Virginia Tech - Wake Forest University School of Biomedical Engineering & Sciences
VTech Works (Virginia Tech)Not a member yet
122049 research outputs found
Sort by
Structure–Property Relationships in Hybrid Crystalline Materials for Multifunctional Light–Matter Interactions
No full textDoctor of PhilosophyLight and matter can interact in powerful ways when the light is intense enough. This phenomenon, known as optical nonlinearity, is at the heart of modern technologies that generate new colors of light, process information at ultrafast speeds, and enable quantum communication. However, finding materials that exhibit strong and stable nonlinear responses under everyday conditions remains a major challenge. Many existing materials only work at very low temperatures or degrade quickly when exposed to light, air, or heat.
This dissertation explores new strategies for designing hybrid materials that combine the flexibility of organic molecules with the robustness of inorganic frameworks to achieve strong, room-temperature nonlinear optical behavior. We show how solvent molecules, hydrogen bonding, and supramolecular templates, such as crown ethers, can be used to fine-tune crystal structures and enhance light–matter interactions in a controlled, reversible way. One key discovery is that common solar-cell perovskites can be transformed into nonlinear optical materials through molecular templating, giving rise to bright light emission, improved stability, and even recyclability. These materials can be converted back to their original perovskite form without producing any waste, offering a sustainable approach to material design.
We further extend this concept to multiferroic systems, where electric, magnetic, and optical properties coexist and interact. By integrating chiral (handed) molecules with magnetic components, we develop materials that can detect and respond differently to left- and right-circularly polarized light, an important step toward next-generation optical sensors and imaging devices.
Overall, this dissertation establishes new molecular design principles for stable, tunable, and multifunctional hybrid materials, bridging the fields of nonlinear optics, photonics, and quantum technologies. These advances open up pathways toward more efficient optical communication systems, reconfigurable photonic circuits, and light-controlled magnetic devices operating under ambient conditions
Study on measuring Neutrino interactions with the ICARUS detector and addressing its cosmic ray background.
No full textThe Short Baseline Neutrino (SBN) program at Fermilab is the world's most sensitive research environment where to search for sterile neutrinos at the electronvolt mass scale. The program makes use of three liquid argon time projection chambers sequentially positioned along the Booster Neutrino Beam, in this setup ICARUS serves as the far detector. The primary goal of the program is to prove or disprove anomalous results from previous experiments that imply the existence of sterile neutrinos. ICARUS was moved from its original deep underground location at LNGS in Italy to Fermilab. At Fermilab ICARUS is installed on the surface introducing a new challenge to its physics program in the form of cosmic ray contamination. To meet this challenge a Cosmic Ray Tagger (CRT) system was designed and implemented with a 4 coverage. This thesis presents a comprehensive examination of the CRT system design, implementation, and performance, demonstrating its critical role in enabling precision neutrino physics measurements in surface environments. The thesis also presents the application of the combined ICARUS detector and CRT system capabilities for neutrino-argon cross-section measurements using the off-axis NuMI neutrino beam, focusing on the muon neutrino charged-current inclusive channel. The integration of advanced cosmic ray rejection techniques with high-resolution liquid argon imaging technology establishes important precedents for future surface-based neutrino detectors and contributes essential measurements for understanding neutrino-nucleus interactions relevant to long-baseline oscillation experiments.Doctor of PhilosophyNeutrinos are among the most abundant particles in the universe, however they rarely interact with matter and as such are very difficult to detect. With time, experiments grew more sophisticated and not only were they able to detect neutrinos but they were able to discover that neutrinos come in three different ``flavors'' and they can change from one flavor to another as they travel through space and time. This phenomenon is referred to as neutrino oscillation. It critically requires that neutrinos have mass while neutrinos are massless according to the Standard Model of Particle Physics.
