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Spectator String Axions: Messages from the Early Universe
Get PDFString theory compactifications generically predict the existence of a rich spectrum of axion- like fields, the so-called Axiverse, whose masses and couplings are determined by the geometry and flux structure of the compactification. In this thesis, we explore the cosmological and phenomenological implications of such axions, combining insights from both Type IIB orientifold and heterotic E8 × E8 Calabi-Yau compactifications.
We initiate the characterization of the generic structure of the heterotic axiverse, mapping the axion mass spectrum and the effective couplings of axions to gauge fields. This analysis reveals model-independent constraints on their role in solving the strong CP problem, contributing to dark matter, and mediating hidden-visible sector interactions.
We further investigate inflationary scenarios where spectator axions couple to hidden gauge sec- tors via Chern-Simons interactions, leading to distinctive multi-peak features in the scalar and tensor spectra. We study axion-gauge field models with transient fast-roll phases, showing how they can enhance spectral distortions while satisfying large-scale CMB bounds, and identifying the challenges of controlling such dynamics in non-Abelian scenarios. These models can pro- duce a “gravitational-wave forest” spanning several decades in frequency, with the nHz band potentially explaining recent pulsar timing array signals. We analyze the complementary role of CMB spectral distortions in constraining the scalar sector, and identify the details of the string theory compactification that naturally realize the required couplings in the string landscape.
Finally, we examine non-perturbative dynamics in the early universe, focusing on axion produc- tion via parametric resonance during preheating in string inflation models. Kinetic couplings and moduli-dependent masses lead to generalized Mathieu equations, enabling efficient produc- tion of heavy axions that can overclose the universe unless inflationary parameters are suitably constrained.
Taken together, these results demonstrate how string theory provides a natural framework for embedding rich axion sectors, and how their cosmological dynamics offer unique observational windows, from gravitational waves to spectral distortions, into the high-energy physics of the early universe
Who Flourishes in School? An Integrative Examination of Student Personality and Academic Self-Concepts across Learning Environments
Get PDFEducation has been integral to human societies throughout history, and successful education benefits both individuals and communities. Educational success is especially critical throughout the developmental phase of adolescence. Adolescents face age-specific developmental tasks that refer to academic performance and individual development. Theoretical perspectives emphasise that (academic) development results from transactions between individual characteristics and contextual conditions. Accordingly, individual self-perceptions such as student personality and academic self-concept contribute to academic performance. At the same time, contextual conditions including student sociodemographic characteristics, classroom peers, and teachers shape students’ individual development of self-perceptions. Along these lines this dissertation integrated theoretical perspectives from developmental, personality, motivational, and educational psychology and studied the role of student personality and academic self-concept in academic performance and their development within the school context. Thereby, it addressed three overarching research aims. First, it examined how student personality and academic self-concepts relate to each other and jointly contribute to academic performance. Second, it investigated the role of individual self-perceptions in social inequalities relating to individual sociodemographic characteristics. Third, it inspected how peers and teachers shape the development of individual self-perceptions.
To address these overarching aims, this dissertation comprises three studies that took different perspectives on the role of individual self-perceptions in education. Study 1 integrated student personality and academic self-concepts and examined their role in social inequalities. More specifically, it tested the interrelations between and conjoint predictivity of student personality and academic self-concepts, as well as their moderating role in social inequalities. To do so, it applied latent moderated regression models to two large-scale samples of German secondary school students with diverse sociodemographic compositions. Study 2 addressed whether classroom peers shape the development of student personality. It provides a thorough investigation of how the classroom personality composition contributes to students’ individual personality development by applying three different strategies of estimating multilevel structural equation models. Lastly, Study 3 applied (moderated) conditional latent growth curve models to predict academic self-concept development by student personality, teaching behaviour, and their respective interplay. Altogether, the three studies provide comprehensive insights into the role of student personality and academic self-concepts within the school environment, as well as the complexity of transactions between students and the school environment. Specifically, results support the interrelatedness and indicate interactive effects of the two self-perceptions on academic performance, while also revealing important differences across academic domains. Moreover, student personality and academic self-concepts potentially reinforce social inequalities. Lastly, the results support interactions between student personality and teaching behaviour in predicting academic self-concept (development), while pointing toward the need for further research on the role of classroom peers in individual personality development.
