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Improving Thermal and Disease Resilience in Caribbean Corals through Symbiont Associations: Implications for Coral Intervention Strategies
No full textCoral reefs are tremendously valuable ecosystems, but have declined globally due to multiple stressors. Reef-building corals (order Scleractinia) form obligate symbiosis with unicellular dinoflagellates (family Symbiodiniaceae), underpinning the success of these organisms in shallow tropical seas worldwide. Importantly, different algal symbiont types can modulate coral host traits such as thermal tolerance, growth rate, and disease resistance. This dissertation provides a framework to increase thermal tolerance and modulate disease resistance in the coral host through symbiont manipulations. Chapter 1 presents an introduction to the main themes of the dissertation. Chapter 2 tests how 12 Caribbean coral species alter their symbiont community following a controlled bleaching and recovery experiment to varying amounts of heat stress. Then, Chapter 3 quantifies the drivers of thermal tolerance in 172 colonies of Acropora palmata, a key reef building coral, from four nurseries representing 125 unique genets harboring both Symbiodinium fitti and the heat tolerant Durusdinium trenchii. Next, Chapter 4 evaluates the increase in thermal tolerance and growth dynamics of A. palmata when hosting Durusdinium versus Symbiodinium. Then, Chapter 5 uses algal symbiont cultures to examine symbiont phenotypes outside the coral host in response to stony coral tissue loss disease (SCTLD). Finally, Chapter 6 refines symbiont cultures as model systems by assessing the size of the SCTLD pathogen through exposing five symbiont species to six different seawater treatments. Chapter 7 describes the broader implications of this dissertation and identifies avenues of future work. Taken together, algal symbionts can alter key phenotypes in corals, which can be studied within and without the coral host. As many corals exhibit remarkable symbiont flexibility, algal symbiont manipulations, provide opportunities for scalable intervention efforts on many coral species that can increase their resilience to continued climate stressors.</p
The Epidemiology of the Long-term Care Needs of Older Adults in the United States: An Analysis of the HERO CARE Survey and National Health and Aging Trends Study
No full textThe 65 and over population will more than double by 2050 and become more racially and ethnically diverse. With the projected demographic shift, supporting older adults with long-term care (LTC) needs is a public health priority. LTC includes long-term services and supports (LTSS) designed to help with activities of daily living (ADLs) and instrumental activities of daily living (IADLs). First, we aimed to evaluate the dynamic cross-sectional, autoregressive, and cross-lagged associations between the intensity of weekly care hours, total LTC needs and total unmet LTC needs among community-dwelling older adults aged 65 and over in the United States who participated in the National Health and Aging Trends Study. We applied a random intercept cross-lagged panel model and found reciprocal associations between intensity of weekly care hours and total number of LTC needs in later years. Second, we used data from the HERO CARE survey to 1) characterize Veterans across levels of hierarchy of ADL and IADL problems, 2) compare Veterans across degree of need for help, and 3) identify the prevalence of ADL and IADL combination patterns. Our findings demonstrate that Veterans are demographically and clinically different by the hierarchy of ADL and IADL impairment and degree of need for help. Third, we aimed to 1) describe the prevalence of being homebound by race, ethnicity and rurality among Veterans with ADL or IADL problems, 2) describe the characteristics of homebound and non-homebound Veterans, 3) evaluate the prevalence of ADL and IADL unmet needs overall and by homebound status, race, ethnicity, and rurality, and 4) evaluate the association between homebound status and ADL and IADL unmet need stratified by race, ethnicity, and rurality. Our findings show that homebound Veterans are more likely to experience unmet needs and highlight the need for more targeted research on minority Veterans. Overall, this dissertation identified pathways, patterns, and prevalence of LTC needs and unmet needs to provide valuable information to align LTSS with the needs of older adults and those of their caregivers. </p
Tools to Engineer and Modulate π-Conjugated Superstructures at Equilibrium and Non-Equilibrium States
