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Quick Response Codes in Extension Outreach Communications: Insights from a Visual Content Analysis and Educators’ Perceptions
Get PDFIncreased smartphone use presents an opportunity to enhance the creative inclusion of Quick Response (QR) codes in extension outreach efforts. Tailoring extension programs to communicate with specific audiences has been identified as essential, highlighting the need for targeted and context-specific strategies. The development of QR code technology has provided a unique approach that allows extension professionals to target clientele with specific extension messages and programs. While extension has a commendable record in educational delivery through traditional forms of outreach, research on how best to employ digital tools with extension audiences is thin at best. Though the rising popularity of QR codes for information exchange is certain, there is still a gap in knowledge about the factors influencing their acceptance and usefulness in extension outreach. Employing social science methodologies including content analysis and semi-structured interviews, this dissertation study assessed the current QR code usage in extension outreach media outlets and described extension agents’ perceptions through semi-structured interviews in the Ozark district of Arkansas. The first article of this study incorporated a content analysis of 105 extension outreach graphics to assess the placement of codes in the outreach communications. The second article was a qualitative study, involving semi-structured interviews with twelve extension professionals. The study shed light on agents\u27 perceptions, adoption patterns, and challenges related to QR code usage. This formative study ascertained local perspectives and priorities, which could then be used to drive communication strategies. It is envisaged that the findings and recommendations of this study will lead to the development of a framework that can be utilized to improve audience-specific communication programming and strategies throughout the area in the southern region where the research was conducted
Contrastive Learning Techniques for Fraud Detection
Get PDFDetecting fraud in computing platforms involves identifying malicious user sessions, often using deep learning models, but several challenges hinder effective deployment. Attackers can craft diverse malicious sessions that closely resemble normal ones, complicating the learning of robust decision boundaries. While supervised contrastive learning offers a promising solution through class-specific clustering, its potential remains underexplored. Real-world datasets typically contain few labeled malicious sessions and many normal ones, creating an open-set anomaly detection challenge. Costly expert annotation further limits labeled data, especially for smaller organizations, leading to Positive Unlabeled (PU) learning and noisy label learning issues. Organizations are increasingly turning to LLMs for their adaptability, minimal retraining needs, and the capability of In-Context Learning (ICL) to adapt to evolving fraud patterns, though this potential is not yet fully realized. This dissertation addresses these challenges using supervised contrastive learning to develop practical fraud detection frameworks, with key contributions outlined below.
We present a robust supervised contrastive learning based fraud detection framework which operates in the open-set anomaly detection setting;
We present a supervised contrastive learning based fraud detection framework which operates in the PU learning setting;
We present a supervised contrastive learning based fraud detection framework which operates in the noisy label setting.
We present an ICL based framework for coded fraud text and hate speech detection which leverages supervised contrastive learning for demonstration selection
Variation in Stress Response Regulation Across Natural Isolates of \u3ci\u3eSaccharomyces cerevisiae\u3c/i\u3e
Get PDFThe stress response of Saccharomyces cerevisiae is a valuable area of study for understanding cellular adaptation mechanisms that govern survival in fluctuating environments. This dissertation investigates stress response regulation in yeast through the roles of Hog1 mitogen-activated protein kinase (MAPK) and the post-transcriptional regulator Mkt1, a key post-transcriptional regulator, in diverse wild yeast isolates. Hog1 is traditionally known for its central role in osmotic stress regulation in the high-osmolarity glycerol (HOG) pathway. This study expands the functional scope of Hog1 to include oxidative and ethanol-induced stress responses.
In parallel, we investigate post-transcriptional regulation of stress responses by the Mkt1 interactome, linking Mkt1 to metabolic and translational regulation. Using SILAC-based proteomics, we outline the dynamic nature of the Mkt1 interactome.
We further address the pitfalls of ribonucleoprotein complex procedures in RNA-protein interaction studies, proposing enhanced protocols for more comprehensive investigations into stress-induced gene regulation.
