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The Cauchy problem for the linearised Einstein equation and the Goursat problem for wave equations
(2017)
In this thesis, we study two initial value problems arising in general relativity. The first is the Cauchy problem for the linearised Einstein equation on general globally hyperbolic spacetimes, with smooth and distributional initial data. We extend well-known results by showing that given a solution to the linearised constraint equations of arbitrary real Sobolev regularity, there is a globally defined solution, which is unique up to addition of gauge solutions. Two solutions are considered equivalent if they differ by a gauge solution. Our main result is that the equivalence class of solutions depends continuously on the corre- sponding equivalence class of initial data. We also solve the linearised constraint equations in certain cases and show that there exist arbitrarily irregular (non-gauge) solutions to the linearised Einstein equation on Minkowski spacetime and Kasner spacetime.
In the second part, we study the Goursat problem (the characteristic Cauchy problem) for wave equations. We specify initial data on a smooth compact Cauchy horizon, which is a lightlike hypersurface. This problem has not been studied much, since it is an initial value problem on a non-globally hyperbolic spacetime. Our main result is that given a smooth function on a non-empty, smooth, compact, totally geodesic and non-degenerate Cauchy horizon and a so called admissible linear wave equation, there exists a unique solution that is defined on the globally hyperbolic region and restricts to the given function on the Cauchy horizon. Moreover, the solution depends continuously on the initial data. A linear wave equation is called admissible if the first order part satisfies a certain condition on the Cauchy horizon, for example if it vanishes. Interestingly, both existence of solution and uniqueness are false for general wave equations, as examples show. If we drop the non-degeneracy assumption, examples show that existence of solution fails even for the simplest wave equation. The proof requires precise energy estimates for the wave equation close to the Cauchy horizon. In case the Ricci curvature vanishes on the Cauchy horizon, we show that the energy estimates are strong enough to prove local existence and uniqueness for a class of non-linear wave equations. Our results apply in particular to the Taub-NUT spacetime and the Misner spacetime. It has recently been shown that compact Cauchy horizons in spacetimes satisfying the null energy condition are necessarily smooth and totally geodesic. Our results therefore apply if the spacetime satisfies the null energy condition and the Cauchy horizon is compact and non-degenerate.
In the present work side-chain polystyrenes were synthesized and characterized, in order to be applied in multilayer OLEDs fabricated by solution process techniques. Manufacture of optoelectronic devices by solution process techniques is meant to decrease significantly fabrication cost and allow large scale production of such devices.
This dissertation focusses in three series, enveloped in two material classes. The two classes differ to each other in the type of charge transport exhibited, either ambipolar transport or electron transport. All materials were applied in all-organic solution processed green Ir-based devices.
In the first part, a series of ambipolar host materials were developed to transport both charge types, holes and electrons, and be applied especially as matrix for green Ir-based emitters. It was possible to increase devices efficacy by modulating the predominant charge transport type. This was achieved by modification of molecules electron transport part with more electron-deficient heterocycles or by extending the delocalization of the LUMO. Efficiencies up to 28.9 cd/A were observed for all-organic solution-process three layer devices.
In the second part, suitability of triarylboranes and tetraphenylsilanes as electron transport materials was studied. High triplet energies were obtained, up to 2.95 eV, by rational combination of both molecular structures. Although the combination of both elements had a low effect in materials electron transport properties, high efficiencies around 24 cd/A were obtained for the series in all-organic solution-processed two layer devices.
In the last part, benzene and pyridine were chosen as the series electron-transport motif. By controlling the relative pyridine content (RPC) solubility into methanol was induced for polystyrenes with bulky side-chains. Materials with RPC ≥ 0.5 could be deposited orthogonally from solution without harming underlying layers. From the best of our knowledge, this is the first time such materials are applied in this architecture showing moderate efficiencies around 10 cd/A in all-organic solution processed OLEDs.
Overall, the outcome of these studies will actively contribute to the current research on materials for all-solution processed OLEDs.
Direct anthropogenic influences on the Earth’s subsurface during drilling, extraction or injection activities, can affect land stability by causing subsidence, uplifts or lateral displacements. They can occur in localized as well as in uninhabited and inhabited regions. Thus the associated risks for humans, infrastructure, and environment must be minimized. To achieve this, appropriate surveillance methods must be found that can be used for simultaneous monitoring during such activities. Multi-temporal synthetic aperture radar interferometry (MT-InSAR) methods like the Persistent Scatterer Interferometry (PSI) and the Small BAseline Subsets (SBAS) have been developed as standard approaches for satellite-based surface displacement monitoring. With increasing spatial resolution and availability of SAR sensors in recent years, MT-InSAR can be valuable for the detection and mapping of even the smallest man-made displacements.
This doctoral thesis aims at investigating the capacities of the mentioned standard methods for this purpose, and comprises three main objectives against the backdrop of a user-friendly surveillance service:
(1) the spatial and temporal significance assessment against leveling, (2) the suitability evaluation of PSI and SBAS under different conditions, and (3) the analysis of the link between surface motion and subsurface processes.
Two prominent case studies on anthropogenic induced subsurface processes in Germany serve as the basis for this goal. The first is the distinct urban uplift with severe damages at Staufen im Breisgau that has been associated since 2007 with a failure to implement a shallow geothermal energy supply for an individual building. The second case study considers the pilot project of geological carbon dioxide (CO2) storage at Ketzin, and comprises borehole drilling and fluid injection of more than 67 kt CO2 between 2008 and 2013. Leveling surveys at Staufen and comprehensive background knowledge of the underground processes gained from different kinds of in-situ measurements at both locations deliver a suitable basis for this comparative study and the above stated objectives. The differences in location setting, i.e. urban versus rural site character, were intended to investigate the limitations in the applicability of PSI and SBAS.
For the MT-InSAR analysis, X-band images from the German TerraSAR-X and TanDEM-X satellites were acquired in the standard Stripmap mode with about 3 m spatial resolution in azimuth and range direction. Data acquisition lasted over a period of five years for Staufen (2008-2013), and four years for Ketzin (2009-2013). For the first approximation of the subsurface source, an inversion of the InSAR outcome in Staufen was applied. The modeled uplift based on complex hydromechanical simulations and a correlation analysis with bottomhole pressure data were used for comparison with MT-InSAR measurements at Ketzin.
In response to the defined objectives of this thesis, a higher level of detail can be achieved in mapping surface displacements without in-situ effort by using MT-InSAR in comparison to leveling (1). A clear delineation of the elliptical shaped uplift border and its magnitudes at different parts was possible at Staufen, with the exception of a vegetated area in the northwest. Vegetation coverage and the associated temporal signal decorrelation are the main limitations of MT-InSAR as clearly demonstrated at the Ketzin test site. They result in insufficient measurement point density and unwrapping issues. Therefore, spatial resolutions of one meter or better are recommended to achieve an adequate point density for local displacement analysis and to apply signal noise reduction. Leveling measurements can provide a complementary data source here, but require much effort pertaining to personnel even at the local scale. Horizontal motions could be identified at Staufen by only comparing the temporal evolution of the 1D line of sight (LOS) InSAR measurements with the available leveling data. An exception was the independent LOS decomposition using ascending and descending data sets for the period 2012-2013. The full 3D displacement field representation failed due to insufficient orbit-related, north-south sensitivity of the satellite-based measurements. By using the dense temporal mapping capabilities of the TerraSAR-X/TanDEM-X satellites after every 11 days, the temporal displacement evolution could be captured as good as that with leveling.
With respect to the tested methods and in the view of generality, SBAS should be preferred over PSI (2). SBAS delivered a higher point density, and was therefore less affected by phase unwrapping issues in both case studies. Linking surface motions with subsurface processes is possible when considering simplified geophysical models (3), but it still requires intensive research to gain a deep understanding.
The goal of this thesis is related to the question how to introduce and combine simultaneously plasmonic and photoswitching properties to different nano-objects. In this thesis I investigate the complexes between noble metal nanoparticles and cationic surfactants containing azobenzene units in their hydrophobic tail, employing absorption spectroscopy, surface zeta-potential, and electron microscopy.
In the first part of the thesis, the formation of complexes between negatively charged laser ablated spherical gold nanoparticles and cationic azobenzene surfactants in trans- conformation is explored. It is shown that the constitution of the complexes strongly depends on a surfactant-to-gold molar ratio. At certain molar ratios, particle self-assembly into nanochains and their aggregation have been registered. At higher surfactant concentrations, the surface charge of nanoparticles turned positive, attributed to the formation of the stabilizing double layer of azobenzene surfactants on gold nanoparticle surfaces. These gold-surfactant complexes remained colloidally stable. UV light induced trans-cis isomerization of azobenzene surfactant molecules and thus perturbed the stabilizing surfactant shell, causing nanoparticle aggregation. The results obtained with silver and silicon nanoparticles mimick those for the comprehensively studied gold nanoparticles, corroborating the proposed model of complex formation.
In the second part, the interaction between plasmonic metal nanoparticles (Au, Ag, Pd, alloy Au-Ag, Au-Pd), as well as silicon nanoparticles, and cis-isomers of azobenzene containing compounds is addressed. Cis-trans thermal isomerization of azobenzenes was enhanced in the presence of gold, palladium, and alloy gold-palladium nanoparticles. The influence of the surfactant structure and nanoparticle material on the azobenzene isomerization rate is expounded. Gold nanoparticles showed superior catalytic activity for thermal cis-trans isomerization of azobenzenes. In a joint project with theoretical chemists, we demonstrated that the possible physical origin of this phenomenon is the electron transfer between azobenzene moieties and nanoparticle surfaces.
In the third part, complexes between gold nanorods and azobenzene surfactants with different tail length were exposed to UV and blue light, inducing trans-cis and cis-trans isomerization of surfactant, respectively. At the same time, the position of longitudinal plasmonic absorption maximum of gold nanorods experienced reversible shift responding to the changes in local dielectric environment. Surface plasmon resonance condition allowed the estimation of the refractive index of azobenzene containing surfactants in solution.
Persistently high unemployment rates are a major threat to the social cohesion in many societies. To moderate the consequences of unemployment industrialized countries spend substantial shares of their GDP on labor market policies, while in recent years there has been a shift from passive measures, such as transfer payments, towards more activating elements which aim to promote the reintegration into the labor market. Although, there exists a wide range of evidence about the effects of traditional active labor market policies (ALMP) on participants’ subsequent labor market outcomes, a deeper understanding of the impact of these programs on the job search behavior and the interplay with long-term labor market outcomes is necessary. This allows policy makers to improve the design of labor market policies and the allocation of unemployed workers into specific programs. Moreover, previous studies have shown that many traditional ALMP programs, like public employment or training schemes, do not achieve the desired results. This underlines the importance of understanding the effect mechanisms, but also the need to develop innovative programs that are more effective. This thesis extends the existing literature with respect to several dimensions.
First, it analyzes the impact of job seekers’ beliefs about upcoming ALMPs programs on the effectiveness of realized treatments later during the unemployment spell. This provides important insights with respect to the job search process and relates potential anticipation effects (on the job seekers behavior before entering a program) to the vast literature evaluating the impact of participating in an ALMP program on subsequent outcomes. The empirical results show that training programs are more effective if the participants expect participation ex ante, while expected treatment effects are unrelated to the actual labor market outcomes of participants. A subsequent analysis of the effect mechanisms shows that job seekers who expect to participate also receive more information by their caseworker and show a higher willingness to adjust their search behavior in association with an upcoming ALMP program. The findings suggest that the effectiveness of training programs can be improved by providing more detailed information about the possibility of a future treatment early during the unemployment spell.
Second, the thesis investigates the effects of a relatively new class of programs that aim to improve the geographical mobility of unemployed workers with respect to the job search behavior, the subsequent job finding prospects and the returns to labor market mobility. To estimate the causal impact of these programs, it is exploited that local employment agencies have a degree of autonomy when deciding about the regional-specific policy mix. The findings show that the policy style of the employment agency indeed affects the job search behavior of unemployed workers. Job seekers who are assigned to agencies with higher preferences for mobility programs increase their search radius without affecting the total number of job applications. This shift of the search effort to distant regions leads to a higher probability to find a regular job and higher wages. Moreover, it is shown that participants in one of the subsidy programs who move to geographically distant region a earn significantly higher wages, end up in more stable jobs and face a higher long-run employment probability compared to non-participants.
Third, the thesis offers an empirical assessment of the unconfoundedness assumption with respect to the relevance of variables that are usually unobserved in studies evaluating ALMP programs. A unique dataset that combines administrative records and survey data allows us to observe detailed information on typical covariates, as well as usually unobserved variables including personality traits, attitudes, expectations, intergenerational information, as well as indicators about social networks and labor market flexibility. The findings show that, although our set of usually unobserved variables indeed has a significant effect on the selection into ALMP programs, the overall impact when estimating treatment effects is rather small.
Finally, the thesis also examines the importance of gender differences in reservation wages that allows assessing the importance of special ALMP programs targeting women. In particular, when including reservation wages in a wage decomposition exercise, the gender gap in realized wages becomes small and statistically insignificant. The strong connection between gender differences in reservation wages and realized wages raises the question how these differences in reservation wages are set in the first place. Since traditional covariates cannot sufficiently explain the gender gap in reservation wages, we perform subgroup analysis to better understand what the driving forces behind this gender gap are.
This cumulative dissertation consists of five chapters. In terms of research content, my thesis can be divided into two parts. Part one examines local interactions and spillover effects between small regional governments using spatial econometric methods. The second part focuses on patterns within municipalities and inspects which institutions of citizen participation, elections and local petitions, influence local housing policies.
Functional nanoporous carbon-based materials derived from oxocarbon-metal coordination complexes
(2017)
Nanoporous carbon based materials are of particular interest for both science and industry due to their exceptional properties such as a large surface area, high pore volume, high electroconductivity as well as high chemical and thermal stability. Benefiting from these advantageous properties, nanoporous carbons proved to be useful in various energy and environment related applications including energy storage and conversion, catalysis, gas sorption and separation technologies. The synthesis of nanoporous carbons classically involves thermal carbonization of the carbon precursors (e.g. phenolic resins, polyacrylonitrile, poly(vinyl alcohol) etc.) followed by an activation step and/or it makes use of classical hard or soft templates to obtain well-defined porous structures. However, these synthesis strategies are complicated and costly; and make use of hazardous chemicals, hindering their application for large-scale production. Furthermore, control over the carbon materials properties is challenging owing to the relatively unpredictable processes at the high carbonization temperatures.
In the present thesis, nanoporous carbon based materials are prepared by the direct heat treatment of crystalline precursor materials with pre-defined properties. This synthesis strategy does not require any additional carbon sources or classical hard- or soft templates. The highly stable and porous crystalline precursors are based on coordination compounds of the squarate and croconate ions with various divalent metal ions including Zn2+, Cu2+, Ni2+, and Co2+, respectively. Here, the structural properties of the crystals can be controlled by the choice of appropriate synthesis conditions such as the crystal aging temperature, the ligand/metal molar ratio, the metal ion, and the organic ligand system. In this context, the coordination of the squarate ions to Zn2+ yields porous 3D cube crystalline particles. The morphology of the cubes can be tuned from densely packed cubes with a smooth surface to cubes with intriguing micrometer-sized openings and voids which evolve on the centers of the low index faces as the crystal aging temperature is raised. By varying the molar ratio, the particle shape can be changed from truncated cubes to perfect cubes with right-angled edges.
These crystalline precursors can be easily transformed into the respective carbon based materials by heat treatment at elevated temperatures in a nitrogen atmosphere followed by a facile washing step. The resulting carbons are obtained in good yields and possess a hierarchical pore structure with well-organized and interconnected micro-, meso- and macropores. Moreover, high surface areas and large pore volumes of up to 1957 m2 g-1 and 2.31 cm3 g-1 are achieved, respectively, whereby the macroscopic structure of the precursors is preserved throughout the whole synthesis procedure.
Owing to these advantageous properties, the resulting carbon based materials represent promising supercapacitor electrode materials for energy storage applications. This is exemplarily demonstrated by employing the 3D hierarchical porous carbon cubes derived from squarate-zinc coordination compounds as electrode material showing a specific capacitance of 133 F g-1 in H2SO4 at a scan rate of 5 mV s-1 and retaining 67% of this specific capacitance when the scan rate is increased to 200 mV s-1.
In a further application, the porous carbon cubes derived from squarate-zinc coordination compounds are used as high surface area support material and decorated with nickel nanoparticles via an incipient wetness impregnation. The resulting composite material combines a high surface area, a hierarchical pore structure with high functionality and well-accessible pores. Moreover, owing to their regular micro-cube shape, they allow for a good packing of a fixed-bed flow reactor along with high column efficiency and a minimized pressure drop throughout the packed reactor. Therefore, the composite is employed as heterogeneous catalyst in the selective hydrogenation of 5-hydroxymethylfurfural to 2,5-dimethylfuran showing good catalytic performance and overcoming the conventional problem of column blocking.
Thinking about the rational design of 3D carbon geometries, the functions and properties of the resulting carbon-based materials can be further expanded by the rational introduction of heteroatoms (e.g. N, B, S, P, etc.) into the carbon structures in order to alter properties such as wettability, surface polarity as well as the electrochemical landscape. In this context, the use of crystalline materials based on oxocarbon-metal ion complexes can open a platform of highly functional materials for all processes that involve surface processes.
Personal Big Data
(2017)
Many users of cloud-based services are concerned about questions of data privacy. At the same time, they want to benefit from smart data-driven services, which require insight into a person’s individual behaviour. The modus operandi of user modelling is that data is sent to a remote server where the model is constructed and merged with other users’ data. This thesis proposes selective cloud computing, an alternative approach, in which the user model is constructed on the client-side and only an abstracted generalised version of the model is shared with the remote services.
In order to demonstrate the applicability of this approach, the thesis builds an exemplary client-side user modelling technique. As this thesis is carried out in the area of Geoinformatics and spatio-temporal data is particularly sensitive, the application domain for this experiment is the analysis and prediction of a user’s spatio-temporal behaviour.
The user modelling technique is grounded in an innovative conceptual model, which builds upon spatial network theory combined with time-geography. The spatio-temporal constraints of time-geography are applied to the network structure in order to create individual spatio-temporal action spaces. This concept is translated into a novel algorithmic user modelling approach which is solely driven by the user’s own spatio-temporal trajectory data that is generated by the user’s smartphone.
While modern smartphones offer a rich variety of sensory data, this thesis only makes use of spatio-temporal trajectory data, enriched by activity classification, as the input and foundation for the algorithmic model. The algorithmic model consists of three basal components: locations (vertices), trips (edges), and clusters (neighbourhoods).
After preprocessing the incoming trajectory data in order to identify locations, user feedback is used to train an artificial neural network to learn temporal patterns for certain location types (e.g. work, home, bus stop, etc.). This Artificial Neural Network (ANN) is used to automatically detect future location types by their spatio-temporal patterns. The same is done in order to predict the duration of stay at a certain location. Experiments revealed that neural nets were the most successful statistical and machine learning tool to detect those patterns. The location type identification algorithm reached an accuracy of 87.69%, the duration prediction on binned data was less successful and deviated by an average of 0.69 bins. A challenge for the location type classification, as well as for the subsequent components, was the imbalance of trips and connections as well as the low accuracy of the trajectory data. The imbalance is grounded in the fact that most users exhibit strong habitual patterns (e.g. home > work), while other patterns are rather rare by comparison. The accuracy problem derives from the energy-saving location sampling mode, which creates less accurate results.
Those locations are then used to build a network that represents the user’s spatio-temporal behaviour. An initial untrained ANN to predict movement on the network only reached 46% average accuracy. Only lowering the number of included edges, focusing on more common trips, increased the performance. In order to further improve the algorithm, the spatial trajectories were introduced into the predictions. To overcome the accuracy problem, trips between locations were clustered into so-called spatial corridors, which were intersected with the user’s current trajectory. The resulting intersected trips were ranked through a k-nearest-neighbour algorithm. This increased the performance to 56%. In a final step, a combination of a network and spatial clustering algorithm was built in order to create clusters, therein reducing the variety of possible trips. By only predicting the destination cluster instead of the exact location, it is possible to increase the performance to 75% including all classes.
A final set of components shows in two exemplary ways how to deduce additional inferences from the underlying spatio-temporal data. The first example presents a novel concept for predicting the ‘potential memorisation index’ for a certain location. The index is based on a cognitive model which derives the index from the user’s activity data in that area. The second example embeds each location in its urban fabric and thereby enriches its cluster’s metadata by further describing the temporal-semantic activity in an area (e.g. going to restaurants at noon).
The success of the client-side classification and prediction approach, despite the challenges of inaccurate and imbalanced data, supports the claimed benefits of the client-side modelling concept. Since modern data-driven services at some point do need to receive user data, the thesis’ computational model concludes with a concept for applying generalisation to semantic, temporal, and spatial data before sharing it with the remote service in order to comply with the overall goal to improve data privacy. In this context, the potentials of ensemble training (in regards to ANNs) are discussed in order to highlight the potential of only sharing the trained ANN instead of the raw input data.
While the results of our evaluation support the assets of the proposed framework, there are two important downsides of our approach compared to server-side modelling. First, both of these server-side advantages are rooted in the server’s access to multiple users’ data. This allows a remote service to predict spatio-in the user-specific data, which represents the second downside. While minor classes will likely be minor classes in a bigger dataset as well, for each class, there will still be more variety than in the user-specific dataset. The author emphasises that the approach presented in this work holds the potential to change the privacy paradigm in modern data-driven services. Finding combinations of client- and server-side modelling could prove a promising new path for data-driven innovation.
Beyond the technological perspective, throughout the thesis the author also offers a critical view on the data- and technology-driven development of this work. By introducing the client-side modelling with user-specific artificial neural networks, users generate their own algorithm. Those user-specific algorithms are influenced less by generalised biases or developers’ prejudices. Therefore, the user develops a more diverse and individual perspective through his or her user model. This concept picks up the idea of critical cartography, which questions the status quo of how space is perceived and represented.
Borehole instabilities are frequently encountered when drilling through finely laminated, organic rich shales (Økland and Cook, 1998; Ottesen, 2010; etc.); such instabilities should be avoided to assure a successful exploitation and safe production of the contained unconventional hydrocarbons. Borehole instabilities, such as borehole breakouts or drilling induced tensile fractures, may lead to poor cementing of the borehole annulus, difficulties with recording and interpretation of geophysical logs, low directional control and in the worst case the loss of the well. If these problems are not recognized and expertly remedied, pollution of the groundwater or the emission of gases into the atmosphere can occur since the migration paths of the hydrocarbons in the subsurface are not yet fully understood (e.g., Davies et al., 2014; Zoback et al., 2010). In addition, it is often mentioned that the drilling problems encountered and the resulting downtimes of the wellbore system in finely laminated shales significantly increase drilling costs (Fjaer et al., 2008; Aadnoy and Ong, 2003).
In order to understand and reduce the borehole instabilities during drilling in unconventional shales, we investigate stress-induced irregular extensions of the borehole diameter, which are also referred to as borehole breakouts. For this purpose, experiments with different borehole diameters, bedding plane angles and stress boundary conditions were performed on finely laminated Posidonia shales. The Lower Jurassic Posidonia shale is one of the most productive source rocks for conventional reservoirs in Europe and has the greatest potential for unconventional oil and gas in Europe (Littke et al., 2011).
In this work, Posidonia shale specimens from the North (PN) and South (PS) German basins were selected and characterized petrophysically and mechanically. The composition of the two shales is dominated by calcite (47-56%) followed by clays (23-28%) and quartz (16-17%). The remaining components are mainly pyrite and organic matter. The porosity of the shales varies considerably and is up to 10% for PS and 1% for PN, which is due to a larger deposition depth of PN. Both shales show marked elasticity and strength anisotropy, which can be attributed to a macroscopic distribution and orientation of soft and hard minerals. Under load the hard minerals form a load-bearing, supporting structure, while the soft minerals compensate the deformation. Therefore, if loaded parallel to the bedding, the Posidonia shale is more brittle than loaded normal to the bedding. The resulting elastic anisotropy, which can be defined by the ratio of the modulus of elasticity parallel and normal to the bedding, is about 50%, while the strength anisotropy (i.e., the ratio of uniaxial compressive strength normal and parallel to the bedding) is up to 66%. Based on the petrophysical characterization of the two rocks, a transverse isotropy (TVI) was derived. In general, PS is softer and weaker than PN, which is due to the stronger compaction of the material due to the higher burial depth.
Conventional triaxial borehole breakout experiments on specimens with different borehole diameters showed that, when the diameter of the borehole is increased, the stress required to initiate borehole breakout decreases to a constant value. This value can be expressed as the ratio of the tangential stress and the uniaxial compressive strength of the rock. The ratio increases exponentially with decreasing borehole diameter from about 2.5 for a 10 mm diameter hole to ~ 7 for a 1 mm borehole (increase of initiation stress by 280%) and can be described by a fracture mechanic based criterion. The reduction in borehole diameter is therefore a considerable aspect in reducing the risk of breakouts. New drilling techniques with significantly reduced borehole diameters, such as "fish-bone" holes, are already underway and are currently being tested (e.g., Xing et al., 2012).
The observed strength anisotropy and the TVI material behavior are also reflected in the observed breakout processes at the borehole wall. Drill holes normal to the bedding develop breakouts in a plane of isotropy and are not affected by the strength or elasticity anisotropy. The observed breakouts are point-symmetric and form compressive shear failure planes, which can be predicted by a Mohr-Coulomb failure approach. If the shear failure planes intersect, conjugate breakouts can be described as "dog-eared” breakouts.
While the initiation of breakouts for wells oriented normal to the stratification has been triggered by random local defects, reduced strengths parallel to bedding planes are the starting point for breakouts for wells parallel to the bedding. In the case of a deflected borehole trajectory, therefore, the observed failure type changes from shear-induced failure surfaces to buckling failure of individual layer packages. In addition, the breakout depths and widths increased, resulting in a stress-induced enlargement of the borehole cross-section and an increased output of rock material into the borehole. With the transition from shear to buckling failure and changing bedding plane angle with respect to the borehole axis, the stress required for inducing wellbore breakouts drops by 65%.
These observations under conventional triaxial stress boundary conditions could also be confirmed under true triaxial stress conditions. Here breakouts grew into the rock as a result of buckling failure, too. In this process, the broken layer packs rotate into the pressure-free drill hole and detach themselves from the surrounding rock by tensile cracking. The final breakout shape in Posidonia shale can be described as trapezoidal when the bedding planes are parallel to the greatest horizontal stress and to the borehole axis. In the event that the largest horizontal stress is normal to the stratification, breakouts were formed entirely by shear fractures between the stratification and required higher stresses to initiate similar to breakouts in conventional triaxial experiments with boreholes oriented normal to the bedding.
In the content of this work, a fracture mechanics-based failure criterion for conventional triaxial loading conditions in isotropic rocks (Dresen et al., 2010) has been successfully extended to true triaxial loading conditions in the transverse isotropic rock to predict the initiation of borehole breakouts. The criterion was successfully verified on the experiments carried out.
