RSS 1.0UA Graduate and Undergraduate Research
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The graduate and undergraduate research collections share, archive and preserve research from University of Arizona students. Collections include honors theses, master's theses, and dissertations, in addition to capstone and other specialized research and presentation topics.
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EVOLUTION OF POLITICAL CAMPAIGNING: A COMPREHENSIVE ANALYSIS OF CHANGING DYNAMICS OF CAMPAIGN STRATEGIES AND VOTER DATAIn today's rapidly changing political climate, political campaigns must stay ahead of the curve and adapt to engage a diverse and technologically savvy electorate effectively. This paper explores the significant shifts and the evolution of political contact, focusing on the impact of changes in outreach strategies and technological advancements. By exploring how campaigns have adapted their contact and communication strategies, this paper aims to provide a blueprint for modern campaign engagement. Additionally, the paper delves into the evolution of voter data analysis, political polling techniques, and the potential for future adaptation in campaign strategies. By examining these key factors, this paper provides insights into how campaigns can tailor their messages and outreach efforts to specific groups of voters, ultimately enhancing their ability to connect with and mobilize supporters.
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UNDERSTANDING THE ROLE OF THE NUCLEOSOME REMODELING AND DEACETYLASE COMPLEX IN GLUCOCORTICOID GENE EXPRESSIONCreating therapies that minimize off target effects is essential for disease treatment but a comprehensive understanding of the underlying mechanisms are crucial. Lysine deacetylase inhibitors are approved for clinical use in treatment of several diseases but the full effects are not understood. Specific lysine deacetylase inhibitors have been found to have a significant effect on metabolism leading to the discovery of the interplay between glucocorticoid receptor activated genes and lysine deacetylase enzymes. These enzymes are present in multi-protein complexes of which the functions are poorly understood. Furthermore functions of the individual subunits of each of these complexes need to be explored. The Smith lab aims to determine the mechanisms through which lysine deacetylases activate glucocorticoid gene transcription. This project is specifically seeking to identify the role of the lysine deacetylase 1/2 containing nucleosome remodeling complex.
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EQUITABLE DEVELOPMENT OF THE CLEAN ENERGY WORKFORCEThe development of the clean energy industry is commensurate with employment opportunities for the national workforce, and as the industry progresses it is vital that equity is ensured. The purpose of this research is to evaluate the current position of the clean energy workforce, and subsequently provide suggestions for increasing equity and expanding the industry in a way representative of the communities it serves. After consulting peer-reviewed articles and journals on the clean energy workforce, a series of partially- structured online interviews were conducted to focus on authentic interactions that individuals have observed in their experience with the clean energy industry and/or the local workforce. Along with prior research, conversations with several stakeholders were analyzed and multiple areas of the workforce that require specific focus were identified. The clean energy workforce operates on an individual basis, essentially in absence of communication between the government and local organizations working to implement clean energy. One key piece in increasing equity for the clean energy workforce involves outreach to underserved and marginalized communities. Increasing equity in the clean energy industry, the root of this research, demands the promotion of diversity as a core attribute of all organizations involved. The clean energy industry, at its origin with the Justice40 Initiative, aims to provide equitable opportunities and benefits. During the development of the clean energy workforce, orienting employers and stakeholders around the importance of recruiting diverse individuals in every position and ensuring that marginalized individuals are included is fundamental. The intense need for assistance in subsidizing the clean energy workforce requires increased awareness surrounding the benefits of implementation. The possibility of transitioning society into a more sustainable one is met directly with a hopeful workforce in search of a living wage.
