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Marine shallow water systems as natural sources of mercury to local systems
No full textHydrothermal systems transfer heat and mass through circulating water in a permeable geological formation. The circulating water (hydrothermal fluid) undergoes multiple subsurface processes, gaining and losing constituents dependent upon physical, geological, and chemical factors. According to Beaulieu and Szafranski (2020), a total of 184 systems are confirmed active across the globe. Of these, 43 are considered MSWHS (above 200 m depth). Areas of emission are characterized by diffuse fluid or gas emission (diffuse), or distinct localized points of emission (point sources). Both types of emission can be sedimented or unsedimented dependent upon local conditions.
The goal of the doctoral project was to provide a fundamental understanding of Hg prevalence in MSWHS from three systems (Milos, Greece; Vulcano, Italy; Panarea, Italy). Each system presented unique environmental conditions where Hg was known to be present. The study area on Milos contained multiple areas of diffuse emission and point sources at depths of less than 5 m. Emission was a mixture of fluids, gases, and brines, with extensive microbial white mat activity. The study area on Vulcano dominantly emitted gases at depths of less than 5 m with limited white mat activity. The study areas on Panarea were at greater depth (5 to 30 m), were a mixture of gas and fluid, with greater biodiversity present than the other sites. White mat activity on Panarea was limited. Primary indicators of Hg emission were evaluated and the effect of MSWHS on local environments were investigated as both direct (e.g., through mercury rich gases to the atmosphere) and indirect (e.g., transport and dissolution of precipitated mercury particles). Each study location represented a unique MSWHS, where environmental conditions greatly affected Hg concentrations in emitted fluids and gases. Additionally, the relationship between Hg and the local environment revealed further information on the subsurface environment of the MSWHS.
Samples were collected from diffuse and point sources at approximately 10 cm depth where possible (e.g., sedimented) through PTFE tubes. Gases were collected in Tedlar© bags at the sediment-water interface. Analysis was completed through CV-AFS (THg, Hgdiss, Hg0, DMHg, Hggas, THg in sediments), and gas chromatography (MMHg).
Organic species of Hg were not present above detection limits within the hydrothermal fluids sampled at any site. Fluid samples were generally comprised of Hg bound to colloids and particles greater than 0.45 µm (THg). Concentrations of THg within sampled hydrothermal fluids ranged from below local background seawater values (0.5 to 5 pM) to 249 nM. Bound and unbound Hg in filtered (0.45 µm) samples (Hgdiss) generally represented a small portion of THg (BDL to 273 pM). Additionally, Hg0 was not generally a significant portion of THg (BDL to 5.3 pM). Therefore, the greatest Hg specie in hydrothermal fluid was Hg2+, the vast majority bound to colloids and particles > 0.45 µm. Within hydrothermal gases, total Hg (Hggas) ranged from below detection limits to 2,792 nmol / m3.
The greatest indicators of high Hg concentrations within gases and fluids were associated with the rate of flow and the presence of sedimentation. Higher rates of flow, particularly when paired with high temperatures, generally indicated high Hg concentrations within the fluid or gas. However, the presence of sedimentation overlying the hydrothermal source greatly decreased the concentration. Higher rates of flow limited the temporal exposure of hydrothermal fluids and gases to surrounding material, were associated with higher temperatures, and tended to prevent sedimentation at the orifice of the hydrothermal source. However, where sedimentation was present at the orifice, high flow rates were not associated with high Hg concentrations.
The effect of MSWHS on local environments was evident through sediment and seawater samples collected at each location. Background sediment samples collected at each site were within normal values. Accumulations of Hg within sediments associated with hydrothermal sources was observed (0.3 to 49.5 nmol / g). However, these accumulations were limited to direct interaction with the point source. Samples taken centimeters away from hydrothermal sources did not show significant Hg accumulation compared to background samples (0.3 to 0.5 nmol / g). The effect of MSWHS on overlying seawater was most dramatically observed in Panarea and Vulcano. In Baia di Levante on the island of Vulcano, the combination of a high density of MSWHS activity coupled with shallow water (< 1 m), resulted in accumulations up to 186 pM THg. Off the coast of Panarea, at La Calcara, a vertical profile directly above the main point source maintained elevated THg (< 1.1 pM) over 20 m of depth.
