Virginia Tech - Wake Forest University School of Biomedical Engineering & Sciences
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Virginia Tech - U.S. Forest Service Housing Commentary
No full textProvides information on housing growth and construction, and wood use in the construction industry
Household Water Quality - Culpeper County
No full textHousehold water quality in Culpeper County, Virginia
2020 Peanut Variety and Quality Evaluation Results. I. Agronomic and Grade Data
No full textDue to suitability to the environmental conditions and existence of a strong peanut industry tailored to process primarily the large-seeded Virginia-type peanut, growers in Virginia, North Carolina, and South Carolina generally grow Virginia-type cultivars. In the view of a common interest in the Virginia-type peanut, the three states are working together through a multi-state project, the Peanut Variety Quality Evaluation (PVQE), to evaluate advanced breeding lines and commercial cultivars throughout their production regions. The objectives of this project are: 1) to determine yield, grade, quality, and disease response of commercial cultivars and advanced breeding lines at various locations in Virginia and the Carolinas, 2) develop a database for Virginia-type peanut to allow research-based selection of the best genotypes by growers, industry, and the breeding programs, and 3) to identify the most-suited peanut genotypes for various regions that can be developed into varieties. This report contains agronomic and grade data of the PVQE tests in 2020
Progress in Organic Coatings
Full text linkThis study proposes a sustainable alternative to conventional plastic coatings in packaging by developing a biodegradable coating system based on polylactic acid (PLA) and polyhydroxyalkanoate (PHA). A novel spray coating technique followed by hot pressing was used to apply PLA/PHA blends onto kraft pulp paper. This approach aimed to enhance mechanical strength, barrier properties, and water resistance while maintaining compostability. The coating behavior was strongly influenced by the PLA to PHA ratio. PLA formed a dense surface layer that effectively sealed pores, while PHA penetrated more deeply into the fibrous matrix, filling internal voids. These complementary roles contributed differently to the mechanical and barrier properties. In particular, the 50:50 PLA/PHA blend showed the most balanced results, achieving the lowest oxygen transmission rate and improved tensile strength. The thermogravimetric analysis further confirmed enhanced thermal stability in all coated samples compared to uncoated paper, with the degradation temperature profile shifting depending on the polymer composition. However, coatings with excessive PHA content showed surface irregularities and reduced barrier performance due to poor film formation. Overall, this work demonstrates that compositional tuning of PLA and PHA enables multifunctional coatings with improved mechanical, thermal, and barrier properties. The proposed spray-based method offers a scalable, eco-friendly solution for high-performance biodegradable packaging.Accepted versio
Molecules
No full textMicroorganisms wage constant chemical battles against one another as they compete for space and scarce nutrients, particularly within animal-associated habitats. Here, binary assays were used to investigate chemical interactions among Flavobacteriaceae within Neverita delessertiana egg collars, a moon snail common to the Gulf Coast. Analysis of 140 distinct pairings revealed eight that exhibited growth-inhibitory activity. Chemical evaluation of the crude extract from Cellulophaga omnivescoria EM610, which inhibited the growth of three other Flavobacteriaceae, resulted in the isolation of bacillimidazoles A (1) and E (2), two previously characterized metabolites, isolated from a marine Bacillus species. Further work demonstrated that these compounds are readily formed spontaneously by condensation of 2,3-butanedione with phenethylamine and/or tryptamine. Tandem mass spectrometry analysis of the chemical extracts of individual moon snail egg collars revealed the presence of bacillimidazole A in 62% of the egg collars.Published versio
Regulation of Intestinal Development and Function in Early-Life Pigs
