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A New Numerical Multiphase Flow Model of Water Droplets Dielectrophoretic-Induced Air Dehumidification
No full textHumidity control plays a vital role in maintaining healthy indoor environments and enhancing the performance of industrial processes. Conventional dehumidification systems, which predominantly rely on vapor compression cycles, are highly energy-intensive due to the requirement of cooling air well below its dew point. This research presents an alternative, energy-efficient approach to air dehumidification based on electric field-induced condensation. A comprehensive numerical investigation is conducted to analyze the interaction between humid airflow and electrically charged water droplets within a duct subjected to a high-gradient electric field, to assess the contribution of electrostatic forces—particularly dielectrophoretic effects—to enhanced vapor condensation.
A hybrid Eulerian–Lagrangian framework is implemented on OpenFOAM® version 9. A dedicated electro-condensation model is developed to simulate the growth of electro-sprayed droplets, incorporating the Rayleigh charge limit and dielectrophoretic condensation dynamics. The electrospray process is represented as a cone-jet stabilized by surface tension, aerodynamic drag, electrostatic forces, and gravity. Experimental validation conducted in the author’s laboratory demonstrates strong agreement with simulation results. The numerical study is extended to evaluate downstream dehumidification performance using cyclone separators. The combination of electro-condensation with centrifugal separation is shown to improve condensate collection and flow regulation. In addition to the numerical analyses, an analytical model is formulated to investigate droplet growth under the influence of an electric field and the dielectrophoresis phenomenon. This research presents a novel and scalable methodology for electric field-assisted air dehumidification, contributing to the advancement of energy-efficient humidity control technologies for residential and industrial applications
Problems in Computational Algebraic Geometry: Lefschetz Properties and Toric Varieties
Full text linkThe first chapter gives the mathematical background needed for the subsequent chapters.
The second chapter consists of the publication [16], a joint work with Hal Schenck, in which
the we examine the influence of geometry on the weak Lefschetz property. We show that with
a certain configuration of points in projective space, their Artnian reduction does have the weak
Lefschetz property. We then generalize this result to a Boij-S¨oderberg theoretic condition on
Betti tables of Artinian algebras.
In the third chapter, the focus shifts to toric varieties and results on the Castelnuovo-
Mumford regularity of toric surfaces. Inspired by a result of L’vovsky in 1996, we show
that the combinatorics of a projective toric surface can provide a combinatorial bound on the
Castelnuovo-Mumford regularity. An overview is given on the tools used to approach this
problem, and the chapter closes with some open questions
Modifiable Health Behaviors and Mitochondrial Oxidative Stress: A Dual Approach to Addressing Obesity and Cardiovascular Wellness
No full textCardiovascular diseases (CVDs) remain one of the leading causes of mortality in the United States and worldwide[1, 2]. Elevated blood pressure (BP), or hypertension (HTN), is a significant risk factor and contributor to CVD[2, 3]. Additional risk factors for the development of HTN and CVD include excessive dietary sodium (Na+)[4, 5] and obesity[6]. High dietary Na+ is also associated with obesity, which may mediate some of the long-term consequences of high Na+ intake and the corresponding development of CVD[7, 8]
HTN, obesity, and excessive dietary Na+ are considered modifiable risk factors in CVD development, and mediating these risk factors can subsequently decrease CVD risk. Unfortunately, there is an alarming trend in the United States indicating HTN, excess dietary Na+, and obesity prevalence have not improved in recent decades[2, 9]. In fact, nine out of ten American adults consume more than the 2300mg/day recommendation for daily intake of Na+, and four out of ten American adults are classified as obese[7]. Thus, there is a critical need for strategies to counteract and prevent HTN, reduce excess dietary Na+, and decrease obesity rates to reduce the burden of CVD in the United States.
