Length scales of dynamic heterogeneities of low and high molecular weight glass formers from multidimensional NMR

Das Ziel der vorliegenden Arbeit ist die Untersuchung der räumlichen und zeitlichen Aspekte der heterogenen Dynamik in Modellglasbildnern. Dabei wird vor allem die langsame alpha-Relaxationsdynamik oberhalb des Glasüberganges Tg untersucht. Die nukleare Magnetresonanz zeigt ihre einmalige Vielseitigkeit bei der Untersuchung molekularer Dynamik, wenn die angewandten Techniken und Experimente durch Simulationen unterstützt werden. Die räumliche Aspekt dynamischer Heterogenitäten wird untersucht durch ein reduziertes vierdimensionales Spindiffusionsexperiment (4D3CP), ein Experiment, das Reorientierungsraten örtlich korreliert. Eine Simulation dieses Experimentes an einem System harter Kugeln liefert wertvolle Informationen über die Auswertemethode des 4D3CP Experiments. Glycerol und o-terphenyl werden durch das 4D3CP Experiment untersucht. Die erhaltenen Resultate werden mit bereits publizierten Daten des polymeren Glasbildners PVAc verglichen. Während PVAc und o-terphenyl eine Längenskale von 3.7 nm bzw. 2.9 nm aufweisen, ist die Längenskale von Glycerol signifikant kleiner bei 1.1 nm. Ein neues Experiment, welches sensitiv auf Translationsbewegung reagiert, wird vorgestellt. Durch Verwendung eines pi-Impulszuges kann eine separate Evolution unter dem Hamiltonian der dipolaren Kopplung und der chemischen Verschiebungsanisotropie erreicht werden.

Nature and origin of ultramafic lamprophyres and carbonatites from the borders of the Labrador Sea

Die Ränder des Labrador Meeres wurden während des späten Neoproterozoikums intensiv von karbonatreichen silikatischen Schmelzen durchsetzt. Diese Schmelzen bildeted sich bei Drucken zwischen ca. 4-6 GPa (ca. 120-180 km Tiefe) an der Basis der kontinentalen Mantel-Lithosphäre. Diese Magmengenerierung steht in zeitlichem und räumlichem Zusammenhang mit kontinentalen Extensionsprozessen, welche zu beiden Seiten des sich öffnenden Iapetus-Ozeans auftraten.

EPR spectroscopic investigation of membrane protein structure and folding on light harvesting complex LHCIIb

Structure and folding of membrane proteins are important issues in molecular and cell biology. In this work new approaches are developed to characterize the structure of folded, unfolded and partially folded membrane proteins. These approaches combine site-directed spin labeling and pulse EPR techniques. The major plant light harvesting complex LHCIIb was used as a model system. Measurements of longitudinal and transversal relaxation times of electron spins and of hyperfine couplings to neighboring nuclei by electron spin echo envelope modulation(ESEEM) provide complementary information about the local environment of a single spin label. By double electron electron resonance (DEER) distances in the nanometer range between two spin labels can be determined. The results are analyzed in terms of relative water accessibilities of different sites in LHCIIb and its geometry. They reveal conformational changes as a function of micelle composition. This arsenal of methods is used to study protein folding during the LHCIIb self assembly and a spatially and temporally resolved folding model is proposed. The approaches developed here are potentially applicable for studying structure and folding of any protein or other self-assembling structure if site-directed spin labeling is feasible and the time scale of folding is accessible to freeze-quench techniques.

