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Double Backpropagation with Applications to Robustness and Saliency Map Interpretability
Full text linkThis thesis is concerned with works in connection to double backpropagation, which is a phenomenon that arises when first-order optimization methods are applied to a neural network's loss function, if this contains derivatives. Its connection to robustness and saliency map interpretability is explained
Stable carbon isotopic studies of microbial lipids from distinct geochemical marine environments
Full text linkSedimentary microbial lipids are widely used as sensitive indicators of environmental conditions in paleoenvironmental and biogeochemical studies. Nonetheless, systematic isotopic investigations of microbial lipids to constrain their sources, modes of production, and turnover remain fragmentary. In order to decipher the information encoded in sedimentary archaeal and bacterial lipids in different marine depositional environments, I conducted carbon isotopic analysis of marine environmental samples (Chapter III and IV) and laboratory-based stable isotope probing (SIP) experiments (Chapter V). Chapter III provides fundamental constraints on archaeal activity, sources of archaeal lipids, and preservation signatures in diverse marine sediments. This is, to my knowledge, the first systematic comparison of stable carbon isotopic compositions of archaeal core lipids (CLs) and intact polar lipids (IPLs). Results from lipid analysis are interpreted in the context of geochemical data in contrasting depositional regimes, including a transect from the Rhone River delta into the western Mediterranean Sea, the anoxic Black Sea, Marmara Sea, and sapropel layers in the Eastern Mediterranean Sea. Mass balance calculation along the transect of the Western Mediterranean Sea proved that terrestrial input of archaea into marine sediments can be substantial (up to 42%) and suggests caution when reconstructing such inputs based on existing molecular proxies, such as BIT (Branched isoprenoid tetraether index). Similar I 13C values of core and intact polar crenarchaeol strongly suggest that the alkyl moieties are not synthesized de novo, thus indicating that intact polar crenarchaeol is either a fossil relic from planktonic archaea or a product of lipid recycling by benthic archaea. By contrast, an average offset in I 13C values of 2.6a degree between core and intact polar caldarchaeol indicates active in-situ activity of benthic archaea. To further constrain the sources and turnover of sedimentary archaeal lipids, we compared the stable carbon isotopic compositions of archaeal IPLs and CLs through the oxic, suboxic and anoxic water column and in high resolution within an 8-m deep sediment core in the Black Sea (Chapter IV). The comparison between the water column and surface samples suggests that archaea residing in the lower suboxic zone are the main source of lipids found in surface sediments, including a large fraction of IPLs. The isotopic offset between core and intact caldarchaeol indicates sedimentary in-situ production by benthic archaea. Based on a two endmember mixing model, an average of 34% sedimentary intact polar caldarchaeol is likely produced by benthic archaea. Two independent isotope mass balance calculations suggested that on average 35% and 18% of CL-caldarchaeol are derived from IPL degradation in sediment. In addition to the analysis of environmental samples, laboratory-based SIP provides us another distinct perspective to understand the microbial-mediated processes in marine sediments, for example, anaerobic oxidation of methane (AOM). Their enrichment cultures have been increasingly purified but still contain additional community members, even after years of repeated dilution and inoculation. In order to investigate the potential heterotrophic activity of the microorganisms coexisting with AOM consortia, I performed an L-leucine-3-13C (13C-leu) labeling study on a mesophilic AOM enrichment culture (Chapter V). Our results showed that most 13C-Leu incorporation was observed in bacterial fatty acids, especially iso and anteiso-branched C15:0 and C17:0, but very limited in archaeal ether lipids. Interestingly, these incorporation patterns were independent of the addition of methane to the enrichments, suggesting the ancillary heterotopic bacteria (e.g. Anaerolineae and Spirochaetes) are the main producers of these 13C-labeled lipids rather than AOM consortia. These ancillary heterotopic bacteria probably thrive on the amino acids derived from AOM necromass and likely explain the common absence of AOM lipid signals in sedimentary records. This thesis highlights the presence of various archaeal lipid inputs from terrestrial, planktonic and sedimentary sources into marine sediments. New lipids are continuously produced and degraded by microorganisms in the active subseafloor biosphere. The incubation experiment suggests that heterotrophic bacteria may play a pivotal role in necromass turnover in marine sediments
Fisheries Assessment and Trophic Modelling of Tono, Bontanga and Golinga Reservoirs, Ghana
Full text linkDue to the dispersed nature of inland fisheries, most individual systems are rarely adequately assessed or monitored, therefore reliable data on the target stocks are largely unavailable to implement management strategies. This thesis focuses on Tono, Bontanga and Golinga reservoirs in northern Ghana which contribute significantly to food nutrition and community livelihoods. The thesis presents studies that demonstrate how differences in reservoir use patterns, reservoir morphometry and physicochemical characteristics influence ecosystem structures and fisheries resource productivity. To improve the estimation of current harvest potential of West African reservoirs, the relationship between total annual fish catch and reservoir surface area was modelled, which compared to a previous model, indicated that catches from reservoirs in the region have more than doubled over the last two decades. The cichlid species Oreochromis niloticus, Sarotherondon galilaeus, and Coptodon zillii were found to be heavily exploited in all three reservoirs. The giraffe catfish, Auchenoglanis occidentalis was found only in Tono and Bontanga reservoirs. In Bontanga, the catfish stock is fully exploited. While in Tono, the giraffe catfish is underexploited, the current fishing mortality could be doubled to increase yield. While fisheries productivity (per unit surface area), is inversely related to lake size, we conclude that the use of small reservoirs in populated semi-arid environments for both irrigated farming and fisheries production is unsustainable due to problems associated with seasonal water loss, siltation and aquatic habitat degradation. The findings of this thesis suggest that the use of man-made lakes and respective catchment areas should be assessed and managed carefully to prevent the loss of nutrition and livelihoods contributions