The extended failure criterion and the conclusions from the laboratory and numerical work may help to reduce the risk of borehole breakouts in unconventional shales.
Development of a reliable and environmentally friendly synthesis for fluorescence carbon nanodots
(2017)
Carbon nanodots (CNDs) have generated considerable attention due to their promising properties, e.g. high water solubility, chemical inertness, resistance to photobleaching, high biocompatibility and ease of functionalization. These properties render them ideal for a wide range of functions, e.g. electrochemical applications, waste water treatment, (photo)catalysis, bio-imaging and bio-technology, as well as chemical sensing, and optoelectronic devices like LEDs. In particular, the ability to prepare CNDs from a wide range of accessible organic materials makes them a potential alternative for conventional organic dyes and semiconductor quantum dots (QDs) in various applications. However, current synthesis methods are typically expensive and depend on complex and time-consuming processes or severe synthesis conditions and toxic chemicals. One way to reduce overall preparation costs is the use of biological waste as starting material. Hence, natural carbon sources such as pomelo peal, egg white and egg yolk, orange juice, and even eggshells, to name a few; have been used for the preparation of CNDs. While the use of waste is desirable, especially to avoid competition with essential food production, most starting-materials lack the essential purity and structural homogeneity to obtain homogeneous carbon dots. Furthermore, most synthesis approaches reported to date require extensive purification steps and have resulted in carbon dots with heterogeneous photoluminescent properties and indefinite composition. For this reason, among others, the relationship between CND structure (e.g. size, edge shape, functional groups and overall composition) and photophysical properties is yet not fully understood. This is particularly true for carbon dots displaying selective luminescence (one of their most intriguing properties), i.e. their PL emission wavelength can be tuned by varying the excitation wavelength.
In this work, a new reliable, economic, and environmentally-friendly one-step synthesis is established to obtain CNDs with well-defined and reproducible photoluminescence (PL) properties via the microwave-assisted hydrothermal treatment of starch, carboxylic acids and Tris-EDTA (TE) buffer as carbon- and nitrogen source, respectively. The presented microwave-assisted hydrothermal precursor carbonization (MW-hPC) is characterized by its cost-efficiency, simplicity, short reaction times, low environmental footprint, and high yields of approx. 80% (w/w). Furthermore, only a single synthesis step is necessary to obtain homogeneous water-soluble CNDs with no need for further purification.
Depending on starting materials and reaction conditions different types of CNDs have been prepared. The as-prepared CNDs exhibit reproducible, highly homogeneous and favourable PL properties with narrow emission bands (approx. 70nm FWHM), are non-blinking, and are ready to use without need for further purification, modification or surface passivation agents. Furthermore, the CNDs are comparatively small (approx. 2.0nm to 2.4nm) with narrow size distributions; are stable over a long period of time (at least one year), either in solution or as a dried solid; and maintain their PL properties when re-dispersed in solution. Depending on CND type, the PL quantum yield (PLQY) can be adjusted from as low as 1% to as high as 90%; one of the highest reported PLQY values (for CNDs) so far.
An essential part of this work was the utilization of a microwave synthesis reactor, allowing various batch sizes and precise control over reaction temperature and -time, pressure, and heating- and cooling rate, while also being safe to operate at elevated reaction conditions (e.g. 230 ±C and 30 bar). The hereby-achieved high sample throughput allowed, for the first time, the thorough investigation of a wide range of synthesis parameters, providing valuable insight into the CND formation. The influence of carbon- and nitrogen source, precursor concentration and -combination, reaction time and -temperature, batch size, and post-synthesis purification steps were carefully investigated regarding their influence on the optical properties of as-synthesized CNDs. In addition, the change in photophysical properties resulting from the conversion of CND solution into solid and back into the solution was investigated. Remarkably, upon freeze-drying the initial brown CND-solution turns into a non-fluorescent white/slightly yellow to brown solid which recovers PL in aqueous solution. Selected CND samples were also subject to EDX, FTIR, NMR, PL lifetime (TCSPC), particle size (TEM), TGA and XRD analysis. Besides structural characterization, the pH- and excitation dependent PL characteristics (i.e. selective luminescence) were examined; giving inside into the origin of photophysical properties and excitation dependent behaviour of CNDs. The obtained results support the notion that for CNDs the nature of the surface states determines the PL properties and that excitation dependent behaviour is caused by the “Giant Red-Edge Excitation Shift” (GREES).
Im kognitiven Vulnerabilitäts-Stress-Modell der Depression von A.T. Beck (1967, 1976) spielen dysfunktionale Einstellungen bei der Entstehung von Depression in Folge von erlebtem Stress eine zentrale Rolle. Diese Theorie prägt seit Jahrzehnten die ätiologische Erforschung der Depression, jedoch ist die Bedeutung dysfunktionaler Einstellungen im Prozess der Entstehung einer Depression insbesondere im Kindes- und Jugendalter nach wie vor unklar. Die vorliegende Arbeit widmet sich einigen in der bisherigen Forschung wenig behandelten Fragen. Diese betreffen u. a. die Möglichkeit nichtlinearer Effekte dysfunktionaler Einstellungen, Auswirkungen einer Stichprobenselektion, Entwicklungseffekte sowie die Spezifität etwaiger Zusammenhänge für eine depressive Symptomatik.
Zur Beantwortung dieser Fragen wurden Daten von zwei Messzeitpunkten der PIER-Studie, eines großangelegten Längsschnittprojekts über Entwicklungsrisiken im Kindes- und Jugendalter, genutzt. Kinder und Jugendliche im Alter von 9 bis 18 Jahren berichteten zweimal im Abstand von ca. 20 Monaten im Selbstberichtsverfahren über ihre dysfunktionalen Einstellungen, Symptome aus verschiedenen Störungsbereichen sowie über eingetretene Lebensereignisse.
Die Ergebnisse liefern Evidenz für ein Schwellenmodell, in dem dysfunktionale Einstellungen unabhängig von Alter und Geschlecht nur im höheren Ausprägungsbereich eine Wirkung als Vulnerabilitätsfaktor zeigen, während im niedrigen Ausprägungsbereich keine Zusammenhänge zur späteren Depressivität bestehen. Eine Wirkung als Vulnerabilitätsfaktor war zudem nur in der Subgruppe der anfänglich weitgehend symptomfreien Kinder und Jugendlichen zu beobachten. Das Schwellenmodell erwies sich als spezifisch für eine depressive Symptomatik, es zeigten sich jedoch auch (teilweise ebenfalls nichtlineare) Effekte dysfunktionaler Einstellungen auf die Entwicklung von Essstörungssymptomen und aggressivem Verhalten. Bei 9- bis 13-jährigen Jungen standen dysfunktionale Einstellungen zudem in Zusammenhang mit einer Tendenz, Stress in Leistungskontexten herbeizuführen.
Zusammen mit den von Sahyazici-Knaak (2015) berichteten Ergebnissen aus der PIER-Studie weisen die Befunde darauf hin, dass dysfunktionale Einstellungen im Kindes- und Jugendalter – je nach betrachteter Subgruppe – Ursache, Symptom und Konsequenz der Depression darstellen können. Die in der vorliegenden Arbeit gezeigten nichtlinearen Effekte dysfunktionaler Einstellungen und die Effekte der Stichprobenselektion bieten eine zumindest teilweise Erklärung für die Heterogenität früherer Forschungsergebnisse. Insgesamt lassen sie auf komplexe – und nicht ausschließlich negative – Auswirkungen dysfunktionaler Einstellungen schließen. Für eine adäquate Beurteilung der „Dysfunktionalität“ der von A.T. Beck so betitelten Einstellungen erscheint daher eine Berücksichtigung der betrachteten Personengruppe, der absoluten Ausprägungen und der fraglichen Symptomgruppen geboten.
The classical Navier-Stokes equations of hydrodynamics are usually written in terms of vector analysis. More promising is the formulation of these equations in the language of differential forms of degree one. In this way the study of Navier-Stokes equations includes the analysis of the de Rham complex. In particular, the Hodge theory for the de Rham complex enables one to eliminate the pressure from the equations. The Navier-Stokes equations constitute a parabolic system with a nonlinear term which makes sense only for one-forms. A simpler model of dynamics of incompressible viscous fluid is given by Burgers' equation. This work is aimed at the study of invariant structure of the Navier-Stokes equations which is closely related to the algebraic structure of the de Rham complex at step 1. To this end we introduce Navier-Stokes equations related to any elliptic quasicomplex of first order differential operators. These equations are quite similar to the classical Navier-Stokes equations including generalised velocity and pressure vectors. Elimination of the pressure from the generalised Navier-Stokes equations gives a good motivation for the study of the Neumann problem after Spencer for elliptic quasicomplexes. Such a study is also included in the work.We start this work by discussion of Lamé equations within the context of elliptic quasicomplexes on compact manifolds with boundary. The non-stationary Lamé equations form a hyperbolic system. However, the study of the first mixed problem for them gives a good experience to attack the linearised Navier-Stokes equations. On this base we describe a class of non-linear perturbations of the Navier-Stokes equations, for which the solvability results still hold.
Galaxies evolve on cosmological timescales and to study this evolution we can either study the stellar populations, tracing the star formation and chemical enrichment, or the dynamics, tracing interactions and mergers of galaxies as well as accretion. In the last decades this field has become one of the most active research areas in modern astrophysics and especially the use of integral field spectrographs furthered our understanding. This work is based on data of NGC 5102 obtained with the panoramic integral field spectrograph MUSE. The data are analysed with two separate and complementary approaches: In the first part, standard methods are used to measure the kinematics and than model the gravitational potential using these exceptionally high-quality data. In the second part I develop the new method of surface brightness fluctuation spectroscopy and quantitatively explore its potential to investigate the bright evolved stellar population.
Measuring the kinematics of NGC 5102 I discover that this low-luminosity S0 galaxy hosts two counter rotating discs. The more central stellar component co-rotates with the large amount of HI gas. Investigating the populations I find strong central age and metallicity gradients with a younger and more metal rich central population. The spectral resolution of MUSE does not allow to connect these population gradients with the two counter rotating discs.
The kinematic measurements are modelled with Jeans anisotropic models to infer the gravitational potential of NGC 5102. Under the self-consistent mass-follows-light assumption none of the Jeans models is able to reproduce the observed kinematics. To my knowledge this is the strongest evidence evidence for a dark matter dominated system obtained with this approach so far. Including a Navarro, Frenk & White dark matter halo immediately solves the discrepancies. A very robust result is the logarithmic slope of the total matter density. For this low-mass galaxy I find a value of -1.75 +- 0.04, shallower than an isothermal halo and even shallower than published values for more massive galaxies. This confirms a tentative relation between total mass slope and stellar mass of galaxies.
The Surface Brightness Fluctuation (SBF) method is a well established distance measure, but due to its sensitive to bright stars also used to study evolved stars in unresolved stellar populations. The wide-field spectrograph MUSE offers the possibility to apply this technique for the first time to spectroscopic data. In this thesis I develop the spectroscopic SBF technique and measure the first SBF spectrum of any galaxy. I discuss the challenges for measuring SBF spectra that rise due to the complexity of integral field spectrographs compared to imaging instruments.
Since decades, stellar population models indicate that SBFs in intermediate-to-old stellar systems are dominated by red giant branch and asymptotic giant branch stars. Especially the later carry significant model uncertainties, making these stars a scientifically interesting target. Comparing the NGC 5102 SBF spectrum with stellar spectra I show for the first time that M-type giants cause the fluctuations. Stellar evolution models suggest that also carbon rich thermally pulsating asymptotic giant branch stars should leave a detectable signal in the SBF spectrum. I cannot detect a significant contribution from these stars in the NGC 5102 SBF spectrum.
I have written a stellar population synthesis tool that predicts for the first time SBF spectra. I compute two sets of population models: based on observed and on theoretical stellar spectra. In comparing the two models I find that the models based on observed spectra predict weaker molecular features. The comparison with the NGC 5102 spectrum reveals that these models are in better agreement with the data.
Throughout all different socio-historical tensions undergone by the Latin American modernit(ies), the literary-historical production as well as the reflection on the topic - regional, national, supranational and/or continental – have been part of the critical and intellectual itinerary of very significant political and cultural projects, whose particular development allows the analysis of the socio-discursive dynamics fulfilled by the literary historiography in the search of a historical conscience and representation of the esthetic-literary processes.
In present literary and cultural Central American literary studies, the academic thought on the development of the literary historiography has given place to some works whose main objects of study involve a significant corpus of national literature histories published mainly in the 20th century, between the forties and the eighties. Although these studies differ greatly from the vast academic production undertaken by the literary critics in the last two decades, the field of research of the literary historiography in Central America has made a theoretical-methodological effort, as of the eighties and until now, to analyze the local literary-historical productions.
However, this effort was carried out more systematically in the last five years of the 20th century, within the Central American democratic transition and post-war context, when a national, supra national and transnational model of literary history was boosted. This gave place to the creation and launching of the project Hacia una Historia de las Literaturas Centroamericanas (HILCAS) at the beginning of the new millennium.
Given the ideological relevance which the literary historiography has played in the process of the historical formation of the Hispano-American States, and whose philological tradition has also had an impact in the various Central American nation states, the emergence of this historiographic project marks an important rupture in relation with the national paradigms, and it is also manifested in a movement of transition and tension with regard to the new cultural, comparative and transareal dynamics, which seek to understand the geographical, transnational, medial and transdisciplinary movements within which the esthetic narrative processes and the idea and formation of a critical Central American subject gain shape.
Taking this aspect into account, our study puts forward as its main hypothesis that the historiographic thought developed as a consequence of the project Hacia una Historia de las Literaturas Centroamericanas (HILCAS) constitutes a socio-discursive practice, which reflects the formation of a historic-literary conscience and of a critical intellectual subject, an emergence that takes place between the mid-nineties and the first decade of the 21st century.
In this respect, and taking as a basis the general purpose of this investigation indicated before, the main justification for our object of study consists of making the Central American historiographic reflection visible as a part of the epistemological and cultural changes shown by the Latin American historiographic thought, and from which a new way of conceptualization of the space, the coexistence and the historic conscience emerge with regard to the esthetic-literary practices and processes.
Based on the field and hypothesis stated before, the general purpose of this research is framed by the socio-discursive dimension fulfilled by the Latin American literary historiography, and it aims to analyze the Central American historical-literary thought developed between the second half of the nineties and the beginning of the first decade of the 21st century.
Import and decomposition of dissolved organic carbon in pre-dams of drinking water reservoirs
(2017)
Dissolved organic carbon (DOC) depicts a key component in the aquatic carbon cycle as well as for drinking water production from surface waters. DOC concentrations increased in water bodies of the northern hemisphere in the last decades, posing ecological consequences and water quality problems. Within the pelagic zone of lakes and reservoirs, the DOC pool is greatly affected by biological activity as DOC is simultaneously produced and decomposed. This thesis aimed for a conceptual understanding of organic carbon cycling and DOC quality changes under differing hydrological and trophic conditions. Further, the occurrence of aquatic priming was investigated, which has been proposed as a potential process facilitating the microbial decomposition of stable allochthonous DOC within the pelagic zone.
To study organic carbon cycling under different hydrological conditions, quantitative and qualitative investigations were carried out in three pre-dams of drinking water reservoirs exhibiting a gradient in DOC concentrations and trophic states. All pre-dams were mainly autotrophic in their epilimnia. Discharge and temperature were identified as the key factors regulating net production and respiration in the upper water layers of the pre-dams. Considerable high autochthonous production was observed during the summer season under higher trophic status and base flow conditions. Up to 30% of the total gained organic carbon was produced within the epilimnia. Consequently, this affected the DOC quality within the pre-dams over the year and enhanced characteristics of algae-derived DOC were observed during base flow in summer. Allochthonous derived DOC dominated at high discharges and oligotrophic conditions when production and respiration were low. These results underline that also small impoundments with typically low water residence times are hotspots of carbon cycling, significantly altering water quality in dependence of discharge conditions, temperature and trophic status. Further, it highlights that these factors need to be considered in future water management as increasing temperatures and altered precipitation patterns are predicted in the context of climate change.
Under base flow conditions, heterotrophic bacteria preferentially utilized older DOC components with a conventional radiocarbon age of 195-395 years before present (i.e. before 1950). In contrast, younger carbon components (modern, i.e. produced after 1950) were mineralized following a storm flow event. This highlights that age and recalcitrance of DOC are independent from each other. To assess the ages of the microbially consumed DOC, a simplified method was developed to recover the respired CO2 from heterotrophic bacterioplankton for carbon isotope analyses (13C, 14C). The advantages of the method comprise the operation of replicate incubations at in-situ temperatures using standard laboratory equipment and thus enabling an application in a broad range of conditions.
Aquatic priming was investigated in laboratory experiments during the microbial decomposition of two terrestrial DOC substrates (peat water and soil leachate). Thereby, natural phytoplankton served as a source of labile organic matter and the total DOC pool increased throughout the experiments due to exudation and cell lysis of the growing phytoplankton. A priming effect for both terrestrial DOC substrates was revealed via carbon isotope analysis and mixing models. Thereby, priming was more pronounced for the peat water than for the soil leachate. This indicates that the DOC source and the amount of the added labile organic matter might influence the magnitude of a priming effect. Additional analysis via high-resolution mass spectrometry revealed that oxidized, unsaturated compounds were more strongly decomposed under priming (i.e. in phytoplankton presence). Given the observed increase in DOC concentrations during the experiments, it can be concluded that aquatic priming is not easily detectable via net concentration changes alone and could be considered as a qualitative effect.
The knowledge gained from this thesis contributes to the understanding of aquatic carbon cycling and demonstrated how DOC dynamics in freshwaters vary with hydrological, seasonal and trophic conditions. It further demonstrated that aquatic priming contributes to the microbial transformation of organic carbon and the observed decay of allochthonous DOC during transport in inland waters.
For several decades, researchers have tried to explain how speakers of more than one language (multilinguals) manage to keep their languages separate and to switch from one language to the other depending on the context. This ability of multilingual speakers to use the intended language, while avoiding interference from the other language(s) has recently been termed “language control”.
A multitude of studies showed that when bilinguals process one language, the other language is also activated and might compete for selection. According to the most influential model of language control developed over the last two decades, competition from the non-intended language is solved via inhibition. In particular, the Inhibitory Control (IC) model proposed by Green (1998) puts forward that the amount of inhibition applied to the non-relevant language depends on its dominance, in that the stronger the language the greater the strength of inhibition applied to it. Within this account, the cost required to reactivate a previously inhibited language depends on the amount of inhibition previously exerted on it, that is, reactivation costs are greater for a stronger compared to a weaker language. In a nutshell, according to the IC model, language control is determined by language dominance.
The goal of the present dissertation is to investigate the extent to which language control in multilinguals is affected by language dominance and whether and how other factors might influence this process. Three main factors are considered in this work: (i) the time speakers have to prepare for a certain language or PREPARATION TIME, (ii) the type of languages involved in the interactional context or LANGUAGE TYPOLOGY, and (iii) the PROCESSING MODALITY, that is, whether the way languages are controlled differs between reception and production.
The results obtained in the four manuscripts, either published or in revision, indicate that language dominance alone does not suffice to explain language switching patterns. In particular, the present thesis shows that language control is profoundly affected by each of the three variables described above. More generally, the findings obtained in the present dissertation indicate that language control in multilingual speakers is a much more dynamic system than previously believed and is not exclusively determined by language dominance, as predicted by the IC model (Green, 1998).
The timing and location of the two largest earthquakes of the 21st century (Sumatra, 2004 and Tohoku 2011, events) greatly surprised the scientific community, indicating that the deformation processes that precede and follow great megathrust earthquakes remain enigmatic. During these phases before and after the earthquake a combination of multi-scale complex processes are acting simultaneously: Stresses built up by long-term tectonic motions are modified by sudden jerky deformations during earthquakes, before being restored by multiple ensuing relaxation processes.
This thesis details a cross-scale thermomechanical model developed with the aim of simulating the entire subduction process from earthquake (1 minute) to million years’ time scale, excluding only rupture propagation. The model employs elasticity, non-linear transient viscous rheology, and rate-and-state friction. It generates spontaneous earthquake sequences, and, by using an adaptive time-step algorithm, recreates the deformation process as observed naturally over single and multiple seismic cycles. The model is thoroughly tested by comparing results to those from known high- resolution solutions of generic modeling setups widely used in modeling of rupture propagation. It is demonstrated, that while not modeling rupture propagation explicitly, the modeling procedure correctly recognizes the appearance of instability (earthquake) and correctly simulates the cumulative slip at a fault during great earthquake by means of a quasi-dynamic approximation.
A set of 2D models is used to study the effects of non-linear transient rheology on the postseismic processes following great earthquakes. Our models predict that the viscosity in the mantle wedge drops by 3 to 4 orders of magnitude during a great earthquake with magnitude above 9. This drop in viscosity results in spatial scales and timings of the relaxation processes following the earthquakes that are significantly different to previous estimates. These models replicate centuries long seismic cycles exhibited by the greatest earthquakes (like the Great Chile 1960 Earthquake) and are consistent with the major features of postseismic surface displacements recorded after the Great Tohoku Earthquake.
The 2D models are also applied to study key factors controlling maximum magnitudes of earthquakes in subduction zones. Even though methods of instrumentally observing earthquakes at subduction zones have rapidly improved in recent decades, the characteristic recurrence interval of giant earthquakes (Mw>8.5) is much larger than the currently available observational record and therefore the necessary conditions for giant earthquakes are not clear. Statistical studies have recognized the importance of the slab shape and its surface roughness, state of the strain of the upper plate and thickness of sediments filling the trenches. In this thesis we attempt to explain these observations and to identify key controlling parameters. We test a set of 2D models representing great earthquake seismic cycles at known subduction zones with various known geometries, megathrust friction coefficients, and convergence rates implemented. We found that low-angle subduction (large effect) and thick sediments in the subduction channel (smaller effect) are the fundamental necessary conditions for generating giant earthquakes, while the change of subduction velocity from 10 to 3.5 cm/yr has a lower effect. Modeling results also suggest that having thick sediments in the subduction channel causes low static friction, resulting in neutral or slightly compressive deformation in the overriding plate for low-angle subduction zones. These modeling results agree well with observations for the largest earthquakes. The model predicts the largest possible earthquakes for subduction zones of given dipping angles. The predicted maximum magnitudes exactly threshold magnitudes of all known giant earthquakes of 20th and 21st centuries.
The clear limitation of most of the models developed in the thesis is their 2D nature. Development of 3D models with comparable resolution and complexity will require significant advances in numerical techniques. Nevertheless, we conducted a series of low-resolution 3D models to study the interaction between two large asperities at a subduction interface separated by an aseismic gap of varying width. The novelty of the model is that it considers behavior of the asperities during multiple seismic cycles. As expected, models show that an aseismic gap with a narrow width could not prevent rupture propagation from one asperity to another, and that rupture always crosses the entire model. When the gap becomes too wide, asperities do not interact anymore and rupture independently. However, an interesting mode of interaction was observed in the model with an intermediate width of the aseismic gap: In this model the asperities began to stably rupture in anti-phase following multiple seismic cycles. These 3D modeling results, while insightful, must be considered preliminary because of the limitations in resolution.
The technique developed in this thesis for cross-scale modeling of seismic cycles can be used to study the effects of multiple seismic cycles on the long-term deformation of the upper plate. The technique can be also extended to the case of continental transform faults and for the advanced 3D modeling of specific subduction zones. This will require further development of numerical techniques and adaptation of the existing advanced highly scalable parallel codes like LAMEM and ASPECT.
The functioning of the surface water-groundwater interface as buffer, filter and reactive zone is important for water quality, ecological health and resilience of streams and riparian ecosystems. Solute and heat exchange across this interface is driven by the advection of water. Characterizing the flow conditions in the streambed is challenging as flow patterns are often complex and multidimensional, driven by surface hydraulic gradients and groundwater discharge. This thesis presents the results of an integrated approach of studies, ranging from the acquisition of field data, the development of analytical and numerical approaches to analyse vertical temperature profiles to the detailed, fully-integrated 3D numerical modelling of water and heat flux at the reach scale. All techniques were applied in order to characterize exchange flux between stream and groundwater, hyporheic flow paths and temperature patterns.
The study was conducted at a reach-scale section of the lowland Selke River, characterized by distinctive pool riffle sequences and fluvial islands and gravel bars. Continuous time series of hydraulic heads and temperatures were measured at different depths in the river bank, the hyporheic zone and within the river. The analyses of the measured diurnal temperature variation in riverbed sediments provided detailed information about the exchange flux between river and groundwater. Beyond the one-dimensional vertical water flow in the riverbed sediment, hyporheic and parafluvial flow patterns were identified. Subsurface flow direction and magnitude around fluvial islands and gravel bars at the study site strongly depended on the position around the geomorphological structures and on the river stage. Horizontal water flux in the streambed substantially impacted temperature patterns in the streambed. At locations with substantial horizontal fluxes the penetration depths of daily temperature fluctuations was reduced in comparison to purely vertical exchange conditions.
The calibrated and validated 3D fully-integrated model of reach-scale water and heat fluxes across the river-groundwater interface was able to accurately represent the real system. The magnitude and variations of the simulated temperatures matched the observed ones, with an average mean absolute error of 0.7 °C and an average Nash Sutcliffe Efficiency of 0.87. The simulation results showed that the water and heat exchange at the surface water-groundwater interface is highly variable in space and time with zones of daily temperature oscillations penetrating deep into the sediment and spots of daily constant temperature following the average groundwater temperature. The average hyporheic flow path temperature was found to strongly correlate with the flow path residence time (flow path length) and the temperature gradient between river and groundwater. Despite the complexity of these processes, the simulation results allowed the derivation of a general empirical relationship between the hyporheic residence times and temperature patterns. The presented results improve our understanding of the complex spatial and temporal dynamics of water flux and thermal processes within the shallow streambed. Understanding these links provides a general basis from which to assess hyporheic temperature conditions in river reaches.
Trends in precipitation over Germany and the Rhine basin related to changes in weather patterns
(2017)
Precipitation as the central meteorological feature for agriculture, water security, and human well-being amongst others, has gained special attention ever since. Lack of precipitation may have devastating effects such as crop failure and water scarcity. Abundance of precipitation, on the other hand, may as well result in hazardous events such as flooding and again crop failure. Thus, great effort has been spent on tracking changes in precipitation and relating them to underlying processes. Particularly in the face of global warming and given the link between temperature and atmospheric water holding capacity, research is needed to understand the effect of climate change on precipitation.
The present work aims at understanding past changes in precipitation and other meteorological variables. Trends were detected for various time periods and related to associated changes in large-scale atmospheric circulation. The results derived in this thesis may be used as the foundation for attributing changes in floods to climate change. Assumptions needed for the downscaling of large-scale circulation model output to local climate stations are tested and verified here.
In a first step, changes in precipitation over Germany were detected, focussing not only on precipitation totals, but also on properties of the statistical distribution, transition probabilities as a measure for wet/dry spells, and extreme precipitation events.
