113588 research outputs found
Sort by
Performance Evaluation of Nitrate-Nitrogen Sensing Technologies in Organic and Conventional Iceberg Lettuce Systems under Subsurface Drip Irrigation
Get PDFEfficient nitrogen management in arid agricultural regions such as Yuma County, Arizona requires close coordination of irrigation and fertilizer applications because water movement within the soil profile directly affects nitrogen dynamics and plant uptake efficiency. This study evaluated near-real-time nitrate-N sensing technology under organic and conventional iceberg lettuce (Lactuca sativa) production systems using subsurface drip irrigation. Field trials were conducted during the Fall 2024–Spring 2025 growing season at the University of Arizona Yuma Agricultural Center on a Gila silt loam soil.Appreciation is given to the Western Alliance to Expand Student Opportunities (WAESO) for funding the internship students who contributed to this project
Modeling and Analysis of Black Carbon in the Third Pole: From Emissions to Snowmelt
No full textHigh Mountain Asia (HMA), often referred to as the Third Pole and Asia's water tower, sustains the livelihood of over 30% of our global population. However, increasing anthropogenic activities within developing economies in the vicinity of HMA's glaciers threaten the sustainability of this water tower. Deposition of light-absorbing particles from these human activities (LAPs, particularly black carbon (BC) and dust) and their interactions with regional climate have been found to contribute to accelerated snowmelt and glacier retreat in the last few decades. There are significant uncertainties in our understanding of how LAPs interact with the cryospheric interface, their sources, transport/removal across HMA, and their representation in Earth system models, precluding accurate predictions and assessments of their impacts. This dissertation addresses some of these gaps by integrating across available observations, a fully coupled novel regional reanalysis, inverse modeling, and machine learning diagnostics to quantify the impacts of LAPs, particularly BC, on HMA’s cryosphere and their key emission sources. First, this dissertation introduces and evaluates MATCHA, a high-resolution (12 km), fully coupled hydroclimate-chemical reanalysis for Asia spanning 17 years between 2003 to 2019. MATCHA provides a first-of-its-kind regional dataset that accounts for aerosol-snowpack interactions, tags BC emissions across major regions and sectors, and assimilates satellite data for chemical species. Second, tagged estimates of BC from MATCHA are leveraged within a hierarchical Bayesian inversion framework constrained by 91 observation sites across HMA, to quantify regional and sectoral BC source contributions and assess model biases, revealing significant underestimations in prior emission inventories, particularly for anthropogenic sources in remote locations and biomass burning. Subsequently, this work investigates the impact of LAPs on HMA's cryosphere, utilizing statistical and machine learning methods with network theory to help unravel the non-linear interactions between aerosols and meteorological processes impacting snowmelt. My findings demonstrate that these coupled aerosol-meteorology interactions are statistically significant and an underrepresented contributor to snow cover variability, especially during the late snowmelt season, where BC and large-scale circulation emerge as dominant factors. The results also reveal inconsistencies in how feedbacks between dust, temperature, and circulation are represented across state-of-the-art reanalyses, highlighting the need for improved representation of these feedbacks in the development of Earth system models. Overall, this dissertation provides a quantitative, observationally-constrained assessment of BC, its sources, and its complex interactions with HMA's cryosphere. By investigating biases in emissions and modeled aerosol-meteorology-snow processes, the results emphasize the need to refine emission inventories, develop region-specific model-coupled parameterizations, and implement targeted policies to mitigate LAPs-related pollution. Furthermore, it introduces a novel diagnostic framework and allied techniques that can assist in evaluating structural biases in current models, informing targeted model developments and observational monitoring strategies to improve Earth system predictability and future projections of freshwater availability in this climate-vulnerable region
Structures and Energetics of Bicyclic Organic Molecules Using Photoelectron Spectroscopy
No full textOrganic molecules are important in chemistry and relevant to many applications. The bicyclic molecules of anthranil, 1,2-benzisoxazole, and benzoxazole are all made from a benzene
ring and a five-membered ring containing a nitrogen and oxygen atoms. They are often used as scaffolds in medicinal chemistry and drug design. However, despite their notable use in
synthesis, not much is known about the energetics of these molecules. Using photoelectron spectroscopy, the adiabatic electron affinities of anthranilyl and 1,2-benzisoxazolyl were
