http://hdl.handle.net/10900/42133 2026-07-22T20:00:24Z http://hdl.handle.net/10900/181834 Neue Wege zur Untersuchung der THz-Strahlungsemission intrinsischer Josephson-Kontakte in Bi2Sr2CaCu2O8+δ und von Quantenkaskadenlasern Dorsch, Eric Innerhalb des Frequenzbereichs der sogenannten THz-L¨ucke finden sich unter ande- rem die zwei THz-Emitter-Klassen des Quantenkaskadenlasers (QCL) und des Kuprat- Supraleiters Bi2Sr2CaCu2O8+δ (BSCCO). Zur Generierung elektromagnetischer Strah- lung unterscheiden sich beide in ihrer Funktionsweise fundamental: inmitten einer QCL- Kavit¨at beteiligen sich einzelne Elektronen an den Intersubband- ¨Uberg¨angen, die zur Emission beitragen; wohingegen der intrinsische Josephson-Effekt auf dem koh¨arenten Transport von Cooper-Paaren basiert und in einer BSCCO-Kavit¨at die Entstehung von komplexen Vortex-Dynamiken zur Folge hat und damit verkn¨upft, spezielle Moden- Konfigurationen erm¨oglicht. Die genaue r¨aumliche Verteilung der emittierten THz-Strahlung durch den r¨aumlich komplexen Stromfluss innerhalb des BSCCO-Emitters ist noch nicht gut verstanden. Das erste Ziel der vorliegenden Arbeit beinhaltete die spektrale Aufl¨osung und Ana- lyse der emittierten THz-Strahlung eines Quantenkaskadenlasers wie auch eines THz- Emitters aus BSCCO - in Verbindung mit hoch-angeregten Rydberg-Atomen, die hier- mit einen neuartigen Detektor f¨ur THz-Strahlung realisieren w¨urden. Zum Zweiten sollten sowohl das Nahfeld als auch das Fernfeld des THz-Wechselfeldes mithilfe von Josephson-Kontakten aus dem Hochtemperatursupraleiter YBa2Cu3O7 (YBCO) im Volumen oberhalb einer emittierenden BSCCO-Kavit¨at r¨aumlich aufgel¨ost werden, um offene Fragen bzgl. der r¨aumlichen Verteilung des elek- tromagnetischen Feldes in der N¨ahe der BSCCO-Emitter zu untersuchen. Drittens sollten umfassende Fourier-Analysen in speziellen elektrischen Konfigurationen nah-gekoppelter BSCCO-Kavit¨aten abschließend die Beobachtung von subharmonischen Signal-Anteilen erm¨oglichen. Dies k¨onnte interessant sein, um die emit- tierte THz-Strahlung von (leichter zug¨anglichen) h¨oheren Frequenzen in einen (schwerer zug¨anglichen) niederfrequenten Frequenzbereich zu transferieren. Bezogen auf den Versuch der Einkopplung eines THz-Wechselfeldes in einen atomaren Rydberg-Zustand, gelang es w¨ahrend der Experimentierphase, einen QCL zuverl¨assig im Strom-gepulsten Betrieb hinweg zu betreiben und zeitlich lange Frequenz-Scans zu reali- sieren. Mit kompakten Detektor-Klassen wie dem pyroelektrischen Detektor im Verbund mit Lock-In-Verfahren, konnte eine wesentlich leichterer Handhabung und Justage der THz-Wechselfelder erreicht werden. Im Bild des differentiellen Widerstands bestrahlter IV-Kennlinien von YBCO-Josephson- Kontakten, erreichte die Wahl geeigneter mathematischer Parameter eine zweidimensio- nale Aufl¨osung des Fernfeldes einer vermessenen BSCCO-Probe (Proof of Concept). Fourier-Laufzeit-Analysen erm¨oglichten die Korrelation m¨oglicher Nebenfrequenzen in bolometrisch-interferometrisch erhaltenen Frequenzspektren zweier nah-gekoppelter (¨uber eine Spaltbreite von 500 nm) BSCCO-Kavit¨aten einer elektrischen aktiv/passiv- Konstellation. Bestimmte Strom-und Spannungseinstellungen scheinen potentiell sub- harmonische Signalanteile und wom¨ogliche Vielfache jener, beg¨unstigt zu haben. 2026-07-22T00:00:00Z http://hdl.handle.net/10900/181827 YBa2Cu3O7 Josephson Nano Devices Fabricated by Focused Helium Ion Beam Irradiation Schmid, Christoph Superconducting electronics enables quantum-accurate metrology, ultrasensitive magnetometry, and terahertz (THz) devices. The established Nb technologies are constrained by a low operating temperature and a limited high-field/high-frequency performance. In the framework of this dissertation, a fabrication platform for high-transition-temperature superconducting nano-devices based on epitaxially grown YBa_2Cu_3O_7 (YBCO) films patterned by focused helium-ion-beam (He-FIB) irradiation is described. He-FIB irradiation locally displaces oxygen atoms in YBCO and allows to continuously tune the superconducting properties without material removal, enabling direct-write creation of weak links, resistive regions, and insulating barriers with nanometer-scale precision. This