Now showing items 1-20 of 14780

• #### LONGITUDINAL DRIVER BASED MAGNETIC RESONANCE ELASTOGRAPHY

Magnetic Resonance Elastography (MRE) is a non-invasive imaging technique used to determine the elastic properties of biological tissues. It can be used to aid the diagnosis of pathologies (such as tumors and fibrosis) which result in the variation of tissue stiffness. In this thesis, a MR elastography system was developed for use in a clinical setting. A pressure-based longitudinal driver was built to generate the shear waves. An elastography pulse sequence with motion encoding gradients was designed based on the gradient-echo and the spin-echo sequences. The pulse sequence included the ability to switch the motion encoding along any of the three coordinate axes depending on the direction of motion to be measured. Wave images were obtained by acquiring phase data for different time offsets in the motion cycle. An elastogram was computed from the phase data using the Local Frequency Estimation (LFE) algorithm. The validity of the method was experimentally verified using silicone and agar gel phantoms of varying stiffnesses. The performance of the gradient-echo and spin-echo sequences were investigated for different motion encoding gradient parameters.
• #### Visual Attention to the Clinician's Face and Morpheme Acquisition during Conversational Recast Treatment

Purpose. Enhanced Conversational Recast treatment is an input-based language therapy technique designed to help children with language disorders acquire missing grammatical morphemes in their speech. This version of conversational recast treatment requires clinicians to obtain the child’s attention before delivering each recast. This study examined the relationship between children’s looking behaviors in response to the clinician’s attentional cues and target morpheme acquisition. Method. Children received approximately 5 conversational recast treatment sessions per week for a total of 5 weeks. Progress was monitored through generalization probes assessing target morpheme use in untreated contexts. Video recordings of sessions were coded for children’s visual attention to their clinician’s face during the delivery of each treatment dose (i.e., recast). Reliability of coding was high. Results. Correlations between looking behaviors in response to attentional cues and performance on measures of generalization of morpheme use indicated a significant but negative association. Discussion. The results suggest that providing attentional cues prior to delivering treatment doses during conversational recast treatment may detract from the child’s attention to the relevant linguistic input, and decrease learning. Caution is warranted about this conclusion due to the possibility of clinician bias, and because coding from videos resulted in varying numbers of usable data points per session and per child.
• #### An Ecological and Human Health Risk Assessment of the Upper Santa Cruz River Using Environmental Management Tools

Many cities are bolstering their groundwater and surface water supplies by directly discharging treated wastewater effluent into the environment; the treated water may permeate through the vadose zone and into the aquifer, thereby recharging groundwater, and the surficial flow of the discharge allows otherwise ephemeral rivers to flow perennially. The Nogales International Wastewater Treatment Plant (NIWTP) releases effluent wastewater directly into the Santa Cruz River. The Santa Cruz River flows between the United States and Mexico through several metropolitan areas. An issue of critical concern is the long-term impact of the discharge of treated effluent from the NIWTP to surface water and groundwater quality in the region. Several factors including failing infrastructure, operational limitations, and continued rapid population growth impart complexity to this issue. The affected community is generally low- to middle-income, so the costs for obtaining and maintaining new and advanced treatment options necessary for the removal of contaminants of emerging concern is economically burdensome. A recent study has shown that the discharge point of the NIWTP is in an area of high aquifer vulnerability, and there is evidence of environmental contamination from the presence of cadmium, chromium, copper, nickel, nitrates, and zinc, among other compounds. The objective of this study is to identify and assess areas of potential soil and groundwater pollution and associated risk to environmental and human health using modeling and environmental management tool analyses.
• #### Land Disturbance Influences Seed-Microbe Associations in a Semi-Arid Ecosystem: Microbial Recruitment and Student Engagement

All terrestrial plants in natural and altered ecosystems form symbiotic relationships with microbes. The outcomes of these relationships can be detrimental or beneficial, depending on the confluence of plant genotypes, microbial genotypes, and environmental factors. This thesis focuses on the identification of beneficial microbes that infect seeds in the context of natural and altered environments, and describes how that topic can be used as a platform for a STEM-focused outreach experience for high school students. I first examined the abundance, diversity, and composition of soilborne fungi that infect seeds of a restoration plant, focusing on gradients of land degradation at the Santa Rita Experimental Range (SRER) of southeastern Arizona. I tested the predictions that (1) beneficial microbes would differ as a function of land disturbance, and (2) such effects of disturbance would be mitigated by plant cover. I identified a set of potentially beneficial microbes that may be used in revegetation strategies in disturbed soils. I then translated this experimental approach to form the centerpoint of a multidisciplinary outreach program, which I developed and implemented as an immersive summer program that combines scientific investigation with outreach to underrepresented youth in STEM. Thus this thesis addresses both a scientific question of applied significance as well as a societal need for training and diversification in STEM.
• #### A 7.5X Afocal Zoom Lens Design and Kernel Aberration Correction Using Reversed Ray Tracing Methods

