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New Frontiers in String Algorithms and Nearest Neighbour Search
No full textThis thesis revolves arounds two main frameworks of problems: (i) String Problems, such as the Longest Increasing Subsequence (LIS), Longest Common Subsequence (LCS) and the Edit Distance (ED); and (ii) Approximate Nearest Neighbour Search Problems under different metrics.
For String Problems, we show the following results:* For ED, a constant approximation algorithm which runs in near-linear time. In particular, an algorithm for approximating the edit distance between two strings of length in time ¹⁺^ up to a constant factor, for any > 0.
* For parametrized LIS, the first sub-polynomial (in the parameter) approximation. In particular, we show that for any ∈ ℕ and = (1), there exists a (randomized) - algorithm that, given a sequence of length with LIS ≥ , approximates the LIS up to a factor of 1/⁰⁽¹⁾ in ⁰⁽¹⁾ time.
* For LCS, we give the first sub-polynomial approximation in linear time.
For Approximate Nearest Neighbour Search Problems, we show the following results:* The first instance of a~simple, practical algorithm that provably leverages data-dependent hashing to improve upon data-oblivious LSH.
* We introduce the notion of metric embeddings into similarity measures over ℝ₊^, and use such new embeddings to develop Approximate Nearest Neighbor Search (ANN) algorithms which improve the approximation factor exponentially on the (longstanding) state-of-the-art on two important metrics:
* Edit distance over length- strings: poly(log ) approximation;
* _ over ℝ^, for > 2: (log ) approximation (known to be asymptotically optimal in the relevant models of computation).
While the two frameworks might apriori feel unrelated, recent progress have shown they are ultimately intertwined. First and foremost, both frameworks have proven to be core problems in the area of fine-grained complexity, where conditional hardness has been shown under the Strong Exponential Time Hypothesis (SETH), among other conjectures. Second, the algorithmic techniques for solving the frameworks are inter-related, and we will use Similarity Search techniques to solve string problems and vice versa
Band structure degeneracies and edge states in square lattice media and their deformations
No full textWe study the spectral properties of conservative linear wave systems modeling two-dimensional periodic "bulk" media, as well as "edge" media formed by the junction of two distinct bulk media. In both scenarios, we consider the cases of (1) periodic bulk media possessing the symmetries of a square lattice, and (2) linear deformations of such media. The dissertation is divided in two parts:
In part one, we begin with a spatially infinite bulk medium modeled by the Schrödinger operator H = -Δ + V, where the potential V is real-valued, periodic with respect to a square lattice, and invariant under the symmetry group of the square. The band structure of H is known to contain quadratic band degeneracy points [43, 44]; see also [8]. We prove that, under typical small linear deformations of V, each quadratic band degeneracy splits into a pair of nearby (tilted, elliptical) conical degeneracies, or Dirac points. Further, we show that both types of degeneracies are lifted upon the introduction of appropriate symmetry-breaking perturbations, and discuss the topology of the now non-degenerate bands.
In part two, we consider a class of Schrödinger operators, modeling either an undeformed or deformed square lattice bulk medium, perturbed by a spatially non-compact line defect commensurate with the underlying periodic bulk medium. For both cases (1) and (2), we construct edge states, which propagate parallel to the interface but are localized transverse to it. The edge states bifurcate from the band structure degeneracies associated with the unperturbed bulk medium; the bifurcation is controlled by effective (homogenized) edge Hamiltonians derived via multiple-scale analysis. In case (1), the bifurcation is governed by a matrix Schrödinger operator; in case (2), it is governed by a pair of Dirac operators. We present analytical results as well as numerical simulations, all consistent with the bulk-edge correspondence principle of topological physics
Probing Alkali-ion Battery Safety Hazards Using Calorimetric Techniques
No full textSince their invention in the 1980s, alkali-ion batteries, especially the lithium-ion battery, have become the dominant choice in electrified technologies ranging from small portable electronics to e-mobility devices to large stationary storage systems. As performance has been optimized and prices have decreased, the demand for these devices has skyrocketed, especially in dense urban areas where personal e-mobility devices have become an efficient mode of travel.
An unfortunate consequence of the adoption of these devices is the increasing amount of reported failure events resulting in fires and explosions, affecting lives and damaging property. Understanding the underlying mechanism of battery failure is critical to future design and use of these systems.
In this dissertation, calorimetry and lab-scale cost aware experimental design were used to test different abuse scenarios to provide a better framework to determine critical safety parameters. These methods were conducted on high and low energy dense lithium systems and beyond-lithium systems. Future experiments for these experimental methods and the outlook of holistic battery safety is discussed
Crucible of a Freedom Church: Building Culture of the African Methodist Episcopal Church in the United States, 1790s-1920s
No full textThis study examines how cultural, economic, and political conditions affected the building culture of the African Methodist Episcopal Church from the 1790s to the 1920s. Although scholarly discourse has highlighted the immense role the AME Church played in the creation of the modern-day Black Church, architectural historians are beginning to fully appreciate the connection between this institution’s building history and the ontological evolution of Blackness and perceptions of such in the United States.