thesis accumulates four publications that together provide a deeper insight into the well-established barrier-type Josephson junction and a spectrum of applications. Single JJs and JJ arrays embedded in antenna structures are presented to realize a THz detector, which could lay the foundation of a high-transition-temperature voltage standard. Furthermore, a superconducting diode with record figures of merit is presented. To broaden the range of possible applications, He-FIB induced YBCO resistors are presented, which allow for the fabrication of nano constriction-type Josephson junctions on the resolution limit of the He-FIB. These ultra-small junctions are investigated in SQUIDs and THz antennas to demonstrate their feasibility. 2026-07-22T00:00:00Z http://hdl.handle.net/10900/181806 Biochemical Reconstitution of the Budding Yeast Meiotic Chromosomal Axis Chen, Linda Dissertation gesperrt bis zum 30.06.2028!; The production of gametes requires a specialised cell division to divide the genome, thus enabling the faithful transmission of genetic material from one generation to the next. This process is known as meiosis, the hallmark of which is meiotic recombination. A striking feature here is the physical exchange of DNA between homologous chromosomes, also known as crossing over, which is essential for ensuring that chromosomes segregate accurately. Moreover, genetic exchange between homologous chromosomes promotes species diversity – contributing to the overall evolution of Eukarya. It begins with the highly regulated formation of double-stranded DNA breaks (DSBs) throughout the genome, which take place within the context of a DNA-loop and proteinaceous axis structure. Crucially, a sub-set of these breaks must be repaired using the homologous chromosome as a template, as this is a pre-requisite for crossover formation. In Saccharomyces cerevisiae, this inter-homolog biased repair is ensured by a meiosis-specific protein complex: Hop1-Red1-Mek1 (HRM). Hop1 and Red1 form the structural basis of the proteinaceous axis, whereas Mek1 kinase is involved in both mediating inter-homolog bias as well as meiotic progression. Considerable in vivo efforts have been conducted to understand the functions of these proteins in meiosis, however there is limited knowledge about how HRM form a complex. Moreover, the assembly mechanism of the budding yeast axis itself is still poorly understood on the molecular stage. To extend our understanding of the molecular determinants required for the assembly of the HRM complex, I utilised an in vitro structural biochemistry approach. I investigated how the HRM complex is established and activated by designing a series of protein truncations and mutants, and revealed previously unrecognised roles for the N-terminus of Red1 in its interaction with Hop1 and Mek1. To characterise the enzymatic properties of Mek1, I recapitulated the meiotic conditions required for kinase activation in vitro. Finally, I explored the potential roles that the axis plays in the recruitment of key DSB machinery and cross-over formation proteins. Through this work, I propose a novel model whereby the HRM complex is potentially assembled and primed temporally early on to mediate inter-homolog bias at the onset of meiotic DSBs. The results presented here address the long-standing question regarding how Mek1 is recruited to axial sites and provide insight into the importance of the meiotic chromosome axis in mediating multiple branches of meiotic recombination in budding yeast. 2028-06-30T00:00:00Z http://hdl.handle.net/10900/181805 Narrative Comprehension and Inference Processes Across the Lifespan: The Impact of Stress and Aging Varkentin, Ekaterina In today’s media-saturated environment, defined by widespread smartphone use and accelerating globalization, the delivery of content through visual narratives has become the prevailing norm. Individuals encounter narratives in nearly all areas of daily life, from professional settings to recreational activities, whether reading the morning newspaper, following a work presentation, or interpreting airplane safety instructions. The ability to comprehend narratives is a fundamental cognitive skill across the lifespan and has therefore