Doctoral Dissertations

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https://hdl.handle.net/10919/11041

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The making of impact: Causal validity and epistemic justice in international development impact evaluation
Travis, Elli Madeleine (Virginia Tech, 2025-06-16)
This dissertation investigates the manifestation and negotiation of causal validity and epistemic justice in international development impact evaluation (IDIE), with a specific focus on agricultural interventions. Drawing on Ernest House's (1980) assertion that evaluations should be not only true but also just, and Donald Campbell's (1986) reconceptualization of internal validity as "local molar causal validity," the study examines how evaluators balance methodological rigor with inclusive knowledge production. Through narrative-reflective interviews with nine evaluators representing diverse methodological perspectives, the research employs Eyal's (2013) "expertise as network" as well as research on evaluation's concepts of validity as a conceptual framework, exploring how causation and justice are part of an interconnected network of agents, concepts, devices, and institutional arrangements affect impact determination. Findings reveal multiple causality conceptions in practice, with evaluators acknowledging the counterfactual as necessary but insufficient for robust causal claims, aligning with Campbell's nuanced view of validity. Analysis utilizing Byskov's (2021) conditions for epistemic injustice and House and Howe's (2000) Deliberative Democratic Evaluation framework demonstrates that evaluators employ various strategies to promote epistemic justice while negotiating practical constraints. The study presents a four-quadrant matrix delineating elements that: (1) inhibit epistemic justice while promoting causal validity; (2) inhibit causal validity while promoting epistemic justice; (3) inhibit both; and (4) promote both. This framework illuminates potential areas of methodological and disciplinary convergence between evaluation approaches, highlighting contextual sensitivity, inclusive research practices, and methodological flexibility as practices that simultaneously advance both the causal validity championed by Campbell and the justice-oriented validity advocated by House. The findings have significant implications for evaluation practice, especially amid the structural transformations occurring within international development organizations.
Design and Development of a Socratic Intelligent Tutoring System: Leveraging Agentic AI for Asynchronous Online Learning
Kayanuma, Bryce Platt (Virginia Tech, 2025-06-16)
Shape memory polymers with improved shape recovery properties in focused ultrasound fields
Xi, Jiaxin (Virginia Tech, 2025-06-16)
Shape memory polymers (SMPs) have garnered significant attention for their remarkable ability to recover deformations upon external stimulation, making them highly suitable for biomedical devices, soft robotics, and deployable systems. Among the various activation mechanisms, focused ultrasound (FUS) has emerged as a promising non-invasive and spatially selective stimulus, capable of inducing localized heating via viscous polymer chain shearing. However, the material design strategies enabling efficient and rapid shape recovery under FUS remain underexplored. This dissertation aims to develop, characterize, and computationally model acrylate-based SMPs and their composites, focusing on enhancing actuation efficiency under FUS. To accommodate miniaturized biomedical systems, fibrous SMPs are fabricated via electrospinning, where fiber morphology is tuned through polymer concentration and flow rate. The electrospun webs exhibit 100% shape recovery and variable fixity ratios, with fiber diameter significantly influencing thermal and mechanical properties. We systematically design SMP networks with tunable glass transition temperatures and hydrophilic/hydrophobic properties to investigate the role of water uptake in FUS-induced shape recovery. Experimental results reveal that pre-immersion of hydrophilic SMPs facilitates faster and more complete recovery, attributed to water-induced plasticization and improved acoustic coupling. To achieve advanced actuation functions, a two-way shape memory polymer (2W-SMP) based on crosslinked poly(ethylene-co-vinyl acetate) is developed. This polymer demonstrates reversible motions, enabling applications such as gripping, self-rolling, and jumping in soft robotic systems. Furthermore, boron nitride (BN) nanoplatelets are incorporated into SMP matrices to enhance thermal conductivity and actuation performance. Under FUS, BN-filled composites exhibit a 75% improvement in recovery ratio compared to unfilled SMPs, owing to more efficient heat transfer and reduced activation thresholds. Complementing experimental studies, fully atomistic molecular dynamics (MD) simulations are employed to examine the role of crosslinking density on thermomechanical properties and shape memory behavior. The simulations demonstrate that increased crosslinking enhances stiffness, glass transition temperature, and recovery efficiency, while identifying the molecular-scale mechanisms driving ultrasound-induced shape change. Collectively, this work provides a comprehensive framework for the design and optimization of ultrasound-responsive SMPs through multi-scale experimental and computational approaches. The findings offer critical insights into the interplay between polymer structure, water interaction, filler reinforcement, and acoustic actuation, advancing the development of tunable SMP systems for biomedical and soft robotic applications.