No full textSupramolecular assemblies are ubiquitous in biological systems and often regulate vital complex cellular tasks. Nature has mastered the ability to engineer sophisticated hierarchical assemblies with emergent behaviors and structure-function properties. Supramolecular chemistry, drawing inspiration from the complex assemblies in biological systems, attempts to mimic nature's proficiency in creating complex materials through noncovalent interactions. This field has significantly advanced the past two decades, offering a plethora of supramolecular systems that can self-organize into tailored architectures under thermodynamic control. Yet, biological functionalities often emerge from configurations that transcend these global energy minima, venturing into non-equilibrium states where kinetic traps and metastable assemblies exist. Recent decades have seen a concerted effort to navigate the potential energy landscape with molecular precision, enabling the reconfiguration of building blocks from equilibrium to dynamic, nonequilibrium states. This exploration has been pivotal in developing materials that exhibit emergent behaviors akin to those found in living systems, which constantly consume energy to maintain non-equilibrium states. Amongst the numerous building blocks capable of self-assembly, π-conjugated chromophores stand out for their capacity to transfer energy and conduct electricity when doped, showcasing the potential for creating materials that respond dynamically to environmental stimuli. This thesis leverages such building blocks, focusing on naphthalene diamide and porphyrin systems, to generate supramolecular systems with manipulable structure-function properties in different thermodynamic states. </p
Dissecting the Cellular and Molecular Mechanisms in Venous Remodeling and Arteriovenous Fistula Maturation
No full textAs of 2023, approximately 800,000 people suffer from End Stage Renal Disease (ESRD) in the United States, with nearly 70% relying on hemodialysis through a vascular access as their renal replacement therapy. The preferred way to establish vascular access is through an arteriovenous fistula (AVF), which are surgically created by anastomosing a vein to a nearby artery. When the vein is connected to the arterial circulation, it is exposed to supraphysiological flow rates (more than 20x the normal venous flow), wall shear stress, and an increased oxidative load. The venous adaptation to these conditions, known as venous remodeling, results in a thicker wall and larger luminal diameter. However, the molecular mechanisms behind this remarkable adaptation remain unclear. After surgical creation, the AVF has two possible outcomes; 1) AVF failure, defined by flow rates below 600mL/min, and a diameter of less than 6mm or 2) AVF maturation which means flow rates above 600mL/min, larger diameter and functioning as a suitable conduit for repeated vascular access. Unfortunately, 40-50% of all AVFs fail to become viable for hemodialysis without an intervention, exposing an already vulnerable patient population to additional surgical procedures and limiting their access to lifesaving hemodialysis sessions. AVF failure is associated with stenosis or narrowing of the venous lumen which is secondary to medial fibrosis of the vein and neointimal hyperplasia.</p
Religiosity as Moderator of the Relationship Between Religious Discrimination and Quality of Life
No full textThis dissertation explores the prevalence and impact of religious discrimination toward Muslim nurses working in the United States, employing a comprehensive analysis that incorporates the Stress and Coping Model and the Intersectionality Framework. Data collection started in December of 2023, during a period marked by a significant surge in Islamophobia, influenced by the ongoing conflict between Palestine and Israel. This dissertation aimed to investigate how this heightened environment affected the experiences of Muslim nurses. The findings reveal notable levels of perceived religious discrimination, with 82% of the sample reporting medium to high level of religious discrimination. This proportion suggests that approximately 4 out of every 5 Muslim nurses experience significant religious discrimination in their workplace. This dissertation identified that individual factors such as age, gender, and years in the U.S., along with professional factors like clinical experience and location, significantly influenced perceptions of discrimination. Positive religious coping strategies were found to moderate but not mitigate the effects of religious discrimination on work-related quality of life, contradicting some previous research findings. Overall, this research highlights the complex and multifaceted nature of religious discrimination faced by Muslim nurses, underscoring the need for ongoing dialogue, policy development, and targeted interventions to promote an inclusive and equitable work environment in the health care sector.</p
