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Glial-neuronal interactions affecting larval locomotor patterns in Drosophila melanogaster
No full textDas Nervensystem besteht aus Neuronen, die elektrische Signale leiten, und Gliazellen, die u.a. isolierende oder modulatorische Aufgaben besitzen. In dieser Arbeit wurde die Interaktion beider Zelltypen in der Larve der Fruchtfliege "Drosophila melanogaster" untersucht. Dafür wurden verschiedene Kommunikationswege in der Gliazelle manipuliert und die Effekte auf zwei larvale Fluchtreaktionen wurden analysiert. Rollen reagierte sensibler auf Gliazellmanipulation als rückwärts kriechen. Zudem zeigte sich, dass ephaptische Kopplung – eine unerwünschte neuronale Aktivierung durch fehlende gliale Isolation der neuronalen Axone - im Nerv, nicht im Gehirn, stattfindet. Axone beteiligter sensorischer Neurone gruppieren sich in Nerven und lokalisieren in großen, gemischten Faszikeln. Außerdem beeinflusst der genetische Hintergrund larvales Verhalten von Drosophila und der optogenetische Ionenkanal CsChrimson ist über dem Balancer TM6B nicht stabil inseriert.The nervous system consists of neurons, which conduct electrical signals, and glial cells, which have, among other things, insulating or modulatory functions. In this study, the interaction of both cell types was investigated in the larva of the fruit fly Drosophila melanogaster. For this purpose, different communication pathways in glial cells were manipulated, and the effects on two larval escape responses were analyzed. Rolling reacted more sensitively to glial cell manipulation than backward crawling. Furthermore, it was shown that ephaptic coupling—an unintended neuronal activation caused by absent glial insulation of neuronal axons—occurs in nerves and not within the central brain. In nerves, axons of the involved sensory neurons cluster in groups in large, mixed fascicles. In addition, the genetic background influences larval behavior of Drosophila, and the optogenetic ion channel CsChrimson is not stably inserted over the balancer TM6B
Impact of COVID-19 School Closures on German High-School Graduates' Perceived Stress: A Structural Equation Modeling Study of Personal and Contextual Resources
No full textCOVID-19 school closures forced German high-school graduates (Abitur 2022 cohort) to prepare for their final examinations with lengthy learning times at home. Guided by transactional stress theory, we tested how personal resources—self-regulated learning (SRL) skills and academic self-efficacy—and contextual resources—perceived teacher support and teacher digital competence—jointly predicted perceived stress during exam preparation. A cross-sectional online survey (June–July 2022) yielded complete data from N = 2379 students (68% female; Mage = 18.3). Six latent constructs were measured with 23 items and showed adequate reliability (0.71 ≤ α/ω ≤ 0.89). A six-factor CFA fit the data acceptably (CFI = 0.909, RMSEA = 0.064). The structural equation model (CFI = 0.935, RMSEA = 0.064) explained 35% of the variance in stress and 23% of the variance in SRL—action. Academic self-efficacy (β = −0.31, p < 0.001), perceived support (β = −0.28, p < 0.001), teacher digital competence (β = −0.08, p < 0.001), COVID-19 learning disruptions (β = +0.13, p < 0.001), and gender (male = 0.32 SD lower stress, p < 0.001) had direct effects on stress. SRL—action's direct path was small and non-significant (β = −0.02). Teacher digital competence also reduced stress indirectly through greater perceived support (standardized indirect β = −0.11, p < 0.001). The results highlight self-efficacy and perceived instructional support as the most potent buffers of pandemic-related stress, whereas cancelled lessons added strain. Boosting teachers' digital pedagogical skills has a dual payoff—raising students' sense of support and lowering their stress
Impact of Routine and Selective Preoperative Endoscopic Retrograde Cholangiopancreatography with Stent Placement on Postoperative and Oncologic Outcomes Following Pancreaticoduodenectomy for Pancreatic Ductal Adenocarcinoma
