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Kriterien für Wälzlagerstähle für das Induktionshärten
Full text linkInduction hardening of bearing components offers advantages over other hardening techniques like low energy consumption and connected emissions, superior mechanical properties and the use of low alloyed steel grades. The used steel alloy for induction hardening has a pronounced impact on the hardening result. The dissertation aims at identifying a suitable and robust bearing steel for induction hardening. Based on a literature study, potential bearing steels were selected and compared in terms of heat treatment robustness using a dilatometer. Larger hardness of the prior microstructures as well as low alloyed steel grades were shown to reveal a robust hardening result. The rolling contact fatigue performance was evaluated as one important property of bearing steels. Larger carbon contents or as-heat treated hardness showed superior behavior for classical measures of rolling contact fatigue performance, while lower carbon contents led to smaller and less crack appearance. The roles of different alloying elements, prior austenite grains sizes and residual stresses were discussed. A medium carbon steel was identified as a good compromise revealing a robust heat treatment result and good fatigue performance
Manifold-Based Sensorimotor Representations for Bootstrapping of Mobile Agents
Full text linkSubject of this thesis is the development of a domain-independent algorithm that allows an autonomous system to process sequences of the sensorimotor interaction with its environment and to assign a geometric interpretation to its motor capabilities. We utilize Lie groups, smooth manifolds endowed with a group structure, that allow for an elegant representation of geometric operations as a central foundation for such a sensorimotor representation. Expressing motor controls with respect to the manifold structure allows us to transform the sensorimotor interaction sequence into a specific set of data points. Finding a manifold and a transformation that minimizes an intrinsic conflict function corresponds to finding a topological structure that is the best fit for expressing the sensorimotor space the entity resides in. Experiments in a virtual environment are conducted that show the applicability of the approach with respect to different sensor and motor configurations
Development of cold-water coral mounds in the southern Alboran Sea (Western Mediterranean Sea) since the last interglacial
Full text linkCold-water coral (CWC) mounds are formed due to the sustained growth of CWCs over geological timescales (thousands to tens of thousands of years). These seabed structures are discovered along continental margins of the Atlantic Ocean and its marginal seas. They are important archives for reconstructing the long-term development of CWCs and coral mounds. However, our knowledge about the coral mound formation and associated sedimentary processes is still limited. In the Mediterranean Sea, most CWC mounds were discovered in the so-called West and East Melilla CWC mound province (WMCP and EMCP, respectively). Particularly, coral mounds in the EMCP are arranged into four sub-clusters, each marked by specific morphologies and dimensions. The coral mound formation in the northern and westernmost sub-clusters of the EMCP has been reconstructed, whereas little is known about the history of coral mounds formation in the other unexplored sub-clusters of the EMCP, as well as the entire WMCP. Therefore, this thesis focuses on the CWC mound development in the southern Alboran Sea and the dominant environmental factors favoring the coral mound formation
From biotech to bioeconomy: New empirical evidence on the technological transition to plant-based bioeconomy based on patent data
Full text linkNowadays environmental and climate issues have brought the topic of bioeconomy to the political agenda around the world. Plant-based bioeconomy (pBE) has a key role in securing sustainable supplies of energy, food and raw materials for increasingly aging and growing societies. However, the technological roots and development path of pBE are far from being fully understood. Accordingly, we seek to contribute to an in-depth understanding of how biotechnology innovations affected the emergence of bioeconomy by exploring the technological field evolution of plant-based patent applications between 1995 and 2015 in Germany. We employ patent citation data and conduct forward citation analysis to trace technological trajectories within plant-based biotechnology. We extend previous work by combining patent-based citation analysis with text-mining approach. Main path analysis allows the identification of main players within plant-based biotechnology over time. Our explorations reveal dominant and also peripheral technologies within the sphere of plant-based applications and provide us in this way with a more comprehensive understanding of the field s technological evolution. Our findings suggest a transition from basic biotechnological research towards more sustainability- and medicine-related technological orientation in the field
