UC Santa Cruz

The chemistry of the heavier pnictogens has shaped medicine for centuries, from the earliest therapeutic applications to the modern use of pnictogen compounds in treating infectious disease and the emergence of radioisotopes for diagnostic imaging and targeted radiotherapy. Despite this rich history, many aspects of heavier pnictogen chemistry remain incompletely understood, particularly the relationships between molecular structure, electronic properties, and chemical reactivity in complex biological environments. Addressing these fundamental questions is essential for the rational development of next-generation pnictogen-based therapeutics, diagnostics, and ligand design.This dissertation investigates fundamental aspects of arsenic, antimony, and bismuth chemistry through four complementary studies spanning historical medicinal chemistry, redox reactivity, coordination chemistry, and ligand design. First, the long-debated structure of Ehrlich's arsphenamine is revisited through a critical examination of historical evidence and modern structural characterization, providing a new perspective on one of medicinal chemistry's most influential compounds. Second, a series of arylarsonic acids are examined as redox-activated prodrugs to elucidate how electronic structure governs reduction kinetics, ligand exchange, and biological activity, establishing structure-reactivity relationships that inform the design of modern arsenic therapeutics. Third, the synthesis and characterization of small molecule tricysteinylpnictines are explored as simplified models for understanding the coordination environments of arsenic, antimony, and bismuth in sulfur-rich proteins, providing insight into the structural principles that underlie biological recognition and reactivity. Finally, principles of hard–soft acid– base chemistry are applied to the development of new chelators for heavy pnictogens, with the goal of enabling the stable coordination of medically relevant radioisotopes for future imaging and therapeutic applications.Collectively, this dissertation illustrates that common themes link seemingly disparate problems in heavier pnictogen chemistry. These studies establish fundamental structure-reactivity relationships that provide a foundation for future advances in medicinal, biological, and radiochemical applications of the heavier pnictogens.

Human disturbance is one of the most pervasive forces shaping wildlife behavior, and there is growing recognition that human presence itself acts as a distinct form of disturbance. Outdoor recreation is an increasingly popular form of human presence with potential impacts on wildlife, particularly large carnivores whose large spatial and energetic requirements frequently bring them into close contact – and conflict – with people. As interest in outdoor recreation grows, so too does the need to understand it’s impact on wildlife behavior so that we can develop management strategies that support the interests of both people and wildlife. In my dissertation I explore how outdoor recreation impacts mountain lion (Puma concolor) behavior and how we can apply our understanding of human-mountain interactions to develop effective management strategies that promote human-carnivore coexistence. First, I quantify mountain lion response to recreational activity using a novel metric of recreation intensity. I then explore individual variation in mountain lion response to recreation and ask if differences in individual behavioral responses scale up to affect the risk of human-mountain lion conflict (Chapter 1). Next, I investigate the efficacy of two novel behavioral modification strategies that aim to reduce the potential for human-mountain lion conflict on recreational landscapes (Chapter 2). These tools offer non-lethal alternatives to carnivore management in high-human use areas and attempt to reduce potential conflict by reducing spatiotemporal overlap between people and carnivores. Finally, I apply our findings to develop a human-mountain lion interaction management plan that synthesizes what we know about mountain lion ecology to develop management recommendations that support the long-term population persistence of mountain lions in the Santa Cruz Mountains (Chapter 3). This work attempts to integrate novel research findings with applied management practices to support the long-term conservation of carnivore populations living on human-dominated landscapes.

