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Iron oxide driven methanogenesis and methanotrophy in methanic sediments of Helgoland Mud Area, North Sea
Get PDFElevated dissolved iron concentrations (Fe2 ), as signpost for on-going iron oxide reduction in the methanic zone, are currently being detected in a wide range of marine environments. The various mechanisms that result in Fe2 release into porewater are a subject of intense debate amongst sediment geo-microbiologists. While abiotic cryptic sulfur cycling is suggested for some sites, biotic mechanisms potentially mediate iron reduction in many other sites, including the Helgoland Mud Area, North Sea. Iron oxide dependent anaerobic oxidation of methane (Fe-AOM) is primarily hypothesised as the biotic mechanism driving iron reduction in the methanic zone but organic matter degradation linked iron reduction could also play a role. Beyond geochemical data however, physiological evidence demonstrating that these processes occur and the microorganisms involved is rather scarce. In chapter two, a short-term radiotracer based experiment revealed that Fe-AOM is indeed feasible in the methanic zone of Helgoland Mud Area, albeit at very low rates under close to in situ conditions (0.095 A /- 0.03 nmol cm 3 d 1). Despite the low rates, these estimates represent the first demonstration of Fe-AOM in a marine environment bearing geochemical preconditions for Fe-AOM to occur in situ. Additionally in long-term incubations, various iron oxides (lepidocrocite, hematite and magnetite) stimulated Fe-AOM in sediments from the methanic zone. Especially with crystalline magnetite, ANME-2a were highly enriched after 250 days showing clearly, and for the first time, that ANME-2a are involved in Fe-AOM. Previous studies from the Helgoland Mud Area revealed that aromatic hydrocarbons are likely the preferred fermentation substrate in the methanic zone. This may have led to the strong correlations between fermentative bacteria, methanogenic archaea (which use fermentation products) and Fe2 concentrations. Chapter three investigated this possibility further, initially in sediment incubations and subsequently in highly enriched cultures. With benzoate as the only carbon substrate, enrichment efforts with crystalline iron oxides (magnetite and hematite) led to concurrent iron reduction and methanogenesis from benzoate degradation. In contrast, with poorly crystalline lepidocrocite, benzoate degradation and methanogenesis was slower. Thus, concurrent reduction of crystalline iron oxides facilitates organic matter degradation while poorly crystalline lepidocrocite inhibits the process. Therefore, a likely scenario might be in play in Helgoland Mud Area, whereby buried crystalline iron oxide phases which make up to 1.6 weight % of sediment volume could be advantageous to the microbial communities. These crystalline iron oxides likely facilitate methanogenic organic matter degradation while being reduced concurrently, thereby contributing to the Fe2 pool detected in porewater. Additionally, we uncovered the clostridial family Halobacteroidaceae as previously unknown benzoate degraders from marine sediments. In chapter four, sediment incubations with an easily fermentable substrate (glucose) revealed that crystalline iron oxides could act as conduits for electron transfer, as electron acceptors for iron reduction or act as both under various temperature regimes. Furthermore, iron reduction was more favorable under lower temperatures than at mesophilic conditions and dissimilatory iron reducers from the order Desulfuromonadales were enriched during iron reduction. These findings substantially advance the current state of the art regarding the biotic mechanisms that drive the apparent concurrent iron reduction in methanic zones of marine sediments. Besides providing direct evidence for Fe-AOM, the body of work presented in this thesis demonstrates the various ways iron oxides could facilitate methanogenic organic matter degradation in ferruginous methanic marine sediments. The exact molecular guides for these various processes should be subject of future studies
Interview with Dr. Beverley Foulks McGuire on video-gaming, Buddhism, and death
No full textDr. Beverley Foulks McGuire speaks with editor John W. Borchert about her new research on video-gaming, death, and Buddhis
Topologieoptimierter Verbund von Aluminium und Stahl zur lokalen Steifigkeitserhöhung von Druckgussbauteilen
