Physical Sciences and Mathematics Commons^™

Factorized Electron-Nuclear Dynamics: Theory Development And Implementation, Julian Stetzler

Theses and Dissertations

In the Born-Oppenheimer (BO) approximation, nuclei are treated as classical particles. The theoretical and computational approaches that go beyond it are impractical for all but the smallest chemical systems. However, such methods are necessary to simulate many photochemical and biological processes. This thesis discusses two important topics of research in this feld: frst, improving electronic structure theory to efciently describe quantum nuclei; second, developing a scalable quantum dynamics method, the factorized electron-nuclear dynamics (FENDy).

Following the BO approximation, the electronic structure of molecules is routinely examined for static arrangements of point nuclei, which is a highly useful premise but not …

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 …

Continuum Observations Of Water Maser Sites, Aman Khan

Theses and Dissertations from DePaul University

Stars form in cores deep within cold (10 K) clouds of hydrogen gas. As material is accreted onto the central object inside these cores (the protostar), powerful outflows that channel mass away from the protostar are also launched. The launching mechanism for these outflows is still not fully understood. This thesis presents observations of the 22 GHz continuum emission from two star-forming regions, NGC 7129 FIRS2 and IC 1396-n. The immediate aim of these observations is to find where this continuum emission is coming from, particularly if it is free-free emission from a jet or outflow, and the long term …

Personality Predictors Of Cybersecurity Vulnerability: Insights From Self-Reports And Stimulated Threat Scenarios, Saroja Roy Grandhi

Psychology Theses & Dissertations

In this cyber dependent and enabled era, understanding the role of human factors in digital security is essential. This study investigates the relationship between Big-Five personality traits and cybersecurity behaviors by examining both self-reported and stimulated behaviors in security threat scenarios. Participants completed validated questionnaires to report their personality traits, cybersecurity practices and engage in task-based stimulations to capture behaviors such as phishing detection, password creation, and response to security alerts. The study tested whether higher conscientiousness, openness, and agreeableness would be associated with stronger cybersecurity practices and smaller discrepancies between self-reported and observed behaviors. And, whether greater extraversion and …

Dissection Of The Quintuple Product, With Applications, Tim Huber, James Mclaughlin, Dongxi Ye

School of Mathematical & Statistical Sciences Faculty Publications

This work considers the m-dissection (for m≢0(mod3)">m≢0(mod3)) of the general quintuple productQ(z,q)=(z,q/z,q;q)∞(qz2,q/z2;q2)∞.">Q(z,q)=(z,q/z,q;q)∞(qz2,q/z2;q2)∞.Multiple novel applications arise from this m-dissection. For example, we derive the general partition identityDS(mn+(m2−1)/24)=(−1)(m+1)/6bm(n), for all n≥0,">DS(mn+(m2−1)/24)=(−1)(m+1)/6bm(n), for all n≥0,where m≡5(mod6)">m≡5(mod6) is a square-free positive integer relatively prime to 6; DS(n)">DS(n) is defined, for S the set of positive integers containing no multiples of m, to be the number of partitions of n into an even number of distinct parts from S minus the number of partitions of n into an odd number of distinct parts from S; and …

Soliton Solutions To The Coupled Sasa–Satsuma Equation Under Mixed Boundary Conditions, Changyan Shi, Xiyao Chen, Guangxiong Zhang, Chengfa Wu, Bao-Feng Feng

School of Mathematical & Statistical Sciences Faculty Publications

In this paper, we derive general bright–dark soliton solutions to the coupled Sasa–Satsuma (CSS) equation using the Kadomtsev–Petviashvili reduction method. Since the CSS equation is a special case of the four-component Hirota equation, our approach begins with the construction of two-bright-two-dark soliton solutions for the four-component Hirota equation. By imposing specific parameter constraints, these solutions are subsequently reduced to the bright–dark soliton solutions of the CSS equation. Finally, the dynamical behaviours of the one- and two-bright–dark soliton solutions are thoroughly analysed and illustrated.

Short-Term Electricity Price Forecasting With Constrained Regressors, Mucun Sun, Li Zhang, Yifeng Gao

Computer Science Faculty Publications

The volatility of electricity price presents a challenge to market participants as their decision-making process are highly depend on the accuracy of price forecasts. However, there is growing empirical evidence of increasing price volatility and price spikes in electricity markets as a result of variable renewable energy generation, extreme weather events, and other factors. The distribution shift caused by spikes in electricity price data differentiates the forecasting tasks from other renewable energy sources. Moreover, the observations may be compromised by cyberattacks and thus not available in the testing phase. To this end, we propose a Similarity-Enhanced Electricity Decomposition Forecasting model …

Upper Ocean Cycling Of Iron South Of The Polar Front: Biological Patterns And Processes, Luis M. Laglera, Santos-Echeandía, Viena Puigcorbé, Christine Klass, Dieter Wolf-Gladrow

Research outputs 2022 to 2026

Samples from the upper 300 m along the 52°S band, south of the Antarctic Polar Front in the Atlantic sector of the Southern Ocean, including a 3-week monitoring of a persistent bloom, were analyzed to advance our understanding of iron cycling and supply to recurrent phytoplankton blooms. We measured dissolved Fe (dFe, <0.2 μm) and labile particulate iron using a mild acid leach (pLFe^48h) targeting primarily detrital and fecal material. Particulate iron was partitioned into size classes to distinguish small, “slow” sinking particles (<53 μm) from large, “fast” sinking particles (>53 μm), while intermediate fractions were analyzed to investigate aggregation and export processes. Across all stations, dFe exhibited a consistent vertical structure, including a previously undescribed …

Evaluating The Collision-Coalescence Process In Idealized Cloud Convection Using Large-Eddy Simulations With Lagrangian Microphysics, Yangze Ren, Kamal Kant Chandrakar, Fan Yang, Raymond Shaw

Michigan Tech Publications

Drizzle initiation through the collision and coalescence of cloud droplets plays a crucial role in warm cloud precipitation. Recent theoretical studies suggest that the influence of collisional growth on the droplet size distribution can be quantified by a non‐dimensional drizzle number (Dz). Here, large‐eddy simulations with Lagrangian microphysics are employed to evaluate the theory by simulating a tall convection‐cloud chamber under various conditions. Results show that the smaller the Dz, the larger the impact of collisions on the right tail of the droplet size distribution, consistent with the theory. The simulations confirm that the collision rate can be estimated from …

Breathing Kagome Lattice-Based Nb3i8 Monolayer: Theoretical Insights Into Enhanced Hydrogen Evolution Catalysis, Narender Kumar, Radha Somaiya, Ravindra Pandey, Nacir Tit

Michigan Tech Publications

Photocatalytic water splitting is a promising strategy for clean energy production, but its efficiency is restricted by poor light absorption, charge recombination, and slow reaction kinetics in photocatalytic materials. To address these challenges, a breathing Kagome lattice-based Nb3I8 monolayer is considered in the present study. Its photocatalytic performance is assessed via descriptors including the effective d-band center, spin-dependent carrier mobility, Gibbs free energy, and exchange-current density. The results based on density functional theory predict that the Nb3I8 monolayer is a type II magnetic semiconductor, with spin-up and spin-down bandgap energies of 1.06 and 1.77 eV, respectively. The application of biaxial …