Physical Sciences and Mathematics Commons^™

Examining Marine Fungal Nitrous Oxide Production, Qintiantian Nong

Theses and Dissertations

Nitrous oxide (N2O), a potent greenhouse gas, can be produced by microorganisms inhabiting marine environments. While bacterial denitrification is a major source of N2O, the role of marine fungi in this process remains poorly constrained. This thesis investigates the contribution of marine fungi to N2O production from salt marsh sediments, while also isolating new N2O-producing marine fungi and advancing methodological approaches for quantifying denitrification. First, we conducted experiments to quantify the fungal contribution to N2O production using salt and brackish marsh sediments collected from the North Inlet–Winyah Bay National Estuarine Research Reserve in South Carolina during the summer and winter …

Contributions Toward Understanding The Weak Lefschetz Property For Two Classes Of Almost Complete Intersection Ideals, Matthew Davidson Booth

Theses and Dissertations

In 1980, Richard Stanley proved that Artinian monomial complete intersections enjoy the strong Lefschetz property in characteristic zero. Since his landmark result, the strong and weak Lefschetz properties (SLP and WLP) have garnered attention from an increasing number of mathematicians from an ever-broadening swath of the mathematical community. Indeed, the Lefschetz properties have been scrutinized for their relation to algebraic invariants such as Betti numbers and the Hilbert function as well as their links from commutative algebra to other branches of mathematics.

However, the Lefschetz properties are also quite subtle; the aforementioned result due to Stanely is a rather rare …

Rating Ai Models For Robustness Through A Causal Lens, Kausik Lakkaraju

Theses and Dissertations

As Artificial Intelligence (AI) systems become increasingly powerful and widely accessible, trustworthiness remains a major barrier to their adoption in critical domains such as finance and healthcare. With the advent of large language models (LLMs) that can perform multiple tasks with strong empirical performance, users increasingly rely on these black-box AI services to obtain recommendations, analyze text, and support everyday decisions. However, real-world incidents and empirical studies show that these systems can be overly sensitive to small changes in input, producing outputs that shift substantially under minor perturbations. In addition, models have been reported to exhibit stereotypical behavior and systematic …

Exploring The Efficiency Of Logistic Models With Opt-Out Designs In Discrete Choice Experiment And Their Applications, Dai Fang

Theses and Dissertations

A discrete choice experiment is usually conducted in economics background to measure how consumers would like to trade off attributes of a product, service, or policy. In this experiment, respondents are provided different hypothetical combinations of varied components by using an experimental design such as the full factorial design, which fully represents the all combinations of attributes and levels. The mathematical background of a discrete choice experiments is based random utility theory, in which either positive or negative values are given each characteristic and the weighted sum values of each choice given in the experiment will be compared. This experiment …

Evidence Of Metal-Microcystin Complexation And Its Potential Role In Environmental Fate, Ashley Marie Womer

Theses and Dissertations

Microcystins that enter freshwater systems pose a threat to human health therefore their fate and transport throughout the water column have been intensively studied. While sediment has been regarded as an environmental fate for microcystin (MC), less is known about the molecular mechanisms by which microcystin interacts with the sediment and/or the thermodynamic stability of these interactions. While microcystin has a half-life in lake water on the order of weeks, microcystin adsorbed to sediment can be detected hundreds of years later1-2. Microcystin has been desorbed from these sediments with various EDTA solutions, therefore, work is presented to support the hypothesis …

Surface Salinity Variability And Loop Current Frontal Eddy Activity In The Gulf Of Mexico, Pamela Jo Lee

Theses and Dissertations

The Gulf of Mexico (GoM) is a dynamic semi-enclosed basin where mesoscale and submesoscale circulation regulate the distribution of freshwater, nutrients, and biological productivity. The Loop Current System (LCS), which includes the Loop Current (LC), Loop Current Eddies (LCEs), and Loop Current Frontal Eddies (LCFEs), exerts the dominant control on basin-wide circulation. These features interact with freshwater input from the Mississippi-Atchafalaya River System (MARS) and with saline inflow from the Caribbean, resulting in variability in sea surface salinity (SSS) and chlorophyll-a (Chl-a) across a range of spatial and temporal scales. A primary focus of this work is understanding how the …