The ecology of eastern small-footed bats at Shenandoah National Park
Kalen, Nicholas James (Virginia Tech, 2025-06-16)
Several aspects of rock-dwelling eastern small-footed bat (Myotis leibii) ecology remain poorly resolved including the species' local distributions and abundance within their range, maternity habits, and thermoregulatory strategies. Broadly rare, eastern small-footed bats appear to be largely localized to mountainous habitats that feature their preferred roosting habitat, emergent rock features and talus slopes. Following initial reports of mortality from the bat epidemic white-nose syndrome, eastern small-footed bats were reviewed for protection under the endangered species act but were rejected due to lack of significant evidence of declines and overall understanding of their broadscale abundance. In response, a novel method of conducting visual searches of rock outcrops and talus slopes was developed to detect the presence of summer day-roosting eastern small-footed bats. I explored a novel methodology expanding on this technique, whereby I conducted visual searches of talus slopes at Shenandoah National Park, Virginia, modeled bat abundance by topographic variables, and predicted bat abundance to talus slopes throughout the park to talus slopes classified with algorithms utilizing high-definition imagery and a topographic index measuring terrain ruggedness. Eastern small-footed bats were widespread and relatively abundant at Shenandoah National Park, occurring in the majority of sampled talus slopes and topographic conditions. The top abundance model included covariates aspect, elevation, topographic exposure index (TEI), vector ruggedness measure (VRM), and talus area and had a pseudo R-squared of 0.58. Aspect, elevation, VRM, and area positively influenced bat abundance, whereas TEI negatively influenced abundance. Eastern small-footed bats were most abundant in positions with increased solar exposure, which drove model performance. The abundance model estimated 1,330 eastern small -footed bats roosting in talus slopes throughout Shenandoah National Park. I also documented the phenology, roost use, thermoregulatory patterns, and roost and social network dynamics and of a maternity colony of eastern small-footed bats. Eastern small-footed bat females formed a cohesive social network that used rock crevice roosts in a fission-fusion dynamic similar to tree-roosting bat species, exhibiting similar network dynamics centralized to a primary, central node roost. Natality was high and all females were either pregnant or lactating. Parturition occurred synchronously in mid-June. The maternity colony was philopatric to a large talus slope receiving high solar exposure and featuring large boulders and a dense concentration of large crevices. To evaluate thermoregulatory ecology and foraging activity periods, I used temperature-sensing radio transmitters to record bat skin temperatures pregnant and lactating eastern small-footed bats. All bats engaged in torpor every day but pregnant and lactating eastern small-footed bats engaged in distinctly different thermoregulatory patterns, in which pregnant bats generally used shallower torpor and shorter torpor periods compared to lactating bats that more frequently engaged in deep torpor. These regulating and conforming thermoregulatory strategies were similar to observations of little brown bats (M. lucifugus) and suggest respective strategies offer energetic trade-offs supportive of each reproductive phase. Pregnant and lactating eastern small-footed bats also exhibited significantly differing foraging periods, in which pregnant bats left day roosts for longer continuous periods, whereas lactating bats left for short, sometimes multiple forage bouts returning to day roosts in between. Differences in foraging periods may reflect the foraging efficiency, maternal responsibilities, and energetic requirements associated with thermoregulatory strategies of each reproductive phase. Both pregnant and lactating eastern small-footed bats passively rewarmed in day roosts, supporting the importance of solar exposure to abundance model. Energetic savings from daily torpor and that likely contributes to their maternity habits, day roost selection, and spatial abundance.
Honors College as Whitespace: An Institutional Ethnography
Roberts, Elizabeth Burdette (Virginia Tech, 2025-06-13)
This dissertation brings together the theory of whitespace and institutional ethnography to examine how whiteness operates within collegiate honors education. Situated within sociological theories of whiteness, race in higher education, and honors education, the project addresses a significant gap: the racialized dynamics of honors colleges remain understudied. Drawing on artist-activist Tema Okun's (2021) articulation of white supremacy cultural norms, I analyze the data generated to explore how whiteness manifests within honors colleges. Through institutional ethnography across three case sites—including interviews with honors practitioners, content analysis of organizing documents, and critical autoethnographic accounts from my experience as an admissions counselor—I trace how whiteness structures the ruling relations of honors education. This study explores whether and how honors colleges enact white supremacy culture, how whiteness exists within organizational logics and practices, and how honors practitioners navigate these dynamics. In addition to mapping the ruling relations for each of the three case sites, I construct both an ideal-type and an experience-based map of the ruling relations of honors education broadly. From there, I identify how characteristics of white supremacy culture (Okun 2021) and mechanisms of whiteness (Moore 2020) shape the social and structural organization of honors colleges. Ultimately, I argue that honors colleges function as whitespaces, privileging whiteness by design. The project concludes by offering possibilities and questions for disrupting whiteness and reimagining honors education through both a critical and liberatory lens.