Petrogenetic evolution of Uralian-Alaskan-type mafic-ultramafic complexes in the southern and middle Urals, Russia

The PhD thesis at hand consists of three parts and describes the petrogenetic evolution of Uralian-Alaskan-type mafic ultramafic complexes in the Ural Mountains, Russia. Uralian-Alaskan-type mafic-ultramafic complexes are recognized as a distinct class of intrusions. Characteristic petrologic features are the concentric zonation of a central dunite body grading outward into wehrlite, clinopyroxenite and gabbro, the absence of orthopyroxene and frequently occurring platinum group element (PGE) mineralization. In addition, the presence of ferric iron-rich spinel discriminates Uralian-Alaskan-type complexes from most other mafic ultramafic rock assemblages. The studied Uralian-Alaskan-type complexes (Nizhnii Tagil, Kytlym and Svetley Bor) belong to the southern part of a 900 km long, N–S-trending chain of similar intrusions between the Main Uralian Fault to the west and the Serov-Mauk Fault to the east. The first chapter of this thesis studies the evolution of the ultramafic rocks tracing the compositional variations of rock forming and accessory minerals. The comparison of the chemical composition of olivine, clinopyroxene and chromian spinel from the Urals with data from other localities indicates that they are unique intrusions having a characteristic spinel and clinopyroxene chemistry. Laser ablation-ICPMS (LA-ICPMS ) analyses of trace element concentrations in clinopyroxene are used to calculate the composition of their parental melt which is characterized by enriched LREE (0.5-5.2 prim. mantle) and other highly incompatible elements (U, Th, Ba, Rb) relative to the HREE (0.25-2.0 prim. mantle). A subduction-related geotectonic setting is indicated by a positive anomaly for Sr and negative anomalies for Ti, Zr and Hf. The mineral compositions monitor the evolution of the parental magmas and decipher differences between the studied complexes. In addition, the observed variation in LREE/HREE (for example La/Lu = 2-24) can be best explained with the model of an episodically replenished and erupted open magma chamber system with the extensive fractionation of olivine, spinel and clinopyroxene. The data also show that ankaramites in a subduction-related geotectonic setting could represent parental magmas of Uralian-Alaskan-type complexes. The second chapter of the thesis discusses the chemical variation of major and trace elements in rock-forming minerals of the mafic rocks. Electron microprobe and LA-ICPMS analyses are used to quantitatively describe the petrogenetic relationship between the different gabbroic lithologies and their genetic link to the ultramafic rocks. The composition of clinopyroxene identifies the presence of melts with different trace element abundances on the scale of a thin section and suggests the presence of open system crustal magma chambers. Even on a regional scale the large variation of trace element concentrations and ratios in clinopyroxene (e.g. La/Lu = 3-55) is best explained by the interaction of at least two fundamentally different magma types at various stages of fractionation. This requires the existence of a complex magma chamber system fed with multiple pulses of magmas from at least two different coeval sources in a subduction-related environment. One source produces silica saturated Island arc tholeiitic melts. The second source produces silica undersaturated, ultra-calcic, alkaline melts. Taken these data collectively, the mixing of the two different parental magmas is the dominant petrogenetic process explaining the observed chemical variations. The results further imply that this is an intrinsic feature of Uralian-Alaskan-type complexes and probably of many similar mafic-ultramafic complexes world-wide. In the third chapter of this thesis the major element composition of homogeneous and exsolved spinel is used as a petrogenetic indicator. Homogeneous chromian spinel in dunites and wehrlites monitors the fractionation during the early stages of the magma chamber and the onset of clinopyroxene fractionation as well as the reaction of spinel with interstitial liquid. Exsolved spinel is present in mafic and ultramafic rocks from all three studied complexes. Its composition lies along a solvus curve which defines an equilibrium temperature of 600°C, given that spinel coexists with olivine. This temperature is considered to be close to the temperature of the host rocks into which the studied Uralian-Alaskan-type complexes intruded. The similarity of the exsolution temperatures in the different complexes over a distance of several hundred kilometres implies a regional tectonic event that terminated the exsolution process. This event is potentially associated with the final exhumation of the Uralian-Alaskan-type complexes along the Main Uralian Fault and the Serov-Mauk Fault in the Uralian fold belt.

