VTechWorks
VTechWorks provides global access to Virginia Tech scholarship, including journal articles, books, theses, dissertations, conference papers, slide presentations, technical reports, working papers, administrative documents, videos, images, and more by faculty, students, and staff. Faculty can deposit items to VTechWorks from Elements, including journal articles covered by the University open access policy. Email vtechworks@vt.edu for help.
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More than 50 freely available and openly licensed textbooks are among our most downloaded items.
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Recent Submissions
Transit time modeling framework for predicting freshwater salinization in urban catchments
Bhide, Shantanu V.; Grant, Stanley B.; McGuire, Kevin J.; Prestegaard, Karen; Kaushal, Sujay S.; Sekellick, Andrew J.; Rippy, Megan A.; Schenk, Todd; Curtis, Shannon; Gomez-Velez, Jesus D.; Hotchkiss, Erin R.; Vikesland, Peter J.; Saksena, Siddharth (Elsevier, 2026-03)
The salinity of inland freshwaters is rising globally, particularly in urban watersheds where winter road deicers are widely applied. Attributing stream salinity dynamics to specific sources and transport pathways remains challenging due to episodic salt inputs, engineered drainage, and strong coupling between hydrology and subsurface storage. We present a modeling framework that couples climate-driven deicer build-up and wash-off with transient transit time distribution theory to simulate salt transport through drainage, interflow, and groundwater pathways. Applied to an urban watershed in Northern Virginia (USA), the model reproduces ten years of high-frequency stream salinity measurements across daily-to-decadal timescales. The calibrated model implies an average deicer application of 206 tonnes Cl yr−1, or roughly one 20 kg bag of rock salt person−1 yr−1 when normalized by the 20,000 people living in the watershed. In winter months, higher infiltration routes a large fraction of snowmelt and deicers into shallow subsurface pathways, enhancing vadose-zone and interflow contributions to stream salinity. Limited subsurface storage capacity and seasonal hydrologic turnover flush excess chloride from the vadose zone and groundwater during subsequent summer storms. By linking climate-driven deicer inputs, hydrologic connectivity, and stream water age, the framework provides a transferable basis for diagnosing and managing freshwater salinization in urban watersheds.
Identifying the psychological, behavioral, and neural effects of dance on young adults with ADHD
Tasnim, Noor E. (Virginia Tech, 2026-02-03)
Attention-deficit/hyperactivity disorder (ADHD) is emerging as a growing public health challenge in the United States. More than 15 million adults in the United States are diagnosed with ADHD in adulthood. Moreover, stimulant refill rates are increasing while patients struggle to get their ADHD medications. Although more adults are seeking help for ADHD, primary care settings continue to fall short of meeting quality-of-care standards for accurate diagnosis and effective treatment. To address this issue, this dissertation set out to accomplish the following aims: 1) Examine the psychological, behavioral, and neural predictors of ADHD symptomatology in young adults and 2) Study the acute effects of dance and exercise on the psychological, behavioral, and neural outcomes of ADHD in this population. For Aim 1) 67 young adults (Ages: 18-24, Sex: Male [N=18], Female [N=49]) completed a series of mental health questionnaires, executive function tasks, and balance assessments while wearing a 64- electrode electroencephalography cap. Depressive symptoms, sex, alpha (8-12 Hz) power in the Right Paracentral Lobule, and P3b Mean Amplitude were the greatest predictors of self-reported symptoms on the Adult ADHD Self-Report Scale v1.1. For Aim 2) 63 of these participants (Sex: Male [N = 17], Female [N = 46]) were assigned, through stratified randomization, to one of three 30-minute interventions associated with a dance exergame: 1) sitting and watching the game, 2) riding a bike to the game, 3) dancing along with/playing the game. Participants underwent the same series of assessments about 1 week after their first visit but underwent their assigned intervention before all assessments took place. Biking and dancing suppressed alpha power in brain regions associated with attentional networks and improved cognitive flexibility. Dance, but not biking, specifically suppressed alpha activity in regions associated with top-down attentional control. The identification of significant neural predictors and nonpharmacological treatment outcomes associated with attention can guide future standards in the diagnosis and treatment of adults with ADHD.
