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The correlations between the chemical structures of the 2,5-diphenyl-1,3,4-oxadiazole compounds and their corresponding vapour deposited film structures on Si/SiO2 were systematically investigated with AFM, XSR and IR for the first time. The result shows that the film structure depends strongly on the substrate temperature (Ts). For the compounds with ether bridge group, the film periodicity depends linearly on the length of the aliphatic chain. The films based on those oxadiazols have ordered structure in the investigated substrate temperature region, while die amide bridged compounds form ordered film only at high Ts due to the formation of intermolecular H-bond. The tilt angle of most molecules is determined by the pi-pi complexes between the molecules. The intermolecular interaction between head groups leads to the structural transformation during the thermal treatment after deposition. All the ether bridged oxadiazoles form films with bilayer structure, while amide bridged oxadiazole form film bilayer structure only when the molecule has a head group.
Chemical transformations and hydraulic processes in soil and groundwater often lead to an apparent retention of nitrate in lowland catchments. Models are needed to evaluate the interaction of these processes in space and time. The objectives of this study are i) to develop a specific modelling approach by combining selected modelling tools simulating N-transport and turnover in soils and groundwater of lowland catchments, ii) to study interactions between catchment properties and nitrogen transport. Special attention was paid to potential N-loads to surface waters. The modelling approach combines various submodels for water flow and solute transport in soil and groundwater: The soil-water- and nitrogen-model mRISK-N, the groundwater flow model MODFLOW and the solute transport model RT3D. In order to investigate interactions of N-transport and catchment characteristics, the distribution and availability of reaction partners have to be taken into account. Therefore, a special reaction-module is developed, which simulates various chemical processes in groundwater, such as the degradation of organic matter by oxygen, nitrate, sulphate or pyrite oxidation by oxygen and nitrate. The model approach is applied to different simulation, focussing on specific submodels. All simulation studies are based on field data from the Schaugraben catchment, a pleistocene catchment of approximately 25 km², close to Osterburg(Altmark) in the North of Saxony-Anhalt. The following modelling studies have been carried out: i) evaluation of the soil-water- and nitrogen-model based on lysimeter data, ii) modelling of a field scale tracer experiment on nitrate transport and turnover in the groundwater as a first application of the reaction module, iii) evaluation of interactions between hydraulic and chemical aquifer properties in a two-dimensional groundwater transect, iv) modelling of distributed groundwater recharge and soil nitrogen leaching in the study area, to be used as input data for subsequent groundwater simulations, v) study of groundwater nitrate distribution and nitrate breakthrough to the surface water system in the Schaugraben catchment area and a subcatchment, using three-dimensional modelling of reactive groundwater transport. The various model applications prove the model to be capable of simulating interactions between transport, turnover and hydraulic and chemical catchment properties. The distribution of nitrate in the sediment and the resulting loads to surface waters are strongly affected by the amount of reactive substances and by the residence time within the aquifer. In the Schaugraben catchment simulations, it is found that a period of 70 years is needed to raise the average seepage concentrations of nitrate to a level corresponding to the given input situation, if no reactions are considered. Under reactive transport conditions, nitrate concentrations are reduced effectively. Simulation results show that groundwater exfiltration does not contribute considerably to the nitrate pollution of surface waters, as most nitrate entering soils and groundwater is lost by denitrification. Additional sources, such as direct inputs or tile drains have to be taken into account to explain surface water loads. The prognostic value of the models for the study site is limited by uncertainties of input data and estimation of model parameters. Nevertheless, the modelling approach is a useful aid for the identification of source and sink areas of nitrate pollution as well as the investigation of system response to management measures or landuse changes with scenario simulations. The modelling approach assists in the interpretation of observed data, as it allows to integrate local observations into a spatial and temporal framework.
Sprachverstehen mit Cochlea-Implantat : EKP-Studien mit postlingual ertaubten erwachsenen CI-Trägern
(2004)
Entsprechend der sogenannten Set-point-Theorie besitzt jeder Mensch eine individuell festgelegte Körpermasse, die über große Zeiträume konstant gehalten und gegen Abweichungen verteidigt wird. Es wird angenommen, dass der Körper auf noch unbekannte Weise Änderungen in der Körpermasse per se wahrnimmt und daraufhin Mechanismen aktiviert, die zur Regenerierung der ursprünglichen Masse führen. In dieser Arbeit wurde die Hypothese getestet, dass eine künstliche Erhöhung der Körpermasse zu einer kompensatorischen Reduktion in der Körpermasse führt, um das Ausgangsgewicht wieder zu regenerieren. Die Körpermasse von männlichen und weiblichen Mäusen wurde akut durch die Implantation von Gewichten mit einer Masse von 10% der aktuellen Körpermasse in die Bauchhöhle erhöht. Bei Gültigkeit der Set-point-Theorie sollte die Körpermassereduktion der Masse des zusätzlichen Gewichtsimplantats entsprechen. Die Mäuse reagierten auf die künstlich erhöhte Körpermasse geschlechtsspezifisch. Männchen zeigten eine partielle Reduktion in der Körpermasse. Weibchen zeigten langfristig jedoch keine Änderungen in der Körpermasse. Die Reduktion der Körpermasse erfolgte bei den Männchen durch eine Abnahme in der Fettmasse. Die fettfreie Masse war in beiden Geschlechtern nicht verändert. Änderungen in der Körpermasse wurden vor allem durch Änderungen in der Energieaufnahme hervorgerufen. Ein Einfluss des Energieumsatzes auf Änderungen in der Körpermasse konnte nicht nachgewiesen werden. Die Regulation der Körpermasse entsprechend eines massespezifischen Set-points konnte partiell für die Männchen gezeigt werden. Bei den Männchen könnte daher die Wahrnehmung der Körpermasse in die Regulation der Körpermasse teilweise integriert sein. Weibchen verminderten ihre Körpermasse dagegen trotz der künstlichen Körpermasseerhöhung nicht. Das führte zur Bewahrung der Energiereserven und spricht eher für die Regulation der Körpermasse entsprechend des notwendigen Energiebedarfs im Vergleich zu Änderungen in der Körpermasse per se. Diese Ergebnisse zeigen, dass die Regulation der Körpermasse geschlechtsspezifischen Mechanismen unterliegt. Dementsprechend sind auch geschlechtsspezifische Ansätze zur Therapie von Übergewicht und Adipositas notwendig.
Robotic telescopes & Doppler imaging : measuring differential rotation on long-period active stars
(2004)
The sun shows a wide variety of magnetic-activity related phenomena. The magnetic field responsible for this is generated by a dynamo process which is believed to operate in the tachocline, which is located at the bottom of the convection zone. This dynamo is driven in part by differential rotation and in part by magnetic turbulences in the convection zone. The surface differential rotation, one key ingredient of dynamo theory, can be measured by tracing sunspot positions.To extend the parameter space for dynamo theories, one can extend these measurements to other stars than the sun. The primary obstacle in this endeavor is the lack of resolved surface images on other stars. This can be overcome by the Doppler imaging technique, which uses the rotation-induced Doppler-broadening of spectral lines to compute the surface distribution of a physical parameter like temperature. To obtain the surface image of a star, high-resolution spectroscopic observations, evenly distributed over one stellar rotation period are needed. This turns out to be quite complicated for long period stars. The upcoming robotic observatory STELLA addresses this problem with a dedicated scheduling routine, which is tailored for Doppler imaging targets. This will make observations for Doppler imaging not only easier, but also more efficient.As a preview of what can be done with STELLA, we present results of a Doppler imaging study of seven stars, all of which show evidence for differential rotation, but unfortunately the errors are of the same order of magnitude as the measurements due to unsatisfactory data quality, something that will not happen on STELLA. Both, cross-correlation analysis and the sheared image technique where used to double check the results if possible. For four of these stars, weak anti-solar differential rotation was found in a sense that the pole rotates faster than the equator, for the other three stars weak differential rotation in the same direction as on the sun was found.Finally, these new measurements along with other published measurements of differential rotation using Doppler imaging, were analyzed for correlations with stellar evolution, binarity, and rotation period. The total sample of stars show a significant correlation with rotation period, but if separated into antisolar and solar type behavior, only the subsample showing anti-solar differential rotation shows this correlation. Additionally, there is evidence for binary stars showing less differential rotation as single stars, as is suggested by theory. All other parameter combinations fail to deliver any results due to the still small sample of stars available.