A Combined Observational And Reanalysis Approach To Beaufort Gyre Freshening, Christina Mccarty Gregory

Theses and Dissertations

The freshwater (FW) content in the Arctic plays a critical role in the global climate by influencing the regional physical and biological processes, large-scale ocean circulation in the North Atlantic, sea-ice albedo, and other crucial climate parameters. Located in the Canadian Basin, the Beaufort Gyre (BG) is the largest retainer of FW in the Arctic. Here we examine the dynamics of the BG between 2016-2018 using satellite-derived products and ocean reanalysis parameters. Our results demonstrate that the characteristics of BG during the years of this study are a complex combination of various processes. The Ekman-induced FW fluxes were separated into …

Continuous Imaging Of The Shallow Subsurface Of Horry County Using Gpr And Auger Data, Chase William Robinson

Theses and Dissertations

Welded barrier systems are common along passive margins globally and make up approximately 15% of the coastlines around the world. The subsurface facies assemblages of welded barrier systems record depositional histories and past sea-level dynamics, but their complicated depositional architecture can be problematic for understanding aspects like groundwater flow and freshwater-saltwater exchange. Most studies of modern welded barrier sedimentary systems using ground penetrating radar (GPR) rely on a few 100 meters of subsurface data supplemented with a few drill cores. In this study, we used over 75 km of 100MHz and 25MHz GPR data and 195 auger drill logs collected …

A Study Of Type Ia Supernova Spectra, David Edwins

Theses and Dissertations

Type Ia Supernova already represent a valuable tool for astronomical exploration by providing a bright standardizable candle, however, they also represent an opportunity to observe the matter in the universe along the line of sight. A study of the spectra of Type Ia supernovae reveals a variety of contamination of these spectra at a variety of locations, including the Milky Way galaxy, a source likely local to the original supernova and an as yet unidentified source of contamination. Further, Type Ia Supernova appear to change with the redshift of the supernova.

The Use Of Machine-Learning Interatomic Potentials To Study Bulk Properties Of Aqueous Zn Ion Batteries, Ria Vasdev

Theses and Dissertations

Aqueous Zn-ion batteries (AZIBs) have emerged as a promising energy storage tech- nology owing to their high Coulombic efciency and low environmental impact. However, their practical development is impeded by limited cycling stability, pri- marily caused by parasitic side reactions occurring at the anode surface. These side reactions are strongly infuenced by the bulk solvation structure of Zn-based elec- trolytes, which remains challenging to characterize using conventional experimental techniques. Machine-learning interatomic potentials (MLIPs) provide a powerful computational approach to investigate these systems and can be employed to eluci- date the bulk structural properties of Zn electrolytes.

Raman Spectroscopy Of Biological Molecules And Inorganic Compounds, Jasmine Ervin Gardner

Theses and Dissertations

This dissertation describes the use of multiple Raman spectroscopic techniques for the detection and characterization of non-hazardous organic and inorganic compounds. The first two applications involve the use of Raman and surface enhanced Raman spectroscopy to thoroughly analyze autoinducers (AI) produced by gram negative bacteria. The second set of applications involves the use of anti-stokes Raman and resonance Raman spectroscopy to remotely detect inorganic compounds at distances of up to 12 meters away.

