Electronic Theses and Dissertations - Open Access
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12588/2237
This collection contains electronic UTSA theses and dissertations (ETDs), primarily from 2005 to present. The collection is not comprehensive; search the UTSA Library Catalog for a complete list of UTSA theses and dissertations.
All of the ETDs in this collection are available to the general public. However, authors are able to request an embargo. Embargoed ETDs will not be downloadable until after their embargo expires.
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Item Factors affecting the growth of Verbesina virginica(2008) Gagliardi, Jason W.Verbesina virginica (frost weed) is a tall, perennial, herbaceous plant that has been observed to occur in Bexar County, Texas primarily under established tree canopies such as Quercus fusiformis (scrub live oak) and Ulmus crassifolia (cedar elm). The distribution of Verbesina virginica, and possible factors affecting its distribution are not well reported. To better understand these factors, a combination of field studies, greenhouse experiments, and leaf level Li-Cor gas exchange analysis were utilized to examine species distribution, determine the species' nutrient requirements, and the plants response to various light levels, respectively. Over five transects, extending from a canopy into an adjacent open grassland, 283 total plants were counted. Of those, 98.9% (280 plants) were found inside the canopy dripline. Mean soil depth along the transects was highly variable and not significantly different from one location to another. However, a light gradient was found ranging from low light beneath the canopy (207 +/- 53 mumol CO2 · m-2 · sec-1) and increasing into the open grassland (2126 +/- 71 mumol CO2 · m-2 · sec -1). Overall, dry plant mass and leaves per plant increased with increased nutrient additions however, the plants did tolerate the native low nutrient Patrick soil. Gas exchange measurements for Verbesina virginica over 19 light levels ranging from 0 to 2000 mumol · m-2 · sec-1 found its maximum rate of photosynthesis (Amax) to be 12.68 +/- 1.40 mumol CO2 · m-2 · sec-1, while its mean dark respiration (Rd) was 0.75 mumol CO2 · m-2 · sec -1. The mean light saturation point (Lsat) for V. virginica was 287.74 mumol · m-2 · sec-1, and mean light compensation point (Lcp) was 16.2 mumol · m-2 · sec-1. These results fall within established ranges reported for understory species, and together with observed field distributions suggest that Verbesina virginica is a shade species.Item Hydrometeorological analysis of flooding events in San Antonio, Texas(2008) Chintalapudi, SingaiahFlash flooding is the second leading cause of weather-related deaths in the United States. Texas is the state with most flood/flash flood deaths. San Antonio, the 7th largest city in the nation, is located in one of the most flash-flood prone regions in North America and has experienced a number of flooding events in the last decade (2002, 2004, and 2007). South Central Texas is particularly vulnerable to floods due to: (1) proximity to a moist air source (the Gulf of Mexico); (2) the Balcones Escarpment, which concentrates rainfall runoff; (3) a tendency for synoptic scale features to become cut-off and stall over the area; and (4) decaying tropical cyclones stalling over the area. Research into the benefits and potential applications of a physically-based, distributed hydrological model is being encouraged by increases in the availability of distributed watershed data and advances in computing power. This study used the Gridded Surface Subsurface Hydrological Model (GSSHA) to examine the hydrologic response of Leon Creek, Salado Creek, and Upper San Antonio River basins located in San Antonio, Texas to four major floods. The main source of precipitation input to the hydrologic model was the NEXt-generation RADar (NEXRAD) Multi-sensor Precipitation Estimator. Simulated discharges of flooding events produced by GSSHA model compared very well with the observed discharges.Item PBL preparation for physician assistant facilitators(2008) Midla, George S.This study explores facilitator preparation for a physician assistant (PA) problem based learning (PBL) program. A qualitative study approach was used to investigate the experiences of seven faculty members from two separate PA PBL programs within the continental United States. Data was collected through interviews using open-ended questions that were recorded and analyzed. The results revealed important themes related to topics that addressed the faculty participants' personal experiences when first beginning this method of teaching. Issues addressed included the facilitator's outlook towards PBL, previous experiences which helped to make a smoother transition into their teaching position, approaches that assisted in preparing faculty and students to teach and learn in a PBL program, academic resources referenced by faculty members, and the use of nonclinical tutors in a PA PBL program.Item The border between remembering and forgetting: El Paso, Texas, and