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In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC1im]+[NTf2]- and [C4C1im]+[I]-). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
Herein we present an efficient synthesis of a biomimetic probe with modular construction that can be specifically bound by the mannose binding FimH protein – a surface adhesion protein of E. coli bacteria. The synthesis combines the new and interesting DBD dye with the carbohydrate ligand mannose via a Click reaction. We demonstrate the binding to E. coli bacteria over a large concentration range and also present some special characteristics of those molecules that are of particular interest for the application as a biosensor. In particular, the mix-and-measure ability and the very good photo-stability should be highlighted here.
Die vorgelegte Dissertation präsentiert wissenschaftliche Ergebnisse, die in der Zeit vom Dezember 2012 bis August 2016, erarbeitet wurden. Der zentrale Inhalt der Arbeit ist die Simulation von Röntgenabsorptionsprozessen von verschiedenen Systemen in kondensierter Phase. Genauer gesagt, werden Nahkantenabsorptions- (NEXAFS) sowie Röntgenphotoelektronenspektren (XPS) berechnet. In beiden Fällen wird ein Röntgenphoton von einem molekularen System absorbiert. Aufgrund der hohen Photonenenergie wird ein stark gebundenes kernnahes Elektron angeregt. Bei der XPS gelangt dieses mit einer zu messenden kinetischen Energie in Kontinuumszustände. In Abhängigkeit der eingestrahlten Photonenenergie und der kinetischen Energie des austreten Elektrons, kann die Bindungsenergie berechnet werden, welche die zentrale Größe der XPS ist. Im Falle der NEXAFS-Spektroskopie wird das kernnahe Elektron in unbesetzte gebundene Zustände angeregt. Die zentrale Größe ist die Absorption als Funktion der eingestrahlten Photonenenergie. Das erste Kapitel meiner Arbeit erörtert detailliert die experimentellen Methoden sowie die daraus gewonnenen charakteristischen Größen.
Die experimentellen Spektren zeigen oft viele Resonanzen, deren Interpretation aufgrund fehlender Referenzmaterialien schwierig ist. In solchen Fällen bietet es sich an, die Spektren mittels quantenchemischer Methoden zu simulieren. Der dafür erforderliche mathematisch-physikalische Methodenkatalog wird im zweiten Kapitel der Arbeit erörtert.
Das erste von mir untersuchte System ist Graphen. In experimentellen Arbeiten wurde die Oberfläche mittels Bromplasma modifiziert. Die im Anschluss gemessenen NEXAFS-Spektren unterscheiden sich maßgeblich von den Spektren der unbehandelten Oberfläche. Mithilfe periodischer DFT-Rechnungen wurden verschiedene Gitterdefekte sowie bromierte Systeme untersucht und die NEXAFS-Spektren simuliert. Mittels der Simulationen können die Beiträge verschiedener Anregungszentren analysiert werden. Die Berechnungen erlauben den Schluss, dass Gitterdefekte maßgeblich für die entstandenen Veränderungen verantwortlich sind.
Polyvinylalkohol (PVA) wurde als zweites System behandelt. Hierbei sollte untersucht werden, wie groß der Einfluss der Molekularbewegung auf die Verbreiterung der Peaks im XP-Spektrum ist. Des Weiteren wurde untersucht, wie groß der Einfluss von intermolekularen Wechselwirkungen auf die Peakpositionen und Peakverbreiterung ist. Für die Berechnung dieses Systems wurde eine Kombination aus molekulardynamischen und quantenchemischen Methoden verwendet. Als Strukturen dienten Oligomermodelle, die unter dem Einfluss eines (ab initio) Potentials propagiert wurden. Entlang der erstellten Trajektorie wurden Schnappschüsse der Geometrien extrahiert und für die Berechnung der XP-Spektren verwendet. Die Spektren werden bereits mithilfe klassischer Molekulardynamik sehr gut reproduziert. Die erhaltenen Peakbreiten sind verglichen mit dem Experiment allerdings zu klein. Die Hauptursache der Peakverbreiterung ist die Molekularbewegung. Intermolekulare Wechselwirkungen verschieben die Peakpositionen um 0.6 eV zu kleineren Anregungsenergien.
Im dritten Teil der Arbeit stehen die NEXAFS-Spektren von ionischen Flüssigkeiten (ILs) im Fokus. Die experimentell gefundenen Spektren zeigen eine komplexe Struktur mit vielen Resonanzen. In der Arbeit wurden zwei ILs untersucht. Als Geometrien verwenden wir Clustermodelle, die aus experimentellen Kristallstrukturen extrahiert wurden. Die berechneten Spektren erlauben es, die Resonanzen den Anregungszentren zuzuordnen. Außerdem kann eine erstmals gemessene Doppelresonanz simuliert und erklärt werden. Insgesamt kann die Interpretation der Spektren mithilfe der Simulation signifikant erweitert werden.
