens when this distinction is not duly heeded: Gordon Baker and Peter Hacker’s idea that the rule-following remarks have a special significance for his project of dissolving philosophical problems as such. I furnish an argument to the effect that their idea that the clarification of the rules of grammar of the particular expression “following a rule” could answer a question about rules of grammar in general rests on a conflation of the two logical levels on which “use” occurs in the rule-following remarks, and that it leads into a regress. I then show that Gustafsson’s view – despite its decisive advance over Baker and Hacker – contains a version of that same idea, and that it likewise leads into a regress. Finally, I show that Kuusela’s idea of a special significance of the model “meaning as use” for the whole of the method of stating rules for the use of words is open to a regress argument of a similar kind as that he himself advances against Baker and Hacker. I conclude that in order to avoid such a regress, we need to reject the idea that the grammatical remark “The meaning of a word is its use in the language” – because of the occurrence of “use” in it – stood in any special relation to the method of dissolving philosophical problems by describing the use of words. Rather, we need to take this method as independent from this outcome of the investigation of the use of the particular word “meaning”.
In this thesis entitled “Saccharide Recognition - Boronic acids as Receptors in Polymeric Networks” different aspects of boronic acid synthesis, their analysis and incorporation or attachment to different polymeric networks and characterisation thereof were investigated. The following key aspects were considered: • Provision of a variety of different characterised arylboronic acids and benzoboroxoles • Attachment of certain derivatives to nanoparticles and the characterisation of saccharide binding by means of isothermal titration calorimetry and displacement assay (ARS) to enhance the association constant to saccharides at pH 7.4 • Enhancement of selectivity in polymeric systems by means of molecular imprinting using fructose as template and a polymerisable benzoboroxole as functional monomer for the recognition at pH 7.4 (Joined by a diploma thesis of F. Grüneberger) • Development of biomimetic saccharide structures and the development of saccharide (especially glucose and fructose) binding MIPs by using these structures as template molecules. In the first part of the thesis different arylboronic acid derivatives were synthesised and their binding to glucose or fructose was investigated by means of isothermal titration calorimetry (ITC). It could be derived, which is in parallel to the literature, that derivatives bearing a methylhydroxyl-group in ortho-position to the boron (benzoboroxole) exhibit in most cases a two-fold higher association constant compared to the corresponding phenylboronic acid derivative. To gain a deeper understanding NMR spectroscopy and mass spectrometry with the benzoboroxole and glucose or fructose was performed. It could be shown that the exchange rate in terms of NMR time scale is quite slow since in titration experiments new peaks appeared. Via mass spectrometry of a mixture between benzoboroxole and glucose or fructose, different binding stoichiometries could be detected showing that the binding of saccharides is comparable with their binding to phenylboronic acid. In addition, the use of Alizarin Red S as an electrochemical reporter was described for the first time to monitor the saccharide binding to arylboronic acids not only with spectroscopy. Here, the redox behaviour and the displacement were recorded by cyclic voltammograms. In the second part different applications of boronic acids in polymeric networks were investigated. The attachment of benzoboroxoles to nanoparticles was investigated and monitored by means of isothermal titration calorimetry and a colourimetric assay with Alizarin Red S as the report dye. The investigations by isothermal titration calorimetry compared the fructose binding of arylboronic acids and benzoboroxoles coupled to these nanoparticles and “free” in solution. It could be shown that the attached derivatives showed a higher binding constant due to an increasing entropy term. This states for possible multivalent binding combined with a higher water release. Since ITC could not characterise the binding of glucose to these nanoparticles due to experimental restrictions the glucose binding at pH 7.4 was shown with ARS. Here, the displacement of ARS by fructose and also glucose could be followed and consequently these nanoparticles can be used for saccharide determination. Within this investigation also the temperature stability of these nanoparticles was examined and after normal sterilisation procedures (121°C, 20 min.) the binding behaviour was still unchanged. To target the selectivity of the used polymeric networks, molecular imprinting was used as a technique for creating artificial binding pockets on a molecular scale. As functional monomer 3-methacrylamidobenzoboroxole was introduced for the recognition of fructose. In comparison to polymers prepared with vinylphenylboronic acid the benzoboroxole containing polymer had a stronger binding at pH 7.4 which was shown for the first time. In addition, another imprinted polymer was synthesised especially for the recognition of glucose and fructose employing biomimetic saccharide analogues as template molecule. The advantage to use the saccharide analogues is the defined template-functional monomer complex during the polymerisation which is not the case, for example, for glucose-boronic acid interaction. The biomimetic character was proven through structural superimposition of crystal structures of the analogues with already described crystal structures of boronic acid esters of glucose and fructose. A molecularly imprinted polymer was synthesised with vinylphenylboronic acid as the functional monomer to show that both glucose and fructose are able to bind to the polymer which was predicted by the structural similarity of the analogues. The major scientific contributions of this thesis are • the determination of binding constants for some, not yet reported saccharide – boronic acid / benzoboroxole pairs, • the use of ARS as electrochemical reporter for saccharide detection, • the thermodynamic characterisation of a saccharide binding nanoparticle system containing benzoboroxole and functioning at pH 7.4, • the use of a polymerisable benzoboroxole as functional monomer for saccharide recognition in neutral, aqueous environments • and the synthesis and utilisation of biomimetic saccharide analogues as template molecules especially for the development of a glucose binding MIP.
Die neuen Anforderungen an Schulleitungen im Zuge gesellschaftlicher, schulpolitischer und schulinterner Entwicklungen sind erheblich (Huber, 2008). Diese in der Literatur breit geteilte Einschätzung schlägt sich bislang nicht ausreichend in Forschungsaktivitäten zur Gesundheit schulischer Führungskräfte nieder – im Unterschied zu der ausgiebigen Forschung zur Lehrergesundheit, die für die Lehrer durchgängig eine kritische Gesundheitslage feststellt. Besondere Aufmerksamkeit erzielte dabei die Potsdamer Lehrerstudie (Schaarschmidt, 2004). Sie belegte unter anderem auch die Einflussmöglichkeiten der Schulleitung auf die Lehrergesundheit. Die vorliegende Arbeit verfolgt zwei Ziele: Erstens wird die aktuelle Schulleitungsforschung um empirische Daten zur gesundheitlichen Situation von n = 484 Schulleitungen aus Brandenburg und Baden-Württemberg ergänzt. Zweitens wird die Bedeutung der Schulleitung für die Lehrergesundheit näher untersucht, indem empirische Daten aus Führungsfeedbackverfahren mit n = 12 Schulleitungen und n = 332 Lehrern in Baden-Württemberg und Hessen herangezogen werden. Das diagnostische Verfahren AVEM (“Arbeitsbezogenes Verhaltens- und Erlebensmuster“, Schaarschmidt & Fischer, 1996/2003) dient als methodische Grundlage. Es erhebt Selbsteinschätzungen zum arbeitsbezogenen Verhalten und Erleben und weist auf mögliche Risiken im Sinne psychischer oder psychosomatischer Gefährdung hin. Das Instrument erfasst mit 66 Items 11 Dimensionen (z.B. Distanzierungsfähigkeit). Auf diese Weise ist es möglich, die befragte Person einem von vier arbeitsbezogenen Verhaltens- und Erlebensmustern zuzuordnen: Muster G (Gesundheitsideal), Muster S (Schonungstendenz gegenüber beruflichen Anforderungen), Risikomuster A (überhöhtes Engagement), Risikomuster B (Resignation). Zudem werden Fragen zu schulischer Führung eingesetzt, die sich aus vorhandenen Fragebögen speisen. Mit Hilfe einer exploratorischen Faktorenanalyse können sechs Faktoren identifiziert werden: Persönliche emotionale Wertschätzung und Fürsorge, optimistische Zukunftsorientierung, konstruktives Management des Schulbetriebs, Förderung von Weiterbildung und pädagogischem Diskurs, Präsenz/Ansprechbarkeit und Partizipationsorientierung. Zu der ersten Fragestellung zeigt sich für die befragten Schulleitungen im Mittel ein gesundheitlich recht positives Bild – gerade im Kontrast zu den befragten Lehrern. Für die befragten Schulleitungen wird eine signifikant günstigere AVEM-Musterkonstellation festgestellt: Der Anteil des Musters G ist bei den Schulleitungen deutlich höher, der Anteil des Musters B deutlich niedriger und der Anteil des Musters A in etwa gleich groß. Die AVEM-Ergebnisse schlagen sich bei den befragten Schulleitungen in unmittelbaren Gesundheitsindikatoren nieder. Für bestimmte Untergruppen herrscht allerdings ein gesundheitlich vergleichsweise kritisches Bild vor, nämlich tendenziell für Schulleitungen in Brandenburg, für weibliche Schulleitungen und Schulleitungen an Grund- und Förderschulen. Eine hohe Unterrichtsverpflichtung ist mit einem größeren Anteil an Risikomustern verbunden. Ein hohes Maß an erlebter Autonomie – insbesondere im sozial-interaktiven Bereich mit den Lehrern (d.h. bei Auswahl, Einstellung und Beurteilung von Lehrern sowie bei der innerschulischen Arbeitsorganisation und kollegialen Zusammenarbeit) – geht dagegen mit jeweils günstigeren AVEM-Musterkonstellationen einher. Zur Beantwortung der zweiten Fragestellung wird eine methodisch anspruchsvolle Mehrebenenanalyse durchgeführt, die die hierarchische Anordnung der Daten angemessen behandelt. Für die wahrgenommene soziale Unterstützung durch die Schulleitung wird dabei eine negative Beziehung zur subjektiven Bedeutsamkeit der Arbeit und der Verausgabungsbereitschaft der befragten Lehrer gefunden. Hingegen ergibt sich ein positiver Zusammenhang zwischen der erlebten Förderung von Weiterbildung und pädagogischem Diskurs und dem Erfolgserleben der befragten Lehrer. Ebenso hängt die wahrgenommene Führung durch die Schulleitung in ihrer Gesamtheit in positiver Weise mit der Lebenszufriedenheit der befragten Lehrer zusammen. Es sei betont, dass ausschließlich Effekte nachgewiesen werden, die auf die individuelle Ebene der Lehrer zurückgehen, d.h. es scheint – was den Zusammenhang zwischen erlebter Führung und Lehrergesundheit angeht – auf die subjektive Wahrnehmung des Führungsverhaltens der Schulleitung durch den/die jeweilige(n) Lehrer/in anzukommen. Eine erste theoretische Skizze zu wesentlichen Determinanten von Schulleitungsgesundheit wird vorgeschlagen. Empfehlungen für die Schulleitungspraxis umfassen die Reduzierung der Unterrichtsverpflichtung, die Erweiterung von Autonomie im sozial-interaktiven Bereich mit den Lehrern und die systematische Etablierung von Mitarbeitergesprächen zur Ausgestaltung individueller Führungsbeziehungen zwischen Schulleitungen und Lehrern.
