6949 research outputs found
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Advancements in parallel actuation: modeling, design, and applications
No full textParallel actuation is both a solution and a challenge. Compared to serially actuated systems, it offers significant advantages in speed, accuracy, and efficiency. These improvements arise from transmitting motion through multiple mechanical branches simultaneously. However, this same characteristic also introduces new challenges at two distinct levels. First, the usable work-space is often significantly reduced, leading to designs that are highly task-specific. Second, the complexity of modeling increases, which has historically hindered the widespread adoption of optimal control algorithms compared to serial architectures. Furthermore, modern demands for increased robot compliance — to enhance adaptability, energy efficiency, and safety — stand in contrast to the inherently rigid nature of traditional parallel robots.
This work addresses these challenges through various approaches. In the first part, belt-driven designs that lie at the intersection of serial and parallel architectures are explored. It is demonstrated that such systems enable high-speed movements within large work-spaces, thereby applying trajectory optimization methods. Additionally, the possibility to extend the usable work-space of parallel kinematic machines is exemplified. The second part focuses on compliant parallel actuation, showing that stiffness control can be achieved with a minimal number of actuators. It also introduces a novel concept combining soft-shell actuation with parallel linkages. The third part investigates various dynamic modeling techniques for parallel kinematic machines and provides a comparative analysis of their suitability for trajectory optimization
Die körperliche Aktivität im Kontext von gesundem Altern in Deutschland
No full textDer fortschreitende demographische Wandel und der damit zusammenhängenden Anstieg der Anzahl älterer Erwachsener führt zu einer Vielzahl an neuen Herausforderungen für Gesellschaft, Gesundheitswesen und Sozialsystem. Der Erhalt einer guten Gesundheit ist daher eine zentrale Aufgabe. Häufig resultieren gesundheitliche Probleme im Alter aus chronischen Erkrankungen, denen mit gesundheitsbewusstem Verhalten und Präventionsmaßnahmen entgegengesteuert werden kann. Daher wurde in dieser Arbeit die Rolle der körperlichen Aktivität im Kontext von gesundem Altern in Deutschland untersucht, mit Fokus auf dem sozioökonomischen Status, der Zeitverwendung sowie dem Geschlecht. Zur Beantwortung wurden drei Publikationen herangezogen, die in internationalen wissenschaftlichen Fachzeitschriften veröffentlicht wurden. Als Basis der Analysen dienten Fragebogendaten, objektiv erhobene Daten einer Bewegungsmessung mit Akzelerometern sowie einer körperlichen Untersuchung aus dem Projekt OUTDOOR ACTIVE. Die Ergebnisse zeigten einen positiven Zusammenhang zwischen sozioökonomischem Status und objektiv gemessener körperlicher Aktivität bei den Männern, jedoch nicht bei den Frauen. Zudem konnten Geschlechtsunterschiede hinsichtlich der verwendeten Zeit für verschiedene Aktivitätsdomänen gefunden werden. Die Ergebnisse deuten darauf hin, dass mehr Zeit für Freizeitaktivitäten und aktive Mobilität sowie eine höhere objektiv gemessene körperliche Aktivität mit einem verringerten Risiko für verschiedene gesundheitliche Einschränkungen zusammenhängen. Der gefundene Geschlechtsunterschied hinsichtlich der körperlichen Funktionsfähigkeit konnte zum Teil durch Gesundheitsindikatoren und chronische Erkrankungen erklärt werden. Die Ergebnisse stärken die Evidenzlage bezüglich körperlicher Aktivität und gesundem Altern in Deutschland. Sie liefern zudem Erkenntnisse, die bei der Entwicklung von Präventions- und Gesundheitsförderungsmaßnahmen für ältere Erwachsene berücksichtigt werden sollten
Neural correlates of acute-induced stress and decision-making under risk: an fMRI study
No full textMany situations in daily life require making risky decisions under stressful conditions. In the
current behavioral literature, the effects of stress on risky decision-making are inconsistent,
and there is limited research investigating post-stress risky decisions from a neural
perspective. Identifying neural correlates of post-stress risky decision-making might help to
improve the targeted behavioral interventions for risk adjustment. Furthermore, the
investigation of post-stress risky decisions from a neuroscientific perspective might shed
light on underlying neural/cognitive mechanisms that can moderate the impact of stress on
decision-making and offer insights unattainable through behavioral methods alone.