In allen Systemen wurde zur Berechnung des NEXAFS-Spektrums eine auf Dichtefunktionaltheorie basierende Methode verwendet (die sogenannte Transition-Potential Methode). Gängige wellenfunktionsbasierte Methoden, wie die Konfigurationswechselwirkung mit Einfachanregungen (CIS), zeigen eine starke Blauverschiebung, wenn als Referenz eine Hartree-Fock Slaterdeterminante verwendet wird. Wir zeigen, dass die Verwendung von kernnah-angeregten Determinanten sowohl das resultierende Spektrum als auch die Anregungsenergien deutlich verbessert. Des Weiteren werden auch Referenzen aus Dichtefunktionalrechnungen getestet. Zusätzlich werden auch Referenzen mit gebrochenen Besetzungszahlen für kernnahe Elektronen verwendet. In der Arbeit werden die Resultate der verschiedenen Referenzen miteinander verglichen. Es zeigt sich, dass Referenzen mit gebrochenen Besetzungszahlen das Spektrum nicht weiter verbessern. Der Einfluss der verwendeten Elektronenstrukturmethode ist eher gering.
Surface-enhanced Raman scattering (SERS) is a promising tool to obtain rich chemical information about analytes at trace levels. However, in order to perform selective experiments on individual molecules, two fundamental requirements have to be fulfilled. On the one hand, areas with high local field enhancement, so-called “hot spots”, have to be created by positioning the supporting metal surfaces in close proximity to each other. In most cases hot spots are formed in the gap between adjacent metal nanoparticles (NPs). On the other hand, the analyte has to be positioned directly in the hot spot in order to profit from the highest signal amplification. The use of DNA origami substrates provides both, the arrangement of AuNPs with nm precision as well as the ability to bind analyte molecules at predefined positions. Consequently, the present cumulative doctoral thesis aims at the development of a novel SERS substrate based on a DNA origami template. To this end, two DNA-functionalized gold nanoparticles (AuNPs) are attached to one DNA origami substrate resulting in the formation of a AuNP dimer and thus in a hot spot within the corresponding gap. The obtained structures are characterized by correlated atomic force microscopy (AFM) and SERS imaging which allows for the combination of structural and chemical information.
Initially, the proof-of principle is presented which demonstrates the potential of the novel approach. It is shown that the Raman signal of 15 nm AuNPs coated with dye-modified DNA
(dye: carboxytetramethylrhodamine (TAMRA)) is significantly higher for AuNP dimers arranged on a DNA origami platform in comparison to single AuNPs. Furthermore, by attaching single TAMRA molecules in the hot spot between two 5 nm AuNPs and optimizing the size of the AuNPs by electroless gold deposition, SERS experiments at the few-molecule level are presented. The initially used DNA origami-AuNPs design is further optimized in many respects. On the one hand, larger AuNPs up to a diameter of 60 nm are used which are additionally treated with a silver enhancement solution to obtain Au-Ag-core-shell NPs. On the other hand, the arrangement of both AuNPs is altered to improve the position of the dye molecule within the hot spot as well as to decrease the gap size between the two particles. With the optimized design the detection of single dye molecules (TAMRA and cyanine 3 (Cy3)) by means of SERS is demonstrated. Quantitatively, enhancement factors up to 10^10 are estimated which is sufficiently high to detect single dye molecules.
In the second part, the influence of graphene as an additional component of the SERS substrate is investigated. Graphene is a two-dimensional material with an outstanding combination of electronical, mechanical and optical properties. Here, it is demonstrated that
single layer graphene (SLG) replicates the shape of underlying non-modified DNA origami
substrates very well, which enables the monitoring of structural alterations by AFM imaging.
In this way, it is shown that graphene encapsulation significantly increases the structural
stability of bare DNA origami substrates towards mechanical force and prolonged exposure
to deionized water.
Furthermore, SLG is used to cover DNA origami substrates which are functionalized with a
40 nm AuNP dimer. In this way, a novel kind of hybrid material is created which exhibits
several advantages compared to the analogue non-covered SERS substrates. First, the fluorescence background of dye molecules that are located in between the AuNP surface and SLG is efficiently reduced. Second, the photobleaching rate of the incorporated dye molecules is decreased up to one order of magnitude. Third, due to the increased photostability of the investigated dye molecules, the performance of polarization-dependent series measurements on individual structures is enabled. This in turn reveals extensive information about the dye molecules in the hot spot as well as about the strain induced within the graphene lattice.