Dietary fiber intake impacts CVD development via several mechanisms. Increased dietary fiber is associated with reduced HTN risk and improved cardiovascular health[2]. Higher fiber intake is also inversely associated with obesity[10, 11]. Most Americans do not consume adequate amounts of daily fiber[12]. The standard American diet is comprised of a lot of ultra-processed foods containing excess Na+ and little to no fiber[13]. The manufacturing process includes adding excess Na+ for taste and shelf-life and typically removes the fiber from grain during the food processing[14, 15]. The mechanisms through which high Na+[16, 17] and obesity contribute to high BP and decreased vascular health include oxidative stress[18, 19], inflammation[20, 21] and reduced nitric oxide (NO) bioavailability[22, 23]. Dietary fiber impacts these mechanisms through the conversion by gut microbiota into short-chain fatty acids (SCFAs), which have antioxidant[24, 25] and anti-inflammatory properties[26]. Recent preclinical data indicate high dietary fiber or SCFAs can improve BP and cardiovascular health in the context of heart failure and HTN[27]. In humans, there is promising evidence of a SCFA-boosting prebiotic starch intake leading to an improvement in BP in patients with HTN[28]. These data suggest a potentially important interplay between Na+ and fiber for cardiometabolic health.
There is also preclinical data demonstrating high Na+ intake impairs mitochondrial function by increasing BP, decreases ATP production, and increases oxidative stress, apoptosis, and calcium uptake[28]. Several studies also demonstrate mitochondrial-targeted antioxidants improving vascular health in older adults and patient populations[29-31]. While obesity is associated with higher oxidative stress[19], there is less information on the importance of mitochondrial-derived oxidative stress on vascular health in the context of obesity. Collectively, these data inform our two central hypotheses that 1) dietary Na+ indexed to fiber (i.e., Na+/Fiber) is associated with body composition and cardiovascular health, and 2) that mitochondrial oxidative stress contributes to poorer cardiovascular health in the context of obesity. We will test the hypotheses using two specific aims:
Specific Aim One: To determine whether Na+/Fiber is associated with body composition and cardiovascular health in apparently healthy adults.
Hypothesis One: Higher Na+/Fiber from 3-day food and fluid records will be associated with higher body mass index (BMI), waist:hip, peripheral and central BP, increased (i.e., worse) arterial stiffening assessed via carotid-femoral pulse wave velocity (cfPWV), and reduced vascular function assessed via brachial artery flow-mediated dilation (FMD).
Specific Aim Two: To determine whether mitochondrial oxidative stress contributes to impaired cardiovascular health in individuals with obesity.
Hypothesis Two: An acute high dose of the mitochondrial antioxidant MitoQ will reduce peripheral BP, central BP, and cfPWV, and will improve FMD, in participants who are overweight and obese.
This study identified distinct hemodynamic alterations in individuals with obesity, including elevated blood pressure and signs of vascular strain. Due to the relatively healthy nature of the cohort, MitoQ supplementation showed limited efficacy in improving vascular function. However, a novel contribution of this work is the identification of the dietary sodium-to-fiber (Na⁺/Fiber) ratio as a potential risk marker for cardiovascular health. These findings contribute to the growing body of literature highlighting the importance of early risk identification and targeted prevention strategies for improving cardiovascular outcomes
Analytical Framework for Evaluating Wind Hazard Vulnerability of Light Wood-Frame Buildings
Full text linkLight wood-frame construction constitutes most of the residential building inventory in the United States. The vulnerability of wood-frame buildings to wind hazards and a wide variability in observed performance have motivated research efforts toward understanding precisely how and why wood-frame structural failures occur and how wind damage can be effectively and economically mitigated in future events. Probabilistic analysis of wind performance has been an important strand within these efforts. The wind performance of a structure is essentially a function of structural resistance and wind load intensity, with sources of epistemic and stochastic uncertainty present in both resistance and load. This dissertation aims at a systematic examination of structural and aerodynamic factors that contribute uncertainty to wood-frame wind performance. The analysis framework is composed of two complementary models. (1) A structural vulnerability model evaluates wind uplift resistance by a Monte Carlo method in which probability distributions are assigned to factors like framing member spacing, wood species, and fastener