Matching Items (504)
Description

Soiled: An Environmental Podcast is a six episode series where common environmental topics are discussed and misconceptions surrounding these topics are debunked.

ContributorsJones, Cassity Rachelle (Co-author) / Kuta, Tiffany (Co-author) / Turner, Natalie (Co-author) / Boyer, Mackenzie (Thesis director) / Ward, Kristen (Committee member) / School of Life Sciences (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

The use of enzyme-catalyst interfaces is underexplored in the field of biocatalysis, particularly in studies on enabling novel reactivity of enzymes. For this thesis, the HaloTag® protein tagging platform was proposed as a bioconjugation method for a pinacol coupling reaction using lipases, as a model for novel reactivities proceeding via

The use of enzyme-catalyst interfaces is underexplored in the field of biocatalysis, particularly in studies on enabling novel reactivity of enzymes. For this thesis, the HaloTag® protein tagging platform was proposed as a bioconjugation method for a pinacol coupling reaction using lipases, as a model for novel reactivities proceeding via ketyl radical intermediates and hydrogen-bonding-facilitated redox attenuation. After an initial lipase screening of 9 lipases, one lipase (Candida rugosa) was found to perform the pinacol coupling of p-anisaldehyde under standard conditions (fluorescein and 530nm light, 3% yield). Based on a retrosynthetic analysis for the photocatalyst-incorporated HaloTag® linker, the intermediates haloamine 1 and aldehyde 6 were synthesized. Further experiments are underway or planned to complete linker synthesis and conduct pinacol coupling experiments with a bioconjugated system. This project underscores the promising biocatalytic promiscuity of lipases for performing reactions proceeding through ketyl radical intermediates, as well as the underdeveloped potential of incorporating bioengineering principles like bioconjugation into biocatalysis to overcome kinetic barriers to electron transfer and optimize biocatalytic reactions.

ContributorsMcrae, Kenna Christine (Author) / Biegasiewicz, Kyle (Thesis director) / Ghirlanda, Giovanna (Committee member) / Moore, Ana (Committee member) / Department of Physics (Contributor) / School of Human Evolution & Social Change (Contributor) / School of International Letters and Cultures (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description

The COVID-19 pandemic places significant strain on the U.S. healthcare system due to the high number of coronavirus cases. During the pandemic, there was much unknown about the virus, its course of the disease, COVID-19 diagnosis, treatments, or other imperative information needed to contain the virus. Resources within the healthcare

The COVID-19 pandemic places significant strain on the U.S. healthcare system due to the high number of coronavirus cases. During the pandemic, there was much unknown about the virus, its course of the disease, COVID-19 diagnosis, treatments, or other imperative information needed to contain the virus. Resources within the healthcare system, such as PPE and healthcare workers, were in short supply and exacerbated the difficulty of managing the viral outbreak. Peer-reviewed articles suggest that telehealth, the application of electronic information and telecommunication technologies in healthcare, proved useful in public health and clinical care during the 2020 public health emergency due to a novel virus. The scoping review broadly assessed themes of telehealth’s strengths and weaknesses during the COVID-19 pandemic. These findings could suggest how virtual medicine may be a helpful tool to improve access in addition to the quality of care in the future of medicine. Assessments of case studies suggest that telehealth helped provide care to large patient volumes by aiding with communication, data collection, triage, remote patient monitoring, and critical care. Limitations of expanding telehealth subsequent to the pandemic include, but not limited to, a lack of national standards for practice and restrictions of utility for certain populations. Populations may include those with low socioeconomic status, specific cultural practices, and beliefs, or physical and cognitive ability barriers. Outlining the benefits and limitations of telehealth may suggest how virtual medicine can provide valuable in day-to-day medical practices and other pathogenic outbreaks.