long been a central focus of research. Despite the extensive body of work, a limited understanding remains of how pervasive life factors, such as stress, health conditions, and lifestyle-related influences, shape narrative comprehension. As these factors become increasingly prevalent in contemporary society, understanding how individuals process and navigate narratives is not only theoretically important but also of growing societal relevance. Thus, the central question of this dissertation is how narrative comprehension and inference generation are shaped by long-term and short-term influences, as well as by factors such as age and education. Across three empirical chapters, the studies presented in this dissertation provide insights into the mechanisms underlying narrative comprehension and examine how these mechanisms are modulated by these diverse influences. A central focus throughout is the role of aging. After introducing the theoretical overview of this dissertation, Chapter 2 investigates the role of long-term protective factors (physical and mental activity, social connectedness) and risk factors (depression, anxiety, chronic pain, long-term stress, poor sleep) as well as the role of age, education, and modality (textual vs. pictorial) for narrative comprehension. The results indicated a general advantage for pictorial over textual narratives, although this effect decreased with age. Narrative comprehension was largely resilient to age, education, and long-term protective and risk factors. Performance correlated with memory but not with other cognitive abilities, highlighting its specificity within the broader cognitive domain. Chapter 3 examines the effects of acute, short-term stress on narrative comprehension in different age groups. The results revealed that acute stress negatively affected visual narrative comprehension in younger adults, whereas the comprehension performance of older adults remained stable. Similarly, younger adults reported lower confidence in their responses under stress, while older adults’ confidence levels were unaffected. These findings highlight the interplay between visual narrative comprehension, stress, and aging, suggesting that with advancing age and experience, individuals may develop more differentiated event schemas that render their comprehension processes more resilient to acute stress. Chapter 4 examines how acute stress affects the generative processes involved in narrative comprehension, thereby offering a more comprehensive understanding of how stress shapes this cognitive function. The findings revealed that inference generation, in contrast to inference recognition, remained stable across both age and education groups and was unaffected by acute stress. These results highlight the resilience of generative and creative cognitive processes, even under challenging conditions, and suggest that the ability to construct coherent narrative connections may be particularly robust to short-term stress. Overall, these findings support a view of narrative comprehension as both dynamic and resilient. On the one hand, comprehension appears to be fundamentally stable across the lifespan and largely resistant to chronic influences, indicating that well-integrated cognitive systems help maintain coherent meaning even in the face of age-related changes. On the other hand, comprehension is sensitive to short-term situational factors in specific ways. For instance, inference recognition processes are affected by acute stress in younger adults, whereas inference generation remains largely stable across all age groups under stress. This distinction suggests that different cognitive mechanisms support different components of narrative comprehension. Recognition relies more on immediate retrieval and evaluative processes, making it more vulnerable to external influences, while generative processes involve constructive integration and creative elaboration, rendering them more resilient even under challenging conditions. From an applied standpoint, the findings endorse the use of pictorial materials in diverse contexts and provide important insights for fostering age-inclusive participation and for guiding educational systems. 2026-07-22T00:00:00Z