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Role of Borrelia Unfed Tick Induced Protein (BtiP) in the Colonization of the Lyme Disease Agent Within Tick and Mammalian Hosts
Get PDFBorrelia burgdorferi (Bb), the agent of Lyme disease, is transmitted to humans and other vertebrate hosts following the bite of infected Ixodes scapularis tick. Regulation of gene expression influenced by signals prevalent in the tick vector and vertebrate hosts is key to the survival, transmission and colonization of Bb during it natural infectious cycle. Deletion of Borrelia host adaptation Regulator (BadR), a major regulator of gene expression in Bb, resulted in de-repression of rpoS and the rpoS-dependent regulon critical for adaptation of Bb in mammalian hosts while several other determinants likely crucial for the tick-phase of infection were down-regulated. One down-regulated protein in the badR mutant was designated as Borrelia unfed tick induced Protein (BtiP) with no known function although there are two domains resembling a PEGA domain and a sulfatase modifying factor 1/formyglycine-generating enzyme (SUMF1/FGE). BtiP, however, does not encode for the glutamic acid (?E?) in the PEGA domain and lacks typical copper binding residues in the SUMF1/FGE domain, suggesting either a lack of functional homology or reflects a novel role for this protein in the pathophysiology of Bb. BtiP is upregulated in conditions mimicking that of the unfed tick and is downregulated in the badR mutant suggesting a role for BadR in regulating btiP. Overexpression of btiP results in decreased expression of several proteins associated with the mammalian phase of infection such as Outer surface protein C (OpsC) and Decorin binding protein A (DbpA). Consistent with proteins levels of select mammalian phase induced proteins, the transcript levels of the major regulator for these two genes, rpoS , was also elevated when btiP is overexpressed, implying that BtiP could be affecting rpoS indirectly via hitherto unknown mechanisms. The present study underscores the importance that hypothetical proteins could play in the overall pathogenesis of Bb and the need to characterize hypothetical proteins that can uncover novel mechanisms of patho-physiology of Bb during different stages of its infectious cycle in the tick vector and a variety of mammalian hostsMolecular Microbiology and Immunolog
SEOs in the Bizarro World of Meme Stocks
Get PDFThis study examines how meme stocks, defined as stocks with viral social media attention on Reddit WallStreetBets, deviate from traditional financial expectations associated with seasoned equity offerings (SEOs). I find that meme stock companies are more likely to initiate an SEO. Contrary to the typical pattern where issuers strategically inflate earnings before SEOs, meme stock companies exhibit less pre-offering earnings management than other firms. Compared with regular stocks that have average SEO abnormal returns of -2.66%, meme stock companies on average experience positive abnormal returns of 2.07% around SEO announcements. These findings underscore the need to reevaluate established theories on corporate strategies and market reactions in the digital era.Accountin
Essays in Corporate Finance
Get PDFThis dissertation delves into corporate financing decisions, exploring the implications of the composition of capital structures and examining dynamics in lease financing. The first essay studies the relation between corporate cash holdings and financing source granularity (the level of dispersion of a firm's various external financing sources across its capital structure). I document a negative relationship between financing source granularity and cash holdings, which is more pronounced in financially constrained firms, which are likely to have a greater precautionary demand for cash holdings. I also find that during the 2008–2009 financial crisis, firms with more granular financing structures (built up pre-crisis) maintained lower cash ratios compared to otherwise similar firms. Additionally, low-granularity firms place on average a higher value on an extra dollar of cash relative to high-granularity firms. Overall, these findings support the view that the diversification benefits of financing source granularity are larger at the margin for financially constrained firms, reducing their precautionary demand for cash holdings.
The second essay investigates how three key provisions of the Tax Cuts and Jobs Act of 2017 (TCJA) affect firms' use of operating leases in their financing mix. Firms may use operating leases to sidestep TCJA's limitations on tax deductions of debt interest. TCJA's new provisions on bonus depreciation for equipment and the treatment of net operating losses (NOLs) are also likely to affect firms' leasing incentives. Using a panel dataset of U.S. firms from 2015 to 2021, the research employs a difference-in-differences methodology and finds that firms impacted by the TCJA's limitations on interest deductions increase their operating leases and have a greater tendency to shift from non-lease debt financing to lease financing. Findings also indicate that firms impacted by the bonus depreciation provision of the TCJA reduce their operating leases as a percentage of total assets. Furthermore, I find that firms affected by the TCJA's limitations on net operating loss (NOL) carrybacks and carryforwards increase their use of operating leases relative to asset purchases. Overall, these findings support the view that the TCJA had significant effects on firms' financing decisions about operating leases.
