Matching Items (16)
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The overall goal of this research project was to assess the feasibility of investigating the effects of microgravity on mineralization systems in unit gravity environments. If possible to perform these studies in unit gravity earth environments, such as earth, such systems can offer markedly less costly and more concerted research

The overall goal of this research project was to assess the feasibility of investigating the effects of microgravity on mineralization systems in unit gravity environments. If possible to perform these studies in unit gravity earth environments, such as earth, such systems can offer markedly less costly and more concerted research efforts to study these vitally important systems. Expected outcomes from easily accessible test environments and more tractable studies include the development of more advanced and adaptive material systems, including biological systems, particularly as humans ponder human exploration in deep space. The specific focus of the research was the design and development of a prototypical experimental test system that could preliminarily meet the challenging design specifications required of such test systems. Guided by a more unified theoretical foundation and building upon concept design and development heuristics, assessment of the feasibility of two experimental test systems was explored. Test System I was a rotating wall reactor experimental system that closely followed the specifications of a similar test system, Synthecon, designed by NASA contractors and thus closely mimicked microgravity conditions of the space shuttle and station. The latter includes terminal velocity conditions experienced by both innate material systems, as well as, biological systems, including living tissue and humans but has the ability to extend to include those material test systems associated with mineralization processes. Test System II is comprised of a unique vertical column design that offered more easily controlled fluid mechanical test conditions over a much wider flow regime that was necessary to achieving terminal velocities under free convection-less conditions that are important in mineralization processes. Preliminary results indicate that Test System II offers distinct advantages in studying microgravity effects in test systems operating in unit gravity environments and particularly when investigating mineralization and related processes. Verification of the Test System II was performed on validating microgravity effects on calcite mineralization processes reported earlier others. There studies were conducted on calcite mineralization in fixed-wing, reduced gravity aircraft, known as the `vomit comet' where reduced gravity conditions are include for very short (~20second) time periods. Preliminary results indicate that test systems, such as test system II, can be devised to assess microgravity conditions in unit gravity environments, such as earth. Furthermore, the preliminary data obtained on calcite formation suggest that strictly physicochemical mechanisms may be the dominant factors that control adaptation in materials processes, a theory first proposed by Liu et al. Thus the result of this study may also help shine a light on the problem of early osteoporosis in astronauts and long term interest in deep space exploration.
ContributorsSeyedmadani, Kimia (Author) / Pizziconi, Vincent (Thesis advisor) / Towe, Bruce (Committee member) / Alford, Terry (Committee member) / Arizona State University (Publisher)
Created2013
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Biological diversity is threatened by increasing anthropogenic modification of natural environments and increasing demands on natural resources. Sonoran desert tortoises (Gopherus morafkai) currently have Candidate status under the Endangered Species Act (ESA) based on health and habitat threats. To ensure this animal persists in the midst of multiple threats requires

Biological diversity is threatened by increasing anthropogenic modification of natural environments and increasing demands on natural resources. Sonoran desert tortoises (Gopherus morafkai) currently have Candidate status under the Endangered Species Act (ESA) based on health and habitat threats. To ensure this animal persists in the midst of multiple threats requires an understanding of the life history and ecology of each population. I looked at one physiological and one behavioral aspect of a population of tortoises at the Sugarloaf Mountain (SL) study site in central Arizona, USA. I used 21 years of capture-recapture records to estimate growth parameters of the entire population. I investigated habitat selection of juvenile tortoises by selecting 117 locations of 11 tortoises that had been tracked by radio-telemetry one to three times weekly for two years, selecting locations from both summer active season and during winter hibernation. I compared 22 microhabitat variables of tortoise locations to random SL locations to determine habitat use and availability. Male tortoises at SL reach a greater asymptotic length than females, and males and females appear to grow at the same rate. Juvenile tortoises at the SL site use steep rocky hillsides with high proportions of sand and annual vegetation, few succulents, and enclosed shelters in summer. They use enclosed shelters on steep slopes for winter hibernation. An understanding of these features can allow managers to quantify Sonoran desert tortoise habitat needs and life history characteristics and to understand the impact of land use policies.
ContributorsBridges, Andrew (Author) / Bateman, Heather L (Thesis advisor) / Miller, William (Committee member) / Ulrich, Jon (Committee member) / Arizona State University (Publisher)
Created2012
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Like individual organisms, complex social groups are able to maintain predictable trajectories of growth, from initial colony foundation to mature reproductively capable units. They do so while simultaneously responding flexibly to variation in nutrient availability and intake. Leafcutter ant colonies function as tri-trophic systems, in which the ants harvest vegetation

