Now showing items 1-20 of 20274

    • Sulfur Based Polymers and Polymer Magnetic Nanoparticle Composites: Novel Materials for Next Generation IR & Magneto-Optics

      Pyun, Jeffrey; Carothers, Kyle Jordan; McGrath, Dominic V.; Lichtenberger, Dennis L.; Loy, Douglas (The University of Arizona., 2022)
      This dissertation reports on new material developments as detailed in three chapters discussing the development of high Verdet constant materials containing magnetic nanoparticles (NPs) and one chapter discussing sulfur-containing polymers for infrared (IR) optics applications. The first three chapters will cover the synthesis and characterization of different types of magnetic nanoparticles followed by their incorporation into polymer systems to generate composite materials. Further, the processing techniques utilized to generate magneto-optic (MO) devices from these composites will be discuss as well as their performance related to both the processing methodology used and the properties of the nanoparticles. For chapters 2 and 3, additional experimental information and supporting data can be found in the corresponding appendix chapters. The fourth chapter will cover recent work analyzing the transparency of polymer materials in the IR.The first chapter is the first comprehensive review summarizing the field of high Verdet constant MO materials. The Faraday effect is a type of MO phenomenon where the polarization direction of linearly polarized light is rotated when passing through transparent media under the application of a magnetic field along the direction of the light propagation. At a certain wavelength and temperature, the angle of rotation is directly proportional to the strength of the magnetic field, the path length of the medium, and the Verdet constant of the material. For MO devices, maximizing the rotation angle of the light is desired for device miniaturization and fabrication cost and can be accomplished by increasing any of the aforementioned parameters, but for devices with size constraints and with the limitations of sustainable magnetic fields, high Verdet constant materials are desired. The development of high Verdet constant materials has been ongoing since the discovery of the Faraday effect in the mid-1800s and has come to encompass a variety of material classes from hard matter glasses, crystals, and ceramics, to soft matter small molecules and synthetic polymers, and some composite materials containing both hard and soft matter. The most widely used materials for MO applications have traditionally been glasses and crystals with Verdet constants on the order of 103-104 °/T·m at room temperature when measured in the visible to near-IR range. However, more recent work has shown promising soft matter systems composed of small molecules, polymers, and nanoparticle-polymer nanocomposites with enhanced Verdet constants ranging from 104-106 °/T·m. Chapter 1 is designed to give a broad overview of the different types of high Verdet constant materials with an emphasis on the recent development ultra-high Verdet constant materials such as conjugated polymers and nanoparticle-polymer composites. The second chapter will discuss the preparation of polymer-nanoparticle composite Faraday rotators. As mentioned previously, most applications of Faraday rotators use a variety of hard matter materials to accomplish MO rotation. These materials are however limited by low Verdet constants (when compared to many soft matter systems) which has led to an increased interest in soft matter both for increased Verdet constants and for enhanced processing capabilities. The new type of MO material discussed is based on MO active cobalt ferrite (CoFe2O4) nanoparticles combined with poly(styrene) (PS) to form solution-processable composites. This study examines the importance of exchanging the surface ligands on the CoFe2O4 nanocrystals to polymer ligands that are more compatible with the PS phase of the composite. With surface compatible ligands, the NPs could be dispersed in a polymer matrix at variable loadings from 2.5-15 wt%. The solution processing techniques employed for this system allowed the MO response to be tuned by simply varying the NP loading and the number of layers in the composite. The Faraday rotators were prepared by a multilayer polymer film construct wherein alternating layers of the NP-polymer composite and cellulose acetate were spin coated allowing for an increased path length of the MO active NP-polymer layers with protective layers of cellulose acetate. These multilayered Faraday rotators demonstrated a nearly 10X increase in Verdet constant compared to a terbium gallium garnet reference material at 1310 nm and demonstrated the importance of exploring soft MO materials for enhanced MO responsive materials. The third chapter will discuss an expansion on the previous work with CoFe2O4-polymer composites. The previous work established a construct for how Faraday rotators could be produced by solution-processing using alternating layers of MO active materials to achieve a strong MO response. In this work polymer coated cobalt (Co) nanoparticles were used and offered several advantages over the previously used CoFe2O4 NPs. The synthetic strategy employed to produced Co NPs uses a native polystyrene ligand which eliminated the ligand exchange processing step and provided enhanced dispersion in the polystyrene matrix. This enhanced dispersion allowed for NP loadings up to an astonishing 50 wt% with the same tunability as the previous system. In addition to solution processing, the enhanced dispersion allowed for the formation of composites that could be melt-processed into free standing films with significantly increased thicknesses. The synthetic strategies employed additionally allowed for the synthesis of a range of particle sizes from 9 to 17 nm. This allowed, for the first time, a systematic study Verdet constant with the size dependent magnetic properties of the NPs. Due to both the increased NP loading and a stronger magnetic moment from Co NPs compared to CoFe2O4 NPs the measured Verdet constants were 2-3 orders of magnitude higher than our reference terbium gallium garnet material or our previous NP-polymer composites. The fourth chapter will cover recent work on IR imaging and the importance of uniform reporting techniques for IR transparency. There have been recent reports of new IR transparent polymers that only report the IR transparency measurement as thin films. This chapter demonstrated that thin films of poly(methyl methacrylate) PMMA (a demonstrably poorly IR transmissive polymer) could mistakenly be described as an IR transparent, transmissive optical polymer. To definitively illustrate the non-uniformity of polymer films and windows reported for IR optics, PMMA windows of progressively increasing thickness were prepared for FTIR measurements to quantity optical transmittance in the IR spectrum, along with MWIR imaging experiments. These results were then compared to poly(sulfur-random-diisopropenylbenzene) (poly(S-r-DIB)), our previously established MWIR transparent polymer. The report provided both qualitative and quantitative analysis of PMMA and p(S-r-DIB) and how only reporting on thin film properties of polymers can lead to misrepresentation of the polymer’s IR transparency. These results set a standard for how IR transparency in polymers should be reported.
    • Applications of Psychological Game Theory to Self-Handicapping and Auctions