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VIOLENCE AS THE SACRED: GANG STRUCTURES AND VIOLENCE AS A FORM OF SOCIAL (DIS)ORGANIZATION AND MEANING-MAKINGThe present research considers the influence of structural conditions of poverty, inequality, and historical discrimination on the formation of gang units and the use of violence as a normative means of survival, social organization and meaning-making within gang units. The theoretical contributions and research of Wilson et al and Hawkins et al serve as the foundation for a model describing a cyclical process of gang influence, in which the structural conditions of resource scarce and spatially compressed neighborhoods incentivize dynamics of conflictive ethnocentrism and violence, which are given meaning through social dynamics defined by in-group and out-group relations to violence as a form of social capital, which exacerbates inter-group conflict as affinity groups vie to assert their exclusive claim to violence and worsen structural conditions as a result. This study argues that the described process possesses religious characteristics, particularly in the consecration of violence among gangs as a value which sets the in-group and individuals associated with the in-group apart from others. The religious theories and approaches of Rene Girard, Emile Durkheim, Jonathan Haidt, and Mircea Eliade clarify the religious character of violence in gang structures and provide an understanding of the role of violence as an example of the totemic principle. The outcome of research determines that violence as the totemic principle creates a social order of gang affiliated “elect” and non-affiliated “laity”, which eventually breaks down as different groups compete and split in the process of expansion and assertion of unique claims to violence.
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ADDRESSING TRANSPORTATION BARRIERS TO IMPROVE HEALTHCARE ACCESS IN ARIZONATransportation barriers are major in rural Arizona to adequate healthcare access, affecting very substantial proportions of underserved populations like low SES, historically marginalized, and geographically isolated. This essay explores how transportation and environmental factors relate to healthcare access across the state of Arizona, highlighting rural communities' unique challenges in general and those specifically relating to the Sonoran Desert area. The characteristic topography and harsh conditions of the Sonoran Desert alone foster special problems in terms of the development of transportation facilities, fostering isolated healthcare access. It is proposed in this paper that an amelioration of the harmful effects of these transportation constraints be undertaken by working on the causes and careful investigation of multiple interactions among various factors affecting healthcare access in rural Arizona communities. The paper's discussions focused on differences related to urban-rural disparities in transportation policies and funding, lack of transportation infrastructure, and a digital divide affecting the implementation of telehealth. The successful rural transportation methods offer lessons for conquering these barriers. Expanding internet connectivity, enhancing digital literacy, and shifting deeply held attitudes are important in fully meeting what is a very great potential for telehealth. These are multifaceted solutions through fair healthcare reforms, increasing broadband access, and providing better healthcare for all to improve well-being while enhancing the quality of life for thousands of rural citizens living in the state of Arizona: accessibility of quality healthcare. In Arizona, how transportation, environmental factors, and access to healthcare are interrelated has been an issue of growing concern over the recent past for several segments of society, such as rural communities, generally underserved populations, those with lower SES, and groups with historical marginalization and Native American tribal nations (Arizona Health Improvement Plan, 2021; Arpey et al., 2017). Such communities vary in aspects of geographical isolation, lack of resources, and shortage or reduced access to important services, such as health facilities. Thus, these communities generally have poorer health status compared to their metropolitan counterparts. Unique challenges of the physical terrain and environment, which also include the Sonoran Desert, pose distinct issues for transportation infrastructure that contribute to gaps in access to healthcare (Arizona-Sonora Desert Museum, 2019). This paper contends that addressing transportation challenges in the rural parts of Arizona is one way to minimize the extent of their negative environmental impacts on barriers to healthcare access among those most marginally located, who carry the greatest load of these challenges. We will do so by investigating how these different factors interact in complex ways to tease out feasible solutions toward better healthcare access and promoting health outcomes for all communities in Arizona.
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ATTACK OF THE KILLER POLLEN: CAN CHRONIC INFLAMMATION FROM ALLERGIES LEAD TO THE DEVELOPMENT OF DEPRESSION?Allergies are very common world-wide, affecting between 10-30% of the population. (American Academy of Allergy, Asthma & Immunology [AAAAI], 2024b). In the United States, more than 1 in every 4 individuals has some form of allergy (Centers for Disease Control and Prevention [CDC], 2023a). A Type I hypersensitivity reaction is the mechanism underlying many allergic diseases, including allergic rhinitis and asthma (Cohen, 2023). During this reaction, the body releases inflammatory mediators, such as histamine, and other signaling molecules called cytokines. This is an incorrect immune response by the body to harmless allergens (substances that cause allergies). Chronic exposure to allergens may also lead to a persistent release of these substances, causing chronic inflammation (Galli et al., 2008). Interestingly, histamine and cytokines have also been implicated in the development of depression (Hersey et al., 2022; Osimo et al., 2020). Histamine release increases the permeability of the blood-brain barrier (BBB), potentially allowing for substances like histamine itself to cross into the brain (Abbott, 2000). In the brain, histamine can lower available levels of serotonin and dopamine, which are both associated with depression (Cowen & Browning, 2015; Dunlop & Nemeroff, 2007; Threlfell et al., 2004; Varaschin et al., 2018). Additionally, pro-inflammatory cytokines can also cross the BBB and have been associated with dysregulation of systems in the brain, ultimately resulting in symptoms of depression (Yang et al., 2022). Current rates of depression and other mental illnesses are very high, while access to mental health services in the U.S. remains low (Rapfogel, 2022; Word Health Organization, 2023a). Treating allergies may be one beneficial target in the prevention of depressive symptoms or as an intervention for the treatment of depression.