Although SLG can significantly influence the SERS substrate in the aforementioned ways, all
those effects are strongly related to the extent of contact with the underlying AuNP dimer.
Physikalische Hydrogele gewinnen derzeit als Zellsubstrate zunehmend an Interesse, da Viskoelastizität oder Stressrelaxation ein bedeutender Parameter in der Mechanotransduktion ist, der bisher vernachlässigt wurde. In dieser Arbeit wurden multi-funktionelle Polyurethane entworfen, die über einen neuartigen Gelierungsmechanismus physikalische Hydrogele bilden. In Wasser bilden die anionischen Polyurethane spontan Aggregate, welche durch elektrostatische Abstoßung in Lösung gehalten werden. Eine schnelle Gelierung kann von hier aus durch Ladungsabschirmung erreicht werden, wodurch die Aggregation voranschreitet und ein Netzwerk ausgebildet wird. Dies kann durch die Zugabe von verschiedenen Säuren oder Salzen geschehen, sodass sowohl saure (pH 4 - 5) als auch pH-neutrale Hydrogele erhalten werden können. Während konventionelle Hydrogele auf Polyurethan-Basis in der Regel durch toxische isocyanat-haltige Präpolymere hergestellt werden, eignet sich der hier beschriebene physikalische Gelierungsmechanismus für in situ Anwendungen in sensitiven Umgebungen. Sowohl Härte als auch Stressrelaxation der Hydrogele können unabhängig voneinander über einen breiten Bereich eingestellt werden. Darüberhinaus zeichnen sich die Hydrogele durch exzellente Stressregeneration aus.
Luhmann in da Contact Zone
(2016)
Our aim in this contribution is to productively engage with the abstractions and complexities of Luhmann’s conceptions of society from a postcolonial perspective, with a particular focus on the explanatory powers of his sociological systems theory when it leaves the realms of Europe and ventures to describe regions of the global South. In view of its more recent global reception beyond Europe, our aim is to thus – following the lead of Dipesh Chakrabarty – provincialize Luhmann’s system theory especially with regard to its underlying assumptions about a global “world society”. For these purposes, we intend to revisit Luhmann in the post/colonial contact zone: We wish to reread Luhmann in the context of spaces of transcultural encounter where “global designs and local histories” (Mignolo), where inclusion into and exclusion from “world society” (Luhmann) clash and interact in intricate ways. The title of our contribution, ‘Luhmann in da Contact Zone’ is deliberately ambiguous: On the one hand, we of course use ‘Luhmann’ metonymically, as representative of a highly complex theoretical design. We shall cursorily outline this design with a special focus on the notion of a singular, modern “world society”, only to confront it with the epistemic challenges of the contact zone. On the other hand, this critique will also involve the close observation of Niklas Luhman as a human observer (a category which within the logic of systems theory actually does not exist) who increasingly transpires in his late writings on exclusion in the global South. By following this dual strategy, we wish to trace an increasing fracture between one Luhmann and the other, between abstract theoretical design and personalized testimony. It is by exploring and measuring this fracture that we hope to eventually be able to map out the potential of a possibly more productive encounter between systems theory and specific strands of postcolonial theory for a pluritopic reading of global modernity.
Recollecting Bones
(2016)
In the same “guarded, roundabout and reticent way” which Lindsay Barrett invokes for Australian conversations about imperial injustice, Germans, too, must begin to more systematically explore, in Paul Gilroy’s words, “the connections and the differences between anti-semitism and anti-black and other racisms and asses[s] the issues that arise when it can no longer be denied that they interacted over a long time in what might be seen as Fascism’s intellectual, ethical and scientific pre-history” (Gilroy 1996: 26). In the meantime, we need to care for the dead. We need to return them, first, from the status of scientific objects to the status of ancestral human beings, and then progressively, and proactively, as close as possible to the care of those communities from whom they were stolen.
Kleine Kosmopolitismen
(2016)
Postcolonial Justice
(2016)
Postcolonial Piracy
(2016)
Media piracy is a contested term in the academic as much as the public debate. It is used by the corporate industries as a synonym for the theft of protected media content with disastrous economic consequences. It is celebrated by technophile elites as an expression of freedom that ensures creativity as much as free market competition. Marxist critics and activists promote flapiracy as a subversive practice that undermines the capitalist world system and its structural injustices. Artists and entrepreneurs across the globe curse it as a threat to their existence, while many use pirate infrastructures and networks fundamentally for the production and dissemination of their art. For large sections of the population across the global South, piracy is simply the only means of accessing the medial flows of a progressively globalising planet.
