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Ruff Persistence : the Role of Pre-sexual Selection and Male-male Partner Choice in Maintaining Intraspecific Diversity
No full textThe Ruff, Calidris pugnax, a Eurasian wader, is an ideal study system for researching intraspecific diversity. Ruffs have drastically different sex roles during reproduction. Most males spend the breeding season intensively competing over matings with females, providing no parental care for chicks. Whilst most females choose mates from display grounds, incubate nests, and rear chicks. Ruffs also have extreme size and appearance variation across demographic classes. Males can be up to 70% heavier than females and most males develop elaborate nuptial plumage in comparison to females. Further, males have three phenotypically distinct mating morphs: first, Independents, aggressive males that jealously guard display courts on leks. Second, Satellites, non-aggressive males that cooperatively display with Independents to gain fertilisations. Third, Faeders, males that sneak copulations on leks through female mimicry. Three supergene haplotype combinations underlie the different morphs. Independents carry two copies of the ancestral haplotype whereas Satellites and Faeders carry one ancestral haplotype and their own morph-specific inversion haplotypes. A break point within the gene CENPN on both inversion haplotypes leads to homozygote lethality. Adult Satellites and Faeders are also rare in the Ruff population, possibly because of this genetic handicap. However, the Satellite and Faeder haplotypes are thousands to millions of years old indicating that the inversion morphs must have a way of balancing their fitness with Independents.
I examined two processes that may help the maintenance of Ruff morph diversity. First, I examined the hypothesis that sex- and morph-specific constraints on development during ontogeny of chicks, leads to sex- and morph-specific differences in pre-sexual selection, which in turn may favour females and the Faeder male. Second, I examined the hypothesis that Satellite males are able to use co-display partner choice to optimize their mating success. I split my thesis into two parts, one for each of my two hypotheses. Part I, including Chapter 1, covers the pre-sexual selection in the Ruff sexes and morphs. Specifically, Chapter 1 examines how delays in Independent male development and fledging ages leads to demographic changes in Ruff cohorts from hatching to post-fledging. My co-authors and I used multiple simulations of a single cohort matrix model informed with wild, aviary, and literature data to project both changes in the sex ratio, and pre-sexual selection. Further, we used two forms of sensitivity analysis to examine the impacts of demographic complexity in our model and the demographic vital rate contributions to the post-fledge sex and morph ratios. Our model predicted a 20% decline in male frequency from hatching to fledging which is consistent with independent empirical observations of southward migrating juveniles. The sensitivity analyses of demographic complexity revealed that sex differences in vital rates explained more variation in the sex and morph ratios than vital rate differences across morphs and within the sexes. The most important demographic contributions to the sex and morph ratios were sex-specific intrinsic mortality and fledging ages between Independent males and females. The increase in Satellite male and stability in Faeder male frequencies indicates that variation in viability selection before maturation may help to maintain morph diversity in the Ruff.
Part II, of my thesis, includes Chapters 2 and 3, which are dedicated to male-male co-display between territorial Independents, aka Residents, and Satellites. Chapter 2 utilizes a community game model informed with literature data to predict Resident and Satellite partner choice for co-display. Because it is unclear how co-display alters female choice, we included four scenarios for this parameter in our model of Resident/Satellite co-display. We present the ‘Skew’ scenario, in the main text, because under that scenario Satellites obtained the percent of lek copulations that were closest to empirical estimates from the literature and could do so on all modelled lek sizes. Here, Residents, in general, would co-display with Satellites instead of opting for single-display. Further, Satellite males should choose Resident co-display partners of mid- to low-rank on medium lek sizes in order to maximize their mating success and achieve copulation rates equal to those in natural populations. In Chapter 3, I used data from a captive Ruff population to examine the formation probability, duration of co-displays, and variation in Satellite co-display rewards. Further, I tested the key prediction, from Chapter 2, that Satellite copulation success increases with descending