      Dufwenberg, Martin; Mannahan, Rachel; Blume, Andreas; Deimen, Inga; Friedenberg, Amanda (The University of Arizona., 2022)
      Psychological game theory, established by Geanakoplos, Pearce, and Stacchetti (1989) and extended by Battigalli and Dufwenberg (2009), is a framework that allows players in games to have belief-dependent utilities. Belief-dependent utilities are useful for capturing preferences such as reciprocity, anger, guilt, and image concerns among others. Throughout the three chapters in this dissertation, I use the framework of psychological game theory to analyze two applications: self-handicapping and auctions. In my first chapter, I model rational agents with preferences for maintaining self-esteem. These preferences are belief-dependent, in that the agent's utility depend on a function of their ex post expectation of their own ability level, which they initially do not know. If this function is strictly concave, these agents may seek out actions that inhibit their performance. This phenomenon is called self-handicapping. I then consider policy implications if the population has self-esteem concerns. I use the theory from my first chapter to derive testable hypotheses, which I implement in my second chapter. Specifically, I design an experiment to test for self-handicapping behavior. Subjects answer questions from a Raven's Progressive Matrices test, a test of intelligence. Each question includes an option to randomize the answer choice, a self-handicapping strategy. The subjects are exposed to different information about their scores. This varies the impact of the Raven's test on their self-esteem. I hypothesize that there will be more use of randomization when subjects receive more information about their scores. Finally, in my third chapter, I characterize the pure strategy equilibria in complete information auctions when bidders have reciprocity preferences. The equilibria under standard preferences persist, but two additional types of equilibria arise. In the Refusing to Lose equilibrium, the winning bidder does not have the highest value for the item. This type of equilibrium is sustained by negative reciprocity. In the Kind Ties equilibrium, three or more bidders tie for the winning bid at a price below all of their values for the item. This type of equilibrium is sustained by positive reciprocity.
    • Abnormal Anatomy of the Auditory Cortex in Schizophrenic Brains with Auditory Hallucinations

      Musiek, Frank; Bushor, Jillian; Velenovsky, David; Norrix, Linda; Ruiz, John (The University of Arizona., 2022)
      Background: Evolving research in the psychiatric literature has suggested that the auditory cortex region is smaller in people with schizophrenia who experience auditory hallucinations than in normal control individuals. These findings are not without controversy. While there has been significant research considering volumetric variance in pathologic brains with AH, there is a paucity of data considering the influence of morphology and surface area of primary auditory structures. Purpose: The purpose of this set of studies was to evaluate and compare the following variables in schizophrenic and control brains, both between groups and between hemispheres within groups: surface area of Heschl’s gyrus (HG) and planum temporale (PT), length of the Sylvian fissure (SF), length of the posterior extending ramus of the SF, and the morphological variants of HG, PT, and the posterior ramus. Evidence of morphologic variance or surface area differences in populations that are prone to experiencing auditory hallucinations may provide new or additional insight into the role of these neuroanatomical structures in central auditory processing during auditory hallucinations. Hypothesis: Based on the previous literature we had several hypotheses: (1) in separate structure analyses with regards to surface area, there will be reduced asymmetry for primary auditory structures (HG & PT) in schizophrenic brains with hallucinations compared to controls; (2) there will be reduced typical asymmetry in Sylvian fissure (SF) length for schizophrenic brains with hallucinations compared to controls; and (3) there will be consistent patterns of morphologic differences in at least one category of Heschl’s gyrus, planum temporale, or posterior ramus variants between schizophrenic brains with hallucinations and control brains. Methods: Imaging analysis was conducted using BrainVISA Anatomist software and MRIcron software to assess 51 control brains (102 hemispheres) from the Open Access Series of Imaging Studies (OASIS) repository and 51 schizophrenic brains (102 hemispheres) obtained from the NUSDAST (Northwestern University Schizophrenia Data and Software Tools) database. These neuroimaging softwares were used to quantify surface area of HG and PT, morphology of HG and PT, length of SF, and angle of the posterior extending ramus of SF. Results: This study found a lack of typical asymmetry between right and left HG in schizophrenic brains, and a significantly larger HG in the right hemisphere of controls compared to schizophrenics. There was also reduced asymmetry of the SF length in schizophrenics compared to controls. No significant findings were established for either PT surface area or morphological classifications of HG, PT, or posterior ramus. Key Words: Auditory Hallucinations, auditory cortex, anatomy, Heschl’s gyrus, planum temporale, superior temporal gyrus, Sylvian fissure, posterior ramus, ascending ramus, schizophrenia Abbreviations: Auditory Hallucinations (AH), central auditory nervous system (CANS), Heschl’s gyrus (HG), planum temporale (PT), planum polare (PP), primary auditory cortex (A1), Sylvian fissure (SF), schizophrenia (SZ), superior temporal plane (STP), supramarginal gyrus (SMG), region of interest (ROI)
    • Abnormal Anatomy of the Auditory Cortex in Schizophrenic Brains with Auditory Hallucinations: A Systematic Review