This dissertation contributes to our understanding of the role of individual self-perceptions in educational success and provides three overarching implications. First, it corroborates the utility of integrating different theoretical perspectives on the role of individual self-perceptions in education as an interdisciplinary perspective best reflects the complex interactive relations between individual self-perceptions and with contextual conditions. Second, it illustrates the impact of methodological aspects such as the specific measures used, sample composition, and modelling strategies, and elucidates how methodological diversity can contribute to a differentiated understanding of individual self-perceptions in education. Lastly, this dissertation substantiates the crucial role of teachers by illuminating their role in social inequalities and in shaping students’ academic self-perceptions. Accordingly, teachers are valuable targets for educational policies and interventions, as their behavior can contribute to reducing social disparities and supporting individual student development. Nevertheless, future research should aim for further refinements by implementing advanced research designs across various educational systems that tap into the causality of associations, incorporate multi-method measures, and disentangle inter- and intraindividual variations in developmental trajectories
Verschiedene Sichtweisen auf multiple q-Zetawerte
Get PDFEin -Analogon eines Multiplen Zetawerts ist eine -Reihe, welche (nach eventueller Modifikation) im Grenzwert einen Multiplen Zetawert ergibt. Ebenso wie die Multiplen Zetawerte erfüllen auch deren -Analoga viele Linearrelationen in Analogie zu den Multiplen Zetawerten. Oftmals ist es praktisch, für die Untersuchung der algebraischen Struktur Multipler Zetawerte deren~-Analoga zu betrachten, um nicht gewollte Effekte reeller Zahlen zu umgehen. Diese Arbeit widmet sich nun der Struktur dieser -Analoga. Wir stellen hierfür unterschiedliche Zugangsmöglichkeiten vor: Einen algebraischen, einen kombinatorischen und einen analytischen.
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Der algebraische Zugang untersucht die \Q-Algebra der -Analoga, , mit altbekannten Mitteln wie der Dualität und der stuffle-Produkt-Darstellung des Produkts von~-Analoga. Hierbei werden eine spezielle Klasse von Linearrelationen systematisch ausgenutzt, um neue Resultate, insbesondere hinsichtlich einer Vermutung aus Bachmanns Dissertation, zu erlangen. Hierfür werden sogenannte formale Multiple~-Zetawerte, wie in Burmesters Dissertation eingeführt, verwendet, welche die betrachteten~-Analoga hinsichtlich der betrachteten Klasse von Relationen algebraisch abstrahiert. Die genann- te Vermutung von Bachmann sagt aus, dass die Algebra der formalen Multiplen~-Zetawerte~\Zq mit der Unteralgebra \Zqz übereinstimmt, wobei~\Zqz durch ihre Definition zunächst wesentlich 'kleiner' als erscheint. Wir werden diese Vermutung weiter verfeinern und geben einen präziseren Ansatz als bislang bekannt zu einem (hoffentlich) allgemeinen Beweis der Vermutung, welcher nach wie vor offen bleibt.
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Der kombinatorische Zugang hingegen führt über sogenannte markierte Partitionen, welche Partitionen sind, in deren Young-Diagramm Zeilen und Spalten auf gewisse Weise markiert sind. Sämtliche -Analoga Multipler Zetawerte sind die Erzeugendenreihe von speziellen markierten Partitionen, wie aus meiner Masterarbeit bereits bekannt ist. Nachdem in letzterer geklärt wurde, wie Dualität durch markierte Partitionen beschrieben werden kann, geben wir nun eine explizite Beschreibung des stuffle-Produkts auf dem Level der markierten Partitionen. Dies ist innovativ, da sich hieraus ein tieferes Verständnis des stuffle-Produkts ableiten lässt. Zudem kann nun vermutungsweise jede Linearrelation zwischen Multiplen~-Zetawerten durch markierte Partitionen beschrieben werden, da Dualität und stuffle-Produkt vermutungsweise alle solche Linearrelationen implizieren. Eine zukunftsweisende Frage ist, wie sich markierte Partitionen zum Beweis algebraischer Vermutungen über Multiple~(-)Zetawerte einsetzen lassen.
