This dissertation seeks to answer two primary questions stemming from the war between the United States and Mexico: 1) What methods did the United States Army Quartermaster Department employ during the war to achieve their goals of supporting armies in the field? 2) In executing these methods, what lasting impact did the presence of the Quartermaster Department leave on the Lower Río Grande borderland, specifically South Texas during the interwar period from 1848-1860? In order to obtain a complete understanding of what the Department did during the war, a discussion of the creation, evolution, and methodology of the Quartermaster Department lays the foundation for effective analysis of the department's wartime methods and post-war influence. It is equally essential to understand the history of South Texas prior to the Mexican War under the successive control of Spain, Mexico and the United States and how that shaped the wartime situation. The wartime discussion of Department operations is divided into three chapters, reflecting each of the main theaters and illustrating the respective methods and influence within each area. The final two chapters address the impact of the war on South Texas and how the presence of the Quartermaster Department on the Río Grande served as a catalyst for economic, social, and political changes in this borderland region. Combining primary source analysis of wartime logistics with a synthesis of divergent military and social histories of the Lower Río Grande borderland demonstrates the influence of the Department on South Texas during the mid-nineteenth century. The presence of the Quartermaster Department created an economic environment that favored Anglo-American entrepreneurs, allowing them to grow in wealth and begin to supplant the traditional Tejano/Mexican-American power structure in South Texas. Despite remaining an ethnic minority, Anglos used this situational advantage to dominate the region politically. This outcome shaped South Texas for decades to follow.

Sandstone modal compositions and detrital zircon U-Pb analysis of the Paleocene-Eocene Wilcox Group of the southern Gulf Coast of Texas indicate long-distance sediment transport primarily from volcanic and basement sources to the west, northwest and southwest. The Wilcox Group of south Texas represents the earliest series of major post-Cretaceous pulses of sand deposition along the western margin of the Gulf of Mexico (GoM). Laramide basement uplifts have long been held to be the provenance of the Wilcox Group, implying that initiation of basement uplifts was the driving factor for this transition from carbonate sedimentation to clastic deposition. To determine the provenance of the Wilcox Group and test this conventional hypothesis, 40 thin sections were point-counted using the Gazzi-Dickinson method to determine sandstone composition and 10 detrital zircon samples were analyzed by LA-ICP-MS to determine U-Pb age spectra for each of the sampled areas. Modal data for sand grain populations suggest mixed sources including basement rocks, magmatic arc rocks and subordinate sedimentary rocks for the Wilcox Group. Zircon age spectra for these sandstones reveal a complex grain assemblage derived from older sediments and crystalline rocks ranging in age from Archean to Cenozoic. Sediment was primarily derived from Laramide uplifted crystalline blocks of the central and southern Rocky Mountains, the Cordilleran arc of western North America, and arc related extrusive and intrusive igneous rock of northern Mexico. Comparisons of Upper and Lower Wilcox zircon age spectra show that more arc related material was deposited in the Lower Wilcox, whereas more basement material was deposited in the Upper Wilcox. / text

Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1574. Adviser: Elaine Symanski. Includes bibliographical references.

There is an increased need for bilingual education programs throughout the U.S. as a result of the increasing bilingual population, especially Spanish-English bilinguals. With the implementation of such programs there also exists the need to be aware of issues that affect bilinguals and their language learning experience. One of these issues that has been investigated among foreign language learners, but less among bilinguals, is the issue of language anxiety. This case study reports the findings gathered from classroom observations, a language survey, focus group interviews and teacher interviews in order to better understand the issue of language anxiety among heritage language learners on the border. The information gathered from student and teacher participants at a high school in South Texas describes students' language background and attitudes toward language learning as well as teachers' background, beliefs about language teaching. Results include responses from both students and teachers in reference to what creates language anxiety and what can be done in the classroom to mitigate its effects. Results indicate that language anxiety is not the issue of greatest concern, although some lower proficient bilinguals experience it. Rather, it was found that poor classroom management has the ability to affect nearly every other aspect of a language class, directly affecting language expectations, language use, classroom routine, attitudes, and even the level of language anxiety. Due to poor classroom management, a very low expectation has been set for these students and as a result, there is also a low percentage of students who experience language anxiety. Recommendations for improving bilingual language classes come from students' comments during focus group interviews.