As climate conditions become warmer and drier, there is an increased threat to agricultural productivity. Increased temperatures and reduced water availability can impede crop performance and reduce yields. However, the relative effects of drought on different crops and the consequences for yield is less well understood, specifically, the physiological and structural principles that underpin crop performance under water deficit. Understanding the limits of economically important crops, especially as growers transition towards more sustainable forms of agriculture, is critical. In order for these transitions to occur, it is useful to identify the crop varieties and the suite of traits that will allow them to thrive under limited resources. To identify these suite of traits that allow crops to survive under water deficit, I studied a combination of physiological, anatomical, and morphological traits in strawberries, tomatoes, and beans, grown under well-watered and water-deficit conditions. In the first chapter titled “Physiological and yield tradeoffs among ten strawberry (Fragaria x ananasssa Duch.) cultivars under reduced irrigation frequency”, I hypothesized that strawberry cultivars subjected to reduced water availability would have a variety of physiological traits that would lead to tradeoffs in drought resistance and hydraulic efficiency. To test this hypothesis, I compared physiological traits among 10 different cultivars of strawberries that were commercially grown at Driscoll’s Berries facilities under regular irrigation and a 50% decline in irrigation. I found that water stress consistently increased leaf thickness and fruit soluble solids (°Brix) while reducing stomatal conductance, phloem fraction, and fruit size, revealing trade-offs between water conservation and yield. In Chapter 2, “The structure-function tradeoffs of the dry-farm adapted, heirloom tomato Solanum lycopersicum L., var. Dirty Girl”, I build upon the results of Chapter 1 in a different system of sustainable agriculture called dry-farming. Dry-farming is a method for growing crops under little to no irrigation. I hypothesized that dry-farm adapted varieties of tomatoes have adapted to mitigate drought stress under minimal water input through a variety of physiological traits, such as increased resistance to embolism. To test this hypothesis, I compared two popular California varieties of organic tomatoes, the dry-farm-adapted Dirty Girl and the non-adapted Cherokee Purple, under irrigated and dry-farm conditions. I observed that dry-farming conditions reduced individual plant yield by 35.32% in Dirty Girl and 59.91% in Slicer, indicating a stronger decline in Slicer, although this difference is not statically supported by significant interaction dry-farmed. This result is bolstered by enhanced carbon acquisition traits in Dirty Girls, including greater plant height, which was supported by increased leaf vein density, and root vessel diameters, two proxies pointing to greater hydraulic conductance.. Concurrently, these plants expressed drought-tolerant traits such as a safer xylem network (smaller stem vessel diameters), increased leaf thickness (leaf mass per area), increased resistance to leaf wilting (lower water potential at turgor loss point), and increased embolism resistance in stems. To expand on the novel research of dry-farming, Chapter 3, “The physiological tradeoffs of dry-farm adapted Phaseolus vulgaris L. (common bean) varieties”, further investigates the traits I observed in Chapter 2. However, this study focuses on a two-year experiment with three varieties of common bean, which rely on water to form below ground associations with nitrogen-fixing bacteria. Like Chapter 2, I grew different bean varieties (Hopi, Black, and Green) under irrigated and dry-farmed conditions to test the hypothesis that dry-farm adapted varieties have adapted to mitigate drought stress through a variety of physiological traits. Across both years, dry-farming significantly reduced yield in all varieties despite shifts in anatomical traits associated with drought tolerance, with more pronounced effects in 2024, a warmer growing season. However, Hopi beans invested more carbon resources toward reproductive output, resulting in the highest dry mass per pod across all varieties, treatments, and years. Overall, this work explores the importance of studying physiology, morphology, anatomy, and soil traits of multiple crop varieties in the context of sustainable agriculture. The information obtained in this project is essential for informing future breeding work and farming management.

This thesis forms part of a collaborative project to establish the existence of nontrivial smooth extrinsic biharmonic maps from ℝ4 into 𝕊𝑛 through a min–max construction based on biharmonic replacement. After applying stereographic projection and removable singularity, such maps correspond to extrinsic quasi-biharmonic maps from 𝕊4 into 𝕊𝑛 . This approach is particularly relevant when 𝑛 ≥ 5, since 𝜋4(𝕊𝑛 ) = 0, and hence every map from 𝕊4 to 𝕊𝑛 is null-homotopic. As a result, classical methods such as the direct method in calculus of variations or heat-flow methods within a nontrivial homotopy class cannot be used to construct nontrivial critical points. This project aims to generalize Colding and Minicozzi’s min-max framework for harmonic maps to the case of biharmonic maps. In this thesis, we establish a compactness result for almost biharmonic maps with bounded energy which forms the essential analytical part of the broader min–max framework. In our setting, almost biharmonicity is formulated through local biharmonic replacements rather than a perturbed Euler–Lagrange equation. Under a uniform energy bound, we prove that the min-max sequence arising from this biharmonic replacement procedure bubble-converges subsequentially to a finite collection of quasi-biharmonic maps from 𝕊4 into 𝕊𝑛.