It can be concluded that MSWHS contribute Hg to the local environment. The extent of impact is largely controlled by environmental factors (e.g., flow rate and sedimentation). However, immediate removal to sediments after emission to overlying seawater is not supported. Rather, Hg is transported away from point sources and areas of diffuse emission. Therefore, the impact of MSWHS on Hg cycling may extend beyond the immediate local area
Exploring the role of excitatory-inhibitory dynamics in synaptic plasticity, memory stability, and neural coding
No full textThis thesis provides an exploration of the brain's neural dynamics, shedding light on the mechanisms underlying learning, memory retention, neural synchronization, and sensory processing. Through a comprehensive series of studies, we explore how neurons adjust their connections in response to specific patterns, a fundamental aspect of memory and learning. This synaptic plasticity demonstrates a tight balance between different neural adaptations, allowing the brain to retain old memories while continuously forming new ones. The Investigation proceeds with an investigation of collective neural behavior, in particular the transitions between different firing states within networks of neurons. Our results characterize the critical points that govern these transitions, contributing significantly to the understanding of large-scale neural coordination. This insight highlights the importance of maintaining a balance between excitatory and inhibitory neurons, which directly impacts the brain's ability to process information and maintain functional states. Delving deeper into the mechanisms of sensory processing, our study examines the brain's response to visual stimuli, specifically under circumstances that generate gamma oscillations in the visual cortex. The interaction between external stimuli and brain wave activity shows layer-specific effects, providing a detailed insight into the neural basis of perception and cognition. In conclusion, this thesis presents a focused view of neural function, from synaptic alterations to network dynamics and sensory processing. It highlights the brain's remarkable capacity for stability amidst constant change, a foundational aspect underpinning the continuity of memory and the adaptability of learning. The collective findings of study offer profound implications for both neuroscience and the development of advanced artificial neural systems, emphasizing the necessity of intricate balancing in both natural and artificial learning environments
Method of simulation based support generation for laser powder-bed fusion processes of metals
No full textDiese Arbeit befasst sich mit der simulationsbasierten Erzeugung von Stützstrukturen für metallbasierte Laser Beam Melting (LBM) Verfahren. Dazu wurde eine Methode entwickelt, welche simulationsbasiert den Verzug des Bauteils während des Aufbaus analysiert und Pin-Supports (Konus-Stützen) dort platziert, wo dieser am größten ist. Die Aufbausimulation des Bauteils erfolgt mit Hilfe einer Finite Elemente (FE) Rechnung unter Verwendung der
Mechanical Process Equivalent (MPE) Methode. Nach dem Platzieren einer neuen Stütze wird die Simulation auf die Schicht zurück gesetzt, in welcher der Pin das erste mal einen Einfluss auf das Bauteil hat und von dort fortgesetzt. Dieser Vorgang wird solange wiederholt, bis der Aufbau des Bauteils vollständig abgeschlossen ist. Auf diese Weise wird eine Stützstruktur erzeugt, welche den mechanischen Anforderungen des Bauteils während des Aufbaus genügt und somit einen sicheren Fertigungsprozess gewährleisten soll. Diese Struktur wird um eine weitere, deutlich feinere Struktur ergänzt, welche die Prozesswärme
aus dem Bauteil ableiten soll um Überhitzungseffekte zu vermeiden. Validiert wird die Methode anhand verschiedener Beispiele aus dem Dentalbereich. Dazu werden dentale Versorgungen aus einer Cobalt-Chrom Legierung mit diesen Stützstrukturen gefertigt.
Die Darstellung der Pins in der Simulation erfolgt durch Dreibeine aus Linienelementen. Um den Aufbau des Materials der Stütze selbst zu berücksichtigen wird jedes neu aktivierte Dreibein mit einer effektiven Vorspannung versehen. Zur Abschätzung dieser initialen Belastung der Stützstruktur und um die generelle Robustheit der Methode zu beurteilen, wurden umfängliche Konvergenzanalysen für die Entwicklung der Spannungen und des Verzuges während der MPE Simulation durchgeführt
Unraveling the fidelity of virtual reality interactions: effects of realism in object manipulation and embodiment
No full textImmersive experiences created with multisensory and interactive virtual reality (VR) technology can feel incredibly realistic. Many factors of the system and the user determine the fidelity of VR interactions, that is, how closely an interaction resembles the reference interaction to be simulated. The human-computer interaction (HCI) research presented in this dissertation is a step towards unraveling and better understanding the different aspects of interaction fidelity in VR that cover user input, computer simulation, sensory feedback, and the user's experience.
