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Collection Description

Collection of student theses and dissertations from as early as 1939, but mainly from 2010 to present.

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Variables influencing contextualized moral reasoning
The purpose of this study was to explore cross-situational consistency in moral reasoning. Based on Kohlberg's developmental theory, which hypothesizes within-subject consistency of moral reasoning, adults' moral rationales were analyzed. The investigation centered on whether the moral reasoning utilized in response to abstract, remote, hypothetical moral dilemmas differed from the reasoning employed in more concrete situations. The design utilized paper and pencil instruments in group administered settings with 161 college students. The Ethical Reasoning Inventory and the revised Objective Assessment of Moral Development were used as the abstract and contextualized measures of moral reasoning. Respondent demographic characteristics, respondent past moral crisis experience, the format of the moral development instrument, and the contextual characteristics of the moral conflict situation were hypothesized as influencing moral reasoning. A within-subjects post-hoc analysis was undertaken utilizing an array of multivariate techniques. Discriminant function analysis was employed in building a predictive model of situationally influenced moral reasoning. Five significant findings emerged. First, a low--but significant--correlation existed between abstract and contextualized moral reasoning ability. Second, verbal ability was correlated positively with contextualized moral reasoning ability. This relationship held even when controlling for age, gender, ethnicity, marital status and past experience. Third, past moral conflict experience was inversely related to moral maturity on remote content dilemmas. Fourth, both male and female respondents were influenced by two contextual features, i.e. the gender and socioeconomic status (SES) characteristics of the moral dilemma model. Contexts involving male and female low SES models evoked less mature reasoning. Fifth, an 80% accuracy rate was obtained when using the canonical discriminant function to predict respondent level of moral maturity in contexts involving male and female low SES models., San Diego State University; Claremont Graduate School, Digitization of this archival thesis was made possible through a generous donation from Robin B. Luby.
Vascular contributions to neurocognitive impairment among older persons with HIV
HIV-associated neurocognitive impairment (NCI) is highly prevalent in the modern era of combination antiretroviral therapy, and older persons (50 years and older) are particularly vulnerable to the burden of HIV-associated NCI. In addition, cardiovascular disease is increasingly observed in HIV. Three studies were conducted to investigate the association between markers of vascular risk and NC function among persons living with HIV/AIDS. For all three studies, participants completed standardized neurobehavioral and neuromedical assessments. NC function was evaluated using a well-validated comprehensive battery. The first study evaluated the relationships among markers of vascular remodeling, arterial stiffness (measured by pulse pressure, PP), and NC function among older HIV-seropositive (HIV+; n = 72) and HIV-seronegative (n = 36) adults. A biomarker of vascular remodeling was associated with greater PP and worse NC function. PP had a quadratic relationship with NC function, such that lower and higher PP values, relative to the entire sample mean, were associated with worse NC function. These findings indicate that vascular remodeling may contribute to arterial stiffening and changes in PP, which, in turn, deleteriously affect NC function. The second study assessed the impact of disturbances in coagulation on NC function in the same cohort of older HIV+ and HIV-seronegative adults. Coagulation moderated the effect of HIV on NC function, such that greater coagulation imbalance was associated with poorer NC function among HIV+ participants. The moderating effect of coagulation on neurocognition was driven by procoagulant but not anticoagulant or fibrinolytic biomarkers. These findings indicate that procoagulation may exert a detrimental effect on NC function among older HIV+ adults. Lastly, the third study aimed to examine the association between visit-to-visit variability in blood pressure (BPV) and NC change in a well-characterized HIV+ cohort (N = 533). BPV was not significantly associated with rate of NC change; however, baseline PP was a significant predictor of rate of NC change. These findings suggest that arterial stiffness might be a crucial factor impacting NC function over time among HIV+ adults. The findings of these studies indicate that vascular remodeling, arterial stiffening, and procoagulation may contribute to poorer NC outcomes among HIV+ persons. Biomarkers of vascular processes may provide valuable information regarding the prognosis and risk stratification of HIV+ adults for NCI.
Vector Field Generator for a Direct Mapping of the First Order Poincaré Sphere
Includes bibliographical references (pages 75-76)., This thesis presents an optical system able to generate all polarization states on the zero order Poincaré sphere. An important characteristic of the zero order sphere is its spatial uniformity. This means that the polarization of the beam is uniform. This characterization can be proven using polarizers. Any change in the polarization of the beam will be consistent for all points in the beam. This is not necessarily true for all types of polarization states. There are new polarization states that are spatially variant in which the polarization is no longer uniform. The assumption that the polarization at one point in the beam is the same at all points is no longer valid. These are defined as higher order polarization states which have their own Poincaré spheres that are similar to the zero order sphere but are spatially variant. The higher order polarization states are the focus of this thesis. Maxwell's equations are shown and the solution for light is derived. From this, Jones vectors are used to describe the polarization and how they relate to the Poincaré sphere. Jones matrices are applied to the incoming polarization state to reflect the changes a waveplate causes to the system, and how to create a rotator to rotate the axis of polarization. The matrices describe an optical system consisting of a variable waveplate and a rotator created from 2 quarter waveplates and an additional variable waveplate that able to change the latitude and longitude of a polarization state on the Poincaré sphere. The system is able to achieve any coordinate on the surface of the sphere. The system is applied to the zero order Poincaré sphere and the positive and negative first order Poincaré sphere. Experimental results are presented and agree with theory.