Multiwavelength spectra of active galactic nuclei (AGN) are affected by intrinsic AGN emission mechanisms fueled by the source environment and cosmic propagation along our line of sight (LoS), neither of which is fully understood. This thesis explores the former through multiwavelength data analysis and modeling of a particular blazar using a synchrotron-self-Compton model, and the latter specifically LoS effects due to photon-induced electromagnetic cascades developing in and out of cosmic voids through simulations of energetic (E> 100 MeV) photon propagation over cosmological distances.Three very high-energy (E > 100 GeV) states of the distant (20.45±0.10) blazar 1ES 0647+250 observed by the Very Energetic Radiation Imaging Telescope Array System are identified, and the emission zone is modeled using a leptonic synchrotron-self-Compton and blob-in-jet framework. It is found that one of the simplest scenarios that can describe the multiwavelength properties of the three states is a change in both the magnetic field strength of the emitting region's environment and the spectral index (below the break energy) of the electron energy distribution.2 Simulations of gamma-ray-emitting AGN at three redshifts (2 = 0.1, 0.4, and 0.7) and in four cosmic void configurations are conducted, where a void is parameterized by a region with magnetic field strength Bvoid = 0 and a non-void is defined by BIGMF 10-13 G; these are extreme assumptions about the magnetic field strength both in and out of voids. The spectral energy distributions of the detected photons show that the location of the void has a dramatic impact on the (detected) cascade flux under the extreme conditions considered in this thesis. An AGN in a void can result in a flux that is more than an order of magnitude greater than when the AGN is in a high-magnetic field BIGMF 10-13 G environment. The cascade emission appears as an enhanced MeV to GeV spectrum, which can increase the number of AGN that are detected by the Fermi Large Area Telescope when compared to other AGN catalogs, provided the AGN lie along lines of sight that intersect a high void fraction.

This dissertation investigates works of Li Xiaojiang (1951-2025), a foundational figure in the development of women’s studies in post-socialist China who received comparatively little attention in international scholarship. Li has been criticized for essentialist understanding of sex and gender and for advocating women’s self-improvement in ways that appeared complicit with China’s state-led modernization and emerging market economy. Without dismissing these criticism, this dissertation argues that they capture only part of Li’s theoretical and political significance. Reading her work across four decades, I recover a sustained concern with a fundamental political question: how might women cultivate subjective capacity and political agency under conditions that seem to leave little for either? The dissertation traces Li thought roughly chronologically. I first examine her writings of the 1980s for which she received the most criticism for. Drawing on the body of texts that her critics did not pay much attention to, I argue that despite her explicit language of gender essentialism, her account of subjectivation as synthesis of the Self and the society contains the conceptual resource for a theory of transformative agency embedded in social construction. I then turn to the 1990s debates over women’s return to the home, showing how Li distinguished herself from many of her contemporary feminist scholars by shifting attention from constatations over formal rights to the preservation of a public space in which women could continue to participate in public discussions and thus cultivate their subjective capacities. Finally, I examine her later writings and argue that even her retreat from conventional politics and turn towards the pursuit of Truth constituted an attempt to preserve spaces for intellectual and political freedom under increasingly restrictive conditions. Drawing on Eve Kosofsky Sedgwick’s concept of reparative reading, this dissertation argues that critical scholarship can attend simultaneously to the limitations of a thinker and to the possibilities contained within her thought. Li’s work, I argue, offers not a finished theory but a sustained effort of locate political agency where politics appears impossible, and to preserve the possibility of freedom and hope under conditions that offer little reason for either.

