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.

Recent Submissions

Protecting Apple Blossoms from Spring Frost: The Potential and Limitations of Cryoprotectants

Jahed, Khalil R.; Sherif, Sherif M. (Virginia Cooperative Extension, 2026-10-21)

Spring frost presents a major abiotic constraint on apple production, with shifting climates increasing the risk of early bloom exposure to sub-zero temperatures. To evaluate alternative mitigation strategies, we tested the efficacy of four commercial foliar cryoprotectants (KDL, ThermoMax, Glacier, and diKap) on 'Pink Lady' apple blossoms across three growing seasons. Biochemical analyses revealed that these applications enhance frost resilience by triggering the accumulation of protective metabolites, specifically proline and non-structural carbohydrates, which minimize cellular dehydration and membrane rupture. Field evaluations demonstrated that cumulative sub-zero exposure time is the primary driver of floral mortality, with a critical lethal threshold of approximately 30 minutes. Although freezes exceeding two hours overwhelmed all treatments, specific applications such as ThermoMax and diKap successfully preserved 5?6% of king flowers under severe stress, a margin physiologically sufficient to maintain a commercial crop load. Furthermore, these pre-bloom treatments proved safe for commercial implementation, presenting no negative effects on fruit quality and occasionally improving harvest size, sweetness, and firmness.

Protecting Peaches from Spring Frost: Delaying Bloom with JA Inhibition

Jahed, Khalil R.; Sherif, Sherif M. (Virginia Cooperative Extension, 2026-08-26)

Spring frost threatens temperate fruit production by damaging early-blooming floral tissues. Modulating bloom phenology offers a viable mitigation strategy. Because jasmonic acid (JA) promotes budbreak, we hypothesized that JA inhibitors could delay peach flowering. Over three seasons (2023-2025), two JA inhibitors, propyl gallate and antipyrine, were applied as foliar sprays to "Redhaven" and "Sunhigh" peach cultivars. Antipyrine consistently delayed full bloom by 2 to 5 days across years and cultivars. Propyl gallate induced delays of 1 to 3 days, exhibiting higher inter-annual variability dependent on early spring temperatures. Crucially, neither compound negatively impacted final fruit set at harvest. Furthermore, treatments maintained essential fruit quality attributes, including firmness and total soluble solids, while, in some cases, enhancing fruit size. These findings demonstrate that bloom delay offers a novel, resource-efficient strategy to protect deciduous orchards from late spring frost damage without compromising yield or quality.

Naphthaleneacetic Acid: A Key Tool for Reducing Preharvest Fruit Drop and Sustaining Apple Red Coloration

Tipu, Mohammad; Jahed, Khalil R.; Sherif, Sherif M. (Virginia Cooperative Extension, 2025-09-17)

Preharvest fruit drop (PFD) causes significant yield losses in ‘Honeycrisp’ apples. This study evaluated naphthaleneacetic acid (NAA), aminoethoxyvinylglycine (AVG), and their combined application for PFD management, assessing fruit retention and quality for two growing seasons. All treatments generally reduced PFD compared to controls, with AVG, commercially known as “ReTain” (Valent BioSciences LLC), often showing the greatest reduction. However, ReTain consistently impaired red fruit color development. In contrast, NAA, commercially available as “Refine” (Fine Americas, Inc.), effectively controlled PFD without negatively impacting color or firmness, and it improved fruit sweetness. These findings highlight that while both can reduce drop, Refine provides a better balance for ‘Honeycrisp’ growers by mitigating PFD while preserving or enhancing key quality attributes like color and sweetness compared to ReTain.

Multi-Scale Characterization of Mining-Induced Deformation Using Radar

Tascione, Matthew Alex (Virginia Tech, 2026-10-22)