Vegetation and fluvial geomorphology dynamics after fire in urban mediterranean riparian areas
The role of non-native riparian vegetation in urban fire regimes within Mediterranean riverine systems (Med-sys) is not well documented. A combination of satellite indices and in field surveys were used to investigate the impact of non-native), riparian, or upland vegetation on the spatial and temporal variability of fire severity and canopy loss was compared across eleven fires in southern California. Satellite-based metrics, differenced Normalized Burn Severity (dNBR) and differenced Normalized Difference Vegetation Index (dNDVI), were approximated for native and non-native vegetation for 0, 1, and 3 years after fire. Generally, the riparian class burned more severely and experienced a greater loss of green canopy than the upland land class. The presence of invasive vegetation affected the distribution of burn severity and canopy loss. On average, across both upland and riparian regions, fires with native vegetation cover burned at a higher severity and resulted in larger immediate loss of canopy than fires with non-native vegetation. The lower burn severity observed in the fires with non-native vegetation suggests a rapid regrowth of non-native grasses immediately after fire, resulting in a smaller measured canopy loss relative to native vegetation. A case study of the Del Cerro fire (San Diego, California) was used to compare observations of native and non-native vegetation and fluvial morphology in the upland and riparian regions. Field observations noted rapidly re-sprouting invasive grass species such as Arundo donax (Giant Reed). While, satellite-based metrics underestimated the initial green canopy loss after urban fires as did volumetric data derived from three-dimensional terrestrial laser scanning data (TLS). Fire damaged trees and chaparral and decomposition of burned branches contributed of vegetation volume throughout the first six months following the fire, exceeding the combined density of resprouting vegetation. The presence of Arundo donax significantly increased channel instability in the riparian region and encouraged the deposition of sediments in the floodplain (accretion). This geomorphological mechanism can promote riparian desiccation and fire risk. Ultimately, this work builds considerably upon our current knowledge of wildfire and recovery processes and informs understanding of the post fire mechanisms and anthropogenic feedbacks unique to urban Med-sys., San Diego State University
Ventricular wall shear stress under LVAD support
Heart failure (HF) occurs when the heart pumping fail to convey enough oxygenated, nutrients-rich blood to the organs. Over 5 million Americans suffers from HF and about four thousands of patients on the waiting list for heart transplantation. However, considering the shortage of healthy donor hearts and transplantation compatibility, Left Ventricle Assist Device (LVAD) was widely transplanted to the patient with end-stage HF while lacking donor heart. The LVAD is a pump that surgeons connect to the heart and aorta of heart failure patients, and boosts the blood flow to the tissues of the body. The wide applications of LVAD save numerous patients and enhance their life quality. However, implantation causes the alterations of hemodynamic and biomechanics. When the LVAD is pumping, the pressure in the heart is lowered, which affects the biomechanics of the aortic valve (AV), producing a decrease in opening area and duration as well as a reduction in flow through the aortic valve. These alterations may result in changes in the shear across the AV leaflets, which is an important signal for maintaining valve function. It is not known how the changes in biomechanics produced by the LVAD affect shear stress on the ventricular side of the AV leaflets. Our goal is to assess the shear alteration trend on the aortic valve leaflets during different LVAD support conditions. Our initial hypothesis is that ventricular wall shear stress remains constant as LVAD speed increases. The experiment was operated in the SDSU cardiac simulator by the previous study, and the hemodynamic data was recorded in the LabView system. Then theoretical calculation based on Wormaley equation was performed according to the data analyzed from the Labview system by Matlab and LabChart. To validate the theoretical assumption, Computer Assis Engineering (CAE) was adopted. The approach was to develop a computational model of the AV that could be solved for different levels of LVAD support. Eight 3-D models of the AV and root were developed via SolidWorks to match the experimental measurements. ANSYS CFD and ICEM CFD are applied to simulate the AV subjected to the loading conditions reported by the experiments., San Diego State University
Verification of specialized fire dynamics simulator for wildfire applications
In large parts of the US the chaparral zone typifies the natural landscape. Chaparral habitat is one of grass lands containing short vegetation where larger shrubs dot the landscape. This creates a wildfire scenario where flames spread across the grasslands (fuel bed) and, if conditions are right, will ignite the overhead vegetation (crown fuel) in the shrubs. An effort to study this type of fire spread has taken place over the years. Dr. Watcharapong Tachajapong and researchers at UC Riverside and the Pacific Southwest Research Station of the USDA Forest Service conducted a series of experiments that examined to effects of altering various parameters related to fire behavior. In addition to the experimental work there have been previous efforts of Drew Castle at SDSU and Dr. William Mell to model this these experiments using Fire Dynamic Simulator. This work is being continued in this body of research with more simulations performed in an updated specialized version of FDS6 to model certain scenarios that were created in UC Riverside experiments. Other bodies of research also exist around the areas of Froude number scaling, flame tilt angle, and numerical modeling of wildfires and were used as a basis of comparison to the simulation results. In the case of the comparisons between the UC Riverside experiments and this research, there were strong correlations between the numerical model results and the experimental results for cold flow behavior, flame rate of spread (ROS) and flame tilt angle. Flame spread from surface fuel to crown had mixed correlation to the experiments. Results were also compared against literature on flame tilt angle and were found to be substantially different than predicted by the literature (around 75% difference). Froude number scaling predictions compared very closely between the experimental scale and the naturally occurring wildfires. The correlation factor associated with wind velocity was also compared and found to closely match between the predicted difference on flame ROS and that in the numerical models., San Diego State University