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Network Coding and Wireless Physical-layer Secret-key Generation From Unequal Erasure Protection (UEP) to Unequal Security Protection (USP)
No full textThe general abstraction of this thesis is the relationships between two seemingly unrelated topics, which are network coding and wireless physical-layer secret-key generation (WPSG). As build-ups to such relationships, some specific aspects of each topic are discussed in detail at first. To begin with, network coding issues of unequal erasure protection (UEP) and degree distribution distortion of LT-coded symbols are presented. After that, the analysis regarding key length and security enhancement in WPSG is given. Towards the end, relationships between network coding and WPSG are revealed in two aspects, which are security protocols using network coding and scalable security based on the weakly secure network coding concept
Profile of Polyphenols in a European Diet
No full textDietary phenolic compounds are secondary metabolites, widely distributed in the plant kingdom and consumed in large amounts in the human diet. Studies have shown a positive correlation between an increased consumption of polyphenols and a reduced risk of cardiovascular disease, neurodegenerative diseases and certain types of cancer, suggesting that these compounds are beneficial for human health. Besides the strong antioxidant capacities, dietary polyphenols have been shown to posses other properties by which cell activities are regulated. An accurate assessment on the nature and distribution of these compounds in diet enables epidemiological analysis to realize the relation between the intake of these substances and the risk of development of several diseases. Such an assessment requires a polyphenol intake database to support clinical and epidemiological studies. The present research studies the main contributors to human polyphenol intake in a typical European diet by profiling the polyphenol content of a number of selected fruits and vegetables contributing most to an average European daily polyphenol intake. A total of 42 methanolic extractions from the fleshes and peels of 20 different fruits and vegetables were prepared and subjected to chemical characterisation using HPLC interfacing of an ESI-Ion Trap mass spectrometer or an ESI-TOF mass spectrometer. The peaks in tandem MS chromatograms were assigned based on the structural information of the most commonly occurring food polyphenols reported in the literature. The presence of more than 60 different compounds was confirmed using this method. For most fruits and vegetables the number of qualitatively observed polyphenols was considerably lower than reported in the literature. However, around 20 compounds not previously described in the literature could be identified. Storage of the samples was investigated and it was observed that after 12 months refrigeration, the majority of phenolic constituents had decomposed. A new approach, Van Krevelen analysis, was applied for identification of further unassigned peaks in the mass spectra. Findings on polyphenolic contents of the samples, compared and confirmed with the literature and the polyphenolic compounds which have not been reported in a specific fruit or vegetable so far, reported for each sample individuall
Raman Spectroscopic Probing of Key Biological Events Tumorigenesis, Hsp70 Chaperon Mechanisms, and Therapy Response
No full textLight scattering is the simplest and most common scenario where incident light with a certain energy or color corresponding to a given frequency, is bounced o any object or particle in all directions. While most of this scattered light appears unchanged (having the same color), Raman scattering represents a very small portion of the scattered light that has different colors corresponding to many components with frequencies different from that of the incident light. The Raman shifts, or the frequency differences observed in Raman scattering, represent the corresponding amounts of energy that are exchanged between a material system and the light incident on it, and which can fit into possible transitions within the material system. Therefore, the collection of all Raman shifts (Raman spectrum) for a given material are characteristic of the material properties, providing a way to identify and/or discriminate different molecular systems. The Raman process, as just defined, is linear, and is termed resonant Raman if the incident light frequency matches that of an electronic transition in the molecule, or surface enhanced Raman if the irradiated molecule is in close contact with a rough metal surface. Nonlinear Raman scattering involves multi-photon interactions. In this thesis, Raman spectroscopy is applied as a noninvasive and nondestructive tool for the investigation of biological systems including biomolecules, cells, and tissue, both in vivo and in vitro. In particular, this thesis addresses key biological events such as cancer transformation and development, biological rhythm and hormonal deregulation, Hsp70 phenotypic variation and chaperon properties, and therapy response. In addition, a