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Paradoxical sets and the Axiom of Choice
No full textParadoxe Mengen treten in vielen Bereichen der Mathematik auf. Diese Mengen werden unter Verwendung des Auswahlaxioms konstruiert und weisen kontraintuitive Eigenschaften auf, wie beispielsweise die Vitali-Menge oder das Banach-Tarski-Paradoxon. Die zentrale Frage dieser Arbeit ist, ob bestimmte Fragmente des Auswahlaxioms aus der Existenz spezifischer paradoxer Mengen abgeleitet werden können. Wir liefern mehrere negative Antworten auf diese Frage. Insbesondere zeigen wir, dass es Modelle der ZFC-Mengenlehre ohne eine Wohlordnung der reellen Zahlen gibt, die dennoch eine Zerlegung des dreidimensionalen euklidischen Raums in Einheitskreise enthalten. Darüber hinaus entwickeln wir einen allgemeinen Rahmen für die Konstruktion ähnlicher Modelle für andere paradoxe Mengen unter bestimmten Bedingungen der Erweiterbarkeit und Amalgamierung. Zudem präsentieren wir einige Ergebnisse zum Transzendenzgrad der reellen Zahlen über bestimmten mengentheoretischen Teilkörpern.Paradoxical sets appear in many areas of mathematics. These are sets that are constructed using the Axiom of Choice and exhibit counterintuitive properties, examples include the Vitali set and the Banach-Tarski paradox. The central question of this thesis is whether certain fragments of the Axiom of Choice can be recovered from the existence of specific paradoxical sets. We provide several negative answers to this question. In particular, we show that there exist models of ZFC without a well-ordering of the reals that still contain a partition of three-dimensional Euclidean space into unit circles. Furthermore, we develop a general framework for constructing similar models for other paradoxical sets, under certain conditions of extendability and amalgamation. We also include some results on the transcendence degree of the reals over certain set theoretical subfields
Rapid and reversible optical switching of cell membrane area by an amphiphilic azobenzene
No full textCellular membrane area is a key parameter for any living cell that is tightly regulated to avoid membrane damage. Changes in area-to-volume ratio are known to be critical for cell shape, but are mostly investigated by changing the cell volume via osmotic shocks. In turn, many important questions relating to cellular shape, membrane tension homeostasis and local membrane area cannot be easily addressed because experimental tools for controlled modulation of cell membrane area are lacking. Here we show that photoswitching an amphiphilic azobenzene can trigger its intercalation into the plasma membrane of various mammalian cells ranging from erythrocytes to myoblasts and cancer cells. The photoisomerization leads to a rapid (250-500 ms) and highly reversible membrane area change (ca 2 % for erythrocytes) that triggers a dramatic shape modulation of living cells
Struggle in the bubble - a prospective study on the effect of remote learning and distance education on confidence in practical surgical skills acquired during COVID-19
No full textBackground: The coronavirus disease (COVID-19) has significantly changed healthcare systems and medical education. Universities were required to develop innovative curricula based on remote and distance education to continue medical education. This prospective questionnaire-based study aimed to investigate the impact of COVID-19-associated remote learning on the surgical training of medical students. Methods: A 16-item questionnaire-based survey was distributed to medical students at the University Hospital of Münster before and after a surgical skills laboratory (SSL). Two cohorts were included: summer semester 2021 (COV-19), with rigorous social-distancing restrictions requiered SSL to be remotely, and winter semester 2021 (postCOV-19), in which the SSL was provided as a face-to-face, hands-on course. Results: Both, cohorts showed a significant improvement in self-assessment of pre- and post-course confidence. While no significant difference in the average gain in self-confidence for sterile working was observed between the two cohorts, improvement in self-confidence was significantly higher in the COV-19 cohort regarding skin suturing and knot tying (p < 0.0001). However the average improvement regarding history and physical was significantly higher in the postCOV-19 cohort (p < 0.0001). In subgroup analysis, gender-associated differences varied in the two cohorts and were not related to specific subtasks, while age-stratified analysis revealed superior results for younger students. Conclusion: The results of our study underline the usability, feasibility, and adequacy of remote learning for the surgical training of medical students. The on-site distance education version, presented in the study, allows the continuing of hands-on experience in a safe environment in compliance with governmental social-distancing restrictions
Supply chain network resilience:a guideline for investigating and adapting the structure of supply chain networks for resilience
