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An Integrated Study Of Instrument Performance And Scientific Yield: Evaluation Of The Grape Design, Karla Georgina Onate Melecio

Doctoral Dissertations

This dissertation presents the end-to-end development, characterization, and in-flight validation of the 3-dimensional Gamma-Ray Polarimeter Experiment (GRAPE), a wide-field-of-view (FoV) Compton polarimeter designed for high-energy astrophysics. The primary scientific motivation is to address unresolved questions in the physics of Gamma-Ray Burst (GRB) jets, for which gamma-ray polarimetry is a critical diagnostic. GRAPE is designed to measure the degree and angle of $\gamma$-ray polarization within a targeted energy band of \SIrange{50}{500}{keV} to cover the peak energy output (E$_{pk}$) of observed GRB spectra. This work establishes the instrument's scientific readiness through two principal contributions. First, the instrument's fundamental low-energy response was characterized …

Evaluating The Role Of Seaweeds In Dairy Production: Impacts On In Vitro Ruminal Fermentation, And In Vivo Mineral Utilization And Metabolic Status, William Mitchell Sims

Doctoral Dissertations

Dietary inclusion of seaweed in ruminant diets has been studied for more than 5 decades. Early research in seaweed focused primarily on potential health benefits, but recent interest has shifted the paradigm for its use as a nutritional tool to mitigate greenhouse gas emissions. As new seaweeds are identified for their ability to reduce gas emissions, the pendulum will swing once more to understand the impact seaweeds have on ruminant health and production. The overall objective of this dissertation is to investigate digestibility and fermentation, as well as alterations in metabolic and mineral status in ruminants fed various seaweed species. …

Development And Characterization Of Bulk Dsdna-Based Materials Using Biologically Derived Plasmid Dna, Wynter Amythyst Paiva

Doctoral Dissertations

Double-stranded DNA (dsDNA) exhibits many unique sequence-independent properties that remain underutilized in materials science. The exceptional length, solubility, biocompatibility, imageability, molecular recognition capabilities, and topological control of DNA makes it an ideal candidate for the creation of bespoke biomaterials and investigation of fundamental relationships in polymer physics. Unfortunately, translation of DNA-based materials from the microscale to macroscale has been hindered by source constraints and limitations in chemical modification of biologically derived DNA. This work seeks to expand the utility of dsDNA from the benchtop to real world applications. Establishing dsDNA as a commodity polymer will aid in the development of …

The Baroclinic Route To Acoustic Streaming: Mechanisms Of Mean-Flow Generation And Heat Transport In Acoustically-Forced Stratified Fluids, Remil Mushthaq

Doctoral Dissertations

Standing acoustic waves in density-stratified fluids confined within horizontal channels generate fluctuating vorticity baroclinically, driving mean streaming flows that are much stronger and qualitatively distinct from classical Rayleigh streaming. Theoretical and numerical studies have shown that these baroclinic acoustic streaming flows can reach speeds comparable to the maximum speed of the oscillatory sound-wave field, enabling fully two-way wave/mean-flow coupling: the streaming flow modifies the background density field, which then alters the structure of the acoustic waves. Extending this framework, Massih (2022) quantified the heat-transfer enhancement arising from baroclinic streaming as a function of the channel aspect ratio (δ). The present …

Investigation Of Cross-Flow Turbines With Varying Structural And Surface Properties, Nicole Marone

Doctoral Dissertations

The oceans are a largely untapped resource with regard to their tidal, wave, and ocean current energy potential and could significantly contribute to clean energy objectives. Cross-flow turbines (CFTs) can be used to extract energy from tidal currents and provide electrical energy to the power grid. However, one of their main barriers to market entry is their levelized cost of energy (LCOE), which at present is still quite high. Three parameters that have not previously been studied together, and that could make CFTs more cost-competitive, include the use of less rigid and less expensive materials, a reduction in the number …

Adrift: The Influence Of Shelf Circulation And Larval Dispersal On Coastal Biogeography At Basin And Global Scales, Will Lush

Doctoral Dissertations

The dispersal of larvae plays an important role in determining the distribution of benthic meroplanktonic organisms in the coastal ocean. The work presented in this defense uses biophysical modeling approaches to examine the interaction of larval dispersal with coastal circulation and the impact of these interactions on contemporary coastal biogeography at global scales.I begin by presenting a novel method for validating numerical dispersal estimates against drifter observations from the Global Drifter Program. We find that median dispersal estimates match observations to within 5 percent, while model estimates underpredict the spread of drifters around this median by between 30 and 50 …