Cells, circuits, and development of the mouse lateral geniculate nucleus
Stebbins, Katelyn (Virginia Tech, 2025-06-13)
In the visual system, retinal axons transmit visual information from external stimuli to numerous and distinct brain regions. In rodents, one major area that is densely innervated by retinal input is the visual thalamus. The mouse visual thalamus serves as a powerful model system to understand sensory circuit development based on its orderly structure and ease of accessibility for experimental manipulation. Within the visual thalamus, the lateral geniculate nucleus (LGN) is divided into three distinct regions: ventral LGN (vLGN), dorsal LGN (dLGN), and the intergeniculate leaflet (IGL). Previous studies have characterized the cytoarchitecture and circuitry of dLGN, which is crucial for classical image-forming vision. However, the molecular resolution of subtypes and the connection between subtypes of retinal ganglion cells with those cell types in dLGN remains unresolved. vLGN is known to be associated with non-image-forming vision, though its complete neurochemistry, cytoarchitecture, and afferent and efferent circuitry remain unresolved, raising fundamental questions about its functional role within the visual system. Identifying the structure and function of neural circuits related to vision is crucial for understanding how light exerts its influence on programming an individual's circadian cycle, mood disorders, fear perception, and perception and interaction with the environment. We employed state-of-the-art single-nucleus sequencing to identify a comprehensive list of cells in both dLGN and vLGN. Using this knowledge, we next explored the development of cell-type specific layers in the vLGN. In situ hybridization, immunohistochemistry, and genetic reporter lines revealed that the subtype-specific layering of retinorecipient cells in vLGNe is established during embryonic development. Taken together, the studies in this dissertation have not only identified novel subtypes of dLGN and vLGN cells but also point to new means of organizing visual information into parallel pathways by anatomically creating distinct sensory channels. This subtype-specific organization may be key to understanding how LGN receives, processes, and transmits light-derived signals in the visual system. Elucidating these pathways gives potentially generalizable principles in how sensory information is organized in the brain.
Design and Control of a Structurally Elastic Humanoid Robot
Herron, Connor William (Virginia Tech, 2025-06-13)
In upcoming decades, humanoid robots are expected to fill the current labor crisis by completing simple behaviors such as lifting and delivering heavy objects around a factory, sorting components, and placing parts onto an engineering build for an assembly line. Unlike other robots that have a fixed base, legged robots must rely on switching contact states and apply forces to the ground to navigate which poses several control and state estimation challenges. Currently, humanoid robots are manufactured with rigid metal linkages that are extremely complex and require an expert machinist leading to cost increases. Instead, this work presents the design and control of the 3D-printed humanoid robot, PANDORA. As opposed to contemporary approaches that incorporate the elastic element into the actuator mechanisms, PANDORA is designed to be compliant under load, or in other words, structurally elastic. This design approach lowers manufacturing cost and time, design complexity, and assembly time while introducing controls challenges in state estimation, joint and whole-body control. This work specifically focuses on the low-level hardware design at the firmware level, the joint control approach which must deal with the unmodeled structural elastic linkages, the corresponding state estimation challenges that are caused by the link elasticity, and the design of an orientation-based planner towards spatial objective planning for bipedal locomotion.
Structure-Activity Relationship Studies of Mitochondrial Uncouplers and PilB Inhibitors
Quinlan III, Joseph Edward (Virginia Tech, 2025-06-13)
Obesity is a chronic, noncommunicable disease caused by the excessive accumulation of body fat. Rates of diagnosis have been increasing in the late 20th and early 21st centuries, with associated comorbidities also on the rise. Consequently, obesity has become a growing health epidemic globally. Development of novel pharmacological therapeutics with limited side effects is thus desirable. Chemical mitochondrial uncouplers are protonophoric, lipophilic small-molecules that transport protons from the mitochondrial intermembrane space into the matrix independent of ATP synthase, thus uncoupling nutrient oxidation from ATP production. Such a mechanism has been previously shown to be effective in mouse obesity models. Our previous work identified BAM15 (EC50 1.5 M) as a potent and efficacious mitochondrial uncoupler with potential for obesity treatment. In this study, we investigate in vitro and in vivo properties of hydroxylamine and hydrazine BAM15 derivatives and reveal the high uncoupling nature of these compounds. Our structure-activity relationship (SAR) studies demonstrated that the hydroxylamine BAM15 analogs are more potent than hydrazine ones, with particular note of hydroxylamine ester derivatives being the most efficacious of all structures assayed. For example, the most efficacious of the hydrazine series was 1.12.1 with an EC50 value of 4.6 M and 103% activity of BAM15 while compound 1.11.5 was the best among the hydroxylamine series with EC50 value of 340 nM and 118% BAM15 mitochondrial uncoupling activity in rat L6 myoblasts. Pharmacokinetic profiling of 1.12.1 and 1.11.5 indicated low exposure (2-220 nM) and short half-life (15-27 min) in mice. In