ContributorsBlock, Andrea (Author) / Tanner, Rene (Thesis director) / Maienschein, Jane (Committee member) / Marvasti, Farshad (Committee member) / School of Life Sciences (Contributor, Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description
CMOS technology is expected to enter the 10nm regime for future integrated circuits (IC). Such aggressive scaling leads to vastly increased variability, posing a grand challenge to robust IC design. Variations in CMOS are often divided into two types: intrinsic variations and process-induced variations. Intrinsic variations are limited by fundamental

CMOS technology is expected to enter the 10nm regime for future integrated circuits (IC). Such aggressive scaling leads to vastly increased variability, posing a grand challenge to robust IC design. Variations in CMOS are often divided into two types: intrinsic variations and process-induced variations. Intrinsic variations are limited by fundamental physics. They are inherent to CMOS structure, considered as one of the ultimate barriers to the continual scaling of CMOS devices. In this work the three primary intrinsic variations sources are studied, including random dopant fluctuation (RDF), line-edge roughness (LER) and oxide thickness fluctuation (OTF). The research is focused on the modeling and simulation of those variations and their scaling trends. Besides the three variations, a time dependent variation source, Random Telegraph Noise (RTN) is also studied. Different from the other three variations, RTN does not contribute much to the total variation amount, but aggregate the worst case of Vth variations in CMOS. In this work a TCAD based simulation study on RTN is presented, and a new SPICE based simulation method for RTN is proposed for time domain circuit analysis. Process-induced variations arise from the imperfection in silicon fabrication, and vary from foundries to foundries. In this work the layout dependent Vth shift due to Rapid-Thermal Annealing (RTA) are investigated. In this work, we develop joint thermal/TCAD simulation and compact modeling tools to analyze performance variability under various layout pattern densities and RTA conditions. Moreover, we propose a suite of compact models that bridge the underlying RTA process with device parameter change for efficient design optimization.
ContributorsYe, Yun, Ph.D (Author) / Cao, Yu (Thesis advisor) / Yu, Hongbin (Committee member) / Song, Hongjiang (Committee member) / Clark, Lawrence (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively

Semiconductor nanowires (NWs) are one dimensional materials and have size quantization effect when the diameter is sufficiently small. They can serve as optical wave guides along the length direction and contain optically active gain at the same time. Due to these unique properties, NWs are now very promising and extensively studied for nanoscale optoelectronic applications. A systematic and comprehensive optical and microstructural study of several important infrared semiconductor NWs is presented in this thesis, which includes InAs, PbS, InGaAs, erbium chloride silicate and erbium silicate. Micro-photoluminescence (PL) and transmission electron microscope (TEM) were utilized in conjunction to characterize the optical and microstructure of these wires. The focus of this thesis is on optical study of semiconductor NWs in the mid-infrared wavelengths. First, differently structured InAs NWs grown using various methods were characterized and compared. Three main PL peaks which are below, near and above InAs bandgap, respectively, were observed. The octadecylthiol self-assembled monolayer was employed to passivate the surface of InAs NWs to eliminate or reduce the effects of the surface states. The band-edge emission from wurtzite-structured NWs was completely recovered after passivatoin. The passivated NWs showed very good stability in air and under heat. In the second part, mid-infrared optical study was conducted on PbS wires of subwavelength diameter and lasing was demonstrated under optical pumping. The PbS wires were grown on Si substrate using chemical vapor deposition and have a rock-salt cubic structure. Single-mode lasing at the wavelength of ~3000-4000 nm was obtained from single as-grown PbS wire up to the temperature of 115 K. PL characterization was also utilized to demonstrate the highest crystallinity of the vertical arrays of InP and InGaAs/InP composition-graded heterostructure NWs made by a top-down fabrication method. TEM-related measurements were performed to study the crystal structures and elemental compositions of the Er-compound core-shell NWs. The core-shell NWs consist of an orthorhombic-structured erbium chloride silicate shell and a cubic-structured silicon core. These NWs provide unique Si-compatible materials with emission at 1530 nm for optical communications and solid state lasers.
ContributorsSun, Minghua (Author) / Ning, Cun-Zheng (Thesis advisor) / Yu, Hongbin (Committee member) / Carpenter, Ray W. (Committee member) / Johnson, Shane (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Semiconductor devices are generally analyzed with relatively simple equations or with detailed computer simulations. Most text-books use these simple equations and show device diagrams that are frequently very simplified and occasionally incorrect. For example, the carrier densities near the pinch-off point in MOSFETs and JFETs and the minority carrier density