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Der analytische Zugang zuletzt beschäftigt sich mit dem asymptotischen Verhalten von~-Analoga. Hierbei gibt es zwei unterschiedliche asymptotische Verhalten zu untersuchen: Indem man (t>0) setzt und die asymptotische Entwicklung des -Analogons für~ betrachtet. Oder indem man das asymptotische Verhalten der Koeffizienten von der entsprechenden~-Reihe für untersucht. Beides stellt sich als schwierig heraus, sodass beide Ansätze in dieser Arbeit die asymptotische Entwicklung nur von speziellen~-Analoga liefern und die Entwicklung für allgemeine -Analoga von Multiplen Zetawerten als weiteren Forschungsgegenstand offen lässt. Jedoch gibt der gewählte Ansatz über die asymptotische Entwicklung der Fourierkoeffizienten mittels der Kreismethode nach Wright die asymptotische Entwicklung sehr vieler weiterer, in der Zahlentheorie und darüber hinaus, relevanter -Reihen.
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\noindent Durch jede der drei Herangehensweise an die algebraische Struktur von -Analoga Multipler Zetawerte werden neue Fragestellungen aufgeworfen und zugleich Wege zur Fortsetzung aufgezeigt
Netzwerkanalyse neuartiger Glycosyltransferasen aus dem Phylum Bacteroidota
Get PDFGlycosyltransferasen sind die entscheidenden Biokatalysatoren der enzymatischen Glykosylierung. Dieser Prozess ist einer von zahlreichen biologischen Modifizierungsvorgängen an Zellen, genetischem Material oder wie im Falle der Glykosylierung an Molekülen, die überall auf der Welt zu finden sind.
Beim Modifizierungsprozess der Glykosylierung, werden Kohlenhydratstrukturen an Proteine, Lipide oder andere Moleküle übertragen. Die Glykosylierung kann sowohl durch Enzyme katalysiert werden als auch ohne den Einfluss von Enzymen erfolgen. Dies wird dann als Glykation bezeichnet. Die enzymatische Glykosylierung wird durch Enzyme, die zu der Klasse der Transferasen zählen, genauer den Glycosyltransferasen katalysiert. Diese Enzyme übertragen aktivierte Zuckermoleküle, sogenannte Nukleotidzucker, auf verschiedenste Akzeptormoleküle. Der Modifikationsprozess verändert die Struktur und Funktion des jeweiligen Moleküls, wodurch sich Eigenschaften wie Stabilität oder Bioverfügbarkeit ändern können. Beispielhaft können hier Polyphenole genannt werden, die mit einer Vielzahl von vorteilhaften Eigenschaften, wie entzündungshemmend oder krebsvorbeugend in Verbindung gebracht werden, aber auf Grund ihrer schlechten Wasserlöslichkeit eine geringe Bioverfügbarkeit aufweisen. Diese Verfügbarkeit kann durch den Modifizierungsprozess der Glykosylierung erhöht werden.
Diese Arbeit befasste sich gezielt mit der Identifizierung und Charakterisierung neuartiger Glycosyltransferasen. Besonderer Fokus lag dabei auf der Erschließung neuer, dem Phylum Bacteroidota zuzuordnenden Glycosyltransferasen. Als Ausgangspunkt diente ein auf Grundlage von Sequenzen bereits beschriebener Glycosyltransferasen moduliertes Hidden Markov Model (Tabelle 25). Mit diesem Model wurden Datenbanken durchsucht, woraus mehr als 100 potenzielle Treffer für Glycosyltransferasen codierenden Genen resultierten. Eine Auswahl an 15 vielversprechenden Datenbankeinträgen, basierend auf Phylums-Zugehörigkeit, Sequenzlänge und/oder Verwandtschaft zu bereits bekannten GTs, wurden für genauere Untersuchungen ausgewählt. Von diesen konnte schließlich bei 6 Glycosyltransferasen (GT-HH01 – GT-HH06) glykosidische Aktivität nachgewiesen werden. Anschließend wurde auch das Substratspektrum, sowie die Expressionsfähigkeit für zukünftige in vitro Assays untersucht.