the Holocaust(2008) Doran, Erin E.This thesis examines the development of collective memory regarding the Holocaust in El Paso, Texas. The local chapter of the National Council of Jewish Women aided refugees fleeing Nazi Germany and the rest of the European continent prior to the entrance of the United States into the war and the implementation of the Final Solution. After the war, a small group of Holocaust survivors permanently made El Paso their home. In the 1980s, one particular Holocaust survivor began collecting Holocaust-era artifacts which eventually grew into the El Paso Holocaust Museum and Study Center. In many ways, the memory of the Holocaust as a global event has overshadowed the local history of El Paso during the same period, despite the fact that Jewish women in the city actively participated in rescue efforts. This study discusses how the local population has learned about the Holocaust, how the event has been remembered, and the implications of that memory for El Paso, the Holocaust survivors, the city's Jewish community, and the effects on the city's history.Item Strategies for the analysis of biologically active compounds by capillary electrophoresis and microchip-capillary electrophoresis(2009) Mora, Maria FernandaSensitive, selective, and cost-effective analysis of biomolecules (phenols, amino acids, etc.) is important in clinical, environmental, and industrial fields. Capillary electrophoresis (CE) is one of the most used analytical techniques offering high performance, reagent economy, speed, automation capabilities, and miniaturization. At the microchip scale, CE also provides custom design, reduced consumption of reagents and sample, low waste generation, increased analysis speed, and portability. In this proposal the analysis by microchip-CE was divided in two main steps: the separation step and the detection step. The main goal of this dissertation was to investigate different strategies to improve the analytical performance of both of these steps. Based in the stated goal, the specific aims of the current dissertation were to investigate: (1) the electrophoretic/electrochemical effects of different surface coatings. (2) the interaction of selected enzymes with nanomaterials. Regarding the dynamic modification of the capillary surface, a very simple method for the coating of fused silica capillaries with a natural clay was developed. Some remarkable advantages of this coating procedure include stability, constant mu EOF at alkaline pH values, low cost of the reagents employed, and the possibility of using it in microchip devices. On the other side, the electrophoretic effects of surfactants with different chain lengths were also studied as a dynamic modification for the separation of six phenolic compounds. As a result of the adsorption of surfactants to the PDMS surface, reductions in the migration times and improvements in peak skew (S) were observed for all the surfactants when compared to bare PDMS. Surfactants offer a convenient and versatile approach to decrease analyte-wall interactions, improve peak shape, and decrease analysis time. Regarding the electrochemical detection, the addition of anionic surfactants can also produce improvements in the electrochemical detection of some phenolic compounds by enhancing interactions between the analyte and the electrode surface.Item Border places, frontier spaces: Deconstructing ideologies of the Southwest(2009) Barrera, Cordelia ElizaIn this dissertation, I bring together Border Theory and frontier ideologies in the Southwest to argue that the search for individual identity via the historiographic re-telling of stories is central to uncovering the metaphorical power of border places and frontier spaces. Cross-cultural re-tellings allow me to reconstruct these tropes syncretically to transcend individual difference with the aim of cohering the experiences of Anglo, Native American, Mexican-American, and Chicana/o cultures. A close reading of works by Chicana/os, Mexican-Americans, American Indians, and Euro-Americans in the Southwest points to parallel ideas of the need for an inclusive, third space consciousness to usher social, political, and cultural change on the borderlands. The movement of the works I critically study through the lens of border theory involves a response, as well as a challenge to Euro-centered ways of seeing and presenting the world. Works by authors as diverse as Cormac McCarthy, Larry McMurtry, Leslie Marmon Silko, Arturo Islas, Américo Paredes, and Eve Raleigh and Jovita González, provide the base from which I examine ideas about storytelling, time, personal identity, and the bond between individuals and a Southwestern geography. Importantly, these works either demand alternative conceptions of understanding time, place, and space, or reveal how the linearity of Euro-centered conceptions of time, place, and space have resulted--ironically--in the false utopian visions of a conquering people.Item Biomechanical model of human leg motion(2009) Bird, Marcos AllenEach year, around 6 million Americans visit either orthopedic surgeons or