This work describes the use of Raman spectroscopy for the characterization and discrimination of signaling molecules used in bacterial communication. Our initial work shows the potential of …

Stimuli-Responsive Hybrid Materials: From Fundamental Photophysics To Tunable Properties, Grace C. Thaggard

Theses and Dissertations

Photochromic materials exhibit properties that can be dynamically tailored as a function of light exposure and represent a rapidly expanding field driven by applications ranging from molecular computing, nanotechnology, or photopharmacology to programable heterogeneous catalysis. For example, the possibility to tune a material’s catalytic activity “on demand” through exposure to a noninvasive stimulus is a transformative concept that could shift the paradigm in chemical industry by allowing for in-situ suppression of byproduct formation, isolation of reactive intermediates, and even control over product yield and selectivity. Development of the mentioned photochromic materials is based on stimuli-responsive molecular building blocks which undergo …

A Dynamical Systems Analysis Of Amyloid-Beta Production, Caroline Lloyd

Theses and Dissertations

Alzheimer’s disease is characterized by the presence of beta-amyloid (A𝛽) plaques in the brain, caused by an accumulation of misfolded A𝛽 proteins. Research suggests that hallmark proteins involved in neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, and Amyotrophic Lateral Sclerosis (ALS) exhibit prion- like behavior. This means that the misfolded, pathogenic proteins influence non- pathogenic proteins to misfold. There is also a small rate of spontaneous conversion which causes A𝛽 to misfold without the presence of pathogenic proteins. Additionally, events that limit blood flow to the brain, such as strokes or direct trauma, are known to increase A𝛽 in …

Quantifying And Characterizing Microplastics In North Inlet And Winyah Bay Estuaries, Sc, Emily Grace Contract

Theses and Dissertations

Microplastics (1 μm to 5 mm) accumulate in the bodies of marine organisms and negatively impact their health. Microplastics have also been linked to birth defects, endocrine disruption, and cancer in humans. This study quantified, characterized, and compared microplastics in a protected estuary (North Inlet Estuary, South Carolina) and an estuary impacted by anthropogenic activities (Winyah Bay, South Carolina). Water samples were taken from three sites in each estuary from February 2025 to December 2025. The samples were digested, filtered, then examined visually for microplastics. Plastic particles were extracted and analyzed by Raman microscopy to obtain polymer content. Results indicate …

Polyvinylidene Difluoride As A Platform For Photonic Circuits, Caleb Duff

Theses and Dissertations

Integrated photonic circuits represent a promising avenue for advancing computing capabilities by replacing electrons with photons as information carriers. This transition necessitates a comprehensive and innovative approach as the well understood requirements for electronic circuits are replaced by the needs of photonic circuits. This work will discuss topological photonics and one of many recent successes in their use to create near scatter free states. This work will then discuss progress towards creating an electromechanical platform using polyvinylidene difluoride [(C2H2F2)n], the platform’s benefits, and how the platform has been tested. This platform would have the potential to create reconfigurable photonic circuits, …

Coastal Development Effects On Estuarine Benthic Microalgal Communities, Henry Christopher Guy

Theses and Dissertations

As key drivers of neritic primary productivity, benthic microalgae (BMA) play essential roles in biogeochemical cycling and estuarine food webs. When considered alongside their shallow, restricted habitats, BMA contribute disproportionately to global carbon fixation. However, the extent of human impact on BMA communities is largely unknown. This study aimed to quantify anthropogenic forcing through specific abiotic drivers of benthic microalgal success. BMA biomass, community composition, porewater nutrients, and sediment composition were measured within two South Carolina Estuaries. North Inlet and Murrells Inlet share similar geographic and morphological characteristics but differ significantly in terms of watershed population. Dissolved phosphate, nitrate, and …

Semi-Supervised Galaxy Morphology Classification Using Convolutional Vision Transformers, Emily Miller Christen

Theses and Dissertations

Galaxy morphology classification is an essential task for understanding galaxy evolution, but modern high-redshift surveys such as JADES produce a large number of unlabeled images that cannot be handled with traditional manual or supervised learning methods. This work explores a semi-supervised transfer learning framework that leverages labeled data from Galaxy Zoo 2 to classify morphologies in James Webb Space Telescope JADES observations. A pretrained Convolutional Vision Transformer is adapted to the new imaging domain and refined using pseudo-labeling on unlabeled data. Experiments simulating JADES imaging conditions show that reduced resolution and noise significantly impact the separability of certain morphology classes, …