The third essay studies the relation between corporate leasing policy and debt granularity, which is defined as the level of dispersion of a firm's debt structure. I document a negative relationship between debt granularity and operating leases, indicating that firms with a more flexible (less concentrated) debt structure use lower levels of leases relative to debt levels. I document that higher asset redeployability amplifies the inverse relation between debt granularity and operating leases. These results are consistent with a firm using leases less relative to debt when the debt structure is more flexible, especially when the firm's asset redeployability is high.Financ
Characteristics and Transport Rates of Mud Aggregates in the Lower San Antonio River
Get PDFIt has long been assumed that all fine-grained sediment is transported in suspension and deposited in low energy environments. However, recent studies have shown that mud can also be transported as bedload in the form of aggregates. This study investigates the characteristics of mud aggregates and their contribution to the total bedload in the lower San Antonio River, Texas. Using bedload samples collected at sampling sites near Floresville, Kenedy, and Goliad, aggregates larger than 2 mm in size were assessed for clast size, constituent grain sizes, color, roundness, and density, and compared to potential source material from the channel. Rating curves developed for the transport rates of aggregates, the gravel fraction, and total bedload were used to computed annual loads with the magnitude-frequency approach. Mud aggregates range from 2 to 11 mm in size, consist mainly of mud, appear gray in color, are moderately rounded, and average 1.99 g/cm3 in grain density. The contribution of aggregates to the total bedload is small, with proportions ranging from 0.001% to 0.32% at the study sites. The effective discharge transports 11% of the annual aggregate load at Floresville and Goliad but 15% at Kenedy. Half of the aggregates are transported by low to intermediate flows. While the presence of aggregates enhances overall bedload magnitude, their limited contribution suggests negligible impact on channel morphology. This study provides challenges to the interpretation of paleoenvironments associated with mud dominated units. Additionally, it demonstrates that mud aggregates are transported as bedload and appears to be the first study to quantify transport rates in a modern environment.Earth and Planetary Science
Comprehension after Concussion: An Analysis of the Impact of Mild Traumatic Brain Injury and Related Symptoms on Sentence and Word-Pair Comprehension
Get PDFMillions suffer a concussion, or mild traumatic brain injury (mTBI), annually. Some will experience persistent symptoms, like slow processing, poor sleep quality, and difficulty carrying a conversation, which can also occur in non-injured individuals. This dissertation explored how mTBI-related symptoms in both injured and non-injured populations affect word and sentence-level comprehension. A multi-methodology approach, which included self-reported symptoms, event-related potentials (ERP), and behavioral measures, was used. Chapter 1 reviews mTBI and language comprehension literature and presents a scoping review of available clinical tools. Chapter 2 presents a listening comprehension study where higher neurobehavioral symptoms after chronic mTBI resulted in slower sentence processing times only when instructions were provided with no time constraints. Chapter 3 presents a self-paced reading comprehension study where the P600, an ERP index for grammatical errors, was equivalent in amplitude for both injured and non-injured groups but was more focally distributed and correlated with sleep quality after chronic mTBI. Chapter 4 presents a word-pair paradigm where non-injured individuals actively predicted a noun after reading an adjective, which created high predictable, low predictable, or incongruent word pairs. Symptoms did not modulate the N400 effect, an ERP index of meaning comprehension, though post-hoc analyses suggested potential avenues for future research. Chapter 5 revealed the importance of validating stimuli obtained from lexical databases for comprehension studies. Chapter 6 presents conclusions and future directions for this nascent research area. This dissertation demonstrates the value of a multi-method approach and the importance of considering symptoms when investigating language comprehension after chronic mTBI.Neuroscience, Developmental and Regenerative Biolog
Beyond the Bachelor's Degree: A Study of First-Generation Graduate Students' Experiences
Get PDFThis study aimed to explore the academic and psychological experiences of first-generation graduate students (FGGS) compared to their continuing-generation counterparts. Utilizing a combination of a MANOVA, ANOVAs, and regression analyses, the research assessed differences in academic success metrics such as GPA, research productivity, and thesis/dissertation progress as well as variables including academic self-efficacy, impostor syndrome, and psychological distress. Overall, findings revealed no significant differences in most variables based on generational status. However, the regression analysis showed impostor syndrome as a notable predictor of psychological distress, with higher levels associated with increased distress. These findings suggest that while generation status alone may not impact academic outcomes directly, impostor syndrome contributes meaningfully to mental health challenges. Future research should continue to investigate the specific challenges FGGS may face and explore target support strategies to improve both their academic outcomes and psychological well-being.Psycholog
The Role of Cultural Identities with Color Evasiveness and Racist Attitudes
