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Membrane adhesion is a fundamental biological process in which membranes are attached to neighboring membranes or surfaces. Membrane adhesion emerges from a complex interplay between the binding of membrane-anchored receptors/ligands and the membrane properties. In this work, we study membrane adhesion mediated by lipid-anchored saccharides using microsecond-long full-atomistic molecular dynamics simulations. Motivated by neutron scattering experiments on membrane adhesion via lipid-anchored saccharides, we investigate the role of LeX, Lac1, and Lac2 saccharides and membrane fluctuations in membrane adhesion.
We study the binding of saccharides in three different systems: for saccharides in water, for saccharides anchored to essentially planar membranes at fixed separations, and for saccharides anchored to apposing fluctuating membranes. Our simulations of two saccharides in water indicate that the saccharides engage in weak interactions to form dimers. We find that the binding occurs in a continuum of bound states instead of a certain number of well-defined bound structures, which we term as "diffuse binding".
The binding of saccharides anchored to essentially planar membranes strongly depends on separation of the membranes, which is fixed in our simulation system. We show that the binding constants for trans-interactions of two lipid-anchored saccharides monotonically decrease with increasing separation. Saccharides anchored to the same membrane leaflet engage in cis-interactions with binding constants comparable to the trans-binding constants at the smallest membrane separations. The interplay of cis- and trans-binding can be investigated in simulation systems with many lipid-anchored saccharides. For Lac2, our simulation results indicate a positive cooperativity of trans- and cis-binding. In this cooperative binding the trans-binding constant is enhanced by the cis-interactions. For LeX, in contrast, we observe no cooperativity between trans- and cis-binding. In addition, we determine the forces generated by trans-binding of lipid-anchored saccharides in planar membranes from the binding-induced deviations of the lipid-anchors. We find that the forces acting on trans-bound saccharides increase with increasing membrane separation to values of the order of 10 pN.
The binding of saccharides anchored to the fluctuating membranes results from an interplay between the binding properties of the lipid-anchored saccharides and membrane fluctuations. Our simulations, which have the same average separation of the membranes as obtained from the neutron scattering experiments, yield a binding constant larger than in planar membranes with the same separation. This result demonstrates that membrane fluctuations play an important role at average membrane separations which are seemingly too large for effective binding. We further show that the probability distribution of the local separation can be well approximated by a Gaussian distribution. We calculate the relative membrane roughness and show that our results are in good agreement with the roughness values reported from the neutron scattering experiments.
Domestication syndrome has resulted in the large loss of genetic variation of crop plants. Because of such genetic loss, productivity of various beneficial secondary (specialized) metabolites that protect against abiotic/biotic stresses, has been narrowed in many domesticated crops. Many key regulators or structural genes of secondary metabolic pathways in the domesticated as well as wild tomatoes are still largely unknown. In recent studies, metabolic quantitative trait loci (mQTL) analysis using the population of introgression lines (ILs), each containing a single introgression from Solanum pennellii (wild tomato) in the genetic background of domesticated tomato (M82, Solanum lycopersicum), has been used for investigation of metabolic regulation and key genes involved in both primary and secondary metabolism. In this thesis, three research projects, i) understanding of metabolic linkage between branched chain amino acids (BCAAs) and secondary metabolism using antisense lines of BCAAs metabolic genes, ii) investigation of novel key genes involved in tomato secondary metabolism and fruit ripening, iii) mapping of drought stress responsive mQTLs in tomato, are presented and discussed. In the first part, metabolic linkage between leucine and secondary metabolism is investigated by analyzing antisense lines of four key genes (ketol-acid reductoisomerase, KARI; dihydroxy-acid dehydratase, DHAD; isopropylmalate dehydratase, IPMD and branched chain aminotransferases1, BCAT1) found previously in mQTL of leucine contents. Obtained results indicate that KARI might be a rate limiting enzyme for iC5 acyl-sucrose synthesis in young leaf but not in red ripe fruits. By integrating obtained results with previous reports, inductive metabolic linkage between BCAAs and other secondary metabolic pathways at DHAD transcriptional levels in fruit is proposed. In the second part, candidate genes that are involved in secondary metabolism and fruit ripening in tomato were found by the approach of expression quantitative trait loci (eQTL) analysis. To predict functions of those candidate genes, functional validation by virus induced gene silencing and transient overexpression were performed. Results obtained by analyzing T0 overexpression and artificial miRNA lines for some of those candidates confirm their predicted functions, for example involved in fruit ripening (WD40, Solyc04g005020) and iC5 acyl-sucrose synthesis (P450, Solyc03g111940). In the third part, mapping of drought stress responsive mQTLs was performed using 57 S. pennellii ILs population. Evaluation of genetic architecture of mQTL analysis resulted in identifying drought responsive ILs (11-2, 8-3-1, 10-1-1 and 3-1). Location of well characterized regulators in these ILs helped to filter potential new key genes involved in drought stress tolerance. Obtained results suggests us our approaches could be viable for narrowing down potential candidates involved in creating interspecific variation in secondary metabolite content and at the level of fruit ripening.
In the era of social networks, internet of things and location-based services, many online services produce a huge amount of data that have valuable objective information, such as geographic coordinates and date time. These characteristics (parameters) in the combination with a textual parameter bring the challenge for the discovery of geospatiotemporal knowledge. This challenge requires efficient methods for clustering and pattern mining in spatial, temporal and textual spaces.
In this thesis, we address the challenge of providing methods and frameworks for geospatiotemporal data analytics. As an initial step, we address the challenges of geospatial data processing: data gathering, normalization, geolocation, and storage. That initial step is the basement to tackle the next challenge -- geospatial clustering challenge. The first step of this challenge is to design the method for online clustering of georeferenced data. This algorithm can be used as a server-side clustering algorithm for online maps that visualize massive georeferenced data. As the second step, we develop the extension of this method that considers, additionally, the temporal aspect of data. For that, we propose the density and intensity-based geospatiotemporal clustering algorithm with fixed distance and time radius.
Each version of the clustering algorithm has its own use case that we show in the thesis.
In the next chapter of the thesis, we look at the spatiotemporal analytics from the perspective of the sequential rule mining challenge. We design and implement the framework that transfers data into textual geospatiotemporal data - data that contain geographic coordinates, time and textual parameters. By this way, we address the challenge of applying pattern/rule mining algorithms in geospatiotemporal space. As the applicable use case study, we propose spatiotemporal crime analytics -- discovery spatiotemporal patterns of crimes in publicly available crime data.
The second part of the thesis, we dedicate to the application part and use case studies. We design and implement the application that uses the proposed clustering algorithms to discover knowledge in data. Jointly with the application, we propose the use case studies for analysis of georeferenced data in terms of situational and public safety awareness.
Continuous insight into biological processes has led to the development of large-scale, mechanistic systems biology models of pharmacologically relevant networks. While these models are typically designed to study the impact of diverse stimuli or perturbations on multiple system variables, the focus in pharmacological research is often on a specific input, e.g., the dose of a drug, and a specific output related to the drug effect or response in terms of some surrogate marker.
To study a chosen input-output pair, the complexity of the interactions as well as the size of the models hinders easy access and understanding of the details of the input-output relationship.
The objective of this thesis is the development of a mathematical approach, in specific a model reduction technique, that allows (i) to quantify the importance of the different state variables for a given input-output relationship, and (ii) to reduce the dynamics to its essential features -- allowing for a physiological interpretation of state variables as well as parameter estimation in the statistical analysis of clinical data. We develop a model reduction technique using a control theoretic setting by first defining a novel type of time-limited controllability and observability gramians for nonlinear systems. We then show the superiority of the time-limited generalised gramians for nonlinear systems in the context of balanced truncation for a benchmark system from control theory.
The concept of time-limited controllability and observability gramians is subsequently used to introduce a state and time-dependent quantity called the input-response (ir) index that quantifies the importance of state variables for a given input-response relationship at a particular time.
We subsequently link our approach to sensitivity analysis, thus, enabling for the first time the use of sensitivity coefficients for state space reduction. The sensitivity based ir-indices are given as a product of two sensitivity coefficients. This allows not only for a computational more efficient calculation but also for a clear distinction of the extent to which the input impacts a state variable and the extent to which a state variable impacts the output.
The ir-indices give insight into the coordinated action of specific state variables for a chosen input-response relationship.
Our developed model reduction technique results in reduced models that still allow for a mechanistic interpretation in terms of the quantities/state variables of the original system, which is a key requirement in the field of systems pharmacology and systems biology and distinguished the reduced models from so-called empirical drug effect models. The ir-indices are explicitly defined with respect to a reference trajectory and thereby dependent on the initial state (this is an important feature of the measure). This is demonstrated for an example from the field of systems pharmacology, showing that the reduced models are very informative in their ability to detect (genetic) deficiencies in certain physiological entities. Comparing our novel model reduction technique to the already existing techniques shows its superiority.
The novel input-response index as a measure of the importance of state variables provides a powerful tool for understanding the complex dynamics of large-scale systems in the context of a specific drug-response relationship. Furthermore, the indices provide a means for a very efficient model order reduction and, thus, an important step towards translating insight from biological processes incorporated in detailed systems pharmacology models into the population analysis of clinical data.
The North China Plain (NCP) is one of the most productive and intensive agricultural regions in China. High doses of mineral nitrogen (N) fertiliser, often combined with flood irrigation, are applied, resulting in N surplus, groundwater depletion and environmental pollution. The objectives of this thesis were to use the HERMES model to simulate the N cycle in winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) double crop rotations and show the performance of the HERMES model, of the new ammonia volatilisation sub-module and of the new nitrification inhibition tool in the NCP. Further objectives were to assess the models potential to save N and water on plot and county scale, as well as on short and long-term. Additionally, improved management strategies with the help of a model-based nitrogen fertiliser recommendation (NFR) and adapted irrigation, should be found.
Results showed that the HERMES model performed well under growing conditions of the NCP and was able to describe the relevant processes related to soil–plant interactions concerning N and water during a 2.5 year field experiment. No differences in grain yield between the real-time model-based NFR and the other treatments of the experiments on plot scale in Quzhou County could be found. Simulations with increasing amounts of irrigation resulted in significantly higher N leaching, higher N requirements of the NFR and reduced yields. Thus, conventional flood irrigation as currently practised by the farmers bears great uncertainties and exact irrigation amounts should be known for future simulation studies. In the best-practice scenario simulation on plot-scale, N input and N leaching, but also irrigation water could be reduced strongly within 2 years. Thus, the model-based NFR in combination with adapted irrigation had the highest potential to reduce nitrate leaching, compared to farmers practice and mineral N (Nmin)-reduced treatments. Also the calibrated and validated ammonia volatilisation sub-module of the HERMES model worked well under the climatic and soil conditions of northern China. Simple ammonia volatilisation approaches gave also satisfying results compared to process-oriented approaches. During the simulation with Ammonium sulphate Nitrate with nitrification inhibitor (ASNDMPP) ammonia volatilisation was higher than in the simulation without nitrification inhibitor, while the result for nitrate leaching was the opposite. Although nitrification worked well in the model, nitrification-born nitrous oxide emissions should be considered in future. Results of the simulated annual long-term (31 years) N losses in whole Quzhou County in Hebei Province were 296.8 kg N ha−1 under common farmers practice treatment and 101.7 kg N ha−1 under optimised treatment including NFR and automated irrigation (OPTai). Spatial differences in simulated N losses throughout Quzhou County, could only be found due to different N inputs. Simulations of an optimised treatment, could save on average more than 260 kg N ha−1a−1 from fertiliser input and 190 kg N ha−1a−1 from N losses and around 115.7 mm a−1 of water, compared to farmers practice. These long-term simulation results showed lower N and water saving potential, compared to short-term simulations and underline the necessity of long-term simulations to overcome the effect of high initial N stocks in soil.
Additionally, the OPTai worked best on clay loam soil except for a high simulated denitrification loss, while the simulations using farmers practice irrigation could not match the actual water needs resulting in yield decline, especially for winter wheat. Thus, a precise adaption of management to actual weather conditions and plant growth needs is necessary for future simulations. However, the optimised treatments did not seem to be able to maintain the soil organic matter pools, even with full crop residue input. Extra organic inputs seem to be required to maintain soil quality in the optimised treatments.
HERMES is a relatively simple model, with regard to data input requirements, to simulate the N cycle. It can offer interpretation of management options on plot, on county and regional scale for extension and research staff. Also in combination with other N and water saving methods the model promises to be a useful tool.
The growing energy demand of the modern economies leads to the increased consumption of fossil fuels in form of coal, oil, and natural gases, as the mains sources. The combustion of these carbon-based fossil fuels is inevitably producing greenhouse gases, especially CO2. Approaches to tackle the CO2 problem are to capture it from the combustion sources or directly from air, as well as to avoid CO2 production in energy consuming sources (e.g., in the refrigeration sector). In the former, relatively low CO2 concentrations and competitive adsorption of other gases is often leading to low CO2 capacities and selectivities. In both approaches, the interaction of gas molecules with porous materials plays a key role. Porous carbon materials possess unique properties including electric conductivity, tunable porosity, as well as thermal and chemical stability. Nevertheless, pristine carbon materials offer weak polarity and thus low CO2 affinity. This can be overcome by nitrogen doping, which enhances the affinity of carbon materials towards acidic or polar guest molecules (e.g., CO2, H2O, or NH3). In contrast to heteroatom-free materials, such carbon materials are in most cases “noble”, that is, they oxidize other matter rather than being oxidized due to the very positive working potential of their electrons. The challenging task here is to achieve homogenous distribution of significant nitrogen content with similar bonding motives throughout the carbon framework and a uniform pore size/distribution to maximize host-guest interactions. The aim of this thesis is the development of novel synthesis pathways towards nitrogen-doped nanoporous noble carbon materials with precise design on a molecular level and understanding of their structure-related performance in energy and environmental applications, namely gas adsorption and electrochemical energy storage.
A template-free synthesis approach towards nitrogen-doped noble microporous carbon materials with high pyrazinic nitrogen content and C2N-type stoichiometry was established via thermal condensation of a hexaazatriphenylene derivative. The materials exhibited high uptake of guest molecules, such as H2O and CO2 at low concentrations, as well as moderate CO2/N2 selectivities. In the following step, the CO2/N2 selectivity was enhanced towards molecular sieving of CO2 via kinetic size exclusion of N2. The precise control over the condensation degree, and thus, atomic construction and porosity of the resulting materials led to remarkable CO2/N2 selectivities, CO2 capacities, and heat of CO2 adsorption. The ultrahydrophilic nature of the pore walls and the narrow microporosity of these carbon materials served as ideal basis for the investigation of interface effects with more polar guest molecules than CO2, namely H2O and NH3.
H2O vapor physisorption measurements, as well as NH3-temperature programmed desorption and thermal response measurements showed exceptionally high affinity towards H2O vapor and NH3 gas. Another series of nitrogen-doped carbon materials was synthesized by direct condensation of a pyrazine-fused conjugated microporous polymer and their structure-related performance in electrochemical energy storage, namely as anode materials for sodium-ion battery, was investigated.
All in all, the findings in this thesis exemplify the value of molecularly designed nitrogen-doped carbon materials with remarkable heteroatom content implemented as well-defined structure motives. The simultaneous adjustment of the porosity renders these materials suitable candidates for fundamental studies about the interactions between nitrogen-doped carbon materials and different guest species.
Supercapacitors are electrochemical energy storage devices with rapid charge/discharge rate and long cycle life. Their biggest challenge is the inferior energy density compared to other electrochemical energy storage devices such as batteries. Being the most widely spread type of supercapacitors, electrochemical double-layer capacitors (EDLCs) store energy by electrosorption of electrolyte ions on the surface of charged electrodes. As a more recent development, Na-ion capacitors (NICs) are expected to be a more promising tactic to tackle the inferior energy density due to their higher-capacity electrodes and larger operating voltage. The charges are simultaneously stored by ion adsorption on the capacitive-type cathode surface and via faradic process in the battery-type anode, respectively. Porous carbon electrodes are of great importance in these devices, but the paramount problems are the facile synthetic routes for high-performance carbons and the lack of fundamental understanding of the energy storage mechanisms. Therefore, the aim of the present dissertation is to develop novel synthetic methods for (nitrogen-doped) porous carbon materials with superior performance, and to reveal a deeper understanding energy storage mechanisms of EDLCs and NICs.
The first part introduces a novel synthetic method towards hierarchical ordered meso-microporous carbon electrode materials for EDLCs. The large amount of micropores and highly ordered mesopores endow abundant sites for charge storage and efficient electrolyte transport, respectively, giving rise to superior EDLC performance in different electrolytes. More importantly, the controversial energy storage mechanism of EDLCs employing ionic liquid (IL) electrolytes is investigated by employing a series of porous model carbons as electrodes. The results not only allow to conclude on the relations between the porosity and ion transport dynamics, but also deliver deeper insights into the energy storage mechanism of IL-based EDLCs which is different from the one usually dominating in solvent-based electrolytes leading to compression double-layers.
The other part focuses on anodes of NICs, where novel synthesis of nitrogen-rich porous carbon electrodes and their sodium storage mechanism are investigated. Free-standing fibrous nitrogen-doped carbon materials are synthesized by electrospinning using the nitrogen-rich monomer (hexaazatriphenylene-hexacarbonitrile, C18N12) as the precursor followed by condensation at high temperature. These fibers provide superior capacity and desirable charge/discharge rate for sodium storage. This work also allows insights into the sodium storage mechanism in nitrogen-doped carbons. Based on this mechanism, further optimization is done by designing a composite material composed of nitrogen-rich carbon nanoparticles embedded in conductive carbon matrix for a better charge/discharge rate. The energy density of the assembled NICs significantly prevails that of common EDLCs while maintaining the high power density and long cycle life.