Shifting the spatial focus to the Rhine catchment as one of the major water lifelines of Europe and the largest river basin in Germany, detected trends in precipitation and other meteorological variables were analysed in relation to states of an ``optimal'' weather pattern classification. The weather pattern classification was developed seeking the best skill in explaining the variance of local climate variables.
The last question addressed whether observed changes in local climate variables are attributable to changes in the frequency of weather patterns or rather to changes within the patterns itself. A common assumption for a downscaling approach using weather patterns and a stochastic weather generator is that climate change is expressed only as a changed occurrence of patterns with the pattern properties remaining constant. This assumption was validated and the ability of the latest generation of general circulation models to reproduce the weather patterns was evaluated.
% Paper 1
Precipitation changes in Germany in the period 1951-2006 can be summarised briefly as negative in summer and positive in all other seasons. Different precipitation characteristics confirm the trends in total precipitation: while winter mean and extreme precipitation have increased, wet spells tend to be longer as well (expressed as increased probability for a wet day followed by another wet day). For summer the opposite was observed: reduced total precipitation, supported by decreasing mean and extreme precipitation and reflected in an increasing length of dry spells.
Apart from this general summary for the whole of Germany, the spatial distribution within the country is much more differentiated. Increases in winter precipitation are most pronounced in the north-west and south-east of Germany, while precipitation increases are highest in the west for spring and in the south for autumn. Decreasing summer precipitation was observed in most regions of Germany, with particular focus on the south and west.
The seasonal picture, however, was again differently represented in the contributing months, e.g.\ increasing autumn precipitation in the south of Germany is formed by strong trends in the south-west in October and in the south-east in November. These results emphasise the high spatial and temporal organisation of precipitation changes.
% Paper 2
The next step towards attributing precipitation trends to changes in large-scale atmospheric patterns was the derivation of a weather pattern classification that sufficiently stratifies the local climate variables under investigation. Focussing on temperature, radiation, and humidity in addition to precipitation, a classification based on mean sea level pressure, near-surface temperature, and specific humidity was found to have the best skill in explaining the variance of the local variables. A rather high number of 40 patterns was selected, allowing typical pressure patterns being assigned to specific seasons by the associated temperature patterns. While the skill in explaining precipitation variance is rather low, better skill was achieved for radiation and, of course, temperature.
Most of the recent GCMs from the CMIP5 ensemble were found to reproduce these weather patterns sufficiently well in terms of frequency, seasonality, and persistence.
% Paper 3
Finally, the weather patterns were analysed for trends in pattern frequency, seasonality, persistence, and trends in pattern-specific precipitation and temperature. To overcome uncertainties in trend detection resulting from the selected time period, all possible periods in 1901-2010 with a minimum length of 31 years were considered. Thus, the assumption of a constant link between patterns and local weather was tested rigorously. This assumption was found to hold true only partly. While changes in temperature are mainly attributable to changes in pattern frequency, for precipitation a substantial amount of change was detected within individual patterns.
Magnitude and even sign of trends depend highly on the selected time period. The frequency of certain patterns is related to the long-term variability of large-scale circulation modes.
Changes in precipitation were found to be heterogeneous not only in space, but also in time - statements on trends are only valid for the specific time period under investigation. While some part of the trends can be attributed to changes in the large-scale circulation, distinct changes were found within single weather patterns as well.
The results emphasise the need to analyse multiple periods for thorough trend detection wherever possible and add some note of caution to the application of downscaling approaches based on weather patterns, as they might misinterpret the effect of climate change due to neglecting within-type trends.
This study was inspired by the desire to contribute to literature on performance management from the context of a developing country. The guiding research questions were: How do managers use performance information in decision making? Why do managers use performance information the way they do? The study was based on theoretical strands of neo-patrimonialism and new institutionalism. The nature of the inquiry informed the choice of a qualitative case study research design. Data was assembled through face-to-face interviews, some observations, and collection of documents from managers at the levels of the directorate, division, and section/units. The managers who were the focus of this study are current or former staff members of the state departments in Kenya’s national Ministry of Agriculture, Livestock, and Fisheries as well as from departments responsible for coordination of performance related reforms.
The findings of this study show that performance information is regularly produced but its use by managers varies. Examples of use include preparing reports to external bodies, making decisions for resource re-allocation, making recommendations for rewards and sanctions, and policy advisory. On categorizing the forms of use as passive, purposeful, political or perverse, evidence shows that they overlap and that some of the forms are so closely related that it is difficult to separate them empirically.
On what can explain the forms of use established, four factors namely; political will and leadership; organizational capacity; administrative culture; and managers’ interests and attitudes, were investigated. While acknowledging the interrelatedness and even overlapping of the factors, the study demonstrates that there is explanatory power to each though with varying depth and scope. The study thus concludes that: Inconsistent political will and leadership for performance management reforms explain forms of use that are passive, political and perverse. Low organizational capacity could best explain passive and some limited aspects of purposeful use. Informal, personal and competitive administrative culture is associated with purposeful use and mostly with political and perverse use. Limited interest and apprehensive attitude are best associated with passive use.
The study contributes to the literature particularly in how institutions in a context of neo-patrimonialism shape performance information use. It recommends that further research is necessary to establish how neo-patrimonialism positively affects performance oriented reforms. This is interesting in particular given the emerging thinking on pockets of effectiveness and developmental patrimonialism. This is important since it is expected that performance related reforms will continue to be advocated in developing countries in the foreseeable future.
Thermal cis-trans isomerization of azobenzene studied by path sampling and QM/MM stochastic dynamics
(2017)
Azobenzene-based molecular photoswitches have extensively been applied to biological systems, involving photo-control of peptides, lipids and nucleic acids. The isomerization between the stable trans and the metastable cis state of the azo moieties leads to pronounced changes in shape and other physico-chemical properties of the molecules into which they are incorporated. Fast switching can be induced via transitions to excited electronic states and fine-tuned by a large number of different substituents at the phenyl rings. But a rational design of tailor-made azo groups also requires control of their stability in the dark, the half-lifetime of the cis isomer. In computational chemistry, thermally activated barrier crossing on the ground state Born-Oppenheimer surface can efficiently be estimated with Eyring’s transition state theory (TST) approach; the growing complexity of the azo moiety and a rather heterogeneous environment, however, may render some of the underlying simplifying assumptions problematic.
In this dissertation, a computational approach is established to remove two restrictions at once: the environment is modeled explicitly by employing a quantum mechanical/molecular mechanics (QM/MM) description; and the isomerization process is tracked by analyzing complete dynamical pathways between stable states. The suitability of this description is validated by using two test systems, pure azo benzene and a derivative with electron donating and electron withdrawing substituents (“push-pull” azobenzene). Each system is studied in the gas phase, in toluene and in polar DMSO solvent. The azo molecules are treated at the QM level using a very recent, semi-empirical approximation to density functional theory (density functional tight binding approximation). Reactive pathways are sampled by implementing a version of the so-called transition path sampling method (TPS), without introducing any bias into the system dynamics. By analyzing ensembles of reactive trajectories, the change in isomerization pathway from linear inversion to rotation in going from apolar to polar solvent, predicted by the TST approach, could be verified for the push-pull derivative. At the same time, the mere presence of explicit solvation is seen to broaden the distribution of isomerization pathways, an effect TST cannot account for.
Using likelihood maximization based on the TPS shooting history, an improved reaction coordinate was identified as a sine-cosine combination of the central bend angles and the rotation dihedral, r (ω,α,α′). The computational van’t Hoff analysis for the activation entropies was performed to gain further insight into the differential role of solvent for the case of the unsubstituted and the push-pull azobenzene. In agreement with the experiment, it yielded positive activation entropies for azobenzene in the DMSO solvent while negative for the push-pull derivative, reflecting the induced ordering of solvent around the more dipolar transition state associated to the latter compound. Also, the dynamically corrected rate constants were evaluated using the reactive flux approach where an increase comparable to the experimental one was observed for a high polarity medium for both azobenzene derivatives.
We analyze an inverse noisy regression model under random design with the aim of estimating the unknown target function based on a given set of data, drawn according to some unknown probability distribution. Our estimators are all constructed by kernel methods, which depend on a Reproducing Kernel Hilbert Space structure using spectral regularization methods.
A first main result establishes upper and lower bounds for the rate of convergence under a given source condition assumption, restricting the class of admissible distributions. But since kernel methods scale poorly when massive datasets are involved, we study one example for saving computation time and memory requirements in more detail. We show that Parallelizing spectral algorithms also leads to minimax optimal rates of convergence provided the number of machines is chosen appropriately.
We emphasize that so far all estimators depend on the assumed a-priori smoothness of the target function and on the eigenvalue decay of the kernel covariance operator, which are in general unknown. To obtain good purely data driven estimators constitutes the problem of adaptivity which we handle for the single machine problem via a version of the Lepskii principle.
Culture-driven innovation
(2017)
This cumulative dissertation deals with the potential of underexplored cultural sources for innovation.
Nowadays, firms recognize an increasing demand for innovation to keep pace with an ever-growing dynamic worldwide competition. Knowledge is one of the most crucial sources and resource, while until now innovation has been foremost driven by technology. But since the last years, we have been witnessing a change from technology's role as a driver of innovation to an enabler of innovation. Innovative products and services increasingly differentiate through emotional qualities and user experience. These experiences are hard to grasp and require alignment in innovation management theory and practice.
This work cares about culture in a broader matter as a source for innovation. It investigates the requirements and fundamentals for "culture-driven innovation" by studying where and how to unlock cultural sources. The research questions are the following: What are cultural sources for knowledge and innovation? Where can one find cultural sources and how to tap into them?
The dissertation starts with an overview of its central terms and introduces cultural theories as an overarching frame to study cultural sources for innovation systematically. Here, knowledge is not understood as something an organization owns like a material resource, but it is seen as something created and taking place in practices. Such a practice theoretical lens inheres the rejection of the traditional economic depiction of the rational Homo Oeconomicus. Nevertheless, it also rejects the idea of the Homo Sociologicus about the strong impact of society and its values on individual actions. Practice theory approaches take account of both concepts by underscoring the dualism of individual (agency, micro-level) and structure (society, macro-level). Following this, organizations are no enclosed entities but embedded within their socio-cultural environment, which shapes them and is also shaped by them.
Then, the first article of this dissertation acknowledges a methodological stance of this dualism by discussing how mixed methods support an integrated approach to study the micro- and macro-level. The article focuses on networks (thus communities) as a central research unit within studies of entrepreneurship and innovation.
The second article contains a network analysis and depicts communities as central loci for cultural sources and knowledge. With data from the platform Meetup.com about events etc., the study explores which overarching communities and themes have been evolved in Berlin's start up and tech scene.
While the latter study was about where to find new cultural sources, the last article addresses how to unlock such knowledge sources. It develops the concept of a cultural absorptive capacity, that is the capability of organizations to open up towards cultural sources. Furthermore, the article points to the role of knowledge intermediaries in the early phases of knowledge acquisition. Two case studies on companies working with artists illustrate the roles of such intermediaries and how they support firms to gain knowledge from cultural sources.
Overall, this dissertation contributes to a better understanding of culture as a source for innovation from a theoretical, methodological, and practitioners' point of view. It provides basic research to unlock the potential of such new knowledge sources for companies - sources that so far have been neglected in innovation management.
Bobrowski hatte nach dem Abitur die Absicht geäußert, Kunstgeschichte zu studieren, doch Krieg und Kriegsgefangenschaft vereitelten seinen Plan: Der Wehrmachtsangehörige wurde einzig im Winter 1941/1942 für ein Studiensemester an der Universität Berlin vom Kriegsdienst freigestellt. Nachhaltig beeindruckt war Bobrowski insbesondere von der Vorlesung „Deutsche Kunst der Goethezeit“ des Lehrstuhlinhabers Wilhelm Pinder. Trotz eines grundlegenden Einflusses ist indessen zu keinem Zeitpunkt Pinders ideologischer Hintergrund in Bobrowskis Gedichten manifest geworden. Nach der Rückkehr aus sowjetischer Gefangenschaft an Weihnachten 1949 war für den mittlerweile Zweiunddreißigjährigen an ein Studium nicht mehr zu denken. Die lebenslange intermediale Auseinandersetzung mit Werken der bildenden Kunst in seinem Œuvre kann indessen als Ausdruck seiner vielfältigen kulturgeschichtlichen Interessen und Neigungen interpretiert werden. Die Lebensphasen des Dichters korrelieren mit einer motivischen Entwicklung seiner Bildgedichte: Insbesondere half ihm die unantastbare Ästhetik bedeutender Kunstwerke, das Grauen der letzten Kriegsjahre und die Entbehrungen in sowjetischer Kriegsgefangenschaft zu überwinden. Didaktisch-moralische Zielsetzungen prägten zunächst die in den Jahren nach seiner Heimkehr entstandenen Gedichte, bevor sich Bobrowski inhaltlich und formal von diesem Gedichttypus zu lösen vermochte und vermehrt Gedichte zu schreiben begann, die kulturgeschichtliche Dimensionen annahmen und historische, mythologische, biblische und religionsphilosophische Themen in epochenübergreifende Zusammenhänge stellten. Die Gedichte über die Künstler Jawlensky und Calder berühren gleichzeitig kulturlandschaftliche Aspekte. Im letzten Lebensjahrzehnt interessierte sich Bobrowski zunehmend für die Kunst des 20. Jahrhunderts, während die moderne Architektur aus seinem Werk ausgeklammert blieb.
Architektur bildet eine Leitmotivik in Bobrowskis lyrischem Werk. Die übertragene Bedeutungsebene der in den Gedichten benannten sakralen und profanen Einzelbauten, aber auch der städtischen und dörflichen Ensembles sowie einzelner Gebäudeteile, verändert sich mehrfach im Laufe der Jahre. Ausgehend von traditionellen, paargereimten Jugendgedichten in jambischem Versmaß, in denen architektonische Elemente Teil einer Wahrnehmung bilden, die alles Außerästhetische ausblendet, wandelt sich der Sinngehalt der Sakral- und Profanbauten in Bobrowskis lyrischem Werk ein erstes Mal während den Kriegsjahren in Russland, die der Wehrmachtsangehörige am Ilmensee verbracht hat. In den damals entstandenen Oden zeugen die architektonischen Relikte von Leid, Tod und Zerstörung. Noch fehlt indessen der später so zentrale Gedanke der Schuld, der erst im Rückblick auf jene Zeit in den Gedichten, die nach der Rückkehr aus der Kriegsgefangenschaft bis zu Bobrowskis frühem Tod entstanden sind, thematisiert worden ist.
Gegen Ende des Kriegs und in den Jahren der Kriegsgefangenschaft besinnt sich Bobrowski erneut auf Heimatthemen, und die Architektur in seinen Gedichten wird zu einem ästhetisch überhöhten Fluchtpunkt seiner Sehnsucht nach Ostpreußen und dem Memelgebiet. In Kriegsgefangenschaft tritt erstmals der Aspekt des Sublimen in seinen Gedichten auf, und zwar sowohl bezogen auf die Malerei als auch auf die Architektur. Dieser Gedanke wird einerseits nach der Rückkehr nach Berlin in den Gedichten über die Architektur gotischer Kathedralen und das bauliche Erbe des Klassizismus weitergesponnen, doch steht in den damals entstandenen Gedichten das Kulturerbe Europas auch für historisches Unrecht und eine schwere, weit zurückreichende Schuld.
Von dieser auf den ganzen Kontinent bezogenen Kritik wendet sich Bobrowski in den nachfolgenden Jahren ab und konzentriert sich auf die Schuld der Deutschen gegenüber den Völkern Osteuropas. Damit erhält auch die Architektur in seinen Gedichten eine neue Bedeutung. Die Relikte der Ritterburgen des deutschen Ordens zeugen von der Herrschaft der mittelalterlichen Eroberer und verschmelzen dabei mit der Natur: Das Zeichenhafte der Architektur wird Teil der Landschaft. Im letzten Lebensjahrzehnt entstehen vermehrt Gedichte, die sich auf Parkanlagen und städtische Grünräume beziehen.
Der Dichter hat sich nicht nur auf persönliche Erfahrungen, sondern mitunter auch auf Bildquellen abstützt, ohne dass er das Original je gesehen hätte. Nur schwer zugänglich sind die Gedichte über Chagall und Gauguin ohne die Erkenntnis, dass sie sich auf Bildvorlagen in schmalen, populärwissenschaftlichen Büchern beziehen, die Bobrowski jeweils kurz vor der Niederschrift der entsprechenden Gedichte erworben hat. Anders verhält es sich mit jenen russischen Kirchen, die Eingang in sein lyrisches Werk gefunden haben. Bobrowski hat sie alle selbst im Krieg gesehen, und die meisten scheinen noch heute zu bestehen und können mit einiger Sicherheit identifiziert werden, wozu auch die Briefe des Dichters aus jener Zeit beitragen.
Trunk loading and back pain
(2017)
An essential function of the trunk is the compensation of external forces and loads in order to guarantee stability. Stabilising the trunk during sudden, repetitive loading in everyday tasks, as well as during performance is important in order to protect against injury. Hence, reduced trunk stability is accepted as a risk factor for the development of back pain (BP). An altered activity pattern including extended response and activation times as well as increased co-contraction of the trunk muscles as well as a reduced range of motion and increased movement variability of the trunk are evident in back pain patients (BPP). These differences to healthy controls (H) have been evaluated primarily in quasi-static test situations involving isolated loading directly to the trunk. Nevertheless, transferability to everyday, dynamic situations is under debate. Therefore, the aim of this project is to analyse 3-dimensional motion and neuromuscular reflex activity of the trunk as response to dynamic trunk loading in healthy (H) and back pain patients (BPP).
A measurement tool was developed to assess trunk stability, consisting of dynamic test situations. During these tests, loading of the trunk is generated by the upper and lower limbs with and without additional perturbation. Therefore, lifting of objects and stumbling while walking are adequate represents. With the help of a 12-lead EMG, neuromuscular activity of the muscles encompassing the trunk was assessed. In addition, three-dimensional trunk motion was analysed using a newly developed multi-segmental trunk model. The set-up was checked for reproducibility as well as validity. Afterwards, the defined measurement set-up was applied to assess trunk stability in comparisons of healthy and back pain patients.
Clinically acceptable to excellent reliability could be shown for the methods (EMG/kinematics) used in the test situations. No changes in trunk motion pattern could be observed in healthy adults during continuous loading (lifting of objects) of different weights. In contrast, sudden loading of the trunk through perturbations to the lower limbs during walking led to an increased neuromuscular activity and ROM of the trunk. Moreover, BPP showed a delayed muscle response time and extended duration until maximum neuromuscular activity in response to sudden walking perturbations compared to healthy controls. In addition, a reduced lateral flexion of the trunk during perturbation could be shown in BPP.
It is concluded that perturbed gait seems suitable to provoke higher demands on trunk stability in adults. The altered neuromuscular and kinematic compensation pattern in back pain patients (BPP) can be interpreted as increased spine loading and reduced trunk stability in patients. Therefore, this novel assessment of trunk stability is suitable to identify deficits in BPP. Assignment of affected BPP to therapy interventions with focus on stabilisation of the trunk aiming to improve neuromuscular control in dynamic situations is implied. Hence, sensorimotor training (SMT) to enhance trunk stability and compensation of unexpected sudden loading should be preferred.
Im Sinne des Refinements von Tierversuchen sollen alle Bedingungen während der Zucht, der Haltung und des Transports von zu Versuchszwecken gehaltenen Tieren und alle Methoden während des Versuchs so verbessert werden, dass die verwendeten Tiere ein minimales Maß an potentiellem Distress, Schmerzen oder Leiden erfahren. Zudem soll ihr Wohlbefinden durch die Möglichkeit des Auslebens speziesspezifischer Verhaltensweisen und die Anwendung tierschonender Verfahren maximal gefördert werden. Zur Etablierung von Grundsätzen des Refinements sind grundlegende Kenntnisse über die physiologischen Bedürfnisse und Verhaltensansprüche der jeweiligen Spezies unabdingbar. Die Experimentatoren sollten das Normalverhalten der Tiere kennen, um potentielle Verhaltensabweichungen, wie Stereotypien, zu verstehen und interpretieren zu können. Standardisierte Haltungsbedingungen von zu Versuchszwecken gehaltenen Mäusen weichen in diversen Aspekten von der natürlichen Umgebung ab und erfordern eine gewisse Adaptation. Ist ein Tier über einen längeren Zeitraum unfähig, sich an die gegebenen Umstände anzupassen, können abnormale Verhaltensweisen, wie Stereotypien auftreten. Stereotypien werden definiert als Abweichungen vom Normalverhalten, die repetitiv und ohne Abweichungen im Ablauf ausgeführt werden, scheinbar keiner Funktion dienen und der konkreten Umweltsituation nicht immer entsprechen.
Bisher war unklar, in welchem Ausmaß stereotypes Verhalten den metabolischen Phänotyp eines Individuums beeinflusst. Ziel dieser Arbeit war es daher, das stereotype Verhalten der FVB/NJ-Maus erstmals detailliert zu charakterisieren, systematisch zusammenzutragen, welche metabolischen Konsequenzen dieses Verhalten bedingt und wie sich diese auf das Wohlbefinden der Tiere und die Verwendung stereotyper Tiere in Studien mit tierexperimentellem Schwerpunkt auswirken.
Der Versuch begann mit der Charakterisierung der mütterlichen Fürsorge in der Parentalgeneration. Insgesamt wurden 35 Jungtiere der F1-Generation vom Absatz an, über einen Zeitraum von 11 Wochen einzeln gehalten, kontinuierlich beobachtet, bis zum Versuchsende wöchentlich Kotproben gesammelt und das Körpergewicht bestimmt. Zusätzlich erfolgten begleitende Untersuchungen wie Verhaltenstests und die Erfassung der physischen Aktivität und metabolischer Parameter. Anschließend wurden u.a. die zerebralen Serotonin- und Dopamingehalte, fäkale Glucocorticoidlevels, hepatisches Glykogen und muskuläre Glykogen- und Triglyceridlevels bestimmt.
Nahezu unabhängig von der mütterlichen Herkunft entwickelte sich bei mehr als der Hälfte der 35 Jungtiere in der F1-Generation stereotypes Verhalten. Diese Daten deuten darauf hin, dass es keine Anzeichen für das Erlernen oder eine direkte genetische Transmission stereotypen Verhaltens bei der FVB/NJ-Maus gibt. Über den gesamten Beobachtungszeitraum zeichneten sich die stereotypen FVB/NJ-Mäuse durch ein eingeschränktes Verhaltensrepertoire aus. Zu Gunsten der erhöhten Aktivität und des Ausübens stereotypen Verhaltens lebten sie insgesamt weniger andere Verhaltensweisen (Klettern, Graben, Nagen) aus. Darüber hinaus waren Stereotypien sowohl im 24-Stunden Open Field Test als auch in der Messeinrichtung der indirekten Tierkalorimetrie mit einer erhöhten Aktivität und Motilität assoziiert, während die circadiane Rhythmik nicht divergierte. Diese erhöhte körperliche Betätigung spiegelte sich in den niedrigeren Körpergewichtsentwicklungen der stereotypen Tiere wieder. Außerdem unterschieden sich die Körperfett- und Körpermuskelanteile.
Zusammenfassend lässt sich sagen, dass das Ausüben stereotypen Verhaltens zu Differenzen im metabolischen Phänotyp nicht-stereotyper und stereotyper FVB/NJ-Mäuse führt. Im Sinne der „Guten Wissenschaftlichen Praxis“ sollte das zentrale Ziel jedes Wissenschaftlers sein, aussagekräftige und reproduzierbare Daten hervorzubringen. Jedoch können keine validen Resultate von Tieren erzeugt werden, die in Aspekten variieren, die für den vorgesehenen Zweck der Studie nicht berücksichtigt wurden. Deshalb sollten nicht-stereotype und stereotype Individuen nicht innerhalb einer Versuchsgruppe randomisiert werden. Stereotype Tiere demzufolge von geplanten Studien auszuschließen, würde allerdings dem Gebot des zweiten R’s – der Reduction – widersprechen. Um Refinement zu garantieren, sollte der Fokus auf der maximal erreichbaren Prävention stereotypen Verhaltens liegen. Diverse Studien haben bereits gezeigt, dass die Anreicherung der Haltungsumwelt (environmental enrichment) zu einer Senkung der Prävalenz von Stereotypien bei Mäusen führt, dennoch kommen sie weiterhin vor. Daher sollte environmental enrichment zukünftig weniger ein „Kann“, sondern ein „Muss“ sein – oder vielmehr: der Goldstandard. Zudem würde eine profunde phänotypische Charakterisierung dazu beitragen, Mausstämme zu erkennen, die zu Stereotypien neigen und den für den spezifischen Zweck am besten geeigneten Mausstamm zu identifizieren, bevor ein Experiment geplant wird.
The field of nanophotonics focuses on the interaction between electromagnetic radiation and matter on the nanometer scale. The elements of nanoscale photonic devices can transfer excitation energy non-radiatively from an excited donor molecule to an acceptor molecule by Förster resonance energy transfer (FRET). The efficiency of this energy transfer is highly dependent on the donor-acceptor distance. Hence, in these nanoscale photonic devices it is of high importance to have a good control over the spatial assembly of used fluorophores. Based on molecular self-assembly processes, various nanostructures can be produced. Here, DNA nanotechnology and especially the DNA origami technique are auspicious self-assembling methods. By using DNA origami nanostructures different fluorophores can be introduced with a high local control to create a variety of nanoscale photonic objects. The applications of such nanostructures range from photonic wires and logic gates for molecular computing to artificial light harvesting systems for artificial photosynthesis.
In the present cumulative doctoral thesis, different FRET systems on DNA origami structures have been designed and thoroughly analyzed. Firstly, the formation of guanine (G) quadruplex structures from G rich DNA sequences has been studied based on a two-color FRET system (Fluorescein (FAM)/Cyanine3 (Cy3)). Here, the influences of different cations (Na+ and K+), of the DNA origami structure and of the DNA sequence on the G-quadruplex formation have been analyzed. In this study, an ion-selective K+ sensing scheme based on the G-quadruplex formation on DNA origami structures has been developed. Subsequently, the reversibility of the G-quadruplex formation on DNA origami structures has been evaluated. This has been done for the simple two-color FRET system which has then been advanced to a switchable photonic wire by introducing additional fluorophores (FAM/Cy3/Cyanine5 (Cy5)/IRDye®700). In the last part, the emission intensity of the acceptor molecule (Cy5) in a three-color FRET cascade has been tuned by arranging multiple donor (FAM) and transmitter (Cy3) molecules around the central acceptor molecule. In such artificial light harvesting systems, the excitation energy is absorbed by several donor and transmitter molecules followed by an energy transfer to the acceptor leading to a brighter Cy5 emission. Furthermore, the range of possible excitation wavelengths is extended by using several different fluorophores (FAM/Cy3/Cy5). In this part of the thesis, the light harvesting efficiency (antenna effect) and the FRET efficiency of different donor/transmitter/acceptor assemblies have been analyzed and the artificial light harvesting complex has been optimized in this respect.
