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Influence of Ag Nanoparticle Loading on Dye and Salt Removal Efficiency of Graphene Oxide Membranes
No full textNano-engineered materials, particularly two-dimensional (2D) nanomaterials and advanced desalination membranes, are poised to play a transformative role in addressing global water scarcity through efficient purification technologies. Among these, graphene oxide (GO)-based nanofiltration membranes have emerged as promising candidates due to their high mechanical strength, tunable surface chemistry, and exceptional molecular sieving properties. However, despite these advantages, the practical deployment of GO membranes in aqueous environments is hindered by critical limitations, most notably, structural swelling and interlayer expansion due to water intercalation. This phenomenon compromises the long-term selectivity and ion/dye rejection performance of the membranes. To mitigate these drawbacks, the incorporation of nanoparticles such as silver nanoparticles (Ag NPs) has been explored to enhance membrane stability, reduce swelling, and improve overall filtration efficiency. Ag NPs not only stabilize the GO structure through interlayer interactions but also contribute antimicrobial and fouling-resistant properties, making them ideal candidates for wastewater treatment applications. While numerous studies have demonstrated the performance enhancement of GO membranes upon Ag NP incorporation, a systematic understanding of how Ag NP concentration affects rejection performance, particularly for organic dyes, remains incomplete. This research aims to address that gap by investigating the role of Ag NP loading concentration on the structural and functional properties of GO membranes. GO–Ag NP composite membranes were fabricated on polyether sulfone (PES) substrates via vacuum-assisted filtration, utilizing a series of Ag NP loadings to evaluate their influence on nanofiltration performance. A comprehensive suite of characterization techniques was employed: X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess changes in interlayer spacing (d-spacing) and pore morphology; UV-VIS spectroscopy was used to quantify dye concentrations in the feed and permeate, enabling calculation of rejection efficiency; Fourier-transform infrared spectroscopy (FTIR) provided insight into chemical interactions between Ag NPs and GO functional groups; contact angle measurements via a Ramé-Hart goniometer quantified surface wettability, while dead-end filtration experiments evaluated salt and dye rejection behavior. The results revealed that Ag NP concentration modulates the pore size and interfacial properties of the GO membrane, directly impacting its permeability and selectivity. Increased Ag NP content led to changes in hydrophilicity and d-spacing, influencing both the water transport rate and the membrane's ability to reject charged and neutral species. This study identifies optimal nanoparticle loading conditions that balance flux and rejection efficiency, offering a pathway for designing GO-based nanofiltration membranes with tailored performance for specific wastewater treatment scenarios
Novel Counterflow Reactor for Continuous Templated Synthesis of Semiconductor Nanocrystals
No full textSemiconductor nanocrystals are a class of materials exhibiting size-dependent and tunable optical and electronic properties. This allows for many different applicational usages such as display devices and biological. The commercial development of these nanocrystals requires the advancement of synthesis techniques that are scalable, as well as being both economical and environmentally friendly; simultaneously allowing for the control of the nanocrystals such as size, shape, and size distribution. The typical technique is the hot injection method which involves rapid injection of an organometallic precursor into a hot coordinating solvent where the nanocrystals grow as a function of time. Trying to commercialize this has many limitations including incomplete mixing, high cost, flammability and toxicity of the reactants, as well is an operator intensive process. Templated synthesis of nanocrystals has distinct advantages, including the ability to have precise control over the nanoparticle features such as the particle size, shape, and size distribution. The template consists of a stable microemulsion formed by the self-assembly of an amphiphilic block copolymer in the presence of both a polar and non-polar solvent. This microemulsion contains a group-II salt in the dispersed phase which is then contacted with a group-VI hydride gas reactant inside the nanodomains of the microemulsion. This technique is easily scalable to a continuous synthesis utilizing a packed bed reactor operated in counterflow where the gas phase reactant enters from the bottom of the reactor while the microemulsion is fed from the top of the reactor causing a concentration gradient allowing for the most efficient and cost-effective use of the reactants. The development of this reactor is explored as well as the optimization of the process by exploring different packing sizes, gas flow rates, as well as the startup conditions for the reactor. To increase the optical properties of the nanoparticles synthesized with this technique a post-processing technique involving both extraction from the microemulsion and functionalizing the nanocrystals surface was developed
How Much is My Future: A Quantitative Analysis of Tuition Deregulation