The Central Andes host large reserves of base and precious metals. The region represented, in 2017, an important part of the worldwide mining activity. Three principal types of deposits have been identified and studied: 1) porphyry type deposits extending from central Chile and Argentina to Bolivia, and Northern Peru, 2) iron oxide-copper-gold (IOCG) deposits, extending from central Peru to central Chile, and 3) epithermal tin polymetallic deposits extending from Southern Peru to Northern Argentina, which compose a large part of the deposits of the Bolivian Tin Belt (BTB). Deposits in the BTB can be divided into two major types: (1) tin-tungsten-zinc pluton-related polymetallic deposits, and (2) tin-silver-lead-zinc epithermal polymetallic vein deposits.
Mina Pirquitas is a tin-silver-lead-zinc epithermal polymetallic vein deposit, located in north-west Argentina, that used to be one of the most important tin-silver producing mine of the country. It was interpreted to be part of the BTB and it shares similar mineral associations with southern pluton related BTB epithermal deposits. Two major mineralization events related to three pulses of magmatic fluids mixed with meteoric water have been identified. The first event can be divided in two stages: 1) stage I-1 with quartz, pyrite, and cassiterite precipitating from fluids between 233 and 370 °C and salinity between 0 and 7.5 wt%, corresponding to a first pulse of fluids, and 2) stage I-2 with sphalerite and tin-silver-lead-antimony sulfosalts precipitating from fluids between 213 and 274 °C with salinity up to 10.6 wt%, corresponding to a new pulse of magmatic fluids in the hydrothermal system. The mineralization event II deposited the richest silver ores at Pirquitas. Event II fluids temperatures and salinities range between 190 and 252 °C and between 0.9 and 4.3 wt% respectively. This corresponds to the waning supply of magmatic fluids. Noble gas isotopic compositions and concentrations in ore-hosted fluid inclusions demonstrate a significant contribution of magmatic fluids to the Pirquitas mineralization although no intrusive rocks are exposed in the mine area.
Lead and sulfur isotopic measurements on ore minerals show that Pirquitas shares a similar signature with southern pluton related polymetallic deposits in the BTB. Furthermore, the major part of the sulfur isotopic values of sulfide and sulfosalt minerals from Pirquitas ranges in the field for sulfur derived from igneous rocks. This suggests that the main contribution of sulfur to the hydrothermal system at Pirquitas is likely to be magma-derived. The precise age of the deposit is still unknown but the results of wolframite dating of 2.9 ± 9.1 Ma and local structural observations suggest that the late mineralization event is younger than 12 Ma.
Predation drives coexistence, evolution and population dynamics of species in food webs, and has strong impacts on related ecosystem functions (e.g. primary production). The effect of predation on these processes largely depends on the trade-offs between functional traits in the predator and prey community. Trade-offs between defence against predation and competitive ability, for example, allow for prey speciation and predator-mediated coexistence of prey species with different strategies (defended or competitive), which may stabilize the overall food web dynamics. While the importance of such trade-offs for coexistence is widely known, we lack an understanding and the empirical evidence of how the variety of differently shaped trade-offs at multiple trophic levels affect biodiversity, trait adaptation and biomass dynamics in food webs. Such mechanistic understanding is crucial for predictions and management decisions that aim to maintain biodiversity and the capability of communities to adapt to environmental change ensuring their persistence.
In this dissertation, after a general introduction to predator-prey interactions and tradeoffs, I first focus on trade-offs in the prey between qualitatively different types of defence (e.g. camouflage or escape behaviour) and their costs. I show that these different types lead to different patterns of predator-mediated coexistence and population dynamics, by using a simple predator-prey model. In a second step, I elaborate quantitative aspects of trade-offs and demonstrates that the shape of the trade-off curve in combination with trait-fitness relationships strongly affects competition among different prey types: Either specialized species with extreme trait combinations (undefended or completely defended) coexist, or a species with an intermediate defence level dominates. The developed theory on trade-off shapes and coexistence is kept general, allowing for applications apart from defence-competitiveness trade-offs. Thirdly, I tested the theory on trade-off shapes on a long-term field data set of phytoplankton from Lake Constance. The measured concave trade-off between defence and growth governs seasonal trait changes of phytoplankton in response to an altering grazing pressure by zooplankton, and affects the maintenance of trait variation in the community. In a fourth step, I analyse the interplay of different tradeoffs at multiple trophic levels with plankton data of Lake Constance and a corresponding tritrophic food web model. The results show that the trait and biomass dynamics of the different three trophic levels are interrelated in a trophic biomass-trait cascade, leading to unintuitive patterns of trait changes that are reversed in comparison to predictions from bitrophic systems. Finally, in the general discussion, I extract main ideas on trade-offs in multitrophic systems, develop a graphical theory on trade-off-based coexistence, discuss the interplay of intra- and interspecific trade-offs, and end with a management-oriented view on the results of the dissertation, describing how food webs may respond to future global changes, given their trade-offs.
The Himalayas are a region that is most dependent, but also frequently prone to hazards from changing meltwater resources. This mountain belt hosts the highest mountain peaks on earth, has the largest reserve of ice outside the polar regions, and is home to a rapidly growing population in recent decades. One source of hazard has attracted scientific research in particular in the past two decades: glacial lake outburst floods (GLOFs) occurred rarely, but mostly with fatal and catastrophic consequences for downstream communities and infrastructure. Such GLOFs can suddenly release several million cubic meters of water from naturally impounded meltwater lakes. Glacial lakes have grown in number and size by ongoing glacial mass losses in the Himalayas. Theory holds that enhanced meltwater production may increase GLOF frequency, but has never been tested so far. The key challenge to test this notion are the high altitudes of >4000 m, at which lakes occur, making field work impractical. Moreover, flood waves can attenuate rapidly in mountain channels downstream, so that many GLOFs have likely gone unnoticed in past decades. Our knowledge on GLOFs is hence likely biased towards larger, destructive cases, which challenges a detailed quantification of their frequency and their response to atmospheric warming. Robustly quantifying the magnitude and frequency of GLOFs is essential for risk assessment and management along mountain rivers, not least to implement their return periods in building design codes.
Motivated by this limited knowledge of GLOF frequency and hazard, I developed an algorithm that efficiently detects GLOFs from satellite images. In essence, this algorithm classifies land cover in 30 years (~1988–2017) of continuously recorded Landsat images over the Himalayas, and calculates likelihoods for rapidly shrinking water bodies in the stack of land cover images. I visually assessed such detected tell-tale sites for sediment fans in the river channel downstream, a second key diagnostic of GLOFs. Rigorous tests and validation with known cases from roughly 10% of the Himalayas suggested that this algorithm is robust against frequent image noise, and hence capable to identify previously unknown GLOFs. Extending the search radius to the entire Himalayan mountain range revealed some 22 newly detected GLOFs. I thus more than doubled the existing GLOF count from 16 previously known cases since 1988, and found a dominant cluster of GLOFs in the Central and Eastern Himalayas (Bhutan and Eastern Nepal), compared to the rarer affected ranges in the North. Yet, the total of 38 GLOFs showed no change in the annual frequency, so that the activity of GLOFs per unit glacial lake area has decreased in the past 30 years. I discussed possible drivers for this finding, but left a further attribution to distinct GLOF-triggering mechanisms open to future research.
This updated GLOF frequency was the key input for assessing GLOF hazard for the entire Himalayan mountain belt and several subregions. I used standard definitions in flood hydrology, describing hazard as the annual exceedance probability of a given flood peak discharge [m3 s-1] or larger at the breach location. I coupled the empirical frequency of GLOFs per region to simulations of physically plausible peak discharges from all existing ~5,000 lakes in the Himalayas. Using an extreme-value model, I could hence calculate flood return periods. I found that the contemporary 100-year GLOF discharge (the flood level that is reached or exceeded on average once in 100 years) is 20,600+2,200/–2,300 m3 s-1 for the entire Himalayas. Given the spatial and temporal distribution of historic GLOFs, contemporary GLOF hazard is highest in the Eastern Himalayas, and lower for regions with rarer GLOF abundance. I also calculated GLOF hazard for some 9,500 overdeepenings, which could expose and fill with water, if all Himalayan glaciers have melted eventually. Assuming that the current GLOF rate remains unchanged, the 100-year GLOF discharge could double (41,700+5,500/–4,700 m3 s-1), while the regional GLOF hazard may increase largest in the Karakoram.
To conclude, these three stages–from GLOF detection, to analysing their frequency and estimating regional GLOF hazard–provide a framework for modern GLOF hazard assessment. Given the rapidly growing population, infrastructure, and hydropower projects in the Himalayas, this thesis assists in quantifying the purely climate-driven contribution to hazard and risk from GLOFs.
Interactions and feedbacks between tectonics, climate, and upper plate architecture control basin geometry, relief, and depositional systems. The Andes is part of a longlived continental margin characterized by multiple tectonic cycles which have strongly modified the Andean upper plate architecture. In the Andean retroarc, spatiotemporal variations in the structure of the upper plate and tectonic regimes have resulted in marked along-strike variations in basin geometry, stratigraphy, deformational style, and mountain belt morphology. These along-strike variations include high-elevation plateaus (Altiplano and Puna) associated with a thin-skin fold-and-thrust-belt and thick-skin deformation in broken foreland basins such as the Santa Barbara system and the Sierras Pampeanas. At the confluence of the Puna Plateau, the Santa Barbara system and the Sierras Pampeanas, major along-strike changes in upper plate architecture, mountain belt morphology, basement exhumation, and deformation style can be recognized. I have used a source to sink approach to unravel the spatiotemporal tectonic evolution of the Andean retroarc between 26 and 28°S. I obtained a large low-temperature thermochronology data set from basement units which includes apatite fission track, apatite U-Th-Sm/He, and zircon U-Th/He (ZHe) cooling ages. Stratigraphic descriptions of Miocene units were temporally constrained by U-Pb LA-ICP-MS zircon ages from interbedded pyroclastic material.
Modeled ZHe ages suggest that the basement of the study area was exhumed during the Famatinian orogeny (550-450 Ma), followed by a period of relative tectonic quiescence during the Paleozoic and the Triassic. The basement experienced horst exhumation during the Cretaceous development of the Salta rift. After initial exhumation, deposition of thick Cretaceous syn-rift strata caused reheating of several basement blocks within the Santa Barbara system. During the Eocene-Oligocene, the Andean compressional setting was responsible for the exhumation of several disconnected basement blocks. These exhumed blocks were separated by areas of low relief, in which humid climate and low erosion rates facilitated the development of etchplains on the crystalline basement. The exhumed basement blocks formed an Eocene to Oligocene broken foreland basin in the back-bulge depozone of the Andean foreland. During the Early Miocene, foreland basin strata filled up the preexisting Paleogene topography. The basement blocks in lower relief positions were reheated; associated geothermal gradients were higher than 25°C/km. Miocene volcanism was responsible for lateral variations on the amount of reheating along the Campo-Arenal basin. Around 12 Ma, a new deformational phase modified the drainage network and fragmented the lacustrine system. As deformation and rock uplift continued, the easily eroded sedimentary cover was efficiently removed and reworked by an ephemeral fluvial system, preventing the development of significant relief. After ~6 Ma, the low erodibility of the basement blocks which began to be exposed caused relief increase, leading to the development of stable fluvial systems. Progressive relief development modified atmospheric circulation, creating a rainfall gradient. After 3 Ma, orographic rainfall and high relief lead to the development of proximal fluvial-gravitational depositional systems in the surrounding basins.
Sinkholes and depressions are typical landforms of karst regions. They pose a considerable natural hazard to infrastructure, agriculture, economy and human life in affected areas worldwide. The physio-chemical processes of sinkholes and depression formation are manifold, ranging from dissolution and material erosion in the subsurface to mechanical subsidence/failure of the overburden. This thesis addresses the mechanisms leading to the development of sinkholes and depressions by using complementary methods: remote sensing, distinct element modelling and near-surface geophysics.
In the first part, detailed information about the (hydro)-geological background, ground structures, morphologies and spatio-temporal development of sinkholes and depressions at a very active karst area at the Dead Sea are derived from satellite image analysis, photogrammetry and geologic field surveys. There, clusters of an increasing number of sinkholes have been developing since the 1980s within large-scale depressions and are distributed over different kinds of surface materials: clayey mud, sandy-gravel alluvium and lacustrine evaporites (salt). The morphology of sinkholes differs depending in which material they form: Sinkholes in sandy-gravel alluvium and salt are generally deeper and narrower than sinkholes in the interbedded evaporite and mud deposits. From repeated aerial surveys, collapse precursory features like small-scale subsidence, individual holes and cracks are identified in all materials. The analysis sheds light on the ongoing hazardous subsidence process, which is driven by the base-level fall of the Dead Sea and by the dynamic formation of subsurface water channels.
In the second part of this thesis, a novel, 2D distinct element geomechanical modelling approach with the software PFC2D-V5 to simulating individual and multiple cavity growth and sinkhole and large-scale depression development is presented. The approach involves a stepwise material removal technique in void spaces of arbitrarily shaped geometries and is benchmarked by analytical and boundary element method solutions for circular cavities. Simulated compression and tension tests are used to calibrate model parameters with bulk rock properties for the materials of the field site. The simulations show that cavity and sinkhole evolution is controlled by material strength of both overburden and cavity host material, the depth and relative speed of the cavity growth and the developed stress pattern in the subsurface. Major findings are: (1) A progressively deepening differential subrosion with variable growth speed yields a more fragmented stress pattern with stress interaction between the cavities. It favours multiple sinkhole collapses and nesting within large-scale depressions. (2) Low-strength materials do not support large cavities in the material removal zone, and subsidence is mainly characterised by gradual sagging into the material removal zone with synclinal bending. (3) High-strength materials support large cavity formation, leading to sinkhole formation by sudden collapse of the overburden. (4) Large-scale depression formation happens either by coalescence of collapsing holes, block-wise brittle failure, or gradual sagging and lateral widening.
The distinct element based approach is compared to results from remote sensing and geophysics at the field site. The numerical simulation outcomes are generally in good agreement with derived morphometrics, documented surface and subsurface structures as well as seismic velocities. Complementary findings on the subrosion process are provided from electric and seismic measurements in the area.
Based on the novel combination of methods in this thesis, a generic model of karst landform evolution with focus on sinkhole and depression formation is developed. A deepening subrosion system related to preferential flow paths evolves and creates void spaces and subsurface conduits. This subsequently leads to hazardous subsidence, and the formation of sinkholes within large-scale depressions. Finally, a monitoring system for shallow natural hazard phenomena consisting of geodetic and geophysical observations is proposed for similarly affected areas.
Plasmonic metal nanostructures can be tuned to efficiently interact with light, converting the photons into energetic charge carriers and heat. Therefore, the plasmonic nanoparticles such as gold and silver nanoparticles act as nano-reactors, where the molecules attached to their surfaces benefit from the enhanced electromagnetic field along with the generated energetic charge carriers and heat for possible chemical transformations. Hence, plasmonic chemistry presents metal nanoparticles as a unique playground for chemical reactions on the nanoscale remotely controlled by light. However, defining the elementary concepts behind these reactions represents the main challenge for understanding their mechanism in the context of the plasmonically assisted chemistry.
Surface-enhanced Raman scattering (SERS) is a powerful technique employing the plasmon-enhanced electromagnetic field, which can be used for probing the vibrational modes of molecules adsorbed on plasmonic nanoparticles. In this cumulative dissertation, I use SERS to probe the dimerization reaction of 4-nitrothiophenol (4-NTP) as a model example of plasmonic chemistry. I first demonstrate that plasmonic nanostructures such as gold nanotriangles and nanoflowers have a high SERS efficiency, as evidenced by probing the vibrations of the rhodamine dye R6G and the 4-nitrothiophenol 4-NTP. The high signal enhancement enabled the measurements of SERS spectra with a short acquisition time, which allows monitoring the kinetics of chemical reactions in real time.
To get insight into the reaction mechanism, several time-dependent SERS measurements of the 4-NTP have been performed under different laser and temperature conditions. Analysis of the results within a mechanistic framework has shown that the plasmonic heating significantly enhances the reaction rate, while the reaction is probably initiated by the energetic electrons. The reaction was shown to be intensity-dependent, where a certain light intensity is required to drive the reaction. Finally, first attempts to scale up the plasmonic catalysis have been performed showing the necessity to achieve the reaction threshold intensity. Meanwhile, the induced heat needs to quickly dissipate from the reaction substrate, since otherwise the reactants and the reaction platform melt. This study might open the way for further work seeking the possibilities to quickly dissipate the plasmonic heat generated during the reaction and therefore, scaling up the plasmonic catalysis.
