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Molecular charachterization of alkane-metabolizing archaea
No full textAlkanes are carbon compounds composed exclusively of carbon and hydrogen. They are the main constituents of natural gas, petroleum, and fossil fuels and, thus, influence both the climate and human activity. Alkanes play an important role in anoxic ocean sediments and hydrothermal systems, where they can leak into the ocean. In these environments, microbes modulate both the release and the consumption of alkanes: either through the biogenic formation of methane by methane-producing archaea (methanogens), or the biological consumption of alkanes by anaerobic alkane-oxidizing archaea (ANKA). Methanogens and ANKA share evolutionary history and metabolic features, but they function differently. Unlike methanogens, ANKA depend on sulfate-reducing bacteria (SRB) or other extracellular electron acceptors to oxidize alkanes, in part by the reversal of the metabolism of methanogens. Both methanogens and ANKA play an important role in carbon cycling in energy-limited ecosystems. However, little is known about their anabolic pathways or how electrons and carbon flow from catabolic substrates to anabolic products. In this thesis, I describe a novel ethane-oxidizing archaeon and investigate the anabolism of select ANKA and methanogens.
In Chapter 2 (Manuscript 1), I describe Candidatus Ethanoperedens ambientalis, the first ethane oxidizer known to grow at room temperature. The ethane oxidizer forms consortia with a member of the Desulfobacteriota, Cand. Desulfosymmachos locustemperatii, of the Seep-SRB1d clade. Their syntrophic interaction likely relies on direct interspecies electron transfer. Both partners assimilate dissolved inorganic carbon as a carbon source. I also found that the disaccharide trehalose was by far the most abundant sugar in enrichments of Cand. E. ambientalis. In Chapter 3 (Manuscript 2), I expanded the search for disaccharides across multiple ANKA enrichments and demonstrated that trehalose and other disaccharides are present at similar abundances to those found in Cand. E. ambientalis enrichments. I developed a bioinformatic pipeline that demonstrated that trehalose metabolism was common across the partner bacteria of ANKA. However, metabolomics showed substantial amounts of trehalose only in ANKA enrichments where the ANKA had substantial trehalose metabolism. I also show that ANKA and their partner bacteria readily share trehalose metabolism through horizontal gene transfer. In Chapter 4 (Manuscript 3), I explore electron flow and anabolism in pure cultures of Methanothermococcus thermolithotrophicus, currently the only methanogen known to grow on sulfate. I examine how M. thermolithotrophicus remodels its transcriptome in response to sulfur sources, and how this in turn affects how M. thermolithotrophicus shuttles electrons from catabolic substrates to anabolic products. In this study, we also observed the overexpression of a putative viral-like element and identified the likely capsid protein using artificial intelligence–based protein modeling. In Chapter 5, I synthesize the findings of my doctoral research. I discuss the implications of my findings on the energy landscape of ethane oxidation, the potential roles and sources of disaccharides in ANKA consortia, and how sulfur acts as an environmental modulator of transcriptional resources in M. thermolithotrophicus
Religionssensibilität in der Sozialen Arbeit. Zur Relevanz einer religionssensiblen Arbeit und den damit einhergehenden Bedarfen und Herausforderungen für pädagogische Fachkräfte. Am Beispiel von der Arbeit mit unbegleiteten minderjährigen Geflüchteten in der stationären Jugendhilfe in Bremen
No full textDiese Arbeit beleuchtet die Herausforderungen und Bedarfe von Fachkräften in der sozialen Arbeit mit unbegleiteten minderjährigen Flüchtlingen (umF) in Bremen. Sie thematisiert die Bedeutung einer religionssensiblen Sozialen Arbeit, die darauf abzielt, die religiösen und kulturellen Hintergründe der Klient*innen zu respektieren und in die pädagogische Praxis zu integrieren.
Anhand von Expert*inneninterviews wird untersucht, wie gut die Konzepte der
Religionssensibilität in der Praxis umgesetzt werden und welche Kompetenzen Fachkräfte
benötigen, um effektiv mit religiösen Themen und Praktiken umzugehen. Die Analyse zeigt, dass viele Fachkräfte täglich mit den religiösen Bedürfnissen ihrer Klient*innen konfrontiert sind, jedoch häufig nicht über das notwendige Wissen oder die Reflexionsfähigkeiten verfügen. Die Ergebnisse der Untersuchung verdeutlichen die Dringlichkeit einer fundierten Ausbildung in theologischen und religionswissenschaftlichen Inhalten sowie die Notwendigkeit regelmäßiger Fortbildungen. Zudem werden Impulse für eine verbesserte Teamarbeit und interdisziplinäre Kooperationen gegeben, um die Herausforderungen in der praktischen Arbeit zu meistern.
