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Dislocation-induced local and global photoconductivity enhancement and mechanisms in iron-doped SrTiO3
No full textDislocations have a tremendous potential to alter band structure and transport properties. However, their impact on the optoelectronic properties of metal oxides is not thoroughly studied. This is mostly due to the early work on classical semiconductors, where dislocations are found to have detrimental effects. In this study, a simple method is developed to introduce a high density of dislocations over a large macroscopic volume of Fe-doped SrTiO3 single crystals. As a result, the photoconductivity revealed by static and dynamic measurements increases by at least one order of magnitude. A detailed analysis based on photo-Hall, spectral photoresponsivity, time-resolved photocurrent, and conductive AFM, focusing on the quantum paraelectric state of SrTiO3, is presented to shed light on the possible mechanisms behind higher generated photocurrent. These findings indicate that the increased photoconductivity results from a higher charge carrier generation rate due to new energy states induced by dislocations, possibly accompanied by an enhancement of electron effective mass
Migrationssensibler Fremdsprachenunterricht – Voraussetzungen, Lerngelegenheiten und Ziele am sogenannten dritten Ort. Einführung in den Themenschwerpunkt
No full textDass die neuen Bildungsstandards für die 1. Fremdsprache eine „plurilinguale und interkulturelle Diskurskompetenz“ (KMK 2023: 6) als übergeordnete Zielkompetenz setzen, ist durchaus bemerkenswert: erstens, weil erstmals in der Geschichte der Fachpräambeln für den fremdsprachlichen Unterricht der Mehrsprachigkeits- und der Kompetenzbegriff eine Verbindung eingehen; zweitens, weil nun auch eine Form von Mehrsprachigkeit adressiert wird, die nicht aus dem Fach und Bildungssystem heraus entsteht. Plurilinguale Kompetenz wird als Lernvoraussetzung gefasst, die aufgrund von „Erfahrungen mit unterschiedlichen Registern, Dialekten, Herkunftssprachen“ (ebd.) bereits vorhanden und durch die im Unterricht vermittelte(n) Fremdsprache(n) noch auszubauen sei. Auf Herkunftssprachen geht das Dokument eingangs unter Bezugnahme auf die „Heterogenität der Schülerinnen und Schüler“ und ihren „sozialen und kulturellen Hintergrund“ (ebd.: 3) ein. Während Heterogenität zunächst noch als Herausforderung für den individuellen Bildungserfolg im Sinne der Standarderreichung anklingt (vgl. ebd.), sind Herkunftssprachen im weiteren Dokument ausschließlich als Ressource markiert (diskursive und kommunikative Mittel, Strategien, Lexikogrammatik, soziolinguistisches und -kulturelles Wissen, vgl. ebd.: 7). Dabei wird herkunftssprachliches Vorwissen meist sprachlich (Standards zu Lesen, Sprechen, Schreiben, Sprachbewusstheit, Sprachlernkompetenz, vgl. ebd.: 12‒16 und 23‒25; Dietrich-Grappin 2024: 83‒86), seltener kulturell gefasst (Standards zu Mediation/Sprachmittlung, interkulturelle Kompetenz, vgl. KMK 2023: 17‒18 und 20‒21). Diese neue bildungspolitische Entwicklung in Deutschland, die ihren Ausgang auf europäischer Ebene nahm (vgl. Council of Europe 2018; Dietrich-Grappin 2024), wirft nicht nur hierzulande die Frage nach dem Verhältnis von Fremdsprachenunterricht (FSU) und Migration auf, der wir im Rahmen des vorgelegten Themenschwerpunkts nachgehen möchten. Im Folgenden stellen wir definitorische Überlegungen zum Schwerpunktthema (Kap. 1) und das Spektrum bisheriger Forschungszugänge vor, das sich in die empirische Kompetenz- und Einstellungsforschung aus der Perspektive der Lernenden (Kap 2), Einstellungsforschung zur Lehrperspektive (Kap. 3) sowie Beiträge zur Weiterentwicklung von Unterrichtsmaterial (Kap. 4) und zur Diskussion von Lern- und Bildungszielen (Kap. 5) gliedert. Die Beiträge dieses Themenhefts sind jeweils einem Forschungszugang zugeordnet und werden am Ende eines Abschnitts vorgestellt
(Meta-)Narrationen – Beschreibend-reflexive Zugänge zu lebensweltlicher Mehrsprachigkeit in der Lehramtsausbildung
