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A Morse-theoretic approach to family Floer homology
Get PDFThis dissertation introduces a new model of the family Floer approach to Kontsevich's homological mirror symmetry conjecture constructed via Morse theoretic technology. Homological mirror symmetry (HMS) asserts a derived equivalence between the Fukaya category of a symplectic manifold X and the category of coherent sheaves on its mirror Xˇ. On the other hand, the family Floer program gives a modern reinterpretation of the construction of a Strominger--Yau--Zaslow (SYZ) mirror, and this mirror space typically comes equipped with a functor from the Fukaya category of X into coherent sheaves on Xˇ which can be used to prove HMS as asserted.
In order to give an analogous presentation of this story, we define the Morse--Fukaya algebra A associated to a suitable class of SYZ fibrations π : X → B; this is a curved A∞-algebra determined by a Morse function on the total space X, taking coefficients in analytic functions on its rigid analytic mirror space. For an appropriate choice of Morse function, A can be understood as a (suitably deformed) algebra of Čech cochains valued in polyvector fields on Xˇ. We then construct an A∞-functor from (a suitable subcategory of) the Fukaya category of X into the category mod-A of modules over A implementing the expected correspondence. Along the way we record comparison maps which together witness invariance of our constructions under a change of auxiliary technical choices.Mathematic
Quantifying tropospheric OH concentrations and coal methane emissions using remote sensing
Get PDFThis thesis is divided into two parts. In Chapter 1, I use an analytical Bayesian inversion framework to show what we can (and cannot) learn from Thermal Infrared (TIR) and Shortwave Infrared (SWIR) satellite observations of methane. In Chapter 2, I demonstrate how to develop national coal-mine methane inventories with aircraft campaigns using high- resolution hyperspectral instruments, with a view towards recently-launched hyperspectral satellite constellations. An abstract for each chapter follows.
Chapter 1. The hydroxyl radical (OH) is the main oxidant in the troposphere and controls the lifetime of many atmospheric pollutants including methane. Global annual mean tropospheric OH concentrations ([OH]) have been inferred since the late 1970s using the methyl chloroform (MCF) proxy. However, concentrations of MCF are now approaching the detection limit, and a replacement proxy is urgently needed. Previous inversions of GOSAT satellite measurements of methane in the SWIR have shown success in quantifying [OH] independently of methane emissions, and observing system simulations have suggested that TIR measurements may provide additional constraints on OH. Here we combine TIR satellite observations of methane from AIRS with SWIR observations from GOSAT in a three-year (2013-2015) analytical Bayesian inversion optimizing both methane emissions and OH concentrations. We examine how much information can be achieved on the interannual, seasonal, and latitudinal features of the OH distribution using information from MCF data as well as the ACCMIP ensemble of global atmospheric chemistry models to construct a full prior error covariance matrix for OH concentrations for use in the inversion. This is
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essential to avoid overfit to observations. Our results show that GOSAT alone is sufficient to quantify [OH] and its interannual variability independently of methane emissions, and that AIRS adds little information. The ability to constrain the latitudinal variability of OH is limited by strong error correlations. There is no information on OH at mid-latitudes, but there is some information on the NH/SH interhemispheric ratio, showing this ratio to be lower than currently simulated in models. There is also some information on the seasonal variation of OH concentrations, though it mainly confirms that simulated by models. Future satellite observations of methane will continue to improve our understanding of methane emissions and consequently [OH] and its interannual variability.