Like individual organisms, complex social groups are able to maintain predictable trajectories of growth, from initial colony foundation to mature reproductively capable units. They do so while simultaneously responding flexibly to variation in nutrient availability and intake. Leafcutter ant colonies function as tri-trophic systems, in which the ants harvest vegetation to grow a fungus that, in turn, serves as food for the colony. Fungal growth rates and colony worker production are interdependent, regulated by nutritional and behavioral feedbacks. Fungal growth and quality are directly affected by worker foraging decisions, while worker production is, in turn, dependent on the amount and condition of the fungus. In this dissertation, I first characterized the growth relationship between the workers and the fungus of the desert leafcutter ant Acromyrmex versicolor during early stages of colony development, from colony foundation by groups of queens through the beginnings of exponential growth. I found that this relationship undergoes a period of slow growth and instability when workers first emerge, and then becomes allometrically positive. I then evaluated how mass and element ratios of resources collected by the ants are translated into fungus and worker population growth, and refuse, finding that colony digestive efficiency is comparable to digestive efficiencies of other herbivorous insects and ruminants. To test how colonies behaviorally respond to perturbations of the fungus garden, I quantified activity levels and task performance of workers in colonies with either supplemented or diminished fungus gardens, and found that colonies adjusted activity and task allocation in response to the fungus garden size. Finally, to identify possible forms of nutrient limitation, I measured how colony performance was affected by changes in the relative amounts of carbohydrates, protein, and phosphorus available in the resources used to grow the fungus garden. From this experiment, I concluded that colony growth is primarily carbohydrate-limited.
ContributorsClark, Rebecca, 1981- (Author) / Fewell, Jennifer H (Thesis advisor) / Mueller, Ulrich (Committee member) / Liebig, Juergen (Committee member) / Elser, James (Committee member) / Harrison, Jon (Committee member) / Arizona State University (Publisher)
Created2011
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With the ongoing drought surpassing a decade in Arizona, scholars, water managers and decision-makers have heightened attention to the availability of water resources, especially in rapidly growing regions where demand may outgrow supplies or outpace the capacity of the community water systems. Community water system managing entities and the biophysical

With the ongoing drought surpassing a decade in Arizona, scholars, water managers and decision-makers have heightened attention to the availability of water resources, especially in rapidly growing regions where demand may outgrow supplies or outpace the capacity of the community water systems. Community water system managing entities and the biophysical and social characteristics of a place mediate communities' vulnerability to hazards such as drought and long-term climate change. The arid southwestern Phoenix metropolitan area is illustrative of the challenges that developed urban areas in arid climates face globally as population growth and climate change stress already fragile human-environmental systems. This thesis reveals the factors abating and exacerbating differential community water system vulnerability to water scarcity in communities simultaneously facing drought and rapid peri-urban growth. Employing a grounded, qualitative comparative case study approach, this thesis explores the interaction of social, biophysical and institutional factors as they effect the exposure, sensitivity and adaptive capacity of community water systems in Cave Creek and Buckeye, Arizona. Buckeye, once a small agricultural town in the West Valley, is wholly dependent on groundwater and currently planning for massive development to accommodate 218,591 new residents by 2020. Amid desert hills and near Tonto National Forest in the North Valley, Cave Creek is an upscale residential community suffering frequent water outages due to aging infrastructure and lack of system redundancy. Analyzing interviews, media accounts and policy documents, a narrative was composed explaining how place based factors, nested within a regional institutional water management framework, impact short and long-term vulnerability. This research adds to the library of vulnerability assessments completed using Polsky et al.'s Vulnerability Scoping Diagram and serves a pragmatic need assisting in the development of decision making tools that better represent the drivers of placed based vulnerability in arid metropolitan regions.
ContributorsZautner, Lilah (Author) / Larson, Kelli (Thesis advisor) / Bolin, Bob (Committee member) / Chhetri, Netra (Committee member) / Arizona State University (Publisher)
Created2011
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This dissertation consists of three essays on modern economic growth and structural transformation, in particular touching on the reallocation of labor across industries, occupations, and employment statuses.

The first chapter investigates the quantitative importance of non-employment in the labor market outcomes for the United States. During the last 50 years, production

This dissertation consists of three essays on modern economic growth and structural transformation, in particular touching on the reallocation of labor across industries, occupations, and employment statuses.

The first chapter investigates the quantitative importance of non-employment in the labor market outcomes for the United States. During the last 50 years, production has shifted from goods to services. In terms of occupations, the routine employment share decreased, giving way to increases in manual and abstract ones. These two patterns are related, and lower non-employment had an important role. A labor allocation model where goods, market services, and home services use different tasks as inputs is used for quantitative exercises. These show that non-employment could significantly slow down polarization and structural transformation, and induce significant displacement within the labor force.