This dissertation is concerned with the relation between qualitative phonological organization in the form of syllabic structure and continuous phonetics, that is, the spatial and temporal dimensions of vocal tract action that express syllabic structure. The main claim of the dissertation is twofold. First, we argue that syllabic organization exerts multiple effects on the spatio-temporal properties of the segments that partake in that organization. That is, there is no unique or privileged exponent of syllabic organization. Rather, syllabic organization is expressed in a pleiotropy of phonetic indices. Second, we claim that a better understanding of the relation between qualitative phonological organization and continuous phonetics is reached when one considers how the string of segments (over which the nature of the phonological organization is assessed) responds to perturbations (scaling of phonetic variables) of localized properties (such as durations) within that string. Specifically, variation in phonetic variables and more specifically prosodic variation is a crucial key to understanding the nature of the link between (phonological) syllabic organization and the phonetic spatio-temporal manifestation of that organization. The effects of prosodic variation on segmental properties and on the overlap between the segments, we argue, offer the right pathway to discover patterns related to syllabic organization. In our approach, to uncover evidence for global organization, the sequence of segments partaking in that organization as well as properties of these segments or their relations with one another must be somehow locally varied. The consequences of such variation on the rest of the sequence can then be used to unveil the span of organization. When local perturbations to segments or relations between adjacent segments have effects that ripple through the rest of the sequence, this is evidence that organization is global. If instead local perturbations stay local with no consequences for the rest of the whole, this indicates that organization is local.
Due to its bioavailability and (bio)degradability, poly(lactide) (PLA) is an interesting polymer that is already being used as packaging material, surgical seam, and drug delivery system. Dependent on various parameters such as polymer composition, amphiphilicity, sample preparation, and the enantiomeric purity of lactide, PLA in an amphiphilic block copolymer can affect the self-assembly behavior dramatically. However, sizes and shapes of aggregates have a critical effect on the interactions between biological and drug delivery systems, where the general understanding of these polymers and their ability to influence self-assembly is of significant interest in science.
The first part of this thesis describes the synthesis and study of a series of linear poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA)-based amphiphilic block copolymers with varying PLA (hydrophobic), and poly(ethylene glycol) (PEG) (hydrophilic) chain lengths and different block copolymer sequences (PEG-PLA and PLA-PEG). The PEG-PLA block copolymers were synthesized by ring-opening polymerization of lactide initiated by a PEG-OH macroinitiator. In contrast, the PLA-PEG block copolymers were produced by a Steglich-esterification of modified PLA with PEG-OH.
The aqueous self-assembly at room temperature of the enantiomerically pure PLLA-based block copolymers and their stereocomplexed mixtures was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Spherical micelles and worm-like structures were produced, whereby the obtained self-assembled morphologies were affected by the lactide weight fraction in the block copolymer and self-assembly time. The formation of worm-like structures increases with decreasing PLA-chain length and arises from spherical micelles, which become colloidally unstable and undergo an epitaxial fusion with other micelles. As shown by DSC experiments, the crystallinity of the corresponding PLA blocks increases within the self-assembly time. However, the stereocomplexed self-assembled structures behave differently from the parent polymers and result in irregular-shaped clusters of spherical micelles. Additionally, time-dependent self-assembly experiments showed a transformation, from already self-assembled morphologies of different shapes to more compact micelles upon stereocomplexation.
In the second part of this thesis, with the objective to influence the self-assembly of PLA-based block copolymers and its stereocomplexes, poly(methyl phosphonate) (PMeP) and poly(isopropyl phosphonate) (PiPrP) were produced by ring-opening polymerization to implement an alternative to the hydrophilic block PEG. Although, the 1,8 diazabicyclo[5.4.0]unde 7 ene (DBU) or 1,5,7 triazabicyclo[4.4.0]dec-5-ene (TBD) mediated synthesis of the corresponding poly(alkyl phosphonate)s was successful, however, not so the polymerization of copolymers with PLA-based precursors (PLA-homo polymers, and PEG-PLA block copolymers). Transesterification, obtained by 1H-NMR spectroscopy, between the poly(phosphonate)- and PLA block caused a high-field shifted peak split of the methine proton in the PLA polymer chain, with split intensities depending on the used catalyst (DBU for PMeP, and TBD for PiPrP polymerization). An additional prepared block copolymer PiPrP-PLLA that wasn’t affected in its polymer sequence was finally used for self-assembly experiments with PLA-PEG and PEG-PLA mixing.
This work provides a comprehensive study of the self-assembly behavior of PLA-based block copolymers influenced by various parameters such as polymer block lengths, self-assembly time, and stereocomplexation of block copolymer mixtures.
Back pain is a problem in adolescent athletes affecting postural control which is an important requirement for physical and daily activities whether under static or dynamic conditions. One leg stance and star excursion balance postural control tests are effective in measuring static and dynamic postural control respectively. These tests have been used in individuals with back pain, athletes and non-athletes without first establishing their reliabilities. In addition to this, there is no published literature investigating dynamic posture in adolescent athletes with back pain using the star excursion balance test. Therefore, the aim of the thesis was to assess deficit in postural control in adolescent athletes with and without back pain using static (one leg stance test) and dynamic postural (SEBT) control tests.
Adolescent athletes with and without back pain participated in the study. Static and dynamic postural control tests were performed using one leg stance and SEBT respectively. The reproducibility of both tests was established. Afterwards, it was determined whether there was an association between static and dynamic posture using the measure of displacement of the centre pressure and reach distance respectively. Finally, it was investigated whether there was a difference in postural control in adolescent athletes with and without back pain using the one leg stance test and the SEBT.
Fair to excellent reliabilities was recorded for the static (one leg stance) and dynamic (star excursion balance) postural control tests in the subjects of interest. No association was found between variables of the static and dynamic tests for the adolescent athletes with and without back pain. Also, no statistically significant difference was obtained between adolescent athletics with and without back pain using the static and dynamic postural control test.
One leg stance test and SEBT can be used as measures of postural control in adolescent athletes with and without back pain. Although static and dynamic postural control might be related, adolescent athletes with and without back pain might be using different mechanisms in controlling their static and dynamic posture. Consequently, static and dynamic postural control in adolescent athletes with back pain was not different from those without back pain. These outcome measures might not be challenging enough to detect deficit in postural control in our study group of interest.
The current thesis examined how second language (L2) speakers of German predict upcoming input during language processing. Early research has shown that the predictive abilities of L2 speakers relative to L1 speakers are limited, resulting in the proposal of the Reduced Ability to Generate Expectations (RAGE) hypothesis. Considering that prediction is assumed to facilitate language processing in L1 speakers and probably plays a role in language learning, the assumption that L1/L2 differences can be explained in terms of different processing mechanisms is a particularly interesting approach. However, results from more recent studies on the predictive processing abilities of L2 speakers have indicated that the claim of the RAGE hypothesis is too broad and that prediction in L2 speakers could be selectively limited. In the current thesis, the RAGE hypothesis was systematically put to the test.
In this thesis, German L1 and highly proficient late L2 learners of German with Russian as L1 were tested on their predictive use of one or more information sources that exist as cues to sentence interpretation in both languages, to test for selective limits. The results showed that, in line with previous findings, L2 speakers can use the lexical-semantics of verbs to predict the upcoming noun. Here the level of prediction was more systematically controlled for than in previous studies by using verbs that restrict the selection of upcoming nouns to the semantic category animate or inanimate. Hence, prediction in L2 processing is possible. At the same time, this experiment showed that the L2 group was slower/less certain than the L1 group. Unlike previous studies, the experiment on case marking demonstrated that L2 speakers can use this morphosyntactic cue for prediction. Here, the use of case marking was tested by manipulating the word order (Dat > Acc vs. Acc > Dat) in double object constructions after a ditransitive verb. Both the L1 and the L2 group showed a difference between the two word order conditions that emerged within the critical time window for an anticipatory effect, indicating their sensitivity towards case. However, the results for the post-critical time window pointed to a higher uncertainty in the L2 group, who needed more time to integrate incoming information and were more affected by the word order variation than the L1 group, indicating that they relied more on surface-level information. A different cue weighting was also found in the experiment testing whether participants predict upcoming reference based on implicit causality information. Here, an additional child L1 group was tested, who had a lower memory capacity than the adult L2 group, as confirmed by a digit span task conducted with both learner groups. Whereas the children were only slightly delayed compared to the adult L1 group and showed the same effect of condition, the L2 speakers showed an over-reliance on surface-level information (first-mention/subjecthood). Hence, the pattern observed resulted more likely from L1/L2 differences than from resource deficits.
The reviewed studies and the experiments conducted show that L2 prediction is affected by a range of factors. While some of the factors can be attributed to more individual differences (e.g., language similarity, slower processing) and can be interpreted by L2 processing accounts assuming that L1 and L2 processing are basically the same, certain limits are better explained by accounts that assume more substantial L1/L2 differences. Crucially, the experimental results demonstrate that the RAGE hypothesis should be refined: Although prediction as a fast-operating mechanism is likely to be affected in L2 speakers, there is no indication that prediction is the dominant source of L1/L2 differences. The results rather demonstrate that L2 speakers show a different weighting of cues and rely more on semantic and surface-level information to predict as well as to integrate incoming information.
A central insight from psychological studies on human eye movements is that eye movement patterns are highly individually characteristic. They can, therefore, be used as a biometric feature, that is, subjects can be identified based on their eye movements. This thesis introduces new machine learning methods to identify subjects based on their eye movements while viewing arbitrary content. The thesis focuses on probabilistic modeling of the problem, which has yielded the best results in the most recent literature. The thesis studies the problem in three phases by proposing a purely probabilistic, probabilistic deep learning, and probabilistic deep metric learning approach. In the first phase, the thesis studies models that rely on psychological concepts about eye movements. Recent literature illustrates that individual-specific distributions of gaze patterns can be used to accurately identify individuals. In these studies, models were based on a simple parametric family of distributions. Such simple parametric models can be robustly estimated from sparse data, but have limited flexibility to capture the differences between individuals. Therefore, this thesis proposes a semiparametric model of gaze patterns that is flexible yet robust for individual identification. These patterns can be understood as domain knowledge derived from psychological literature. Fixations and saccades are examples of simple gaze patterns. The proposed semiparametric densities are drawn under a Gaussian process prior centered at a simple parametric distribution. Thus, the model will stay close to the parametric class of densities if little data is available, but it can also deviate from this class if enough data is available, increasing the flexibility of the model. The proposed method is evaluated on a large-scale dataset, showing significant improvements over the state-of-the-art. Later, the thesis replaces the model based on gaze patterns derived from psychological concepts with a deep neural network that can learn more informative and complex patterns from raw eye movement data. As previous work has shown that the distribution of these patterns across a sequence is informative, a novel statistical aggregation layer called the quantile layer is introduced. It explicitly fits the distribution of deep patterns learned directly from the raw eye movement data. The proposed deep learning approach is end-to-end learnable, such that the deep model learns to extract informative, short local patterns while the quantile layer learns to approximate the distributions of these patterns. Quantile layers are a generic approach that can converge to standard pooling layers or have a more detailed description of the features being pooled, depending on the problem. The proposed model is evaluated in a large-scale study using the eye movements of subjects viewing arbitrary visual input. The model improves upon the standard pooling layers and other statistical aggregation layers proposed in the literature. It also improves upon the state-of-the-art eye movement biometrics by a wide margin. Finally, for the model to identify any subject — not just the set of subjects it is trained on — a metric learning approach is developed. Metric learning learns a distance function over instances. The metric learning model maps the instances into a metric space, where sequences of the same individual are close, and sequences of different individuals are further apart. This thesis introduces a deep metric learning approach with distributional embeddings. The approach represents sequences as a set of continuous distributions in a metric space; to achieve this, a new loss function based on Wasserstein distances is introduced. The proposed method is evaluated on multiple domains besides eye movement biometrics. This approach outperforms the state of the art in deep metric learning in several domains while also outperforming the state of the art in eye movement biometrics.
Organic semiconductors are a promising class of materials. Their special properties are the particularly good absorption, low weight and easy processing into thin films. Therefore, intense research has been devoted to the realization of thin film organic solar cells (OPVs). Because of the low dielectric constant of organic semiconductors, primary excitations (excitons) are strongly bound and a type II heterojunction needs to be introduced to split these excitations into free charges. Therefore, most organic solar cells consist of at least an electron donor and electron acceptor material. For such donor acceptor systems mainly three states are relevant; the photoexcited exciton on the donor or acceptor material, the charge transfer state at the donor-acceptor interface and the charge separated state of a free electron and hole. The interplay between these states significantly determines the efficiency of organic solar cells. Due to the high absorption and the low charge carrier mobilities, the active layers are usually thin but also, exciton dissociation and free charge formation proceeds rapidely, which makes the study of carrier dynamics highly challenging.
Therefore, the focus of this work was first to install new experimental setups for the investigation of the charge carrier dynamics in complete devices with superior sensitivity and time resolution and, second, to apply these methods to prototypical photovoltaic materials to address specific questions in the field of organic and hybrid photovoltaics.
Regarding the first goal, a new setup combining transient absorption spectroscopy (TAS) and time delayed collection field (TDCF) was designed and installed in Potsdam. An important part of this work concerned the improvement of the electronic components with respect to time resolution and sensitivity. To this end, a highly sensitive amplifier for driving and detecting the device response in TDCF was developed. This system was then applied to selected organic and hybrid model systems with a particular focus on the understanding of the loss mechanisms that limit the fill factor and short circuit current of organic solar cells.
The first model system was a hybrid photovoltaic material comprising inorganic quantum dots decorated with organic ligands. Measurements with TDCF revealed fast free carrier recombination, in part assisted by traps, while bias-assisted charge extraction measurements showed high mobility. The measured parameters then served as input for a successful description of the device performance with an analytical model.
With a further improvement of the instrumentation, a second topic was the detailed analysis of non-geminate recombination in a disordered polymer:fullerene blend where an important question was the effect of disorder on the carrier dynamics. The measurements revealed that early time highly mobile charges undergo fast non-geminate recombination at the contacts, causing an apparent field dependence of free charge generation in TDCF experiments if not conducted properly. On the other hand, recombination the later time scale was determined by dispersive recombination in the bulk of the active layer, showing the characteristics of carrier dynamics in an exponential density of state distribution. Importantly, the comparison with steady state recombination data suggested a very weak impact of non-thermalized carriers on the recombination properties of the solar cells under application relevant illumination conditions.
Finally, temperature and field dependent studies of free charge generation were performed on three donor-acceptor combinations, with two donor polymers of the same material family blended with two different fullerene acceptor molecules. These particular material combinations were chosen to analyze the influence of the energetic and morphology of the blend on the efficiency of charge generation. To this end, activation energies for photocurrent generation were accurately determined for a wide range of excitation energies. The results prove that the formation of free charge is via thermalized charge transfer states and does not involve hot exciton splitting. Surprisingly, activation energies were of the order of thermal energy at room temperature. This led to the important conclusion that organic solar cells perform well not because of predominate high energy pathways but because the thermalized CT states are weakly bound. In addition, a model is introduced to interconnect the dissociation efficiency of the charge transfer state with its recombination observable with photoluminescence, which rules out a previously proposed two-pool model for free charge formation and recombination. Finally, based on the results, proposals for the further development of organic solar cells are formulated.
In light of the debate on the consequences of competitive contracting out of traditionally public services, this research compares two mechanisms used to allocate funds in development cooperation—direct awarding and competitive contracting out—aiming to identify their potential advantages and disadvantages.
The agency theory is applied within the framework of rational-choice institutionalism to study the institutional arrangements that surround two different money allocation mechanisms, identify the incentives they create for the behavior of individual actors in the field, and examine how these then transfer into measurable differences in managerial quality of development aid projects. In this work, project management quality is seen as an important determinant of the overall project success.
For data-gathering purposes, the German development agency, the Gesellschaft für Internationale Zusammenarbeit (GIZ), is used due to its unique way of work. Whereas the majority of projects receive funds via direct-award mechanism, there is a commercial department, GIZ International Services (GIZ IS) that has to compete for project funds.
The data concerning project management practices on the GIZ and GIZ IS projects was gathered via a web-based, self-administered survey of project team leaders. Principal component analysis was applied to reduce the dimensionality of the independent variable to total of five components of project management. Furthermore, multiple regression analysis identified the differences between the separate components on these two project types. Enriched by qualitative data gathered via interviews, this thesis offers insights into everyday managerial practices in development cooperation and identifies the advantages and disadvantages of the two allocation mechanisms.
The thesis first reiterates the responsibility of donors and implementers for overall aid effectiveness. It shows that the mechanism of competitive contracting out leads to better oversight and control of implementers, fosters deeper cooperation between the implementers and beneficiaries, and has a potential to strengthen ownership of recipient countries. On the other hand, it shows that the evaluation quality does not tremendously benefit from the competitive allocation mechanism and that the quality of the component knowledge management and learning is better when direct-award mechanisms are used. This raises questions about the lacking possibilities of actors in the field to learn about past mistakes and incorporate the finings into the future interventions, which is one of the fundamental issues of aid effectiveness. Finally, the findings show immense deficiencies in regard to oversight and control of individual projects in German development cooperation.
Cette thèse d’urbanisme s’est donnée pour objectif de réfléchir à l’avenir des gares métropolitaines françaises et allemandes à horizon 2050. Elle porte une interrogation sur les fondements de la gare comme objet urbain conceptuel (abordé comme un système) et pose comme hypothèse qu’il serait en quelque sorte doté de propriétés autonomes. Parmi ces propriétés, c’est le processus d’expansion et de dialogue sans cesse renouvelé et conflictuel, entre la gare et son tissu urbain environnant, qui guide cette recherche ; notamment dans le rapport qu’il entretient avec l’hypermobilité des métropoles. Pour ce faire, cette thèse convoque quatre terrains d’études : les gares principales de Cologne et de Stuttgart en Allemagne et les gares de Paris-Montparnasse et Lyon-Part-Dieu en France ; et commence par un historique détaillé de leurs évolutions morphologiques, pour dégager une série de variables architectoniques et urbaines. Il procède dans un deuxième temps à une série d’analyse prospective, permettant de juger de l’influence possible des politiques publiques en matière transports et de mobilité, sur l’avenir conceptuel des gares. Cette thèse propose alors le concept de système-gare, pour décrire l’expansion et l’intégration des gares métropolitaines avec leur environnement urbain ; un processus de négociation dialectique qui ne trouve pas sa résolution dans le concept de gare comme lieu de vie/ville. Elle invite alors à penser la gare comme une hétérotopie, et propose une lecture dépolarisée et déhiérarchisée de ces espaces, en introduisant les concepts d’orchestre de gares et de métagare. Cette recherche propose enfin une lecture critique de la « ville numérique » et du concept de « mobilité comme service. » Pour éviter une mise en flux tendus potentiellement dommageables, l’application de ces concepts en gare ne pourra se soustraire à une augmentation simultanée des espaces physiques.
