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Physical Review Research / Wave packet dynamics in parabolic optical lattices : from Bloch oscillations to long-range dynamical tunneling
No full textWe investigate the dynamics of wave packets in a parabolic optical lattice formed by combining an optical lattice with a global parabolic trap. Our study examines the phase space representation of the system's eigenstates by comparing them to the classical phase space of a pendulum, to which the system effectively maps. The analysis reveals that quantum states can exhibit mixed dynamics by straddling the separatrix. A key finding is that the dynamics around the separatrix enables the controlled creation of highly nonclassical states, distinguishing them from the classical oscillatory or rotational dynamics of the pendulum. By considering a finite momentum of the initial wave packet, we demonstrate various dynamical regimes. Furthermore, a slight energy mismatch between nearly degenerate states localized at opposite turning points of the trap potential results in controlled long-range dynamical tunneling. These results can be interpreted as quantum beating between a clockwise rotating and a counterclockwise rotating pendulum.Usman Ali, Martin Holthaus, and Torsten Meie
Satzung zur Änderung der Besonderen Bestimmungen der Prüfungsordnung für den Bachelorstudiengang Lehramt an Berufskollegs mit dem Unterrichtsfach Englisch an der Universität Paderborn : vom 15. Juli 2025
Get PDFUnderstanding the impact of gender and migration on high-ability students’ behavior: Exploring behavioral differences in business, law, and engineering students throughout their academic careers
Get PDFUsing a large sample with detailed information on 32,296 high-ability business, law, and engineering students, we explore gender- and migration-related differences in behaviour to better understand the persistent under-representation of women and migrants in the executive suites of German companies. Since in this homogenous group of ‘highachievers‘, students are quite similar in their intellectual abilities, observable differences in behaviour can be mainly attributed to differences in gender- and migration-related preference patterns. We find that irrespective of migration background, men are more likely to pursue activities that increase their human capital, such as completing a doctorate, while women tend to engage in lower-level temporary jobs and complete their studies faster. In contrast, in this selective sample of high-ability students, migration background has a marginal effect on students’ behaviour only. Perhaps most surprising, we find that the behaviour of women with a migration background – who potentially face ‘double discrimination‘ – is not different from that of their male peers.Lisa Beck-Werz, Bernd Frick, Thomas Fritz and Fabian Lensin
Physical Review Research / Spectral and temporal properties of type-II parametric down-conversion : The impact of losses during state generation
No full textIn this paper, we theoretically study the spectral and temporal properties of pulsed spontaneous parametric down-conversion (SPDC) generated in lossy waveguides. Our theoretical approach is based on the formalism of Gaussian states and the Langevin equation, which is elaborated for weak parametric down-conversion and photon-number-unresolved click detection. Using the example of frequency-degenerate type-II SPDC generated under the pump-idler group-velocity-matching condition, we show how the joint-spectral intensity, mode structure, normalized second-order correlation function, and Hong-Ou-Mandel interference pattern depend on internal losses of the SPDC process. We found that the joint-spectral intensity is almost insensitive to internal losses, while the second-order correlation function shows a strong dependence on them, being different for the signal and idler beams in the presence of internal losses. Based on the sensitivity of the normalized second-order correlation function, we show how its measurement can be used to experimentally determine internal losses.Denis A. Kopylov, Michael Stefszky, Torsten Meier, Christine Silberhorn, and Polina R. Sharapov
Gleichstellungsplan der Fakultät für Kulturwissenschaften der Universität Paderborn : vom 22. September 2025
Get PDFQuantenchemische Rechnungen und Synthesen stickstoffreicher Kohlenstoffnitride
