In dieser Arbeit wurde die durch Bestrahlung mit schnellen Neutronen bedingte Materialalterung von Reaktordruckbehälterstählen untersucht. Das Probenmaterial umfasste unbestrahlte, bestrahlte und ausgeheilte RDB-Stähle russischer und westlicher Reaktoren sowie Eisenbasis-Modelllegierungen. Mittels Neutronen-Kleinwinkelstreuung ließen sich bestrahlungsinduzierte Leerstellen/Fremdatom-Cluster unterschiedlicher Zusammensetzung mit mittlerem Radius um 1.0 nm nachweisen. Ihr Volumenanteil steigt mit der Strahlenbelastung monoton, aber im allgemeinen nicht linear an. Der Einfluss der Elemente Cu, Ni und P auf den Prozess der Clusterbildung konnte herausgearbeitet werden. Eine Wärmebehandlung oberhalb der Bestrahlungstemperatur reduziert den Anteil der Strahlendefekte bis hin zu deren vollständiger Auflösung. Die Änderungen der mechanischen Eigenschaften der Werkstoffe lassen sich eindeutig auf die beobachteten Gefügemodifikationen zurückführen. Die abgeleiteten Korrelationen können als Hilfsmittel zur Vorhersage des Materialverhaltens bei fortgeschrittener Betriebsdauer von Leistungsreaktoren mit herangezogen werden.

The investigation of reactor pressure vessel (RPV) material from the decommissioned Greifswald nuclear power plant representing the first generation of Russian-type WWER-440/V-230 reactors offers the opportunity to evaluate the real toughness response. The Greifswald RPVs of 4 units represent different material conditions as follows: • Irradiated (Unit 4), • irradiated and recovery annealed (Units 2 and 3), and • irradiated, recovery annealed and re-irradiated (Unit1). The recovery annealing of the RPV was performed at a temperature of 475° for about 152 hours and included a region covering ±0.70 m above and below the core beltline welding seam. Material samples of a diameter of 119 mm called trepans were extracted from the RPV walls. The research program is focused on the characterisation of the RPV steels (base and weld metal) across the thickness of the RPV wall. This report presents test results measured on the trepans from the beltline welding seam No. SN0.1.4. and forged base metal ring No. 0.3.1. of the Units 1 2 and 4 RPVs. The key part of the testing is focussed on the determination of the reference temperature T0 of the Master Curve (MC) approach following the ASTM standard E1921 to determine the facture toughness, and how it degrades under neutron irradiation and is recovered by thermal annealing. Other than that the mentioned test results include Charpy-V and tensile test results. Following results have been determined: • The mitigation of the neutron embrittlement of the weld and base metal by recovery annealing could be confirmed. • KJc values of the weld metals generally followed the course of the MC though with a large scatter. • There was a large variation in the T0 values evaluated across the thickness of the multilayered welding seams. • The T0 measured on T-S oriented SE(B) specimens from different thickness locations of the welding seams strongly depended on the intrinsic structure along the crack front. • The reference temperature RT0 determined according to the “Unified Procedure for Lifetime Assessment of Components and Piping in WWER NPPs - VERLIFE” and the fracture toughness lower bound curve based thereon are applicable on the investigated weld metals. • A strong scatter of the fracture toughness KJc values of the recovery annealed and re-irradiated and the irradiated base metal of Unit 1 and 4, respectively is observed with clearly more than 2% of the values below the MC for 2% fracture probability. The application of the multimodal MC-based approach was more suitable and described the temperature dependence of the KJc values in a satisfactory manner. • It was demonstrated that T0 evaluated according to the SINTAP MC extension represented the brittle fraction of the data sets and is therefore suitable for the nonhomogeneous base metal. • The efficiency of the large-scale thermal annealing of the Greifswald WWER 440/V230 Unit 1 and 2 RPVs could be confirmed.