Frailty and sarcopenia share some underlying characteristics like loss of muscle mass, low muscle strength, and low physical performance. Imaging parameters and functional examinations mainly assess frailty and sarcopenia criteria; however, these measures can have limitations in clinical settings. Therefore, finding suitable biomarkers that reflect a catabolic muscle state e.g. an elevated muscle protein turnover as suggested in frailty, are becoming more relevant concerning frailty diagnosis and risk assessment.
3-Methylhistidine (3-MH) and its ratios 3-MH-to-creatinine (3-MH/Crea) and 3 MH-to-estimated glomerular filtration rate (3-MH/eGFR) are under discussion as possible biomarkers for muscle protein turnover and might support the diagnosis of frailty. However, there is some skepticism about the reliability of 3-MH measures since confounders such as meat and fish intake might influence 3-MH plasma concentrations. Therefore, the influence of dietary habits and an intervention with white meat on plasma 3-MH was determined in young and healthy individuals. In another study, the cross-sectional associations of plasma 3-MH, 3-MH/Crea and 3-MH/eGFR with the frailty status (robust, pre-frail and frail) were investigated.
Oxidative stress (OS) is a possible contributor to frailty development, and high OS levels as well as low micronutrient levels are associated with the frailty syndrome. However, data on simultaneous measures of OS biomarkers together with micronutrients are lacking in studies including frail, pre-frail and robust individuals. Therefore, cross-sectional associations of protein carbonyls (PrCarb), 3-nitrotyrosine (3-NT) and several micronutrients with the frailty status were determined.
A validated UPLC-MS/MS (ultra-performance liquid chromatography tandem mass spectrometry) method for the simultaneous quantification of 3-MH and 1-MH (1 methylhistidine, as marker for meat and fish consumption) was presented and used for further analyses. Omnivores showed higher plasma 3-MH and 1-MH concentrations than vegetarians and a white meat intervention resulted in an increase in plasma 3-MH, 3 MH/Crea, 1-MH and 1-MH/Crea in omnivores. Elevated 3-MH and 3-MH/Crea levels declined significantly within 24 hours after this white meat intervention. Thus, 3-MH and 3-MH/Crea might be used as biomarker for muscle protein turnover when subjects did not consume meat 24 hours prior to blood samplings.
Plasma 3-MH, 3-MH/Crea and 3-MH/eGFR were higher in frail individuals than in robust individuals. Additionally, these biomarkers were positively associated with frailty in linear regression models, and higher odds to be frail were found for every increase in 3 MH and 3-MH/eGFR quintile in multivariable logistic regression models adjusted for several confounders. This was the first study using 3-MH/eGFR and it is concluded that plasma 3-MH, 3-MH/Crea and 3-MH/eGFR might be used to identify frail individuals or individuals at higher risk to be frail, and that there might be threshold concentrations or ratios to support these diagnoses.
Higher vitamin D3, lutein/zeaxanthin, γ-tocopherol, α-carotene, β-carotene, lycopene and β-cryptoxanthin concentrations and additionally lower PrCarb concentrations were found in robust compared to frail individuals in multivariate linear models. Frail subjects had higher odds to be in the lowest than in the highest tertile for vitamin D3 α-tocopherol, α-carotene, β-carotene, lycopene, lutein/zeaxanthin, and β cryptoxanthin, and had higher odds to be in the highest than in the lowest tertile for PrCarb than robust individuals in multivariate logistic regression models. Thus, a low micronutrient together with a high PrCarb status is associated with pre-frailty and frailty.
Restful choreographies
(2019)
Business process management has become a key instrument to organize work as many companies represent their operations in business process models. Recently, business process choreography diagrams have been introduced as part of the Business Process Model and Notation standard to represent interactions between business processes, run by different partners. When it comes to the interactions between services on the Web, Representational State Transfer (REST) is one of the primary architectural styles employed by web services today. Ideally, the RESTful interactions between participants should implement the interactions defined at the business choreography level.
The problem, however, is the conceptual gap between the business process choreography diagrams and RESTful interactions. Choreography diagrams, on the one hand, are modeled from business domain experts with the purpose of capturing, communicating and, ideally, driving the business interactions. RESTful interactions, on the other hand, depend on RESTful interfaces that are designed by web engineers with the purpose of facilitating the interaction between participants on the internet. In most cases however, business domain experts are unaware of the technology behind web service interfaces and web engineers tend to overlook the overall business goals of web services. While there is considerable work on using process models during process implementation, there is little work on using choreography models to implement interactions between business processes. This thesis addresses this research gap by raising the following research question: How to close the conceptual gap between business process choreographies and RESTful interactions? This thesis offers several research contributions that jointly answer the research question.
The main research contribution is the design of a language that captures RESTful interactions between participants---RESTful choreography modeling language. Formal completeness properties (with respect to REST) are introduced to validate its instances, called RESTful choreographies. A systematic semi-automatic method for deriving RESTful choreographies from business process choreographies is proposed. The method employs natural language processing techniques to translate business interactions into RESTful interactions. The effectiveness of the approach is shown by developing a prototypical tool that evaluates the derivation method over a large number of choreography models.
In addition, the thesis proposes solutions towards implementing RESTful choreographies. In particular, two RESTful service specifications are introduced for aiding, respectively, the execution of choreographies' exclusive gateways and the guidance of RESTful interactions.
The immense popularity of online communication services in the last decade has not only upended our lives (with news spreading like wildfire on the Web, presidents announcing their decisions on Twitter, and the outcome of political elections being determined on Facebook) but also dramatically increased the amount of data exchanged on these platforms. Therefore, if we wish to understand the needs of modern society better and want to protect it from new threats, we urgently need more robust, higher-quality natural language processing (NLP) applications that can recognize such necessities and menaces automatically, by analyzing uncensored texts. Unfortunately, most NLP programs today have been created for standard language, as we know it from newspapers, or, in the best case, adapted to the specifics of English social media.
This thesis reduces the existing deficit by entering the new frontier of German online communication and addressing one of its most prolific forms—users’ conversations on Twitter. In particular, it explores the ways and means by how people express their opinions on this service, examines current approaches to automatic mining of these feelings, and proposes novel methods, which outperform state-of-the-art techniques. For this purpose, I introduce a new corpus of German tweets that have been manually annotated with sentiments, their targets and holders, as well as lexical polarity items and their contextual modifiers. Using these data, I explore four major areas of sentiment research: (i) generation of sentiment lexicons, (ii) fine-grained opinion mining, (iii) message-level polarity classification, and (iv) discourse-aware sentiment analysis. In the first task, I compare three popular groups of lexicon generation methods: dictionary-, corpus-, and word-embedding–based ones, finding that dictionary-based systems generally yield better polarity lists than the last two groups. Apart from this, I propose a linear projection algorithm, whose results surpass many existing automatically-generated lexicons. Afterwords, in the second task, I examine two common approaches to automatic prediction of sentiment spans, their sources, and targets: conditional random fields (CRFs) and recurrent neural networks, obtaining higher scores with the former model and improving these results even further by redefining the structure of CRF graphs. When dealing with message-level polarity classification, I juxtapose three major sentiment paradigms: lexicon-, machine-learning–, and deep-learning–based systems, and try to unite the first and last of these method groups by introducing a bidirectional neural network with lexicon-based attention. Finally, in order to make the new classifier aware of microblogs' discourse structure, I let it separately analyze the elementary discourse units of each tweet and infer the overall polarity of a message from the scores of its EDUs with the help of two new approaches: latent-marginalized CRFs and Recursive Dirichlet Process.
Simulating the impact of herbicide drift exposure on non-target terrestrial plant communities
(2019)
In Europe, almost half of the terrestrial landscape is used for agriculture. Thus, semi-natural habitats such as field margins are substantial for maintaining diversity in intensively managed farmlands. However, plants located at field margins are threatened by agricultural practices such as the application of pesticides within the fields. Pesticides are chemicals developed to control for undesired species within agricultural fields to enhance yields. The use of pesticides implies, however, effects on non-target organisms within and outside of the agricultural fields. Non-target organisms are organisms not intended to be sprayed or controlled for. For example, plants occurring in field margins are not intended to be sprayed, however, can be impaired due to herbicide drift exposure. The authorization of plant protection products such as herbicides requires risk assessments to ensure that the application of the product has no unacceptable effects on the environment. For non-target terrestrial plants (NTTPs), the risk assessment is based on standardized greenhouse studies on plant individual level. To account for the protection of plant populations and communities under realistic field conditions, i.e. extrapolating from greenhouse studies to field conditions and from individual-level to community-level, assessment factors are applied. However, recent studies question the current risk assessment scheme to meet the specific protection goals for non-target terrestrial plants as suggested by the European Food Safety Authority (EFSA). There is a need to clarify the gaps of the current risk assessment and to include suitable higher tier options in the upcoming guidance document for non-target terrestrial plants.
In my thesis, I studied the impact of herbicide drift exposure on NTTP communities using a mechanistic modelling approach. I addressed main gaps and uncertainties of the current risk assessment and finally suggested this modelling approach as a novel higher tier option in future risk assessments. Specifically, I extended the plant community model IBC-grass (Individual-based community model for grasslands) to reflect herbicide impacts on plant individuals. In the first study, I compared model predictions of short-term herbicide impacts on artificial plant communities with empirical data. I demonstrated the capability of the model to realistically reflect herbicide impacts. In the second study, I addressed the research question whether or not reproductive endpoints need to be included in future risk assessments to protect plant populations and communities. I compared the consequences of theoretical herbicide impacts on different plant attributes for long-term plant population dynamics in the community context. I concluded that reproductive endpoints only need to be considered if the herbicide effect is assumed to be very high. The endpoints measured in the current vegetative vigour and seedling emergence studies had high impacts for the dynamic of plant populations and communities already at lower effect intensities. Finally, the third study analysed long-term impacts of herbicide application for three different plant communities. This study highlighted the suitability of the modelling approach to simulate different communities and thus detecting sensitive environmental conditions.
Overall, my thesis demonstrates the suitability of mechanistic modelling approaches to be used as higher tier options for risk assessments. Specifically, IBC-grass can incorporate available individual-level effect data of standardized greenhouse experiments to extrapolate to community-level under various environmental conditions. Thus, future risk assessments can be improved by detecting sensitive scenarios and including worst-case impacts on non-target plant communities.
Business process management is an established technique for business organizations to manage and support their processes. Those processes are typically represented by graphical models designed with modeling languages, such as the Business Process Model and Notation (BPMN).
Since process models do not only serve the purpose of documentation but are also a basis for implementation and automation of the processes, they have to satisfy certain correctness requirements. In this regard, the notion of soundness of workflow nets was developed, that can be applied to BPMN process models in order to verify their correctness. Because the original soundness criteria are very restrictive regarding the behavior of the model, different variants of the soundness notion have been developed for situations in which certain violations are not even harmful.
All of those notions do only consider the control-flow structure of a process model, however. This poses a problem, taking into account the fact that with the recent release and the ongoing development of the Decision Model and Notation (DMN) standard, an increasing number of process models are complemented by respective decision models. DMN is a dedicated modeling language for decision logic and separates the concerns of process and decision logic into two different models, process and decision models respectively.
Hence, this thesis is concerned with the development of decisionaware soundness notions, i.e., notions of soundness that build upon the original soundness ideas for process models, but additionally take into account complementary decision models. Similar to the various notions of workflow net soundness, this thesis investigates different notions of decision soundness that can be applied depending on the desired degree of restrictiveness. Since decision tables are a standardized means of DMN to represent decision logic, this thesis also puts special focus on decision tables, discussing how they can be translated into an unambiguous format and how their possible output values can be efficiently determined.
Moreover, a prototypical implementation is described that supports checking a basic version of decision soundness. The decision soundness notions were also empirically evaluated on models from participants of an online course on process and decision modeling as well as from a process management project of a large insurance company. The evaluation demonstrates that violations of decision soundness indeed occur and can be detected with our approach.
Binaries play an important role in observational and theoretical astrophysics. Since the mass and the chemical composition are key ingredients for stellar evolution, high-resolution spectroscopy is an important and necessary tool to derive those parameters to high confidence in binaries. This involves carefully measured orbital motion by the determination of radial velocity (RV) shifts and sophisticated techniques to derive the abundances of elements within the stellar atmosphere.
A technique superior to conventional cross-correlation methods to determine RV shifts in known as spectral disentangling. Hence, a major task of this thesis was the design of a sophisticated software package for this approach. In order to investigate secondary effects, such as flux and line-profile variations, imprinting changes on the spectrum the behavior of spectral disentangling on such variability is a key to understand the derived values, to improve them, and to get information about the variability itself. Therefore, the spectral disentangling code presented in this thesis and available to the community combines multiple advantages: separation of the spectra for detailed chemical analysis, derivation of orbital elements, derivation of individual RVs in order to investigate distorted systems (either by third body interaction or relativistic effects), the suppression of telluric contaminations, the derivation of variability, and the possibility to apply the technique to eclipsing binaries (important for orbital inclination) or in general to systems that undergo flux-variations.
This code in combination with the spectral synthesis codes MOOG and SME was used in order to derive the carbon 12C/13C isotope ratio (CIR) of the benchmark binary Capella. The observational result will be set into context with theoretical evolution by the use of MESA models and resolves the discrepancy of theory and observations existing since the first measurement of Capella's CIR in 1976.
The spectral disentangling code has been made available to the community and its applicability to completely different behaving systems, Wolf-Rayet stars, have also been investigated and resulted in a published article.
Additionally, since this technique relies strongly on data quality, continues development of scientific instruments to achieve best observational data is of great importance in observational astrophysics. That is the reason why there has also been effort in astronomical instrumentation during the work on this thesis.
Die Wissenschaftsfreiheit ist ein Grundrecht, dessen Sinn und Auslegung im Rahmen von Reformen des Hochschulsystems nicht nur der Justiz, sondern auch der Wissenschaft selbst immer wieder Anlass zur Diskussion geben, so auch im Zuge der Einführung des so genannten Qualitätsmanagements von Studium und Lehre an deutschen Hochschulen. Die vorliegende Dissertationsschrift stellt die Ergebnisse einer empirischen Studie vor, die mit einer soziologischen Betrachtung des Qualitätsmanagements unterschiedlicher Hochschulen zu dieser Diskussion beiträgt.
Auf Grundlage der Prämisse, dass Verlauf und Folgen einer organisationalen Innovation nur verstanden werden können, wenn der alltägliche Umgang der Organisationsmitglieder mit den neuen Strukturen und Prozessen in die Analyse einbezogen wird, geht die Studie von der Frage aus, wie Akteurinnen und Akteure an deutschen Hochschulen die Qualitätsmanagementsysteme ihrer Organisationen nutzen. Die qualitative inhaltsanalytische Auswertung von 26 Leitfaden-Interviews mit Prorektorinnen und -rektoren, Qualitätsmanagement-Personal und Studiendekaninnen und -dekanen an neun Hochschulen ergibt, dass die Strategien der Akteursgruppen an den Hochschulen im Zusammenspiel mit strukturellen Aspekten unterschiedliche Dynamiken entstehen lassen, mit denen Implikationen für die Lehrfreiheit verbunden sind: Während die Autonomie der Lehrenden durch das Qualitätsmanagement an einigen Hochschulen unterstützt wird, sind sowohl Autonomie als auch Verantwortung für Studium und Lehre an anderen Hochschulen Gegenstand andauernder Konflikte, die auch das Qualitätsmanagement einschließen.
This dissertation investigates the impact of the economic and fiscal crisis starting in 2008 on EU climate policy-making. While the overall number of adopted greenhouse gas emission reduction policies declined in the crisis aftermath, EU lawmakers decided to introduce new or tighten existing regulations in some important policy domains. Existing knowledge about the crisis impact on EU legislative decision-making cannot explain these inconsistencies. In response, this study develops an actor-centred conceptual framework based on rational choice institutionalism that provides a micro-level link to explain how economic crises translate into altered policy-making patterns. The core theoretical argument draws on redistributive conflicts, arguing that tensions between ‘beneficiaries’ and ‘losers’ of a regulatory initiative intensify during economic crises and spill over to the policy domain. To test this hypothesis and using social network analysis, this study analyses policy processes in three case studies: The introduction of carbon dioxide emission limits for passenger cars, the expansion of the EU Emissions Trading System to aviation, and the introduction of a regulatory framework for biofuels. The key finding is that an economic shock causes EU policy domains to polarise politically, resulting in intensified conflict and more difficult decision-making. The results also show that this process of political polarisation roots in the industry that is the subject of the regulation, and that intergovernmental bargaining among member states becomes more important, but also more difficult in times of crisis.