measured. Anthranilyl has two distinct states, nearly overlapping electronic adiabatic electronic affinities of 3.12 eV and 3.34 eV, while for 1,2-benzisoxazolyl only one state is observed around 2.94 eV. The completion of these experiments allows for a broader comparison to be made between the isomer family and the five-membered rings. Combined with previous work done for the other three molecules, the effect that location of the heteroatoms has on the energies and electronic structures of the radical states can be analyzed. The results indicate that anthranilyl has the largest EA of the bicyclic isomers and the addition of the benzene ring causes additional ?-stabilization. The similarities in the behaviors between the bicyclic rings and the five-membered rings show that the addition of the benzene does not always have a large effect. This work brings light to the relationship between molecules in an isomer family and the effect that moving the heteroatoms can have
Exploring the Clinical Utility of Genetic Testing in Patients with Primary Hyperparathyroidism
No full textPrimary hyperparathyroidism (PHPT) is a common endocrine disorder characterized by increased levels of serum calcium and parathyroid hormone. Although frequently sporadic, a genetic etiology can be confirmed, usually through multi-gene panels, by the identification of germline pathogenic or likely pathogenic variants (GPVs) in at least ten genes in 10-30% of PHPT cases, with important implications for management. Recently published expert guidelines by the American Society for Bone and Mineral Research (ASBMR) recommend genetic testing for patients with PHPT who are under the age of 30, have multiglandular involvement, and/or a family history of hypercalcemia or a PHPT-related condition. We reviewed the medical records of 31 unrelated patients referred for a genetic evaluation for PHPT to calculate the diagnostic rate of testing and compare the phenotypes of patients by testing outcome. The diagnostic rate of genetic testing in patients with PHPT in this study was similar to other rates reported in the literature. As expected, six out of seven individuals with positive genetic testing results were found to meet ASBMR criteria. Importantly, exome sequencing (ES) performed in individuals identified to have an atypical phenotype identified GPVs in genes not included in PHPT multi-gene panels, which was the most common testing modality. These results highlight the utility of genetic testing in patients with PHPT and the role of ES in patients with atypical phenotypic presentations. Larger studies will be beneficial to further investigate the utility of ES in these disorders
"We Only Have to Be Lucky Once": Political Opportunity and Strategic Oscillation in South Africa and Northern Ireland
No full textResistance movements rarely follow a linear path: they adapt as political environments open or close, and as internal debates and resource pressures shape what strategies remain viable. However, much of the literature reduces violent and nonviolent resistance to a fixed binary, obscuring how campaigns shift between them in response to changing political opportunities. This thesis asks: how do movements engaged in both violent and nonviolent resistance negotiate between these strategies, and what roles do political opportunity, leadership dynamics, cost-benefit analysis, and resource constraints play in those decisions? I develop the concepts of strategic oscillation — the deliberate return to earlier violent or nonviolent tactics — and tactical hybridity, the simultaneous pursuit of multiple approaches. Using qualitative case studies of the anti-apartheid movement in South Africa and the Irish republican movement in Northern Ireland, I trace how both campaigns began as nonviolent struggles, adopted armed tactics when major state repression narrowed political openings, and ultimately returned to nonviolence when new opportunities emerged. South Africa leveraged international legitimacy and sanctions to expand nonviolent pressure, while Irish republicans drew on diaspora support and internal factional contestation to sustain violence longer before shifting toward electoral politics and negotiations. The analysis finds that movements do not simply react to repression or marginalization; they interpret and exploit shifting political opportunities, weighing legitimacy, resources, and leadership priorities in deciding when to escalate or de-escalate. Understanding these oscillations reframes resistance as an adaptive process driven by how movements navigate the openings and constraints of their political environment over time
An Analysis of Street Design at Fatal Pedestrian Crash Sites in Tucson, Arizona
No full textSustainable Built Environments Senior Capstone ProjectThe Tucson metropolitan area is the third-deadliest metropolitan area for pedestrians in the United States. Pedestrian fatalities nationwide are increasing. This study analyzes street design elements at sites of fatal pedestrian crashes in the City of Tucson to identify features that are associated with higher rates of pedestrian fatalities. While pedestrian fatalities have seen a rise over the last decade due to factors not inherently linked to street design, such as driver distraction, vehicle weight, hood height, and pedestrian inebriation or distraction, it is critical to utilize street design as a mitigating factor in the wake of these challenges.