No full textThe small intestine's plasticity allows for rapid structural and functional adaptions in response to external stimuli. The early postnatal phase is a critical developmental window, during which diet transitions and stress can have lasting effects on overall health and productivity. Attenuated growth performance and feed efficiency may exacerbate production losses and have significant economic implications on the swine industry. Historically, the industry used in-feed antibiotics as growth promoters, but their ban has left the need for nutritional or pharmacological strategies that mitigate intestinal inflammation. Additionally, knowledge gaps remain regarding how Wnt/ β-catenin and Notch signaling pathways influence intestinal remodeling during the early life of pigs. Collectively, these gaps highlight the need for targeted nutritional or molecular interventions during critical developmental phases during the early life of pigs. Topics examined herein focus on development changes of the gastrointestinal tract. The first study evaluated the effects of different concentrations of cannabidiol (CBD) supplementation on intestinal inflammation and function at weaning. Pre-weaned pigs received one of four treatments: low (10 mg/kg CBD, n=8), medium (25 mg/kg, n=8), high (50 mg/kg, n=8) and control (0 mg/kg, n=8) once a day for 5 days starting one day before weaning. The medium dose showed greater lactase (P = 0.003) and maltase (P = 0.042) activities in the jejunum, and increased lactase activity in the ileum (P = 0.020). Jejunal IL-β concentrations were greater in control pigs (P = 0.014) compared with other treatments, while mRNA abundance of intestinal integrity markers varied among treatment groups, with CLDN4 reduced in low pigs (P= 0.045), ZO-1 reduced across all treatments compared with controls (P=0.012), and CCL2 reduced in high pigs (P=0.018). CASP6 was elevated in low pigs (P = 0.012), and TNFα was reduced in medium pigs (P = 0.031). Morphology and goblet cell measurements had no differences. Overall, CBD supplementation had limited effects on intestinal inflammation and function in newly weaned pigs, but the medium dose showed the greatest changes in the jejunum. The second study focused on early life intestinal epithelial development by analyzing the duodenum, jejunum, and ileum of 70 pigs sampled at 0, 7, 20, 22, 25, and 28 days of age (n=10 pigs/day). Frozen tissues were assessed for brush border activity and found shifts in enzymatic activity coinciding with luminal content changes. Formalin- fixed tissues were used for histological analysis, cell phenotyping, and RNA in situ hybridization. Morphological analysis showed an in increased villus height and crypt depth in early life and decreased postweaning. Expression of Sox9 (duodenum, jejunum, ileum P <0.001) and Ki67 (duodenum P = 0.008; ileum P = 0.039) were increased at birth and postweaning reflecting intestinal growth and remodeling. Sucrase Isomaltase (duodenum P = 0.025; jejunum and ileum P <0.001) increased from birth to weaning, coinciding with changes in disaccharidase activity. Somatostatin (duodenum, jejunum, ileum P <0.001) was greatest at birth and at weaning, reflecting adaptions to changes in luminal contents. Goblet cells (duodenum, jejunum, ileum P <0.001) increased until weaning suggesting heightened mucus production in response to compromised barrier integrity. These results were supported by Ussing Chamber assays of fresh jejunal tissue. Reduced transepithelial resistance (jejunum P <0.001) combined with enhanced glucose (jejunum P <0.001) and glutamine (jejunum P <0.001) active transport at birth and postweaning described increased permeability and increased energy demands. Molecular signaling pathways, Wnt/β-catenin and Notch, were evaluated to better understand how stem cell proliferation and cell fate determination are regulated from birth to weaning. Wnt3 (duodenum P = 0.001) and β-catenin (duodenum, jejunum, ileum P <0.001) expression was increased at birth and postweaning, promoting stem cell proliferation to support intestinal remodeling. Notch-1 (duodenum and jejunum P <0.001; ileum P = 0.009) and Hes-1 (duodenum P = 0.007; jejunum P = 0.004; ileum P <0.001) expression increased at birth and postweaning, driving enterocyte differentiation. Together these findings highlight the rapid and coordinated intestinal remodeling pigs undergo during early life and the molecular pathways that drive intestinal development during early life of pigs, and potential targets to develop nutritional interventions that enhance nutrient utilization.Doctor of PhilosophyThe small intestine can change structure and function in response to diet and stress. From birth to weaning, there are many significant life events that could have lasting effects on a pig's health and growth. Poor growth caused by inefficient feed digestion and absorption can lead to economic losses in pig production. Historically, the industry used antibiotics to remedy these losses. However, with the loss of antibiotics as a key production tool, other nutritional strategies to support intestinal health are needed. Despite this, there is limited understanding of how intestinal development occurs from birth to weaning through molecular pathways such as Wnt/β-catenin and Notch signaling pathways. There