Aktuelle Publikationen

Vanadium dioxide is a strongly correlated material with an ultrafast first-order phase transition between monoclinic/insulator and rutile/metallic close to room temperature. The unusual and complex properties of this transition make VO₂ one of the most heavily investigated materials in modern condensed matter physics. Consequently, high-quality single crystals are in large demand. Here we report the growth of mm-sized VO2 crystals by thermal decomposition of liquid V₂O₅ at ∼1000∘C. Time-resolved zirconia sensor measurements of the oxygen release reveal that the crystal growth rate is limited by liquid-phase diffusion; the properties of the gaseous environment, which were previously assumed to be decisive, are almost insignificant. Consequently, large and stoichiometric single crystals of VO₂ can be obtained at lower temperatures and gas purities than usually applied. These results signify the role of gas-liquid diffusion in crystal growth and will simplify future research on VO₂ and related materials for applications in ultrafast electronics and thermal energy management.

This paper investigates the influence of educational tracking on immigrant educational expectation gaps in Sweden, England, the Netherlands, and Germany. To account for heterogeneity in immigrant children's origin countries, this paper additionally focuses on the educational selectivity of immigrant parents. The article argues that with a greater degree of tracking, students receive stronger track signals about their ability and their future opportunities, which should reduce the influence of immigrant parents’ aspirations and mitigate immigrant students’ lower responsiveness to school ability. As a result, immigrant students in countries with a high degree of tracking should have less inflated expectations that are more similar to ethnic majority students. Additionally, the moderating effect that tracking can have on the influence of parental aspirations on immigrant students’ educational expectations should mitigate the beneficial effect of immigrant parents’ selectivity in highly versus lowly tracked countries. Findings based on two waves of the CILS4EU data reveal that second-generation immigrant students have higher educational expectations than ethnic majority students in all countries except Germany. No significant differences are found relating to parents’ educational selectivity. The results support the assumption that stronger track signals in countries with a higher degree of tracking lead to higher responsiveness to school ability among second-generation immigrant students. No support is found for a reduced influence of parental aspirations on the immigrant expectation gap in countries with a higher tracking degree. This study contributes to research on immigrant expectation gaps by highlighting the specific mechanisms through which tracking influences operate.

When it comes to the selection of adequate movements, people may apply varying strategies. Explicit if-then rules, compared to implicit prospective action planning, can facilitate action selection in young healthy adults. But aging alters cognitive processes. It is unknown whether older adults may similarly, profit from a rule-based approach to action selection. To investigate the potential effects of aging, the Rule/Plan Motor Cognition (RPMC) paradigm was applied to three different age groups between 31 and 90 years of age. Participants selected grips either instructed by a rule or by prospective planning. As a function of age, we found a general increase in a strategy-specific advantage as quantified by the difference in reaction time between plan- and rule-based action selection. However, in older age groups, these differences went in both directions: some participants initiated rule-based action selection faster, while for others, plan-based action selection seemed more efficient. The decomposition of reaction times into speed of the decision process, action encoding, and response caution components suggests that rule-based action selection may reduce action encoding demands in all age groups. There appears a tendency for the younger and middle age groups to have a speed advantage in the rule task when it comes to information accumulation for action selection. Thus, one influential factor determining the robustness of the rule-based efficiency effect across the lifespan may be presented by the reduced speed of information uptake. Future studies need to further specify the role of these parameters for efficient action selection.

1. Parasitic plants have been shown to affect soil-organic-matter (SOM) decomposition, but the mechanism is unknown. As arbuscular mycorrhizal fungi (AMF) can affect decomposition and compete with parasitic plants for carbon, we hypothesized that parasitic plants can indirectly regulate SOM decomposition by suppressing the effects of AMF on decomposition.

2. To test this hypothesis, we conducted two container experiments in which the herbaceous plant Bidens pilosa was inoculated with the AMF Rhizophagus intraradices or not, and Cuscuta australis or not. In one experiment, we provided SOM within hyphae-in-growth bags as ¹³C-/¹⁵ N-labelled maize leaves and in the other experiment as phytate-P. We assessed growth and nutrient uptake of B. pilosa, growth of C. australis, the SOM remaining in the hyphae-in-growth bags, and the bacterial communities.

3. Parasitization increased the ¹³C and decreased the organic P remaining in the bags, but only in the presence of the extraradical AMF hyphae. AMF decreased the ¹³C and increased the organic P remaining in the absence of the parasite, but not in the presence of the parasite.