Reflections of Lusáni Cissé
(2016)
Sexual Aggression Victimization and Perpetration among Male and Female College Students in Chile
(2016)
Evidence on the prevalence of sexual aggression among college students is primarily based on studies from Western countries. In Chile, a South American country strongly influenced by the Catholic Church, little research on sexual aggression among college students is available. Therefore, the purpose of the present study was to examine the prevalence of sexual aggression victimization and perpetration since the age of 14 (the legal age of consent) in a sample of male and female students aged between 18 and 29 years from five Chilean universities (N = 1135), to consider possible gender differences, and to study the extent to which alcohol was involved in the reported incidents of perpetration and victimization. Sexual aggression victimization and perpetration was measured with a Chilean Spanish version of the Sexual Aggression and Victimization Scale (SAV-S), which includes three coercive strategies (use or threat of physical force, exploitation of an incapacitated state, and verbal pressure), three victim-perpetrator constellations (current or former partners, friends/acquaintances, and strangers), and four sexual acts (sexual touch, attempted sexual intercourse, completed sexual intercourse, and other sexual acts, such as oral sex). Overall, 51.9% of women and 48.0% of men reported at least one incident of sexual victimization, and 26.8% of men and 16.5% of women reported at least one incident of sexual aggression perpetration since the age of 14. For victimization, only few gender differences were found, but significantly more men than women reported sexual aggression perpetration. A large proportion of perpetrators also reported victimization experiences. Regarding victim-perpetrator relationship, sexual aggression victimization and perpetration were more common between persons who knew each other than between strangers. Alcohol use by the perpetrator, victim, or both was involved in many incidents of sexual aggression victimization and perpetration, particularly among strangers. The present data are the first to provide a systematic and detailed picture of sexual aggression among college students in Chile, including victimization and perpetration reports by both men and women and confirming the critical role of alcohol established in past research from Western countries.
Rapidly uplifting coastlines are frequently associated with convergent tectonic boundaries, like subduction zones, which are repeatedly breached by giant megathrust earthquakes. The coastal relief along tectonically active realms is shaped by the effect of sea-level variations and heterogeneous patterns of permanent tectonic deformation, which are accumulated through several cycles of megathrust earthquakes. However, the correlation between earthquake deformation patterns and the sustained long-term segmentation of forearcs, particularly in Chile, remains poorly understood. Furthermore, the methods used to estimate permanent deformation from geomorphic markers, like marine terraces, have remained qualitative and are based on unrepeatable methods. This contrasts with the increasing resolution of digital elevation models, such as Light Detection and Ranging (LiDAR) and high-resolution bathymetric surveys.
Throughout this thesis I study permanent deformation in a holistic manner: from the methods to assess deformation rates, to the processes involved in its accumulation. My research focuses particularly on two aspects: Developing methodologies to assess permanent deformation using marine terraces, and comparing permanent deformation with seismic cycle deformation patterns under different spatial scales along the M8.8 Maule earthquake (2010) rupture zone. Two methods are developed to determine deformation rates from wave-built and wave-cut terraces respectively. I selected an archetypal example of a wave-built terrace at Santa Maria Island studying its stratigraphy and recognizing sequences of reoccupation events tied with eleven radiocarbon sample ages (14C ages). I developed a method to link patterns of reoccupation with sea-level proxies by iterating relative sea level curves for a range of uplift rates. I find the best fit between relative sea-level and the stratigraphic patterns for an uplift rate of 1.5 +- 0.3 m/ka.
A Graphical User Interface named TerraceM® was developed in Matlab®. This novel software tool determines shoreline angles in wave-cut terraces under different geomorphic scenarios. To validate the methods, I select test sites in areas of available high-resolution LiDAR topography along the Maule earthquake rupture zone and in California, USA. The software allows determining the 3D location of the shoreline angle, which is a proxy for the estimation of permanent deformation rates. The method is based on linear interpolations to define the paleo platform and cliff on swath profiles. The shoreline angle is then located by intersecting these interpolations. The
accuracy and precision of TerraceM® was tested by comparing its results with previous assessments, and through an experiment with students in a computer lab setting at the University
of Potsdam.
