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From Chaos to Order: Assessing the Foundations of Emergent Gravity
No full textThe exploration of the relationship between gravity and thermodynamics has provided valuable insights into the search for a unified framework that reconciles gravity with quantum mechanics. In the 1970s, Jacob Bekenstein and Stephen Hawking established the thermodynamic nature of black holes, demonstrating that they possess entropy and thermal characteristics. Building on this foundation, Ted Jacobson’s work in the 1990s revealed a direct connection between the Einstein Field Equations and the thermodynamics of local causal horizons, hinting at a deeper link between gravity and thermodynamics. In the 2000s, Erik Verlinde introduced an entropic perspective on gravity, proposing that gravity arises as an entropic force driven by changes in information entropy. These developments suggest that gravity may fundamentally emerge from thermodynamic principles, prompting an inquiry into the nature of gravitational phenomena and their potential unification with quantum mechanics.
This dissertation explores the philosophical implications of emergence and reduction in thermodynamic approaches to quantum gravity. The historical development of emergent gravity is examined, tracing mechanistic explanations of gravity back to Isaac Newton. The validity of black hole thermodynamics is also assessed, countering recent philosophical skepticism by demonstrating that considerations of semiclassical quantum effects, such as the Unruh and Hawking effects, render such skepticism unfounded. Furthermore, the concepts of emergence and reduction are analyzed within the framework of Thermodynamic Gravity, revealing that it presents a case of emergence that remains consistent with reduction. Additionally, the principle of holography is explored in the context of Holographic Gravity, where I argue that gravity emerges as a manifestation of multi-scale entanglement relations
Evaluating the Influence of Risk Perception, Cultural Worldviews, and HIV Testing on HPV Vaccination Intention among Haitian Migrant Women
No full textBackground: Haitian women have one of the highest incidence rates of cervical cancer in the United States and are disproportionately affected by HIV. This dual disease burden is relevant as HIV significantly increases the risk of cervical cancer. Cervical cancer can be prevented through immunization with the human papillomavirus (HPV) vaccine, however HPV vaccination among Haitian women remains low. Studies have highlighted a key role of affect (i.e. emotions) influenced by cultural worldviews, in the rapid, automatic formulation of cancer risk perceptions and cancer prevention behaviors. Yet, this has been unexplored among Haitian women. This exploratory sequential mixed-methods study assessed the influence of affective cancer risk perception, cultural worldviews, and HIV testing on HPV vaccination intention among Haitian migrant women in South Florida.
Methods: Participants completed qualitative interviews (N=25) exploring cultural worldviews and affective risk perception towards cervical cancer. Qualitative data was subsequently used to develop and test the psychometric properties of a cultural worldviews scale influencing cervical cancer risk and behaviors. Participants completed cross-sectional surveys (N=151) which included cultural worldview items and items measuring sociodemographics, affective risk perception , cervical cancer knowledge, along with other variables influencing HPV vaccination intention commonly cited in the literature.
Results: Women in qualitative interviews described cultural practices and beliefs influencing cervical cancer risk, and endorsed affective risk perception domains which shaped their perceived susceptibility to cervical cancer. The scale measuring cultural worldviews developed from qualitative interviews demonstrated robust validity and reliability (Cronbach’s alpha=0.79). Analysis of survey data revealed statistically significant interactions between HIV testing and affective risk perception (negative affect [OR=1.84 , 95% CI [1.09,3.10], p=0.02], defensive pessimism [OR=4.23, 95% CI [1.39,12.91], p=0.011], cognitive causation [OR=0.67, 95% CI [0.42,1.01], p=0.06] ) and cultural worldviews (OR=0.67, 95% CI [0.48,0.93], p=0.02) on HPV vaccination intention.
