Light Detection and Ranging (LiDAR) is increasingly common in forestry applications, yet relatively little research has evaluated its use in quantifying carbon stocks in afforested bottomland hardwood forests. This study relates forest structural field measurements to metrics derived from low pulse density LiDAR data to assess the use of LiDAR in characterization of planted bottomland hardwood oak stands. Univariate and multivariate linear regressions were performed with field and LiDAR variables to determine relationships. The height-related field dependent variables average height, maximum height, and individual tree volume had the highest adjusted R-squared values of 0.5-0.6 (P<0.0001) for the univariate models and adjusted R-squared values of 0.70-0.79 for the multivariate models. These findings suggest that low-density LiDAR is capable of assessing forest structure and suggests that further research evaluating LiDAR quantification of bottomland hardwood carbon stocks is warranted.

No description available.

A new fully integrated wavelength stabilization scheme based on grating-coupled surface-emitting lasers is explored. This wavelength stabilization scheme relies on two gratings. The first grating is fabricated on the p-side of the semiconductor laser in close proximity to the laser waveguide such that it couples light out of the guided mode of the waveguide into a propagating mode in the substrate; this grating is known as the grating coupler. The second grating is fabricated on the n-side of the substrate such that for the stabilization wavelength, this second grating operates in the Littrow condition and is known as the feedback grating. Furthermore with the proper design of the two gratings, the feedback grating will operate under total internal reflection conditions allowing a near unity retro-reflection of the light of the stabilization wavelength. The grating coupler and feedback grating together comprise a dual grating reflector (DGR). The DGR wavelength stabilization scheme is investigated both theoretically by means of numerical modeling and experimentally by integration of a DGR as a wavelength selective reflector into a single quantum well semiconductor laser with a gain peak centered at 975nm. Numerical modeling predicts a peak reflection of approximately 70% including losses and a spectral width of 0.3nm. The integration of a DGR into a semiconductor laser proved both the efficacy of the scheme and also allowed us to experimentally determine the effective reflectivity to be on the order of 62%; the spectral width of light output from these devices is typically on the order of 0.2nm. Furthermore, these devices had light-current characteristic slopes greater than 0.84W/A operating under continuous wave conditions. The DGR was then modified to provide a reflection with two spectral peaks. A semiconductor device incorporating this dual wavelength DGR was fabricated and tested. These devices showed a peak optical power of in excess of 5.5W and a light-current characteristic slope of 0.86W/A in quasi continuous wave operation; these devices also exhibit a large operating current range in which both wavelengths have comparable output powers. Another modified DGR design was investigated for the purpose of providing an even narrower spectral reflection. Devices incorporating this modified design provided an output with a spectral width as narrow as 0.06nm. DGRs were also integrated into an extremely broad area device of an unorthodox geometry; square devices that lase in two orthogonal directions were fabricated and tested. The last idea investigated was combining a DGR wavelength stabilized laser with a tapered semiconductor optical amplifier into a master oscillator power amplifier device, with the optical coupling between the two components provided by identical grating couplers disposed on the p-side surfaces of each of the devices. These master oscillator power amplifiers provide a peak power of 32W when operating under quasi continuous wave operation.

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No description available.

No description available.