By reading primary material created by AMEs alongside reviewing secondary material focused on the religious, sociological, and political history of the AME Church, I look to unearth how Black Church building embodied issues of class, identity, and respectability amongst the AMEs. This work acknowledges that the AME culture of building formed within a crucible marred by the vestiges of slavery, violence, and discrimination against Black Americans in the United States. As such, by complicating racialized minorities as architectural protagonists reacting to their material conditions, this architectural narrative explores Protestant architectural trends in several key AME Church building projects and AME print culture centered on expanding the church, while also challenging racist assumptions about Black people through building and design
Land Banking for Large-scale Land-based Investment: A Responsible Investment Perspective
Get PDFPublic banking of land for private investment appears to have emerged since the 2007–2008 global financial crisis as a common yet under-researched policy mechanism. A snapshot investigation revealed that a number of countries, particularly low- and middle-income countries (including Botswana, Ethiopia, Ghana, India, Indonesia, Kenya, and Tanzania), have attempted or are pursuing land banking policies to encourage large-scale land-based investment (LSLBI). Information about these mechanisms, including their existence and efficacy, is scant. If not done responsibly, land banking for this purpose could have far-reaching implications for local communities and risks perpetuating the same problems associated with LSLBI that decades of study have revealed. This issue paper recommends careful consideration of land banking for LSLBI as a policy mechanism and deeper research to better understand its implications for sustainable development
Regional Impacts of International Tourism Boycott: A China-Japan Conflict
Get PDFWe examine the regional impacts of a Sino-Japan territorial dispute that sparked a Chinese consumer boycott of travel to Japan from August, 2012. We find that the boycott caused large and regionally heterogenous effects in Japan. The boycott’s negative impacts are larger for Japanese prefectures with higher pre-boycott dependency on visitors, especially tourists, from China. While the intensity of the boycott effects is strongest within the first six months, we find significant negative impacts even when averaging across 24 months post-boycott. Our results demonstrate the importance of diversification across traveler types and countries of origin in providing travel services.
Keywords: Consumer boycott; Travel services trade; Tourism; Diaoyu/Senkaku Dispute; Regional impacts; Political conflict
JEL classification codes: F14, F51, F52, Z3
Influenza as Recurrent Foe: The Rockefeller Foundation’s War on Influenza and the Politics of “Preparedness” during the Twentieth Century
No full textThis Dissertation explores concerted efforts by scientific experts and the state to control and mitigate epidemic and pandemic influenza risks during the twentieth century. Using historical methodologies, this Dissertation asserts that the Rockefeller Foundation’s International Health Division (IHD) developed core conceptualizations of and strategies for epidemic and pandemic influenza control and “preparedness” between the interwar period and World War II. Within the IHD, the “influenza problem” reflected persistent scientific uncertainties–as related to the causative agent of respiratory illness, influenza etiology, and the nature of influenza immunity–as well as concerns related to epidemic and pandemic control within the nation. Domestic concerns exacerbated following the deadly 1918-1919 influenza pandemic. As an epidemic- and pandemic-prone pathogen, influenza reflected not simply a health threat, but a social, political, and economic disrupter.
Rockefeller influenza research agendas supported the creation of coordinated laboratory networks for influenza specimen collection and population “observation” within parts of the United States, South America, the Caribbean, and Central Europe; these networks transformed influenza science and possibilities for influenza surveillance domestically and internationally. Furthermore, the Rockefeller Foundation spearheaded the creation of multiple experimental influenza vaccines during World War II through collaborations between IHD experts, grantees at domestic universities, research institutions abroad, and the United States military. To Rockefeller leadership, this diverse influenza programming filled a crucial gap in the national security apparatus that could not be adequately addressed by the state during the interwar period. Influenza programming reflected a particular vision of pandemic “preparedness” rooted in the preservation of North American political and economic interests and the anticipation of pandemic crises from certain regions of the globe. This vision of pandemic influenza “preparedness” persisted through the twentieth century with the advent of coordinated surveillance and epidemiological communication networks as led by the World Health Organization (WHO).
This dissertation argues that the Rockefeller Foundation’s diverse framings of influenza risks and expansive laboratory and expert networks directly influenced the creation of WHO influenza programming following World War II. This included the formation of the World Influenza Centre in 1948 and the institutionalization of the Global Influenza Surveillance Network (GISN) in 1952. WHO influenza programming expanded throughout the second half of the twentieth century in the context of the Cold War and multiple influenza pandemics crises. By the end of the 1970s, national and global influenza priorities materialized in the form of “pandemic influenza preparedness plans” and Western experts and governments widely accepted and shaped this “preparedness” guidance. Therefore, this Dissertation directly challenges assertions in secondary scholarship that infectious disease “preparedness,” and by extension influenza “preparedness,” is a Cold War era construction
Early Risk Detection for Infection-Related Hospitalization or Emergency Department Visits Among Home Healthcare Patients
No full textBackground:
Home healthcare patients, often elderly with multiple chronic conditions, face high risks of infection-related hospitalizations and emergency department visits. Existing post-acute care risk-prediction models rely solely on structured electronic health record data and neglect information in clinical notes. They also lack temporal awareness to track changing patient risk and rarely assess fairness across diverse patient groups. To address these gaps, this dissertation aimed to: 1) systematically review existing infection models in post-acute care; 2) developed a pipeline to extract structured infection indicators from home healthcare clinical notes; and 3) build and evaluate a sequence-aware deep learning model for dynamic, equitable infection-related risk prediction.