emergency rooms due to knee problems, and rehabilitation of the knee joint costs $470 million annually in the US. Such extremely high cost demands an auxiliary device, a rehabilitation robot, to facilitate the recuperation of the knee and requires a good description of limb motion. To reduce the cost of recuperation by limiting physical therapy sessions, an intelligent brace enabling accurate positioning of the impaired limb while simultaneously providing assistance or resistance forces to assist the patient's movements is needed. Development of the rehabilitation robot requires a good description of limb motion. Extensive research has been carried out to investigate the biomechanical properties of muscles, ligaments, and bones in static situation. Previous studies have also characterized effects of leg swing on the stability of running motion and the motion profiles of the human leg during walking or jumping. However, the dynamic motion profiles have not linked the model parameters to measured biomechanical properties of muscles, ligaments, and knee damping. Accordingly, in this study we have developed a mathematical model of human leg motion using Lagrangian mechanics to describe dynamic motion profiles of the human leg. The mathematical model used mechanical components such as springs, links, and dashpots to approximate the biological components within the leg. The model parameters are chosen based on published biological experiments. The mathematical model was simulated with MATLAB and validated via comparison of the model predictions against real human leg motion profiles. Our mathematical model can predict the motion profiles of human leg motion and provides a foundation for the development of a rehabilitation robot to assist patient recovery from knee surgery and replacement.Item Servant leadership in higher education: An analysis of the perceptions of higher education employees regarding servant leadership practices at varying types of institutions(2009) McDougle, Lisa R.The purpose of this study is to determine if there is a significant difference in the perceptions of higher education employees regarding servant leadership practices at their respective institutions. This study was conducted at two different institutions and with all employment levels including workforce, management and top administration. Research participants were asked to complete the Organizational Leadership Assessment instrument as developed by Laub (1999) in order to answer two research questions: (1) Are there significant differences between the perceptions of employees in various role groups regarding servant leadership practices within their own institutions? (2) Are there significant differences between the perceptions of employees at different types of institutions (public 2-year and public 4-year) regarding servant leadership practices? The results of the data showed a significant difference in the perceptions of administrators regarding servant leadership practices as compared to the workforce group. This was true at both institutions. Additionally, when comparing employee groups across institutions, a significant difference was found between the administrators at the two-year institution and the workforce group of the four-year institution.Item Semantics and syntax in sentence comprehension: An analysis of their relationship in time using event-related potentials(2009) Guajardo, Lourdes F.A central issue in psycholinguistics is how we process semantic and grammatical information and how these processes interact during online comprehension. Previous studies have yielded inconclusive results on how and when this interaction occurs; it is unclear whether these processes are continuously interacting or if they only interact at a later stage. The purpose of this study was to examine this interaction using the N400 and P600 as indices of semantic and grammatical processing, respectively. Native speakers of Spanish were presented with Spanish sentences containing a target adjective that was either semantically and grammatically correct or disagreed in meaning, grammatical gender, or both with the preceding noun. The adjectives were embedded in a range of weakly to strongly constraining sentences in order to compare the interaction effect as a function of contextual constraint. Semantic violations elicited a robust N400 effect followed by a late positivity, while grammatical gender violations elicited a left-lateralized negativity followed by a P600 effect. The interaction of semantics and gender was observed only at the P600 time window. Interestingly, sentential constraint modulated the onset latency of the N400 to semantic violations, while the P600 due to gender violations was modulated by constraint in a graded fashion. The findings seem to support late interaction models whereby semantic and grammatical processes are initially independent and interact only at a later phase. However, the interaction may be modulated by the amount of contextual information available, as both processors are combining efforts to predict upcoming words.Item Obstacle-avoiding