All Faculty Deposits

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https://hdl.handle.net/10919/70873

The "All Faculty Deposits" collection contains works deposited by faculty and appointed delegates from the Elements (EFARs) system. For help with Elements, see Frequently Asked Questions on the Provost's website. In general, items can only be deposited if the item is a scholarly article that is covered by Virginia Tech's open access policy, or the item is openly licensed or in the public domain, or the item is permitted to be posted online under the journal/publisher policy, or the depositor owns the copyright. See Right to Deposit on the VTechWorks Help page. If you have questions email us at vtechworks@vt.edu.

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Now showing 1 - 20 of 6235

Modifying the Asynchronous Jacobi Method for Data Corruption Resilience
Vogl, Christopher J.; Atkins, Zachary R.; Fox, Alyson; Miedlar, Agnieszka; Ponce, Colin (Society for Industrial and Applied Mathematics, 2024-10-09)
Moving scientific computation from high-performance computing (HPC) and cloud computing (CC) environments to devices on the edge, i.e., physically near instruments of interest, has received tremendous interest in recent years. Such edge computing environments can operate on data in situ, offering enticing benefits over data aggregation to HPC and CC facilities that include avoiding costs of transmission, increased data privacy, and real-time data analysis. Because of the inherent unreliability of edge computing environments, new fault-tolerant approaches must be developed before the benefits of edge computing can be realized. Motivated by algorithm-based fault tolerance, a variant of the asynchronous Jacobi (ASJ) method is developed that achieves resilience to data corruption by rejecting solution approximations from neighbor devices according to a bound derived from convergence theory. Numerical results on a two-dimensional Poisson problem show that the new rejection criterion, along with a novel approximation to the shortest path length on which the criterion depends, restores convergence for the ASJ variant in the presence of certain types data corruption. Numerical results are obtained for when the singular values in the analytic bound are approximated. Additional linear systems are also explored, one with a more dense sparsity pattern and one that includes advection. All results indicate that successful resilience to data corruption depends on whether the bound tightens fast enough to reject corrupted data before the iteration evolution deviates significantly from that predicted by the convergence theory defining the bound. This observation generalizes to future work on algorithm-based fault tolerance for other asynchronous algorithms, including upcoming approaches that leverage Krylov subspaces.
Global stability analysis using the method of Reduction Of Dissipativity Domain
Jafari, Reza; Hagan, Martin (IEEE, 2011-07)
This paper describes a modification to the method of Reduction Of Dissipativity Domain with Linear Boundaries (RODD-LB1) which was introduced by Barabanov and Prokharov [7]. The RODD method is a computational technique for the global stability analysis of nonlinear dynamic systems. In this paper we introduce an extension to the original RODD method that is designed to speed up convergence. The efficiency of the extended algorithm is demonstrated through numerical examples.
Enhanced precision in robot arm positioning: A nonlinear damping approach for flexible joint manipulators
Jafari, Amir Hossein; Dhaouadi, Rached; Jafari, Reza (Wiley, 2024-06-22)
This article introduces an advanced nonlinear controller designed for optimizing the performance of a single‐link robot arm featuring a flexible joint. The proposed nonlinear control strategy incorporates a Proportional‐Integral (PI) controller in conjunction with a nonlinear velocity feedback component, aimed at providing effective nonlinear damping and suppressing vibrations. To validate the controller's performance, extensive simulations are conducted utilizing machine learning techniques within the Python environment. The performance of the proposed nonlinear damping controller is benchmarked against a conventional linear cascaded P‐PI control structure, with both controllers fine‐tuned using the Nelder‐Mead algorithm. Simulation results demonstrate that the nonlinear damping controller yields substantial improvements in the dynamic behavior of the robot axis arm, showcasing superior step and sinusoidal position tracking performance, along with active vibration damping capabilities. This research contributes valuable insights into the enhanced nonlinear control strategies for flexible‐joint robot arms, offering promising advancements in their overall dynamic performance.
