OOPS - Oldenburger Online-Publikations-Server (Univ. Oldenburg)
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An adaptive leaky-integrate and firing probability model of an electrically stimulated auditory nerve fiber
Get PDFMost neural models produce a spiking output and often represent the stochastic nature of the spike generation process via a stochastic output. Nonspiking neural models, on the other hand, predict the probability of a spike occurring in response to a stimulus. We propose a nonspiking model for an electrically stimulated auditory nerve fiber, which not only predicts the total probability of a spike occurring in response to a biphasic pulse but also the distribution of the spike time. Our adaptive leaky-integrate and firing probability (aLIFP) model can account for refractoriness, facilitation, accommodation, and long-term adaptation. All model parameters have been fitted to single cell recordings from electrically stimulated cat auditory nerve fibers. Afterward, the model was validated on recordings from auditory nerve fibers from cats and guinea pigs. The nonspiking nature of the model makes it fast and deterministic while still accounting for the stochastic nature of the spike generation process. Therefore, the relationship between the input to the model or model parameters and the model's output can be observed more directly than with stochastically spiking models
System configuration to enhance co-simulation for decision support
Get PDFThe development of complex ecosystems in the mobility domain and beyond require comprehensive support by simulation and virtual engineering methodologies. This work contributes to the field of co-simulation and its application for decision support for complex infrastructure decisions by the example of planning public charging infrastructure for electric mobility in Germany. Setting up a framework which embeds a co-simulation system into a framework that accounts for multi-criteria decision support, the arising challenges in system configuration as well as result analysis and interpretation are addressed. Within the system configuration, the advance compared to the state-of-the-art of system handling comprises the traceability over multiple abstraction layers, the consistent parametrisation of a heterogeneous system of multiple models by using Natural Language Processing (NLP), automated parameter transformation and the integrated usage of future structured scenarios
Uncertainty reduction for robust wind farm control strategies
Get PDFThe aim of this dissertation is to improve the prerequisites for effective wind farm control strategies by reducing uncertainties in determining and predicting the ambient flow field. Lidar systems can assist in this regard, but are susceptible to errors in positioning. Therefore, methods have been derived to accurately determine their orientation and levelling in offshore wind farms. Further uncertainties arise from the wind vanes, which have been shown to systematically overestimate yaw errors. A correction has been designed that significantly improves their measurements. Additionally, a real-time flow model was constructed to predict the flow evolution, particularly the wind speed and direction at downstream turbines. Finally, a robust wind farm control strategy was developed that considers uncertainties in wind direction using stochastic optimisation
Deprivation and stroke incidence, treatment and mortality in Germany
No full textBackground: Previous research suggests that regional deprivation significantly influences the risk of stroke. However, little is known about regional differences in stroke incidence and mortality within Germany.
Methods: We utilized data from the Diagnosis Related Groups statistics (2016-2019) and the German Federal Register of Physicians (2019). We used negative binomial regression analysis to investigate the relationship between the German Index of Multiple Deprivation 2015, covering 401 districts and district-free cities in Germany, and stroke incidence, treatment, and mortality.
Results: The adjusted rate ratios of stroke incidence and mortality with the highest deprivation level compared with the least deprived area were 1.16 (95% CI [1.14, 1.17]) and 1.19 (95% CI [1.14, 1.23]), respectively. Furthermore, this study showed that the density of physicians was higher in district-free cities than in districts.
Conclusions: The findings document a relationship between regional deprivation and stroke incidence and mortality, and call for a more targeted approach to stroke prevention in deprived regions
Functionally graded anode catalyst layers for PEM water electrolysis
Get PDFDie Abhängigkeit von teuren und seltenen Ir-Katalysatoren behindert die großtechnische Einführung der PEM Wasserelektrolyse. Ansätze zur Erhöhung der Aktivität und der Senkung der erforderlichen Beladung der Katalysatorschicht können dieses Problem lösen. Hier werden verschiedene Synthesen von geträgerten Ir Katalysatoren verglichen und bewertet und dann in Anodenkatalysatorschichten mit Gradientenaufbau verwendet. Diese Schichten setzen sich aus mehreren Teilschichten zusammen, um die Auswirkungen des Gradienten-Designs auf die Leistung der Elektrolysezelle und die Möglichkeit einer insgesamt geringeren Ir-Beladung zu bewerten. Die Gradienten werden mit einer variablen Beladung von Ir-Partikeln auf dem Träger und damit der Ir-Beladung sowie einem variablen Ionomergehalt entlang der Dicke der Katalysatorschicht hergestellt. Umfassende elektrochemische Charakterisierungen ergaben vielversprechende Effekte und eine verbesserte Leistung für beide Varianten des Gradienten-Designs
Tailored nanophononic wavefields probed by nano-focused electron pulses in ultrafast transmission electron microscopy
Get PDFThe first part of the cumulative thesis within ultrafast transmission electron microscopy (UTEM) deals with properties of multi-electron pulses emitted by laser-driven field emitters. Different mechanisms for the temporal and spatial broadening of multi-electron pulses by intrapulse Coulomb interactions are clearly identified, and stochastic and mean-field effects during acceleration in a strong electric field near the emitter tip are unveiled.