Collectively, this dissertation offers new knowledge on the complexity of stress adaptation in S. cerevisiae, and the importance of strain-specific variation within stress response pathways, demonstrating the value of studying natural variation in molecular studies. The work not only advances the understanding of Hog1 and Mkt1 in stress regulation but also gives an overall perspective of how natural genetic variation influences cellular responses to environmental stress
Impacts of Toxic Fescue Seed Consumed by Pregnant Heifers on Maternal Blood Flow and Offspring Growth Parameters: Potential for Melatonin as a Therapeutic to Improve Offspring Growth
No full textThe southeastern United States is home to endophyte-infected (E+), toxic, tall fescue grass. Consumption of E+ fescue by livestock has been linked to fescue toxicosis, a disease reported to cost the United States beef industry around $1 billion in annual losses. The primary objective of this dissertation was to evaluate the influence of pregnant cattle consuming E+ seed during gestation on uterine artery blood flow and growth performance of female offspring. The secondary objective was to investigate melatonin supplementation as a mitigation strategy for expected fescue-associated decreases in uterine artery blood flow and offspring growth performance. The study reported in chapter II investigates the influence of pregnant heifers consuming E+ seed with (M) or without (NM) melatonin supplementation during mid-late gestation on uterine artery hemodynamics, plasma prolactin (PRL) and melatonin (MEL) concentrations, as well as total antioxidant capacity (TAC). Body weight, total uterine artery blood flow (TBF), ipsilateral uterine artery blood flow (BF), ipsilateral uterine artery blood flow as a proportion of body weight (BF/BW), ipsilateral and contralateral uterine artery diameters, and PRL were decreased and ipsilateral uterine artery pulsatility index (PI) was increased in pregnant heifers consuming E+ seed relative to endophyte-free fescue (E-) seed. Concentration of MEL and TAC were increased for M heifers relative to NM heifers. The study reported in chapter III investigates the influence of pregnant heifers consuming E+ seed with M or NM during mid-late gestation on growth performance of female offspring. Gestation length, birth weight, 205-d weaning weight (205-d WW), and post-weaning weights were decreased in calves born to dams that consumed E+ relative to E- seed. Calf birth weight tended to be increased in calves born to M dams relative to NM dams. Calf 205-d WW was decreased in calves born to E+/NM dams relative to E-/NM, E-/M, and E+/M. Ultrasonic estimate of ribeye area (UREA) was decreased in calves born to E+/NM dams relative to E-/NM and E+/M. The study reported in chapter IV investigates the influence of pregnant heifers consuming E+ seed or E- seed during mid-late gestation on feedlot performance and carcass characteristics of female offspring. Dams consuming E+ seed during gestation produced calves with decreased pre-feedlot body weight (BW), UREA, UFAT, ultrasonic estimate of rump fat (URUMP), feedlot BW, hot carcass weight (HCW), back fat (FT), yield grade (YG), and income relative to offspring born to dams consuming E- seed. Percentage of retail product was increased in calves born to dams consuming E+ seed relative to E- seed perhaps due to increased fat trimming. In summary, consumption of E+ seed by pregnant heifers during mid-late gestation resulted in decreased uterine artery blood flow and offspring growth rates. Decreased growth rates were maintained through the feedlot stage and carcasses generated decreased income. Such losses could translate to a decreased return on investment for the producer and packer. However, melatonin supplementation to pregnant dams consuming E+ seed appeared to rescue fescue-associated losses in offspring weaning weight and ribeye area at weaning, indicating potential as a mitigation strategy
Evaluation of Fluridone in Rice