Methods:
This dissertation comprised three studies. First, a systematic review identified common predictors, data sources, and methodological gaps in post-acute care infection models. Second, we developed an information-extraction pipeline using instruction-tuned large language models with parameter-efficient tuning and targeted data augmentation to extract structured infection indicators from home healthcare clinical notes. Third, in a retrospective cohort of home healthcare admissions, we combined structured electronic health record features and text-derived indicators to train sequence-aware deep learning models predicting first-time infection-related hospitalizations and emergency department visits within 30 days of home healthcare admission. We evaluated models on performance (e.g., area under the precision–recall curve), risk-stratification utility, interpretability, and fairness across demographic and socioeconomic subgroups.
Results:
The systematic review highlighted the need for post-acute care infection models to incorporate socio-environmental determinants, leverage multi-modal data, and adopt rigorous evaluation strategies. The infection indicator extraction pipeline achieved a partial micro F1-score of 0.88 and maintained strong format adherence, with data augmentation improving performance on rare indicators and in handling specialized terminology. The sequence-aware deep learning models, especially a Bi-LSTM integrating both structured and text-derived features, outperformed non-sequential baselines, achieving an area under the precision–recall curve of 0.88 for a four-day prediction window. Identified key predictors included baseline clinical profiles (e.g., prior hospitalizations, comorbidity burden, functional dependency) and dynamic features (e.g., home visit intensity, pulse rate change, malnutrition status), with the importance of dynamic features peaking in the most recent visits. A three-tier risk stratification concentrated over 77 percent of infection events within the top 5 percent highest-risk group. Model performance remained equitable across evaluated subgroups.
Conclusion:
This research offers a robust, actionable approach for dynamic infection-related risk prediction in home healthcare. It demonstrates the feasibility of using instruction-tuned large language models to extract structured infection indicators in resource-constrained settings and validates sequence-aware deep learning that integrates multi-source data for equitable and interpretable risk assessment. These advances support continuous, evidence-based monitoring and proactive management of infection risk, ultimately enabling personalized care planning in home healthcare
Geometrías radicales: militancia y experimentación en el cine, la música y la arquitectura de los largos sesenta en América Latina
No full textThis dissertation proposes a reconsideration of the relationship between political militancy and artistic experimentation during the Latin American long sixties, with emphasis on the early cinema of Raúl Ruiz, the music of Sergio Ortega, Frederic Rzewski and Yuji Takahashi, and the architecture of the collective Arquitetura Nova in Brazil. Far from being a subordination of art to the dogmas of the revolutionary left, these experiences constitute moments of formal and radical political exploration, where aesthetic forms are articulated with social mobilization.
The objective of the project is to dismantle a series of tropes that have dominated cultural criticism since the 1980s, according to which militant art would have been eminently literal, vertical, homogeneous, and refractory to experimentation.
The dissertation concludes that militancy in the socialist or communist parties from different latitudes was not incompatible with radical experimentation in the art of the long 1960s. Many of the most audacious forms of Latin American art emerged precisely from the internal tensions and impasses of the movements and parties themselves, which appear here as structuring principles within the works. The radical geometries that these experiences deployed in their production were new ways of articulating artistic experimentation with political processes.
The dissertation seeks to restore the critical power of militant art by showing that it was capable of avoiding dogmatism, cultivating heterodoxy and enriching the repertoires and political imaginaries even of contemporary movements. These legacies appear not as archives of the past but as tools to face the present and build the future
Violence as Device: The Poetics and Politics of Russophone Literary Culture
No full textThis dissertation brings together Russian Formalist literary theory, selected works in critical theory, and close readings in Russophone verbal culture, and investigates the relationship between violence, power, and literature in the Soviet and post-Soviet periods. It builds on the work of the Russian Formalism literary criticism movement, not simply as a method of literary analysis but as a historically situated and politically implicated way of thinking about power and language. Formalists’ theoretical insights are placed in dialogue with Georges Sorel’s reflections on myth and political violence, Walter Benjamin’s concept of Gewalt, Michel Foucault’s analysis of power as governmentality, and theories of mass cultural production of Benjamin and Theodor Adorno.
Each chapter stages a triangulation between Russian Formalist literary theory, critical theory, and a close reading of a literary text or discursive object. The theoretical findings of this dissertation present a novel and productive approach to addressing the question of violence and power in verbal culture—one that is sensitive to the complexities of artistic representation and attentive to its impact. In doing so, the study contributes to ongoing debates about the entanglements of literature with politics, including its potential role in systems of repression and propaganda, and brings to these concerns an account of how the very fabric of literature—its poetics—is tied up in power dynamics