Edamame, also known as edible soybean, is a crop with growing demand in the United States. Currently much of the edamame consumed in the United States is imported, but it has potential to be grown domestically, in Virginia and other mid-Atlantic states. With the introduction of a new crop, however, comes new challenges, such as novel pests. The broad-headed bugs (Hemiptera: Alydidae), a relatively insignificant pest of conventional soybean, have been observed in high numbers on edamame in Virginia. Their piercing-sucking feeding may produce dark marks on edamame beans that could result in economic losses. However, little research has been conducted on the pest status or management of these bugs in edamame. This study aims to determine their pest potential to edamame by investigating their distribution throughout the state, damage to the crop, and avenues for chemical control. An important element in determining the pest potential of an insect is its distribution throughout an area. The distribution of broad-headed bugs in Virginia was last thoroughly investigated in 1975, and the research has scarcely been updated since. With advances in technology, however, it is now possible to crowd-source data from citizen scientists to supplement museum and field collection data. The first portion of this study explores the species of broad-headed bugs present in Virginia, and their distribution throughout the state. This was achieved using museum specimens, field-collected specimens, and photographs from the social network iNaturalist. By manually checking iNaturalist identifications of broad-headed bugs using a key, I was able to determine that iNaturalist is 96% accurate at identifying North American broad-headed bugs to species. Through the combination of museum, field, and iNaturalist data, I also found evidence of two species of broad-headed bug at elevations never before seen in Virginia, the first broad-headed bug ever found on the Eastern Shore of Virginia, as well as the first documented sighting of Hyalymenus tarsatus Fabricus in Virginia. The level of injury that broad-headed bugs cause to edamame is presently unknown. The second portion of this study compares the density-damage relationship of broad-headed bugs on edamame to that of the brown marmorated stink bug (Halyomorpha halys Stahl), a known pest of edamame. Through a cage study conducted in Whitethorne, Virginia, I found that broad-headed bugs cause significant damage to edamame at densities of 10 insects per plant, but still less damage than that of brown marmorated stink bugs. Currently, no economic injury thresholds exist for broad-headed bugs, or brown marmorated stink bugs on edamame. Determining the density-damage relationship of these insects on edamame may contribute to the creation of these thresholds in the future. The third portion of this study is the first attempt at evaluating chemical control of the broad-headed bugs on edamame. I performed a bioassay evaluation of four commercial selective insecticides including the following: flupyradifurone and sulfoxaflor, both with a mode of action similar to neonicotinoids, but with reduced non-target effects; the diamide cyclaniliprole, and a novel venom-like peptide insecticide, GS-omega/kappa-Hxtx-Hv1a. Each of the insecticides caused significant mortality of Alydus eurinus (Say) adults. This thesis serves as a starting point in evaluating the potential threat of broad-headed bugs to Virginia's edamame production. / Master of Science in Life Sciences / Alydids are a group of true bugs, often referred to as broad-headed bugs. Not many species are known to occur in Virginia. However, after research began in Virginia in 2018 to develop edible soybean (edamame) for production in the state, we observed high densities of broad-headed bugs feeding on edamame pods on research farms and commercial fields. Broad-headed bug feeding may produce dark marks that leave edamame beans unmarketable. Very little is known about the pest status or management of broad-headed bugs as a crop pest, or about their distribution and biology in general. This study aims to address these questions. An important element in determining the pest potential of an insect is its distribution throughout an area. The distribution of broad-headed bugs in Virginia was last thoroughly investigated in 1975, and the research has scarcely been updated since. With advances in technology, however, it is now possible to crowd-source data from citizen scientists to supplement museum and field collection data. The first portion of this study explores the species of broad-headed bugs present in Virginia, and their distribution throughout the state. This was achieved using museum specimens, field-collected specimens, and photographs from the web and mobile application iNaturalist. By manually checking iNaturalist identifications of broad-headed bugs using an identification key, I was able to determine that iNaturalist is 96% accurate at identifying North American broad-headed bugs to species. Through the combination of museum, field, and iNaturalist data, I also found evidence of two species of broad-headed bug at elevations not previously reported, the first broad-headed bug ever found on the Eastern Shore of Virginia, as well as the first documented sighting of Hyalymenus tarsatus (Fabricus) in Virginia. The second portion of this study compares the damage of broad-headed bugs on edamame to that of the brown marmorated stink bug, a known pest of edamame. By caging broad-headed bugs on edamame plants in Whitethorne, Virginia, I found that they cause significant damage to edamame at 10 insects per plant, but still less damage than that of brown marmorated stink bugs. Determining the density-damage relationship of these insects on edamame may determine their potential as a pest, as well as inform growers when to apply insecticides. The third portion of this study is the first attempt at determining avenues of chemical control of the broad-headed bug Alydus eurinus (Say), one of the two most likely species to be a pest of edamame. I performed a laboratory evaluation of four commercial selective insecticides including the following: flupyradifurone and sulfoxaflor, both with a mode of action similar to neonicotinoids, but with reduced non-target effects; the diamide cyclaniliprole, and a novel venom-like peptide insecticide, GS-omega/kappa-Hxtx-Hv1a. These insecticides have limited detrimental effects on beneficial organisms. Each of the insecticides was effective against A. eurinus. This study serves as a starting point in evaluating the potential threat of broad-headed bugs to Virginia's edamame production.