No full textThe increasing pressure of Palmer amaranth [Amaranthus palmeri (S.) Watson] in rice (Oryza sativa L.) fields demands new chemical control options to manage this weed. The recent labeling of fluridone on this crop from the three-leaf rice stage offers an additional residual herbicide for battling Palmer amaranth; however, research is needed to evaluate its effectiveness and rice tolerance. Field experiments were conducted to evaluate Palmer amaranth control and rice tolerance to fluridone across different locations in Arkansas in 2022, 2023, and 2024. Preemergence (PRE) applications of fluridone at 168 g ai ha⁻1; (1× label rate) and 336 g ai ha⁻1; (2× label rate) caused severe crop injury to several rice cultivars, leading to grain yield reductions of up to 49% in eight of the most commonly grown cultivars in Arkansas in a flooded rice production. The cultivar DG263L exhibited injury levels of up to 50% and 32% following PRE and three-leaf applications at the 1× rate, respectively, with yield reductions observed at both application timings, indicating low tolerance to fluridone. When comparing ten application timings from 20 days preplant to postflood applications, the treatments near planting caused the greatest injury to rice grown in a delayed-flood system and the applications at PRE and delayed-preemergence decreased rice grain yield. Therefore, fluridone should not be used at early rice stages, as indicated by the label. Additionally, fluridone applied in mixture with standard rice herbicides at the three-leaf growth stage increased injury by up to 8 percentage points compared to the standard herbicide alone. No yield or groundcover reductions were detected with the addition of fluridone, indicating this herbicide can be applied with other rice herbicides for improved weed control while posing minimal risk to the crop. In a furrow-irrigated rice system, PRE applications of fluridone at the 2× label rate caused 8% to 34% injury; however, no yield reduction was observed. In the same system, fluridone at the 1× and 2× label rates reduced Palmer amaranth density by at least 65% and 88%, respectively, four weeks after treatment compared to the nontreated control. Furthermore, the addition of florpyrauxifen-benzyl postemergence following a PRE application of fluridone at 0.5×, 1×, or 2× label rates reduced Palmer amaranth escapes and decreased seed production by at least 94% compared to fluridone alone at rice maturity. Although florpyrauxifen-benzyl resulted in lower weed densities at the end of the season, the presence of remaining weeds likely contributed to lower rice grain yield compared to treatments where no weeds were present. Thus, sequential applications of other effective herbicides are necessary for season-long Palmer amaranth management
Detecting Item Preknowledge in Longitudinally-Collected Assessment Data
No full textEducational assessment policymakers and stakeholders have recently called for assessments that incorporate instruction and learning into the assessment process (e.g., through-course assessment and longitudinal certification assessments). A feature of these assessments is repeated measurements of examinee ability intended to inform learning interventions. Though these longitudinally-administered assessments are often designed to be more flexible for examinees, the increased flexibility presents testing practitioners with unique challenges in maintaining the integrity of exam scores. These assessments, often characterized by on-demand or continuous administration, necessitate repeated use of items over time. Repeating items increases the risk of compromised items that may lead to examinees with item preknowledge, thereby compromising the validity of score interpretations.
Test security, and more specifically, item preknowledge, has received much attention among researchers. Given the recency of longitudinally-administered assessments, however, test security statistics applied to longitudinally-collected assessment data have received little or no attention. Beyond increased security threats, these assessments introduce challenges to item preknowledge detection because of systematic (e.g., change in examinee ability) and unsystematic (e.g., unreliability in proficiency estimation) influences. Nonetheless, longitudinally-collected assessment data may provide additional possibilities for detecting aberrant response behavior not possible in point-in-time assessment contexts.