Lithospheric plates move over the low viscosity asthenosphere balancing several forces. The driving forces include basal shear stress exerted by mantle convection and plate boundary forces such as slab pull and ridge push, whereas the resisting forces include inter-plate friction, trench resistance, and cratonic root resistance. These generate plate motions, the lithospheric stress field and dynamic topography which are observed with different geophysical methods. The orientation and tectonic regime of the observed crustal/lithospheric stress field further contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. Using numerical models previous studies were able to identify major forces generating stresses in the crust and lithosphere which also contribute to the formation of topography as well as driving lithospheric plates. They showed that the first-order stress pattern explaining about 80\,\% of the stress field originates from a balance of forces acting at the base of the moving lithospheric plates due to convective flow in the underlying mantle. The remaining second-order stress pattern is due to lateral density variations in the crust and lithosphere in regions of pronounced topography and high gravitational potential, such as the Himalayas and mid-ocean ridges. By linking global lithosphere dynamics to deep mantle flow this study seeks to evaluate the influence of shallow and deep density heterogenities on plate motions, lithospheric stress field and dynamic topography using the geoid as a major constraint for mantle rheology. We use the global 3D lithosphere-asthenosphere model SLIM3D with visco-elasto-plastic rheology coupled at 300 km depth to a spectral model of mantle flow. The complexity of the lithosphere-asthenosphere component allows for the simulation of power-law rheology with creep parameters accounting for both diffusion and dislocation creep within the uppermost 300 km.
First we investigate the influence of intra-plate friction and asthenospheric viscosity on present-day plate motions. Previous modelling studies have suggested that small friction coefficients (µ < 0.1, yield stress ~ 100 MPa) can lead to plate tectonics in models of mantle convection. Here we show that, in order to match present-day plate motions and net rotation, the frictional parameter must be less than 0.05. We are able to obtain a good fit with the magnitude and orientation of observed plate velocities (NUVEL-1A) in a no-net-rotation (NNR) reference frame with µ < 0.04 and minimum asthenosphere viscosity ~ 5*10e19 Pas to 10e20 Pas. Our estimates of net rotation (NR) of the lithosphere suggest that amplitudes ~ 0.1-0.2 °/Ma, similar to most observation-based estimates, can be obtained with asthenosphere viscosity cutoff values of ~ 10e19 Pas to 5*10e19 Pas and friction coefficient µ < 0.05.
The second part of the study investigates further constraints on shallow and deep mantle heterogeneities causing plate motion by predicting lithosphere stress field and topography and validating with observations. Lithosphere stresses and dynamic topography are computed using the modelling setup and rheological parameters for prescribed plate motions. We validate our results with the World Stress Map 2016 (WSM2016) and the observed residual topography. Here we tested a number of upper mantle thermal-density structures. The one used to calculate plate motions is considered the reference thermal-density structure. This model is derived from a heat flow model combined with a sea floor age model. In addition we used three different thermal-density structures derived from global S-wave velocity models to show the influence of lateral density heterogeneities in the upper 300 km on model predictions. A large portion of the total dynamic force generating stresses in the crust/lithosphere has its origin in the deep mantle, while topography is largely influenced by shallow heterogeneities. For example, there is hardly any difference between the stress orientation patterns predicted with and without consideration of the heterogeneities in the upper mantle density structure across North America, Australia, and North Africa. However, the crust is dominant in areas of high altitude for the stress orientation compared to the all deep mantle contribution.
This study explores the sensitivity of all the considered surface observables with regards to model parameters providing insights into the influence of the asthenosphere and plate boundary rheology on plate motion as we test various thermal-density structures to predict stresses and topography.
Underground coal gasification (UCG) has the potential to increase worldwide coal reserves by developing coal resources, currently not economically extractable by conventional mining methods. For that purpose, coal is combusted in situ to produce a high-calorific synthesis gas with different end-use options, including electricity generation as well as production of fuels and chemical feedstock. Apart from the high economic potentials, UCG may induce site‐specific environmental impacts, including ground surface subsidence and pollutant migration of UCG by-products into shallow freshwater aquifers. Sustainable and efficient UCG operation requires a thorough understanding of the coupled thermal, hydraulic and mechanical processes, occurring in the UCG reactor vicinity. The development and infrastructure costs of UCG trials are very high; therefore, numerical simulations of coupled processes in UCG are essential for the assessment of potential environmental impacts. Therefore, the aim of the present study is to assess UCG-induced permeability changes, potential hydraulic short circuit formation and non-isothermal multiphase fluid flow dynamics by means of coupled numerical simulations. Simulation results on permeability changes in the UCG reactor vicinity demonstrate that temperature-dependent thermo-mechanical parameters have to be considered in near-field assessments, only. Hence, far-field simulations do not become inaccurate, but benefit from increased computational efficiency when thermo-mechanical parameters are maintained constant. Simulations on potential hydraulic short circuit formation between single UCG reactors at regional-scale emphasize that geologic faults may induce hydraulic connections, and thus compromise efficient UCG operation. In this context, the steam jacket surrounding high-temperature UCG reactors plays a vital role in avoiding UCG by-products escaping into freshwater aquifers and in minimizing energy consumption by formation fluid evaporation. A steam jacket emerges in the close reactor vicinity due to phase transition of formation water and is a non-isothermal flow phenomenon. Considering this complex multiphase flow behavior, an innovative conceptual modeling approach, validated against field data, enables the quantification and prediction of UCG reactor water balances. The findings of this doctoral thesis provide an important basis for integration of thermo-hydro-mechanical simulations in UCG, required for the assessment and mitigation of its potential environmental impacts as well as optimization of its efficiency.
This dissertation explores whether the processing of ellipsis is affected by changes in the complexity of the antecedent, either due to added linguistic material or to the presence of a temporary ambiguity. Murphy (1985) hypothesized that ellipsis is resolved via a string copying procedure when the antecedent is within the same sentence, and that copying longer strings takes more time. Such an account also implies that the antecedent is copied without its structure, which in turn implies that recomputing its syntax and semantics may be necessary at the ellipsis gap. Alternatively, several accounts predict null effects of antecedent complexity, as well as no reparsing. These either involve a structure copying mechanism that is cost-free and whose finishing time is thus independent of the form of the antecedent (Frazier & Clifton, 2001), treat ellipsis as a pointer into content-addressable memory with direct access (Martin & McElree, 2008, 2009), or assume that one structure is ‘shared’ between antecedent and gap (Frazier & Clifton, 2005).
In a self-paced reading study on German sluicing, temporarily ambiguous garden-path clauses were used as antecedents, but no evidence of reparsing in the form of a slowdown at the ellipsis site was found. Instead, results suggest that antecedents which had been reanalyzed from an initially incorrect structure were easier to retrieve at the gap. This finding that can be explained within the framework of cue-based retrieval parsing (Lewis & Vasishth, 2005), where additional syntactic operations on a structure yield memory reactivation effects.
Two further self-paced reading studies on German bare argument ellipsis and English verb phrase ellipsis investigated if adding linguistic content to the antecedent would increase processing times for the ellipsis, and whether insufficiently demanding comprehension tasks may have been responsible for earlier null results (Frazier & Clifton, 2000; Martin & McElree, 2008). It has also been suggested that increased antecedent complexity should shorten rather than lengthen retrieval times by providing more unique memory features (Hofmeister, 2011). Both experiments failed to yield reliable evidence that antecedent complexity affects ellipsis processing times in either direction, irrespectively of task demands.
Finally, two eye-tracking studies probed more deeply into the proposed reactivation-induced speedup found in the first experiment. The first study used three different kinds of French garden-path sentences as antecedents, with two of them failing to yield evidence for reactivation. Moreover, the third sentence type showed evidence suggesting that having failed to assign a structure to the antecedent leads to a slowdown at the ellipsis site, as well as regressions towards the ambiguous part of the sentence. The second eye-tracking study used the same materials as the initial self-paced reading study on German, with results showing a pattern similar to the one originally observed, with some notable differences.
Overall, the experimental results are compatible with the view that adding linguistic material to the antecedent has no or very little effect on the ease with which ellipsis is resolved, which is consistent with the predictions of cost-free copying, pointer-based approaches and structure sharing. Additionally, effects of the antecedent’s parsing history on ellipsis processing may be due to reactivation, the availability of multiple representations in memory, or complete failure to retrieve a matching target.
Data profiling is the computer science discipline of analyzing a given dataset for its metadata. The types of metadata range from basic statistics, such as tuple counts, column aggregations, and value distributions, to much more complex structures, in particular inclusion dependencies (INDs), unique column combinations (UCCs), and functional dependencies (FDs). If present, these statistics and structures serve to efficiently store, query, change, and understand the data. Most datasets, however, do not provide their metadata explicitly so that data scientists need to profile them.
While basic statistics are relatively easy to calculate, more complex structures present difficult, mostly NP-complete discovery tasks; even with good domain knowledge, it is hardly possible to detect them manually. Therefore, various profiling algorithms have been developed to automate the discovery. None of them, however, can process datasets of typical real-world size, because their resource consumptions and/or execution times exceed effective limits.
In this thesis, we propose novel profiling algorithms that automatically discover the three most popular types of complex metadata, namely INDs, UCCs, and FDs, which all describe different kinds of key dependencies. The task is to extract all valid occurrences from a given relational instance. The three algorithms build upon known techniques from related work and complement them with algorithmic paradigms, such as divide & conquer, hybrid search, progressivity, memory sensitivity, parallelization, and additional pruning to greatly improve upon current limitations. Our experiments show that the proposed algorithms are orders of magnitude faster than related work. They are, in particular, now able to process datasets of real-world, i.e., multiple gigabytes size with reasonable memory and time consumption.
Due to the importance of data profiling in practice, industry has built various profiling tools to support data scientists in their quest for metadata. These tools provide good support for basic statistics and they are also able to validate individual dependencies, but they lack real discovery features even though some fundamental discovery techniques are known for more than 15 years. To close this gap, we developed Metanome, an extensible profiling platform that incorporates not only our own algorithms but also many further algorithms from other researchers. With Metanome, we make our research accessible to all data scientists and IT-professionals that are tasked with data profiling. Besides the actual metadata discovery, the platform also offers support for the ranking and visualization of metadata result sets.
Being able to discover the entire set of syntactically valid metadata naturally introduces the subsequent task of extracting only the semantically meaningful parts. This is challenge, because the complete metadata results are surprisingly large (sometimes larger than the datasets itself) and judging their use case dependent semantic relevance is difficult. To show that the completeness of these metadata sets is extremely valuable for their usage, we finally exemplify the efficient processing and effective assessment of functional dependencies for the use case of schema normalization.
Proteins are molecules that are essential for life and carry out an enormous number of functions in organisms. To this end, they change their conformation and bind to other molecules. However, the interplay between conformational change and binding is not fully understood. In this work, this interplay is investigated with molecular dynamics (MD) simulations of the protein-peptide system Mdm2-PMI and by analysis of data from relaxation experiments.
The central task it to uncover the binding mechanism, which is described by the sequence of (partial) binding events and conformational change events including their probabilities. In the simplest case, the binding mechanism is described by a two-step model: binding followed by conformational change or conformational change followed by binding. In the general case, longer sequences with multiple conformational changes and partial binding events are possible as well as parallel pathways that differ in their sequences of events. The theory of Markov state models (MSMs) provides the theoretical framework in which all these cases can be modeled. For this purpose, MSMs are estimated in this work from MD data, and rate equation models, which are related to MSMs, are inferred from experimental relaxation data.
The MD simulation and Markov modeling of the PMI-Mdm2 system shows that PMI and Mdm2 can bind via multiple pathways. A main result of this work is a dissociation rate on the order of one event per second, which was calculated using Markov modeling and is in agreement with experiment. So far, dissociation rates and transition rates of this magnitude have only been calculated with methods that speed up transitions by acting with time-dependent, external forces on the binding partners. The simulation technique developed in this work, in contrast, allows the estimation of dissociation rates from the combination of free energy calculation and direct MD simulation of the fast binding process. Two new statistical estimators TRAM and TRAMMBAR are developed to estimate a MSM from the joint data of both simulation types.
In addition, a new analysis technique for time-series data from chemical relaxation experiments is developed in this work. It allows to identify one of the above-mentioned two-step mechanisms as the mechanism that underlays the data. The new method is valid for a broader range of concentrations than previous methods and therefore allows to choose the concentrations such that the mechanism can be uniquely identified. It is successfully tested with data for the binding of recoverin to a rhodopsin kinase peptide.
I. Ceric ammonium nitrate (CAN) mediated thiocyanate radical additions to glycals
In this dissertation, a facile entry was developed for the synthesis of 2-thiocarbohydrates and their transformations. Initially, CAN mediated thiocyanation of carbohydrates was carried out to obtain the basic building blocks (2-thiocyanates) for the entire studies. Subsequently, 2-thiocyanates were reduced to the corresponding thiols using appropriate reagents and reaction conditions. The screening of substrates, stereochemical outcome and the reaction mechanism are discussed briefly (Scheme I).
Scheme I. Synthesis of the 2-thiocyanates II and reductions to 2-thiols III & IV.
An interesting mechanism was proposed for the reduction of 2-thiocyanates II to 2-thiols III via formation of a disulfide intermediate. The water soluble free thiols IV were obtained by cleaving the thiocyanate and benzyl groups in a single step. In the subsequent part of studies, the synthetic potential of the 2-thiols was successfully expanded by simple synthetic transformations.
II. Transformations of the 2-thiocarbohydrates
The 2-thiols were utilized for convenient transformations including sulfa-Michael additions, nucleophilic substitutions, oxidation to disulfides and functionalization at the anomeric position. The diverse functionalizations of the carbohydrates at the C-2 position by means of the sulfur linkage are the highlighting feature of these studies. Thus, it creates an opportunity to expand the utility of 2-thiocarbohydrates for biological studies.
Reagents and conditions: a) I2, pyridine, THF, rt, 15 min; b) K2CO3, MeCN, rt, 1 h; c) MeI, K2CO3, DMF, 0 °C, 5 min; d) Ac2O, H2SO4 (1 drop), rt, 10 min; e) CAN, MeCN/H2O, NH4SCN, rt, 1 h; f) NaN3, ZnBr2, iPrOH/H2O, reflux, 15 h; g) NaOH (1 M), TBAI, benzene, rt, 2 h; h) ZnCl2, CHCl3, reflux, 3 h.
Scheme II. Functionalization of 2-thiocarbohydrates.
These transformations have enhanced the synthetic value of 2-thiocarbohydrates for the preparative scale. Worth to mention is the Lewis acid catalyzed replacement of the methoxy group by other nucleophiles and the synthesis of the (2→1) thiodisaccharides, which were obtained with complete β-selectivity. Additionally, for the first time, the carbohydrate linked thiotetrazole was synthesized by a (3 + 2) cycloaddition approach at the C-2 position.
III. Synthesis of thiodisaccharides by thiol-ene coupling.
In the final part of studies, the synthesis of thiodisaccharides by a classical photoinduced thiol-ene coupling was successfully achieved.
Reagents and conditions: 2,2-Dimethoxy-2-phenylacetophenone (DPAP), CH2Cl2/EtOH, hv, rt.
Scheme III. Thiol-ene coupling between 2-thiols and exo-glycals.
During the course of investigations, it was found that the steric hindrance plays an important role in the addition of bulky thiols to endo-glycals. Thus, we successfully screened the suitable substrates for addition of various thiols to sterically less hindered alkenes (Scheme III). The photochemical addition of 2-thiols to three different exo-glycals delivered excellent regio- and diastereoselectivities as well as yields, which underlines the synthetic potential of this convenient methodology.
The aim of this thesis is to develop approaches to automatically recognise the structure of argumentation in short monological texts. This amounts to identifying the central claim of the text, supporting premises, possible objections, and counter-objections to these objections, and connecting them correspondingly to a structure that adequately describes the argumentation presented in the text.
The first step towards such an automatic analysis of the structure of argumentation is to know how to represent it. We systematically review the literature on theories of discourse, as well as on theories of the structure of argumentation against a set of requirements and desiderata, and identify the theory of J. B. Freeman (1991, 2011) as a suitable candidate to represent argumentation structure. Based on this, a scheme is derived that is able to represent complex argumentative structures and can cope with various segmentation issues typically occurring in authentic text.
In order to empirically test our scheme for reliability of annotation, we conduct several annotation experiments, the most important of which assesses the agreement in reconstructing argumentation structure. The results show that expert annotators produce very reliable annotations, while the results of non-expert annotators highly depend on their training in and commitment to the task.
We then introduce the 'microtext' corpus, a collection of short argumentative texts. We report on the creation, translation, and annotation of it and provide a variety of statistics. It is the first parallel corpus (with a German and English version) annotated with argumentation structure, and -- thanks to the work of our colleagues -- also the first annotated according to multiple theories of (global) discourse structure.
The corpus is then used to develop and evaluate approaches to automatically predict argumentation structures in a series of six studies: The first two of them focus on learning local models for different aspects of argumentation structure. In the third study, we develop the main approach proposed in this thesis for predicting globally optimal argumentation structures: the 'evidence graph' model. This model is then systematically compared to other approaches in the fourth study, and achieves state-of-the-art results on the microtext corpus. The remaining two studies aim to demonstrate the versatility and elegance of the proposed approach by predicting argumentation structures of different granularity from text, and finally by using it to translate rhetorical structure representations into argumentation structures.
In this thesis, stochastic dynamics modelling collective motions of populations, one of the most mysterious type of biological phenomena, are considered. For a system of N particle-like individuals, two kinds of asymptotic behaviours are studied : ergodicity and flocking properties, in long time, and propagation of chaos, when the number N of agents goes to infinity. Cucker and Smale, deterministic, mean-field kinetic model for a population without a hierarchical structure is the starting point of our journey : the first two chapters are dedicated to the understanding of various stochastic dynamics it inspires, with random noise added in different ways. The third chapter, an attempt to improve those results, is built upon the cluster expansion method, a technique from statistical mechanics. Exponential ergodicity is obtained for a class of non-Markovian process with non-regular drift. In the final part, the focus shifts onto a stochastic system of interacting particles derived from Keller and Segel 2-D parabolicelliptic model for chemotaxis. Existence and weak uniqueness are proven.
In littoral zones of lakes, multiple processes determine lake ecology and water quality. Lacustrine groundwater discharge (LGD), most frequently taking place in littoral zones, can transport or mobilize nutrients from the sediments and thus contribute significantly to lake eutrophication. Furthermore, lake littoral zones are the habitat of benthic primary producers, namely submerged macrophytes and periphyton, which play a key role in lake food webs and influence lake water quality. Groundwater-mediated nutrient-influx can potentially affect the asymmetric competition between submerged macrophytes and periphyton for light and nutrients. While rooted macrophytes have superior access to sediment nutrients, periphyton can negatively affect macrophytes by shading. LGD may thus facilitate periphyton production at the expense of macrophyte production, although studies on this hypothesized effect are missing.
The research presented in this thesis is aimed at determining how LGD influences periphyton, macrophytes, and the interactions between these benthic producers. Laboratory experiments were combined with field experiments and measurements in an oligo-mesotrophic hard water lake.
In the first study, a general concept was developed based on a literature review of the existing knowledge regarding the potential effects of LGD on nutrients and inorganic and organic carbon loads to lakes, and the effect of these loads on periphyton and macrophytes. The second study includes a field survey and experiment examining the effects of LGD on periphyton in an oligotrophic, stratified hard water lake (Lake Stechlin). This study shows that LGD, by mobilizing phosphorus from the sediments, significantly promotes epiphyton growth, especially at the end of the summer season when epilimnetic phosphorus concentrations are low. The third study focuses on the potential effects of LGD on submerged macrophytes in Lake Stechlin. This study revealed that LGD may have contributed to an observed change in macrophyte community composition and abundance in the shallow littoral areas of the lake. Finally, a laboratory experiment was conducted which mimicked the conditions of a seepage lake. Groundwater circulation was shown to mobilize nutrients from the sediments, which significantly promoted periphyton growth. Macrophyte growth was negatively affected at high periphyton biomasses, confirming the initial hypothesis.
More generally, this thesis shows that groundwater flowing into nutrient-limited lakes may import or mobilize nutrients. These nutrients first promote periphyton, and subsequently provoke radical changes in macrophyte populations before finally having a possible influence on the lake’s trophic state. Hence, the eutrophying effect of groundwater is delayed and, at moderate nutrient loading rates, partly dampened by benthic primary producers. The present research emphasizes the importance and complexity of littoral processes, and the need to further investigate and monitor the benthic environment. As present and future global changes can significantly affect LGD, the understanding of these complex interactions is required for the sustainable management of lake water quality.
Recognizing, understanding, and responding to quantities are considerable skills for human beings. We can easily communicate quantities, and we are extremely efficient in adapting our behavior to numerical related tasks. One usual task is to compare quantities. We also use symbols like digits in numerical-related tasks. To solve tasks including digits, we must to rely on our previously learned internal number representations.
This thesis elaborates on the process of number comparison with the use of noisy mental representations of numbers, the interaction of number and size representations and how we use mental number representations strategically. For this, three studies were carried out.
In the first study, participants had to decide which of two presented digits was numerically larger. They had to respond with a saccade in the direction of the anticipated answer. Using only a small set of meaningfully interpretable parameters, a variant of random walk models is described that accounts for response time, error rate, and variance of response time for the full matrix of 72 digit pairs. In addition, the used random walk model predicts a numerical distance effect even for error response times and this effect clearly occurs in the observed data. In relation to corresponding correct answers error responses were systematically faster. However, different from standard assumptions often made in random walk models, this account required that the distributions of step sizes of the induced random walks be asymmetric to account for this asymmetry between correct and incorrect responses.
Furthermore, the presented model provides a well-defined framework to investigate the nature and scale (e.g., linear vs. logarithmic) of the mapping of numerical magnitude onto its internal representation. In comparison of the fits of proposed models with linear and logarithmic mapping, the logarithmic mapping is suggested to be prioritized.
Finally, we discuss how our findings can help interpret complex findings (e.g., conflicting speed vs. accuracy trends) in applied studies that use number comparison as a well-established diagnostic tool. Furthermore, a novel oculomotoric effect is reported, namely the saccadic overschoot effect. The participants responded by saccadic eye movements and the amplitude of these saccadic responses decreases with numerical distance.
For the second study, an experimental design was developed that allows us to apply the signal detection theory to a task where participants had to decide whether a presented digit was physically smaller or larger. A remaining question is, whether the benefit in (numerical magnitude – physical size) congruent conditions is related to a better perception than in incongruent conditions. Alternatively, the number-size congruency effect is mediated by response biases due to numbers magnitude. The signal detection theory is a perfect tool to distinguish between these two alternatives. It describes two parameters, namely sensitivity and response bias. Changes in the sensitivity are related to the actual task performance due to real differences in perception processes whereas changes in the response bias simply reflect strategic implications as a stronger preparation (activation) of an anticipated answer. Our results clearly demonstrate that the number-size congruency effect cannot be reduced to mere response bias effects, and that genuine sensitivity gains for congruent number-size pairings contribute to the number-size congruency effect.
Third, participants had to perform a SNARC task – deciding whether a presented digit was odd or even. Local transition probability of irrelevant attributes (magnitude) was varied while local transition probability of relevant attributes (parity) and global probability occurrence of each stimulus were kept constantly. Participants were quite sensitive in recognizing the underlying local transition probability of irrelevant attributes. A gain in performance was observed for actual repetitions of the irrelevant attribute in relation to changes of the irrelevant attribute in high repetition conditions compared to low repetition conditions. One interpretation of these findings is that information about the irrelevant attribute (magnitude) in the previous trial is used as an informative precue, so that participants can prepare early processing stages in the current trial, with the corresponding benefits and costs typical of standard cueing studies.
Finally, the results reported in this thesis are discussed in relation to recent studies in numerical cognition.
Natural products and their derivatives have always been a source of drug leads. In particular, bacterial compounds have played an important role in drug development, for example in the field of antibiotics. A decrease in the discovery of novel leads from natural sources and the hope of finding new leads through the generation of large libraries of drug-like compounds by combinatorial chemistry aimed at specific molecular targets drove the pharmaceutical companies away from research on natural products. However, recent technological advances in genetics, bioinformatics and analytical chemistry have revived the interest in natural products. The ribosomally synthesized and post-translationally modified peptides (RiPPs) are a group of natural products generated by the action of post-translationally modifying enzymes on precursor peptides translated from mRNA by ribosomes. The great substrate promiscuity exhibited by many of the enzymes from RiPP biosynthetic pathways have led to the generation of hundreds of novel synthetic and semisynthetic variants, including variants carrying non-canonical amino acids (ncAAs). The microviridins are a family of RiPPs characterized by their atypical tricyclic structure composed of lactone and lactam rings, and their activity as serine protease inhibitors. The generalities of their biosynthetic pathway have already been described, however, the lack of information on details such as the protease responsible for cleaving off the leader peptide from the cyclic core peptide has impeded the fast and cheap production of novel microviridin variants. In the present work, knowledge on leader peptide activation of enzymes from other RiPP families has been extrapolated to the microviridin family, making it possible to bypass the need of a leader peptide. This feature allowed for the exploitation of the microviridin biosynthetic machinery for the production of novel variants through the establishment of an efficient one-pot in vitro platform. The relevance of this chemoenzymatic approach has been exemplified by the synthesis of novel potent serine protease inhibitors from both rationally-designed peptide libraries and bioinformatically predicted microviridins. Additionally, new structure-activity relationships (SARs) could be inferred by screening microviridin intermediates. The significance of this technique was further demonstrated by the simple incorporation of ncAAs into the microviridin scaffold.
During the course of millions of years, evolutionary forces have shaped the current distribution of species and their genetic variability, by influencing their phylogeny, adaptability and probability of survival. Southeast Asia is an extraordinary biodiverse region, where past climate events have resulted in dramatic changes in land availability and distribution of vegetation, resulting likewise in periodic connections between isolated islands and the mainland. These events have influenced the way species are distributed throughout this region but, more importantly, they influenced the genesis of genetic diversity. Despite the observation that a shared paleo-history resulted in very diverse species phylogeographic patterns, the mechanisms behind these patterns are still poorly understood.
In this thesis, I investigated and contrasted the phylogeography of three groups of ungulate species distributed within South and Southeast Asia, aiming to understand what mechanisms have shaped speciation and geographical distribution of genetic variability. For that purpose, I analysed the mitogenomes of historical samples, in order to account for populations from the entire range of species distributions – including populations that no longer exist. This thesis is organized in three manuscripts, which correspond to the three investigated groups: red muntjacs, Rusa deer and Asian rhinoceros.
Red muntjacs are a widely distributed species and occur in very different habitats. We found evidence for gene-flow among populations of different islands, indicative of their ability to utilize the available land corridors. However, we described also the existence of at least two dispersal barriers that created population differentiation within this group; one isolated Sundaic and Mainland populations and the second separated individuals from Sri Lanka.