Chapter 2. Underground coal mines are important global sources of methane but emis- sion estimates are uncertain. Emission estimates for individual mines from Carbon Mapper aircraft remote sensing surveys in the U.S. agree within 20% with direct measurements used for national emission reporting (IPCC Tier 3 estimate). Such direct measurements are unavailable in most countries, which rely on estimated emission factors (EFs) applied to coal production rates. We find that EFs from IPCC Tier 1 and Model for Calculating Coal Mine Methane (MC2M) methods would overestimate U.S. emissions threefold due to incorrect dependence on mine depth. An IPCC Tier 2 method using measured basin-specific mine gas content agrees with direct emission measurements but does not account for gob well emissions and requires gas content data that are generally unavailable. We show that limited Carbon Mapper surveys successfully estimate basin-specific EFs for ventilation shafts and gob wells, enabling estimates of basin- and national-scale emissions.Earth and Planetary Science
We Never Said You Weren’t Exposed: Risk in the Aftermath of the Train Derailment in East Palestine, Ohio
No full textThis thesis focuses on the cleanup of the February 2023 train derailment in East Palestine, Ohio, and ensuing concerns over its management. The primary focus is on the Environmental Protection Agency’s (EPA) role in the response: did EPA and relevant authorities manage and communicate risk effectively? A particular emphasis is placed on the cleanup of local waterways, a controversy representative of the wider cleanup. This thesis analyzes risk management and communication within the stream cleanup and broader controversy in three manners. First, by a journalistic account of how residents have responded to uncertainty, displaying the narrative of the crisis and psychologies present in town in the aftermath of a crisis: people who can and can not ‘move on.’ This split is often based on personal experience or harm. Second: by analyzing the theoretical grounds for controversy over the cleanup, grounding East Palestine’s events in existing literature on risk perception and assessment. Dispute in East Palestine arose due to incongruities between authorities and residents in risk characterization, leading to a lack of trust between the two. This points to a need for the analytic-deliberative model of risk assessment in crisis situations. Finally, a preliminary risk assessment is conducted for the stream cleanup based on conclusions from previous chapters, employing environmental fate models to analyze authorities’ decisions. All analysis is informed by interviews with EPA officials, residents, and relevant third parties. East Palestine is a cautionary tale: once trust in government is lost, it may not be regained.Environmental Science and Engineering A
Algorithms for Fair Redistricting
Get PDFRedistricting is the act of dividing land into geographic regions, called districts, for political or administrative purposes. The most notable---and contentious---example comes from the United States House of Representatives, where seats are apportioned among states according to their respective populations following a decennial census, then assigned to political districts, with each district holding a separate election for a single representative. Political redistricting occurs periodically at other state and local levels, alongside other forms of redistricting for non-political purposes, such as the determination of school attendance zones. In all of these settings, there is a vast space of possible outcomes to consider and a compelling need for fairness and transparency.
In this thesis, we design algorithms for various redistricting tasks and provide theoretical underpinnings for existing algorithms. We begin by considering the initial task of seat apportionment, exploring the space of randomized allocation methods satisfying strong fairness guarantees while eliminating unwanted correlations across states. We then turn to the task of drawing redistricting maps that are provably fair, using ideas and results from the Cake-Cutting model in fair division. Finally, we contribute new algorithms and theory for the task of sampling random redistricting maps, with the aim of building robust statistical tests for assessing partisan fairness.Engineering and Applied Sciences - Computer Scienc
Understanding Peripheral Biological Variability in Posttraumatic Stress Disorder: Omics and Causal Approaches
No full textPosttraumatic stress disorder (PTSD) is the quintessential trauma-related psychiatric disorder that profoundly impacts long-term health. A growing body of literature links PTSD to elevated risks for cardiometabolic diseases and premature mortality, with stress-activated biological processes in both central and peripheral systems discussed as potential mechanisms. Recent studies assessing associations between PTSD and biological differences in markers obtained from peripheral tissues (e.g., inflammatory markers) have highlighted promising directions for improving our understanding of PTSD pathophysiology and health consequences. However, current knowledge remains limited regarding the relevance of different types of biological data and the utility of various methodological approaches. This dissertation examines links between PTSD symptoms and three types of biological data derived from peripheral blood samples: metabolomics, DNA methylation (DNAm), and triglycerides. Applying novel approaches in our investigations, we aimed to improve the characterization of PTSD-related biological differences and explore their implications for long-term health.
In Chapter 1, we pursued the first large-scale, population-based metabolome-wide investigation of PTSD, using plasma metabolomics data from three subsamples (total N=2,835 women) nested within the Nurses’ Health Study II (NHSII). Building on prior metabolomic analyses of depression and anxiety, our results revealed shared and distinct metabolic alterations linked to PTSD versus depression or anxiety. Notably, we identified 29 metabolites (primarily elevated glycerophospholipids and glycerolipids) associated with persistent PTSD symptoms but not with remitted PTSD. Our findings highlight the considerable metabolic impact of chronic, non-remitted PTSD symptoms and provide insights into mechanisms that may underlie elevated cardiometabolic disease risk in individuals experiencing PTSD symptoms.
In Chapter 2, we offered a proof-of-principle for using DNA methylation data from peripheral blood samples to identify subtypes of trauma-exposed civilians with meaningful differences in PTSD symptoms and health. Exploratory analyses were performed in a subsample of women in NHSII (N=707), with external validation in the Detroit Neighborhood Health Study (N=324), a longitudinal cohort of predominantly non-Hispanic African American men and women. While specific subtype classifications remain preliminary, our study demonstrated that peripheral DNAm profiles may capture both short-term and long-term information about PTSD symptom severity and physical health. This work supports the utility of a multivariate approach linking biological variation to symptom and health heterogeneity.