Alle neu identifizierten Transferasen waren in der Lage die Flavonoide Quercetin und Naringenin zu glykosylieren. Besonders auffällig ist, dass die Glycosyltransferasen GT-HH01, GT-HH02 und GT-HH03 auch das Stilbenoid Oxyresveratrol glykosylieren können. Neben den experimentellen Untersuchungen, erfolgten auch eine in-silico Analyse der neuen Enzyme. Dabei wurde unteranderem der Faltungstyp der neuen Glycosyltransferasen moduliert, als auch erstmalig ein Interaktionsnetzwerk aller charakterisierten GTs erstellt. Alle sechs neuen Glycosyltransferasen weisen den Faltungstyp B auf, welcher aus zwei beta-alpha-beta Faltblättern besteht. Des Weiteren geht aus dem Interaktionsnetzwerk hervor, dass sich fast alle beschriebenen GTs in drei große Cluster unterteilen lassen. Die meisten der bekannten Glycosyltransferasen stammen aus den Phyla Pseudomonadota und Actinobacteria. Daneben stellte sich heraus, dass sich durch die Fokussierung auf das Phylum Bacteroidota in dieser Arbeit, die Anzahl der aus diesem Phylum bekannten Glycosyltransferasen nahezu verdoppelt werden konnte.
Diese Ergebnisse zeigen das enorme Potenzial des Phylums Bacteroidota in Bezug auf die Identifizierung und Erschließung neuartiger Glycosyltransferasen, sowie der daraus resultierenden potenziellen zukünftigen Anwendung in der Biotechnologie.Glycosyltransferases are the key biocatalysts of enzymatic glycosylation. This process is one of numerous biological modification processes on cells, genetic material or, as in the case of glycosylation, molecules that can be found all over the world.
At the glycosylation modification process, carbohydrate structures are transferred to proteins, lipids or other molecules. Glycosylation can be catalyzed by enzymes as well as without the influence of enzymes. This is then referred to as glycation. Enzymatic glycosylation is catalyzed by enzymes belonging to the class of transferases, more precisely glycosyltransferases. These enzymes transfer activated sugar molecules, so-called nucleotide sugars, to various acceptor molecules. The modification process changes the structure and function of the respective molecule, which can alter properties such as stability or bioavailability. Examples include polyphenols, which are associated with a variety of beneficial properties such as anti-inflammatory or cancer-preventing but have low bioavailability due to their poor water solubility. This availability can be increased by the modification process of glycosylation.
This work was specifically concerned with the identification and characterization of novel glycosyltransferases. Special focus was placed on the identification of new glycosyltransferases belonging to the phylum Bacteroidota. A Hidden Markov Model (Table 25) was modulated on the basis of sequences of already described glycosyltransferases served as a starting point. This model was used to search in various databases and results in more than 100 potential hits for genes encoding glycosyltransferases. A selection of 15 promising database entries, based on phylum affiliation, sequence length and/or relationship to already known GTs, were selected for further investigation. Of these, 6 glycosyltransferases (GT-HH01 - GT-HH06) were found to have glycosidic activity. Subsequently, the substrate spectrum as well as the expression capacity for future in vitro assays were investigated.
All newly identified transferases were able to glycosylate the flavonoids quercetin and naringenin. It is particularly striking that the glycosyltransferases GT-HH01, GT-HH02 and GT-HH03 can also glycosylate the stilbenoid oxyresveratrol. In addition to the experimental studies, the new enzymes were also analyzed in silico. Among other things, the folding type of the new glycosyltransferases was modulated, and an interaction network of all characterized GTs was created for the first time. All six new glycosyltransferases show the folding type B, which consists of two beta-alpha-beta leaflets. Furthermore, the interaction network shows that nearly all described GTs can be divided into three large clusters. Most of the known glycosyltransferases originate from the phyla Pseudomonadota and Actinobacteria. In addition, it turned out that by focusing on the phylum Bacteroidota in this work, the number of glycosyltransferases known from this phylum could be almost doubled.
These results show the enormous potential of the phylum Bacteroidota with regard to the identification and development of novel glycosyltransferases, as well as the resulting potential future application in biotechnology
Selbstverwaltung in der Fischerei auf Nordseegarnelen (Crangon crangon): Potenziale, Wahrnehmungen und Herausforderungen
Get PDFEffective fisheries management increasingly relies on science-based harvest strategies that prioritize long-term ecosystem and stock sustainability over short-term yields. For short-lived and data-limited species like the North Sea Brown Shrimp (Crangon crangon), the use of traditional stock assessments is hampered by high natural mortality, rapid population turnover, and incomplete or inconsistent data on fishing effort. At the core of the harvest strategies for such species are thus harvest control rules (HCRs)—predefined protocols that regulate fishing opportunities based on real-time or near-real-time indicators of stock status.