No full textUnderstanding attitudes perpetuating racism and racist systems is an essential avenue of research (Loyd & Gaither, 2018). In the modern-day context, racism often takes the form of blaming disparities not on systems of inequity and oppression but on individuals themselves (Keum et al., 2018). In contrast, colorblindness or color evasiveness is the belief that racism and racist ideology do not exist or matter (Keum et al., 2018). Racism results in people actively discriminating against minoritized populations, and color evasiveness disregards the issue. Prior research has indicated that racial identity is associated with racist attitudes among non-Hispanic Whites (Pope-Davis & Ottavi, 1994). Still, these studies have primarily utilized a unidimensional conceptualization of racial identity. This gap is problematic because ethnic/racial identity (ERI) is a multidimensional construct that captures how individuals navigate their attitudes and feelings about their ethnic/racial (Umaña-Taylor et al., 2014)). In addition, past research has ignored U.S. identity (USI) development, another critical component of one’s cultural identity (Meca et al., 2023). Addressing this gap, the proposed study will utilize a sample of 428 college students (74.9% female, Mage=20.58, SD=2.37) to examine the unique association between dimensions of ERI and USI with color evasiveness and racist ideology among non-Hispanic White college students utilizing two separate linear regressions were estimated to determine the associations between dimensions of ERI and USI with Racism and color evasiveness.Psycholog
Who are you calling generic?: Using Generic XML normalization rules for ETDs in Primo VE
No full textPresentation given at the Ex Libris Southcentral Users Group (ELSUG) conference, December 2024.In 2024, UTSA Libraries started hosting electronic theses and dissertations (ETDs) in our DSpace institutional repository. This presentation will describe the process by which those ETDs were added to the library’s Primo VE discovery system, using a discovery import profile and custom normalization rules. Because of the particular metadata needs of theses and dissertations, we chose not to use Primo’s standard Dublin Core normalization rules; instead, we used a more detailed metadata output from DSpace and created Generic XML normalization rules in Primo. I will discuss why we chose this method, examples of how we used normalization rules to manipulate the ETD metadata, and challenges and trade-offs with using Generic XML normalization rules. Primo VE’s Generic XML normalization rules are not especially well documented, so my goal with this presentation is to provide tips and examples to help other libraries create customized normalization rules that fit their needs.Librar
Hypercomplex Automatic Differentiation Finite Element Method in Transient Heat Transfer Problems. Study Case: Powder Bed Fusion of Metals Using a Laser Beam
Get PDFThe full text of this item is not available at this time because the author has placed this item under an embargo until September 11, 2025.The dissertation comprises three papers focused on advancing methodologies for analyzing and optimizing the Powder Bed Fusion of Metals using a Laser Beam (PBF-LB/M) process. The first paper presents a novel approach that combines complex-variable differentiation theory with finite element formulation for transient heat transfer analysis, enabling efficient and accurate first-order sensitivities. Validation against analytical solutions and comparative analysis with finite differentiation demonstrate the robustness and speed of the proposed method. The second paper introduces a method integrating HYPercomplex-based Automatic Differentiation (HYPAD) with transient thermal simulations via the Finite Element Method (FEM) for sensitivity analysis in PBF-LB/M processes. This method significantly reduces computational time while maintaining accuracy, offering superior efficiency compared to conventional methods. The third paper extends the application of HYPAD-FEM to conduct sensitivity analysis of temperature history in PBF-LB/M builds, identifying influential parameters and proposing improvements for the process. The integration of HYPAD-FEM facilitates efficient computation of sensitivities, enabling rapid decision-making for process refinement. Overall, these papers contribute to advancing the understanding and optimization of PBF-LB/M processes, providing powerful tools for researchers and practitioners in the field.Mechanical Engineerin
Black Women's Life Writing and the Representation of Medical Injustices
No full textThis research analyzes how Bettina Judd and Roxane Gay utilize Black feminist theories to amplify their voices and reveal the continual dehumanization of Black women. Black feminist thought, rooted in the activism of the Combahee River Collective, confronts the unique and intersecting oppressions faced by Black women through multiple forms of marginalization, such as race, gender, sexuality, and class, defined Kimberl‚ Crenshaw's theory of intersectionality. As Black feminist thought evolves, theories such as critical fabulation, misogynoir, and Roxane Gay?s bad feminism work to form a framework for understanding how Black women?s oppression is shaped by overlapping social identities and systems of power, and the need for an inclusive, intersectional approach to liberation. In her autobiographical poetry collection Patient, Bettina Judd uses Black feminist methods such as critical fabulation and misogynoir to give agency back to the women silenced through the historical archive; in turn, Judd amplifies her own voice and medical experience to highlight her own body?s violation and demoralization. Roxane Gay?s memoir, Hunger: A Memoir of (My) Body, explores the negative societal stereotypes of obese bodies through a critique of the weight loss industry and diet culture. Through the use of her theory of bad feminism, Gay reinvents the image of her body to emphasize its abuse. Judd and Gay serve as reminders that we must actively fight for equitable care for all women and dismantle the hegemonic systems that perpetuate medical maltreatment.Englis