The second chapter, coauthored with Bart Hobijn and Todd Schoellman, looks at the demographic structure of structural transformation. More than half of labor reallocation during structural transformation is due to new cohorts disproportionately entering growing industries. This suggests substantial costs to labor reallocation. A model of overlapping generations with life-cycle career choice under switching costs and structural transformation is studied. Switching costs accelerate structural transformation, since forward-looking workers enter growing industries in anticipation of future wage growth. Most of the impact of switching costs shows on relative wages.

The third chapter establishes that job polarization is a global phenomenon. The analysis of polarization is extended from a group of developed countries to a sample of 119 economies. At all levels of development, employment shares in routine occupations have decreased since the 1980s. This suggests that routine occupations are becoming increasingly obsolete throughout the world, rather than being outsourced to developing countries. A development accounting framework with technical change at the \textit{task} level is proposed. This allows to quantify and extrapolate task-specific productivity levels. Recent technological change is biased against routine occupations and in favor of manual occupations. This implies that in the following decades, world polarization will continue: employment in routine occupations will decrease, and the reallocation will happen mostly from routine to manual occupations, rather than to abstract ones.
ContributorsVindas Quesada, Alberto José (Author) / Hobijn, Bart (Thesis advisor) / Bick, Alexander (Committee member) / Ventura, Gustavo (Committee member) / Arizona State University (Publisher)
Created2019
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Unmanned aerial vehicles have received increased attention in the last decade due to their versatility, as well as the availability of inexpensive sensors (e.g. GPS, IMU) for their navigation and control. Multirotor vehicles, specifically quadrotors, have formed a fast growing field in robotics, with the range of applications spanning from

Unmanned aerial vehicles have received increased attention in the last decade due to their versatility, as well as the availability of inexpensive sensors (e.g. GPS, IMU) for their navigation and control. Multirotor vehicles, specifically quadrotors, have formed a fast growing field in robotics, with the range of applications spanning from surveil- lance and reconnaissance to agriculture and large area mapping. Although in most applications single quadrotors are used, there is an increasing interest in architectures controlling multiple quadrotors executing a collaborative task. This thesis introduces a new concept of control involving more than one quadrotors, according to which two quadrotors can be physically coupled in mid-flight. This concept equips the quadro- tors with new capabilities, e.g. increased payload or pursuit and capturing of other quadrotors. A comprehensive simulation of the approach is built to simulate coupled quadrotors. The dynamics and modeling of the coupled system is presented together with a discussion regarding the coupling mechanism, impact modeling and additional considerations that have been investigated. Simulation results are presented for cases of static coupling as well as enemy quadrotor pursuit and capture, together with an analysis of control methodology and gain tuning. Practical implementations are introduced as results show the feasibility of this design.
ContributorsLarsson, Daniel (Author) / Artemiadis, Panagiotis (Thesis advisor) / Marvi, Hamidreza (Committee member) / Berman, Spring (Committee member) / Arizona State University (Publisher)
Created2016
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This dissertation examined how anxiety levels and social competence change across the course of early elementary school, as well as how individual differences at the transition to kindergarten may influence these trajectories. Previous research has supported unidirectional relations among anxiety and social competence, but few studies explore how inter- and

This dissertation examined how anxiety levels and social competence change across the course of early elementary school, as well as how individual differences at the transition to kindergarten may influence these trajectories. Previous research has supported unidirectional relations among anxiety and social competence, but few studies explore how inter- and intra-individual changes in social competence and anxiety may be related across time. From a developmental perspective, studying these trajectories following the transition to kindergarten is important, as cognitive and emotion regulation capacities increase markedly across kindergarten, and the relative success with which children navigate this transition can have a bearing on future social and emotional functioning across elementary school. In addition, given gender differences in anxiety manifestation and social competence development broadly, gender differences were also examined in an exploratory manner. Data from parent and teacher reports of a community sample of 291 children across kindergarten, 1st, and 2nd grades were analyzed. Results from bivariate growth models revealed steeper increases in anxiety, relative to peers in the sample, were associated with steeper decreases in social competence across time. This finding held after controlling for externalizing behavior problems at each time point, which suggests that relations among anxiety and social competence may be independent of other behavior problems commonly associated with poor social adjustment. Temperament variables were associated with changes in social competence, such that purportedly "risky" temperament traits of higher negative emotionality and lower attention control were associated with concurrently lower social competence in kindergarten, but with relatively steeper increases in social competence across time. Temperament variables in kindergarten were unrelated with changes in anxiety across time. Gender differences in relations among anxiety in kindergarten and growth in social competence also were revealed. Findings for teacher and parent reports of child behavior varied. Results are discussed with respect to contexts that may drive differences between parent and teacher reports of child behavior, as well as key developmental considerations that may help to explain why kindergarten temperament variables examined herein appear to predict changes in social competence but not changes in anxiety levels.
ContributorsParker, Julia Humphrey (Author) / Pina, Armando A. (Thesis advisor) / Grimm, Kevin (Committee member) / Doane, Leah D. (Committee member) / Valiente, Carlos (Committee member) / Arizona State University (Publisher)
Created2016
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Executive Casework, Inc. is a custom commercial mill working company based in San<br/>Jose, CA. Although the company originally only focused on cabinets, it has expanded to include custom reception desks and solid surface countertops to meet demand. The company founded by David and Mark Brown has humble beginnings, originally located