The theme of this dissertation is the quantitative characterization of mining-induced deformation using radar methods. Underground excavation can produce fractures that reduce roof stability and surface deformation that may affect mine-related or public infrastructure. However, these responses are difficult to characterize because fractures are concealed within the rock mass and surface deformation may extend across large areas. The principal contribution of this dissertation is the development of quantitative radar-based approaches that extend beyond detecting deformation to measuring its geometry, magnitude, spatial distribution, and evolution across multiple scales. Ground-penetrating radar (GPR) data were acquired on the roof of an underground salt mine to detect fractures concealed within the rock mass. Radar observations were calibrated and validated using fractures logged in drillholes, enabling quantitative estimates of fracture location and aperture. GPR detected fractures with apertures as small as approximately 1 mm and mapped substantial variations in aperture along individual fractures. The results demonstrate that GPR can noninvasively quantify mining-induced fractures beyond the discrete locations sampled by drilling. A dense grid of GPR profiles was subsequently used to reconstruct 15 laterally continuous fractures as three-dimensional surfaces with measured aperture. The fractures are shallowly dipping, approximately planar extensional features, with fracture intensity greatest near the mine roof and decreasing upward into the rock mass. Fracture size and aperture exhibit substantial variability and do not scale according to a simple linear elastic fracture mechanics model. Although the number of fractures limits population-scale statistical inference, the measurements provide rare field-based three-dimensional constraints on fracture geometries and network statistics commonly inferred from lower-dimensional observations or numerical models. Interferometric synthetic aperture radar (InSAR) was used to characterize surface deformation across the southwest Wyoming trona mining district. Ascending and descending Sentinel-1 observations spanning approximately 19 months were combined to estimate vertical displacement. Six subsidence features and one apparent-uplift feature were identified, with peak cumulative subsidence ranging from 62 to 198 mm. The features differed substantially in spatial extent, geometry, cumulative displacement volume, temporal evolution, tilt, and curvature. Longwall-associated features were generally compact, whereas room-and-pillar-associated features were more elongated. However, variability among features associated with the same mining method shows that mining method alone did not determine the surface response. These results show that displacement magnitude alone does not adequately characterize mining-related surface deformation. Together, these studies demonstrate the ability of radar methods to quantitatively characterize mining-induced deformation from millimeter-scale fracture opening to kilometer-scale surface displacement. These complementary approaches provide field-based constraints on the geomechanical response to underground excavation and measurements relevant to mine safety and surface infrastructure.

Satellite Geodesy for Monitoring of Land Subsidence and Assessing Coastal and Transportation Infrastructure Resilience

Dasho, Oluwaseyi Adeola (Virginia Tech, 2026-10-22)

Land subsidence, the downward component of vertical land motion (VLM), increases the vulnerability of coastal communities by deforming critical infrastructure and lowering land relative to rising coastal water levels. However, subsidence is commonly represented by sparse point observations or broad-scale estimates that do not resolve deformation at the spatial scales of individual infrastructure assets, reclaimed districts, and densely populated coastal neighborhoods. This dissertation investigates the magnitude, spatial variability, physical controls, and hazard implications of VLM across coastal infrastructure, reclaimed land, and rapidly urbanizing coastal cities. It applies GNSS-referenced, multitemporal Interferometric Synthetic Aperture Radar (InSAR) approaches to characterize VLM; evaluates persistent subsidence using geological, geotechnical, and historical information; and assesses consequences for differential settlement, relative sea-level rise (RSLR), and coastal flood exposure. Chapter 2 of this dissertation presents the first systematic InSAR assessment of differential subsidence along runways at 15 major U.S. airports, showing that San Francisco International Airport (SFO) subsides fastest (9.2 ± 0.2 mm/yr) and Los Angeles International Airport slowest (2.0 ± 0.2 mm/yr), with 3.9% of runway area at medium-to-very-high damage risk. Chapter 3 focuses on SFO as a representative case study, integrating dense InSAR time series (2017-2024) with subsurface stratigraphy and construction records to show that subsidence exceeding -10.0 mm/yr is concentrated where thick, compressible Young Bay Mud underlies hydraulically placed fill, and that construction history and paleoenvironmental setting jointly explain a meaningful share of the spatial variance in settlement. Chapter 4 broadens the lens to a global assessment of VLM across reclaimed coastal land in 20 major cities on five continents, revealing localized subsidence exceeding 30 mm/yr, with 20% of reclaimed land facing moderate to severe high differential-settlement hazard, and subsidence-driven relative sea-level rise (RSLR) that frequently exceeds background eustatic sea-level rise. Chapter 5 extends this framework to Africa's data-scarce coastlines, providing the first high-resolution, continent-wide estimate of VLM for 20 major African coastal cities and showing that incorporating localized subsidence into IPCC AR6 sea-level projections substantially increases projected flood exposure, affecting more than 7 million people, over one million buildings, and roughly USD 180 billion in assets by 2050. Together, these studies demonstrate that InSAR-derived, spatially explicit VLM is essential for accurately characterizing infrastructure vulnerability and coastal flood risk, and that globally averaged or GIA-only estimates of land motion systematically understate the hazard faced by reclaimed lands, coastal airports, and rapidly urbanizing coastal megacities.

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