Resident mating rank, and a key assumption, of the game model, that a Satellite’s ability to monopolize copulations within a co-display increases with descending mating rank of their Resident partner. Co-display formation probability and duration, and Satellite rewards increased with descending mating rank. These results did not match the predictions under the ‘Skew’ scenario in Chapter 2, but did match the prediction under another scenario called the ‘Uniform Proportion’ scenario. Further one of the assumptions of the model in Chapter 2, i.e. the max proportion of copulations a Satellite could obtain within a co-display did not match the results from Chapter 3. This suggests that further experiments and observations of natural Ruff populations are needed to fully understand Resident/Satellite co-display dynamics.publishe
Langzeitstabilität der Ladungsträgerlebensdauer in kristallinem p-Typ und n-Typ Silizium bei Beleuchtung und erhöhter Temperatur
No full textDas Ziel dieser Arbeit ist es, ein tieferes Verständnis der Prozess- und Materialabhängigkeit der Langzeitstabilität in monokristallinen Silizium zu gewinnen. Es wird untersucht, inwieweit die Degradationsmechanismen im verwendeten Wafermaterial selbst sowie in spezifischen Schritten der Solarzellenfertigung, insbesondere Hochtemperaturprozessen, zu finden sind. Durch die gezielte Verknüpfung dieser Aspekte soll ein umfassendes Verständnis der Langzeitstabilität entstehen, um Degradationsmechanismen besser zu verstehen und deren Reduzierung oder Vermeidung zu ermöglichen. Besonderes Augenmerk liegt auf den Wechselwirkungen zwischen Verunreinigungselementen wie Aluminium, Gallium und Phosphor im Wafermaterial mit Wasserstoff aus der Passivierungsschicht.publishe
Let's Chat about This : A Template for Well-Aligned AI Integration in Schools
No full textArtificial Intelligence (AI) in general and chatbots in particular are gaining more and more attention in education. However, there are several barriers hindering teachers from using chatbots in the classroom. Based on existing empirical research on the use of chatbots in the classroom, we identify these barriers and derive systemic requirements. We suggest Retrieval-Augmented Generation (RAG) systems as an adequate solution. Unfortunately, commercial RAG systems fail to harness the full potential of this technology. Based on a requirement and market analysis, we present a locally hosted open-source, lowcode RAG system template, which fulfills the requirements for use in school. We report lessons learned from our work with a Professional Learning Community (PLC) with teachers, where we continuously test and discuss our RAG system template.accepte
Auswirkungen von Ufermauern unter dem Einfluss von Wind- und Schiffswellen am nördlichen Bodenseeufer : Bericht der AG Umweltphysik am Limnologischen Institut der Universität Konstanz für das SuBoLakes-Projekt (Az. 35825/01) der Deutschen Bundesstiftung Umwelt (DBU)
No full textpublishe
Between Beveridge and Bismarck : Preferences for redistribution through public pensions
No full textWe examine preferences for redistribution in Germany’s public pension system as well as notions of fairness of the system, using survey and experimental data from citizens and politicians. Our findings reveal a
widespread rejection of strict proportionality between contributions and benefits, with strong support for greater redistribution to low earners. Information on inequalities in life expectancy reduces perceived fairness and increases support for redistribution among voters and politically moderate legislators. The study also reveals significant knowledge gaps about the basic features of the existing pension scheme among citizens. We demonstrate that policy-relevant information influences fairness perceptions.publishe
The ubiquitin-like modifier FAT10 is not essential for MHC-I antigen presentation
No full textIntroduction: The presentation of pathogen-derived antigens on major histocompatibility complex (MHC) class I is crucial for the antiviral immune response. Degradation of intracellular pathogen-derived proteins by the 26S proteasome generates peptides that can be loaded on MHC-I molecules and presented to cytotoxic T cells. The cytokine-inducible ubiquitin-like modifier (ULM) HLA-F adjacent transcript 10 (FAT10) is encoded in the MHC locus and targets its substrates for proteasomal degradation. Therefore, it acts as an alternative signal for protein degradation, indicating a role in generating the peptide pool for MHC-I presentation. In this study, we aimed to elucidate the role of FAT10 in MHC class I presentation.
Methods: Using different human and mouse cell lines deficient for FAT10, the effect of FAT10 on MHC-I surface expression and recovery was studied. For the evaluation of antigen presentation of viral and endogenous epitopes, T cell hybridoma assays and flow cytometry analysis were used.
