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The Magnetoplasmadynamic (MPD) thruster is an electromagnetic thruster that produces a higher specific impulse than conventional chemical rockets and greater thrust densities than electrostatic thrusters, but the well-known operational limit---referred to as ``onset"---imposes a severe limitation efficiency and lifetime. This phenomenon is associated with large fluctuations in operating voltage, high

The Magnetoplasmadynamic (MPD) thruster is an electromagnetic thruster that produces a higher specific impulse than conventional chemical rockets and greater thrust densities than electrostatic thrusters, but the well-known operational limit---referred to as ``onset"---imposes a severe limitation efficiency and lifetime. This phenomenon is associated with large fluctuations in operating voltage, high rates of electrode erosion, and three-dimensional instabilities in the plasma flow-field which cannot be adequately represented by two-dimensional, axisymmetric models. Simulations of the Princeton Benchmark Thruster (PBT) were conducted using the three-dimensional version of the magnetohydrodynamic (MHD) code, MACH. Validation of the numerical model is partially achieved by comparison to equivalent simulations conducted using the well-established two-dimensional, axisymmetric version of MACH. Comparisons with available experimental data was subsequently performed to further validate the model and gain insights into the physical processes of MPD acceleration. Thrust, plasma voltage, and plasma flow-field predictions were calculated for the PBT operating with applied currents in the range $6.5kA < J < 23.25kA$ and mass-flow rates of $1g/s$, $3g/s$, and $6g/s$. Comparisons of performance characteristics between the two versions of the code show excellent agreement, indicating that MACH3 can be expected to be as predictive as MACH2 has demonstrated over multiple applications to MPD thrusters. Predicted thrust for operating conditions within the range which exhibited no symptoms of the onset phenomenon experimentally also showed agreement between MACH3 and experiment well within the experimental uncertainty. At operating conditions beyond such values , however, there is a discrepancy---up to $\sim20\%$---which implies that certain significant physical processes associated with onset are not currently being modeled. Such processes are also evident in the experimental total voltage data, as is evident by the characteristic ``voltage hash", but not present in predicted plasma voltage. Additionally, analysis of the predicted plasma flow-field shows no breakdown in azimuthal symmetry, which is expected to be associated with onset. This implies that perhaps certain physical processes are modeled by neither MACH2 nor MACH3; the latter indicating that such phenomenon may not be inherently three dimensional and related to the plasma---as suggested by other efforts---but rather a consequence of electrode material processes which have not been incorporated into the current models.
ContributorsParma, Brian (Author) / Mikellides, Pavlos G (Thesis advisor) / Squires, Kyle (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
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Description
Microchannel heat sinks can possess heat transfer characteristics unavailable in conventional heat exchangers; such sinks offer compact solutions to otherwise intractable thermal management problems, notably in small-scale electronics cooling. Flow boiling in microchannels allows a very high heat transfer rate, but is bounded by the critical heat flux (CHF). This

Microchannel heat sinks can possess heat transfer characteristics unavailable in conventional heat exchangers; such sinks offer compact solutions to otherwise intractable thermal management problems, notably in small-scale electronics cooling. Flow boiling in microchannels allows a very high heat transfer rate, but is bounded by the critical heat flux (CHF). This thesis presents a theoretical-numerical study of a method to improve the heat rejection capability of a microchannel heat sink via expansion of the channel cross-section along the flow direction. The thermodynamic quality of the refrigerant increases during flow boiling, decreasing the density of the bulk coolant as it flows. This may effect pressure fluctuations in the channels, leading to nonuniform heat transfer and local dryout in regions exceeding CHF. This undesirable phenomenon is counteracted by permitting the cross-section of the microchannel to increase along the direction of flow, allowing more volume for the vapor. Governing equations are derived from a control-volume analysis of a single heated rectangular microchannel; the cross-section is allowed to expand in width and height. The resulting differential equations are solved numerically for a variety of channel expansion profiles and numbers of channels. The refrigerant is R-134a and channel parameters are based on a physical test bed in a related experiment. Significant improvement in CHF is possible with moderate area expansion. Minimal additional manufacturing costs could yield major gains in the utility of microchannel heat sinks. An optimum expansion rate occurred in certain cases, and alterations in the channel width are, in general, more effective at improving CHF than alterations in the channel height. Modest expansion in height enables small width expansions to be very effective.
ContributorsMiner, Mark (Author) / Phelan, Patrick E (Thesis advisor) / Herrmann, Marcus (Committee member) / Chen, Kangping (Committee member) / Arizona State University (Publisher)
Created2011
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Description
A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in

