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- Genre: Doctoral Dissertation
Description
In this thesis, we present the study of several physical properties of relativistic mat- ters under extreme conditions. We start by deriving the rate of the nonleptonic weak processes and the bulk viscosity in several spin-one color superconducting phases of quark matter. We also calculate the bulk viscosity in the nonlinear and anharmonic regime in the normal phase of strange quark matter. We point out several qualitative effects due to the anharmonicity, although quantitatively they appear to be relatively small. In the corresponding study, we take into account the interplay between the non- leptonic and semileptonic weak processes. The results can be important in order to relate accessible observables of compact stars to their internal composition. We also use quantum field theoretical methods to study the transport properties in monolayer graphene in a strong magnetic field. The corresponding quasi-relativistic system re- veals an anomalous quantum Hall effect, whose features are directly connected with the spontaneous flavor symmetry breaking. We study the microscopic origin of Fara- day rotation and magneto-optical transmission in graphene and show that their main features are in agreement with the experimental data.
ContributorsWang, Xinyang, Ph.D (Author) / Shovkovy, Igor (Thesis advisor) / Belitsky, Andrei (Committee member) / Easson, Damien (Committee member) / Peng, Xihong (Committee member) / Vachaspati, Tanmay (Committee member) / Arizona State University (Publisher)
Created2013
Description
Numerical simulations are very helpful in understanding the physics of the formation of structure and galaxies. However, it is sometimes difficult to interpret model data with respect to observations, partly due to the difficulties and background noise inherent to observation. The goal, here, is to attempt to bridge this gap between simulation and observation by rendering the model output in image format which is then processed by tools commonly used in observational astronomy. Images are synthesized in various filters by folding the output of cosmological simulations of gasdynamics with star-formation and dark matter with the Bruzual- Charlot stellar population synthesis models. A variation of the Virgo-Gadget numerical simulation code is used with the hybrid gas and stellar formation models of Springel and Hernquist (2003). Outputs taken at various redshifts are stacked to create a synthetic view of the simulated star clusters. Source Extractor (SExtractor) is used to find groupings of stellar populations which are considered as galaxies or galaxy building blocks and photometry used to estimate the rest frame luminosities and distribution functions. With further refinements, this is expected to provide support for missions such as JWST, as well as to probe what additional physics are needed to model the data. The results show good agreement in many respects with observed properties of the galaxy luminosity function (LF) over a wide range of high redshifts. In particular, the slope (alpha) when fitted to the standard Schechter function shows excellent agreement both in value and evolution with redshift, when compared with observation. Discrepancies of other properties with observation are seen to be a result of limitations of the simulation and additional feedback mechanisms which are needed.
ContributorsMorgan, Robert (Author) / Windhorst, Rogier A (Thesis advisor) / Scannapieco, Evan (Committee member) / Rhoads, James (Committee member) / Gardner, Carl (Committee member) / Belitsky, Andrei (Committee member) / Arizona State University (Publisher)
Created2012
Description
Understanding the temperature structure of protoplanetary disks (PPDs) is paramount to modeling disk evolution and future planet formation. PPDs around T Tauri stars have two primary heating sources, protostellar irradiation, which depends on the flaring of the disk, and accretional heating as viscous coupling between annuli dissipate energy. I have written a "1.5-D" radiative transfer code to calculate disk temperatures assuming hydrostatic and radiative equilibrium. The model solves for the temperature at all locations simultaneously using Rybicki's method, converges rapidly at high optical depth, and retains full frequency dependence. The likely cause of accretional heating in PPDs is the magnetorotational instability (MRI), which acts where gas ionization is sufficiently high for gas to couple to the magnetic field. This will occur in surface layers of the disk, leaving the interior portions of the disk inactive ("dead zone"). I calculate temperatures in PPDs undergoing such "layered accretion." Since the accretional heating is concentrated far from the midplane, temperatures in the disk's interior are lower than in PPDs modeled with vertically uniform accretion. The method is used to study for the first time disks evolving via the magnetorotational instability, which operates primarily in surface layers. I find that temperatures in layered accretion disks do not significantly differ from those of "passive disks," where no accretional heating exists. Emergent spectra are insensitive to active layer thickness, making it difficult to observationally identify disks undergoing layered vs. uniform accretion. I also calculate the ionization chemistry in PPDs, using an ionization network including multiple charge states of dust grains. Combined with a criterion for the onset of the MRI, I calculate where the MRI can be initiated and the extent of dead zones in PPDs. After accounting for feedback between temperature and active layer thickness, I find the surface density of the actively accreting layers falls rapidly with distance from the protostar, leading to a net outward flow of mass from ~0.1 to 3 AU. The clearing out of the innermost zones is possibly consistent with the observed behavior of recently discovered "transition disks."
