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A Study of the Thermodynamic Properties of Nd-C and Ce-C TRISO Fission Product Binary Systems
No full textTRISO fuels are proposed for portable and modular power reactor technologies. Expansion is dependent upon improvements to safety through a thorough understanding of fission product behavior as related to functional containment design philosophies. Significant knowledge gaps exist in the thermodynamic behavior of neodymium and cerium fission products solubility in graphite, which play a role in the qualification of TRISO fuels. DSC measurements were conducted on Nd-C and Ce-C carbide fission products to expand upon calculated phase equilibria. Various crucible tests, calibrant experimentation, sample generation and sample preparation techniques, and new thermodynamic measurements have been performed. New phase equilibria were produced to improve Nd-C and Ce-C phase diagrams and further inform models of fission product behavior within TRISO fuels. The following phase transition temperatures are reported for Nd-C, with an error of &plusmn;32.7 &deg;C: 10 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>844.6</mn></mrow></semantics></math></inline-formula> &deg;C, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>891.2</mn></mrow></semantics></math></inline-formula> &deg;C, and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>911.2</mn></mrow></semantics></math></inline-formula> &deg;C; 16 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>724.1</mn></mrow></semantics></math></inline-formula> &deg;C and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>771.2</mn></mrow></semantics></math></inline-formula> &deg;C; 20 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>731.8</mn></mrow></semantics></math></inline-formula> &deg;C; 25 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>726.1</mn></mrow></semantics></math></inline-formula> &deg;C and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>762.2</mn></mrow></semantics></math></inline-formula> &deg;C; 30 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>718.5</mn></mrow></semantics></math></inline-formula> &deg;C and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>976.4</mn></mrow></semantics></math></inline-formula> &deg;C; 35 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>825.1</mn></mrow></semantics></math></inline-formula> &deg;C and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>995.3</mn></mrow></semantics></math></inline-formula> &deg;C; 40 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1274.6</mn></mrow></semantics></math></inline-formula> &deg;C. The following phase transition temperatures are reported for Ce-C with an error of &plusmn;32.7 &deg;C: 20 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>878.6</mn></mrow></semantics></math></inline-formula> &deg;C; 32 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>714.7</mn></mrow></semantics></math></inline-formula> &deg;C and 857 &deg;C; 67 mol%C&mdash;<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1138.7</mn></mrow></semantics></math></inline-formula> &deg;C.Physics and Astronom
Volatile-rich Sub-Neptunes as Hydrothermal Worlds: The Case of K2-18 b
No full textTemperate exoplanets between the sizes of Earth and Neptune, known as "sub-Neptunes", have emerged as intriguing targets for astrobiology. Yet, it is unknown whether these planets resemble Earth-like terrestrial worlds with a habitable ocean [1], Neptune-like giant planets with deep atmospheres and no habitable surface [2-4], or something in-between [1, 5]. Yu et. al [2] proposed that the observed atmospheric composition may reveal the lower-boundary conditions of temperate sub-Neptunes. Recently, the transmission spectra of two canonical sub-Neptunes, K2-18 b and TOI-270 d, have become available to test this theory. However, the existing proposed lower boundary conditions have not been able to simultaneously explain the retrieved atmospheric concentrations of ~1% CH₄, ~1% CO₂, and non-detection of CO for both planets [1, 4, 6]. In this work, we investigate whether a global supercritical water ocean can explain the JWST observations of K2-18 b-like sub-Neptunes through equilibrium aqueous geochemical calculations. This possibility for an exoplanet has yet to receive quantitative treatment.
We model the ratios of CH₄/CO₂ and CO/CO₂ at the aqueous-gas phase saturation boundary by calculating the equilibrium and Henry’s Law constants using the Deep Earth Water (DEW) model [7]. To match with the observed CH₄/CO₂ and CO/CO₂ ratios of K2-18 b [1], our calculated CH₄/CO₂ ratios correspond to an ocean temperature range of ~710-1170 K, and our calculated CO/CO₂ ratios are consistent with ocean temperatures below ~1070 K. These findings indicate that K2-18 b could harbor a global supercritical water ocean in the temperature range of ~710-1070 K. While our current understanding of the upper-temperature limit for life indicates that familiar life cannot survive in this ocean, this work takes the first step towards understanding how a global supercritical ocean influences observable atmospheric characteristics on K2-18 b and precludes its habitability.