Understanding stars, their magnetic activity phenomena and the underlying dynamo action is the foundation for understanding 'life, the universe and everything' - as stellar magnetic fields play a fundamental role for star and planet formation and for the terrestrial atmosphere and climate. Starspots are the fingerprints of magnetic field lines and thereby the most important sign of activity in a star's photosphere. However, they cannot be observed directly, as it is not (yet) possible to spacially resolve the surfaces of even the nearest neighbouring stars. Therefore, an indirect approach called 'Doppler imaging' is applied, which allows to reconstruct the surface spot distribution on rapidly rotating, active stars. In this work, data from 11 years of continuous spectroscopic observations of the active binary star EI Eridani are reduced and analysed. 34 Doppler maps are obtained and the problem of how to parameterise the information content of Doppler maps is discussed. Three approaches for parameter extraction are introduced and applied to all maps: average temperature, separated for several latitude bands; fractional spottedness; and, for the analysis of structural temperature distribution, longitudinal and latitudinal spot-occurrence functions. The resulting values do not show a distinct correlation with the proposed activity cycle as seen from photometric long-term observations, thereby suggesting that the photometric activity cycle is not accompanied by a spot cycle as seen on the Sun. The general morphology of the spot pattern on EI Eri remains persistent for the whole period of 11 years. In addition, a detailed parameter study is performed. Improved orbital parameters suggest that EI Eri might be complemented by a third star in a wide orbit of about 19 years. Preliminary differential rotation measurements are carried out, indicating an anti-solar orientation.
Zwischen 1990 und 1994 wurden rund 1000 Liegenschaften, die in der ehemaligen DDR von der Sowjetarmee und der NVA für militärische Übungen genutzt wurden, an Bund und Länder übergeben. Die größten Truppenübungsplätze liegen in Brandenburg und sind heute teilweise in Großschutzgebiete integriert, andere Plätze werden von der Bundeswehr weiterhin aktiv genutzt. Aufgrund des militärischen Betriebs sind die Böden dieser Truppenübungsplätze oft durch Blindgänger, Munitionsreste, Treibstoff- und Schmierölreste bis hin zu chemischen Kampfstoffen belastet. Allerdings existieren auf fast allen Liegenschaften neben diesen durch Munition und militärische Übungen belasteten Bereichen auch naturschutzfachlich wertvolle Flächen; gerade in den Offenlandbereichen kann dies durchaus mit einer Belastung durch Kampfmittel einhergehen. Charakteristisch für diese offenen Flächen, zu denen u.a. Zwergstrauchheiden, Trockenrasen, wüstenähnliche Sandflächen und andere nährstoffarme baumlose Lebensräume gehören, sind Großflächigkeit, Abgeschiedenheit sowie ihre besondere Nutzung und Bewirtschaftung, d.h. die Abwesenheit von land- und forstwirtschaftlichem Betrieb sowie von Siedlungsflächen. Diese Charakteristik war die Grundlage für die Entwicklung einer speziell angepassten Flora und Fauna. Nach Beendigung des Militärbetriebs setzte dann in weiten Teilen eine großflächige Sukzession – die allmähliche Veränderung der Zusammensetzung von Pflanzen- und Tiergesellschaften – ein, die diese offenen Bereiche teilweise bereits in Wald verwandelte und somit verschwinden ließ. Dies wiederum führte zum Verlust der an diese Offenlandflächen gebundenen Tier- und Pflanzenarten. Zur Erhaltung, Gestaltung und Entwicklung dieser offenen Flächen wurden daher von einer interdisziplinären Gruppe von Naturwissenschaftlern verschiedene Methoden und Konzepte auf ihre jeweilige Wirksamkeit untersucht. So konnten schließlich die für die jeweiligen Standortbedingungen geeigneten Maßnahmen eingeleitet werden. Voraussetzung für die Einleitung der Maßnahmen sind zum einen Kenntnisse zu diesen jeweiligen Standortbedingungen, d.h. zum Ist-Zustand, sowie zur Entwicklung der Flächen, d.h. zur Dynamik. So kann eine Abschätzung über die zukünftige Flächenentwicklung getroffen werden, damit ein effizienter Maßnahmeneinsatz stattfinden kann. Geoinformationssysteme (GIS) spielen dabei eine entscheidende Rolle zur digitalen Dokumentation der Biotop- und Nutzungstypen, da sie die Möglichkeit bieten, raum- und zeitbezogene Geometrie- und Sachdaten in großen Mengen zu verarbeiten. Daher wurde ein fachspezifisches GIS für Truppenübungsplätze entwickelt und implementiert. Die Aufgaben umfassten die Konzeption der Datenbank und des Objektmodells sowie fachspezifischer Modellierungs-, Analyse- und Präsentationsfunktionen. Für die Integration von Fachdaten in die GIS-Datenbank wurde zudem ein Metadatenkatalog entwickelt, der in Form eines zusätzlichen GIS-Tools verfügbar ist. Die Basisdaten für das GIS wurden aus Fernerkundungsdaten, topographischen Karten sowie Geländekartierungen gewonnen. Als Instrument für die Abschätzung der zukünftigen Entwicklung wurde das Simulationstool AST4D entwickelt, in dem sowohl die Nutzung der (Raster-)Daten des GIS als Ausgangsdaten für die Simulationen als auch die Nutzung der Simulationsergebnisse im GIS möglich ist. Zudem können die Daten in AST4D raumbezogen visualisiert werden. Das mathematische Konstrukt für das Tool war ein so genannter Zellulärer Automat, mit dem die Flächenentwicklung unter verschiedenen Voraussetzungen simuliert werden kann. So war die Bildung verschiedener Szenarien möglich, d.h. die Simulation der Flächenentwicklung mit verschiedenen (bekannten) Eingangsparametern und den daraus resultierenden unterschiedlichen (unbekannten) Endzuständen. Vor der Durchführung einer der drei in AST4D möglichen Simulationsstufen können angepasst an das jeweilige Untersuchungsgebiet benutzerspezifische Festlegungen getroffen werden.