Conclusion: Affective risk perception , cultural worldviews , and past HIV testing behaviors may have a significant role in HPV vaccination intention. When there is no prior experience of a disease, and minimal knowledge is available, these constructs can shape an individual’s appraisal of their disease risk and guide their health decisions
Random Forest for Hypothesis Testing: Development and Application to Cancer Detection
Full text linkHypothesis testing is the foundation of scientific inquiry. Contemporary data for hypothesis testing includes thousands of variables collected on a cohort composed of a small number of samples. From these data, machine learning technologies are employed to evaluate various hypotheses and statistics about an outcome, such as the presence or absence of a disease. We here ask a question that has been challenging to answer: does a set of variables provide enough relevant information about an outcome? We answer this question in this thesis by: (1) reducing this question (also known as the k-sample testing problem) to the well-known independence testing problem, (2) using a kernel decision forests, which are popular tools for classification and regression, to develop a new hypothesis test, and (3) estimate information-theoretic quantities directly from random forest which allows us to quantify uncertainty within the data set. We show the value of these approaches through extensive mathematical theory, simulated experiments, and applications to cancer detection. Specifically, when developing cancer detection models, we find that combinations of variable sets often decrease rather than increase sensitivity over the optimal single variable set. Based on these results, we suggest that our algorithms can more efficiently and reliably answer this question than existing approaches
Optimization Strategies for Efficient Robotic Automation in Industrial Manufacturing Processes
Full text linkThe deployment of Automated Guided Vehicles (AGVs) and Autonomous Mobile Robots (AMRs) plays a key role in modernizing industrial operations by enhancing efficiency, precision, and adaptability. This study explores strategies for optimizing AGV and AMR deployment across diverse factory environments, focusing on system integration, workflow automation, and long-term scalability.
Case studies from three manufacturing facilities demonstrate practical implementation: (1) A large-scale AMR system at Grundfos in Houston, Texas, transported heavy-duty racks, addressing complex layouts and dynamic workflows. (2) A lightweight AMR at TE Manufacturing in Greensboro, North Carolina, efficiently handled small racks for compact and high-speed operations. (3) An autonomous forklift AMR at Pentair in North Carolina optimized logistics by managing heavy loads safely and precisely.
Key challenges include factory layout adaptation, seamless integration, fleet management, and real-time communication. Advanced technologies such as adaptive path planning, sensor fusion, and cloud-based monitoring enhance performance. This research provides practical recommendations, highlighting the potential of autonomous robotics to optimize manufacturing, reduce downtime, and improve efficiency, contributing to smart and sustainable industrial automation
PRECISION SYNTHESIS AND OPTICAL PROPERTY OF COMPLEX SILICON−SILICON MOLECULAR AND POLYMERIC FRAMEWORKS
No full textThe structure of crystalline silicon has inspired synthetic chemists to design molecular and polymeric cyclosilanes for well-defined novel silicon materials with tunable optical properties. This dissertation describes synthetic strategies of constructing complex ladder cyclosilanes and polymeric cyclosilanes and the relationships between microstructures and optical properties. A series of cyclosilane homo- and copolymers are synthesized by hydrocoupling polymerization. Their optical properties exhibit connectivity-dependence, which results from different σ-conjugation pathways introduced by distinctive linkages. This is the first demonstration of the main chain control of polysilane optical properties. Besides, we report on the syntheses of two series of ladder cyclohexasilanes from mono- to tricyclic structures, which rank among the most complex oligosilanes yet synthesized. Their microstructure-optical property-relationships are examined by experimental and theoretical study. Anion-induced epimerization on cyclosilanes is assumed to go through a pentavalent intermediate. We use 1,2-disubstitued cyclohexasilane to investigate the epimerization mechanism. These results extend the synthetic scope of molecular and polymeric cyclosilanes, as well as deepen our understanding on electronic and optical properties of Si-Si framework
Mechanisms of growth abnormalities in two germline disorders of H3K27me3
No full textMendelian disorders of the epigenetic machinery (MDEMs) result from pathogenic germline variants in genes encoding writers, erasers, and readers of histone marks. This emerging class of rare disorders shares features such as growth abnormalities and intellectual disability or developmental delay; however, the molecular mechanisms underlying these common characteristics remain elusive. Here we investigate two disorders centered upon H3K27me3. Weaver syndrome (WS) is caused by variants in EZH2, a H3K27me3 methyltransferase (writer), whereas Kabuki syndrome 2 (KS2) is caused by variants in KDM6A, a demethylase (eraser) targeting the same mark.
We first modeled the skeletal overgrowth of WS in transgenic mice bearing the most common patient variant, EZH2 p.R684C. Compared to Ezh2 +/+ littermates, Ezh2 R684C/+ mice exhibited greater femoral cross-sectional tissue area, and increased mineral apposition rate (MAR) in vivo. Since MAR is a measure of osteoblast activity, we differentiated primary bone marrow mesenchymal stem cells (BM-MSCs) towards osteoblasts. Ezh2 R684C/+ cells indeed showed enhanced osteogenic potential by Alizarin red staining. We next performed RNA-seq, which indicated that Ezh2 R684C/+ cells had a collective dysregulation of osteoblast differentiation genes, as well as the BMP (bone morphogenetic protein) pathway. Finally, we demonstrated that an inhibitor targeting the opposing erasers of H3K27me3, KDM6A and KDM6B, was able to substantially reverse the effects of the R684C allele at both the phenotypic and transcriptional levels.