Predator-prey interactions provide central links in food webs. These interaction are directly or indirectly impacted by a number of factors. These factors range from physiological characteristics of individual organisms, over specifics of their interaction to impacts of the environment. They may generate the potential for the application of different strategies by predators and prey. Within this thesis, I modelled predator-prey interactions and investigated a broad range of different factors driving the application of certain strategies, that affect the individuals or their populations. In doing so, I focused on phytoplankton-zooplankton systems as established model systems of predator-prey interactions.
At the level of predator physiology I proposed, and partly confirmed, adaptations to fluctuating availability of co-limiting nutrients as beneficial strategies. These may allow to store ingested nutrients or to regulate the effort put into nutrient assimilation. We found that these two strategies are beneficial at different fluctuation frequencies of the nutrients, but may positively interact at intermediate frequencies. The corresponding experiments supported our model results. We found that the temporal structure of nutrient fluctuations indeed has strong effects on the juvenile somatic growth rate of {\itshape Daphnia}.
Predator colimitation by energy and essential biochemical nutrients gave rise to another physiological strategy. High-quality prey species may render themselves indispensable in a scenario of predator-mediated coexistence by being the only source of essential biochemical nutrients, such as cholesterol. Thereby, the high-quality prey may even compensate for a lacking defense and ensure its persistence in competition with other more defended prey species.
We found a similar effect in a model where algae and bacteria compete for nutrients. Now, being the only source of a compound that is required by the competitor (bacteria) prevented the competitive exclusion of the algae. In this case, the essential compounds were the organic carbon provided by the algae. Here again, being indispensable served as a prey strategy that ensured its coexistence.
The latter scenario also gave rise to the application of the two metabolic strategies of autotrophy and heterotrophy by algae and bacteria, respectively. We found that their coexistence allowed the recycling of resources in a microbial loop that would otherwise be lost. Instead, these resources were made available to higher trophic levels, increasing the trophic transfer efficiency in food webs.
The predation process comprises the next higher level of factors shaping the predator-prey interaction, besides these factors that originated from the functioning or composition of individuals. Here, I focused on defensive mechanisms and investigated multiple scenarios of static or adaptive combinations of prey defense and predator offense. I confirmed and extended earlier reports on the coexistence-promoting effects of partially lower palatability of the prey community. When bacteria and algae are coexisting, a higher palatability of bacteria may increase the average predator biomass, with the side effect of making the population dynamics more regular. This may facilitate experimental investigations and interpretations. If defense and offense are adaptive, this allows organisms to maximize their growth rate. Besides this fitness-enhancing effect, I found that co-adaptation may provide the predator-prey system with the flexibility to buffer external perturbations.
On top of these rather internal factors, environmental drivers also affect predator-prey interactions. I showed that environmental nutrient fluctuations may create a spatio-temporal resource heterogeneity that selects for different predator strategies. I hypothesized that this might favour either storage or acclimation specialists, depending on the frequency of the environmental fluctuations.
We found that many of these factors promote the coexistence of different strategies and may therefore support and sustain biodiversity. Thus, they might be relevant for the maintenance of crucial ecosystem functions that also affect us humans. Besides this, the richness of factors that impact predator-prey interactions might explain why so many species, especially in the planktonic regime, are able to coexist.
Fold and thrust belts are characteristic features of collisional orogen that grow laterally through time by deforming the upper crust in response to stresses caused by convergence. The deformation propagation in the upper crust is accommodated by shortening along major folds and thrusts. The formation of these structures is influenced by the mechanical strength of décollements, basement architecture, presence of preexisting structures and taper of the wedge. These factors control not only the sequence of deformation but also cause differences in the structural style.
The Himalayan fold and thrust belt exhibits significant differences in the structural style from east to west. The external zone of the Himalayan fold and thrust belt, also called the Subhimalaya, has been extensively studied to understand the temporal development and differences in the structural style in Bhutan, Nepal and India; however, the Subhimalaya in Pakistan remains poorly studied. The Kohat and Potwar fold and thrust belts (herein called Kohat and Potwar) represent the Subhimalaya in Pakistan. The Main Boundary Thrust (MBT) marks the northern boundary of both Kohat and Potwar, showing that these belts are genetically linked to foreland-vergent deformation within the Himalayan orogen, despite the pronounced contrast in structural style. This contrast becomes more pronounced toward south, where the active strike-slip Kalabagh Fault Zone links with the Kohat and Potwar range fronts, known as the Surghar Range and the Salt Range, respectively. The Surghar and Salt Ranges developed above the Surghar Thrust (SGT) and Main Frontal Thrust (MFT). In order to understand the structural style and spatiotemporal development of the major structures in Kohat and Potwar, I have used structural modeling and low temperature thermochronolgy methods in this study. The structural modeling is based on construction of balanced cross-sections by integrating surface geology, seismic reflection profiles and well data. In order to constrain the timing and magnitude of exhumation, I used apatite (U-Th-Sm)/He (AHe) and apatite fission track (AFT) dating. The results obtained from both methods are combined to document the Paleozoic to Recent history of Kohat and Potwar.
The results of this research suggest two major events in the deformation history. The first major deformation event is related to Late Paleozoic rifting associated with the development of the Neo-Tethys Ocean. The second major deformation event is related to the Late Miocene to Pliocene development of the Himalayan fold and thrust belt in the Kohat and Potwar. The Late Paleozoic rifting is deciphered by inverse thermal modelling of detrital AFT and AHe ages from the Salt Range. The process of rifting in this area created normal faulting that resulted in the exhumation/erosion of Early to Middle Paleozoic strata, forming a major unconformity between Cambrian and Permian strata that is exposed today in the Salt Range. The normal faults formed in Late Paleozoic time played an important role in localizing the Miocene-Pliocene deformation in this area. The combination of structural reconstructions and thermochronologic data suggest that deformation initiated at 15±2 Ma on the SGT ramp in the southern part of Kohat. The early movement on the SGT accreted the foreland into the Kohat deforming wedge, forming the range front. The development of the MBT at 12±2 Ma formed the northern boundary of Kohat and Potwar. Deformation propagated south of the MBT in the Kohat on double décollements and in the Potwar on a single basal décollement. The double décollement in the Kohat adopted an active roof-thrust deformation style that resulted in the disharmonic structural style in the upper and lower parts of the stratigraphic section. Incremental shortening resulted in the development of duplexes in the subsurface between two décollements and imbrication above the roof thrust. Tectonic thickening caused by duplexes resulted in cooling and exhumation above the roof thrust by removal of a thick sequence of molasse strata. The structural modelling shows that the ramps on which duplexes formed in Kohat continue as tip lines of fault propagation folds in the Potwar. The absence of a double décollement in the Potwar resulted in the preservation of a thick sequence of molasse strata there. The temporal data suggest that deformation propagated in-sequence from ~ 8 to 3 Ma in the northern part of Kohat and Potwar; however, internal deformation in the Kohat was more intense, probably required for maintaining a critical taper after a significant load was removed above the upper décollement. In the southern part of Potwar, a steeper basement slope (β≥3°) and the presence of salt at the base of the stratigraphic section allowed for the complete preservation of the stratigraphic wedge, showcased by very little internal deformation. Activation of the MFT at ~4 Ma allowed the Salt Range to become the range front of the Potwar. The removal of a large amount of molasse strata above the MFT ramp enhanced the role of salt in shaping the structural style of the Salt Range and Kalabagh Fault Zone. Salt accumulation and migration resulted in the formation of normal faults in both areas. Salt migration in the Kalabagh fault zone has triggered out-of-sequence movement on ramps in the Kohat.
The amount of shortening calculated between the MBT and the SGT in Kohat is 75±5 km and between the MBT and the MFT in Potwar is 65±5 km. A comparable amount of shortening is accommodated in the Kohat and Potwar despite their different widths: 70 km Kohat and 150 km Potwar. In summary, this research suggests that deformation switched between different structures during the last ~15 Ma through different modes of fault propagation, resulting in different structural styles and the out-of-sequence development of Kohat and Potwar.
Carbonate-rich silicate and carbonate melts play a crucial role in deep Earth magmatic processes and their melt structure is a key parameter, as it controls physical and chemical properties. Carbonate-rich melts can be strongly enriched in geochemically important trace elements. The structural incorporation mechanisms of these elements are difficult to study because such melts generally cannot be quenched to glasses, which are usually employed for structural investigations. This thesis investigates the influence of CO2 on the local environments of trace elements contained in silicate glasses with variable CO2 concentrations as well as in silicate and carbonate melts. The compositions studied include sodium-rich peralkaline silicate melts and glasses and carbonate melts similar to those occurring naturally at Oldoinyo Lengai volcano, Tanzania.
The local environments of the three elements yttrium (Y), lanthanum (La) and strontium (Sr) were investigated in synthesized glasses and melts using X-ray absorption fine structure (XAFS) spectroscopy. Especially extended X-ray absorption fine structure spectroscopy (EXAFS) provides element specific information on local structure, such as bond lengths, coordination numbers and the degree of disorder. To cope with the enhanced structural disorder present in glasses and melts, EXAFS analysis was based on fitting approaches using an asymmetric distribution function as well as a correlation model according to bond valence theory. Firstly, silicate glasses quenched from high pressure/temperature melts with up to 7.6 wt % CO2 were investigated. In strongly and extremely peralkaline glasses the local structure of Y is unaffected by the CO2 content (with oxygen bond lengths of ~ 2.29 Å). Contrary, the bond lengths for Sr-O and La-O increase with increasing CO2 content in the strongly peralkaline glasses from ~ 2.53 to ~ 2.57 Å and from ~ 2.52 to ~ 2.54 Å, respectively, while they remain constant in extremely peralkaline glasses (at ~ 2.55 Å and 2.54 Å, respectively). Furthermore, silicate and unquenchable carbonate melts were investigated in-situ at high pressure/temperature conditions (2.2 to 2.6 GPa, 1200 to 1500 °C) using a Paris-Edinburgh press. A novel design of the pressure medium assembly for this press was developed, which features increased mechanical stability as well as enhanced transmittance at relevant energies to allow for low content element EXAFS in transmission. Compared to glasses the bond lengths of Y-O, La-O and Sr-O are elongated by up to + 3 % in the melt and exhibit higher asymmetric pair distributions. For all investigated silicate melt compositions Y-O bond lengths were found constant at ~ 2.37 Å, while in the carbonate melt the Y-O length increases slightly to 2.41 Å. The La-O bond lengths in turn, increase systematically over the whole silicate – carbonate melt joint from 2.55 to 2.60 Å. Sr-O bond lengths in melts increase from ~ 2.60 to 2.64 Å from pure silicate to silicate-bearing carbonate composition with constant elevated bond length within the carbonate region.
For comparison and deeper insight, glass and melt structures of Y and Sr bearing sodium-rich silicate to carbonate compositions were simulated in an explorative ab initio molecular dynamics (MD) study. The simulations confirm observed patterns of CO2-dependent local changes around Y and Sr and additionally provide further insights into detailed incorporation mechanisms of the trace elements and CO2. Principle findings include that in sodium-rich silicate compositions carbon either is mainly incorporated as a free carbonate-group or shares one oxygen with a network former (Si or [4]Al) to form a non-bridging carbonate. Of minor importance are bridging carbonates between two network formers. Here, a clear preference for two [4]Al as adjacent network formers occurs, compared to what a statistical distribution would suggest. In C-bearing silicate melts minor amounts of molecular CO2 are present, which is almost totally dissolved as carbonate in the quenched glasses.
The combination of experiment and simulation provides extraordinary insights into glass and melt structures. The new data is interpreted on the basis of bond valence theory and is used to deduce potential mechanisms for structural incorporation of investigated elements, which allow for prediction on their partitioning behavior in natural melts. Furthermore, it provides unique insights into the dissolution mechanisms of CO2 in silicate melts and into the carbonate melt structure. For the latter, a structural model is suggested, which is based on planar CO3-groups linking 7- to 9-fold cation polyhedra, in accordance to structural units as found in the Na-Ca carbonate nyerereite. Ultimately, the outcome of this study contributes to rationalize the unique physical properties and geological phenomena related to carbonated silicate-carbonate melts.
Oscillatory systems under weak coupling can be described by the Kuramoto model of phase oscillators. Kuramoto phase oscillators have diverse applications ranging from phenomena such as communication between neurons and collective influences of political opinions, to engineered systems such as Josephson Junctions and synchronized electric power grids. This thesis includes the author's contribution to the theoretical framework of coupled Kuramoto oscillators and to the understanding of non-trivial N-body dynamical systems via their reduced mean-field dynamics.
The main content of this thesis is composed of four parts. First, a partially integrable theory of globally coupled identical Kuramoto oscillators is extended to include pure higher-mode coupling. The extended theory is then applied to a non-trivial higher-mode coupled model, which has been found to exhibit asymmetric clustering. Using the developed theory, we could predict a number of features of the asymmetric clustering with only information of the initial state provided.
The second part consists of an iterated discrete-map approach to simulate phase dynamics. The proposed map --- a Moebius map --- not only provides fast computation of phase synchronization, it also precisely reflects the underlying group structure of the dynamics. We then compare the iterated-map dynamics and various analogous continuous-time dynamics. We are able to replicate known phenomena such as the synchronization transition of the Kuramoto-Sakaguchi model of oscillators with distributed natural frequencies, and chimera states for identical oscillators under non-local coupling.
The third part entails a particular model of repulsively coupled identical Kuramoto-Sakaguchi oscillators under common random forcing, which can be shown to be partially integrable. Via both numerical simulations and theoretical analysis, we determine that such a model cannot exhibit stationary multi-cluster states, contrary to the numerical findings in previous literature. Through further investigation, we find that the multi-clustering states reported previously occur due to the accumulation of discretization errors inherent in the integration algorithms, which introduce higher-mode couplings into the model. As a result, the partial integrability condition is violated.
Lastly, we derive the microscopic cross-correlation of globally coupled non-identical Kuramoto oscillators under common fluctuating forcing. The effect of correlation arises naturally in finite populations, due to the non-trivial fluctuations of the meanfield. In an idealized model, we approximate the finite-sized fluctuation by a Gaussian white noise. The analytical approximation qualitatively matches the measurements in numerical experiments, however, due to other periodic components inherent in the fluctuations of the mean-field there still exist significant inconsistencies.
Im Rahmen dieser Dissertation konnten neue Kalium- und Natrium-Ionen Fluoreszenzfarbstoffe von der Klasse der Fluoroionophore synthetisiert und charakterisiert werden. Sie bestehen aus einem N Phenylazakronenether als Ionophor und unterschiedlichen Fluorophoren und sind über einen π-konjugierten 1,2,3-Triazol-1,4-diyl Spacer verbunden. Dabei lag der Fokus während ihrer Entwicklung darauf, diese in ihrer Sensitivität, Selektivität und in ihren photophysikalischen Eigenschaften so zu funktionalisieren, dass sie für intra- bzw. extrazelluläre Konzentrationsbestimmungen geeignet sind.
Durch Variation der in ortho Position der N-Phenylazakronenether befindlichen Alkoxy-Gruppen und der fluorophoren Gruppe der Fluoroionophore konnte festgestellt werden, dass die Sensitivität und Selektivität für Kalium- bzw. Natrium-Ionen jeweils durch eine bestimmte Isomerie der 1,2,3-Triazol-1,4-diyl-Einheit erhöht wird. Des Weiteren wurde gezeigt, dass durch eine erhöhte Einschränkung der N,N-Diethylamino-Gruppe des Fluorophors eine Steigerung der Fluoreszenzquantenausbeute und eine Verschiebung des Emissionsmaximums auf über 500 nm erreicht werden konnte. Die Einführung einer Isopropoxy-Gruppe an einem N-Phenylaza-[18]krone-6-ethers resultierte dabei in einem hoch selektiven Kalium-Ionen Fluoroionophor und ermöglichte eine in vitro Überwachung von 10 – 80 mM Kalium-Ionen. Die Substitution einer Methoxy-Gruppe an einem N-Phenylaza-[15]krone-5-ether kombiniert mit unterschiedlich N,N-Diethylamino-Coumarinen lieferte hingegen zwei Natrium-Ionen Fluoroionophore, die für die Überwachung von intra- bzw. extrazellulären Natrium-Ionen Konzentrationen geeignet sind.
In einem weiteren Schritt wurden N-Phenylaza-[18]krone-6-ether mit einem Fluorophor, basierend auf einem [1,3]-Dioxolo[4,5-f][1,3]benzodioxol-(DBD)-Grundgerüst, funktionalisiert. Die im Anschluss durchgeführten spektroskopischen Untersuchungen ergaben, dass die Isopropoxy-Gruppe in ortho Position des N-Phenylaza-[18]krone-6-ether in einen für extrazelluläre Kalium-Ionen Konzentrationen selektiven Fluoroionophor resultierte, der die Konzentrationsbestimmungen über die Fluoreszenzintensität und -lebensdauer ermöglicht.
In einem abschließenden Schritt konnte unter Verwendung eines Pyrens als fluorophore Gruppe ein weiterer für extrazelluläre Kalium-Ionen Konzentrationen geeigneter Fluoroionophor entwickelt werden. Die Bestimmung der Kalium-Ionen Konzentration erfolgte hierbei anhand der Fluoreszenzintensitätsverhältnisse bei zwei Emissionswellenlängen.
Insgesamt konnten 17 verschiedene neue Fluoroionophore für die Bestimmung von Kalium- bzw. Natrium-Ionen synthetisiert und charakterisiert werden. Sechs dieser neuen Moleküle ermöglichen in vitro Messungen der intra- oder extrazellulären Kalium- und Natrium-Ionen Konzentrationen und könnten zukünftig für in vivo Konzentrationsmessungen verwendet werden.