Mechanische Beanspruchungen verändern bei nahezu jeder Zelle ihre Funktion und ihre Form. Wir interessieren uns besonders für die durch mechanische Beanspruchungen hervorgerufene Effekte im Blutgefäßsystem, dessen Innenseite von den sogenannten Endothelzellen ausgekleidet ist, die eine Permeabilitätsbarriere zwischen Blut und Gewebe darstellen. Durch den Blutstrom sind diese Zellen permanent einer erheblichen mechanischen Beanspruchung ausgesetzt, die nicht nur ihre Form, sondern auch ihre Funktionen wesentlich verändert. Wir haben in unserem Labor einen experimentellen Aufbau entwickelt, mit dem wir erstmalig zeigen konnten, dass laminare Strömungen zu einer Verstärkung der endothelialen Barrierefunktion führen und so vermutlich der Entwicklung der Gefäßverkalkung entgegenwirken. Neben diesen Experimenten wird das neue System auch zur dynamischen Untersuchung der Zellhaftung auf Biomaterialien verwendet. / Mechanical loads change the function and morphology of nearly every cell. We are particularly interested in the effects of mechanical loads on the endothelial cells which line the inner surface of blood vessels and control the exchange of water and solutes between blood and tissue (barrier function). These cells are exposed permanently to mechanical forces from the blood stream, which induces changes not only in cell morphology but also in function. We have developed an experimental setup which allows the endothelial barrier function to be measured under defined flow conditions. We have demonstrated for the first time that laminar shear stress enhances the endothelial barrier function, and thus a possible explanation for the anti-arteriosclerotic effect. Importantly, our setup can also be used to dynamically test the adhesion of cells on biomaterials.

Endothelzellen bilden eine monozellulare Grenzschicht in Blutgefäßen. Ihre Migration ist ein kritischer Teilschritt bei der Gefäßbildung, zum Beispiel während der Wundheilung. Obwohl bereits eine Reihe der dafür relevanten Mediatoren und pathogenen Determinanten bekannt sind, fehlt bisher eine quantitative Analyse der molekularen Mechanismen der Gefäßbildung und Zellmigration. Voraussetzung dafür sind Verfahren zur automatisierten Bestimmung von Zelltrajektorien in Sequenzen von Mikroskopaufnahmen migrierender Zellverbände. Dazu wurde ein statistisches Modell entwickelt, welches die Segmentierung und Verfolgung von Zellen in Bildsequenzen ermöglicht. Im vorliegenden Beitrag stellen wir dieses Modell vor, diskutieren die sich daraus ergebenden Lern- und Erkennungsalgorithmen und präsentieren erste Resultate. / Mechanical loads change the function and morphology of nearly every cell. We are particularly interested in the effects of mechanical loads on the endothelial cells which line the inner surface of blood vessels and control the exchange of water and solutes between blood and tissue (barrier function). These cells are exposed permanently to mechanical forces from the blood stream, which induces changes not only in cell morphology but also in function. We have developed an experimental setup which allows the endothelial barrier function to be measured under defined flow conditions. We have demonstrated for the first time that laminar shear stress enhances the endothelial barrier function, and thus a possible explanation for the anti-arteriosclerotic effect. Importantly, our setup can also be used to dynamically test the adhesion of cells on biomaterials.