a separate study, we investigated the structure-activity relationship of benserazide in the pursuit of treating drug-resistant bacterial diseases. Antimicrobial resistance is an imminent health threat worldwide due to the increasing resistances to common antibiotics of many lethal pathogens. Overuse and underdevelopment of novel antibiotics, which target bacterial cell survival, has exacerbated the problem by enabling bacteria to develop resistance mechanisms to their mechanisms of action. Development of alternative treatments for drug-resistant microbes is thus of paramount importance. Targeting virulence factors, non-vital components of pathogens that enable them to cause disease such as the type IV pilus construction enzyme PilB, is a strategy of treatment. PilB is a highly conserved hexameric ATPase responsible for pilus generation and is thus obligatorily involved in bacterial type IV pilus use. Previously, the type IV pilus has been shown to be critically important in the pathogenesis of various drug-resistant microorganisms and so presents as a suitable drug target. Recently, we reported the discovery of a potent inhibitor of PilB, the Parkinson's Disease-treating drug benserazide (IC50 3.68 μM). Herein, we report the SAR profiling of benserazide analogues and identify key moieties that enable PilB inhibition. We found that bis-hydroxyl groups on the ortho position of the aryl ring, a rigid imine, and exchange of the serine for a thiol have resulted in marked improvement in potency. Our studies identified 2.12.3 as a PilB inhibitor with an IC50 of 580 nM and selectivity for PilB over an unrelated ATPase, apyrase. These compounds provide the chemical tools to validate virulence factors as antibacterial mechanisms of action.
Teaching from Within: Developing Culturally Responsive Classroom Management Through Personal Philosophy
Powers, Kia Sarika (Virginia Tech, 2025-06-13)
Given the increased ethnic, social, cultural, and linguistic demographics in US public schools, culturally responsive classroom management (CRCM) can positively influence students' academic achievement and social engagement. Culturally responsive classroom management can decrease discipline and referral rates of students, particularly students of color. Research studies support that culturally responsive classroom management positively impacts students' academic achievement and social engagement. However, few studies have investigated elementary schools using the CRCM framework. This qualitative study investigated elementary school teachers' understanding and perceptions of classroom management (CM), specifically focusing on culturally responsive classroom management (CRCM). This study involved seven public school elementary teachers through semi-structured interviews. The participants were asked to describe their classroom management philosophies and explain the classroom management strategies and practices they implement in their classrooms. Findings from this study suggest the importance of culturally responsive classroom management to accommodate the many different cultural identities of students in US schools.
The Asteroid Miners: Space Mining and Resource Making in the Commercial Space Era
Mandel, Savannah Lann (Virginia Tech, 2025-06-13)
In 2019, two news articles announced that the "asteroid mining bubble had burst." One, written by prolific space industry journalist, Jeff Foust, explained that the question of whether or not the space mining industry had "boomed" or "bubbled" had been answered, as almost all existing space mining companies at the time had been acquired by other corporations or had gone bankrupt. According to Foust, space mining was a space industry goal which had simply been "too long-term and too far-fetched". Space mining startups which had emerged in the early 2010s required long-term funding, focused technological development, and substantial, persistent, financial backing — none of which they had received. The existence of these articles prompts many questions. First, if an asteroid mining bubble had burst, when had it existed? To what extent had there been "asteroid mining"? And if the bubble had burst, then why have corporations like Astroforge — which also aim to mine space objects— emerged in 2022, years after the bubble supposedly burst? Why do they think they can succeed in such an arguably far-fetched venture where all others have failed? Have they failed? Beyond this, one also might wonder, when did interest in space mining begin and more importantly — why did it begin? At what point did space objects, such as asteroids, comets, meteors, moons and planets, become subjects of commercial interest rather than simply scientific interest? Using ethnographic and archival methods, this dissertation explores the rise and fall of the space mining industry. It makes contributions to three subfields within Science and Technology Studies — social studies of outer space, studies of failure, and studies on colonialism— as it demonstrates how space objects were made resources and what the "failure" of the space mining industry generated. It makes three primary arguments: (1) That the "fall of the space miners" was a failure which was generative, anticipated, and taken advantage of (2) that space mining was real in the way it was realized (3) and that while space mining contributed to a greater project to colonize outer space, colonization also contributed to the commodification of space objects. In sum, this dissertation argues that asteroids, moons and other space objects have become commodities through a process of colonization and space industry commercialization and that this process generated unanticipated byproducts. This dissertation also uses theories of socio-technical systems as a way of understanding scientific and technological development.