Diese Arbeit liefert somit nicht nur eine fundierte Analyse der aktuellen Situation, sondern auch konkrete Empfehlungen zur Optimierung der Sozialen Arbeit mit umF, die für den Fachbereich von großer Relevanz sind.1
On the Dynamics of Time, Space and Quanta - Essential Results for Space Flight and Navigation
No full textSpace flights are very important for navigation, communication, as well as for the exploration of weather, climate, geophysics, celestial bodies, time and space.
Space navigation requires synchronized clocks. Clocks are subject to relativistic time dilation. However, relativity theory does not predict adequate frames, which are essential for the prediction of time dilation. As a provisional solution of that frame problem, the International Astronomical Union (IAU) recommends celestial reference systems: a geocentric and a heliocentric or barycentric reference system.
In order to solve the problem of predicting adequate frames, we propose new tools: a three clock device, a ballistic device, a levitating device, and a new symmetry.
With the above tools, we show that each clock onboard every spacecraft has an adequate frame, so that the clock has a uniquely and correctly determined velocity and time dilation. Since, these adequate frames determine the propagation of time, they are physically essential, and must be identified:
Near an isolated celestial body, a frame at rest in the local gravitational field is adequate.
Near several celestial bodies, their fields and frames move relative to each other. Therefore, the space that determines the propagation of time separates into moving parts, and their fields exhibit linear superposition. The above derived separation of space is additionally confirmed by a new space paradox. Due to the linear superposition of fields, the celestial reference systems recommended by the IAU are approximately adequate near their celestial bodies.
A systematic investigation of the above derived separate parts of space, spacetime or volume in nature provides an indivisible description of curvature of spacetime, gravity and quanta. Based on that, the linear superposition of moving fields is solved with help of quantum expectation values of velocity that exactly predict the time of clocks onboard spacecrafts. Summarizing, we see that celestial reference systems are approximate solutions of the above frame problem, whereas expectation values provide an exact solution.
We use data from former space flights as tests, and we propose further space flights to areas between celestial reference frames, as well as additional measurements on Earth.
We elaborate a universal reference system and derive its universal time dilation. We use the measured and derived Hubble tension as a first test.
We identify idealized and realistic principles in general relativity and quantum physics.
Our results are in precise accordance with observation. Thereby, no fit has been executed, and no additional hypothesis has been introduced.
We derive our findings in a systematic, clear and smooth manner. We summarize our results by definitions, propositions and theorems. Our results are adequate for classes from grade 10 or higher, courses, research clubs, enthusiasts, observers, experimentalists, mathematicians, scientists, researchers …1
A Longitudinal Approach to the Analysis of Social Media Engagement: The Case of Anger-Driven Climate-Skeptic Message Propagation During the 2021 German Elections
No full textSocial media have become an important space for political agenda formation and mobilization, with user engagement playing a key role in spreading messages. Accordingly, prior research has extensively examined social media users’ engagement and sharing behaviors. In this study, we examine the advantages of longitudinal modeling for analyzing social media engagement compared with cross-sectional approaches, focusing on the relationship between emotional reactions—particularly anger—and content propagation. Although cross-sectional approaches are commonly used to analyze social media data, engagement patterns are inherently temporal and therefore naturally call for a longitudinal, time-sensitive approach. We argue that longitudinal methods can be more effective than cross-sectional ones for analyzing time-evolving engagement dynamics. These methods indeed represent a middle ground between familiar cross-sectional approaches and sophisticated time-series techniques, avoiding some pitfalls of the former while relying on simpler assumptions than the latter. Longitudinal methods, in fact, reduce omitted variable bias, help account for time-varying factors—including algorithmic amplification and network propagation confounders—and accommodate irregular or sparse social media data. We empirically explore the differences between longitudinal and cross-sectional analysis by comparing estimates of the effect of anger on sharing using 1,137 environmentally themed Facebook posts by