No full textBackground: According to current guidelines, preoperative endoscopic retrograde cholangiopancreatography (ERCP) with biliary stenting (ERCP/stenting) is often necessary in patients with obstructive jaundice due to pancreatic ductal adenocarcinoma (PDAC), including severe jaundice (bilirubin > 250 umol/l), pruritus, cholangitis, cholestatic liver dysfunction, renal failure, severe malnutrition, or delayed surgery for tumors requiring neoadjuvant chemotherapy. We aimed to investigate the impact of preoperative ERCP/stenting on postoperative and long-term outcomes following pancreaticoduodenectomy (PD) for PDAC. Methods: Clinicopathological data of patients who underwent partial/total PD for PDAC between 2012 and 2019 in two hepato-pancreato-biliary centers in Germany and Switzerland were assessed. We compared patients treated with preoperative ERCP/stenting with those directly undergoing surgery according to postoperative morbidity, postoperative mortality, overall survival (OS) and disease-free survival (DFS). Results: During the study period, 192 patients underwent partial/total PD for PDAC. ERCP/stenting was performed in 105 patients, and 87 patients underwent resection without prior intervention. Postoperative 90-day overall morbidity rate (71% vs. 56%, p = 0.029) and superficial surgical site infection (SSI) rate (39% vs. 17%, p < 0.001) were significantly worse following preoperative ERCP/stenting. Major postoperative morbidity rate (18% vs. 21%, p = 0.650), organ/space SSI rate (7% vs. 14%, p = 0.100), and 90-day postoperative mortality rate (4% vs. 2%, p = 0.549) did not significantly differ between the two groups. After excluding 44 patients for whom the indication for ERCP/stenting was not consistent with current guidelines, ERCP/stenting was associated with a higher superficial SSI rate (36% vs. 17%, p = 0.009) and shorter length of stay (12 vs. 16 days, p = 0.004). Median OS (ERCP/stenting: 18 months vs. no ERCP/stenting: 23 months, p = 0.490) and median DFS (ERCP/stenting: 14 months vs. no ERCP/stenting: 18 months, p = 0.645) were independent from the utilization of ERCP/stenting. Conclusions: Preoperative ERCP/stenting in patients with PDAC can be performed without increasing organ/space SSI, major perioperative morbidity, and mortality rates and without worsening oncologic outcomes. However, it is associated with higher superficial SSI rates. If ERCP/stenting is not performed routinely but according to current guidelines, it is also associated with a shorter length of hospital stay. Further refinement of the indications for preoperative ERCP/stenting may reduce superficial SSI rates
Instructional videos on ill-structured mathematical problem-solving processes: The cases of mathematical modeling and proof construction
No full textDie Dissertation befasst sich mit dem mathematischen Modellieren und der Beweiskonstruktion als Problemlöseprozesse und deren Unterstützung durch Erklärvideos. Aufbauend auf dem Forschungsstand zu heuristischen Lösungsbeispielen und didaktischen Prinzipien von Erklärvideos werden in drei Studien Gestaltungskriterien für Erklärvideos zu mathematischen Problemlöseprozessen entwickelt und empirisch untersucht. Die Ergebnisse zeigen, dass Lernende die Videos insbesondere zur Strukturierung eigener Lösungswege als hilfreich empfinden. Elemente wie die Segmentierung entlang von Prozessschritten und Selbsterklärungsaufforderungen fördern dabei prozessbezogenes Wissen. Zudem deuten die Befunde darauf hin, dass Erklärvideos sowohl das Modellieren im schulischen Kontext als auch das Konstruieren von Beweisen im Studium wirksam unterstützen können. Die Arbeit leistet somit einen Beitrag zur Integration von Erklärvideos in die mathematikdidaktische Praxis an Schule und Hochschule.The dissertation deals with mathematical modeling and proof construction as problem-solving processes and their support through instructional videos. Based on the current state of research on heuristic worked examples and principles of instructional video design, design criteria for instructional videos on mathematical problem-solving processes are developed and empirically investigated in three studies. The results show that learners find the videos particularly helpful for structuring their own solution processes. Elements such as segmentation along process steps and self-explanation prompts promote process-related knowledge. In addition, the findings indicate that instructional videos can effectively support both modeling in a school context and proof construction at the undergraduate level. The work thus contributes to the integration of instructional videos into mathematics education at school and university