Nonlinear Adaptive control with High-Gain Observer
Jafari, Reza (2025-06-30)
In this paper we present an adaptive nonlinear output feedback controller with high-gain observer. One of the main challenge with the design of nonlinear adaptive controller is the stability concern. The stability analysis of the overall closed loop system is addressed through the Lyapunov theorem. The performance of the proposed controller with high-gain observer is tested on a single manipulator with flexible joints.
Box-Jenkins Model of Elastic Drive System Using Levenberg-Marquardt Algorithm
Jafari, Reza (Springer Nature, 2024-03-21)
This paper explains the derivation of Box-Jenkins model for the elastic drive system using Levenberg-Marduardt algorithm. The Box-Jenkins model which is the most flexible linear model has been chosen to identify the elastic drive system. The GPAC analysis has been used for the preliminary identification and the Maximum Likelihood Estimator (Levenberg-Marduardt) is used for the parameter estimations. Several models have been developed for the elastic drive system and the simplest model has been chosen. The accuracy of the final model, residual analysis, has been checked using CHI-Square test.
Speech Recognition Using ARMA Model and Levenberg-Marquardt Algorithm
Jafari, Reza; Jafari, Amir H. (Springer, 2024-08-01)
Autoregressive Moving Average (ARMA) is a simple linear model with memory that can be used for speech recognition problems. This is why, this paper utilized the derivation of ARMA model for the speech recognition. The flexibility of ARMA model helps in derivation of an accurate model that recognizes the pronunciation of letter B. The Generalized Partial Autocorrelation (GPAC) analysis has been used for the preliminary identification and the Maximum Likelihood Estimator (Levenberg-Marquardt) is used for the parameter estimations. Several models have been developed to recognize the letter B that are pronounced by a lady 30 times. The simplest model has been chosen at the end. The accuracy of the final model has been checked using χ2 test.
Proteomic insights into breast cancer response to brain cell-secreted factors
Ahuja, Shreya; Lazar, Iuliana M. (Springer, 2024-08-21)
The most devastating feature of cancer cells is their ability to metastasize to distant sites in the body. HER2 + and TN breast cancers frequently metastasize to the brain and stay potentially dormant for years until favorable conditions support their proliferation. The sheltered and delicate nature of the brain prevents, however, early disease detection and effective delivery of therapeutic drugs. Moreover, the challenges associated with the acquisition of brain biopsies add compounding difficulties to exploring the mechanistic aspects of tumor development. To provide insights into the determinants of cancer cell behavior at the brain metastatic site, this study was aimed at exploring the early response of HER2 + breast cancer cells (SKBR3) to factors present in the brain perivascular niche. The neural microenvironment was simulated by using the secretome of a set of brain cells that come first in contact with the cancer cells upon crossing the blood brain barrier, i.e., endothelial cells, astrocytes, and microglia. Cytokine microarrays were used to investigate the secretome mediators of intercellular communication, and proteomic technologies for assessing the changes in the behavior of cancer cells upon exposure to the brain cell-secreted factors. The cytokines detected in the brain secretomes were supportive of inflammatory conditions, while the SKBR3 cells secreted numerous cancer-promoting growth factors that were either absent or present in lower abundance in the brain cell cultures, indicating that upon exposure the SKBR3 cells may have been deprived of favorable conditions for optimal growth. Altogether, the results suggest that the exposure of SKBR3 cells to the brain cell-secreted factors altered their growth potential and drove them toward a state of quiescence, with broader overall outcomes that affected cellular metabolism, adhesion and immune response processes. The findings of this study underscore the key role played by the neural niche in shaping the behavior of metastasized cancer cells, provide insights into the cellular cross-talk that may lead cancer cells into dormancy, and highlight novel opportunities for the development of metastatic breast cancer therapeutic strategies.