Rainfall, snow-, and glacial melt throughout the Himalaya control river discharge, which is vital for maintaining agriculture, drinking water and hydropower generation. However, the spatiotemporal contribution of these discharge components to Himalayan rivers is not well understood, mainly because of the scarcity of ground-based observations. Consequently, there is also little known about the triggers and sources of peak sediment flux events, which account for extensive hydropower reservoir filling and turbine abrasion. We therefore lack basic information on the distribution of water resources and controls of erosion processes. In this thesis, I employ various methods to assess and quantify general characteristics of and links between precipitation, river discharge, and sediment flux in the Sutlej Valley. First, I analyze daily precipitation data (1998-2007) from 80 weather stations in the western Himalaya, to decipher the distribution of rain- and snowfall. Rainfall magnitude frequency analyses indicate that 40% of the summer rainfall budget is attributed to monsoonal rainstorms, which show higher variability in the orogenic interior than in frontal regions. Combined analysis of rainstorms and sediment flux data of a major Sutlej River tributary indicate that monsoonal rainfall has a first order control on erosion processes in the orogenic interior, despite the dominance of snowfall in this region. Second, I examine the contribution of rainfall, snow and glacial melt to river discharge in the Sutlej Valley (s55,000 km2), based on a distributed hydrological model, which covers the period 2000-2008. To achieve high spatial and daily resolution despite limited ground-based observations the hydrological model is forced by daily remote sensing data, which I adjusted and calibrated with ground station data. The calibration shows that the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product systematically overestimates rainfall in semi-arid and arid regions, increasing with aridity. The model results indicate that snowmelt-derived discharge (74%) is most important during the pre-monsoon season (April to June) whereas rainfall (56%) and glacial melt (17%) dominate the monsoon season (July-September). Therefore, climate change most likely causes a reduction in river discharge during the pre-monsoon season, which especially affects the orogenic interior. Third, I investigate the controls on suspended sediment flux in different parts of the Sutlej catchments, based on daily gauging data from the past decade. In conjunction with meteorological data, earthquake records, and rock strength measurements I find that rainstorms are the most frequent trigger of high-discharge events with peaks in suspended sediment concentrations (SSC) that account for the bulk of the suspended sediment flux. The suspended sediment flux increases downstream, mainly due to increases in runoff. Pronounced erosion along the Himalayan Front occurs throughout the monsoon season, whereas efficient erosion of the orogenic interior is confined to single extreme events. The results of this thesis highlight the importance of snow and glacially derived melt waters in the western Himalaya, where extensive regions receive only limited amounts of monsoonal rainfall. These regions are therefore particularly susceptible to global warming with major implications on the hydrological cycle. However, the sediment discharge data show that infrequent monsoonal rainstorms that pass the orographic barrier of the Higher Himalaya are still the primary trigger of the highest-impact erosion events, despite being subordinate to snow and glacially–derived discharge. These findings may help to predict peak sediment flux events and could underpin the strategic development of preventative measures for hydropower infrastructures.
Diese von der Wirtschafts- und Sozialwissenschaftlichen Fakultät der Universität Potsdam angenommene Dissertation thematisiert die Selbstorganisation von Migranten in eigenen Sportvereinen und auf anderen Ebenen des Vereinssports. Sie beruht auf den Ergebnissen eines vom Bundesinstitut für Sportwissenschaft geförderten Forschungsprojekts der Universität Potsdam. Mit mehreren hundert Migrantensportvereinen in ganz Deutschland stellt der Sport einen der wichtigsten Gesellschaftsbereiche für die Selbstorganisation von Zuwanderern dar. Doch obwohl sich Migranten in der Bundesrepublik schon seit den 1960er Jahren in eigenen Sportvereinen zusammenschließen, ist das Thema zuvor noch nicht umfassend untersucht worden. Um diese Forschungslücke zu schließen, stellt die Arbeit Basisinformationen über verschiedene Organisationsformen, typische Entstehungszusammenhänge, spezifische Problemfelder sowie wiederkehrende Konfliktmuster bereit und präsentiert darauf aufbauende Annahmen über die Wirkungen der sportbezogenen Selbstorganisation auf das Verhältnis von Einheimischen und Zuwanderern im Sport, auf die allgemeinen interethnischen Beziehungen und auf den gesamtgesellschaftlichen Integrationsprozess. Daran anknüpfend werden mögliche Konsequenzen aufgezeigt, die die verschiedenen Akteure des Sportsystems aus den dargestellten Forschungsbefunden ziehen können. Die Arbeit basiert auf den Befunden einer in den Jahren 2006 bis 2009 durchgeführten empirischen Untersuchung, in der verschiedene qualitative Methoden eingesetzt wurden, um das Forschungsfeld explorativ, ergebnisoffen und in einer möglichst weiten Perspektive zu beleuchten. In erster Linie bestand diese Feldstudie in einer Interviewreihe, für die 25 Vertreter von Migrantensportvereinen sowie 15 Feldexperten aus verschiedenen Berufsgruppen und Organisationen in Leitfaden-Interviews befragt wurden. Ergänzt wurde die Interviewstudie durch eine Zeitungsanalyse, für die sieben Tages- und Wochenzeitungen nach Artikeln zum Thema durchsucht wurden, sowie gezielte Feldbeobachtungen, etwa beim Besuch von Fußballspielen, bei Versammlungen und Festen sowie in Vereinsheimen. Darüber hinaus wurde eine umfangreiche Internetrecherche durchgeführt, bei der vor allem die Webseiten von über 65 Migrantensportvereinen in Augenschein genommen wurden. In allen Untersuchungsteilen war das Vorgehen des Verfassers stark an der Grounded-Theory-Methode orientiert. Die so gewonnenen Forschungsergebnisse deuten darauf hin, dass eigenständige Migrantensportvereine, die als vorherrschende Form der sportbezogenen Selbstorganisation von Zuwanderern im Mittelpunkt der Arbeit stehen, aus komplexen gesellschaftlichen Inklusions-, Schließungs- sowie Segmentationsprozessen resultieren und interindividuell unterschiedliche Beteiligungsmotive ihrer Mitglieder aufnehmen. Sie stellen typischerweise multifunktionale Hybridorganisationen dar und erbringen für die beteiligten Migranten und deren lokale Gemeinschaften spezifische Integrations-, Repräsentations- und Solidarleistungen, durch die sie sich signifikant von deutschen Sportvereinen und Migrantenorganisationen in anderen Sektoren abheben. Zugleich unterscheiden sich die Migrantensportvereine untereinander hinsichtlich Vereinstätigkeit, Selbstverständnis und Konfliktbeteiligung sehr stark. Ihre Rückwirkung auf den Vereinssport als organisationales Feld, auf die interethnischen Beziehungen in anderen Gesellschaftsbereichen und auf den gesamtgesellschaftlichen Integrationsprozess ist den präsentierten Forschungsergebnissen zufolge gleichfalls sehr ambivalent. Einerseits erbringen Migrantenvereine nicht nur die gleichen gemeinnützigen Leistungen im Bereich der sozialen Integration wie andere Sportvereine auch, sondern entfalten darüber hinaus, indem sie die Integrationsfähigkeit ihrer Mitglieder erhöhen und Personen in den organisierten Sport einbeziehen, die sonst gar keinem Sportverein beitreten würden, spezifische Integrationswirkungen, die andere Sportvereine nicht aufweisen. Andererseits erhöht die Selbstorganisation von Migranten in eigenen Sportvereinen soziale Distanzen und Spannungen zwischen Einheimischen und Zuwanderern, zumal Migrantensportvereine vor allem an den manchmal gewaltvollen Konflikten im Amateurfußball überproportional häufig beteiligt sind. Darüber hinaus stellt ein relativ kleiner Teil der Migrantensportvereine wegen Organisationsdefiziten eine ernste Belastung für die Tätigkeit der Sportverbände dar. Pauschalisierende Negativbewertungen der Vereine werden vom Verfasser jedoch als ungerechtfertigt und nicht sachangemessen zurückgewiesen.
