Physical Sciences and Mathematics Commons^™

Recent Insights Into Electrochemical Sensing Of Per- And Polyfluoroalkyl Substances, Christopher T. Lebarron, Pavithra Hosseini, Seyyedamirhossein Hosseini

Faculty Publications

Per- and polyfluoroalkyl substances (PFAS) are widely studied due to their persistence, prevalence, and harmful effects on human and environmental health. Key challenges include improving detection methodologies, such as lowering detection limits, and developing more sensitive and selective approaches. Given the ubiquity of PFAS, effective sensing must be paired with remediation strategies that transform these pollutants into value-added or less toxic products. This perspective explores recent advances in electrochemical PFAS detection, highlighting challenges and future opportunities.

Large Bandgap Observed On The Surfaces Of Euzn2As2 Single Crystals, Dejia Kong, Siavash Karbasizadeh, Ganesh Narasimha, Paras Regmi, Chenggang Tao, Chenggang Tao, Sai Mu, Rama Vasudevan, Ian Harrison, Rongying Jin, Zheng Gai

Faculty Publications

EuZn₂As₂ (M = Zn, Cd, In, Sn etc.) is an excellent material system for studying magnetism-tuned topological properties. However, discrepancies exist between experimental data and theoretical calculations regarding the bulk and surface bandgaps. In this work, cleaved EuZn₂As₂ crystals are studied using scanning tunneling microscopy/spectroscopy and density functional theory calculations. Triangular-shaped defect-induced modifications in the local density of states help distinguish between Eu-terminated and AsZn-terminated surfaces. While large bandgaps ( ~1.5 eV at 77 K) are observed on both pristine surfaces, the bandgap size is found to be highly sensitive to local heterogeneity, tending …

An Upper-Mesopelagic-Zone Carbon Budget For The Subarctic North Pacific, Brandon M. Stephens, Montserrat Roca-Martí, Amy E. Maas, Vinícius J. Amaral, Samantha Clevenger, Shawnee Traylor, Claudia R. Benitez-Nelson, Philip W. Boyd, Ken O. Buesseler, Craig A. Carlson, Nicolas Cassar, Margaret Estapa, Andrea J. Fassbender, Yibin Huang, Phoebe J. Lam, Oliver Marchal, Susanne Menden-Deuer, Nicola L. Paul, Alyson E. Santoro, David A. Siegel, David P. Nicolson

Faculty Publications

Mesopelagic zone (MZ) carbon budgets comparing supply with demand can be difficult to constrain due to the temporal and spatial offsets between key sources and sinks, their associated uncertainties, and potential sampling biases. To address these challenges, the EXport Processes in the Ocean from RemoTe Sensing (EXPORTS) campaign increased the number and variety of simultaneous measurements to monitor temporal variability in the MZ carbon budget using both a Lagrangian frame of reference and long-term autonomous observations. In this study, we collate a comprehensive combination of new and previously published organic carbon supply and demand measurements collected from the surface (5 …

Electroexcitation Of Nucleon Resonances And Emergence Of Hadron Mass, Patrick Achenbach, Daniel S. Carman, Ralf Gothe, Kyungseon Joo, Victor I. Mokeev, Craig D. Roberts

Faculty Publications

Developing an understanding of phenomena driven by the emergence of hadron mass (EHM) is one of the most challenging problems in the Standard Model. This discussion focuses on the impact of results on nucleon resonance (N*) electroexcitation amplitudes (or γ_vpN*) obtained from experiments during the 6 GeV era in Hall B at Jefferson Lab on understanding EHM. Analyzed using continuum Schwinger function methods (CSMs), these results have revealed new pathways for the elucidation of EHM. A good description of the Δ (1232) 3/2⁺, N (1440) 1/2⁺, and Δ (1600) 3/2^{+ …}

A Survey On Security Applications With Smartnics: Taxonomy, Implementations, Challenges, And Future Trends, Serigo Elizalde, Ali Alsabeh, Ali Mazloum, Samia Choeiri, Elie Kfoury, Jose Gomez, Jorge Crichigno

Faculty Publications

Over the last decade, network applications have grown exponentially, demanding high-speed interconnects. Unfortunately, chip manufacturers are approaching the upper limits of silicon-based computing with slow improvements in computational performance and energy efficiency. This trend has forced the industry to shift paradigms, moving from monolithic architectures to heterogeneous, domain-specific designs. Moreover, the ever-evolving threats compromise digital services and demand more scalable and flexible solutions to ensure service continuity in production networks. Smart Network Interface Cards (SmartNICs) are a product of this new paradigm, integrating domain-specific engines and general-purpose cores to offload various network infrastructure tasks, including those related to security. This …