Combining theoretical, methodological, and empirical research, I present and discuss nine papers focusing on object manipulation and embodiment in the context of interaction fidelity. The presented Interaction Fidelity Model enables a systematic assessment of eight fidelity components with precise definitions and a thorough discussion of their implications. Integrating the HCI loop and previous theories, the model's human-centered perspective can be universally applied to all interactions with any VR system. Furthermore, the specialized Haptic Fidelity Framework allows a detailed assessment of 14 factors determining the fidelity of haptic interfaces.
On this theoretical basis, a series of user studies are analyzed, covering findings on haptic feedback and perception for object manipulation, body visibility in VR sports, visual realism of virtual humans, embedding questionnaires into virtual environments for user research, and VR meetings of an academic team. The quantitative and qualitative analyses demonstrate significant effects of varying interaction fidelity on user performance, task load, sense of body ownership, perceived realism, usability, and user experience. The iterative user research contributes hardware and software prototypes, such as an in-VR questionnaire tool for participants' self-reports, a grip-based interaction technique for force-feedback gloves, a handheld controller with adaptive trigger resistance, and experimental environments built with Unity.
This thesis provides guidelines, illustrative examples, research artifacts, and educational material for designing realistic VR applications, improving how we comprehend and reflect on interaction fidelity in VR research and development. An extensive research agenda highlights promising directions for future investigations of the complex construct of interaction fidelity
Relationen – Das verknüpfende Glied zwischen Positionierung und Widersprechen: Eine Illustration anhand des feministischen Abtreibungsdiskurs
No full textPublikation der U Bremen und U Wien internationalen Studierendenkonferenz »Debattieren, Opponieren, Protestieren – Interdisziplinäre Perspektiven auf sprachliche Praktiken des Widersprechens« 2023.485
Worlds of welfare within the Muslim world. A system approach to the analysis of welfare arrangements in Muslim societies
No full textAlthough there have been efforts to illustrate elements of a potential ‘Islamic welfare state’, there is no academic work dedicated to developing a typology of welfare regimes in Muslim majority countries. The present research is starting with identifying existing patterns of welfare provision among Muslim societies by using available global indicators with collected valid data as a starting point. The main purpose of the research is to explore if there is a unified and homogenous pattern of welfare system within the so-called Muslim World or there are multiple and diverse worlds of welfare provision. Hierarchical and k-means cluster analysis (KCA) were employed to work out a typology of welfare systems among the Muslim majority countries. A welfare system approach was used to select variables for data gathering and analysis. While input, process, output and outcome variables were used to develop a typology of welfare systems in countries under study, context variables were utilized to compare the policy environments which have impacts on the functioning of a welfare system. Findings of the present research showed that a vast diversity of experiences could be witnessed among Muslim majority countries with regard to various aspects of the welfare system. A combination of contextual features with input, output and outcome attributes forms seven types of welfare arrangements: The ‘Rentier social non-democracy system’, the ‘Equality-oriented proto-welfare system’, the ‘Less efficient Proto-welfare system’, the ‘Fragile informal welfare system’, the ‘Failing informal welfare system’, the ‘Failing informal materially-equal system’, and the ‘Failed ill-fare system’. The paper concludes with discussing the main features of these welfare systems and comparing them with existing typologies in the literature as well as some implications for future research in this field.Deutsche Forschungsgemeinschaft (DFG)2
Implications of the neotectonics around the Laptev Sea Rift as a result from (micro-) seismicity analysis
No full textThe Laptev Sea Rift offers an outstanding opportunity to study continental rifting. At the edge of the Laptev Sea, the ultra-slow spreading Gakkel Ridge encounters the continental slope, with the divergent motion continuing on the continent within the Laptev Sea Rift. Due to the isolated location of this unique region at the northern edge of the Arctic Circle in Siberia, geophysical investigations are still relatively rare. The study of earthquakes is a suitable method for exploring geodynamic processes. However, the global network of permanent seismic stations is relatively sparse above the Arctic Circle, resulting in only a vague understanding of the (micro-)seismic activity in the Laptev Sea region, as weaker seismic events simply cannot be detected. The global earthquake catalogue (until 2018) demonstrates a significant distribution of earthquakes clearly defined along the axes of the Gakkel Ridge. In the transition zone, where the ridge meets the continent, a decrease in activity is observed, dispersing into a wider area to the south. In this study, earthquake data recorded at stations of a local, temporary network and arrays were analysed. The data set spans a period of nine months, from August 2016 to April 2017. This study focuses on the neotectonic context to address whether the Laptev Sea Rift is still active and whether the rift region can be defined as a separate tectonic block, such as a microplate
Entwicklung einer integrativen Planungsmethodik für Autoterminals mittels selbststeuernder logistischer Prozesse
No full textAutomobilterminals spielen eine zentrale Rolle in internationalen Fahrzeuglieferketten, indem sie als Knotenpunkte der Supply Chain fungieren. Diese Häfen sehen sich dynamischen Wechselwirkungen und Anforderungen gegenüber, die klassische Terminalplanungsprozesse oft nicht hinreichend bewältigen können. Diese Arbeit entwickelt eine neue Planungsmethodik basierend auf selbststeuernden logistischen Prozessen, um Effizienzsteigerungspotenziale zu erschließen.