Locating Citizenship of Indian Christians
Jeyaraj Samraj, Trevor Jeyaraj (Virginia Tech, 2025-06-13)
Integration of Power Electronics Building Block Using Polyimide Substrates
Rajagopal, Narayanan (Virginia Tech, 2025-06-12)
The advancement of silicon carbide (SiC) devices has enabled a new generation of high-density, fast-switching power converters for automotive, marine, and aerospace applications. One of these converters is the SiC-based Power Electronics Building Block (PEBB), which integrates semiconductor devices, gate drivers, magnetics, and other components into modular, flexible converters. To fully leverage the benefits of SiC and the PEBB concept, this work explores advanced packaging and integration strategies that enhance power density and manufacturability. This research focuses on an advanced converter-level packaging approach, referred to as the common substrate concept, as a replacement for traditional ceramic-based power module converter designs. The common substrate acts as a multifunctional platform that directly mounts and interconnects all essential components, including semiconductor dies, gate drivers, sensors, magnetics, capacitors, and ancillary circuitry. This integrated approach simplifies system architecture, reduces the number of discrete elements, and improves scalability for manufacturing. The key enabling technology behind this concept is a new generation of polyimide substrate and its unique electro-thermal-mechanical behavior. Polyimide substrates offer significantly greater design flexibility than traditional ceramic-based designs. They support thicker copper layers and thinner dielectric layers, which can enhance electrical and thermal performance while enabling higher levels of integration. However, these advantages introduce new challenges. The extreme material parameters of polyimides, such as high capacitive coupling and relatively low thermal conductivity, make it difficult to apply conventional design rules developed for ceramic and epoxy-based substrates. To address this gap, this work completes a comprehensive electro-thermal-mechanical study on polyimide substrates. Finite element analysis (FEA) is used to evaluate the electrical and thermal behavior of polyimide substrates and parametrization of geometric variables is conducted to assess their influence on key performance metrics like thermal resistance and electromagnetic interference (EMI). This design space serves as a guide for navigating tradeoffs and selecting optimal configurations for specific application requirements. In addition to simulation, the research investigates the thermo-mechanical implications of polyimide substrates, particularly the effects of thick copper layers and large-area warpage. Experimental thermal cycling and warpage measurements are conducted to validate the mechanical reliability. These findings help inform limitations of polyimide substrates and highlight tradeoffs for use in high-power applications. To validate the proposed design space, two design points are selected and fabricated into full-bridge 1.7 kV SiC power modules. These prototypes are experimentally evaluated for key performance metrics including hard switching losses, zero-voltage switching (ZVS) range, common-mode EMI, and thermal resistance. The results confirm that switching node capacitance layout is a primary driver of polyimide substrate behavior. These insights are then applied to the design of the PEBB, where the common substrate is refined using the validated design space. This work presents a methodology for designing and implementing polyimide-based substrates in power electronics. By bringing together simulation and experimentation, it provides an understanding of the benefits, limitations, and tradeoffs of polyimide substrate technology and its application in common substrates for future PEBB system.
Frank Lloyd Wright's Chinese Voyages: Travels, Studies, Collections in the Pursuit of Organic Architecture
Zhao, Tianming (Virginia Tech, 2025-06-11)
This study primarily investigates the Chinese voyages of the renowned architect Frank Lloyd Wright (1867-1959) in his quest for organic architecture. While extensive research has been conducted on Wright's influence from Japan, his connections with China have been largely overlooked in scholarly discourse. It is notably underrecognized among Wright scholars that Wright visited China in 1918, marking the beginning of a new chapter in his engagement with Chinese philosophy, art, and culture over the subsequent four decades of his career. This scholarly gap underscores the significant contribution of this research to the field of Wright studies. This dissertation will examine three principal aspects of Wright's influences from China, reflecting three distinct phases of his engagement with Chinese culture: his travels to China in 1918, his study of Chinese philosophy, particularly through the works of Dr. Ku Hung Ming (1857-1928) and his book The Spirit of the Chinese People (1915), and his collection and integration of Chinese artworks into his architectural designs. Through archival research and a detailed examination of his 1943 autobiography, we will initially reconstruct the historical facts surrounding Wright's six-week journey to China in 1918. This investigation will include an analysis of the details and motivations behind this remarkable trip, drawing upon the limited historical evidence available. Building upon this foundation, we will assess the significance of Wright's immersive experience in China for his design philosophy, serving as an empirical basis for the subsequent analysis. During his 1918 travels in China, Wright notably became acquainted with Dr. Ku Hung Ming, a distinguished Chinese scholar, and his theory concerning the Chinese spirit. Our research will then examine the significance of Ku's theory for Wright and explore its potential theoretical connections to Wright's design philosophy, considering that Wright frequently referenced Ku on multiple occasions. Lastly, our study will focus on the specific strategies employed by Wright to integrate the Chinese artworks he collected into his architectural designs, potentially influenced by his experiences in China and his interactions with Dr. Ku. To facilitate our analysis, we will examine three iconic examples from both Taliesin Wisconsin and Taliesin West, where the majority of Wright's Chinese artworks were stored and displayed. These examples include the Bodhisattva statues, glazed tiles, and 'Foo Dogs' sculptures at Taliesin Wisconsin, as well as the "Studio Buddha," Han-style jars, and Shiwan friezes at Taliesin West. The analysis will be supported by data collected from on-site field studies. By comparing the integration of Chinese artworks between the two Taliesins, we aim to uncover the increasing significance of these Chinese artworks to Wright, reflecting his deepening understanding of Chinese art and culture from Taliesin Wisconsin to Taliesin West.