Tracing Cosmic Origins: Investigating Carbon Isotopic Ratios To Unlock Universal Insights, Karthik Gananath Putha

Theses and Dissertations

The universe is made up of a vast and diverse collection of elements. All elements with atomic mass number A > 12, ranging from carbon to iron, are continuously enriched over the course of galactic evolution through stellar nucleosynthesis. In contrast, elements heavier than 56 Fe are primarily synthesized via neutron-capture processes, occurring in Asymptotic Giant Branch (AGB) stars, core-collapse supernovae, and more extreme events such as binary neutron star mergers. These elements are later expelled into the surrounding space through powerful supernova explosions. Overtime, these processes enrich the interstellar medium with heavy elements and thus plays an important role in …

Deep Learning Algorithms For Generative Materials Design And Composition Based Property Prediction, Rongzhi Dong

Theses and Dissertations

The accelerated discovery of novel functional materials is critical for advancing trans- formative technologies in energy storage, electronics, and catalysis. Current discovery strategies, whether experimental trial-and-error or DFT-based computational screen- ing, are fundamentally constrained by the limited size and diversity of existing materials databases and the difculty of building predictive models that generalize beyond known compounds. Despite signifcant progress in both experimental and computational approaches, two central challenges persist in modern materials science: generating large numbers of realistic, stable, and synthesizable materials outside existing databases, and developing machine learning models capable of accurately inferring structures and predicting properties under realistic …

Machine Learning Toward Materials Discovery: From Crystal Mapping And Out-Of-Distribution Property Prediction To Radiation Detection And Emerging Foundation Models., Qinyang Li

Theses and Dissertations

The discovery and optimization of advanced materials are central to addressing global challenges in energy, healthcare, and sustainability. This dissertation develops representation-aware and distribution-aware machine learning frameworks to improve robustness, generalization, and interpretability in materials informatics and radiation detection. The work spans crystal structure mapping, adversarial learning for out-of- distribution prediction, foundation-model-based property prediction, and deep neural classifcation of photon interactions.

A global mapping framework is frst introduced to analyze the inorganic materials space using compositional, structural, physical, and neural descriptors derived from the Materials Project database. By embedding materials into low-dimensional mani- folds, the framework reveals clustering behavior and …

From Experience To Reasoning: Offline Rl Subroutines And Llm-Based Grounding For Sample-Efficient Reinforcement Learning, Jianhai Su

Theses and Dissertations

Improving the learning efficiency of reinforcement learning (RL) agents remains a fundamental challenge, particularly in environments characterized by sparse rewards, long horizons, or partial observability. This dissertation investigates how RL agents can learn more efficiently through two complementary forms of guidance: mechanisms derived purely from an agent’s own experience and mechanisms that leverage reasoning priors from pretrained large language models (LLMs).

On the experience-driven side, the frst study develops a general framework for incorporating ofine RL algorithms as subroutines within an online RL process. In this framework, an agent periodically repurposes its replay bufer as an ofine dataset and applies …

Inferring The Breakdown Scales Of The Chiral Expansions For GA And MN, Andreas Ekström, Daniel R. Phillips, Lucas Platter, Matthias Schindler

Faculty Publications

We apply Bayesian inference to the order-by-order chiral perturbation theory (χPT) expansions for the axial-vector coupling constant g_A and the nucleon mass m_N, and thereby infer the scales at which χPT breaks down for these two observables. Using a pointwise Bayesian analysis, we find that the inferred breakdown scales are notably different for the two observables. For the chiral expansion of g_A, we obtain 251⁺²⁰₋₅₀ MeV and 211⁺²⁰₋₃₀ MeV using two distinct sets of low-energy constants, while for the chiral expansion of m_N we infer a significantly …