Get PDFUnder the premises of weight and stiffness a multiphase optimization is used to shape a longitudinal carrier in a hybrid aluminum - steel design. Goal is to retain the function despite reduced dimensions. Therefore a steel core is integrated via die casting to increase the bending stiffness. Compared to an aluminum design with reinforcing cast ribs, the simulation of the composite reaches the same stiffness without local rips. Under real tests the composite shows an enhancement in stiffness, however can't compare with the monolithic aluminum component. Main reason for that is the required jacketing and the thus thermally induced residual stresses in the cast matrix that leave the aluminum already plasticized. Under certain volume ratio a reinforcement can be achieved, however under an inferior relation between performance and weight compared to monolithic constructions. Therefore the implementation of such composite component has to be assessed under lightweight facets. The developments of the hybrid aluminum - steel longitudinal carrier provide a base for a new way of construction for cast parts that is able to cause a scalable reinforcement without increasing the part dimensions
Verquickung der mathematischen und informatischen Forschung an zivilen deutschen Hochschulen mit der modernen Kriegsführung
Get PDFCentral aspects of modern warfare such as drone attacks, guided missiles, cyber attacks or the use of reconnaissance satellites would not be possible without contemporary mathematical and computer science research. This dissertation will revolve about the following questions: What impact does the connection between military application and civil research have on mathematics and computer science? What impact does the research have on society? And what ethical and societal questions arise from that
Species response curves and niche quantification of vascular plants in the context of reintroduction
No full textThe current loss of biodiversity is one of the most disastrous threats to the earth's biosphere. To save plants from extinction, it is important to understand the relationship between species and their environment, identify the drivers of species distributions and rarity, and develop conservation techniques based on sound ecological knowledge. The present thesis shows that soil factors play a major role in plant species distribution and rarity, as well as in practical conservation techniques, such as plant reintroduction. Both, the limits of ecological niches and soil microbes are important factors in conservation, which deserve more attention in future studies of rare plant species. Reliable predictions of species responses to environmental changes and widely applicable conservation techniques are needed to save endangered species from extinction
Die Perspektiven des Energiedialoges EU-Russland : eine wissenschaftliche Szenarioanalyse
Get PDFThe dissertation deals with the Energy Dialogue between Russia and the European Union, which was institutionalized in 2000, with special reference to the institutional change of the Energy Dialogue. The aim of the present work is to model the possible future pictures of European-Russian energy relations in the form of scenarios. The question is how new challenges, endogenous changes and ongoing transformation processes in global energy markets affect attitudes and preferences in relation to energy cooperation. Perceptions of and responses to these challenges vary in extractive and inclusive institutions. Against this backdrop, institutional change is the focus of attention. In addition, it is of great relevance in which form - adaptation, reform, reorientation or transformation - the institutional change of the energy dialogue will take place. As part of the study of the Energy Dialogue as an international institution, the question is also asked to what extent internal changes in interests affect the institutional course of the Energy Dialogue. One of the main arguments in this paper is that the quality of the endogenous political institutions can influence the political strategies of the actors internationally and contribute to the creation or deterioration of international institutions. In addition, the impact of path-dependent processes on the further development of the energy dialogue and the behavior of the actors should be considered. The scenarios are intended to provide an overview of which influencing factors have the greatest influence on the future development of energy cooperation between Russia and the EU
Low power design of a versatile analog mixed Signal sensor module
Get PDFThe development of space electronics especially for launcher such as Ariane 6 has to fulfill space standards and space requirements provided by the space industries. The standards of the European Cooperation for Space Standardization (ECSS) are used extensively to ensure a development process that meets the space requirements. This standard covers space project management, space product assurance and space engineering. The ECSS is a cooperative effort of the European Space Agency, national Space Agencies and European Industry Associations for the purpose of developing and maintaining common standards. The work presented in this dissertation was carried out to fill the gap of developing wireless sensor network for Ariane launchers. The development process follows the space requirements that demand the sensor node to survive the environmental condition inside the launcher. This makes the work uniquely compared to commercial wireless sensor network development. The versatile analog mixed signal module proposed in this work consists of infrared transmitter, VLC receiver, power management, data processing with digital/analog sensor interface unit and solar cell as energy harvester. The sensor module is used to build wireless sensor network inside the Vehicle Equipment Bay (VEB) of Ariane 5