Low-abundance biosensing is constrained not only by the sensitivity of a transducer, but by the complete sequence of molecular transport, capture, recognition, translation, transduction, and statistical inference. This dissertation develops a unified framework connecting conventional surface-based electrochemical biosensors with single-molecule solid-state nanopore sensing. The framework addresses a central mismatch in miniaturized biosensors: nanoscale devices can respond strongly to an individual binding or translocation event while sampling so little area or volume that rare targets at femtomolar-to-attomolar concentrations are unlikely to reach the sensing region within a practical measurement time.To decouple molecular collection from transducer area, target capture is distributed throughout the sample volume using antibody-functionalized magnetic beads. Each captured recognition event is subsequently converted into an inert, approximately 200 nm dielectric surrogate through biomolecule-to-surrogate (B2S) translation. The same surrogate population is then measured through two independent physical readouts. In the digital branch, individual surrogates are counted as they translocate a giant solid-state nanopore. Applied to Zika virus NS1 in serum, this approach reaches an analytical limit of detection of 103 aM while preserving event-level current amplitude, dwell-time, and arrival-rate information. In the ensemble branch, translated surrogates are electrophoretically deposited onto an unfunctionalized screen-printed gold electrode, where they restrict redox-probe access and suppress square-wave-voltammetric current. Applied to SARS-CoV-2 nucleocapsid antigen, this portable electrochemical implementation achieves a 4.56 aM limit of detection, a 16.57 aM limit of quantification, and a 9.8-decade quantifiable range, and demonstrates feasibility with RT-PCR-characterized patient samples.A forward stochastic model links antigen abundance, magnetic-bead capture, transfer efficiency, surrogate generation, deposition, diffusional-shadow blocking, square-wave-voltammetric response, and measurement uncertainty without fitting the reported assay figures of merit. The measured performance falls within the model’s predicted distributions, and sensitivity analysis identifies nonspecific blank-surrogate count and its reproducibility as the dominant remaining constraints. Collectively, the results show that separating capture from transduction and translating rare molecular recognition events into robust physical surrogates provides a common route from ensemble electrochemical sensing to digital single-particle detection.

Planetary exploration requires extracting physically meaningful information from incomplete measurements acquired under environmental, instrumental, and operational constraints. This dissertation integrates Raman spectroscopy, X-ray diffraction (XRD), mineral physics, and computational analysis to expand the information recoverable from measurements of Mars-relevant materials. Raman spectroscopy provides the central connection among these studies because its vibrational frequencies, intensities, and spectral shapes encode not only mineral identity, but also bonding, hydration, crystallinity, temperature, structural disorder, and crystallographic orientation. Three studies progressively examine mineral phase identification, mineral physical state, and how it is crystallographically organized. A convolutional neural network trained using high-volume, wide within-class Raman datasets and demonstrated robust mineral classification under dusty, low-signal, and otherwise nonideal conditions relevant to Mars. These results establish that physically representative training populations and expert-guided dataset construction are critical to reliable machine-learning interpretation. Chapter 2 included variable-temperature Raman spectroscopy and XRD characterization of progressive dehydration of magnesium perchlorate and magnesium sulfate from -70 to 400°C. Mg(ClO₄)₂ undergoes discrete crystalline hydration transitions, whereas MgSO₄ progressively develops poorly crystalline and X-ray-amorphous products while retaining Raman sensitivity to local sulfate environments. Wilson GF force constants quantitatively connect vibrational frequencies to hydration-dependent changes in tetrahedral bond stiffness and coupling. A previously unreported Fermi resonance in crystalline Mg(ClO₄)₂ provides an additional hydration diagnostic and potential Raman thermometer. These results demonstrate that full-spectrum