Semiconductor devices are generally analyzed with relatively simple equations or with detailed computer simulations. Most text-books use these simple equations and show device diagrams that are frequently very simplified and occasionally incorrect. For example, the carrier densities near the pinch-off point in MOSFETs and JFETs and the minority carrier density in the base near the reverse-biased base-collector junction are frequently assumed to be zero or near zero. Also the channel thickness at the pinch-off point is often shown to approach zero. None of these assumptions can be correct. The research in thesis addresses these points. I simulated the carrier densities, potentials, electric fields etc. of MOSFETs, BJTs and JFETs at and near the pinch-off regions to determine exactly what happens there. I also simulated the behavior of the quasi-Fermi levels. For MOSFETs, the channel thickness expands slightly before the pinch-off point and then spreads out quickly in a triangular shape and the space-charge region under the channel actually shrinks as the potential increases from source to drain. For BJTs, with collector-base junction reverse biased, most minority carriers diffuse through the base from emitter to collector very fast, but the minority carrier concentration at the collector-base space-charge region is not zero. For JFETs, the boundaries of the space-charge region are difficult to determine, the channel does not disappear after pinch off, the shape of channel is always tapered, and the carrier concentration in the channel decreases progressively. After simulating traditional sized devices, I also simulated typical nano-scaled devices and show that they behave similarly to large devices. These simulation results provide a more complete understanding of device physics and device operation in those regions usually not addressed in semiconductor device physics books.
ContributorsYang, Xuan (Author) / Schroder, Dieter K. (Thesis advisor) / Vasileska, Dragica (Committee member) / Yu, Hongbin (Committee member) / Arizona State University (Publisher)
Created2011
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Description
HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy

HgCdTe is the dominant material currently in use for infrared (IR) focal-plane-array (FPA) technology. In this dissertation, transmission electron microscopy (TEM) was used for the characterization of epitaxial HgCdTe epilayers and HgCdTe-based devices. The microstructure of CdTe surface passivation layers deposited either by hot-wall epitaxy (HWE) or molecular beam epitaxy (MBE) on HgCdTe heterostructures was evaluated. The as-deposited CdTe passivation layers were polycrystalline and columnar. The CdTe grains were larger and more irregular when deposited by HWE, whereas those deposited by MBE were generally well-textured with mostly vertical grain boundaries. Observations and measurements using several TEM techniques showed that the CdTe/HgCdTe interface became considerably more abrupt after annealing, and the crystallinity of the CdTe layer was also improved. The microstructure and compositional profiles of CdTe(211)B/ZnTe/Si(211) heterostructures grown by MBE was investigated. Many inclined {111}-type stacking faults were present throughout the thin ZnTe layer, terminating near the point of initiation of CdTe growth. A rotation angle of about 3.5° was observed between lattice planes of the Si substrate and the final CdTe epilayer. Lattice parameter measurement and elemental profiles indicated that some local intermixing of Zn and Cd had taken place. The average widths of the ZnTe layer and the (Cd, Zn)Te transition region were found to be roughly 6.5 nm and 3.5 nm, respectively. Initial observations of CdTe(211)B/GaAs(211) heterostructures indicated much reduced defect densities near the vicinity of the substrate and within the CdTe epilayers. HgCdTe epilayers grown on CdTe(211)B/GaAs(211) composite substrate were generally of high quality, despite the presence of precipitates at the HgCdTe/CdTe interface. The microstructure of HgCdSe thin films grown by MBE on ZnTe/Si(112) and GaSb(112) substrates were investigated. The quality of the HgCdSe growth was dependent on the growth temperature and materials flux, independent of the substrate. The materials grown at 100°C were generally of high quality, while those grown at 140°C had {111}-type stacking defects and high dislocation densities. For epitaxial growth of HgCdSe on GaSb substrates, better preparation of the GaSb buffer layer will be essential in order to ensure that high-quality HgCdSe can be grown.
ContributorsZhao, Wenfeng (Author) / Smith, David J. (Thesis advisor) / McCartney, Martha (Committee member) / Carpenter, Ray (Committee member) / Bennett, Peter (Committee member) / Treacy, Michael J. (Committee member) / Arizona State University (Publisher)
Created2011
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Description
With increasing demand for System on Chip (SoC) and System in Package (SiP) design in computer and communication technologies, integrated inductor which is an essential passive component has been widely used in numerous integrated circuits (ICs) such as in voltage regulators and RF circuits. In this work, soft ferromagnetic core