[1] Madhusudhan et al (2023). ApJL, 956(1). [2] Yu et al (2021). ApJ., 914, 38 [3] Tsai et al (2021). ApJL, 922, L27. [4] Wogan et al (2024). ApJL, 963, L7. [5] Benneke et al (2024). arXiv e-prints, arXiv:2403.03325 [6] Shorttle et al (2024). ApJL, 962(1). [7] Sverjensky et al (2014). GCA, 129, 125.Physics and Astronom
THE RULES OF THE GAME: HOW CHANGES IN THE GOVERNANCE OF THE MARKETPLACE HAVE UNDERMINED DEMOCRACY IN THE UNITED STATES
No full textBetween the 1940s and 1970s, our nation saw widely shared prosperity and nearly equal rates of income growth across all quintiles of the income distribution. Then, beginning in the 1970s, we saw a stunning reversal of this trend. Many explanations for this phenomenon have been proposed, including tax cuts, technological change, immigration, the decline of unions, and judicial decisions. However, each of these explanations assumes that market forces operate under individual rational calculation and social efficiency alone, but forget something crucial: the political quality of market processes and outcomes. That is the distributive implications of each of these phenomena can be explained by changes in the rules governing the economy.
Thus, the explanation for the rise in income inequality, stagnant wage growth for the lower- and middle-class, and for the increased concentration of economic power that characterizes our political economy today is that deliberate changes were made in the predistributive rules governing the economy due to neoliberal influences that rose to prominence in the 1970s. If we examine the difference in economic governance between the New Deal, neoliberal, and neo-Brandeisian regimes, we can see vastly diverging economic outcomes and distributive consequences. The impact of the change from the New Deal regime to the neoliberal regime can be demonstrated through the case of Amazon, in which they have maintained a monopoly in the online retail market by engaging in anti-competitive behavior and have leveraged their massive economic power to heavily influence the government. The Biden administration then ushered in the neo-Brandeisian regime, which filed an antitrust case against Amazon to address their poor market behavior. Although this regime was short-lived, it demonstrated something crucial: that we can use the antitrust tools from the New Deal to bring back the widely shared prosperity our nation once enjoyed.Political Science and Geograph
Pray the ADHD Away? An Analysis of the Intergenerational Nexus of Religion, Symptoms, and Diagnosis
No full textAttention-deficit/hyperactivity disorder (ADHD) is one of the most commonly diagnosed neurodevelopmental disorders in the U.S. and is linked to a higher risk of comorbid mental and physical health problems and shorter life expectancies. Outcomes suggest ADHD’s impact extends beyond the individual, affecting society through rising costs in disability, healthcare, caregiving, education, unemployment, and lost productivity. Despite significant personal and societal costs, research often prioritizes treatment over prevention. While previous studies have contributed to understanding ADHD’s causes and consequences, little is known about the intersection of religiosity and ADHD. This gap is notable, considering religiosity is associated with greater social resources, lower stress, healthier lifestyles, better mental and physical health, and longer life expectancies. Given that religiosity is associated with nearly everything that is associated with ADHD, this study will utilize data from The National Longitudinal Study of Adolescent to Adult Health (Add Health) to explore the role of religiosity in ADHD across the life course and generations. Specifically, it will examine the following research questions: (1) Do levels of ADHD symptoms vary by level of religiosity? (2) Do rates of ADHD symptoms vary by level of religiosity? (3) Does the pathogenesis of ADHD, operationalized as the association between symptoms and subsequent diagnosis, vary by religiosity? (4) Does the intergenerational transmission of ADHD diagnosis vary by level of religiosity? This research will contribute to the general study of ADHD by exploring the novel role of religiosity and the specific study of religion and mental health by exploring an understudied outcome.Sociolog
La Situación Infeliz - A Demographic Examination of Resilience in Spanish Colonial San Antonio
No full textThis dissertation included two fundamental research objectives. The first research objective resulted in the design and compilation of demographic data sets that provided the basis for a new historical demographic examination of Spanish Colonial San Antonio, 1718-1802. The attainment of the first research objective allowed comparative analysis of the new demographic results with the earlier demographic work of Tjarks (1974) and Meacham’s (2000). The second research objective was the presentation of the new demographic results and an analysis of those results using a resilience theoretical framework.