Second, the two Rusa species investigated here revealed another consequence of the historical land connections. While the two species were monophyletic, we found evidence of hybridisation in Java, facilitated by the expansion of the widespread sambar, Rusa unicolor. Consequently, I found that all the individuals of Javan deer, R. timorensis which were transported to the east of Sundaland by humans, to be of hybrid descent.
In the last manuscript, we were able to include samples from the extinct mainland populations of both Sumatran and Javan rhinoceros. The results revealed a much higher genetic diversity of the historical populations than ever reported for the contemporaneous survivors. Their evolutionary histories revealed a close relationship to climatic events of the Pleistocene but, more importantly, point out the vast extent of genetic erosion within these two endangered species.
The specific phylogeographic history of the species showed some common patters of genetic differentiation that could be directly linked to the climatic and geological changes on the Sunda Shelf during the Pleistocene. However, by contrasting these results I discussed that the same geological events
did not always result in similar histories. One obvious example was the different permeability of the land corridors of Sundaland, as the ability of each species to utilize this newly available land was directly related to their specific ecological requirements. Taken together, these results have an important contribution to the general understanding of evolution in this biodiversity hotspot and the main drivers shaping the distribution of genetic diversity, but could also have important consequences for taxonomy and conservation of the three investigated groups.
All life-sustaining processes are ultimately driven by thousands of biochemical reactions occurring in the cells: the metabolism. These reactions form an intricate network which produces all required chemical compounds, i.e., metabolites, from a set of input molecules. Cells regulate the activity through metabolic reactions in a context-specific way; only reactions that are required in a cellular context, e.g., cell type, developmental stage or environmental condition, are usually active, while the rest remain inactive. The context-specificity of metabolism can be captured by several kinds of experimental data, such as by gene and protein expression or metabolite profiles. In addition, these context-specific data can be assimilated into computational models of metabolism, which then provide context-specific metabolic predictions.
This thesis is composed of three individual studies focussing on context-specific experimental data integration into computational models of metabolism. The first study presents an optimization-based method to obtain context-specific metabolic predictions, and offers the advantage of being fully automated, i.e., free of user defined parameters. The second study explores the effects of alternative optimal solutions arising during the generation of context-specific metabolic predictions. These alternative optimal solutions are metabolic model predictions that represent equally well the integrated data, but that can markedly differ. This study proposes algorithms to analyze the space of alternative solutions, as well as some ways to cope with their impact in the predictions.
Finally, the third study investigates the metabolic specialization of the guard cells of the plant Arabidopsis thaliana, and compares it with that of a different cell type, the mesophyll cells. To this end, the computational methods developed in this thesis are applied to obtain metabolic predictions specific to guard cell and mesophyll cells. These cell-specific predictions are then compared to explore the differences in metabolic activity between the two cell types. In addition, the effects of alternative optima are taken into consideration when comparing the two cell types. The computational results indicate a major reorganization of the primary metabolism in guard cells. These results are supported by an independent 13C labelling experiment.
Tremendous progress in the development of thin film solar cell techniques has been made over the last decade. The field of organic solar cells is constantly developing, new material classes like Perowskite solar cells are emerging and different types of hybrid organic/inorganic material combinations are being investigated for their physical properties and their applicability in thin film electronics. Besides typical single-junction architectures for solar cells, multi-junction concepts are also being investigated as they enable the overcoming of theoretical limitations of a single-junction. In multi-junction devices each sub-cell operates in different wavelength regimes and should exhibit optimized band-gap energies. It is exactly this tunability of the band-gap energy that renders organic solar cell materials interesting candidates for multi-junction applications. Nevertheless, only few attempts have been made to combine inorganic and organic solar cells in series connected multi-junction architectures. Even though a great diversity of organic solar cells exists nowadays, their open circuit voltage is usually low compared to the band-gap of the active layer. Hence, organic low band-gap solar cells in particular show low open circuit voltages and the key factors that determine the voltage losses are not yet fully understood. Besides open circuit voltage losses the recombination of charges in organic solar cells is also a prevailing research topic, especially with respect to the influence of trap states.
The exploratory focus of this work is therefore set, on the one hand, on the development of hybrid organic/inorganic multi-junctions and, on the other hand, on gaining a deeper understanding of the open circuit voltage and the recombination processes of organic solar cells.
In the first part of this thesis, the development of a hybrid organic/inorganic triple-junction will be discussed which showed at that time (Jan. 2015) a record power conversion efficiency of 11.7%. The inorganic sub-cells of these devices consist of hydrogenated amorphous silicon and were delivered by the Competence Center Thin-Film and Nanotechnology for Photovoltaics in Berlin. Different recombination contacts and organic sub-cells were tested in conjunction with these inorganic sub-cells on the basis of optical modeling predictions for the optimal layer thicknesses to finally reach record efficiencies for this type of solar cells.
In the second part, organic model systems will be investigated to gain a better understanding of the fundamental loss mechanisms that limit the open circuit voltage of organic solar cells. First, bilayer systems with different orientation of the donor and acceptor molecules were investigated to study the influence of the donor/acceptor orientation on non-radiative voltage loss. Secondly, three different bulk heterojunction solar cells all comprising the same amount of fluorination and the same polymer backbone in the donor component were examined to study the influence of long range electrostatics on the open circuit voltage. Thirdly, the device performance of two bulk heterojunction solar cells was compared which consisted of the same donor polymer but used different fullerene acceptor molecules. By this means, the influence of changing the energetics of the acceptor component on the open circuit voltage was investigated and a full analysis of the charge carrier dynamics was presented to unravel the reasons for the worse performance of the solar cell with the higher open circuit voltage. In the third part, a new recombination model for organic solar cells will be introduced and its applicability shown for a typical low band-gap cell. This model sheds new light on the recombination process in organic solar cells in a broader context as it re-evaluates the recombination pathway of charge carriers in devices which show the presence of trap states. Thereby it addresses a current research topic and helps to resolve alleged discrepancies which can arise from the interpretation of data derived by different measurement techniques.
Die vorliegende Studie beschäftigt sich mit dem Berufseinstieg von Lehrpersonen und untersucht Zusammenhänge zwischen der Nutzung von Lerngelegenheiten, sozialer Kooperation, individuellen Determinanten und Kompetenzselbsteinschätzungen, die erstmalig in dieser Zusammenstellung überprüft worden sind.
Die Literaturrecherche machte deutlich, dass der Berufseinstieg eine besonders wichtige Phase für die berufliche Sozialisation darstellt. Die Nutzung von Lerngelegenheiten wurde empirisch noch nicht sehr oft untersucht vor allem nicht im Zusammenhang mit individuellen Determinanten und die Kooperation meist nur unter dem Fokus der Bedeutung für die Schule.
An der empirischen Untersuchung nahmen 223 berufseinsteigende Lehrkräfte aus dem Allgemeinen Pflichtschulbereich in Niederösterreich teil, die verpflichtend in den ersten beiden Dienstjahren Fortbildungen besuchen müssen. Diese Situation ist einzigartig in Österreich, da es nur in diesem Bundesland seit 2011 eine verpflichtend zu besuchende Berufseinstiegsphase gibt. Ab 2019 wird es in Österreich eine Induktionsphase für alle Lehrkräfte geben, die in den Beruf einsteigen.
Mit Hilfe von Strukturgleichungsmodellen wurden die Zusammenhänge untersucht und es zeigte sich, dass es diese in allen Bereichen gibt. Am Ende konnte ein neues Theoriemodell zur Nutzung von Lerngelegenheiten abgeleitet werden, das sich in Theorien zu professionellen Kompetenzentwicklung und zu Lernen in Aus-, Fortund Weiterbildung einordnen lässt.
The first main goal of this thesis is to develop a concept of approximate differentiability of higher order for subsets of the Euclidean space that allows to characterize higher order rectifiable sets, extending somehow well known facts for functions. We emphasize that for every subset A of the Euclidean space and for every integer k ≥ 2 we introduce the approximate differential of order k of A and we prove it is a Borel map whose domain is a (possibly empty) Borel set. This concept could be helpful to deal with higher order rectifiable sets in applications.
The other goal is to extend to general closed sets a well known theorem of Alberti on the second order rectifiability properties of the boundary of convex bodies. The Alberti theorem provides a stratification of second order rectifiable subsets of the boundary of a convex body based on the dimension of the (convex) normal cone. Considering a suitable generalization of this normal cone for general closed subsets of the Euclidean space and employing some results from the first part we can prove that the same stratification exists for every closed set.
Understanding the distribution of species is fundamental for biodiversity conservation, ecosystem management, and increasingly also for climate impact assessment. The presence of a species in a given site depends on physiological limitations (abiotic factors), interactions with other species (biotic factors), migratory or dispersal processes (site accessibility) as well as the continuing
effects of past events, e.g. disturbances (site legacy). Existing approaches to predict species distributions either (i) correlate observed species occurrences with environmental variables describing abiotic limitations, thus ignoring biotic interactions, dispersal and legacy effects (statistical species distribution model, SDM); or (ii) mechanistically model the variety of processes determining species distributions (process-based model, PBM). SDMs are widely used due to their easy applicability and ability to handle varied data qualities. But they fail to reproduce the dynamic response of species distributions to changing conditions. PBMs are expected to be superior in this respect, but they need very specific data unavailable for many species, and are often more complex and require more computational effort. More recently, hybrid models link the two approaches to combine their respective strengths.
In this thesis, I apply and compare statistical and process-based approaches to predict species distributions, and I discuss their respective limitations, specifically for applications in changing environments. Detailed analyses of SDMs for boreal tree species in Finland reveal that nonclimatic predictors - edaphic properties and biotic interactions - are important limitations at the treeline, contesting the assumption of unrestricted, climatically induced range expansion. While the estimated SDMs are successful within their training data range, spatial and temporal model transfer fails. Mapping and comparing sampled predictor space among data subsets identifies spurious extrapolation as the plausible explanation for limited model transferability. Using these findings, I analyze the limited success of an established PBM (LPJ-GUESS) applied to the same problem. Examination of process representation and parameterization in the PBM identifies implemented processes to adjust (competition between species, disturbance) and missing processes that are crucial in boreal forests (nutrient limitation, forest management). Based on climatic correlations shifting over time, I stress the restricted temporal transferability of bioclimatic limits used in LPJ-GUESS and similar PBMs. By critically assessing the performance of SDM and PBM in this application, I demonstrate the importance of understanding the limitations of the
applied methods.
As a potential solution, I add a novel approach to the repertoire of existing hybrid models. By simulation experiments with an individual-based PBM which reproduces community dynamics resulting from biotic factors, dispersal and legacy effects, I assess the resilience of coastal vegetation to abrupt hydrological changes. According to the results of the resilience analysis, I then modify temporal SDM predictions, thereby transferring relevant process detail from PBM to
SDM. The direction of knowledge transfer from PBM to SDM avoids disadvantages of current hybrid models and increases the applicability of the resulting model in long-term, large-scale applications. A further advantage of the proposed framework is its flexibility, as it is readily extended to other model types, disturbance definitions and response characteristics.
Concluding, I argue that we already have a diverse range of promising modelling tools at hand, which can be refined further. But most importantly, they need to be applied more thoughtfully. Bearing their limitations in mind, combining their strengths and openly reporting underlying assumptions and uncertainties is the way forward.
Modern welfare states aim at designing unemployment insurance (UI) schemes which minimize the length of unemployment spells. A variety of institutions and incentives, which are embedded in UI schemes across OECD countries, reflect this attempt. For instance, job seekers entering UI are often provided with personal support through a caseworker. They also face the requirement to regularly submit a minimum number of job applications, which is typically enforced through benefit cuts in the case of non-compliance. Moreover, job seekers may systematically receive information on their re-employment prospects. As a consequence, UI design has become a complex task. Policy makers need to define not only the amount and duration of benefit payments, but also several other choice parameters. These include the intensity and quality of personal support through caseworkers, the level of job search requirements, the strictness of enforcement, and the information provided to unemployed individuals. Causal estimates on how these parameters affect re-employment outcomes are thus central inputs to the design of modern UI systems: how much do individual caseworkers influence the transition out of unemployment? Does the requirement of an additional job application translate into increased job finding? Do individuals behave differently when facing a strict versus mild enforcement system? And how does information on re-employment prospects influence the job search decision? This dissertation proposes four novel research designs to answer this question. Chapters one to three elaborate quasi-experimental identification strategies, which are applied to large-scale administrative data from Switzerland. They, respectively, measure how personal interactions with caseworkers (chapter one), the level of job search requirements (chapter two) and the strictness of enforcement (chapter three) affect re-employment outcomes. Chapter four proposes a structural estimation approach, based on linked survey and administrative data from Germany. It studies how over-optimism on future wage offers affects the decision to search for work, and how the provision of information changes this decision.
Ecosystem services (ESs) are defined as the contributions that ecosystems make to human wellbeing and are increasingly being used as an approach to explore the importance of ecosystems for humans through their valuation. Although value plurality has been recognised long before the mainstreaming of ESs research, socio-cultural valuation is still underrepresented in ESs assessments. It is the central goal of this PhD dissertation to explore the ability of socio-cultural valuation methods for the operationalisation of ESs research in land management. To address this, I formulated three research objectives that are briefly outlined below and relate to the three studies conducted during this dissertation.
The first objective relates to the assessment of the current role of socio-cultural valuation in ESs research. Human values are central to ESs research yet non-monetary socio-cultural valuation methods have been found underrepresented in the field of ESs science. In regard to the unbalanced consideration of value domains and conceptual uncertainties, I perform a systematic literature review aiming to answer the research question: To what extent have socio-cultural values been addressed in ESs assessments.
The second objective aims to test socio-cultural valuation methods of ESs and their relevance for land use preferences by exploring their methodological opportunities and limitations. Socio-cultural valuation methods have only recently become a focus in ESs research and therefore bear various uncertainties in regard to their methodological implications. To overcome these uncertainties, I analysed responses to a visitor survey. The research questions related to the second objective were: What are the implications of different valuation methods for ESs values? To what extent are land use preferences explained by socio-cultural values of ESs?
The third objective addressed in this dissertation is the implementation of ESs research into land management through socio-cultural valuation. Though it is emphasised that the ESs approach can assist decision making, there is little empirical evidence of the effect of ESs knowledge on land management. I proposed a way to implement transdisciplinary, spatially explicit research on ESs by answering the following research questions: Which landscape features underpinning ESs supply are considered in land management? How can participatory approaches accounting for ESs be operationalised in land management?
The empirical research resulted in five main findings that provide answers to the research questions. First, this dissertation provides evidence that socio-cultural values are an integral part of ESs research. I found that they can be assessed for provisioning, regulating, and cultural services though they are linked to cultural services to a greater degree. Socio-cultural values have been assessed by monetary and non-monetary methods and their assessment is effectively facilitated by stakeholder participation. Second, I found that different methods of socio-cultural valuation revealed different information. Whereas rating revealed a general value of ESs, weighting was found more suitable to identify priorities across ESs. Value intentions likewise differed in the distribution of values, generally implying a higher value for others than for respondents themselves. Third, I showed that ESs values were distributed similarly across groups with differing land use preferences. Thus, I provided empirical evidence that ESs values and landscape values should not be used interchangeably. Fourth, I showed which landscape features important for ESs supply in a Scottish regional park are not sufficiently accounted for in the current management strategy. This knowledge is useful for the identification of priority sites for land management. Finally, I provide an approach to explore how ESs knowledge elicited by participatory mapping can be operationalised in land management. I demonstrate how stakeholder knowledge and values can be used for the identification of ESs hotspots and how these hotspots can be compared to current management priorities.
This dissertation helps to bridge current gaps of ESs science by advancing the understanding of the current role of socio-cultural values in ESs research, testing different methods and their relevance for land use preferences, and implementing ESs knowledge into land management. If and to what extent ESs and their values are implemented into ecosystem management is mainly the choice of the management. An advanced understanding of socio-cultural valuation methods contributes to the normative basis of this management, while the proposal for the implementation of ESs in land management presents a practical approach of how to transfer this type of knowledge into practice. The proposed methods for socio-cultural valuation can support guiding land management towards a balanced consideration of ESs and conservation goals.
The central aim of this thesis is to demonstrate the benefits of innovative frequency-based methods to better explain the variability observed in lake ecosystems. Freshwater ecosystems may be the most threatened part of the hydrosphere. Lake ecosystems are particularly sensitive to changes in climate and land use because they integrate disturbances across their entire catchment. This makes understanding the dynamics of lake ecosystems an intriguing and important research priority. This thesis adds new findings to the baseline knowledge regarding variability in lake ecosystems. It provides a literature-based, data-driven and methodological framework for the investigation of variability and patterns in environmental parameters in the time frequency domain.
Observational data often show considerable variability in the environmental parameters of lake ecosystems. This variability is mostly driven by a plethora of periodic and stochastic processes inside and outside the ecosystems. These run in parallel and may operate at vastly different time scales, ranging from seconds to decades. In measured data, all of these signals are superimposed, and dominant processes may obscure the signals of other processes, particularly when analyzing mean values over long time scales. Dominant signals are often caused by phenomena at long time scales like seasonal cycles, and most of these are well understood in the limnological literature. The variability injected by biological, chemical and physical processes operating at smaller time scales is less well understood. However, variability affects the state and health of lake ecosystems at all time scales. Besides measuring time series at sufficiently high temporal resolution, the investigation of the full spectrum of variability requires innovative methods of analysis.
Analyzing observational data in the time frequency domain allows to identify variability at different time scales and facilitates their attribution to specific processes. The merit of this approach is subsequently demonstrated in three case studies. The first study uses a conceptual analysis to demonstrate the importance of time scales for the detection of ecosystem responses to climate change. These responses often occur during critical time windows in the year, may exhibit a time lag and can be driven by the exceedance of thresholds in their drivers. This can only be detected if the temporal resolution of the data is high enough. The second study applies Fast Fourier Transform spectral analysis to two decades of daily water temperature measurements to show how temporal and spatial scales of water temperature variability can serve as an indicator for mixing in a shallow, polymictic lake. The final study uses wavelet coherence as a diagnostic tool for limnology on a multivariate high-frequency data set recorded between the onset of ice cover and a cyanobacteria summer bloom in the year 2009 in a polymictic lake. Synchronicities among limnological and meteorological time series in narrow frequency bands were used to identify and disentangle prevailing limnological processes.
Beyond the novel empirical findings reported in the three case studies, this thesis aims to more generally be of interest to researchers dealing with now increasingly available time series data at high temporal resolution. A set of innovative methods to attribute patterns to processes, their drivers and constraints is provided to help make more efficient use of this kind of data.
Für den Industrialisierungsprozess von Entwicklungs- und Schwellenländern haben ausländische Direktinvestitionen (ADI) eine wichtige Funktion. Sie können zum einen zu einer Erhöhung des industriellen Output des Ziellandes führen und zum anderen als Träger von technologischem Wissen fungieren. Neues Wissen kann den Empfängerländern der ADI durch Spillovereffekte und Technologietransfers ausländischer Tochterunternehmen zufließen. Diese Arbeit soll Antworten auf die Fragen geben, durch welche Mechanismen Spillovereffekte und Technologietransfers ausgelöst werden und wie Entwicklungs- und Schwellenländern diesen Wissenszufluss zur Beschleunigung ihres Industrialisierungsprozesses einsetzen können. Hierfür wird ein Konzept zur Förderung von Spillovereffekten entwickelt. Weiterhin wird ein theoretisches Modell entwickelt, in dem der Technologietransfer ausländischer Exportplattformen erstmals in Abhängigkeit des Anteils der Vorprodukte, die im Gastland nachgefragt werden, untersucht. In den Fallstudien Irland und Malaysia werden die Ergebnisse des theoretischen Modells sowie des entwickelten Konzepts illustriert.
Ziel der vorliegenden Arbeit war die Synthese und Charakterisierung von anisotropen Goldnanopartikeln in einer geeigneten Polyelektrolyt-modifizierten Templatphase. Der Mittelpunkt bildet dabei die Auswahl einer geeigneten Templatphase, zur Synthese von einheitlichen und reproduzierbaren anisotropen Goldnanopartikeln mit den daraus resultierenden besonderen Eigenschaften. Bei der Synthese der anisotropen Goldnanopartikeln lag der Fokus in der Verwendung von Vesikeln als Templatphase, wobei hier der Einfluss unterschiedlicher strukturbildender Polymere (stark alternierende Maleamid-Copolymere PalH, PalPh, PalPhCarb und PalPhBisCarb mit verschiedener Konformation) und Tenside (SDS, AOT – anionische Tenside) bei verschiedenen Synthese- und Abtrennungsbedingungen untersucht werden sollte.
Im ersten Teil der Arbeit konnte gezeigt werden, dass PalPhBisCarb bei einem pH-Wert von 9 die Bedingungen eines Röhrenbildners für eine morphologische Transformation von einer vesikulären Phase in eine röhrenförmige Netzwerkstruktur erfüllt und somit als Templatphase zur formgesteuerten Bildung von Nanopartikeln genutzt werden kann.
Im zweiten Teil der Arbeit wurde dargelegt, dass die Templatphase PalPhBisCarb (pH-Wert von 9, Konzentration von 0,01 wt.%) mit AOT als Tensid und PL90G als Phospholipid (im Verhältnis 1:1) die effektivste Wahl einer Templatphase für die Bildung von anisotropen Strukturen in einem einstufigen Prozess darstellt. Bei einer konstanten Synthesetemperatur von 45 °C wurden die besten Ergebnisse bei einer Goldchloridkonzentration von 2 mM, einem Gold-Templat-Verhältnis von 3:1 und einer Synthesezeit von 30 Minuten erzielt. Ausbeute an anisotropen Strukturen lag bei 52 % (Anteil an dreieckigen Nanoplättchen von 19 %). Durch Erhöhung der Synthesetemperatur konnte die Ausbeute auf 56 % (29 %) erhöht werden.
Im dritten Teil konnte durch zeitabhängige Untersuchungen gezeigt werden, dass bei Vorhandensein von PalPhBisCarb die Bildung der energetisch nicht bevorzugten Plättchen-Strukturen bei Raumtemperatur initiiert wird und bei 45 °C ein Optimum annimmt.
Kintetische Untersuchungen haben gezeigt, dass die Bildung dreieckiger Nanoplättchen bei schrittweiser Zugabe der Goldchlorid-Präkursorlösung zur PalPhBisCarb enthaltenden Templatphase durch die Dosierrate der vesikulären Templatphase gesteuert werden kann. In umgekehrter Weise findet bei Zugabe der Templatphase zur Goldchlorid-Präkursorlösung bei 45 °C ein ähnlicher, kinetisch gesteuerter Prozess der Bildung von Nanodreiecken statt mit einer maximalen Ausbeute dreieckigen Nanoplättchen von 29 %.
Im letzten Kapitel erfolgten erste Versuche zur Abtrennung dreieckiger Nanoplättchen von den übrigen Geometrien der gemischten Nanopartikellösung mittels tensidinduzierter Verarmungsfällung. Bei Verwendung von AOT mit einer Konzentration von 0,015 M wurde eine Ausbeute an Nanoplättchen von 99 %, wovon 72 % dreieckiger Geometrien hatten, erreicht.
Das Thema der vorliegenden Arbeit ist die semantische Suche im Kontext heutiger Informationsmanagementsysteme. Zu diesen Systemen zählen Intranets, Web 3.0-Anwendungen sowie viele Webportale, die Informationen in heterogenen Formaten und Strukturen beinhalten. Auf diesen befinden sich einerseits Daten in strukturierter Form und andererseits Dokumente, die inhaltlich mit diesen Daten in Beziehung stehen. Diese Dokumente sind jedoch in der Regel nur teilweise strukturiert oder vollständig unstrukturiert. So beschreiben beispielsweise Reiseportale durch strukturierte Daten den Zeitraum, das Reiseziel, den Preis einer Reise und geben in unstrukturierter Form weitere Informationen, wie Beschreibungen zum Hotel, Zielort, Ausflugsziele an.
Der Fokus heutiger semantischer Suchmaschinen liegt auf dem Finden von Wissen entweder in strukturierter Form, auch Faktensuche genannt, oder in semi- bzw. unstrukturierter Form, was üblicherweise als semantische Dokumentensuche bezeichnet wird. Einige wenige Suchmaschinen versuchen die Lücke zwischen diesen beiden Ansätzen zu schließen. Diese durchsuchen zwar gleichzeitig strukturierte sowie unstrukturierte Daten, werten diese jedoch entweder weitgehend voneinander unabhängig aus oder schränken die Suchmöglichkeiten stark ein, indem sie beispielsweise nur bestimmte Fragemuster unterstützen. Hierdurch werden die im System verfügbaren Informationen nicht ausgeschöpft und gleichzeitig unterbunden, dass Zusammenhänge zwischen einzelnen Inhalten der jeweiligen Informationssysteme und sich ergänzende Informationen den Benutzer erreichen.
Um diese Lücke zu schließen, wurde in der vorliegenden Arbeit ein neuer hybrider semantischer Suchansatz entwickelt und untersucht, der strukturierte und semi- bzw. unstrukturierte Inhalte während des gesamten Suchprozesses kombiniert. Durch diesen Ansatz werden nicht nur sowohl Fakten als auch Dokumente gefunden, es werden auch Zusammenhänge, die zwischen den unterschiedlich strukturierten Daten bestehen, in jeder Phase der Suche genutzt und fließen in die Suchergebnisse mit ein. Liegt die Antwort zu einer Suchanfrage nicht vollständig strukturiert, in Form von Fakten, oder unstrukturiert, in Form von Dokumenten vor, so liefert dieser Ansatz eine Kombination der beiden. Die Berücksichtigung von unterschiedlich Inhalten während des gesamten Suchprozesses stellt jedoch besondere Herausforderungen an die Suchmaschine. Diese muss in der Lage sein, Fakten und Dokumente in Abhängigkeit voneinander zu durchsuchen, sie zu kombinieren sowie die unterschiedlich strukturierten Ergebnisse in eine geeignete Rangordnung zu bringen. Weiterhin darf die Komplexität der Daten nicht an die Endnutzer weitergereicht werden. Die Darstellung der Inhalte muss vielmehr sowohl bei der Anfragestellung als auch bei der Darbietung der Ergebnisse verständlich und leicht interpretierbar sein.
Die zentrale Fragestellung der Arbeit ist, ob ein hybrider Ansatz auf einer vorgegebenen Datenbasis die Suchanfragen besser beantworten kann als die semantische Dokumentensuche und die Faktensuche für sich genommen, bzw. als eine Suche die diese Ansätze im Rahmen des Suchprozesses nicht kombiniert. Die durchgeführten Evaluierungen aus System- und aus Benutzersicht zeigen, dass die im Rahmen der Arbeit entwickelte hybride semantische Suchlösung durch die Kombination von strukturierten und unstrukturierten Inhalten im Suchprozess bessere Antworten liefert als die oben genannten Verfahren und somit Vorteile gegenüber bisherigen Ansätzen bietet. Eine Befragung von Benutzern macht deutlich, dass die hybride semantische Suche als verständlich empfunden und für heterogen strukturierte Datenmengen bevorzugt wird.