Focal Engine: Filling A Gap Between Game Engines And Big-Data Scientific Visualization Packages, Kindrat Beregovyi

Doctoral Dissertations

This dissertation presents Focal Engine, a novel 3D visualization engine designed to bridge the gap between game engines and scientific visualization tools. Game engines offer accessible interfaces and high-performance rendering but struggle with large-scale scientific datasets, while tools like ParaView and VTK handle complex data structures effectively but lack intuitive editing capabilities and modern rendering features. Focal Engine combines the accessibility and rendering performance of game engines with the data handling capabilities and analytical tools of scientific visualization platforms. The engine's capabilities are validated through multiple applications and projects, for example: HabiCAT 3D performs 3D complexity measurements on ocean floor …

Exploring Generation Z Student Satisfaction In Radiography Programs Within A Southern State: Development And Application Of A Survey Instrument For Leadership Use, Brittany Seruntine Smith

Doctoral Dissertations

This dissertation employed a sequential exploratory mixed-methods design to examine the extent to which Generation Z students in radiography programs within a southern state perceive that their needs and expectations are being fulfilled. Additionally, the study examined how program leaders perceived and plan to utilize the survey and its findings within the cycle of continuous program improvement and accreditation readiness. A Likert-scale survey instrument was constructed by cross-referencing Generation Z’s characteristics, needs, and expectations with JRCERT standards. Items were refined through target population focus groups and validated using Lawshe’s Content Validity Ratio. The validated instrument was then administered to Generation …

Secret Key Generation Based On The Physical Layer Characteristics For Iot Networks, Abdullah Dakhlallah Alshamdayn

Doctoral Dissertations

The rapid expansion of low-resource devices, coupled with advances in telecommunications, has significantly increased the number of connected devices and enabled the development of affordable, energy-efficient, portable, and high-performance sensors for diverse applications. However, this convenience comes with security and privacy concerns related to the reliability of hardware, software, and communication infrastructure. The extensive interconnectivity of limited-resource devices and the transmission of large data volumes pose significant security challenges in wireless networks. The future wireless technologies, such as 5G, will enable the transfer of critical data, including personal, financial, military, and industrial information, necessitating secure communication in wireless networks. Generally, …

For The Good Times: The Influence Of Leaders' Regret On Risk-Taking Behavior In Decision-Making, Ashley Elizabeth Owen

Doctoral Dissertations

Regret is a powerful and often underexplored emotion that significantly shapes leadership decision-making, particularly in high-stakes environments where the consequences of choices have lasting impacts on individuals, organizations, and communities. The researcher utilized qualitative research to explore how various forms of regret, including anticipatory regret, self-blame regret, and existential regret, influence risk-taking behavior and decision-making processes among higher education leaders within the University of Louisiana System. Drawing upon behavioral decision theory, regret theory, prospect theory, and emotional intelligence frameworks, the study aimed to understand how leaders experience, process, and respond to the emotional dynamics of regret within complex organizational settings. …

Towards Robust Autonomous Systems: Handling Multi-Modal Uncertainties In Gps-Denied Environments, Vivya Kalidindi

Doctoral Dissertations

This dissertation focuses on designing a robust and uncertainty-aware framework for autonomous systems operating in GPS-denied environments, such as indoor infrastructures, underground tunnels, and lunar surfaces. The proposed framework addresses the challenges posed by multi-modal uncertainties, including sensor noise, distributional shifts under adverse conditions, and conflicting decision-making preferences. These challenges compromise the reliability and adaptability of autonomous platforms. To overcome these challenges, the proposed framework adopts a layered architecture that integrates advanced methodologies across the sensing, perception, and decision-making layers. At the sensing layer, an Edge-Kalman Filter combined with a density ratio-based update mechanism is employed to reduce aleatoric uncertainty …

Evaluating The Effects Of Agricultural Management Practices On Beneficial Arthropod Communities, Isaac Newton Ativor

Doctoral Dissertations

Arthropods provide essential ecosystem services to our agricultural landscapes. These ecosystem services include biological control of pest organisms, including weed seeds, and plant pollination. Concerningly, however, there has been a global decline in insect populations over the last decade, a major cause of which is agricultural intensification. Previous research has demonstrated that agricultural management practices can strongly influence the species composition and abundance of arthropod communities, and therefore presumably the ecosystem services or disservices these organisms provide; however, our understanding of these interactions remains limited. I conducted three studies to investigate whether agricultural practices common in annual row crop (tillage …