Understanding the Role of Social Norms in Natural Resource Co-Management
Franco, Caetano Lucas Borges (Virginia Tech, 2025-06-11)
This dissertation investigated how social norms have been conceptualized, integrated and applied to understand cooperation in natural resources co-management. While interest in social norms is growing across disciplines, they remain relatively underexplored within conservation social psychology, even as research expands in response to urgent social and environmental challenges. This research brought together theoretical and empirical insights from social and cultural psychology, behavioral economics, and institutional analysis to explore how social norms influence individual and collective behavior in institutional arrangements for co-managed natural resources. The first chapter presented a systematic review of 46 empirical studies that examine social norms in natural resource co-management. The analysis revealed that only a fifth of the studies provided explicit definitions of social norms, and those that do exhibit diverse conceptual orientations. The integration of key theoretical components of social norms—such as empirical and normative expectations, reference networks, social sanctions, and conditional preferences—is uneven. Many studies cited norms as important for fostering stewardship and compliance but fall short in specifying behavioral mechanisms. The chapter called for greater conceptual clarity and methodological rigor to advance the use of social norms in interdisciplinary research on environmental governance. The second chapter developed a conceptual framework to integrate social norms into the study of resource co-management. This chapter merged insights from social and cultural psychology, economic behavior, institutional analysis, and natural resources management studies. It started by differentiating social norms from formal rules, setting the stage for understanding their complex interactions. The framework defined social norms as social expectations to which individuals are expected to conform, which influence behavior in terms of care about others' approval or disapproval. It emphasized the interdependence of social norms at both individual and collective levels, and how they impact broader practices and cultural dynamics. It also explored the reciprocal relationship between personal behavior and group norms, facilitating collective decision-making and gradual change. The framework provided practical guidance for identifying leverage points where social norms can be harnessed to improve natural resources governance and collective action. The third chapter empirically tested the relationship between individual behavioral orientations, social norms, and rule adherence in the community-based management of Arapaima gigas in the Brazilian Amazon. Based on face-to-face interviews with nearly 500 fishers in 46 rural villages, the study analyzed rule adherence with three key rules: minimum size limits, closed season, and prohibited lakes. Using randomized response techniques and Bayesian regression models, the results showed that cooperative orientations and stronger social norms are associated with greater compliance in some domains, while competitive orientations and high empirical expectations of rule-breaking predict noncompliance. Findings demonstrated that the effects of social norms are heterogeneous and rule-specific, underscoring the need for context-sensitive approaches to co-management. Together, these chapters advanced a more nuanced understanding of how social norms operate in natural resource co-management systems. The dissertation emphasized that identification and mobilization of social norms—coupled with formal institutions and behavioral traits—can enable more adaptive, inclusive, and effective co-management strategies to social and environmental governance.
The legacy of macroevolution: understanding and predicting evolutionary responses to novel environments
Howell, Bailey Keith (Virginia Tech, 2025-06-10)
Understanding how species will respond to global change is a major challenge for biologists. Two factors that play an important role are evolutionary constraints and contingencies. Evolutionary constraints are limitations on how species can adapt and change imposed by past evolutionary history, which could be driven by genetic, developmental, or functional variation. Evolutionary contingencies are chance events or evolutionary pathways that affect how species will respond to challenges and can lead to differences in species responses even when exposed to the same environmental pressures. Studying macroevolution of morphological traits and changes in microhabitat usage allows us to investigate the roles of these processes in generating variation in response to different habitats, and accounting for scale allows us to gain a more holistic picture of evolution. Understanding the role of evolutionary history is necessary to predict species responses to global change. In this work I focus on evolution within lizards as these species use a variety of different habitats and the relationship between morphology and microhabitat use has been studied extensively. We investigated the evolution of hindlimb allometry across lizards and identified that the majority of variation in lizards can be explained under a Brownian motion model of evolution, although we did identify contingent evolution in skinks. We then investigated the evolution of hindlimb length and adhesive toepad size in two "model clades" for studying urban tolerance and invasion biology. We identified evidence for evolutionary contingencies in the two clades with opposite patterns of trait evolution for each clade. We then used phylogenetic information, species traits, climate, and geographic data to predict species invasion probabilities across 486 lizard species. We found that incorporating phylogenetic information allowed us to ac- count for complex or difficult to measure traits and improved our models performance. We then developed a feature selection procedure to compare species traits with randomly simulated phylogenetic traits in order to identify if these traits contained additional predictive power beyond phylogenetic information. Taken together these results highlight the importance of evolutionary constraint and contingency in the predictability of evolution and the utility of phylogenetic information for predicting future responses to environmental change.