German political parties during the 2021 federal election, focusing on Alternative für Deutschland (AfD) and Die Grünen (The Greens), which represent opposite ends of the environmental policy spectrum. Cross-sectional estimates were derived using three sampling strategies: the last observation per post, the first post-election observation, and a randomly selected observation per post. Bayesian multilevel regression with a negative binomial specification was applied across both longitudinal and cross-sectional models. Our results indicate that longitudinal modeling yields more conservative and precise estimates, whereas cross-sectional methods tend to exaggerate effect sizes and interparty differences. All models suggest that anger is positively associated with sharing for AfD and negatively for Die Grünen, but longitudinal analysis provides greater inferential stability by controlling for time-invariant confounders and algorithmic amplification. Overall, the findings underscore the value of incorporating temporal dynamics into social media research, while also highlighting the challenges of applying longitudinal approaches to digital trace data, particularly with regard to data access.005
Generative KI als Spiegelraum: Zur Rolle dialogischer Systeme in der transformativen Bildung für nachhaltige Entwicklung (Preprint)
No full textDer Beitrag untersucht die dialogischen Potenziale generativer KI-Systeme wie ChatGPT im Kontext transformativer Bildung für nachhaltige Entwicklung (BNE). Ausgehend von der These, dass KI kein neutrales Werkzeug, sondern ein kultureller Spiegelraum ist, analysiert der Text, wie kollektives Prompting zu einer neuen Kulturtechnik werden kann. Die Nutzer:innen treten dabei nicht nur als Konsumierende, sondern als Mitgestaltende epistemischer Prozesse auf. Anhand theoretischer Perspektiven (u. a. Haraway, Barad, Butler) und eines visionären Bildungskonzepts – dem „KI-Flashmob für Nachhaltigkeit“ – wird aufgezeigt, wie sprachliche Interaktion mit KI zur reflexiven und politischen Praxis werden kann. Der Beitrag plädiert für eine aktive Aneignung dieser neuen Form digitaler Kommunikation, in der Sprache als Medium gesellschaftlicher Gestaltung verstanden wird, für eine demokratische und nachhaltige KI-Kultur von morgen.21523
Influence of metal vapor on the welding arc
No full textDie Lichtbogenstabilität verbessert sich durch die Kombination des
Lichtbogenschweißens mit dem Laserstrahlschweißprozess im Laserstrahl-Lichtbogen-
Hybridschweißen. Der laserinduzierte Metalldampf wird dabei als stabilisierender
Faktor betrachtet. Zur Untersuchung der Mechanismen, insbesondere des Einflusses des
Metalldampfs, wurde eine experimentelle, orthogonale Prozesskombination eingesetzt.
Diese Methode ermöglichte es, andere Einflüsse des Hybridprozesses zu minimieren.
Die Ergebnisse zeigten eine Destabilisierung des Lichtbogens durch den
laserinduzierten Metalldampfeinfluss. Die Destabilisierung resultierte aus der Summe
negativer Einflüsse auf die Lichtbogenleitfähigkeit in der verwendeten
Prozesskombination. Im realen Hybridprozess wird aufgrund günstigerer Bedingungen
eine Stabilisierung erwartet
Extraction of time-dependent properties from medical ultrasound image series
No full textMedical ultrasound offers the unique possibility to gather real-time image series, providing insights into dynamic processes of the human body. The interpretation of the acquired sequences, however, can be challenging, especially when the dynamic property of interest is superimposed by, for example, respiratory motion. This thesis investigates how to automate the extraction of time-dependent properties from motion-affected ultrasound image series considering two concrete use cases.
The first part deals with extracting two image features from contrast-enhanced ultrasound (CEUS) acquisitions of liver lesions, which are relevant for diagnosis. Both features characterise the distribution of the contrast agent in the lesion compared to normal liver tissue over time. Deep learning-based classifiers are exploited on a large collection of 500 labelled heterogeneous CEUS acquisitions. The influence of aspects such as motion compensation and data representation on the classification result is systematically analysed.
In the second part, a use case from physiotherapy is explored in which segmental stabilising exercises are incorporated to treat low back pain. During those exercises, the contraction status of the abdominal muscles can be monitored via ultrasound imaging. Automating the extraction of this status has the potential to enable wearable ultrasound biofeedback devices which can be used for example during home training. Several deep learning-based segmentation algorithms for the three relevant abdominal muscles are evaluated, using time series acquired from volunteers performing exercises.Also, different strategies to assess the contraction state from the obtained segmentations are explored.
