We consider integrodifference equations (IDEs), which are of the form N_{t+1}(x) = \int K(x-y)F(N_t(y))dy, where K is a probability distribution and F is a growth function. It is already known that for monotone growth functions, solutions of the IDE will have spreading speeds and are sometimes in the form of travelling waves. We are interested in the case where F has a stable 2-point cycle, namely for the Ricker function and the logistic function [May, 1975]. It was claimed in [Kot, 1992] that the solution of this IDE alternates between two profiles, all the while moving with a certain speed. However, simulations revealed that not only do the profiles alternate, but the solution is a succession of two travelling objects with different speeds. Using the theory from [Weinberger, 1982], we can prove the existence of two speeds and establish their theoretical formulas. To explain the succession of travelling objects, we relate to the concept of dynamical stabilization [Malchow, 2002].

On August 15, 2007, Pisco, Peru was hit by an earthquake of Magnitude (Mw) = 8.0 which triggered multiple liquefaction induced lateral spreads. The subduction earthquake lasted for approximately 100 seconds and showed a complex rupture. From the geotechnical perspective, the Pisco earthquake was significant for the amount of soil liquefaction observed. A massive liquefaction induced seaward displacement of a marine terrace was observed in the Canchamana complex. Later analysis using the pre- and post-earthquake images showed that the lateral displacements were concentrated only on some regions. Despite the lateral homogeneity of the marine terrace, some cross-sections showed large displacements while others had minimal displacements. The detailed documentation of this case-history makes it an ideal case-study for the determination of the undrained strength of the liquefied soils; hence, the main objective of this research is to use the extensive data from the Canchamana Slide to estimate the shear strength of the liquefied soils. In engineering practice, the undrained strength of liquefied soil is typically estimated by correlating SPT-N values to: 1) absolute value of residual strength, or 2) residual strength ratio. Our research aims to contribute an important data point that will add to the current understanding of the residual strength of liquefied soils. / Master of Science

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Hypolimnetic oxygenation systems, such as linear bubble-plume diffusers, are used to improve raw water quality. Linear bubble-plume diffusers were installed in Spring Hollow Reservoir (SHR) and Carvins Cove Reservoir (CCR). Diffusers induce mixing that aids distribution of oxygen throughout the hypolimnion. The induced mixing also creates an undesirable effect by increasing hypolimnetic oxygen demand (HOD). Nevertheless, oxygenation systems are commonly used and long-term oxygenation is hypothesized to actually decrease HOD. Increased oxygen concentrations in combination with the induced mixing affect the location of the oxic/anoxic boundary relative to the sediment water interface. If the oxic/anoxic boundary is pushed beneath the sediment/water interface, the concentrations of soluble iron and manganese in the bulk water are reduced. This work was performed to further validate a recently published bubble-plume model that predicts oxygen addition rates and the elevation in the reservoir where the majority of the oxygen is added. Also, the first field observations of a theoretically expected secondary plume are presented. Model predicted addition rates were compared to observed accumulation rates to evaluate HOD over a wide range of applied gas flow rates. Observations in both reservoirs showed evidence of horizontal spreading that correlated well with plume-model predictions and of vertical spreading below diffuser elevations, showing oxygen penetration into the sediment. Experimental observations of a theoretically expected secondary plume structure also correlated well with model predictions. Plume-induced mixing was shown to be a function of applied gas flow rates, and was observed to increase HOD. HOD was also observed to be independent of bulk hypolimnion oxygen concentration, indicating that the increase in oxygen concentration is not the cause of the increased HOD. Long-term oxygenation resulted in an overall decrease in background HOD as well as a decrease in induced HOD during diffuser operation. Elevated oxygen concentrations and mixing, which occur naturally during destratification and artificially during oxygenation, were observed to coincide with low dissolved metal concentrations in CCR. Movement of the oxic/anoxic boundary out of the sediment, which is also common during stratified periods, appears to facilitate transport of reduced Mn to the overlying waters. Hypolimnetic oxygenation increased oxygen concentrations throughout the hypolimnion, including down to the SWI, and induced mixing, although not to the extent observed during destratification. Subsequently, elevated Mn concentrations were observed to be restricted to the benthic waters located immediately over the sediments, while bulk (hypolimnion) water Mn concentrations remained low. The good agreement between the model and the experimental data show that the model can be used as a predictive tool when designing and operating bubble-plume diffusers. Linear bubble-plume diffusers provide sufficient horizontal and vertical spreading to enable oxygen to reach the sediments. Hypolimnetic oxygenation, despite the increased HOD, is a viable method to manage the negative consequences of hypolimnetic anoxia in water-supply reservoirs. / Ph. D.

Die Kopplung zwischen neuronaler Aktivität und cerebralem Blutfluss ist ein fundamentaler Prozess, der alle cerebralen Funktionen begleitet. Das Thema meiner Habilitation ist die Entdeckung einer neuen Ischämievariante, bei der neuronale Aktivierung eine cerebrale Ischämie auslöst, indem sich die Kopplung zwischen neuronaler Aktivierung und cerebralem Blutfluss umkehrt. Diese Umkehrung wird durch Produkte roter Blutkörperchen im Subarachnoidalraum hervorgerufen. Die eigentümlichste Eigenschaft dieser Ischämievariante ist ihre Wanderung im cerebralen Cortex gemeinsam mit der Welle neuronaler Aktivierung. Deshalb habe ich das Phänomen cortical spreading ischaemia genannt. Das vorgestellte tierexperimentelle Modell könnte für die verzögerten ischämischen neurologischen Defizite nach Subarachnoidalblutung Implikationen besitzen. Die Verbindung mit diesem klinischen Syndrom basiert auf: (a) der Induktion der cortical spreading ischaemia durch Produkte roter Blutkörperchen im Subarachnoidalraum, (b) der Übereinstimmung im Läsionsmuster mit corticalen ischämischen Infarkten, und (c) den therapeutischen Effekten von Nimodipin und mässiger hypervolämischer Hämodilution im klinischen Syndrom und im Tiermodell. Mit Hilfe dieses Modells ist es zum ersten Mal gelungen, experimentell die Hypothese zu bestätigen, dass Produkte roter Blutkörperchen eine cerebrale Ischämie induzieren können. Ich hoffe, dass das Modell dazu beitragen wird, neue Strategien bei der Behandlung von Patienten mit Subarachnoidalblutung zu entwickeln. / The coupling between neuronal activity and cerebral blood flow is a fundamental process, which underpins all cerebral functions. The topic of my Habilitation is the discovery of a new variant of ischaemia in which neuronal activation triggers a cerebral ischaemic event through the inversion of the coupling between neuronal activation and cerebral blood flow. This inversion occurs when red blood cell products are present in the subarachnoid space. The most distinct feature of this variant of ischaemia is its propagation in the cerebral cortex together with the wave of neuronal activation. Therefore, I named the phenomenon cortical spreading ischaemia . The presented animal model may have implications for the delayed ischaemic neurological deficits after subarachnoid haemorrhage. The link with this clinical syndrome has been based: (a) on the induction of cortical spreading ischaemia by red blood cell products in the subarachnoid space, (b) the correspondence between the characteristic patterns of the cortical ischaemic lesions, and (c) the therapeutic effects of nimodipine and moderate hypervolaemic haemodilution in clinical syndrome and animal model. With the aid of this model, it was possible to experimentally confirm the hypothesis that red blood cell products can induce cerebral ischaemia. I hope that the model will contribute to develop new strategies for the treatment of patients with subarachnoid haemorrhage.

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Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 171-186). Also available on the World Wide Web.