Carbonate platforms contain a wealth of information regarding the changing biota, sea level, ocean-chemistry, and climate of the Cretaceous Period. The Comanche platform of the northern Gulf of Mexico represents a vast, long-lived carbonate system that extended from west Texas through the Florida panhandle. In central and south Texas, excellent outcrops and an extensive suite of subsurface data provide an opportunity to document the evolution of this system, from the shoreline to the shelf-margin and slope. This study examines the changing facies, platform morphologies, and shelf-margin architectures of the mixed carbonate-siliciclastic, middle-Hauterivian to lower-Campanian interval. Stratigraphic results are integrated with stable-isotope geochemistry to document the detrimental effects of oceanic anoxic events on the carbonate platform. Seven second-order, transgressive-regressive supersequences of 3-14 Myr duration are defined in south Texas using sequence stratigraphic analysis of shelf-interior facies successions. Second-order supersequences are subdivided into several third-order depositional sequences of 1-3 Myr duration. In these sequences, facies proportions and stratal geometries of the shelf-interior are found to be the result of changing platform morphology and temporal evolution from distally-steepened ramp to rimmed-shelf depositional profiles. Shelf-margin trajectories, stratigraphic architectures, and facies proportions are a function of long-term accommodation trends expressed in second-order supersequences. These characteristics are modified by lateral variability in the underlying structural/tectonic setting and localized syndepositional faulting. The stratigraphic equivalents of oceanic anoxic events 1a, 1b, 1d, 2, and 3 are documented in the Cretaceous section of south Texas. These oceanic anoxic events coincided with maximum flooding zones of supersequences and are linked to carbonate platform drowning events on four separate occasions. The occurrence of oceanic anoxic events is found to be a fundamental driver of carbonate platform morphology, faunal composition, and facies evolution in transgressive-regressive supersequences of the northern Gulf of Mexico. / text

The respective kinetics of bacterial leucine aminopeptidase and [beta]-glucosidase activities were investigated to improve understanding of factors controlling activity and hydrolytic capacity in estuarine organic-poor sands. Depth distributions of enzyme activity and bulk organic matter content were determined in sediments of Aransas Bay and Copano Bay Texas, to investigate enzyme dynamics as related to the geochemical properties of the sediment. Vertical profiles of activity in sediment showed that the enzymes were more active at the surface and that the potential hydrolysis rate of leucine aminopeptidase was higher than that of [beta]-glucosidase. Vertical patterns of enzyme activity correlated (weakly) with variations in sediment organic matter (TOC, TN, and carbohydrates) content. Enrichments of sediment samples with monomeric organic compounds and inorganic nutrients did not affect leucine aminopeptidase and [beta]-glucosidase activities in short- and long-term incubations. Enzyme activity was independent of nutrient availability and suggested that microbial communities were not nutrient-limited. Time-course assays of bacterial hydrolysis of TOC, TN, and carbohydrates provided information about how substrate limitation may affect enzyme activity. Positive correlations between bulk TOC and TN content and enzyme activity indicated enzyme dependence on polymeric substrate content. Induction of enzyme activity after sediment enrichments with specific labile compounds confirmed the importance of available organic substrate to enzyme hydrolysis efficiency. A kinetic approach established the occurrence of enzyme inhibition and its effects on enzyme hydrolytic capacity. The addition of a specific-enzyme substrate to sediment samples modified enzyme parameters and indicated that a substrate-reversible type of inhibitor could reduce enzyme hydrolytic capacity. The addition of polyphenol, as a natural inhibitor of enzyme activity, to the sediment resulted in a concomitant reduction of leucine aminopeptidase activity and ammonium regeneration rate, and thus demonstrated a close coupling between enzyme activity and sediment ammonium regeneration. These research results demonstrate the dynamic nature of the hydrolytic enzymes, provide information about the mechanisms of induction and inhibition of activity, and demonstrate some implications of reducing the hydrolytic capacity to organic matter decomposition and nutrient regeneration rates. / text

The number of Hispanic-Serving Institutions (HSIs) is on the rise. Research suggests that institutions designated as HSIs graduate over fifty percent of Latinos enrolled in college (Santiago, 2006). However, few studies have examined the campus climate of HSIs and how such climate may influence the degree attainment of first-generation, Mexican American students. Considering the instrumental role HSIs have had in advancing the number of Latinos in postsecondary education, this study investigates the campus climate of an HSI along the U.S.-Mexico Border. By utilizing the theoretical frameworks of funds of knowledge (Moll, Amanti, Neff & Gonzalez, 1992) and organizational habitus (McDonough, 1997) this qualitative study involved first-generation, Mexican American students, faculty, and administrators from the University of Texas-Pan American (UTPA). Data collection methods included: student focus groups, individual interviews, observations, reflective notes and a review of relevant documents. Instrumentation used for this study incorporated a student questionnaire as well as pre-established interview questions. Findings revealed students’ perceptions of a Border HSIs, the experiences they describe as helpful in allowing them to obtain a degree; and the institutional characteristics faculty and administrators found critical in allowing first-generation, Mexican American students to persist. This study builds upon a pilot conducted in 2009-2010, that assessed Latino students’ perceptions of HSIs. The goal of this study is 1) to contribute to the literature on first-generation, Mexican American student success and 2) to further enrich our knowledge about the campus climate of Border HSIs and their role in degree attainment of Latinos. / text