Synthesis Of Inorganic Actinide Compounds With Neptunium, Plutonium, And Americium, Travis Kelly Deason

Theses and Dissertations

There is a rush of countries around the world making the switch to greener energy sources. Nuclear energy power plants are an integral part of the shift from fossil fuels, but there are concerns over the best way to handle nuclear waste. Most of the nuclear waste is currently disposed of by incorporating the waste into a glass form through vitrification, but research into alternative waste forms, such as promising crystalline materials, could provide a more robust method of containment. Research on actinide materials is lacking due to the dangers of working with radioactive material and there are few labs …

Purification Of Uranium Tetrafluoride Using Ammonium Bifluoride, Kyle R. Foster, Juliano Schorne-Pinto, Ronald E. Booth, Annabelle Husek, Mina Aziziha, Hunter B. Tisdale, Bernie W.N. Fitzpatrick, Hans Conrad Zur Loye, Markus H.A. Piro, Theodore M. Besmann

Faculty Publications

A method of purification for UF₄ utilizing NH₄HF₂ was investigated to remove oxygen and hydrate impurities from the salt. The original salt exhibited a melting point at 915–920 °C, which corresponds to the eutectic temperature of the UF4-UO2 system, showing clear signs of oxygen contamination. To purify the salt, an air-tight reaction vessel inside an argon glovebox was used to react UF4/NH4HF2 mixtures at elevated temperatures under a continuous flow of inert gas. The process yielded a significantly purer UF4 salt as confirmed via inert gas fusion, X-ray diffraction, differential scanning calorimetry and inductively coupled plasma-optical …

Redundant Functions Of Mir156-Targeted Squamosa Promoter Binding Protein-Like Transcription Factors In Promoting Cauline Leaf Identity, Darren Manuela, Liren Du, Qi Zhang, Yifei Liao, Tieqiang Hu, Jim P. Fouracre, Mingli Xu

Faculty Publications

No abstract provided.

Crystal Growth, Thermal, Optical, Magnetic And Electrochemical Properties Of Mo2Ta2O11, Md Abdullah Al Muhit, Alevtina A. Maksimova, Sean C. Wechsler, Habiba Binte Kashem, Gopabandhu Panigrahi, Gregory Morrison, Morgan Stefik, Hans Conrad Zur Loye

Faculty Publications

Single crystals of the transition metal oxide Mo2Ta2O11 were grown for the first time using molten flux synthesis. The compound crystalizes in the trigonal space group R 3‾m (no. 166) with lattice parameters a = b = 5.6267(1) Å and c = 25.1424(6) Å and a unit cell volume of 689.36(3) ų. The structure of Mo2Ta2O11 is composed of alternating layers of TaO6 octahedra and MoO4 tetrahedra connected via corner-sharing. CaH2 was used to achieve a partial low temperature reduction of Mo2Ta2O11. The electrochemical lithiation of polycrystalline Mo2Ta2O11 was also investigated for the first time. Mo2Ta2O11 underwent a …

Process-Grounded Knowledge-Infused Learning And Decision Making, Kaushik Roy

Theses and Dissertations

This dissertation introduces process-grounded knowledge-infused learning and reasoning, a novel framework for integrating domain-expertise-based process knowledge into the learning and reasoning mechanisms of artificial intelligence systems. This approach is designed to produce controlled, transparent, and reliable predictions in critical tasks such as medical diagnosis and recommendation. By focusing on the case study of mental illness diagnosis and recommendation—where decision-making must be grounded in processes such as disorder-specific diagnostic criteria—this work demonstrates methods to embed structured decision-making directly into the system architecture during both training and inference. This integration facilitates end-to-end training and reasoning while ensuring that outputs strictly adhere to …

Rapid Charging Lithium-Ion Batteries: Structure, Morphology, And Methodology, Sean Cade Wechsler

Theses and Dissertations

The initial commercialization and subsequent development of the lithium-ion battery (LIB) in 1991 has revolutionized the way that humans power devices, cars, and homes and led to the advent of many technologies that seemed impossible just half a century ago. As LIBs are integrated into more of daily life through handheld devices, wearable medical devices, transportation, and grid-level energy storage, the demand for fast charging and high energy density increases rapidly. To design a battery with these favorable qualities, an understanding of the effect of electrode crystal structure and electrode morphology on the ionic/electronic transport and failure modes must be …

An Efficient Detection And Deep Clustering Based Pipeline For Reliable Rodent Ultrasonic Vocalization Analysis, Sabah S. Anis

Theses and Dissertations

Ultrasonic vocalizations (USVs) are critical for understanding rodents' emotional states and social behaviors. However, manual analysis of USVs is time-consuming, subjective, and prone to errors. This thesis presents an automated pipeline that addresses these challenges by performing efficient USV detection and clustering. The proposed approach significantly reduces the time and effort needed to analyze USV data while improving accuracy and reproducibility.