The overall objective of the study is an elaboration of quantitative methods for national conservation planning, coincident with the international approach ('hotspots' approach). This objective requires a solution of following problems: 1) How to estimate large scale vegetation diversity from abiotic factors only? 2) How to adopt 'global hotspots' approach for bordering of national biodiversity hotspots? 3) How to set conservation targets, accounting for difference in environmental conditions and human threats between national biodiversity hotspots? 4) How to design large scale national conservation plan reflecting hierarchical nature of biodiversity? The case study for national conservation planning is Russia. Conclusions: · Large scale vegetation diversity can be predicted to a major extent by climatically determined latent heat for evaporation and geometrical structure of landscape, described as an altitudinal difference. The climate based model reproduces observed species number of vascular plant for different areas of the world with an average error 15% · National biodiversity hotspots can be mapped from biotic or abiotic data using corrected for a country the quantitative criteria for plant endemism and land use from the 'global hotspots' approach · Quantitative conservation targets, accounting for difference in environmental conditions and human threats between national biodiversity hotspots can be set using national data for Red Data book species · Large scale national conservation plan reflecting hierarchical nature of biodiversity can be designed by combination of abiotic method at national scale (identification of large scale hotspots) and biotic method at regional scale (analysis of species data from Red Data book)
A polymer is a large molecule made up of many elementary chemical units, joined together by covalent bonds (for example, polyethylene). Polyelectrolytes (PELs) are polymer chains containing a certain amount of ionizable monomers. With their specific properties PELs acquire big importance in molecular and cell biology as well as in technology. Compared to neutral polymers the theory of PELs is less understood. In particular, this is valid for PELs in poor solvents. A poor solvent environment causes an effective attraction between monomers. Hence, for PELs in a poor solvent, there occurs a competition between attraction and repulsion. Strong or quenched PELs are completely dissociated at any accessible pH. The position of charges along the chain is fixed by chemical synthesis. On the other hand, in weak or annealed PELs dissociation of charges depends on solution pH. For the first time the simulation results have given direct evidence that at rather poor solvents an annealed PEL indeed undergoes a first-order phase transition when the chemical potential (solution pH) reaches at a certain value. The discontinuous transition occurs between a weakly charged compact globular structure and a strongly charged stretched configuration. At not too poor solvents theory predicts that globule would become unstable with respect to the formation of pearl-necklaces. The results show that pearl-necklaces exist in annealed PELs indeed. Furthermore, as predicted by theory, the simulation results have shown that annealed PELs display a sharp transition from a highly charged stretched state to a weakly charged globule at a critical salt concentration.
Even though the structure of the plant cell wall is by and large quite well characterized, its synthesis and regulation remains largely obscure. However, it is accepted that the building blocks of the polysaccharidic part of the plant cell wall are nucleotide sugars. Thus to gain more insight into the cell wall biosynthesis, in the first part of this thesis, plant genes possibly involved in the nucleotide sugar interconversion pathway were identified using a bioinformatics approach and characterized in plants, mainly in Arabidopsis. For the computational identification profile hidden markov models were extracted from the Pfam and TIGR databases. Mainly with these, plant genes were identified facilitating the “hmmer” program. Several gene families were identified and three were further characterized, the UDP-rhamnose synthase (RHM), UDP-glucuronic acid epimerase (GAE) and the myo-inositol oxygenase (MIOX) families. For the three-membered RHM family relative ubiquitous expression was shown using variuos methods. For one of these genes, RHM2, T-DNA lines could be obtained. Moreover, the transcription of the whole family was downregulated facilitating an RNAi approach. In both cases a alteration of cell wall typic polysaccharides and developmental changes could be shown. In the case of the rhm2 mutant these were restricted to the seed or the seed mucilage, whereas the RNAi plants showed profound changes in the whole plant. In the case of the six-membered GAE family, the gene expressed to the highest level (GAE6) was cloned, expressed heterologously and its function was characterized. Thus, it could be shown that GAE6 encodes for an enzyme responsible for the conversion of UDP-glucuronic acid to UDP-galacturonic acid. However, a change in transcript level of variuos GAE family members achieved by T-DNA insertions (gae2, gae5, gae6), overexpression (GAE6) or an RNAi approach, targeting the whole family, did not reveal any robust changes in the cell wall. Contrary to the other two families the MIOX gene family had to be identified using a BLAST based approach due to the lack of enough suitable candidate genes for building a hidden markov model. An initial bioinformatic characterization was performed which will lead to further insights into this pathway. In total it was possible to identify the two gene families which are involved in the synthesis of the two pectin backbone sugars galacturonic acid and rhamnose. Moreover with the identification of the MIOX genes a genefamily, important for the supply of nucleotide sugar precursors was identified. In a second part of this thesis publicly available microarray datasets were analyzed with respect to co-responsive behavior of transcripts on a global basis using nearly 10,000 genes. The data has been made available to the community in form of a database providing additional statistical and visualization tools (http://csbdb.mpimp-golm.mpg.de). Using the framework of the database to identify nucleotide sugar converting genes indicated that co-response might be used for identification of novel genes involved in cell wall synthesis based on already known genes.
My thesis is concerned with several new noise-induced phenomena in excitable neural models, especially those with FitzHugh-Nagumo dynamics. In these effects the fluctuations intrinsically present in any complex neural network play a constructive role and improve functionality. I report the occurrence of Vibrational Resonance in excitable systems. Both in an excitable electronic circuit and in the FitzHugh-Nagumo model, I show that an optimal amplitude of high-frequency driving enhances the response of an excitable system to a low-frequency signal. Additionally, the influence of additive noise and the interplay between Stochastic and Vibrational Resonance is analyzed. Further, I study systems which combine both oscillatory and excitable properties, and hence intrinsically possess two internal frequencies. I show that in such a system the effect of Stochastic Resonance can be amplified by an additional high-frequency signal which is in resonance with the oscillatory frequency. This amplification needs much lower noise intensities than for conventional Stochastic Resonance in excitable systems. I study frequency selectivity in noise-induced subthreshold signal processing in a system with many noise-supported stochastic attractors. I show that the response of the coupled elements at different noise levels can be significantly enhanced or reduced by forcing some elements into resonance with these new frequencies which correspond to appropriate phase-relations. A noise-induced phase transition to excitability is reported in oscillatory media with FitzHugh-Nagumo dynamics. This transition takes place via noise-induced stabilization of a deterministically unstable fixed point of the local dynamics, while the overall phase-space structure of the system is maintained. The joint action of coupling and noise leads to a different type of phase transition and results in a stabilization of the system. The resulting noise-induced regime is shown to display properties characteristic of excitable media, such as Stochastic Resonance and wave propagation. This effect thus allows the transmission of signals through an otherwise globally oscillating medium. In particular, these theoretical findings suggest a possible mechanism for suppressing undesirable global oscillations in neural networks (which are usually characteristic of abnormal medical conditions such as Parkinson′s disease or epilepsy), using the action of noise to restore excitability, which is the normal state of neuronal ensembles.