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TESTING EFFECT ACROSS TYPICAL DEVELOPMENTThe study of episodic memory has been an emerging body of research since the 1970's. Various learning strategies for episodic recall have been developed and tested, such as repetition and testing-based learning. Previous research has been completed observing testing-based learning over periods of delay in children and adolescents. Until now, no studies have observed recall performance using a 6 month delay in typically developing children. Participants in our study completed the deferred imitation (DI) paradigm, a method of measuring the retention of memory patterns over periods of delay. In this paradigm, (N = 72) 3 to 17-year-old participants were presented with sequences that fell into one of three modeling conditions: model model model (MMM), model model delay (MMD), and model model test (MMT). The purpose of this study was to observe if learning through different modeling conditions affected retrieval and recall performance across development. Actions and pairs completed were used as measurement of retrieval abilities. The preliminary results of this study indicate that the testing condition allows for greater recall performance during delays of 1 month and 6 months, while the model condition resulted in less recall at delays of 1 month and 6 months. While the results were consistent across children, they did not differ with age. This study further supports the testing effect and the benefits of testing-based learning across development.
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Variable Selection in Economic Applications of Remotely Sensed Weather Data: Evidence from the LSMS-ISAThe rise in the availability of remotely sensed weather data has resulted in economists predicting different outcomes using rainfall as an explanatory or instrumental variable (IV). We analyze 174 papers to identify common rainfall metrics used as an instrument and show the extent of their ad hoc use in predicting a range of outcomes. We use agricultural productivity as a case study to examine the suitability of using different rainfall metrics as an IV. To that extent, we test the predictive power of the 14 most common rainfall metrics in the economics literature, calculated through six remote sensing products across six countries, on agricultural productivity. We find a large amount of heterogeneity in the performance of rainfall metrics. We also find concerning evidence about the validity of using rainfall metrics as an instrument, especially regarding possible exclusion restriction violations and weak instrument problems. Our findings emphasize the need for researchers to carefully select and justify their use of a particular rainfall metric to improve the reliability of their analysis.
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Unveiling Sources of Resilience and Social Support Dimensions: Honoring Mexican Immigrant Experiences and their Migration Journeys in a Borderlands Community Based Participatory ProjectFor decades, migration from Mexico to the U.S. has been a persistent phenomenon. Immigrants of Mexican origin often report experiences of discrimination, violence, and racism, describing these as a dehumanization of their human rights (Sabo et al., 2014). Research indicates that immigrants’ experiences often involve trauma and lack of basic resources, leading to significant physical and mental health consequences, including life-threatening risks, stress, and depression (Philbin & Ayón, 2016; Salas et al., 2013). These risks and economic hardships can lead to psychological distress, such as depressive symptoms, especially in low-income communities (Masarik & Conger, 2017). As a result, a better understanding of potential resources of resilience and social support for immigrants from Mexican origins in the borderlands is essential.In this dissertation, the three projects aim to better understand the sources of resilience and social support available to immigrants residing in the Southwestern region of the nation as they face challenges. The knowledge gained from this dissertation will inform future research, practice, and policy on immigrant well-being, especially among parents. The purpose is to inform better strategies to boost mental health, ultimately increasing resilience processes and social support networks among historically marginalized immigrant populations. Employing a community-based participatory research approach and a culturally responsive perspective, this dissertation outlines the essential components for exploring, identifying, and evaluating resources that serve immigrant families in the Arizona border region in the post-pandemic era. Keywords: immigration, resilience, social support, evaluation, families, CBPR.