interpretation and quantitative vibrational analysis can constrain hydration, bonding, crystallinity, metastability, and environmental history beyond mineral identification alone. Chapter 3 investigates co-registered Raman and synchrotron XRD rasters of Martian shergottite NWA 13276 using combined semi-supervised, human-in-the-loop mineral identification with E-WIMV texture reconstruction. Olivine exhibits strong non-random lattice preferred orientation, while its ~810–870 cm⁻¹ Raman doublet varies systematically with crystallographic orientation, establishing Raman intensity as an orientation-sensitive observable with potential applications to Perseverance rover SuperCam measurements on Mars. This dissertation advances planetary spectroscopy from mineral classification toward physically constrained inference, demonstrating how independent crystallographic measurements, systematic experiments, mineral physics, and expert-guided computation can transform spectral variability from an analytical complication into information about mineral state, structure, and geological history. La exploración planetaria requiere extraer información físicamente significativa de mediciones incompletas adquiridas bajo restricciones ambientales, instrumentales y operativas. Esta tesis integra espectroscopia Raman, difracción de rayos X (XRD), física de minerales, y análisis computacional para ampliar la información recuperable de mediciones de materiales relevantes para Marte. La espectroscopia Raman proporciona la conexión central entre estos estudios porque sus frecuencias vibratorias, intensidades, y formas espectrales codifican no solo la identidad mineral, sino también los enlaces, la hidratación, la cristalinidad, la temperatura, el desorden estructural, y la orientación cristalográfica. Tres estudios examinan progresivamente la identificación de fases minerales, el estado físico de los minerales, y cómo se organiza cristalográficamente. Una red neuronal convolucional entrenada utilizando conjuntos de datos Raman de gran volumen, con amplia variabilidad intraclase y demostró una clasificación robusta de minerales bajo condiciones polvorientas, de baja señal, y otras condiciones no ideales relevantes para Marte. Estos resultados establecen que las poblaciones de entrenamiento físicamente representativas y la construcción de conjuntos de datos guiada por expertos son fundamentales para una interpretación fiable mediante aprendizaje automático. El Capítulo 2 incluyó espectroscopia Raman a temperatura variable y caracterización mediante XRD de la deshidratación progresiva del perclorato de magnesio y el sulfato de magnesio desde -70 hasta 400°C. Mg(ClO₄)₂ experimenta transiciones discretas de hidratación cristalina, mientras que MgSO₄ desarrolla progresivamente productos poco cristalinos y amorfos a los rayos X mientras conserva la sensibilidad Raman a los entornos locales del sulfato. Las constantes de fuerza Wilson GF conectan cuantitativamente las frecuencias vibratorias con cambios dependientes de la hidratación en la rigidez y el acoplamiento de los enlaces tetraédricos. Una resonancia de Fermi no reportada previamente en Mg(ClO₄)₂ cristalino proporciona un diagnóstico adicional de hidratación y un posible termómetro Raman. Estos resultados demuestran que la interpretación del espectro completo y el análisis vibracional cuantitativo pueden restringir la hidratación, los enlaces, la cristalinidad, la metaestabilidad, y la historia ambiental más allá de la mera identificación mineral. El Capítulo 3 investiga barridos Raman y XRD de sincrotrón corregistrados de la shergottita marciana NWA 13276 utilizando una identificación mineral combinada semisupervisada, con intervención humana y reconstrucción de textura E-WIMV. El olivino presenta una fuerte orientación preferente de red no aleatoria, mientras que su doblete Raman de ~810–870 cm⁻¹ varía sistemáticamente con la orientación cristalográfica, estableciendo la intensidad Raman como una magnitud observable sensible a la orientación con posibles aplicaciones a las mediciones de SuperCam del rover Perseverance en Marte.Esta tesis hace avanzar la espectroscopia planetaria desde la clasificación mineral hacia la inferencia físicamente restringida, demostrando cómo las mediciones cristalográficas independientes, los experimentos sistemáticos, la física de minerales, y la computación guiada por expertos pueden transformar la variabilidad espectral de una complicación analítica en información sobre el estado mineral, la estructura, y la historia geológica.