Block copolymers are receiving increasing attention in the literature. Reports on amphiphilic block copolymers have now established the basis of their self-assembly behavior: aggregate sizes, morphologies and stability can be explained from the absolute and relative block lengths, the nature of the blocks, the architecture and also solvent selectiveness. In water, self-assembly of amphiphilic block copolymers is assumed to be driven by the hydrophobic. The motivation of this thesis is to study the influence on the self-assembly in water of A b B type block copolymers (with A hydrophilic) of the variation of the hydrophilicity of B from non-soluble (hydrophobic) to totally soluble (hydrophilic). Glucose-modified polybutadiene-block-poly(N-isopropylacrylamide) copolymers were prepared and their self-assembly behavior in water studied. The copolymers formed vesicles with an asymmetric membrane with a glycosylated exterior and poly(N-isopropylacrylamide) on the inside. Above the low critical solution temperature (LCST) of poly(N-isopropylacrylamide), the structure collapsed into micelles with a hydrophobic PNIPAM core and glycosylated exterior. This collapse was found to be reversible. As a result, the structures showed a temperature-dependent interaction with L-lectin proteins and were shown to be able to encapsulate organic molecules. Several families of double hydrophilic block copolymers (DHBC) were prepared. The blocks of these copolymers were biopolymers or polymer chimeras used in aqueous two-phase partition systems. Copolymers based on dextran and poly(ethylene glycol) blocks were able to form aggregates in water. Dex6500-b-PEG5500 copolymer spontaneously formed vesicles with PEG as the “less hydrophilic” barrier and dextran as the solubilizing block. The aggregates were found to be insensitive to the polymer's architecture and concentration (in the dilute range) and only mildly sensitive to temperature. Variation of the block length, yielded different morphologies. A longer PEG chain seemed to promote more curved aggregates following the inverse trend usually observed in amphiphilic block copolymers. A shorter dextran promoted vesicular structures as usually observed for the amphiphilic counterparts. The linking function was shown to have an influence of the morphology but not on the self-assembly capability in itself. The vesicles formed by dex6500-b-PEG5500 showed slow kinetics of clustering in the presence of Con A lectin. In addition both dex6500-b-PEG5500 and its crosslinked derivative were able to encapsulate fluorescent dyes. Two additional dextran-based copolymers were synthesized, dextran-b-poly(vinyl alcohol) and dextran-b-poly(vinyl pyrrolidone). The study of their self-assembly allowed to conclude that aqueous two-phase systems (ATPS) is a valid source of inspiration to conceive DHBCs capable of self-assembling. In the second part the principle was extended to polypeptide systems with the synthesis of a poly(N-hydroxyethylglutamine)-block-poly(ethylene glycol) copolymer. The copolymer that had been previously reported to have emulsifying properties was able to form vesicles by direct dissolution of the solid in water. Last, a series of thermoresponsive copolymers were prepared, dextran-b-PNIPAMm. These polymers formed aggregates below the LCST. Their structure could not be unambiguously elucidated but seemed to correspond to vesicles. Above the LCST, the collapse of the PNIPAM chains induced the formation of stable objects of several hundreds of nanometers in radius that evolved with increasing temperature. The cooling of these solution below LCST restored the initial aggregates. This self-assembly of DHBC outside any stimuli of pH, ionic strength, or temperature has only rarely been described in the literature. This work constituted the first formal attempt to frame the phenomenon. Two reasons were accounted for the self-assembly of such systems: incompatibility of the polymer pairs forming the two blocks (enthalpic) and a considerable solubility difference (enthalpic and entropic). The entropic contribution to the positive Gibbs free energy of mixing is believed to arise from the same loss of conformational entropy that is responsible for “the hydrophobic effect” but driven by a competition for water of the two blocks. In that sense this phenomenon should be described as the “hydrophilic effect”.
The creation of complex polymer structures has been one of the major research topics over the last couple of decades. This work deals with the synthesis of (block co-)polymers, the creation of complex and stimuli-responsive aggregates by self-assembly, and the cross-linking of these structures. Also the higher-order self-assembly of the aggregates is investigated. The formation of poly-2-oxazoline based micelles in aqueous solution and their simultaneous functionalization and cross-linking using thiol-yne chemistry is e.g. presented. By introducing pH responsive thiols in the core of the micelles the influence of charged groups in the core of micelles on the entire structure can be studied. The charging of these groups leads to a swelling of the core and a decrease in the local concentration of the corona forming block (poly(2-ethyl-2-oxazoline)). This decrease in concentration yields a shift in the cloud point temperature to higher temperatures for this Type I thermoresponsive polymer. When the swelling of the core is prohibited, e.g. by the introduction of sufficient amounts of salt, this behavior disappears. Similar structures can be prepared using complex coacervate core micelles (C3Ms) built through the interaction of weakly acidic and basic polymer blocks. The advantage of these structures is that two different stabilizing blocks can be incorporated, which allows for more diverse and complex structures and behavior of the micelles. Using block copolymers with either a polyanionic or a polycationic block C3Ms could be created with a corona which contains two different soluble nonionic polymers, which either have a mixed corona or a Janus type corona, depending on the polymers that were chosen. Using NHS and EDC the micelles could easily be cross-linked by the formation of amide bonds in the core of the micelles. The higher-order self-assembly behavior of these core cross-linked complex coacervate core micelles (C5Ms) was studied. Due to the cross-linking the micelles are stabilized towards changes in pH and ionic strength, but polymer chains are also no longer able to rearrange. For C5Ms with a mixed corona likely network structures were formed upon the collapse of the thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm), whereas for Janus type C5Ms well defined spherical aggregates of micelles could be obtained, depending on the pH of the solution. Furthermore it could be shown that Janus micelles can adsorb onto inorganic nanoparticles such as colloidal silica (through a selective interaction between PEO and the silica surface) or gold nanoparticles (by the binding of thiol end-groups). Asymmetric aggregates were also formed using the streptavidin-biotin binding motive. This is achieved by using three out of the four binding sites of streptavidin for the binding of one three-arm star polymer, end-functionalized with biotin groups. A homopolymer with one biotin end-group can be used to occupy the last position. This binding of two different polymers makes it possible to create asymmetric complexes. This phase separation is theoretically independent of the kind of polymer since the structure of the protein is the driving force, not the intrinsic phase separation between polymers. Besides Janus structures also specific cross-linking can be achieved by using other mixing ratios.