The purpose of this dissertation was to develop and examine methods for identifying examinees exhibiting item preknowledge in a longitudinal assessment framework. This dissertation comprises three studies that may help testing organizations administering longitudinally-administered assessments develop a suite of test security statistics. By leveraging the information from longitudinal data, the first study extends preexisting test security statistics developed for point-in-time assessments to evaluate for changes in examinee response behavior. The second study extends test security statistics specifically developed to detect sudden changes in examinee response behavior to detect whether and when an examinee begins exhibiting item preknowledge throughout a longitudinal assessment. The third study examines if test security programs should adopt specialized longitudinal statistics, such as those from studies one and two, or if conventional point-in-time methods are sufficient. The three studies comprise simulation studies to assess the test security statistics\u27 performance in realistic testing conditions and applied examples to showcase their practical use and limitations with real data
Controls on Nutrient and Sediment Export in a Non-perennial Agricultural Stream
No full textClimate change is expected to increase flow variability and intermittency in streams, changing the magnitude and timing nutrient and sediment delivery. This may exacerbate water quality issues in agricultural landscapes, where nutrient and sediment inputs are often elevated. Elevated nutrients can drive eutrophication in downstream waterways, and excess sediment loss can decrease primary productivity. Non-perennial headwater streams are particularly vulnerable to the impacts of climate change and agriculture as they serve as key sites for nutrient cycling at the terrestrial-aquatic interface. Despite their importance, the interactive effects of agriculture and stream intermittency, as well as unpaved roads in rural watersheds are understudied.
Here, we sampled the Brush Creek watershed (5,165 ha), a non-perennial tributary of Beaver Lake Reservoir, Northwest Arkansas’s primary drinking water source. In Brush Creek, ~45% of land cover is dedicated to poultry production and pastureland, and there are 190 km of unpaved roads. I conducted monthly baseflow sampling for nitrate (NO3--N) and soluble reactive phosphorus (SRP) export from October 2023-September 2024. While both NO3--N and SRP increased moving downstream as surface connectivity increased, I found that only NO3--N loads increased simultaneously with percent of upstream sites flowing. I also found NO3--N loads were higher in subwatersheds with greater %pasture/hay, suggesting that fertilizers may be a potential NO3--N source in the watershed. My results indicate surface connectivity in Brush Creek controls the timing and spatial patterns of nutrient loss, where %pastureland controls the magnitude of NO3--N loss. Overall, my findings suggest management should focus on periods of hydrologic reconnection and in subwatersheds with more pasturelands to effectively protect downstream water quality.
Beginning in February 2024, I also sampled at baseflow monthly for total suspended sediments (TSS) and collected samples opportunistically during four storm events to understand local (i.e., type of road crossing) and watershed-scale (i.e., land cover/use) controls on sediment loss from unpaved roads. Surprisingly, mean TSS yields downstream vs. upstream of road crossings were comparable, especially at bridge and culvert sites, indicating these types of road crossings may not be critical sources of TSS to streams. At the watershed scale, we found that TSS load increased as the total length of unpaved roads and area of pastureland in a subwatershed increased (Simple Linear Regression; R2=0.24, p\u3c0.001 for both). Finally, we documented higher TSS yields during stormflow than at baseflow (26.87 ± 6.82 vs. 0.38 ± 0.04 kg km-2 day-1; unpaired t-test, p\u3c0.01). Our findings indicate that unpaved road networks are key contributors to sediment export in rural watersheds. As such, BMP implementation should focus on unpaved roads to effectively protect downstream water quality in regions with extensive unpaved road networks.