      Musiek, Frank; Schefer, Madelyn; Velenovsky, David; Norrix, Linda; Ruiz, John (The University of Arizona., 2022)
      Background: Due to the high prevalence of auditory hallucinations in schizophrenic individuals (60-80%; Lim et al., 2016), this review will focus on evidence of neuroanatomical abnormalities found in key auditory structures of this clinical population. Identifying atypical anatomy of these areas can inform our understanding of the mechanisms underlying the experience of auditory hallucinations as well as potential deficits in central auditory processing, providing a rationale for the involvement of audiologists in diagnosis and treatment of auditory hallucinations. Purpose: The goal of this review is to describe the auditory neuroanatomical differences in schizophrenic individuals who experience auditory hallucinations compared to normal individuals who do not. Further, it will also explore how these differences in neuroanatomy may be related to central auditory processing dysfunction and auditory hallucinations. Methods: A review of existing literature published from 1960-2020 was conducted to summarize and compare neuroanatomical abnormalities of key auditory structures in schizophrenic brains. Relevant studies published between the years of 1960 and 2020 were identified using the following online databases: Google Scholar, PubMed, PSYCnet, and Mendeley, as well as books, chapters, and bibliographies. For each of the listed databases, search terms included “schizophrenia” AND “auditory hallucinations” AND “auditory cortex” AND “anatomy” AND “Sylvian fissure” OR “superior temporal gyrus” OR “Heschl’s gyrus” OR “planum temporale” OR “(central) auditory processing dysfunction” OR “dichotic listening”. Results: Findings from previous anatomical studies are in strong agreement, having identified structural abnormalities of Heschl’s gyrus, planum temporale, and the Sylvian fissure in schizophrenic brains, suggesting that these auditory structures potentially play a role in the experience of auditory hallucinations. Conclusion/Discussion: This review summarizes and compares available evidence of neuroanatomical abnormalities in the auditory cortex of individuals with schizophrenia who experience auditory hallucinations. Anatomical studies investigating auditory structures in schizophrenic brains indicate abnormalities of Heschl’s gyrus, planum temporale, and the Sylvian fissure, particularly a reduction in hemispheric asymmetries. These anatomical deviations have implications for functional auditory processing. Evidence of the involvement of these key auditory structures provides rationale for audiologists to collaborate with psychiatrists in the diagnosis and treatment of auditory hallucinations. This review also suggests the need for future research to investigate potential correlations between neuroanatomical variances in schizophrenic brains and audiological findings. Key Words: Auditory Hallucinations, schizophrenia, auditory cortex, structure, anatomy, superior temporal gyrus, Heschl’s gyrus, planum temporale, Sylvian fissure, central auditory processing, dichotic listening Abbreviations: Auditory hallucinations (AH), auditory verbal hallucinations (AVH), central auditory nervous system (CANS), inner speech model (ISM), corpus callosum (CC), superior temporal gyrus (STG), Heschl’s gyrus (HG), planum temporale (PT), gray matter (GM), gray matter volume (GMV), white matter (WM), white matter volume (WMV), anterior cingulate cortex (ACC), temporo-parietal junction (TPJ), right ear advantage (REA)
    • Scatter Based Novel Imaging Systems

      Ashok, Amit; Yang, Shu; Peng, Leilei; Pau, Stanley K.H. (The University of Arizona., 2022)
      Imaging is the process of reproduction of an object’s form. Image science is a multidisciplinary field concerned with the generation, collection, duplication, analysis, modification, and visualization of images.Traditionally, the image of an object is generated by gathering optical power reflected or absorbed by the object directly with a detector array in a one-to-one manner. For example, in optical photography, reflected or emitted photons from object are directly captured by optical elements (e.g. lens, mirror) and focused onto a detector array. However, in many scenarios where such direct imaging is not feasible, one is forced to gather information that is only indirectly related to the object. In some extreme cases, we are forced to work with only scattered photons from the object of interest. In this work, we explore two of these special cases and propose two novel indirect imaging (scattering-based) approaches operating at different wavelengths. The first indirect imaging approach we consider a novel non-line-of-sight (NLOS) imaging technique. Non-line-of-sight imaging refers to the imaging of an object that is not directly visible from the viewer/imaging perspective. A classic NLOS setup usually involves emission and collection of photons actively with time-of-flight measurements. To accurately measure a photon’s traveling time, most approaches employ expensive and exotic optical sources and detectors such as ultrafast laser and ultra high-resolution single photon avalanche detector (SPAD). In this work, we instead propose a novel passive NLOS imaging method that works with ambient light illumination and employs only commonly available imaging elements. We develop a light path order based image formation model, a learning-based model parameter estimation process, and successfully demonstrate instant passive NLOS imaging. We discussed the limitation of this technique and possible applications We then shift our focus to ultra-short wavelength or higher photon energy. In this part, we study a different type of imaging referred to as X-ray diffraction tomography (XRDT). X-ray diffraction tomography is a tomographic imaging of the coherent scattering profile (X-ray form factor) of an object and its material. Coherent scattering is one of three forms of photon interactions possible in the X-ray photon energy ranging from 10 kev to 200 kev. It occurs when X-ray photon energy is relatively small compared to the ionization energy of the atom. When a coherent scattering event happens, the photon does not have enough energy to liberate the electron from its bound state and no energy transfer occurs. Instead, the X-ray photon gains momentum from the micro-structure of the material and undergoes a change in its direction (scatter). Therefore, the scatter direction contains vital information of the micro-structure of the material and is unique to different materials. The scattering pattern is called momentum transfer function or X-ray form factor. It is considered as the golden standard in material classification. In this work, we explore the inherent sparsity in the X-ray form factors and develop a sparsity regularized reconstruction algorithm to perform maximum-a-posteriori estimation for X-ray diffraction tomography. We demonstrate the possibility of achieving higher energy resolution with limited number of photon, which allows our system to run on a lower signal-to-noise ratio.
    • Peridynamics for Failure Prediction in the Presence of Material Nonlinearity and Finite Deformation

