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DEVELOPING ORGANIC THERMOELECTRICS AND FUNCTIONAL ELECTRONICS USING CONDUCTING POLYMERS AND ORGANIC-INORGANIC COMPOSITES FOR ENERGY CONVERSION, STORAGE AND SENSING APPLICATIONS
No full textCurrent thermoelectric technologies, dominated by inorganic materials such as Bi-Te compounds, efficiently convert low-grade waste heat into electricity. However, their toxicity, rigidity, scarcity and energy-intensive processing limit their wide applications. In contrast, organic thermoelectrics, with the advantages of mechanical flexibility, material abundance and low-temperature and low-pressure processing, offer promising alternatives.
This work presents three studies on organic thermoelectrics. Chapter 1 explores the doping effects of Lewis acid, tris(pentafluorophenyl) borane (BCF) on the thermoelectric performance of pgBTTT, a thiophene-based conjugated polymer with oligoethylene glycol side chains. F4TCNQ, a well-established dopant, was utilized as a reference. A series of characterizations were performed to unravel the interaction mechanism between dopants and polymers. Chapter 2 investigates a much less well-studied class of organic thermoelectrics, ionically conductive polymers. Our initial focus was two chloride-based ionic polymers, but their poor air stability led to transient, irreproducible Seebeck coefficient and hence resulting in unstable properties. To overcome this issue, the polymers were later modified with hydrophobic ions to improve air stability. In particular, BF4- - and PF6--based ionic polymers showed reliable ionic conductivity and reproducible Seebeck coefficients at 40% relative humidity. Chapter 3 introduced conjugated alkylthiophene polymers with terminally functionalized side chains with varying structure as thermoelectric sensors for NO2 detection. NO2 absorption enhanced the conductivities of the polymers, highlighting NO2’s role in inducing charge carrier generation and transport. This method serves as a convenient tool to study physics associated behind the thermoelectric properties governing the sensing response and mechanism.
In Chapter 4, we shifted our focus from organic thermoelectrics to dielectric capacitors that store energy electrostatically. We report the development of two micron-thick nanodielectric capacitors: NiO:PS and ZnSe:PS capacitors – featuring low-loading spherical NiO and ZnSe nanoparticles embedded in a polystyrene (PS) matrix. The nanofillers enhance the breakdown strength of the dielectric composite compared to pristine PS. Our findings underscore the critical role of dilute nanofillers in boosting the dielectric performance of polymer-based capacitors.
My thesis aims to illuminate the chemistry of organic thermoelectrics and nanodielectric materials, paving the way for the development of future energy technologies
When Cities Win: How Local Governments Reclaim Power in the Face of State Preemption
Get PDFDespite their formal subordination in the American federal system, local governments sometimes successfully resist state preemption. This dissertation develops and empirically examines a theory of how localities overcome their legally subordinate status to maintain or restore control over contested policy domains. Drawing on insights from American Political Development, social movement theory, and research on state capacity, I argue that successful local resistance emerges through the dynamic interaction of three key mechanisms: opportunity structure, strategic interaction, and cost-benefit calibration.
The opportunity structure mechanism encompasses historically constructed institutional and political contexts that enable or constrain local resistance, including constitutional provisions, political conditions, legal frameworks, and social factors. Strategic interaction explains how resistance strategies emerge through dynamic interactions between multiple actors, emphasizing formal and informal tactical deployment and cross-jurisdictional coalition building. Cost-benefit calibration describes how local resistance succeeds by altering state calculations about preemption enforcement through political costs, administrative capacity constraints, and strategic enforcement choices.
Using process tracing, this work examines three cases that vary in constitutional design, political context, and resistance outcomes: Maine’s food sovereignty movement (2011–2017), Georgia’s rent control preemption (1984–present), and North Carolina’s nondiscrimination ordinance conflict (2015–2020). Sources include newspaper coverage, constitutional and legislative texts, municipal ordinances, and historical scholarship. In Maine, strong localist traditions and a competitive political landscape enabled localities to achieve statewide legislative protection for food sovereignty. In contrast, Georgia’s centralized political structure and entrenched property rights norms foreclosed Atlanta’s efforts to overturn rent control preemption, despite sustained local advocacy. Finally, North Carolina illustrates how economic pressure and national mobilization can compel state retreat—even under a centralized constitutional regime—though the outcome was a negotiated compromise, not a full local victory.