No full textEreignisse der letzten Jahre wie die Corona-Pandemie oder die Blockade des Suez Kanals haben gezeigt wie störungsempfindlich moderne Lieferketten sind. Bestehend aus einem komplexen Netz an Zulieferern und Produktionsstandorten wird es nahezu unmöglich konkrete Risiken zu identifizieren und zu beseitigen. Stattdessen ist es wichtig die Resilienz von Lieferketten zu stärken, welche es ihnen erlaubt die direkten Folgen von Störungen abzumildern und sich schnell von den negativen Konsequenzen zu erholen. Diese Dissertation untersucht das Konzept der Lieferkettenresilienz mit Hilfe der Graphentheorie, welche es erlaubt Strukturen von Lieferketten zu modellieren, im Hinblick auf Schwachstellen zu analysieren und mit Hilfe geeigneter Algorithmen zu verbessern. Besonderen Wert wird hierbei daraufgelegt, die Ergebnisse mit realen Datensätzen zu evaluieren.The events of recent years, such as the COVID-19 pandemic or the blockage of the Suez Canal, have shown how vulnerable modern supply chains are to disruptions. Consisting of a complex network of suppliers and production sites, it becomes nearly impossible to identify and eliminate specific risks. Instead, it is crucial to strengthen the resilience of supply chains, allowing them to mitigate the immediate consequences of disruptions and recover quickly from their negative effects. This dissertation explores the concept of supply chain resilience using graph theory, which allows for the modeling of supply chain structures, analyzing them for weaknesses, and improving them through appropriate algorithms. Special emphasis is placed on evaluating the results with real-world datasets
Supporting the differential diagnosis of connective tissue diseases with neurological involvement by blood and cerebrospinal fluid flow cytometry
No full textObjective: Neurological manifestations of autoimmune connective tissue diseases (CTD) are poorly understood and difficult to diagnose. We here aimed to address this shortcoming by studying immune cell compositions in CTD patients with and without neurological manifestation. Methods: Using flow cytometry, we retrospectively investigated paired cerebrospinal fluid (CSF) and blood samples of 28 CTD patients without neurological manifestation, 38 CTD patients with neurological manifestation (N-CTD), 38 non-inflammatory controls, and 38 multiple sclerosis (MS) patients, a paradigmatic primary neuroinflammatory disease. Results: We detected an expansion of plasma cells in the blood of both N-CTD and CTD compared to non-inflammatory controls and MS. Blood plasma cells alone distinguished the clinically similar entities N-CTD and MS with high discriminatory performance (AUC: 0.81). Classical blood monocytes indicated higher disease activity in systemic lupus erythematosus (SLE) patients. Surprisingly, immune cells in the CSF did not differ significantly between N-CTD and CTD, while CD4+ T cells and the CD4+/CD8+ ratio were elevated in the blood of N-CTD compared to CTD. Several B cell-associated parameters partially overlapped in the CSF in MS and N-CTD. We built a machine learning model that distinguished N-CTD from MS with high discriminatory power using either blood or CSF.
Conclusion: We here find that blood flow cytometry alone surprisingly suffices to distinguish CTD with neurological manifestations from clinically similar entities, suggesting that a rapid blood test could support clinicians in the differential diagnosis of N-CTD
The Musashi RNA-binding proteins in female cancers: insights on molecular mechanisms and therapeutic relevance
No full textRNA-binding proteins have increasingly been identified as important regulators of gene expression given their ability to bind distinct RNA sequences and regulate their fate. Mounting evidence suggests that RNA-binding proteins are involved in the onset and progression of multiple malignancies, prompting increasing interest in their potential for therapeutic intervention. The Musashi RNA binding proteins Musashi-1 and Musashi-2 were initially identified as developmental factors of the nervous system but have more recently been found to be ubiquitously expressed in physiological tissues and may be involved in pathological cell behavior. Both proteins are increasingly investigated in cancers given dysregulation in multiple tumor entities, including in female malignancies. Recent data suggest that the Musashi proteins serve as cancer stem cell markers as they contribute to cancer cell proliferation and therapy resistance, prompting efforts to identify mechanisms to target them. However, as the picture remains incomplete, continuous efforts to elucidate their role in different signaling pathways remain ongoing. In this review, we focus on the roles of Musashi proteins in tumors of the female – breast, endometrial, ovarian and cervical cancer – as we aim to summarize current knowledge and discuss future perspectives
Transformation durch Tugend?:"Grüne politische Urteilsbildung" als Schlüssel zu nachhaltigkeitsförderlichen Deliberationsverfahren