Proteomic assessment of SKBR3/HER2+ breast cancer cellular response to Lapatinib and investigational Ipatasertib kinase inhibitors
Karcini, Arba; Mercier, Nicole R.; Lazar, Iuliana M. (Frontiers, 2024-08-29)
Introduction: Modern cancer treatment strategies aim at achieving cancer remission by using targeted and personalized therapies, as well as harnessing the power of the immune system to recognize and eradicate the cancer cells. To overcome a relatively short-lived response due to resistance to the administered drugs, combination therapies have been pursued. Objective: The objective of this study was to use high-throughput data generation technologies such as mass spectrometry and proteomics to investigate the broader implications, and to expand the outlook, of such therapeutic approaches. Specifically, we investigated the systems-level response of a breast cancer cell line model to a mixture of kinase inhibitors that has not been adopted yet as a standard therapeutic regime. Methods: Two critical pathways that sustain the growth and survival of cancer cells, EGFR and PI3K/AKT, were inhibited in SKBR3/HER2+ breast cancer cells with Lapatinib (Tyr kinase inhibitor) and Ipatasertib (Ser/Thr kinase inhibitor), and the landscape of the affected biological processes was investigated with proteomic technologies. Results: Over 800 proteins matched by three unique peptide sequences were affected by exposing the cells to the drugs. The work corroborated the anti-proliferative activity of Lapatinib and Ipatasertib and uncovered a range of impacted cancer-supportive hallmark processes, among which immune response, adhesion, and migration emerged as particularly relevant to the ability of drugs to effectively suppress the proliferation and dissemination of cancer cells. Changes in the expression of key cancer drivers such as oncogenes, tumor suppressors, EMT and angiogenesis regulators underscored the inhibitory effectiveness of drugs on cancer proliferation. The supplementation of Lapatinib with Ipatasertib further affected additional transcription factors and proteins involved in gene expression, trafficking, DNA repair, and development of multidrug resistance. Furthermore, over fifty of the impacted proteins represent approved or investigational targets in the DrugBank database, which through their protein-protein interaction networks can inform the selection of effective therapeutic partners. Conclusion: Altogether, the exposure of SKBR3/HER2+ cells to Lapatinib and Ipatasertib kinase inhibitors uncovered a broad plethora of yet untapped opportunities that can be further explored for enhancing the anti-cancer effects of each drug as well as of many other multi-drug therapies that target the EGFR/ERBB2 and PI3K/AKT pathways.
COHERENT: Latest Results and Future Prospects
Link, Jonathan M. (2024-10-31)
Circadian clock gene polymorphisms implicated in human pathologies
Janoski, Jesse R.; Aiello, Ignacio; Lundberg, Clayton W.; Finkielstein, Carla V. (Cell Press, 2024-06-12)
Circadian rhythms, ~24 h cycles of physiological and behavioral processes, can be synchronized by external signals (e.g., light) and persist even in their absence. Consequently, dysregulation of circadian rhythms adversely affects the well-being of the organism. This timekeeping system is generated and sustained by a genetically encoded endogenous mechanism composed of interlocking transcriptional/translational feedback loops that generate rhythmic expression of core clock genes. Genome-wide association studies (GWAS) and forward genetic studies show that SNPs in clock genes influence gene regulation and correlate with the risk of developing various conditions. We discuss genetic variations in core clock genes that are associated with various phenotypes, their implications for human health, and stress the need for thorough studies in this domain of circadian regulation.