similarity metrics and shortest path problems(2009) Cook, Atlas F., IVSimilarity metrics are functions that measure the similarity of geometric objects. The motivation for studying similarity metrics is that these functions are essential building blocks for areas such as computer vision, robotics, medical imaging, and drug design. Although similarity metrics are traditionally computed in environments without obstacles, we use shortest paths to compute similarity metrics in simple polygons, in polygons with polygonal holes, and on polyhedral surfaces. We measure the length of a path either by Euclidean distance or by the number of turns on the path. We also compute shortest paths that steer a medical needle through a sequence of treatment points in the plane. This technique could be used in biopsy procedures to take multiple tissue samples with a single puncture of the skin. Such an algorithm could also be applied to brachytherapy procedures that implant radioactive pellets at many cancerous locations. Computing shortest paths for medical needles is a challenging problem because medical needles cut through tissue along circular arcs and have a limited ability to turn. Although optimal substructure can fail, we compute globally optimal paths with a wavefront propagation technique.Item A structural reliability based method for identifying critical locations(2009) Domyancic, Laura C.System reliability calculation for large-scale structural systems is complex due to the large number of potential failure locations and failure modes unless a priori knowledge can be used to significantly reduce the number of failure locations and modes. However, a priori knowledge may not be available for future aircraft systems that operate in new environments---such as hypersonic---or consist of unconventional designs with limited production runs. To address this issue, a fast filtering algorithm based on first order reliability methods (FORM) has been developed to numerically quantify the error incurred by filtering a limit state. A "filtering error" is calculated based on a certain limit state's contribution to the system probability of failure. This is compared to a chosen error tolerance to determine if a limit state is critical to the structural reliability or should be filtered. Three hierarchical levels for finding the FORM solutions of the system limit states are presented. The first level is fast and scalable to large models and provides closed-form FORM solutions. Higher levels provide more accurate solutions with added computational expense. In this way, the problem of a very large system can be reduced by orders of magnitude by the initial filtering to only its critical locations. These locations can then be analyzed in detail at one of the higher level methods. Numerous examples show the accuracy, efficiency, and limitations of the new algorithm. In most examples, Monte Carlo sampling was used to verify the critical locations. In all cases the filtering algorithm identified the same critical locations when sampling was performed on the linear limit states. The method is therefore most useful for problems with small probabilities of failure where sampling becomes computationally prohibitive. The method is tied to the limitations of FORM and may be unsuitable for highly non-linear problems.Item Implementing language policy for deaf students from Spanish-speaking homes: The case of agents in a Texas school district(2010) Compton, Sarah E.Language policy implementation is a complex, multilayered process that produces both planned and unplanned outcomes. Understanding the policy implementation process can be achieved by identifying the agents, layers, and processes of language planning and policy activities, analyzing the layers independently, and examining the relationships among the layers. With respect to deaf education policy, such a multidimensional approach calls for attention to federal, state, and district guidelines as well as to how individuals act as policy-implementing agents when determining appropriate educational contexts for deaf students. Considering these dimensions, this thesis begins by explicating how U.S. special education policy functions as de facto language policy for deaf students. A textual analysis of the Individuals with Disabilities Education Improvement Act of 2004 is presented highlighting ways in which agents can pry open implementational space that promotes multilingual, multimodal education. Turning to implementation in local contexts, I draw on data from a multi-sited, qualitative case study of a Texas school district to show how individuals (un)knowingly act as policy-implementing agents and how their beliefs about language and education policy influences the degree to which they open up multilingual, multimodal ideological and implementational space within deaf education policies. Implications for deaf students' access to multilingual, multimodal educational environments are discussed, illuminating how deaf students' language acquisition is influenced by the educational contexts within which they are placed.Item