Cognitive decline is one of the most common symptoms from neuropathology as well as a part of natural aging. While there may be a number of factors that contribute to age-related cognitive decline, previous research has shed a light on the role of chronic hypertension. The effect of hypertension on cognitive decline through small vessel disease is referred to as Vascular Cognitive Impairment and Dementia (VCID). However, the exact molecular pathology behind VCID is not very well understood. Using a non-human primate model of hypertensive aging with the Macaca mulatta, (more commonly known as the Rhesus Macaque) this project builds on previous research implicating collagen IV as part of the cascade of molecular changes that occur in VCID. This project evaluated collagen IV thickness around blood vessels in the corpus callosum and cingulum bundle of normotensive and hypertensive monkeys. as well as determined vessel properties such as total vessel area and perimeter length to evaluate the relationship to scores from the subjects cognitive testing batteries. The results from this project will allow for an examination of the effects on hypertension on vascular properties and possible mechanisms for the development of cognitive impairments. Data collected from this research shows significant differences of collagen IV thickness in the Corpus Callosum between hypertensive and normotensive groups. Similarly, in the cingulum bundle we see that the difference between these groups in collagen IV thickness is trending towards significance. The relationship between average collagen IV densities, blood pressure at perfusion, and cognitive testing scores also showed trending relationships in both the cingulum bundle and the corpus callosum. These results demonstrate how prolonged hypertension can negatively influence cognitive abilities and implicates increases in collagen IV around small vessels in white matter as a significant factor in the molecular cascade which results in cognitive impairment.

No description available.

The goal of the present study is to investigate the effect of different scenarios of core degradation in a Nordic-type BWR (boiling water reactor) on the reactor pressure vessel failure mode and timing. Specifically we consider the effects of (i) in-vessel pressure, (ii) melt properties. Control rod guide tube (CRGT) cooling and cooling of the debris from the top are considered as severe accident management (SAM) measures in this study. We also consider the question about minimal amount of debris that can be retained inside the reactor pressure vessel (RPV). Analysis is carried out with coupled (i) Phase-change Effective Convectivity (PECM) model implemented in Fluent for prediction of the debris and melt pool heat transfer, and (ii) structural model of the RPV lower head implemented in ANSYS for simulation of thermo-mechanical creep. The coupling is done through transient thermal load predicted by PECM and applied as a boundary condition in ANSYS analysis. Results of the analysis suggest that applying only CRGT and top cooling is insufficient for maintaining vessel integrity with 0.4 m deep (~12 tons) corium melt pool. The failure of the vessel by thermally induced creep can be expected starting from 5.3 h after the dryout of the debris bed in the lower plenum. However, earlier failure of the instrumentation guide tubes (IGTs) is possible due to melting of the nozzle welding. The internal pressure in the vessel in the range between 3 to 60 bars has no significant influence on the mode and location of the global RPV wall failure. However, depressurization of the vessel can delay RPV wall failure by 46 min for 0.7 m (~ 30 tons) and by 24 min for 1.9 m (~ 200 tons) debris bed. For 0.7 m pool case, changes in vessel pressure from 3 to 60 bars caused changes in liquid melt mass and superheat from ~18 tons at 180 K to ~13 tons at 100 K superheat, respectively. The same changes in pressure for 1.9 m case caused changes in liquid melt mass and superheat from ~40 tons at 42 K to ~10 tons at about 8 K superheat, respectively. Investigation of the influence of melt pool properties on the mode and timing of the vessel failure suggest that the thermo-mechanical creep behavior is most sensitive to the thermal conductivity of solid debris. Both vessel wall and IGT failure timing is strongly dependent on this parameter. For given thermal conductivity of solid debris, an increase in Tsolidus or Tliquidus generally leads to a decrease in liquid melt mass and superheat at the moment of vessel wall failure. Applying models for effective thermal conductivity of porous debris helps to further reduce uncertainty in assessment of the vessel failure and melt ejection mode and timing. Only in an extreme case with Tsolidus, Tliquidus range larger than 600 K, with thermal conductivity of solid 0.5 W∙m‑1∙K‑1 and thermal conductivity of liquid melt 20 W∙m‑1∙K‑1, a noticeable vessel wall ablation and melting of the crust on the wall surface was observed. However, the failure was still caused by creep strain and the location of the failure remained similar to other considered cases. / APRI-8