Cyber-Resilient Control of Synchronous Condensers
Sharifi, Fatemeh (Virginia Tech, 2025-06-10)
The growing integration of inverter-based resources (IBR) within electrical power systems leads to new challenges to grid stability in weak networks and creates heightened cybersecurity vulnerabilities due to the extensive reliance on information and communication technologies. This dissertation investigates and proposes methodologies to enhance the stability and resilience of contemporary power systems through sophisticated control and detection frameworks for synchronous condensers (SC). The research establishes robust exciter control algorithms that effectively address nonlinear dynamics and measurement uncertainties present in weak grid environments while simultaneously developing advanced techniques for the detection and localization of false data injection attacks (FDIA). A comprehensive cyber-resilient exciter control architecture is formulated, integrating these approaches to ensure system stability under both physical uncertainties and malicious cyber intrusions. The efficacy of the proposed methodologies is substantiated through theoretical analysis and PSCAD/EMTDC simulations, demonstrating reliable voltage regulation capabilities and robust cyberattack mitigation strategies. These contributions facilitate sustainable power system operation in environments characterized by high IBR penetration, thereby advancing the power system security and stability.
Understanding the role of phages in the mammalian gut microbiome
Franklin, Hollyn Claire (Virginia Tech, 2025-06-10)
A healthy gut microbiome supports a stable microbial community that regulates immune responses, defends against pathogens, maintains gut barrier integrity, and modulates metabolic processes. Disruptions of the balanced microbial community, followed by effects on host health, often called dysbiosis, have been associated with alterations in phage composition. However, whether these changes are correlational or causative has remained unresolved for many years. The complex tripartite interactions within the gut microbiome between phage, bacteria, and host health are difficult to study. To study these interactions within the gut microbiome, murine models have been beneficial through manipulation of the gut. Gnotobiotic mice have been used to look closely at the interactions between bacteria and phage and the effect on host metabolism. However, these models are limited, using only a defined set of host-phage pairs, as recapitulating the dynamic and diverse nature of the gut microbiome comes with difficulty. In this context, multiple studies were conducted to elucidate the role of phages within the gut microbiome and their impact on host health. The significance of phage in the gut microbiota remains poorly understood due, in part, to the absence of an animal model that allows for a comparative study of conditions with or without phages while retaining the microbial diversity attained by conventional colonization. In Chapter II, we describe the development of a murine model, the bacteriophage-conditional mouse model (BaCon), that manipulates endogenous gut phage, shedding light on how the viral community impacts the microbial community and host health. Initially, we describe a mouse model that uses a broadly available chemical compound, acriflavine, to preferentially deplete virulent phages from the gut. We then show that gut phage density can be reconstituted by oral gavage. Using the BaCon mouse model, we revealed that while phages have comparatively minimal impact during equilibrium conditions, they can increase the potency of ampicillin against commensal gut bacteria. Collectively, our work identifies virulent gut phages as potential sources of bacterial variability during significant perturbations. The murine model analysis was done using in vitro and in vivo experiments, laboratory culturing experiments, and metagenomic analysis, including 16S rRNA and whole virome sequencing. Through the manipulation of gut phage by acriflavine, we wondered if there could be more compounds that impact phage. In Chapter III, we screened two compound libraries from Targetmol (2,484 compounds) and APExBIO (2,726 compounds) against E. coli and T4 phage. We identified compounds from different drug classes, particularly at low concentrations (15 µM and 50 µM), that inhibited or enhanced phage activity. In future studies, we plan to test these identified compounds against additional host-phage pairs in vitro and evaluate these compounds in an in vivo mouse model, assessing potential disruption to the gut phage community and microbiota. This research suggests that phage impacts the microbial community and host health.