Forging Their Legacy: Cooperation and Accommodation in the Lower Rio Grande Valley is an examination of the relationships created during the mid-nineteenth century between Anglo and Tejano elites in the five counties that make up the Lower Rio Grande Valley. Conducted through a quantitative lens, the five-chapter study seeks to demonstrate that, although the period between 1848 and 1870 was fraught with conflict and violence, the Anglo and Tejano elite of the Lower Rio Grande Valley came together in cooperation in order not only to survive these troubling times but to prosper. The thesis begins by identifying and analyzing the economic and political elite in the Lower Rio Grande Valley during the 1850s. A new crop of Anglo immigrants arrived with the Mexican-American War, but only a small number willing to assimilate to local Tejano culture were able to leave their mark on the Lower Valley. Chapter 4 relates the effect of the Civil War on the elite of the Lower Valley. It explores the profitable cotton trade during the war and the struggle that both Anglo and Tejano elites faced during Reconstruction. The thesis concludes with a macro-analysis of the twenty-two-year period from 1848-1870. It summarizes overall trends found in both the Anglo and Tejano elite communities and challenges the often-repeated argument of rapid dispossession by Anglos.

We consider a class of periodic preventive maintenance (PM) optimization problems, for a single piece of equipment that deteriorates with time or use, and can be repaired upon failure, through corrective maintenance (CM). We develop analytical and simulation-based optimization models that seek an optimal periodic PM policy, which minimizes the sum of the expected total cost of PMs and the risk-averse cost of CMs, over a finite planning horizon. In the simulation-based models, we assume that both types of maintenance actions are imperfect, whereas our analytical models consider imperfect PMs with minimal CMs. The effectiveness of maintenance actions is modeled using age reduction factors. For a repairable unit of equipment, its virtual age, and not its calendar age, determines the associated failure rate. Therefore, two sets of parameters, one describing the effectiveness of maintenance actions, and the other that defines the underlying failure rate of a piece of equipment, are critical to our models. Under a given maintenance policy, the two sets of parameters and a virtual-age-based age-reduction model, completely define the failure process of a piece of equipment. In practice, the true failure rate, and exact quality of the maintenance actions, cannot be determined, and are often estimated from the equipment failure history. We use a Bayesian approach to parameter estimation, under which a random-walk-based Gibbs sampler provides posterior estimates for the parameters of interest. Our posterior estimates for a few datasets from the literature, are consistent with published results. Furthermore, our computational results successfully demonstrate that our Gibbs sampler is arguably the obvious choice over a general rejection sampling-based parameter estimation method, for this class of problems. We present a general simulation-based periodic PM optimization model, which uses the posterior estimates to simulate the number of operational equipment failures, under a given periodic PM policy. Optimal periodic PM policies, under the classical maximum likelihood (ML) and Bayesian estimates are obtained for a few datasets. Limitations of the ML approach are revealed for a dataset from the literature, in which the use of ML estimates of the parameters, in the maintenance optimization model, fails to capture a trivial optimal PM policy. Finally, we introduce a single-stage and a two-stage formulation of the risk-averse periodic PM optimization model, with imperfect PMs and minimal CMs. Such models apply to a class of complex equipment with many parts, operational failures of which are addressed by replacing or repairing a few parts, thereby not affecting the failure rate of the equipment under consideration. For general values of PM age reduction factors, we provide sufficient conditions to establish the convexity of the first and second moments of the number of failures, and the risk-averse expected total maintenance cost, over a finite planning horizon. For increasing Weibull rates and a general class of increasing and convex failure rates, we show that these convexity results are independent of the PM age reduction factors. In general, the optimal periodic PM policy under the single-stage model is no better than the optimal two-stage policy. But if PMs are assumed perfect, then we establish that the single-stage and the two-stage optimization models are equivalent. / text