Quantitative geospatial analysis of pedestrian crash sites in Tucson found that 87% of fatal crashes occurred on arterial streets. 76% of fatal crashes occurred during the night. On average, there were 2.1 streetlights within 100ft of a fatal crash and 3 streetlights within 100ft of a nonfatal crash. The rate of fatal crashes was higher than the city rate on roads with speed limits at or above 35 mph, and on roads with 2 or more lanes in each direction. Ward 5 had a fatal crash rate of 16.2%, while Ward 4 had a fatal crash rate of only 7%.
To address the rise in pedestrian fatalities, street design in Tucson should prioritize a reduction in speed limits, implemented in conjunction with traffic calming measures, and the installation of street lighting along all major streets and routes in Tucson.This item is part of the Sustainable Built Environments collection. For more information, contact http://sbe.arizona.edu
Translational Insights on Aging and Neurodegenerative Disease from Preclinical Neuroimaging
No full textThe dissertation entitled Translational Insights on Aging and Neurodegenerative Disease from Preclinical Neuroimaging describes a collection of studies that investigate age-related brain changes and neurodegenerative processes in non-human animal models, including ferrets and bonnet macaques, using advanced neuroimaging techniques. One study, Section 2 Ferret Brain Structure and Aging Characterization with Multi-variate MRI, focuses on structural Magnetic Resonance imaging, Cerebral Blood Flow imaging, and diffusion metrics in ferrets, revealing aging-related tissue changes, subtle structural alterations, and highlighting the need for machine learning and longitudinal data to refine these findings. The second study, Section 3 Multi-Metric Quantitative MRI Identifies Spatially Distinct Age-Related Brain Differences in Female Bonnet Macaques, employs a data-driven, voxelwise analysis of high-resolution ex vivo quantitative MRI (qMRI) in bonnet macaques, using a multi-metric approach to detect age-related differences in brain morphometry and microstructure, emphasizing the importance of combining diffusion, relaxometry, and morphometry in aging research. The third study, Section 4 Development of Pathologic Aging Animal Model, explores the development of a tau/amyloid seed model in ferrets, employing precise stereotaxic targeting and MRI to track tau/amyloid migration, with ex vivo analyses suggesting microstructural alterations. Collectively, these studies underline the potential of multi-parametric neuroimaging to enhance our understanding of age-related brain changes and neurodegenerative mechanisms, while also addressing the technical challenges of imaging resolution and sample size limitations in animal models.Release after 04/28/202
Do Gender and Gender Inequality Inform the Migration Decisions of Skilled Workers?
No full textThis dissertation explores how gender and gender inequality shape skilled workers’ migration decisions, with particular focus on the flow to the United States. Building on scholarship in gender and migration as well as academic mobility, it expands our understanding of migration pathways among the highly educated. Gender serves as a central sorting mechanism in skilled migration flows, influencing each step of the migration process. Grounded in sociology’s core concern with the relationship between structure and agency, I examine gender at two levels: individual gender as a personal attribute, and gender inequality as a societal structure. This framework illuminates how macro-level inequalities and micro-level decisions together shape international migration patterns. This dissertation traces gender effects across migration pathways, from initial migration through return. Chapter 1 (Appendix A) examines who migrates by analyzing educational selectivity patterns. Using South Korea as a case study, I find that women immigrants to the US are more educationally selective than men, suggesting that educated women are more likely to emigrate than their male counterparts. This pattern indicates how gender inequality may drive the “brain drain” (or brain circulation) of talented women. Supplementary analysis of Chapter 1 (Appendix A-2) provides qualitative evidence demonstrating how gender functions as a migration driver. The analysis reveals that gender inequality motivates migration through two privilege-mediated mechanisms: explicit barriers and implicit constraints. Chapter 2 (Appendix B) investigates who pursues PhDs abroad, revealing non-linear effects of gender inequality. In low-inequality contexts, women are more likely than men to receive US PhDs. However, this pattern reverses in high-inequality contexts, where women become less likely than men to pursue US doctoral degrees. This U-shaped relationship illuminates the complex barriers operating at different inequality levels. Finally, Chapter 3 (Appendix C) analyzes return migration after PhD training. The results show that home country gender inequality deters women’s return; as gender inequality increases, women PhD recipients become less likely to return home. This pattern demonstrates how countries with high gender inequality lose female talent in the global competition for skilled workers.