Cell mechanics and cell-cell interactions of fibroblasts from Dupuytren's Patient : Atomic Force Microscopy Investigation
Full text linkCells as a biological entity of tissue, itself made of biomolecules such as mostly proteins, lipids and carbohydrates, creates its own meshwork of biopolymers named extracellular matrix (ECM) particularly fibroblasts. With the advanced light and force microscopies, inter-cellular, cell-ECM and intracellular signaling pathways are deeply explored either by tagging the biomolecule of interest with fluorophores or by applying certain forces(in the order of pN to nN). In the field of mechanobiology, interplay between cell function and physical forces are studied using biophysical tools thatprobe their diverse mechanisms. Cells exert forces( inside-out signalling)and also respond to physical forces from their micro-environment( outside-in signalling) through participation of chain of varying protein signaling molecules. Actin molecules from cytoskeleton family form filaments in the cytoplasmic side of the cell and myosin walk on these filaments generates contractile tension. These traction forces get transmitted to the extracellular matrixof the cell or to the neighboring cells through protein complexes such as integrin and cadherins, respectively. Fibroblasts,from the mesenchymal family, are the abundant cells found in the connective tissue. Basically, fibroblasts synthesize,degrade and maintain the extracellular matrix components of the tissue. Fibroblasts, by acquiring different phenotypes called protomyofibroblast/myofibroblast, play a huge participation in various connective tissue related diseases. Myofibroblast are large cells possessing large bundles of actin filaments of isomers named alpha smooth muscle actin (I /--SMA). On the other hand, protomyofibroblast share the similar characteristic appearance but shows I /--SMA negative large stress fibres. In Dupuytrena s disease, thesemyofibroblasts persists and deform the surrounding matrix environment thus results in tissue stiffening and further leads to tissue contracture. Existing various biophysical tools maps forces such as tractile force, cell-cell interaction force and cell-ECM interaction force. One among such tool is Atomic Force Microscopy, a multifunctional toolbox in cellular biology to observe various cell types mechanics. Observing cell viscoelastic properties by application of controlled force (nanonewton) to the adherent cell become more common in the biomedical community. This thesis demonstrates the measurement of viscoelastic properties of fibroblast of different phenotypes extracted from a Dupuytrena s diseased patient and ECM derived from various tissues.The bio-mechanical interplay between cell and ECM has been studied with careful design of the AFM experiments. Fibroblasts extracted from the cords and nodular region of the palmar fascia exhibits myofibroblast phenotype and migrate slower than the fibroblast extracted from dermal and scar region. Normal and scar fibroblasts migrate faster in the wound healing assay.On the decellularized matrices, scar fibroblasts exhibitprotomyofibroblast phenotype by expressing large stress fibres. Whereas, normal fibroblasts derived from the dermal region express the healthy phenotypic appearance. From AFM based Single-cell force spectroscopy (SCFS), cell-cell interaction force measurements evaluatethe homophilic and heterophilic cadherinpairs mechanical bond strength expressed in homo-cellular (fibroblast of similar phenotype) and hetero-cellular (fibroblast-epithelial cell) arrangements. SCFS measurements also illustrate the significant role of actomyosin contractile apparatus in cadherin extracellular iidomain binding dynamics. With this evidence, SCFS setup has become an excellent spectroscopic tool to study the intracellular signalingcascades that are linked to the extracellular domain consisting transmembrane proteins such as cadherins. Therefore, an understanding of the unique fibroblasts mechanobiology is necessary to study the healthy and diseased tissue dynamics. The cell-cell and cell-ECM bio-chemical and bio-mechanical cues are strongly interdependent. Finally, the current thesis opens the basic understanding of the fibroblasts biophysical properties using AFM nano-mechanical tool and unravels the fibroblasts biomechanical function in sub-tissue level biology
Fucoidan degradation by marine bacteria