Both use cases showed that motion can affect the assessment of dynamic image features in ultrasound. Using effective algorithms, it can be controlled to some extent, enabling the use of information along the sequence to retrieve the desired properties
Plume dispersal in the Arctic Ocean - the Aurora Site at Gakkel Ridge
No full textThis thesis assesses the dispersal of the hydrothermal plume at the Aurora Vent Site in the Arctic Ocean, based on observational data and complemented by a numerical ocean model. The theoretical background of hydrothermal plumes in the Arctic is presented and the methods used are explained. This includes the processing of data acquired from a CTD probe, water samples and an oceanographic mooring with respect to the hydrographic setting and to the tracers for identification of the hydrothermal fluid. In addition a setup for simulating the plume dispersal with the Regional Ocean Modelling System is described. The observational results reveal a plume that ascends up to a height of 1200 m and spreads laterally to at least a distance of 2500 m, although a strong core is confined to a much smaller area. The plume dispersal is highly inhomogeneous for the different investigated tracers. This, as well as the small horizontal extent is explained by the presence of slow currents that are altered by tidal or inertial oscillations. A similar vertical extent can be obtained from the model simulation. However in regards to the currents and horizontal extent, the simulation shows large discrepancies compared to the observations, therefore suggestions for improving the model setup are presented
Die Integration sozialer Angebote in die hausärztliche Versorgung mit dem Konzept „Social Prescribing“
No full textHintergrund: Die sozialen Determinanten beeinflussen das Wohlbefinden und die Gesundheit eines Menschen. Obwohl Hausärzt*innen täglich soziale Probleme bei ihren Patient*innen wahrnehmen, arbeiten hausärztliche Praxen kaum interprofessionell mit sozialen Angeboten zusammen. Social Prescribing (SP) bietet eine Möglichkeit, die Zusammenarbeit zu stärken, indem Patient*innen – oft durch „Link Worker“ – mit lokalen Unterstützungsangeboten, Gruppen oder Aktivitäten in Kontakt gebracht werden.
Ziel: Indem die hausärztlichen Perspektive auf Patient*innen mit sozialen Problemen sowie die intendierten theoriegeleiteten Wirkweisen von SP untersucht werden, soll diese Dissertation das Entwickeln akzeptierter und wirksamer Interventionen unterstützen.
Methoden: In einem Scoping Review mit veröffentlichtem Studienprotokoll wurde eine systematische Übersicht von Theorien erstellt, die in Studien verwendet wurden, um SP zu planen oder zu evaluieren. In einer web-basierten Querschnittsstudie wurde untersucht, wie Hausärzt*innen in europäischen Ländern SP wahrnehmen und praktizieren. In einer weiteren web-basierten Querschnittsstudie wurden die Perspektiven hausärztlich tätiger Ärzt*innen in Bremen auf die Vermittlung von Patient*innen mit sozialen Problemen an nicht-medizinische Angebote erfasst.
Ergebnisse: Der Scoping Review identifizierte elf Theorien die von 16 Studien in 18 Berichten beschrieben wurden. Alle Theorien wurden für die Evaluation und keine für die Planung der SP-Intervention genutzt. Alle wurden genutzt um Zusammenhänge zu erklären und manche zusätzlich um beispielsweise Leitfäden für Interviews zu erstellen oder Outcomes und Messinstrumente zu bestimmen. In der europäischen Erhebung (n=208) verwiesen 32 % (n=66) der Hausärzt*innen ihre Patient*innen regelmäßig über ein formelles System an Gruppen und Gemeinschaftsaktivitäten. Bremer Ärzt*innen der hausärztlichen Versorgung (n=45) gaben an, im Median 10 % der Patient*innen mit erkanntem Unterstützungsbedarf weiterzuvermitteln. 33 (73 %) der Bremer Ärzt*innen fühlten sich belastet, wenn sie nicht vermitteln konnten. Ärzt*innen beider Befragungen erwarteten von einer zentralen Anlaufstelle bzw. SP positive Auswirkungen auf die Gesundheit ihrer Patient*innen und ihre eigene Arbeitszufriedenheit.