From out of the fields: Migrant student success in a post-secondary community college setting(2010) Alaniz, Monica JeanThis study examines factors that contribute to migrant student success while navigating a post-secondary community college setting. While the majority of studies dealing with migrant education use a deficit approach---concentrating on the factors that inhibit student success---this study asks why certain migrant students at South Texas College in the Rio Grande Valley in Texas are successful. Using a qualitative case-study approach, seven primary participants (academically successful migrant students) and eight secondary participants (individuals who contributed to the primary participants' academic success) were interviewed to discover which aspects of their lives have contributed to their academic success. This study found that successful migrant students show resiliency having been able to succeed due to the support of their parents, family, and friends, their altruistic attitudes, and their ability to see beyond the present to a future where their educational achievements will allow them to lead better lives for themselves while contributing to the betterment of their families and their families' futures. It also found that community colleges need to practice better tracking of migrant students in order to support these students in their academic journeys.Item Analysis of overpressure generating mechanisms in different tectonic settings(2010) Al-Najrani, FahadOverpressure occurs at depth where formation fluid pressure exceeds hydrostatic pressure. A literature review of 56 overpressured basins out of ∼600 worldwide documented various overpressure generating mechanisms. Overpressure incidences are statistically analyzed by their hosting tectonic settings. The main mechanisms cited for those overpressured basins are disequilibrium compaction (∼60%), hydrocarbon generation (∼23%), tectonic compression (∼14%) and diagenesis (∼3%). The most common tectonic setting of surveyed basins with overpressured fluid conditions is the continental passive margin setting (∼26%). Disequilibrium compaction is found to be the main overpressure generating mechanism in all tectonic settings. Basin age is an important variable to be considered because tectonic settings can change through time. The main contribution of this study is a table with percentages to be used in predicting possible overpressure generating mechanisms in a new or a reevaluated overpressured basin.Item Examining morphological transitioning in Candida albicans through the modulation of FKH2(2010) Cobb, Susan LeeCandida albicans, a human pathogenic fungus, has the ability to transition between three principal morphologies in response to environmental cues: yeast, pseudohyphae, and true hyphae. Previous research shows that the yeast-to-pseudohyphae and yeast-to-hyphae transitions are reversible. What is unclear is whether C. albicans pseudohyphae must first revert to yeast before becoming hypha. A recent study in this lab with a tetracycline-regulatable tet-RFG1 strain suggested that pseudohyphal cells revert back to yeast before transitioning to hyphae. C. albicans morphological flexibility allows it to persist in a wide range of host niches and the yeast-to-hyphae transition is believed to be a requisite virulence factor. The elucidation of the complex mechanisms behind these transitioning phenomena will hasten our pursuit of more effective drug targets in the treatment of disease. In this study, we describe the production, characterization, and use of a novel fkh2Delta-tetFKH2 strain to investigate C. albicans morphological transitioning. Fkh2p is an important cell cycle transcription factor and the null mutant grows constitutively as pseudohyphae. A single tet-regulatable copy of FKH2 inserted at the RP10 locus allows the tight regulation of FKH2 expression in the presence or absence of the tetracycline derivative doxycycline. This regulatable allele gives us the opportunity to grow Candida albicans as pseudohyphae by depleting FKH2 and examining hyphal induction as Fkh2p is restored.Item Interface engineered multifunctional oxide thin films with optimized properties(2010) Collins, Gregory RoyIn our world today, energy has become one of the most valuable resources, in particular, renewable and clean energy sources. The research presented here represents an investigation into three separate areas of this topic. In thin film applications, the ordered structures as well as the inherent thinness of the films precludes the normal physics found in bulk materials. Characterizations of films of this type can provide information on molecular level charge transfer processes of the film layer materials since diffusive properties are minimal. With the control given by pulsed laser deposition methods, film and interface structure can be altered allowing for an examination of these effects on the materials properties. For the electrolyte and cathode materials, this equates to finding thermal and PO2 dependencies for electronic and ionic transport. For barium titanate, aside