Despite being one of Europe’s most valuable fisheries, the North Sea Brown Shrimp has lacked regular stock assessment and population-based management measures, relying instead on technical measures. However, advances in growth rate modelling and integrated international datasets have revealed evidence of growth overfishing, highlighting the need for formal management. In response, a collaborative management framework was established, culminating in Marine Stewardship Council (MSC) certification of the main fleets and the adoption of a self-regulatory management plan based on Landings per Unit Effort (LPUE) thresholds, effort restrictions and gear modifications to reduce growth overfishing and delimit the risk of potential recruitment overfishing.
This dissertation provides a comprehensive analysis of the recent dynamics in the Brown shrimp stock, the effectiveness of current management approaches, and the challenges faced in implementing effective and accepted management measures.
In Chapter I, monthly VMS and logbook data of the North Sea Brown shrimp fleets of Denmark, Netherlands and Germany from 2009 to 2018 were analysed for trends and regional patterns in five subareas. Effort increased by 12% while landings decreased by 9% from the first five to the second five years of the time series. All areas showed a significant decreasing trend of LPUE in the fishery of the first quarter of the year from 2009 to 2018. Fishing effort in Dutch and East Frisian waters during winter was negatively correlated with LPUE in the same and adjacent areas in March – April. Furthermore, highly significant negative correlations were found between fishing effort in January and February in Dutch waters and LPUE in July and August in areas further north, explaining up to 86% of the variance. Together our results support the hypothesis that early recruitment in the Northern areas partially depends on a new cohort coming from the south and that reduced recruitment in Northern areas may be a consequence of previous local depletion of egg-bearing females further south. Egg bearing shrimp appear to concentrate in southern areas in January and February and migrate to adjacent northern areas for larval release in March and April. The findings demonstrate that neither environmental drivers nor predation pressure alone can fully explain the recent decline in stock abundance. Instead, fishing pressure—especially during critical winter months when the stock appears most vulnerable—emerges as a key factor influencing population trends. To prevent economic and ecological consequences for the shrimp stock and the fishery, transboundary management measures need to be considered and implemented. Further investigations of migration and drift patterns of brown shrimp are recommended.
In Chapter II, the effectiveness of the current HCR is quantified and alternative, more stringent HCR designs are tested under two plausible scenarios: a general reduction in stock abundance and a recruitment failure event, both representing common risks for short-lived stocks. A comprehensive shrimp population simulation model, parameterized with recent fisheries and biological data from the German Exclusive Economic Zone, replicates the seasonal patterns of growth, mortality, and fishery removals. The performance of HCR designs was evaluated in terms of their effects on shrimp biomass, egg production, landings, and total fishing effort. Results demonstrate that all HCR variants yield modest improvements in LPUE, biomass, and egg production relative to unmanaged scenarios, while annual landings remain largely unchanged. Importantly, the magnitude and speed of stock recovery depend considerably on the stringency of the effort reduction. The currently implemented approach, which employs stepwise weekly effort limits when LPUE reference points are breached, achieves only moderate effort reductions (averaging 12–19%), with limited capacity to rebuild biomass after major declines. In contrast, simulated approaches involving greater reductions in weekly fishing time or short complete fishery closures (up to 99% effort cut for two weeks) trigger much faster LPUE recovery and higher increases in spawning biomass and egg production, especially following recruitment failure scenarios. However, such drastic measures could pose operational difficulties and may be less acceptable to stakeholders due to increased variability in landings and disruption to fleet activities.
The current harvest control rule, based on empirical LPUE thresholds, provides a necessary foundation, but simulation results indicate that this mechanism may be insufficiently responsive under serious stock declines. More drastic, short-term reductions in effort, informed by timely and accurate abundance indices, are likely needed to prevent stock and fishery collapse, and could even result in increased future yields without compromising market supply.
In Chapter III, the self-management regime of the North Sea Brown Shrimp fishery was analyzed, drawing on Ostrom’s design principles for robust self-governance of common-pool resources. The study employs a quantitative survey of shrimp fishers, complemented by qualitative insights, to examine user perceptions of the self-governance system. Fishermen’s attitudes toward management efficacy, enforcement, participation, and adaptation to local conditions were assessed across three clusters of fishers.