It is known that the efficiency of organic light-emitting devices (OLEDs) is strongly influenced by the ’quality′ of the thin films [1]. On the basis of this conviction, the work presented in this thesis aimed to obtain a better understanding of the structure of organic thin films of general interest in the field of organic light emitting devices by using scanning probe microscopies (SPMs). A not yet reported crystal structure of quaterthiophene film grown on potassium hydrogen (KHP) is determined by optical measurements, a simulation program, diffraction at both normal incidence and grazing angle and AFM. The crystal cell is triclinic with parameters a = 0.721 nm, b = 0.632 nm, c = 0.956 nm and a = 91°, b = 91.4°, g = 91° [2]. The morphologies of four organic thin films deposited on gold are characterized by ultra high vacuum scanning tunneling microscopy (UHV-STM). Terraces in an hexanethiol monolayer, lamellar structures in an azobenzenethiol monolayer, rods in a a poly(paraphenylenevinylene) oligomer film and a granular morphology in an oxadiazole film are shown. The topographies of a series of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) films deposited on indium-tin oxide (ITO) and gold obtained from dispersions with PEDOT:PSS weight ratios of 1:20, 1:6 and 1:1 are investigated by AFM. It is demonstrated that the films show the same topography on gold and on ITO. It is shown that the PEDOT films eliminate the spike features of ITO. It is reported that PEDOT 1:20 and 1:6 appear indistinguishable between each other but different from PEDOT 1:1 (the most conductive). Coupling STM and I-d measurements, a not yet reported structural model of PEDOT 1:1 on gold is obtained [3]. In this model the surface presents grains and the bulk particles/domains rich in PEDOT embedded in a PEDOT-poor matrix. The equation of conductivity is derived. A STM investigation of four PEDOT films deposited on ITO obtained from dispersions with the same PEDOT:PSS weight ratio of 1:1 is carried out [4]. The films differ either for the presence of sorbitol or for a different synthetic route (and they present different conductivities). For the first time a quantitative and qualitative correlation between the nanometer-scale morphology of PEDOT films with and without sorbitol and their conductivity is established.
Identifikation des mitochondrialen Proteins Frataxin als stoffwechselmodulierenden Tumorsuppressor
(2004)
Die Krebsentstehung wurde vor rund 80 Jahren auf veränderten zellulären Energiestoffwechsel zurückgeführt. Diese Hypothese konnte bisher weder experimentell bewiesen noch widerlegt werden. Durch den Einsatz zweier Modellsysteme mit unterschiedlicher Expression des mitochondrialen Proteins Frataxin konnte in der vorliegenden Arbeit gezeigt werden, dass der mitochondriale Energiestoffwechsel einen Einfluss auf die Tumorentstehung zu besitzen scheint. Eine Reduktion des mitochondrialen Energiestoffwechsels wurde durch die hepatozytenspezifische Ausschaltung des mitochondrialen Proteins Frataxin in Mäusen erreicht. Der durch das Cre-/loxP-Rekombinasesystem erreichte organspezifische Knock-out wurde auf Transkriptions- und Translationsebene nachgewiesen. Anhand verminderter Aconitaseaktivität, geringeren Sauerstoffverbrauches und reduzierten ATP-Gehaltes im Lebergewebe wurde ein signifikant verminderter Energiestoffwechsel dargestellt. Zwar entsprach die Genotypenverteilung in den Versuchsgruppen der erwarteten Mendelschen Verteilung, dennoch war die mittlere Lebenserwartung der Knock-out-Tiere mit ca. 30 Wochen stark reduziert. Bereits in jungem Alter war bei diesen Tieren die Ausbildung von präneoplastischen Herden zu beobachten. Mit proteinbiochemischen Nachweistechniken konnte in Lebergewebe 4-8 Wochen alter Tiere eine verstärkte Aktivierung des Apoptosesignalweges (Cytochrom C im Zytosol, verstärkte Expression von Bax) sowie eine Modulation stressassoziierter Proteine (geringere Phosphorylierungsrate p38-MAPK, vermehrte Expression HSP-25, verminderte Expression HSP-70) aufgezeigt werden. Im inversen Ansatz wurde eine Steigerung des mitochondrialen Energiestoffwechsels durch stabile transgene Frataxinüberexpression in zwei Kolonkarzinomzelllinien erreicht. Diese Steigerung zeigte sich durch erhöhte Aconitaseaktivität, erhöhten Sauerstoffverbrauch, gesteigertes mitochondriales Membranpotenzial und erhöhten ATP-Gehalt in den Zellen. Die frataxinüberexprimierenden Zellen wuchsen signifikant langsamer als Kontrollzellen und zeigten im Soft-Agar-Assay und im Nacktmausmodell ein deutlich geringeres Potenzial zur Ausbildung von Kolonien bzw. Tumoren. Mittels Immunoblot war hier eine vermehrte Phosphorylierung der p38-MAPK festzustellen. Die zusammenfassende Betrachtung beider Modelle zeigt, dass ein reduzierter mitochondrialer Energiestoffwechsel durch Regulation der p38-MAPK und apoptotischer Signalwege ein erhöhtes Krebsrisiko zu verursachen vermag.
Recurrence plots, a rather promising tool of data analysis, have been introduced by Eckman et al. in 1987. They visualise recurrences in phase space and give an overview about the system's dynamics. Two features have made the method rather popular. Firstly they are rather simple to compute and secondly they are putatively easy to interpret. However, the straightforward interpretation of recurrence plots for some systems yields rather surprising results. For example indications of low dimensional chaos have been reported for stock marked data, based on recurrence plots. In this work we exploit recurrences or ``naturally occurring analogues'' as they were termed by E. Lorenz, to obtain three key results. One of which is that the most striking structures which are found in recurrence plots are hinged to the correlation entropy and the correlation dimension of the underlying system. Even though an eventual embedding changes the structures in recurrence plots considerably these dynamical invariants can be estimated independently of the special parameters used for the computation. The second key result is that the attractor can be reconstructed from the recurrence plot. This means that it contains all topological information of the system under question in the limit of long time series. The graphical representation of the recurrences can also help to develop new algorithms and exploit specific structures. This feature has helped to obtain the third key result of this study. Based on recurrences to points which have the same ``recurrence structure'', it is possible to generate surrogates of the system which capture all relevant dynamical characteristics, such as entropies, dimensions and characteristic frequencies of the system. These so generated surrogates are shadowed by a trajectory of the system which starts at different initial conditions than the time series in question. They can be used then to test for complex synchronisation.
We calculate the additional carbon emissions as a result of the conversion of natural land in a process of urbanisation; and the change of carbon flows by “urbanised” ecosystems, when the atmospheric carbon is exported to the neighboring territories, from 1980 till 2050 for the eight regions of the world. As a scenario we use combined UN and demographic model′s prognoses for regional total and urban population growth. The calculations of urban areas dynamics are based on two models: the regression model and the Gamma-model. The urbanised area is sub-divided on built-up, „green“ (parks, etc.) and informal settlements (favelas) areas. The next step is to calculate the regional and world dynamics of carbon emission and export, and the annual total carbon balance. Both models give similar results with some quantitative differences. In the first model, the world annual emissions attain a maximum of 205 MtC/year between 2020-2030. Emissions will then slowly decrease. The maximum contributions are given by China and the Asia and Pacific regions. In the second model, world annual emissions increase to 1.25 GtC in 2005, beginning to decrease afterwards. If we compare the emission maximum with the annual emission caused by deforestation, 1.36GtC per year, then we can say that the role of urbanised territories (UT) is of a comparable magnitude. Regarding the world annual export of carbon by UT, we observe its monotonous growth by three times, from 24 MtC to 66 MtC in the first model, and from 249 MtC to 505 MtC in the second one. The latter, is therefore comparable to the amount of carbon transported by rivers into the ocean (196-537 MtC). By estimating the total balance we find that urbanisation shifts the total balance towards a “sink” state. The urbanisation is inhibited in the interval 2020-2030, and by 2050 the growth of urbanised areas would almost stop. Hence, the total emission of natural carbon at that stage will stabilise at the level of the 1980s (80 MtC per year). As estimated by the second model, the total balance, being almost constant until 2000, then starts to decrease at an almost constant rate. We can say that by the end of the XXI century, the total carbon balance will be equal to zero, when the exchange flows are fully balanced, and may even be negative, when the system begins to take up carbon from the atmosphere, i.e., becomes a “sink”.