The Ubiquitin-Proteasome System (UPS) affects beta-cell survival and function
No full textLoss of insulin-producing pancreatic beta-cells is the hallmark of both type 1 diabetes and type 2 diabetes. The mechanism and the components involved in beta-cell death and failure are not yet fully clarified. Identification of key signaling components that promote beta-cell death, understanding their mechanisms of action in detail is crucial in disease pathogenesis as well as for novel therapeutic interventions to halt beta-cell failure during development and progression of diabetes. The ubiquitin-proteasome system (UPS) regulates the stability of many proteins involved in important cellular processes: cell cycle progression, cell differentiation, cell signaling pathways and apoptosis. In this work, I identified two genes within the proteasomal protein control system that are dysregulated in beta-cells under diabetic conditions; F-box protein 28, a substrate recruiting a component of the Skp1-Cul1-F-box (SCF) ligase complex (SCFFBXO28) and the deubiquitinase USP1. Both UPS components have an important function in beta-cell survival in diabetes. F-box only protein 28 (FBXO28) is part of the ubiquitination machinery, namely of the E-3 Ubiquitin Ligase complex that recruits proteins for degradation or for altering their localization or functional activities. My results show that FBXO28 protein levels were reduced under diabetic conditions. Loss of FBXO28 induced beta-cell death, whereas its overexpression improved beta-cell survival, and regulated expression of beta-cell transcription factor NEUROD1 without altering insulin secretion as well as of several beta-cell identity and functional genes. This suggests FBXO28 acts as a pro-survival protein in beta-cells. On the contrary, Ubiquitin-specific protease 1 (USP1), a member of the USP family and a well-known deubiquitinating enzyme (DUB) impairs beta-cell survival in diabetes. USP1 is responsible for removing ubiquitin from substrate proteins and thus influences cellular processes such as survival, differentiation, immunity, and DNA damage response (DDR). Genetic depletion or pharmacological inhibition of USP1 blocked beta-cell death in several experimental models of diabetes in vitro and ex vivo. While DDR signals were elevated in diabetes, USP1 inhibition attenuated the DDR in islets suggesting that the anti-apoptotic action of USP1 inhibition is mediated through suppression of DDR. I have identified a novel function of USP1 in the control of beta-cell survival as potential therapeutic target for the suppression of beta-cell death in diabetes. Taken together, my data highlight the importance of an appropriate expression and activation of ubiquitin-proteasome components for pancreatic beta-cell survival. My results prove that the ubiquitin-proteasome plays a key role in beta-cell survival/failure in diabetes. Further in-depth understanding of the UPS system in beta-cells and establishing its pathways would open up novel approaches towards diabetes therapy
A Study on Measure-Geometric Laplacians on the Real Line
Get PDFIn this thesis, we consider measure-geometric differential operators on the real line as they were introduced by Freiberg and Zähle in 2002. We define derivatives and Laplace operators with respect to different types of compactly supported finite measures . We first discuss the class of continuous measures . We deduce a harmonic calculus for and from the classical (weak) analysis. It is shown that the eigenvalues of do not depend on the chosen measure and the eigenfunctions are given explicitly. The results are illustrated through examples of (fractal) measures. In the following, the framework of Freiberg and Zähle is extended by dropping the condition that the measures are atomless. We consider distributions which have finite support and define analogous operators and . Using that they act on finite-dimensional function spaces, we give matrix representations for both operators and obtain analytic properties for them. General observations on the spectral properties of are discussed and compared to the atomless case. For uniform discrete probability distributions, we determine the eigenvalues and eigenfunctions of the associated Laplacian. We then study measures which have a continuous and an atomic part. Again we define the operators and and obtain properties similar to those for weak first and second order derivatives. We give a systematic way to calculate the eigenvalues and eigenfunctions of and determine them for two leading examples. Differences and similarities to the previous cases are discussed and problems for the general solution of the eigenvalue problem are indicated