With increasing demand for System on Chip (SoC) and System in Package (SiP) design in computer and communication technologies, integrated inductor which is an essential passive component has been widely used in numerous integrated circuits (ICs) such as in voltage regulators and RF circuits. In this work, soft ferromagnetic core material, amorphous Co-Zr-Ta-B, was incorporated into on-chip and in-package inductors in order to scale down inductors and improve inductors performance in both inductance density and quality factor. With two layers of 500 nm Co-Zr-Ta-B films a 3.5X increase in inductance and a 3.9X increase in quality factor over inductors without magnetic films were measured at frequencies as high as 1 GHz. By laminating technology, up to 9.1X increase in inductance and more than 5X increase in quality factor (Q) were obtained from stripline inductors incorporated with 50 nm by 10 laminated films with a peak Q at 300 MHz. It was also demonstrated that this peak Q can be pushed towards high frequency as far as 1GHz by a combination of patterning magnetic films into fine bars and laminations. The role of magnetic vias in magnetic flux and eddy current control was investigated by both simulation and experiment using different patterning techniques and by altering the magnetic via width. Finger-shaped magnetic vias were designed and integrated into on-chip RF inductors improving the frequency of peak quality factor from 400 MHz to 800 MHz without sacrificing inductance enhancement. Eddy current and magnetic flux density in different areas of magnetic vias were analyzed by HFSS 3D EM simulation. With optimized magnetic vias, high frequency response of up to 2 GHz was achieved. Furthermore, the effect of applied magnetic field on on-chip inductors was investigated for high power applications. It was observed that as applied magnetic field along the hard axis (HA) increases, inductance maintains similar value initially at low fields, but decreases at larger fields until the magnetic films become saturated. The high frequency quality factor showed an opposite trend which is correlated to the reduction of ferromagnetic resonant absorption in the magnetic film. In addition, experiments showed that this field-dependent inductance change varied with different patterned magnetic film structures, including bars/slots and fingers structures. Magnetic properties of Co-Zr-Ta-B films on standard organic package substrates including ABF and polyimide were also characterized. Effects of substrate roughness and stress were analyzed and simulated which provide strategies for integrating Co-Zr-Ta-B into package inductors and improving inductors performance. Stripline and spiral inductors with Co-Zr-Ta-B films were fabricated on both ABF and polyimide substrates. Maximum 90% inductance increase in hundreds MHz frequency range were achieved in stripline inductors which are suitable for power delivery applications. Spiral inductors with Co-Zr-Ta-B films showed 18% inductance increase with quality factor of 4 at frequency up to 3 GHz.
ContributorsWu, Hao (Author) / Yu, Hongbin (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Cao, Yu (Committee member) / Chickamenahalli, Shamala (Committee member) / Arizona State University (Publisher)
Created2013
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Description

The Beck Depression Inventory II (BDI-II) and the Patient Health Questionnaire 9 (PHQ-9) are highly valid depressive testing tools used to measure the symptom profile of depression globally and in South Asia, respectively (Steer et al., 1998; Kroenke et al, 2001). Even though the South Asian population comprises only