The past decades are characterized by various efforts to provide complete sequence information of genomes regarding various organisms. The availability of full genome data triggered the development of multiplex high-throughput assays allowing simultaneous measurement of transcripts, proteins and metabolites. With genome information and profiling technologies now in hand a highly parallel experimental biology is offering opportunities to explore and discover novel principles governing biological systems. Understanding biological complexity through modelling cellular systems represents the driving force which today allows shifting from a component-centric focus to integrative and systems level investigations. The emerging field of systems biology integrates discovery and hypothesis-driven science to provide comprehensive knowledge via computational models of biological systems. Within the context of evolving systems biology, investigations were made in large-scale computational analyses on transcript co-response data through selected prokaryotic and plant model organisms. CSB.DB - a comprehensive systems-biology database - (http://csbdb.mpimp-golm.mpg.de/) was initiated to provide public and open access to the results of biostatistical analyses in conjunction with additional biological knowledge. The database tool CSB.DB enables potential users to infer hypothesis about functional interrelation of genes of interest and may serve as future basis for more sophisticated means of elucidating gene function. The co-response concept and the CSB.DB database tool were successfully applied to predict operons in Escherichia coli by using the chromosomal distance and transcriptional co-responses. Moreover, examples were shown which indicate that transcriptional co-response analysis allows identification of differential promoter activities under different experimental conditions. The co-response concept was successfully transferred to complex organisms with the focus on the eukaryotic plant model organism Arabidopsis thaliana. The investigations made enabled the discovery of novel genes regarding particular physiological processes and beyond, allowed annotation of gene functions which cannot be accessed by sequence homology. GMD - the Golm Metabolome Database - was initiated and implemented in CSB.DB to integrated metabolite information and metabolite profiles. This novel module will allow addressing complex biological questions towards transcriptional interrelation and extent the recent systems level quest towards phenotyping.
Fault planes of large earthquakes incorporate inhomogeneous structures. This can be observed in teleseismic studies through the spatial distribution of slip and seismic moment release caused by the mainshock. Both parameters are often concentrated on patches on the fault plane with much higher values for slip and moment release than their adjacent areas. These patches are called asperities which obviously have a strong influence on the mainshock rupture propagation. Condition and properties of structures in the fault plane area, which are responsible for the evolution of such asperities or their significance on damage distributions of future earthquakes, are still not well understood and subject to recent geo-scientific studies. In the presented thesis asperity structures are identified on the fault plane of the Mw=8.0 Antofagasta earthquake in northern Chile which occurred on 30th of July, 1995. It was a thrust-type event in the seismogenic zone between the subducting pacific Nazca plate and the overriding South American plate. In cooperation of the German Task Force for Earthquakes and the CINCA'95 project a network of up to 44 seismic stations was set up to record the aftershock sequence. The seaward extension of the network with 9 OBH stations increased significantly the precision of hypocenter determinations. They were distributed mainly on the fault plane itself around the city of Antofagasta and Mejillones Peninsula. The asperity structures were recognized here by the spatial variations of local seismological parameters; at first by the spatial distribution of the seismic b-value on the fault plane, derived from the magnitude-frequency relation of Gutenberg-Richter. The correlation of this b-value map with other parameters like the mainshock source time function, the gravity isostatic residual anomalies, the aftershock radiated seismic energy distribution and the vp/vs ratios from a local earthquake tomograhpy study revealed some ideas about the composition and asperity generating processes. The investigation of 295 aftershock focal mechanism solutions supported the resulting fault plane structure and proposed a 3D similar stress state in the area of the Antofagasta fault plane.
The goal of this work was to study the binding of ions to polymers and lipid bilayer membranes in aqueous solutions. In the first part of this work, the influence of various inorganic salts and polyelectrolytes on the structure of water was studied using Isothermal Titration Calorimetry (ITC). The heat of dilution of the salts was used as a scale of water structure making and breaking of the ions. The heats of dilution could be attributed to the Hofmeister Series. Following this, the binding of Ca2+ to poly(sodium acrylate) (NaPAA) was studied. ITC and a Ca2+ Ion Selective Electrode were used to measure the reaction enthalpy and binding isotherm. Binding of Ca2+ ions to PAA, was found to be highly endothermic and therefore solely driven by entropy. We then compared the binding of ions to the one-dimensional PAA polymer chain to the binding to lipid vesicles with the same functional groups. As for the polymer, Ca2+ binding was found to be endothermic. Binding of calcium to the lipid bilayer was found to be weaker than to the polymer. In the context of these experiments, it was shown that Ca2+ not only binds to charged but also to zwitterionic lipid vesicles. Finally, we studied the interaction of two salts, KCl and NaCl, to a neutral polymer gel, PNIPAAM, and to the ionic polymer PAA. Combining calorimetry and a potassium selective electrode we observed that the ions interact with both polymers, whether containing charges or not.
Die Hochwasserereignisse der letzten Jahre haben Mängel bei der schnellen Verfügbarkeit des klassischen Darstellungs-, Entscheidungs- und Analyseinstruments Karte offenbart. Die Erfahrungen von 1997 und 2002 verdeutlichen, dass eine homogene digitale Datengrundlage, die neben rein topographischen zusätzlich auch fachspezifische Informationen des Hochwasserschutzes enthält, für eine effektive Bekämpfung solcher Ereignisse notwendig ist. Mit den Daten des ,Amtlichen Topographisch-Kartographischen Informationssystems’ (ATKIS) liegen topographische Basisdaten in graphikfreier Form als digitales Landschaftsmodell (DLM) flächendeckend für die Bundesrepublik vor. Anhand der exemplarischen Ableitung von nutzerorientierten Kartenmodellen aus diesen graphikfreien Daten wurde deren Eignung für den besonderen Verwendungszweck im Rahmen eines Hochwasserschutz-Informationssystems überprüft. Als Anwendungsbeispiel wurde das Gebiet der Ziltendorfer Niederung, die während des Oder-Hochwassers 1997 überflutet wurde, gewählt. In Expertengesprächen wurden zunächst Inhalte identifiziert, die für einen wirksamen Hochwasserschutz Relevanz besitzen; diese Inhalte wurden anschließend analog zum ATKIS-Systemdesign strukturiert und als Objekte eines separaten Objektbereichs im digitalen Fachmodell (DFM) erfasst. Bei der Ableitung von (Bildschirm-) Karten aus den graphikfreien Daten wurden jeweils unterschiedliche Kriterien für die Basiskarte und die Fachinhalte berücksichtigt. Dabei wurden verschiedene kartographische Regeln und Gesetze mit dem Ziel der prägnanten Visualisierung und damit der eindeutigen Lesbarkeit der Karten angewendet. Beispielhaft sei hier die Schaffung einer visuellen Hierarchie zwischen Basiskarte und Fachinhalten genannt. Die besonderen Nutzungsbedingungen von Karten im Einsatzfall erfordern u.a., dass die Karten auch von Personen, die nur über geringe oder keine Erfahrung im Umgang mit Karten verfügen, schnell und einfach zu lesen sind, um so eine sichere Informationsvermittlung zu gewährleisten. Voraussetzung dafür ist einerseits die Beschränkung auf die Darstellung der wesentlichen Inhalte, andererseits die Verwendung leicht lesbarer Kartenzeichen. Aus diesem Grund wurden einheitliche Kartenzeichen zur Darstellung der Fachinhalte entwickelt, die entweder aus allgemein bekannten Symbolen, aus den im Katastrophenschutz üblicherweise verwendeten sog. taktischen Zeichen oder aus Fachzeichen des Hochwasserschutzes abgeleitet wurden. Die entwickelten Kartenmodelle wurden abschließend in qualitativen Experteninterviews in Bezug auf ihre Qualität und Verwendbarkeit im Hochwasserschutz geprüft. Die Auswertung der Interviews ergab eine insgesamt positive Beurteilung der Karten für den Einsatz in Hochwasserschutz-Informationssystemen. Damit leistet die vorliegende Arbeit einen Beitrag zur Entwicklung von (Bildschirm-) Karten zur Unterstützung bei der Entscheidungsfindung im Katastrophenmanagement.
