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Damping properties and morphological characteristics of primary feathers
Get PDFFlight provides to the birds efficient locomotion and occupation of various habitats. Wings and feathers sustain strong forces and vibration during flapping flight. Excessive vibration can lead to the stronger energy consumption, noise production and can therefore negatively impact the flight stability. Hence, it is reasonable to hypothesize that the primary feathers develop damping mechanisms to mitigate vibrations. Although feather microstructures have been well investigated, their damping properties still lack a systematic study. Here, this study shows that the primary flight feathers are capable of various damping mechanisms related to different structures. In the shafts and barbs, the cortex and gradient foam support the mechanical bending and decay vibrations. The first indication of graded damping properties was related to the morphology of the shaft (foam cells size, area ratio of foam to cortex, and percentage of foam). In the vanes, there are three different types of structures related to the reduction of damping. First, we performed experiments to compare damping properties between feathers with vanes and the bare shaft without vanes. After trimming vanes, the damping ratio decreased by 38-60%. Second, the damping of zipped vanes and unzipped vanes was studied under normal air pressure. The results indicate that the zipped vanes have higher damping ratios. The planar surface of zipped vanes is responsible for aerodynamic damping, contributing 20% to 50% to the whole damping in a feather. Thirdly, the damping tests between zipped and unzipped vanes in vacuum were performed. Structural damping demonstrates 3.3 times (at vertical deflection) and 2.3 times (at horizontal deflection) difference in damping ratio between zipped and unzipped feathers in vacuum
Galois-Abstieg von Kac–Moody symmetrischen Räumen
Get PDFIn dem Artikel "Kac–Moody symmetric spaces" aus dem Jahr 2020 haben die Autoren Freyn, Hartnick, Horn und Köhl eine Theorie der Kac–Moody symmetrischen Räume entwickelt, die eine Verallgemeinerung der Theorie der Riemannschen symmetrischen Räume vom nicht-kompakten Typ ist. Die Einführung dieses Begriffs basiert auf der Definition eines abstrakten symmetrischen Raums, die O. Loos gab. Die Grundlage von Loos’ Definition ist eine Gruppe mit einer Involution. Daher ist die Wahl der Kac–Moody Gruppe ist somit ein zentraler Schritt. Die Autoren des Artikels haben reelle zentrierte Kac–Moody Gruppen nicht-affinen Typs gewählt, da sie die kleinstmögliche Realisierung eines solchen symmetrischen Raumes erreichen wollten. Da die Theorie der Kac–Moody symmetrischen Räume ein junger Zweig der Kac–Moody Theorie ist, sind viele Bereiche noch nicht erforscht und es ist von Interesse, symmetrische Räume zu untersuchen, die zu einer allgemeineren Klasse von Kac–Moody Gruppen gehören. In dieser Dissertation wird eine Theorie für reelle und komplexe Kac–Moody symmetrische Räume beliebigen Typs entwickelt. Dazu betrachtet der Autor Kac–Moody Gruppen, die mit dem Wurzeldatum D_Kac konstruiert werden und folglich einen größeren Torus besitzen und damit nicht zentriert sind. Der Autor verallgemeinert die wichtigsten Aussagen und Konzepte aus dem Artikel "Kac–Moody symmetric spaces" für die gewählte Art von Kac–Moody Gruppen. Am Ende dieser Arbeit nutzt der Autor den Galois-Abstieg, welcher von B. Rémy für Kac–Moody Gruppen entwickelt wurde, um die Grundlagen der Theorie der Kac–Moody symmetrischen Räume für fast-zerfallende Kac–Moody Gruppen zu entwickeln
Shaping the helper T cell landscape: from naive to effectors
Get PDFHelper T (Th) lymphocytes play a key role in our immunity, orchestrating responses to various pathogens, vaccines, host proteins, microbiota, environmental antigens, and cancers. The development and function of Th cells depend on their T cell receptors (TCR). Each individual T cell progenitor acquires its TCR-encoding genes through stochastic genome recombination within TCRα and TCRβ loci. Collectively, TCRs of independent T cells contribute to an extremely diverse TCR repertoire. The TCR repertoire serves to recognize a large pool of distinct peptide antigens presented within major histocompatibility complexes (MHC). The interaction with MHC plays a central role in the development and function of T cells. Thus, T cell progenitors’ survival and early commitment to a Th lineage in thymus depends on MHC class II (MHC-II) recognition and the corresponding TCR signaling. Later peripheral recognition of antigens presented within MHC-II involves naive and memory Th lymphocytes in immune responses. Activated Th cells acquire specific helper phenotypes, which control the development of immune responses of an appropriate type, facilitating pathogen clearance and tissue homeostasis. Later, the exact antigen specificity and the linked Th phenotype are preserved in the form of Th memory clones, providing stable response patterns to familiar antigens. Studying the thymic and peripheral fate selection by Th cells may help to mechanically understand the successes and failures of our immune system to develop protective responses in infectious diseases, vaccinations, and cancers, as well as the generation of immune tolerance to microbiota-derived and host antigens
Molecular and Cellular Mechanisms for Microbial Discrimination in Sponges