The Beck Depression Inventory II (BDI-II) and the Patient Health Questionnaire 9 (PHQ-9) are highly valid depressive testing tools used to measure the symptom profile of depression globally and in South Asia, respectively (Steer et al., 1998; Kroenke et al, 2001). Even though the South Asian population comprises only 23% of the world’s population, it represents one-fifth of the world’s mental health disorders (Ogbo et al., 2018). Although this population is highly affected by mental disorders, there is a lack of culturally relevant research on specific subsections of the South Asian population.<br/><br/>As such, the goal of this study is to investigate the differences in the symptom profile of depression in native and immigrant South Asian populations. We investigated the role of collective self-esteem and perceived discrimination on mental health. <br/><br/>For the purpose of this study, participants were asked a series of questions about their depressive symptoms, self-esteem and perceived discrimination using various depressive screening measures, a self-esteem scale, and a perceived discrimination scale.<br/><br/>We found that immigrants demonstrated higher depressive symptoms than Native South Asians as immigration was viewed as a stressor. First-generation and second-generation South Asian immigrants identified equally with somatic and psychological symptoms. These symptoms were positively correlated with perceived discrimination, and collective self-esteem was shown to increase the likelihood of these symptoms.<br/><br/>This being said, the results from this study may be generalized only to South Asian immigrants who come from highly educated and high-income households. Since seeking professional help and being aware of one’s mental health is vital for wellbeing, the results from this study may spark the interest in an open communication about mental health within the South Asian immigrant community as well as aid in the restructuring of a highly reliable and valid measurement to be specific to a culture.

ContributorsMurthy, Nithara (Co-author) / Swaminathan, Manasa (Co-author) / Vogel, Joanne (Thesis director) / Kwan, Sau (Committee member) / Department of Psychology (Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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In 2014 alone, 40% of all drug abuse-related emergency department visits involved cocaine, and despite the detrimental effects there is still no FDA approved treatment for cocaine use disorders (CUDs; Dawn, 2014). Studies show that serotonin 1B receptor (5HT1BR) agonists modulate cocaine abuse-related behaviors in opposite directions depending on the

In 2014 alone, 40% of all drug abuse-related emergency department visits involved cocaine, and despite the detrimental effects there is still no FDA approved treatment for cocaine use disorders (CUDs; Dawn, 2014). Studies show that serotonin 1B receptor (5HT1BR) agonists modulate cocaine abuse-related behaviors in opposite directions depending on the phase of the addiction cycle in male rats. In particular, the selective 5HT1BR agonist, CP94,253, facilitates cocaine intake during maintenance of daily cocaine self-administration. Paradoxically, after 21 days of abstinence, CP94,253 attenuates cocaine intake in male rats on a low effort fixed ratio 5 (FR5) and a high effort progressive ratio (PR) schedule of reinforcement. PR measures motivation as it requires an exponentially increasing number of lever responses to obtain the next reinforcer after a successful reinforcer. In contrast to male rats, we recently found CP94,253 attenuates cocaine intake before and after abstinence on an FR5 schedule of reinforcement in female rats, suggesting the attenuating effects of CP94,253 on cocaine intake is not dependent on a period of abstinence in females. However, the effect of CP94,253 on motivation for cocaine has not yet been examined in female rats. Therefore, we addressed this gap in the present study. Female Sprague-Dawley rats were trained to self-administer 0.375 mg/kg, IV cocaine or to obtain sucrose pellets (45 mg) on a PR schedule of reinforcement and were then pretreated with vehicle or CP94,253 (3.2, 5.6 and 10 mg/kg, SC) prior to their self-administration session. A separate cohort was pretreated with CP94,253 to examine the effects of CP94,253 on cocaine-seeking behavior (i.e., operant responses when cocaine is no longer available) and spontaneous locomotion after 21 or 60 days of abstinence. The preliminary findings show that CP94,253 has minimal impacts on decreasing cocaine intake on a PR schedule in female rats but decreases cue reactivity up to 60 days after abstinence in female rats. These findings suggest that 5-HT1BR agonists may be useful treatments for cocaine craving.

ContributorsRuscitti, Brielle Allesandra (Author) / Neisewander, Janet (Thesis director) / Powell, Gregory (Committee member) / Scott, Samantha (Committee member) / School of Life Sciences (Contributor, Contributor) / School of Human Evolution & Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05