Ziel der vorliegenden Arbeit war die Entwicklung einer SNP-Genotypisierungsmethode mit auf Mikroarrays immobilisierten PCR-Produkten. Für die Analyse wurde ein faseroptischer Affinitätssensor bzw. ein Durchfluss-Biochip-Scanner mit integrierter Fluoreszenzdetektion verwendet. An den immobilisierten Analyten (PCR-Produkten) wurde eine Fluoreszenzoligonukleotidsonde hybridisiert und anschließend die Dissoziation der Sonde im Fluss verfolgt. Die Diskriminierung von Wildtyp- und Mutanten-DNA erfolgte durch die kinetische Auswertung der Dissoziationskurven sowie durch die Analyse der Fluoreszenzintensität. Die Versuche am faseroptischen Affinitätssensor zeigten, dass DNA-DNA-Hybride sowohl von Oligonukleotiden als auch von PCR-Produkten ein typisches Dissoziationsverhalten aufweisen, wobei fehlgepaarte Hybride eine signifikant schnellere Dissoziation zeigen als perfekt passende Hybride. Dieser Geschwindigkeitsunterschied lässt sich durch den Vergleich der jeweiligen kinetischen Geschwindigkeitskonstanten kD quantitativ erfassen. Da die Kopplung des Analyten an der Chipoberfläche sowie die Hybridisierungs- und Dissoziationsparameter essentiell für die Methodenentwicklung war, wurden die Parameter für ein optimales Spotting und die Immobilisierung von PCR-Produkten ermittelt. Getestet wurden die affine Kopplung von biotinylierten PCR-Produkten an Streptavidin-, Avidin- und NeutrAvidin-Oberflächen sowie die kovalente Bindung von phosphorylierten Amplifikaten mit der EDC/Methylimidazol-Methode. Die besten Ergebnisse sowohl in Spotform und -homogenität als auch im Signal/Rausch-Verhältnis wurden an NeutrAvidin-Oberflächen erreicht. Für die Etablierung der Mikroarray-Genotypisierungsmethode durch kinetische Analyse nach einem Hybridisierungsexperiment wurden Sondenlänge, Puffersystem, Spotting-Konzentration des Analyten sowie Temperatur optimiert. Das Analysensystem erlaubte es, PCR-Produkte mit einer Konzentration von 250 ng/µl in einem HEPES-EDTA-NaCl-Puffer auf mit NeutrAvidin beschichtete Glasträger zu spotten. In den anschließenden Hybridisierungs- und Dissoziationsexperimenten bei 30 °C konnte die Diskriminierung von homocygoter Wildtyp- und homocygoter Mutanten- sowie heterocygoter DNA am Beispiel von Oligonukleotid-Hybriden erreicht werden. In einer Gruppe von 24 homocygoten Patienten wurde ein Polymorphismus im SULT1A1-Gen analysiert. Sowohl durch kinetische Auswertung als auch mit der Analyse der Fluoreszenzintensität wurde der Genotyp der Proben identifiziert. Die Ergebnisse wurden mit dem Referenzverfahren, der Restriktionschnittstellenanalyse (PCR-RFLP) validiert. Lediglich ein Genotyp wurde falsch bestimmt, die Genauigkeit lag bei 96%. In einer Gruppe von 44 Patienten wurde der Genotyp eines SNP in der Adiponectin-Promotor-Region untersucht. Nach Vergleich der Analysenergebnisse mit denen eines Referenzverfahrens konnten lediglich 14 der untersuchten Genotypen bestätigt werden. Ursache für die unzureichende Genauigkeit der Methode war vor allem das schlechte Signal/Rausch-Verhältnis. Zusammenfassend kann gesagt werden, dass das in dieser Arbeit entwickelte Analysesystem für die Genotypisierung von Einzelpunktmutationen geeignet ist, homocygote Patientenproben zuverlässig zu analysieren. Prinzipiell ist das auch bei heterocygoter DNA möglich. Da nach aktuellem Kenntnisstand eine SNP-Analysemethode an immobilisierten PCR-Produkten noch nicht veröffentlicht wurde, stellt das hier entwickelte Verfahren eine Alternative zu bisher bekannten Mikroarray-Verfahren dar. Als besonders vorteilhaft erweist sich der reverse Ansatz der Methode. Der hier vorgestellte Ansatz ist eine kostengünstigere und weniger hoch dimensionierte Lösung für Fragestellungen beispielsweise in der Ernährungswissenschaft, bei denen meist eine mittlere Anzahl Patienten auf nur einige wenige SNPs zu untersuchen ist. Wenn es gelingt, durch die Weiterentwicklung der Hardware bzw. weiterer Optimierung, eine Verbesserung des Signal/Rausch-Verhältnisses und damit die Diskriminierung von heterocygoter DNA zu erreichen, kann diese Methode zukünftig bei der Analyse von mittelgroßen Patientengruppen alternativ zu anderen Genotypisierungsmethoden verwendet werden.
Consumer attitudes towards genetically modified foods in Europe : structure and changeability
(2004)
Genetically modified foods have been at the center of debate in European consumer policy in the last two decades. Although the quasi-moratorium has been lifted in May 2004 and the road to the market is in principle reopened, strategies for product introduction are lacking. The aim of the research is to assess potential barriers in the area of consumer acceptance and suggest ways in which they can be overcome. After a short history of the genetically modified foods debate in Europe, the existing literature is reviewed. Although previous research converges in its central results, issues that are more fundamental have remained unresolved. Based on classical approaches in attitude research and modern theories of social cognition, a general model of the structure, function and dynamics of whole systems of attitudes is developed. The predictions of the model are empirically tested based on an attitude survey (N = 2000) and two attitude change experiments (N = 1400 and N = 750). All three studies were conducted in parallel in four EU member states. The results show that consumer attitudes towards genetically modified foods are embedded into a structured system of general socio-political attitudes. The system operates as a schema through which consumers form global evaluations of the technology. Specific risk and benefit judgments are mere epiphenomena of this process. Risk-benefit trade-offs, as often presupposed in the literature, do not appear to enter the process. The attitudes have a value-expressive function; their purpose is not just a temporary reduction of complexity. These properties render the system utterly resistant to communicative interventions. At the same time, it exerts stong anchoring effects on the processing of new information. Communication of benefit arguments can trigger boomerang effects and backfire on the credibility of the communicator when the arguments contrast with preexisting attitudes held by the consumer. Only direct sensory experience with high-quality products can partially bypass the system and lead to the formation of alternative attitude structures. Therefore, the recommended market introduction strategy for genetically modified foods is the simultaneous and coordinated launch of many high-quality products. Point of sale promotions should be the central instrument. Information campaigns, on the other hand, are not likely to have an effect on the product and technology acceptance of European consumers.
