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Multi-Functional Optical Coherence Tomography Assesses Skin Involvement in Systemic Sclerosis
No full textSystemic sclerosis (SSc), or scleroderma, is a chronic autoimmune disorder characterized by fibrosis in the skin and internal organs. SSc has a five-year post-diagnosis survival rate of 77.9%, declining to 55.5% after ten years, and a median survival of approximately 11 years, making early diagnosis and classification important for assessing disease progression and patient survival. The modified Rodnan skin score (mRSS) is the standard for evaluating skin severity in SSc, involving palpation of 17 body sites with scores from 0 (normal) to 3 (severe). Despite being the standard, mRSS requires extensive training for accurate scoring. Thus, an objective tool for evaluating skin fibrosis could revolutionize clinical trials and patient management by improving treatment approvals. My doctoral research focuses on developing a novel technique utlizing optical coherence tomography (OCT) to assess the skin's morphological, mechanical, and microvascular characteristics in SSc patients. OCT is a noninvasive imaging modality with optimal depth (1-2 mm) and resolution (5-15 μm) for detailed characterization of skin fibrosis. It quantitatively measures various tissue parameters, making it well-suited for detecting SSc-related changes. Optical coherence elastography (OCE), an extension of OCT, can enhance assessment by measuring the mechanical properties of skin. Additionally, OCT angiography (OCTA), another extension of OCT, can map the microvasculature affected by SSc, offering another dataset. In my dissertation, I discuss the use of multifunctional OCT for assessing skin involvement in SSc patients. A multifunctional OCT system was developed to detect structural, mechanical, and vascular changes in the skin. Its reliability and operational performance were tested in a murine model of SSc-like fibrosis. The results of the study confirmed that multifunctional OCT could detect alterations in mechanical properties, morphology, and vascular characteristics in murine skin. The system was then converted to a clinic-friendly mobile format at UTHealth. Data was collected from 55 patients and 20 healthy controls, showing high correlation in distinguishing patients from controls but a low-to-moderate correlation with histopathology and qPCR measurements. The next step of this project will be to acquire longitudinal data to evaluate the system's capabilities in detecting changes in skin as the disease progresses in the same cohort of patients
Computational Modeling and Simulation of Viscoelastic Granular Packings
No full textIn the domain of granular materials, understanding the mechanical properties of soft, viscoelastic systems is paramount due to their widespread relevance in both industrial and natural environments. A comprehensive understanding of their compaction behavior is essential for optimizing processes and designing efficient systems. This thesis investigates rate-dependent mechanics of two dimensional (2D) viscoelastic granular packings, aiming to unravel the complex relationship between particle-level properties and macroscopic responses. We perform a suite of finite element simulations under rate-dependent uniaxial compaction. The study commences with an analysis of a granular lattice featuring particles arranged in a square packing, revealing two distinct regimes in force-displacement behavior influenced by loading time-scale and rate-dependent porosity evolution. This investigation extends to polydisperse packings, examining the impact of initial porosity. Analytical models are formulated to predict force-displacement and porosity evolution, enhancing our comprehension of compaction processes. A particle packing algorithm is introduced to generate assemblies compatible to Finite element analysis (FEA) environment, offering the capability to use different particle size distributions (PSDs) and equipped with post-processing options. The thesis also presents systematic study of local statistics of large assemblies for different PSDs by using the aforementioned post-processing options. A concept of microstructurally equivalent statistical volume elements (ME-SVEs) is introduced to capture characteristics of the large parent assembly efficiently. A specific focus is given to interface strength in deformable granular systems, particularly in the context of vitrimers compaction. An analytical model is developed to investigate the evolution of chain density at the interface between different networks, resulting in a transient advection-diffusion-reaction (ADR) equation. The influence of temperature and association-dissociation rates on interface welding has also been presented. Overall, the findings in this thesis expand our understanding of 2D viscoelastic granular systems, offering insights for process optimization and designing materials with tailored mechanical properties
Spatiotemporal Variations in the Radiant Energy Budgets of Mars and Earth
No full textA planetary body’s radiant energy budget is a critical geophysical parameter in the context of its climate. For a terrestrial planet, the delicate balancing between the absorbed solar power and emitted thermal power is directly responsible for the circulatory behavior its atmosphere (and oceans, in Earth’s case). Practically, energy budgets are challenging to measure, and investigations thereof beyond Earth are constricted by limited datasets. This dissertation investigates the energy budgets of Mars and Earth.