Neutrino experiments in the last 20 years stumbled upon puzzling results that could not be explained by the simple assumption that there are only three kind of neutrinos, suggesting there might be a fourth type of neutrino that is called sterile. The Short Baseline Neutrino program at Fermilab was designed to solve this mystery using a set of high resolution detectors known as Liquid Argon Time Projection Chambers (LArTPC's). The program uses three large detectors filled with liquid argon positioned at different distances along a neutrino beam. ICARUS-T600 is the largest of these detectors, containing 476 tons of liquid argon, and serves as the farthest detector from the neutrino source. ICARUS was originally built to operate deep underground in Italy, where the surrounding rock naturally blocked cosmic rays from space. When the detector was moved to Fermilab and placed near the surface, these cosmic rays became a large background for the experiment. To address this problem an advanced Cosmic Ray Tagger system that surrounds the detector and can identify when cosmic rays pass through was built, allowing researchers to distinguish between cosmic ray events and genuine neutrino interactions. This thesis describes the design and construction of this cosmic ray detection system and demonstrates how it enables precise measurements of neutrino interactions with argon nuclei. These measurements are important not only for searching for sterile neutrinos but also for understanding how neutrinos interact with matter, which is essential for future neutrino experiments. The successful operation of this surface-based detector establishes important techniques that will benefit the next generation of neutrino research facilities
Scalable and Reconfigurable True-Time Delay Line for Integrated Radio-Frequency Recurrent Neural Processors
No full textThis paper presents a scalable and tunable delay-line architecture for analog recurrent neural networks (RNNs) operating directly in the RF-domain. Previous research has shown the RF-domain RNNs are capable of performing real-time anomaly detection in wireless systems while reducing the inference latency of the wireless system to be one RF clock cycle. The original RF-domain RNN structure relies on a passive tapped transmission line delay for sequential input samples, limiting the architecture's scalability, power efficiency, and frequency adaptability. Transmission lines have too much attenuation, become impractically large for chip integration, and are untunable. To eliminate these limitations, the passive transmission line delay is replaced with an active delay line made up of cascaded gm-C all-pass filter (APF) cells. The APF cells achieve true-time delay while maintaining low attenuation, low power consumption, high linearity, and have reconfigurable delay characteristics. The proposed solution utilizes compact integration, signal preservation along the delay line, and dynamic tuning for different carrier frequencies or true-time delay needs. A full model of the active delay line and it's integration with the RF-RNN architecture is developed in GlobalFoundaries 65-nm BiCMOS technology. The model includes delay characterization, analysis of loading effects, and noise analysis. The simulation results show that the gm-C APF delay network enables scalable RF-RNN implementations while maintaining anomaly classification performance accuracy under realistic timing variations. This work demonstrates a key step towards practical RF-domain neural processors capable of supporting real-time wireless systems for 5G and beyond.Master of ScienceThis paper presents an analog circuit implementation of a compact and tunable delay line for recurrent neural networks (RNNs) designed entirely in the radio-frequency (RF) domain. Previous research proves that a fully RF implementation of an RNN (referred to as RF-RNN) is able to identify and classify irregularities in incoming RF signals while greatly reducing the processing time. The previous RF-RNN implementation used a transmission line to delay the input RF signal for real-time sampling of the signal. The transmission line however, imposed many constraints on RF-RNN system including the inability to scale larger due the area inefficiency of the transmission line, the reduction of the input signal's amplitude, and inability to adapt to different input frequencies. To solve these constraints, the transmission line is replaced with the proposed active gm-C all-pass filter (APF) delay circuit. The APF circuit has a compact design, little effect on the input signal's amplitude, and can be adjusted for a range of input frequencies or desired delays. A full model of the active APF delay circuit is developed and it's delay, implementation to the RF-RNN, and non-ideal side effects, such as the introduction of unwanted delay variation, is tested and analyzed. The results show improvements in the RF-RNNs scalability and adaptability while maintaining accuracy for identifying and classifying irregularities. This work demonstrates a key step towards implementing RF-domain RNNs into the wireless communication systems of today and the future
Effective Instructional Practices and Models to Prepare ELLs for State Mandated Testing
No full textThe United States has a growing population of English language learners (ELLs) who travel from other countries for various reasons and become fluent in the English language. In the educational field today in the U.S. achievement is measured by standardized-test scores through state mandated testing (Ferlazzo, 2025). Educators also have various types of instructional models to help English language students learn more effectively. According to Kaplan (2019), research indicates that ELLs learn best by being immersed with general education students, not being taught in isolation and having additional support from an instructional model. There are many suggestions to best prepare ELLs for state mandated testing and to identify what is most appropriate is essential to an ELLs academic success. The purpose of this qualitative study is to identify the perceptions of English language teachers perspectives on effective instructional practices and models to prepare English language learners for state mandated testing. This study was administered in two Virginia school divisions using semi-structured interviews. This study generated several findings and implications. In the discoveries, practicing vocabulary, building background knowledge, and building visuals were identified as ways to assist ELLs in learning the English language, in addition to building relationships. Being knowledgeable on working with ELLs is how educators will be able to help them reach English language proficiency. Administrators and educators need to be able to work together to find a way to address the challenges ELLs face when participating in state mandated testing. Doctor of EducationIn the U.S. school system today, we have many English language learners who come to America for various reasons. ELLs are tasked with learning not only the English language, but also to pass state mandated tests. Standardized testing in the U.S. is at the forefront of learning, which places an expectation on not only students, but also teachers and administrators. Educators and administrators are responsible for ensuring ELLs pass state mandated tests while learning the English language. ELLs are faced with a multitude of challenges in addition to learning the English language. There are several instructional models that assist ELLs in learning and performing on standardized tests. The purpose of this qualitative study is to identify the perceptions of English language teacher perspectives on effective instructional practices and models to prepare ELLs for state mandated testing. ESL teachers and administrators were interviewed in two school divisions in Virginia to find out the best methods of instruction to use when teaching ELLs. A possible future study recommendation would be to compare ELLs performances on state mandated tests using various models of instruction
Campus to Commonwealth
No full textThe Land-Use Value Assessment Program (LUVA) has provided tax relief for qualifying agricultural, horticultural, open space, and forest land for over 50 years by allowing land to be assessed at its use value rather than market value, helping preserve rural land. LUVA at Virginia Tech develops these use-value estimates for the Virginia Department of Taxation using two State Land Evaluation Advisory Council (SLEAC) approved methods, the capitalized rental rate approach and the capitalized income approach, which are reviewed annually by SLEAC.
