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Microbial Oxidation of Methane in Aquatic Systems Illuminated by Functional Metagenomics
Get PDFFreshwater and marine environments are hotspots of methane cycling. Vast amounts of methane, a potent greenhouse gas, are produced predominantly in the sediments of these environments but very little eventually escapes to the atmosphere due to the activity of methane-oxidizing microorganisms. These microorganisms are pivotal in regulating methane emissions from the oceans and freshwater systems and their study therefore transcends scientific curiosity and is of global relevance to society as a whole. Despite their importance, the knowledge about these microorganisms is restricted to cultured isolates and little is known about the physiology of environmentally-relevant uncultured species. Using culture-independent functional metagenomics in combination with physiological experiments, this thesis aims to improve our understanding of the individual metabolic potential and activity that underlie the ecophysiology and environmental relevance of several uncultured methane-oxidizing microorganisms
Die Bedeutung sozialer Netzwerke für den Berufswahlprozess junger Erwachsener : eine sozial-kognitive und netzwerkanalytische Untersuchung-
Get PDFThe aim of this work, which consists of three different studies, is to understand the meaning of social networks for the vocational choice process. The first study examines the function and impact of peer networks for vocational choices. Results show positive relations between influencing vocational choices and a) being close friends, b) having the same gender, c) having the same ethnic background. The aim of the second study is a better understanding of how friendship, vocational self-efficacy beliefs and vocational outcome expectations belong together. Results indicate that strong ties to close friends are associated with social cognitive variables. These effects were found for vocational self-efficacy expectations and for the vocational outcome expectations -interest- and -income-.The third study investigates sensitive transition processes in young adultsa development. The study ask about the type formation of social convoys and analyses changes in the social convoy system
Qualität im betrieblichen Bildungsmanagement : Stakeholder, Kriterien, Standardisierbarkeit
Get PDFQuality in corporate learning management is hard to measure since it lacks theoretical foundation and practical frameworks. The dissertation first discovers the six main stakeholders of corporate education and their learning needs. Via desk research and interview analysis as grounded theory it sets up a list of more than 100 practical criteria of how to ensure and improve corporate learning management. These criteria are grouped around a solid learning value concept and are discussed for the possibilities of their standardisation as practical guideline
Relativistic accretion onto compact objects
Get PDFThe present PhD thesis summarises results on analytical accretion models obtained during my PhD studies in 2014a 2018. I present a new ansatz for specific angular momentum-angular velocity dependence for perfect fluid in circular motion around a Kerr black hole. With this ansatz new solutions for toroidal configurations were obtained. I discuss here in detail the dynamical properties of these configurations and results of their application as initial conditions for accretion simulations with 2-D HARM code. For the case of circular motion in the NUT spacetime I present my results on characteristic circular geodesics radii in it. These results are further used for modelling perfect fluid tori with constant specific angular momentum (Polish Doughnuts). Characteristic changes in the patterns of circular motion of perfect fluid due to presence of the NUT parameter are discussed. The last part of the work presents a pre-study of accretion of spinning particles/fluids onto Kerr black holes. I discuss our results on spin-induced advance in last stable orbits and its relevance for accretion models
Tight-Binding based Investigation of Semiconductor Quantum Dots and Molybdenum Disulfide Nanobubbles : From Atomic Structure to Optical Spectra
No full textThe present work achieves an understanding of the interplay between morphology, electronic, and optical properties of semiconductor nanostructures for single-photon emission. The latter is important for various quantum information applications, including future quantum communication devices. In the first part of this thesis, III-V semiconductor quantum dots are investigated. These systems have emerged as promising candidates for deterministic single-photon sources due to high repetition rates, integrability into electrical devices, and tunable Emission energy. In particular, we analyze two different quantum dot systems, which are capable of single-photon emission in the technologically important telecom C-band. The electronic single-particle energies and wave functions are calculated using a nearest neighbour sp3s empirical tight-binding (TB) model. Strain arising from lattice mismatch of the constituent materials is calculated atomistically by employing a valence-force field method. The theoretical model is based on realistic quantum dot geometries and concentration profiles, which are obtained from transmission electron microscopy. When using the measured results for a representative quantum dot geometry as well as experimentally reconstructed alloy concentrations, a combination of strain-field and TB calculations is able to reproduce the quantum dot emission wavelength in agreement with the experimentally determined photoluminescence spectrum. The inhomogeneous broadening of the latter can be related to calculated variations of the emission wavelength for the experimentally deduced In-concentration fluctuations and size variations. The results provide a deeper understanding of the interplay between morphology, electronic, and optical properties of semiconductor quantum dots. In the second part of this thesis, we investigate atomically thin layers of transition metal dichalcogenides (TMDCs), which have recently emerged as a new class of optically active materials for opto-electronic applications. These systems offer a relative ease of fabrication and the potential for large-scale applications. Engineering of the local confinement Situation can lead to discretized states, which opens the possibility for deterministic single-photon generation. One possible platform are molybdenum disulfide nanobubbles that develop when air is enclosed during the stacking of layers. An analysis of strain and dielectric effects in nanostructures reveals that an interplay of these physical effects leads to the formation of confined quantum-dot-like single-particle states that give rise to single-photon emission. The confinement of these states is caused by a wrinkling of the material, that supports the formation of strain-induced pockets. The results provide a deeper understanding of the interplay between strain, dielectric effects, electronic, and optical properties of TMDC nanostructures