      Madenci, Erdogan; Behera, Deepak Kumar; Venkataramani, Shankar C.; Zhupanska, Olesya; Silling, Stewart A.; Spencer, Benjamin W. (The University of Arizona., 2022)
      This study examines the failure modeling of materials exhibiting nonlinear behavior and reduced dimension structures using peridynamic (PD) theory. Among the existing PD models, PD constitutive correspondence approach is adopted in the development. PD correspondence approach offers a way to use constitutive equations from classical continuum mechanics by defining a nonlocal deformation gradient tensor. However, using the original definition of deformation gradient leads to spurious oscillations in the solution. This work uses a bond-associated deformation gradient with the peridynamic differential operator to eliminate these oscillations. The numerical modeling assumes the quasi-static loading conditions, and the solution is obtained using the implicit technique with the Intel PARDISO solver using the exact tangent stiffness matrix. PD models are systematically developed for rubber-like materials, polymers exhibiting high stretch, and epoxy adhesives. The force density vectors for rubber materials are derived using the neo-Hookean constitutive equation. The weak form of PD equilibrium is used to impose the boundary conditions directly on the last layer of material points. Stretch-based criterion is used to eliminate interaction during failure simulations. The validity for predicting damage is demonstrated through simulations of experiments concerning progressive damage growth in pre-notched styrene-butadiene rubber sheets. The formulation is then extended for the polymer that can sustain high stretches. Anand’s model and Talamini-Mao-Anand’s model are used to derive force density vectors. The fidelity of this PD model for predicting large deformation, progressive damage, and rupture is established by comparison with experimental measurements of polymer sheets with defects under displacement-controlled tensile loading. To model epoxy adhesives, a viscoelastic material model in the presence of finite deformation is employed to derive the force density vectors. The relaxation modulus for the time-dependent behavior of the viscoelastic material is described in terms of the Prony series. The model performs well in predicting interface failure of lap joint configurations. A new approach is presented to impose traction and displacement boundary conditions while solving for the strong form of PD equilibrium equations without a fictitious boundary layer. The domain is split into inner, outer, and boundary layer regions. In the “interior” region, the equilibrium equations are based on the nonordinary state-based (NOSB) peridynamics. In the “outer” region, the equilibrium equation is derived based on PD differential operator (PDDO). The PD form of traction components based on the PDDO enables the imposition of traction conditions in the actual “boundary layer” region. The displacement constraints are also enforced directly in the real boundary layer. The present approach is free of the unphysical displacement kinks near the boundaries. Also, the displacement predictions maintain the smoothness between the outer and inner regions. The displacement predictions agree well with FE results for all combinations of boundary conditions. The approach is adopted to model the creep behavior of stainless steel at high temperatures. Liu and Murakami's creep damage model is adopted to derive the force density vector. The approach is validated by considering the creep deformation of uniaxial and 2D plane stress stainless steel specimens subjected to a range of constant stress. The results compare well with the experimental measurements and analytical solutions. A generalized PD beam model is formulated based on the Simo-Reissner beam theory. The governing equations are developed based on the form invariance of the first law of thermodynamics under rigid body motion. Nonlocal measures of strain and curvature are defined using the PD differential operator (PDDO). By employing a quadratic strain energy density function for the material response, the present approach is validated by considering numerical examples of beams undergoing large deformation.
    • Improving Soil Water Retention and Nutrient Availability Using Carbon Inputs in Desert Croplands

      Blankinship, Joseph C.; Hoglund, Shelby Rae; Fidel, Rivka B.; Jacobs, Katherine L.; Schuch, Ursula K. (The University of Arizona., 2022)
      Considering that the southwestern United States provides many of the specialty crops to feed the entire nation, it is vital to maximize use of water and fertilizer in croplands in this region. Meanwhile, intensifying droughts exacerbate cropland dependence on irrigation water. Therefore, solutions are needed to maintain cropland productivity. Adding carbon-rich organic amendments temporarily improves soil properties by increasing water and nutrient retention, but benefits are short-lived as organic amendments degrade quickly in hot, arid climates. Biochar is an organic amendment that can potentially improve long-term cropland soil health, which is the ability of soil to store and provide water and nutrients for plant growth. Biochar provides a relatively stable carbon source and can increase water and nutrient retention. Most studies on the effectiveness of biochar for these purposes have been conducted in temperate agroecosystems, but few studies examine effects of biochar on soil properties in croplands of the desert southwest U.S. Therefore, the purpose of this research is to deepen understanding of effects of carbon inputs (i.e. biochar and compost) to retain more water and provide plant-available nutrients in an irrigated desert cropland.
    • Reframing Anxiety as Excitement in Job Seekers: A Within-Person Field Experiment

      Gabriel, Allison S.; MacGowan, Rebecca Lee; Ellis, Aleksander P.J.; Slaughter, Jerel E. (The University of Arizona., 2022)
      While job seeker’s anxiety may be adaptive (e.g., Gabriel et al., 2021), it may also undermine individual’s weekly experiences of self-efficacy (e.g., Bandura, 1997), inhibiting job search behaviors. Prior scholarship (Brooks, 2014) finds that individuals who reappraise anxiety as excitement improve their performance outcomes and mitigate the negative effects of anxiety. Drawing from the social cognitive theory of self-regulatory behavior (Bandura, 1997; 2001) and the broaden-and-build theory of positive emotions (Fredrickson, 2001), I conducted a weekly emotion reappraisal intervention reframing job seeker’s job search anxiety as job search excitement. Results of the field experiment indicated that the intervention was positively related to feelings of excitement about the forthcoming week of job seeking. Further, these feelings of excitement were positively related to both creative job search and networking self-efficacy. At the end of the week, job seekers who had done the intervention and experienced excitement and creative and networking self-efficacy related to their job search reported engaging in focused job search effort as well as effort towards finding their dream job. As such, this intervention provides a promising avenue for improving weekly job search experiences.
    • Food Aid and Kitchen Controversies: Cooking Together in the City of Hope