My thesis highlights the importance of targeted BMPs in agricultural areas with intermittent streams. These practices should focus on periods of hydrologic reconnection, pasture-dominated subwatersheds, and managing sediment loss from unpaved roads to mitigate both nutrient and sediment loss. My research supports the importance of proper land management for protecting downstream water quality as climate change magnifies flow variability and intermittency
Design and Implementation of Asynchronous Communication in Multi-Chiplet Systems: A Comparative Study of Pseudo-Crossbar and Bus Architectures
Get PDFSystem-on-Chip (SoC) complexity continues to present challenges in global clock distribution and power management. The Globally Asynchronous Locally Synchronous (GALS) approach addresses these issues by enabling asynchronous communication between locally synchronous chiplets. This thesis details the design and implementation of two GALS architectures employing asynchronous handshaking protocols through Multi-Threshold CMOS NULL Convention Logic (MTNCL). The first architecture, a pseudo-crossbar, uses arbiters and multiplexers/demultiplexers (MUX/DEMUX) for prioritized and dynamic communication between chiplets. The second, a bus-based approach, employs D-latches to manage communication sequentially with predetermined interrupts. This research explores the detailed implementation, functional distinctions, scalability, and integration trade-offs inherent to each design. The insights gained provide practical guidance for future advancements in embedded asynchronous communication system
In Situ Studies on Lithium Dendrite Growth Using Optical Microscopy
No full textThis thesis presents an in-situ optical microscopy technique for observing dendritic deposition of lithium ions onto lithium metal electrodes. Current research methods and findings using in-situ and operando optical microscopy are discussed. Future works relevant to lithium metal anode implementation are explored. This paper discusses the procedure for constructing an effective in-situ optical microscopy visualization cell and the difficulties that arise during construction. Lithium metal symmetrical cells were constructed with 1 M bis(trifluoromethane)sulfonimide lithium salt (LiTFSI) in 1:1 by volume dioxolane/dimethoxyethane (DOL/DME) electrolyte (i.e., 1 M LiTFSI in 1:1 DOL/DME, referred to as the ether electrolyte) and with 1.2 M lithium hexafluorophosphate (LiPF6) in 3:7 by weight ethylene carbonate/ethyl methyl carbonate (EC/EMC) electrolyte (i.e., 1.2 M LiPF6 in 3:7 EC/EMC, referred to as the carbonate electrolyte). The dendrite morphology in these electrolytes was compared via in-situ optical microscopy (OM) imaging, in-situ electrochemical impedance spectroscopy (EIS), and ex-situ scanning electron microscopy (SEM). Comparative experiments are conducted with symmetrical lithium metal coin cells in the same electrolytes. In the ether electrolyte studies, in-situ OM reveals a nearly uniform distribution of dendrite nucleation sites across the lithium metal surface, with a constant increase in thickness throughout the plating half-cycle at various current densities. The lithium deposition in the carbonate electrolyte exhibited sporadic nucleation sites with large discrepancies in growth rate of each dendrite. Ex-situ SEM investigations of the working electrode in ether electrolyte studies revealed large, uniform filament size across the electrode. The working electrode in the carbonate electrolyte study showcased dendrites with a morphology resembling a bush, with individual filaments too small to analyze. These dendrites were also variable in size and easily broken or removed from the surface. EIS was utilized to examine the development of the native layer on the surface of the lithium metal before electrochemical cycling as well as to investigate the impedance across the cell after a plating half-cycle. All studies using the ether electrolyte exhibited lower impedance than the same experiments with the carbonate electrolyte. All of these results indicate that the ether electrolyte is more compatible with lithium metal and promotes a beneficial solid electrolyte interphase for electrochemical cycling
Simulations of Richtmyer-Meshkov Instability using high order WENO methods
Get PDFTurbulent mixing due to hydrodynamic instabilities occurs in a broad spectrum of engineering, astrophysical and geophysical applications. Theory, experiment, and numerical simulation help us to understand the dynamics of interface instabilities between two fluids. This thesis presents an increasingly accurate and robust front tracking method for the numerical simulations of shock-induced turbulent mixing known as Richtmyer-Meshkov Instability (RMI). Front tracking is an adaptive computational method, where the interface instability is explicitly represented as lower dimensional manifolds moving through a rectangular grid. All the cell-center states (density, velocity and pressure) are updated using higher order weighted essentially non-oscillatory (WENO) scheme. Performance of fifth- and ninth-order WENO schemes, with and without monotonicity-preserving bounds, as well as the WENOZ method, for the one-dimensional Sod shock tube, shock-entropy wave interaction problem and a scalar advection test problem are presented. Then the Richtmyer--Meshkov instability (RMI) between air and SF6 simulations are performed in order to show the improvements achieved using the new method. The fifth- and ninth-order WENO schemes with and without monotonicity preserving bounds are explored in the numerical solution of the shock-driven interface problem