Get PDFSponges (Porifera) are basal metazoans that feed on and establish symbiotic associations with microbes. How sponges discriminate between bacteria to digest as food, incorporate as symbionts, or eliminate as pathogens remains unknown. This thesis aimed to study mechanisms for microbial discrimination in sponges. Mechanisms likely to modulate sponge-microbe interactions are introduced (Chapter 1). The host transcriptomic response upon seawater and symbiont microbial consortia encounter was characterized by RNASeq in two sponges (Chapter 2). Aplysina aerophoba showed little differential gene expression and no participation of receptors, whereas Dysidea avara responded by regulating NLRs suggesting that microbial discrimination is driven by the repertoire of immune genes as well as to what degree they are induced. On the cellular level, an in-vivo phagocytosis assay was established in Halichondria panicea combining incubations with microalgae, bacteria, and latex beads with cell dissociation and fluorescence-activated cell sorting (FACS) to quantify particle incorporation into sponge cells (Chapter 3). After 30 min particles were predominantly incorporated into choanocyte-like cells and appeared to be translocated to archaeocyte-like cells after 60 min. Lastly, the established assay was combined with proteomic analysis to investigate H. panicea’s phagocytic response upon exposure to a “native” and a “foreign” Vibrio isolate (Chapter 4). Vibrio incorporation into sponge cells was indiscriminate, but the distribution of vibrios into different cell types differed between isolates. Phagocytic-related proteins were in a higher abundance in the foreign vs. the native treatment. These results indicate that bacterial discrimination in H. panicea occurs after internalization leading to differences in the processing of foreign vs native vibrio types
Mechanisms of C. elegans microbiota-mediated protection
Get PDFMicroorganisms live in close association with multicellular organisms, with which they form complex networks of interdependent relationships. This microbiota is essential in protecting the host against pathogen infection, commonly referred to as colonization resistance or microbiota-mediated protection. Although microbiota-mediated protection is a well-known phenomenon, the underlying molecular mechanisms remain largely unknown. This thesis aims to comprehensively understand these mechanisms, focusing on the two natural microbiota isolates Pseudomonas lurida MYb11 and Pseudomonas fluorescens MYb115 of the host model organism Caenorhabditis elegant. Using a reductionist approach, I individually exposed the worm to these isolates, revealing diverse effects on life history traits. MYb115 demonstrated neutrality, while MYb11 acted as a pathobiont, shortening lifespan but enhancing fertility. MYb11 increased the abundance of proteins related to the innate immune response, suggesting it primes C. elegans' immune system. MYb115 influenced intestinal cell components, fortifying the epithelial barrier for indirect protection. Importantly, MYb115-mediated protection relied on the non-canonical MYb115 iterative type 1 polyketide synthase biosynthesis gene cluster, producing bacterial sphingolipids. These sphingolipids influenced C. elegans tolerance to Bt247 infection by altering host sphingolipid metabolism. Microbiota-derived sphingolipids emerged as crucial outputs of bacterial polyketide synthase, demonstrating their role in host protection. This thesis enhances our understanding of microbiota-mediated protection, unraveling mechanisms from both host and bacterial perspectives
Language Design for Reactive Systems: On Modal Models, Time, and Object Orientation in Lingua Franca and SCCharts
Get PDFReactive systems play a crucial role in the embedded domain. They continuously interact with their environment, handle concurrent operations, and are commonly expected to provide deterministic behavior to enable application in safety-critical systems. In this context, language design is a key aspect, since carefully tailored language constructs can aid in addressing the challenges faced in this domain, as illustrated by the various concurrency models that prevent the known pitfalls of regular threads. Today, many languages exist in this domain and often provide unique characteristics that make them specifically fit for certain use cases. This thesis evolves around two distinctive languages: the actor-oriented polyglot coordination language Lingua Franca and the synchronous statecharts dialect SCCharts. While they take different approaches in providing reactive modeling capabilities, they share clear similarities in their semantics and complement each other in design principles. This thesis analyzes and compares key design aspects in the context of these two languages. For three particularly relevant concepts, it provides and evaluates lean and seamless language extensions that are carefully aligned with the fundamental principles of the underlying language. Specifically, Lingua Franca is extended toward coordinating modal behavior, while SCCharts receives a timed automaton notation with an efficient execution model using dynamic ticks and an extension toward the object-oriented modeling paradigm
Closer and greener? Firms' global value chain participation and sustainability