simple fabrication of special metallic nanoparticles and the interaction of a simple biomolecule at metal substrates are also covered. Combining different Raman techniques, the focus is not only to demonstrate the diagnostic capability of Raman spectroscopy for cancer and/or other pathological conditions. It is also directed toward noninvasive targeting of disease biomarkers for a possible understanding of the molecular basis of disease onset and development. First, using a model cell line for skin carcinoma, it is demonstrated that Raman scattering not only can help to discriminate healthy skin keratinocytes from their cancerous counterparts, but also can provide molecular insights into genetic instabilities in the human keratinocytes cells HaCaT. Furthermore, the potential for Raman monitoring of lymphoma incidence and histological subtypes in subjects at risk is evaluated using spleen tissue of a lymphoma mouse model. Another animal model (Djungarian hamsters) is used to test Raman spectroscopy as an approach for the study of the biological rhythm associated with rhythmic hormonal regulation of the reproductive system in photoperiodically sensitive breeding mammals. This work highlights the possibility for noninvasive and nondestructive phenotypic sorting of cells sublines. In this respect, Raman microscopy has been used to gain specific insights into intracellular mechanisms leading to Hsp70 chaperon properties and associated phenotypic variation in colon carcinoma sublines. Additionally, in situ Raman monitoring of drug response has been achieved in this work. Finally, it is shown that biocompatible metal nanoparticles with specific geometry, and promising for molecular targeting, can be easily and reliably fabricated. Surface enhanced Raman studies on the simplest amino acid glycine reveal that, proteinaceous compounds can behave and interact in a complex concentration-dependent manner at metal interfaces. In this respect special designs for the fabrication of nanometal substrates can be beneficial for surface enhanced Raman investigations of biological systems
Knowledge Transfer in Teams and Its Role for the Prevention of Knowledge Loss
No full textWith the demographic change and the imminent waves of retirement, a threat of knowledge loss for organizations becomes more and more apparent. In my dissertational work, I focused on knowledge transfer within work teams as one important means to counteract this development. More specifically, I first investigated, in a cross-sectional survey study in two German mid-sized companies, how knowledge transfer can be encouraged or impaired, and what kind of distinctions have to be made (e.g., effects at different levels of analysis) to reach conclusive and valid results when examining knowledge transfer. In a second study, which was again a survey study, conducted at three branches of a German public administration, I took a closer look at intergenerational knowledge transfer. The aim was to investigate if there is naturally more knowledge transfer from older to younger employees. Thus, age effects at three different levels, the dyadic level (age difference between two employees), the individual level (age), and the team level (age diversity) were examined. As both, the first and the second research questions rather focus on predictors of knowledge transfer, the third research aim was to investigate what happens to knowledge transfer in situations of a threat of knowledge loss for the organization. To this end, I examined, based on data from the second study, if employees share less knowledge when they intend or expect to leave the organization. For all three research questions, data were analyzed using multilevel analyses, taking into account the nested data structure of employees in teams, and simultaneously investigating predictors at different levels. Following an introductory chapter, the three empirical parts are described in more detail, providing theoretical background, methods used, and results obtained as well as a discussion of results for each research paper. The dissertation concludes with a general discussion of the findings of the different papers
Vertical Economies of Scope in Electricity Supply: Analysing the Costs of Ownership Unbundling
No full textMotivated by the movement towards ownership unbundling in Europeʹs energy sector, this PhD study analyses the cost effects of a vertical separation of the electricity supply stages from a theoretical and an empirical perspective. I covers the results of three research articles. The first article provides a literature review of previous theoretical and empirical studies on vertical scope economies. The measurement of these integration economies quantifies the expected cost increases that result from separating the electricity supply stages. Results are presented for different types of unbundling, as cost effects depend on the precise location of the ownership split along the supply chain. Efficiency losses may occur due to coordination effects and market risk effects. Reviewing previous studies shows that pure ʺnetwork unbundlingʺ, i.e. a separation networks from the competitive stages