Dynamics, rheology and critical properties of colloidal fluid mixtures

Liquids under the influence of external fields exhibit a wide range of intriguing phenomena that can be markedly different from the behaviour of a quiescent system. This work considers two different systems — a glassforming Yukawa system and a colloid-polymer mixture — by Molecular Dynamics (MD) computer simulations coupled to dissipative particle dynamics. The former consists of a 50-50 binary mixture of differently-sized, like-charged colloids interacting via a screened Coulomb (Yukawa) potential. Near the glass transition the influence of an external shear field is studied. In particular, the transition from elastic response to plastic flow is of interest. At first, this model is characterised in equilibrium. Upon decreasing temperature it exhibits the typical dynamics of glassforming liquids, i.e. the structural relaxation time τα grows strongly in a rather small temperature range. This is discussed with respect to the mode-coupling theory of the glass transition (MCT). For the simulation of bulk systems under shear, Lees-Edwards boundary conditions are applied. At constant shear rates γ˙ ≫ 1/τα the relevant time scale is given by 1/γ˙ and the system shows shear thinning behaviour. In order to understand the pronounced differences between a quiescent system and a system under shear, the response to a suddenly commencing or terminating shear flow is studied. After the switch-on of the shear field the shear stress shows an overshoot, marking the transition from elastic to plastic deformation, which is connected to a super-diffusive increase of the mean squared displacement. Since the average static structure only depends on the value of the shear stress, it does not discriminate between those two regimes. The distribution of local stresses, in contrast, becomes broader as soon as the system starts flowing. After a switch-off of the shear field, these additional fluctuations are responsible for the fast decay of stresses, which occurs on a time scale 1/γ˙ . The stress decay after a switch-off in the elastic regime, on the other hand, happens on the much larger time scale of structural relaxation τα. While stresses decrease to zero after a switch-off for temperatures above the glass transition, they decay to a finite value for lower temperatures. The obtained results are important for advancing new theoretical approaches in the framework of mode-coupling theory. Furthermore, they suggest new experimental investigations on colloidal systems. The colloid-polymer mixture is studied in the context of the behaviour near the critical point of phase separation. For the MD simulations a new effective model with soft interaction potentials is introduced and its phase diagram is presented. Here, mainly the equilibrium properties of this model are characterised. While the self-diffusion constants of colloids and polymers do not change strongly when the critical point is approached, critical slowing down of interdiffusion is observed. The order parameter fluctuations can be determined through the long-wavelength limit of static structure factors. For this strongly asymmetric mixture it is shown how the relevant structure factor can be extracted by a diagonalisation of a matrix that contains the partial static structure factors. By presenting first results of this model under shear it is demonstrated that it is suitable for non-equilibrium simulations as well.

Characterization of structure and dynamics of submicrometric systems via fluorescence correlation spectroscopy

The presented thesis revolves around the study of thermally-responsive PNIPAAm-based hydrogels in water/based environments, as studied by Fluorescence Correlation Spectroscopy (FCS).rnThe goal of the project was the engineering of PNIPAAm gels into biosensors. Specifically, a gamma of such gels were both investigated concerning their dynamics and structure at the nanometer scale, and their performance in retaining bound bodies upon thermal collapse (which PNIPAAm undergoes upon heating above 32 ºC).rnFCS’s requirements, as a technique, match the limitations imposed by the system. Namely, the need to intimately probe a system in a solvent, which was also fragile and easy to alter. FCS, on the other hand, both requires a fluid environment to work, and is based on the observation of diffusion of fluorescents at nanomolar concentrations. FCS was applied to probe the hydrogels on the nanometer size with minimal invasivity.rnVariables in the gels were addressed in the project including crosslinking degree; structural changes during thermal collapse; behavior in different buffers; the possibility of decreasing the degree of inhomogeneity; behavior of differently sized probes; and the effectiveness of antibody functionalization upon thermal collapse.rnThe evidenced results included the heightening of structural inhomogeneities during thermal collapse and under different buffer conditions; the use of annealing to decrease the inhomogeneity degree; the use of differently sized probes to address different length scale of the gel; and the successful functionalization before and after collapse.rnThe thesis also addresses two side projects, also carried forward via FCS. One, diffusion in inverse opals, produced a predictive simulation model for diffusion of bodies in confined systems as dependent on the bodies’ size versus the characteristic sizes of the system. The other was the observation of interaction of bodies of opposite charge in a water solution, resulting in a phenomenological theory and an evaluation method for both the average residence time of the different bodies together, and their attachment likelihood.