I combined the methods developed to analyze wave-built and wave-cut terraces to assess regional patterns of permanent deformation along the (2010) Maule earthquake rupture. Wave-built terraces are tied using 12 Infra Red Stimulated luminescence ages (IRSL ages) and shoreline angles in wave-cut terraces are estimated from 170 aligned swath profiles. The comparison of coseismic slip, interseismic coupling, and permanent deformation, leads to three areas of high permanent uplift, terrace warping, and sharp fault offsets. These three areas correlate with regions of high slip and low coupling, as well as with the spatial limit of at least eight historical megathrust ruptures (M8-9.5). I propose that the zones of upwarping at Arauco and Topocalma reflect changes in frictional properties of the megathrust, which result in discrete boundaries for the propagation of mega earthquakes.
To explore the application of geomorphic markers and quantitative morphology in offshore areas I performed a local study of patterns of permanent deformation inferred from hitherto unrecognized drowned shorelines at the Arauco Bay, at the southern part of the (2010) Maule earthquake rupture zone. A multidisciplinary approach, including morphometry, sedimentology, paleontology, 3D morphoscopy, and a landscape Evolution Model is used to recognize, map, and assess local rates and patterns of permanent deformation in submarine environments. Permanent deformation patterns are then reproduced using elastic models to assess deformation rates of an active submarine splay fault defined as Santa Maria Fault System. The best fit suggests a reverse structure with a slip rate of 3.7 m/ka for the last 30 ka. The register of land level changes during the earthquake cycle at Santa Maria Island suggest that most of the deformation may be accrued through splay fault reactivation during mega earthquakes, like the (2010) Maule event. Considering a recurrence time of 150 to 200 years, as determined from historical and geological observations, slip between 0.3 and 0.7 m per event would be required to account for the 3.7 m/ka millennial slip rate. However, if the SMFS slips only every ~1000 years, representing a few megathrust earthquakes, then a slip of ~3.5 m per event would be required to account for the long- term rate. Such event would be equivalent to a magnitude ~6.7 earthquake capable to generate a local tsunami.
The results of this thesis provide novel and fundamental information regarding the amount of permanent deformation accrued in the crust, and the mechanisms responsible for this accumulation at millennial time-scales along the M8.8 Maule earthquake (2010) rupture zone. Furthermore, the results of this thesis highlight the application of quantitative geomorphology and the use of repeatable methods to determine permanent deformation, improve the accuracy of marine terrace assessments, and estimates of vertical deformation rates in tectonically active coastal areas. This is vital information for adequate coastal-hazard assessments and to anticipate realistic earthquake and tsunami scenarios.
Seit der Einführung von Antibiotika in die medizinische Behandlung von bakteriellen Infektionskrankheiten existiert ein Wettlauf zwischen der Evolution von Bakterienresistenzen und der Entwicklung wirksamer Antibiotika. Während bis in die 80er Jahre verstärkt an neuen Antibiotika geforscht wurde, gewinnen multiresistente Keime heute zunehmend die Oberhand. Um einzelne Pathogene erfolgreich nachzuweisen und zu bekämpfen, ist ein grundlegendes Wissen über den Erreger unumgänglich. Bakterielle Proteine, die bei einer Infektion vorrangig vom Immunsystem prozessiert und präsentiert werden, könnten für die Entwicklung von Impfstoffen oder gezielten Therapeutika nützlich sein. Auch für die Diagnostik wären diese immundominanten Proteine interessant. Allerdings herrscht ein Mangel an Wissen über spezifische Antigene vieler pathogener Bakterien, die eine eindeutige Diagnostik eines einzelnen Erregers erlauben würden.
Daher wurden in dieser Arbeit vier verschiedene Humanpathogene mittels Phage Display untersucht: Neisseria gonorrhoeae, Neisseria meningitidis, Borrelia burgdorferi und Clostridium difficile. Hierfür wurden aus der genomischen DNA der vier Erreger Bibliotheken konstruiert und durch wiederholte Selektion und Amplifikation, dem sogenannten Panning, immunogene Proteine isoliert. Für alle Erreger bis auf C. difficile wurden immunogene Proteine aus den jeweiligen Bibliotheken isoliert. Die identifizierten Proteine von N. meningitidis und B. burgdorferi waren größtenteils bekannt, konnten aber in dieser Arbeit durch Phage Display verifiziert werden. Für N. gonorrhoeae wurden 21 potentiell immunogene Oligopeptide isoliert, von denen sechs Proteine als neue zuvor unbeschriebene Proteine mit immunogenem Charakter identifiziert wurden. Von den Phagen-präsentierten Oligopeptide der 21 immunogenen Proteine wurden Epitopmappings mit verschiedenen polyklonalen Antikörpern durchgeführt, um immunogene Bereiche näher zu identifizieren und zu charakterisieren. Bei zehn Proteinen wurden lineare Epitope eindeutig mit drei polyklonalen Antikörpern identifiziert, von fünf weiteren Proteinen waren Epitope mit mindestens einem Antikörper detektierbar. Für eine weitere Charakterisierung der ermittelten Epitope wurden Alaninscans durchgeführt, die eine detaillierte Auskunft über kritische Aminosäuren für die Bindung des Antikörpers an das Epitop geben.