4. Our results demonstrate that parasitic plants can regulate the decomposition of organic materials indirectly by suppressing the effect of the extraradical AMF hyphae on decomposition. In other words, parasitic plants can regulate SOM decomposition indirectly via a multitrophic cascading effect. Our study helps to unravel the mechanisms of a sophisticated hidden ecological process, and is an important step forward in elucidating the roles of parasitic plants in soil nutrient cycling.

Employing new and original survey data collected in three waves (April/May and November 2020 as well as May 2021) in Germany, this paper studies the dynamics of individual-level support for additional health care spending. A first major finding is that, so far, health care spending preferences have not radically changed during the Covid-19 pandemic, at least at the aggregate level. A more detailed analysis reveals, secondly, that individual-level support for additional spending on health care is strongly conditioned by performance perceptions and, to a lesser extent, general political trust. Citizens who regard the system as badly (well) prepared to cope with the crisis are more likely to support (oppose) additional spending. Higher levels of political trust are also positively associated with spending support, but to a lesser degree. The paper concludes by discussing the implications of these findings for policy-making and welfare state politics in the post-pandemic era.

A neglected topic in empirical research on national identity is its stability at the individual level, and this is especially true for its content, that is, the meaning elements that people associate with the concept of nation. In this article, we study the stability of key dimensions of national-identity content. We ask three simple questions: How stable is national-identity content—as captured in the ethnic/civic framework—at the level of individual citizens? Are there clear differences in stability across subgroups? What are the implications of interindividual differences in stability? Analyzing data from four waves of a large-scale panel survey of German citizens (N = 4,654) collected over a five-year period (2016–21), we show that there is high but not perfect stability of the degree to which individuals subscribe to ethnic and civic criteria of nationhood. Second, we find little difference in stability as a function of several theoretically selected characteristics. Third, we show that the association between national-identity content and relevant political attitudes (immigration attitudes and far-right party support) increases with intraindividual stability. These findings have important implications for our understanding of how national-identity content is shaped and mobilized and how it can influence political attitudes and behaviors.

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dc.contributor.author: Dörken, Veit; Steinecke, Hilke; Jagel, Armin

Understanding why animals organize in collective states is a central question of current research in, e.g., biology, physics, and psychology. More than 50 years ago, W.D. Hamilton postulated that the formation of animal herds may simply result from the individual‘s selfish motivation to minimize their predation risk. The latter is quantified by the domain of danger (DOD) which is given by the Voronoi area around each individual. In fact, simulations show that individuals aiming to reduce their DODs form compact groups similar to what is observed in many living systems. However, despite the apparent simplicity of this problem, it is not clear what motional strategy is required to find an optimal solution. Here, we use the framework of Multi Agent Reinforcement Learning (MARL) which gives the unbiased and optimal strategy of individuals to solve the selfish herd problem. We demonstrate that the motivation of individuals to reduce their predation risk naturally leads to pronounced collective behaviors including the formation of cohesive swirls. We reveal a previously unexplored rather complex intra-group motion which eventually leads to a evenly shared predation risk amongst selfish individuals.

Prolactin (PRL) is a multifunctional hormone of broad physiological importance, and is involved in many aspects of fish reproduction, including the regulation of live birth (viviparity) and both male and female parental care. Previous research suggests that PRL also plays an important reproductive role in syngnathid fishes (seahorses, pipefish and seadragons), a group with a highly derived reproductive strategy, male pregnancy - how the PRL axis has come to be co-opted for male pregnancy remains unclear. We investigated the molecular evolution and expression of the genes for prolactin and its receptor (PRLR) in an evolutionarily diverse sampling of syngnathid fishes to explore how the co-option of PRL for male pregnancy has impacted its evolution, and to clarify whether the PRL axis is also involved in regulating reproductive function in species with more rudimentary forms of male pregnancy. In contrast to the majority of teleost fishes, all syngnathid fishes tested carry single copies of PRL and PRLR that cluster genetically within the PRL1 and PRLRa lineages of teleosts, respectively. PRL1 gene expression in seahorses and pipefish is restricted to the pituitary, while PRLRa is expressed in all tissues, including the brood pouch of species with both rudimentary and complex brooding structures. Pituitary PRL1 expression remains stable throughout pregnancy, but PRLRa expression is specifically upregulated in the male brood pouch during pregnancy, consistent with the higher affinity of pouch tissues for PRL hormone during embryonic incubation. Finally, immunohistochemistry of brood pouch tissues reveals that both PRL1 protein and PRLRa and Na+/K+ ATPase-positive cells line the inner pouch epithelium, suggesting that pituitary-derived PRL1 may be involved in brood pouch osmoregulation during pregnancy. Our data provide a unique molecular perspective on the evolution and expression of prolactin and its receptor during male pregnancy, and provide the foundation for further manipulative experiments exploring the role of PRL in this unique form of reproduction.