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The Spatial and Dynamic Patterns of Climate Variability and Change in the United StatesMany adaptation and mitigation measures related to climate change require a temporally relevant understanding and for action to be taken at all levels of political jurisdiction. We analyze the developments of county experiences from the years 1895 to 2023 within the CONUS, Western U.S., Arizona, and Minnesota by employing numerous methods. The first descriptive statistical methods examine overall trends and discern how average, maximum, and minimum temperatures and precipitation patterns have changed in variability, spatial variation, as well as how the distributions have developed over time. Polarization indices are then used to analyze how the climatic experiences of counties have grown, be it more similar or less similar. We find that, for most counties, temperature variables have decreased in variability and precipitation has negligibly changed, implying a convergence of temperature ranges and minute shifts in the variability of precipitation. For most counties, the polarization of temperature variables has also decreased, while the polarization of precipitation has changed very little, suggesting that county experiences of temperature across the United States have generally become more alike and that precipitation experiences have changed little. Meanwhile, elements of spatial variation are exhibited through varying levels of significance across our selected regions, and the primarily opposing directions of results in Arizonan summers, which frequently exhibit increases in both variability and polarization.
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The Seasonal Variability of Trace Metals and their Transport Mechanisms in Intermittent StreamsMany intermittent and ephemeral washes drain metals-rich catchments, but the natural concentrations andtransport mechanisms of metals in their streamwater discharge are mostly unknown. In the 1960s, anomalously high metal content detected in southeastern Arizona streams led to the discovery of porphyry copper deposits in upstream areas of the Santa Rita Mountains. Although no large-scale mining operations have yet occurred, ground preparation activities have taken place in a catchment that is drained by the Barrel Canyon wash. Mine disturbances have the potential to not only impact water quality in Barrel Canyon, but also downstream in Davidson Canyon and in Cienega Creek Natural Preserve—sections of which are designated as “Outstanding Arizona Waters” by the State of Arizona. In addition to compiling historical records of trace metals concentrations in Davidson Canyon and CienegaCreek since 2002, this study also collected 128 new samples at four different sites between January 2021 and February 2024. Three of the four sites are connected in series via ephemeral surface washes and intermittent/perennial sections of streamflow, and could be potentially impacted by mobilized contaminants originating from the porphyry copper deposit in the Santa Rita Mountains. The fourth site is a perennial reach of Lower Cienega Creek, and is upstream of potential contamination originating from the Santa Rita Mountains. ISCO autosamplers were installed and used at each site to capture stormwater discharge brought on by heavy rains and monsoonal thunderstorms. Additionally, surface water baseflow at each site was frequently sampled throughout the study’s sample-collection period. Results from all four sites indicate that the concentrations of trace metals and major dissolved ions instormflow generally have opposite behaviors. When groundwater-fed baseflow is the primary contributor to streamflow, the concentrations of both particulate and dissolved trace metals are low, while the concentrations of major dissolved ions are high. During stormflow, when the stream is composed mostly of precipitation runoff, dissolved ion concentrations are low, while the concentrations of both particulate and dissolved trace metals are at their highest. These results suggest that the sources of trace metals in the Davidson Canyon and Cienega Creek subwatersheds are not from groundwater, but instead are being flushed out from the soil profile at relatively shallow depths during heavy rains. A seasonal cycle of dissolved arsenic concentrations increasing and decreasing in tandem withstreamwater temperature was observed at the three sites connected in series. Dissolved arsenic concentrations at the fourth site were generally higher but also more variable than at the other three sites. Possible reasons for these observed trends, such as the redox environment and the activity of iron-cycling microbes are discussed. Results from water quality analyses were compared to relevant federal and state water quality standardsspecific to trace metals. 14 of the 128 new samples exceeded at least one water quality standard, and many samples exceeded multiple different standards concurrently. 11 out of the 14 samples that exceeded thresholds were found in either Barrel Canyon or Davidson Canyon—the two sites closest to potential mine runoff. The five primary contaminants of concern were arsenic, lead, copper, iron, and zinc. This study found evidence that the concentrations of trace metals in Barrel Canyon wash, DavidsonCanyon, and Lower Cienega Creek have increased from their historic norms, beginning around late 2022. In particular, dissolved zinc concentrations in baseflow were found at unprecedented levels. It is possible that metals-rich soil from the Santa Rita Mountains was disturbed during mine preparation activities, and is now reacting with and/or being transported downstream by oxygenated rainwater, causing metals concentrations to increase along the drainage flow path. These results highlight the vital importance of continual water quality monitoring in areas that could be impacted by mining activities.