For Tax Year 2026, SLEAC adopted LUVA’s updated estimates, which show an average statewide decrease of 958 per acre. Sixty percent of localities experienced decreases, reflecting recent agricultural challenges such as lower government payments, declining grain prices, and high input costs. While localities are not required to adopt these values, lower use-values can reduce tax burdens and encourage the continued preservation of Virginia’s rural and productive lands
Empathetic Educational Environments: Advancing Cultural Sensitivity of Trauma Through Storytelling in the Secondary-level English Classroom
No full textThis exploratory sequential mixed methods study addresses the critical gap in trauma-informed educational research by centering trauma survivors' voices as foundational knowledge for developing pedagogical interventions. First, through comprehensive evaluation of a teacher preparation program, classroom observations across diverse Virginia schools, educator professional development (n =7), and in-depth interviews trauma survivors (n =15), this research reveals significant deficits in trauma-informed practices within secondary education settings. The study introduces "misbehaving forms," alternative narrative structures that deliberately resist conventional academic constraints to accommodate the non-linear nature of trauma expression. This concept emerged with survivor narratives describing how traditional formats failed to capture their authentic experiences. These qualitative findings then informed the development of a storytelling intervention, which was implemented in three sections of a secondary English class and measured through an adapted Self-Determination Theory questionnaire assessing autonomy, competence, and relatedness. Two sections of the English class (n = 39) received the intervention, and one section remained as the control (n =16). With this questionnaire, quantitative results demonstrated statistically significant improvements in the intervention participants' student autonomy (p = 0.0309), competence (p = 0.0069), and creative expression (p < 0.001). The integration of qualitative and quantitative findings validates the effectiveness of survivor-informed pedagogical approaches while establishing a methodological framework for centering marginalized voices in educational research. The research challenges traditional academic hierarchies that exclude survivor wisdom while providing practical strategies for creating trauma-informed learning environments that support both academic achievement and emotional healing.Doctor of PhilosophyThis study explored how schools can better support students who have experienced trauma. Various research methods, including observations, a pilot study, and 15 interviews, showed that many teachers lack the training and tools to help these students effectively. A key finding was that traditional school assignments, such as standard essays with strict formats, do not work well for authentic expression, something that trauma survivors need. This is because trauma memories do not follow a neat, linear pattern, making it more difficult to engage in a consistent retelling. Based on what survivors said they needed during the interviews, an innovative storytelling intervention was created that gave students more freedom and flexibility. It was tested with 55 high school English students: 39 participated in the unique creative expression assignment while 16 continued with classroom lessons that did not use the innovative storytelling approaches. The results were promising. Students in the storytelling intervention reported feeling more independent in their learning, more confident in their abilities, and more creative in their expression. These improvements were statistically significant, meaning they were not just due to chance. This research shows that when educators listen to trauma survivors and design teaching methods based on their experiences, students benefit academically and emotionally. It provides practical ways for teachers to create classroom environments where healing and learning can happen together
Diffusiophoresis and Auto Stratification in Rapidly Drying Colloidal Suspensions
No full textBecause of the coupled effects of diffusion, advection, and phoretic transport under non-equilibrium conditions, polydisperse colloidal suspensions exhibit interesting auto-stratification phenomena during rapid drying, where particles of different sizes segregate into layered structures. The physical mechanism responsible for these phenomena is believed to be diffusiophoresis, which refers to the phoretic motion of a particle driven by the concentration gradients of other solutes in the suspension. Although molecular diffusiophoresis, where salts with a molecular size much smaller than the phoretic particles serve as the solutes, is well documented, colloidal diffusiophoresis in polydisperse suspensions displays new features that are not well understood. In this dissertation, a model is developed to enable a systematic study of colloidal diffusiophoresis with molecular dynamics simulation, where the solutes are also colloidal particles with sizes