This thesis investigates the processing of non-canonical word orders and whether non-canonical orders involving object topicalizations, midfield scrambling and particle verbs are treated the same by native (L1) and non-native (L2) speakers. The two languages investigated are Norwegian and German.
32 L1 Norwegian and 32 L1 German advanced learners of Norwegian were tested in two experiments on object topicalization in Norwegian. The results from the online self-paced reading task and the offline agent identification task show that both groups are able to identify the non-canonical word order and show a facilitatory effect of animate subjects in their reanalysis. Similarly high error rates in the agent identification task suggest that globally unambiguous object topicalizations are a challenging structure for L1 and L2 speakers alike.
The same participants were also tested in two experiments on particle placement in Norwegian, again using a self-paced reading task, this time combined with an acceptability rating task. In the acceptability rating L1 and L2 speakers show the same preference for the verb-adjacent placement of the particle over the non-adjacent placement after the direct object. However, this preference for adjacency is only found in the L1 group during online processing, whereas the L2 group shows no preference for either order.
Another set of experiments tested 33 L1 German and 39 L1 Slavic advanced learners of German on object scrambling in ditransitive clauses in German. Non-native speakers accept both object orders and show neither a preference for either order nor a processing advantage for the canonical order. The L1 group, in contrast, shows a small, but significant preference for the canonical dative-first order in the judgment and the reading task.
The same participants were also tested in two experiments on the application of the split rule in German particle verbs. Advanced L2 speakers of German are able to identify particle verbs and can apply the split rule in V2 contexts in an acceptability judgment task in the same way as L1 speakers. However, unlike the L1 group, the L2 group is not sensitive to the grammaticality manipulation during online processing. They seem to be sensitive to the additional lexical information provided by the particle, but are unable to relate the split particle to the preceding verb and recognize the ungrammaticality in non-V2 contexts.
Taken together, my findings suggest that non-canonical word orders are not per se more difficult to identify for L2 speakers than L1 speakers and can trigger the same reanalysis processes as in L1 speakers. I argue that L2 speakers’ ability to identify a non-canonical word order depends on how the non-canonicity is signaled (case marking vs. surface word order), on the constituents involved (identical vs. different word types), and on the impact of the word order change on sentence meaning. Non-canonical word orders that are signaled by morphological case marking and cause no change to the sentence’s content are hard to detect for L2 speakers.
Prevalence and Predictors of Sexual Aggression Victimization and Perpetration in Chile and Turkey
(2017)
Background: Although sexual aggression is recognized as a serious issue worldwide, the current knowledge base is primarily built on evidence from Western countries, particularly the U.S. For the present doctoral research, Chile and Turkey were selected based on theoretical considerations to examine the prevalence as well as predictors of sexual aggression victimization and perpetration. The first aim of this research project was to systematically review the available evidence provided by past studies on this topic within each country. The second aim was to empirically study the prevalence of experiencing and engaging in sexual aggression since the age of consent among college students in Chile and Turkey. The third aim was to conduct cross-cultural analyses examining pathways to victimization and perpetration based on a two-wave longitudinal design.
Methods: This research adopted a gender-inclusive approach by considering men and women in both victim and perpetrator roles. For the systematic reviews, multiple-stage literature searches were performed, and based on a predefined set of eligibility criteria, 28 studies in Chile and 56 studies in Turkey were identified for inclusion. A two-wave longitudinal study was conducted to examine the prevalence and predictors of sexual aggression among male and female college students in Chile and Turkey. Self-reports of victimization and perpetration were assessed with a Chilean Spanish or Turkish version of the Sexual Aggression and Victimization Scale. Two path models were conceptualized in which participants’ risky sexual scripts for consensual sex, risky sexual behavior, sexual self-esteem, sexual assertiveness, and religiosity were assessed at T1 and used as predictors of sexual aggression victimization and perpetration at T2 in the following 12 months, mediated through past victimization or perpetration, respectively. The models differed in that sexual assertiveness was expected to serve different functions for victimization (refusal assertiveness negatively linked to victimization) and perpetration (initiation assertiveness positively linked to perpetration).
Results: Both systematic reviews revealed that victimization was addressed by all included studies, but data on perpetration was severely limited. A great heterogeneity not only in victimization rates but also in predictors was found, which may be attributed to a lack of conceptual and methodological consistency across studies. The empirical analysis of the prevalence of sexual aggression in Chile revealed a victimization rate of 51.9% for women and 48.0% for men, and a perpetration rate of 26.8% for men and 16.5% for women. In the Turkish original data, victimization was reported by 77.6% of women and 65.5% of men, whereas, again, lower rates were found for perpetration, with 28.9% of men and 14.2% of women reporting at least one incident. The cross-cultural analyses showed, as expected, that risky sexual scripts informed risky sexual behavior, and thereby indirectly increased the likelihood of victimization and perpetration at T2 in both samples. More risky sexual scripts were also linked to lower levels of refusal assertiveness in both samples, indirectly increasing the vulnerability to victimization at T2. High sexual self-esteem decreased the probability of victimization at T2 through higher refusal assertiveness as well as through less risky sexual behavior also in both samples, whereas it increased the odds of perpetration at T2 via higher initiation assertiveness in the Turkish sample only. Furthermore, high religiosity decreased the odds of perpetration and victimization at T2 through less risky sexual scripts and less risky sexual behavior in both samples. It reduced the vulnerability to victimization through less risky sexual scripts and higher refusal assertiveness in the Chilean sample only. In the Turkish sample only, it increased the odds of perpetration and victimization through lower sexual self-esteem.
Conclusions: The findings showed that sexual aggression is a widespread problem in both Chile and Turkey, contributing cross-cultural evidence to the international knowledge base and indicating the clear need for implementing policy measures and prevention strategies in each country. Based on the results of the prospective analyses, concrete implications for intervention efforts are discussed.
In Germany more than 200.000 persons die of cancer every year, which makes it the second most common cause of death. Chemotherapy and radiation therapy are often combined to exploit a supra-additive effect, as some chemotherapeutic agents like halogenated nucleobases sensitize the cancerous tissue to radiation. The radiosensitizing action of certain therapeutic agents can be at least partly assigned to their interaction with secondary low energy electrons (LEEs) that are generated along the track of the ionizing radiation. In the therapy of cancer DNA is an important target, as severe DNA damage like double strand breaks induce the cell death. As there is only a limited number of radiosensitizing agents in clinical practice, which are often strongly cytotoxic, it would be beneficial to get a deeper understanding of the interaction of less toxic potential radiosensitizers with secondary reactive species like LEEs. Beyond that LEEs can be generated by laser illuminated nanoparticles that are applied in photothermal therapy (PTT) of cancer, which is an attempt to treat cancer by an increase of temperature in the cells. However, the application of halogenated nucleobases in PTT has not been taken into account so far. In this thesis the interaction of the potential radiosensitizer 8-bromoadenine (8BrA) with LEEs was studied. In a first step the dissociative electron attachment (DEA) in the gas phase was studied in a crossed electron-molecular beam setup. The main fragmentation pathway was revealed as the cleavage of the C-Br bond. The formation of a stable parent anion was observed for electron energies around 0 eV. Furthermore, DNA origami nanostructures were used as platformed to determine electron induced strand break cross sections of 8BrA sensitized oligonucleotides and the corresponding nonsensitized sequence as a function of the electron energy. In this way the influence of the DEA resonances observed for the free molecules on the DNA strand breaks was examined. As the surrounding medium influences the DEA, pulsed laser illuminated gold nanoparticles (AuNPs) were used as a nanoscale electron source in an aqueous environment. The dissociation of brominated and native nucleobases was tracked with UV-Vis absorption spectroscopy and the generated fragments were identified with surface enhanced Raman scattering (SERS). Beside the electron induced damage, nucleobase analogues are decomposed in the vicinity of the laser illuminatednanoparticles due to the high temperatures. In order to get a deeper understanding of the different dissociation mechanisms, the thermal decomposition of the nucleobases in these systems was studied and the influence of the adsorption kinetics of the molecules was elucidated. In addition to the pulsed laser experiments, a dissociative electron transfer from plasmonically generated ”hot electrons” to 8BrA was observed under low energy continuous wave laser illumination and tracked with SERS. The reaction was studied on AgNPs and AuNPs as a function of the laser intensity and wavelength. On dried samples the dissociation of the molecule was described by fractal like kinetics. In solution, the dissociative electron transfer was observed as well. It turned out that the timescale of the reaction rates were slightly below typical integration times of Raman spectra. In consequence such reactions need to be taken into account in the interpretation of SERS spectra of electrophilic molecules. The findings in this thesis help to understand the interaction of brominated nucleobases with plasmonically generated electrons and free electrons. This might help to evaluate the potential radiosensitizing action of such molecules in cancer radiation therapy and PTT.
Via their powerful radiation, stellar winds, and supernova explosions, massive stars (Mini & 8 M☉) bear a tremendous impact on galactic evolution. It became clear in recent decades that the majority of massive stars reside in binary systems. This thesis sets as a goal to quantify the impact of binarity (i.e., the presence of a companion star) on massive stars. For this purpose, massive binary systems in the Local Group, including OB-type binaries, high mass X-ray binaries (HMXBs), and Wolf-Rayet (WR) binaries, were investigated by means of spectral, orbital, and evolutionary analyses.
The spectral analyses were performed with the non-local thermodynamic equillibrium (non-LTE) Potsdam Wolf-Rayet (PoWR) model atmosphere code. Thanks to critical updates in the calculation of the hydrostatic layers, the code became a state-of-the-art tool applicable for all types of hot massive stars (Chapter 2). The eclipsing OB-type triple system δ Ori served as an intriguing test-case for the new version of the PoWR code, and provided key insights regarding the formation of X-rays in massive stars (Chapter 3). We further analyzed two prototypical HMXBs, Vela X-1 and IGR J17544-2619, and obtained fundamental conclusions regarding the dichotomy of two basic classes of HMXBs (Chapter 4). We performed an exhaustive analysis of the binary R 145 in the Large Magellanic Cloud (LMC), which was claimed to host the most massive stars known. We were able to disentangle the spectrum of the system, and performed an orbital, polarimetric, and spectral analysis, as well as an analysis of the wind-wind collision region. The true masses of the binary components turned out to be significantly lower than suggested, impacting our understanding of the initial mass function and stellar evolution at low metallicity (Chapter 5). Finally, all known WR binaries in the Small Magellanic Cloud (SMC) were analyzed. Although it was theoretical predicted that virtually all WR stars in the SMC should be formed via mass-transfer in binaries, we find that binarity was not important for the formation of the known WR stars in the SMC, implying a strong discrepancy between theory and observations (Chapter 6).
The ionosphere, which is strongly influenced by the Sun, is known to be also affected by meteorological processes. These processes, despite having their origin in the troposphere and stratosphere, interact with the upper atmosphere. Such an interaction between atmospheric layers is known as vertical coupling. During geomagnetically quiet times, when near-Earth space is not under the influence of solar storms, these processes become important drivers for ionospheric variability. Studying the link between these processes in the lower atmosphere and the ionospheric variability is important for our understanding of fundamental mechanisms in ionospheric and meteorological research.
A prominent example of vertical coupling between the stratosphere and the ionosphere are the so-called stratospheric sudden warming (SSW) events that occur usually during northern winters and result in an increase in the polar stratospheric temperature and a reversal of the circumpolar winds. While the phenomenon of SSW is confined to the northern polar stratosphere, its influence on the ionosphere can be observed even at equatorial latitudes. During SSW events, the connection between the polar stratosphere and the equatorial ionosphere is believed to be through the modulation of global atmospheric tides. These tides are fundamental for the ionospheric E-region wind dynamo that generates electric fields and currents in the ionosphere. Observations of ionospheric currents indicate a large enhancement of the semidiurnal lunar tide in response to SSW events. Thus, the semidiurnal lunar tide becomes an important driver of ionospheric variability during SSW events.
In this thesis, the ionospheric effect of SSW events is investigated in the equatorial region, where a narrow but an intense E-region current known as the equatorial electrojet (EEJ) flows above the dip equator during the daytime. The day-to-day variability of the EEJ can be determined from magnetic field records at geomagnetic observatories close to the dip equator. Such magnetic data are available for several decades and allows to investigate the impact of SSW events on the EEJ and, even more importantly, helps in understanding the effects of SSW events on the equatorial ionosphere. An excellent long-term record of the geomagnetic field at the equator from 1922 onwards is available for the observatory Huancayo in Peru and is extensively utilized in this study.
The central subject of this thesis is the investigation of lunar tides in the EEJ during SSW events by analyzing long time series. This is done by estimating the lunar tidal amplitude in the EEJ from the magnetic records at Huancayo and by comparing them to measurements of the polar stratospheric wind and temperature, which led to the identification of the known SSW events from 1952 onwards. One goal of this thesis is to identify SSW events that predate 1952. To this end, superposed epoch analysis (SEA) is employed to establish a relationship between the lunar tidal power and the wind and temperature conditions in the lower atmosphere. A threshold value for the lunar tidal power is identified that is discriminative for the known SSW events. This threshold is then used to identify lunar tidal enhancements, which are indicative for any historic SSW events prior to 1952. It can be shown, that the number of lunar tidal enhancements and thus the occurrence frequency of historic SSW events between 1926 and 1952 is similar to the occurrence frequency of the known SSW events from 1952 onwards.
Next to the classic SSW definition, the concept of polar vortex weakening (PVW) is utilized in this thesis. PVW is defined for higher latitudes and altitudes (≈ 40km) than the classical SSW definition (≈ 32km). The correlation between the timing and magnitude of lunar tidal enhancements in the EEJ and the timing and magnitude of PVW is found to be better than for the classic SSW definition. This suggests that the lunar tidal enhancements in the EEJ are closely linked to the state of the middle atmosphere.
Geomagnetic observatories located in different longitudes at the dip equator allow investigating the longitudinally dependent variability of the EEJ during SSW events. For this purpose, the lunar tidal enhancements in the EEJ are determined for the Peruvian and Indian sectors during the major SSW events of the years 2006 and 2009. It is found that the lunar tidal amplitude shows similar enhancements in the Peruvian sector during both SSW events, while the enhancements are notably different for the two events in the Indian sector.
In summary, this thesis shows that lunar tidal enhancements in the EEJ are indeed correlated to the occurrence of SSW events and they should be considered a prominent driver of low latitude ionospheric variability. Secondly, lunar tidal enhancements are found to be longitudinally variable. This suggests that regional effects, such as ionospheric conductivity and the geometry and strength of the geomagnetic field, also play an important role and have to be considered when investigating the mechanisms behind vertical coupling.
During the drug discovery & development process, several phases encompassing a number of preclinical and clinical studies have to be successfully passed to demonstrate safety and efficacy of a new drug candidate. As part of these studies, the characterization of the drug's pharmacokinetics (PK) is an important aspect, since the PK is assumed to strongly impact safety and efficacy. To this end, drug concentrations are measured repeatedly over time in a study population. The objectives of such studies are to describe the typical PK time-course and the associated variability between subjects. Furthermore, underlying sources significantly contributing to this variability, e.g. the use of comedication, should be identified. The most commonly used statistical framework to analyse repeated measurement data is the nonlinear mixed effect (NLME) approach. At the same time, ample knowledge about the drug's properties already exists and has been accumulating during the discovery & development process: Before any drug is tested in humans, detailed knowledge about the PK in different animal species has to be collected. This drug-specific knowledge and general knowledge about the species' physiology is exploited in mechanistic physiological based PK (PBPK) modeling approaches -it is, however, ignored in the classical NLME modeling approach.
Mechanistic physiological based models aim to incorporate relevant and known physiological processes which contribute to the overlying process of interest. In comparison to data--driven models they are usually more complex from a mathematical perspective. For example, in many situations, the number of model parameters outrange the number of measurements and thus reliable parameter estimation becomes more complex and partly impossible. As a consequence, the integration of powerful mathematical estimation approaches like the NLME modeling approach -which is widely used in data-driven modeling -and the mechanistic modeling approach is not well established; the observed data is rather used as a confirming instead of a model informing and building input.
Another aggravating circumstance of an integrated approach is the inaccessibility to the details of the NLME methodology so that these approaches can be adapted to the specifics and needs of mechanistic modeling. Despite the fact that the NLME modeling approach exists for several decades, details of the mathematical methodology is scattered around a wide range of literature and a comprehensive, rigorous derivation is lacking. Available literature usually only covers selected parts of the mathematical methodology. Sometimes, important steps are not described or are only heuristically motivated, e.g. the iterative algorithm to finally determine the parameter estimates.
Thus, in the present thesis the mathematical methodology of NLME modeling is systemically described and complemented to a comprehensive description,
comprising the common theme from ideas and motivation to the final parameter estimation. Therein, new insights for the interpretation of different approximation methods used in the context of the NLME modeling approach are given and illustrated; furthermore, similarities and differences between them are outlined. Based on these findings, an expectation-maximization (EM) algorithm to determine estimates of a NLME model is described.
Using the EM algorithm and the lumping methodology by Pilari2010, a new approach on how PBPK and NLME modeling can be combined is presented and exemplified for the antibiotic levofloxacin. Therein, the lumping identifies which processes are informed by the available data and the respective model reduction improves the robustness in parameter estimation. Furthermore, it is shown how apriori known factors influencing the variability and apriori known unexplained variability is incorporated to further mechanistically drive the model development. Concludingly, correlation between parameters and between covariates is automatically accounted for due to the mechanistic derivation of the lumping and the covariate relationships.
A useful feature of PBPK models compared to classical data-driven PK models is in the possibility to predict drug concentration within all organs and tissue in the body. Thus, the resulting PBPK model for levofloxacin is used to predict drug concentrations and their variability within soft tissues which are the site of action for levofloxacin. These predictions are compared with data of muscle and adipose tissue obtained by microdialysis, which is an invasive technique to measure a proportion of drug in the tissue, allowing to approximate the concentrations in the interstitial fluid of tissues. Because, so far, comparing human in vivo tissue PK and PBPK predictions are not established, a new conceptual framework is derived. The comparison of PBPK model predictions and microdialysis measurements shows an adequate agreement and reveals further strengths of the presented new approach.
We demonstrated how mechanistic PBPK models, which are usually developed in the early stage of drug development, can be used as basis for model building in the analysis of later stages, i.e. in clinical studies. As a consequence, the extensively collected and accumulated knowledge about species and drug are utilized and updated with specific volunteer or patient data. The NLME approach combined with mechanistic modeling reveals new insights for the mechanistic model, for example identification and quantification of variability in mechanistic processes. This represents a further contribution to the learn & confirm paradigm across different stages of drug development.
Finally, the applicability of mechanism--driven model development is demonstrated on an example from the field of Quantitative Psycholinguistics to analyse repeated eye movement data. Our approach gives new insight into the interpretation of these experiments and the processes behind.
Anthropogenically amplified erosion leads to increased fine-grained sediment input into the fluvial system in the 15.000 km2 Kharaa River catchment in northern Mongolia and constitutes a major stressing factor for the aquatic ecosystem. This study uniquely combines the application of intensive monitoring, source fingerprinting and catchment modelling techniques to allow for the comparison of the credibility and accuracy of each single method. High-resolution discharge data were used in combination with daily suspended solid measurements to calculate the suspended sediment budget and compare it with estimations of the sediment budget model SedNet. The comparison of both techniques showed that the development of an overall sediment budget with SedNet was possible, yielding results in the same order of magnitude (20.3 kt a- 1 and 16.2 kt a- 1).
Radionuclide sediment tracing, using Be-7, Cs-137 and Pb-210 was applied to differentiate sediment sources for particles < 10μm from hillslope and riverbank erosion and showed that riverbank erosion generates 74.5% of the suspended sediment load, whereas surface erosion contributes 21.7% and gully erosion only 3.8%. The contribution of the single subcatchments of the Kharaa to the suspended sediment load was assessed based on their variation in geochemical composition (e.g. in Ti, Sn, Mo, Mn, As, Sr, B, U, Ca and Sb). These variations were used for sediment source discrimination with geochemical composite fingerprints based on Genetic Algorithm driven Discriminant Function Analysis, the Kruskal–Wallis H-test and Principal Component Analysis. The contributions of the individual sub-catchment varied from 6.4% to 36.2%, generally showing higher contributions from the sub-catchments in the middle, rather than the upstream portions of the study area.
The results indicate that river bank erosion generated by existing grazing practices of livestock is the main cause for elevated fine sediment input. Actions towards the protection of the headwaters and the stabilization of the river banks within the middle reaches were identified as the highest priority. Deforestation and by lodging and forest fires should be prevented to avoid increased hillslope erosion in the mountainous areas. Mining activities are of minor importance for the overall catchment sediment load but can constitute locally important point sources for particular heavy metals in the fluvial system.
Approaching physical limits in speed and size of today's magnetic storage and processing technologies demands new concepts for controlling magnetization and moves researches on optically induced magnetic dynamics. Studies on photoinduced magnetization dynamics and their underlying mechanisms have been primarily performed on ferromagnetic metals. Ferromagnetic dynamics bases on transfer of the conserved angular momentum connected with atomic magnetic moments out of the parallel aligned magnetic system into other degrees of freedom.
In this thesis the so far rarely studied response of antiferromagnetic order to ultra-short optical laser pulses in a metal is investigated. The experiments were performed at the FemtoSpex slicing facility at the storage ring BESSY II, an unique source for ultra-short elliptically polarized x-ray pulses. Laser-induced changes of the 4f-magnetic order parameter in ferro- and antiferromagnetic dysprosium (Dy), were studied by x-ray methods, which yield directly comparable quantities. The discovered fundamental differences in the temporal and spatial behavior of ferro- and antiferrmagnetic dynamics are assinged to an additional channel for angular momentum transfer, which reduces the antiferromagnetic order by redistributing angular momentum within the non-parallel aligned magnetic system, and hence conserves the zero net magnetization. It is shown that antiferromagnetic dynamics proceeds considerably faster and more energy-efficient than demagnetization in ferromagnets. By probing antiferromagnetic order in time and space, it is found to be affected along the whole sample depth of an in situ grown 73 nm tick Dy film. Interatomic transfer of angular momentum via fast diffusion of laser-excited 5d electrons is held responsible for the out-most long-ranging effect. Ultrafast ferromagnetic dynamics can be expected to base on the same origin, which however leads to demagnetization only in regions close to interfaces caused by super-diffusive spin transport. Dynamics due to local scattering processes of excited but less mobile electrons, occur in both magnetic alignments only in directly excited regions of the sample and on slower pisosecond timescales. The thesis provides fundamental insights into photoinduced magnetic dynamics by directly comparing ferro- and antiferromagnetic dynamics in the same material and by consideration of the laser-induced magnetic depth profile.
Der technologische Wandel stellt Organisationen vor die Herausforderung, Innovationen möglichst schnell produktiv zu nutzen und damit einen Wettbewerbsvorteil zu erzielen. Der Erfolg der Technologieeinführung hängt stark mit der Schaffung von Akzeptanz bei den Mitarbeitern zusammen. Bestehende Ansätze wie die Diffusionstheorie (Rogers, 2003) oder das Technology Acceptance Model (Davis, 1989; Venkatesh und Davis, 1996; Venkatesh und Davis, 2000; Venkatesh, Morris u. a., 2003) widmen sich dem Organisationskontext jedoch nur am Rande. Ihre Modelle zielen auf die Übernahme einer Technologie in freier Entscheidung und im Marktkontext ab. Weiterhin beleuchten sie den Widerstand gegen Neuerungen nicht, welcher sich bei der verpflichtenden Übernahme bilden kann. Zur Untersuchung der Technologieeinführung und von Akzeptanzbildungsprozessen in Organisationen sind sie daher nur begrenzt nutzbar.
Das Ziel dieser Arbeit ist es daher, den spezifischen Einfluss des Kontextes Organisation auf die Akzeptanz und das Nutzungsverhalten herauszuarbeiten. Konkreter soll die Forschungsfrage geklärt werden, welchen Einfluss unterschiedliche Organisationstypen auf die Akzeptanz- und Nutzungsdynamik innerhalb von Organisationen haben. Hierfür wird die Erweiterung und Synthese bestehender Modelle der Akzeptanzforschung um organisationsspezifische Attribute vorgenommen. Das resultierende Modell erfasst die dynamische Entwicklung innerhalb der Organisation und ermöglicht damit die Beobachtung des Wandels. Die Funktionsweise des entwickelten Modells soll in einem Simulationsexperiment demonstriert und die Wirkung unterschiedlicher Organisationsformen verdeutlicht werden.
Das Modell vereint daher zwei Perspektiven: Die personale Perspektive fasst Akzeptanz als kognitiv-psychischen Prozess auf individueller Ebene. Dieser basiert auf den Kalkülen und Entscheidungen einzelner Personen. Zentral sind hierfür die Beiträge der Diffusionstheorie (Rogers, 2003) sowie das Technology Acceptance Model in seinen diversen Weiterentwicklungen und Veränderungen (Davis, 1989; Venkatesh und Davis, 1996; Venkatesh und Davis, 2000; Venkatesh, Morris u. a., 2003). Individuelle Faktoren aus unterschiedlichen Fit-Theorien (Goodhue und Thompson, 1995; Floyd, 1986; Liu, Lee und Chen, 2011; Parkes, 2013) werden genutzt, um diese Modelle anzureichern. Neben der Entwicklung
einer positiven, förderlichen Einstellung muss jedoch auch die Ablehnung und das offene Opponieren gegen die Innovation berücksichtigt werden (Patsiotis, Hughes und Webber, 2012).
Die organisatorische Perspektive hingegen sieht Akzeptanzentscheidungen eingebettet in den sozialen Kontext der Organisation. Die gegenseitige Beeinflussung basiert auf der Beobachtung der Umgebung und der Internalisierung sozialen Drucks. Dem steht in Organisationen die intendierte Beeinflussung in Form von Steuerung gegenüber. Beide Vorgänge formen das Akzeptanz- oder das Nutzungsverhalten der Mitarbeiter. Ausgehend von einem systemtheoretischen Organisationsbegriff werden unterschiedliche Steuerungsmedien (Luhmann, 1997; Fischer, 2009) vorgestellt. Diese können durch Steuerungsakteure
(Change Agents, Management) intendiert eingesetzt werden, um den Akzeptanz- und Nutzungsprozess über Interventionen zu gestalten.
Die Wirkung der Medien unterscheidet sich in verschiedenen Organisationstypen. Zur Analyse unterschiedlicher Organisationstypen werden die Konfigurationen nach Mintzberg (1979) herangezogen. Diese zeichnen sich durch unterschiedliche Koordinationsmechanismen aus, welche wiederum auf dem Einsatz von Steuerungsmedien beruhen.
Die Demonstration der Funktionsweise und Analysemöglichkeiten des entwickelten Modells erfolgt anhand eines Simulationsexperiments mittels der Simulationsplattform AnyLogic. Das Gültigkeitsspektrum wird anhand einer Sensitivitätsanalyse geprüft.