First, the first meridional profiles of Mars’ energy budget are generated at seasonal and annual timescales from long-term, multi-instrument measurements returned by Mars Global Surveyor in Martian orbit. Mars, being a dry, dusty planet with a thin atmosphere, no oceans, and a fairly eccentric orbit, experiences temperamental interseasonal variations with significant hemispheric asymmetry. Near perihelion, global dust storms further perturb these transient, yet periodic energy imbalances. These results are immediately applied to analyze the CO2 budget of Mars’ ice caps.
Secondly, Mars’ energy budget is compared to that of Earth, which is derived from modern, high fidelity radiance measurements provided by CERES-EBAF. Owing to the unique environments and characteristics of each planet, their energy budgets are dissimilar. Earth, with a much thicker atmosphere, a global ocean, and nearly circular orbit, exhibits smaller, consistent seasonal varia- tions. Annually, Mars’ energy budget features large polar excesses with minor equatorial deficits – the opposite is true for Earth.
Finally, a deeper reanalysis of Earth’s energy budget demonstrates the scientific potential of large datasets. We examine ENSO (El Niño–Southern Oscillation) and its role within Earth’s energy budget during the years 2001–2022. They are strongly correlated – consistent with historical record. Variations in each energy budget component over the tropical Pacific Ocean were able to exceed 10% of their background values – 20% for net power. Principal component analysis further reaffirms ENSO’s state as the dominant source of tropical radiance anomalies and troubleshoots the performance of models. In the future, when more complete datasets are compiled for other planets, these procedures can serve as a foundation for exploring otherworldly climates
International Students at U.S. Community Colleges: How Do Course-Taking Patterns Influence Associate Degree Completion and Four-Year Transfer?
No full textBackground: While international students have traditionally enrolled in four-year institutions, more are now opting for community colleges as a pathway to transfer. Analyzing course-taking patterns is a key method for predicting student success in community colleges. While course-taking patterns are commonly studied to assess early academic progress, their potential role in predicting time to degree completion or transfer is often overlooked. This gap is particularly evident for international students. Purpose: The purpose of this quantitative study was to investigate the association between course-taking patterns and time to associate degree completion or four-year transfer of international students attending a large, urban community college system in Texas. This study seeks to answer three questions: (1) What are the demographic characteristics, program of study, and course enrollment outcomes of international students attending a large, urban community college system in Texas? (2) What are the student profiles based on course-taking patterns among international students?, and (3) How do different student profiles predict the time to associate degree completion or four-year transfer among international students? Methods: This is a longitudinal transcript data analysis. The sample (N = 671) included a cohort of associate degree-seeking international students who first enrolled in Fall 2016. Data analysis included (1) descriptive statistics, (2) Latent Class Analysis (LCA) to identify course-taking subgroups, and (3) Discrete-Time Competing Risk Survival Analysis to examine subgroup outcomes over time. Findings: LCA identified three classes of course-taking patterns: (1) foundational pathway, (2) transition pathway, and (3) accelerated pathway. Key findings revealed that international students follow distinct course-taking pathways that significantly influence their academic outcomes. Students in the accelerated pathway demonstrated the highest rates of degree completion or transfer and progressed more quickly through college-level coursework. In contrast, those in the foundational pathway experienced lower completion rates and high dropout/stopout risks, often due to developmental and ESL needs. Race and ethnicity also emerged as important factors, with Asian and Black international students showing higher success rates than their White peers. Conclusion. These results underscore the critical role of early academic momentum and structured pathways in promoting successful outcomes for international students at U.S. community colleges
Fluorinated Sandwich Diimine Palladium and Nickel Complexes: Synthesis, Activity, and Applications
No full textPolyethylene is the most produced plastic in the world. Much of this plastic is produced using early transition metal catalysts. While efficient, these catalysts have limitations. To address these issues, late transition metal catalysts were developed by Brookhart in 1996. While initial reports were promising, there was room for improvement. This led our group to develop sandwich diimine catalysts, which were able to suppress chain transfer better than the original catalyst. However, these catalysts were less active than the original system. In Chapter 2, this issue was addressed by developing fluorinated sandwich diimine complexes. These complexes were found to be more active and stable and produced more branched polyethylene than the previously reported sandwich complexes. Additionally, the fluorinated palladium sandwich complex was able to use hydrogen gas to reduce polymer molecular weight without the loss of catalyst activity. The nickel system was highly active and stable with the ability to produce polyethylene with molecular weights ranging from 1 to 40M Da, and branching ranging from 10 branches per 1000 carbons to 100 branches per 1000 carbons. In Chapter 3, we show that these catalysts are able to polymerize 1-hexene and propylene under living polymerization conditions. Given the efficiency of the nickel systems, they were used to create block copolymers with blocks of linear and highly branched polyethylene by changing reaction conditions during ethylene polymerization. In Chapter 4, functionalized polyethylene-polypropylene diblocks were produced by iron-catalyzed “catalyzed chain growth polymerization” with diethyl zinc. This enabled low molecular weight diblocks to be made. Unfortunately, polymer production was inefficient and was competitive with β-H elimination. Finally, Chapter 5 explored the synthesis of polyethylene-polyketone block copolymers using a fluorinated sandwich diimine palladium catalyst. While this catalyst was able to produce polyketone by copolymerizing ethylene and carbon monoxide, the catalyst quickly decomposed under these conditions. As consequence, only polyethylene-polyketone diblocks with very low polyketone incorporation could be obtained