ContributorsLesniak, Michael V., III (Author) / Desch, Steven J. (Thesis advisor) / Scannapieco, Evan (Committee member) / Timmes, Francis (Committee member) / Starrfield, Sumner (Committee member) / Belitsky, Andrei (Committee member) / Arizona State University (Publisher)
Created2012
Description
This thesis deals with the first measurements done with a cold neutron beam at the Spallation Neutron Source at Oak Ridge National Laboratory. The experimental technique consisted of capturing polarized cold neutrons by nuclei to measure parity-violation in the angular distribution of the gamma rays following neutron capture. The measurements presented here for the nuclei Chlorine ( 35Cl) and Aluminum ( 27Al ) are part of a program with the ultimate goal of measuring the asymmetry in the angular distribution of gamma rays emitted in the capture of neutrons on protons, with a precision better than 10-8, in order to extract the weak hadronic coupling constant due to pion exchange interaction with isospin change equal with one ( hπ 1). Based on theoretical calculations asymmetry in the angular distribution of the gamma rays from neutron capture on protons has an estimated size of 5·10-8. This implies that the Al parity violation asymmetry and its uncertainty have to be known with a precision smaller than 4·10-8. The proton target is liquid Hydrogen (H2) contained in an Aluminum vessel. Results are presented for parity violation and parity-conserving asymmetries in Chlorine and Aluminum. The systematic and statistical uncertainties in the calculation of the parity-violating and parity-conserving asymmetries are discussed.
ContributorsBalascuta, Septimiu (Author) / Alarcon, Ricardo (Thesis advisor) / Belitsky, Andrei (Committee member) / Doak, Bruce (Committee member) / Comfort, Joseph (Committee member) / Schmidt, Kevin (Committee member) / Arizona State University (Publisher)
Created2012
Description
As the world energy demand increases, semiconductor devices with high energy conversion efficiency become more and more desirable. The energy conversion consists of two distinct processes, namely energy generation and usage. In this dissertation, novel multi-junction solar cells and light emitting diodes (LEDs) are proposed and studied for high energy conversion efficiency in both processes, respectively. The first half of this dissertation discusses the practically achievable energy conversion efficiency limit of solar cells. Since the demonstration of the Si solar cell in 1954, the performance of solar cells has been improved tremendously and recently reached 41.6% energy conversion efficiency. However, it seems rather challenging to further increase the solar cell efficiency. The state-of-the-art triple junction solar cells are analyzed to help understand the limiting factors. To address these issues, the monolithically integrated II-VI and III-V material system is proposed for solar cell applications. This material system covers the entire solar spectrum with a continuous selection of energy bandgaps and can be grown lattice matched on a GaSb substrate. Moreover, six four-junction solar cells are designed for AM0 and AM1.5D solar spectra based on this material system, and new design rules are proposed. The achievable conversion efficiencies for these designs are calculated using the commercial software package Silvaco with real material parameters. The second half of this dissertation studies the semiconductor luminescence refrigeration, which corresponds to over 100% energy usage efficiency. Although cooling has been realized in rare-earth doped glass by laser pumping, semiconductor based cooling is yet to be realized. In this work, a device structure that monolithically integrates a GaAs hemisphere with an InGaAs/GaAs quantum-well thin slab LED is proposed to realize cooling in semiconductor. The device electrical and optical performance is calculated. The proposed device then is fabricated using nine times photolithography and eight masks. The critical process steps, such as photoresist reflow and dry etch, are simulated to insure successful processing. Optical testing is done with the devices at various laser injection levels and the internal quantum efficiency, external quantum efficiency and extraction efficiency are measured.