The purpose of this thesis is to make a broadband antireflection coating configuration known as a quarter-wave stack consisting of one layer of titania and of one layer of silica nanoparticles. We utilize much that is already known about silica nanoparticle deposition. The first objective of this thesis is deposition and characterization of titania nanoparticle films deposited on glass microscope slides by a technique known as Ionic Self-Assembled Multilayers or ISAM deposition. This technique takes advantage of the electrostatic attraction between oppositely charged materials and ideally results in a uniform nanoparticle film whose thickness and optical properties can be tightly controlled. Deposition of a quarter-wave stack based on ISAM deposition of silica and titania nanoparticles is significantly simpler and less expensive than alternative deposition methods. Initial attempts to deposit titania films were unsuccessful because of excess diffuse scattering due to inhomogeneities in the film. In order to reduce diffuse scattering, two approaches were considered. The first approach was to improve the deposition process itself by experimenting with different values of deposition parameters such as solution pH and solution molarity. The other approach focused on removing the large nanoparticle aggregates from the colloidal solutions of titania nanoparticles that were suspected to be responsible for rough film surfaces resulting in diffuse scattering. This approach was successful. In addition, evidence suggested that surface roughness contributed more to diffuse scattering than the bulk of the films. After minimizing diffuse scattering from titania nanoparticle films, we used known results from research on silica nanoparticle films to deposit quarter-wave stacks consisting of one layer of titania nanoparticles with high refractive index and one layer of silica nanoparticles with low refractive index. This contrast in refractive indices is a desirable characteristic of quarter-wave stacks. The thicknesses and refractive indices of the two layers in the quarter-wave stacks were measured by ellipsometry and compared to the nominal thicknesses of these layers. Finally, the reflectance was derived from a model of the quarter-wave stack and was compared to the measured reflectance. It was found that construction of a quarter-wave stack by ISAM is possible but that it will be necessary to acquire data from more experiments. / Ph. D.

The threat from infectious diseases dates as far back as prehistoric times. Pathogens continue to pose serious challenges to human health. The emergence and spread of diseases such as HIV/AIDS, Severe Acute Respiratory Syndrome (SARS), avian influenza, and the threats of bioterrorism have made infectious diseases major public health concerns. Despite many successes in the discovery of anti-infective medications, the treatment of infectious diseases faces serious challenges, which include (i) the emergence and reemergence of infectious pathogens, (ii) the ability of pathogens to adapt and develop resistance to drugs, and (ii) a shortage in the development and discovery of new anti-infective drugs. Host-Oriented Broad-Spectrum (HOBS) treatments have the promising potential to alleviate these problems. The HOBS treatment paradigm focuses on finding drug targets in human host that are simultaneously effective against a wide variety of infectious agents and toxins. In this dissertation, we present a computational approach to predict HOBS treatments by integrative analysis of three types of data, namely, (a) gene expression data representing host responses upon infection by a pathogen, (b) annotations of genes to pre-defined biological pathways and processes, and (iii) genes that are targets of known drugs. Our methods combine gene set-level enrichment with biclustering. We applied our approach to a compendium of gene expression data sets derived from host cells exposed to bacterial or to fungal pathogens, to functional annotation data from multiple databases, and to drug targets from DrugBank. We present putative host drug targets and drugs with extensive support in the literature for their potential to treat multiple bacterial and fungal infections. These results showcase the potential of our computational approach to predict HOBS drug targets that may be effective against two or more pathogens. Our study takes a clean-slate approach that promises to yield unsuspected or unknown associations between pathogens and biological processes, and thus discern candidate gene/proteins to be further probed as HOBS targets. Furthermore, by focusing on host responses to pathogens as captured by transcriptional data, our proposed approach stimulates host-oriented drug target identification, which has potential to alleviate the problem of drug resistance. / Ph. D.

The presence of delay-inducing defects is causing increasing concern in the semiconductor industry today. To test for such delay-inducing defects, scan-based transition fault testing techniques are being implemented. There exist organized techniques to generate test patterns for the transition fault model and the two popular methods being used are Broad-side delay test (Launch-from-capture) and Skewed load delay test (Launch-from-shift). Each method has its own drawbacks and many practical issues are associated with pattern generation and application. Our work focuses on the implementation and comparison of these transition fault testing techniques on multiple industrial ASIC designs. In this thesis, we present results from multiple designs and compare the two techniques with respect to test coverage, pattern volume and pattern generation time. For both methods, we discuss the effects of multiple clock domains, tester hardware considerations, false and multi-cycle paths and the implications of using a low cost tester. We then consider the implications of pattern volume on testing both stuck-at and transition faults and the effects of using transition fault patterns to test stuck-at faults. Finally, we present results from our analysis on switching activity of nets in the design, while executing transition fault patterns. / Master of Science