measurements. (2) An aerodynamic vulnerability model, composed of regression neural networks trained on wind tunnel data, evaluates wind uplift intensity in terms of factors like roof shape, roof slope, and wind direction. Separately, these models provide a rational basis for comparing (1) system-level resistance across different wood-frame load paths and (2) expected wind uplift intensities across different low-rise geometries. The third element of the framework is a sensitivity analysis that operates on the models independently — to examine how structural and aerodynamic factors respectively influence resistance and load — as well as on a combined model that allows uncertainty in wind performance to be traced back to fundamental building characteristics. The framework lends itself to a range of applications, including wind-resistant design and wind speed estimation
Impact of Messaging on Veterinarians’ Willingness to Implement Means Safety Protocols
No full textVeterinarians exhibit an increased risk for suicide compared to the general population, which appears to be partially attributable to their access to and knowledge about pentobarbital – the most common drug used for humane euthanasia. One way to reduce suicide risk for veterinarians is increasing means safety. Storing pentobarbital in an additional lockbox has been demonstrated to be an acceptable and feasible means safety protocol for veterinarians, but additional research is necessary to investigate the best way to advertise this protocol. The current study investigated how messaging influenced veterinarians’ willingness to implement an extra lockbox and their acceptability ratings of the advertisement by randomizing 444 veterinarians to view one of four graphics across two messaging factors: preventing participants’ own suicide versus preventing suicide among their coworkers, and DEA regulations versus empirical data supporting means safety protocols. For willingness, those randomized to the empirical data conditions exhibited a greater increase than those randomized to the DEA conditions. For acceptability, we found statistically significant main effects for both factors, such that those randomized to the coworker or empirical data conditions reported higher acceptability of messaging than those randomized to self or DEA conditions, respectively. Additionally, we tested three moderators (i.e. belief in means substitution; reported likelihood of the participant or a coworker attempting suicide) and found mixed evidence of their impact. Finally, we collected qualitative data from participants on their suggestions for the graphics. Overall, our study demonstrates that means safety advertisements for veterinarians should emphasize both empirical data and protecting coworkers
Development and Evaluation of Space-Resilient Polymers: Additively Manufacturable Polymer- Lunar Regolith Composites and Shape Memory Deployable Space Structures
No full textThis thesis investigates two crucial areas related to polymer applications in space: the development of 3D printable polymer-lunar regolith composites for in-situ resource utilization (ISRU) and the long-term performance of shape memory polymers (SMPs) in the low-Earth orbit (LEO) environment. By advancing knowledge in these domains, this research significantly contributes to laying the foundation for sustainable and efficient space exploration and habitation.
Chapter 3 focuses on developing 3D printable polymer-lunar regolith composites, a vital step towards enabling ISRU and additive manufacturing of custom parts on the lunar surface. The study systematically investigated how varying lunar regolith loading levels and particle sizes impact composite material performance, developing a thorough understanding of their processing parameters and material properties. This understanding is critical for efficient and cost-effective lunar base construction. The research uncovered general trends regarding how these factors influence material characteristics, providing key insights for advancing the viability of polymer- regolith composites in lunar manufacturing.
Chapter 4 evaluates the long-term performance of various thermoplastic and thermoset SMPs exposed to the harsh LEO environment. This study investigated changes in the macromolecular structure, viscoelastic properties, and shape memory response of these polymers after a 6-month exposure as part of the MISSE-17 mission. The research developed a general understanding of how these materials behave and degrade in space, identifying the broad effects of the LEO environment on unprotected SMPs and the benefits of protective coatings. It also broadly distinguished the performance characteristics of thermoplastic versus thermoset SMPs in this context. These insights are crucial for understanding SMP degradation mechanisms and informing design considerations for reliable, lightweight, and cost-effective SMP-based deployable space structures.