In the second part, structural dynamics within an ultrathin double-layer system as a source of acoustic phonons are discussed, both theoretically and experimentally. An analytical model was developed to describe the frequency spectrum of localized acoustic resonances in bilayer systems. Experimentally, phonons emitted by a bilayer stripe into a single-crystalline membrane are monitored with high spatiotemporal resolution provided by ultrafast convergent beam electron diffraction. Based on the corresponding analytical model, Lamb waves preferentially at resonance frequencies of the bilayer system are identified
Beweggründe von Patienten und Patientinnen zum Aufsuchen der Notaufnahme anstelle der ambulanten Strukturen - Eine Patient:innenbefragung in den Oldenburger Notaufnahmen
Get PDFSteigende Fallzahlen stellen die Gesundheitsversorgung vor ein zunehmendes Problem. Mittels standardisierte schriftliche Befragung durch Fragebögen wurden in Notaufnahmen die Beweggründe von Patient:innen untersucht.
Es wurden 354 Fragebögen analysiert. Über die Hälfte suchte keinen Kontakt zu ambulanten Strukturen (54,1 %), wobei eine geschlossene Praxis (39,7 %) und die Erwartung besserer medizinischer Versorgung (17,9 %) genannt wurden. Trotz Kontakt erfolgte der Besuch der Notaufnahme aufgrund der Weiterleitung ohne Einweisung (24,0%) sowie Empfehlung bei Verschlimmerung vorstellig zu werden (19,9 %). Die
Bereitschaftspraxis war 68,4 % der Befragten bekannt.
Eine verbesserte Kenntnis über alternative ambulante Versorgungsstrukturen sowie eine verstärkte Patient:innenlenkung könnte sinnvoll zur Reduktion der Fallzahlen sein. Eine gemeinsame Nutzung der Ressourcen von ambulanten und stationären Versorgungsstrukturen sollte forciert werden
Synthese von kohlenstoffbasierten Photokatalysatoren für die selektive Transformation organischer Moleküle und die photokatalytische Wasserspaltung
Get PDFDie Herstellung von polymerem Kohlenstoffnitrid und verwandten Materialien aus Melamin bei unterschiedlichen Temperaturen und Synthesezeiten wird mit der Herstellung aus Harnstoff verglichen. Hierbei zeigen sich in Abhängigkeit des Ausgangsmaterial unterschiedliche Zwischenstufen. Die Katalysatoren werden sowohl für die photokatalytische Wasserstoff-entwicklung als auch für die photokatalytische Reduktion von 5-Hydroxymethylfurfural zu 2,5-Bis(hydroxymethyl)furan untersucht. Des Weiteren werden die polymeren Kohlenstoffnitride für den Einsatz als Katalysator in einer heterogenen photokatalytischen Hydroaminoalkylierung, einer α-Aminoalkylierung und zusammen mit WO3 als Z-Schema für die photokatalytische Wasserspaltung untersucht
Preparation and Characterization of Nanoporous Copper and its Application in Electrosynthesis of Cyclic Carbonates
Get PDFDealloying is a powerful method to fabricate nanoporous (np) materials for electrochemical synthesis and catalysis. This dissertation consists of two parts. The first discusses how adjusting the dealloying parameters (e.g. electrolyte solution) of Zn80Cu20 alloy ribbons to control the nanostructure of np-Cu ribbons. For example, the adsorbed chloride anions in HCl enhance the surface diffusivity of Cu, leading to the formation of larger ligaments, while the slow diffusivity of Cu (hydr)oxide species in NaOH results in smaller ligaments. The second part focuses on the utilization of the np-Cu ribbons as a cathode material for the electrosynthesis of cyclic carbonates such as 1,2-butylene carbonate and propylene carbonate from carbon dioxide and epoxides under mild conditions. Altogether, this dissertation provides deeper insights into the reaction mechanism of cyclic carbonates formation on Cu-based electrodes and allows tuning the structural properties of np-Cu