This paper provides new insights into the analysis of vocative structures that co-occur with a sentence by bridging two previously independent domains of linguistic research: wh-interrogatives and vocatives. More specifically, we investigate in which positions Spanish speakers accept vocatives in wh-interrogatives introduced by different wh-phrases. The results of an acceptability judgment task indicate that our participants highly accept initial and final vocatives in all wh-interrogatives. For middle vocatives, the results differ across wh-phrases. While the participants accept middle vocatives in wh-interrogatives introduced by por qué (‘why’) and d-linked wh-phrases, they reject them in bare wh-interrogatives. These findings require a modification of the syntactic analysis of vocatives. Initial vocatives are placed above ForceP, while middle and final vocatives are analyzed in two different positions, in an upper and a lower VocaddrP in the left periphery.

Silver (Ag) pastes are widely used in the global market for most solar cell architectures. Thereby, lead (Pb) is no longer wanted in productions for environmental reasons. In this work, a model for the contact formation between Pb-free, tellurium oxide (TeO2) containing screen-printable Ag pastes and silicon is presented. It is shown that Te plays a key role in this model. Te is not only an important part in etching the surface passivation layers with TeO2 dissolving the dielectric layer but also for a formation of the contacts with Te forming a compound consisting of Ag2Te. Using EDX mapping, local contact regions can be examined and interpreted for contact formation. The used paste system enables far more flexible paste mixturing leading to a novel developed commercial paste which is on a par with other pastes used in industry concerning the resulting contact properties. This is also demonstrated in this work by the very low contact resistivity of less than 1 mΩcm2 over a wide range of firing peak temperatures. It is additionally shown that good resistivities can be achieved on both n+- and p+-doped regions.

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction (NJ) of skeletal muscles. The major MG autoantigen is nicotinic acetylcholine receptor. Other autoantigens at the NJ include MuSK, LRP4 and agrin. Autoantibodies to the intra-sarcomeric striated muscle-specific gigantic protein titin, although not directed to the NJ, are invaluable biomarkers for thymoma and MG disease severity. Thymus and thymoma are critical in MG mechanisms and management. Titin autoantibodies bind to a 30 KDa titin segment, the main immunogenic region (MIR), consisting of an Ig-FnIII-FnIII 3-domain tandem, termed I109-I111. In this work, we further resolved the localization of titin epitope(s) to facilitate the development of more specific anti-titin diagnostics. For this, we expressed protein samples corresponding to 8 MIR and non-MIR titin fragments and tested 77 anti-titin sera for antibody binding using ELISA, competition experiments and Western blots. All anti-MIR antibodies were bound exclusively to the central MIR domain, I110, and to its containing titin segments. Most antibodies were bound also to SDS-denatured I110 on Western blots, suggesting that their epitope(s) are non-conformational. No significant difference was observed between thymoma and non-thymoma patients or between early- and late-onset MG. In addition, atomic 3D-structures of the MIR and its subcomponents were elucidated using X-ray crystallography. These immunological and structural data will allow further studies into the atomic determinants underlying titin-based autoimmunity, improved diagnostics and how to eventually treat titin autoimmunity associated co-morbidities.

Introduction: Language policies are often aimed at changing language behaviours, yet it is notoriously difficult to assess their effects. This study investigates language use and competence in the Indigenous Sámi populations of Norway and Sweden in light of the national-level policies the two countries have adopted.

Methods: We provide a cross-country comparison of relevant educational, linguistic and budgetary policies in Sweden and Norway. Next, we present novel data from a survey with 5,416 Sámi and non-Sámi participants in 20 northern municipalities, examining Sámi language use and proficiencies across generations and contexts. Lexical proficiency in North Sámi was tested in a small subset of participants.

Results: Sámi language use has dropped considerably over the past three generations. Only a small proportion of Sámi are highly fluent and use a Sámi language with their children (around 4% in Sweden and 11% in Norway). One fifth of Sámi adults use a Sámi language at least ‘occasionally’, and use is most common in the home context. Sámi language knowledge remains negligible in the majority population.

Discussion: The higher levels of language use and proficiency in Norway seem at least in part to reflect the more favourable policies adopted there. In both countries, more work is needed to increase speaker numbers, also in the majority population.

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dc.contributor.author: Rothman, Jason; Bayram, Fatih; DeLuca, Vincent; Di Pisa, Grazia; Andoni Duñabeitia, Jon; Gharibi, Khadij; Hao, Jiuzhou; Kolb, Nadine; Kubota, Maki; Kupisch, Tanja