Schlussfolgerung: Obwohl nur 16 Studien die Verwendung einer Theorie beschrieben, wurden verschiedene Theorien auf unterschiedliche Weise für SP genutzt. Die Verwendung von Theorien kann eine Möglichkeit sein, um Unklarheiten hinsichtlich der Definition von Zielgruppen und Wirkmechanismen zu verringern. Die Ergebnisse beider Befragungen zeigten eine positive Haltung der Ärzt*innen zur engeren Zusammenarbeit mit sozialen Angeboten. Dennoch wurden nur wenige Patient*innen weitervermittelt. Weitere Forschung zur Perspektive anderer Professionen des Praxisteams und von sozialen Angeboten ist nötig
Pore-scale numerical investigation of solute transport variability in fractured rocks: from fracture surface topography to pore space heterogeneity
No full textThe heterogeneity of mineralogical and hydraulic properties in fractured crystalline rocks plays a critical role in accurately assessing the subsurface transport of radionuclides. This doctoral thesis combines both experimental and simulation approaches to examine the geometric and mineral heterogeneity affecting the primary reactive transport processes in fracture-matrix systems, including advection, diffusion, and surface reactions. A significant aspect of this study is the introduction of a cross-scale topographic analysis method, with a focus on the interactions between fluid transport and surface reactivity.
Fractures serve as the primary transport pathways for solutes in so-called crystalline rocks. Solute species migrate rapidly through fractures by advection, but this process is partly retarded by diffusion and adsorption. Accurately characterizing the geometric and topological structure of fractures is critical because it affects the assessment of solute dispersion within fractures, as well as the coupling between fluid flow and surface reactions. Surface topographic features can vary with different mineral composition, their grain size, and their grain surface. Therefore, we implemented a fracture model constructed from computed tomography (CT) images with modified surface detail in order to simulate solute transport under different surface roughness conditions. We introduced a cross-scale surface analysis tool (power spectra density, PSD) to evaluate the length scale sensitivity in surface modifications. We found that increasing the scale of surface topography does not always result in a linear or steady change in breakthrough curves (BTCs). This finding provides valuable guidance for using simplified or oversimplified geometries in reactive transport modeling.
In the rock volume surrounding fractures in crystalline rocks, solute species are primarily transported by diffusion through intergranular pores and microfractures that connected to the fractures, controlled by, varying effective diffusivities. Fracture mineralization, such as calcite, occurs quite frequently. The resulting channeling effect increases with the degree of mineralization, ultimately shifting transport from the advection regime to the diffusion regime and lowering migration. To quantitatively analyze the resulting transport in such complex systems, we conducted an in-situ diffusion experiment using positron emission tomography (PET) scanning. This experiment allowed us to quantify transport behavior and elucidate the role of heterogeneous, multigeneration fracture precipitates in influencing radionuclide migration. The reactivity of mineral surfaces determines the efficiency with which dissolved species are adsorbed or desorbed, and thus, the quantitative assessment of possible retention. The heterogeneity of nano- and microtopographic surfaces results in different reaction rates. Surfaces with a higher density of reactive sites, such as kink sites and edges, exhibit higher reaction rates than plateau surfaces. Concurrently, this micro-topographically induced variation in intrinsic surface reactivity continuously alters the surface topography. The coupling of surface evolution and reaction rate is crucial for the parameterization of pore-scale reactive transport models, which require the consideration of time-dependent variables. Linking the evolution of reactive surfaces across spatial (from nanometers to millimeters) and temporal scales with their reaction patterns answers a central question: Can the reaction rate be treated as a stable parameter across space and time? This question is becoming increasingly urgent given the demand for improved predictability of reactive transport models, particularly with regard to long-term radionuclide migration prediction. This work demonstrates for the first time that the quantitative variability of the reaction rate is stationary, establishing a stationary microtopography of the reactive surface. This dissertation provides a comprehensive analysis of how geometric and mineralogical heterogeneity in fractured rock types influences radionuclide transport through advection, diffusion, and reactivity. By integrating the aforementioned topics of reactive transport, it contributes to a better understanding of the controlling mechanisms of nuclear disposal. Based on this analysis, the dissertation proposes the use of specific geometry and reactivity parameters to enhance the predictive capabilities of existing reactive transport models in complex fractured rocks. Overall, this work contributes to the improved safety assessment of the geological disposal of high-level radioactive waste