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The Role of Dopamine on Inhibition in the Mouse RetinaOne truly remarkable feature of the retina is its ability to adapt to a wide range of lightintensities over the span of minutes. The retina is a sensory organ that must be sensitive in low light conditions while also being able to maintain a high degree of resolution of its outputs during large amounts of input. While several mechanisms likely mediate this phenomenon, one source of regulation is in the neuromodulator dopamine. Dopamine is a known neuromodulator in the central nervous system and binds to one of five dopamine receptors, three of which are located in the mouse retina. Dopamine is produced by a subset of amacrine cells known as the dopaminergic amacrine cells. The release of dopamine in the retina is thought to be a gradual secretion throughout the day, dependent on increasing light levels. The subsequent binding of dopamine to one of its receptors mediates differential modulatory effects depending on the receptor subtype and the cell type targeted. Much of the work involved in measuring the effects of dopamine in the retina has involved perfusing dopamine or applying dopamine like agonists and antagonists that are specific to D1, D2, or D4 receptors. However, these receptors each reside on multiple cell types and even subtypes. The role of this work is to determine how dopamine modulates neural signaling at specific connections by utilizing a technique known as optogenetics to isolate inhibitory circuitry in the retina and determine if dopamine is modulating circuitry directly. Electrophysiological measurements of single neurons and light-evoked potentials across the retina are used to determine the direction and scale of such modulation. Understanding the role of dopamine in modulating neural signals in the retina is important for understanding how vision is processed throughout changing light conditions. Additionally, as the most peripheral part of the central nervous system, the retina gives important insight into the modulatory capacities of dopamine in the rest of the brain. This may be particularly important in the study of some diseases such as Parkinson’s and diabetes, demonstrating early homeostatic shifts in dopamine mediated neurocircuitry.
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The Optical Truss Interferometer: A Convenient Solution for Picometer Sensitivity in the LISA Telescopes and BeyondThe Laser Interferometer Space Antenna (LISA) is a planned space-based gravitational wave detector whose purpose is to observe the gravitational spectrum between 0.1 mHz - 1 Hz. The detector is formed by three spacecraft, each separated by 2.5 million km in a heliocentric orbit trailing behind the Earth. Each spacecraft is equipped with two telescopes that expand outgoing laser beams and compress a small fraction of large incoming beams from the other two spacecraft. These laser relays form the basis of the interferometry that will measure fluctuations in the distance between free-flying test masses aboard each spacecraft with a sensitivity goal of 10 pm/√Hz. Dimensional changes in the telescopes will contribute directly to the optical path of the interferometers, leading to a 1 pm/√Hz stability requirement for each telescope. The optical truss interferometer (OTI) is a contingent subsystem proposed for the LISA telescopes to aid in the verification of a 1 pm/√Hz optical path length stability. By mounting compact fiber-coupled units to the telescope structure to form Fabry-Perot cavities whose baselines are proportional to the telescope length, the dimensional stability of each cavity can be monitored with heterodyne readout methods. We have designed and developed prototype OTI units to demonstrate the capability of measuring stable structures, such as the LISA telescope, with a 1 pm/√Hz sensitivity using a set of freely mountable fiber-injected cavities. This dissertation will detail the design, development, and proof-of-concept for the optical truss interferometer as a powerful ``plug and play'' solution for the LISA telescope and ground testing of prototype stable structures.