Measurement of the pair production of b-jets in proton-proton collisions at root out s = 7 TeV with the ATLAS detector

In hadronischen Kollisionen entstehen bei einem Großteil der Ereignisse mit einem hohen Impulsübertrag Paare aus hochenergetischen Jets. Deren Produktion und Eigenschaften können mit hoher Genauigkeit durch die Störungstheorie in der Quantenchromodynamik (QCD) vorhergesagt werden. Die Produktion von \textit{bottom}-Quarks in solchen Kollisionen kann als Maßstab genutzt werden, um die Vorhersagen der QCD zu testen, da diese Quarks die Dynamik des Produktionsprozesses bei Skalen wieder spiegelt, in der eine Störungsrechnung ohne Einschränkungen möglich ist. Auf Grund der hohen Masse von Teilchen, die ein \textit{bottom}-Quark enthalten, erhält der gemessene, hadronische Zustand den größten Teil der Information von dem Produktionsprozess der Quarks. Weil sie eine große Produktionsrate besitzen, spielen sie und ihre Zerfallsprodukte eine wichtige Rolle als Untergrund in vielen Analysen, insbesondere in Suchen nach neuer Physik. In ihrer herausragenden Stellung in der dritten Quark-Generation könnten sich vermehrt Zeichen im Vergleich zu den leichteren Quarks für neue Phänomene zeigen. Daher ist die Untersuchung des Verhältnisses zwischen der Produktion von Jets, die solche \textit{bottom}-Quarks enthalten, auch bekannt als $b$-Jets, und aller nachgewiesener Jets ein wichtiger Indikator für neue massive Objekte. In dieser Arbeit werden die Produktionsrate und die Korrelationen von Paaren aus $b$-Jets bestimmt und nach ersten Hinweisen eines neuen massiven Teilchens, das bisher nicht im Standard-Modell enthalten ist, in dem invarianten Massenspektrum der $b$-Jets gesucht. Am Large Hadron Collider (LHC) kollidieren zwei Protonenstrahlen bei einer Schwerpunktsenergie von $\sqrt s = 7$ TeV, und es werden viele solcher Paare aus $b$-Jets produziert. Diese Analyse benutzt die aufgezeichneten Kollisionen des ATLAS-Detektors. Die integrierte Luminosität der verwendbaren Daten beläuft sich auf 34~pb$^{-1}$. $b$-Jets werden mit Hilfe ihrer langen Lebensdauer und den rekonstruierten, geladenen Zerfallsprodukten identifiziert. Für diese Analyse müssen insbesondere die Unterschiede im Verhalten von Jets, die aus leichten Objekten wie Gluonen und leichten Quarks hervorgehen, zu diesen $b$-Jets beachtet werden. Die Energieskala dieser $b$-Jets wird untersucht und die zusätzlichen Unsicherheit in der Energiemessung der Jets bestimmt. Effekte bei der Jet-Rekonstruktion im Detektor, die einzigartig für $b$-Jets sind, werden studiert, um letztlich diese Messung unabhängig vom Detektor und auf Niveau der Hadronen auswerten zu können. Hiernach wird die Messung zu Vorhersagen auf nächst-zu-führender Ordnung verglichen. Dabei stellt sich heraus, dass die Vorhersagen in Übereinstimmung zu den aufgenommenen Daten sind. Daraus lässt sich schließen, dass der zugrunde liegende Produktionsmechanismus auch in diesem neu erschlossenen Energiebereich am LHC gültig ist. Jedoch werden auch erste Hinweise auf Mängel in der Beschreibung der Eigenschaften dieser Ereignisse gefunden. Weiterhin können keine Anhaltspunkte für eine neue Resonanz, die in Paare aus $b$-Jets zerfällt, in dem invarianten Massenspektrum bis etwa 1.7~TeV gefunden werden. Für das Auftreten einer solchen Resonanz mit einer Gauß-förmigen Massenverteilung werden modell-unabhängige Grenzen berechnet.