In Chapter 3, we examined the bidirectional relationship between PTSD and circulating triglycerides, triangulating evidence from a summary data-based two-sample Mendelian randomization study and observational analyses in NHSII. Our findings supported an effect of PTSD on elevated triglyceride levels, whereas the impact of triglycerides on PTSD risk appeared limited. By carefully considering potential biases in each design and performing a series of sensitivity analyses to address these concerns, this study improved our understanding of the causal relationship between PTSD and triglycerides.
Taken together, findings from these three studies highlight the importance of understanding peripheral biological differences linked to trauma and PTSD. Both broad, hypothesis-generating strategies and focused, hypothesis-testing investigations can offer valuable insights. A key direction for future work is to assess the extent to which these biological differences may mediate long-term health risks related to PTSD.Population Health Science
Leasing Out Sovereignty; The proliferation of Chinese Surveillance Technologies in Africa
No full textIn the everyday lexicon, digital technology is simply an instrument, a functional conduit that automatically realizes ends. Contrary to this supposition, we can explore digital technology as a political and cultural artifact that embodies values embedded in postcolonial societies. This dissertation project, based on ethnographic, documentary, and archival research, discusses digital technology's functional architecture and how it operates as the preeminent artifact to envision developed futures. The project investigates how Chinese surveillance technology has proliferated throughout Africa, particularly in Kenya, and examines the technological fix as an aspiration for improving the capabilities of the postcolonial state to bolster social order and spur economic development.
The project's principal goal is to examine the effects of digital technology on (i) state sovereignty and the governance of local populations, including the management of crime and the enforcement of economic regulation; (ii) civil society, concerning the sense of in/security, and of un/freedom it instills in citizens; and (iii) patterns of social and material inequality. What, further, are its hidden, unintended consequences in Kenya, and what particularities, if any, emerge from its postcolonial context? And, finally, what does the spread of Chinese digital infrastructure, as exemplified by the case study here, augur for China's future in Africa? These questions have significant implications for Africa and the global order at large. This project seeks to resolve these questions by focusing on the procurement and use of digital surveillance technology.African and African American Studie
Changes in the Sky: The Rise and Fall of Weather Control in the Twentieth-Century United States
Get PDFThis dissertation investigates American efforts to control the weather in the mid-twentieth century, and the many debates and controversies that those efforts provoked. Focusing on the 1940s to 1970s, it traces the rise and fall of cloud seeding: a controversial technology in which people put chemicals into clouds, in hopes of controlling everything from rainfall to sunshine, hurricanes to drought, local seasons to the global climate. Developed in 1946, cloud seeding quickly spread across the United States and the world. From booster development projects in the Southwest to top-secret climate warfare in Vietnam, cloud seeding provoked fierce debates—political, legal, scientific, ethical, environmental—about the dynamic, shifting relationship between people and the skies. Some believed that cloud seeding would bring a climate utopia. Others feared a climate apocalypse. And still others maintained that weather control was and always would be impossible. By the late 1970s, weather control seemed more elusive—and controversial—than ever before. The national preoccupation peaked and began to wane.
Ultimately, this dissertation argues that the rise and fall of weather control constituted both the apotheosis and failure of modern, secular ideas about controlling nature. Grounded in archival research, it combines historical and cultural studies with theoretical frameworks from the environmental humanities, science and technology studies (STS), political theory, and religious studies. To trace the hype, ambivalence, and conflict provoked by weather control, it weaves together newspapers and popular media; government, corporate, scientific, and legal records; and the personal papers of figures involved. Through these archives, it examines how the weather became an object of rationalization (through the production of knowledge, maps, experiments), militarization (through new forms of weaponry and warfare), capitalization (through agricultural and economic development), legalization (through new laws, regulations, court cases, and property regimes), and politicization (through postwar liberalism and conservatism in the U.S., as well as capitalist-democratic and communist ideologies abroad). Together, these processes can be understood as the attempted secularization and modernization of the sky. This dissertation explores how and why they failed.