Adversarial Two-Party Quantum Interactions in Cryptography and Machine Learning
Bansal, Akshay (Virginia Tech, 2025-06-10)
Two-party adversarial interactions are of fundamental importance in the study of cryptography and machine learning, as they allow us to work in dynamic environments to model and adapt to various challenges, fostering reliability and robustness. In this thesis, we first consider such interactions in the domain of information-theoretic cryptography, where we propose new protocols and security bounds involving various two-party primitives such as coin flipping, bit commitment, and variants of oblivious transfer. We begin by developing the mathematical framework of stochastic selection, which is potentially useful for devising new protocols with improved security for a combination of various tasks. We then use this idea to develop the first protocols for Rabin oblivious transfer that offer partial information-theoretic security and also provide a non-trivial lower bound on its security. We also relax some of the more commonly used assumptions to consider the security of protocols in broader compositions and independently, allowing for devices that may be potentially malicious. In the former setting, we demonstrate that the weak coin flipping task -- which enjoys almost perfect standalone security -- may not be immune to attacks when used in larger compositions. In the latter, we establish the impossibility of determining the inner workings of a shared quantum mechanical device -- a phenomenon commonly known as self-testing -- in the presence of an adversary. Finally, we consider a slightly different task in a similar setting, where we discuss the classical online learnability of various quantum objects. We prove a sublinear regret bound for learning over general subsets of positive semidefinite matrices via the regularized follow-the-leader algorithm and apply it to various settings involving the learning of quantum objects. For concrete applications, we present a sublinear regret bound for learning quantum states, effects, channels, interactive measurements, strategies, co-strategies, and collections of inner products of pure states. In proving our regret bound, we establish various matrix analysis results useful in quantum information theory, including a generalization of Pinsker's inequality for arbitrary positive semidefinite operators with possibly different traces, which may be of independent interest in the study of more general classes of divergences.
Decoding the Transcriptional Specificity of Auxin Signaling: A Synthetic Biology Approach
Taylor, Joseph Sylvester (Virginia Tech, 2025-06-10)
Auxin is a central regulator of nearly all aspects of plant growth, development, and environmental response. Despite its broad roles, the mechanisms by which a single hormone elicits such diverse and context-specific transcriptional responses remain unclear. These responses are primarily mediated by the nuclear auxin signaling pathway, which consists of ARF transcriptional activators, Aux/IAA repressors, and TIR1/AFB auxin receptors that work together to modulate gene expression. Functional diversity within these modular components, such as differences in DNA binding, protein-protein interactions, subcellular localization, and co-expression patterns is believed to act in concert to tune auxin signaling specificity. In support of our efforts to decode auxin signaling specificity, we developed an open-source, R-based analysis pipeline to process flow cytometry data generated by protoplast transient expression assays. This reproducible workflow automates transformation-based reporter analysis, streamlining quantification of gene expression and effector function in high-throughput experiments. To understand the functional diversity in ARF-mediated transcriptional responses, we performed RNA sequencing of Arabidopsis protoplasts transiently expressing irrepressible ARF variants to determine if they have distinct downstream regulatory targets. Transcriptomic analysis revealed that while each ARF appears to regulate largely overlapping sets of genes, they do so with varying efficiencies. Gene clusters preferentially regulated by specific ARFs were associated with distinct biological processes, aligning with the known developmental roles of those specific ARFs. While our transcriptomic analysis suggested that ARFs can drive distinct transcriptional outputs independently of Aux/IAAs, the extent to which specific ARF-Aux/IAA interactions contribute to this specificity remained unclear. To determine whether specific ARF-Aux/IAA interactions also contribute to transcriptional specificity, we developed a synthetic system that isolates these interactions using a recombinant protein-interaction domain from an animal ortholog. The system was validated through structural prediction, yeast two-hybrid assays, and protoplast transient expression assays. This system serves as the closest approximation to date of native ARF-Aux/IAA interactions, providing a powerful tool to dissect signaling specificity at the level of individual protein pairings. Together, the development of a streamlined data analysis pipeline, transcriptional profiling, and a synthetic interaction system provides both computational and experimental tools that advance our understanding of auxin signaling specificity. Ultimately, these insights will help explain how a single hormone can direct a vast array of developmental and environmental responses in plants.
Yall Aint Heard Us? Black Identity and Belonging in Appalachian Virginia
Robinson, Jacob Elijah (Virginia Tech, 2025-06-10)
Appalachia is often portrayed through dominant narratives as a raceless region, yet it has long been home to black communities whose histories, experiences, and existences remain overlooked. This research explores black identity, belonging, and lived experience in Appalachian Virginia, a space frequently excluded from racial examination. Utilizing interviews, demographic data, and autoethnography, this study centers black voices to explore the construction of identity and resistance to systemic inequality. To understand how black life in Appalachian Virginia is shaped by regional, social, and economic shifts, I investigate three guiding questions: 1) What social inequalities do black residents face in Appalachian Virginia? 2) How do black individuals and communities navigate, negate, and narrate racism and exclusion? and 3) How do black residents conceptualize and construct their racial identities? This study documents the reality that black life in Appalachian Virginia is characterized by systematic exclusion, yet the folks in the region have navigated and negated race and racism through avoidance and social ties. Ultimately, this study expands knowledge of how race and space interact in Appalachian Virginia, challenges the perception of a raceless Appalachia, and contributes to the understanding of identity creation in white spaces.

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