Results: In our study, using model antigens and FAT10-deficient cells, we found that the absence of FAT10 does not affect the abundance of MHC-I molecules or the generation of endogenous and virus-derived MHC-I epitopes. Furthermore, we demonstrated that the cytotoxic T cell response to different viruses remains unchanged in FAT10-deficient mice compared to wild-type mice.
Discussion: In summary, our findings indicate that the lack of FAT10 does not impact antigen presentation or the cytotoxic T-cell response across a number of different MHC-I-restricted peptides. Hence, we conclude that the contribution of FAT10 to MHC-I antigen presentation has previously been overestimated.publishe
Investigation of the structure and dynamics of amorphous calcium carbonate by NMR : stabilization by poly-aspartate and comparison to monohydrocalcite
No full textThe chemical environments of the 1 H and 13 C nuclei in amorphous calcium carbonate are surprisingly similar to those in monohydrocalcite. H-bonds, however, have weakened and permit 180° flips of the structural water molecules.publishe
The effects of climate on bat morphology across space and time
No full textAccording to Bergmann's and Allen's rules, climate change may drive morphological shifts in species, affecting body size and appendage length. These rules predict that species in colder climates tend to be larger and have shorter appendages to improve thermoregulation. Bats are thought to be sensitive to climate and are therefore expected to respond to climatic changes across space and time. We conducted a phylogenetic meta-analysis on > 27 000 forearm length (FAL) and body mass (BM) measurements from 20 sedentary European bat species to examine body size patterns. We assessed the relationships between body size and environmental variables (winter and summer temperatures, and summer precipitation) across geographic locations, and also analysed temporal trends in body size. We found sex-specific morphological shifts in the body size of European bats in response to temperature and precipitation patterns across space, but no clear temporal changes due to high interspecific variability. Across Europe, male FAL decreased with increasing summer and winter temperatures, and BM increased with greater precipitation. In contrast, both FAL and BM of female bats increased with summer precipitation and decreased with winter temperatures. Our data can confirm Bergmann's rule for both males and females, while females' BM variations are also related to summer precipitation, suggesting a potential link to resource availability. Allen's rule is confirmed only in males in relation to summer temperature, while in females FAL and BM decrease proportionally with increasing temperature, maintaining a constant allometric relationship incompatible with Allen's rule. This study provides new insights into sex and species-dependent morphological changes in bat body size in response to temperature and precipitation patterns. It highlights how body size variation reflects adaptations to temperature and precipitation patterns, thus providing insights into potential species-level morphological responses to climate change across Europe.publishe
Facile construction of mechanically robust and highly osteogenic materials for bone regeneration
No full textHydrogel-based materials exhibit great potential in tissue engineering. However, their mechanical weakness limits applications in hard tissue regeneration, especially under load-bearing conditions. Although various strengthening strategies have been applied, the achieved mechanical response of hydrogels still lags behind the mechanics of natural bone. In this study, we present a novel mineralization approach to fabricate mechanically robust and highly osteogenic mineralized hydrogels. Cross-linking between deprotonated chains of poly(acrylic acid) (PAA) and divalent cations has led to formation of hydrogels with a compressive strength and elastic modulus of 0.3 ± 0.1 kPa and 1.3 ± 0.2 kPa, respectively. Subsequent in situ formation of nano-calcium hydroxide crystals remarkably increased the compressive strength and modulus to 7.9 ± 0.6 MPa and 339.3 ± 31.4 MPa, respectively, surpassing those of trabecular bone. Moreover, the mineralized hydrogels demonstrated remarkable osteogenic potential in vivo, exhibiting immunoregulatory activity, promoting early angiogenesis, and accelerating fracture healing at weeks 4 and 8. The mechanism of osteogenesis was further revealed by transcriptome sequencing, indicating that the mineralized hydrogels regulated the translation of extracellular matrix and biomineralization. Overall, our study presents a pioneering and cost-effective method for fabricating materials with exceptional mechanical strength and strong osteogenic properties, offering a promising avenue for load-bearing bone repair applications of hydrogel-based materials.publishe