Matching Items (161)
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
Objective: To assess and quantify the effect of state’s price transparency regulations (hereafter, PTR) on healthcare pricing.
Data Sources: I use the Healthcare Cost and Utilization Project’s Nationwide Inpatient Sample (NIS) from 2000 to 2011. The NIS is a 20% sample of all inpatient claims. The Manhattan Institute supplied data on the availability of health savings accounts in each state. State PTR implementation dates were gathered by Hans Christensen, Eric Floyd, and Mark Maffett of University of Chicago’s Booth School of Business by contacting the health department, hospital association, or website controller in each state.
Study Design: The NIS data was collapsed by procedure, hospital, and year providing averages for the dependent variable, Cost, and a host of covariates. Cost is a product of Total Charges within the NIS and the hospital’s Cost to Charge ratio. A new binary variable, PTR, was defined as ‘0’ if the year was strictly less than the disclosure website’s implementation date, ‘1’ for afterwards, and missing for the year of implementation. Then, using multivariate OLS regression with fixed effect modeling, the change in cost from before to after the year of implementation is estimated.
Principal Findings: The analysis estimates the effect of PTR to decrease the average cost per procedure by 7%. Specifications identify within state, within hospital, and within procedure variation, and reports that 78% of the cost decrease is due to within-hospital, within-procedure price discounts. An additional model includes the interaction of PTR with the prevalence of health savings accounts (hereafter, HSAs) and procedure electivity. The results show that PTR lowers costs by an additional 3 percent with each additional 10 percentage point increase in the availability of HSAs. In contrast, the cost reductions from PTR were much smaller for procedures more frequently coded as elective.
Conclusions: The study concludes price transparency regulations can lead to a decrease in a procedure’s costs on average, primarily through price discounts and slightly through lower cost procedures, but not due to patients moving to cheaper hospitals. This implies that hospitals are taking initiative and lowering prices as the competition’s prices become publically available suggesting that hospitals – not patients – are the biggest users of price transparency websites. Hospitals are also finding some ways to provide cheaper alternatives to more expensive procedures. State regulators should evaluate if a better metric other than charge prices, such as expected out-of-pocket payments, would evoke greater patient participation. Furthermore, states with higher prevalence of HSAs experience greater effects of PTR as expected since patients with HSAs have greater incentives to lower their costs. Patients should expect a shift towards plans that offer these types of savings accounts since they’ve shown to have a reduction of health costs on average per procedure in states with higher prevalence of HSAs.
Data Sources: I use the Healthcare Cost and Utilization Project’s Nationwide Inpatient Sample (NIS) from 2000 to 2011. The NIS is a 20% sample of all inpatient claims. The Manhattan Institute supplied data on the availability of health savings accounts in each state. State PTR implementation dates were gathered by Hans Christensen, Eric Floyd, and Mark Maffett of University of Chicago’s Booth School of Business by contacting the health department, hospital association, or website controller in each state.
Study Design: The NIS data was collapsed by procedure, hospital, and year providing averages for the dependent variable, Cost, and a host of covariates. Cost is a product of Total Charges within the NIS and the hospital’s Cost to Charge ratio. A new binary variable, PTR, was defined as ‘0’ if the year was strictly less than the disclosure website’s implementation date, ‘1’ for afterwards, and missing for the year of implementation. Then, using multivariate OLS regression with fixed effect modeling, the change in cost from before to after the year of implementation is estimated.
Principal Findings: The analysis estimates the effect of PTR to decrease the average cost per procedure by 7%. Specifications identify within state, within hospital, and within procedure variation, and reports that 78% of the cost decrease is due to within-hospital, within-procedure price discounts. An additional model includes the interaction of PTR with the prevalence of health savings accounts (hereafter, HSAs) and procedure electivity. The results show that PTR lowers costs by an additional 3 percent with each additional 10 percentage point increase in the availability of HSAs. In contrast, the cost reductions from PTR were much smaller for procedures more frequently coded as elective.
Conclusions: The study concludes price transparency regulations can lead to a decrease in a procedure’s costs on average, primarily through price discounts and slightly through lower cost procedures, but not due to patients moving to cheaper hospitals. This implies that hospitals are taking initiative and lowering prices as the competition’s prices become publically available suggesting that hospitals – not patients – are the biggest users of price transparency websites. Hospitals are also finding some ways to provide cheaper alternatives to more expensive procedures. State regulators should evaluate if a better metric other than charge prices, such as expected out-of-pocket payments, would evoke greater patient participation. Furthermore, states with higher prevalence of HSAs experience greater effects of PTR as expected since patients with HSAs have greater incentives to lower their costs. Patients should expect a shift towards plans that offer these types of savings accounts since they’ve shown to have a reduction of health costs on average per procedure in states with higher prevalence of HSAs.