Thus, in this dissertation, functional Magnetic Resonance Imaging (fMRI) was employed to
assess the neural correlates of stress as well as post-stress risky decision-making. The study
consisted of four experimental blocks: stress, post-stress decision-making, control, and post
control decision-making. The design was within-subject and all participants were subjected
to stress and control conditions in a counterbalanced order. Both stress and control
conditions were followed by a “decision-making under risk” task directly after the stress
exposure in a single fMRI session with a concurrent Electrodermal Activity (EDA)
measurement to confirm the stress manipulation. Stress was induced by asking participants
to solve mental arithmetic tasks under time pressure & social-evaluative threat while
receiving negative feedback. During the decision-making task, participants chose between a
safe and a risky option (binary lottery task) with monetary incentives and known
probabilities of winning.
Self-reported stress levels and EDA data confirmed that the stress induction was successfully
implemented. Participants took less risky decisions post-stress than post-control. An fMRI
contrast analysis revealed that the right fronto-opercular and the left anterior part of the
dorsolateral prefrontal cortex (dlPFC; an area critical for executive functioning and cognitive
control) exhibited significantly lower activation during decisions post-stress than decisions
post-control.
The results indicate that decisions taken immediately after exposure to the acute stressor
are associated with reduced activation in the regions of the dlPFC, possibly leading to less
deliberate and less risky decision-making post-stress. Interventions to increase dlPFC
activation might be suitable to improve the quality of decision-making post-stress, alleviating
the effects of stress
Incorporating status bias into prejudice research
No full textIs prejudice against social groups rooted in intergroup distinctions or in the groups' low status? Whereas much research has focused on the former idea, this dissertation examines the latter. This form of prejudice is of particular concern as it puts members of disadvantaged groups at further disadvantage through prejudice and discrimination targeted against them. To consider this form of prejudice, I propose incorporating status bias, the tendency to prefer high-status groups over low-status groups, into prejudice research. Building on Social Dominance Theory, I conceptualize status bias as rooted in objective group status, consistent with the idea that it reinforces actual group-based inequalities. Throughout seven empirical studies using various study designs and methods, this dissertation examines status bias and its contributions to two major issues in prejudice research: the ideological foundations of prejudice and its reduction through intergroup contact. The results demonstrate that status bias forms group evaluations jointly with other biases and varies in its strength across evaluations of different kinds of target groups. Moreover, distinguishing between status bias and ingroup bias is promising for the study of the ideological foundations of prejudice, particularly SDO and RWA. Both ideologies were previously thought to motivate ingroup bias; however, this research did not differentiate it from status bias. The results reveal that SDO was not associated with stronger ingroup bias; instead, it was associated with stronger status bias, suggesting that incorporating the distinction between the biases into research on the ideological foundations of prejudice is a promising approach. Furthermore, distinguishing between status bias and ingroup bias can improve the assessment of the effectiveness of interventions to reduce prejudice. As such, intergroup contact was associated with weaker ingroup bias but stronger status bias. This pattern has previously been unobserved due to the lack of distinction between biases. Together, the findings demonstrate the merit of incorporating status bias into different fields of prejudice research
Recordings of cosmogenic beryllium in marine sediments during the Laschamps geomagnetic dipole low: implications for synchronization of paleo archives and geomagnetic field reconstructions
No full textCosmogenic beryllium (10Be) is produced in the Earth’s atmosphere during the nuclear cascade initiated by the collision of galactic cosmic rays with the nuclei of atmospheric atoms. The production rate of 10Be is therefore globally influenced by the solar and geomagnetic fields. It exhibits both a latitudinal and an altitudinal gradient, with the highest production rate in the polar stratosphere and the lowest in the equatorial troposphere. 10Be is removed from the atmosphere, primarily through wet deposition, and is globally recorded in various paleo archives, such as ice or sediment cores. Given the correlation between the 10Be production rate and Earth’s magnetic shielding and solar activity, 10Be is a valuable tool for the reconstruction of both in the past. Additionally, the global modulation of its production rate renders 10Be an effective synchronization tool for diverse paleo archives. Yet, additional factors may also affect the recorded production rate signal. Recent atmospheric mixing models suggest a latitude-dependent influence of geomagnetic field variations on 10Be records. Consequently, depending on the selected record, the global 10Be production rate change may be either over- or underestimated. In marine sediments, several other influences must be accounted for, including the residence time of beryllium in the water column, changes in sedimentation rates or scavenging efficiency, benthic fluxes of beryllium, bioturbation, and potential sediment re-deposition. Additionally, especially for synchronization purposes, it is imperative to measure marine sediment cores with the highest possible resolution.