is a lack of knowledge regarding how these pathways control intestinal development from birth to weaning. The first study examined if supplementing pigs with cannabidiol (CBD) could reduce postweaning intestinal inflammation and improve digestion and absorption of nutrients. One day prior to weaning, pigs were orally supplemented with different doses of CBD for a total of five days. The medium dose resulted in slight improvements in digestive enzyme activity and reduced inflammation in the small intestine. Measures of intestinal structure and goblet cells did not change based on treatment. The second study examined how the small intestine develops from birth to weaning. Intestinal samples from 70 pigs were collected from birth to one week postweaning. Structural measurements increased after birth, but decreased after weaning. Intestinal markers for stem cells (Sox9) and cell proliferation (Ki67) increased at birth and after weaning, reflecting increased intestinal growth and remodeling. Digestive function was measured and expression of mature absorptive enterocytes (sucrase-isomaltase) increased as did brush border enzyme activity during diet transitions. Hormone secreting cells (somatostatin) increased at birth and postweaning reflecting times when the gastrointestinal tract shifts in luminal contents slows motility to enhance digestive and absorption. Goblet cell numbers increased until weaning with a subsequent decrease, thereafter, indicating reduced mucosal protection. Ussing chamber assays had increased permeability and increased glucose and glutamine active transport at birth and postweaning, reflecting a shift in energy demands. Analysis of molecular mechanisms revealed Wnt/β-catenin and Notch-1/Hes-1 expression increased at birth and postweaning, supporting stem cell proliferation and differentiation towards absorptive enterocytes. Together these studies demonstrate how rapid changes in morphological structure, digestive enzyme activity, cell proliferation and differentiation are coordinated to achieve optimal digestion and absorption of nutrients from birth to weaning. A better understanding of these developmental changes will help target nutritional strategies to improve nutrient digestion, absorption and overall grow performance in pigs
Measuring Performance in Complex Adaptive Systems: An Agent-Based Approach to Managerial and Technological Change
No full textDoctor of PhilosophyIn today's fast-paced and unpredictable world, organizations must constantly adapt to stay efficient, innovative, and competitive. This dissertation explores how organizational performance can be better understood and measured by viewing the organization as a Complex Adaptive System (CAS), a dynamic network of socio-technical systems including people, teams, and technologies that continuously evolve and respond to change.
To measure how well these systems perform over time, this research uses advanced models from the efficiency measurement paradigm, such as the Malmquist Index (MI) and Hicks-Moorsteen Index (HMI). These models can track improvements in how resources are used (efficiency) and progress in innovation or technology (productivity shifts), considering both managerial and technological perspectives. This dissertation separates managerial and technological change efficiency analysis over multiple time periods for CASs, constituting a major contribution of this dissertation. Furthermore, the study creates a flexible and powerful system by linking a simulation platform with data analysis tools in testing ideas, performing sensitivity analyses, and validating results using real-world data.
At the heart of this study is a computer simulation model called Complex Adaptive Productive Efficiency Model (CAPEM). This dissertation dives into model version 2.0 (CAPEM 2.0), which builds on previous versions of CAPEM. CAPEM 2.0 integrates new insights from complexity science and behavioral theory in simulating how diverse parts of an organization interact, learn, and make decisions, especially in decentralized environments. A guiding metaphor in this research is "flocking," which has inspired me through the way birds move as a group. Just as birds adjust their paths based on the movements of leaders and nearest neighbors, like peers around them, people and teams in organizations often appear to adapt their actions based on local information, collaboration, and feedback.
A case study involving deregulated power plants (DPPs) demonstrates how CAPEM 2.0 can assist in uncovering which factors have the optimal impact on system-wide outcomes. For example, it reveals how certain roles, behaviors, or conditions can excessively affect an organization's success by providing crucial guidance for decision-makers who operate in dynamic environments.