Results indicate limited perceived need for management among fishers, with only a minority recognizing stock decline despite scientific evidence of increased fishing mortality and growth overfishing. While the fishery’s biological and institutional characteristics—restricted user group, monopolistic market structure, and homogeneity in economic interests—are conducive to self-governance, significant challenges remain. Notably, trust is lacking in the fairness and effectiveness of monitoring and enforcement, particularly across national producer organizations (POs). Many fishers express skepticism about the impact of measures such as increased mesh size, viewing technical adjustments as easily circumvented. Effort reduction is more widely accepted, especially during periods of low stock, but regionalization of management is resoundingly rejected in favor of equal treatment for all fleet segments.
Fishermen report feeling insufficiently involved in the development and ongoing adaptation of management measures, leading to perceptions of remote, top-down decision-making—potentially undermining legitimacy and compliance. Nevertheless, there is strong interest, especially among less mobile, home-port-based fishers, for increased participatory roles in management design and rule-making.
The North Sea Brown Shrimp fishery illustrates both the potential and limitations of self-management frameworks. While user-led regulation can stabilize and add value to the fishery, persistent gaps exist between scientific advice, institutional frameworks, and user perceptions. Addressing these gaps will require enhanced communication of scientific findings, fostering trust among user groups and POs, broader stakeholder engagement, and greater transparency in enforcement
Inactivation mechanisms of pathogenic bacteria in fruit juices by conventional and non-thermal treatments
Get PDFIn response to growing consumer interest in minimally processed foods, the food industry seeks preservation technologies that ensure microbiological safety without compromising nutritional and sensory quality. While thermal processing is widely used in fruit juice and nectar production, it can lead to nutrient loss and undesirable changes in product quality. Alternative methods, such as high-pressure processing (HPP) and pulsed electric fields (PEF), offer promising non-thermal alternatives. To validate these technologies safely, surrogate microorganisms - non-pathogenic strains that mimic pathogen behavior - are essential.
This cumulative thesis aimed to select suitable surrogate microorganisms for foodborne pathogens in strawberry and cherry nectar. The influence of the selected inactivation technology and the food matrix in which the bacteria are located on the determined D- and z-values was also examined. Additionally, the transcriptomic response of Escherichia coli to thermal and non-thermal treatments was investigated using RNA-Seq.
Based on thermal resistance analysis, E. coli ATCC 11229 was identify as a suitable surrogate for tested Salmonella enterica strains, and E. coli ATCC 8739 for Shiga-toxin producing E. coli O157:H7 and O113:21. Additionally, a strong influence of the selected inactivation method and the dry matter content on the D-values was demonstrated. Transcriptomic analysis revealed that E. coli ATCC 8739 shows a similar response to thermal and high-pressure stress. Interestingly, the application of pulsed electric field, despite the lack of cell inactivation, strongly induced upregulation of genes, especially those related to metabolism.
This work contributes to applied microbiology by identifying two suitable surrogate strains for validating microbial inactivation in fruit juice processing. Furthermore, it examines important aspects related to the thermal resistance of microorganisms and compares how innovative preservation technologies affect gene expression in E. coli
Engineered Nanoparticles with Recombinant Thrombolytic Agents for Targeted Drug Delivery in Ischemic Stroke with Magnetic Particle Imaging (MPI) and the Development and Characterization of optimized MPI Tracers
No full textMagnetic Particle Imaging (MPI), introduced in 2005, is a novel, radiation-free imaging modality with high sensitivity and the ability to provide quantitative tracer signals without interference from tissues or bones. MPI's unique features, including its capability for magnetic navigation and functional imaging, make it a promising tool for various medical applications.