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Teacher Efficacy and Impacts of Justice Centered Inclusive Settings on Multiply Marginalized and Underrepresented Preschool StudentsWithin educational systems across the nation, traditionally marginalized and multiply marginalized and underrepresented (MMU) groups, composed of students of color, students with dis/abilities, students living in poverty and/or emergent bilinguals, continue to be excluded and segregated, perpetuating discriminatory practices both inside and outside of school spaces. Inclusive systems however, provide a more equitable and higher quality education for all children and are instrumental in shifting discriminatory attitudes beyond classroom walls. Preschools provide the first context where children interact with the world and people outside their homes. They are prime spaces to develop social relationships and a sense of belonging rooted in seeing the value of diversity. When students of diverse abilities, backgrounds and ethnicities play, socialize and learn together, respect and understanding grow. The interplay of race, language, ability, class, and age are examined through the long history of educational reform policies that have targeted MMU students with less than impactful results. One possible way forward may lie in supporting educator recognition of dysconscious racism and dysconscious ableism and actively shifting deficit based perceptions through justice centered and inclusive educational settings. An underlying theme of this discussion is how fostering teacher efficacy for social justice and knowledge of Dis/Crit Classroom Ecology and its four components of Dis/Crit Resistance, Curriculum, Pedagogy and Solidarity can engender equitable educational outcomes concerning opportunity gaps, identification of special services and exclusionary discipline practices.Key Terms: Multiply Marginalized and Underrepresented (MMU), early childhood, inclusion, dysconscious racism, dysconscious ableism, Dis/Crit Classroom Ecology, Social Cognitive Theory, teacher efficacy
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Sparsity-Aware Hardware-Software Co-design of Spiking Neural Network AcceleratorsSpiking Neural Networks (SNNs) are bio-inspired event-driven alternatives to Artificial Neural Networks (ANNs), offering the potential for energy-efficient artificial intelligence (AI) in resource-constrained edge devices. Sparsity, the concept of activating only a small fraction of neurons at any given time, is a fundamental principle that plays a crucial role in achieving energy and computational efficiency in SNNs. However, current studies exploiting sparsity often lack thorough design space analysis, overlooking the potential workload imbalances caused by irregular sparse patterns across different tasks. Furthermore, existing Sparse Matrix-Dense Matrix multiplication (SpMM) kernels, widely used in ANNs, are sub-optimal for SNNs due to their unique multiplication-free property, necessitating the development of specialized hardware acceleration techniques. This dissertation makes two major contributions. The first contribution explores the factors that shape sparsity in SNNs and their impact on performance. We systematically investigate the effects of key training hyperparameters such as Surrogate Gradient (SG), neuronal parameters, and low-bit quantization, across diverse workloads. Our findings reveal novel insights into how these factors contribute to sparsity and provide guidance for optimizing SNN efficiency. We demonstrate a novel approach to SNN hardware-software co-design: by selecting surrogate functions that inherently induce lower firing rates, we can significantly reduce energy consumption without sacrificing accuracy. Secondly, we propose novel hardware designs to explicitly exploit sparsity in SNN accelerators, aiming to maximize energy efficiency and computational throughput. We propose a sparse design that employs a priority encoder for spike train compression and implements output-product (OP) tiling to achieve balanced workload parallelization. Building on this, we further propose a hybrid hardware design that seamlessly integrates this sparse core with a dense core. The hybrid approach is particularly well-suited for direct-coded SNNs, which directly process input samples without the need for an explicit encoding scheme, thus exhibiting varying degrees of sparsity across different layers. We rigorously evaluate our work through extensive simulations and FPGA-based prototyping, demonstrating the potential of our proposed approach to achieve significant efficiency gains in SNN accelerators compared to the state-of-the-art, all without compromising accuracy.