All Native Microbial Amendments Not Made Equal: One Location Optimizes Ecological Restoration Metrics
No full textEcological restoration projects often suffer from poor plant performance and soil erosion. Recent studies support using microbial soil amendments to bolster restoration outcomes. Moreover, native whole-soil amendments have been shown to outperform commercial amendments. However, native soil amendment donor locations may differ in their soil microbial community composition, structure or function, which may change the efficacy of restoration. Using a greenhouse experiment, we investigated the differential impacts of native soil amendments from 11 established coastal dunes—each with unique land use histories and biotic and abiotic characteristics—across the Texas Gulf Coast on communities of five native dune plants. In comparison to sterile equivalents, live amendments improved plant community performance, diversity, arbuscular mycorrhizal (AM) fungi colonization and the density of AM fungal extra-radical hyphae (ERH), which is strongly connected to soil stability. The extent of improvement varied significantly by the soil amendment’s location of origin. The best-performing soil amendment had a 2-3-fold increase in community total biomass compared to all other live treatments. There were no significant effects of soil amendment origin when sterile treatments were isolated, indicating that the microbial community is driving the changes in restoration metrics, as opposed to the abiotic soil characteristics. The best-performing soil amendments originated from dunes with high plant species richness and ERH. Previous research has shown that restoring native microbial communities is critical for overall restoration success; this study takes that principle a step further, encouraging restoration practitioners to not only restore the native microbial community but to optimize it
The Relationship Between Maternal Personality Pathology and Parent Emotion Socialization: The Moderating Effect of Reflective Function
No full textAbundant research has demonstrated that mothers with personality pathology, specifically borderline personality disorder (BPD), encounter notable challenges when parenting. However, there is a paucity in research examining parenting within mothers with personality pathology using levels of personality functioning (LPF) as defined by the Alternative Model for Personality Disorders. No studies have examined the relationship between maternal LPF and parent emotion socialization (PES), or the process by which parents shape their children’s ability to express and regulate their emotions, which has the potential to confer the risk of developing psychopathology in children with a genetic predisposition to personality pathology when unsupportive in nature. Further, the impact that reflective functioning (RF), a type of mentalizing used within attachment relationships, has on the relationship between maternal personality pathology and PES has not been examined despite the protective nature of RF. Against this background, the current study used a sample of 149 mothers from across the United States (ages 21 – 53, M = 34.88 years) to test three aims: 1) examine relations between maternal LPF and PES; 2) evaluate group differences between mothers with BPD, a useful proxy for LPF, and healthy control mothers on PES; 3) examine the moderating role of RF on the relationship between maternal LPF and PES. The Level of Personality Functioning Scale Brief Form 2.0 (LPFS-BF 2.0) was used to measure maternal LPF, the Coping with Children’s Negative Emotions Scale (CCNES) was used to measure PES, and the Reflective Functioning Questionnaire – 8 item form (RFQ-8) was used to measure maternal RF. Findings indicated that maternal LPF was positively correlated with non- supportive PES and negatively correlated with supportive PES. While controlling for mother age, which was identified as a covariate, mothers with BPD and healthy controls were not found to systematically differ in their use of supportive or non-supportive PES. Further, while controlling for mother and child ages, RF did not have a significant moderating effect on the relationships between maternal LPF and supportive and non-supportive PES. Taken together, findings suggest that increasing supportive PES and decreasing non-supportive PES could be helpful treatment targets for mothers with personality dysfunction
Academic Momentum Patterns in CTE Dual Enrollment: Analyzing Credit Accumulation, Postsecondary Matriculation, and Credential Completion
No full textBackground: CTE dual enrollment is expanding amid policy shifts promoting collaboration between schools and colleges. Unlike academic pathways, CTE's impact on college enrollment and completion is understudied. Demographic factors like race, gender, and location shape access and outcomes. This study explores credit accumulation and academic momentum to inform strategies that improve post-secondary success for diverse CTE student populations. Purpose: This quantitative study examines how CTE dual enrollment participation influences college enrollment and credential completion, using Wang’s academic momentum framework. Conducted using data from a Texas community college system serving over 20,000 dual enrollment students, it explores: (1) the relationship between CTE credit accumulation and post-secondary outcomes, and (2) how race, gender, and high school location associate with matriculation and credential completion. Findings aim to inform equitable program