No full textObwohl sprachliche Vielfalt in der Schweiz gesetzlich geregelt ist und gefördert wird, funktioniert ein Grossteil der Kantone einsprachig. Auch im schulischen Kontext dominieren nach wie vor monolingual geprägte Normvorstellungen. In diesem Zusammenhang interessiert uns, wie Menschen mit anderen Erstsprachen als Deutsch in biografisch-narrativen Interviews mit Lehramtsstudierenden über mehrsprachiges Aufwachsen in der Deutschschweiz berichten, und wie dieses ko-konstruierte Wissen von den Studierenden in Metatexten reflektiert wird. Mit Bezug auf narrativ-biographische Zugänge, die wir in der soziolinguistischen und diskursorientierten Erzählforschung verorten, ergründen wir zudem, inwiefern narrativ-sprachbiographische Zugänge in der Hochschullehre helfen, monolingual geprägte Normvorstellungen zu hinterfra-gen und Mehrsprachenkompetenz zu normalisieren
The crustal stress field of Germany: a refined prediction
No full textInformation about the absolute stress state in the upper crust plays a crucial role in the planning and execution of, e.g., directional drilling, stimulation and exploitation of geothermal and hydrocarbon reservoirs. Since many of these applications are related to sediments, we present a refined geomechanical–numerical model for Germany with focus on sedimentary basins, able to predict the complete 3D stress tensor. The lateral resolution of the model is 2.5 km, the vertical resolution about 250 m. Our model contains 22 units with focus on the sedimentary layers parameterized with individual rock properties. The model results show an overall good fit with magnitude data of the minimum (Shmin) and maximum horizontal stress (SHmax) that are used for the model calibration. The mean of the absolute stress differences between these calibration data and the model results is 4.6 MPa for Shmin and 6.4 MPa for SHmax. In addition, our predicted stress field shows good agreement to several supplementary in-situ data from the North German Basin, the Upper Rhine Graben and the Molasse Basin
Forest gaps increase true bug diversity by recruiting open land species
No full textForests canopy gaps play an important role in forest ecology by driving the forest mosaic cycle and creating conditions for rapid plant reproduction and growth. The availability of young plants, which represent resources for herbivores, and modified environmental conditions with greater availability of light and higher temperatures, promote the colonization of animals. Remarkably, the role of gaps on insect communities has received little attention and the source of insects colonizing gaps has not been studied comprehensively. Using a replicated full-factorial forest experiment (treatments: Gap; Gap + Deadwood; Deadwood; Control), we show that following gap creation, there is a rapid change in the true bug (Heteroptera) community structure, with an increase in species that are mainly recruited from open lands. Compared with closed-canopy treatments (Deadwood and Control), open canopy treatments (Gap and Gap + Deadwood) promoted an overall increase in species (+ 59.4%, estimated as number of species per plot) and individuals (+ 76.3%) of true bugs, mainly herbivores and species associated to herbaceous vegetation. Community composition also differed among treatments, and all 17 significant indicator species (out of 117 species in total) were associated with the open canopy treatments. Based on insect data collected in grasslands and forests over an 11-year period, we found that the species colonizing experimental gaps had greater body size and a greater preference for open vegetation. Our results indicate that animal communities that assemble following gap creation contain a high proportion of habitat generalists that not occurred in closed forests, contributing significantly to overall diversity in forest mosaics
The sum of its parts: Analysis of federated byzantine agreement systems
No full textFederated Byzantine Agreement Systems (FBASs) are a fascinating new paradigm in the context of consensus protocols. Originally proposed for powering the Stellar payment network, FBASs can instantiate Byzantine quorum systems without requiring out-of-band agreement on a common set of validators; every node is free to decide for itself with whom it requires agreement. Sybil-resistant and yet energy-efficient consensus protocols can therefore be built upon FBASs, and the "decentrality" possible with the FBAS paradigm might be sufficient to reduce the use of environmentally unsustainable proof-of-work protocols. In this paper, we first demonstrate how the robustness of individual FBASs can be determined, by precisely determining their safety and liveness buffers and