generation and retail, results in synergy losses between 2 and 5 percent due to coordination costs. Unbundling options that lead to a separation between generation and retail lead to a permanent cost increase of 15 percent and more due to the additional market risk effect. The second article confirms these results by applying a multi-stage cost function approach. Results show that separating generation from retail appears to be the most costly alternative with an average cost increase of 12 to 17 percent. The European case of transmission unbundling leads to a cost increase of approximately 4 percent. The third article presents an empirical study based on a frontier benchmarking approach that compares different ʺefficiency frontiersʺ for integrated and separate provision of electricity. Similar to the econometric study, a generation-retail split is the most costly option with an average cost increase of 18 percent (coordination and risk effects), while transmission unbundling leads to an average cost increase below 2 percent (coordination effects)
Vibrio spp. in the German Bight
No full textPathogenic Vibrio strains represent an increasing health issue in European waters, but profound investigations on Vibrio spp. are lacking, especially in northern European waters. This thesis represents a pilot study for the German Bight, investigating the Vibrio community extensively, with special emphasis on V. parahaemolyticus. Insights into abundance, community composition and response to environmental parameters of Vibrio spp. at Helgoland Roads (North Sea, Germany) were obtained. Using a cultivation-independent approach, Vibrio numbers up to 3.37 x 104 cells x mL 1 were detected at Helgoland Roads. Targeting solely potentially pathogenic Vibrio spp., numbers up to 4.3 x 103 N x L-1 (water, plankton) and 240 MPN x g 1 (shellfish) were quantified using a selective cultivation approach. In the course of this thesis, a broad range of microbiological and molecular biological methods have been evaluated regarding the usefulness for the investigation of Vibrio spp. and the potentially pathogenic species V. parahaemolyticus. A reliable, cost- and labor-effective approach was defined including (i) the sequencing of the rpoB gene (encoding the RNA polymerase β-subunit) to differentiate even closely related Vibrio species, (ii) the use of the toxR gene as specific marker for V. parahaemolyticus, (iii) the screening for the virulence-associated genes tdh and trh, and (iv) the performance of genomic fingerprinting using ERIC-PCR to identify the intraspecies variability of V. parahaemolyticus and its close relative V. alginolyticus at Helgoland Roads. Applying this polyphasic approach, we gathered insights into the Vibrio community at Helgoland Roads. Vibrio strains were isolated from seawater, plankton and shellfish and the species V. parahaemolyticus appeared to be the second most abundant species at Helgoland Roads, behind its close relative V. alginolyticus. None of the V. parahaemolyticus strains carried the virulence-associated genes tdh or trh, but several strains were proven positive for hemolytic activity. Based on genomic fingerprinting of V parahaemolyticus and V. alginolyticus strains, three distinct groups became evident. One group represented V. parahaemolyticus, the second one V. alginolyticus. The third group was located in between the two species, displaying the high genomic plasticity and intraspecific variability of Vibrio spp.. To be able to estimate the distribution and dynamics of Vibrio spp. in response to environmental conditions, we assessed the effects of environmental parameters on the Vibrio community. High temperature in combination with events of low salinity and high abundance of phytoplankton led to increased Vibrio numbers at Helgoland Roads. The influence of the parameters, however, varied between the seasons. The population of the potentially pathogenic species V. parahaemolyticus at Helgoland Roads appeared to be structured by a complex combination of parameters, including temperature, NO3 , salinity, dinoflagellates, SiO2, secchi depth and NO2. Changing environmental conditions might not only lead to increasing numbers of Vibrio spp. in the German Bight, but also to a community shift towards potentially pathogenic species such as V. parahaemolyticus. Being the first profound study on Vibrio spp. in the German Bight, this thesis represents an invaluable first step towards the understanding of this important microbial group, harboring the potential pathogen V. parahaemolyticus, in northern European waters
Taxonomic and genetic analysis of Marinobacter sp. HP15 and its chemotactic behaviour towards the diatom Thalassiosira weissflogii