development and policy. Methods: This quantitative study used institutional data from 12,076 students who participated in CTE dual enrollment from Fall 2014 to Spring 2024. Binary logistic regression analyzed how personal (gender, race), contextual (GPA, credits, credential attainment), and institutional (school type, CTE discipline, district classification) factors influenced postsecondary matriculation and credential completion outcomes. Results: The study showed that academic momentum, particularly credit hour accumulation and GPA, strongly predicted both matriculation and credential completion among CTE dual enrollment students. Students with higher momentum were more likely to persist and succeed. Additionally, demographic factors—such as race, gender, and geographic location—significantly influenced outcomes. Female students and those from higher-performing or suburban high schools were more likely to complete credentials. Racial disparities were present, with students of color less likely to complete and matriculate. These results suggest that both individual academic factors and systemic demographic contexts shape student success in CTE dual enrollment pathways. Conclusion: This study reveals how student, academic, and institutional factors influence credential completion and matriculation in CTE dual enrollment. Findings underscore the need for equity-focused program design and further research to understand diverse learner outcomes. Insights support improving CTE pathways to better serve underrepresented students and guide future policy and practice
Limited Frequency Bandwidth on the Inverse Scattering Model and the Effects on Seismic Processing Goals
No full textSeismic exploration aims to determine the properties of the Earth's subsurface by analyzing the recorded wavefield to locate and characterize geological formations with hydrocarbon potential. A crucial component in this process is the frequency content of the seismic source. The absence of certain frequencies, particularly low frequencies, can significantly affect the resolution and accuracy of subsurface imaging and inversion techniques. Low-frequency waves offer enhanced depth penetration and stability, making them essential for seismic applications such as full-waveform inversion and near-surface characterization. This study seeks to determine the effects of missing frequency components, especially low frequencies, on seismic data processing within the framework of the Inverse Scattering Series (ISS). The ISS provides a multidimensional inversion methodology that directly estimates subsurface properties and reflector’s location from reflection data, fulfilling objectives such as the free surface and multiple removal. This research derives analytical expressions for the first two terms, α_1 (z) and α_2 (z), of the ISS under three scenarios: (1) missing low-frequency components, (2) missing high-frequency components, and (3) band-limited sources lacking both. The derivations are performed for one-dimensional and three-dimensional acoustic models, with constant density and varying velocity, and are compared with known expressions derived by previous researchers under the assumption of a seismic source with all frequencies available. Results indicate that when some frequencies are absent, α_1 (z) and α_2 (z) cannot be fully determined; instead, estimated expressions (α_1 (z)_est and α_2 (z)_est) are acquired. The study concludes that limited frequency bandwidth, particularly at low frequencies, has a large effect on inversion. However, imaging appears less affected. Broaden low-frequency bandwidth in seismic sources can significantly improve the reliability of the estimation of both subsurface property and location, and as a result increasing the probability of success for drilling operations and hydrocarbon production
The Perceptions of Coaches Teaching Character Education to Student-Athletes
No full textBackground: Due to the United States having one of the world’s highest levels of single-parent homes, over the past 20 years, there has been increased federal funding and implementation of character education curricula in the United States. Purpose: This study examined the perceptions of coaches teaching character education to student-athletes. This research allows the reader to learn how coaches perceive teaching character education lessons to their student-athletes. Method: Qualitative research was the best approach for this study to identify topics or perceptions that needed to be explored. This research interviewed six high school coaches utilizing semi-structured interviews. Results: The coaches’ perceptions revealed five central themes. Teaching lifelong lessons was the first; all coaches perceived character education as a tool to teach lifelong lessons to their student-athletes. The second theme is implementing character education campuswide. The research indicated that integrating character education lessons with English classes can be done efficiently and effectively for students. There are two types of character education, was revealed as the third theme. All coaches identified that character education can and should be taught in two forms: formal and informal. Five of the six coaches received only informal character education in high school and have learned that teaching formal character education is the new initiative in the past ten years. Effective character education was identified as the fourth theme; all six coaches believe character education should be taught free of standardization, and character educators should teach what they deem most appropriate for their students for character education to be effective. The last theme identified was that standards-based curriculum and character education complement each other. Five coaches perceive that character education and standards-based curriculum go hand in hand. In terms of one being more important than the other, not one coach mentioned standards-based curriculum being more critical. Conclusion: The data revealed that these coaches perceive teaching character education as vital. Character education is a subject that should be taught without the lessons tied to a standardized curriculum