Overall, this research offers a new way to think about performance in complex systems. It emphasizes the importance of adaptive strategies, decentralized decision-making, and innovation-driven efficiency. CAPEM 2.0 gives analysts and policymakers an approach for designing systems that advance and innovate as they continue to evolve and improve over time
Toward Thorough and Practical Integration Testing of Replicated Data Systems
No full textHighly available applications rely on replicated data, but complex event interleavings between application logic and replicated data libraries (RDLs) often cause subtle integration bugs. Detecting such bugs is challenging due to the inherent nondeterminism of distributed execution, as certain bugs can only manifest under specific interleavings. Correctness testing, therefore, requires replaying all possible interleavings—a challenging task due to the combinatorial explosion of the interleaving space. My doctoral dissertation addresses this challenge with ER-, a middleware framework that exercises all possible interleavings between the application code and RDL; it also eliminates redundant and impossible interleavings via novel pruning techniques. Initial results show that ER- successfully reproduces 12 real-world bugs across multiple opensource RDLs while significantly reducing the interleaving search space. Our ongoing work extends this foundation with interleaving prioritization, ranking interleavings execution by their likelihood of exposing faults—particularly those introduced by recent code changes, thus accelerating bug discovery. This research supports developers responsible for ensuring the correctness and reliability of replicated data systems.Published versio
Control of chiral optical and spin properties in low-dimensional perovskites
No full textIn materials design, the dimensional reduction from three-dimensional (3D) to two-dimensional (2D) metal halide perovskites represents a paradigm shift that expands the chemical space, introducing new variables such as metal species, enantiomers, and ionic compositions for property engineering. While 3D perovskites are constrained by geometric tolerance factors to small monovalent cations and a limited set of simple organic molecules, 2D perovskites can accommodate large organic spacer cations between inorganic layers, enabling diverse organic cations incorporation. This expanded molecular design allows the introduction of chirality through chiral organic cations, an approach unattainable in conventional 3D systems. Consequently, chiral 2D hybrid perovskites combine the favorable optoelectronic properties of the inorganic substructure with chirality-induced symmetry breaking, giving rise to spin-selective and circularly polarized optical phenomena.
The introduction of chiral organic cations breaks inversion and mirror symmetries and induces unique structural behavior in the absence of external magnetic fields, e.g., circularly polarized second harmonic generation and Rashba spin splitting. Notably, spin-selective charge transport in such materials differs from chirality-induced spin selectivity (CISS), originating instead from momentum-dependent spin splitting in the inorganic substructure rather than from helical organic pathways. Such features present practical avenues for high-performance quarter-wave plates, spin light-emitting diodes, spin-photovoltaic devices, and quantum information architectures.
This dissertation presents a comprehensive investigation into controlling chiral optical and spin properties in low-dimensional perovskites, encompassing rational structure design, advanced synthesis methods, and fundamental mechanism elucidation. The introductory chapter traces the evolution from conventional 3D to low-dimensional architectures and highlights the transition from achiral to chiral organic cationss. Subsequent chapters provide detailed analyses of the structural and functional advantages of 2D perovskites, outlining design principles and specialized synthesis techniques such as water–oil interface growth. Crystallographic analyses reveal that chiral systems exhibit broken inversion symmetry and intrinsic lattice distortions, which underpin their strong chiroptical responses. Chiral optical properties are explored, with emphasis on the coupling of circularly polarized photoluminescence and second harmonic generation (SHG). Chiral perovskites exhibit SHG intensities an order of magnitude higher than those of conventional KDP crystals and unprecedented circularly polarized SHG ratios. Density functional theory calculations elucidate mechanistic insights through the analysis of Bir–Aronov–Pikus and D'yakonov–Perel' spin relaxation pathways.
In Chapter 3, we demonstrated that incorporating mixed chiral cations (R-MBA and R-THFA) in low-dimensional lead iodide perovskites effectively enhances spin polarization and prolongs spin lifetime. Systematic variation of the MBA:THFA ratio identified (R-MBA)1.5(R-THFA)0.5PbI4 (3:1) as optimal, achieving a spin polarization of ~0.14 and a spin lifetime three times longer than (R-MBA)2PbI4 and five times longer than (R-THFA)2PbI4 at room temperature. Spin-resolved transient absorption spectroscopy revealed that spin lifetime directly determines spin polarization, with both following identical concentration-dependent trends. Temperature-dependent studies confirmed that both Elliott–Yafet and D'yakonov–Perel' mechanisms contribute to spin relaxation. The superior performance of the 3:1 system arises from defect passivation by THFA's N and O atoms, which suppresses EY relaxation, and a lower excitonic binding energy that weakens DP relaxation. These results establish mixed chiral-cation engineering as an effective approach for controlling spin dynamics in 2D perovskites and offer new routes toward high-performance spintronic devices.