Zunächst wird der Problembereich analysiert und die Eignung selbststeuernder Prozesse als Lösungsprinzip untersucht. In der Hauptstudienphase werden theoretische Erkenntnisse anhand eines realen Automobilterminals überprüft. Darauf aufbauend wird eine Planungsmethodik entwickelt, die auf pheromonbasierten Selbststeuerungsmethoden basiert. Simulationsstudien an einem generischen Terminalmodell und einem realen Automobilterminalmodell evaluieren die Leistungsfähigkeit der neuen Methodik.
Die Ergebnisse zeigen, dass die entwickelte Methode Schwachstellen klassischer Planungsprozesse überwinden und die logistische Leistung von Terminals unter dynamischen Bedingungen steigern kann. Die Analyse der Umsetzungsanforderungen und der erarbeitete Handlungsleitfaden verdeutlichen, dass die Implementierung der Lösung unter realen Einsatzbedingungen mit geringem Aufwand möglich ist. Die Methodik hat somit eine hohe praktische Relevanz und bietet eine Grundlage für weitere Forschung, beispielsweise um die Parametrisierung zu optimieren oder neue Selbststeuerungsansätze zu entwickeln
Claims data analysis of drug therapy for patients with multiple sclerosis in Germany
No full textMultiple sclerosis (MS) is the most common chronic inflammatory autoimmune disease of the central nervous system (CNS). While the use of MS drugs in routine care is well studied quantitatively, current data on the implementation of the requirements within the Summary of Product Characteristics (SmPC) and the consideration of guideline recommendations are insufficient. In addition, little is known about the implementation of a cost-effective drug therapy. Therefore, the aim of this thesis is to answer these open questions about drug use in MS. A routine data analysis was conducted on the use of drugs for MS between 2017 and 2020 using claims data from around 10 million insured members of the Techniker Krankenkasse (TK). This data was used to determine the outpatient prescription prevalence of various MS drugs. Overall, 54.95 % of MS patients were prescribed disease-modifying therapies (DMTs) for immunotherapy. Only 0.37 % of MS patients received rituximab off-label. Glatiramer acetate was prescribed to 13.04 % of MS patients. Of these only a small proportion were generic prescriptions. 23.15 % of MS patients were treated with glucocorticoids for acute relapse therapy without having previously received DMTs. Prescriptions for symptom-related drugs were given to a total of 51.38 % of patients. This included fampridine prescriptions for 11.29 % of patients, of whom 57.91 % received the drug for a continuous period of at least seven months. The observed proportion of 45.05 % of MS patients without a DMT prescription suggests that at least some of these patients may be undersupplied with DMTs. The low relevance of rituximab in MS therapy despite its designation as a recognised alternative treatment in the guidelines could be attributed to the barriers to off-label use in Germany. The low relevance of generic glatiramer acetate compared to the originator product is striking. The observation that 57.91 % of fampridine treatments continued for at least seven months raises questions as the SmPC requires the initial therapy attempt in non-responders to be limited to two to four weeks whilst the literature assumes a responder rate of less than 40 %. It is possible that the time-limit for treatment of non-responders is not adequately considered by physicians. Further research is needed to verify the assumptions made
Trockene und thermischen Verarbeitung von PEO-basierten Festkörperelektrolyten für Festkörperbatterien
No full textThe growing world population and the resulting increase in energy demand, as well as the need to store energy, is an unstoppable process that science, industry, and politics need to address together. This means that new electrical energy storage systems must be developed, or existing ones need to be optimized to meet future energy needs. Next-generation energy storage systems, such as all solid-state batteries (ASSBs), have attracted increasing attention in recent decades due to their high energy and power density.
The aim of this thesis is to investigate the relationship between the dry process of polymer-based SEs using melt extrusion and the material behavior with respect to the upscaling of polymer-based SEs. Therefore, a concept is developed from the investigation of small quantities using a laboratory kneader to the investigation of larger quantities in kilo-scale using a twin-screw extruder