Multisector Impacts and Responses to Extreme Heat and Energy Affordability in a Changing Climate
No full textThe multisector impacts of extreme heat are a growing global threat. Across the world, diverse actors are responding to these challenges, but knowledge on who is responding and what strategies they deploy is lacking. Within developed, high income countries like the United States, the interactions between the building and energy sectors are particularly important for modulating residential extreme heat exposure. Previous research has documented how households forgo comfortable thermal environments at home and/or critical expenses to maintain an affordable energy bill. However, these studies have inadequately captured cumulative exposures to extreme heat and have failed to consider how residential heat exposure can interact with energy burden to influence intersectional risks. Although not explicitly designed as heat responses, energy assistance programs are being retooled and expanded to help households manage both high energy bills and extreme temperatures at home, but information on the efficacy of the most common response, energy bill assistance, is virtually nonexistent. Through three research chapters, this dissertation unites the fields of equity-oriented adaptation science and multisector dynamics to addresses these key knowledge gaps. I leverage a mixed-methods approach that spans disciplines, blending systematic review, community-engaged research, machine learning, fuzzy-set qualitative comparative analysis, and statistics and econometrics. Combined, this dissertation provides a comprehensive overview of global to local responses to extreme heat, focusing on the interconnected housing–energy nexus.</p
Leveraging Bayesian Machine Learning to Elucidate Brain-Based Biomarkers of Cognitive Aging
No full textCognitive aging is characterized by normative change involving multiple neuropsychological domains. For some individuals, age-related decline crosses a threshold signaling the beginning of pathological decline. A wealth of potential predictors of negative cognitive aging have been proposed, including cerebrospinal fluid (CSF) and blood-based biomarkers of known neurological pathologies, novel biomarkers of the central and peripheral nervous systems, structural and functional magnetic resonance imaging, diffusion tensor imaging, arterial spin labeling, and a range of cardiovascular, metabolic, and neuroinflammatory indicators. This study sought to integrate the wide number of biometrics available by leveraging advancements in Bayesian machine learning for the purpose of identifying the most salient predictors of cognitive trajectories across multiple neuropsychological domains. Results suggest baseline neuropsychological functioning, global hypometabolism, morphometry, and CSF biomarkers are consistent predictors of decline. Additionally regional volumetrics and indicators of pathology burden demonstrated specificity to trajectories of memory and executive functions.</p
Phylogenetic History and Transcriptional Landscape of Giant Endogenous Viral Elements in Polar Microeukaryotes: Implications for Host Genomic Content, Functional Physiology, and Environmental Adaptation
No full textLarge double-stranded DNA viruses (phylum Nucleocytoviricota), also known as Nucleocytoplasmic Large DNA Viruses (NCLDV), are a group of eukaryote infecting ‘giant viruses’ with genomes over 2.5 megabase pairs (Mbp) and are characterized by their unprecedented genomic complexity. Recently, giant viruses were discovered to endogenize their DNA within the host, leaving signatures of Giant Endogenous Viral Elements (GEVEs) within a wide range of eukaryotic genomes. Little is understood about the functionality of these endogenous elements, and their roles in host physiology, and possibly adaptation. This study analyzed nine previously sequenced microeukaryote genomes for GEVEs using a customized bioinformatic workflow to assess viral diversity and specific virus-host interactions within the polar environments, and genomic contributions from endogenous elements. Through core gene analysis, four distinct viral orders were noted within these microeukaryotes, identifying specific virus-host interactions that have not yet been characterized in the polar regions. Giant endogenous viral elements contributed over 30,000 genes to these polar hosts, providing diverse functions, with several genes possibly involved in stress response. Chlamydomonas sp. ICE-L, an Antarctic sea-ice alga, harbored over 400 endogenous elements within its genome, contributing >27,000 genes to this microalga. Analyzing the publicly available Chlamydomonas ICE-L transcriptome data in response to varying UV, temperature, and salinity treatments, we found that numerous GEVE-encoded genes in this alga are differentially expressed in response to various environmental stressors. These results suggest that the GEVEs in polar microeukaryotes are transcriptionally dynamic and endow their host with crucial genes necessary for environmental adaptation.</p