ContributorsSabol, Joshua Lawrence (Author) / Reiser, Mark (Thesis director) / Ketcham, Jonathan (Committee member) / Dassanayake, Maduranga (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Supply Chain Management (Contributor)
Created2015-05
Description
Currently, the medical industry employs an acute treatment process centered on responsiveness and restoration. This method fails those with chronic illness who require disease management and proactivity. As a solution, the medical industry has implemented programs focused on providing integrated, coordinated care. This project examines two primary models to accommodate chronically ill patients: Accountable Care Organizations (ACOs) and Patient Centered Medical Homes (PCMHs). Specifically, this paper examines the data from Pioneer and Medicare Shared Savings Program ACOs. In the aggregate, the data indicate that these programs have been unsuccessful due to several key issues: a lack of patient and physician engagement, failure to incentivize medical professionals and failed collaboration between both ACOs and PCMHs. Remedying these issues would improve the ability of both ACOs and PCMHs to provide integrated, comprehensive care to patients with chronic illnesses.
ContributorsWoods, Cassie Marie (Author) / Ketcham, Jonathan (Thesis director) / Samper, Adriana (Committee member) / Barrett, The Honors College (Contributor) / Department of Marketing (Contributor)
Created2015-05
Description
The healthcare industry is currently facing significant changes. One of the changes in the industry is a movement towards patient-focused care, which considers the patient as a person and the impact of care on the person. Patient experience is part of patient-focused care, and has similarities to the marketing term customer experience, which contributes to happier customers and long-term financial growth and success for businesses. This thesis defines current issues in patient experience as it relates to hospital manager decision making. Through secondary research, this thesis demonstrates what patient experience is, the role it plays in healthcare and hospital settings, the pressures on hospitals to increase patient experience performance, how patient experience performance is measured, and what strategies or action drive improvements under current performance measurements. Many studies and articles exist examining each of these issues individually. However, these sources do not comprehensively define patient experience in hospitals with perspective on how this influences hospital strategy and decision-making. Previous works on patient experience from the perspective of hospital strategy do not include considerations for recent industry shifts, most notably the Patient Protection and Affordable Care Act. The collected definitions in this thesis provide guidance of relevant concerns hospital managers consider when formulating organization-wide strategy related to patient experience. This thesis explains how patient experience contributes to the success of hospitals in the short-term, medium-term, and long-term and how patient experience may shift its focus over time. Short-term concerns include specific regulations and definitions from the Centers for Medicare and Medicaid services, responsible for over half of all payments to hospitals. Conforming to CMS standards is a matter of survival for most hospitals in the short-term. Hospitals are adjusting to rules and payment models not in existence just two years ago. First, hospitals will adapt, and then hospitals will strive to optimize under new standards as well as respond to adjustments in the rules over the next several years. After patient experience standards are well established, certain aspects of patient experience will be part of long-term differentiation and success for hospitals. Responding comprehensively to the shift towards improving patient experience is a critical aspect for hospitals to weather the many changes in the healthcare industry. Patient experience will provide better care to patients and better financial health to the hospitals that perform above patient experience standards.
ContributorsWilton, Kara Alexandra (Author) / Ketcham, Jonathan (Thesis director) / Ostrom, Amy (Committee member) / Barrett, The Honors College (Contributor) / W. P. Carey School of Business (Contributor) / Department of Supply Chain Management (Contributor) / Department of Marketing (Contributor)
Created2014-05
Description
Prenatal care is a widely administered preventative care service, and its adequate use has been shown to decrease poor infant and maternal health outcomes. Today however, in the United States, preterm birth rates remain among the highest in the industrialized world, with low socioeconomic women having the highest risk of preterm births. This group of women also face the greatest barriers to access adequate prenatal care in the United States. This paper explores the viability of short message service to help bridge gaps in prenatal care for low socioeconomic women in the United States and provides areas for further research.
ContributorsMiles, Kelly Nicole (Author) / Ketcham, Jonathan (Thesis director) / Santanam, Raghu (Committee member) / Barrett, The Honors College (Contributor) / W. P. Carey School of Business (Contributor) / Department of Marketing (Contributor) / Department of Finance (Contributor)
Created2014-05
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
The Patient Protection and Affordable Care Act of 2010 was created as an overhaul of the US Healthcare system with a goal of getting all American citizens and legal residents healthcare that was both affordable and of good quality. Now almost a year removed from it going into effect, this study looks to determine how the ACA has worked in getting individuals who were previously uninsured and required charitable-based healthcare into health insurance programs within a small population in Arizona. This study evaluates the type of insurance program, the quality and ease of access of the care, and the general affordability of the healthcare. This study found that 75% of individuals surveyed had gained health insurance in the last year, with 95% expecting to be insured for 2015. The large majority rated the quality of their care and the accessibility of it as good, with corresponding increased use of primary care providers as a health resource. The affordability of the care was still a major issue for those who were found to be uninsured and for those who were insured. Despite affordability issues, self-reported measures of general health and access to care were reported by the majority of respondents to have improved over the last 12 months.
ContributorsHonan, Timothy Francis (Author) / Ketcham, Jonathan (Thesis director) / Jehn, Megan (Committee member) / Barrett, The Honors College (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor)
Created2015-05