To begin with, a beryllium purification protocol for measuring 10Be with accelerator mass spectrometry (AMS) was developed. This protocol ensures high sample throughput at a low cost while simultaneously yielding samples that perform well in the AMS. This method employs precipitation reactions and utilizes only standard laboratory materials and equipment. A comparative analysis of this method was conducted against an established protocol based on hydroxide precipitations and column chromatography. Although the method resulted in slightly lower sample purity and yield, this did not adversely affect the AMS measurement. In contrast to the established method, the approach is significantly more cost-effective and enables a two- to threefold increase in sample throughput.
To gain a better understanding of the various influences on the recorded 10 Be signal, several marine sediment cores were analyzed. To assess influences on the 10Be recording in marine sediments, three cores were analyzed for their 10Be/9Be ratios during the Laschamps geomagnetic dipole low (∼ 41 ka BP). Although all cores are influenced by the Antarctic Circumpolar Current (ACC) and exhibit high sedimentation rates, differing depositional conditions and influences are present. A rapid and distinct increase in the 10Be/9Be ratios by 50 – 80 percent was observed in all cores during the Laschamps event, which corresponds with changes in the respective paleomagnetic inclinations. However, when compared to 10Be data from ice cores, it was found that all sediment cores were influenced to varying extents by oceanic residence times of 10Be. The short oceanic residence time of beryllium at core PS67/197-1 is consistent with published data for the region, while the longer one of core PS75/054-1 suggests that at least a portion of the scavenged beryllium originates from the pelagic Pacific. In core PS97/085-3, indications of a temporary increase in terrigenous influence were observed. Other sedimentary processes did not significantly affect the 10Be/9Be ratios of the cores. Despite the attenuation effects of residence time and the variable terrigenous influence observed in core PS97/085-3, it was found that the 10Be/9Be ratios are fundamentally suitable for synchronizing different regions and archives.
The latitude-dependent distribution of 10Be deposition was investigated by comparing published 10Be sediment data and ice core records during the Laschamps event with the data in this thesis. Variations in 10Be deposition during the Laschamps event were examined in relation to latitude and compared with modeled 10Be deposition rate changes derived from different geomagnetic field reconstructions (LSMOD.2, GGFSS70, Black Sea, GLOPIS-75), in conjunction with the atmospheric mixing model GEOS-Chem. It was found that the results align well with the atmospheric mixing model, which postulates incomplete mixing of 10 Be in the atmosphere before deposition, revealing a lower amplitude of deposition at higher latitudes compared to lower ones. Furthermore, the global deposition rate change during the Laschamps event was estimated, yielding a value that supports the geomagnetic field model LSMOD.2, while indicating that the production rate change derived from GLOPIS-75 may be overestimated. Overall, the gap between geomagnetic field models and atmospheric transport models of 10Be, as well as data-based reconstructions, was narrowed by this study. Notably, it was demonstrated that the global 10Be production rate increased by 117 – 133 percent during the Laschamps event. Although this figure exceeds previous estimates derived from ice core data, it remains insufficient to fully reconstruct the production rate changes of 14C based on 14C measurements
Gesundheitsmonitoring im Kontext von Migration - Strategien und Konzepte zur verbesserten Repräsentation
No full textDeutschland ist, nach den USA, das zweithäufigste Zielland internationaler Migration. Dennoch sind Menschen mit eigener oder familiärer Einwanderungsgeschichte nicht bevölkerungsanteilig im Gesundheitsmonitoring des Robert Koch-Instituts repräsentiert, was Analysen zu gesundheitlicher Ungleichheit im Kontext Migration erschwert. Zudem steht die Public Health-Forschung auch auf konzeptioneller Ebene vor der Herausforderung, die Vielfalt der Bevölkerung adäquat zu adressieren. Das Konzept Migrationshintergrund wird in Surveys oft unterschiedlich operationalisiert, was die Vergleichbarkeit beeinträchtigt. Darüber hinaus fasst es Menschen in unterschiedlichen Lebenslagen zusammen und erschwert so die Identifikation gesundheitlichen Ungleichheiten zugrundeliegender Erklärungsfaktoren. Die Arbeit eröffnet Strategien, um beiden Herausforderungen zu begegnen. Für eine verbesserte Einbindung in Gesundheitssurveys haben sich beispielsweise Übersetzungen sowie das Angebot mehrerer Teilnahmemodi als zielführend erwiesen. Besonders erfolgsversprechend ist der persönliche Kontakt, um unterrepräsentierte Subgruppen, wie beispielsweise Menschen mit niedriger Bildung, besser für die Forschung zu gewinnen. Auf der konzeptionellen Ebene wurden Empfehlungen zur Erhebung und Analyse migrationsbezogener Determinanten in der Public Health-Forschung erarbeitet, die für die Zukunft statt zusammenfassender Kategorien wie Migrationshintergrund die Nutzung von migrationsbezogenen Einzelindikatoren vorsehen, die in Analysen in Zusammenschau mit sozialen Determinanten der Gesundheit betrachtet werden sollten, wie beispielsweise sozioökonomische Lage oder Arbeits- und Wohnbedingungen. Basierend auf dem bevölkerungsanteiligen Einschluss von Menschen mit Einwanderungsgeschichte ins Gesundheitsmonitoring sowie unter Verwendung differenzierter Konzepte in der Datenerhebung und -analyse lassen sich gesundheitlichen Ungleichheiten zugrunde liegende Faktoren perspektivisch besser sichtbar machen