ContributorsWu, Songnan (Author) / Zhang, Yong-Hang (Thesis advisor) / Menéndez, Jose (Committee member) / Ponce, Fernando (Committee member) / Belitsky, Andrei (Committee member) / Schroder, Dieter (Committee member) / Arizona State University (Publisher)
Created2010
Description
2019 coronavirus disease (COVID-19) remains a pressing health concern, especially with lagging youth vaccination rates despite its evident benefits. Given the significant role of vaccination in safeguarding individual and community health, this dissertation sought to explore how the use of serious games may offer hope for addressing the COVID-19 vaccine coverage gap among youths. This dissertation collected, appraised, and synthesized existing evidence on serious game-based vaccination interventions, finding increased youths’ vaccine knowledge but limited effectiveness in boosting their vaccination intentions and uptake. Using serious game in youth health education considered key attributes including gamification, game mechanics, educational, health-related content, and objective, tailored for youth and adaptability, real life relevance, engagement, interactivity, safe environment, feedback, and assessment. Stemming from technological advances and interdisciplinary collaborations, these games provided experiences that resonated with diverse populations. Outcomes from such educational games have shown improved health knowledge, attitudes, and behaviors, improved self-efficacy and reduced health disparities. The dissertation also presented a pilot study randomization control trial (RCT) on a COVID- 19 game-based intervention (vs. usual care) targeting unvaccinated youth, showing its feasibility, acceptability and positive influence on vaccine knowledge, vaccination intention and uptake. Partnering with key stakeholders and adapting game designs for ongoing relevance could contribute to intervention effectiveness in promoting youth vaccination, catering to diverse needs and preferences.
ContributorsOu, Lihong (Author) / Reifsnider, Elizabeth (Thesis advisor) / Chen, Angela Chia-Chen (Committee member) / Todd, Michael (Committee member) / Amresh, Ashish (Committee member) / Mun, Chung Jung (Committee member) / Arizona State University (Publisher)
Created2023
Description
Tools designed to help match people with behaviors they identify as likely to lead to a successful behavioral outcome remain under-researched. This study assessed the effect of a participant-driven behavior-matching intervention on 1) the adoption of a new behavior related to fruit and vegetable (F&V) consumption, 2) study attrition, and 3) changes in F&V consumption. In this two-arm randomized controlled trial, 64 adults who did not meet standard F&V recommendations were allocated to an intervention (n=33) or control group (n=31). Participants in the intervention group ranked 20 F&V-related behaviors according to their perceived likelihood of engagement in the behavior and their perception of the behavior’s efficacy in increasing F&V consumption. Participants in the intervention group were subsequently shown the list of 20 behaviors in order of their provided rankings, with the highest-ranked behaviors at the top, and were asked to choose a behavior they would like to perform daily for 4 weeks. The control group chose from a random-order list of the same 20 behaviors to adopt daily for 4 weeks. During the study period, text messages were sent to all participants 90 minutes before their reported bedtime to collect Yes/No data reflecting successful behavior engagement each day. The binary repeated-measures data collected from the text messages was analyzed using mixed-effects logistic regression, differences in attrition were assessed using log-rank analysis, and change scores in F&V consumption were compared between the two groups using the Man-Whitney U test. P<0.05 indicated significance. The rate of successful behavior adoption did not differ significantly between the two groups (b=0.09, 95%CI= -0.81, 0.98, p=0.85). The log rank test results indicated that there was no significant difference in attrition between the two groups (χ2=2.68, df=1, p=0.10). F&V consumption increased significantly over the 4 weeks in the total sample (Z=-5.86, p<0.001), but no differences in F&V change scores were identified between the control and intervention groups (Z=-0.21, p=0.84). The behavior-matching tool assessed in this study did not significantly improve behavior adoption, study attrition, or F&V intake over 4 weeks.
ContributorsCosgrove, Kelly Sarah (Author) / Wharton, Christopher (Thesis advisor) / Adams, Marc (Committee member) / DesRoches, Tyler (Committee member) / Grebitus, Carola (Committee member) / Johnston, Carol (Committee member) / Arizona State University (Publisher)
Created2023
Description
Postpartum depression affects approximately 15% of the childbearing population in the United States and has been linked to a number of negative maternal and infant outcomes. Mothers who rate low in areas of confidence and self-efficacy tend to have lower satisfaction and view their infants as having more negative temperaments. Infants of depressed mothers have been found to have delays in social and emotional growth which can impair their health and future developmental outcomes. The purpose of this study was to determine if there is any evidence to support the hypothesis that maternal depression is associated with infant social and emotional development and maternal role satisfaction among low-income women in rural Arizona. This study employed a repeated measures correlational descriptive prospective longitudinal design using chart reviews analyzing existing clinical data. Purposive sampling was used to select charts of women who participated in the Verde Valley Medical Center branch of the Arizona Healthy Families program. Chart reviews were used to identify charts that met the inclusion criteria of mothers and their infants who completed at least 18 months of the Arizona Healthy Families Program.