The fabrication of 1D nanostrands composed of stimuli responsive microgels has been shown in this work. Microgels are well known materials able to respond to various stimuli from outer environment. Since these microgels respond via a volume change to an external stimulus, a targeted mechanical response can be achieved. Through carefully choosing the right composition of the polymer matrix, microgels can be designed to react precisely to the targeted stimuli (e.g. drug delivery via pH and temperature changes, or selective contractions through changes in electrical current125).
In this work, it was aimed to create flexible nano-filaments which are capable of fast anisotropic contractions similar to muscle filaments. For the fabrication of such filaments or strands, nanostructured templates (PDMS wrinkles) were chosen due to a facile and low-cost fabrication and versatile tunability of their dimensions. Additionally, wrinkling is a well-known lithography-free method which enables the fabrication of nanostructures in a reproducible manner and with a high long-range periodicity.
In Chapter 2.1, it was shown for the first time that microgels as soft matter particles can be aligned to densely packed microgel arrays of various lateral dimensions. The alignment of microgels with different compositions (e.g. VCL/AAEM, NIPAAm, NIPAAm/VCL and charged microgels) was shown by using different assembly techniques (e.g. spin-coating, template confined molding). It was chosen to set one experimental parameter constant which was the SiOx surface composition of the templates and substrates (e.g. oxidized PDMS wrinkles, Si-wafers and glass slides). It was shown that the fabrication of nanoarrays was feasible with all tested microgel types. Although the microgels exhibited different deformability when aligned on a flat surface, they retained their thermo-responsivity and swelling behavior.
Towards the fabrication of 1D microgel strands interparticle connectivity was aspired. This was achieved via different cross-linking methods (i.e. cross-linking via UV-irradiation and host-guest complexation) discussed in Chapter 2.2. The microgel arrays created by different assembly methods and microgel types were tested for their cross-linking suitability. It was observed that NIPAAm based microgels cannot be cross-linked with UV light. Furthermore, it was found that these microgels exhibit a strong surface-particle-interaction and therefore could not be detached from the given substrates. In contrast to the latter, with VCL/AAEM based microgels it was possible to both UV cross-link them based on the keto-enol tautomerism of the AAEM copolymer, and to detach them from the substrate due to the lower adhesion energy towards SiOx surfaces. With VCL/AAEM microgels long, one-dimensional microgel strands could be re-dispersed in water for further analysis. It has also been shown that at least one lateral dimension of the free dispersed 1D microgel strands is easily controllable by adjusting the wavelength of the wrinkled template. For further work, only VCL/AAEM based microgels were used to focus on the main aim of this work, i.e. the fabrication of 1D microgel nanostrands.
As an alternative to the unspecific and harsh UV cross-linking, the host-guest complexation via diazobenzene cross-linkers and cyclodextrin hosts was explored. The idea behind this approach was to give means to a future construction kit-like approach by incorporation of cyclodextrin comonomers in a broad variety of particle systems (e.g. microgels, nanoparticles). For this purpose, VCL/AAEM microgels were copolymerized with different amounts of mono-acrylate functionalized β-cyclodextrin (CD). After successfully testing the cross-linking capability in solution, the cross-linking of aligned VCL/AAEM/CD microgels was tried. Although the cross-linking worked well, once the single arrays came into contact to each other, they agglomerated. As a reason for this behavior residual amounts of mono-complexed diazobenzene linkers were suspected. Thus, end-capping strategies were tried out (e.g. excess amounts of β-cyclodextrin and coverage with azobenzene functionalized AuNPs) but were unsuccessful. With deeper thought, entropy effects were taken into consideration which favor the release of complexed diazobenzene linker leading to agglomerations. To circumvent this entropy driven effect, a multifunctional polymer with 50% azobenzene groups (Harada polymer) was used. First experiments with this polymer showed promising results regarding a less pronounced agglomeration (Figure 77). Thus, this approach could be pursued in the future. In this chapter it was found out that in contrast to pearl necklace and ribbon like formations, particle alignment in zigzag formation provided the best compromise in terms of stability in dispersion (see Figure 44a and Figure 51) while maintaining sufficient flexibility.
For this reason, microgel strands in zigzag formation were used for the motion analysis described in Chapter 2.3. The aim was to observe the properties of unrestrained microgel strands in solution (e.g. diffusion behavior, rotational properties and ideally, anisotropic contraction after temperature increase). Initially, 1D microgel strands were manipulated via AFM in a liquid cell setup. It could be observed that the strands required a higher load force compared to single microgels to be detached from the surface. However, with the AFM it was not possible to detach the strands in a controllable manner but resulted in a complete removal of single microgel particles and a tearing off the strands from the surface, respectively. For this reason, to observe the motion behavior of unrestrained microgel strands in solution, confocal microscopy was used. Furthermore, to hinder an adsorption of the strands, it was found out that coating the surface of the substrates with a repulsive polymer film was beneficial. Confocal and wide-field microscopy videos showed that the microgel strands exhibit translational and rotational diffusive motion in solution without perceptible bending. Unfortunately, with these methods the detection of the anisotropic stimuli responsive contraction of the free moving microgel strands was not possible. To summarize, the flexibility of microgel strands is more comparable to the mechanical behavior of a semi flexible cable than to a yarn. The strands studied here consist of dozens or even hundreds of discrete submicron units strung together by cross-linking, having few parallels in nanotechnology.
With the insights gained in this work on microgel-surface interactions, in the future, a targeted functionalization of the template and substrate surfaces can be conducted to actively prevent unwanted microgel adsorption for a given microgel system (e.g. PVCL and polystyrene coating235). This measure would make the discussed alignment methods more diverse. As shown herein, the assembly methods enable a versatile microgel alignment (e.g. microgel meshes, double and triple strands). To go further, one could use more complex templates (e.g. ceramic rhombs and star shaped wrinkles (Figure 14) to expand the possibilities of microgel alignment and to precisely control their aspect ratios (e.g. microgel rods with homogeneous size distributions).
The present dissertation about teachers’ cultural diversity beliefs and culturally responsive practices includes a general introduction (Chapter 1), a systematic literature review (Chapter 2), three empirical studies (Chapter 3, 4, and 5) and it ends with a general discussion and conclusion (Chapter 6). The major focus of investigation laid in creating a deeper understanding of teachers’ beliefs about cultural diversity and how those beliefs are related to teaching practices, which could or could not be considered to be culturally responsive. In this dissertation, I relied on insights from theoretical perspectives that derived from the field of psychology such as social cognitive theory and intergroup ideologies, as well as from the field of multicultural education such as culturally responsive teaching.
In Chapter 1, I provide the background of this dissertation, with contextual information regarding the German educational system, the theoretical framework used and the main research objectives of each study.
In Chapter 2, I conducted a systematic review of the existing international studies on trainings addressing cultural diversity beliefs with pre-service teachers. More specifically, the aims of the systematic literature review were (1) to provide a description of main components and contextual characteristics of teacher trainings targeting cultural diversity beliefs, (2) report the training effects, and (3) detail the methodological strengths and weaknesses of these studies. By examining the main components and contextual characteristics of teacher trainings, the effects on beliefs about cultural diversity as well as the methodological strengths and weaknesses of these studies in a single review, I took an integrated approach to these three processes. To review the final pool of studies (N = 36) I used a descriptive and narrative approach, relying primarily on the use of words and text to summarise and explain findings of the synthesis.
The three empirical studies that follow, all highlight aspects of how far and how teacher beliefs about cultural diversity translate into real-world practices in schools. In Chapter 3, to expand the validity of culturally responsive teaching to the German context, I aimed at verifying the dimensional structure of German version of the Culturally Responsive Classroom Management Self-Efficacy Scale (CRCMSES; Siwatu, Putman, Starker-Glass, & Lewis, 2015). I conducted Exploratory and Confirmatory Factor Analysis, and run correlations between the subscales of the CRCMSES and a measure of cultural diversity- related stress. Data (n = 504) used for the first empirical study (Chapter 3) were collected in the InTePP-project (Inclusive Teaching Professionalization Panel) in which pre-service teachers’ competencies and beliefs were assessed longitudinally at two universities: the University of Potsdam and the University of Cologne.
In the second empirical study, which forms Chapter 4, the focus is on teachers’ practices resembling school approaches to cultural diversity. In this study, I investigated two research questions: (1a) What types of descriptive norms regarding cultural diversity are perceived by teachers and students with and without an immigrant background and (1b) what is their degree of congruence? Additionally, I was also interested in how are teachers’ and students’ perceptions of descriptive norms about cultural diversity related to practices and artefacts in the physical and virtual school environment? Data for the second empirical study (Chapter 4) were previously collected in a dissertation project of doctor Maja Schachner funded by the federal program “ProExzellenz” of the Free State of Thuringia. Adopting a mixed-methods research design I conducted a secondary analysis of data from teachers’ (n = 207) and students’ (n = 1,644) gathered in 22 secondary schools in south-west Germany. Additional sources of data in this study were based on pictures of school interiors (hall and corridors) and sixth-grade classrooms’ walls (n = 2,995), and screenshots from each school website (n = 6,499).
Chapter 5 addresses the question of how culturally responsive teaching, teacher cultural diversity beliefs, and self-reflection on own teaching are related. More specifically, in this study I addressed two research questions: (1) How does CRT relate to teachers’ beliefs about incorporating cultural diversity content into daily teaching and learning activities? And (2) how does the level of teachers’ self-reflection on their own teaching relate to CRT?
For this last empirical chapter, I conducted a multiple case study with four ethnic German teachers who work in one culturally and ethnically diverse high school in Berlin, using classroom video observations and post-observation interviews.
In the final chapter (Chapter 6), I summarised the main findings of the systematic literature review and three empirical studies, and discuss their scientific and practical implications.
This dissertation makes a significant contribution to the field of educational science to understanding culturally responsive teaching in terms of its measurement, focus on both beliefs and practices and the link between the two, and theoretical, practical, and future study implications.
Introduction: Cystic fibrosis (CF) is a genetic disease which disrupts the function of an epithelial surface anion channel, CFTR (cystic fibrosis transmembrane conductance regulator). Impairment to this channel leads to inflammation and infection in the lung causing the majority of morbidity and mortality. However, CF is a multiorgan disease affecting many tissues, including vascular smooth muscle. Studies have revealed young people with cystic fibrosis lacking inflammation and infection still demonstrate vascular endothelial dysfunction, measured per flow-mediated dilation (FMD). In other disease cohorts, i.e. diabetic and obese, endurance exercise interventions have been shown improve or taper this impairment. However, long-term exercise interventions are risky, as well as costly in terms of time and resources. Nevertheless, emerging research has correlated the acute effects of exercise with its long-term benefits and advocates the study of acute exercise effects on FMD prior to longitudinal studies. The acute effects of exercise on FMD have previously not been examined in young people with CF, but could yield insights on the potential benefits of long-term exercise interventions.
The aims of these studies were to 1) develop and test the reliability of the FMD method and its applicability to study acute exercise effects; 2) compare baseline FMD and the acute exercise effect on FMD between young people with and without CF; and 3) explore associations between the acute effects of exercise on FMD and demographic characteristics, physical activity levels, lung function, maximal exercise capacity or inflammatory hsCRP levels.
Methods: Thirty young volunteers (10 people with CF, 10 non-CF and 10 non-CF active matched controls) between the ages of 10 and 30 years old completed blood draws, pulmonary function tests, maximal exercise capacity tests and baseline FMD measurements, before returning approximately 1 week later and performing a 30-min constant load training at 75% HRmax. FMD measurements were taken prior, immediately after, 30 minutes after and 1 hour after constant load training. ANOVAs and repeated measures ANOVAs were employed to explore differences between groups and timepoints, respectively. Linear regression was implemented and evaluated to assess correlations between FMD and demographic characteristics, physical activity levels, lung function, maximal exercise capacity or inflammatory hsCRP levels. For all comparisons, statistical significance was set at a p-value of α < 0.05.
Results: Young people with CF presented with decreased lung function and maximal exercise capacity compared to matched controls. Baseline FMD was also significantly decreased in the CF group (CF: 5.23% v non-CF: 8.27% v non-CF active: 9.12%). Immediately post-training, FMD was significantly attenuated (approximately 40%) in all groups with CF still demonstrating the most minimal FMD. Follow-up measurements of FMD revealed a slow recovery towards baseline values 30 min post-training and improvements in the CF and non-CF active groups 60 min post-training. Linear regression exposed significant correlations between maximal exercise capacity (VO2 peak), BMI and FMD immediately post-training.
Conclusion: These new findings confirm that CF vascular endothelial dysfunction can be acutely modified by exercise and will aid in underlining the importance of exercise in CF populations. The potential benefits of long-term exercise interventions on vascular endothelial dysfunction in young people with CF warrants further investigation.
Most of the matter in the universe consists of hydrogen. The hydrogen in the intergalactic medium (IGM), the matter between the galaxies, underwent a change of its ionisation state at the epoch of reionisation, at a redshift roughly between 6>z>10, or ~10^8 years after the Big Bang. At this time, the mostly neutral hydrogen in the IGM was ionised but the source of the responsible hydrogen ionising emission remains unclear. In this thesis I discuss the most likely candidates for the emission of this ionising radiation, which are a type of galaxy called Lyman alpha emitters (LAEs). As implied by their name, they emit Lyman alpha radiation, produced after a hydrogen atom has been ionised and recombines with a free electron. The ionising radiation itself (also called Lyman continuum emission) which is needed for this process inside the LAEs could also be responsible for ionising the IGM around those galaxies at the epoch of reionisation, given that enough Lyman continuum escapes. Through this mechanism, Lyman alpha and Lyman continuum radiation are closely linked and are both studied to better understand the properties of high redshift galaxies and the reionisation state of the universe.
Before I can analyse their Lyman alpha emission lines and the escape of Lyman continuum emission from them, the first step is the detection and correct classification of LAEs in integral field spectroscopic data, specifically taken with the Multi-Unit Spectroscopic Explorer (MUSE). After detecting emission line objects in the MUSE data, the task of classifying them and determining their redshift is performed with the graphical user interface QtClassify, which I developed during the work on this thesis. It uses the strength of the combination of spectroscopic and photometric information that integral field spectroscopy offers to enable the user to quickly identify the nature of the detected emission lines. The reliable classification of LAEs and determination of their redshifts is a crucial first step towards an analysis of their properties.
Through radiative transfer processes, the properties of the neutral hydrogen clouds in and around LAEs are imprinted on the shape of the Lyman alpha line. Thus after identifying the LAEs in the MUSE data, I analyse the properties of the Lyman alpha emission line, such as the equivalent width (EW) distribution, the asymmetry and width of the line as well as the double peak fraction. I challenge the common method of displaying EW distributions as histograms without taking the limits of the survey into account and construct a more independent EW distribution function that better reflects the properties of the underlying population of galaxies. I illustrate this by comparing the fraction of high EW objects between the two surveys MUSE-Wide and MUSE-Deep, both consisting of MUSE pointings (each with the size of one square arcminute) of different depths. In the 60 MUSE-Wide fields of one hour exposure time I find a fraction of objects with extreme EWs above EW_0>240A of ~20%, while in the MUSE-Deep fields (9 fields with an exposure time of 10 hours and one with an exposure time of 31 hours) I find a fraction of only ~1%, which is due to the differences in the limiting line flux of the surveys. The highest EW I measure is EW_0 = 600.63 +- 110A, which hints at an unusual underlying stellar population, possibly with a very low metallicity.
With the knowledge of the redshifts and positions of the LAEs detected in the MUSE-Wide survey, I also look for Lyman continuum emission coming from these galaxies and analyse the connection between Lyman continuum emission and Lyman alpha emission. I use ancillary Hubble Space Telescope (HST) broadband photometry in the bands that contain the Lyman continuum and find six Lyman continuum leaker candidates. To test whether the Lyman continuum emission of LAEs is coming only from those individual objects or the whole population, I select LAEs that are most promising for the detection of Lyman continuum emission, based on their rest-frame UV continuum and Lyman alpha line shape properties. After this selection, I stack the broadband data of the resulting sample and detect a signal in Lyman continuum with a significance of S/N = 5.5, pointing towards a Lyman continuum escape fraction of ~80%. If the signal is reliable, it strongly favours LAEs as the providers of the hydrogen ionising emission at the epoch of reionisation and beyond.
The increasing age of worldwide population is a major contributor for the rising prevalence of major pathologies and disease, such as type 2 diabetes, mediated by massive insulin resistance and a decline in functional beta-cell mass, highly associated with an elevated incidence of obesity. Thus, the impact of aging under physiological conditions and in combination with diet-induced metabolic stress on characteristics of pancreatic islets and beta-cells, with the focus on functionality and structural integrity, were investigated in the present dissertation.
Primarily induced by malnutrition due to chronic and excess intake of high caloric diets, containing large amounts of carbohydrates and fats, obesity followed by systemic inflammation and peripheral insulin resistance occurs over time, initiating metabolic stress conditions. Elevated insulin demands initiate an adaptive response by beta-cell mass expansion due to increased proliferation, but prolonged stress conditions drive beta-cell failure and loss. Aging has been also shown to affect beta-cell functionality and morphology, in particular by proliferative limitations. However, most studies in rodents were performed under beta-cell challenging conditions, such as high-fat diet interventions. Thus, in the first part of the thesis (publication I), a characterization of age-related alterations on pancreatic islets and beta-cells was performed by using plasma samples and pancreatic tissue sections of standard diet-fed C57BL/6J wild-type mice in several age groups (2.5, 5, 10, 15 and 21 months).