Sustainable development in Darjeeling Hills, India : ecological and socio-economic aspects for small-scale farmers with supportive observations from Kanagawa, Japan

Organic farming means a holistic application of agricultural land-use, hence, this study aimed to assess ecological and socio-economic aspects that show benefits of the strategy and achievements of organic farming in comparison to conventional farming in Darjeeling District, State of West Bengal, India and Kanagawa Prefecture/Kanto in Central Japan. The objective of this study has been empirically analysed on aspects of crop diversity, yield, income and sales prices in the two study regions, where 50 households each, i.e. in total 100 households were interviewed at farm-level. Therefore, the small sample size does not necessarily reflect the broad-scale of the use and benefit of organic farming in both regions. The problems faced in mountainous regions in terms of agriculture and livelihoods for small-scale farmers, which are most affected and dependant on their immediate environment, such as low yields, income and illegal felling leading to soil erosion and landslides, are analyzed. Furthermore, factors such as climate, soils, vegetation and relief equally play an important role for these farmers, in terms of land-use. To supplement and improve the income of farmers, local NGOs have introduced organic farming and high value organic cash crops such as ginger, tea, orange and cardamom and small income generating means (floriculture, apiary etc.). For non-certified and certified organic products the volume is given for India, while for Japan only certified organic production figures are given, as there are several definitions for organic in Japan. Hence, prior to the implementation of organic laws and standards, even reduced chemical input was sold as non-certified organic. Furthermore, the distribution and certification system of both countries are explained in detail, including interviews with distribution companies and cooperatives. Supportive observations from Kanagawa Prefecture and the Kanto region are helpful and practical suggestions for organic farmers in Darjeeling District. Most of these are simple and applicable soil management measures, natural insect repelling applications and describe the direct marketing system practiced in Japan. The former two include compost, intercropping, Effective Microorganisms (EM), clover, rice husk charcoal and wood vinegar. More supportive observations have been made at organic and biodynamic tea estates in Darjeeling District, which use citronella, neem, marigold, leguminous and soil binding plants for soil management and natural insect control. Due to the close ties between farmers and consumers in Japan, certification is often neither necessary nor wanted by the producers. They have built a confidence relationship with their customers; thus, such measures are simply not required. Another option is group certification, instead of the expensive individual certification. The former aims at lower costs for farmers who have formed a cooperative or a farmers' group. Consumer awareness for organic goods is another crucial aspect to help improve the situation of organic farmers. Awareness is slightly more advanced in Kanto than in Darjeeling District, as it is improved due to the close (sales) ties between farmers and consumers in Kanto. Interviews conducted with several such cooperatives and companies underline the positive system of TEIKEI. The introduction of organic farming in the study regions has shown positive effects for those involved, even though it still in its beginning stages in Darjeeling District. This study was only partly able to assess the benefits of organic agriculture at its present level for Darjeeling District, while more positively for the organic farmers of Kanto. The organic farming practice needs further improvement, encouragement and monitoring for the Darjeeling District farmers by locals, consumers, NGOs and politicians. The supportive observations from Kanagawa Prefecture and the Kanto region are a small step in this direction, showing how, simple soil improvements and thus, yield and income increases, as well as direct sales options can enhance the livelihood of organic farmers without destroying their environment and natural resources.