Interpolated Factored Green's Function (Ifgf) Method Of Acceleration For Electromagnetic Scattering Off Of A Perfectly Electrically Conducting Surface, Mathew D'Amico

Doctoral Dissertations

Boundary integral equation (BIE) methods are advantageous in scattering problems due to their reduction of the problem's dimensionality as well as their automatic satisfaction of far-field radiation conditions. Specifically, for electromagnetic scattering off of perfectly electrically conducting (PEC) geometries, we are concerned with the magnetic field integral equation (MFIE). Typically, BIE implementation is iterative, with each direct integration requiring $\mathcal{O}(N^2)$ operations for a grid size $N$. For large $N$, this incurs very large computation times. To date, all existing methods that reduce the asymptotic operational complexity of evaluating the MFIE integral to $\mathcal{O}(N\log N)$ rely on use of the Fast …

Reentry, Justice Involvement, And Evolving Perspectives: Moving Toward Rehabilitation?, Casey Cavanaugh

Doctoral Dissertations

As prison populations climb, it is inevitable that the vast majority of incarcerated individuals will eventually return to the community. As they return, they face numerous barriers resulting from their incarceration. While it is important to identify barriers to reentry, it is also important to identify facilitators of reentry, which include forces that may mitigate reentry challenges. A tool is needed to measure this comprehensive list of barriers and facilitators, and in doing so, one may identify improvements and successes that stretch beyond merely that of recidivism. “Successful” reentry is typically measured through low recidivism rates, which recent government reports …

Investigations Into Prior Knowledge And Self-Efficacy As Predictors Of Exam Performance In General Chemistry, And Student Interactions With Chemistry Textbooks, Gordon Hunter

Doctoral Dissertations

The first chapter addresses the validity and reliability of the Motivated Strategies for Learning Questionnaire (MSLQ) as a tool for chemistry education research. The study shows that the original MSLQ did not meet modern standards of reliability and presents a modified version that better captures self-efficacy in chemistry-specific contexts. The revised instrument shows improved model fit, reinforcing the importance of refining assessment tools for chemistry education research.The effects of prior knowledge and self-efficacy on student performance in a first-semester general chemistry course are investigated in the second chapter. Self-efficacy, defined as a learner's belief in their capability to successfully accomplish …

Planning Responses To Drinking Water System Emergencies, Jingyan Huang

Doctoral Dissertations

Despite extensive efforts to ensure clean and safe drinking water, drinking water contamination emergencies remain a persistent challenge in the United States. These events can result in widespread public health impacts, economic losses, and long-term environmental damage, particularly when triggered by hazardous chemical releases. Effective management of such crises requires a dual focus on both technical preparedness and human decision-making. This dissertation addresses these challenges through a two-part investigation that bridges pre-incident planning and post-incident response. It is guided by two core research objectives: (1) to evaluate commonly applied emergency countermeasures from both resilience and sustainability perspectives; and (2) to …

Psychological Factors Of Acting Talent And Success: You've Got "It", Lorelei Tierney Himlin

Doctoral Dissertations

The goal of an actor is to become invisible, bringing a character to life so convincingly that the audience forgets the actor exists outside the role. Different schools of acting often describe differing methods of portraying characters to this same general effect. To followers of the Meisner school, for example, “acting is behaving truthfully under imaginary circumstances” (Meisner et al., 1987). The “truthful” part involves creating a comprehensive mental model of a character’s imagined personality in order to fully embody that personality and extrapolate it to a situation. Then the actor uses a variety of acting techniques to think and …

Black Hole-Neutron Star Mergers: Numerical Relativity Studies Of Remnant Matter, Gravitational Waveforms, And Automated Simulation Workflows, Tia Kathleen Martineau

Doctoral Dissertations

Black hole–neutron star (BHNS) mergers are key sources for multimessenger astrophysics, offering insight into strong-field gravity and the behavior of matter at supranuclear densities. This dissertation presents three independent contributions to the study of BHNS systems using the Spectral Einstein Code (SpEC). First, a set of simulations spanning a range of mass ratios, black hole spins, and neutron star equations of state is used to map disruption thresholds and quantify remnant disk masses, unbound ejecta, and ejecta composition. These results are compared to predictions from remnant mass model FNH18, to assess its reliability in accurately predicting the resulting remnant masses …

Multi-Level Characterization And Testing Of Fatigue, Fracture And Creep Of The Ultra-High Strength Low-Alloy Steel Fabricated Via Laser Powder Bed Fusion, Nemanja Kljestan