Findings of this study indicated evidence of a relationship between depression, infant social and emotional development, and maternal role satisfaction. Mothers who had infants that scored higher, with higher being indicative of concern, on the Ages & Stages Questionnaire: Social-Emotional Edition 2 (ASQ:SE 2) had lower role satisfaction scores on the Healthy Families Parenting Inventory (HFPI) and mothers who indicated dissatisfaction at 6 months postpartum were more likely to continue to indicate lower maternal satisfaction at 12 and 18 months postpartum when infant ASQ:SE 2 scores were higher.
Investigating the role of the visiting service providers, such as Healthy Families, and their impact on young families for risk identification and resource support will provide information to policy and lawmakers to aid in decisions for funding and help support young families with the goal of growing strong, healthy families in healthcare deserts like rural Arizona. Keywords: Postpartum depression, maternal depression, infant social and emotional development, maternal role, maternal role satisfaction
ContributorsArgent, Autumn Leif (Author) / Reifsnider, Elizabeth (Thesis advisor) / Hinde, Katie (Committee member) / Todd, Michael (Committee member) / Whisner, Corrie (Committee member) / Arizona State University (Publisher)
Created2024
Description
Job burnout, a prolonged reaction to job stress, includes mental and physical aspects of exhaustion related to professional work life. Linked to individual health-related problems, decreased job satisfaction, poor organizational commitment, and higher turnover, burnout poses a problem for both employees and organizations. The nursing profession identifies the prevalence of burnout and the resulting harmful effects in many settings, yet until now, rural critical access hospital settings have not been considered. To build and maintain a competent, healthy rural nursing workforce that responds innovatively to growing healthcare needs, it is important to examine burnout levels in rural nurses and to identify factors that might be associated with mitigating burnout.
This study focuses on how psychological capital, socio-demographic and organizational work-related factors are associated with burnout in this population. This cross-sectional, descriptive correlational study employed the Maslach Burnout Inventory for Health Professionals, the Psychological Capital Questionnaire, and a sociodemographic questionnaire assessing individual and organizational work-related factors as self-report tools. Descriptive statistics, correlations, and regression analyses were performed to assess aspects of the nurses’ work environment, while describing the relationships among the variables.Means and standard deviations were examined across key variables and compared to reports from other studies. Hypotheses predicted psychological capital would be associated with burnout (negatively associated with emotional exhaustion and depersonalization, positively associated with personal accomplishment), and that individual sociodemographic and organizational work-related factors would also be associated with BO. It was further hypothesized that PsyCap would moderate the relationship between work-related factors and BO.
Maslach Burnout Inventory results reveal similar findings to those in the global sample. However, levels of emotional exhaustion and professional accomplishment were greater in our rural nurse sample compared to published values. Higher levels of psychological capital were found to be related to decreases in depersonalization and correlated to greater professional accomplishment. Psychological capital was not found to moderate associations within this study. Intent to stay more than one year had a strong, negative correlation with emotional exhaustion. The findings suggest burnout in this sample resembles that of the global problem and sets a baseline from which psychological capital trainings may be built.
This study focuses on how psychological capital, socio-demographic and organizational work-related factors are associated with burnout in this population. This cross-sectional, descriptive correlational study employed the Maslach Burnout Inventory for Health Professionals, the Psychological Capital Questionnaire, and a sociodemographic questionnaire assessing individual and organizational work-related factors as self-report tools. Descriptive statistics, correlations, and regression analyses were performed to assess aspects of the nurses’ work environment, while describing the relationships among the variables.Means and standard deviations were examined across key variables and compared to reports from other studies. Hypotheses predicted psychological capital would be associated with burnout (negatively associated with emotional exhaustion and depersonalization, positively associated with personal accomplishment), and that individual sociodemographic and organizational work-related factors would also be associated with BO. It was further hypothesized that PsyCap would moderate the relationship between work-related factors and BO.
