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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Virginia Tech's open access policy enables researchers to deposit the accepted version of scholarly articles with no embargo.
Theses and Dissertations
Virginia Tech was first in the world to require ETDs in 1997, and continues to add scans of older theses and dissertations.
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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
Age-Dependent Determinants of Blood-Derived Monocytes Influence Neuroinflammatory Milieu at the TBI Injury Site
Willison, Andrew Wayne (Virginia Tech, 2025-11-25)
Traumatic brain injury is a leading cause of neurologic injury. Excess and prolonged neuroinflammation post-injury negatively influences recovery outcomes. Blood-derived monocytes are capable of performing efferocytosis, the immunologically silent engulfment of cellular debris, which is critical for removing hazardous cellular corpses and concurrently resolving inflammation. Age-at-injury profoundly effects TBI recovery outcomes also. The phenotypic and functional plasticity of blood-derived monocytes (BDMs), as well as prior studies relating age and BDM activity, place BDMs at the crossroads these two advantageous elements, making them a promising potential therapeutic option for TBI. In this thesis, we assess how juvenile and adult BDMs differ in their response to TBI, hypothesizing that juvenile BDMs will take greater action to discourage neuroinflammation and promote tissue recovery. We performed passive injections of juvenile BDMs into CCI injured adult mice. We immunohistochemically stained the tissue for cell type and polarization state markers, then visualized the injured cortex and hippocampus with fluorescence microcopy probes and 3D reconstruction of confocal images. We quantified the lesion volume, IgG deposition and the infiltration, polarization, engulfment activity, distribution, and morphology of BDMs and resident mononuclear phagocytes during the acute phase of injury. We also looked at the population and polarization of resident mononuclear phagocytes during the chronic phase of TBI. We found an overall reduction in tissue damage in juvenile injected mice, and the injected BDMs acted in a manner that suggests the resolution of harmful inflammation after TBI.
The effects of complex I deficiency on neurogenesis and white matter development in a mouse model of Leigh Syndrome (LS)
Biswas, Sahitya Ranjan (Virginia Tech, 2025-11-25)
Leigh syndrome (LS) is one of the most prevalent inherited mitochondrial disorders in pediatric population, typically presenting in early childhood with psychomotor regression and progressive neurological decline. Current understanding suggests that pathogenic variants affecting mitochondrial respiratory-chain complexes impair oxidative phosphorylation (OXPHOS), leading to bioenergetic failure in vulnerable brain regions resulting in the characteristic bilateral, symmetric deep gray matter lesions observed on MRI. While this neuron-centric perspective helps explain regional vulnerability in LS, it overlooks the substantial mitochondrial demand of neural stem/progenitor cells (NSCs), which generate the majority of the brain cells during the embryonic and early postnatal periods. However, the in vivo consequences of sustained mitochondrial dysfunction during early neurogenesis remain poorly characterized. We leveraged the NDUFS4 knockout (KO) mouse, a well-established model of Complex I (CI) deficiency that recapitulates key clinical and neuropathological features of LS, to test whether sustained CI loss during early development disrupts NSC proliferation and lineage progression and secondarily impairs white matter maturation. Gross neuroanatomical analysis revealed reduced brain weight and decreased hemispheric width. Immunohistochemistry showed an early reduction at postnatal day 14 (P14) in NSC and neuroblast populations within the SVZ, with the neurogenic defect progressing at later timepoints to impaired lineage advancement. To resolve cell type–specific effects of CI deficiency, single-cell RNA sequencing (scRNA-seq) was conducted on the SVZ, which revealed a proliferation deficit in NSCs and intermediate progenitors. This finding was independently validated using neurosphere assays. Transcriptional programs and pathways linked to neurogenesis and oligodendrogenesis were significantly downregulated in KO neural progenitors. Although abundance of oligodendrocyte progenitors in the SVZ was not significantly altered, early and late myelin gene/protein expression was reduced, accompanied by decreased corpus callosum thickness. Together, these early neurodevelopmental defects in neurogenesis and callosal growth offer a potential mechanistic explanation for the developmental delays observed in LS. This work encourages future research into neurogenesis in other primary mitochondrial disorders and neurodegenerative disorders, especially those where developmental delays are a key feature.
