TU Dortmund University
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Early career researchers as stakeholders in university decision‐making in Europe: comparative perspectives
No full textThe voices of academics have traditionally been strong in university decision‐making bodies, where they participated in the shared governance of the university. It has been customary for senior academics to be represented in managing bodies and to exercise control over the key areas of strategy, finance, quality assurance, study programs, and/or human resources. With the new public management reforms that have swept through higher education (HE) systems, the power of academics has been reduced, while managerial guidance has increased, alongside the fostering of universities’ institutional autonomy. At the same time, the power of other stakeholders, such as students or industry representatives, has also been increasing as part and parcel of the governance reforms, albeit to different degrees and at different paces across various HE systems. In this context, this article seeks to examine the role that early career researchers (ECRs) play in university decision‐making bodies across different countries as internal stakeholders. The research is based on seven case studies from seven European and East Mediterranean countries drawing on documentary data and 55 semi‐structured interviews with ECRs and 14 managers, carried out in 2023–2024. Following stakeholder categories distinguished on the basis of their legitimacy, urgency, and power, this article investigates the extent to which ECRs perceive their voices to be heard. The findings show variance between the case studies regarding formal representation, with most universities in the study having limited representation of ECRs in university and faculty/school‐level decision‐making bodies. The voices of ECRs, however, are heard in informal ways
Einfluss einer zusätzlichen Torsion auf das Tragverhalten von Spannbetonträgern
No full textDie vorliegende Dissertation beschäftigt sich mit der Erweiterung eines ingenieurmäßigen Bemessungsmodells zur genaueren Ermittlung der Querkrafttragfähigkeit von Spannbetonträgern mit Plattenbalkenquerschnitten, insbesondere bei gleichzeitiger Beanspruchung durch Biegung (M), Querkraft (V) und Torsion (T). Im Fokus steht die Verifikation des erweiterten Druckbogenmodells (EDBM) unter der kombinierten Beanspruchung mit zusätzlicher Torsion, das gegenüber konventionellen Modellen Tragreserven berücksichtigt, die in der bisherigen Normung unzureichend erfasst worden sind.
Im Rahmen eines umfangreichen experimentellen Versuchsprogramms, durchgeführt an der TU Dortmund im Auftrag der Bundesanstalt für Straßenwesen (BASt), wurden in Kooperation mit der RWTH Aachen und TU München Großversuche an vorgespannten Plattenbalkenträgern als Einfeldträger mit Kragarm durchgeführt, die typische Schubschlankheiten und Belastungszustände von Bestandsbrücken repräsentieren. Mit den Abmessungen von 8,25 m im Feld und 2 m am Kragarm weisen die Versuchsträger ein Alleinstellungsmerkmal für Versuchsträger unter der kombinierten Beanspruchung auf. Der besondere Fokus lag dabei auf der Untersuchung der Interaktion der Schnittgrößen M+V+T in der Biegedruckzone. Es zeigte sich, dass insbesondere die Mitwirkung der Gurtplatte, die normalerweise in der Torsionsbemessung vernachlässigt wird, signifikant zur Tragfähigkeit beitragen kann.
Zur Verifikation der Versuchsergebnisse wurden nichtlineare numerische Analysen mittels der Finite-Elemente-Methode (FEM) durchgeführt. Diese erlaubten nicht nur eine wirklichkeitsnahe Abbildung der Versuchsergebnisse, sondern auch die Durchführung parametergestützter Studien zur Bestimmung einzelner Einflussgrößen, wie etwa Vorspannungsgrad, Gurtbreite und Torsionsbewehrung.