This research contributes to core themes in American political science—power, institutional change, and political resistance—by demonstrating how formally subordinate actors can challenge hierarchical authority through strategic interaction and cost-benefit recalibration. The findings have implications for understanding not only federalism and local autonomy, but broader conditions under which institutional arrangements can be contested and transformed by those they formally constrain
Oral History Interview with Vanessa N. Gamble
No full textThis interview with Vanessa Northington Gamble, MD, PhD, is part of “Moral Histories: Voices and Stories from the Founding Figures of Bioethics,” an oral history project of the Johns Hopkins Berman Institute of Bioethics. Dr. Gamble is University Professor of Medical Humanities at George Washington University and Professor of Health Policy and American Studies. Her areas of expertise include the history and sociology of medicine, the history of race in American medicine, disparities in health care and public health, and Black health and well-being.
Dr. Gamble, a fourth-generation West Philadelphian, describes her family, community, and early education, including the impact of the 16th Street Baptist Church bombing, and the assassination of Martin Luther King, Jr. when she was 15. After graduating from Philadelphia Girls’ High School, she describes her education at Hampshire College where she wrote her senior thesis on the US Public Health Service Syphilis Study. Dr. Gamble recounts her introduction to bioethics as an undergraduate intern at The Hastings Center and her subsequent medical school and graduate student experiences at the University of Pennsylvania where she earned an MD-PhD.
She recalls essential mentors, particularly Dr. Helen Dickens, when she lost both her mother and sister to cancer. During her tenure at the University of Wisconsin-Madison, she recounts her leadership role in securing a presidential apology for the Syphilis Study at Tuskegee, delivered by President Bill Clinton in 1997, which included federal funding for the creation of the National Bioethics Center at Tuskegee University, where she was later director. Dr. Gamble highlights the 2005 conference she convened for Black bioethicists to discuss and propose a Black agenda for bioethics that brought issues of Black health and racial injustices in healthcare to bioethics discussions. She stresses the importance of community engagement and the need to focus on the trustworthiness of institutions, which includes a discussion about vaccine hesitancy in communities of color during the Covid-19 pandemic. The interview concludes with her move to George Washington University, her courses on race and public health, and her evolving work as historian of Black women in medicin
DECIPHERING THE CHEMICAL ABUNDANCES OF THE FIRST GALAXIES AT COSMIC DAWN WITH JWST
Get PDFAstronomers have yet to discover the first generation of stars formed in the universe. These long theorized "Population III" stars would be pristine of heavy elements, or "metals", and likely supermassive, very different from stars we observe today. To find the first stars, we must push our observations as early as possible studying exceptionally small, low mass, metal-poor galaxies. In this thesis, I present an extensive study of MACS0647–JD, the brightest known galaxy within the first 500 million years of cosmic history, magnified by gravitational lensing and observed with cutting-edge JWST imaging and spectroscopy. JWST/NIRCam imaging resolves MACS0647–JD into two distinct components. Through analysis of their physical properties and star formation histories, I find that one clump is younger, while the other appears older, suggesting an early-stage galaxy assembly or merger. Using NIRSpec and MIRI spectroscopy, I measured a direct gas-phase metallicity of 13% solar and a carbon abundance of 60% solar, the first such measurements obtained in the first 500 million years. The elevated carbon abundance may be explained by enrichment from remnants of the first generation of stars. To identify even more primitive galaxies, I conducted a search for extremely metal-poor galaxy (EMPG) candidates using deep, pure-parallel JWST/NIRCam grism spectroscopy. I discovered seven EMPG candidates with metallicities below 2% solar. These galaxies appear to be undergoing starbursts, with high star formation rates (SFR~0.2-2 Msun/yr) and low stellar masses (log(M/Msun)~6.8-7.8). The continued search for distant galaxies, EMPGs, and first star candidates is ongoing, and will undoubtedly transform our understanding of galaxy formation and chemical evolution at cosmic dawn
Essays on Heterogeneous Agent Macroeconomics and Unemployment
Get PDFThis dissertation consists of three chapters that study how the microeconomic characteristics of unemployment shape business cycle dynamics and macroeconomic policy.
The first chapter investigates the macroeconomic consequences of a well documented microeconomic fact: Job loss results in a substantial decline in labor earnings that persists for over 20 years. This chapter argues that this `scarring' effect of unemployment is a key determinant of the speed of a macroeconomic recovery following a recession. I incorporate human capital into a heterogeneous agent New Keynesian model with search and matching frictions. Unemployment scarring, mediated by the fraction of temporary versus permanent layoffs, enables the model to capture both the sluggish recovery from the Great Recession and the swift rebound from the COVID Recession. In particular, the presence of scarring reveals the pivotal role that temporary layoffs fulfilled in preventing a sluggish post-pandemic recovery.
Chapter 2 studies how household beliefs about job finding and job loss evolve over the business cycle. Using expectations data from the Survey of Consumer Expectations and real-time machine learning forecasts, we construct rational benchmarks and show that beliefs adjust slowly and vary widely across households. We embed these patterns in a heterogeneous-agent model. Belief stickiness dampens the initial drop in consumption during downturns but slows recovery by limiting households’ ability to draw down savings once conditions improve.