from the effects of oxygen vacancies, the interface quality between the electrodes and the ferroelectric material determines the effectiveness of energy transfer between these boundaries. That is, poor bonding characteristics or the formation of intermediate layers will introduce inconsistencies and (possibly) unwanted piezoelectric response properties of the material which could introduce parasitic dampening (resistance) of the mechanical vibrations of a piezoelectric transducer, altering its resonant characteristics. The clean reaction products and potential for high power outputs provide a strong impetus into investigations of fuel cell structures to improve their functionality. With conventional applications being dominated by high temperature (>700 °C) cells utilizing YSZ as an electrolyte medium, much gain can be made in efficiency through the lowering of cell operation temperature. The first part of my research focuses on the growth and characterization of a novel multilayered electrolyte structure consisting of alternating layers of GCO and YSZ for use in a medium temperature (400--600 °C) application. Half-cell and whole-cell structures were grown using PLD methods and were characterized using XRD, SEM, TEM and EIS. This multilayered electrolyte structure was found to have a lower activation energy than that previously reported for bulk materials and was found to produce peak power at approximately 600 °C. The second part of this research focused on the growth and characterization of half-cell structures utilizing the perovskite LBCO as the cathode surface and GCO as the electrolyte material. Characterization was performed with XRD, EIS and TEM. Temperature dependent EIS results indicate that found that the oxygen uptake at the interface is fast with an activation energy of approximately 0.46 eV. It was found that the surface oxygen adsorption process is complicated and possibly the product of several rate limiting processes including possibly dissociative adsorption. It was also found that when combined with gadolinia doped ceria as an electrolyte that the interface grain boundaries are influenced by the deposition oxygen partial pressures. The rapid oxygen uptake and low activation energy makes this material a possible candidate for further testing in SOFC applications. The final part of the presented research focused on non-standard deposition conditions of BTO on various substrate materials, including flexible carbon fiber fabric, using PLD methods along with a characterization of these films to explore its application in energy harvesting applications. Perovskites are part of the Ruddlesden-Popper family, with the crystal structure A n+1Bn O3n+1, with n = infinity. Barium titanate (BTO) is a member of the perovskite family and has gained notice not only for its excellent dielectric properties but also as a promising, non-lead-containing, ferroelectric material. Dependency on oxygen partial pressure during film growth was found to have a profound effect on the remnant polarization response and ferroelectric response was observed in films grown at temperatures down to 200 °C. Piezoelectric measurements were made with a resulting measured electric field of 0.4kV/m and a calculated d31 component of 2.74 X 10-14 pC/N. The reasons for this very low (2 orders of magnitude lower than in literature) d31 component are found, by considering the relevant contributions, to be related to the properties of the chosen carbon fiber fabric. However, it was shown that low temperature deposition of barium titanate produced films with reasonable ferroelectric and piezoelectric properties allowing for possible use in some energy harvesting applications.Item Protromic and functional study of Acinetobacter abumannii outer membrane vesicles(2010) Tsai, An-YuAcinetobacter baumannii, a gram-negative aerobic bacterium, is one of the most spread bacteria which can be easily isolated from water, soil, and hospital facilities. It may cause various types of diseases such as respiratory tract infection, urinary tract infection, nosocomial pneumonia and bacteremia. It was noticed that A. baumanii was existed in the blood stream of military people deployed in Iraq and Afghanistan who suffered with serious injury. The treatment for the infection of A. baumannii is limited because it resists to resist nearly 90% of antibiotics. Therefore, to better treat the infection of A. baumannii,the mechanism of infection and virulence factors involved in pathogenecity needed to be studied. Similar to other gram-negative bacteria, outer membrane vesicles (OMVs) secreted by A. baumannii consisted of virulence factors. In my study, the A. baumannii OMVs were isolated and observed under transmission electron microscopy. The proteomic analysis indicated that A. baumannii OMVs consisted of various virulence factors such as OmpA. To understand the function of the A. baumannii OMVs, OMVs were incubated with macrophage cells. Results showed the macrophage cells were lysed when incubated with OMVs compared to cells in the control group which were intact. The quantification of cytotoxicity