In der Simulation lassen sich spezifische Muster der Nutzung und Akzeptanzentwicklung nachweisen. Die Akzeptanz ist durch ein initiales Absinken und ein anschließendes gedämpftes Wachstum gekennzeichnet. Die Nutzung wird in der Organisation hingegen schnell durchgesetzt und verharrt dann auf einem stabilen Niveau. Für die Organisationstypen konnten unterschiedliche Effekte beobachtet werden. So eignet sich die bürokratische Steuerungsform zur Nutzungserhöhung, schafft es jedoch nicht, die Akzeptanz zu steigern. Organisationen, welche eher auf gegenseitige Abstimmung zur Koordination ausgelegt sind, erhöhen die Akzeptanz, jedoch nicht die Nutzung. Weiterhin ist die Entwicklung der Akzeptanz in diesem Organisationstyp sehr unsicher und weist einen hohen Schwankungsbereich auf.
This cumulative doctoral dissertation, based on three publications, is devoted to the investigation of several aspects of azobenzene molecular switches, with the aid of computational chemistry.
In the first paper, the isomerization rates of a thermal cis → trans isomerization of azobenzenes for species formed upon an integer electron transfer, i.e., with added or removed electron, are calculated from Eyring’s transition state theory and activation energy barriers, computed by means of density functional theory. The obtained results are discussed in connection with an experimental study of the thermal cis → trans isomerization of azobenzene derivatives in the presence of gold nanoparticles, which is demonstrated to be greatly accelerated in comparison to the same isomerization reaction in the absence of nanoparticles.
The second paper is concerned with electronically excited states of (i) dimers, composed of two photoswitchable units placed closely side-by-side, as well as (ii) monomers and dimers adsorbed on a silicon cluster. A variety of quantum chemistry methods, capable of calculating molecular electronic absorption spectra, based on density functional and wave function theories, is employed to quantify changes in optical absorption upon dimerization and covalent grafting to a surface. Specifically, the exciton (Davydov) splitting between states of interest is determined from first-principles calculations with the help of natural transition orbital analysis, allowing for insight into the nature of excited states.
In the third paper, nonadiabatic molecular dynamics with trajectory surface hopping is applied to model the photoisomerization of azobenzene dimers, (i) for the isolated case (exhibiting the exciton coupling between two molecules) as well as (ii) for the constrained case (providing the van der Waals interaction with environment in addition to the exciton coupling between two monomers). For the latter, the additional azobenzene molecules, surrounding the dimer, are introduced, mimicking a densely packed self-assembled monolayer. From obtained results it is concluded that the isolated dimer is capable of isomerization likewise the monomer, whereas the steric hindrance considerably suppresses trans → cis photoisomerization.
Furthermore, the present dissertation comprises the general introduction describing the main features of the azobenzene photoswitch and objectives of this work, theoretical basis of the employed methods, and discussion of gained findings in the light of existing literature. Also, additional results on (i) activation parameters of the thermal cis → trans isomerization of azobenzenes, (ii) an approximate scheme to account for anharmonicity of molecular vibrations in calculation of the activation entropy, as well as (iii) absorption spectra of photoswitch–silicon composites obtained from time-demanding wave function-based methods are presented.
Einleitung: Die Erdnussallergie zählt zu den häufigsten Nahrungsmittelallergien im Kindesalter. Bereits kleine Mengen Erdnuss (EN) können zu schweren allergischen Reaktionen führen. EN ist der häufigste Auslöser einer lebensbedrohlichen Anaphylaxie bei Kindern und Jugendlichen. Im Gegensatz zu anderen frühkindlichen Nahrungsmittelallergien entwickeln Patienten mit einer EN-Allergie nur selten eine natürliche Toleranz. Seit mehreren Jahren wird daher an kausalen Therapiemöglichkeiten für EN-Allergiker, insbesondere an der oralen Immuntherapie (OIT), geforscht. Erste kleinere Studien zur OIT bei EN-Allergie zeigten erfolgsversprechende Ergebnisse. Im Rahmen einer randomisierten, doppelblind, Placebo-kontrollierten Studie mit größerer Fallzahl werden in der vorliegenden Arbeit die klinische Wirksamkeit und Sicherheit dieser Therapieoption bei Kindern mit EN-Allergie genauer evaluiert. Des Weiteren werden immunologische Veränderungen sowie die Lebensqualität und Therapiebelastung unter OIT untersucht.
Methoden: Kinder zwischen 3-18 Jahren mit einer IgE-vermittelten EN-Allergie wurden in die Studie eingeschlossen. Vor Beginn der OIT wurde eine orale Provokation mit EN durchgeführt. Die Patienten wurden 1:1 randomisiert und entsprechend der Verum- oder Placebogruppe zugeordnet. Begonnen wurde mit 2-120 mg EN bzw. Placebo pro Tag, abhängig von der Reaktionsdosis bei der oralen Provokation. Zunächst wurde die tägliche OIT-Dosis alle zwei Wochen über etwa 14 Monate langsam bis zu einer Erhaltungsdosis von mindestens 500 mg EN (= 125 mg EN-Protein, ~ 1 kleine EN) bzw. Placebo gesteigert. Die maximal erreichte Dosis wurde dann über zwei Monate täglich zu Hause verabreicht. Im Anschluss erfolgte erneut eine orale Provokation mit EN. Der primäre Endpunkt der Studie war die Anzahl an Patienten der Verum- und Placebogruppe, die unter oraler Provokation nach OIT ≥1200 mg EN vertrugen (=„partielle Desensibilisierung“). Sowohl vor als auch nach OIT wurde ein Hautpricktest mit EN durchgeführt und EN-spezifisches IgE und IgG4 im Serum bestimmt. Außerdem wurden die Basophilenaktivierung sowie die Ausschüttung von T-Zell-spezifischen Zytokinen nach Stimulation mit EN in vitro gemessen. Anhand von Fragebögen wurde die Lebensqualität vor und nach OIT sowie die Therapiebelastung während OIT erfasst.
Ergebnisse: 62 Patienten wurden in die Studie eingeschlossen und randomisiert. Nach etwa 16 Monaten unter OIT zeigten 74,2% (23/31) der Patienten der Verumgruppe und nur 16,1% (5/31) der Placebogruppe eine „partielle Desensibilisierung“ gegenüber EN (p<0,001). Im Median vertrugen Patienten der Verumgruppe 4000 mg EN (~8 kleine EN) unter der Provokation nach OIT wohingegen Patienten der Placebogruppe nur 80 mg EN (~1/6 kleine EN) vertrugen (p<0,001). Fast die Hälfte der Patienten der Verumgruppe (41,9%) tolerierten die Höchstdosis von 18 g EN unter Provokation („komplette Desensibilisierung“). Es zeigte sich ein vergleichbares Sicherheitsprofil unter Verum- und Placebo-OIT in Bezug auf objektive Nebenwirkungen. Unter Verum-OIT kam es jedoch signifikant häufiger zu subjektiven Nebenwirkungen wie oralem Juckreiz oder Bauchschmerzen im Vergleich zu Placebo (3,7% der Verum-OIT-Gaben vs. 0,5% der Placebo-OIT-Gaben, p<0,001). Drei Kinder der Verumgruppe (9,7%) und sieben Kinder der Placebogruppe (22,6%) beendeten die Studie vorzeitig, je zwei Patienten beider Gruppen aufgrund von Nebenwirkungen. Im Gegensatz zu Placebo, zeigten sich unter Verum-OIT signifikante immunologische Veränderungen. So kam es zu einer Abnahme des EN-spezifischen Quaddeldurchmessers im Hautpricktest, einem Anstieg der EN-spezifischen IgG4-Werte im Serum sowie zu einer verminderten EN-spezifischen Zytokinsekretion, insbesondere der Th2-spezifischen Zytokine IL-4 und IL-5. Hinsichtlich der EN-spezifischen IgE-Werte sowie der EN-spezifischen Basophilenaktivierung zeigten sich hingegen keine Veränderungen unter OIT. Die Lebensqualität von Kindern der Verumgruppe war nach OIT signifikant verbessert, jedoch nicht bei Kindern der Placebogruppe. Während der OIT wurde die Therapie von fast allen Kindern (82%) und Müttern (82%) als positiv bewertet (= niedrige Therapiebelastung).
Diskussion: Die EN-OIT führte bei einem Großteil der EN-allergischen Kinder zu einer Desensibilisierung und einer deutlich erhöhten Reaktionsschwelle auf EN. Somit sind die Kinder im Alltag vor akzidentellen Reaktionen auf EN geschützt, was die Lebensqualität der Kinder deutlich verbessert. Unter den kontrollierten Studienbedingungen zeigte sich ein akzeptables Sicherheitsprofil, mit vorrangig milder Symptomatik. Die klinische Desensibilisierung ging mit Veränderungen auf immunologischer Ebene einher. Langzeitstudien zur EN-OIT müssen jedoch abgewartet werden, um die klinische und immunologische Wirksamkeit hinsichtlich einer möglichen langfristigen oralen Toleranzinduktion sowie die Sicherheit unter langfristiger OIT zu untersuchen, bevor das Therapiekonzept in die Praxis übertragen werden kann.
Researchers have made many approaches to study the complexities of the mammalian taste system; however molecular mechanisms of taste processing in the early structures of the central taste pathway remain unclear. More recently the Arc catFISH (cellular compartment analysis of temporal activity by fluorescent in situ hybridisation) method has been used in our lab to study neural activation following taste stimulation in the first central structure in the taste pathway, the nucleus of the solitary tract. This method uses the immediate early gene Arc as a neural activity marker to identify taste-responsive neurons. Arc plays a critical role in memory formation and is necessary for conditioned taste aversion memory formation. In the nucleus of the solitary tract only bitter taste stimulation resulted in increased Arc expression, however this did not occur following stimulation with tastants of any other taste quality. The primary target for gustatory NTS neurons is the parabrachial nucleus (PbN) and, like Arc, the PbN plays an important role in conditioned taste aversion learning.
The aim of this thesis is to investigate Arc expression in the PbN following taste stimulation to elucidate the molecular identity and function of Arc expressing, taste- responsive neurons. Naïve and taste-conditioned mice were stimulated with tastants from each of the five basic taste qualities (sweet, salty, sour, umami, and bitter), with additional bitter compounds included for comparison. The expression patterns of Arc and marker genes were analysed using in situ hybridisation (ISH). The Arc catFISH method was used to observe taste-responsive neurons following each taste stimulation. A double fluorescent in situ hybridisation protocol was then established to investigate possible neuropeptide genes involved in neural responses to taste stimulation.
The results showed that bitter taste stimulation induces increased Arc expression in the PbN in naïve mice. This was not true for other taste qualities. In mice conditioned to find an umami tastant aversive, subsequent umami taste stimulation resulted in an increase in Arc expression similar to that seen in bitter-stimulated mice. Taste-responsive Arc expression was denser in the lateral PbN than the medial PbN. In mice that received two temporally separated taste stimulations, each stimulation time-point showed a distinct population of Arc-expressing neurons, with only a small population (10 – 18 %) of neurons responding to both stimulations. This suggests that either each stimulation event activates a different population of neurons, or that Arc is marking something other than simple cellular activation, such as long-term cellular changes that do not occur twice within a 25 minute time frame. Investigation using the newly established double-FISH protocol revealed that, of the bitter-responsive Arc expressing neuron population: 16 % co-expressed calcitonin RNA; 17 % co-expressed glucagon-like peptide 1 receptor RNA; 17 % co-expressed hypocretin receptor 1 RNA; 9 % co-expressed gastrin-releasing peptide RNA; and 20 % co-expressed neurotensin RNA. This co-expression with multiple different neuropeptides suggests that bitter-activated Arc expression mediates multiple neural responses to the taste event, such as taste aversion learning, suppression of food intake, increased heart rate, and involves multiple brain structures such as the lateral hypothalamus, amygdala, bed nucleus of the stria terminalis, and the thalamus.
The increase in Arc-expression suggests that bitter taste stimulation, and umami taste stimulation in umami-averse animals, may result in an enhanced state of Arc- dependent synaptic plasticity in the PbN, allowing animals to form taste-relevant memories to these aversive compounds more readily. The results investigating neuropeptide RNA co- expression suggest the amygdala, bed nucleus of the stria terminalis, and thalamus as possible targets for bitter-responsive Arc-expressing PbN neurons.
Das Ziel der Arbeit ist die Entwicklung eines heuristischen Bezugsrahmens zur Erklärung der Komplexität im Kontext von Industrie 4.0 und der demografischen Entwicklung aus strukturationstheoretischer Sicht. Dabei sind in Bezug auf die zukünftig zu erwartenden kognitiven Anforderungen an die Beschäftigten die Fragen essentiell, vor welchen Herausforderungen Unternehmen bezüglich der Einstellung und dem Verhalten sowie dem Erfahrungswissen der Beschäftigten stehen und welche Lösungsansätze sich im Umgang mit den Herausforderungen in der Praxis bisher als hilfreich erweisen.
In Kapitel 1 erfolgt zunächst die Beschreibung der Ausgangslage. Es werden die Begriffe Industrie 4.0 und demografische Entwicklung inhaltlich diskutiert und in einen theoretischen Zusammenhang gebracht.
In Kapitel 2 erfolgt die theoretische Fundierung der Arbeit. Dabei wird eine strukturationstheoretische Sicht auf Unternehmen als soziotechnische Systeme eingenommen. Durch diese „nicht deterministische“ Sichtweise wird ein prozessualer Blick auf den Wandlungsprozess in Unternehmen geschaffen, der es möglich macht, die Beschäftigten als aktiv handelnde Akteure im Sinne von „organisieren“ zur Erklärung möglicher Zusammenhänge zwischen Industrie 4.0 und der demografischen Entwicklung mit einzubeziehen. Der soziotechnische Systemansatz und die Strukturationstheorie bilden in diesem Sinne den „Kern“ des zu entwickelnden heuristischen Bezugsrahmens.
Die inhaltliche Gestaltung des theoriebasierten heuristischen Bezugsrahmens erfolgt in Kapitel 3 und Kapitel 4.
Kapitel 3 beschreibt ausgewählte Aspekte zukünftiger Anforderungen an die Arbeit, die durch eine systematische Aufbereitung des derzeitigen Forschungsstandes zu Industrie 4.0 ermittelt wurden. Sie bilden die „Gestaltungsgrenzen“, innerhalb derer sich je nach betrieblicher Situation unterschiedliche neue oder geänderte Anforderungen an die Beschäftigten bei der Gestaltung von Industrie 4.0 ableiten lassen.
In Kapitel 4 werden ausgewählte Aspekte menschlichen Handelns am Beispiel älterer Beschäftigter in Form zweier Schwerpunkte beschrieben.
Der erste Schwerpunkt betrifft mögliche Einflussfaktoren auf die Einstellung und das Verhalten älterer Beschäftigter im Wandlungsprozess aufgrund eines vorherrschenden Altersbildes im Unternehmen. Grundlage hierzu bildete die Stigmatisierungstheorie als interaktionistischer Ansatz der Sozialtheorie.
Mit dem zweiten Schwerpunkt, den ausgewählten handlungstheoretischen Aspekten der Alternsforschung aus der Entwicklungspsychologie, wird eine Lebensspannenperspektive eingenommen. Inhaltlich werden die komplexitätsinduzierten Faktoren, die sich aus handlungstheoretischer Perspektive mit der Adaptation von älteren Beschäftigten an veränderte äußere und persönliche Lebensbedingungen beschäftigen, systematisiert.
Anschließend wird auf Grundlage der bisherigen theoretischen Vorüberlegungen ein erster theoriebasierter Bezugsrahmen abgeleitet.
Kapitel 5 und Kapitel 6 beschreiben den empirischen Teil, die Durchführung teilstrukturierter Interviews, der Arbeit. Ziel der empirischen Untersuchung war es, neben der theoretischen Fundierung den theoriebasierten heuristischen Bezugsrahmen um Praxiserfahrungen zu konkretisieren und gegebenenfalls zu ergänzen. Hierzu wurde auf Grundlage des theoriebasierten heuristischen Bezugsrahmens mittels teilstrukturierter Interviews das Erfahrungswissen von 23 Experten in persönlichen Gesprächen abgefragt.
Nachdem in Kapitel 5 die Vorgehensweise der empirischen Untersuchung beschrieben wird, erfolgt in Kapitel 6 die Beschreibung der Ergebnisse aus der qualitativen Befragung. Hierzu werden aus den persönlichen Gesprächen zentrale Einflussfaktoren bei der Gestaltung und Umsetzung von Industrie 4.0 im Kontext mit der demografischen Entwicklung analysiert und in die übergeordneten Kategorien Handlungskompetenzen, Einstellung/ Verhalten sowie Erfahrungswissen geclustert.
Anschließend wird der theoriebasierte heuristische Bezugsrahmen durch die übergeordneten Kategorien und Faktoren aus den Expertengesprächen konkretisiert und ergänzt.
In Kapitel 7 werden auf Grundlage des heuristischen Bezugsrahmens sowie der Empfehlungen aus den Experteninterviews beispielhaft Implikationen für die Praxis abgeleitet. Es werden Interventionsmöglichkeiten zur Unterstützung einer positiven Veränderungsbereitschaft und einem positiven Veränderungsverhalten für den Strukturwandel aufgezeigt. Hierzu gehören die Anpassung des Führungsverhaltens im Wandlungsprozess, der Umgang mit der Paradoxie von Stabilität und Flexibilität, der Umgang mit Altersstereotypen in Unternehmen, die Unterstützung von Strategien zu Selektion, Optimierung und Kompensation sowie Maßnahmen zur Ausrichtung von Aktivitäten an die Potenzialrisiken der Beschäftigten.
Eine Zusammenfassung, ein Resümee und ein Ausblick erfolgen abschließend in Kapitel 8.
The Yukon Coast in Canada is an ice-rich permafrost coast and highly sensitive to changing environmental conditions. Retrogressive thaw slumps are a common thermoerosion feature along this coast, and develop through the thawing of exposed ice-rich permafrost on slopes and removal of accumulating debris. They contribute large amounts of sediment, including organic carbon and nitrogen, to the nearshore zone.
The objective of this study was to 1) identify the climatic and geomorphological drivers of sediment-meltwater release, 2) quantify the amount of released meltwater, sediment, organic carbon and nitrogen, and 3) project the evolution of sediment-meltwater release of retrogressive thaw slumps in a changing future climate.
The analysis is based on data collected over 18 days in July 2013 and 18 days in August 2012. A cut-throat flume was set up in the main sediment-meltwater channel of the largest retrogressive thaw slump on Herschel Island. In addition, two weather stations, one on top of the undisturbed tundra and one on the slump floor, measured incoming solar radiation, air temperature, wind speed and precipitation. The discharge volume eroding from the ice-rich permafrost and retreating snowbanks was measured and compared to the meteorological data collected in real time with a resolution of one minute.
The results show that the release of sediment-meltwater from thawing of the ice-rich permafrost headwall is strongly related to snowmelt, incoming solar radiation and air temperature. Snowmelt led to seasonal differences, especially due to the additional contribution of water to the eroding sediment-meltwater from headwall ablation, lead to dilution of the sediment-meltwater composition. Incoming solar radiation and air temperature were the main drivers for diurnal and inter-diurnal fluctuations. In July (2013), the retrogressive thaw slump released about 25 000 m³ of sediment-meltwater, containing 225 kg dissolved organic carbon and 2050 t of sediment, which in turn included 33 t organic carbon, and 4 t total nitrogen. In August (2012), just 15 600 m³ of sediment-meltwater was released, since there was no additional contribution from snowmelt. However, even without the additional dilution, 281 kg dissolved organic carbon was released. The sediment concentration was twice as high as in July, with sediment contents of up to 457 g l-1 and 3058 t of sediment, including 53 t organic carbon and 5 t nitrogen, being released.
In addition, the data from the 36 days of observations from Slump D were upscaled to cover the main summer season of 1 July to 31 August (62 days) and to include all 229 active retrogressive thaw slumps along the Yukon Coast. In total, all retrogressive thaw slumps along the Yukon Coast contribute a minimum of 1.4 Mio. m³ sediment-meltwater each thawing season, containing a minimum of 172 000 t sediment with 3119 t organic carbon, 327 t nitrogen and 17 t dissolved organic carbon. Therefore, in addition to the coastal erosion input to the Beaufort Sea, retrogressive thaw slumps additionally release 3 % of sediment and 8 % of organic carbon into the ocean. Finally, the future evolution of retrogressive thaw slumps under a warming scenario with summer air temperatures increasing by 2-3 °C by 2081-2100, would lead to an increase of 109-114% in release of sediment-meltwater.
It can be concluded that retrogressive thaw slumps are sensitive to climatic conditions and under projected future Arctic warming will contribute larger amounts of thawed permafrost material (including organic carbon and nitrogen) into the environment.
Gegenstand der Dissertation ist die Präsentation von Kleidermode in ihr gewidmeten Sonderausstellungen, die in zunehmender Zahl seit den 1990er Jahren in musealen und musemsähnlichen Kontexten veranstaltet werden. Es geht darum, wie Modekörper und vestimentäre Artefakte in diesen Ausstellungen gezeigt werden und welche ästhetischen Erfahrungen sich für die RezipientInnen aus der jeweiligen Konstellation von vestimentärem Objekt und Inszenierungsmittel ergeben können. Das Augenmerk liegt auf der Spannung zwischen dem visuellen Imperativ musealer Zeigepraktiken und den multisensorischen Qualitäten der Kleidermode, v. a. jener hautsinnlichen, die sich aus dem unmittelbaren Kontakt zwischen Körper und Kleid ergeben.
Die zentrale These ist, dass sich das Hautsinnliche der Kleidermode trotz des Berührungsverbots in vielen Ausstellungsinszenierungen zeigen kann. D. h., dass – entgegen häufig wiederholter Behauptungen – ‚der Körper‘, das Tragen und die Bewegung nicht per se oder komplett aus den Kleidern gewichen sind, werden diese musealisiert und ausgestellt. Es findet eine Verschiebung des Körperlichen und Hautsinnlichen, wie das Anfassen, Tragen und Bewegen, in visuelle Darstellungsformen statt. Hautsinnliche Qualitäten der vestimentären Exponate können, auch in Abhängigkeit von den jeweils verwendeten Präsentationsmitteln, von den BesucherInnen in unterschiedlichen Abstufungen sehend oder buchstäblich gespürt werden.
An konkreten Beispielen wird zum einen das Verhältnis von ausgestelltem Kleid und Präsentationsmittel(n) in den Displays untersucht. Dabei stehen folgende Mittel im Fokus, mit deren Hilfe die vestimentären Exponate zur Schau gestellt werden: Vitrinen, Podeste, Ersatzkörper wie Mannequins, optische Hilfsmittel wie Lupen, Bildmedien oder (bewegte) Installationen. Zum anderen wird analysiert, welche Wirkungen die Arrangements jeweils erzielen oder verhindern können, und zwar in Hinblick auf mögliche ästhetische Erfahrungen, die taktilen, haptischen und kinästhetischen Qualitäten der Exponate als BesucherIn sehend oder buchstäblich zu fühlen oder zu spüren. Ob als Identifikation, Projektion, Haptic Vision – es handelt sich um ästhetische Erfahrungen, die sich aus den modischen Kompetenzen der BetrachterInnen speisen und bei denen sich Visuelles und Hautsinnliches oft überlagern.
In der Untersuchung wird eine vernachlässigte, wenn nicht gar unerwünschte Rezeptionsweise diskutiert, die von den AkteurInnen der spezifischen Debatte bspw. als konsumptives Sehen abgewertet wird. Die von mir vorgeschlagene, stärker differenzierende Perspektive ist zugleich eine Kritik an dem bisherigen Diskurs und seinem eng gefassten, teilweise elitären Verständnis von Museum, Bildung und Wissen, mit dem sich AkteurInnen und Institutionen abgrenzen. Der Spezialdiskurs über musealisierte und exponierte Kleidermode steht zudem exemplarisch für die Diskussion, was das Museum, verstanden als Institution, sein kann und soll(te) und ob (und wenn ja, wie) es sich überhaupt noch von anderen Orten und Räumen klar abgrenzen lässt.
Start-up incentives targeted at unemployed individuals have become an important tool of the Active Labor Market Policy (ALMP) to fight unemployment in many countries in recent years. In contrast to traditional ALMP instruments like training measures, wage subsidies, or job creation schemes, which are aimed at reintegrating unemployed individuals into dependent employment, start-up incentives are a fundamentally different approach to ALMP, in that they intend to encourage and help unemployed individuals to exit unemployment by entering self-employment and, thus, by creating their own jobs. In this sense, start-up incentives for unemployed individuals serve not only as employment and social policy to activate job seekers and combat unemployment but also as business policy to promote entrepreneurship. The corresponding empirical literature on this topic so far has been mainly focused on the individual labor market perspective, however. The main part of the thesis at hand examines the new start-up subsidy (“Gründungszuschuss”) in Germany and consists of four empirical analyses that extend the existing evidence on start-up incentives for unemployed individuals from multiple perspectives and in the following directions:
First, it provides the first impact evaluation of the new start-up subsidy in Germany. The results indicate that participation in the new start-up subsidy has significant positive and persistent effects on both reintegration into the labor market as well as the income profiles of participants, in line with previous evidence on comparable German and international programs, which emphasizes the general potential of start-up incentives as part of the broader ALMP toolset. Furthermore, a new innovative sensitivity analysis of the applied propensity score matching approach integrates findings from entrepreneurship and labor market research about the key role of an individual’s personality on start-up decision, business performance, as well as general labor market outcomes, into the impact evaluation of start-up incentives. The sensitivity analysis with regard to the inclusion and exclusion of usually unobserved personality variables reveals that differences in the estimated treatment effects are small in magnitude and mostly insignificant. Consequently, concerns about potential overestimation of treatment effects in previous evaluation studies of similar start-up incentives due to usually unobservable personality variables are less justified, as long as the set of observed control variables is sufficiently informative (Chapter 2).
Second, the thesis expands our knowledge about the longer-term business performance and potential of subsidized businesses arising from the start-up subsidy program. In absolute terms, the analysis shows that a relatively high share of subsidized founders successfully survives in the market with their original businesses in the medium to long run. The subsidy also yields a “double dividend” to a certain extent in terms of additional job creation. Compared to “regular”, i.e., non-subsidized new businesses founded by non-unemployed individuals in the same quarter, however, the economic and growth-related impulses set by participants of the subsidy program are only limited with regard to employment growth, innovation activity, or investment. Further investigations of possible reasons for these differences show that differential business growth paths of subsidized founders in the longer run seem to be mainly limited by higher restrictions to access capital and by unobserved factors, such as less growth-oriented business strategies and intentions, as well as lower (subjective) entrepreneurial persistence. Taken together, the program has only limited potential as a business and entrepreneurship policy intended to induce innovation and economic growth (Chapters 3 and 4).