A numerical study of incremental spin-up and spin-up from rest of a thermally- stratified fluid enclosed within a right circular cylinder with rigid bottom and side walls and stress-free upper surface is presented. Thermally stratified spin-up is a typical example of baroclinity, which is initiated by a sudden increase in rotation rate and the tilting of isotherms gives rise to baroclinic source of vorticity. Research by (Smirnov et al. [2010a]) showed the differences in evolution of instabilities when Dirichlet and Neumann thermal boundary conditions were applied at top and bottom walls. Study of parametric variations carried out in this dissertation confirmed the instability patterns observed by them for given aspect ratio and Rossby number values greater than 0.5. Also results reveal that flow maintained axisymmetry and stability for short aspect ratio containers independent of amount of rotational increment imparted. Investigation on vorticity components provides framework for baroclinic vorticity feedback mechanism which plays important role in delayed rise of instabilities when Dirichlet thermal Boundary Conditions are applied.
ContributorsKher, Aditya Deepak (Author) / Chen, Kangping (Thesis advisor) / Huang, Huei-Ping (Committee member) / Herrmann, Marcus (Committee member) / Arizona State University (Publisher)
Created2011
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Description

Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how the presence of chemical cues affect the perception of visual

Animals encounter information from different resources simultaneously, integrating input from multiple sensory systems before responding behaviorally. When different cues interact with one another, they may enhance, diminish, or have no impact on their responses. In this project, we test how the presence of chemical cues affect the perception of visual cues. Zebrafish (Danio rerio) often use both chemical cues and visual cues to communicate with shoal mates, to assess predation risk, and to locate food. For example, zebrafish rely on both olfactory cues and visual cues for kin recognition, and they frequently use both chemical and visual cues to search for and to capture prey. In zebrafish, the terminal nerve (TN) constitutes the olfacto-visual centrifugal pathway and connects the olfactory bulb with the retina, thus allowing olfactory perception also to activate visual receptors. Past studies have found that the presence of an olfactory cue can modulate visual sensitivity in zebrafish through the terminal nerve pathway. Alternatively, given that zebrafish are highly social, the presence of social chemical cues may distract individuals from responding to other visual cues, such as food and predator visual cues. Foraging and predator chemical cues, including chemical food cues and alarm cues, may also distract individuals from responding to non-essential visual cues. Here, we test whether the response to a visual cue either increases or decreases when presented in concert with alanine, an amino acid that represents the olfactory cues of zebrafish prey. We found that the presence of chemical cues did not affect whether zebrafish responded to visual cues, but that the fish took longer to respond to visual cues when chemical cues were also present. These findings suggest that different aspects of behavior could be affected by the interaction between sensory modalities. We also found that this impact of delayed response was significant only when the visual cue<br/>was weak compared to the strength of the chemical cue, suggesting that the salience of interacting cues may also have an influence on determining the outcomes of the interactions. Overall, the interactive effects of chemicals on an animal’s response to visual cues may also have wide-ranging impacts on behavior including foraging, mating, and evading predators, and the interaction of cues may affect different aspects of the same behavior.