Autonomous ships are one way to increase safety at sea and to decrease environmental impact of marine traveling and shipping. For this application, a good representation of the environment and a physical model of the ship are vital components. By optimizing the trajectory of the ship, a good trade-off between the time duration and energy consumption can be found. In this thesis, a three degree of freedom model that describes the dynamics of a small-scale surface ship is estimated. By using optimal control theory and a grey-box model, the parameters are estimated by defining an optimal control problem (OCP). The optimal solution is found by transcribing the problem into a nonlinear program and solving it using an interior point algorithm. The identification method is tested and validated using simulated data as well as using data from real world experiments. The performance of the estimated models is validated using cross validation. In a second track of this thesis, a trajectory is created in two steps. The first is path planning to find a shortest geometric path between two points. In the second step, the path is converted to a trajectory and is optimized to become dynamically feasible. For this purpose, a roadmap is generated from a modified version of the generalized Voronoi diagram. To find an initial path in the roadmap, the A-star algorithm is utilized and to connect start and goal position to the map a few different methods are examined. An initial trajectory is created by mapping a straight-line trajectory to the initial path, thus connecting time, position and velocity. The final trajectory is found by solving a discrete OCP initialized with the initial trajectory. The OCP contains spatial constraints that ensures that the vessel does not collide with static obstacles. The suggested estimation method resulted in models that could be used for trajectory planning to generate a dynamically feasible trajectory for both simulated and real data. The trajectory generated by the trajectory planner resulted in a collision-free trajectory, satisfying the dynamics of the estimated model, such that the trade-off between time duration and energy consumption is well balanced. Future work consists of implementation of a controller to see if the planned trajectory can be followed by the small-scale ship.

The localization of substance P (SP) binding sites in guinea-pig heart was studied by in vitro autoradiography, and pharmacological effects of SP were examined with isolated heart preparations. Specific binding of [125I]SP was found in association with cardiac parasympathetic ganglia and some coronary arteries. No specific SP binding sites were associated with coronary veins, atria, ventricles, ascending aorta or pulmonary trunk. Local bolus injections of SP (2.5 and 25 nmol) caused a bradycardia which, in some preparations, was followed by a slight tachycardia. SP produced a prominent coronary vasodilator effect after basal perfusion pressure had been elevated by 1 μM vasopressin. The vasodilator response was probably mediated by the SP binding sites associated with the coronary arteries. Bradycardia might be elicited by binding of SP to the receptors present in the parasympathetic ganglia and subsequent release of acetylcholine. It is suggested that these effects of SP on the isolated heart could be of physiological significance.

Compliance is a key feature for the management of non-consumptive wildlife viewing, as it can link management measures to performance and aid in developing recommendations that promote sustainable practices. Whale watching is a prominent wildlife viewing industry that is steadily rising in demand around the world. Managing vessel-cetacean encounters and operator behaviour (both commercial and recreational) is key to limiting impacts on cetaceans, yet the scale of regulatory compliance is often poor or unknown. Although efforts exist to regulate whale watching, challenges arise for the assessment of compliance in marine environments, as they are inherently spatially vast, lack physical boundaries, and can involve mobile stressors (i.e. vessels) and species. Chapter 1 reviews the shift in paradigms from consumptive to non-consumptive activities and highlights challenges for those tasked with managing the growing wildlife tourism industry, and in particular, whale watching. After reviewing a suite of measures prevalent around the world, this chapter then focuses on the Salish Sea’s approach to managing whale watching. This area epitomizes a major whale watching hub and displays complex, multi-jurisdictional and constantly evolving measures. Due to a lack of knowledge in this region, Chapter 2 shifts from theory to practice and assesses regulatory compliance with marine mammal distance regulations from 2018 to 2019 in the Salish Sea. Although compliance was nearly 80%, key drivers including vessel and species type were found to significantly influence non-compliance. Recreational vessels were non-compliant 41.9% of the time and 74.2% of non-compliant encounters occurred around killer whales across both years. The findings of the study demonstrate that case-specific investigation of compliance is necessary as each region is unique in its approach to management. Lastly, recommendations are proposed that can benefit marine managers and policymakers to enhance the performance of measures and subsequently minimize risk to cetaceans. / Graduate