      Alvarez, Maribel; Renkert, Sarah Rachelle; Austin, Diane; Carney, Megan; Green, Linda; Vásquez-León, Marcela (The University of Arizona., 2022)
      Over forty years ago, women across Lima, Perú’s poorest neighborhoods decided to take their community’s need for food into their own hands. Amidst an economic downturn that swept across Latin America in the last decades of the 20th century, these volunteers, the socias, formed comedores populares (communal kitchens). The socias combined their resources to cook for their families, while selling meals at an affordable price to their neighbors, investing all profit in the next day’s meal. In the early 1980s, the Peruvian government began opening state-sponsored comedores, providing participating kitchens with food aid. As state-sponsored comedores have evolved over the past four decades, they have become sites of contested meaning and significance amidst a confluence of embedded structural inequalities, conflicting sociopolitical subjectivities, and a politics of false generosity. While the state has long used the comedores for political ends, a practice which remains entrenched in today’s Peruvian political practices, outside observers have blamed comedores for reproducing irresponsibility, underdevelopment, malnutrition, political corruption, and the perpetuation of systemic injustices. These overlapping complexities have created a context in which comedores are facing increasing pressure to close, forcing socias to fight to keep their kitchens open. Drawing on ethnographic research with state-sponsored comedores in Huaycán, Lima, Perú, colloquially known as ‘The City of Hope,’ this research explores the relationship between the inside meaning of comedores for participating socias and the external challenges socias confront as they struggle to continue cooking together. While food aid programs such as the comedores are unlikely to upend Perú’s underlying structural challenges, for many socias, the comedores are a vital resource for ameliorating the hardships of chronic economic precarity, while also providing a valuable space of social solidarity and camaraderie. In examining these dynamics, this research addresses broader debates around food aid distribution, the violence of precarity, and the value of communal spaces within a neoliberal socioeconomic context. Additionally, in turning to the experiences of comedor socias in Huaycán, this dissertation considers how deep-seated injustices in poor communities have produced predictable and preventable suffering and death due to COVID-19.
    • Accessing the Superintendency: Challenges, Pathways, and Characteristics of Successful Latina Leaders

      Bertrand, Melanie A.; Kelsey, Isabel; Deil-Amen, Regina; Combs, Mary C. (The University of Arizona., 2022)
      Historically in the US, White males have dominated the superintendency accounting for 68.14% (Tienken, 2021). The figures are more despairing when it comes to Latina female superintendents who account for only 1% of superintendents nation-wide (Tienken, 2021). At the time of the study, in Arizona, 6% of Latina females held the superintendency compared to 61% of White males and 32% of White females (ADE, 2021). The disparity between male and female superintendency is concerning especially since 45% of Latinex students attend public schools in Arizona (ADE, 2021). Therefore, for this qualitative study, I used Critical Race Theory and Latino Critical Race Theory as a theoretical framework to research the experiences of 10 aspiring, practicing, and retired superintendents in Arizona K-12 public schools. I used snowball sampling to recruit participants. Data was collected using semi-structured interviews. I used CRT counter-stories to narrate the intersectional realities of Latina leader findings. My findings indicated that the patriarchal hegemonic structure in K-12 public schools presented intersectional, ethnic, gender, and political challenges to Latina leaders’ career mobility. Most of the Latina leaders discussed how the challenges affected their career mobility, causing internal and external effects. However, three of the participants stated that they did not experience challenges related to either race/ethnicity or that their career mobility was not impacted. The findings also revealed that relocating provided out-of-network access to the superindency. Additionally, participants used strategies and resources to manage their challenges and the stress associated with it. Finally, the study highlighted Latina leader’s successes, characteristics, and factors that might prevent Latina leaders from accessing the superintendency. These findings suggest implications for school districts to provide support systems and unbiased hiring practices for Latina leaders. The findings also imply possibilities for inclusion of transformative Latina literature in leadership literature and administrative preparation programs.
    • Good Thinking

      Comesaña, Juan; Kearl, Timothy Rion; McKenna, Michael; Cohen, Stewart; Sartorio, Carolina (The University of Arizona., 2022)
      Good Thinking is a collection of papers about abilities, skills, and know-how and the distinctive but often overlooked—or explained away—role that these phenomena play in various foundational issues in epistemology and action theory. Each chapter, taken on its own, represents a fairly specific intervention into debates in (i) epistemic responsibility, (ii) the nature of inferential justification, and (iii) connections between inference and action. But taken collectively, these chapters constitute fragments of a larger mosaic of commitments about the explanatory priority of abilities in normative theories. One distinctive argumentative strategy employed throughout Good Thinking is its placing special emphasis on what might be called “bad thinking”: defective judgments borne out of cognitive short-circuiting, incoherence or self-doubt, depression, or anxiety. The underlying motivation for this is that much of what we can learn about good thinking is only revealed at the margins, where thinking has in some respects gone bad without being entirely spoiled.
    • Fissure-Fed Volcanism on Mars and Earth

      Hamilton, Christopher W.; Sutton, Sarah; Andrews-Hanna, Jeffrey C.; Byrne, Shane; Carter, Lynn M.; McEwen, Alfred S. (The University of Arizona., 2022)
      I present investigations of the formation and degradation of volcanic landforms associatedwith fissure eruptions on Mars and Earth. A theme of my research is the use remote sensing data to investigate the morphology of landforms and active processes on Mars and the Earth. The morphologies of sinuous channels in Late Amazonian volcanic terrain onMars invite comparisons to channels formed by lava or water on Earth. I tested channel formation hypotheses by lava or water by conducting detailed geomorphological mapping in a region adjacent to the base of Olympus Mons. We interpreted the channels and associated fossae to be formed by alternating episodes of dike-fed fissure eruptions and groundwater release due to subsurface heating by sill emplacement. This alternating sequence of dike and sill emplacement, and associated surface eruptions of lava and water, is evidence of a complex, distributed volcanic system influenced by the tectonic stresses exerted by Olympus Mons as it continued to grow through the Amazonian Period. In a novel field study of the 2014–2015 Holuhraun fissure eruption vents in northernIceland, I created a topographic time series to measure the degradation of a large spatter rampart over the first five years post-eruption. I investigated the effects of spatter deposition on the styles and rates of erosion and found two distinct modes of topographic changes. The interior walls of the vent undergo discrete rockfall events, while the exterior slopes decrease in elevation overall, but show minimal evidence of gravitational sliding of unconsolidated scoria. The results of this study have implications for current vent landform evolution models, which predict slope changes by diffusive processes only. I propose instead a conceptual model that incorporates the probability distribution of rockfalls on the interior and diffusive processes on the exterior to better describe the earliest stages of vent erosion. I also present an analysis of the quality, precision, and accuracy of digital terrainmodels generated with stereo images from the Mars-orbiting High Resolution Imaging Science Experiment (HiRISE) camera, specifically applied to the measurement of active processes with time series of orthorectified images and digital terrain models.
    • Ultra-Sensitive and Selective Whispering Gallery Mode Microtoroid Chemical Sensor