Get PDFDiese Dissertation befasst sich mit theoretischen und experimentellen Untersuchungen zu Kohlenstoffnitriden, einer umfangreichen und vielseitigen Materialklasse basierend auf den beiden Elementen Kohlenstoff und Stickstoff. Aufgrund ihrer katalytischen Eigenschaften, vergleichsweise einfachen Synthesewegen und des Verzichts auf seltene oder toxische Metalle gelten sie als vielversprechend für nachhaltige Anwendungen wie Photokatalyse, Energiespeicherung, Gasadsorption und CO2-Reduktion.Fokus dieser Arbeit bilden Materialien mit extrem hohem Stickstoffanteil, insbesondere CN2. Durch eine systematische, mehrstufige Struktursuche wurden unter Verwendung quantenchemischer Methoden mehrere thermodynamisch stabile polymorphe CN2-Strukturen identifiziert und hinsichtlich ihrer elektronischen Eigenschaften und thermischen Stabilität analysiert. Dabei ließen sich einige Strukturen aufzeigen, welche sowohl dynamisch als auch kinetisch stabil sowie vielversprechende elektronische Eigenschaften für, zum Beispiel, photokatalytische Anwendungen mitbringen. Eine dieser Strukturen wurde anschließend erfolgreich synthetisiert und mithilfe verschiedenster analytischer Methoden charakterisiert und analysiert. Dabei konnten zwei Synthesewege mit unterschiedlichen Vor- und Nachteilen etabliert werden. Das synthetisierte azo-verbrückte Triazol (ABT) zeigt photokatalytische Aktivität, bietet eine elektrochemische Kapazität, und besitzt zudem das Potential durch gezielte strukturelle Modifikation die katalytische Aktivität zu steigern. In den folgenden theoretischen Teilprojekten wurden spezifische Fragestellungen zu CN-Materialien in Kooperation mit experimentellen Arbeitsgruppen untersucht. Darunter ist zum einen das Adsorptionsverhalten von H+ und NH4+ in Na- und H-poly(heptazinimide) (PHI) Systemen, welches, wie gezeigt werden konnte, durch lichtinduzierte Aufladung maßgeblich beeinflusst wird. Des Weiteren wurde der Einfluss von terminalen Gruppen auf die Elektronenstruktur und Adsorptionsenergie in donor-akzeptor-ähnlichen PHI-Systemen, im Hinblick auf die Adsorptionsenergie von O2 und letztlich die photokatalytische Aktivität zur H2O2 Produktion untersucht. Außerdem wurde das Benetzungsverhalten sowie die spezifische Interaktion mit Wasser von C1N1 (Sub)Nanoporen modelliert und analysiert. In allen Fällen konnte die theoretische Modellierung experimentelle Befunde bestätigen, differenzieren und durch mechanistische Einblicke wesentlich erweitern. Die Ergebnisse dieser Arbeit tragen dazu bei, das Struktur-Eigenschafts-Verhältnis stickstoffreicher Kohlenstoffnitride besser zu verstehen und liefern neue Impulse für deren gezielte Weiterentwicklung und Anwendung.This dissertation deals with theoretical and experimental investigations of carbon nitrides, a broad and versatile class of materials based on carbon and nitrogen. Due to their catalytic properties, comparatively simple synthesis routes, and the avoidance of rare or toxic metals, they are considered promising for sustainable applications such as photocatalysis, energy storage, gas adsorption, and CO2 reduction. The focus of this work is on materials with an extremely high nitrogen content, particularly CN2 . Through a systematic, multi-step structure search using quantum chemical methods, several thermodynamically stable polymorphic CN2 structures were identified and analyzed with regard to their electronic properties and thermal stability. Some of these structures were found to be both dynamically and kinetically stable and to exhibit promising electronic properties, for example, for photocatalytic applications. One of these structures was subsequently synthesized and characterized using various analytical methods. Two synthesis routes with different advantages and disadvantages were established. The synthesized azo-bridged triazole (ABT) shows photocatalytic activity and provides electrochemical capacity, and also possesses the potential to enhance its catalytic activity through targeted structural modifications. In the following theoretical subprojects, specific research questions regarding CN materials were investigated in collaboration with experimental research groups. These include the adsorption behavior of H+ and NH4+ in Na- and H-PHI systems, which, as shown, is significantly influenced by photocharging. Furthermore, the influence of terminal groups on the electronic structure and adsorption energy in donor-acceptor-like PHI systems was studied, specifically with regard to the adsorption energy of O2 and ultimately the photocatalytic activity for H2O2 production. In addition, the wettability and specific interaction of water of C1N1 (sub)nanopores was studied. In all cases, theoretical modeling was able to confirm, differentiate, and substantially deepen experimental findings through mechanistic insights. The results of this work contribute to a better understanding of the structure–property relationships of nitrogen-rich carbon nitrides and provide new impulses for their targeted development and application.Karlo Julius Robert Nolkemper ; 1. Gutachter: Prof. Dr. Thomas D. Kühne, 2. Gutachter: Jun. Prof. Dr. Lopez SalasTag der Verteidigung: 30.09.2025Universität Paderborn, Dissertation, 202
