Publication Server of Constructor University Library
Not a member yet
858 research outputs found
Sort by
Time Evolution in Open Quantum Systems - From Exciton Dynamics to Charge Transport
No full textThe research work presented in this thesis concerns the improvement of several theoretical techniques for describing quantum systems coupled to fermionic or bosonic reservoirs. The validity of the aforementioned developments is then numerically investigated to obtain the time-dependent quantum transport of charges or excitons through molecular junctions or aggregates, respectively. The former are single or a short chain of conducting, conjugated molecules wedged between two inert electrodes, acting as active circuit elements, while the latter can be comprehended as light absorbing pigments containing conjugated chains residing within fluctuating protein environments. The model used to describe the quantum transport is a linear chain or aggregates of tight-binding sites coupled to external fermionic or bosonic baths.
The three main formalisms that are presented in this work include quantum master equations (QME), in second order perturbation theory in the system-reservoir coupling, the hierarchical equations of motion (HEOM) scheme for multi-particle bosonic systems as well as a scheme based on time-dependent nonequilibrium Green's functions (NEGF) for non-interacting fermionic systems. The NEGF scheme for time-dependent quantum transport of charge provides the time-dependent current through the systems of sites as well as the on-site population dynamics, while the QME and HEOM schemes for energy transfer dynamics deliver information only about the population or occupation number dynamics for systems coupled to bosonic baths
Frame-theoretic Designs for Future Wireless Communications
No full textMotivated by the historically proven depletion of communication resources, and respectively, by the lack of inherent redundancy necessary for robust and accurate signal processing and identification under orthogonal wireless communications systems, we use in this work over-complete redundant representations, i.e., Frame Theory. To this point, such non-orthogonal signal decompositions provide alternative, yet robust representations, and respectively, aid signal processing of modern and future wireless communications systems beyond the limitations of their traditional orthogonal counterparts.
For instance, the millimeter wave (mmWave) initial access (IA) sparse channel estimation
and training beamforming optimization problems are reduced to the generic frame design of the measurement matrix for compressed sensing (CS). Similarly, for non-orthogonal multiple access (NOMA) systems, the code-domain NOMA (CD-NOMA) transmission is abstracted as a generic linear model based on the synthesis linear operator of a frame. Under this abstraction, valuable information-theoretic insights regarding the optimum design of CD-NOMA multiplexing schemes are extracted. Albeit different, both problems lead interestingly to common frame design principles based on incoherence, representational tightness and unit-normality frame-theoretic attributes.
To provide a full system description, we complement these designs with newly proposed modern signal processing for the sparse recovery of the mmWave channel, or respectively, for the joint multi-user detection (MUD) on the receiving side of a MC-NOMA transceiver. Numerical experiments and software simulations confirm the general theoretic results and highlight, once more, the superiority of the proposed frame-theoretic designs against the existent art
The Shadows of Dreams: Cinema's Layers of Medialization
No full textCinema figures as the crucial site where the anthropological drive to grasp the world in images finds a media outlet. Media in this sense are eternally constituted and re-constituted psychocultural ‘prosthetics’ giving space to sensation, emotion, and thought. This process of medialization condenses and sediments in media artifacts, embodying human experience in an externalized form and inviting our aesthetic engagement. Cinema seen from this perspective consists in a coupling of three anthropologically crucial domains of existence, which assume the shape of layers of medialization.
This project will start with an examination of the cinematic transformation of external physical and social reality. The testing grounds for this will be the strain of sociocritical U.S. horror cinema, the analogous melodrama (where everyday experience becomes horrific), and the movie adaptations of Agatha Christie’s novels.
As recorded motion adds both significance and force to the expressive gestures and poses of the human body, transitional performance states loom large in a medium which gives meaningful forms to the self in action. It is the highly ambiguous nature of physical interactions that sets the parameters for the second chapter, which turns to the cinematic duality of dancing and fighting.
The fascination with seeing oneself from the outside is the third crucial domain this thesis will explore. Cinema provides the material structure for the staging of imaginary processes of projection and identification as compelling apparitions of the self. The claim that the self is in dire need not only of being manufactured, but also of being staged is explored in the final set of film analyses, which focus on the cinema of Werner Herzog.
By way of conclusion, the tension between the ‘reality of pictures’ and ‘pictures of reality’ (a notion explored by Ludwig Pfeiffer across various contexts) is transmuted by the assertion that instances of cinematic experience embody perceptual thought
Exploring Metabolomic Flux and Achieving Prediction Capability in Cocoa Bean Fermentation using Model Systems
No full textCocoa bean fermentation encompasses the successive growth of microbial populations on the bean which results in the diffusion of microbial metabolites into the bean, as well as dramatic increases in temperature. A combination of all these events affect the bean structurally and biochemically and lead to the formation of pleasant flavour and aroma precursors.