Full text linkThe oceans are an important carbon sink that have sequestered about half of all anthropogenic CO2 emissions. Marine carbon cycling is driven by the deposition of photosynthetic micro- and macroalgae in ocean sediments, where carbon is stored over thousands of years. The algal polysaccharide fucoidan is considered to be recalcitrant to microbial degradation and may therefore facilitate long-term carbon storage. Yet, factors that render fucoidan recalcitrant against microbial degradation remain unidentified, hampering our understanding of fucoidans in the carbon cycle. Fucoidans originating from the cell wall of brown algae are often co-extracted with other cell wall components. In Chapter I, I develop a simple step-wise protocol to purify fucoidans from different brown algae. Using mass spectrometry and nuclear magnetic resonance analyses, I describe the highly diverse and branched structures of different fucoidans. In Chapter II, I examine how marine bacteria degrade those complex branched fucoidans. Using genomics, proteomics and biochemistry, I characterize the newly isolated Verrucomicrobium a Lentimonasa sp. CC4 and show that fucoidan degradation requires highly dedicated pathways of over 100 enzymes covering 20% of the a Lentimonasa sp. CC4 proteome. The complexity of these pathways implies that only highly specialized bacteria can effectively degrade fucoidans and gives a clue why it may be recalcitrant. The proteomic analysis of a Lentimonasa sp. CC4 in chapter II suggested that two protein families, S1 15 and GH29, are key in fucoidan degradation. In Chapter III, I biochemically and structurally characterize one S1 15 sulfatase and one GH29 fucosidase, revealing their exo-enzyme activity and a novel catalytic pair of two aspartate residues. This provides insights into the molecular mechanism of exo-enzymatic fucoidan degradation. In Chapter IV, I trace the dynamics of different polysaccharides during a diatom spring bloom in Helgoland. I found that the dominant bloom-forming diatom Chaetoceros socialis secretes fucoidan in dissolved form, which aggregates and accumulates in particles at the end of the bloom. Known enzymes to degrade this polysaccharide are not expressed in the microbial community which indicates that fucoidans are not microbially degraded and act as vector for organic carbon drawdown. To summarize, fucoidans are diverse, highly branched polysaccharides whose degradation requires a large set of enzymes found in very few specialized marine bacteria. Their stability-enhancing properties lead to increased brown algal deposition in coastal sediments and in the open ocean they may acts as aggregation nuclei that enhance aggregation and settling of phytoplankton aggregates. Their abundance, recalcitrant nature and stickiness make fucoidans a likely key players in oceanic carbon sequestration
Related to whom? The impact of organisational and regional capabilities on radical breakthroughs
Full text linkThis paper aims to explain the emergence and diffusion of novel combinations in Germany. On the one hand, it scrutinizes on the effect of internal technological diversity. On the other hand, it looks at interactions with other actors and assesses whether relatedness to the overall regional knowledge base or rather being related to specific regional actors improves radical inventive activity in German organisations. It is demonstrated that the emergence of radical novelty is positively influenced by an optimal degree of internal diversity as well as relatedness to actors at the technological frontier. However, for this radical novelty to diffuse, rather diverse actors and cognitive proximity to the regional knowledge base is important. The results call for a more fine-grained picture in the relatedness debate and deliver interesting insights for inventive organisations in terms of partner choice and policy-makers for future initiatives
Who benefits from radical innovations of SMEs? - Empirical evidence from the German Biotechnology
Full text linkRadical innovations are of key importance from an economic point of view since they bear the potential to trigger the emergence of new technological trends and fuel economic prosperity while simultaneously causing far-reaching structural change processes. In this paper we focus on the transfer channels of radical innovations launched by small and medium-sized firms (SMEs). Based on a unique longitudinal dataset covering the observation period 1996 - 2016, we identify and trace back radical innovations of SMEs in the German Biotech in order to analyze the extent to which SMEs themselves or eventually also other organizations in their direct cooperation surrounding benefit from radical innovations in terms of subsequent innovation performance. Results from panel data count models indicate that direct cooperation partners of radical innovators generally seem to show higher innovative performance than partners of the control group, i.e. not radical innovating statistical twin firms. A more differentiated picture emerges if one considers the geographical and technological proximity of the cooperation partners
Assessing the spatial management of mangroves and small-scale fisheries in protected areas on the Brazilian Amazon coast