Quantitative Analysen magmatischer Gesteine mittels reflexionsspektroskopischer Infrarot-Messungen
(2004)
In this thesis, dynamical structures and manifolds in closed chaotic flows will be investigated. The knowledge about the dynamical structures (and manifolds) of a system is of importance, since they provide us first information about the dynamics of the system - means, with their help we are able to characterize the flow and maybe even to forecast it`s dynamics. The visualization of such structures in closed chaotic flows is a difficult and often long-lasting process. Here, the so-called 'Leaking-method' will be introduced, in examples of simple mathematical maps as the baker- or sine-map, with which we are able to visualize subsets of the manifolds of the system`s chaotic saddle. Comparisons between the visualized manifolds and structures traced out by chemical or biological reactions superimposed on the same flow will be done in the example of a kinematic model of the Gulf Stream. It will be shown that with the help of the leaking method dynamical structures can be also visualized in environmental systems. In the example of a realistic model of the Mediterranean Sea, the leaking method will be extended to the 'exchange-method'. The exchange method allows us to characterize transport between two regions, to visualize transport routes and their exchange sets and to calculate the exchange times. Exchange times and sets will be shown and calculated for a northern and southern region in the western basin of the Mediterranean Sea. Furthermore, mixing properties in the Earth mantle will be characterized and geometrical properties of manifolds in a 3dimensional mathematical model (ABC map) will be investigated.
For recombinant production of proteins for structural and functional analyses, the E. coli expression system is the most widely used due to high yields and straightforward processing. However, particularly the expression of eukaryotic proteins in E. coli is often problematic, e.g. when the protein is not folded correctly and is deposited in insoluble inclusion bodies. In some cases it is favourable to analyse deletion constructs of a protein or an individual protein domain instead of the full-length protein. This implies the generation of a set of expression constructs that need to be characterised. In this work methods to optimise and evaluate in vitro folding of inclusion body proteins as well as high-throughput characterisation of expression constructs were developed. Transferring inclusion body proteins to their native state involves two steps: (a) solubilisation with a chaotropic reagent or a strong ionic detergent and (b) folding of the protein by removal of the chaotrop accompanied by the transfer into an appropriate buffer. The yield of natively folded protein is often substantially reduced due to aggregation or misfolding; it may, however, be improved by certain additives to the folding buffer. These additives need to be identified empirically. In this thesis a screening procedure for folding conditions was developed. To reduce the number of possible combinations of screening additives, empirical observations documented in the literature as well as well known properties of certain screening additives were considered. To decrease the amount of protein and work invested, the screen was miniaturised and automated using a pipetting robot. Twenty rapid dilution conditions for the denatured protein are tested and two conditions for folding of proteins using the detergent/cyclodextrin protein folding system of Rozema et al. (1996). 100 µg protein is used per condition. In addition, eight conditions can be tested for folding of His-tagged proteins (approx. 200 µg) immobilised on metal chelate resins. The screen was successfully applied to fold a human protein, the p22 subunit of dynactin that is expressed in inclusion bodies in E. coli. For p22 dynactin – as is the case for many proteins – there was no biological assay available to assess the success of the folding screen. Protein solubility can not be used as a stringent criterion because beside natively folded protein, soluble misfolded species and microaggregates may occur. This work evaluates methods to detect small amounts of natively folded protein after automated folding screening. Before folding screening with p22 dynactin, two model enzymes, bovine carbonic anhydrase II (CAB) and pig heart mitochondrial malate dehydrogenase, were used for evaluation. Recovered activity after refolding was correlated to different biophysical methods. 8-anilino-1-naphtalenesulfonic acid binding-experiments gave no useful information when refolding CAB, due to low sensitivity and because misfolded protein could not be readily distinguished from native protein. Tryptophan fluorescence spectra of refolded CAB were used to assess the success of refolding. The shift of the intensity maximum to a shorter wavelength, compared to the denaturant unfolded protein, as well as the fluorescence intensity correlated to recovered enzymatic activity. For both model enzymes, analytical hydrophobic interaction chromatography (HIC) was useful to identify refolded samples that contain active enzyme. Compactly folded, active enzyme eluted in a distinct peak in a decreasing ammonium sulfate gradient. The detection limit of analytical HIC was approx. 5 µg. In case of CAB, tryptophan fluorescence spectroscopy and analytical HIC showed that both methods in combination can be useful to rule out false positives or false negatives obtained with one method. These two methods were also useful to identify conditions for folding of p22 dynactin. However, tryptophan fluorescence spectroscopy can lead to false positives because in some cases spectra of soluble microaggregates are not well distinguishable from spectra of natively folded protein. In summary, a fast and reliable screening procedure was developed to make inclusion body proteins accessible to structural or functional analyses. In a separate project, 88 different E. coli expression constructs for 17 human protein domains that had been identified by sequence analysis were analysed using high-throughput purification and folding analysis in order to obtain candidates suitable for structural analysis. After 96 deep-well microplate expression and automated protein purification, solubly expressed protein domains were directly analysed using 1D ¹H-NMR spectroscopy. It was found that isolated methyl group signals below 0.5 ppm are particularly sensitive and reliable probes for folded protein. In addition – similar to the evaluation of a folding screen – analytical HIC proved to be an efficient tool for identifying constructs that yield compactly folded protein. Both methods, 1D ¹H-NMR spectroscopy and analytical HIC, provided complementary results. Six constructs, representing two domains, could be quickly identified as targets that are well suitable for structural analysis. The structure of one of these domains was solved recently by co-workers, the other structure was published by another group during this project.
Taking inspiration from nature, where composite materials made of a polymer matrix and inorganic fillers are often found, e.g. bone, shell of crustaceans, shell of eggs, etc., the feasibility on making composite materials containing chitosan and nanosized hydroxyapatite were investigated. A new preparation approach based on a co-precipitation method has been developed. In its earlier stage of formation, the composite occurs as hydrogel as suspended in aqueous alkaline solution. In order to get solid composites various drying procedures including freeze-drying technique, air-drying at room temperature and at moderate temperatures, between 50oC and 100oC were used. Physicochemical studies showed that the composites exhibit different properties with respect to their structure and composition. IR and Raman spectroscopy probed the presence of both chitosan and hydroxyapatite in the composites. Hydroxyapatite as dispersed in the chitosan matrix was found to be in the nanosize range (15-50 nm) and occurs in a bimodal distribution with respect to its crystallite length. Two types of distribution domains of hydroxyapatite crystallites in the composite matrix such as cluster-like (200-400 nm) and scattered-like domains were identified by the transmission electron microscopy (TEM), X-ray diffraction (XRD) and by confocal scanning laser microscopy (CSLM) measurements. Relaxation NMR experiments on composite hydrogels showed the presence of two types of water sites in their gel networks, such as free and bound water. Mechanical tests showed that the mechanical properties of composites are one order of magnitude less than those of compact bone but comparable to those of porous bone. The enzymatic degradation rates of composites showed slow degradation processes. The yields of degradation were estimated to be less than 10% by loss of mass, after incubation with lysozyme, for a period of 50 days. Since the composite materials were found biocompatible by the in vivo tests, the simple mode of their fabrication and their properties recommend them as potential candidates for the non-load bearing bone substitute materials.