This thesis explores the potential of MPI in accelerating and improving the diagnosis and treatment of ischemic stroke, by immobilizing magnetic nanoparticles with thrombolytic agents, enabling precise delivery to the infarct core. Further, the research investigates the development of tailored MPI tracers to enhance imaging potential. The production and characterization of recombinant thrombolytic proteins, SBP-Amediplase and avi-Amediplase, using the HEK-293-6E cell expression system was successfully achieved. Amediplase and Actilyse® were effectively conjugated to magnetic nanoparticles via ED- Carbodiimide crosslinking, resulting in significantly enhanced binding capacity and thrombolytic activity. In vitro studies showed that Amediplase-conjugated nanoparticles exhibited 75% accelerated clot lysis under a magnetic field, indicating the potential of magnetically targeted thrombolysis in MPI. Seven genetically engineered variants of magnetosomes, biogenic nanoparticles synthesized by magnetotactic bacteria, with different morphological and magnetic properties, were evaluated as promising MPI tracers. The results categorize magnetosomes into promising and non-promising candidates based on their magnetic particle spectrometer (MPS) signal responses. ∆feoAB1, ∆feoAB12, and ∆Fe4, exhibit high signal amplitudes. Notably, ∆feoAB1 shows the strongest signal, with a 2.99-fold increase over Perimag®, and the stability and concentration-dependent signal, with significant magnetic moments, essential for MPI high-resolution. Additionally, the study explores the 3D system matrix for MPI imaging, which resulted in a higher signal-noise-to-ratio of ∆feoAB1 compared to Perimag®, indicating its superior potential for MPI image reconstruction. In conclusion, this research demonstrates the feasibility and effectiveness of MPI for targeted stroke therapy and highlights the importance of developing specialized tracers and thrombolytic agents for enhanced imaging and treatment outcomes.Magnetpartikel-Bildgebung (MPI), eingeführt im Jahr 2005, ist eine neuartige, strahlungsfreie Bildgebungsmethode mit hoher Empfindlichkeit und der Fähigkeit, quantitative Tracersignale ohne Interferenzen durch Gewebe oder Knochen zu liefern. Die einzigartigen Eigenschaften von MPI, einschließlich der Fähigkeit zur magnetischen Navigation und funktionellen Bildgebung, machen es zu einem vielversprechenden Werkzeug für verschiedene medizinische Anwendungen.
Diese Dissertation untersucht das Potenzial der MPI, die Diagnose und Behandlung ischämischer Schlaganfälle zu beschleunigen und zu verbessern. Dies erfolgt durch die Immobilisierung von mit Thrombolytika konjugierten magnetischen Nanopartikeln, wodurch eine präzise Abgabe an den Infarktkern ermöglicht wird.
Weiterhin wird in der vorliegenden Arbeit die Entwicklung maßgeschneiderter MPI-Tracer untersucht, um das Bildgebungspotenzial zu verbessern. Die Produktion und Charakterisierung der rekombinanten thrombolytischen Proteine SBP-Amediplase und Avi-Amediplase wurde unter Verwendung des HEK-293- 6E-Zell-Expressionssystems erfolgreich durchgeführt. Amediplase und Actilyse® wurden über ED-Carbodiimid-Kupplung effektiv an magnetische Nanopartikel konjugiert, was zu einer signifikant verbesserten Bindungskapazität und thrombolytischen Aktivität führte. In-vitro- Studien zeigten, dass Amediplase- konjugierte Nanopartikel unter einem Magnetfeld eine um 75 % beschleunigte Gerinnselauflösung aufwiesen, was auf das Potenzial der magnetisch gezielten Thrombolyse der MPI hinweist. Sieben gentechnisch veränderte Varianten von Magnetosomen - biogenen Nanopartikeln, die von magnetotaktischen Bakterien synthetisiert werden - wurden als vielversprechende MPI-Tracer mit unterschiedlichen morphologischen und magnetischen Eigenschaften evaluiert. Die Ergebnisse kategorisierten Magnetosomen in vielversprechende und weniger vielversprechende Kandidaten, basierend auf ihren Signalantworten im Magnetpartikelspektrometer (MPS). ∆feoAB1, ∆feoAB12 und ∆Fe4 zeigten hohe Signalamplituden. Es ist besonders hervorzuheben, dass ∆feoAB1 das stärkste Signal mit einer 2,99-fachen Erhöhung gegenüber Perimag® zeigte. Dieses konzentrationsabhängige Signal von ∆feoAB1 war stabil mit signifikanten magnetischen Momenten, die für eine hochauflösende MPI erforderlich sind. Darüber hinaus untersuchte die Studie die 3D-Systemmatrix für die MPI- Bildgebung, die zu einem höheren Signal-Rausch-Verhältnis von ∆feoAB1 im Vergleich zu Perimag® führte, und damit größeres Potenzial für die MPI- Bildrekonstruktion hat. Zusammenfassend zeigt diese Arbeit die Umsetzbarkeit und Wirksamkeit von MPI für die gezielte Schlaganfalltherapie und unterstreicht die Bedeutung der Entwicklung spezialisierter Tracer und Thrombolytika für verbesserte Bildgebungs- und Behandlungsergebnisse
Uncovering the effects of Agulhas eddies on low and high internal tide modes and their energetics in high-resolution ICON
Get PDFUntersuchung prädiktiver Parameter der Progression einer kontralateralen Coxarthrose nach Hüft-Totalendoprothese
Get PDFEssays on Migration and Legitimacy: Towards a Cosmopolitan Statism
No full textThis thesis contributes to a central debate in the political philosophy of migration over the legitimacy of the imposition and enforcement of exclusionary immigration policies. It consists of five chapters, which develop arguments that stand on their own but also contribute to a broader account of the legitimacy of immigration restrictions.