Hydrogen Storage: A Nano Sorbent Development, Capacity Assessment, and Structure-Property Relationship Investigation
No full textThe increased consumption of fossil fuels for energy production has led to higher greenhouse gas emissions, necessitating sustainable, low-carbon energy solutions. Efficient hydrogen storage plays a crucial role in this transition, offering promise for energy storage applications. Adsorption-based storage gas (AGS) systems can reduce high-pressure requirements, and improve energy density, cyclability, and system efficiency. However, conventional hydrogen storage technologies face challenges related to cost, safety, and efficiency. This dissertation aims to develop high-performance nanoporous adsorbents optimized for hydrogen uptake and delivery, addressing these limitations. The goal is to meet the Department of Energy’s 2025 hydrogen storage targets of 40 g/L volumetric and 5.5 wt.% gravimetric capacity with intermediate binding energies (ΔH = 15–25 kJ/mol). This research focuses on three key objectives: (1) developing advanced nanoporous sorbents, (2) assessing hydrogen storage capacity under different conditions, and (3) investigating the structure-property relationships for optimizing material performance. Key challenges for AGS technologies include low room-temperature capacities, stability, and efficiency over repeated cycling. This work explores the synthesis and functionalization of advanced nanoporous materials to balance gravimetric and volumetric storage capacities, focusing on working capacities, adsorption-desorption kinetics, binding strength, packing density, and cyclic stability. The dissertation is organized into three phases: (1) enhancing gravimetric storage in activated carbon (AC) at reduced pressures, (2) improving volumetric capacities in metal-organic frameworks (MOFs) through densification, and (3) optimizing graphitic carbon nitride (g-C3N4) for hydrogen storage via combined physisorption and chemisorption mechanisms. This dissertation enhances the design of nanoporous adsorbents, offering scalable hydrogen storage solutions for a sustainable, low-carbon energy future.</p
Trajectories of Religious Coping and Social Support among Black Women Living with HIV in the Context of the COVID-19 Pandemic
No full textAmong Black women living with HIV (BWLWH), religious coping is a frequently used and effective coping strategy that helps one to cope with daily stressors and adverse life events. Furthermore, there is evidence to suggest a cognitive and emotional transition at the time of a chronic health diagnosis that may uniquely impact the process and type of coping that BWLWH choose to recruit. The current study aims to: 1) Quantitatively model changes in religious coping and social support (N=276). 2) Qualitatively understand the process of religious copingstrategies over time and in relation to the turning points of a) an HIV diagnosis and b) the COVID-19 pandemic among BWLWH (N=23). 3) Using a convergent parallel mixed methods design, to explore changes in religious coping after an HIV diagnosis and in the context of the COVID-19 pandemic among BWLWH (N=23). The first study found that religious coping significantly increased over time for participants with high religious coping at baseline, while perceived social support’s decrease over time was not statistically significant. The second study generated themes related to ten primary domains and three secondary domains including, but not limited to, religious coping, COVID-19, resilience, substance use, relationships, health, and common stressors for people living with HIV. In the third study results showed that religious coping was beneficial in managing emotions and involves a deepening of one’s connection with God over time. Findings related to social support were nuanced and speak to the complex role of social support and ways in which it may change over time based on its source. Future research may utilize information from this study to better understand the support systems that exist for BWLWH. The current study’s findings may also inform clinical practice by providing data that demonstrates the dynamic (vs static) nature of religious coping especially in the temporal context of COVID-19..</p