In contrast to WS, KS2 manifests with growth retardation. We described skeletal growth retardation in a mouse model of KS2, Kdm6a tm1d/+, which had shorter femurs and tibias than Kdm6a +/+ littermates as well as other abnormalities in bone parameters. Furthermore, Kdm6a tm1d/+ growth plates were shorter due to decreased hypertrophic chondrocyte size. To further characterize the disruption to chondrocyte function, we generated Kdm6a -/- ATDC5 cell lines and showed that Kdm6a -/- cells exhibited precocious differentiation. This was reminiscent of prior findings in a related disorder, Kabuki syndrome 1 (KS1), which shares a clinical phenotype with KS2 despite separate genetic etiologies. RNA-seq on both KS1 and KS2 chondrocytes revealed a similar transcriptomic signature between the disorders, shedding light on the common pathways between two highly similar MDEMs
Disentangling Retest Effects in Cognitive Aging: Findings From ACHIEVE Study
Full text linkBackground: The ACHIEVE study, a multicenter randomized controlled trial, investigated the effect of hearing intervention on cognitive decline in older adults. However, retest effects - improvements in cognitive performance due to repeated testing – could potentially bias estimates of cognitive trajectories. Our study aimed to evaluate the magnitude of retest effects within ACHIEVE and examine whether retest effects varied by baseline hearing levels (30≤PTA<40 vs. 40≤PTA<70), trial interventions (health education vs. hearing aids), and population sources (ARIC vs. de novo).
Methods: We used data from 977 participants within ACHIEVE who completed in-person cognitive tests at baseline, year 1, and year 3, excluding year 2 due to COVID-19 disruptions. The primary outcome was the global cognitive factor score derived from a neurocognitive battery excluding auditory-dependent tests (Digit Span Backwards and Logical Memory Test). Secondary outcomes include domain-specific factor scores for language, executive function, and memory. The primary exposure was the retest effect, modeled as a binary indicator (0 for baseline test and 1 for subsequent tests). Linear mixed effect models were fitted to estimate the retest effects and longitudinal changes in cognitive scores, adjusting for demographic factors. Interaction terms were incorporated to assess whether the retest effect varied by features of interest.
Results: Significant retest effects emerged for global cognition, executive function, and memory, equating approximately to one year of cognitive decline, but was not observed for language. Participants with poorer baseline hearing exhibited smaller retest effects, while the de novo population showed stronger retest effects compared to ARIC population. Although the hearing intervention did not universally modify retest effects, it notably enhanced retest effects on global cognition and memory within the ARIC subcohort only.
Conclusions: Our findings highlight substantial retest effects in global cognition, executive function, and memory, emphasizing the importance of accounting for them in longitudinal cognitive studies. Tailored analytic strategies are recommended in studies using repeated neuropsychological testing
EXPLORING THE ASSOCIATION BETWEEN SMOKING AND DEMENTIA AMONG A MIDDLE TO OLD AGE POPULATION IN THE UNITED STATES
Full text linkABSTRACT
Background: Smoking is a well-known risk factor for both cardiovascular disease (CVD) and dementia. However, to date, few studies have examined whether CVD mediates the relationship between smoking and dementia or whether this relationship is modified by gender or race.
Methods: This study analyzed data from the 15th wave (2020–2021) of the Health and Retirement Study (HRS), including U.S. adults aged 50 and above. Participants’ self-reported information on smoking and heart disease was used. Dementia diagnosis was based on self- or proxy-report. Logistic regression models were used to estimate the total effect of smoking on dementia (without CVD adjustment), the direct effect of smoking on dementia (adjusting for CVD), and the association between smoking and CVD, controlling for covariates. Mediation analysis assessed whether CVD mediated the relationship, estimating indirect, direct, and total effects. Interaction and stratified analyses evaluated gender and race as potential effect modifiers, adjusting for CVD and covariates.