Aging was accompanied by decreased but sustained islet proliferative potential as well as an induction of cellular senescence. This was associated with a progressive islet expansion to maintain normoglycemia throughout lifespan. Moreover, beta-cell function and mass were not impaired although the formation and accumulation of AGEs occurred, located predominantly in the islet vasculature, accompanied by an induction of oxidative and nitrosative (redox) stress.
The nutritional behavior throughout human lifespan; however, is not restricted to a balanced diet. This emphasizes the significance to investigate malnutrition by the intake of high-energy diets, inducing metabolic stress conditions that synergistically with aging might amplify the detrimental effects on endocrine pancreas. Using diabetes-prone NZO mice aged 7 weeks, fed a dietary regimen of carbohydrate restriction for different periods (young mice - 11 weeks, middle-aged mice - 32 weeks) followed by a carbohydrate intervention for 3 weeks, offered the opportunity to distinguish the effects of diet-induced metabolic stress in different ages on the functionality and integrity of pancreatic islets and their beta-cells (publication II, manuscript).
Interestingly, while young NZO mice exhibited massive hyperglycemia in response to diet-induced metabolic stress accompanied by beta-cell dysfunction and apoptosis, middle-aged animals revealed only moderate hyperglycemia by the maintenance of functional beta-cells. The loss of functional beta-cell mass in islets of young mice was associated with reduced expression of PDX1 transcription factor, increased endocrine AGE formation and related redox stress as well as TXNIP-dependent induction of the mitochondrial death pathway. Although the amounts of secreted insulin and the proliferative potential were comparable in both age groups, islets of middle-aged mice exhibited sustained PDX1 expression, almost regular insulin secretory function, increased capacity for cell cycle progression as well as maintained redox potential.
The results of the present thesis indicate a loss of functional beta-cell mass in young diabetes-prone NZO mice, occurring by redox imbalance and induction of apoptotic signaling pathways. In contrast, aging under physiological conditions in C57BL/6J mice and in combination with diet-induced metabolic stress in NZO mice does not appear to have adverse effects on the functionality and structural integrity of pancreatic islets and beta-cells, associated with adaptive responses on changing metabolic demands. However, considering the detrimental effects of aging, it has to be assumed that the compensatory potential of mice might be exhausted at a later point of time, finally leading to a loss of functional beta-cell mass and the onset and progression of type 2 diabetes.
The polygenic, diabetes-prone NZO mouse is a suitable model for the investigation of human obesity-associated type 2 diabetes. However, mice at advanced age attenuated the diabetic phenotype or do not respond to the dietary stimuli. This might be explained by the middle age of mice, corresponding to the human age of about 38-40 years, in which the compensatory mechanisms of pancreatic islets and beta cells towards metabolic stress conditions are presumably more active.
Supermassive black holes reside in the hearts of almost all massive galaxies. Their evolutionary path seems to be strongly linked to the evolution of their host galaxies, as implied by several empirical relations between the black hole mass (M BH ) and different host galaxy properties. The physical driver of this co-evolution is, however, still not understood. More mass measurements over homogeneous samples and a detailed understanding of systematic uncertainties are required to fathom the origin of the scaling relations.
In this thesis, I present the mass estimations of supermassive black holes in the nuclei of one late-type and thirteen early-type galaxies. Our SMASHING sample extends from the intermediate to the massive galaxy mass regime and was selected to fill in gaps in number of galaxies along the scaling relations. All galaxies were observed at high spatial resolution, making use of the adaptive-optics mode of integral field unit (IFU) instruments on state-of-the-art telescopes (SINFONI, NIFS, MUSE). I extracted the stellar kinematics from these observations and constructed dynamical Jeans and Schwarzschild models to estimate the mass of the central black holes robustly. My new mass estimates increase the number of early-type galaxies with measured black hole masses by 15%. The seven measured galaxies with nuclear light deficits (’cores’) augment the sample of cored galaxies with measured black holes by 40%. Next to determining massive black hole masses, evaluating the accuracy of black hole masses is crucial for understanding the intrinsic scatter of the black hole- host galaxy scaling relations. I tested various sources of systematic uncertainty on my derived mass estimates.
The M BH estimate of the single late-type galaxy of the sample yielded an upper limit, which I could constrain very robustly. I tested the effects of dust, mass-to-light ratio (M/L) variation, and dark matter on my measured M BH . Based on these tests, the typically assumed constant M/L ratio can be an adequate assumption to account for the small amounts of dark matter in the center of that galaxy. I also tested the effect of a variable M/L variation on the M BH measurement on a second galaxy. By considering stellar M/L variations in the dynamical modeling, the measured M BH decreased by 30%. In the future, this test should be performed on additional galaxies to learn how an as constant assumed M/L flaws the estimated black hole masses.
Based on our upper limit mass measurement, I confirm previous suggestions that resolving the predicted BH sphere-of-influence is not a strict condition to measure black hole masses. Instead, it is only a rough guide for the detection of the black hole if high-quality, and high signal-to-noise IFU data are used for the measurement. About half of our sample consists of massive early-type galaxies which show nuclear surface brightness cores and signs of triaxiality. While these types of galaxies are typically modeled with axisymmetric modeling methods, the effects on M BH are not well studied yet. The massive galaxies of our presented galaxy sample are well suited to test the effect of different stellar dynamical models on the measured black hole mass in evidently triaxial galaxies. I have compared spherical Jeans and axisymmetric Schwarzschild models and will add triaxial Schwarzschild models to this comparison in the future. The constructed Jeans and Schwarzschild models mostly disagree with each other and cannot reproduce many of the triaxial features of the galaxies (e.g., nuclear sub-components, prolate rotation). The consequence of the axisymmetric-triaxial assumption on the accuracy of M BH and its impact on the black hole - host galaxy relation needs to be carefully examined in the future.
In the sample of galaxies with published M BH , we find measurements based on different dynamical tracers, requiring different observations, assumptions, and methods. Crucially, different tracers do not always give consistent results. I have used two independent tracers (cold molecular gas and stars) to estimate M BH in a regular galaxy of our sample. While the two estimates are consistent within their errors, the stellar-based measurement is twice as high as the gas-based. Similar trends have also been found in the literature. Therefore, a rigorous test of the systematics associated with the different modeling methods is required in the future. I caution to take the effects of different tracers (and methods) into account when discussing the scaling relations.
I conclude this thesis by comparing my galaxy sample with the compilation of galaxies with measured black holes from the literature, also adding six SMASHING galaxies, which were published outside of this thesis. None of the SMASHING galaxies deviates significantly from the literature measurements. Their inclusion to the published early-type galaxies causes a change towards a shallower slope for the M BH - effective velocity dispersion relation, which is mainly driven by the massive galaxies of our sample. More unbiased and homogenous measurements are needed in the future to determine the shape of the relation and understand its physical origin.
Over the last years there is an increasing awareness that historical land cover changes and associated land use legacies may be important drivers for present-day species richness and biodiversity due to time-delayed extinctions or colonizations in response to historical environmental changes. Historically altered habitat patches may therefore exhibit an extinction debt or colonization credit and can be expected to lose or gain species in the future. However, extinction debts and colonization credits are difficult to detect and their actual magnitudes or payments have rarely been quantified because species richness patterns and dynamics are also shaped by recent environmental conditions and recent environmental changes.
In this thesis we aimed to determine patterns of herb-layer species richness and recent species richness dynamics of forest herb layer plants and link those patterns and dynamics to historical land cover changes and associated land use legacies. The study was conducted in the Prignitz, NE-Germany, where the forest distribution remained stable for the last ca. 100 years but where a) the deciduous forest area had declined by more than 90 per cent (leaving only remnants of "ancient forests"), b) small new forests had been established on former agricultural land ("post-agricultural forests"). Here, we analyzed the relative importance of land use history and associated historical land cover changes for herb layer species richness compared to recent environmental factors and determined magnitudes of extinction debt and colonization credit and their payment in ancient and post-agricultural forests, respectively.
We showed that present-day species richness patterns were still shaped by historical land cover changes that ranged back to more than a century. Although recent environmental conditions were largely comparable we found significantly more forest specialists, species with short-distance dispersal capabilities and clonals in ancient forests than in post-agricultural forests. Those species richness differences were largely contingent to a colonization credit in post-agricultural forests that ranged up to 9 species (average 4.7), while the extinction debt in ancient forests had almost completely been paid. Environmental legacies from historical agricultural land use played a minor role for species richness differences. Instead, patch connectivity was most important. Species richness in ancient forests was still dependent on historical connectivity, indicating a last glimpse of an extinction debt, and the colonization credit was highest in isolated post-agricultural forests. In post-agricultural forests that were better connected or directly adjacent to ancient forest patches the colonization credit was way smaller and we were able to verify a gradual payment of the colonization credit from 2.7 species to 1.5 species over the last six decades.
The thesis comprises three experimental studies, which were carried out to unravel the short- as well as the long-term mechanical properties of shale rocks. Short-term mechanical properties such as compressive strength and Young’s modulus were taken from recorded stress-strain curves of constant strain rate tests. Long-term mechanical properties are represented by the time– dependent creep behavior of shales. This was obtained from constant stress experiments, where the test duration ranged from a couple minutes up to two weeks. A profound knowledge of the mechanical behavior of shales is crucial to reliably estimate the potential of a shale reservoir for an economical and sustainable extraction of hydrocarbons (HC). In addition, healing of clay-rich forming cap rocks involving creep and compaction is important for underground storage of carbon dioxide and nuclear waste.
Chapter 1 introduces general aspects of the research topic at hand and highlights the motivation for conducting this study. At present, a shift from energy recovered from conventional resources e.g., coal towards energy provided by renewable resources such as wind or water is a big challenge. Gas recovered from unconventional reservoirs (shale plays) is considered a potential bridge technology.
In Chapter 2, short-term mechanical properties of two European mature shale rocks are presented, which were determined from constant strain rate experiments performed at ambient and in situ deformation conditions (confining pressure, pc ≤ 100 MPa, temperature, T ≤ 125 °C, representing pc, T - conditions at < 4 km depth) using a Paterson– type gas deformation apparatus. The investigated shales were mainly from drill core material of Posidonia (Germany) shale and weathered material of Bowland (United Kingdom) shale. The results are compared with mechanical properties of North American shales. Triaxial compression tests performed perpendicular to bedding revealed semibrittle deformation behavior of Posidonia shale with pronounced inelastic deformation. This is in contrast to Bowland shale samples that deformed brittle and displayed predominantly elastic deformation. The static Young’s modulus, E, and triaxial compressive strength, σTCS, determined from recorded stress-strain curves strongly depended on the applied confining pressure and sample composition, whereas the influence of temperature and strain rate on E and σTCS was minor. Shales with larger amounts of weak minerals (clay, mica, total organic carbon) yielded decreasing E and σTCS. This may be related to a shift from deformation supported by a load-bearing framework of hard phases (e.g., quartz) towards deformation of interconnected weak minerals, particularly for higher fractions of about 25 – 30 vol% weak phases. Comparing mechanical properties determined at reservoir conditions with mechanical data applying effective medium theories revealed that E and σTCS of Posidonia and Bowland shale are close to the lower (Reuss) bound. Brittleness B is often quoted as a measure indicating the response of a shale formation to stimulation and economic production. The brittleness, B, of Posidonia and Bowland shale, estimated from E, is in good agreement with the experimental results. This correlation may be useful to predict B from sonic logs, from which the (dynamic) Young’s modulus can be retrieved.
Chapter 3 presents a study of the long-term creep properties of an immature Posidonia shale. Constant stress experiments (σ = const.) were performed at elevated confining pressures (pc = 50 – 200 MPa) and temperatures (T = 50 – 200 °C) to simulate reservoir pc, T - conditions. The Posidonia shale samples were acquired from a quarry in South Germany. At stresses below ≈ 84 % compressive strength of Posidonia shale, at high temperature and low confining pressure, samples showed pronounced transient (primary) creep with high deformation rates in the semibrittle regime. Sample deformation was mainly accommodated by creep of weak sample constituents and pore space reduction. An empirical power law relation between strain and time, which also accounts for the influence of pc, T and σ on creep strain was formulated to describe the primary creep phase. Extrapolation of the results to a creep period of several years, which is the typical time interval for a large production decline, suggest that fracture closure is unlikely at low stresses. At high stresses as expected for example at the contact between the fracture surfaces and proppants added during stimulation measures, subcritical crack growth may lead to secondary and tertiary creep. An empirical power law is suggested to describe secondary creep of shale rocks as a function of stress, pressure and temperature. The predicted closure rates agree with typical production decline curves recorded during the extraction of hydrocarbons. At the investigated conditions, the creep behavior of Posidonia shale was found to correlate with brittleness, calculated from sample composition.
In Chapter 4 the creep properties of mature Posidonia and Bowland shales are presented. The observed long-term creep behavior is compared to the short-term behavior determined in Chapter 2. Creep experiments were performed at simulated reservoir conditions of pc = 50 – 115 MPa and T = 75 – 150 °C. Similar to the mechanical response of immature Posidonia shale samples investigated in Chapter 3, creep strain rates of mature Bowland and Posidonia shales were enhanced with increasing stress and temperature and decreasing confining pressures. Depending on applied deformation conditions, samples displayed either only a primary (decelerating) or in addition also a secondary (quasi-steady state) and subsequently a tertiary (accelerating) creep phase before failure. At the same deformation conditions, creep strain of Posidonia shale, which is rich in weak constituents, is tremendously higher than of quartz-rich Bowland shale. Typically, primary creep strain is again mostly accommodated by deformation of weak minerals and local pore space reduction. At the onset of tertiary creep most of the deformation was accommodated by micro crack growth. A power law was used to characterize the primary creep phase of Posidonia and Bowland shale. Primary creep strain of shale rocks is inversely correlated to triaxial compressive strength and brittleness, as described in Chapter 2.
Chapter 5 provides a synthesis of the experimental findings and summarizes the major results of the studies presented in Chapters 2 – 4 and potential applications in the Exploration & Production industry.
Chapter 6 gives a brief outlook on potential future experimental research that would help to further improve our understanding of processes leading to fracture closure involving proppant embedment in unconventional shale gas reservoirs. Such insights may allow to improve stimulation techniques aimed at maintaining economical extraction of hydrocarbons over several years.
The individual’s mental lexicon comprises all known words as well related infor-mation on semantics, orthography and phonology. Moreover, entries connect due to simi-larities in these language domains building a large network structure. The access to lexical information is crucial for processing of words and sentences. Thus, a lack of information in-hibits the retrieval and can cause language processing difficulties. Hence, the composition of the mental lexicon is essential for language skills and its assessment is a central topic of lin-guistic and educational research.
In early childhood, measurement of the mental lexicon is uncomplicated, for example through parental questionnaires or the analysis of speech samples. However, with growing content the measurement becomes more challenging: With more and more words in the mental lexicon, the inclusion of all possible known words into a test or questionnaire be-comes impossible. That is why there is a lack of methods to assess the mental lexicon for school children and adults. For the same reason, there are only few findings on the courses of lexical development during school years as well as its specific effect on other language skills. This dissertation is supposed to close this gap by pursuing two major goals: First, I wanted to develop a method to assess lexical features, namely lexicon size and lexical struc-ture, for children of different age groups. Second, I aimed to describe the results of this method in terms of lexical development of size and structure. Findings were intended to help understanding mechanisms of lexical acquisition and inform theories on vocabulary growth.
The approach is based on the dictionary method where a sample of words out of a dictionary is tested and results are projected on the whole dictionary to determine an indi-vidual’s lexicon size. In the present study, the childLex corpus, a written language corpus for children in German, served as the basis for lexicon size estimation. The corpus is assumed to comprise all words children attending primary school could know. Testing a sample of words out of the corpus enables projection of the results on the whole corpus. For this purpose, a vocabulary test based on the corpus was developed. Afterwards, test performance of virtual participants was simulated by drawing different lexicon sizes from the corpus and comparing whether the test items were included in the lexicon or not. This allowed determination of the relation between test performance and total lexicon size and thus could be transferred to a sample of real participants. Besides lexicon size, lexical content could be approximated with this approach and analyzed in terms of lexical structure.
To pursue the presented aims and establish the sampling method, I conducted three consecutive studies. Study 1 includes the development of a vocabulary test based on the childLex corpus. The testing was based on the yes/no format and included three versions for different age groups. The validation grounded on the Rasch Model shows that it is a valid instrument to measure vocabulary for primary school children in German. In Study 2, I estab-lished the method to estimate lexicon sizes and present results on lexical development dur-ing primary school. Plausible results demonstrate that lexical growth follows a quadratic function starting with about 6,000 words at the beginning of school and about 73,000 words on average for young adults. Moreover, the study revealed large interindividual differences. Study 3 focused on the analysis of network structures and their development in the mental lexicon due to orthographic similarities. It demonstrates that networks possess small-word characteristics and decrease in interconnectivity with age.
Taken together, this dissertation provides an innovative approach for the assessment and description of the development of the mental lexicon from primary school onwards. The studies determine recent results on lexical acquisition in different age groups that were miss-ing before. They impressively show the importance of this period and display the existence of extensive interindividual differences in lexical development. One central aim of future research needs to address the causes and prevention of these differences. In addition, the application of the method for further research (e.g. the adaptation for other target groups) and teaching purposes (e.g. adaptation of texts for different target groups) appears to be promising.