Executive Casework, Inc. is a custom commercial mill working company based in San<br/>Jose, CA. Although the company originally only focused on cabinets, it has expanded to include custom reception desks and solid surface countertops to meet demand. The company founded by David and Mark Brown has humble beginnings, originally located in Mark's garage. Over the last two decades, the company has seen astronomical growth buoyed up by the fast increase in commercial real estate in Silicon Valley.<br/>However, the company is currently facing considerable uncertainty like many others in the industry. These resulting overhead costs, when paired with future uncertainty of demand created by geopolitical trends, work from home, and Covid-19, create a notable problem for Executive Casework, Inc. As such, this thesis will focus on strategic steps Executive Casework, Inc. can make to capitalize on current macrocosmic trends, as well as trends within their own industry. More specifically, it will be a strategic analysis identifying the key external forces driving the fluctuating revenues in the commercial custom mill working industry, followed by an analysis of these external forces (magnitude and longevity). We will end with a framework for capitalizing on these trends by organizationally and physically placing a company like our exemplar company, Executive Casework, in the best position to realize maximum profitability.

ContributorsBrown, Mason Victor (Co-author) / DeMayo, Kieffer (Co-author) / Byrne, Jared (Thesis director) / Koblenz, Blair (Committee member) / Department of Economics (Contributor) / Department of Management and Entrepreneurship (Contributor) / Department of Supply Chain Management (Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
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In the 1930s, George Beadle and Boris Ephrussi discovered factors that affect eye colors in developing fruit flies. They did so while working at the California Institute of Technology in Pasadena, California. (1) They took optic discs (colored fuchsia in the image) from fruit fly larvae in the third instar

In the 1930s, George Beadle and Boris Ephrussi discovered factors that affect eye colors in developing fruit flies. They did so while working at the California Institute of Technology in Pasadena, California. (1) They took optic discs (colored fuchsia in the image) from fruit fly larvae in the third instar stage of development. Had the flies not been manipulated, they would have developed into adults with vermilion eyes. (2) Beadle and Ephrussi transplanted the donor optic discs into the bodies of several types of larvae, including those that would develop with normal colored eyes (brick red), and those that would develop eyes with other shades of red, such as claret, carmine, peach, and ruby (grouped together and colored black in the image). (3a) When implanted into normal hosts that would develop brick red eyes, the transplanted optic disc developed into an eye that also was brick red. (3b) When implanted into abnormal hosts that would develop eyes of some other shade of red, the transplanted optic discs developed into eyes that were vermilion. Beadle and Ephrussi concluded that there was a factor, such as an enzyme or some other protein, produced outside of the optic disc that influenced the color of the eye that developed from the disc.

Created2016-10-11
Description

Fruit flies of the species Drosophila melanogaster develop from eggs to adults in eight to ten days at 25 degrees Celsius. They develop through four primary stages: egg, larva, pupa, and adult. When in the wild, female flies lay their fertilized eggs in rotting fruit or other decomposing material that

Fruit flies of the species Drosophila melanogaster develop from eggs to adults in eight to ten days at 25 degrees Celsius. They develop through four primary stages: egg, larva, pupa, and adult. When in the wild, female flies lay their fertilized eggs in rotting fruit or other decomposing material that can serve as food for the larvae. In the lab, fruit flies lay their fertilized eggs in a mixture of agar, molasses, cornmeal, and yeast. After roughly a day, each egg hatches into a larva. The larva eats the material it finds itself in, and for four days it grows into stages of increasing size, called first-, second-, and third-instar stages. This figure shows a third-instar larva. Each larva has sections of tissue called imaginal discs, from which various parts of the adult anatomy develop. This figure shows the imaginal discs that will develop into antennae (colored purple), eyes (colored red), brain (colored blue), and wings (colored green). After four days, the larva turns into a pupa by making a casing, similar to caterpillars, and grows within the casing. After a four-day metamorphosis, the adult fly then emerges from its pupal casing. Adult males look somewhat different from adult females, as the males have darker rear abdomen segments than do females. The warmer the temperature around the eggs, the faster the flies develop to adults.

Created2016-10-11