This thesis presents a design of an afocal 7.5X zoom lens with maximum resolution of 0.68μm followed by a reversed ray trace method to show and correct kernel aberrations in zoom lens, with some examples. In Chapter 1, some fundamentals of geometric optics are introduced to help understanding lens design, including terminology, aberration theory, and methods to quantify a lens system performance. Chapter 2 starts with a brief introduction on zoom lens system, which includes characterizing the functionalities of different moving groups, the variator and the compensator, different types of zoom lens configurations, evolution of zoom types and lastly several novel applications of zoom lenses. In Chapter 3, design of a 7.5x afocal zoom with maximum resolution of 0.68μm is presented. The process starts with finding a thin lens solution, then a monochromatic thick lens solution; finally a diffraction limited polychromatic thick lens solution is achieved. In Chapter 4, a reversed ray trace method is introduced to identify and correct the kernel aberrations in zoom lens. Some patent examples are used to show kernel aberrations with the reversed ray trace method. Then two optimization examples of the kernel aberrations are given at the end. Chapter 5 concludes the work presented in this thesis, with some suggestions for possible future works.
• #### Lateral Divergence in High Power Laser Diodes: Method of Analysis for Assessing Contributing Factors

Lateral far field blooming or slow axis divergence is a common problem of high-power diode lasers and there are many different factors that contribute. Some of the major factors include temperature, carrier-induced effects, high order modes, mode types, and optical confinement. In this study, these properties were characterized and quantified in order to build a model to assess and simulate lateral divergence. A novel device called a spectral mapper was built to separate out lateral and longitudinal modes and their changes as current is varied. The collected and calculated data was input into LaserMOD, where simulations were run to determine the extent to which core width, mode number and refractive index changes modify the divergence of the device. While the modelling software was unable to support large numbers of modes due to weak confinement and also underestimated refractive index change in multimodal devices, the model and simulations were still able to quantify that more modes led to more lateral divergence. These tests and models can be used to improve coupling performance and hopefully provide insight into how high-power laser diodes can be further integrated with fiber lasers.
• #### Simulation of Phase Measuring Deflectometry of Freeform Surfaces

Optical three-dimensional shape metrology has become a key technology in scientific and industrial applications. Phase Measuring Deflectometry (PMD)is one optical three-dimensional shape metrology technique which is based on two-dimensional fringe patterns measurements for specular reflecting surfaces. There are several configurations of PMD to measure the arbitrary specular surfaces. Here, a single camera is used to capture the reflected image of a single LCD monitor to construct the deflectometry system. Distance laser sensors, multiple cameras, and multiple monitors will not be considered here. This investigation focuses on creating simulated PMD images for an arbitrary specular surface. Such images are useful for testing slope calculations and surface reconstruction algorithms. System geometry calibration and an inverse ray-tracing algorithm are explored. This thesis demonstrates the preliminary results of PMD for a flat mirror, a concave mirror and a freeform surface with the phase shifting method. The specific feature of the image simulation shows the inverse ray-tracing can deduce the captured image correctly. Included is a discussion about the ambiguity of fringe numbers and the uncertainty of the phase value calculation with insufficient fringe sampling.

• #### Integrating Leaf-Microbial Interactions and Leaf Water Content to Understand Leaf Selection by Leafcutter Bees