In dieser Arbeit wird das regionale Klimamodell HIRHAM mit einer horizontalen Auflösung von 50 km und 19 vertikalen Schichten erstmals auf den asiatischen Kontinent angewendet, um die indische Monsunzirkulation unter rezenten und paläoklimatischen Bedingungen zu simulieren. Das Integrationsgebiet des Modells erstreckt sich von etwa 0ºN - 50ºN und 42ºE - 110ºE und bedeckt dabei sowohl die hohe Topographie des Himalajas und Tibet Plateaus als auch den nördlichen Indischen Ozean. Das Ziel besteht in der Beschreibung der regionalen Kopplung zwischen der Monsunzirkulation und den orographischen sowie diabatischen Antriebsmechanismen. Eine 44-jährige Modellsimulation von 1958-2001, die am seitlichen und unteren Rand von ECMWF Reanalysen (ERA40) angetrieben wird, bildet die Grundlage für die Validierung der Modellergebnisse mit Beobachtungen auf der Basis von Stations- und Gitterdatensätzen. Der Fokus liegt dabei auf der atmosphärischen Zirkulation, der Temperatur und dem Niederschlag im Sommer- und Wintermonsun, wobei die Qualität des Modells sowohl in Bezug zur langfristigen und dekadischen Klimatologie als auch zur interannuellen Variabilität evaluiert wird. Im Zusammenhang mit einer realistischen Reproduktion der Modelltopographie kann für die Muster der Zirkulation und Temperatur eine gute Übereinstimmung zwischen Modell und Daten nachgewiesen werden. Der simulierte Niederschlag zeigt eine bessere Übereinstimmung mit einem hoch aufgelösten Gitterdatensatz über der Landoberfläche Zentralindiens und in den Hochgebirgsregionen, der den Vorteil des Regionalmodells gegenüber der antreibenden Reanalyse hervorhebt. In verschiedenen Fall- und Sensitivitätsstudien werden die wesentlichen Antriebsfaktoren des indischen Monsuns (Meeresoberflächentemperaturen, Stärke des winterlichen Sibirischen Hochs und Anomalien der Bodenfeuchte) untersucht. Die Ergebnisse machen deutlich, dass die Simulation dieser Mechanismen auch mit einem Regionalmodell sehr schwierig ist, da die Komplexität des Monsunsystems hochgradig nichtlinear ist und die vor allem subgridskalig wirkenden Prozesse im Modell noch nicht ausreichend parametrisiert und verstanden sind. Ein paläoklimatisches Experiment für eine 44-jährige Zeitscheibe im mittleren Holozän (etwa 6000 Jahre vor heute), die am Rand von einer globalen ECHAM5 Simulation angetrieben wird, zeigt markante Veränderungen in der Intensität des Monsuns durch die unterschiedliche solare Einstrahlung, die wiederum Einflüsse auf die SST, die Zirkulation und damit auf die Niederschlagsmuster hat.
In this thesis, simulations of laser-driven many-electron dynamics in molecules are presented, i.e., the interaction between molecules and an electromagnetic field is demonstrated. When a laser field is applied to a molecular system, a population of higher electronic states takes place as well as other processes, e.g. photoionization, which is described by an appropriate model. Also, a finite lifetime of an excited state can be described by such a model. In the second part, a method is postulated that is capable of describing electron correlation in a time-dependent scheme. This is done by introducing a single-electron entropy that is at least temporarily minimized in a further step.
Soft nanocomposites with enhanced electromechanical response for dielectric elastomer actuators
(2011)
Electromechanical transducers based on elastomer capacitors are presently considered for many soft actuation applications, due to their large reversible deformation in response to electric field induced electrostatic pressure. The high operating voltage of such devices is currently a large drawback, hindering their use in applications such as biomedical devices and biomimetic robots, however, they could be improved with a careful design of their material properties. The main targets for improving their properties are increasing the relative permittivity of the active material, while maintaining high electric breakdown strength and low stiffness, which would lead to enhanced electrostatic storage ability and hence, reduced operating voltage. Improvement of the functional properties is possible through the use of nanocomposites. These exploit the high surface-to-volume ratio of the nanoscale filler, resulting in large effects on macroscale properties. This thesis explores several strategies for nanomaterials design. The resulting nanocomposites are fully characterized with respect to their electrical and mechanical properties, by use of dielectric spectroscopy, tensile mechanical analysis, and electric breakdown tests. First, nanocomposites consisting of high permittivity rutile TiO2 nanoparticles dispersed in thermoplastic block copolymer SEBS (poly-styrene-coethylene-co-butylene-co-styrene) are shown to exhibit permittivity increases of up to 3.7 times, leading to 5.6 times improvement in electrostatic energy density, but with a trade-off in mechanical properties (an 8-fold increase in stiffness). The variation in both electrical and mechanical properties still allows for electromechanical improvement, such that a 27 % reduction of the electric field is found compared to the pure elastomer. Second, it is shown that the use of nanofiller conductive particles (carbon black (CB)) can lead to a strong increase of relative permittivity through percolation, however, with detrimental side effects. These are due to localized enhancement of the electric field within the composite, which leads to sharp reductions in electric field strength. Hence, the increase in permittivity does not make up for the reduction in breakdown strength in relation to stored electrical energy, which may prohibit their practical use. Third, a completely new approach for increasing the relative permittivity and electrostatic energy density of a polymer based on 'molecular composites' is presented, relying on chemically grafting soft π-conjugated macromolecules to a flexible elastomer backbone. Polarization caused by charge displacement along the conjugated backbone is found to induce a large and controlled permittivity enhancement (470 % over the elastomer matrix), while chemical bonding, encapsulates the PANI chains manifesting in hardly any reduction in electric breakdown strength, and hence resulting in a large increase in stored electrostatic energy. This is shown to lead to an improvement in the sensitivity of the measured electromechanical response (83 % reduction of the driving electric field) as well as in the maximum actuation strain (250 %). These results represent a large step forward in the understanding of the strategies which can be employed to obtain high permittivity polymer materials with practical use for electro-elastomer actuation.
Soil moisture is a key state variable that controls runoff formation, infiltration and partitioning of radiation into latent and sensible heat. However, the experimental characterisation of near surface soil moisture patterns and their controls on runoff formation remains a challenge. This subject was one aspect of the BMBF-funded OPAQUE project (operational discharge and flooding predictions in head catchments). As part of that project the focus of this dissertation is on: (1) testing the methodology and feasibility of the Spatial TDR technology in producing soil moisture profiles along TDR probes, including an inversion technique of the recorded signal in heterogeneous field soils, (2) the analysis of spatial variability and temporal dynamics of soil moisture at the field scale including field experiments and hydrological modelling, (3) the application of models of different complexity for understanding soil moisture dynamics and its importance for runoff generation as well as for improving the prediction of runoff volumes. To fulfil objective 1, several laboratory experiments were conducted to understand the influence of probe rod geometry and heterogeneities in the sampling volume under different wetness conditions. This includes a detailed analysis on how these error sources affect retrieval of soil moisture profiles in soils. Concerning objective 2 a sampling strategy of two TDR clusters installed in the head water of the Wilde Weißeritz catchment (Eastern Ore Mountains, Germany) was used to investigate how well “the catchment state” can be characterised by means of distributed soil moisture data observed at the field scale. A grassland site and a forested site both located on gentle slopes were instrumented with two Spatial TDR clusters that consist of up to 39 TDR probes. Process understanding was gained by modelling the interaction of evapotranspiration and soil moisture with the hydrological process model CATFLOW. A field scale irrigation experiment was carried out to investigate near subsurface processes at the hillslope scale. The interactions of soil moisture and runoff formation were analysed using discharge data from three nested catchments: the Becherbach with a size of 2 km², the Rehefeld catchment (17 km²) and the superordinate Ammelsdorf catchment (49 km²). Statistical analyses including observations of pre-event runoff, soil moisture and different rainfall characteristics were employed to predict stream flow volume. On the different scales a strong correlation between the average soil moisture and the runoff coefficients of rainfall-runoff events could be found, which almost explains equivalent variability as the pre-event runoff. Furthermore, there was a strong correlation between surface soil moisture and subsurface wetness with a hysteretic behaviour between runoff soil moisture. To fulfil objective 3 these findings were used in a generalised linear model (GLM) analysis which combines state variables describing the catchments antecedent wetness and variables describing the meteorological forcing in order to predict event runoff coefficients. GLM results were compared to simulations with the catchment model WaSiM ETH. Hereby were the model results of the GLMs always better than the simulations with WaSiM ETH. The GLM analysis indicated that the proposed sampling strategy of clustering TDR probes in typical functional units is a promising technique to explore soil moisture controls on runoff generation and can be an important link between the scales. Long term monitoring of such sites could yield valuable information for flood warning and forecasting by identifying critical soil moisture conditions for the former and providing a better representation of the initial moisture conditions for the latter.