In summary, this thesis furthers scientific understanding of polymer materials within the context of extreme space environments. It achieves crucial insights into the performance of 3D printable polymer-lunar regolith composites and SMP performance in LEO. The knowledge
gained from these studies will expand the capabilities of human space travel, paving the way for the creation of robust, adaptable, and innovative materials for applications in space technology
Computational Investigations of Coenzyme F430 Biosynthesis and Radical S-Adenosyl-L-Methionine Enzyme Catalysis
No full textThis dissertation applies computational techniques to investigate two enzymatic systems: the structurally uncharacterized coenzyme F430 biosynthetic enzyme CfbCD and radical S-adenosyl-L-methionine (RS) enzymes. CfbCD is of particular interest due to its role in synthesizing the essential Ni-containing coenzyme F430, which is bound in the active site of methyl-coenzyme M reductase (MCR)—the enzyme catalyzing the terminal step of methanogenesis. Attempts to engineer methanogenesis into heterologous hosts more amenable to metabolic engineering have been hindered by challenges such as the functional expression of CfbCD, likely due to its unusual and partially unresolved chemistry, as well as its implied structural complexity as a member of the famously complex nitrogenase superfamily. In this work, density functional theory (DFT) and molecular dynamics (MD) simulations are employed to probe the CfbCD reaction mechanism, the structure of its uncharacterized catalytic intermediate, and its protein dynamics. These studies give insight into the catalytic mechanism, support characterization of experimentally observed intermediates, and identify putative binding pockets, catalytic residues, and strong evidence for conformational cooperativity between active sites. Regarding RS enzymes, we build on prior work by Dr. Patrick Donnan, who sought to structurally characterize the canonical intermediate Ω, a key conserved radical initiation species in diverse RS transformations across all domains of life, and intermediates I and II in the catalytic cycle of the noncanonical RS enzyme Dph2 from the diphthamide biosynthetic pathway. While previous studies proposed organometallic structures for Ω and intermediate I containing Fe–C bonds, this study applies broken-symmetry DFT (BS-DFT) to these organometallic models and simple near-attack conformers (SAM-NAC) of [4Fe–4S]-bound S-adenosyl-L-methionine, finding that in both cases SAM-NAC models are more consistent with available spectroscopic data
Real-time Estimates of Logging Equipment Carbon Emissions in the Southeastern United States
No full textWhole tree harvesting using mechanized equipment is widely practiced in Southeastern U.S. forestry, yet limited field data exist on exhaust emissions under real-world conditions. This study addressed this gap by measuring carbon dioxide (CO₂) and carbon monoxide (CO) emissions from active logging machinery using Portable Emissions Measurement Systems (PEMS). Emissions were evaluated across factors including Diesel Exhaust Fluid (DEF) usage, machine type, engine power group, activity type, grapple size, and transmission type. DEF-equipped machines emitted 16.93 g/kWh less CO₂ (p < 0.001) and 0.108 g/kWh less CO (p < 0.001) on average than non-DEF machines. Among equipment types, feller bunchers recorded the highest CO₂ emissions (345.18 g/kWh), followed by skidders (304.63 g/kWh), with loaders emitting the least (221.50 g/kWh). Regression analysis confirmed that loaders emitted 116.98 g/kWh less CO₂ (p < 0.001) than feller bunchers, while skidders emitted 56.20 g/kWh less (p < 0.001). Loaders also maintained the lowest average CO emissions (0.115 g/kWh), compared to 0.008 g/kWh and 0.002 g/kWh for feller bunchers and skidders, respectively. CO₂ emissions were highest during loaded skidding and lowest during idle. Mid-powered machines (165–184 kW) exhibited the highest CO₂ output, while higher-powered units (185–203 kW) were more carbon efficient (p < 0.001). Transmission type also influenced emissions skidders equipped with hydrostatic drives emitted less CO₂ than those using continuously variable transmissions (p < 0.01). These results demonstrate the effectiveness of Tier 4 standards in reducing emissions and underscore the influence of equipment characteristics and operational factors on carbon outputs during logging
Evidence of Heritable Luteal Insufficiency in Portuguese Water Dogs: A Pedigree-Based Investigation
Full text linkReproductive failure and pregnancy loss is devastating for dog owners both financially and emotionally. While infectious agents are the most common causes of canine pregnancy loss, hormonal aberrations are insidious as there are often no accompanying symptoms. Hypoluteoidism results in insufficient serum progesterone (P4) concentrations, causing spontaneous abortion as the first symptom. This condition has been documented in dogs, but the underlying pathophysiology is poorly understood. The current literature supports the basis of hypoluteoidism as genetic, although this has not been proven. This is supported by the fact that sporting and working dog groups have lower progesterone concentrations on average throughout gestation compared to other breeds. Devastatingly, there is no genetic test available for early identification of hypoluteoidism. Our clinical