Multiscale Computational Modeling Of The Cardiopulmonary Consequences Of Postnatal Hyperoxia With Implications For Preterm-Born Children, Salla M. Kim, Filip Jezek, Pim J. A. Oomen, Gregory P. Barton, Feng Gu, Daniel A. Beard, Kara N. Goss, Mitchel J. Colebank, Naomi C. Chesler

Faculty Publications

Moderate to extreme preterm birth (<  32 weeks gestation) affects cardiopulmonary structure and function and is associated with increased risk of heart failure through adulthood. The rat hyperoxia (Hx) model (term born; postnatal Hx exposure) captures biventricular changes, including at the cell and organ scale, and pulmonary vascular remodeling seen in preterm humans. However, synthesizing these measures across scales and organ systems is challenging. We hypothesized that in silico modeling of biventricular mitochondrial, myofiber, and organ-scale function plus circulatory function could capture key features of cardiopulmonary abnormalities due to preterm birth. Therefore, we calibrated a multiscale model to subject-specific biventricular pressure–volume data previously obtained from Hx rats alongside normoxic (Nx) controls to investigate the abnormalities in cardiopulmonary function at multiple scales in this animal model of human preterm birth. The calibrated model demonstrates excellent agreement with the data and captures the expected pulmonary vascular changes and right ventricular dilation seen in preterm-born children. Our multiscale modeling approach captures cardiopulmonary abnormalities across spatial scales and provides an innovative approach to explore the consequences of preterm birth beyond preclinical experimental data alone. This is a foundational step in understanding the impact of preterm birth on cardiopulmonary disease in childhood as well as adulthood.

Optimal Error Estimates Of The Diffuse Domain Method For Second Order Parabolic Equations, Wenrui Hao, Lili Ju, Yuejin Xu

Faculty Publications

In this paper, we study the convergence behavior of the diffuse domain method (DDM) for solving a class of second-order parabolic partial differential equations with Neumann boundary condition posed on general irregular domains. The DDM employs a phase-field function to extend the original parabolic problem to a similar but slightly modified problem defined over a larger rectangular domain that contains the target physical domain. Based on the weighted Sobolev spaces, we rigorously establish the convergence of the diffuse domain solution to the original solution as the interface thickness parameter goes to zero, together with the corresponding optimal error estimates under …

The Blurred Boundaries Of Care: A Qualitative Analysis Of Nurse-Doula Role Conflict, Curisa Mae Tucker Phd, Rn, Maria Mcclam, Kelly Russin Dnp, Rnc-Ob, Chse, Nansi Boghossian, Rachel Gulczinski, Lauren Workman

Faculty Publications

Introduction:

Methods:

Association Between The Dietary Index For Gut Microbiota (Di-Gm) And Colorectal Cancer In The Plco Cohort, Bezawit E. Kase, Angela D. Liese Ph.D., Jiajia Zhang Ph.D., Elizabeth Angela Murphy, Susan E. Steck Phd, Mph, Rd

Faculty Publications

Objectives: The study aimed to examine the association between a dietary index for gut microbiota (DI-GM) and the risk of incident colorectal cancer (CRC). Clarifying the role of diet-induced alterations in the composition and function of gut microbiota on the development of CRC can contribute to prevention efforts. Methods: Participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening trial enrolled in the intervention arm and who completed baseline assessments were included in the analysis (n = 55,685). The DI-GM is a literature-derived index used to score diet quality in terms of maintaining healthy gut microbiota. A time-dependent Cox model …

Association Between The Dietary Index For Gut Microbiota (Di-Gm) And Colorectal Cancer In The Plco Cohort, Bezawit E. Kase, Angela D. Liese, Jiajia Zhang, Elizabeth Angela Murphy, Susan E. Steck

Faculty Publications

Objectives: The study aimed to examine the association between a dietary index for gut microbiota (DI-GM) and the risk of incident colorectal cancer (CRC). Clarifying the role of diet-induced alterations in the composition and function of gut microbiota on the development of CRC can contribute to prevention efforts. Methods: Participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening trial enrolled in the intervention arm and who completed baseline assessments were included in the analysis (n = 55,685). The DI-GM is a literature-derived index used to score diet quality in terms of maintaining healthy gut microbiota. A time-dependent Cox model …