Die Dissertation formuliert drei zentrale Forschungsfragen, die sich mit der Aktivierung zusätzlicher Tragreserven, der Eignung der normativen Interaktionsbedingung und der Anwendbarkeit des EDBM unter M+V+T-Beanspruchung befassen. Auf alle Fragen konnten gesicherte Antworten gegeben werden. Damit leistet die Arbeit einen bedeutenden Beitrag zur Nachrechnung und Ertüchtigung bestehender Spannbetonbrücken und bietet eine fundierte Grundlage für zukünftige Anpassungen der Nachrechnungsrichtlinie
Intersectionality at German universities: empowering teaching staff as change agents with higher education didactic workshops
No full textThe increasing diversity at German universities has been accompanied by the demand to widen participation among all groups of students. This challenges higher education teaching, requiring learning environments that acknowledge diverse experiences and needs. While diversity‐sensitive approaches have been the dominant response, they often address single diversity dimensions in isolation, neglecting intersectional interdependencies and structural power relations. An intersectional perspective, however, shifts the focus to power dynamics, knowledge production, and inclusive educational practices. This article argues that such an approach has a good potential to enable lecturers and students to become change agents by fostering critical thinking, reflective agency, and ethical commitment to dismantling systemic inequalities. This is particularly challenging in the German higher education system, where critical, antidiscriminatory pedagogical perspectives are mostly limited to certain disciplines. At the same time, the teaching staff enjoy extensive teaching autonomy, which provides them with freedom for individual engagement in this area. Therefore, implementing intersectional approaches in teaching requires targeted educational interventions that support teaching staff. Building on the concept of intersectional pedagogy, we introduce a case study of a higher education didactic workshop that was designed to raise awareness of intersectional perspectives in teaching. The findings highlight the potential of such workshops to influence teaching practices and promote the engagement of disciplinary teaching communities with intersectionality. This article concludes by discussing the implications for further developing workshop concepts and empowering teaching staff and students as agents of change within the German higher education system
Exploring nonlinear dynamics in periodically driven time crystal from synchronization to chaotic motion
No full textThe coupled electron-nuclear spin system in an InGaAs semiconductor as testbed of nonlinear dynamics can develop auto-oscillations, resembling time-crystalline behavior, when continuously excited by a circularly polarized laser. We expose this system to deviations from continuous driving by periodic modulation of the excitation polarization, revealing a plethora of nonlinear phenomena that depend on modulation frequency and depth. We find ranges in which the system’s oscillations are entrained with the modulation frequency. The width of these ranges depends on the polarization modulation depth, resulting in an Arnold tongue pattern. Outside the tongue, the system shows a variety of fractional subharmonic responses connected through bifurcation jets when varying the modulation frequency. Here, each branch in the frequency spectrum forms a devil’s staircase. When an entrainment range is approached by going through an increasing order of bifurcations, chaotic behavior emerges. These findings can be described by an advanced model of the periodically pumped electron-nuclear spin system. We discuss the connection of the obtained results to different phases of time matter
The effect of quantum confinement on the spin properties of lead halide perovskites probed by resonant Raman spectroscopy
No full textLead halide perovskites have emerged as exceptional semiconductor materials for photovoltaic and optoelectronic applications, offering easy tunability and lower production costs than conventional semiconductors. Their band gap energy can be adjusted through compositional changes, particularly by modifying the halide content, and through quantum confinement in low-dimensional systems. While the effects of com- position and dimensionality on optical properties are well established, their influence on spin properties is far from being well understood. In this work, the technique of spin-flip Raman spectroscopy is employed to investigate three-, two-, and zero-dimensional lead halide perovskites, focusing on a key band structure parameter defining the coupling of spins to external magnetic fields: the Landé -factor. In particular, the impact of quantum confinement on the carrier -factor is examined in Ruddlesdon-Popper type two- dimensional perovskites and zero-dimensional CsPbBr3 perovskite nanocrystals. The dependence of their -factors on the effective band gap energy is compared to the universal dependence of the electron and hole -factors in three-dimensional lead halide perovskites. This work reveals that while the general trend of both electron and hole -factors follows the bulk dependence, significant deviations in their absolute values occur in two- and zero-dimensional lead halide perovskites, highlighting the pronounced impact of quantum confinement on spin properties. From a technological perspective, it is particularly interesting that the -factor can be engineered by adjusting the number of inorganic layers in 2D perovskites or the size of the nanocrystals. Spin-flip Raman spectroscopy also reveals the domain structure of a bulk MAPbI3 single crystal by identifying the presence of domains with different crystal orientations through the -factor anisotropy. Furthermore, rare