To address this gap, we introduce ContourUSV, a five-step pipeline for USV detection. First, it begins with generating spectrograms from audio recordings, which are then pre-processed to enhance the contrast between USVs and background noise. Key steps include median …

Post-Selection Inference In Regression Models, Qinyan Shen

Theses and Dissertations

This dissertation develops new methodology for valid statistical inference following model selection in various regression settings. We first consider the logistic regression model for a binary response that can only be observed at the group level, as in group testing, and is subject to testing error. With the true responses only partially observed, we employ the expectation-maximization (EM) algorithm to account for missing information in the response data and simultaneously conduct variable selection using the LASSO-penalized log-likelihood function. After variable selection, we extend an existing post-selection inference method based on the polyhedral lemma \parencite{lee2016exact} to make inferences on selected covariates, …

Methods And Applications For Bayesian Semiparametric Survival Analysis, Zile Zhao

Theses and Dissertations

Survival analysis is a cornerstone of biomedical and clinical research and plays an important role in fields as diverse as engineering, actuarial science, and sociology. In this dissertation, we develop new semiparametric Bayesian methodology for three problems from survival analysis: 1) adjustment for treatment crossover in randomized controlled trials (RCTs), 2) multilevel modeling of clustered survival outcomes when the cluster size is also informative, and 3) divide-and-conquer Bayesian inference for massive survival data. Our methods are semiparametric in the sense that we assume the covariates have a linear effect with regard to the log-hazard or the log- survival time; however, …

Quinone-Mediated Extracellular Electron Transfer In Escherichia Coli During Glucose Oxidation Metabolism, Megan Danielle Whisonant

Theses and Dissertations

The growing global demand for energy, ongoing reliance on fossil fuels, and increasing water pollution from industrial and anthropogenic sources present significant environmental challenges. In response to these issues, renewable and sustainable energy sources offer substantial potential for reducing dependence on fossil fuels and ensuring access to clean water. Microbial electrochemical systems (MESs) have emerged as promising, eco-friendly solutions for energy-efficient wastewater treatment and bioremediation. A key challenge in MESs development is facilitating effective electron transfer between microorganisms and electrode surfaces. The first chapter of this thesis discusses the fundamentals of MES types, explains mechanisms of extracellular electron transfer, and …

The Potential Importance Of Microenvironment On Polymer Bound Chemical Reagents, Nathan Joseph Halsteter

Theses and Dissertations

In this thesis will provide a brief history of polymer bound reagents, their uses, and advancements. The importance of polymer microenvironments will be explored using a model kinetic resolution reaction utilizing polymer bound reagents to observe how changes in a polymer’s microenvironment effects the yield and selectivity of a reaction. It was found that there are copious factors that affect polymer bound reagents, and no direct conclusion could be drawn from the study.

Spatio-Temporal Modeling & Goodness Of Fit Testing For Ecological Fire Data, Jedidiah Olof Lindborg

Theses and Dissertations

An analysis of fire data sets resulting from controlled burns was performed. Spatio-temporal models were applied to the data sets to determine which covariates are significant in predicting fire temperature. The data sets were censored and only contain temperatures above 300C, due to a limitation in the measuring device. To handle the censoring, an extrapolation was used to reconstruct the temperatures below 300C. Models were created and run for a data set with the extrapolated temperatures and a data set with all censored temperatures removed. Several aspects of the model were evaluated, such as the chosen hyperparameters, the spatial covariance …

Structure-Activity Relationships Of Isothiourea And Silicon Phthalocyanine Catalysts, Christian J. Harrison

Theses and Dissertations

Efficient organic synthesis often relies on improving catalyst designs and investigating reaction mechanisms to accomplish feats such as high stereoselectivity, low catalyst loadings, and performing sustainable chemistry. Within the field of organocatalysis, intermolecular interactions between a catalyst and a substrate are a large contributing factor to the control of a reaction, including rate and selectivity. Investigating mechanisms can provide information on the type of intermolecular interactions occurring in the reaction, aiding future reaction and catalyst development. This dissertation will explore two recent projects and how probing intermolecular interactions through simple modifications provides information useful for new catalyst designs and properties. …

Regression With Atypical Data: Measurement Error, Periodicity, And Non-Normality, Nicholas W. Woolsey

Theses and Dissertations

Regression is a ubiquitous and fundamental method that can be found in any ele- mentary statistics course. The simplicity and self evidently useful nature of linear regression beguiles a non-negligible portion of researchers into disrespecting assump- tions required by these models, namely in terms of accuracy of covariates and the underlying nature of the data. This disregard can at best lead to meaningless results and at worse cause significant misunderstandings in scientific pursuit.