In Chapter 4, we uncover a previously unrecognized pathway for spin angular momentum transfer, mediated by chiral phonons through chiral–achiral perovskite heterostructures. The spin-resolved transient absorption spectroscopy and simulated Raman scattering used directly captured periodic oscillations of phonon wave packets whose helicity reverses with the handedness of the optical excitation. These chiral phonons — arising from the octahedral framework of R-MBA2PbI4 — carry angular momentum across the interface to the achiral CsPbI3 layer and promote spin transfer without magnetic fields. The reciprocal variations of spin lifetimes between the 2D and 3D layers verify phonon-mediated spin transfer (linking lattice vibrations with spin dynamics). Research on angle- and thickness-dependent transfer efficiency shows that it is a function of crystal orientation and interface morphology, indicating that lattice matching plays an important role. R- and S-based systems show the inversion of the vibrational helicity, confirming the enantioselective nature of this process, and the absence of oscillations in racemic structures confirms the lack of chiral phonons in achiral systems. Collectively, these observations demonstrate that chiral phonons are not only agents of angular momentum in low-dimensional materials but also a novel design paradigm for spintronic and spin-photonic applications.
The final chapter highlights the potential of these findings in practical applications. Chiral perovskites enable cost-effective achromatic quarter-wave plates through intrinsic broadband circular birefringence, replacing complex multilayer designs with single-layer architectures. Spin light-emitting diodes utilizing circularly polarized electroluminescence achieve direct electrical injection and emission of highly polarized light without magnetic fields, with implications for 3D displays, quantum communication, and spin-based information processing. This work establishes chiral low-dimensional perovskites as a versatile platform bridging fundamental spin–photon interactions and next-generation chiroptical and spintronic technologies.Doctor of PhilosophyPerovskites are a remarkable class of semiconductors with the general formula ABX3, where A is a positively charged ion (either an organic molecule such as methylammonium or an inorganic atom such as cesium), B is a metal ion (e.g., lead, copper, or tin), and X is a halide ion (chlorine, bromine, or iodine). These materials have revolutionized modern optoelectronics, enabling breakthroughs in solar cells, lasers, and light-emitting diodes. While traditional perovskites adopt a three-dimensional cubic structure, recent advances have enabled the creation of lower-dimensional variants, 2D sheets, 1D chains, and 0D clusters, expanding their structural and functional versatility.
This dimensional engineering also enables the incorporation of chirality into perovskite frameworks. Chirality, a fundamental property describing non-superimposable mirror-image structures, breaks crystal symmetry when introduced through chiral organic molecules. Such chiral low-dimensional perovskites exhibit unique properties, including the generation and manipulation of circularly polarized light and precise control over electron spin—key features for next-generation quantum and spintronic devices.
This dissertation systematically explores the control of chiral optical and spin phenomena in low-dimensional perovskites. It traces the evolution from traditional 3D to chiral low-dimensional systems, covering material design, synthesis strategies, and structural analysis. The optical and spin studies reveal strong circularly polarized second harmonic generation, circular birefringence, and a newly discovered spin transfer mechanism mediated by chiral phonons, lattice vibrations that carry spin angular momentum. These findings enable simplified, broadband optical components such as single-layer quarter-wave plates and spin-polarized light emitters operating without magnetic fields. Together, these results establish chiral low-dimensional perovskites as a versatile platform bridging fundamental quantum physics with spintronic and optoelectronic technologies
Understanding Tradeoffs of Replicated Data Library Integration Strategies in Multilingual Environments
No full textModern distributed systems replicate data across multiple execution sites by means of special-purpose replicated data libraries (RDLs), which provide read-write data access and synchronization. Programming languages often need to be mixed across replica sites to meet business requirements and resource constraints. Because RDLs are typically written in a single language, integrating them in multilingual environments requires special-purpose code, whose characteristics are poorly understood. We aim to bridge this knowledge gap by reviewing two key strategies for integrating RDLs in multilingual environments: (1) foreign-function interface (FFI) and (2) common data format (CDF). Our preliminary results indicate performance and implementation tradeoffs: CDF offers latency and memory consumption advantages, while incurring an additional implementation burden. With modern distributed systems utilizing multiple languages, our findings can inform the design of RDLs for multilingual replicated data systems.Published versio