Cocoa bean fermentation still remains an uncontrolled and spontaneously-driven process. This means that there is tremendous variety in the quality of fermented beans. A lack of markers makes it difficult to distinguish between good and bad trials of fermentation. Consequently, Western conglomerates that buy fermented beans from farmers can end up shipping large quantities of beans only to discover that they are not suitable for chocolate manufacture.
The experiments described herein were done in order to more accurately study the reactions that underlie the process of fermentation, in order to find biochemical markers defining good-quality fermentations. This was done using chemical-driven and microbial-driven model systems. Cocoa bean fermentation, assessed through bean pH, microbial dynamics and the secretions of microbial metabolites, was successfully reproduced in lab-scale quantities using starter cultures, temperature regimes and submerged incubations.
The main findings of this research were that changes in bean pH led to dramatic changes in terms of protein and polyphenol content and that an optimum pH needed to be reached in order to allow correct proteolysis and flavanol degradation for the formation of cocoa aroma and flavour. Acid influx into the bean also exhibited a preservation effect upon flavanols, which could be beneficial in preserving the health properties of cocoa. A comprehensive understanding of the factors contributing to fermentation through design of experiments also enabled the prediction of outcomes of fermentation trials
Practices of Building and Maintaining Trust in Cross-functional Teams
No full textThis dissertation investigates how cross-functional teams build and maintain trust. Teamwork is challenging and requires trust, a complex process created in the interaction of team members, and embedded in the organizational system. But there is limited research on how cross-functional teams build and maintain trust in practice, and on the meanings and interpretations that team members, managers, and consultants ascribe to trust. Much research explains how team members gather and signal trustworthy information, but not how they interpret this information during team interactions. To address these research gaps, this thesis draws on social practice theory and offers empirical evidence for a practice approach on trust in teams. Team members, managers, and consultants were interviewed and a cross-functional team kick-off was observed to find out how trust as a practice is conceptualized and produced. Qualitative content analysis, metaphor analysis, and interpretive analysis were used to analyze the data. Research findings include several metaphors of trust in cross-functional teams, specific trust-building and maintenance practices, and illustrations of how these practices are produced and reproduced in team interactions. Trust as a social practice thus moves research from the path of demonstrating that trust in teams is important in contexts of high vulnerability and uncertainty, to the path of how trust becomes important in these contexts by meaning and interpretation. Considering these findings, future studies should focus more on the collective patterns of meaningful activities that build and maintain trust, the use of metaphors to study trust in teams, and the nonverbal cues that build and maintain trust
Viruses in the North Sea: viromics and prophage genomics
No full textDespite their small size, viruses have an enormous influence on microbial population dynamics, due to lysis and horizontal gene transfer. Due the high abundance of their hosts, bacteriophages or phages comprise the majority of viruses and provide the largest reservoirs of unexplored genetic diversity in marine environments. The rise of Next Generation Sequencing (NGS) techniques brings new opportunities to investigate the marine virus community. However, there is no current statutory pipeline applied in marine phage ecology. Therefore, this thesis proposes a virus-specific pipeline based on the integration of existing tools and state of the art techniques. The developed pipeline was applied to accomplish the two research aims of this thesis: (1) to analyze the virus community in the North Sea with viromics(virus metagenomics), and (2) to characterize lysogenic phages from potentially pathogenic Vibrio species.
The results of the first part of this thesis show that the virus community is dominated by phages and they are not evenly distributed throughout the North Sea. In general, the coastal virus community was genetically more diverse than the open sea community. The influence of riverine inflow and currents affects the genetic virus diversity with the community carrying genes from a variety of metabolic pathways and other functions.
In the second part, lysogenic Vibrio phages from the North Sea were induced (ca. 40 % of tested isolates) and four phage genomes were characterized. The phages from V. parahaemolyticus (2 tailed phages, 1 filamentous phage) and V. cholerae (1 tailed phage) can integrate into their host genome and might have a role in pathogenicity.
This thesis represents an exemplary study of the virus community in the North Sea, with special emphasis on the marine phages. The settled virus-specific pipeline the obtained insights will contribute to extend the study of the virus diversity dynamics in other marine areas to characterize novel phage groups
Europe’s New Chinese Literature. Authors of Chinese Origin Writing in French and German A Comparative Analysis
No full textEurope’s New Chinese Literature deals with literature — poetry, theater and prose — by authors of Chinese origin using German or French as modes of expression.