No full textAggregation of micro-algae, mainly of diatoms, is an important process in marine pelagic systems leading to the sinking of particulate organic matter in form of marine snow. This process has been studied extensively, but the specific role of heterotrophic bacteria, their genes, gene products, and secondary metabolite signals for this process has largely been neglected. A bilateral model system consisting of the diatom Thalassiosira weissflogii, and the bacterial strain, Marinobacter sp. HP15, was found suitable for an in-depth molecular analysis by attachment assays, TEP production determination, and aggregation experiments. Following the taxonomic and genomic description of the bacterial model strain, its genetic accessibility was demonstrated and the interaction has been studied by molecular and bioinformatics investigations. Chemotaxis- and motility-deficient mutants were generated and their phenotypes were described in appropriate assays in order to investigate the particular role(s) of these processes in diatom-bacteria interactions. HP15 was attracted to diatom homogenate in soft agar assay and chemotaxis-deficient mutants showed a decreased ability to attach to T. weissflogii supporting the importance of chemotaxis in diatom-bacteria interactions. These and future results based on the model system will improve our understanding of bacteria-phytoplankton interactions and how they influence the flux and cycling of carbon during marine snow formation
Empirical Perspectives on Learning at Work
No full textIn todays knowledge economy, many organizations are trying to manage their knowledge base in order to gain and maintain a competitive edge. Yet knowledge in peoples heads can hardly be managed directly, since knowledge transfer involves an active and individual learning effort. Nevertheless, organizations can support learning indirectly. Therefore this study approaches the challenge of knowledge-intensive work from another perspective: How can organizations support informal and individual on-the-job learning? To obtain a ranking of the most important organizational factors that support learning, a fully structured and dynamic survey at a German shipyard was used to measure the intensity of learning and potentially relevant driving or inhibiting factors in different working environments.In der heutigen Wissensgesellschaft versuchen viele Organisationen ihre Wissenbasis besser zu verwalten, zu pflegen und zu nutzen, um einen Wettbewerbsvorteil zu erreichen oder zu sichern. Aber Wissen in den Köpfen von Mitarbeitern kann nur schwerlich durch das Unternehmen direkt verwaltet werden, weil Wissensaustausch individuelle und aktive Lernanstrengungen von den Mitarbeitern erfordert. Daher geht diese Studie die Herausforderung von wissensintensiver Arbeit von einer anderen Perspektive mit folgender Fragestellung an: Wie können Organisationen informelles und individuelles betriebliches Lernen unterstützen?
Um eine Rangliste der wichtigsten organisatorischen Faktoren, die Lernen unterstützen, zu bekommen, wurde eine stark strukturierte und dynamisch funktionierende Umfrage auf einer deutschen Werft durchgeführt. Mit ihr soll die Intensität von Lernen und potentiell relevante Lern-förderlichen oder Lern-behindernden Faktoren in verschiedenen Situationen gemessen werden. Weil der Lernprozess an sich stochastisch ist und aufgrund der vielen Variablen, war es notwendig den neuartigen BOGER Algorithmus für die statistische Analyse zu entwickeln, welcher eine Funktion für automatische und robuste statistische Modellauswahl integriert hat.
Interdisziplinäre Erkenntnisse aus einem breiten Literaturspektrum wie auch die empirische ermittelte Rangliste wurden zusammengefasst in dem neu entwickelten PIA-Modell. "PIA" ist die Abkürzung für "Perspektive einnehmen, Integrieren und Agieren" – siehe Abb. 2.1 auf S. 31. Einige der beschriebenen Wirkungsweisen erklären die Effektivität einiger erprobter und moderner Modelle für die industrielle Praxis, wie z.B. das Toyota Production System oder das EFQM Modell. Beide Modelle legen einen Schwerpunkt auf organisationales Lernen. Daher trägt diese Studie zu einem besseren Verständnis über die Wirkweisen der wichtigsten organisationalen Hebel für eine betriebliche Lernunterstützung bei und vereinfacht damit die Anpassung dieser Modelle in neuen industriellen Kontexten
Temporal and Spatial Variability in the Geochemistry of Hydrothermal Fluids and Hydrothermal Ferromanganese Deposits at the Mid-Atlantic Ridge
No full textHydrothermal circulation at spreading axes plays a fundamental role for global heat and chemical fluxes between the lithosphere, the hydrosphere, and the atmosphere. Slow-spreading ridges, which comprise about 50% of the cumulative global ridge axis length, likely contribute significantly to the overall exchange fluxes. During this study, the fluid geochemistry of five hydrothermal fields, located in different geological environments at the Mid-Atlantic Ridge (MAR), has been investigated: Nibelungen, Logatchev I, and Turtle Pits, Red Lion and Comfortless Cove. It has been demonstrated that fluid-rock interaction in heterogeneous lithosphere at high temperatures displays a unique geochemical fingerprint with respect to key parameters, such as low concentrations of dissolved H2S, Si, Li relative to basaltic-hosted hydrothermal systems, depletion of B relative to seawater and an enriched Δ2HH2O signature. At Nibelungen and Logatchev I, both the alteration of mafic rocks and pervasive serpentinization is evident. Extremely hot vapor-phase fluids at Turtle Pits and Comfortless Cove are venting at pressure-temperature