No full textBackground: In 2003, the Texas Legislature designed, proposed, and implemented a house bill created to curb college tuition growth. House Bill 3015 gave public universities the power to set their respective tuition. However, after two decades of implementation, the House bill has continued to face scrutiny, and its lasting impact remains essential to understand. Purpose: This study aims to expand the literature on the effects of House Bill 3015 on the impact of student access on historically underrepresented students. Specifically, this study seeks to measure the impact of House Bill 3015 on Black and Hispanic student enrollment at Texas public bachelor's degree student awarding institutions. Specifically, this study aims to answer the following research question: How did House Bill 3015 impact enrollment for historically underrepresented students (Black and Hispanic Students) at Texas Public Higher Education Institutions? Methods: To satisfy the design of the quantitative model, non-identifiable data from the National Center for Education Statistics and the Integrated Postsecondary Education Data System are included in this study. The data collected in this study represent student access (i.e., enrollment) and the cost of attendance values of both Texas public universities (treatment) and comparable public universities (control). This study employs a difference in difference model(s) to examine their impact on enrollment for Black and Hispanic students. Results: Comparison descriptive models demonstrated that the rise in the price of attendance matched and even surpassed the increase in peer and similar universities. Conclusion: Differences in difference models analyzed various interactions and showed that the impact of HB 3015 on enrollment patterns for Hispanic and Black students was mixed
A Critical Quantitative Analysis of Factors Influencing Latina Degree Completion and Salary in STEM Fields
No full textBackground: Latina STEM students face discrimination as women and Latin* people. However, eight percent of all STEM degrees awarded are earned by Latinas. What are the driving factors shaping their completion of these degrees? The experiences of successful Latinas in STEM have predominantly been researched using qualitative methods. However, these factors have not been explored quantitatively. Moreover, quantitative studies on Latina in STEM have not used a critical perspective. In this three-manuscript dissertation, I examined how institutional- and student-level factors influence Latina degree completion and post-graduate salary outcomes through a critical and asset-based lens. By addressing these interconnected factors, this study provides a comprehensive understanding of the challenges and opportunities facing Latina students in STEM that informs the development of effective interventions to support their academic success and career advancement. Purpose: The purpose of these three studies was to investigate the institutional-level factors influencing STEM degree completions among Latina students at public, four-year institutions, to uncover the student-level factors affecting the likelihood of Latinas completing STEM degrees, and to explore the relationship between institutional- and student-level factors to post-graduation salary outcomes using nationally representative datasets. Methods: In this study, I employed multiple linear regression, logistic regression, and hierarchical linear regression in conjunction with QuantCrit guided by LatCrit, Community Cultural Wealth, and CritQuant guided by Contextual Mitigating Factors Analysis, for research questions one, two, and three, respectively. Results: In study one, the number of Latina faculty, enrollment size, price, and average grant/scholarship financial aid emerged as significant institutional-level predictors of Latina STEM degree completion. In study two, socioeconomic status, mothers level of education, fathers level of education and participating in a college prep program were significantly related to the likelihood of a Latina obtaining a STEM degree. In study three, mother’s educational level, children, marital status, Carnegie classification, and attending community college for financial reasons were significant predictors of salary for Latina STEM graduates. Conclusion: This dissertation revealed that institutional factors like Latina faculty presence and financial aid, alongside individual socioeconomic and familial influences, impact Latinas' STEM degree attainment and post-graduation salaries
Structural Characterization of the A-domain of Human von Willebrand Factor (vWF) and the αI-domain of Human Integrin αDβ2
No full textDuring vascular injury, the circulating platelets move to the exposed site of the injury and begin the healing process. They do this by adhering to plasma von Willebrand factor (vWF), a circulating plasma protein secreted by endothelial cells, through the platelets’ cell surface glycoprotein called glycoprotein Ibα (GPIbα). While vWF binds platelets at one end, it allows for the platelet aggregation at the site of injury by being immobilized to the exposed sub-endothelial collagen of the damaged tissues. As such, vWF is very integral to maintaining the body hemostasis through the formation of “hemostatic plug” and an aberration to vWF functioning has been linked to blood disorders like thrombosis and hemorrhage. Despite its large, multi-domain nature, three contiguous domains in the N-terminus, the A domains, consisting of the A1, A2 and A3 subdomains, is the most crucial region in the vWF-GPIbα interaction. While the A1 domain contains the binding site for GPIbα, the A3 domain is responsible for immobilization to the subendothelial collagen and the A2 domain is largely responsible for platelet adhesion and contains the cleavage site for ADAMTS13. Despite this understanding, little is known of the three-dimensional structural model of the A domains and the intricacies of the internal dynamics of the structural interplay between the three subdomains towards