comparable to or even larger than the phoretic particles. The results reveal the effects of the strength of the concentration gradient and the size of the phoretic particles on their diffusiophoretic mobility, which provides a foundation to understand the auto-stratification phenomena in rapidly drying colloidal suspensions featuring size dispersity. Further simulations show that mixtures of particles with similar mass but different shapes also stratify upon rapid drying, alluding to the potential effect of particle shape on diffusiophoresis. Also, analytical interaction potentials are developed for disks in two dimensions (2D) based on the Lennard-Jones 12-6 potential. These potentials are used to study the behavior of 2D suspensions of disks, including their equilibrium and drying properties. Auto-stratification is found to also occur in 2D suspensions of bidisperse disks that are rapidly dried. This points to new features of colloidal diffusiophoresis in 2D suspensions. Finally, a facile strategy is proposed to use a binary mixture of solvents to induce and control the stratification of a binary mixture of colloidal particles suspended in the solvent mixture upon solvent evaporation. Overall, this dissertation provides a molecular understanding of colloidal diffusiophoresis and its relation to auto-stratification phenomena in rapid drying by revealing the effects of particle size and shape, system dimensionality, and solvent composition on diffusiophoresis.Doctor of PhilosophyA liquid suspension is a heterogeneous mixture where particles are dispersed in a fluid but do not dissolve. For example, mud is a suspension of fine soil particles like clay, silt, and sometimes fine sand that have sizes varying from microns ( meter) to millimeters ( meter). Similarly, colloidal suspensions contain particles of sizes from nanometers ( meter) to microns. Recent experiments and simulations show that when a colloidal suspension containing small and large particles dries, the particles often do not stay even mixed. Instead, they can develop a layered distribution as the solvent evaporates, and the so-called stratified structure can persist in the final dry film formed by packing particles. These findings point to a cost-effective approach to making multilayered coating films. In this dissertation, I use molecular dynamics simulations, where the motion of each particle and each solvent atom is tracked, to study the drying process of colloidal suspensions. My results help elucidate the molecular mechanisms underlying the stratification phenomena. I further show that stratification occurs not only in suspensions containing spherical particles of different sizes but also in suspensions containing particles of similar sizes but different shapes. Additionally, like 3-dimensional suspensions of spheres, 2-dimensional suspensions of disks of assorted sizes exhibit stratification upon solvent evaporation as well. Finally, I propose a strategy to use a binary solvent mixture, where a solvent of low volatility is mixed with one of high volatility, to induce and control the stratification of a mixture of colloidal particles that have contrasting interactions strengths with the two solvent components. Overall, these results provide a detailed study on stratification of colloidal systems and suggest new ways to design coatings and nanomaterials with precisely controlled internal layering created naturally through drying
Modeling Droplet Impingement Dynamics on Micropillar-Arrayed Viscoelastic Substrates Through Microgeometry-Free and Multiscale Methods
No full textThe droplet impact dynamics on micropillar-arrayed viscoelastic substrates has been thoroughly investigated by two distinct modeling methods, i.e., microgeometry-free and multiscale modeling methods. The viscoelasticity of the micropillar-arrayed substrate is characterized by a five-parameter generalized Maxwell model via the Laplace-Carson transform. In the microgeometry-free modeling, only one general domain containing all the modeled objects is constructed with the detailed geometry of micropillars omitted. In contrast, by multiscale modeling, two different geometric-scale domains are employed to investigate the deformation of individual micropillars in the smaller domain named zoomed-in domain and the effects of the deducted deformation velocity on the fluid field evolution in the larger domain called the zoomed-out domain.
These two methods both have advantages and disadvantages regarding efficiency, accuracy and information completeness and emphasis. The microgeometry-free method serves as an efficient tool to rapidly determine the flow evolution after droplet impingement, while being deficient to accurately describe the individual micropillar deformation. By contrast, the multiscale method can appropriately stress this issue by constructing magnification domains along the bottom micropillar array with the entrapped gas cushioning effect evaluated, which in turn results in a more precise illustration of fluid field evolution. However, due to more details considered, this method becomes much more time consuming and requires significant computational resources.