ContributorsPuffer, Georgie Delilah (Author) / Martins, Emilia (Thesis director) / Suriyampola, Piyumika (Committee member) / Gerkin, Richard (Committee member) / School of Life Sciences (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Humans use emotions to communicate social cues to our peers on a daily basis. Are we able to identify context from facial expressions and match them to specific scenarios? This experiment found that people can effectively distinguish negative and positive emotions from each other from a short description. However, further

Humans use emotions to communicate social cues to our peers on a daily basis. Are we able to identify context from facial expressions and match them to specific scenarios? This experiment found that people can effectively distinguish negative and positive emotions from each other from a short description. However, further research is needed to find out whether humans can learn to perceive emotions only from contextual explanations.

ContributorsCulbert, Bailie (Author) / Hartwell, Leland (Thesis director) / McAvoy, Mary (Committee member) / School of Life Sciences (Contributor) / School of Criminology and Criminal Justice (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Locusts are generalist herbivores meaning that they are able to consume a variety of plants. Because of their broad diet, and ability to respond rapidly to a favorable environment with giant swarms of voracious insects, they are dangerous pests. Their potential impacts on humans increase dramatically when individuals switch from

Locusts are generalist herbivores meaning that they are able to consume a variety of plants. Because of their broad diet, and ability to respond rapidly to a favorable environment with giant swarms of voracious insects, they are dangerous pests. Their potential impacts on humans increase dramatically when individuals switch from their solitarious phase to their gregarious phase where they congregate and begin marching and eventually swarming together. These swarms, often billions strong, can consume the vegetation of enormous swaths of land and can travel hundreds of kilometers in a single day producing a complex threat to food security. To better understand the biology of these important pests we explored the gut microbiome of the South American locust (Schistocerca cancellata). We hypothesized generally that the gut microbiome in this species would be critically important as has been shown in many other species. We extracted and homogenized entire guts from male S. cancellata, and then extracted gut microbiome genomic DNA. Genomic DNA was then confirmed on a gel. The initial extractions were of poor quality for sequencing, but subsequent extractions performed by collaborators during troubleshooting at Southern Illinois University Edwardsville proved more useful and were used for PCR. This resulted in the detections of the following bacterial genera in the gut of S. cancellata: Enterobacter, Enterococcus, Serratia, Pseudomonas, Actinobacter, and Weisella. With this data, we are able to speculate about the physiological roles that they hold within the locust gut generating hypotheses for further testing. Understanding the microbial composition of this species’ gut may help us better understand the locust in general in an effort to more sustainably manage them.

ContributorsGrief, Dustin (Author) / Overson, Rick (Thesis director) / Cease, Arianne (Committee member) / Peterson, Brittany (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Over 40% of adults in the United States are considered obese. Obesity is known to cause abnormal metabolic effects and lead to other negative health consequences. Interestingly, differences in metabolism and contractile performance between obese and healthy weight individuals are associated with differences in skeletal muscle fiber type composition between

Over 40% of adults in the United States are considered obese. Obesity is known to cause abnormal metabolic effects and lead to other negative health consequences. Interestingly, differences in metabolism and contractile performance between obese and healthy weight individuals are associated with differences in skeletal muscle fiber type composition between these groups. Each fiber type is characterized by unique metabolic and contractile properties, which are largely determined by the myosin heavy chain isoform (MHC) or isoform combination that the fiber expresses. In previous studies, SDS-PAGE single fiber analysis has been utilized as a method to determine MHC isoform distribution and single fiber type distribution in skeletal muscle. Herein, a methodological approach to analyze MHC isoform and fiber type distribution in skeletal muscle was fine-tuned for use in human and rodent studies. In the future, this revised methodology will be implemented to evaluate the effects of obesity and exercise on the phenotypic fiber type composition of skeletal muscle.