And third, an empirical analysis on the level of German regional labor markets yields that there is a high regional variation in subsidized start-up activity relative to overall new business formation. The positive correlation between regular start-up intensity and the share among all unemployed individuals who participate in the start-up subsidy program suggests that (nascent) unemployed founders also profit from the beneficial effects of regional entrepreneurship capital. Moreover, the analysis of potential deadweight and displacement effects from an aggregated regional perspective emphasizes that the start-up subsidy for unemployed individuals represents a market intervention into existing markets, which affects incumbents and potentially produces inefficiencies and market distortions. This macro perspective deserves more attention and research in the future (Chapter 5).
In this thesis, I develop a theoretical implementation of prosodic reconstruction and apply it to the empirical domain of German sentences in which part of a focus or contrastive topic is fronted.
Prosodic reconstruction refers to the idea that sentences involving syntactic movement show prosodic parallels with corresponding simpler structures without movement. I propose to model this recurrent observation by ordering syntax-prosody mapping before copy deletion.
In order to account for the partial fronting data, the idea is extended to the mapping between prosody and information structure. This assumption helps to explain why object-initial sentences containing a broad focus or broad contrastive topic show similar prosodic and interpretative restrictions as sentences with canonical word order.
The empirical adequacy of the model is tested against a set of gradient acceptability judgments.
The motivation of this work was to investigate the self-assembly of a block copolymer species that attended little attraction before, double hydrophilic block copolymers (DHBCs). DHBCs consist of two linear hydrophilic polymer blocks. The self-assembly of DHBCs towards suprastructures such as particles and vesicles is determined via a strong difference in hydrophilicity between the corresponding blocks leading to a microphase separation due to immiscibility. The benefits of DHBCs and the corresponding particles and vesicles, such as biocompatibility, high permeability towards water and hydrophilic compounds as well as the large amount of possible functionalizations that can be addressed to the block copolymers make the application of DHBC based structures a viable choice in biomedicine. In order to assess a route towards self-assembled structures from DHBCs that display the potential to act as cargos for future applications, several block copolymers containing two hydrophilic polymer blocks were synthesized. Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone) (PEO-b-PVP) and Poly(ethylene oxide)-b-poly(N-vinylpyrrolidone-co-N-vinylimidazole) (PEO-b-P(VP-co-VIm) block copolymers were synthesized via reversible deactivation radical polymerization (RDRP) techniques starting from a PEO-macro chain transfer agent. The block copolymers displayed a concentration dependent self-assembly behavior in water which was determined via dynamic light scattering (DLS). It was possible to observe spherical particles via laser scanning confocal microscopy (LSCM) and cryogenic scanning electron microscopy (cryo SEM) at highly concentrated solutions of PEO-b-PVP. Furthermore, a crosslinking strategy with (PEO-b-P(VP-co-VIm) was developed applying a diiodo derived crosslinker diethylene glycol bis(2-iodoethyl) ether to form quaternary amines at the VIm units. The formed crosslinked structures proved stability upon dilution and transfer into organic solvents. Moreover, self-assembly and crosslinking in DMF proved to be more advantageous and the crosslinked structures could be successfully transferred to aqueous solution. The afforded spherical submicron particles could be visualized via LSCM, cryo SEM and Cryo TEM.
Double hydrophilic pullulan-b-poly(acrylamide) block copolymers were synthesized via copper catalyzed alkyne azide cycloaddition (CuAAC) starting from suitable pullulan alkyne and azide functionalized poly(N,N-dimethylacrylamide) (PDMA) and poly(N-ethylacrylamide) (PEA) homopolymers. The conjugation reaction was confirmed via SEC and 1H-NMR measurements. The self-assembly of the block copolymers was monitored with DLS and static light scattering (SLS) measurements indicating the presence of hollow spherical structures. Cryo SEM measurements could confirm the presence of vesicular structures for Pull-b-PEA block copolymers. Solutions of Pull-b-PDMA displayed particles in cryo SEM. Moreover, an end group functionalization of Pull-b-PDMA with Rhodamine B allowed assessing the structure via LSCM and hollow spherical structures were observed indicating the presence of vesicles, too.
An exemplified pathway towards a DHBC based drug delivery vehicle was demonstrated with the block copolymer Pull-b-PVP. The block copolymer was synthesized via RAFT/MADIX techniques starting from a pullulan chain transfer agent. Pull-b-PVP displayed a concentration dependent self-assembly in water with an efficiency superior to the PEO-b-PVP system, which could be observed via DLS. Cryo SEM and LSCM microscopy displayed the presence of spherical structures. In order to apply a reversible crosslinking strategy on the synthesized block copolymer, the pullulan block was selectively oxidized to dialdehydes with NaIO4. The oxidation of the block copolymer was confirmed via SEC and 1H-NMR measurements. The self-assembled and oxidized structures were subsequently crosslinked with cystamine dihiydrochloride, a pH and redox responsive crosslinker resulting in crosslinked vesicles which were observed via cryo SEM. The vesicular structures of crosslinked Pull-b-PVP could be disassembled by acid treatment or the application of the redox agent tris(2-carboxyethyl)-phosphin-hydrochloride. The successful disassembly was monitored with DLS measurements.
To conclude, self-assembled structures from DHBCs such as particles and vesicles display a strong potential to generate an impact on biomedicine and nanotechnologies. The variety of DHBC compositions and functionalities are very promising features for future applications.
Background: Consumption of whole-grain, coffee, and red meat were consistently related to the risk of developing type 2 diabetes in prospective cohort studies, but potentially underlying biological mechanisms are not well understood. Metabolomics profiles were shown to be sensitive to these dietary exposures, and at the same time to be informative with respect to the risk of type 2 diabetes. Moreover, graphical network-models were demonstrated to reflect the biological processes underlying high-dimensional metabolomics profiles.
Aim: The aim of this study was to infer hypotheses on the biological mechanisms that link consumption of whole-grain bread, coffee, and red meat, respectively, to the risk of developing type 2 diabetes. More specifically, it was aimed to consider network models of amino acid and lipid profiles as potential mediators of these risk-relations.
Study population: Analyses were conducted in the prospective EPIC-Potsdam cohort (n = 27,548), applying a nested case-cohort design (n = 2731, including 692 incident diabetes cases). Habitual diet was assessed with validated semiquantitative food-frequency questionnaires. Concentrations of 126 metabolites (acylcarnitines, phosphatidylcholines, sphingomyelins, amino acids) were determined in baseline-serum samples. Incident type 2 diabetes cases were assed and validated in an active follow-up procedure. The median follow-up time was 6.6 years.
Analytical design: The methodological approach was conceptually based on counterfactual causal inference theory. Observations on the network-encoded conditional independence structure restricted the space of possible causal explanations of observed metabolomics-data patterns. Given basic directionality assumptions (diet affects metabolism; metabolism affects future diabetes incidence), adjustment for a subset of direct neighbours was sufficient to consistently estimate network-independent direct effects. Further model-specification, however, was limited due to missing directionality information on the links between metabolites. Therefore, a multi-model approach was applied to infer the bounds of possible direct effects. All metabolite-exposure links and metabolite-outcome links, respectively, were classified into one of three categories: direct effect, ambiguous (some models indicated an effect others not), and no-effect.
Cross-sectional and longitudinal relations were evaluated in multivariable-adjusted linear regression and Cox proportional hazard regression models, respectively. Models were comprehensively adjusted for age, sex, body mass index, prevalence of hypertension, dietary and lifestyle factors, and medication.
Results: Consumption of whole-grain bread was related to lower levels of several lipid metabolites with saturated and monounsaturated fatty acids. Coffee was related to lower aromatic and branched-chain amino acids, and had potential effects on the fatty acid profile within lipid classes. Red meat was linked to lower glycine levels and was related to higher circulating concentrations of branched-chain amino acids. In addition, potential marked effects of red meat consumption on the fatty acid composition within the investigated lipid classes were identified.
Moreover, potential beneficial and adverse direct effects of metabolites on type 2 diabetes risk were detected. Aromatic amino acids and lipid metabolites with even-chain saturated (C14-C18) and with specific polyunsaturated fatty acids had adverse effects on type 2 diabetes risk. Glycine, glutamine, and lipid metabolites with monounsaturated fatty acids and with other species of polyunsaturated fatty acids were classified as having direct beneficial effects on type 2 diabetes risk.
Potential mediators of the diet-diabetes links were identified by graphically overlaying this information in network models. Mediation analyses revealed that effects on lipid metabolites could potentially explain about one fourth of the whole-grain bread effect on type 2 diabetes risk; and that effects of coffee and red meat consumption on amino acid and lipid profiles could potentially explain about two thirds of the altered type 2 diabetes risk linked to these dietary exposures.
Conclusion: An algorithm was developed that is capable to integrate single external variables (continuous exposures, survival time) and high-dimensional metabolomics-data in a joint graphical model. Application to the EPIC-Potsdam cohort study revealed that the observed conditional independence patterns were consistent with the a priori mediation hypothesis: Early effects on lipid and amino acid metabolism had the potential to explain large parts of the link between three of the most widely discussed diabetes-related dietary exposures and the risk of developing type 2 diabetes.
Die zerstörungsfreien Prüfungen von Bauwerken mit Hilfe von Ultraschallmessverfahren haben in den letzten Jahren an Bedeutung gewonnen. Durch Ultraschallmessungen können die Geometrien von Bauteilen bestimmt sowie von außen nicht sichtbare Fehler wie Delaminationen und Kiesnester erkannt werden.
Mit neuartigen, in das Betonbauteil eingebetteten Ultraschallprüfköpfen sollen nun Bauwerke dauerhaft auf Veränderungen überprüft werden. Dazu werden Ultraschallsignale direkt im Inneren eines Bauteils erzeugt, was die Möglichkeiten der herkömmlichen Methoden der Bauwerksüberwachung wesentlich erweitert. Ein Ultraschallverfahren könnte mit eingebetteten Prüfköpfen ein Betonbauteil kontinuierlich integral überwachen und damit auch stetig fortschreitende Gefügeänderungen, wie beispielsweise Mikrorisse, registrieren.
Sicherheitsrelevante Bauteile, die nach dem Einbau für Messungen unzugänglich oder mittels Ultraschall, beispielsweise durch zusätzliche Beschichtungen der Oberfläche, nicht prüfbar sind, lassen sich mit eingebetteten Prüfköpfen überwachen. An bereits vorhandenen Bauwerken können die Ultraschallprüfköpfe mithilfe von Bohrlöchern und speziellem Verpressmörtel auch nachträglich in das Bauteil integriert werden. Für Fertigbauteile bieten sich eingebettete Prüfköpfe zur Herstellungskontrolle sowie zur Überwachung der Baudurchführung als Werkzeug der Qualitätssicherung an. Auch die schnelle Schadensanalyse eines Bauwerks nach Naturkatastrophen, wie beispielsweise einem Erdbeben oder einer Flut, ist denkbar.
Durch die gute Ankopplung ermöglichen diese neuartigen Prüfköpfe den Einsatz von empfindlichen Auswertungsmethoden, wie die Kreuzkorrelation, die Coda-Wellen-Interferometrie oder die Amplitudenauswertung, für die Signalanalyse. Bei regelmäßigen Messungen können somit sich anbahnende Schäden eines Bauwerks frühzeitig erkannt werden.
Da die Schädigung eines Bauwerks keine direkt messbare Größe darstellt, erfordert eine eindeutige Schadenserkennung in der Regel die Messung mehrerer physikalischer Größen die geeignet verknüpft werden. Physikalische Größen können sein: Ultraschalllaufzeit, Amplitude des Ultraschallsignals und Umgebungstemperatur. Dazu müssen Korrelationen zwischen dem Zustand des Bauwerks, den Umgebungsbedingungen und den Parametern des gemessenen Ultraschallsignals untersucht werden.
In dieser Arbeit werden die neuartigen Prüfköpfe vorgestellt. Es wird beschrieben, dass sie sich, sowohl in bereits errichtete Betonbauwerke als auch in der Konstruktion befindliche, einbauen lassen. Experimentell wird gezeigt, dass die Prüfköpfe in mehreren Ebenen eingebettet sein können da ihre Abstrahlcharakteristik im Beton nahezu ungerichtet ist. Die Mittenfrequenz von rund 62 kHz ermöglicht Abstände, je nach Betonart und SRV, von mindestens 3 m zwischen Prüfköpfen die als Sender und Empfänger arbeiten. Die Empfindlichkeit der eingebetteten Prüfköpfe gegenüber Veränderungen im Beton wird an Hand von zwei Laborexperimenten gezeigt, einem Drei-Punkt-Biegeversuch und einem Versuch zur Erzeugung von Frost-Tau-Wechsel Schäden. Die Ergebnisse werden mit anderen zerstörungsfreien Prüfverfahren verglichen. Es zeigt sich, dass die Prüfköpfe durch die Anwendung empfindlicher Auswertemethoden, auftretende Risse im Beton detektieren, bevor diese eine Gefahr für das Bauwerk darstellen. Abschließend werden Beispiele von Installation der neuartigen Ultraschallprüfköpfe in realen Bauteilen, zwei Brücken und einem Fundament, gezeigt und basierend auf dort gewonnenen ersten Erfahrungen ein Konzept für die Umsetzung einer Langzeitüberwachung aufgestellt.
To what extent cities can be made sustainable under the mega-trends of urbanization and climate change remains a matter of unresolved scientific debate. Our inability in answering this question lies partly in the deficient knowledge regarding pivotal humanenvironment interactions. Regarded as the most well documented anthropogenic climate modification, the urban heat island (UHI) effect – the warmth of urban areas relative to the rural hinterland – has raised great public health concerns globally. Worse still, heat waves are being observed and are projected to increase in both frequency and intensity, which further impairs the well-being of urban dwellers. Albeit with a substantial increase in the number of publications on UHI in the recent decades, the diverse urban-rural definitions applied in previous studies have remarkably hampered the general comparability of results achieved. In addition, few studies have attempted to synergize the land use data and thermal remote sensing to systematically assess UHI and its contributing factors.
Given these research gaps, this work presents a general framework to systematically quantify the UHI effect based on an automated algorithm, whereby cities are defined as clusters of maximum spatial continuity on the basis of land use data, with their rural hinterland being defined analogously. By combining land use data with spatially explicit surface skin temperatures from satellites, the surface UHI intensity can be calculated in a consistent and robust manner. This facilitates monitoring, benchmarking, and categorizing UHI intensities for cities across scales. In light of this innovation, the relationship between city size and UHI intensity has been investigated, as well as the contributions of urban form indicators to the UHI intensity.
This work delivers manifold contributions to the understanding of the UHI, which have complemented and advanced a number of previous studies. Firstly, a log-linear relationship between surface UHI intensity and city size has been confirmed among the 5,000 European cities. The relationship can be extended to a log-logistic one, when taking a wider range of small-sized cities into account. Secondly, this work reveals a complex interplay between UHI intensity and urban form. City size is found to have the strongest influence on the UHI intensity, followed by the fractality and the anisometry. However, their relative contributions to the surface UHI intensity depict a pronounced regional heterogeneity, indicating the importance of considering spatial patterns of UHI while implementing UHI adaptation measures.
Lastly, this work presents a novel seasonality of the UHI intensity for individual clusters in the form of hysteresis-like curves, implying a phase shift between the time series of UHI intensity and background temperatures. Combining satellite observation and urban boundary layer simulation, the seasonal variations of UHI are assessed from both screen and skin levels. Taking London as an example, this work ascribes the discrepancies between the seasonality observed at different levels mainly to the peculiarities of surface skin temperatures associated with the incoming solar radiation. In addition, the efforts in classifying cities according to their UHI characteristics highlight the important role of regional climates in determining the UHI.
This work serves as one of the first studies conducted to systematically and statistically scrutinize the UHI. The outcomes of this work are of particular relevance for the overall spatial planning and regulation at meso- and macro levels in order to harness the benefits of rapid urbanization, while proactively minimizing its ensuing thermal stress.
Self-adaptive data quality
(2017)
Carrying out business processes successfully is closely linked to the quality of the data inventory in an organization. Lacks in data quality lead to problems: Incorrect address data prevents (timely) shipments to customers. Erroneous orders lead to returns and thus to unnecessary effort. Wrong pricing forces companies to miss out on revenues or to impair customer satisfaction. If orders or customer records cannot be retrieved, complaint management takes longer. Due to erroneous inventories, too few or too much supplies might be reordered.
A special problem with data quality and the reason for many of the issues mentioned above are duplicates in databases. Duplicates are different representations of same real-world objects in a dataset. However, these representations differ from each other and are for that reason hard to match by a computer. Moreover, the number of required comparisons to find those duplicates grows with the square of the dataset size. To cleanse the data, these duplicates must be detected and removed. Duplicate detection is a very laborious process. To achieve satisfactory results, appropriate software must be created and configured (similarity measures, partitioning keys, thresholds, etc.). Both requires much manual effort and experience.
This thesis addresses automation of parameter selection for duplicate detection and presents several novel approaches that eliminate the need for human experience in parts of the duplicate detection process.
A pre-processing step is introduced that analyzes the datasets in question and classifies their attributes semantically. Not only do these annotations help understanding the respective datasets, but they also facilitate subsequent steps, for example, by selecting appropriate similarity measures or normalizing the data upfront. This approach works without schema information.
Following that, we show a partitioning technique that strongly reduces the number of pair comparisons for the duplicate detection process. The approach automatically finds particularly suitable partitioning keys that simultaneously allow for effective and efficient duplicate retrieval. By means of a user study, we demonstrate that this technique finds partitioning keys that outperform expert suggestions and additionally does not need manual configuration. Furthermore, this approach can be applied independently of the attribute types.
To measure the success of a duplicate detection process and to execute the described partitioning approach, a gold standard is required that provides information about the actual duplicates in a training dataset. This thesis presents a technique that uses existing duplicate detection results and crowdsourcing to create a near gold standard that can be used for the purposes above. Another part of the thesis describes and evaluates strategies how to reduce these crowdsourcing costs and to achieve a consensus with less effort.
Information on the contemporary in-situ stress state of the earth’s crust is essential for geotechnical applications and physics-based seismic hazard assessment. Yet, stress data records for a data point are incomplete and their availability is usually not dense enough to allow conclusive statements. This demands a thorough examination of the in-situ stress field which is achieved by 3D geomechanicalnumerical models. However, the models spatial resolution is limited and the resulting local stress state is subject to large uncertainties that confine the significance of the findings. In addition, temporal variations of the in-situ stress field are naturally or anthropogenically induced. In my thesis I address these challenges in three manuscripts that investigate (1) the current crustal stress field orientation, (2) the 3D geomechanical-numerical modelling of the in-situ stress state, and (3) the phenomenon of injection induced temporal stress tensor rotations. In the first manuscript I present the first comprehensive stress data compilation of Iceland with 495 data records. Therefore, I analysed image logs from 57 boreholes in Iceland for indicators of the orientation of the maximum horizontal stress component. The study is the first stress survey from different kinds of stress indicators in a geologically very young and tectonically active area of an onshore spreading ridge. It reveals a distinct stress field with a depth independent stress orientation even very close to the spreading centre. In the second manuscript I present a calibrated 3D geomechanical-numerical modelling approach of the in-situ stress state of the Bavarian Molasse Basin that investigates the regional (70x70x10km³) and local (10x10x10km³) stress state. To link these two models I develop a multi-stage modelling approach that provides a reliable and efficient method to derive from the larger scale model initial and boundary conditions for the smaller scale model. Furthermore, I quantify the uncertainties in the models results which are inherent to geomechanical-numerical modelling in general and the multi-stage approach in particular. I show that the significance of the models results is mainly reduced due to the uncertainties in the material properties and the low number of available stress magnitude data records for calibration. In the third manuscript I investigate the phenomenon of injection induced temporal stress tensor rotation and its controlling factors. I conduct a sensitivity study with a 3D generic thermo-hydro-mechanical model. I show that the key control factors for the stress tensor rotation are the permeability as the decisive factor, the injection rate, and the initial differential stress. In particular for enhanced geothermal systems with a low permeability large rotations of the stress tensor are indicated. According to these findings the estimation of the initial differential stress in a reservoir is possible provided the permeability is known and the angle of stress rotation is observed. I propose that the stress tensor rotations can be a key factor in terms of the potential for induced seismicity on pre-existing faults due to the reorientation of the stress field that changes the optimal orientation of faults.
With recent advances in the area of information extraction, automatically extracting structured information from a vast amount of unstructured textual data becomes an important task, which is infeasible for humans to capture all information manually. Named entities (e.g., persons, organizations, and locations), which are crucial components in texts, are usually the subjects of structured information from textual documents. Therefore, the task of named entity mining receives much attention. It consists of three major subtasks, which are named entity recognition, named entity linking, and relation extraction.
These three tasks build up an entire pipeline of a named entity mining system, where each of them has its challenges and can be employed for further applications. As a fundamental task in the natural language processing domain, studies on named entity recognition have a long history, and many existing approaches produce reliable results. The task is aiming to extract mentions of named entities in text and identify their types. Named entity linking recently received much attention with the development of knowledge bases that contain rich information about entities. The goal is to disambiguate mentions of named entities and to link them to the corresponding entries in a knowledge base. Relation extraction, as the final step of named entity mining, is a highly challenging task, which is to extract semantic relations between named entities, e.g., the ownership relation between two companies.
In this thesis, we review the state-of-the-art of named entity mining domain in detail, including valuable features, techniques, evaluation methodologies, and so on. Furthermore, we present two of our approaches that focus on the named entity linking and relation extraction tasks separately.
To solve the named entity linking task, we propose the entity linking technique, BEL, which operates on a textual range of relevant terms and aggregates decisions from an ensemble of simple classifiers. Each of the classifiers operates on a randomly sampled subset of the above range. In extensive experiments on hand-labeled and benchmark datasets, our approach outperformed state-of-the-art entity linking techniques, both in terms of quality and efficiency.
For the task of relation extraction, we focus on extracting a specific group of difficult relation types, business relations between companies. These relations can be used to gain valuable insight into the interactions between companies and perform complex analytics, such as predicting risk or valuating companies. Our semi-supervised strategy can extract business relations between companies based on only a few user-provided seed company pairs. By doing so, we also provide a solution for the problem of determining the direction of asymmetric relations, such as the ownership_of relation. We improve the reliability of the extraction process by using a holistic pattern identification method, which classifies the generated extraction patterns. Our experiments show that we can accurately and reliably extract new entity pairs occurring in the target relation by using as few as five labeled seed pairs.
Die Elektrosprayionisation (ESI) ist eine der weitverbreitetsten Ionisationstechniken für flüssige Pro-ben in der Massen- und Ionenmobilitäts(IM)-Spektrometrie. Aufgrund ihrer schonenden Ionisierung wird ESI vorwiegend für empfindliche, komplexe Moleküle in der Biologie und Medizin eingesetzt. Überdies ist sie allerdings für ein sehr breites Spektrum an Substanzklassen anwendbar. Die IM-Spektrometrie wurde ursprünglich zur Detektion gasförmiger Proben entwickelt, die hauptsächlich durch radioaktive Quellen ionisiert werden. Sie ist die einzige analytische Methode, bei der Isomere in Echtzeit getrennt und über ihre charakteristische IM direkt identifiziert werden können. ESI wurde in den 90ger Jahren durch die Hill Gruppe in die IM-Spektrometrie eingeführt. Die Kombination wird bisher jedoch nur von wenigen Gruppen verwendet und hat deshalb noch ein hohes Entwick-lungspotential. Ein vielversprechendes Anwendungsfeld ist der Einsatz in der Hochleistungs-flüssigkeitschromatographie (HPLC) zur mehrdimensionalen Trennung. Heutzutage ist die HPLC die Standardmethode zur Trennung komplexer Proben in der Routineanalytik. HPLC-Trennungsgänge sind jedoch häufig langwierig und der Einsatz verschiedener Laufmittel, hoher Flussraten, von Puffern, sowie Laufmittelgradienten stellt hohe Anforderungen an die Detektoren. Die ESI-IM-Spektrometrie wurde in einigen Studien bereits als HPLC-Detektor eingesetzt, war dort bisher jedoch auf Flussratensplitting oder geringe Flussraten des Laufmittels beschränkt.
In dieser kumulativen Doktorarbeit konnte daher erstmals ein ESI IM-Spektrometer als HPLC-Detektor für den Flussratenbereich von 200-1500 μl/min entwickelt werden. Anhand von fünf Publi-kationen wurden (1) über eine umfassende Charakterisierung die Eignung des Spektrometers als HPLC-Detektor festgestellt, (2) ausgewählte komplexe Trenngänge präsentiert und (3) die Anwen-dung zum Reaktionsmonitoring und (4, 5) mögliche Weiterentwicklungen gezeigt.
Erfolgreich konnten mit dem selbst-entwickelten ESI IM-Spektrometer typische HPLC-Bedingungen wie Wassergehalte im Laufmittel von bis zu 90%, Pufferkonzentrationen von bis zu 10 mM, sowie Nachweisgrenzen von bis zu 50 nM erreicht werden. Weiterhin wurde anhand der komplexen Trennungsgänge (24 Pestizide/18 Aminosäuren) gezeigt, dass die HPLC und die IM-Spektrometrie eine hohe Orthogonalität besitzen. Eine effektive Peakkapazität von 240 wurde so realisiert. Auf der HPLC-Säule koeluierende Substanzen konnten über die Driftzeit getrennt und über ihre IM identifi-ziert werden, sodass die Gesamttrennzeiten erheblich minimiert werden konnten. Die Anwend-barkeit des ESI IM-Spektrometers zur Überwachung chemischer Synthesen wurde anhand einer dreistufigen Reaktion demonstriert. Es konnten die wichtigsten Edukte, Zwischenprodukte und Produkte aller Stufen identifiziert werden. Eine quantitative Auswertung war sowohl über eine kurze HPLC-Vortrennung als auch durch die Entwicklung eines eigenen Kalibrierverfahrens, welches die Ladungskonkurrenz bei ESI berücksichtigt, ohne HPLC möglich. Im zweiten Teil der Arbeit werden zwei Weiterentwicklungen des Spektrometers präsentiert. Eine Möglichkeit ist die Reduzierung des Drucks in den intermediären Bereich (300 - 1000 mbar) mit dem Ziel der Verringerung der benötigten Spannungen. Mithilfe von Streulichtbildern und Strom-Spannungs-Kurven wurden für geringe Drücke eine verminderte Freisetzung der Analyt-Ionen aus den Tropfen festgestellt. Die Verluste konnten jedoch über höhere elektrische Feldstärken ausgeglichen werden, sodass gleiche Nachweisgrenzen bei 500 mbar und bei 1 bar erreicht wurden. Die zweite Weiterentwicklung ist ein neuartiges Ionentors mit Pulsschaltung, welches eine Verdopplung der Auflösung auf bis zu R > 100 bei gleicher Sensitivität ermöglichte. Eine denkbare Anwendung im Bereich der Peptidanalytik wurde mit beachtlichen Auflösungen der Peptide von R = 90 gezeigt.