From motivic Chern classes of Schubert cells to their Hirzebruch and CSM classes
Aluffi, Paolo; Mihalcea, Leonardo C.; Schürmann, Jörg; Su, Changjian (American Mathematical Society, 2024-01-01)
The equivariant motivic Chern class of a Schubert cell in a complete flag manifold X = G/B is an element in the equivariant K-theory ring of X to which one adjoins a formal parameter y. In this paper we prove several folklore results about motivic Chern classes, including finding specializations at y = −1 and y = 0; the coefficient of the top power of y; how to obtain Chern-Schwartz-MacPherson (CSM) classes as leading terms of motivic classes; divisibility properties of the Schubert expansion of motivic Chern classes. We collect several conjectures on the positivity, unimodality, and log concavity of CSM and motivic Chern classes of Schubert cells, including a conjectural positivity of structure constants of the multiplication of Poincar´e duals of CSM classes. In addition, we prove a ‘star duality’ for the motivic Chern classes, showing how they behave under the involution taking a vector bundle to its dual. We use the motivic Chern transformation to define two equivariant variants of the Hirzebruch transformation, which appear naturally in the Grothendieck-Hirzebruch-Riemann-Roch formalism. We utilize the Demazure-Lusztig recursions from the motivic Chern class theory to find similar recursions giving the Hirzebruch classes of Schubert cells, their Poincar´e duals, and their Segre versions. We explain the functoriality properties needed to extend the results to partial flag manifolds G/P.
Complete Artworks Without Authors
Trogdon, Kelly (Cambridge University Press, 2024-05)
Genetically complete yet authorless artworks seem possible, yet it is hard to understand how they might really be possible. A natural way to try to resolve this puzzle is by constructing an account of artwork completion on the model of accounts of artwork meaning that are compatible with meaningful yet authorless artworks. However, I argue that such an account of artwork completion is implausible. Therefore, I leave the puzzle unresolved.
Incompletable Grounding and Ontological Economy
Trogdon, Kelly (2025)
Roughly speaking, incompletable grounds are partial grounds that do not, together with other partial grounds, fully ground. I first bolster the overall case for incompletable grounding by arguing that a certain totality fact has incompletable grounds. Then I trace out some interesting consequences for the ontological economy of theories, including those according to which the totality fact obtains.
Evaluating Shifting Trends in Youth Development Volunteerism: University of California 4-H Youth Development Program
Worker, Steven M.; Nayak, Roshan K.; Miner, Gemma; Wilkins, Tamika; Rodriguez, Matthew; Nathaniel, Keith; Cho, Zeva (2024-10-23)
Long-Term Outcomes of Youth Development Programs: California 4-H Alumni Study
Worker, Steven; Nayak, Roshan K.; Iaccopucci, Anne; Marshall-Wheeler, Nicole (2025)
Enumerating rights: more is not always better
Ball, Sheryl B.; Dave, Chetan; Dodds, Stefan (Springer, 2023-05-11)
Contemporary political and policy debate rhetoric increasingly employs the language of ‘rights’: how they are assigned and what entitlements individuals in a society are due. While the obvious constitution design issues surround how rights enumeration affects the relationship between a government and its citizens, we instead analyze how rights framing impacts how citizens interact with each other. We design and implement a novel experiment to test whether social cooperation depends on the enumeration and positive or negative framing of the right of subjects to take a particular action. We find that when rights are framed positively, there exists an ‘entitlement effect’ that reduces social cooperation levels and crowds-out the tendency of individuals to act pro-socially.
Vaccine Hesitancy and Betrayal Aversion
Alsharawy, Abdelaziz; Dwibedi, Esha; Aimone, Jason; Ball, Sheryl B. (Springer, 2022-05-17)
The determinants of vaccine hesitancy remain complex and context specific. Betrayal aversion occurs when an individual is hesitant to risk being betrayed in an environment involving trust. In this pre-registered vignette experiment, we show that betrayal aversion is not captured by current vaccine hesitancy measures despite representing a significant source of unwillingness to be vaccinated. Our survey instrument was administered to 888 United States residents via Amazon Mechanical Turk in March 2021. We find that over a third of participants have betrayal averse preferences, resulting in an 8–26% decline in vaccine acceptance, depending on the betrayal source. Interestingly, attributing betrayal risk to scientists or government results in the greatest declines in vaccine acceptance. We explore an exogenous message intervention and show that an otherwise effective message acts narrowly and fails to reduce betrayal aversion. Our results demonstrate the importance of betrayal aversion as a preference construct in the decision to vaccinate.