maintaining hemostasis in health or otherwise. We, therefore, employed a combination of Small Angle X-Ray Scattering (SAXS) and cryogenic electron microscopy (CryoEM) techniques to model the in-solution structure of the human vWF A-domains (A123 domains) and its gain-of-function (GOF) mutant. Our finding revealed that the A1, A2 and A3 subdomains of the A-domain of the vWF WT exists as a triad with the A1 domain folding back to interact with both the A2 and A3 domains. Conversely, the GOF mutant assumes a linear arrangement of the three A-domains. Our cryoEM structure also revealed an N-terminal protrusion that folded into a globular protein on the A1 domain, which we believe is the long polypeptide (Lp) reported to stalilize the A1 domain and decrease its binding activity for platelets. Cell surface receptors are transmembrane proteins on the surface of cells and play a key role in cellular signaling necessary for biological processes such as cell adhesion, thrombosis, cell migration and trafficking, and immune cells functioning. Cell surface receptors are broadly categorized into G-protein-coupled receptors (GPCRs), Receptors Tyrosine Kinase (RTKs), Ligand-gated ion channels, Toll-like receptors and Integrins based on how they prosecute their signaling roles. Integrin, a mechano-receptor, is perhaps one of the most important cell surface receptors for their roles in long range bi-directional signaling, cell adhesion and cell trafficking. Though the roles of leukocyte-specific receptors also known as β2-integrins (αLβ2, αMβ2, αXβ2, and αDβ2) in the biological function of human cells have been well established, little is known about the effect of divalent metal cations on its newest addition – the αDβ2 integrin. Like other β2-integrins, αDβ2 integrin has a ligand binding domain called αI-domain with a recapitulatory role and a metal-ion dependent adhesion site (MIDAS) motif critical for metal binding. While I-domains are preferentially activated by Mg2+, findings have shown that they also bind other divalent cations. Therefore, we determined the crystal structure of the I-domains of the αDβ2 integrins grown in divalent cations and investigated the roles of divalent cations, including Mg2+, Mn2+, Cd2+, Ni2+, and Zn2+ as well as Malic acid on the geometry of the MIDAS motif. Our findings show that the divalent cations have diverse effects on the geometry of the amino acid residues and water molecules that constitute the MIDAS site. It also revealed information about the free energy (ΔGexc) of exchange of Mg2+ with some divalent metal M2+, with Ca2+ having a net positive ΔGexc and Ni2+ having a net negative ΔGexc depicting how unfavourable it is for Ca2+ to displace Mg2+ from the MIDAS and how favorable it is for Ni2+ to do the same, respectively. Like the leukocyte-specific integrins, collagen-binding integrins are another subclass of integrins with roles in cell adhesion and trafficking among other biological roles. These integrins are so named because they possess a MIDAS region that recognizes the GFOGER motif of the collagen peptides, which is crucial to the binding to integrin by coordinating to the metal ions. While the X-ray crystallography structures of the αI-domain of integrins α1β1 and α2β1 have been established, there is no known structure for α10β1 and α11β1. The lack of known structures for the latter two might not be unconnected to the lack of solubility of the protein in bacterial expression system. Here, we first predicted the model structures of the four collagen receptors using Alphafold and postulated, based on the predicted structures, that glycosylation is important to the biological structures and functions of collagen-receptors. Since bacteria are not capable of glycosylation, it is possible that the existing structures of the I-domain for human integrins α1β1 and α2β1 are not factually correct since the structures cannot account for the possible effect of glycosylation. Here, we report the cloning and expression of soluble αI-domains of human integrin α2β1, α10β1, and α11β1 – in the mammalian expression system for future expression optimization and both structural and functional studies
A Latent Profile Analysis and Longitudinal Examination of Sleep among Children with a History of Maltreatment
No full textChildren adopted from foster care are at increased risk for sleep disturbances and emotional difficulties, yet little is known about how distinct sleep patterns relate to their emotional functioning over time. The present study aimed to (1) identify latent sleep profiles among children adopted from foster care, (2) explore the influence of maltreatment, foster care history, and parent-child sleep interactions on profile membership, and (3) investigate longitudinal associations between sleep profiles and emotional functioning, including depressive and anxiety symptoms. Participants included adoptive foster parents of 362 children (Mage = 5.50 years at Time 1, T1), a subsample of which were assessed approximately four years later at Time 2 (T2; n = 86; Mage = 9.59). At T1, parents completed an online survey assessing their child’s sleep health, foster care history, and maltreatment experiences. Sleep disturbances were assessed using the Child Sleep Habits Questionnaire (CSHQ), and parent-child interactions around sleep were measured with the Parent-Child Sleep Interactions Scale (PSIS). Emotional functioning was evaluated using the Mood and Feelings Questionnaire - Short Form (MFQ) and the NIH Toolbox Fear-Over Anxious Survey and Fear-Separation Anxiety Survey. The T2 survey included the same anxiety and mood measures. Latent sleep profiles were identified using latent profile analysis (LPA) based on T1 sleep variables. Five sleep profiles were identified, characterized by: Good Sleep (GS; 36.0% of the sample), Sleep Onset Problems (SOP; 16.0%), Pre-Sleep/Bedtime Problems (PSBP; 12.9%), Severe Sleep Disturbance (SSD; 12.9%), and Broad Behavioral Sleep Problems (BBSP; 8.6%). Notably, a majority of the T1 sample (64%) fell into one of the four disturbed sleep profiles. Across all four disturbed sleep profiles, sleep problems scores were significantly elevated compared to both normative and clinically referred children, reinforcing the severity of sleep disruptions in this population. Additionally, maltreatment and foster care history variables significantly predicted sleep profile membership. Older age at the time of adoption, in-utero drug exposure, and exposure to domestic violence were the strongest predictors of membership in a disturbed sleep profile. Parent-child sleep interactions, particularly PSIS sleep conflict and sleep dependence, were also associated with all disturbed sleep profiles. Longitudinal analyses revealed an overall reduction in depressive and anxiety symptoms from T1 to T2 and these trajectories of symptoms did not differ by sleep profile over time. Compared to the GS group however, children in the PSBP and BBSP groups had significantly higher depressive symptoms at both time points and children in the PSBP, BBSP, and SSD groups had significantly higher separation and generalized anxiety symptoms at both time points. Overall, findings highlight the importance of addressing sleep disturbances as part of a comprehensive intervention strategy for children even after they leave foster care, especially older children, and children exposed to in-utero drug exposure and domestic violence. Interventions specifically targeting parent-child interactions around sleep may be particularly helpful for reducing sleep and emotion-related risk
Quantum Assisted Optimization and Machine Learning for Coordinated Power and Hydrogen System
No full textThe rapid increase in green energy adoption and the global commitment to zero carbon emissions have catalyzed a transformative interest in hydrogen as a sustainable energy carrier. Hydrogen’s ability to store excess renewable energy and provide carbon-free energy solutions has led to an explosion in research and development efforts. This growing demand for hydrogen systems drives the need for advanced optimization models that can coordinate energy distribution effectively. Our dissertation aims to address this challenge by developing a comprehensive framework that maximizes system profitability while integrating hydrogen storage and distribution. The coordinated operation of energy systems, particularly those involving hydrogen, introduces complexities that require both innovative modeling and computational efficiency to realize the potential of these renewable energy sources. Traditional optimization methods struggle to handle the complexities of these models due to the nonlinearities and mixed-integer nature inherent in hydrogen and energy system operations. The interplay between hydrogen production, storage, and power distribution adds layers of complexity that cannot be adequately addressed using conventional techniques. Recognizing these challenges, our research focuses on a novel formulation that employs Benders decomposition to manage the intricate structure of the mixed-binary nonlinear optimization problem. By splitting the problem into a pure binary master problem and a linear subproblem, we simplify the computation and enhance the model's solvability. This decomposition approach provides a structured method to optimize energy flows, storage strategies, and resource allocation, paving the way for more efficient and practical energy system designs. Furthermore, the advancement of quantum annealing technology presents a promising avenue for solving complex pure binary problems. Quantum annealing has the potential to address computational bottlenecks by efficiently finding solutions within polynomial time, making it a powerful tool for the master problem in our Benders decomposition framework. Our dissertation leverages this technology to accelerate the solution process, demonstrating the viability of quantum-assisted optimization in real-world energy applications. By integrating quantum and classical computing methods, our approach offers a scalable solution for the coordinated operation of hydrogen and power systems. This research not only advances the field of energy optimization but also contributes to the broader goal of achieving a sustainable and carbon-neutral future through innovative, high-performance computational strategies
Investigation of Nitric Oxide Tolerance in Diesel Oxidation Catalysts through Kinetic Characterization
No full textLow-temperature combustion diesel engines enhance fuel efficiency and reduce emissions of nitrogen oxides (NOx) and particulate matter (PM), but at the expense of increased production of carbon monoxide (CO) and unburned hydrocarbons (HC). Platinum group metal (PGM) alloys, such as Pt or Pd, are often employed as diesel oxidation catalysts (DOCs), but they suffer from inhibition by CO and NO. To address the challenge of low-temperature CO oxidation activity in the presence of NO, Cu promoted supported PGM catalysts are of interest. Computational catalysis methods identified Pd/Cu and Pt/Cu alloys could be better than Pt/Pd for CO oxidation at 150°C. We measured CO oxidation rates on Pt/Pd, Pt/Cu, and Pd/Cu samples over a wide range of conditions. Twenty-three global CO oxidation kinetic models were considered and evaluated, distinguished by different CO oxidation rate-determining steps, site oxygen concentration, and the presence of NO in the feed. Parameter fit metrics were used to select the best-performing models, providing insight into the origins of the observed kinetic behaviors. The kinetic relationships for the Pt/Pd catalyst align with previous studies, showing NO competes with CO for adsorption sites and inhibits CO oxidation. The Pd/Cu catalyst exhibits significantly better performance than Pt/Pd in the presence of NO due to minimal NO adsorption. In contrast, Pt/Cu catalyst demonstrates exceptionally high low-temperature CO oxidation activity and the lowest light-off temperature despite similar NO adsorption as the Pt/Pd catalyst. The model confirms that the superior low-temperature activity is attributed to an interfacial reaction of CO from a Pt site with O from a Cu site. This work reinforces the benefits of using computational catalysis methods for discovering new alloys for making sustainable fuels and chemicals including renewable natural gas, green methanol, and green ammonia