      Su, Judith; Li, Cheng; McLeod, Euan; Kolesik, Miro (The University of Arizona., 2022)
      Optical Whispering gallery mode (WGM) microresonators, which benefit from an ultra-high quality (Q) factor and small mode volume to significantly enhance light-matter interaction, stand out from other sensors, and are utilized in a variety of biochemical sensing or physical parameter detection applications. Physical or chemical reactions occurring in the evanescent field of the polymer-treated microtoroid equatorial plane will be translated into variations of the WGM spectra, which will, in turn, be recorded and analyzed through techniques such as frequency locking, balanced detection, and post data processing. The overall platform is known as the Frequency-locked optical whispering evanescent resonator (FLOWER) system. The performance and characteristics of ultra-sensitive and selective WGM gas sensors are evaluated and demonstrated in this dissertation. Two approaches to further improve the system are proposed, one based on plasmonic near-field enhancement to improve the sensitivity and the other on a fiber metrology method using Rayleigh backscattering to eliminate the thermal noise of the sensing system. Finally, another sensing application using the dual-FLOWER system for particle shape analysis is introduced.
    • Group Oriented Strategic Technologies for Adversarial Privacy Enhancement

      Brandimarte, Laura; Brooks, Catherine; Sidi, David; Brandimarte, Laura; Brooks, Catherine; Braitberg, Victor; Bambauer, Jane (The University of Arizona., 2022)
      Privacy-enhancing technologies (PETs) have long been divided according to the role of trust in their design, with “hard” PETs distinguished in particular by an aim to minimize trust. This work adopts a different perspective on PETs, and describes the class of group-oriented strategic technologies for adversarial privacy enhancement (GOSTAPEs) focused on the long term causes and conditions of privacy over time. The work then motivates GOSTAPEs as a research agenda for PET design. A survey of the PET landscape from the hard-/soft- PET perspective is presented first, with the rest of the work falling to separate discussion of group-orientation, adversariality, and strategy. Throughout, the discussion of GOSTAPEs focuses on technologies of measurement, including a botnet used to measure privacy practices on the web, a public transparency and reputation system for data brokers, and a formal measure of database privacy risk based on plausible deniability. The work concludes by gathering themes from the strategic perspective that have emerged, and looking to the future of PET design.
    • Infrared Polarimetry for Remote Sensing

      Kupinski, Meredith K.; Shanks, Kira Ann; Chipman, Russell A.; Wu, Dong L.; Furenlid, Lars R. (The University of Arizona., 2022)
      A more complete understanding of the global distribution of cirrus ice clouds is essential to constraining both long and short-term climate forecasts. Radiometric simulations have shown that joint polarimetric measurements in the sub-mm and long-wave-infrared (LWIR) can significantly increase sensitivity to ice-particle microphysics, however, no existing platforms have polarimetric sensitivity in LWIR. This work describes the design and demonstration of an InfraRed Channeled Spectro-Polarimeter (IRCSP) to address this gap in existing remote sensing technology. The IRCSP utilizes commercially available uncooled microbolometer detectors (UMBs), is less than 10 cm long, has no moving mechanical components, and requires no active thermal control. A robust data-reduction algorithm corrects for both focal plane temperature fluctuations and instrumental polarization error to measure both the AoLP and Degree of Linear Polarization (DoLP) of cold targets. Lab validation studies have demonstrated polarimetric sensitivity to targets with 1.0% DoLP and brightness temperatures of less than 270 K. In 2021, the IRCSP was demonstrated in the near-space environment as a piggyback out of NASA Columbia Scientific Ballooning Facility. Post landing the instrument was retrieved with no damage to the optical payload and collected over 150 minutes of flight data at altitudes above 30 km. These measurements demonstrate the operation of un-cooled microbolometers in the low-pressure environment and are the first known high-altitude observations of a polarized signal from cloud tops in the LWIR. During deployment, the IRCSP reported brightness temperatures between 250-285K with uncertainty of < 1.5K. In addition, the IRCSP detected statistically significant polarization modulation with DoLP between 1 − 20% and preferential AoLP trends. These results support the hypothesis that LWIR polarimetry has the potential to add new sensitivity to existing remote sensing platforms.
    • Examining and Contextualizing Formal and Stylistic Elements in the Marches of Frank Simon

      Nicholson, Chad R.; Kaiser, Timothy Joseph; Shoopman, Chad; Cockrell, Thomas (The University of Arizona., 2022)
      Cornetist, composer, and educator Frank Simon (1889-1967) was a pivotal figure in the history of American bands and, due to his presence on radio, a household name. However, virtually no scholarly attention has been devoted to his march compositions, five of which have lain in obscurity in the University of Arizona’s Frank Simon Memorial Instrumental Library for over half a century.The present study, conducted with access to this archived material, resulted in full-score performance editions of Simon’s Cincinnati Post March, March of the Majorettes, The Statesman March, Here Comes the Band, and The Little Giant. Hundreds of errors and inconsistencies were corrected, rendering these marches fit for performance by modern secondary-, university-, and professional-level ensembles. Simon’s marches are worthy of study for both musical and historical reasons. They retain many of the formal, stylistic, and aesthetic qualities of John Philip Sousa’s marches but reflect a greater emphasis on technical and pedagogical considerations. The full-score editions, with guidelines for performance culled from Simon and his contemporaries, will elucidate how these elements were adapted in the post-Sousa era. Frank Simon devoted a lifetime to keeping quality music in the public consciousness and preserving authentic performance techniques for posterity. It was in this spirit, and in the interest of preserving his memory, that this project was undertaken.
    • AdaptiSPECT-C: Mechanical Design and Front-End Electronics