Only in the last decade the majority of their works was published and became visible to a larger audience, with Dai Sijie and Shan Sa in France and Luo Lingyuan in Germany. The thesis attempts the first comprehensive analysis of this literature using a comparative approach. It scrutinizes the discursive strategies with which the authors of this group position themselves in the literary field. The strategies differ insofar as the writers for example adopt Western stereotypes of China in their works or want to function as cultural ambassadors for China
Insights into the interaction of Marinobacter adhaerens with the diatom Thalassiosira weissflogii by comparative mutant analysis
No full textInteractions between diatoms and heterotrophic bacteria play an important role in the marine biological pump. Diatoms form marine snow aggregates that are used by heterotrophic bacteria as rich nutrient sources. A model system consisting of the γ-proteobacterium, Marinobacter adhaerens HP15, and the diatom, Thalassiosira weissflogii, was used to study diatom-bacteria interactions on a molecular level using various mutants of M. adhaerens HP15.
The assessment of the zinc-sensitive mutant HP15 ΔczcCBA.1/2 in diatom co-cultures with and without zinc stress showed that heavy metal resistance helps bacteria to colonize aggregates. Furthermore, addition of ZnSO4 increased the release of exopolymers by M. adhaerens HP15 and led to a higher rate of bacterial aggregate colonization by both, the wild-type and the mutant.
Co-cultivation of the non-motile mutant ΔfliC and the non-chemotactic mutant ΔcheA showed that at high exopolymer concentrations motility is more important for bacterial attachment to aggregates than chemotaxis. Proteomic analysis suggested that amino acids present in these aggregates are the preferred nutrient source for M. adhaerens HP15. Amino acid quantification confirmed the presence of especially branched chain amino acids in the attached fractions of co-cultures suggesting that the diatom contributes to the amino acid pool therein.
The role of branched chain amino acid uptake for M. adhaerens HP15 was studied with the mutant ΔlivK. M. adhaerens HP15 has five livK genes that are differentially expressed during in vitro growth. The studied livK gene plays only a minor role during in vitro growth despite its previously suggested importance for amino acid uptake in vivo, hinting towards specialized gene expression under different growth conditions.
Overall, this study gives important insights into diatom-bacteria interactions on a molecular level and in terms of exchanged nutrients, dynamics of exopolymer release and bacterial aggregate colonization
Classification of primitive ideals of U(o(\infty)) and U(sp(\infty))
No full textThe purpose of this Ph.D. thesis is to study and classify primitive ideals of the enveloping algebras U(o(\infty)) and U(sp(\infty)). Let g(\infty) denote any of the Lie algebras o(\infty) or sp(\infty). Then g(\infty)=\Bigcap_{n\geq 2}g(2n) for g(2n) = o(2n) or g(2n) = sp(2n), respectively. We show that each primitive ideal I of U(g(1)) is weakly bounded, i.e., I \ U(g(2n)) equals the intersection of annihilators of bounded weight g(2n)-modules. To every primitive ideal I of g(\infty) we attach a unique irreducible coherent local system of bounded ideals, which is an analog of a coherent local system of finite-dimensional modules, as introduced earlier by A. Zhilinskii. As a result, primitive ideals of U(g(\infty)) are parametrized by triples (x;y;Z) where x is a nonnegative integer, y is a nonnegative integer or half-integer, and Z is a Young diagram. In the case of o(1), each primitive ideal is integrable, and our classification reduces to a classification of integrable ideals going back to A. Zhilinskii, A. Penkov and I. Petukhov. In the case of sp(\infty), only 'half' of the primitive ideals are integrable, and nonintegrable primitive ideals correspond to triples (x;y;Z) where y is a half-integer
Thermal Degradation of Food Proteins
No full textProteins, one of the most vital classes of food components, play an important role in the human diet providing the essential amino acids required for tissue maintenance and growth. In many food processes, however, the structure of food proteins might change as a result of various externally applied conditions. Heat treatment, for instance, performed either at a household level or at an industrial scale, may cause alterations in food proteins chemically converting proteins to new products thus altering their property causing desirable or undesirable characteristics. Due to the complexity of the food matrix, very little is known yet regarding the products of the thermal degradation of food proteins.
In this thesis, both intact and digested food proteins derived from bovine milk and hen eggs, have been thermally treated at temperatures ranging from 150 ºC till 250 ºC. The thermal decomposition products have been investigated using LC-MS and a combination of further analytical techniques. Exhaustive chemical conversion of model food proteins has been successfully demonstrated and analytical data generated that describe such changes. However, limitations in high resolution mass spectrometry data of the generated thermal decomposition products did not allow an unambiguous determination of the chemical structures and hence these results remained inconclusive.
In order to elucidate the structures of the thermal degradation products of proteins and the underlying mechanisms that govern their formations, 15 custom pentapeptides were selected and were thermally treated at optimised heating conditions. In total, more than 300 thermal degradation products have been detected and around 200 have been identified. Three representative examples including amide cleavage and DKP formation reaction, oxidation of tryptophan residue, C-terminal decarboxylation and formation of N-terminal dicarbonyls by two distinct reaction pathways have been identified in this thesis and are discussed