conditions above the critical point of seawater (407°C, 298 bars). Such fluids have been sampled for the first time. They are characterized by different heat and chemical fluxes compared to systems in similar geological settings at fast-spreading ridges, likely as function of water depth and depth of heat source. The fluids are strongly enriched in metals and display a unique rare earth element and yttrium (REY) distribution with partly absent Eu anomaly. The variability in REE concentrations and distributions is controlled by precipitation/dissolution of hydrothermal anhydrite in the subseafloor. This study substantiates the relevance of hydrothermal activity at slow-spreading ridges for geochemical exchange budgets. Unique features of slow-spreading MAR hydrothermal systems disclose highly variable fluid compositions depending on the geological setting, physical conditions and tectonic activity, and striking temperature and compositional stability also in actively phase-separating hydrothermal systems, which have profound implications for global chemical fluxes
Recognition of post-translational histone modifications by antibodies and epigenetic reading domains
No full textMolecular epigenetics is described as the study of heritable changes in gene function without alterations in DNA sequence. Epigenetic phenomena are regulated by three interconnected players: DNA methylation, post-translational histone modifications and non-coding RNAs, which are involved in the regulation of many cellular processes including cellular differentiation and transcription. Post-translational histone modifications either directly modulate chromatin structure or they can serve as binding signals for reading domains, which recognize the modifications and mediate most of the biological functions of these modifications. In the present PhD work, we have introduced Celluspots peptide arrays as a tool for the initial screening of putative reading domains interacting with a diverse set of post-translational histone modifications in one experiment in competition. With this tool, we studied the binding specificities of antibodies and reading domains with known as well as unknown primary targets. Furthermore, we studied differences and similarities in substrate recognition of two histone lysine methyltransferases, MLL3 and MLL1, from the same protein family. Celluspots peptide arrays were first validated with antibodies directed towards post-translational histone tail modifications. In this study, we found that most of the antibodies bound well to the modification they had been raised for, but some failed. Some antibodies showed high cross-reactivity and most of the antibodies were inhibited by additional modifications close to the primary one. Furthermore, the comparison of the specificity profiles of antibodies, which had been raised for the same modification, revealed that the binding profiles sometimes differed greatly. Therefore, we did not only validate the method with this approach, but we further introduced Celluspots peptide arrays as a good tool for the quality control of epigenetic antibodies. Additionally, we applied Celluspots peptide arrays for the investigation of the specificity of the interaction of reading domains with known substrate specificity with histone peptides. The results that we obtained with this approach agreed with literature concerning the primary targets of the reading domains, but we also obtained previously unknown information concerning the influence of secondary modifications for the binding affinity to the primary targets of these reading domains. After validation of Celluspots peptide arrays, we screened approximately 20 reading domain candidates and proceeded with the most promising candidates for further analysis. One such candidate is a human polycomb group protein, which was shown to associate with the core components of the Polycomb repressive complex 2. The Polycomb repressive complex 2 is the major histone 3 lysine 27 methyltransferase-containing complex, which tri-methylates this lysine residue. Tri-methylated histone 3 lysine 27 is a post-translational modification, which is associated with transcriptional repression of developmental genes, especially HOX genes. We found that this polycomb group protein recognizes this histone tail modification in a histone variant specific manner. This histone variant is thought to be exclusively expressed in the mammalian testis and we propose that this polycomb group protein is involved in targeting the complex to this histone variant tri-methylated at lysine 27 in the human testis. The histone lysine methyltransferases of the mixed lineage leukemia (MLL) protein family mono-, di- and tri-methylate histone 3 lysine 4. We studied the substrate specificity for two members of this family, MLL3 and MLL1, and revealed that the preferred substrate sequences are different. With these differences in substrate recognition we searched for non-histone targets and found similar, but also different non-histone targets at the peptide level. This is the first time that differences in substrate recognition was observed for MLL methyltransferases, which do no