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Towards the Clinical Application of Magnetoelectric-Powered Bioelectronics
No full textThe clinical application of bioelectronics promises to improve the treatment of diseases by enabling precise modulation and monitoring of human physiology. By eliminating the bulky interconnects and batteries used in traditional bioelectronic devices, battery-free and wirelessly powered devices can be miniaturized extensively, reducing both the complexity of the surgical procedure and the risk to patients. This thesis advances the development of clinically relevant magnetoelectric-powered bioelectronics. We describe several advances in wireless, battery-free systems that resulted from close collaboration with clinicians. First, we present a digitally programmable cortical brain stimulator with a width of 9 mm that is capable of activating cortical activity through the dura. With this, we demonstrate acute motor cortex activation in human patients and chronic motor cortex activation for 30 days in a porcine model, paving the way for long-term cortical neuromodulation with quick and simple procedures. Building on this, we investigate the scalability of bioelectronic systems, demonstrating that magnetoelectric wireless power transfer enables networks of millimeter-sized implants. We show that system efficiency increases as more devices are added, enabling distributed powering of many stimulation nodes. Proof-of-concept networks for spinal cord stimulation and cardiac pacing in porcine models illustrate the potential of this approach for complex, multi-node applications. Finally, we create a passive magnetoelectric backscatter communication system, enabling low-power and robust data transmission across deep tissue interfaces. This system supports real-time physiological monitoring with a miniaturized device, as exemplified by a < 3 mm diameter wireless cardiac sensing node that relays porcine electrocardiogram signals from the surface of a beating heart. The demonstrated technologies show the clinical viability of magnetoelectric-powered wireless, battery-free implants and showcase the potential of the next generation of bioelectronic devices
Essays in Comparative Political Behavior
No full textThis dissertation contributes to comparative political behavior through three essays. The first essay offers a methodological solution for measurement error in ideological surveys ('left-right dyslexia'). The second and third essays investigate political interest, with the former examining its psychological micro-foundations via heuristic processing and the latter exploring its macro-level variation explained by national political structures and context.
Essay one addresses 'left-right dyslexia,' a measurement error where respondents reverse the ideological scale despite the correct understanding of relative ideological positions. It introduces a Bayesian method using political knowledge and party placements to detect and correct this error. Application to Danish survey data shows correction effectiveness varies by political knowledge, confirmed by simulations demonstrating accuracy depends on appropriate prior specifications.
Essay two examines how partisan and ideological cues act as heuristics influencing political interest. An experiment using manipulated news vignettes in UK survey data finds these heuristics boost interest and comprehensibility. Mediation analysis confirms comprehensibility as the key pathway, with a stronger effect among participants correctly identifying the cues, a finding robust to sensitivity checks.
Essay three investigates why political interest varies across democracies, focusing on the role of historical government composition. It specifically argues that systems characterized by multi-party coalition governments sustain higher interest levels, particularly in contexts where political heuristics are already useful. Such systems maintain the relevance of partisan/ideological heuristics during and after elections, unlike single-party dominant systems. Using cross-national survey data and a discounted coalition score developed to account for the temporal effect of government composition, the analysis shows coalition governance history positively predicts political interest, especially in established democracies.
Together, these essays extend political behavior research by developing methods for measurement error detection and correction, identifying psychological mechanisms driving political interest, and analyzing institutional contexts shaping cross-national differences in political interest
Theoretical Principles for Information-Efficient Reasoning under Uncertainty
No full textToday's machines rely on resource-intensive algorithms and specialized hardware to produce intelligent sensorimotor behavior. In contrast, the brain can transform noisy stimuli into effective actions that solve a wide range of tasks using limited experience, operating with modest processing capacity, and consuming less energy than a lightbulb. Neuroscientific research suggests that to achieve this remarkable performance, the brain not only reasons about external factors but also monitors and regulates its internal processes. Incorporating this meta-cognitive ability into artificial systems is attractive, as it may assist agents in better aligning their computational efforts with resource constraints, task requirements, and environment structure. However, the practical implementation of meta-cognition remains an exciting open challenge, especially in uncertain environments. To help bridge this gap, we propose a novel approach to stochastic control that enables the regulation of inference—an internal process through which agents transform noisy observations into beliefs that guide their behavior. We apply our framework to quantitatively examine how meta-cognitive agents solve environments with linear dynamics, Gaussian sources of noise, and quadratic cost functions (LQG environments). Our study reveals that meta-cognition strongly intertwines inference and control dynamics. This coupling reshapes the convex optimization landscape of classic LQG control and leads to intriguing phase transitions in what is worth being optimally inferred. Based on environmental reliability, task demand, and resource availability, the strategies of meta-cognitive agents switch from a costly mechanism that relies on Bayes-optimal inference to multiple combinations of information-efficient inference and error-aware control. Our findings generalize efficient coding ideas in neuroscience, extend the principle of minimal intervention in control, and offer valuable insights that, combined with advancements in low-power hardware, could propel the development of a new wave of artificial intelligent systems capable of matching the outstanding resource efficiency of their biological counterparts
Making the Case for Integrating Youth-Participatory Action Research into Research-Practice Partnerships
No full textAsian American Community Study: Forms and Spaces of Anti-Asian Discrimination in the Houston Area
No full textThe Asian population in the United States has expanded rapidly over the past few decades, more than doubling between 2000 and 2023 to comprise approximately 7% of the total population. Texas is home to one of the largest populations of Asian residents in the country. Within the state, the Houston area has one of the fastest-growing and most ethnically diverse Asian populations nationwide. As such, it is a valuable setting for examining the distinctive experiences and perspectives of Asian residents. Since the COVID-19 pandemic, anti-Asian discrimination has been widely documented across the United States. In the Houston area, roughly 4 in 10 Asian residents reported experiencing some form of discrimination in the past year. Experiences with discrimination are linked to adverse mental health outcomes, including depression, anxiety, and substance use, highlighting the need to better understand the mechanisms and contexts of anti-Asian discrimination. This research brief examines the lived experiences of Asian residents facing anti-Asian discrimination within the highly diverse context of the Houston area. Although the link between anti-Asian discrimination and negative mental health outcomes is well established, less is known about how such discrimination is experienced and the specific contexts in which it occurs. Investigating these lived experiences illuminates the sources and mechanisms of discrimination, offering opportunities for increasing public understanding and encouraging bias-awareness learning that may help prevent future incidents
Electrochemical Lithium Extraction from Brines in a Porous Solid Electrolyte Reactor
No full textLithium demand has been increasing due to its promising applications in energy storage and production. Market projections indicate that lithium demand will continue to rise, while market supply is expected to fall short in demand, creating a gap between the supply and demand chains. As a result, efficient lithium mining has gained significant interest. Conventional lithium mining sources such as ores face several disadvantages, including massive energy consumption, CO2 production, uneven global distribution, and depletion of lithium-rich ore. The alternative sources, brines, have emerged as a promising lithium-rich reserves.