Die vorliegende Arbeit betrachtet Partizipation aus einer interaktionalen Perspektive und nimmt zunächst eine interdisziplinär orientierte Begriffsbestimmung vor. Daran anschließend werden anhand einer Längsschnittstudie Entwicklungsbedingungen sozialer Partizipationskompetenzen im Vorschulalter untersucht und Förderempfehlungen abgeleitet. Partizipation (Teilhabe) soll in Kontexten wie Schule oder Arbeitswelt Entscheidungen demokratisch legitimieren, individuelle Ressourcen ausschöpfen und soziale Grundbedürfnisse des Menschen befriedigen. Ein engeres Verständnis von sozialer Partizipation aus einer interaktionalen Perspektive erfordert die Beteiligung an den Aktivitäten einer bereits bestehenden Gruppe und die Aushandlung eigener Interessen innerhalb dieser Gruppe und wird in der Arbeit als Prozess anhand dreier Phasen (Anbahnung, Projektierung und Realisierung) dargestellt. Im Vorschulalter werden wichtige Grundsteine für eine erfolgreiche soziale Entwicklung und für den Erwerb von sozialen Partizipationskompetenzen gelegt. In der vorliegenden Arbeit wurden deshalb die Zusammenhänge und Wechselwirkungen zwischen sozialen Partizipationskompetenzen (Bereitschaft und Fähigkeit) und (1) kognitiven Leistungsparametern (Intelligenz und Perspektivenübernahme), (2) dem Selbstkonzept und (3) dem Konfliktverhalten (Aggression und Schüchternheit) mit 5- bis 7jährigen Kindern mit Hilfe von Kreuzpfadanalysen untersucht. Zudem wurde die Situationsgebundenheit sozialer Partizipationskompetenzen und die Bedeutung struktureller Parameter der Familie und der Kindertageseinrichtung auf explorativer Ebene analysiert. Die Stichprobe bestand aus 334 Kindern (51,5 % weiblich, Altersdurchschnitt zum ersten Messzeitpunkt 5,4 Jahre) in 71 Kindergartengruppen in 21 Kindertageseinrichtungen in vier Bundesländern. Die längsschnittliche Datenanalyse basiert auf drei Messzeitpunkten. Die Ergebnisse zeigen, dass soziale Partizipationskompetenzen über verschiedene Situationen hinweg bedeutsame, aber nur mäßig ausgeprägte, Zusammenhänge aufweisen. Hohe Ausprägungen kognitiver Leistungsparameter gehen mit hohen Erziehereinschätzungen sozialer Partizipationskompetenzen einher. Über die Zusammenhänge hinaus zeigen sich im Längsschnitt bedeutsame Wechselwirkungen zwischen kognitiver Entwicklung und sozialen Partizipationskompetenzen im Vorschulalter. Selbsteinschätzungen zur eigenen Kompetenz hängen im Vorschulalter hingegen nur gering mit Erziehereinschätzungen der sozialen Partizipationskompetenz zusammen. Im Längsschnitt zeigt sich, dass junge Kinder bei der Beurteilung ihrer Kompetenzen zunächst auf soziale Partizipationserfolge zurückgreifen. Später hingegen scheint der Partizipationserfolg dann umgekehrt eher durch das Selbstbild bedingt zu sein. Geringe Partizipationskompetenzen gehen mit hohen Erziehereinschätzungen beim aggressiven (schwach signifikant) und schüchternen Verhalten (mäßig signifikant) einher. Hinsichtlich der Aggression und des schüchternen Verhaltens ergaben sich längsschnittlich betrachtet nur schwache Wechselwirkungen zur sozialen Partizipationskompetenz. Die Kumulation familiärer Belastungssituationen (z.B. Krankheit und akute Finanznot) stellen eine größere Bedrohung für die kindliche Entwicklung dar als der sozio-ökonomische Status der Familie. Mit Blick auf die Förderung sozialer Partizipationskompetenzen lassen sich die Ergebnisse mit einem sozial-konstruktivistischen Ansatz verbinden. Dessen Ziel ist es, intra- und interpersonelle Konflikte auszulösen, deren erfolgreiche Bewältigung produktive Lernprozesse auf kognitiver, emotionaler und behavioraler Ebene anstoßen.
Organic thin film transistors (TFT) are an attractive option for low cost electronic applications and may be used for active matrix displays and for RFID applications. To extend the range of applications there is a need to develop and optimise the performance of non-volatile memory devices that are compatible with the solution-processing fabrication procedures used in plastic electronics. A possible candidate is an organic TFT incorporating the ferroelectric co-polymer poly(vinylidenefluoride-trifluoroethylene)(P(VDF-TrFE)) as the gate insulator. Dielectric measurements have been carried out on all-organic metal-insulator-semiconductor structures with the ferroelectric polymer poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) as the gate insu-lator. The capacitance spectra of MIS devices, were measured under different biases, showing the effect of charge accumulation and depletion on the Maxwell-Wagner peak. The position and height of this peak clearly indicates the lack of stable depletion behavior and the decrease of mobility when increasing the depletion zone width, i.e. upon moving into the P3HT bulk. The lack of stable depletion was further investigated with capacitance-voltage (C-V) measurements. When the structure was driven into depletion, C-V plots showed a positive flat-band voltage shift, arising from the change in polarization state of the ferroelectric insulator. When biased into accumulation, the polarization was reversed. It is shown that the two polarization states are stable i.e. no depolarization occurs below the coercive field. However, negative charge trapped at the semiconductor-insulator interface during the depletion cycle masks the negative shift in flat-band voltage expected during the sweep to accumulation voltages. The measured output characteristics of the studied ferroelectric-field-effect transistors confirmed the results of the C-V plots. Furthermore, the results indicated a trapping of electrons at the positively charged surfaces of the ferroelectrically polarized P(VDF-TrFE) crystallites near the insulator/semiconductor in-terface during the first poling cycles. The study of the MIS structure by means of thermally stimulated current (TSC) revealed further evidence for the stability of the polarization under depletion voltages. It was shown, that the lack of stable depletion behavior is caused by the compensation of the orientational polarization by fixed electrons at the interface and not by the depolarization of the insulator, as proposed in several publications. The above results suggest a performance improvement of non-volatile memory devices by the optimization of the interface.
Diese Forschungsarbeit widmet sich der Analyse von Stimmungen und Erwartungen im System der Märkte mit Dynamic Partial Least Squares (DPLS) Modellen. Die Analyse komplexer Systeme mit umfangreichen Datensätzen und die Erkennung relevanter Muster erfordern die Verwendung moderner statistischer Verfahren. DPLS-Modelle, eine Variante der Strukturgleichungs-modelle mit Latenten Variablen, werden methodisch erweitert, um mehrere zeitliche Verzögerungsstufen gleichzeitig modellieren zu können. Die ökonometrischen Modelle versuchen, zahlreiche latente Einflussfaktoren und ihre verdeckten Beziehungen zu identifizieren. Als Daten werden rund 80 Indikatoren verwendet von Januar 1991 bis Juni 2010, um Stimmungen, Erwartungen und wirtschaftlich relevanten Größen zu operationalisieren und die Zusammenhänge detailliert zu untersuchen. Die Modellergebnisse zeigen, dass Stimmungen, also die Einschätzung der aktuellen wirtschaftlichen Lage, deutlich mit wirtschaftlichen Größen zusammenhängen, unter anderem mit Investitionen, Auftragseingängen oder Aktienmarktentwicklungen. Die Erwartungen, also die Einschätzung der zukünftigen Entwicklung, bieten eine mittlere bis schwache Prognosekraft für sechs bis maximal achtzehn Monate in die Zukunft. Für kürzere Zeiträume von sechs Monaten sind Stimmungen und Erwartungen die besten verfügbaren Prognosevariablen. Die Analyse der Modellabweichungen erlaubt Rückschlüsse auf wirtschaftstheoretische Konzepte, wie Rationalität der Erwartungen. Auffällig sind scheinbare Phasen der systematischen Über- und Unterbewertungen der aktuellen Situation oder zukünftigen Entwicklung, insbesondere vor und nach Krisensituationen. Die Ergebnisse dieser Arbeit geben somit einen erweiterten Einblick in die empirischen Zusammenhänge subjektiver Einschätzungen mit realen wirtschaftlichen Größen.