ContributorsOhr, Jalonna Rose (Author) / Katsanos, Christos (Thesis director) / Tucker, Derek (Committee member) / Serrano, Nathan (Committee member) / School of Life Sciences (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

In the United States, clinical testing is monitored by the federal and state governments, held to standards to ensure the safety and efficacy of these tests, as well as maintaining privacy for patients receiving a test. In order for the ABCTL to lawfully operate in the state of Arizona, it

In the United States, clinical testing is monitored by the federal and state governments, held to standards to ensure the safety and efficacy of these tests, as well as maintaining privacy for patients receiving a test. In order for the ABCTL to lawfully operate in the state of Arizona, it had to meet various legal criteria. These major legal considerations, in no particular order, are: Clinical Laboratory Improvement Amendments compliance; FDA Emergency Use Authorization (EUA); Health Insurance Portability and Accountability Act compliance; state licensure; patient, state, and federal result reporting; and liability. <br/>In this paper, the EUA pathway will be examined and contextualized in relation to the ABCTL. This will include an examination of the FDA regulations and policies that affect the laboratory during its operations, as well as a look at the different authorization pathways for diagnostic tests present during the COVID-19 pandemic.

ContributorsJenkins, Landon James (Co-author) / Espinoza, Hale Anna (Co-author) / Filipek, Marina (Co-author) / Ross, Nathaniel (Co-author) / Salvatierra, Madeline (Co-author) / Compton, Carolyn (Thesis director) / Rigoni, Adam (Committee member) / Stanford, Michael (Committee member) / School of Life Sciences (Contributor) / School of Politics and Global Studies (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

Within the pediatric hospitalization experience, fear and anxiety are two emotions commonly felt by children of all ages. Hospitalized children can greatly benefit from interventions designed to help them cope with these emotions throughout their medical experiences. This study draws on each of our clinical experiences as volunteers at Phoenix

Within the pediatric hospitalization experience, fear and anxiety are two emotions commonly felt by children of all ages. Hospitalized children can greatly benefit from interventions designed to help them cope with these emotions throughout their medical experiences. This study draws on each of our clinical experiences as volunteers at Phoenix Children’s Hospital, and uses a qualitative analysis of three semi-structured interviews with currently employed Child Life Specialists to understand and analyze the use of medical play, a form of play intervention with a medical theme or medical equipment. We explore the goals and benefits of medical play for hospitalized pediatric patients, the process of using medical play as an intervention, including the activity design process, the assessments and adjustments made throughout the child’s hospitalization, and the considerations and limitations to implementing medical play activities. Ultimately, we found that the element of fun that defines play can be channeled into medical play activities implemented by skilled Child Life Specialists, who are experts in their field, in clinical settings to promote several different and beneficial goals, including pediatric patient coping.

ContributorsAguiar, Lara (Co-author) / Garciapeña, Danae (Co-author) / Loebenberg, Abby (Thesis director) / Swanson, Jodi (Committee member) / School of Life Sciences (Contributor) / Sanford School of Social and Family Dynamics (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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Description

What is being done to promote cultural sensitivity in healthcare settings? To find answers and solutions to the widespread deficit of cultural competence in the health care industry, this case study interviews a varied sample of five physicians consisting of three men and two women in clinical, academic, and administrative

What is being done to promote cultural sensitivity in healthcare settings? To find answers and solutions to the widespread deficit of cultural competence in the health care industry, this case study interviews a varied sample of five physicians consisting of three men and two women in clinical, academic, and administrative positions. The hypothesis was physicians do not receive cultural sensitivity training in medical school and as a result, they have to find other ways to learn about the cultures of their patients. None of the participants had received formal cultural competency training in medical school and all of them found methods to improve their cultural literacy. The study uncovered the cultural training physicians do receive is sporadic and inconsistent, which can cause some disconnect between education and real-life clinical practice. Many solutions to improve cultural competency in health care delivery are presented. The results of this exploratory research should be used to inspire future conversations about cultural competency in health care as well as the creation of support and educational services and materials to medical students and health care workers on improving cultural sensitivity in clinical practice.

ContributorsWilson, Diane Kathleen (Author) / Cortese, Denis (Thesis director) / Estevez, Dulce (Committee member) / School of International Letters and Cultures (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05