The third chapter evaluates and compares the effectiveness of commonly pursued fiscal stimulus policies during recessions. Using a heterogeneous agent model calibrated to match measured spending dynamics over four years following an income shock, we assess the effectiveness of three fiscal stimulus policies employed during recent recessions. Unemployment insurance (UI) extensions are the clear “bang for the buck” winner when effectiveness is measured in utility terms. Stimulus checks are second best and have two advantages (over UI): they arrive and are spent faster, and they are scalable to any desired size. A temporary (two-year) cut in the rate of wage taxation is considerably less effective than the other policies and has negligible effects in the version of our model without a multiplier
WHITE MATTER HEALTH AND DEMENTIA RISK AMONG PERSONS WITH DOWN SYNDROME ACROSS THE LIFESPAN
Get PDFDown syndrome (DS) is a chromosomal disorder resulting from an extra copy of chromosome 21. Individuals with DS typically exhibit intellectual disability (ID) with wide-ranging cognitive and functional variability. Due to triplication of the amyloid precursor protein gene on chromosome 21, most individuals with DS develop Alzheimer’s disease (AD) pathology by age 40, approximately two decades earlier than typically developing (TD) adults. While white matter degeneration and cerebrovascular pathology have been linked to AD in DS, the contribution of white matter health to risk for cognitive decline across the lifespan remains underexplored. This dissertation addresses this gap by examining neuropsychological heterogeneity and its relationship to white matter abnormality using a multimodal, person-centered approach spanning both childhood and adulthood in individuals with DS.
First, growth mixture modeling (GMM) identified distinct trajectories of neuropsychological functioning over a 32-month period in nondemented adults with DS. Two trajectory classes with significant slope differences emerged across five measures: Block design, Cued recall, Beery Buktenica test of visuomotor integration (VMI), Reiss maladaptive behavior, and Vineland adaptive behavior.
Second, logistic regression analyses within each general mixed model (GMM) model evaluated whether baseline global white matter hyperintensity (WMH) and β-amyloid (Aβ) burdens predicted trajectory class membership. WMH burden showed limited associations, while Aβ burden significantly predicted class membership for Block Design, Cued Recall, and VMI. The relationship between Aβ burden and Cued Recall remained significant after adjusting for age and ID severity.
Third, latent profile analysis (LPA) identified shared and distinct neuropsychological profiles in children with DS and TD peers, along with their associations with white matter microstructural integrity. Three latent classes emerged, with children with DS represented in all. Fractional anisotropy values in the superior longitudinal fasciculus II and uncinate fasciculus varied significantly by profile, linking white matter development to early neuropsychological heterogeneity.
Together, this dissertation provides compelling evidence that individuals with DS exhibit distinct neuropsychological trajectories and brain profiles across the lifespan. These findings highlight the potential of cognitive and neuroimaging markers for early detection of AD-related decline and underscore the importance of individualized, developmentally informed strategies for dementia risk monitoring and prevention in the DS population
Teacher Burnout in Urban, College-Preparatory High Schools
Get PDFTeacher stress and burnout can threaten the stability of urban, college-preparatory high schools by negatively impacting educator well-being, instructional quality, and student outcomes. Guided by Bronfenbrenner’s ecological systems theory, the present study examined the prevalence, contributing factors, and support structures related to teacher stress and burnout at Oakridge College-Preparatory High School, a school for students of limited economic resources in Oklahoma City, Oklahoma. A convergent-parallel mixed-methods design was employed. All 17 faculty members were invited to complete the Maslach Burnout Inventory-Educators Survey, the Perceived Stress Scale, and a rank-choice stressor inventory; 11 responded (65%). Semi-structured interviews with five volunteers deepened and triangulated the survey findings. Quantitative results revealed moderate emotional exhaustion, low depersonalization, and high professional accomplishment, indicating resilient yet strained educators. Administrative demands, a heavy instructional workload, and limited professional autonomy emerged as the most salient stressors. Alternatively certified teachers reported higher perceived stress than their traditionally certified colleagues, whereas years of experience was not significantly associated with burnout. Qualitative analysis reinforced these patterns, highlighting the protective role of explicit boundary-setting and the intensification of stress during February–April. Three integrated interventions are proposed: (a) redistributing administrative tasks and assessment deadlines to smooth workload peaks, (b) redesigning instructional coaching and evaluation to foreground autonomy and reflective practice, and (c) establishing a structured induction and mentorship program tailored for alternatively certified educators. By situating teacher burnout within a multilevel ecological framework and grounding proposed interventions in local evidence and existing research, this study contributes a practical foundation for addressing educator well-being in college-preparatory, urban high schools
Oral History Interview with Robert Cook-Deegan
No full textThis interview with Bob Cook-Deegan, MD, is part of “Moral Histories: Voices and Stories from the Founding Figures of Bioethics,” an oral history project of the Johns Hopkins Berman Institute of Bioethics. Prof. Cook-Deegan is a professor in the School for the Future of Innovation in Society and the Consortium for Science, Policy, and Outcomes at Arizona State University. He was the founding director of the Center for Genome Ethics, Law, and Policy at Duke University’s Institute for Genome Sciences and Policy. He served at the Office of Technology Assessment of the United States Congress where he contributed to major reports on emerging biomedical technologies and their societal impacts. He is the author of The Gene Wars: Science, Politics, and the Human Genome, a comprehensive account of the struggle to launch the Human Genome Project. His areas of expertise include genomics, genetic policy, Open Science, health technology, and public policy.