No full textDamit die Nachhaltigkeitstransformation gelingt, müssen Klima- und Nachhaltigkeitsziele in liberalen Demokratien umgesetzt werden, unter anderem durch nachhaltigkeitsförderliche Dialogverfahren. Eine Voraussetzung für deren Erfolg liegt in der kritischen Reflexion und gemeinwohlorientierten Transformation nicht-nachhaltiger Präferenzen durch die Beteiligten. Ein Schlüssel zum Gelingen dieser Präferenztransformation sind Tugenden, argumentiert Carolin Bohn mit Rückgriff auf Ansätze der environmental citizenship und auf die Umwelttugendethik. Zentral sei dabei die "grüne politische Urteilsbildung", eine Version der Aristotelischen phronesis, die in diesem Werk erarbeitet wird und an den Kontext solcher nachhaltigkeitsorientierter Deliberationsverfahren angepasst ist. Durch eine empirische Studie zu entsprechenden Verfahren zeigt die Autorin auf, inwiefern die "grüne politische Urteilsbildung" bereits (unintendiert) ermöglicht wird und diskutiert abschließend ihre Umsetzungspotenziale
Vascular response patterns to targeted therapies in murine breast cancer models with divergent degrees of malignancy
No full textBackground: Response assessment of targeted cancer therapies is becoming increasingly challenging, as it is not adequately assessable with conventional morphological and volumetric analyses of tumor lesions. The tumor microenvironment is particularly constituted by tumor vasculature which is altered by various targeted therapies. The aim of this study was to noninvasively assess changes in tumor perfusion and vessel permeability after targeted therapy in murine models of breast cancer with divergent degrees of malignancy. Methods: Low malignant 67NR or highly malignant 4T1 tumor-bearing mice were treated with either the multi-kinase inhibitor sorafenib or immune checkpoint inhibitors (ICI, combination of anti-PD1 and anti-CTLA4). Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) with i.v. injection of albumin-binding gadofosveset was conducted on a 9.4 T small animal MRI. Ex vivo validation of MRI results was achieved by transmission electron microscopy, immunohistochemistry and laser ablation-inductively coupled plasma-mass spectrometry. Results:
Therapy-induced changes in tumor vasculature differed between low and highly malignant tumors. Sorafenib treatment led to decreased tumor perfusion and endothelial permeability in low malignant 67NR tumors. In contrast, highly malignant 4T1 tumors demonstrated characteristics of a transient window of vascular normalization with an increase in tumor perfusion and permeability early after therapy initiation, followed by decreased perfusion and permeability parameters. In the low malignant 67NR model, ICI treatment also mediated vessel-stabilizing effects with decreased tumor perfusion and permeability, while ICI-treated 4T1 tumors exhibited increasing tumor perfusion with excessive vascular leakage. Conclusion: DCE-MRI enables noninvasive assessment of early changes in tumor vasculature after targeted therapies, revealing different response patterns between tumors with divergent degrees of malignancy. DCE-derived tumor perfusion and permeability parameters may serve as vascular biomarkers that allow for repetitive examination of response to antiangiogenic treatment or immunotherapy
"Verba volant, scripta manent". El libro en la primera era de su reproductibilidad técnica. In memoriam Klaus D. Vervuert
No full textDer Text untersucht die Auswirkungen der Erfindung des Buchdrucks auf die Reproduzierbarkeit und den kulturellen Wert von Büchern. Es wird argumentiert, dass die Massenproduktion von Büchern zur Entzauberung und zum Verlust der "Aura" führte, die Manuskripte besaßen. Die Verbreitung des Buchdrucks hat einerseits den Zugang zu Wissen erleichtert, andererseits jedoch auch Bedenken über die Qualität und Authentizität der verbreiteten Inhalte aufgeworfen. Es wird ein Vergleich zwischen der Ära des Buchdrucks und den modernen digitalen Medien gezogen, wobei ähnliche Herausforderungen und Chancen betont werden.El documento analiza los efectos de la invención de la imprenta en la reproducibilidad y el valor cultural de los libros. Se argumenta que la producción en masa de libros llevó a la desmitificación y pérdida del "aura" que poseían los manuscritos. La difusión de la imprenta facilitó el acceso al conocimiento, pero también generó preocupaciones sobre la calidad y autenticidad de los contenidos difundidos. Se realiza una comparación entre la era de la imprenta y los medios digitales modernos, destacando desafíos y oportunidades similares
"Was hast Du Dir dazu überlegt?" Denkwege von Kindern und Inhalte gleichermaßen in den Blick nehmen:Festschrift für Dagmar Bönig
No full textMit dieser Festschrift anlässlich ihres 65. Geburtstages würdigen wir Dagmar Bönig und ihr herausragendes Wirken in der Mathematikdidaktik. In den vergangenen Jahrzehnten hat sie mit zahlreichen Projekten die mathematische Bildung im Primar- und Elementarbereich sowie die Aus- und Fortbildung von Lehrkräften maßgeblich geprägt. Als Professorin beeinflusste sie mehrere Studierendengenerationen und damit auch zahlreiche heute praktizierende Lehrkräfte. Dabei zeichnet sie sich stets durch ihre wertschätzende und offene Haltung gegenüber kindlichen Ideen aus, die sie ihren Studierenden vorlebt. Die Festschrift vereint eine vielfältige Sammlung von Beiträgen aus Wissenschaft und Praxis. Zu den Autor*innen zählen (ehemalige und aktuelle) Kolleg*innen, Lehrer*innen und Erzieher*innen, von denen viele bei Dagmar Bönig studierten, promovierten oder in Forschungsprojekten mit ihr zusammenarbeiteten. Herausgegeben wird der Band von den Mitgliedern der Arbeitsgruppe Mathematikdidaktik am Fachbereich 12 der Universität Bremen sowie den ehemaligen Mitgliedern Johanna Scharlau und Daniel Walter