Doctoral Dissertations

This dissertation presents a comprehensive experimental investigation of the mechanical behavior of an high-strength low-alloy (HSLA) steel fabricated via laser powder bed fusion (LPBF). The work focuses on fatigue strength, laser shock peening (LSP) effects, creep behavior, fatigue crack growth and fracture toughness. Fatigue strength was assessed using rotating bending tests, showing superior performance of LPBF specimens compared to as-cast materials due to the dual-variant martensitic microstructures. Laser shock peening enhanced fatigue life by inducing compressive residual stresses, delaying crack initiation and slowing crack propagation. Creep behavior was evaluated for different layer thicknesses, with thinner layers improving secondary creep resistance …

Simulations Of Perpendicular Electron Holes, James Patrick Mcclung

Doctoral Dissertations

Bernstein–Greene–Kruskal modes commonly manifest as electron holes and electrostatic solitary waves in space plasmas. These Debye-scale structures are nonlinear solutions to the steady-state Vlasov–Poisson system. Solutions in one dimension are highly tractable mathematically, observationally, and computationally, and are relatively well-understood. Higher-dimensional, magnetized plasmas are less amenable to study, however. Following a 20-year history of theoretical developments in two-dimensional BGK modes, this thesis presents the first high-resolution 2D and 3D simulations thereof. Stability conditions and phase-space dynamics are discovered and discussed. The simulated modes are ultimately compared to observed electron holes and modern width-amplitude relations. In addition, a significant portion of …

Missing Child Incidents Resulting In Death: Distinguishing Features Between False Allegations, Wander-Offs, And True Child Abductions, Madison N. Sundberg-Alley

Doctoral Dissertations

Children are reported missing in the United States for a multitude of reasons every year. Often, law enforcement is tasked with investigating these disappearances and recovering the missing child. In some instances, determining the reason why a child is missing can be challenging. This study focuses on three types of missing child episodes that result in fatality: child abduction homicides (CAH), false allegations of child disappearance (FACD), and wander-offs (WO). This exploratory analysis contributes to a gap in the literature by identifying some possible differences between case types that may assist police in determining the likely explanation for the disappearance. …

Analyzing Regions For The Study Of Localized Fluctuations In The Ground Magnetic Field For The Development Of A Global Risk-Assessment Forecast, Michael Kavanagh Coughlan

Doctoral Dissertations

The dynamic relationship between the solar wind and the Earth's magnetic field can produce rapid changes in the geomagnetic field measured on the ground ($dB_H/dt$). The fluctuations can be highly localized, with differences of up to 100s of nT/min in a small geographic area. The field of space weather is entering a more data-driven era, with enormous amounts of publicly available datasets from satellites and ground measurements. In this work modern machine learning techniques were employed to make forecasting risk-assessment predictions of large and localized $dB_H/dt$, and model explainability methods were employed to understand the non-linear connections being made. These …

Computational String Theory Using Machine Learning, Giorgi Butbaia

Doctoral Dissertations

Low-energy couplings of certain superstring theories are related to the masses of the particles. One of the most promising superstring theories is $\mathcal{N}=1$ supersymmetric $E_8\times E_8$ heterotic string theory. In a certain embedding of the standard model into $E_8\times E_8$ gauge group of the heterotic string, the particle spectrum consists of $(\mathbf{27})^3$, $(\overline{\mathbf{27}})^3$, $(\mathbf{1})^3$ and $\mathbf{1}\cdot \mathbf{27}\cdot\overline{\mathbf{27}}$ couplings. While the $(\overline{\mathbf{27}})^3$ couplings are quasi-topological, the $(\mathbf{27})^3$ explicitly depend on the Ricci-flat metric on Calabi-Yau.

In this dissertation, we explore recently developed techniques for calculating the normalized Yukawa couplings on various Calabi-Yau manifolds. In Chapter 2, we describe a novel architecture, …

Counting Kelp: Development And Assessment Of Modelling Approaches To Improve Understanding Of Kelp Bed Abundance And Resilience In The Gulf Of Maine, Constance N. Tyler

Doctoral Dissertations

Kelp habitats in the Gulf of Maine are threatened by rising ocean temperatures and marine invasions. The replacement of kelps with red turf macroalgae fundamentally alters these habitats and disrupts the ecosystem services they provide. Thorough assessment and monitoring of kelp habitats is needed for proper conservation of these habitats, but most long-term monitoring is performed using traditional survey methods that are restricted in the amount of space they can cover. Habitat modelling approaches are required to expand our knowledge of Gulf of Maine kelp habitats, and to better understand the interactions between kelp and red turf habitats across the …