Promoting diversity in biomedical fields with the Teen Science Ambassador Program
Margherio, Samantha M.; Rountree, Ren; Crooks-Monastra, Jennifer; Brazell, Bradley F.; Bellamy, Rodrick; Squeglia, Lindsay M. (Vanderbilt University Library, 2024-04-17)
Mental health and substance use fields suffer from underrepresentation of racially and ethnically minoritized, first-generation college student, and female members. The homogeny of the current workforce can impede scientific productivity, creativity, and problem-solving in addressing health-related issues. Our team developed the Teen Science Ambassador Program (TSAP) to provide underrepresented minoritized (URM) high school students with science-focused education, research opportunities, and mentoring within their community. The goals of the current study were to describe the logic model and structure of TSAP, provide access to a resource bank to facilitate replication across communities, and present preliminary mixed-methods outcome data to guide development of the program. Qualitative and quantitative results from our first two cohorts (N = 18; 89% girls; 72% Black or African American; 22% Hispanic or Latino; 40% of parents did not have a college degree) indicated TSAP contributed to sustained interest, increased confidence, and enhanced sense of belonging in science-related fields, especially those pertaining to mental health and substance use. These findings highlight the program's promise to facilitate entry and sustainment of URM and female youth within the biomedical sciences. Given the urgent need to promote diversity in the mental health and biomedical workforce, we provide readers with a resource bank to facilitate replication across communities.
Online Allies? Exploring Black Travelers' Perceptions of DMO Social Advocacy Statements
Tucker, Charis N.; McGehee, Nancy G.; Lamoureux, Kristin M. (Sage, 2024-11-25)
Many U.S. destination marketing organizations (DMOs) have utilized social media to express support for the Black community amidst the Black Lives Matter racial justice movement. Current research lacks insight into ways in which Black travelers judge these efforts known as advocacy statements. This study uses a 2 × 2 experimental design to examine how Black travelers evaluate various forms of statements. Additionally, this work explores the mediating role of relational legitimacy between advocacy statements and behavioral intentions and finds it to be significant. Black travelers in this study find statements containing both an image and text to be the most appropriate form of digital social advocacy. Organizations can leverage these findings to create effective advocacy campaigns that go beyond performative acts and reflect substantive policies and strategies.
The importance of peripheral populations in the face of novel environmental change
Hoff, Samantha; Hoyt, Joseph R.; Langwig, Kate E.; Johnson, Luanne; Olson, Elizabeth; O'Dell, Danielle; Pendergast, Casey J.; Herzog, Carl J.; Parise, Katy L.; Foster, Jeffrey T.; Turner, Wendy C. (Royal Society, 2025-01-08)
Anthropogenically driven environmental change has imposed substantial threats on biodiversity, including the emergence of infectious diseases that have resulted in declines of wildlife globally. In response to pathogen invasion, maintaining diversity within host populations across heterogenous environments is essential to facilitating species persistence. White-nose syndrome is an emerging fungal pathogen that has caused mass mortalities of hibernating bats across North America. However, in the northeast, peripheral island populations of the endangered northern myotis (Myotis septentrionalis) appear to be persisting despite infection while mainland populations in the core of the species range have experienced sharp declines. Thus, this study investigated host and environmental factors that may contribute to divergent population responses. We compared patterns of pathogen exposure and infection intensity between populations and documented the environmental conditions and host activity patterns that may promote survival despite disease invasion. For island populations, we found lower prevalence and less severe infections, possibly due to a shorter hibernation duration compared to the mainland, which may reduce the time for disease progression. The coastal region of the northern myotis range may serve as habitat refugia that enables this species to persist despite pathogen exposure; however, conservation efforts could be critical to supporting species survival in the long term.

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