Reactivity and redox behaviour of ferrocenyl substituted pnictogens and chalcogens
No full textThe molecular chemistry of low-valent cations of main group elements has sparked curiosity over the past decades, owing to their unique properties and the promise of a more abundant, cheaper alternative to transition metals in catalysis.
Combining low-valent main group cations with the fruitful chemistry of the iconic ferrocene, this thesis explores the use of the monodentate ferrocenyl (Fc) unit as a ligand in low-coordinate cations of group 15 elements and their derivatives. Additionally, it reports the preparation, structural and spectroscopical characterisation of ferrocenyl substituted pnictogens and tellurides, together with their redox properties. The triferrocenylpnictogens were studied in detail in order to understand the electronic coupling in electrochemically generated monocations.
The electron-rich nature of the Fc ligand allowed for the isolation and full characterisation of the diferrocenylpnictogenium ions. Their molecular structures revealed that such electrophiles are stabilised by intramolecular Fe…E (E = P, As, Sb, Bi) interactions, while still remaining Lewis superacids. The chemical reactivity of the diferrocenylphosphenium ion was investigated as well: the oxidative addition of diaryldichalcogenides, reactions with dienes, alkynes and allenes, and subsequent isolation of a Wheland intermediate of ferrocene all contribute to our understanding of the properties of such highly reactive species, and explore their potential in main-group catalysis
Biogenic and hydrogenous magnetic mineral formation in upward oxygenated sediments of the East Pacific Rise
No full textThe Clarion-Clipperton Zone is a deep-sea area in the eastern Pacific Ocean. Due to low sedimentation rates, the sediment cover in this region is thin and discontinuous. This allows low-temperature hydrothermal activity in the underlying crustal rocks, bringing oxygen and other solutes into the sediments from below. Therefore, the geochemical zonation in the deeper sediments is reversed. The sediment composition, mineral diagenesis and (bio)geochemical processes in this environment have not yet been studied in detail. This work, based on a combination of sediment-magnetic methods and geochemical analyses, investigates the mineralogy and the processes in these hydrothermally influenced sediments. The influx of oxygen from below supports the preservation of magnetic minerals in the sediments and enables reliable magnetic dating over several million years. Hydrothermal oxygen and chemoremanent overprinting have no significant effects. However, it was discovered that microaerophilic magnetotactic bacteria can live deep inside the hydrothermally oxygenated sediments, where no such bacteria have been expected in the past. The secondary biogenic magnetite produced by these bacteria accumulates locally and results in magnetic anomalies and overprinting. This discovery has far-reaching consequences for hydrothermally active deep-sea regions and, in particular, for ridge flank systems
Oysters under anthropogenic pressure: A cellular perspective on the interactive effects of microplastic pollution and climate change
No full textAnthropogenic driven global change is affecting all areas of the world, including the marine realm, and several factors affect the organisms at a given time. Among these, habitat temperature is one of the key driving factors for marine ectotherms. In addition, environmental pollution caused by microplastics (MP; particles < 5mm), which are particularly bioavailable to the smallest filter feeders, has become a global threat. Despite its undeniable ecological relevance, however, most previous studies have neglected potential synergistic effects of MP exposure and climate warming. The present study therefore aimed at enhancing the understanding of the interactive effects of combined exposure to environmentally relevant MP concentrations and climate warming on the cellular stress response of two ecologically and economically important key species from the German North Sea coastal ecosystem: The Pacific oyster (Crassostrea gigas) and the European flat oyster (Ostrea edulis). In two laboratory-based exposure scenarios, this study particularly addressed whether (i) MP exposure induces cellular stress in intertidal C. gigas, (ii) MP exposure enhances the vulnerability of C. gigas to atmospheric heating during low tide, and (iii) combined MP exposure and projected warming by + 3 °C induce interactive effects on cellular stress response of subtidal O. edulis.