Verifying Interchange Reconnection Models For Magnetic Switchbacks Using The Parker Solar Probe And Mms, Emily Owen Mcdougall

Doctoral Dissertations

Ever since their initial observation by the Ulysses probe, many models of magnetic switchbacks were put forth, but relatively little empirical evidence exists to verify these models, especially in terms of the ions that make up the accompanying plasma. I take energetic particle data from the Parker Solar Probe within switchbacks to provide experimental evidence to bolster the interchange reconnection driven models with particular interest in the interchange reconnection driven linear model. Statistical Analysis of switchbacks in the vicinity of CMEs, solar flares, and high-speed streams show properties consistent with the linear interchange reconnection model, and an analysis of switchbacks …

The Assessment Of Language, The Language Of Assessment: Understanding How Language Teachers Support Dynamic, Communicative Language Learning Through Assessment, Rebecca Kelley

Doctoral Dissertations

As language classrooms in K-12 schools in the United States seek to promote students’ proficiency in the language they teach and to prepare students for a multilingual world, the role of assessment in these classrooms is often overlooked. This study draws from theories of formative and dynamic assessment, as well as a socially-constructed view of language and language learning, in order to examine the way in which secondary language teachers plan for, elicit, interpret, and use evidence from classroom assessments in such a way that promotes and supports the language learning happening in the classroom. Through a series of three …

Fine Structure Of Magnetic Reconnection: Impact On Reconnection And Dissipation Rates, Steven Ver Bryck Heuer

Doctoral Dissertations

Magnetic reconnection is a fundamental process in magnetized plasmas where stored magnetic energy is converted to heat and kinetic energy. The objective of this thesis is to examine the role of small-scale structure of the reconnection region and the background plasma conditions on the rate that reconnection converts and dissipates magnetic energy. This is done using in situ data from NASA’s Magnetospheric Multiscale (MMS) mission and particle-in-cell (PIC) simulations of reconnection for different regimes. First, we introduce a new technique for measuring the reconnection rate and demonstrate its accuracy for the simplest regime of reconnection. Next, we show that it …

Resolving The Role Of Wave-Induced Pressure Gradients On The Movement Of Sediments In Nearshore Environments, Melissa Marry

Doctoral Dissertations

Characterizing the hydrodynamic forces responsible for the initiation of sediment motion is fundamental for improved understanding of large-scale sediment transport processes in nearshore environments. Traditional sediment transport models assume incipient sediment motion is only driven by the force applied by bed stress (Bagnold, 1966; Shields, 1936) while more recent work has shown that incipient motion is influenced by the forcing of the horizontal pressure gradient due to surface gravity waves (Foster et al., 2006; Frank et al., 2015; Sleath, 1999). Wave-induced vertical pressure gradients can also destabilize the sediment bed through the process of momentary liquefaction (Florence et al., 2022b; …

Technologies To Support Remote Work For Collaborative Groups, Alberta Ansah

Doctoral Dissertations

The nature of work continues to evolve, particularly in the aftermath of the COVID-19 pandemic. While a substantial number of employees have returned to traditional, in-person work environments, many continue to engage in remote or hybrid work arrangements. Online meetings are a significant aspect of remote work, and while there has been a significant increase in this area, there are still aspects of these meetings that are not fully understood. Existing research in this area has primarily focused on the development of tools to facilitate meeting execution and content management. In contrast, relatively few studies have explored the social dynamics …

Eastern Oyster, Crassostrea Virginica, Genomics In A Well-Mixed Estuarine System: Examining Population Structure, Viability, And Response To Stressors, Alyssa Strickland

Doctoral Dissertations

Eastern oysters, Crassostrea virginica, are foundational estuarine species that contribute to a variety of ecosystem services including water filtration, nutrient cycling, habitat creation, and shoreline protection. However, populations have declined due to disease, overharvesting, habitat loss, and climate change, especially in northern systems such as New Hampshire’s Great Bay Estuary (GBE), located in the Gulf of Maine, one of the world’s fastest warming waters. This dissertation uses genomic and transcriptomic approaches to understand the drivers of population structure, decline, and resilience in GBE oyster populations, aiming to aid restoration and aquaculture. Chapter 1 used low-coverage whole-genome sequencing to understand population …