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Spatio-temporal resolution studies on a highly compact ultrafast electron diffractometer
(2015)
Time-resolved diffraction with femtosecond electron pulses has become a promising technique to directly provide insights into photo induced primary dynamics at the atomic level in molecules and solids. Ultrashort pulse duration as well as extensive spatial coherence are desired, however, space charge effects complicate the bunching of multiple electrons in a single pulse.Weexperimentally investigate the interplay between spatial and temporal aspects of resolution limits in ultrafast electron diffraction (UED) on our ...
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Coherent acoustic phonons in a coupled hexagonal boron nitride-graphite heterostructure
(2024-02-14)
Femtosecond optically excited coherent acoustic phonon modes (CAPs) are investigated in a free-standing van der Waals heterostructure composed of a 20-nm transparent hexagonal boron nitride (hBN) and a 42-nm opaque graphite layer. Employing ultrafast electron diffraction, which allows for the independent evaluation of strain dynamics in the constituent material layers, three different CAP modes are identified within the bilayer stack after the optical excitation of the graphite layer. An analytical model is used to ...
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Bedingungslose ambulante Erziehungshilfen
(2024-02-12)
„Bedingungslose Jugendhilfe“ ist die Bezeichnung für ein offenes politisches Reform- und sozialpädagogisches Forschungsprogramm, das sich gegen die Stigmatisierung von Nutzer_innen erzieherischer Hilfen stellt. In dem Programm wird der Frage nachgegangen, ob es erstrebenswert und praktisch umsetzbar wäre, wenn die Hilfen zur Erziehung unabhängig vom Vorliegen eines erzieherischen Bedarfs als universale Unterstützungsleistungen für alle Kinder, Jugendlichen und ihre Eltern attraktiv und zugänglich wären. Im vorliegenden ...
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Bedingungslose Kinder- und Jugendhilfe
(2024-02-28)
Die Kinder- und Jugendhilfe gilt als öffentliche Infrastruktur der Erziehung und Bildung. Einer Inanspruchnahme von Hilfen zur Erziehung im Rahmen der KJH geht die Feststellung eines erzieherischen Bedarfs voraus. Demnach steht häufig eine Defizitdiagnose elterlicher Erziehung und Bildung am Beginn einer Hilfe, mit nicht selten stigmatisierender Wirkung. Der vorliegende Schwerpunkt beschäftigt sich mit den Perspektiven einer „Bedingungslosen Kinder- und Jugendhilfe“, womit nach den Möglichkeiten einer breiten und ...
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Predicting Lifetime Suicide Attempts in a Community Sample of Adolescents Using Machine Learning Algorithms
(2023-04-24)
Suicide is a major global health concern and a prominent cause of death in adolescents. Previous research on suicide prediction has mainly focused on clinical or adult samples. To prevent suicides at an early stage, however, it is important to screen for risk factors in a community sample of adolescents. We compared the accuracy of logistic regressions, elastic net regressions, and gradient boosting machines in predicting suicide attempts by 17-year-olds in the Millennium Cohort Study (N = 7,347), combining a large ...
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Perfect apples or sustainable production?—Consumer perspectives from Germany
(2023-08-23)
In recent years, environmental problems, such as resource depletion and biodiversity loss, have come to the forefront of society's attention. Consumption of fruits and vegetables from extensive production systems could decrease food loss and increase biodiversity and more sustainable resource use. However, fruits and vegetables from extensive production systems are not always of perfect external quality, and hence, rejected by consumers. To increase acceptance of imperfect fruits, this study aims to better understand ...
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Bond strength, failure criteria and calculation methods for adhesively bonded timber–concrete composites
(2024-04)
The bond strength of adhesively bonded timber–concrete composites (ATCC) with prefabricated concrete elements is usually described using the shear strength of the timber. This approach, however, often fails to consider the actual failure modes of the bondline and also the interaction between shear stresses and stresses perpendicular to the bondline has not yet been comprehensively understood. To address this limitation, a reliable calculation method is required, where stress determination, failure criterion, and ...
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Fluorescence microscopic investigation of PCE superplasticiser adsorption in calcined clay blended cement
(2024-03-31)
Global efforts to minimise carbon dioxide emissions are also leading to attempts to use calcined clays (CC) as a partial substitute for cement in concrete. While the hydration mechanism of such CC blended cements is now well understood, the range of effective admixtures like polycarboxylate ethers (PCE) is limited. There are PCE types that promise relatively high effectiveness, but the mechanisms of action are not yet sufficiently understood. For a detailed understanding of the adsorption of such PCEs, spatially ...
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Galactosamine and mannosamine are integral parts of bacterial and fungal extracellular polymeric substances
(2024-03-22)
Extracellular polymeric substances (EPS) are produced by microorganisms and interact to form a complex matrix called biofilm. In soils, EPS are important contributors to the microbial necromass and, thus, to soil organic carbon (SOC). Amino sugars (AS) are used as indicators for microbial necromass in soil, although the origin of galactosamine and mannosamine is largely unknown. However, indications exist that they are part of EPS. In this study, two bacteria and two fungi were grown in starch medium either with or ...
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Between Trust and Ambivalence: How Does Trainee Teachers’ Perception of the Relationship With Their Mentors Explain How Trainee Teachers Experience Their Work?
(2023-11-23)
The study aims to identify profiles of trainee teachers in terms of their stress and work experiences and to uncover profile differences in regard to dropout intentions and perceived relationships between trainee teachers and their mentors. Based on data from 1,756 German trainee teachers, three distinct stress and work experience profiles could be identified. Trainee teachers with high levels of stress and negative work experiences exhibit higher dropout intentions and experience their relationship with their mentors ...