Interplay of spin–orbit and exchange interaction in a ferromagnet/heavy-metal hybrid system: Ni on W(110)
No full textIn a combined experimental and theoretical study, we investigate the interplay of spin–orbit interaction (SOI) and exchange interaction (XI) in the electronic structure of ultrathin Ni films on W(110). Using spin- and angle-resolved inverse photoemission, we observe that the size of the spin splitting of Ni-related exchange-split states differs for opposite magnetization directions. A quenched spin splitting for one of the magnetization directions reveals a contribution of SOI on an equal footing with XI. Using density-functional theory calculations, we explore the underlying mechanisms responsible for the experimentally observed coupling of SOI and XI. We find that a hybridization between adsorbate and substrate states, along with a high probability density of the respective states at the heavy W nuclei, cause the strong influence of SOI on the Ni-related exchange-split states
Transmigrationsnarrative:Mehrfachmigration und Erinnerungskulturen in der britischen kolonialen Diaspora
No full textThis study explores the potential of transferring the concept of transmigration from the social sciences to anglophone literary and cultural studies to further our understanding of complex forms of mobility (especially multiple migration), translocal identities and their narrativisation. Part 1 explains theoretical foundations regarding transmigration and its relation to diaspora studies in general, spatial theory, transnationalism, globalisation, cosmopolitanism, transculturalism and memory studies. Part 2 is a case study of the Normanist community and its successive 19th-century migrations from the United Kingdom to Canada, Australia and New Zealand, and of the representation of transmigrant identity and memory in literary and nonliterary texts, as well as other forms of cultural expression, from the 19th to the 21st century. This is followed by an outline of further potential case studies and conceptual implications for future work on transmigration in anglophone literary and cultural studies.Die Arbeit untersucht die Übertragbarkeit des sozialwissenschaftlichen Konzepts der Transmigration in die anglistische Literatur- und Kulturwissenschaft als Beitrag zum Verständnis komplexer Formen von Mobilität (hier v.a. Mehrfachmigration), translokaler Identiiäten und deren narrativer Aushandlung. Teil 1 erschließt theoretische Grundlagen zum Transmigrationskonzept und dessen Bezügen zu anderen Bereichen der Migrations- und Diasporaforschung, zur Raumtheorie sowie zu Transnationalismus-, Globalisierungs-, Kosmopolitismus-, Transkulturalismus- und Gedächtnisforschung. Teil 2 ist eine Fallstudie zur Normanist*innengemeinde, die im 19. Jh. von Großbritannien über Kanada und Australien nach Neuseeland auswanderte, sowie zu diesbezüglichen Identitäts- und Erinnerungsdiskursen (19.-21. Jh.) in Literatur sowie anderen Textsorten und kulturellen Ausdrucksformen. Es folgt ein Ausblick auf weitere Fallbeispiele und konzeptuelle Implikationen für künftige anglistische Transmigrationsforschung
Nonrigid motion perception
No full textNichtstarre Bewegung ist ein grundlegender, jedoch untererforschter Aspekt des Sehens. Fluide, Feuer, Rauch, Wolken und Schwärme können sich verformen und ihre Bestandteile austauschen und verletzen so viele Modellannahmen der starren Bewegungswahrnehmung. Diese Dissertation präsentiert einen Stimulus, der einen für nichtstarre Bewegung zuverlässigen Bewegungshinweis isoliert: die Bewegung eines Bewegungsmusters. Drei Studien untersuchten Wahrnehmung, Mechanismus und okulomotorische Interaktion sowie Unterschiede zu Eigen-, biologischer und starrer Bewegung. Die Ergebnisse zeigen, dass die Wahrnehmung der Bewegung eines Bewegungsmusters möglich ist, der zugrunde liegende Mechanismus auf dem Curl des optischen Flusses basiert und ein gesonderter neuronaler Pfad viele der an Bewegungsverarbeitung, Blicksteuerung und visueller Stabilität beteiligte Hirnareale ausschließt.Nonrigid motion is a fundamental yet understudied aspect of vision. Unlike rigid objects, fluids, fire, smoke, clouds, fabrics, and flocks deform and exchange parts over time, violating many assumptions of classic motion-perception models. For this dissertation, a stimulus was developed that isolates one cue that is reliable for nonrigid motion, the movement of a motion pattern. Using this tool, three studies examined perception, mechanism, and oculomotor interaction, and investigated distinctions from self-motion, biological, and rigid motion. Results indicate that nonrigid motion perception relies on moving motion patterns as the dominant cue, the underlying mechanism is based on the curl of the optic flow, and the distinct neuronal pathway of nonrigid motion perception excludes many brain areas involved in motion processing, gaze control, and visual stability