To address the thesis objectives, polystyrene MP microspheres (a mix of 4, 7.5, and 10 µm in size) at environmentally relevant concentrations (0.025 µg L-1 and 25 µg L-1) served as model MP. In a first experiment, intertidal C. gigas were exposed to MP for 16 days under a simulated semidiurnal tidal cycle to investigate possible dose- and time-dependent MP effects at ambient temperature (16 °C). On day 16, oysters were exposed to a gradual atmospheric heating during the last low tide simulation (16–26 °C; 3 °C h-1), with returning seawater (16 °C), in order to analyse possible MP-induced susceptibility to atmospheric heatwaves. In a second full-factorial experimental approach, subtidal O. edulis were exposed to MP for 28 days, either at ambient 20 °C or at + 3 °C elevated temperature (i.e., 23 °C) to investigate possible interactions between chronic MP exposure and future warming.
(i) In-depth analysis revealed dose-dependent MP-induced oxidative stress in the gills of C. gigas, which was evident both at the metabolite level and at the enzymatic level. The antioxidant capacities though appeared to counteract the oxidative stress sufficiently, as no significant oxidative damage to lipids and DNA was observed. (ii) The simulated heating independent of MP induced analogous alterations in C. gigas gill metabolites to those observed following exposure to 25 µg MP L-1 at ambient temperature. Increased intra-specific variability in biomarker responses of MP-exposed oysters after the heating further suggests that heating-induced oxidative stress in the gills of some individuals may be exacerbated by chronic MP exposure. (iii) In contrast to absent effects of both MP exposure and warming when considered individually, the combination of both factors resulted in increased oxidative stress in gills of O. edulis over time. The upregulated antioxidant capacity appeared to be insufficient to fully mitigate the stress, as evidenced by macromolecular oxidative damage to lipids. The present results demonstrate an increased vulnerability of O. edulis to climate warming in response to chronic MP exposure, which should be considered in site selection for successful oyster restoration efforts. In conclusion, in terms of progressive anthropogenic global change, the present study is among the first to provide valuable insights into the interactive potential of combined MP and habitat-specific warming in inducing cytotoxic effects in gills of intertidal C. gigas and subtidal O. edulis
A longitudinal qualitative panel study on settlement experiences of Ukrainian protection-holders in Berlin and Munich. Study Report.
No full textThis study report outlines the background context, research questions and design of the project: A longitudinal qualitative panel study of settlement experiences of Ukrainian protection holders in Berlin and Munich. The project was funded by the Federal Ministry for Family Affairs, Senior Citizens, Women and Youth (Bundesministerium für Familie, Senioren, Frauen und Jugend – BMFSFJ) and conducted from July 2022 - December 2024. The project examined the subjective perspectives of protection-holders from Ukraine regarding their arrival and settlement processes in Germany with regard to the organisation of access to social benefits, healthcare, housing, childcare, and other care work, language training and schooling. Between September 2022 and March 2024, a qualitative longitudinal panel (QLP) study was conducted, including five waves of semi-structured interviews during September–October 2022 (1st wave), November–December 2022 (2nd wave), December 2022–January 2023 (3rd wave), February–March 2023 (4th wave) and February–April 2024 (5th wave). The topics addressed in the interviews included housing and employment situations, childcare, and other care duties, schooling and interactions with state institutions, as well as migration trajectories to and experiences upon arrival in Germany, transnational family and work arrangements and life aspirations. A total of 78 interview transcripts are available at Qualiservice for secondary uses in academic teaching and research.Bundesministerium für Familie, Senioren, Frauen und Jugend (BMFSFJ