In this dissertation we strive propose remedies to violations of specific assump- tions. Namely the assumptions that covariates are either observed without measure- ment error or they …

Reactivity Of Redox-Active Carboranyl Diphosphines And Carboranyl Diphosphoniums: Metal-Free Pathways For Small Molecule Activations And Transformations, Amanda Lynn Humphries

Theses and Dissertations

Transition metal catalysis has been an integral part of synthetic chemistry for its ability to selectively activate strong substrate bonds, promoting numerous crucial transformations. Despite their utility, the precious metals that are often employed in these catalytic reactions suffer from several drawbacks (including high toxicity, low natural abundance, high costs, and low sustainability), increasing the motivation to design suitable metal-free alternatives. Towards this end, several ambiphilic main-group systems have been devised to show metal-like reactivity, such as carbenes, borylenes, and Frustrated Lewis Pairs. This manuscript will describe the ambiphilic reactivity of carborane-based phosphorus compounds, highlighting the unique metallomimetic reactivity that …

Characterizing Dissolved Organic Matter Composition In A Southeastern United States Watershed, Gwendolyn Marcelette Hopper

Theses and Dissertations

Dissolved organic matter (DOM) has important roles in many biogeochemical cycles. DOM is primarily composed of dissolved organic carbon (DOC), nitrogen, and phosphorus, and the processing of DOM is important for nutrient regulation and carbon cycling. In the coastal plains of the southeastern United States, there are many rivers and streams known as “blackwaters” with exceptionally high concentrations of chromophoric dissolved organic matter (CDOM) leached from terrestrial soils, coinciding with a region experiencing some of the nation’s highest rates of development. As changes in land use and climate continue to occur, DOM composition from natural to anthropogenically impacted systems can …

Determination Of Structure-Function Relationships In Hybrid Catalysts On Metal Oxide Supports, Joseph John Kuchta

Theses and Dissertations

Transition metal catalysis has revolutionized chemical synthesis, enabling efficient and selective transformations critical to the pharmaceutical, agricultural, and materials industries. However, traditional methods often rely on expensive, non-sustainable metals and harsh reaction conditions that generate significant waste. This dissertation explores a series of innovations aimed at bridging the gap between homogeneous and heterogeneous catalysis through the development of hybrid catalysts. These systems combine the molecular precision of homogeneous catalysts with the stability and practicality of heterogeneous supports, offering a pathway to more sustainable and scalable catalytic processes.

The first area of focus investigates nickel-based hybrid catalysts as a cost-effective and …

Quantifying Biomass Burning Impacts On Soil Nox Emissions And Reactive Nitrogen Cycling, Olivia Rae Steinbeck

Theses and Dissertations

Nitrogen oxides (NOx = NO + NO₂) are trace gases that play a critical role in the atmosphere by influencing air quality, oxidation chemistry, and the deposition of fixed nitrogen. Historically, NOx emissions have been primarily linked to anthropogenic sources such as fossil fuel combustion, industrial activities, and agriculture. However, as successful legislation has significantly reduced these emissions, the relative importance of natural NOx sources has become an increasing concern. Soil NOx emissions are of particular interest due to their strong temperature dependence and their connection to global climate change. Rising global temperatures are expected to accelerate soil NOx emissions …

Hardware Accelerated Simulation Of Buck Converters Using Physics-Informed Neural Networks, James Clayton Crews

Theses and Dissertations

Physics-informed neural networks (PINNs) are an emerging machine learning method for learning the behavior of physical systems described by governing differential equations. Dc-dc power-electronic converters are used in a variety of industry applications such as motor drives or power supplies where real-time simulation is critical for control and safety. This thesis investigates physics-informed machine learning as an approach to develop a real-time digital twin for dc-dc power converters. Traditional numerical integration methods are used to approximate discretized behavior, and the results are compared with a trained PINN model. Modern ML frameworks (such as PyTorch and TensorFlow/Keras) are used to quickly …