      Furenlid, Lars R.; Richards, Robert Garrett; Gmitro, Arthur F.; Kupinski, Matthew A. (The University of Arizona., 2022)
      Gamma-ray detectors operating under the tracer principle have been widely used in medical imaging for decades. One such application is single-photon computed tomography (SPECT), which reconstructs 3-dimensional images of radiotracer concentration in vivo, revealing regions of biological function inside a body. For most of SPECT's history, the dominant technology used to sense gamma energy deposition events was that of photomultiplier tubes (PMTs). A majority of gamma cameras used in SPECT applications employ an array of PMTs to isolate the location of gamma-ray interaction inside the camera; the collection of PMT signals provides essential information to determine the origin of the gamma-ray emission and reconstruct an image. Recent advances in solid-state detectors have introduced a viable alternative to PMTs as a means to detect signals with single-photon sensitivity: the silicon photomultiplier (SiPM). SiPMs have numerous attractive properties that make them well suited to the tasks required for gamma cameras; namely, fine pixelation, low profile, and high gain. Augmenting an array of PMTs in a gamma camera with SiPMs can produce higher resolution images, enabling radiologists and drug researchers to conduct studies with higher accuracy and lower probability of error. Another major development of the 21st century was the advent of 3-dimensional additive manufacturing techniques using metal. A 3-D tungsten printer enables entirely new geometries to fabricate, including pinhole apertures used as SPECT image forming devices. Moreover, the custom printed pinholes are easily made into formats having adjustable diameters to fine-tune imaging properties in a SPECT session. This, coupled with the new SiPM arrays, forms the foundation of the new technology brought to bear in AdaptiSPECT-C, a stationary clinical whole-brain SPECT imager. AdaptiSPECT-C will be used in drug discovery research targeting neurodegenerative diseases such as Parkinson's and Alzheimer's. The novel incorporation of hybrid PMT / SiPM cameras and dynamically adaptable apertures will produce images at higher resolution and with higher fidelity pharmacokinetic information than rival systems, positioning it as a leading technology in drug development for neurodegenerative disease. This dissertation covers the development of AdaptiSPECT-C hardware, addressing the early performance simulations, the mechanical design of its cameras and gantry structure, and the electrical design of its front-end electronics, with results from prototype unit testing. Ultimately, by demonstrating functional prototype cameras, the work in this dissertation establishes a strong proof-of-concept for AdaptiSPECT-C as a system, and offers a roadmap for its imminent completion.
    • College Students of Spanish Language: A Potential Shift in Language Ideologies

      Rubinstein-Ávila, Eliane; Ziska, Marcy; Chuffe, Eliud; Kayi-Aydar, Hayriye (The University of Arizona., 2022)
      Spanish is the fastest-growing non-English language spoken in the United States (Jenkins, 2018) and the Southwest represents the largest Latinx population growth with the greatest densities of Spanish-speaking communities (Potowski, 2018). Additionally, Spanish is the most widely taught second language in the United States, enrolling more students at the postsecondary level than all other modern languages combined (Burns, 2018). While many academic institutions acclaim language learning as a cultural and linguistic bridge, positive overall attitudes toward Spanish and Spanish-speaking cultures have declined after enrollment in introductory Spanish classes (Acheson & Nelson, 2015). This qualitative research study, conducted at a large land-grant university located in the Southwest, is one of the largest Spanish undergraduate programs in the United States. Serving a 35% Latinx local community, the school’s Latinx student population constitutes 25.3% of its student body. Guided by the theoretical frameworks of LangCrit (Crump, 2014), Raciolinguistics (Alim, Rickford, and Ball, 2016; Flores and Rosa, 2015), and Social Identity Theory (Tajfel, 1978) with data from questionnaires, journals, and in-depth phenomenological interviews, this study explores how language ideologies shape learning Spanish, how identities and experiences with Spanish and Spanish speakers shape those ideologies, and how learners view their own use or nonuse of Spanish in their communities. The findings were surprising due to their oppositional relationship with recent research. This analysis reveals how learners positioned themselves as culturally competent and socially responsible learners, an identity tied to their self-awareness as recipients of unequal racial and linguistic privileges. I show how learners socially distanced themselves from others perceived to be culturally unaware and/or socially irresponsible and how their rejection of language ideologies contributed to their identity positions. Findings suggest an allegiance to English language ideologies as a global lingua franca as learners devalued achieving Spanish linguistic fluency and prioritized developing social and cultural skills. They suggest a shift in dominant language ideological beliefs from previous peer groups. I propose an examination into the evolving sociopolitical and ideological beliefs among cohorts of learners. I advocate for a reexamination of the current over-emphasis on grammar instruction and a greater focus on cultural competence and understanding. Due to learners’ low Spanish language use, they may be ill-equipped to find culturally responsive ways to speak and practice their growing linguistic skills.
    • Essays on Health Economics