Get PDFThe pivotal year 2015 saw the adoption of the 2030 Agenda for Sustainable Development and the Paris Agreement, signifying a global commitment to address social and environmental issues. The Paris Agreement aims to limit the temperature increase to well below 2 degrees Celsius, crucial for averting severe climate-related risks. However, still high global CO2 emissions reveal a significant deviation from this goal, emphasizing the urgent need for global sustainability practices. The doctoral thesis focuses on firms' role in sustainable development through global value chain (GVC) participation, exploring environmental and social dimensions. GVCs connect firms from different countries through the transfer of goods, capital, and labour, presenting an avenue for examining the impact of international business activities on sustainability. The research delves into the role of firms' GVC participation, considering mainly firms’ export activity and GVC positioning. Chapter 2 reviews literature on trade's environmental impact and firms' adoption of environmental innovations, setting the stage for subsequent chapters. Chapter 3 examines the positive association between firms' export activity and environmental innovation adoption in Europe, particularly in laggard economies. Chapter 4 shifts focus to India, exploring CO2 emissions in upstream GVC positions. Findings suggest a negative relationship, with moderation from environmental regulation in export destinations. Chapter 5 explores Corporate Social Responsibility (CSR) along GVCs, incorporating social performance. Empirical analysis using Indian data supports the theoretical model, indicating that downstream firms spend more on CSR
Questions. Questions that need answering.: A qualitative study to create a modell for competence diagnostic for the competence of formulating and reflecting historical questions
Get PDF„Ohne historische Fragen keine Geschichte“ postuliert Waltraud Schreiber mit der Veröffentlichung des FUER-Kompetenzmodells 2007. Ausgangspunkt für individuelle Narrationen bilden folglich historische Fragen. Diese lassen sich hierbei unterteilen in historische Fragen im engeren sowie im weiteren Sinne, aber auch Fragen, die nicht per se historisch sind (Thünemann/Jansen 2018). Im Rahmen des Kompetenz-Strukturmodell ist eine Graduierungslogik zur gezielten Förderung der Kompetenzniveaus erarbeitet worden (Körber 2007). Die Autoren plädieren allerdings für eine weitere Ausdifferenzierung, damit sowohl das Modell als auch die Graduierung adressatengerecht im Geschichtsunterricht eingesetzt werden können (Schreiber et al. 2007). Im Zuge der Ausdifferenzierung für den Geschichtsunterricht rücken die lernenden Subjekte zwangsläufig stärker in den Fokus. Vor diesem Hintergrund ist die Frage entwickelt worden, „Wie kann ein empirisch entwickeltes Instrument zur subjektorientierten Diagnostik der historischen Fragekompetenz als Prototyp figuriert sein?“ Zur Untersuchung sind Essays von Lernenden erhoben und mittels der qualitativen Inhaltsanalyse ausgewertet worden. Die Erkenntnisse aus den gewonnen Daten bilden die Grundlage für die Entwicklung einer graphischen Darstellung zur Darstellung und einer daraus resultierenden Möglichkeit zur Förderung der historischen Fragekompetenz
Biotechnological Production of Carotenoids by Aquatic Microorganisms
Get PDFPopulation growth, higher expectations for a long and healthy life, and climate change are currently major drivers for the development and production of health-promoting, sustainable, and climate-friendly substances. A particular focus is on the food and pharmaceutical sectors, as these directly impact human health. This progress led to an increase in demand for additives improving the properties of food and feed. In this context, carotenoids play an important role. They comprise a group of natural pigments, which are used to color food and feed. The biotechnological production enables a sustainable supply of natural carotenoids, but there is still room for improvements in manufacturing processes. The aim of this work was to support the further development of the biotechnological production of carotenoids by optimizing methods and processes and by searching for new, promising production organisms: 1. The development of a method for the determination of astaxanthin from Haematococcus pluvialis helped to find a good compromise between simple and fast but also accurate measurement procedures. 2. The application of the developed method in the optimization of the downstream process of astaxanthin from H. pluvialis aimed to maximize astaxanthin yield while minimizing process costs and energy consumption. 3. The screening of a Thraustochytriaceae strain collection indicated that some strains are potentially suitable for a sustainable production of carotenoids. The gained comprehensive understanding is essential to improve the necessary production of carotenoids through optimized synthesis and processing, to enable targeted and economical use, and thus to make a lasting contribution to public health and climate protection
Förderung mediendidaktischer und informatischer Kompetenzen von Lehramtsstudierenden: eine Design-Based Research Studie
Get PDFIn der vorliegenden Arbeit wird untersucht, inwieweit die Forderung der KMK (2012, 2017, 2021) nach einer Förderung digitalisierungsbezogener Kompetenzen in allen Schulfächern durch die Lehrkräfte in der universitären Phase der Lehrkräftebildung angebahnt werden kann. Dazu wurden zwei Studien im Design-Based Research-Format durchgeführt, in denen untersucht wurde, wie die Förderung fachspezifischer digitalisierungsbezogener Kompetenzen erfolgen kann. Dabei fiel die Wahl bewusst auf ein MINT-Fach und ein Nicht-MINT-Fach, mit jeweils hohen Studierendenzahlen. Eine Intervention wurde in der Mathematikdidaktik gestaltet, mit dem Fokus auf der Förderung mediendidaktischer Kompetenzen, und eine in der Deutschdidaktik, in der informatische (Lehr-)Kompetenzen im Mittelpunkt standen. Obwohl beide Interventionen einen kleinen Umfang hatten, konnten die Lehramtsstudierenden einen signifikanten Kompetenzzuwachs erzielen, wenn auch nur in einem begrenzten Maß. Den Mathematikstudierenden fiel dabei der Zugang zu mediendidaktischen Fragestellungen leichter als den Deutschstudierenden zu informatischen Themen, dies bildete sich auch in den Ergebnissen ab