Factor Structure of the Newest Vital Sign In People With HIV and Its Association With Health-Related Self-Management
No full textIntroduction: Low health literacy is prevalent in healthy and clinical populations, and plays a role in health behaviors and outcomes. The Newest Vital Sign is as a brief, performance-based test that shows evidence of reliability and validity when used to measure health literacy in English speaking healthy adults and people with HIV (PWH). However, the underlying factor structure of the NVS has been inconsistent across research in different age ranges, countries, and clinical populations. Therefore, the aim of the current study was to confirm the factor structure of the NVS in healthy, English-speaking adults and PWH and examine its association with health-related self-management in PWH. Methods: The study sample consisted of 580 participants that included a healthy, English-speaking group (n = 270) and PWH (n = 310). All participants completed the NVS, Perceived HIV Self-Management Scale (PHIVMS), Beliefs Related to Medication Adherence (BERMA) medication management subscale, and a neurocognitive battery. Confirmatory factor analysis (CFA) was used to test one, two, and three factor models for the items on the NVS. Results: A revised five-item, single factor solution for the NVS best fit the data in both the healthy, English-speaking and PWH samples. A multiple regression predicting health-related self-management from the total score on the NVS and the covariates of education and global cognition was significant (R2 Adjusted = .06, p = .002). However, none of the variables emerged as an independent predictor of health-related self-management (ps > .05). Conclusion: Findings from this study provided evidence of construct validity for the Newest Vital Sign as a measure of health literacy in healthy, English-speaking adults and PWH. The results indicated an association between education, cognition, and scores on the NVS with health-related self-management in PWH. Future research is needed to examine measurement invariance of the NVS along with other psychometric properties (e.g., test-retest reliability) across other clinical populations
Link Between Home and School: A Case Study of Urban High School Parental Involvement
No full textBackground: Parental involvement is one initiative that many researchers agree increases the academic performance of all students, regardless of their economic background or ethnicity. This is particularly significant for urban students of color because it helps bridge the achievement gap between them and their White counterparts. However, traditional definitions of parental involvement typically include teachers' perspectives alone Purpose: This dissertation explored the dynamics of parental involvement in urban high schools and focused on how parents understand, define, and engage in their children’s education. Research Questions: 1. How do urban high school parents understand and define parental involvement? 2. How do urban high school parents describe their participation in their children's education? 3. How do parental involvement activities translate into academic success for urban high school students? 4. How do urban high school parents describe their relationship with school officials? 5. To what extent do urban high school parents believe school officials recognize their funds of knowledge? 6. How do urban high school parents describe school practices that promote cross-cultural awareness and understanding? Methods: Using a qualitative research design, data were collected through online survey questions with a diverse group of parents and school officials from multiple urban high schools utilizing Qualtrics. Results: The findings reveal that parental involvement in urban high schools is multi- faceted and shaped by various factors, including cultural background, socioeconomic status, life experiences, and individual beliefs about education. The study identified several key themes. Parents often define parental involvement beyond traditional metrics, such as attendance at school events, encompassing broader roles like advocating for their children and providing academic and emotional support at home. Many parents felt that school officials undervalued their contributions. The study highlighted parents' challenges in engaging with school systems that may not fully recognize or accommodate their cultural and experiential knowledge. Conclusion: This dissertation concluded with recommendations for both parents and school officials. Parents should proactively share educational and cultural expertise with the school and strive to build relationships of trust by maintaining regular communication with the school. School officials should better recognize and integrate the contributions of urban high school parents, implementing strategies for more inclusive and culturally responsive approaches to parental involvement