Ausgehend von dem neu identifizierten Protein mit immunogenem Charakter NGO1634 wurden 26 weitere Proteine aufgrund ihrer funktionellen Ähnlichkeit ausgewählt und mithilfe bioinformatischer Analysen auf ihre Eignung zur Entwicklung einer diagnostischen Anwendung analysiert. Durch Ausschluss der meisten Proteine aufgrund ihrer Lokalisation, Membrantopologie oder unspezifischen Proteinsequenz wurden scFv-Antikörper gegen acht Proteine mittels Phage Display generiert und anschließend als scFv-Fc-Fusionsantikörper produziert und charakterisiert.
Die hier identifizierten Proteine und linearen Epitope könnten einen Ansatzpunkt für die Entwicklung einer diagnostischen oder therapeutischen Anwendung bieten. Lineare Epitopsequenzen werden häufig für die Impfstoffentwicklung eingesetzt, sodass vor allem die in dieser Arbeit bestimmten Epitope von Membranproteinen interessante Kandidaten für weitere Untersuchungen in diese Richtung sind. Durch weitere Untersuchungen könnten möglicherweise unbekannte Virulenzfaktoren entdeckt werden, deren Inhibierung einen entscheidenden Einfluss auf Infektionen haben könnten.
Diese Arbeit zu Grunde liegenden Forschung zielte darauf ab, neue schmelzbare Acrylnitril-Copolymere zu entwickeln. Diese sollten im Anschluss über ein Schmelzspinnverfahren zur Chemiefaser geformt und im letzten Schritt zur Carbonfaser konvertiert werden. Zu diesem Zweck wurden zunächst orientierende Untersuchungen an unterschiedlichen Copolymeren des Acrylnitril aus Lösungspolymerisation durchgeführt. Die Untersuchungen zeigten, dass elektrostatische Wechselwirkungen besser als sterische Abschirmung dazu geeignet sind, Schmelzbarkeit unterhalb der Zersetzungstemperatur von Polyacrylnitril zu bewirken. Aus der Vielzahl untersuchter Copolymere stellten sich jene mit Methoxyethylacrylat (MEA) als am effektivsten heraus. Für diese Copolymere wurden sowohl die Copolymerisationsparameter bestimmt als auch die grundlegende Kinetik der Lösungspolymerisation untersucht. Die Copolymere mit MEA wurden über Schmelzspinnen zur Faser umgeformt und diese dann untersucht. Hierbei wurden auch Einflüsse verschiedener Parameter, wie z.B. die der Molmasse, auf die Fasereigenschaften und -herstellung untersucht. Zuletzt wurde ein Heterophasenpolymerisationsverfahren zur Herstellung von Copolymeren aus AN/MEA entwickelt; dadurch konnten die Materialeigenschaften weiter verbessert werden. Zur Unterdrückung der thermoplastischen Eigenschaften der Fasern wurde ein geeignetes Verfahren entwickelt und anschließend die Konversion zu Carbonfasern durchgeführt.
Intermontane valley fills
(2016)
Sedimentary valley fills are a widespread characteristic of mountain belts around the world. They transiently store material over time spans ranging from thousands to millions of years and therefore play an important role in modulating the sediment flux from the orogen to the foreland and to oceanic depocenters. In most cases, their formation can be attributed to specific fluvial conditions, which are closely related to climatic and tectonic processes. Hence, valley-fill deposits constitute valuable archives that offer fundamental insight into landscape evolution, and their study may help to assess the impact of future climate change on sediment dynamics.
In this thesis I analyzed intermontane valley-fill deposits to constrain different aspects of the climatic and tectonic history of mountain belts over multiple timescales. First, I developed a method to estimate the thickness distribution of valley fills using artificial neural networks (ANNs). Based on the assumption of geometrical similarity between exposed and buried parts of the landscape, this novel and highly automated technique allows reconstructing fill thickness and bedrock topography on the scale of catchments to entire mountain belts.