What did anticolonial Muslim thinkers contribute to the recasting of political ideas in the global twentieth century? Prevalent scholarship has largely overlooked this significant terrain of thought, which my dissertation seeks to recover and theorize. While anticolonial thinkers and political actors widely celebrated popular sovereignty as a basis for self-determination, many anticolonial Muslim thinkers remained ambivalent about it. Their ambivalence stemmed from a deeper conceptual dilemma about popular sovereignty and its particular relationship to the modern state: that when sovereignty is delegated to the state as the central institution for organizing social and political life, the state often takes on an abstract and autonomous form of its own that, in turn, may ultimately undermine rather than embody the sovereignty of the people.This dissertation shows how four anticolonial Muslim thinkers from South Asia reconstruct Islam’s divine sovereignty to disentangle sovereignty from the state’s exclusive claim and place it with individuals, making them genuinely sovereign. In doing so, it demonstrates how these Muslim thinkers imagine democratic and political visions that are local and collective, driven by everyday ethical practices in Islam. In such visions, the individual’s moral and political life is situated within the state but not solely determined by it; the individual’s social and political life may embrace certain claims of the nation without being subsumed into the ideological framework of nationalism. That is to say, the dissertation excavates how Muslim thinkers envision a nonstatist politics and call for Islamic ethics to be the principal constituent of politics and social life. To realize such a vision of ethical politics, it illustrates how anticolonial Muslim scholars advance incisive critiques of liberal individualism, the idea of a political community organized by the state, and the centrality of enlightenment rationality by deriving conceptual and historiographical resources from Islamic history and tradition of thought. More significantly, it shows how these scholars offer novel theories of the individual, community, and humanism, as well as alternative visions for transforming politics and social life after the removal of empire. These imaginaries engender participatory democratic possibilities set in the ethics of everyday life, thus envisaging a social and political order different from the hegemonic liberal order.

There are many valid reasons for someone to browse the internet privately, and Virtual Private Networks (VPNs) are one method of achieving this. Although primarily used to provide confidentiality and anonymity by encrypting internet traffic and masking IP addresses, users may choose to use a VPN for multiple purposes. However, this raises questions about whether, and how differently, content across the internet is portrayed to VPN users. VPN providers do not all route their traffic the same way, and this study analyzes these differences by investigating two major VPN providers, NordVPN and Surfshark. We measure and quantify the accessibility of popular websites to users of these two VPNs, comparing outcomes against a non-VPN control connection to determine whether, and to what extent, VPN use affects a user's ability to reach and use ordinary websites. This raises a central question: is VPN-related blocking better explained by the network a VPN happens to use, or by where its exit server is physically located? To investigate this, requests to the Tranco top 10,000 domains were compared between each VPN and a non-VPN control connection to measure blocking at full scale. A second set of experiments isolated exit servers by network (ASN) and by physical location across a smaller domain set, allowing the effects of these factors to be compared. At full scale, NordVPN showed 1.59\% VPN-attributable blocking and Surfshark showed 0.42\%. When exit servers were isolated by ASN and location, block-rate variation did not show a clear difference between the two factors, while the network path taken by a request varied substantially with location. These results suggest that VPN-related blocking is not explained by a single infrastructural factor, but instead depends on multiple properties of the network through which a VPN request is routed, including characteristics of the individual exit, network infrastructure, and geographic location. At full scale, NordVPN showed 1.59\% VPN-attributable blocking and Surfshark showed 0.42\%, measured across the Tranco top 10,000 domains using a single exit per provider. Under infrastructure isolation across five ASNs and five countries, crawling top 200 domains, block-rate variation was similar whether ASN or location was held fixed (2.5\% vs. 4.0\% mean within-group range). Per-provider significance testing further found that only a small number of ASNs showed significant differences in blocking. In contrast, network routing varied substantially with exit location: CDN routing varied by 76\% when location was held fixed, compared with 58\% when ASN was held fixed. These results suggest that VPN-related blocking is not explained by a single infrastructural factor, but instead depends on multiple properties of the specific exit and network path through which a VPN request is routed.