Maslach Burnout Inventory results reveal similar findings to those in the global sample. However, levels of emotional exhaustion and professional accomplishment were greater in our rural nurse sample compared to published values. Higher levels of psychological capital were found to be related to decreases in depersonalization and correlated to greater professional accomplishment. Psychological capital was not found to moderate associations within this study. Intent to stay more than one year had a strong, negative correlation with emotional exhaustion. The findings suggest burnout in this sample resembles that of the global problem and sets a baseline from which psychological capital trainings may be built.
ContributorsMcCay, Rebecca (Author) / Larkey, Linda K (Thesis advisor) / Kelly, Lesly (Committee member) / Todd, Michael (Committee member) / Arizona State University (Publisher)
Created2019
Description
Background In the United States (US), first-year university students typically live on campus and purchase a meal plan. In general, meal plans allow the student a set number of meals per week or semester, or unlimited meals. Understanding how students’ use their meal plan, and barriers and facilitators to meal plan use, may help decrease nutrition-related issues.
Methods First-year students’ meal plan and residence information was provided by a large, public, southwestern university for the 2015-2016 academic year. A subset of students (n=619) self-reported their food security status. Logistic generalized estimating equations (GEEs) were used to determine if meal plan purchase and use were associated with food insecurity. Linear GEEs were used to examine several potential reasons for lower meal plan use. Logistic and Linear GEEs were used to determine similarities in meal plan purchase and use for a total of 599 roommate pairs (n=1186 students), and 557 floormates.
Results Students did not use all of the meals available to them; 7% of students did not use their meal plan for an entire month. After controlling for socioeconomic factors, compared to students on unlimited meal plans, students on the cheapest meal plan were more likely to report food insecurity (OR=2.2, 95% CI=1.2, 4.1). In Fall, 26% of students on unlimited meal plans reported food insecurity. Students on the 180 meals/semester meal plan who used fewer meals were more likely to report food insecurity (OR=0.9, 95% CI=0.8, 1.0); after gender stratification this was only evident for males. Students’ meal plan use was lower if the student worked a job (β=-1.3, 95% CI=-2.3, -0.3) and higher when their roommate used their meal plan frequently (β=0.09, 99% CI=0.04, 0.14). Roommates on the same meal plan (OR=1.56, 99% CI=1.28, 1.89) were more likely to use their meals together.
Discussion This study suggests that determining why students are not using their meal plan may be key to minimizing the prevalence of food insecurity on college campuses, and that strategic roommate assignments may result in students’ using their meal plan more frequently. Students’ meal plan information provides objective insights into students’ university transition.
Methods First-year students’ meal plan and residence information was provided by a large, public, southwestern university for the 2015-2016 academic year. A subset of students (n=619) self-reported their food security status. Logistic generalized estimating equations (GEEs) were used to determine if meal plan purchase and use were associated with food insecurity. Linear GEEs were used to examine several potential reasons for lower meal plan use. Logistic and Linear GEEs were used to determine similarities in meal plan purchase and use for a total of 599 roommate pairs (n=1186 students), and 557 floormates.
Results Students did not use all of the meals available to them; 7% of students did not use their meal plan for an entire month. After controlling for socioeconomic factors, compared to students on unlimited meal plans, students on the cheapest meal plan were more likely to report food insecurity (OR=2.2, 95% CI=1.2, 4.1). In Fall, 26% of students on unlimited meal plans reported food insecurity. Students on the 180 meals/semester meal plan who used fewer meals were more likely to report food insecurity (OR=0.9, 95% CI=0.8, 1.0); after gender stratification this was only evident for males. Students’ meal plan use was lower if the student worked a job (β=-1.3, 95% CI=-2.3, -0.3) and higher when their roommate used their meal plan frequently (β=0.09, 99% CI=0.04, 0.14). Roommates on the same meal plan (OR=1.56, 99% CI=1.28, 1.89) were more likely to use their meals together.
Discussion This study suggests that determining why students are not using their meal plan may be key to minimizing the prevalence of food insecurity on college campuses, and that strategic roommate assignments may result in students’ using their meal plan more frequently. Students’ meal plan information provides objective insights into students’ university transition.
Contributorsvan Woerden, Irene (Author) / Bruening, Meg (Thesis advisor) / Hruschka, Daniel (Committee member) / Schaefer, David (Committee member) / Vega-Lopez, Sonia (Committee member) / Adams, Marc (Committee member) / Arizona State University (Publisher)
Created2019