Process-morphology-property Relationships in Strut-like Poly(ether ether ketone) Aerogels Prepared through Thermally Induced Phase Separation
Spiering, Glenn Allen (Virginia Tech, 2025-11-25)
Poly(ether ether ketone) (PEEK) aerogels resulting from gelation in 1,3-diphenyl acetone (DPA) were prepared for the first time. The phase separation mechanism was determined to be solid-liquid phase separation which resulted in the formation of aerogels consisting of crystalline axialites. These axialites formed a strut-like network that had superior compressive properties compared to the globular aerogels previous prepared from the gelation of PEEK in 4-chlorophenol and dichloroacetic acid. It was also found that strut-like PEEK or poly(phenylene sulfide) (PPS) aerogels prepared from gelation in DPA were mechanically robust such that they could resist the forces imposed on the gel during drying. Monolithic strut-like PEEK or PPS aerogels were prepared with vacuum-drying, freeze-drying, and supercritical CO2 extraction with minimal shrinkage and deformation. The weaker globular PEEK aerogel morphologies suffered from considerable shrinkage due to capillary forces or ice crystal growth induced on vacuum-drying or freeze-drying, respectively. Determining the gelation mechanism of PEEK in DPA allowed for effective manipulation of the processing parameters. It was found that changing the gelation temperature improved the mechanical properties of PEEK aerogels. Dissolution temperature can also be lowered to improve the nucleation density of PEEK aerogels.
A Theory of Type Authenticity as Reverential Engagement
Naar, Alexis M. (Virginia Tech, 2025-11-25)
This dissertation develops a theory of type authenticity, offering a novel account of the "hot" evaluative dimensions of organizing, those that are morally resonant and culturally inhabited. It extends accounts of recognition-based social evaluations, such as cognitive legitimacy and typicality. It demonstrates how such judgments can also emerge from reverence, a distinct mechanism grounded in what I describe as actors' and audiences' ontological beliefs. Reverence is the sensed movement of actors and audiences toward what they regard as normatively good and right. From this perspective, type authenticity is defined as a judgment of character that assesses the reverence of a co-performance between actors and audiences in animating the symbolic, cultural, and ethical substance of an institutional practice in a way that resonates with actors' and audiences' ontological beliefs of an institutional practice. This model distinguishes between institutional objects, recognized for their utility, and institutional subjects, revered for their significance. In doing so, it introduces a novel understanding of institutions and categories as possessing ontological in addition to epistemological coherence. The theory is examined through a qualitative, narrative analysis of 20 long-form oral histories of Southern barbecue pitmasters from the Southern Foodways Alliance (SFA) archive. The findings demonstrate that coherence within the category of barbecue is not sustained by shared features or definitions, which often diverge, but by ontological beliefs that animate the practice. Three core beliefs were identified: (1) barbecue is continuous, existing without a distinct beginning or end; (2) barbecue is theatrically performed, which affirms its ontological seriousness; and (3) barbecue is community, where shared doing constitutes its substance. This dissertation makes three contributions to institutional theory. First, it advances a middle-range theory of type authenticity that highlights the normative and ontological dimensions of organizing, complementing existing accounts of recognition and legitimacy. Second, it offers an additional model of category coherence based on reverence. Third, it demonstrates how mission, purpose, and identity operate as symbolic commitments and constitutive elements of organizational management.
Remote sensing for geomorphic and hydrodynamic modeling and process understanding
Prior, Elizabeth Mary (Virginia Tech, 2025-11-25)
River discharge and geomorphic processes controlling floodplain-river interactions are fundamental measures of fluvial geomorphology and important inputs and considerations for hydrodynamic modeling. Due to our anthropogenic dependency and interconnection with rivers, humans have developed technologies and methods to measure and estimate river discharge and fluvial geomorphic change through field techniques, hydrodynamic modeling, and remote sensing. Due to the novelty of remote sensing data, there are still unknowns that need investigation to better understand how these data can be properly applied to our current models and empirical understanding. This dissertation contains three studies that examine how remote sensing, in conjunction with other data sources, can be used to accurately represent terrain at various resolutions in a hydrodynamic model (Chapter 2), characterize and understand dunefields along the Colorado River in the Grand Canyon in relation to geomorphic variables (Chapter 3), and lastly estimate river discharge from radar satellite measurements at river gage locations (Chapter 4).