The public encounter
(2019)
This thesis puts the citizen-state interaction at its center. Building on a comprehensive model incorporating various perspectives on this interaction, I derive selected research gaps. The three articles, comprising this thesis, tackle these gaps. A focal role plays the citizens’ administrative literacy, the relevant competences and knowledge necessary to successfully interact with public organizations. The first article elaborates on the different dimensions of administrative literacy and develops a survey instrument to assess these. The second study shows that public employees change their behavior according to the competences that citizens display during public encounters. They treat citizens preferentially that are well prepared and able to persuade them of their application’s potential. Thereby, they signal a higher success potential for bureaucratic success criteria which leads to the employees’ cream-skimming behavior. The third article examines the dynamics of employees’ communication strategies when recovering from a service failure. The study finds that different explanation strategies yield different effects on the client’s frustration. While accepting the responsibility and explaining the reasons for a failure alleviates the frustration and anger, refusing the responsibility leads to no or even reinforcing effects on the client’s frustration. The results emphasize the different dynamics that characterize the nature of citizen-state interactions and how they establish their short- and long-term outcomes.
Partial melting is a first order process for the chemical differentiation of the crust (Vielzeuf et al., 1990). Redistribution of chemical elements during melt generation crucially influences the composition of the lower and upper crust and provides a mechanism to concentrate and transport chemical elements that may also be of economic interest. Understanding of the diverse processes and their controlling factors is therefore not only of scientific interest but also of high economic importance to cover the demand for rare metals.
The redistribution of major and trace elements during partial melting represents a central step for the understanding how granite-bound mineralization develops (Hedenquist and Lowenstern, 1994). The partial melt generation and mobilization of ore elements (e.g. Sn, W, Nb, Ta) into the melt depends on the composition of the sedimentary source and melting conditions. Distinct source rocks have different compositions reflecting their deposition and alteration histories. This specific chemical “memory” results in different mineral assemblages and melting reactions for different protolith compositions during prograde metamorphism (Brown and Fyfe, 1970; Thompson, 1982; Vielzeuf and Holloway, 1988). These factors do not only exert an important influence on the distribution of chemical elements during melt generation, they also influence the volume of melt that is produced, extraction of the melt from its source, and its ascent through the crust (Le Breton and Thompson, 1988). On a larger scale, protolith distribution and chemical alteration (weathering), prograde metamorphism with partial melting, melt extraction, and granite emplacement are ultimately depending on a (plate-)tectonic control (Romer and Kroner, 2016). Comprehension of the individual stages and their interaction is crucial in understanding how granite-related mineralization forms, thereby allowing estimation of the mineralization potential of certain areas. Partial melting also influences the isotope systematics of melt and restite. Radiogenic and stable isotopes of magmatic rocks are commonly used to trace back the source of intrusions or to quantify mixing of magmas from different sources with distinct isotopic signatures (DePaolo and Wasserburg, 1979; Lesher, 1990; Chappell, 1996). These applications are based on the fundamental requirement that the isotopic signature in the melt reflects that of the bulk source from which it is derived. Different minerals in a protolith may have isotopic compositions of radiogenic isotopes that deviate from their whole rock signature (Ayres and Harris, 1997; Knesel and Davidson, 2002). In particular, old minerals with a distinct parent-to-daughter (P/D) ratio are expected to have a specific radiogenic isotope signature. As the partial melting reaction only involves selective phases in a protolith, the isotopic signature of the melt reflects that of the minerals involved in the melting reaction and, therefore, should be different from the bulk source signature. Similar considerations hold true for stable isotopes.
The Government will create a motivated, merit-based, performance-driven, and professional civil service that is resistant to temptations of corruption and which provides efficient, effective and transparent public services that do not force customers to pay bribes.
— (GoIRA, 2006, p. 106)
We were in a black hole! We had an empty glass and had nothing from our side to fill it with! Thus, we accepted anything anybody offered; that is how our glass was filled; that is how we reformed our civil service.
— (Former Advisor to IARCSC, personal communication, August 2015)
How and under what conditions were the post-Taleban Civil Service Reforms of Afghanistan initiated? What were the main components of the reforms? What were their objectives and to which extent were they achieved? Who were the leading domestic and foreign actors involved in the process? Finally, what specific factors influenced the success and failure Afghanistan’s Civil Service Reforms since 2002? Guided by such fundamental questions, this research studies the wicked process of reforming the Afghan civil service in an environment where a variety of contextual, programmatic, and external factors affected the design and implementation of reforms that were entirely funded and technically assisted by the international community.
Focusing on the core components of reforms—recruitment, remuneration, and appraisal of civil servants—the qualitative study provides a detailed picture of the pre-reform civil service and its major human resources developments in the past. Following discussions on the content and purposes of the main reform programs, it will then analyze the extent of changes in policies and practices by examining the outputs and effects of these reforms.
Moreover, the study defines the specific factors that led the reforms toward a situation where most of the intended objectives remain unachieved. Doing so, it explores and explains how an overwhelming influence of international actors with conflicting interests, large-scale corruption, political interference, networks of patronage, institutionalized nepotism, culturally accepted cronyism and widespread ethnic favoritism created a very complex environment and prevented the reforms from transforming Afghanistan’s patrimonial civil service into a professional civil service, which is driven by performance and merit.
The foreland of the Andes in South America is characterised by distinct along strike changes in surface deformational styles. These styles are classified into two end-members, the thin-skinned and the thick-skinned style. The superficial expression of thin-skinned deformation is a succession of narrowly spaced hills and valleys, that form laterally continuous ranges on the foreland facing side of the orogen. Each of the hills is defined by a reverse fault that roots in a basal décollement surface within the sedimentary cover, and acted as thrusting ramp to stack the sedimentary pile. Thick-skinned deformation is morphologically characterised by spatially disparate, basement-cored mountain ranges. These mountain ranges are uplifted along reactivated high-angle crustal-scale discontinuities, such as suture zones between different tectonic terranes.
Amongst proposed causes for the observed variation are variations in the dip angle of the Nazca plate, variation in sediment thickness, lithospheric thickening, volcanism or compositional differences. The proposed mechanisms are predominantly based on geological observations or numerical thermomechanical modelling, but there has been no attempt to understand the mechanisms from a point of data-integrative 3D modelling. The aim of this dissertation is therefore to understand how lithospheric structure controls the deformational behaviour. The integration of independent data into a consistent model of the lithosphere allows to obtain additional evidence that helps to understand the causes for the different deformational styles. Northern Argentina encompasses the transition from the thin-skinned fold-and-thrust belt in Bolivia, to the thick-skinned Sierras Pampeanas province, which makes this area a well suited location for such a study. The general workflow followed in this study first involves data-constrained structural- and density-modelling in order to obtain a model of the study area. This model was then used to predict the steady-state thermal field, which was then used to assess the present-day rheological state in northern Argentina.
The structural configuration of the lithosphere in northern Argentina was determined by means of data-integrative, 3D density modelling verified by Bouguer gravity. The model delineates the first-order density contrasts in the lithosphere in the uppermost 200 km, and discriminates bodies for the sediments, the crystalline crust, the lithospheric mantle and the subducting Nazca plate. To obtain the intra-crustal density structure, an automated inversion approach was developed and applied to a starting structural model that assumed a homogeneously dense crust. The resulting final structural model indicates that the crustal structure can be represented by an upper crust with a density of 2800 kg/m³, and a lower crust of 3100 kg/m³. The Transbrazilian Lineament, which separates the Pampia terrane from the Río de la Plata craton, is expressed as a zone of low average crustal densities.
In an excursion, we demonstrate in another study, that the gravity inversion method developed to obtain intra-crustal density structures, is also applicable to obtain density variations in the uppermost lithospheric mantle. Densities in such sub-crustal depths are difficult to constrain from seismic tomographic models due to smearing of crustal velocities. With the application to the uppermost lithospheric mantle in the north Atlantic, we demonstrate in Tan et al. (2018) that lateral density trends of at least 125\,km width are robustly recovered by the inversion method, thereby providing an important tool for the delineation of subcrustal density trends.
Due to the genetic link between subduction, orogenesis and retroarc foreland basins the question rises whether the steady-state assumption is valid in such a dynamic setting. To answer this question, I analysed (i) the impact of subduction on the conductive thermal field of the overlying continental plate, (ii) the differences between the transient and steady-state thermal fields of a geodynamic coupled model. Both studies indicate that the assumption of a thermal steady-state is applicable in most parts of the study area. Within the orogenic wedge, where the assumption cannot be applied, I estimated the transient thermal field based on the results of the conducted analyses.
Accordingly, the structural model that had been obtained in the first step, could be used to obtain a 3D conductive steady-state thermal field. The rheological assessment based on this thermal field indicates that the lithosphere of the thin-skinned Subandean ranges is characterised by a relatively strong crust and a weak mantle. Contrarily, the adjacent foreland basin consists of a fully coupled, very strong lithosphere. Thus, shortening in northern Argentina can only be accommodated within the weak lithosphere of the orogen and the Subandean ranges. The analysis suggests that the décollements of the fold-and-thrust belt are the shallow continuation of shear zones that reside in the ductile sections of the orogenic crust. Furthermore, the localisation of the faults that provide strain transfer between the deeper ductile crust and the shallower décollement is strongly influenced by crustal weak zones such as foliation. In contrast to the northern foreland, the lithosphere of the thick-skinned Sierras Pampeanas is fully coupled and characterised by a strong crust and mantle. The high overall strength prevents the generation of crustal-scale faults by tectonic stresses. Even inherited crustal-scale discontinuities, such as sutures, cannot sufficiently reduce the strength of the lithosphere in order to be reactivated. Therefore, magmatism that had been identified to be a precursor of basement uplift in the Sierras Pampeanas, is the key factor that leads to the broken foreland of this province. Due to thermal weakening, and potentially lubrication of the inherited discontinuities, the lithosphere is locally weakened such that tectonic stresses can uplift the basement blocks. This hypothesis explains both the spatially disparate character of the broken foreland, as well as the observed temporal delay between volcanism and basement block uplift.
This dissertation provides for the first time a data-driven 3D model that is consistent with geophysical data and geological observations, and that is able to causally link the thermo-rheological structure of the lithosphere to the observed variation of surface deformation styles in the retroarc foreland of northern Argentina.
This thesis investigates whether multilingual speakers’ use of grammatical constraints in an additional language (La) is affected by the native (L1) and non-native grammars (L2) of their linguistic repertoire.
Previous studies have used untimed measures of grammatical performance to show that L1 and L2 grammars affect the initial stages of La acquisition. This thesis extends this work by examining whether speakers at intermediate levels of La proficiency, who demonstrate mature untimed/offline knowledge of the target La constraints, are differentially affected by their L1 and L2 knowledge when they comprehend sentences under processing pressure. With this purpose, several groups of La German speakers were tested on word order and agreement phenomena using online/timed measures of grammatical knowledge. Participants had mirror distributions of their prior languages and they were either L1English/L2Spanish speakers or L1Spanish/L2English speakers. Crucially, in half of the phenomena the target La constraint aligned with English but not with Spanish, while in the other half it aligned with Spanish but not with English. Results show that the L1 grammar plays a major role in the use of La constraints under processing pressure, as participants displayed increased sensitivity to La constraints when they aligned with their L1, and reduced sensitivity when they did not. Further, in specific phenomena in which the L2 and La constraints aligned, increased L2 proficiency resulted in an enhanced sensitivity to the La constraint. These findings suggest that both native and non-native grammars affect how speakers use La grammatical constraints under processing pressure. However, L1 and L2 grammars differentially influence on participants’ performance: While L1 constraints seem to be reliably recruited to cope with the processing demands of real-time La use, proficiency in an L2 can enhance sensitivity to La constraints only in specific circumstances, namely when L2 and La constraints align.
Optimization is a core part of technological advancement and is usually heavily aided by computers. However, since many optimization problems are hard, it is unrealistic to expect an optimal solution within reasonable time. Hence, heuristics are employed, that is, computer programs that try to produce solutions of high quality quickly. One special class are estimation-of-distribution algorithms (EDAs), which are characterized by maintaining a probabilistic model over the problem domain, which they evolve over time. In an iterative fashion, an EDA uses its model in order to generate a set of solutions, which it then uses to refine the model such that the probability of producing good solutions is increased.
In this thesis, we theoretically analyze the class of univariate EDAs over the Boolean domain, that is, over the space of all length-n bit strings. In this setting, the probabilistic model of a univariate EDA consists of an n-dimensional probability vector where each component denotes the probability to sample a 1 for that position in order to generate a bit string.
My contribution follows two main directions: first, we analyze general inherent properties of univariate EDAs. Second, we determine the expected run times of specific EDAs on benchmark functions from theory. In the first part, we characterize when EDAs are unbiased with respect to the problem encoding. We then consider a setting where all solutions look equally good to an EDA, and we show that the probabilistic model of an EDA quickly evolves into an incorrect model if it is always updated such that it does not change in expectation.
In the second part, we first show that the algorithms cGA and MMAS-fp are able to efficiently optimize a noisy version of the classical benchmark function OneMax. We perturb the function by adding Gaussian noise with a variance of σ², and we prove that the algorithms are able to generate the true optimum in a time polynomial in σ² and the problem size n. For the MMAS-fp, we generalize this result to linear functions. Further, we prove a run time of Ω(n log(n)) for the algorithm UMDA on (unnoisy) OneMax. Last, we introduce a new algorithm that is able to optimize the benchmark functions OneMax and LeadingOnes both in O(n log(n)), which is a novelty for heuristics in the domain we consider.
Thermoresponsive Zellkultursubstrate für zeitlich-räumlich gesteuertes Auswachsen neuronaler Zellen
(2019)
Ein wichtiges Ziel der Neurowissenschaften ist das Verständnis der komplexen und zugleich faszinierenden, hochgeordneten Vernetzung der Neurone im Gehirn, welche neuronalen Prozessen, wie zum Beispiel dem Wahrnehmen oder Lernen wie auch Neuropathologien zu Grunde liegt. Für verbesserte neuronale Zellkulturmodelle zur detaillierten Untersuchung dieser Prozesse ist daher die Rekonstruktion von geordneten neuronalen Verbindungen dringend erforderlich. Mit Oberflächenstrukturen aus zellattraktiven und zellabweisenden Beschichtungen können neuronale Zellen und ihre Neuriten in vitro strukturiert werden. Zur Kontrolle der neuronalen Verbindungsrichtung muss das Auswachsen der Axone zu benachbarten Zellen dynamisch gesteuert werden, zum Beispiel über eine veränderliche Zugänglichkeit der Oberfläche.
In dieser Arbeit wurde untersucht, ob mit thermoresponsiven Polymeren (TRP) beschichtete Zellkultursubstrate für eine dynamische Kontrolle des Auswachsens neuronaler Zellen geeignet sind. TRP können über die Temperatur von einem zellabweisenden in einen zellattraktiven Zustand geschaltet werden, womit die Zugänglichkeit der Oberfläche für Zellen dynamisch gesteuert werden kann. Die TRP-Beschichtung wurde mikrostrukturiert, um einzelne oder wenige neuronale Zellen zunächst auf der Oberfläche anzuordnen und das Auswachsen der Zellen und Neuriten über definierte TRP-Bereiche in Abhängigkeit der Temperatur zeitlich und räumlich zu kontrollieren. Das Protokoll wurde mit der neuronalen Zelllinie SH-SY5Y etabliert und auf humane induzierte Neurone übertragen. Die Anordnung der Zellen konnte bei Kultivierung im zellabweisenden Zustand des TRPs für bis zu 7 Tage aufrecht erhalten werden. Durch Schalten des TRPs in den zellattraktiven Zustand konnte das Auswachsen der Neuriten und Zellen zeitlich und räumlich induziert werden. Immunozytochemische Färbungen und Patch-Clamp-Ableitungen der Neurone demonstrierten die einfache Anwendbarkeit und Zellkompatibilität der TRP-Substrate.
Eine präzisere räumliche Kontrolle des Auswachsens der Zellen sollte durch lokales Schalten der TRP-Beschichtung erreicht werden. Dafür wurden Mikroheizchips mit Mikroelektroden zur lokalen Jouleschen Erwärmung der Substratoberfläche entwickelt. Zur Evaluierung der generierten Temperaturprofile wurde eine Temperaturmessmethode entwickelt und die erhobenen Messwerte mit numerisch simulierten Werten abgeglichen. Die Temperaturmessmethode basiert auf einfach zu applizierenden Sol-Gel-Schichten, die den temperatursensitiven Fluoreszenzfarbstoff Rhodamin B enthalten. Sie ermöglicht oberflächennahe Temperaturmessungen in trockener und wässriger Umgebung mit hoher Orts- und Temperaturauflösung. Numerische Simulationen der Temperaturprofile korrelierten gut mit den experimentellen Daten. Auf dieser Basis konnten Geometrie und Material der Mikroelektroden hinsichtlich einer lokal stark begrenzten Temperierung optimiert werden. Ferner wurden für die Kultvierung der Zellen auf den Mikroheizchips eine Zellkulturkammer und Kontaktboard für die elektrische Kontaktierung der Mikroelektroden geschaffen.
Die vorgestellten Ergebnisse demonstrieren erstmalig das enorme Potential thermoresponsiver Zellkultursubstrate für die zeitlich und räumlich gesteuerte Formation geordneter neuronaler Verbindungen in vitro. Zukünftig könnte dies detaillierte Studien zur neuronalen Informationsverarbeitung oder zu Neuropathologien an relevanten, humanen Zellmodellen ermöglichen.