Morphometrics of Southern Ocean diatoms using high throughput imaging and semi-automated image analysis
Get PDFSince the ADIAC project, which ended more than 15 years ago, not much progress in automating morphometric analysis of diatoms from slide-mounted material has been published, and no ready-to-use system has become available. This thesis work is the first to implement such a system completely, covering all aspects of the underlying imaging and image processing pipeline, by combining a commercially available slide scanning microscope with my diatom morphometry software SHERPA. I was able to show the applicability as well as the potential of this approach by executing a series of smaller and two large-scale morphometry projects. The extensive sampling sizes, which were made possible only by the new workflow, enabled the first observations of life cycle related size distribution changes of Fragilariopsis kerguelensis in its natural habitat, leading to hypotheses on influences of reproduction, grazing and environmental changes in one of the most important diatom species of the Southern Ocean. In a second large-scale investigation, SHERPA's precise morphometric measurements revealed a second F. kerguelensis morphotype, which has not been recognized before, even though the species, as well as the very material I analyzed, have been investigated intensely before by experienced diatomists; a result not disqualifying their work, but rather underlining that explicit and precise quantification of morphological information has a strong potential to generate novel scientific insights. This new morphotype has implications on the utilization of paleo-proxies which are based on geometrical valve features of F. kerguelensis. Differentiating both morphotypes might improve established methods and possibly provides a new proxy for summer sea surface temperature
R/V METEOR cruise report M142, Drilling Gas Hydrates in the Danube Deep-Sea Fan, Black Sea, Varna - Varna - Varna, 04 November - 22 November - 09 December 2017.
Get PDFBias and precision in early phase adaptive oncology studies and its consequences for confirmatory trials
Get PDFThe need for a more efficient drug development process led to migration from the traditional fixed-sample clinical trial designs to group-sequential and adaptive designs, especially in early phases of clinical drug development. This, however, came with challenges in inference, since many of these newly proposed designs come without respective methods for statistical inference. In this dissertation, we study the estimation methods for oncology phase II group-sequential and adaptive designs in terms of bias and precision, and we propose new estimation methods for a new class of adaptive designs. We then evaluate the consequences, in terms of power, of using estimates from these designs to plan phase III trial. We also study and propose new approaches to adjust these estimates, based on the observed data, before employing them in planning of phase III sample size, in order to reach the desired power. Literature review showed that many estimation methods have been proposed for the classical single-arm two-stage group-sequential designs with a binary endpoint, which are the most commonly used designs in oncology trials of phase II. Simulation studies showed that the uniformly minimum variance unbiased estimator is the best amongst them in terms of bias and mean square error. However, for the adaptive group-sequential designs, these estimation methods have poor performance. Our proposed estimation methods in oncology phase II adaptive designs showed better performance as compared to the naive maximum likelihood estimator. A direct use of estimates from phase II adaptive designs to plan phase III results in underpowered phase III trials. Therefore, adjusting (discounting) these estimates beforehand is necessary. The amount of discounting, however, depends on the estimator, with our proposed estimators requiring less discounting as compared to the naive maximum likelihood estimator. Our proposed adjustment approaches show power improvements, which are similar across different estimators and design scenarios
The Prediction of Professional Success in Apprenticeship: The Role of Cognitive and Non-Cognitive Abilities, of Interests and Personality
Get PDFContext: We addressed the issue of person-job-fit by focussing on both professional success and work satisfaction. Publications studying the predictive validity of (cognitive) ability, personality, or vocational interest alone have shown relationships with professional success or work satisfaction for each predictor separately. Nevertheless, these predictors have rarely been studied simultaneously. Methods: To this end we tested the incremental validity of abilities, traits, and interests in a sample from diverse occupations: In 648 apprentices and students from five different branches (Food, Tech, People, Office, Craft) the (incremental) contributions of 3 intelligence factors (verbal, numerical, spatial), 3 alternative abilities (social-emotional, creative, practical), 4 conscientiousness facets, other big five factors (O, E, A, N), and of 14 professional interests were analysed regarding prediction of GPA in professional schools and school/job satisfaction. Results: Intelligence and conscientiousness were best predictors, followed by social-emotional competence and interests, whereas other traits provided marginal contribu-tions. Predictors varied between branches, mostly following expectations. The testbattery allowed a very good prediction of apprenticeship success (max. 37%), but for some branches prediction was considerably lower. Conclusion: Criteria for person-job-fit are not swappable, neither are the predictors. Professional success was mostly predicted by a different predictor set namely ability and the personality dimension of conscientiousness then satisfaction, which was mostly predicted by non-interest in a certain occupation. As a practical implication, we concludethat choosing the right candidate for a certain branch one needs to use a broad set ofpredictor variables. Besides cognitive ability also personality and vocational interests had predictive validity for an individuals person-job-fit
Book Review: History of Vocational Education and Training in Europe
Get PDFThe book is volume 14 in the series Studies in Vocational and Continuing Education. Series editors are Philipp Gonon & Anja Heikkinen. Volume 14, History of Vocational Education and Training in Europe: Cases, Concepts and Challenges is edited by Esther Berner, Professor for Educational Science, Helmut-Schmidt University in Hamburg, Germany, and Philipp Gonon, Professor for VET and Teacher Training, University of Zurich, Switzerland