In addition to its historical significance, this research holds contemporary relevance, as climate change and geoengineering have sparked fierce debates over the wisdom of controlling the skies through technology. By narrating the strange and understudied history of weather control, “Changes in the Sky” contributes to critical, interdisciplinary studies on the politics of nature and the ethics of technology in the twentieth century, and today.American Studie
Development of an exosome-based tagging method to label CD8+ T effector cells that immune surveil arteriolar endothelium for transcriptional characterization
No full textT cell function is highly regulated during acute viral infection to ensure an effective immune response. Upon antigen exposure, T cells experience a unidirectional differentiation that can be studied based on the increased expression of CX3CR1. Previous work from our group has identified a subset of CX3CR1hi CD8+ T effector cells that patrol along vessel walls, mostly on arterioles, enabling a rapid response to endothelial viral infections. In an attempt to isolate and characterize patrolling CD8+ effector T cells, we used Kaede (a photoconvertible protein) to specifically label intravascular T cells interacting with the endothelium at a given time point. However, this method can neither distinguish patrolling cells interacting with the endothelial wall for different periods of time nor the signal strength they receive, thus producing a heterogenous outcome with cells at various stages of patrolling. To further study patrolling T cells, we have developed a complementary approach using endothelium-derived fluorescent exosomes to tag T cells actively interacting with arterioles. This technique allows us to obtain a sizable amount of better synchronized T effectors for in depth characterization. In this regard, bulk RNA-seq unveiled a proliferating transcriptional gene signature for patrolling CD8+ T cells. This result is in agreement with the scRNA-seq data obtained with the Kaede model. Moreover, we also detected multiple Trav, Traj, Trbv and Trbj genes specifically upregulated in either patrolling or circulating T cells in both transcriptional analyses. However, by analyzing the VJ combinations and CDR regions of individual cells detected by TCR clonotyping, minor differences were identified. Finally, using a predictive software for transcriptional regulators (BART, Binding Analysis for Regulation of Transcription), we found a striking amount of epigenetic modulators upregulated preferentially in patrolling CD8+ effector T cells, indicating that these effector cells might be experiencing active epigenetic regulation. These findings suggest that CD8+ effector T cells interacting with arteriolar endothelium during the anti-viral immune response receive signals that shape them at transcriptional and epigenetic level.Graduate Educatio
The Geometry of Secondary Terms in Arithmetic Statistics
Get PDFIn this thesis, we prove the existence of a secondary term for the count of cubic extensions of the function field of fixed absolute norm of discriminant. We show that the number of cubic extensions with absolute norm of discriminant equal to is , where and are explicit constants and only depends on .
This builds on the work of Bhargava-Shankar-Tsimerman and Taniguchi-Thorne, who proved the existence of a secondary term for the count of cubic extensions of with bounded discriminant. Our approach uses a parametrization of Miranda and Casnati-Ekedahl, which can be seen as a geometric version of the classical parametrization by binary cubic forms used by Davenport-Heilbronn. This allows us to count and sieve for smooth curves embedded in Hirzebruch surfaces, in the same spirit as Zhao and Gunther.Mathematic
Effects of chronic social isolation on somatosensory circuit development and behaviors
No full textLight touch is critical for social communication across the lifespan for humans and other mammals. The COVID-19 pandemic demonstrates how social and sensory inputs, including touch, are deprived due to chronic social isolation, which can be detrimental to our mental and physical health. Previous studies on animal models of chronic social isolation have demonstrated various behavioral changes, while the relationship between changes in tactile circuits and other complex
behaviors remain unclear. Light touch processing from the body skin is initiated through the activation of low-threshold mechanoreceptor neurons (LTMRs), which synapse onto heterogeneous populations of spinal cord interneurons and projection neurons that process and transmit tactile information to the brain. In addition, corticospinal neurons with cell bodies in the primary somatosensory cortex innervate the spinal cord dorsal horn; through connections with a range of spinal cord interneurons, corticospinal neurons play a significant role in the gating of touch information and act as a ‘filter’ to selectively control which tactile information ascends to higher brain centers. Whether and how chronic social isolation affects the development of tactile circuits and behaviors is of particular interest of my thesis study.
Using conditional mouse genetics, histology, electrophysiology, and behavioral assays, we found that chronic social isolation during the post-weaning period leads to profound behavioral changes, as well as anatomical, and functional changes in somatosensory circuits. We found that post-weaning social isolation leads to behavioral hyperreactivity to innocuous light touch stimuli. We also found that post-weaning social isolation leads to an increased number and increased firing rates of spinal cord neurons in response to light touch stimuli. Further, we found that post-weaning social isolation leads to decreased corticospinal neuron innervations in the spinal cord dorsal horn, as well as decreased firing rates of spinal cord neurons in response to direct somatosensory cortex stimulation. More specifically, we found that post-weaning social isolation leads to decreased firing rates of spinal cord inhibitory parvalbumin (PV) interneurons in response to somatosensory cortex stimulations, suggesting that post-weaning social isolation weakens the connections between corticospinal neurons and inhibitory PV interneurons that ultimately causes tactile hypersensitivity in mice. In line with this, modulating distinct subsets of spinal cord interneurons, such as inhibitory Ror interneurons and excitatory PV interneurons, might be sufficient to affect
tactile sensitivities. Together, this work reveals the importance of social touch during post-weaning development in governing the normal development of tactile behaviors and circuits in mice.Neuroscienc