Role Of Wadsley Defects And Cation Disorder To Enhance Monb12O33 Diffusion, Cj Sturgill, Manish Kumar, Nima Karimitari, Iva Millisavljevic, Coby S. Collins, Aaron Hegler, Hsin-Yun Joy Chao, Santosh Kiran Balijepalli, Scott T. Misture, Christopher Sutton, Morgan Stefik

Faculty Publications

Wadsley-Roth (WR) niobates have emerged as high-rate anode materials that can combine rapid ionic diffusion with good electronic conductivity. WR compounds have been defect-enhanced by limited annealing, however, such materials often contain multiple types of defects. In particular, both Wadsley defects (variable block size) and transition metal disorder have the potential to modify transport rates, however the corresponding effects are not well understood mechanistically. Here, MoNb12O33 (MNO) was calcined at two different temperatures to compare a defect-rich condition (MNO-800) with a proximal order-rich condition (MNO-900) as assessed through XRD, XANES, EXAFS, and STEM characterizations. Galvanostatically cycled lithium half cells of …

First-Order Axial Perturbation Of The Reissner–Nordström Metric Against A Possible Parity-Violating Gravity Background, Abhishek Rout, Brett David Altschul

Faculty Publications

We study axial perturbations of Reissner–Nordström black holes within the general frame-work of parity-violating modified gravity theories. We derive the governing equations for a class of frame-dragging perturbations, focusing on the symmetry structure and radial dependence of the perturbed metric component, describing its behavior across three distinct regions: near the singularity (r → 0), between the inner and outer Reissner–Nordström horizons (r− < r < r+), and in the asymptotic exterior regime (r → ∞). Using a combination of analytical and numerical methods, we analyze the solutions for varying black hole charge-to-mass ratios (Q/M) and angular momentum parameters (l). Key findings include the suppression of perturbations by the electromagnetic field for higher Q/M; the emergence of radial resonance-like behavior for specific l values; and a high degree of symmetry for solutions in the extremal limit (Q/M ∼ 1), attributed to the AdS2 × S 2 near-horizon geometry. The WKB approximation is employed to study the high-l regime, revealing quantized radial resonance modes and singular behavior in the extremal limit. Additionally, we explore the role of boundary conditions and the possibility of a Chern–Simons field Θ as the source of the parity violation, showing that consistency and the behavior of the perturbations under time reversal demand a constant field (and thus no actually observable Chern–Simons effects) at leading order. These results provide a basis for further analysis of the stability and dynamical properties of charged black holes in parity-violating theories, with potential experimental signatures in gravitational wave observations.

Dietary Inflammatory Index And Objective Disease Activity In Ibd: No Association Found, Rúbia Moresi Vianna De Oliveira, Ana Carolina Junqueira Vasques, Stefhani Andrioli Romero, Nitin Shivappa Mbbs, Mph, Ph.D., Michael David Wirth, James Hébert Scd, Glaucia Fernanda Soares Ruppert Reis, Cristiane Kibune Nagasako

Faculty Publications

Background

Inflammatory Bowel Disease (IBD) involves genetic and environmental factors, but the relationship between disease activity, adiposity, and diet remains unclear.

Objective

To investigate the association between endoscopic/radiological activity of IBD, body adiposity, and the Dietary Inflammatory Index with or without adjustment for energy density (E-DII or DII).

Method

An observational, cross-sectional study was carried out. Endoscopic activity was defined by an endoscopic Mayo score >2, Crohn’s Disease Endoscopic Index of Severity (CDEIS) > 5, and/or the presence of a deep ulcer in any intestinal segment. Body adiposity was estimated using the body mass index, waist circumference, and waist-hip ratio (WHR). …