Although the microgeometry-free and multiscale modeling methods are implemented via distinct procedures, they share some common aspects such as using the general larger domain to define the macroscopic flow evolution and leveraging the generalized Maxwell model to characterize substrate viscoelasticity. This indicates that these two methods are interrelated rather than independent. Therefore, they together substantially demonstrate the evolution of droplet and the deformation of micropillar array, and significantly provide meaningful clues to understand fluid-structure interaction with enormous geometric-scale inconsistency and complex physical properties involved.Doctor of PhilosophyDroplet impingement on micropillar-arrayed viscoelastic substrates entails multiscale geometric configurations and complex viscoelastic characteristics of the micropillar array, which render accurate modeling challenging, especially when the droplet-micropillar interaction and the entrapped ambient gas cushioning between neighboring micropillars are considered.
This dissertation leverages two different modeling methods to investigate the spreading film evolution resulting from the droplet impact and quantify the micropillar deformation. These two methods have their own advantages and disadvantages when compared to each other. In detail, the microgeometry-free modeling method can fast simulate the droplet dynamics on micropillar-arrayed substrate under various physical conditions, while the individual micropillar deformation remains a hidden point in this modeling and can only be approximated by the deformation of specific discretization cells along the bottom boundary. On the contrary, the detailed deformation for each individual micropillar can be delineated by the multiscale modeling with constructing magnification domains, which correspond to specific portions of the bottom micropillar array within the general domain. Meanwhile, since the geometric configuration of the micropillars is constructed in the multiscale modeling, the cushioning effect of the entrapped ambient gas on the micropillar deformation can also be evaluated appropriately. Nonetheless, higher accuracy and more involved information indicate consumption of more computational resources, which should be assessed during the actual implementation.
According to the modeling results by the microgeometry modeling, higher impact velocity U_i, greater ambient pressure P_a and smaller surface tension σ all contribute to a more intense splash occurrence, which is also consistent with the Kelvin-Helmholtz Instability theory. Within the multiscale modeling framework, the deformation of micropillars is computed explicitly so that both the magnitude and directional oscillations can be analyzed after droplet impingement. Furthermore, the entrapped gas cushioning can be examined through the fact that under some impact velocities, the largest deformation across various gap densities appears at a lower gap density (0.10 or 0.15) rather than at the highest gap density (0.20). This phenomenon becomes more prominent with increasing impact velocity.
In essence, our investigation of droplet impingement dynamics on micropillar-arrayed substrate through the microgeometry-free and multiscale modeling methods sheds light on accurately determining the liquid-gas interface evolution and specifically computing the deformation of micropillar array. These two methods are of substantial significance and offer profound insights into future investigations of droplet impingement dynamics on microstructured viscoelastic surfaces
Journal of the American Chemical Society
No full textThe inherently sluggish single-electron transfer from copper(I) complexes to alkyl halides remains a central bottleneck in copper-catalyzed cross-coupling chemistry. Here, we introduce a conceptually distinct strategy that overcomes this limitation by harnessing the unique reactivity of the carbon dioxide radical anion (CO2·–) to undergo efficient single-electron transfer to alkyl bromides. The strategy relies on the generation of CO2·– via Cu-catalyzed C–H bond activation of the formate anion. CO2·– then undergoes an efficient single-electron transfer to alkyl bromides to generate alkyl radicals for subsequent Cu-catalyzed transformations. A broad range of unactivated alkyl bromides and structurally diverse nucleophiles─including heteroaryl amines, sulfonamides, anilines, sulfinates, and nitriles─are efficiently coupled to afford C(sp3)–N, C(sp3)–S, and C(sp3)–C bonds in good to excellent yields. The cost-effectiveness and simplicity of this protocol enable decagram-scale synthesis while facilitating rapid reaction optimization and library synthesis for late-stage diversification of drug molecules through high-throughput experimentation.Published versio
The Journal of Physical Chemistry B
No full textα-Synuclein (α-Syn) is an intrinsically disordered protein (IDP) whose aggregation into fibrils is implicated in Parkinson's disease (PD). While benign α-Syn aggregation frequently occurs, off-target aggregates are implicated in disease progression. Although most mechanisms of toxic α-Syn aggregate formation are unknown, high concentrations of salt ions have been shown to systematically result in faster aggregation. Previous work suggests that salt slows water in the hydration shell of α-Syn, promoting intermolecular interactions. Here, we use polarizable molecular dynamics (MD) to investigate the interactions between α-Syn and water in response to an increased NaCl concentration. While we also find that the water in the hydration shell of the nonamyloid-β component (NAC) domain slows down with increasing salt concentration, the water in the hydration shell of the N- and C-terminal domains accelerates. The segments of the N- and C-terminal domains that show faster water diffusion kinetics corroborate with truncation experiment results. Overall, our work suggests that α-Syn aggregation is related to partial salt-induced dehydration of the N- and C-terminal domains.Published versio