Gegenstand der Arbeit ist die lichtinduzierte Orientierung von multifunktionalen Polymeren, die u.a. für die Herstellung von optischen Schichten in Flüssigkristalldisplays verwendet werden können. Dafür wurden Polymere entwickelt, die wenigstens eine mesogene und eine lichtsensitive Gruppe enthalten. Diese Gruppen zeigen Eigenschaften, die für die Orientierung der kompletten Polymerfilme verantwortlich sind. Das Material wird dafür zunächst in einem ersten Schritt kurz mit linear polarisiertem Licht bestrahlt, wobei richtungsabhängig eine photochemische Reaktion an der lichtsensitiven Gruppe erfolgt und dadurch ein "Orientierungskeim" gelegt wird. Durch die thermische Ausrichtung der mesogenen Gruppen an den photochemisch generierten "Orientierungskeimen" erfolgt die komplette Orientierung des Filmes in einem zweiten Schritt. Dadurch wird eine hohe optische Anisotropie erhalten. Dieses Verfahren wurde als Zwei-Stufen-Bulk-Orientierungsprozess bezeichnet. In der vorliegenden Arbeit wurden die Photoreaktionen verschiedener lichtsensitiver Gruppen, wie z. B. Azobenzen, Stilben und Zimtsäureester und deren Orientierungsfähigkeit in flüssigkristallinen Polymeren untersucht. Der Orientierungsprozess wurde durch die Wahl geeigneter Bestrahlungsbedingungen optimiert. Die Effizienz der Orientierung wurde anhand der sich verändernden winkelabhängigen Absorptionseigenschaften und der Doppelbrechung des Materials analysiert. Es wurde gezeigt, dass eine effiziente lichtinduzierte Orientierung bei einer Vielzahl von flüssigkristallinen Polymeren realisierbar ist. So wurde z. B. erstmalig gefunden, dass durch eine Photo-Fries-Orientierung eine hohe optische Anisotropie erhalten werden kann. Außerdem wurde eine neue lichtsensitive Gruppe auf der Basis von Donor-Akzeptor-substituiertem Ethen entwickelt, die farbneutral ist und durch polarisiertes UV-Licht sowohl orientiert als auch re-orientiert werden kann. Es wurden weiterhin Polymere entwickelt, die zusätzlich zu den photosensitiven und flüssigkristallinen Einheiten, fluoreszierende Gruppen enthalten. Die Auswahl geeigneter Fluoreszenzverbindungen erfolgte aufgrund ihrer anisometrischen Form, ihrer Ordnungsparameter in einer niedermolekularen Flüssigkristallmischung und ihrer Photostabilität. Das Orientierungsverhalten von ausgewählten Fluorophoren wurde in sechs Ter- und zwei Copolymeren untersucht. Das Prinzip der Orientierung beruht auf einer kooperativen Ausrichtung der Seitengruppen. Aus diesem Grund kommt dem Nachweis der Kooperativität in der vorliegenden Arbeit eine besondere Stellung zu. Durch lichtinduzierte Bulk-Orientierung wurden Filme erhalten, welche durch eine richtungsabhängige Fluoreszenz und Absorption im sichtbaren- oder UV-Bereich charakterisiert sind. Die Fluoreszenz wird durch einige lichtsensitive Verbindungen komplett gelöscht. Die wahlweise erhaltenen anisotropen Filme von farbigen, fluoreszierenden oder farbneutralen Verbindungen, die zudem in kleinen Pixeln von wenigen Mikrometern orientiert werden können, eröffnen vielfältige Möglichkeiten für den Einsatz von multi-funktionalen Polymeren als optische Schichten in Flüssigkristalldisplays.
Systems of elasticity theory
(2004)
This work deals with the connection between two basic phenomena in Nonlinear Dynamics: synchronization of chaotic systems and recurrences in phase space. Synchronization takes place when two or more systems adapt (synchronize) some characteristic of their respective motions, due to an interaction between the systems or to a common external forcing. The appearence of synchronized dynamics in chaotic systems is rather universal but not trivial. In some sense, the possibility that two chaotic systems synchronize is counterintuitive: chaotic systems are characterized by the sensitivity ti different initial conditions. Hence, two identical chaotic systems starting at two slightly different initial conditions evolve in a different manner, and after a certain time, they become uncorrelated. Therefore, at a first glance, it does not seem to be plausible that two chaotic systems are able to synchronize. But as we will see later, synchronization of chaotic systems has been demonstrated. On one hand it is important to investigate the conditions under which synchronization of chaotic systems occurs, and on the other hand, to develop tests for the detection of synchronization. In this work, I have concentrated on the second task for the cases of phase synchronization (PS) and generalized synchronization (GS). Several measures have been proposed so far for the detection of PS and GS. However, difficulties arise with the detection of synchronization in systems subjected to rather large amounts of noise and/or instationarities, which are common when analyzing experimental data. The new measures proposed in the course of this thesis are rather robust with respect to these effects. They hence allow to be applied to data, which have evaded synchronization analysis so far. The proposed tests for synchronization in this work are based on the fundamental property of recurrences in phase space.
Die immunologische Kontrazeption mittels Zona pellucida (ZP) Proteinen gilt als vielversprechender Ansatz für die Reproduktionskontrolle verwilderter Haus- und Wildtierbestände. Da die Applikation von nativer ZP mit Nebenwirkungen verbunden ist, wird die Verwendung einzelner ZP Peptide als Bestandteil kontrazeptiver Vakzine als besonders aussichtsreich erachtet. Das Prinzip dieser nebenwirkungsfreien ZP Immunisierung ist die gezielte Trennung der Entzündungsreaktionen auslösenden T-Zell-Epitope der ZP von den kontrazeptiv wirkenden B-Zell-Epitopen. Niedermolekulare synthetische oder rekombinante Peptide allein sind gering immunogen und können somit keine ausreichende Immunantwort induzieren. Die Verwendung von Peptiden für die immunologische Kontrazeption erfordert daher ein „Vakzin-Design“, d. h. die gezielte Kombination der Peptide mit immunstimulierenden Substanzen (Liposomen, Carrierproteinen, Adjuvantien). Zielstellung der vorliegenden Arbeit war die Untersuchung des Potentials synthetischer Peptide für die Immunokontrazeption von verwilderten Hauskatzen (Felis catus). Dazu wurden zunächst relevante B-Zell-Epitope des felinen Zona pellucida Proteins, ZPB2, identifiziert und synthetisiert. Zwei der synthetischen Peptide (P3, P6) wurden zur Herstellung von Antikörpern an BSA konjugiert und zusammen mit Freundschem Adjuvans in Ratten verimpft. Die kontrazeptive Relevanz beider Peptide sowie der Ratten Anti-Peptid Antiseren wurde im in vitro Befruchtungssystem der Hauskatze geprüft. Zur Untersuchung der Immunogenität der Peptide in der Zielspezies Hauskatze erfolgte die Entwicklung von Vakzin-Prototypen für die einmalige Applikation. Neben der Eruierung der Stärke und Dauer der Immunantwort wurde durch Verpaarung der Tiere auch das kontrazeptive Potential in vivo abgeschätzt.