Transcriptional bases of acclimation in the kelp, Saccharina latissima, from gametophytes to sporophytes
Full text linkKelps, algae of the order Laminariales, are important ecosystem engineers in temperate to Arctic coastal waters. They form marine forests that support complex communities by providing habitat for several taxa, they provide coastal defense and contribute significantly to climate change mitigation and adaptation by acting as carbon sink. However, these marine forests are threatened by impacts of anthropogenic-driven climate change. Hence, a better understanding of the acclimation mechanisms taking place in the sugar kelp Saccharina latissima across its life history stages is necessary to predict emerging environmental pressures, potential range shifts and, thus, future distributions. This study revealed novel insights into the molecular mechanisms of acclimation and adaptive responses of a keystone, but non-model species, for which only limited genomic information has been available previously. It also became evident that transcriptomic data do not necessarily match observations made on the physiological level, but are likely to reflect emerging constraints to cellular function and overall individual performance at an early stage. Furthermore, the differences in response towards environmental drivers across different latitudes, life history stages and sexes emphasize the need for integrative approaches in order to facilitate predictions on species performance in natural as well as aquaculture systems in the face of large-scale environmental change
Task-adaptable, Pervasive Perception for Robots Performing Everyday Manipulation
Full text linkIntelligent robotic agents that help us in our day-to-day chores have been an aspiration of robotics researchers for decades. More than fifty years since the creation of the first intelligent mobile robotic agent, robots are still struggling to perform seemingly simple tasks, such as setting or cleaning a table. One of the reasons for this is that the unstructured environments these robots are expected to work in impose demanding requirements on a robota s perception system. Depending on the manipulation task the robot is required to execute, different parts of the environment need to be examined, the objects in it found and functional parts of these identified. This is a challenging task, since the visual appearance of the objects and the variety of scenes they are found in are large. This thesis proposes to treat robotic visual perception for everyday manipulation tasks as an open question-asnswering problem. To this end RoboSherlock, a framework for creating task-adaptable, pervasive perception systems is presented. Using the framework, robot perception is addressed from a systema s perspective and contributions to the state-of-the-art are proposed that introduce several enhancements which scale robot perception toward the needs of human-level manipulation. The contributions of the thesis center around task-adaptability and pervasiveness of perception systems. A perception task-language and a language interpreter that generates task-relevant perception plans is proposed. The task-language and task-interpreter leverage the power of knowledge representation and knowledge-based reasoning in order to enhance the question-answering capabilities of the system. Pervasiveness, a seamless integration of past, present and future percepts, is achieved through three main contributions: a novel way for recording, replaying and inspecting perceptual episodic memories, a new perception component that enables pervasive operation and maintains an object belief state and a novel prospection component that enables robots to relive their past experiences and anticipate possible future scenarios. The contributions are validated through several real world robotic experiments that demonstrate how the proposed system enhances robot perception
The collapse of cooperation: The endogeneity of institutional break-up and its asymmetry with emergence
Full text linkDecline and break-up of institutionalized cooperation, at all levels, has occurred frequently. Some of its concomitants, such as international migration, have become topical in the globalized world. Aspects of the phenomenon have also become known as failing states. However, the focus in most social sciences has been on institutional emergence and persistence, not collapse. We develop an endogenous explanation of collapsing institutions. Collapse may be an implication of the very economic success of institutionalized cooperation and of increasing system complexity, when cognitive conditions for effective collective decision-making do not proportionately evolve. Moreover, we show that collapse is not a simple logical reverse of emergence. Rather, institutions break up at different factor constellations than the ones prevailing at emergence. We approach endogenous institutional break-up and its asymmetry from various paradigmatic and disciplinary perspectives, employing psychology, anthropology, network analysis, and institutional economics. These perspectives cover individuals, groups, interaction-arenas, populations, and social networks
Körperliche Aktivität im höheren Lebensalter im Kontext sozialer Ungleichheiten. Ungleichheitseffekte von Public-Health-Interventionen zur Förderung körperlicher Aktivität