Understanding the Mechanistic Pathways of Layered Oxide Cathode Synthesis for Sodium-Ion Batteries
Promi, Anika Tabassum (Virginia Tech, 2025-12-16)
Sodium-ion batteries (SIBs) offer cost-effective and earth-abundant complementary technology to lithium-based systems, positioning them as promising candidates for large-scale energy storage to meet the world's exponentially growing energy demands. This dissertation investigates the interconnected roles of precursor chemistry, interfacial solid-liquid interactions, and calcination pathways involved in the synthesis of Ni-Fe-Mn –based layered oxide cathodes for sodium-ion batteries. It begins by examining equimolar Ni-Fe-Mn hydroxide precursors synthesized byammonia- and citrate-based co-precipitation routes, comparing their morphological control, stoichiometric accuracy, and structural homogeneity under varying reaction conditions. Motivated by the challenges observed in synthesis, the second study shifts focus to a fundamental investigation of metal–ligand interactions at the solid–liquid interface. Using in-situ synchrotron X-ray fluorescence microscopy and statistical modeling, we quantify how pH and metal identity influence interfacial dissolution-redeposition dynamics of multiple transition metals in alkaline media and reveal metal-specific spatial–temporal trends within multicomponent systems.Subsequent chapters shift focus to the high-temperature solid-state transformation of these precursors into NaNi1/3Fe1/3Mn1/3O2 cathodes. First, we analyze the mechanistic reaction pathway of sodium carbonate-based calcination, identifying key stages of precursor dehydration, major intermediate formation, and grain growth behavior. We then systematically investigate how variations in precursor design route and sodium source influence calcination behavior, demonstrating that structural and morphological differences govern distinct phase evolution pathways, ranging from topotactic transformations to complex multistep transformation. Finally, we extend this methodology to Mn-rich systems for P2-type sodium layered oxides, demonstrating that citrate-based strategies can yield favorable particle morphologies across a range of manganese-rich compositions, despite challenges associated with Mn precipitation. Across these studies, we establish a framework for linking precursor synthesis to downstream calcination outcomes, offering new insights into optimizing reaction parameters for more efficient synthesis of sodium-ion layered oxide cathodes.
Family and Friend Support, Strain, and Loneliness Among Dementia Caregivers in Rural Appalachia
Stanfill-Carrillo, Brenda Liana (Virginia Tech, 2026-02-04)
Background: Loneliness, defined as a perceived deficit in the quantity or quality of social relationships, is associated with a range of adverse physical and mental health outcomes. Understanding contributors to loneliness among caregivers of people living with dementia (PLwD) is therefore an important public health concern. Family caregivers, particularly spouses or adult children, report higher levels of loneliness compared to non-caregivers and some other caregiver groups. This vulnerability may stem from time constraints on social activities, misunderstandings within existing relationships regarding care management, and losses in shared experiences as dementia progresses. Across the life course, family and friends serve as important sources of social support and relational connection, both of which may be associated with lower loneliness.
Research Questions and hypotheses: Guided by Perlman and Peplau’s definition of loneliness and the Stress Process Model, this thesis examined whether perceived support and strain from caregivers’ family and friends are associated with loneliness among spousal and adult child caregivers of PLwD living in rural Appalachia, above and beyond caregiving demands. Caregiver relationships with the PLwD (wife, husband, daughter, son) were examined categorically to account for differences in relational roles and expectations. It was hypothesized that (1) caregiver relationship type would be associated with loneliness, with wives reporting the highest levels, and (2) greater family strain would be associated with higher loneliness, whereas greater family and friend support would be associated with lower loneliness.
Methodology: Data were drawn from the Families in Appalachia Caring for Elders with Alzheimer’s Disease (FACES) study (N = 141). A three-step hierarchical multiple linear regression analysis was conducted to examine associations between caregiver relationship type, perceived family and friend support, perceived family and friend strain, and loneliness, controlling for unsupervised time and assistance with personal activities of daily living.
Results: Wives reported higher levels of loneliness than husbands, daughters, and sons. After accounting for caregiving demands and relationship type, higher perceived family strain was associated with higher loneliness, whereas greater perceived friend support was associated with lower loneliness. Family support and friend strain were not significantly associated with loneliness in the final model.
Implications: Findings suggest that perceived relationship quality, rather than the mere presence or number of social ties, is central to understanding loneliness among caregivers of PLwD in rural Appalachia. While friend support was associated with lower loneliness, addressing familial strain in caregiver interventions and psychosocial programming may be particularly relevant for efforts aimed at reducing caregiver loneliness.
A Qualitative Exploration of School-Based Intervention Needs Among Rural Appalachian Youth
Winograd, Dayna Gael (Virginia Tech, 2025-12-05)
Disordered eating is prevalent in the United States, with over 20% of children and adolescents reporting some form of disordered eating. Eating disorders are associated with detrimental physical effects and co-occurring mental health difficulties. One population that appears to be at high risk for developing disordered eating symptoms is rural youth. Unfortunately, rural youth often do not receive treatment for their disordered eating symptoms due to myriad care barriers, including geographical restrictions and financial constraints. School-based interventions offer promise to address such barriers and increase access to treatment among this vulnerable group. This study represents a first step at identifying rural youth needs and formatting preferences for a school-based intervention. Participants were 11 rural adolescents (Mage = 15.09) from Appalachia. Participants reported their demographic characteristics in surveys and completed a semi-structured interview assessing their needs and formatting preferences for a school-based intervention for disordered eating. Data were analyzed using inductive thematic analysis; the following themes emerged. Rural youth reported that an intervention should promote healthy and balanced eating, teach social media literacy, and discuss external factors and overlapping mental health difficulties, and de-emphasize the value of weight and shape. Rural youth also suggested that the intervention design take into consideration logistical and cultural factors of rural communities. These data suggest that rural youth’s treatment preferences align with existing school-based interventions for disordered eating. However, modifications may be needed to address logistical and cultural factors that may impact acceptability and feasibility of school-based eating disorder interventions in rural communities