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Seamless Coupling of Peridynamics with Finite Element Method for the Simulation of Material Failure and DamagePeridynamic (PD) theory, based on the concept of material point interactions over a finite distance through long-range forces, results in the integral form of the equation of motion. It offers a uniform mathematical framework suitable for analyzing the mechanics of diverse systems, from discrete entities to continuous or discontinuous media. This feature allows for damage nucleation at multiple, unspecified sites and its propagation along complex, unguided paths. The finite element method (FEM) accurately predicts material deformation using existing constitutive models while incorporating specific fracture criteria for damage propagation. However, these criteria rely on local stress and strain fields and are significantly influenced by mesh size, limiting their accuracy. Additionally, predicting damage can be cumbersome due to undefined displacement derivatives at discontinuities. Although PD theory is highly effective for failure prediction, it incurs higher computational costs compared to FEM due to its nonlocal nature. Therefore, integrating PD with FEM to capitalize on their respective advantages is a key motivation. Coupling PD and FEM presents challenges due to the nonlocal nature of PD with volume constraints and the local nature of FEM with surface constraints. This study introduces a framework for conducting single- and dual-horizon bond-based (BB), ordinary state-based (OSB), and non-ordinary state-based (NOSB) PD analysis within ANSYS, utilizing its native MATRIX27 elements. Traditional PD models assume a single horizon, leading to spurious wave reflections and ghost forces in non-uniform meshes. The dual horizon PD concept allows for non-uniform discretization. The coupling approach uses the weak form of PD governing equations, integrating PD and FE regions by sharing the same nodes along their interface without overlap or constraint conditions. The PD domain is divided into three regions to ensure equilibrium equations are satisfied and to impose boundary conditions directly, eliminating the need for a fictitious layer. Failure mechanisms are introduced gradually with dynamic updates to MATRIX27 element coefficients. This study also introduces the coupling of BB, OSB, and NOSB PD models with traditional FE elements in ANSYS for structures with initial strain, considering a known temperature profile and capturing the effect of thermal strain on the coupled PD-FE model's response. Finally, it introduces the PD-FE coupling methodology to model structural response in the presence of geometric and material nonlinearity. The solution to the governing equations is achieved through implicit solution methods. The accuracy of this approach is validated by comparing it with results from finite element analysis in scenarios without failure for quasi-static and dynamic analysis. The comparisons indicate excellent agreement under plane stress and plane strain assumptions, including quasi-static and dynamic loading conditions.
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Revegetation Strategies for Ecological RestorationSeed-based revegetation is often unsuccessful in ecological restoration efforts in drylands, mainly due to an unfavorable environment for germination and establishment, as well as poorly understood germination behaviors of restoration-relevant plant species. We conducted two experiments in order to first identify potential revegetation methods for enhancing emergence and establish through the use of seed balls, and then to identify specific germination behaviors of a pollinator restoration plant known as milkweed (plants belonging to the genus Asclepias). In our seedball field experiment, we tested different seed ball types by observing how altering seedball shapes and additives impacted emergence and establishment. We found that overall, seedballs significantly enhanced early emergence, but had no long term beneficial effects on establishment, with no significant differences between the seedball types. We then conducted a germination study of various milkweed species sourced from different regions throughout the U.S. to detect differences in germination behaivour in response to warm incubation temperatures and cold stratification. Overall we found that dormant milkweed populations responded postively to a six week period of cold stratification, but that two southern populations of A. asperula and A.syriaca may have higher sensitivty to warm incubation temperature. We also found that non dormant milkweeds displayed similar germinaiton rates across a range of warm incubation temperatures, but that one populuation of A. incarnata may have higher sensitivty to warm incubation temperature while two populations of A. angustifiulia and A. speciosa have a stronger preference for warmer incubation temperatures. We suspect these differences in germinaiton behavior are linked to last frost date and precipitation seasonality of the source climate.
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Resilience for Trauma and Adverse Events Among Firefighter First RespondersPurpose: This quality improvement project’s purpose was to educate firefighter first responders at Rural Metro Fire Department on resiliency practices to increase understanding of resiliency and the likelihood of adopting resiliency practices to better cope with memories of adverse events while on duty to reduce PTSD.Background: Firefighters’ repeated exposure to high-stress situations can lead to symptoms of PTSD. Existing research suggests firefighters with resiliency skills cope with chronic exposure to trauma and adverse events and have decreased symptoms of PTSD, compared to first responders who do not. Methods: Firefighter crew members with the Rural Metro Fire Department volunteered to participate in this quality improvement project. Participants were given a 15-minute PowerPoint educational discussion, a post-retrospective survey in paper printed form, and a resiliency information handout to keep. Results: Five firefighter participants completed the post-retrospective survey. Based on the data, there was an increase in firefighter’s knowledge and intent to use resilience practices plus an improvement in understanding and comfort in using resilience skills. Also, data shows firefighter participants felt this quality improvement resilience education would be beneficial for firefighters’ mental health. Conclusions: This quality improvement project suggests alternative interventions for PTSD among firefighter first responders beneficial to improving resilience skills for this population. Utilizing resilience as a belief allows first responders to acknowledge their stressors, advocate for their own mental health, and influence a support system of first responders.