double spin-flip processes involving two electrons or two holes are detected. Next to spin-flip processes, confined acoustic phonon modes are discovered in the Raman spectra of CsPbBr3 nanocrystals. A comparison of experimental results and density functional theory calculations enable the identification of these phonon modes and offers a complementary optical tool to probe structural properties such as the shape, structural phase, and size of the nanocrystals that are, in turn, key to understanding spin interactions.Blei-Halogen-Perowskite haben sich als herausragende Halbleitermaterialien für Photovoltaik- und Optoelektronik-Anwendungen etabliert, da sie im Vergleich zu konventionellen Halbleitern eine ein- fache Anpassbarkeit und geringere Produktionskosten bieten. Ihre Bandlückenenergie kann durch Kompositionsänderungen, insbesondere durch Modifikation des Halogens, und durch quantenmechanische Einschränkung in niedrigdimensionalen Systemen angepasst werden. Während die Auswirkungen der Zusammensetzung und Dimensionalität auf die optischen Eigenschaften weitestgehend bekannt sind, ist ihr Einfluss auf die Spin-Eigenschaften nicht vollständig verstanden. In dieser Arbeit wird die Technik der Spin- Flip-Raman-Spektroskopie verwendet, um drei-, zwei- und null-dimensionale Blei-Halogen-Perowskite zu untersuchen, wobei ein wichtiger Bandstrukturparameter im Fokus steht, der die Kopplung der Spins an äußere Magnetfelder beschreibt: der Landé -Faktor. Besonders wird der Einfluss der quantenmechanischen Einschränkung auf den -Faktor der Ladungsträger in zwei-dimensionalen Ruddlesdon-Popper Perowskiten und null-dimensionalen CsPbBr3-Perowskit-Nanokristallen untersucht. Die Abhängigkeit ihrer -Faktoren von der effektiven Bandlückenenergie wird mit der universellen Abhängigkeit der -Faktoren von Elektronen und Löchern in dreidimensionalen Blei-Halogen-Perowskiten verglichen. Diese Arbeit zeigt, dass, obwohl der allgemeine Trend der -Faktoren für Elektronen und Löcher der Bulk- Abhängigkeit folgt, signifikante Abweichungen in ihren absoluten Werten in zwei- und null-dimensionalen Blei-Halogen-Perowskiten auftreten, was den starken Einfluss der quantenmechanische Einschränkung auf die Spin-Eigenschaften verdeutlicht. Aus technologischer Sicht ist es besonders interessant, dass der -Faktor durch Anpassung der Anzahl der anorganischen Schichten in 2D-Perowskiten oder der Größe der Nanokristalle gezielt eingestellt werden kann. Des Weiteren wird Spin-Flip-Raman-Spektroskopie verwendet um die strukturelle Domänenstruktur eines MAPbI3-Einkristalls zu untersuchen und anhand einer -Faktor-Anisotropie Bereiche mit unterschiedlichen Kristallorientierungen zu identifizieren. Darüber hinaus werden seltene Doppel-Spin-Flip-Prozesse beobachtet, in denen zwei Elektronen oder zwei Löcher involviert sind. Neben Spin-Flip-Prozessen werden in den Raman-Spektren von CsPbBr3-Nanokristallen eingeschränkte akustische Phonon-Moden entdeckt. Ein Vergleich der experimentellen Ergebnisse mit Dichtefunktional-Berechnungen ermöglicht die Identifikation dieser Phonon-Moden und bietet ein ergän- zendes optisches Werkzeug zur Untersuchung der Form, strukturellen Phase und Größe der Nanokristalle, die wiederum entscheidend sind, um Spin-Wechselwirkungen zu verstehen
Constraints on CP violating Yukawa couplings in Standard Model Effective Field Theory
No full textThis thesis explores the constraints on CP-violating Yukawa couplings within the framework of Standard Model Effective Field Theory (SMEFT). In the Standard Model of particle physics (SM) such couplings do not exist but are motivated by the baryon asymmetry of the universe (BAU).
Higher-dimensional operators of SMEFT induce deviations of the SM Yukawa interactions. We present their leading-order contributions to the fundamental electric dipole moments (EDM) of the SM fermions and the effective interactions with the Higgs boson through the derivation of
Wilson coefficients (WC). A comprehensive global analysis is performed with the tool GAMBIT, combining EDM experimental limits with data from the Large Hadron Collider (LHC) to extract constraints on the CP-violating phases of both light and heavy fermion Yukawa couplings.
Up to six WCs are scanned simultaneously. For the calculation of collider observables, we use HiggsSignals and HiggsBounds interfaced with GAMBIT while we use self-written code for the calculation of log-likelihoods for the EDMs. Due to the differing dependencies of the
observables on the WCs non-trivial correlations between the EDM and the LHC constraints are found
Ultrafast unidirectional spin Hall magnetoresistance driven by terahertz light field
No full textThe ultrafast control of magnetisation states in magnetically ordered systems poses significant technological challenges yet is vital for the development of memory devices that operate at picosecond timescales or terahertz (THz) frequencies. Despite considerable efforts achieving convenient ultrafast readout of magnetic states remains an area of active investigation. For practical applications, energy-efficient and cost-effective electrical detection is highly desirable. In this context, unidirectional spin-Hall magnetoresistance (USMR) has been proposed as a straightforward two-terminal geometry for the electrical detection of magnetisation states in magnetic heterostructures. In this work, we demonstrate that USMR is effective at THz frequencies, enabling picosecond time readouts initiated by light fields. We observe ultrafast USMR in various ferromagnet/heavy metal thin film heterostructures via THz second-harmonic generation. Our findings, along with temperature-dependent measurements of USMR, reveal a substantial contribution from electron-magnon spin-flip scattering, highlighting the potential for all-electrical detection of THz magnon modes