Results: Smoking was significantly associated with dementia risk, showing a total effect (95% CI: 2.76e-6, 0.00031; p < 0.05), a direct effect (95% CI: 4.28e-7, 0.000276; p < 0.05), and an indirect effect mediated through CVD (95% CI: 1.17e-6, 0.000290; p < 0.05). Stratified analysis showed a significant association between smoking and dementia among females (OR = 1.31; 95% CI: 1.06, 1.63) and White populations (OR = 1.35; 95% CI: 1.08, 1.69), whereas no statistically significant associations were observed among males (OR = 1.24; 95% CI: 0.82, 1.89), Blacks (OR = 1.04; 95% CI: 0.64, 1.69), Hispanics (OR = 1.46; 95% CI: 0.87, 2.46), or other races (OR = 1.15; 95% CI: 0.53, 2.53). Interaction analyses indicated that neither gender (p: 0.76) nor race (p: 0.68) were modifiers of the smoking-dementia relationship.
Conclusions: Smoking was associated with dementia both directly and indirectly through CVD. Stratified analyses showed significant associations between smoking and dementia only among females and White populations. However, the interaction analyses indicated that gender and race were not modifiers of the relationship. Further research with larger and more balanced samples is needed to assess potential effect modification by gender and race
A finite-dimensional functional for circle segmentation, with applications to pupil tracking
Full text linkIn this thesis we propose a novel circle tracking active contour model that directly evolves a flexible initial circle without relying on edge detection or finely tuned initialization. Two variants are introduced: a full gradient descent (R5) that jointly optimizes center, radius, and region intensity parameters, and a reduced gradient descent (R3) that computes region intensities in closed form. We present experiments on different eye images, on brain CT slices, and on approximately circular objects. The results demonstrate that R5 achieves substantially higher intersection‐over‐union (IoU) and lower center and radius errors than classical Hough transform, while requiring minimal hyperparameter tuning. The proposed circle tracking framework provides a versatile, data‐driven approach to circular object segmentation with strong accuracy and robustness
IMPLEMENTATION OF HIV TREATMENT SUPPORT STRATEGIES FOR FEMALE SEX WORKERS LIVING WITH HIV IN SOUTH AFRICA
No full textBackground. In South Africa, 62% of female sex workers (FSW) are living with HIV, with many experiencing suboptimal treatment outcomes. Antiretroviral therapy (ART) is free and widely available, but among FSW, inconsistent access and adherence limits its effectiveness. This dissertation assessed determinants and mechanisms underlying the implementation of two HIV treatment support strategies, described engagement with strategies, and characterized the role of sex worker-specific programming utilization.
Methods. This dissertation used data from the Siyaphambili Study, a trial testing two HIV treatment support strategies aimed to promote viral suppression among a FSW living with HIV in South Africa. First, we characterized strategy implementation determinants using the Consolidated Framework for Implementation Research (CFIR). Secondly, we generated mechanisms underlying strategy implementation and effectiveness using a combined CFIR/realist-informed evaluation. Next, we identified longitudinal patterns of strategy engagement using group-based trajectory modeling, describing factors associated with each engagement trajectory and the association with clinical outcomes. Finally, we identified correlates of receiving HIV care and treatment from the TB HIV care sex worker program.
Results. Twelve CFIR constructs across three domains emerged as facilitating, hindering, or having mixed effects on strategy implementation, with three constructs weakly operating distinctly between strategies. Four ‘context+mechanim=outcome’ configurations emerged: 1. Needs of FSW+relative advantage of strategy=appropriateness for FSW, 2. Work infrastructure/available resources/knowledge resources+strategy design=feasibility of implementation, 3. Partnerships/relational connections/communication+strategy complexity/adaptability=fidelity of implementation, and 4. FSW capability+FSW opportunity/motivation=strategy effectiveness. We identified four strategy engagement trajectories. A quarter of FSW were consistently engaged, and FSW in this trajectory were more likely to be older, single, on ART at enrollment, and retained and virally suppressed at 18-months. Finally, we found FSW not receiving ART care from the sex worker-specific HIV program implementing Siyaphambili were more vulnerable, at increased risk for suboptimal HIV treatment outcomes, and at risk for onward HIV transmission due to inconsistent condom use.
Conclusions. Patient-centered HIV services that address the unmet treatment needs of FSW will optimize health and support HIV epidemic control. Understanding who these strategies worked for, as well as the determinants and mechanisms in which they operated, informs future strategy design and implementation among FSW at greatest need