Taken together, these findings underscore how gender inequality creates cumulative migration effects throughout migration cycles. First, selection effects emerge as educated women leave high gender inequality countries. Second, access barriers arise as gender inequality restricts opportunities for international education. Third, retention challenges occur as women avoid returning to countries with persistent gender inequality. These patterns imply that gender inequality shapes global talent flows and reinforces knowledge production inequalities in the global academic landscape.
Release after 06/25/202
Defining Endogenous Clearance Mechanisms of Full-Length TDP-43 and Its Disease-Prone Isoforms
No full textAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by motor neuron atrophy, resulting in paralysis and respiratory failure. A pathological hallmark in >95% of ALS patients is the cytoplasmic mislocalization and aggregation of the RNA-binding protein TDP-43. Pathological N- or C-terminal truncated TDP-43 isoforms are associated with ALS, and reducing their levels, along with full-length cytoplasmic TDP-43, improves viability in various ALS cell models. However, the mechanisms by which cells normally degrade full-length and truncated TDP-43 isoforms remain incompletely understood. Here, I demonstrate that in addition to previously identified degradation pathways, the endolysosomal pathway plays a significant role in TDP-43 clearance. In yeast, I identified adaptors of the E3 Ub ligase Rsp5 that aid in TDP-43 degradation. In HEK293 cells, I confirmed that NEDD4 (Rsp5 homolog) ubiquitinates TDP-43 with K63-linked ubiquitin chains, consistent with endolysosomal degradation. To further investigate endogenous full-length TDP-43 and isoform-specific clearance mechanisms, I have constructed various full-length TDP-43 and isoform-expressing yeast strains under β-estradiol inducible promoters for use in genome-wide dot blot screens. These screens will identify which genes or drugs have the most significant effect on full-length TDP-43/isoform levels within the cell, which can then be further explored in human cells. This approach may allow for the identification of isoform-specific degradation pathways that do not target full-length TDP-43, uncovering new therapeutic strategies for ALS that mitigate toxicity without compromising the essential functions of full-length TDP-43
Asymptotic Analysis of Wave Packets in High-Speed Boundary Layers
No full textAsymptotic methods are utilized as computationally inexpensive tools to analyze the linear evolution of three-dimensional and two-dimensional wave packets in compressible boundary layers. Parallel and quasi-parallel spatial Linear Stability Theory (LST) are employed to formulate integrals that describe wave packet development. The Steepest Descent method and a related but simplified so-called ‘Gaussian Model’ are applied to asymptotically evaluate the integral with respect to frequency for the case of two-dimensional wave packets and the double integral with respect to frequency and spanwise wavenumber for the case of three- dimensional wave packets. Focus is placed on supersonic and hypersonic flat plate boundary layers, where wave packets are dominated by first mode and Mack’s second mode instabilities, respectively. In the case of wave packets dominated by Mack’s second mode, limitations of the ‘Gaussian Model’ become pronounced. Conversely, and as expected, the Steepest Descent method offers higher accuracy, but unexpected challenges emerge for quasi-parallel boundary layers due to the presence of synchronization between discrete modes—a phenomenon unique to Mack’s second mode instability. Discussions of these challenges along with efforts to address them are presented. Since discrete mode synchronization is absent in first mode instabilities, both Steepest Descent and the ‘Gaussian Model’ can be successfully applied for wave packets dominated by first mode instabilities. Finally, for the case of second mode dominated wave packets, asymptotic predictions for wave packets are compared with results from Linearized Navier-Stokes computations. Good agreement is found for the dominant frequency and time of wave packet arrival, as a function of downstream distance, whereas wave packet amplitudes are not predicted as accurately