The compilation and analysis of the new demographic databases demonstrated similarities as well as differences with earlier research. The reflexive expansion of the data resulted in finer granular detail on several demographic subjects, particularly the consequences of highly skewed male sex ratios including early age at first marriage/singulate mean age at marriage, serial marriage of women and men, a single-never-married men. The role of high male mortality from violent encounters with Native Americans is also examined in greater detail. The sources of and the importance of in-migration and major in-migration events on San Antonio is also examined in finer detail. Finally, all of these are examined through the lens of resilience theory to frame and account for the policies, actions and inactions that directly affected total population in eighteenth century San Antonio.Anthropolog
Navigating the Post-Pandemic Classroom: The Impact of COVID-19-Related Stress on Academic and Student Mental Health Outcomes in Undergraduate Students
No full textThe COVID-19 pandemic significantly disrupted global education systems, leading to widespread academic and psychological challenges for undergraduate students. This study examined the lingering effects of COVID-related stress on academic outcomes—Grade Point Average (GPA), academic engagement, and academic self-efficacy—as well as student mental health, including stress, anxiety, and depression. The moderating role of social support was also explored to determine whether it buffered negative psychological or academic outcomes. Participants (N = 411) were undergraduate students who completed an online survey via Qualtrics, which included validated instruments assessing mental health, academic functioning, and pandemic-related stress. Correlational analyses and multiple regressions were conducted to evaluate associations among key variables and test for moderation effects. Results indicated that COVID-related stress was significantly associated with elevated depression, anxiety, and stress, but was not significantly related to GPA, engagement, or self-efficacy. The findings suggest that while students continue to experience the psychological burden of the pandemic, their academic performance may remain resilient. Social support did not significantly moderate the relationship between COVID-related stress and academic or mental health outcomes. These results highlight the complexity of post-pandemic adjustment and emphasize the need for continued institutional support aimed at student mental health and
academic sustainability. This research contributes to the growing understanding of how students are navigating the long-term impacts of the pandemic in higher education contexts.Psycholog
San Antonio Tricentennial Educator Resources
No full textIncludes information about speakers, presentations, and workshop venues from the San Antonio Tricentennial Summer Institute for Educators
Polyamines Impact Histone Methylation Landscape and Pluripotency State in Mouse Embryonic Stem Cells
No full textMutations affecting chromatin factors are among the hallmarks of malignancy, developmental disorders, and neurological diseases. Less well-understood are polyamines – small, positively charged molecules that interact with nucleic acids and organize chromatin fiber topology. Mutations in Spermine synthase (SMS) gene encoding the final enzyme in the polyamine biosynthesis cascade cause Snyder-Robinson Syndrome (SRS, OMIM: 309583), a disease characterized by intellectual disability, craniofacial abnormalities, and fatal premature aging. Further, imbalance in cellular polyamine levels is associated with several cancers as well as aging and neurodegeneration. Yet in vivo functions of polyamines remain poorly understood, and how polyamine deficit causes disease is unknown. Our results demonstrated that polyamine depletion synergizes with 2i induction of naïve pluripotency in mouse ES cells (mESCs), inducing major increase in repressive H3K27me3 mark as documented by Western blot. We also found that depletion of polyamines in mESCs results in increased expression of both pluripotency and differentiation marker genes. Since both gene types are regulated by Polycomb repressive complex 2 (PRC2) in ES cells, it is possible that polyamine depletion results in failure of Polycomb-driven repression independent (i.e. downstream) of histone methylation.Molecular Microbiology and Immunolog
Musical Investigations: Research Perspectives on a Master's Recital
No full textThis document explores research topics on Sergei Rachmaninoff’s Six Romances: Opus 8, Camille Nickerson’s Five Creole Songs, and Vincenzo Bellini’s “Qui la voce” from I Puritani. The first chapter explores Rachmaninoff’s adherence to tradition and the musical styles of Romantic Period at the turn of the 20th century, when contemporaries were exploring serialism and atonality. The second chapter introduces Nickerson’s Five Creole Songs in the wake of Louisiana’s long history of colonialism and cultural intermixing. An analysis of the songs, and the intermixing of culturally diverse musical elements, demonstrates Louisiana’s history of creolization. The final chapter investigates “Qui la voce” as a case study of Bellini’s compositional style, highlighting his operatic innovations. Together, these chapters offer a deeper understanding of the tradition, cultural exchange, and innovation exemplified in these works.Musi
Effect of Bacterial Infection By-products on the Corrosion and Passivation of Titanium Bone-implants in Simulated Synovial Fluid
No full textTitanium (Ti) is widely used in dental and orthopedic implants due to its biocompatibility, favorable mechanical properties, and relatively low corrosion susceptibility.1 Compared to alternative materials, Ti offers a high initial success rate of over 98% in the first two years post-operation.2 However, implant failure remains a concern, with long-term survival rates declining to 85–90% at ten years and as low as 58% at 25 years.3, 4 Corrosion is a major contributing factor to implant failure5, particularly in the presence of bacterial byproducts. With approximately 800,0006 knee replacement surgeries performed annually in the United States and an expected increase to four million joint replacements per year by 20302, understanding implant longevity is critical.
This study investigates the impact of lipopolysaccharide (LPS), a byproduct released from gram-negative bacterial biofilms during infection, on the corrosion and self-healing behavior of Ti (Grades 2, 4, and 5) in simulated synovial fluid (SSF) at physiological temperature (37°C) using electrochemical techniques. Based on the Pourbaix diagram, the self-healing process of Ti involves the sequential formation of TiO, Ti2O3, and ultimately a TiO2 passive layer following initial corrosion. LPS was found to reduce the corrosion current density of polished Ti, indicating an initial inhibitory effect on corrosion. However, it had no impact on the passivation current density of aged or pristine Ti, suggesting that its influence is limited to the early stages of oxidation. While LPS accelerates the formation of a natural passivation layer, the self-healed oxide is structurally inferior to the native TiO2 layer. Electrochemical impedance spectroscopy (EIS) modeling suggests that the naturally formed passivation layer is porous and significantly thinner, raising concerns about its long-term protective capability. These findings highlight the need for further investigation into the stability of Ti implants in infection-prone environments.Biomedical and Chemical Engineerin