This study provides an overview of different methods of lithium extraction, highlighting their advantages and limitations, and proposes potential solutions to improve their efficiency. Furthermore, the thesis explores different membrane-based extraction approaches that could selectively extract lithium over competing cations in brines, such as sodium. The primary membranes investigated include ceramic-based membranes (e.g., NASICON-type membranes) and polymer-based membranes incorporating crown-ethers
Randomized Zero Forcing
No full textOn a given graph G = (V, E) where each vertex can be colored blue or white, a zero forcing set on G describes a starting set of vertices to color blue, where every other vertex is colored white, such that by applying an iterative deterministic coloring rule, all vertices of G will be blue after a number of iterations. Probabilistic zero forcing and randomized zero forcing are variations of zero forcing where the iterative color changing rule is no longer deterministic but rather probabilistic. One desired quantity in probabilistic and randomized zero forcing would be the expected propagation time, which can be seen as the probabilistic analogue to the number of iterations required to color all vertices blue in zero forcing. In this thesis, computational implementations for finding expected propagation time are explored, along with other theoretical results pertaining to randomized zero forcing on special families of graphs
Asymptotic Analysis of Stochastic Cell Proliferation Mechanisms with Applications in Cancer and Hematopoiesis
No full textThis thesis develops and analyzes stochastic models of cell proliferation with a focus on asymptotic behavior in the contexts of cancer evolution and hematopoiesis. We first study a countable-type branching process model inspired by the “tug-of-war” between driver and passenger mutations in tumor evolution. We identify two evolutionary regimes, driver dominance and passenger dominance, determined by the relative mutation rates. These regimes exhibit contrasting long-term behaviors: driver dominance leads to transience and unbounded fitness, while passenger dominance yields a limiting distribution, indicating stabilization of fitness over time. Next, we construct a two-compartment stochastic model of hematopoiesis that incorporates regulatory mechanisms. We derive functional laws of large numbers and central limit theorems to characterize mean-field behavior and fluctuations. We introduce a metric for regulatory effectiveness based on fluctuation magnitude around steady states, thereby offering insights into the robustness of hematopoietic regulation. Finally, we extend the modeling framework to multistage tumorigenesis under homeostatic regulation. Using large-scale approximations, we identify trichotomies of qualitative behaviors in the mean-field dynamics and characterize asymptotic properties of variance functions under two biologically relevant fitness regimes
Who Remains ‘College, Career, and Military Ready’ in the Context of a Shifting Accountability Framework?
No full textOver the past two decades, U.S. states have developed education accountability frameworks to ensure students have access to opportunities for success after graduation. These efforts vary; some states emphasize academic indicators like test scores, while others focus on career and technical education or work-based learning. Texas policymakers developed the A-F Accountability System with an emphasis on preparing students for the future through new College, Career, and Military Readiness (CCMR) indicators. What began in 2013 with a flexible graduation structure and reduced testing has evolved into a multifaceted rating system shaped by legislative directives, ongoing input from advisory committees, shifting workforce demands, and a changing understanding of postsecondary success. This study investigates Texas’ accountability landscape, focusing on the development and impact of the state’s CCMR standards
The Priming Effect of Bereavement on the Relationship between Early Life Stress and Depression: A Longitudinal Study using The Stress Sensitization Model
No full textEarly life stress (ELS) is a well-established social determinant of health with long-term physical and mental health challenges, with enduring effects on psychological function. Building on the stress sensitization model, this longitudinal study investigated whether bereavement—a common and severe adult stressor—exacerbates depressive responses in individuals with a history of early life stress. Specifically, we examined the priming effect of bereavement on the ELS-depression relationship. Using data from three visits collected from recently bereaved adults and matched non-bereaved controls, we assessed depressive symptoms, alongside validated measures of childhood adversity and relevant covariates. We hypothesized that (1) higher levels of ELS would be associated with higher levels of depressive symptoms, (2) bereaved individuals would exhibit higher levels of depressive symptoms than non-bereaved controls, and (3) bereavement status would moderate the ELS-depression relationship, such that the association would be stronger in bereaved participants than in non-bereaved controls. Our findings supported all three hypotheses, establishing a robust body of evidence demonstrating that early life stress and bereavement status interact such that individuals subject to both risk factors experience more severe depressive symptoms than those subject to one or neither risk factor. This study significantly advances our psychoneuroimmunological understanding of how early adversity primes adults for heightened psychological vulnerability during bereavement, offering new insights into mechanisms underlying stress-related health disparities and new directions for prevention and intervention in mental health