Second, I used the new method for estimating the spatial distribution of post-glacial sediments that are stored in the entire European Alps. A comparison with data from exploratory drillings and from geophysical surveys revealed that the model reproduces the measurements with a root mean squared error (RMSE) of 70m and a coefficient of determination (R2) of 0.81. I used the derived sediment thickness estimates in combination with a model of the Last Glacial Maximum (LGM) icecap to infer the lithospheric response to deglaciation, erosion and deposition, and deduce their relative contribution to the present-day rock-uplift rate. For a range of different lithospheric and upper mantle-material properties, the results suggest that the long-wavelength uplift signal can be explained by glacial isostatic adjustment with a small erosional contribution and a substantial but localized tectonic component exceeding 50% in parts of the Eastern Alps and in the Swiss Rhône Valley. Furthermore, this study reveals the particular importance of deconvolving the potential components of rock uplift when interpreting recent movements along active orogens and how this can be used to constrain physical properties of the Earth’s interior.
In a third study, I used the ANN approach to estimate the sediment thickness of alluviated reaches of the Yarlung Tsangpo River, upstream of the rapidly uplifting Namche Barwa massif. This allowed my colleagues and me to reconstruct the ancient river profile of the Yarlung Tsangpo, and to show that in the past, the river had already been deeply incised into the eastern margin of the Tibetan Plateau. Dating of basal sediments from drill cores that reached the paleo-river bed to 2–2.5 Ma are consistent with mineral cooling ages from the Namche Barwa massif, which indicate initiation of rapid uplift at ~4 Ma. Hence, formation of the Tsangpo gorge and aggradation of the voluminous valley fill was most probably a consequence of rapid uplift of the Namche Barwa massif and thus tectonic activity.
The fourth and last study focuses on the interaction of fluvial and glacial processes at the southeastern edge of the Karakoram. Paleo-ice-extent indicators and remnants of a more than 400-m-thick fluvio-lacustrine valley fill point to blockage of the Shyok River, a main tributary of the upper Indus, by the Siachen Glacier, which is the largest glacier in the Karakoram Range. Field observations and 10Be exposure dating attest to a period of recurring lake formation and outburst flooding during the penultimate glaciation prior to ~110 ka. The interaction of Rivers and Glaciers all along the Karakorum is considered a key factor in landscape evolution and presumably promoted headward erosion of the Indus-Shyok drainage system into the western margin of the Tibetan Plateau.
The results of this thesis highlight the strong influence of glaciation and tectonics on valley-fill formation and how this has affected the evolution of different mountain belts. In the Alps valley-fill deposition influenced the magnitude and pattern of rock uplift since ice retreat approximately 17,000 years ago. Conversely, the analyzed valley fills in the Himalaya are much older and reflect environmental conditions that prevailed at ~110 ka and ~2.5 Ma, respectively. Thus, the newly developed method has proven useful for inferring the role of sedimentary valley-fill deposits in landscape evolution on timescales ranging from 1,000 to 10,000,000 years.
Introduction: Adequate cognitive function in patients is a prerequisite for successful implementation of patient education and lifestyle coping in comprehensive cardiac rehabilitation (CR) programs. Although the association between cardiovascular diseases and cognitive impairments (CIs) is well known, the prevalence particularly of mild CI in CR and the characteristics of affected patients have been insufficiently investigated so far.
Methods: In this prospective observational study, 496 patients (54.5 ± 6.2 years, 79.8% men) with coronary artery disease following an acute coronary event (ACE) were analyzed. Patients were enrolled within 14 days of discharge from the hospital in a 3-week inpatient CR program. Patients were tested for CI using the Montreal Cognitive Assessment (MoCA) upon admission to and discharge from CR. Additionally, sociodemographic, clinical, and physiological variables were documented. The data were analyzed descriptively and in a multivariate stepwise backward elimination regression model with respect to CI.
Results: At admission to CR, the CI (MoCA score < 26) was determined in 182 patients (36.7%). Significant differences between CI and no CI groups were identified, and CI group was associated with high prevalence of smoking (65.9 vs 56.7%, P = 0.046), heavy (physically demanding) workloads (26.4 vs 17.8%, P < 0.001), sick leave longer than 1 month prior to CR (28.6 vs 18.5%, P = 0.026), reduced exercise capacity (102.5 vs 118.8 W, P = 0.006), and a shorter 6-min walking distance (401.7 vs 421.3 m, P = 0.021) compared to no CI group. The age- and education-adjusted model showed positive associations with CI only for sick leave more than 1 month prior to ACE (odds ratio [OR] 1.673, 95% confidence interval 1.07–2.79; P = 0.03) and heavy workloads (OR 2.18, 95% confidence interval 1.42–3.36; P < 0.01).
Conclusion: The prevalence of CI in CR was considerably high, affecting more than one-third of cardiac patients. Besides age and education level, CI was associated with heavy workloads and a longer sick leave before ACE.