Bob Cook-Deegan recounts his childhood in Denver as the son of a physician. He discusses his early academic career, his undergraduate years at Harvard, his time at the University of Colorado Medical School, and his decision to pursue medical research. He also talks about becoming a father and maintaining a work-life balance with his two children and wife, Kathryn. Cook Deegan shares his experience researching Alzheimer’s disease, as well as his rotation at the National Institutes of Health. Dr. Cook-Deegan details his work at the Office of Technology Assessment (OTA), including reports on aging, biotech, and the Human Genome Project, and offers an account of its eventual demise due to political changes. Other topics include the history of the Bermuda Principles, the role of political administrations on health policy, the current turn to Open Science, and Cook-Deegan's own relationship to collecting oral histories. He concludes the conversation with a reflection on the Trump administration’s recent decision to cut funding for many science-funding agencies
CHARACTERIZING ALLERGEN PROCESSING AND MHCII EXPRESSION CAPABILITIES IN AIRWAY EPITHELIAL CELLS DURING AIRWAY ALLERGY
No full textThe increasing prevalence of allergic airway diseases highlights the need to understand their underlying mechanisms. These diseases are characterized by type 2 immune responses in the lungs, sustained by dysregulated innate immune mediators. Airway epithelial cells play a critical role in initiating and perpetuating the allergic response and are gaining recognition as active participants in immune responses through MHCII-mediated antigen presentation to T cells. Understanding the mechanisms regulating MHCII expression on airway epithelial cells and their capacity to process and present allergens is crucial for developing targeted therapies for allergic asthma.
To understand their contribution to the allergic cascade, we investigate lower airway epithelial cells' allergen processing and MHCII expression capabilities. The results demonstrate the ability of these cells to uptake and process allergens as well as express MHCII, highlighting their potential as active participants in the adaptive immune response within the airways
Oral history of Dr. Jonathan Johns and Dr. Taurence Bishop
No full textIn this interview, Dr. Warren Hayman speaks with Dr. Jonathan Johns and Dr. Taurence Bishop. Both Dr. Johns and Dr. Bishop are graduates of Dunbar High School (1990 and 1994 respectively).
Jonathan went on to earn a Bachelor of Science from Johns Hopkins University and an MD from the University of Pittsburgh School of Medicine. As an OBGYN physician he opened a private practice where he worked for many years; now he is at Kittitas Valley Hospital. Jonathan reflected on his experiences in the program, the curriculum, the research positions, and the connections he made (like Dr. Mark Rogers). Jonathan spoke about teachers that stood out (Dr. Gladden, Dr. Rasheed, Mr. Hughes, Mr. Brown). Additionally, he reflects on what made him want to be a doctor, sharing a memory about his mom. Jonathan voices appreciation for Dr. Hayman, indicating that Dr. Hayman is one of the individuals who was instrumental in making him the person he is today.
After Dunbar, Taurence went on to Morgan State University to study chemistry. He went to Howard University, College of Dentistry, completing his degree in 2003. He did a general practice residency in Christiana Hospital, then opened private practice in 2006. He is an Attending at Christiana Hospital for oral surgery and Hospital Medicine faculty. Taurence shares how influential the Hopkins Dunbar Program was to him; it allowed him to meet great mentors and form relationships with local dentists. He also felt more prepared for the rigors of college. He mentions some of the same teachers that Jonathan named that impacted him (also Mrs. Denton, and Señor Marshal) and reflected on how his mom helped set him up to achieve his ultimate childhood goal of being a dentist. Taurence comments that meeting Dr. Hayman was a life-changing event for him and expresses appreciation. Both Jonathan and Taurence share advice for current and future Dunbar alumni