Full text linkMangroves are important providers of ecosystem services. Despite their relevance for conservation, they have been impacted by dynamic drivers that are causing loss of mangrove area worldwide. In Brazil, mangrove conservation strategies, such as spatial planning and protected areas, have not been fully implemented due to data deficiency on various social-ecological aspects of mangroves, including the spatial dynamics of small-scale fisheries. This thesis aims to investigate how multiple knowledge systems and assessment methods, including the ecosystem-based approach, participatory mapping, and GPS tracking can be combined for integrated management of mangrove protected areas, having as focus study areas two extractive reserves (RESEXs) in northeastern Para, Brazil. In order to achieve an ecosystem-based management approach, mangrove ecosystems need to be managed as an integrated system, and interconnections with other coastal ecosystems must be assessed and taken into account. Regarding the spatial management of small-scale fisheries that take place in mangroves, this research shows that a combination of participatory mapping and GPS tracking can help identify fishing areas and the origin of the crab demand for each area. These findings can be applied to the spatial management of the crab fisheries, including integrated zoning strategies for protected areas. This thesis also proposes a framework to establish the starting geographic level for integrated spatial planning. In northeastern Para, the spatial management of the four existing protected areas needs to be done in an integrated manner
A multi-method approach to study the geodynamic evolution of eastern Dronning Maud Land in East Antarctica by integrating geophysical data with surface geology
Full text linkPlanet Earth has not always been as it appears today. Since billions of years, continents have been drifting continually caused by lateral variations of mantle density resulting in convection. Analyzing the movement of lithospheric plates back in eartha s history is essential for the determination of the shape of ancient supercontinents. It further provides paleogeographic information and is vital for biogeographic and climate studies. Whereas the break-up of the former extensive landmass of Gondwana can be reconstructed fairly well by analyzing seafloor-spreading anomalies of the oceanic crust, the amalgamation of Gondwana still needs to be understood in more detail. This is because oceanic crust, that rarely exceeds 180 million years in age, does not provide any direct evidence for the amalgamation of Gondwana in Late Neoproterozoic/Early Palaeozoic times as well as for older supercontinent cycles. East Antarctica, once centerpiece of Gondwana, can be considered a rather stable region as it has not been affected by orogenic processes since the Early Paleozoic except for its Palaeo-Pacific margin. Furthermore, the Antarctic plate is mainly surrounded by mid-ocean ridges and features continental rift systems widely related to the break-up of Gondwana. Therefore, exposed regions that can be found in Sor Rondane, East Antarctica, are well suited for studying the formation and break-up of Gondwana as well as preceding collision and break-up processes. Sor Rondane is situated in eastern Dronning Maud Land and exposes the contact zone of crustal blocks of different origin and architecture. Therefore, it is considered to be a site of at least one suture between East and West Gondwana. This study examines the final amalgamation and break-up history of Gondwana by investigating Sor Rondane and adjacent regions. To answer those questions, a detailed understanding of the crustal architecture is essential. This encompasses the number of involved crustal fragments, the location of their boundaries and their geological evolution. Moreover, this comprises the structural and metamorphic evolution as well as the shallow crustal dynamics of Sor Rondane. Due to the extensive ice-coverage of this region, the study of exposed rocks by various geological methods was combined with regional aerogeophysical investigations. In the austral summers 2010/11 and 2011/12, structural field work and geological sampling were executed by the Federal Institute for Geosciences and Natural Resources (BGR). Additional airborne geophysical surveys were flown in collaboration with the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), between 2010 and 2015. The data set includes ice-penetrating radar, aeromagnetic and aerogravity measurements. These combined geological and geophysical data sets are used to analyse the structure and composition of rock units and enable to map units beneath the ice not accessible to geological methods. For instance, fault systems may correlate with magnetic lineaments gained from aeromagnetic anomaly data. These can be tracked over large distances underneath the ice and thus facilitate interpretations at a larger scale