therefore enabling a comparison with threshold-based quorum systems. Using simulations and example node configuration strategies, we then empirically investigate the hypothesis that while FBASs can be bootstrapped in a bottom-up fashion from individual preferences, strategic considerations should additionally be applied by node operators in order to arrive at FBASs that are robust and amenable to monitoring. Finally, we investigate the reported "open-membership" property of FBASs. We observe that an often small group of nodes is exclusively relevant for determining liveness buffers and prove that membership in this top tier is conditional on the approval by current top tier nodes if maintaining safety is a core requirement
Multicaloric effect in FeRh, exploiting the thermal hysteresis in a multi-stimuli cycle combining pulsed magnetic field and uniaxial load
No full textLarge magnetocaloric effects can be observed in materials with first-order magneto-structural phase transition. However, materials with large thermal hysteresis show a reduced effect in moderate fields (~2 T) because the external field is insufficient to induce a fully reversible transformation. The hysteresis can be overcome or even exploited by applying a second external stimulus. A multi-stimuli test bench has been built to demonstrate the multicaloric effect in FeRh alloy using a pulsed magnetic field up to 9 T and a uniaxial stress of up to 700 MPa. A cyclic multicaloric effect of ±2.5 K could be observed for a sequential application of a pulsed field of 3 T and a uniaxial stress of 700 MPa. The interplay among external field strength, thermal hysteresis, and the transition width enables the use of pulsed magnetic fields and allows a decoupling of the applied magnetic field and the heat transfer process in the multi-stimuli cycle
Accuracy Evaluation of 3D Pose Reconstruction Algorithms Through Stereo Camera Information Fusion for Physical Exercises with MediaPipe Pose
No full textIn recent years, significant research has been conducted on video-based human pose estimation (HPE). While monocular two-dimensional (2D) HPE has been shown to achieve high performance, monocular three-dimensional (3D) HPE poses a more challenging problem. However, since human motion happens in a 3D space, 3D HPE offers a more accurate representation of the human, granting increased usability for complex tasks like analysis of physical exercise. We propose a method based on MediaPipe Pose, 2D HPE on stereo cameras and a fusion algorithm without prior stereo calibration to reconstruct 3D poses, combining the advantages of high accuracy in 2D HPE with the increased usability of 3D coordinates. We evaluate this method on a self-recorded database focused on physical exercise to research what accuracy can be achieved and whether this accuracy is sufficient to recognize errors in exercise performance. We find that our method achieves significantly improved performance compared to monocular 3D HPE (median RMSE of 30.1 compared to 56.3, p-value below 10−6) and can show that the performance is sufficient for error recognition
An Accelerated Successive Convex Approximation Scheme With Exact Step Sizes for L1-Regression
No full textWe consider the minimization of ℓ1-regularized least-squares problems. A recent optimization approach uses successive convex approximations with an exact line search, which is highly competitive, especially in sparse problem instances. This work proposes an acceleration scheme for the successive convex approximation technique with a negligible additional computational cost. We demonstrate this scheme by devising three related accelerated algorithms with provable convergence. The first introduces an additional descent step along the past optimization trajectory in the variable update, that is inspired by Nesterov's accelerated gradient method and uses a closed-form step size. The second performs a simultaneous descent step along both the best response and the past trajectory, thereby finding a two-dimensional step size, also in closed-form. The third algorithm combines the previous two approaches. All algorithms are hyperparameter-free. Empirical results confirm that the acceleration approaches improve the convergence rate compared to benchmark algorithms, and that they retain the benefits of successive convex approximation also in non-sparse instances