Die Empirie des beginnenden 21. Jahrhunderts weist mehr autoritäre Regime aus als am Ende des 20. Jahrhunderts angenommen. Die gegenwärtige Autoritarismusforschung versucht die Fortdauer dieses Regimetyps in Hinblick auf die politischen Institutionen zu erklären – dabei bleiben politische Akteure, die nicht zum Herrschaftszentrum gehören, außen vor.
Das vorliegende Projekt untersucht die Rolle und Funktion politischer Opposition in autoritären Regimen. Es wird davon ausgegangen, dass sich an der Opposition eine signifikante Charakteristik autoritärer Regime manifestiert. Das akteurszentrierte Projekt ist der qualitativ orientierten Politikwissenschaft zuzurechnen und verknüpft das Autoritarismuskonzept von Juan Linz mit klassischen Ansätzen der Oppositionsforschung und macht diese Theorien für die gegenwärtige Autoritarismusforschung nutzbar.
Die eigens entwickelte elitenorientierte Oppositionstypologie wird am Beispiel Kenias im Zeitraum 1990-2005 angewendet. Die Oppositionsgruppen werden im Institutionengefüge autoritärer Regime verortet und ihr politisches Agieren in den Dimensionen Handlungsstatus, Handlungsüberzeugung und Handlungsstrategie analysiert. Unter Beachtung der historisch gewachsenen regionalen und kulturellen Spezifika wird angenommen, dass generelle, Regionen übergreifende Aussagen zur Opposition in autoritären Regimen getroffen werden können: Kein Oppositionstyp kann allein einen Herrschaftswechsel bewirken. Der Wechsel bzw. die Fortdauer der Herrschaft hängt von der Dominanz bestimmter Oppositionstypen im Oppositionsgeflecht sowie der gleichzeitigen Schwäche anderer Oppositionstypen ab.
Durch die konzeptionelle Beschäftigung mit Opposition sowie deren empirische Erschließung soll ein substantieller Beitrag für die notwendige Debatte um autoritäre Regime im 21. Jahrhundert geleistet werden.
The Earth’s shallow subsurface with sedimentary cover acts as a waveguide to any incoming wavefield. Within the framework of my thesis, I focused on the characterization of this shallow subsurface within tens to few hundreds of meters of sediment cover. I imaged the seismic 1D shear wave velocity (and possibly the 1D compressional wave velocity). This information is not only required for any seismic risk assessment, geotechnical engineering or microzonation activities, but also for exploration and global seismology where site effects are often neglected in seismic waveform modeling.
First, the conventional frequency-wavenumber (f - k) technique is used to derive the dispersion characteristic of the propagating surface waves recorded using distinct arrays of seismometers in 1D and 2D configurations. Further, the cross-correlation technique is applied to seismic array data to estimate the Green’s function between receivers pairs combination assuming one is the source and the other the receiver. With the consideration of a 1D media, the estimated cross-correlation Green’s functions are sorted with interstation distance in a virtual 1D active seismic experiment. The f - k technique is then used to estimate the dispersion curves. This integrated analysis is important for the interpretation of a large bandwidth of the phase velocity dispersion curves and therefore improving the resolution of the estimated 1D Vs profile.
Second, the new theoretical approach based on the Diffuse Field Assumption (DFA) is used for the interpretation of the observed microtremors H/V spectral ratio. The theory is further extended in this research work to include not only the interpretation of the H/V measured at the surface, but also the H/V measured at depths and in marine environments. A modeling and inversion of synthetic H/V spectral ratio curves on simple predefined geological structures shows an almost perfect recovery of the model parameters (mainly Vs and to a lesser extent Vp). These results are obtained after information from a receiver at depth has been considered in the inversion.
Finally, the Rayleigh wave phase velocity information, estimated from array data, and the H/V(z, f) spectral ratio, estimated from a single station data, are combined and inverted for the velocity profile information. Obtained results indicate an improved depth resolution in comparison to estimations using the phase velocity dispersion curves only. The overall estimated sediment thickness is comparable to estimations obtained by inverting the full micortremor H/V spectral ratio.
We study the interplay between analysis on manifolds with singularities and complex analysis and develop new structures of operators based on the Mellin transform and tools for iterating the calculus for higher singularities. We refer to the idea of interpreting boundary value problems (BVPs) in terms of pseudo-differential operators with a principal symbolic hierarchy, taking into account that BVPs are a source of cone and edge operator algebras. The respective cone and edge pseudo-differential algebras in turn are the starting point of higher corner theories. In addition there are deep relationships between corner operators and complex analysis. This will be illustrated by the Mellin symbolic calculus.