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Repression in Conflict-Affected States: The Role of United Nations Peace OperationsSince the inception of the United Nations, peace operations have been employed to respond to wars, political violence, and fragile political contexts. For the first 42 years, from 1948 to 1990, these consisted of enforcement peacekeeping operations and small-footprint individual representatives of United Nations components, or Good Offices Engagements. Since 1990, special political missions have filled a gap between these intervention options. These missions consist of international and domestic personnel in the field, tasked with mandates ranging from human rights monitoring to election observation to security sector reform. As the United Nations moves away from peacekeeping, political missions are increasingly replacing engagements around the world. However, the literature on peace operations has lagged behind. In this dissertation, I addresses the gap by engaging with recent work on political missions and identifying how longstanding peacekeeping literature applies to political missions. Further, we know little about the impact of these political missions on important outcomes, like violent state repression. In Chapter 3, I find that political missions and peacekeeping are determined especially by domestic factors, and this is particularly true for sequencing between mission types -- replacement of peacekeeping with political missions is significantly driven by the length of United Nations engagement in host countries. In Chapter 4, I find tentative evidence that political missions can reduce the severity and incidence of government-perpetrated killings, like peacekeeping. Political missions seem to operate in somewhat different environments from peacekeeping, which then impacts their ability to constrain state use of violence against civilians. In Chapter 5, I build on some existing work to define nonviolent repression and locate it within the concept of positive peace in conflict-affected states; I identify how peacekeeping operations and political missions differently affect the severity of this repression, finding that peacekeeping is effective at improving conditions for civil society but political missions have unclear effects. These chapters especially contribute to the literature on United Nations peace operations by applying lessons from the existing literature on peacekeeping to political missions; these chapters add to work on repression by discussing nonviolent repressive tactics and developing a principal-agent framework around constraints on repressive agents. The findings about similar violent repression reducing effects of political missions as peacekeeping is a positive, but the minimal effect on nonviolent repression highlights an area that the UN and academics should consider more closely moving forward.
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Remote Sensing of Aboveground Vegetation Structure, Biomass, and Water Content Across Spatial and Temporal ScalesVegetation plays a critical role in the interaction of terrestrial carbon, water, energy, and nutrient cycles at the Earth's surface, influencing global biospheric-atmospheric exchanges of carbon and water and regulating the climate system. However, natural and human-induced disturbances are increasingly affecting ecosystems, leading to reduced carbon storage by vegetation. Satellite remote sensing is used for spatiotemporal estimation of key vegetation variables such as structure, aboveground biomass (AGB), and vegetation water content (VWC), but coarse pixel resolution poses challenges for accurate calibration and validation of these estimates. In this dissertation, I explored novel remote sensing technologies and techniques to improve structure, AGB, and VWC estimation across multiple spatial and temporal scales. I incorporated environmental disturbance factors to benchmark the temporal sensitivity of these estimates to large-scale biomass change and to evaluate their accuracy in quantifying disturbance-driven biomass loss. Appendix A focused on enriching annual AGB estimates in North American arctic-boreal ecosystems using integrated of microwave and optical-multispectral satellite observations. This approach enhanced spatial AGB across the region and improved detection of biomass loss driven by large-scale wildfires. Appendix B explored the application of close-range photogrammetry and derived ultra-high spatial resolution 3D models for extracting structural plant information, improving biomass quantification, and assessing the impacts of physical disturbance for three morphologically distinct dryland shrub species. We found that the model integrating canopy area and mean shrub height yielded the most accurate species-agnostic AGB estimate, and adequately captured biomass loss driven by physical disturbance. Appendix C evaluated tower-level microwave reflectance and its relationship with eddy covariance flux measurements, vegetation greenness, soil moisture, and satellite microwave observations in a semi-arid grassland ecosystem during the summer 2021 growing season. While correlations were generally strong during the greening phase of the growing season, they were considerably weaker during the browning phase. We concluded this was driven by the temporal lag of tower-level microwave reflectance and attributed this to its high sensitivity to late-season residual vegetation moisture. Collectively, these findings advance understanding of remote sensing applications and techniques to improve capabilities for spatial estimation and temporal monitoring of vegetation properties which are central to global carbon and water cycles.