Subcellular compartmentation of primary carbon metabolism in mesophyll cells of Arabidopsis thaliana
(2011)
Metabolism in plant cells is highly compartmented, with many pathways involving reactions in more than one compartment. For example, during photosynthesis in leaf mesophyll cells, primary carbon fixation and starch synthesis take place in the chloroplast, whereas sucrose is synthesized in the cytosol and stored in the vacuole. These reactions are tightly regulated to keep a fine balance between the carbon pools of the different compartments and to fulfil the energy needs of the organelles. I applied a technique which fractionates the cells under non-aqueous conditions, whereby the metabolic state is frozen at the time of harvest and held in stasis throughout the fractionation procedure. With the combination of non-aqueous fractionation and mass spectrometry based metabolite measurements (LC-MS/MS, GC-MS) it was possible to investigate the intracellular distributions of the intermediates of photosynthetic carbon metabolism and its products in subsequent metabolic reactions. With the knowledge about the in vivo concentrations of these metabolites under steady state photosynthesis conditions it was possible to calculate the mass action ratio and change in Gibbs free energy in vivo for each reaction in the pathway, to determine which reactions are near equilibrium and which are far removed from equilibrium. The Km value and concentration of each enzyme were compared with the concentrations of its substrates in vivo to assess which reactions are substrate limited and so sensitive to changes in substrate concentration. Several intermediates of the Calvin-Benson cycle are substrates for other pathways, including dihydroxyacetone-phosphate (DHAP,sucrose synthesis), fructose 6-phosphate (Fru6P, starch synthesis), erythrose 4-phosphate (E4P,shikimate pathway) and ribose 5-phosphate (R5P, nucleotide synthesis). Several of the enzymes that metabolise these intermediates, and so lie at branch points in the pathway, are triose-phosphate isomerase (DHAP), transketolase (E4P, Fru6P), sedoheptulose-1,7-bisphosphate aldolase (E4P) and ribose-5-phosphate isomerase (R5P) are not saturated with their respective substrate as the metabolite concentration is lower than the respective Km value. In terms of metabolic control these are the steps that are most sensitive to changes in substrate availability, while the regulated irreversible reactions of fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase are relatively insensitive to changes in the concentrations of their substrates. In the pathway of sucrose synthesis it was shown that the concentration of the catalytic binding site of the cytosolic aldolase is lower than the substrate concentration of DHAP, and that the concentration of Suc6P is lower than the Km of sucrose-phosphatase for this substrate. Both the sucrose-phosphate synthase and sucrose-phosphatase reactions are far removed from equilibrium in vivo. In wild type A. thaliana Columbia-0 leaves, all of the ADPGlc was found to be localised in the chloroplasts. ADPglucose pyrophosphorylase is localised to the chloroplast and synthesises ADPGlc from ATP and Glc1P. This distribution argues strongly against the hypothesis proposed by Pozueta-Romero and colleagues that ADPGlc for starch synthesis is produced in the cytosol via ADP-mediated cleavage of sucrose by sucrose synthase. Based on this observation and other published data it was concluded that the generally accepted pathway of starch synthesis from ADPGlc produced by ADPglucose pyrophosphorylase in the chloroplasts is correct, and that the alternative pathway is untenable. Within the pathway of starch synthesis the concentration of ADPGlc was found to be well below the Km value of starch synthase for ADPGlc, indicating that the enzyme is substrate limited. A general finding in the comparison of the Calvin-Benson cycle with the synthesis pathways of sucrose and starch is that many enzymes in the Calvin Benson cycle have active binding site concentrations that are close to the metabolite concentrations, while for nearly all enzymes in the synthesis pathways the active binding site concentrations are much lower than the metabolite concentrations.
In the present work synchronization phenomena in complex dynamical systems exhibiting multiple time scales have been analyzed. Multiple time scales can be active in different manners. Three different systems have been analyzed with different methods from data analysis. The first system studied is a large heterogenous network of bursting neurons, that is a system with two predominant time scales, the fast firing of action potentials (spikes) and the burst of repetitive spikes followed by a quiescent phase. This system has been integrated numerically and analyzed with methods based on recurrence in phase space. An interesting result are the different transitions to synchrony found in the two distinct time scales. Moreover, an anomalous synchronization effect can be observed in the fast time scale, i.e. there is range of the coupling strength where desynchronization occurs. The second system analyzed, numerically as well as experimentally, is a pair of coupled CO₂ lasers in a chaotic bursting regime. This system is interesting due to its similarity with epidemic models. We explain the bursts by different time scales generated from unstable periodic orbits embedded in the chaotic attractor and perform a synchronization analysis of these different orbits utilizing the continuous wavelet transform. We find a diverse route to synchrony of these different observed time scales. The last system studied is a small network motif of limit cycle oscillators. Precisely, we have studied a hub motif, which serves as elementary building block for scale-free networks, a type of network found in many real world applications. These hubs are of special importance for communication and information transfer in complex networks. Here, a detailed study on the mechanism of synchronization in oscillatory networks with a broad frequency distribution has been carried out. In particular, we find a remote synchronization of nodes in the network which are not directly coupled. We also explain the responsible mechanism and its limitations and constraints. Further we derive an analytic expression for it and show that information transmission in pure phase oscillators, such as the Kuramoto type, is limited. In addition to the numerical and analytic analysis an experiment consisting of electrical circuits has been designed. The obtained results confirm the former findings.
Mechanistische und kinetische Untersuchungen von komplexen zellulären Prozessen in situ sind in den vergangenen Jahren durch den Einsatz photoaktivierbarer Biomoleküle, sogenannter caged Verbindungen, möglich geworden. Bei den caged Verbindungen handelt es sich um photolabile inaktive Derivate von biologisch aktiven Molekülen, aus denen durch ultraviolettes Licht mit Hilfe einer photochemischen Reaktion die natürliche, biologisch aktive Substanz schnell freigesetzt werden kann. Im Rahmen der vorliegenden Arbeit wurden caged Verbindungen von den Neurotransmittern Octopamin und Dopamin, dem Octopamin-Antagonist Epinastin, den Proteinsyntheseinhibitoren Emetin und Anisomycin, dem Protonophor CCCP und dem Riechstoff Bourgeonal hergestellt. Zur Synthese dieser caged Verbindungen wurden sowohl bekannte als auch verschiedene im Rahmen dieser Arbeit neu entwickelte photolabile Schutzgruppen mit einem (Cumarin-4-yl)methyl- bzw. einem 2-Nitrobenzyl-Gerüst eingesetzt. Entsprechende Syntheseverfahren wurden erarbeitet. Anschließend erfolgte eine umfassende physikalisch-chemische sowie photochemische Charakterisierung der erhaltenen caged Verbindungen. Dabei wurde besonders auf gute Löslichkeit in Wasser bei physiologischer Ionenstärke, schnelle und effiziente Photoreaktivität, hohe Extinktion bei Wellenlängen von 350-430 nm und gute solvolytische Stabilität bei geringer Toxizität der freigesetzten Schutzgruppe geachtet. Ein Schwerpunkt bei der photochemischen Charakterisierung bildeten die Untersuchungen zur Quantifizierung der 2-Photonen-Anregung, uncaging action cross-sections, der Cumarinylmethyl-caged Verbindungen, aufgrund ihrer Bedeutung für die Photofreisetzung von Biomolekülen, da die gleichzeitige Absorption von 2 IR-Photonen eine höhere dreidimensionale Auflösung und eine wesentlich tiefere Gewebepenetration erlaubt. Mit Hilfe von Kooperationspartnern wurden zeitaufgelösten Fluoreszenz- und IR-Messungen an verschiedenen (Cumarin-4-yl)methoxycarbonyl-caged Modellverbindungen durchgeführt, mit denen die Geschwindigkeitskonstanten k1 und kdecarb des Photolysemechanismus ermittelt wurde. Am Ende folgten die Anwendungserprobungen ausgewählter caged Verbindungen in einem Translationsassay bzw. in Zelluntersuchungen.