caused by OMVs showed that the mortality rate reached 80% when 0.02 ug/ml OMVs were added. In my study, the OMVs were isolated and observed. The virulence factors were identified by proteomic analysis and OMVs are toxic to macrophage cells in vitro.Item Electrochemical sensors based on enzymes, biopolymers and nanoparticles(2010) Wooten, Marilyn DehasseThe work described in this Dissertation includes three research projects, designed to make a contribution to the field of electrochemical sensors and biosensors. The electrochemical, spectroscopic, and microscopic analyses were used to explain encountered phenomena. The first project (Chapter 3) describes a unique case of minimally destructive activation of carbon nanotubes (CNT) toward the electro-oxidation of dihydronicotinamide adenine dinucleotide (NADH). NADH is an important biomolecule because it acts as a co-factor of hundreds of dehydrogenase enzymes and a biomarker of metabolic disorders. The proof-of-concept experiments are also presented for the development of new reagentless biosensors based on the activated CNT and NAD+-dependent dehydrogenases. The second project (Chapter 4) is focused on the non-enzymatic direct determination of glucose at gold electrodes in physiologically relevant neutral buffer solutions. Electrochemical determination of glucose at the conventional gold disc electrodes is compared with that at electrodes based on gold nanoparticles and gold nanostructured films. In addition, the effects of the ionic composition of a solution on the electrochemical determination of glucose at gold surfaces are also documented. The third project (Chapter 5) probes the role of the direct electron transfer (DET) between the enzyme glucose oxidase and CNT in electrochemical biosensing of glucose. It shows that the proper understanding of the mechanistic aspects of biosensing is critically important to the progress in development of a new generation of electrochemical devices including the mediatorless electrochemical biosensors and DET-based biological fuel cells.Item Verification and modification a program for calculating the area of intersection of a cone and voxel(2010) Ting, Chun-HsiuPreviously, to investigate the informational content of Compton camera data, a program was written to calculate the area of intersection of a cone with a voxel. In writing the program, an existing subroutine was modified and used. However in doing this modification, no effort was made to improve the portion of the original code that was unchanged. Moreover, little effort was made to verify that the overall program worked correctly. The main objective of this thesis is to verify the performance of the overall program and improve the unchanged code of the modified subroutine. To verify the performance of the overall program, a new program was written to display a voxel-wise image of the cones created by the overall program. These images verified that the overall program was, in fact, working correctly. To improve the subroutine, the logic of the unchanged code was improved. The new logic was verified and was seen to be working correctly. However, it was determined that this improvement had a negligible impact on the performance of the overall program.Item Parallelism and error reduction in a high performance environment(2010) Castaldo, Anthony M.This dissertation details contributions made by the author to the field of computer science while working to improve the performance of a state-of-the-art linear algebra library intended for use on commodity platforms. These platforms and libraries have become a de facto standard for most scientific researchers. There are three significant contributions to the field. The superblock family of summation algorithms generalizes the dot product and its error analysis, and allows floating point error to be controlled with a desired target bound and performance loss and with workspace determined at compile time. It demonstrates empirically that theoretical error bounds are good predictors of actual errors. The opposite had been asserted by leading experts in the field. The Master Last algorithm identifies and corrects a heretofore unknown performance drain in multi-core parallelism, Parallel Management Overhead (PMO). The author reduced PMO by as much as two orders of magnitude, and sped up QR and LU matrix factorizations (heavily used by researchers) as much as 65%, and asymptotically as much as 45%. Finally, in the Parallel Cache Assignment algorithm, the author realized the goal of exploiting the "collective cache" of all the cores in a multi-core system for a tightly coupled algorithm with high data dependencies requiring extreme synchronization. This allowed parallelization of some heavily used (and heavily researched) operations in linear algebra, panel factorizations, without changing the flop counts or arithmetic, a feat that had defied parallel researchers for many years. The result was superlinear speedup (as much as 19 times faster for an eight core system) for the QR panel factorization over the previous state of the art serial implementation.