Theriogenology team has identified a pedigree of Portuguese Water Dogs (PWDs) in which multi-generational hypoluteoidism has been confirmed. Specifically, two affected individuals (a dam and daughter) have been identified. The two affected individuals were monitored throughout two pregnancies each, in which endogenous serum P4 fell below baseline prior to Day 63 of gestation. Fortunately, as a result of specialty level care, these pregnancies were successfully managed and maintained using a synthetic progestin and intense monitoring, resulting in four successful litters. Interestingly, two unaffected females have also been also identified, which allows us a unique opportunity to investigate the heritability pattern and possible underlying physiology. Using canine whole genome sequencing technologies, and in collaboration with geneticists from the Department of Pathobiology, our team is aiming to identify a causative genetic mutation for hypoluteoidism. Long-term, with a genetic marker identified, we can develop a diagnostic test to screen at-risk individuals, without necessitating a specialist, and identify high-risk pregnancies to ensure proper care during gestation. Luteal phase deficiency (LPD) is the synonymous disorder in humans, and there is currently no definitive diagnosis in women with this condition. Thus, outcomes may be translational and will serve as a springboard to understand of the complex pathophysiology behind premature luteal failure in the canine, and potentially human, species
Disentangling the Interplay: Caregiving Styles, Self-Efficacy, Academic Entitlement, and College Students’ Academic Engagement
No full textThe purpose of the study is to explore the relationship among caregiving styles, self-efficacy, academic entitlement, and academic engagement of college students. Drawing on Bandura’s Social Cognitive Theory, the study seeks to unravel the interplays among these factors. By doing so, the study aims to enrich the existing body of literature. Additionally, I expect the findings to provide insights for educators, educational professionals, and policymakers to better understand factors that impact students’ engagement so as to inform effective pedagogical practices to facilitate college students’ academic success.
Academic engagement is widely acknowledged as critical for students’ academic success. Although there has been increasing attention drawn to college students’ class involvement, there remains a paucity of research exploring how caregiving styles, self-efficacy, and student entitlement collectively impact student engagement. Previous research has often focused on a singular aspect of caregiving styles, leaving a holistic examination of caregiving style factors relatively unexplored. Additionally, there has been controversy as to the impact of authoritarian caregiving styles on student engagement, and limited evidence regarding the permissive caregiving style on academic engagement. Furthermore, gaps exist in how self-efficacy and entitlement mediate the relationship between specific caregiving styles and academic engagement. Nevertheless, inconsistent results remain as to the relationship between self-efficacy and academic entitlement. Moreover, most of the research has focused on caregiving styles’ impact on children and adolescents, with far less attention to how caregiving styles affect college students’ engagement. Hence, it is important to understand how these factors contribute to college students’ academic engagement so as to facilitate their learning success.
A hypothesized model was generated based on research questions and previous empirical studies. A total of 1,199 students participated in this study. All participants completed an online survey hosted via Qualtrics. The survey packet consisted of a total of 98 items with a demographic questionnaire, the Parenting Style and Dimensions Questionnaire, the Self-Efficacy for Learning and Performance Subscale from Motivation Strategies Learning Questionnaire, the Academic Entitlement Questionnaire, and the Student Engagement Scale. Structural Equation Modeling was employed as the primary data analysis method.
The results indicated that the authoritative caregiving style had a direct, significant positive effect on academic engagement, while the authoritarian caregiving style had a direct, significant negative effect on engagement. The permissive caregiving style didn’t show a significant effect on engagement. Self-efficacy was identified as a strong positive predictor of academic engagement, whereas academic entitlement was negatively correlated with engagement. As to the impact of caregiving style on self-efficacy and academic entitlement, only the permissive caregiving style significantly negatively impacted self-efficacy. Neither authoritative nor authoritarian styles showed a significant effect on self-efficacy. However, all three caregiving styles had significant positive effects on academic entitlement. Self-efficacy was identified as a significant mediator in the relationship between permissive caregiving style and student academic engagement, while academic entitlement acted as a significant mediator across all caregiving styles. Lastly, self-efficacy was found to be a significant negative predictor of academic entitlement. The study concluded by discussing the findings in the broader literature and highlighting the pedagogical implications