Full text linkReducing health inequalities is a priority for public health. Social inequalities in physical activity are discussed to be an important determinant of health inequalities. Public health interventions to promote physical activity have the potential to reduce health inequalities, but may also unintentionally increase them. Therefore, there is a need for evaluating equity-specific effects of interventions, potentially arising during intervention uptake, acceptance, and efficacy. This cumulative dissertation examined whether and how potential equity-specific effects of public health interventions to promote physical activity among older adults are currently evaluated and what implications for research and practice can be derived. The applied methods comprised a quantitative data analysis, a systematic review, qualitative expert interviews, exploratory literature searches, a methodological workshop, and the establishment of an international cooperation for re-analyzing data of existing intervention studies. The results indicate that 1) changes in activity behavior among older men and women differ by socioeconomic characteristics, 2) studies of universal interventions to promote physical activity among older adults currently rarely consider equity-specific effects when evaluating the interventions' efficacy, 3) the use of logic models is a potential tool for planning, implementing, and interpreting the analysis of equity-specific intervention effects, and 4) developing a joint strategy for re-analyzing data of existing intervention studies regarding social inequalities in intervention acceptance and efficacy is feasible. Because equity-specific effects of interventions to promote physical activity among older adults are currently rarely evaluated, little is known about the impact of these interventions on health inequalities in the older population. In order to close this evidence gap, equity-specific effects of existing interventions should be evaluated through re-analyzing existing data. Moreover, equity-specific effects of new interventions should be evaluated by analyses specified a priori. Systematic reviews and meta-analyses should be conducted to systematically synthesize and appraise the results of these (re-)analyses. Based on this evidence, recommendations for future interventions should be derived. This would allow for the design of interventions most likely to reduce and not unintentionally increase social inequalities in physical activity among older adults
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 combing 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
Assessment of sustainable tourism development in Windhoek, Namibia : Development and implementation of an adapted criteria catalogue in line with respective local conditions.
Full text linkThe aim of this master thesis is to assess, analyse and evaluate the sustainability of a tourism destination while taking the local conditions into consideration by adapting the assessment instrument. The case study of the city Windhoek in Namibia is used to identify particular local features and make them measurable using an adapted criteria catalogue. In addition to a comprehensive secondary analysis, the database consists of different qualitative and quantitative methods, which are conducted during a field research phase in the form of expert interviews, visitor and local surveys and observations at relevant POIs. The content and statistical evaluation of the data is the basis for the assessment of the indicators, the sustainability dimensions and the global evaluation of sustainability in the destination. The weaknesses identified in the course of the research are then recorded in the form of recommended actions. As this thesis is part of the development policy cooperation between the City of Bremen and the City of Windhoek, the communication platform, to make the research results available to the City of Windhoek, has been established. Besides the adaptation of the catalogue, a refinement of the method for future measurement and evaluation of sustainability in destinations with different framework conditions is developed. Based on a critical reflection and the issue of the applicability of the model to other destinations, technical and content-related recommendations for the catalogue adaptation to local circumstances are made
An analysis of design reuse in the development of small body nanolander and surface science stations : Supporting reuse, modular design and platforming with Model Based Systems Engineering
No full textDesign reuse, i.e. reuse of design artefacts of space missions is gaining more importance in the frame of cost efficiency improvement i.e. getting more science out of the limited funding in space systems development. This has found application in the Earth orbiting spacecraft sector, but may also be of interest for deep space scientific missons. This thesis contributes to the practice of design reuse with the development and demonstation of a method for a more systematic reuse approach as compared to the ad-hoc reuse widely common. Using a real life reuse case from an ESA phase A mission concept study, the process is described based on a developed general ontology of system design under consideration of the pecularities of a deep space scientific misson and uses Model-Based Systems Engineering methods. A Reuse Matrix has been proposed as a tool to analyse reuse effort a-priori based on individual delta development effort of components and the propagation of changes over the component borders. The latter are shown to be depending on aspects such as the number of interfaces and the number of constraints involved in the change propagation, as well as the extent of change of the latter. Three different case studies are presented: (1) a single reuse scenario, which develops a mission concept for a MASCOT-derived Phobos surface station using the presented method and derives the reuse matrix for this special case; (2) a platform based design-for-reuse analysis, which determines requirements and derives a platform approach for nanolander systems based on the MASCOT lander heritage and (3) a modular lunar infrastructure designed for a special case of reuse of the same system design for different use cases in one mission scenario. The three case studies prove the general applicability of the process and the usability of the Reuse Matrix, which benefits from the existence of a desciptive system model including system requirements, functional breakdown and physical allocation, as well as connected performance models which are fed with the information stored in the system model. The MASCOT lander system design has been demonstrated as very well suited for effective reuse and shows to be a good starting point for a platform-based family of nanolander for a broad variety of small and airless bodies