Observed to expected lung area to head circumference ratio (O/E LHR) in fetuses with congenital anomalies of the kidney and urinary tract (CAKUT): assessment and evaluation as predictive factor for acute postnatal outcome—a single center study
No full textIntroduction: To assess the observed to expected lung area to head circumference ratio (O/E LHR) in fetuses with congenital anomalies of the kidney and urinary tract (CAKUT) and to explore its value as a potential predictive factor for postnatal outcome. Methods: A retrospective single-center study was conducted on pregnancies complicated by CAKUT between 2007 and 2018. The lung-to-head ratio (LHR) was calculated for each fetus by two independent observers. Correlations between O/E LHR and various perinatal outcome factors were assessed with Spearman's rank correlation. Furthermore, nominal logistic regression was performed to assess O/E LHR as predictive factor for respiratory distress in newborn. Results: Of 64 pregnancies complicated by CAKUT, 23 were terminated. In the 41 cases of continuation of pregnancy, newborn presenting respiratory distress with need for respiratory support in the delivery room showed earlier gestational age at onset of amniotic fluid abnormalities and at birth. Although median O/E LHR and median single deepest pocket (SDP) of amniotic fluid were significantly smaller in newborn that did develop respiratory distress with need of respiratory support in the delivery room, neither O/E LHR nor SDP were accurate predictors for the development of respiratory distress. Conclusions: Our data show that O/E LHR alone cannot serve as a predictive marker for fetal outcome in pregnancies complicated by CAKUT, though it might still be a helpful parameter together with detailed renal ultrasound evaluation, onset of amniotic fluid abnormality and SDP, particularly in its extreme values
Open Access
No full textOpen Access – der freie Zugang zu wissenschaftlichen Informationen im Internet – hat sich seit den 1990er Jahren zu einer komplexen Publikationspraxis mit erheblichen Auswirkungen auf das wissenschaftliche Verlagswesen entwickelt. Entstanden aus finanziellen Problemen rund um die Kosten für Abonnements von Fachzeitschriften und ermöglicht durch technische Entwicklungen, haben die Prinzipien und Verfahren des Open-Access-Veröffentlichens mit der Zeit viele Wissenschaftler:innen dazu gebracht, ihre Erkenntnisse frei zugänglich zu veröffentlichen, und viele Verlage dazu bewegt, sich neuen Geschäftsmodellen zu öffnen. Open Access hat neben verschiedenen Spielarten von Publikationswegen auch neue finanzielle Probleme generiert und dabei grundlegende Probleme im Wissenschaftsbetrieb aufgedeckt; es hat in den letzten rund 40 Jahren die jahrhundertealte symbiotische Beziehung zwischen Wissenschaft und Verlagen grundlegend verändert.
Dieses Kapitel gibt einen kurzen Überblick mit dem Fokus auf die aktuelle Situation in Deutschland
The fundamental groupoid: Topology, Haar system and actions
No full textWe equip the fundamental groupoid π1(X) of a locally path connected and semilocally simply connected space X with the Whisker topology to make it a topological groupoid. Then the equivalence of the Whisker topology and the quotient of the compactopen topology on the path space of X is proved. This topological groupoid is locally trivial and not étale. We prove that the fundamental groupoid of a topological group, in particular a Lie group, is a transformation groupoid. To understand when π1(X) is locally compact or Hausdorff, we study its point-set topology. We discuss the existence and give a description of a Haar system on π1(X). For the last main result, let E be the category of π1(X)-spaces for which the momentum maps are local homeomorphisms. We show that this category is isomorphic to that of the covering spaces of X. Using this, we give different characterizations
for the free or proper actions in E