Chapter 2 of this dissertation determines how hydrodynamic model results (water depths, water velocities, and inundation extent) are affected by drone lidar DEM resolution and computational mesh resolution over 1.5 km of Stroubles Creek in Blacksburg, Virginia, USA. This was done by running several simulations of a hydrodynamic model with various resolutions of computational mesh (1 m and 2 m) and DEM (0.1 m, 0.25 m, 0.5 m, 1 m, and 2 m). We found that for water depths, the largest differences between simulations occurred laterally throughout the floodplain, whereas for water velocities differences were concentrated along the channel-floodplain boundary. The water depth and velocity differences were not correlated with lidar ground point density. We also found that the inundation extent was dependent on DEM resolution. Lastly, changing DEM resolution was found to be equivalent to altering floodplain roughness by up to 12% for water depths and 44% for water velocities. These findings show that the modeler's choice of terrain resolution and computational mesh resolution do matter and should be considered in the context of features that are expected to affect flow in the floodplain.
Chapter 3 consists of a study that focuses on characterizing and developing geomorphic understanding of aeolian dunefields along the Colorado River in the Grand Canyon, USA. These 58 dunefields were formed by pre-dam floods and are now disconnected from the river and represent the sediment matrix in the Grand Canyon that are currently used for modern recreation, biota habitat, and protect hundreds of archaeological sites of historical and indigenous importance. They are now maintained only by wind-blown sand from modern sandbars along the Colorado River. Motivated by their importance and threatened sediment supply from hydropower dam operations, this study determines how dunefield area is influenced by aeolian-fluvial interactions, climate, river hydrology and geomorphology, and canyon physiography variables derived from remote sensing data, hydrodynamic modeling results, and field observations. We found that dunefield area is significantly influenced by pre-dam river width and the distance from dunefield center to river center, thus demonstrating that having enough accommodation space to grow, while still being near their primary sediment source allows dunefields to be maintained. Additionally, from the 196 dunes that were measured from remotely sensed digital terrain data, migration rates varied from 0.01 m/year to 3.0 m/year and dune heights varied from 2.0 m to 8.2 m, with climbing/parabolic dunes being the most common morphological type (n = 88). We end our study by proposing an analog study between Grand Canyon dunefields and dunefields found in the Valles Marineris canyon system on Mars to better understand and constrain planetary sediment budgets and primary wind patterns to dictate sediment transport in these unique geomorphic settings.
Lastly, Chapter 4 of this dissertation consists of assessing and characterizing performance of empirical equations used to estimate river discharge from data collected by the Surface Water and Ocean Topography (SWOT) satellite with comparison back to river discharge measured at gage locations. The SWOT satellite was launched in December 2022 and is the first satellite ever to explicitly include river measurements and discharge estimation in its science goals. This study was motivated by previous findings that demonstrated how empirical equation agreement with SWOT data correlates with the success of Mass-Conserved Flow Law Inversion algorithms, which are used to estimate roughness and cross-sectional area, both parameters that cannot be detected by SWOT but are necessary to estimate river discharge. Due to variable SWOT measurement quality, we heavily filtered and cleaned the data, allowing for 68 river gages to be used in our study. We then evaluated five empirical discharge equations, two variations of the Manning-Gaukler-Strickler equation and three rating curve equations, and compared these modeled discharge data back to field data collected at river gages. We found that the stage rating curve performed the best in comparison to field data since SWOT was successful in consistently measuring water surface elevations and its variability in many rivers. We also determined that SWOT river width potentially contains high amounts of uncertainty, thus any empirical equation that contained SWOT width had poor performance. Our study shows that there are advantages to allowing consideration of multiple empirical discharge equations due to variation in SWOT measurement quality.