Functional Data Analysis On Life Expectancy And Healthcare Expenditure, Hagen Sanchez

Theses and Dissertations

This study analyzes the life expectancy for 237 countries from 1950-2023 and the healthcare expenditure for 50 countries from 1970-2022, and how life expectancy and healthcare expenditure relate to each other. Functional Principal Components Analysis was used to analyze the life expectancy and healthcare expenditure for each of the countries. Additionally, the regions of the countries were analyzed to identify any regional trends for the life expectancy data. Due to missing data and the structure of the healthcare data, multiple imputation methods and Principal Component Analysis techniques were explored for the healthcare data. Furthermore, a simulation study was conducted to …

Explorations In Extremal Combinatorics: Graph Spectra, Codegree Squared Sum Of Hypergraphs And Lin-Lu-Yau Ricci Curvature, George Henry Brooks

Theses and Dissertations

This dissertation explores a variety of extremal problems in spectral graph theory, hypergraph Tur\'an theory in the $\ell_2$-norm, and Lin-Lu-Yau Ricci curvature. We begin by studying the maximization of linear combinations of eigenvalues in relation to the adjacency matrix of a graph. For a graph $G$ on $n$ vertices, we order its eigenvalues $\lambda_1 \geq \dots \geq \lambda_n$. First, we study a generalization of the maximum spread. Specifically, we consider the $(i,j)$-spread, defined as $\lambda_{i+1}-\lambda_{n-j}$, and aim to maximize that quantity over all simple graphs on $n$ vertices. We establish asymptotic bounds for all $i,j\geq 0$ and identify infinitely many …

Autoregressive Modeling Of Dna Molecule Shapes Accompanied By An Empirical Assessment Of The Ljung-Box Test, David William Custer

Theses and Dissertations

The assumption of independence rarely holds in real-world data. Correlated observations are ubiquitous, especially in sequential contexts where time series models are essential for capturing temporal dependence. This study analyzed six groups of damaged and undamaged DNA sequences, where an "F" in the middle of a sequence indicates damage. One biological aim is to understand how DNA regenerates with the assistance of proteins that recognize damaged regions. Motivated by empirical support for AR(2) modeling, we fit autoregressive models to the first three principal component scores of each DNA group, capturing the dominant structure in the data. We conducted model diagnostics, …

Mo Isotopes In The Aleutian And Costa Rican Arcs: Source Variability And Juvenile Crust Formation, Ekaterina Rojas Kolomiets

Theses and Dissertations

Chemical and physical transfer between the surface, lithosphere and asthenosphere at subduction zones leads to arc magmatism and continental crust (CC) production. Subduction zones magmas and associated volcanic products sample a variety of magmatic sources that contribute to their chemical compositions in various proportions. This dissertation contributes to the study of subduction zones magmatism by assessing the relative role of subduction inputs (sediments, altered oceanic crust – AOC – and serpentinite) as flux agents in the arc magmatism and in CC formation in subduction zones under the scope of Mo isotope systematics.

I present the first Mo isotope analyses form …

Exploring The Self-Assembly Of Functional Bis-Urea Macrocycles: M-Terphenyl Bis Urea Macrocycles And Triphenylamine Bis-Urea Macrocycles, Gamage Isuri Pramodya Wijesekera

Theses and Dissertations

Porous materials have gained significant attention due to their diverse applications in catalysis, separation, and molecular storage. Among them, self-assembled macrocycles represent a unique class of functional materials that leverage non-covalent interactions to form well-defined architectures with pores of controlled size. This thesis explores the design, synthesis, and self-assembly of bis-urea macrocycles in both solid-state and solution-phase environments, with a particular focus on supramolecular polymerization mechanisms and the emergence of kinetically trapped states.

The first chapter of this thesis presents a detailed overview of self-assembled porous materials, categorizing them based on pore dimensions and discussing their significance in catalysis, separation, …

Two Dimensional Van Der Waals Magnet, Cheongheon Lee

Theses and Dissertations

Conventional charge-based memory has reached its limits in improving energy efficiency while scaling down size. Consequently, memory utilizing 2D magnetic materials has emerged as an alternative. 2D Van der Waals (VdW) magnets are ultrathin magnets with unique properties that make them optimal for this purpose. Utilizing the weak interlayer coupling via VdW interaction has enhanced the possibility of integrating diverse materials to create heterostructures. The integration of spintronics requires not only stable magnetization but also an effective switching mechanism. Various external influences have been experimentally tested, such as the proximity effect, external magnetic field, gate voltage, and temperature dependence. This …