In the present thesis, the self-assembly of multi thermoresponsive block copolymers in dilute aqueous solution was investigated by a combination of turbidimetry, dynamic light scattering, TEM measurements, NMR as well as fluorescence spectroscopy. The successive conversion of such block copolymers from a hydrophilic into a hydrophobic state includes intermediate amphiphilic states with a variable hydrophilic-to-lipophilic balance. As a result, the self-organization is not following an all-or-none principle but a multistep aggregation in dilute solution was observed. The synthesis of double thermoresponsive diblock copolymers as well as triple thermoresponsive triblock copolymers was realized using twofold-TMS labeled RAFT agents which provide direct information about the average molar mass as well as residual end group functionality from a routine proton NMR spectrum. First a set of double thermosensitive diblock copolymers poly(N-n-propylacrylamide)-b-poly(N-ethylacrylamide) was synthesized which differed only in the relative size of the two blocks. Depending on the relative block lengths, different aggregation pathways were found. Furthermore, the complementary TMS-labeled end groups served as NMR-probes for the self-assembly of these diblock copolymers in dilute solution. Reversible, temperature sensitive peak splitting of the TMS-signals in NMR spectroscopy was indicative for the formation of mixed star-/flower-like micelles in some cases. Moreover, triple thermoresponsive triblock copolymers from poly(N-n-propylacrylamide) (A), poly(methoxydiethylene glycol acrylate) (B) and poly(N-ethylacrylamide) (C) were obtained from sequential RAFT polymerization in all possible block sequences (ABC, BAC, ACB). Their self-organization behavior in dilute aqueous solution was found to be rather complex and dependent on the positioning of the different blocks within the terpolymers. Especially the localization of the low-LCST block (A) had a large influence on the aggregation behavior. Above the first cloud point, aggregates were only observed when the A block was located at one terminus. Once placed in the middle, unimolecular micelles were observed which showed aggregation only above the second phase transition temperature of the B block. Carrier abilities of such triple thermosensitive triblock copolymers tested in fluorescence spectroscopy, using the solvatochromic dye Nile Red, suggested that the hydrophobic probe is less efficiently incorporated by the polymer with the BAC sequence as compared to ABC or ACB polymers above the first phase transition temperature. In addition, due to the problem of increasing loss of end group functionality during the subsequent polymerization steps, a novel concept for the one-step synthesis of multi thermoresponsive block copolymers was developed. This allowed to synthesize double thermoresponsive di- and triblock copolymers in a single polymerization step. The copolymerization of different N-substituted maleimides with a thermosensitive styrene derivative (4-vinylbenzyl methoxytetrakis(oxyethylene) ether) led to alternating copolymers with variable LCST. Consequently, an excess of this styrene-based monomer allowed the synthesis of double thermoresponsive tapered block copolymers in a single polymerization step.
In this work, the development of a new molecular building block, based on synthetic peptides derived from decorin, is presented. These peptides represent a promising basis for the design of polymer-based biomaterials that mimic the ECM on a molecular level and exploit specific biological recognition for technical applications. Multiple sequence alignments of the internal repeats of decorin that formed the inner and outer surface of the arch-shaped protein were used to develop consensus sequences. These sequences contained conserved sequence motifs that are likely to be related to structural and functional features of the protein. Peptides representative for the consensus sequences were synthesized by microwave-assisted solid phase peptide synthesis and purified by RP-HPLC, with purities higher than 95 mol%. After confirming the desired masses by MALDI-TOF-MS, the primary structure of each peptide was investigated by 1H and 2D NMR, from which a full assignment of the chemical shifts was obtained. The characterization of the peptides conformation in solution was performed by CD spectroscopy, which demonstrated that using TFE, the peptides from the outer surface of decorin show a high propensity to fold into helical structures as observed in the original protein. To the contrary, the peptides from the inner surface did not show propensity to form stable secondary structure. The investigation of the binding capability of the peptides to Collagen I was performed by surface plasmon resonance analyses, from which all but one of the peptides representing the inner surface of decorin showed binding affinity to collagen with values of dissociation constant between 2•10-7 M and 2.3•10-4 M. On the other hand, the peptides representative for the outer surface of decorin did not show any significant interaction to collagen. This information was then used to develop experimental demonstration for the binding capabilities of the peptides from the inner surface of decorin to collagen even when used in more complicated situations close to possible appications. With this purpose, the peptide (LRELHLNNN) which showed the highest binding affinity to collagen (2•10-7 M) was functionalized with an N-terminal triple bond in order to obtain a peptide dimer via copper(I)-catalyzed cycloaddition reaction with 4,4'-diazidostilbene-2,2'-disulfonic acid. Rheological measurements showed that the presence of the peptide dimer was able to enhance the elastic modulus (G') of a collagen gel from ~ 600 Pa (collagen alone) to ~ 2700 Pa (collagen and peptide dimer). Moreover, it was shown that the mechanical properties of a collagen gel can be tailored by using different molar ratios of peptide dimer respect to collagen. The same peptide, functionalized with the triple bond, was used to obtain a peptide-dye conjugate by coupling it with N-(5'-azidopentanoyl)-5-aminofluorescein. An aqueous solution (5 vol% methanol) of the peptide dye conjugate was injected into a collagen and a hyaluronic acid (HA) gel and images of fluorescence detection showed that the diffusion of the peptide was slower in the collagen gel compared to the HA gel. The third experimental demonstration was gained using the peptide (LSELRLHNN) which showed the lower binding affinity (2.3•10-4 M) to collagen. This peptide was grafted to hyaluronic acid via EDC-chemistry, with a degree of functionalization of 7 ± 2 mol% as calculated by 1H-NMR. The grafting was further confirmed by FTIR and TGA measurements, which showed that the onset of decomposition for the HA-g-peptide decreased by 10 °C compared to the native HA. Rheological measurements showed that the elastic modulus of a system based on collagen and HA-g-peptide increased by almost two order of magnitude (G' = 200 Pa) compared to a system based on collagen and HA (G' = 0.9 Pa). Overall, this study showed that the synthetic peptides, which were identified from decorin, can be applied as potential building blocks for biomimetic materials that function via biological recognition.
Im Mittelpunkt dieser Arbeit stehen virtuelle 3D-Stadtmodelle, die Objekte, Phänomene und Prozesse in urbanen Räumen in digitaler Form repräsentieren. Sie haben sich zu einem Kernthema von Geoinformationssystemen entwickelt und bilden einen zentralen Bestandteil geovirtueller 3D-Welten. Virtuelle 3D-Stadtmodelle finden nicht nur Verwendung als Mittel für Experten in Bereichen wie Stadtplanung, Funknetzplanung, oder Lärmanalyse, sondern auch für allgemeine Nutzer, die realitätsnah dargestellte virtuelle Städte in Bereichen wie Bürgerbeteiligung, Tourismus oder Unterhaltung nutzen und z. B. in Anwendungen wie GoogleEarth eine räumliche Umgebung intuitiv erkunden und durch eigene 3D-Modelle oder zusätzliche Informationen erweitern. Die Erzeugung und Darstellung virtueller 3D-Stadtmodelle besteht aus einer Vielzahl von Prozessschritten, von denen in der vorliegenden Arbeit zwei näher betrachtet werden: Texturierung und Visualisierung. Im Bereich der Texturierung werden Konzepte und Verfahren zur automatischen Ableitung von Fototexturen aus georeferenzierten Schrägluftbildern sowie zur Speicherung oberflächengebundener Daten in virtuellen 3D-Stadtmodellen entwickelt. Im Bereich der Visualisierung werden Konzepte und Verfahren für die multiperspektivische Darstellung sowie für die hochqualitative Darstellung nichtlinearer Projektionen virtueller 3D-Stadtmodelle in interaktiven Systemen vorgestellt. Die automatische Ableitung von Fototexturen aus georeferenzierten Schrägluftbildern ermöglicht die Veredelung vorliegender virtueller 3D-Stadtmodelle. Schrägluftbilder bieten sich zur Texturierung an, da sie einen Großteil der Oberflächen einer Stadt, insbesondere Gebäudefassaden, mit hoher Redundanz erfassen. Das Verfahren extrahiert aus dem verfügbaren Bildmaterial alle Ansichten einer Oberfläche und fügt diese pixelpräzise zu einer Textur zusammen. Durch Anwendung auf alle Oberflächen wird das virtuelle 3D-Stadtmodell flächendeckend texturiert. Der beschriebene Ansatz wurde am Beispiel des offiziellen Berliner 3D-Stadtmodells sowie der in GoogleEarth integrierten Innenstadt von München erprobt. Die Speicherung oberflächengebundener Daten, zu denen auch Texturen zählen, wurde im Kontext von CityGML, einem international standardisierten Datenmodell und Austauschformat für virtuelle 3D-Stadtmodelle, untersucht. Es wird ein Datenmodell auf Basis computergrafischer Konzepte entworfen und in den CityGML-Standard integriert. Dieses Datenmodell richtet sich dabei an praktischen Anwendungsfällen aus und lässt sich domänenübergreifend verwenden. Die interaktive multiperspektivische Darstellung virtueller 3D-Stadtmodelle ergänzt die gewohnte perspektivische Darstellung nahtlos um eine zweite Perspektive mit dem Ziel, den Informationsgehalt der Darstellung zu erhöhen. Diese Art der Darstellung ist durch die Panoramakarten von H. C. Berann inspiriert; Hauptproblem ist die Übertragung des multiperspektivischen Prinzips auf ein interaktives System. Die Arbeit stellt eine technische Umsetzung dieser Darstellung für 3D-Grafikhardware vor und demonstriert die Erweiterung von Vogel- und Fußgängerperspektive. Die hochqualitative Darstellung nichtlinearer Projektionen beschreibt deren Umsetzung auf 3D-Grafikhardware, wobei neben der Bildwiederholrate die Bildqualität das wesentliche Entwicklungskriterium ist. Insbesondere erlauben die beiden vorgestellten Verfahren, dynamische Geometrieverfeinerung und stückweise perspektivische Projektionen, die uneingeschränkte Nutzung aller hardwareseitig verfügbaren, qualitätssteigernden Funktionen wie z.