Enhancing students’ skill and will for academic writing : evaluation of a writing intervention in higher education
Get PDFAcademic writing poses high demands on students’ skills as well as on their will when it comes to regulating their writing activities. Writing centers offer manifold interventions that ought to help students dealing with those demands. Evaluation of these interventions are rather scarce and little is known about their effects. In our study, we focused on three aspects that are closely related to writing performance: self-efficacy for self-regulation of academic writing, implicit theories about writing ability, and metacognitive strategy knowledge about writing. We investigated the variables in a pretest-posttest design including three points of measurement to track down the effects of a standardized intervention that is regularly offered by a writing center at a midsized German university. We hypothesized significant positive effects after workshop attendance. Results indicate that students perceive themselves as being more able to regulate their writing activities after taking part in the intervention. Furthermore, their theories about writing ability became more malleable. Students’ metacognitive strategy knowledge did not significantly change after the intervention. Based on the results, we outline suggestions for the evaluation of writing center interventions in higher education.Christiane Jöhren (TU Dortmund University, Germany), Katrin B. Klingsieck (University of Paderborn, Germany), Ingrid Scharlau (University of Paderborn, Germany
Young, Male, Experienced: What factors drive overconfidence? : Empirical evidence from marathon running
Get PDFThe effects of overconfidence have substantial and far-reaching economic as well as social implications. A large body of literature has confirmed that overestimating one's own abilities hinders accurate decision-making and considerably influences the quality of decisions, thus leading to substantial negative consequences. In our study, we explore how gender, age, and prior experience affect the occurrence of overconfidence. We investigate these factors within the context of marathon races by analyzing the slowdown of runners, which is seen as a direct and inevitable reaction to the overestimation of one’s initial race pace. We confirm the large body of previous studies by revealing a clear gender gap: men have a stronger tendency toward overconfidence. Furthermore, we show that age correlates with overconfidence, with particularly young and old individuals overestimating their potential performance. Moreover, the present study illustrates that the tendency for overconfident behavior increases with experience.Lisa Beck-Wer
Effects of (meta)cognitive strategy instruction on the development of self-efficacy for self-regulation in academic writing
Get PDFAcademic writing is a complex task and writers need to be adequately supported to master its demands. Previous studies have shown that strategy instruction supports writers and influences writing performance. This paper investigates the development of students’ self efficacy for self-regulation in academic writing (SSAW) in an experimental intervention study. We examined the effects of three strategy instruction treatments in a randomized sample of 128 university students. Selected cognitive and metacognitive strategies were trained. We used latent neighbor change analyses including multiple group comparisons to track down short- and long-term effects among three points of measurement (pre, post, and six-week follow-up). We also accounted for the influence of writing beliefs that were assessed prior to the intervention. Results provide evidence for a beneficial impact of metacognitive strategies in writing instructions.Christiane Jöhren (TU Dortmund University, Germany), Anke Wischgoll (TU Dortmund University, Germany), Katrin B. Klingsieck (University of Paderborn, Germany