      Taylor, Evan; Hao, Yuge; Langer, Ashley; Fishback, Price; Pantano, Juan (The University of Arizona., 2022)
      The first two chapters investigates the issues that arose after individuals experienced certain shocks that affected their health. Chapter 1 focuses on the short-run and long-run effect of childhood maltreatment on mental health. Chapter 2 investigates the effect of a new medication, PrEP, on individuals’ risky sexual behaviors and sexually transmitted infections. The last chapter exams the relationship between individuals’ timing pattern of working and their success in the setting of online game streaming. Time Heals All Wound? Childhood Maltreatment and Mental Health Empirical evidence has shown that maltreatment may cause serious damage to the human capital development of children and result in negative outcomes in their adulthood. Mental health may be one of the underlying mechanisms through which maltreatment affects human capital accumulation. Using the data from the Longitudinal Study of Adolescent to Adult Health, I examined the relationship between childhood maltreatment and mental health both in the short run and in the long run. The results show the childhood experience of maltreatment imposes negative effect on mental health. The effect is at least significant in the long run, suggesting that the effect is long-lasting and does not necessarily fade away as time passes. Females are on average more vulnerable to maltreatment than males. Experiencing multiple forms of maltreatment would impose a worse effect on mental health compared to single form of maltreatment. PrEP, Risky Sexual Behaviors and STIs Pre-exposure prophylaxis, or PrEP, is a daily medicine for people at high risk of contracting HIV to lower their chance of getting infected. Clinical studies show that PrEP can be highly effective, reducing the risk of contracting HIV by more than 90\%. Despite the great effectiveness of PrEP in preventing HIV infection, there is concern that PrEP may lead some people to more risky behaviors, such as reducing their use of condoms and increasing their number of sexual partners. Using public data from the Multicenter AIDS Cohort Study, this paper empirically examines such concern. Exploiting the panel nature of the data, we use a difference-in-difference model to study the effect of PrEP on risky sexual behaviors and other sexually transmitted infections (STIs). Our analysis shows that PrEP makes individuals more likely to engage in unprotected anal sex, have more sexual partners, and more likely to contract syphilis. The Early Bird Gets the Worm: Strategic timing to live-stream on Huya.com Using scraped data from an online video game live streaming platform, I study the streamers' strategic decisions of when to go online and the effects of these timing pattern on their success on the platform. Live streamers as the content creators face different amount of audience during different times of the day as the website traffic fluctuates over the course of 24 hours. They also face different levels of competition as the number of online streamers change in each hour. I use a simple model of streamers' behaviors as benchmark of market equilibrium and study how the real data deviate from the model predictions. The result show live streamers exhibit over competition and decreased gains in rush hour and in contrast they also present under competition and increased gains in the slow hour. Potential rationales are discussed to explain such phenomenon.
    • An Ethnographic Case Study of Adolescent English Learner (EL) Writing in a High School Science Program

      Gilmore, Perry; Yaylali, Ali Osman; Combs, Mary Carol; Staples, Shelley; Wood, Marcy (The University of Arizona., 2022)
      With shifting language policies, English learners (ELs) with various language proficiencies take English language development and other content area courses simultaneously. Therefore, language and literacy development in secondary science classrooms is increasingly becoming important for ELs’ education. Science courses introduce ELs to unique disciplinary writing practices and science registers. The written academic-science register is characterized by complex linguistic features (e.g., nouns, nominalizations, and noun phrasal structures) which assist in information-packaging and precision in writing (Biber & Clark, 2022; Biber & Conrad, 2019, Biber & Gray, 2016). However, surveys of writing in the U.S. secondary schools showed that the emphasis placed on effective scientific writing and science language in classrooms is inadequate given the instructional priorities to teach content (Applebee & Langer, 2011a; Drew et al., 2017). Furthermore, for adolescent EL writers, scientific writing and register which contribute to ELs’ academic literacy development are insufficiently scaffolded (Enright, 2010, 2013; Enright & Gilliland, 2011; Kibler, 2011). Though disciplinary writing and linguistic demands might pose challenges for ELs, few studies have investigated ELs’ experiences in scientific writing and their developing understanding of science register in secondary schools. In order to develop appropriate writing pedagogies, it is important for teachers to understand the disciplinary writing culture in high school science programs. An analysis of specific writing tasks (e.g., purpose, audience) is therefore a necessary step to describe the writing practices. To support ELs in their specific challenges, teachers must also identify ELs’ writing processes and experiences. Finally, by examining ELs’ perspectives on scientific writing and register, teachers will grasp how ELs’ understanding of disciplinary practices and language are developing. To this end, this dissertation explores ELs’ writing experiences in major science writing tasks and their awareness of science register through interviews, writing samples, and classroom observations. A situational analysis of five writing tasks provides an ethnographic description of writing across four high school science courses. Another component of this dissertation is an examination of ELs’ personal experiences with science writing tasks. Lastly, ELs’ developing understanding of scientific writing and register is investigated using a comparative method grounded in corpus-based register studies. The findings indicate that science courses integrate short writing daily and few extended writing tasks throughout the year. Limited EL engagement in science learning and writing was a critical finding as an impact of ELs’ developing language proficiencies as well as remote learning during the recent Covid-19 pandemic. In coping with the writing tasks, ELs brought some critical assets to science writing situations such as translanguaging and technology use for translation. However, ELs struggled with sentence constructions and precise language use. Patchwriting was common in writing tasks, which required the use of teacher-provided resources (e.g., teacher notes, scientific articles). ELs’ understanding of scientific writing practices and register demonstrate their struggles with writing and certain misconceptions regarding disciplinary practices and language use in science classrooms. ELs also show high sensitivity to vocabulary, a characteristic of science register, compared to other register features such as grammatical structures. ELs’ writing and learning experiences influence register perspectives. Some teachers were more dedicated to knowing ELs better and engaging them in science through multiple forms of actions (e.g., after-school meetings, texting). Such dedication positively impacted ELs’ experiences in writing and science learning. Deliberate attention to complex grammatical structures for specificity in evidence-based writing is suggested while other pedagogical considerations are offered such as adding variety to writing genres and varied audiences. The findings are useful to develop instructional pedagogies and support systems for EL writing and language development in secondary schools. Literacy and teacher education programs can also utilize such research for equitable teaching and disciplinary writing practices.