~B. Bildraumgradienten oder anisotroper Texturfilterung. Beide Verfahren sind generisch und unterstützen verschiedene Projektionstypen. Sie ermöglichen die anpassungsfreie Verwendung gängiger computergrafischer Effekte wie Stilisierungsverfahren oder prozeduraler Texturen für nichtlineare Projektionen bei optimaler Bildqualität. Die vorliegende Arbeit beschreibt wesentliche Technologien für die Verarbeitung virtueller 3D-Stadtmodelle: Zum einen lassen sich mit den Ergebnissen der Arbeit Texturen für virtuelle 3D-Stadtmodelle automatisiert herstellen und als eigenständige Attribute in das virtuelle 3D-Stadtmodell einfügen. Somit trägt diese Arbeit dazu bei, die Herstellung und Fortführung texturierter virtueller 3D-Stadtmodelle zu verbessern. Zum anderen zeigt die Arbeit Varianten und technische Lösungen für neuartige Projektionstypen für virtueller 3D-Stadtmodelle in interaktiven Visualisierungen. Solche nichtlinearen Projektionen stellen Schlüsselbausteine dar, um neuartige Benutzungsschnittstellen für und Interaktionsformen mit virtuellen 3D-Stadtmodellen zu ermöglichen, insbesondere für mobile Geräte und immersive Umgebungen.
Active Galactic Nuclei (AGN) are powered by gas accretion onto supermassive Black Holes (BH). The luminosity of AGN can exceed the integrated luminosity of their host galaxies by orders of magnitude, which are then classified as Quasi-Stellar Objects (QSOs). Some mechanisms are needed to trigger the nuclear activity in galaxies and to feed the nuclei with gas. Among several possibilities, such as gravitational interactions, bar instabilities, and smooth gas accretion from the environment, the dominant process has yet to be identified. Feedback from AGN may be important an important ingredient of the evolution of galaxies. However, the details of this coupling between AGN and their host galaxies remain unclear. In this work we aim to investigate the connection between the AGN and their host galaxies by studying the properties of the extendend ionised gas around AGN. Our study is based on observations of ~50 luminous, low-redshift (z<0.3) QSOs using the novel technique of integral field spectroscopy that combines imaging and spectroscopy. After spatially separating the emission of AGN-ionised gas from HII regions, ionised solely by recently formed massive stars, we demonstrate that the specific star formation rates in several disc-dominated AGN hosts are consistent with those of normal star forming galaxies, while others display no detectable star formation activity. Whether the star formation has been actively suppressed in those particular host galaxies by the AGN, or their gas content is intrinsically low, remains an open question. By studying the kinematics of the ionised gas, we find evidence for non-gravitational motions and outflows on kpc scales only in a few objects. The gas kinematics in the majority of objects however indicate a gravitational origin. It suggests that the importance of AGN feedback may have been overrated in theoretical works, at least at low redshifts. The [OIII] line is the strongest optical emission line for AGN-ionised gas, which can be extended over several kpc scales, usually called the Narrow-Line Region (NLR). We perform a systematic investigation of the NLR size and determine a NLR size-luminosity relation that is consistent with the scenario of a constant ionisation parameter throughout the NLR. We show that previous narrow-band imaging with the Hubble Space Telescope underestimated the NLR size by a factor of >2 and that the continuum AGN luminosity is better correlated with the NLR size than the [OIII] luminosity. These affects may account for the different NLR size-luminosity relations reported in previous studies. On the other hand, we do not detect extended NLRs around all QSOs, and demonstrate that the detection of extended NLRs goes along with radio emission. We employ emission line ratios as a diagnostic for the abundance of heavy elements in the gas, i.e. its metallicity, and find that the radial metallicity gradients are always flatter than in inactive disc-dominated galaxies. This can be interpreted as evidence for radial gas flows from the outskirts of these galaxies to the nucleus. Recent or ongoing galaxy interactions are likely responsible for this effect and may turn out to be a common prerequisite for QSO activity. The metallicity of bulge-dominated hosts are systematically lower than their disc-dominated counterparts, which we interpret as evidence for minor mergers, supported by our detailed study of the bulge-dominated host of the luminous QSO HE 1029-1401, or smooth gas accretion from the environment. In this line another new discovery is that HE 2158-0107 at z=0.218 is the most metal poor luminous QSO ever observed. Together with a large (30kpc) extended structure of low metallicity ionised gas, we propose smooth cold gas accretion as the most likely scenario. Theoretical studies suggested that this process is much more important at earlier epochs of the universe, so that HE 2158-0107 might be an ideal laboratory to study this mechanism of galaxy and BH growth at low redshift more detailed in the furture.
Plants and some unicellular algae store carbon in the form of transitory starch on a diurnal basis. The turnover of this glucose polymer is tightly regulated and timely synthesis as well as mobilization is essential to provide energy for heterotrophic growth. Especially for starch degradation, novel enzymes and mechanisms have been proposed recently. However, the catalytic properties of these enzymes and their coordination with metabolic regulation are still to be discovered. This thesis develops theoretical methods in order to interpret and analyze enzymes and their role in starch degradation. In the first part, a novel description of interfacial enzyme catalysis is proposed. Since the initial steps of starch degradation involve reactions at the starch-stroma interface it is necessary to have a framework which allows the derivation of interfacial enzyme rate laws. A cornerstone of the method is the introduction of the available area function - a concept from surface physics - to describe the adsorption step in the catalytic cycle. The method is applied to derive rate laws for two hydrolases, the Beta-amylase (BAM3) and the Isoamylase (DBE/ISA3), as well as to the Glucan, water dikinase (GWD) and a Phosphoglucan phosphatase (DSP/SEX4). The second part uses the interfacial rate laws to formulate a kinetic model of starch degradation. It aims at reproducing the stimulatory effect of reversible phosphorylation by GWD and DSP on the breakdown of the granule. The model can describe the dynamics of interfacial properties during degradation and suggests that interfacial amylopectin side-chains undergo spontaneous helix-coil transitions. Reversible phosphorylation has a synergistic effect on glucan release especially in the early phase dropping off during degradation. Based on the model, the hypothesis is formulated that interfacial phosphorylation is important for the rapid switch from starch synthesis to starch degradation. The third part takes a broader perspective on carbohydrate-active enzymes (CAZymes) but is motivated by the organization of the downstream pathway of starch breakdown. This comprises Alpha-1,4-glucanotransferases (DPE1 and DPE2) and Alpha-glucan-phosphorylases (Pho or PHS) both in the stroma and in the cytosol. CAZymes accept many different substrates and catalyze numerous reactions and therefore cannot be characterized in classical enzymological terms. A concise characterization is provided by conceptually linking statistical thermodynamics and polymer biochemistry. Each reactant is interpreted as an energy level, transitions between which are constrained by the enzymatic mechanisms. Combinations of in vitro assays of polymer-active CAZymes essential for carbon metabolism in plants confirmed the dominance of entropic gradients. The principle of entropy maximization provides a generalization of the equilibrium constant. Stochastic simulations confirm the results and suggest that randomization of metabolites in the cytosolic pool of soluble heteroglycans (SHG) may contribute to a robust integration of fluctuating carbon fluxes coming from chloroplasts.