In Chapter 1, I introduce the debate between statists and cosmopolitans over the question whether states have a right to exclude prospective migrants from their territory, and I outline my central contribution to this debate. I distinguish a justice-dimension and a legitimacy-dimension of this debate, and I explain how I conceptualize the legitimacy of immigration restrictions. Next, I outline my account of the legitimacy of immigration restrictions, and locate this account in the literature.
I describe my account as a "cosmopolitan statism", as it draws inspiration from Kant's theory of "cosmopolitan law" and combines elements of statist and cosmopolitan views in a novel way.
In the chapter "Claiming Authority across Borders", I defend the central tenets of my account of the legitimacy of immigration restrictions.
This account constitutes a novel intermediary position in the long-standing debate between statists and cosmopolitans, which is why I describe it as a "cosmopolitan statism". My central thesis is that states can legitimately enforce immigration restrictions, but only if they claim that migrants are required to obey their immigration laws, and if these claims are actually valid. In contrast to many cosmopolitans, I argue that migrants are often required to obey foreign immigration laws, so that states can routinely make valid claims to legitimate authority vis-á-vis prospective migrants. But in contrast to many statists, I argue that states subject migrants to their political rule once they expect them to obey their immigration laws, and that the political subjection of migrants grounds additional obligations towards them that are substantially more demanding than statists usually acknowledge.
My defense of the legitimacy of immigration restrictions assumes that individuals do not have a moral right to global freedom of movement.
But this assumption is controversial, as prominent open borders advocates defend such a right. In the chapter "Rights, Interests, and the Problem of Generality", I develop a constructive critique of the methodology that informs the most influential arguments for a moral human right to immigrate, the interest-based approach to the justification of moral rights. The critical part of my discussion revolves around a methodological challenge that I call the "problem of generality", which undermines most interest-based arguments, including the arguments for a human right to immigrate. The constructive part of my discussion shows that the problem of generality can be solved, although this solution significantly complicates interest-based arguments.
The notion of enforceable moral duties plays a central role in discussions of justice and of political legitimacy. My account of the legitimacy of immigration restrictions also invokes this notion, as I argue that migrants have enforceable moral duties to accept their exclusion if states have the authority to impose morally binding immigration laws.
However, we still lack a convincing philosophical account of the phenomenon of enforceable moral duties, which is why a recent contribution diagnoses a "puzzle of enforceability". I address this puzzle in the chapter the "The Bundle Account of Enforceable Duties", where I argue that duties are enforceable just in case they are embedded in specific bundles of Hohfeldian moral positions. The puzzling question why certain duties are enforceable therefore dissolves into smaller non-puzzling questions concerning the justifiability of specific moral positions.
In the Chapter "Resistance at the Border, Self-Defense and Legitimate Injustice", I respond to an influential argument in the migration literature, according to which unjustly excluded migrants can always resist their exclusion in self-defense. I respond to this argument because it implies that unjust immigration restrictions are generally also illegitimate, as legitimate exercises of political power normally do not justify defensive resistance. I show that this argument fails because states often have a liberty right to rule over their borders, even when they exercise this liberty right to enforce substantively unjust immigration policies.
This result then also informs my cosmopolitan statist account of the legitimacy of immigration restrictions.
A widely held view in the migration literature holds that all migrants whom states admit territorially must be put on a path to citizenship within a reasonable time frame. This view is typically based on the assumption that denizens – resident non-citizens – will be subjected to domination and will be deprived of the social basis of self-respect unless they are fully included in the democratic process. In the chapter "Denizenship and Democratic Equality", Suzanne Bloks and I argue that the original citizenship of some denizens can function as a substitute for their full democratic inclusion, as it can effectively protect them from domination, and provide them with the social bases of self-respect.
We accordingly conclude that a politically passive guest status for denizens can, even in the long-run, be fully democratically legitimate, at least for denizens who are themselves citizens of democratic polities