Introduction: Leafcutter bees (Megachile spp.) are a cosmopolitan group of solitary bees that are important pollinators for agricultural crops and wild plants. These bees make brood nests lined with semi-circular pieces cut from leaves selected from various plant species. The physical and chemical characteristics of leaves selected for nesting should be important in supporting the survival and health of larvae. Surprisingly, little is known about leaf selection: why are certain leaves chosen by leafcutter bees while others on the same plant are not? This study examined whether antifungal chemical properties, water content, or the presence of endophytic symbionts may be factors why leafcutter bees choose leaves for nests. I hypothesized that leaves cut by Megachilids show more antifungal activity than uncut leaves to provide better protection of larvae from fungal infection. Along with this hypothesis, it was further predicted that leaf water content of leaves selected by Megachilids would have lower water content compared to leaves not selected and that leaves selected would have fewer culturable endophytes. Methods: The study was conducted in Tucson, Arizona, in the Sonoran Desert biome of the southwestern USA. My study included three introduced plant species that are used by leafcutter bees: Nicotiana glauca (Solanaceae), Punica granatum (Lythraceae), and Rosa sp. (Rosaceae). I collected leaves from each species, including those cut by bees and those on the same plants that were not cut by bees in the same timeframe. I evaluated in vitro the growth of representative fungi in response to leaf discs from these cut and uncut leaves. I measured water content of these leaves by comparing fresh mass to dry mass. To test for the presence of endophytic symbionts, discs from cut and uncut leaves were surface-sterilized, placed on a standard growth medium, and observed over two weeks. Results: I found no meaningful differences in water content between cut and uncut leaves. Culturable endophytes were not common in these leaves. However, I observed a significant difference in antifungal activity: contrary to expectations, more enhanced growth of focal fungi was observed to and on leaves that were cut when compared to uncut leaves. Conclusion: Leaves cut by leafcutter bees had more enhanced growth to and on fungi in vitro than uncut leaves. This result was unexpected, as I anticipated that leaves cut by bees would have more antifungal activity than uncut leaves, potentially protecting larvae from fungal infection during development. My finding raises the possibility that cut leaves may attract potentially beneficial fungi, including the leaf-symbiotic fungi used in my assays, but exclude potentially harmful fungi not evaluated here. In future work I will examine the prediction that the fungi attracted to cut leaves have a greater capacity to inhibit insect-pathogenic fungi than fungi that are not attracted to cut leaves. It is also possible that fungal infection is less a threat to leafcutter bees than kleptoparasitism, such that the affinity of cut vs. uncut leaves to parasitic insects should be investigated in future studies. Finally, it is plausible that microbes not considered here -- such as epiphyllous microbes -- could influence bees’ selection of leaves, as illustrated in ongoing work inspired in part by this thesis (Pryor et al., 2019).
• #### The Evaluation of Stormwater Runoff to Recharge Groundwater for Use at Fort Irwin, California

The use of modeling tools to predict the amount of stormwater that is generated from impervious areas will be imperative for urban planners and developers in arid and semi-arid regions in the future. The National Training Center (NTC) in Fort Irwin, California is located within the Mojave Desert, a region that is increasingly water stressed. The Automated Geospatial Watershed Assessment (AGWA) tool is a GIS based modeling tool that can be used for water conservation planning. In the AGWA tool, there is a hydrologic model, KINEROS2, that has been developed and tested in a semi-arid environment. This model will be used to determine stormwater runoff volumes that are generated by observed rain events and to predict runoff for future storms. Because the NTC only gets three to four inches of rain per year, a scenario analysis using NOAA Precipitation Frequency Data Server data and historical observations will also be performed using the AGWA tool to gain an understanding of the differences in model parameterizations at the site. Within Fort Irwin, there is existing stormwater infrastructure that aids in the facilitation of infiltration. More specifically, the Sleepy Hollow neighborhood has implemented stormwater collection methods to keep runoff on site, and they consist of a stormwater detention basin, controlled release of flood waters, and a drywell to enhance infiltration locally. To monitor the detention basin, the installation of a compound v-notch weir, pressure transducers, a Barologger, weather station, and weighing bucket rain gage took place in November 2017, and has been monitoring the site since. Soil samples also were taken on site in order to characterize the hydrologic soil parameters for input into KINEROS2. This thesis summarizes the preliminary modeling results based on three observed rainfall events and assesses the differences in multiple soil and rainfall parameterizations and their impact on surface water modeling at Fort Irwin.
• #### The Second New England School and Helen Hopekirk: A Case Study in American Music Historiography

In 1904, Amy Beach praised a fellow musician in this way: “As a composer, you give us work of remarkable beauty in its themes and their harmonious background, and of solid worth in their development.” Earlier in 1897, George Chadwick wrote to the same musician about a piano position at the New England Conservatory, “I would like to offer you the position first of all.” One might guess Beach and Chadwick were addressing another member of the so-called “Second New England School,” a group of figures often credited as a pioneering force in American Classical music, but it was actually written to Helen Hopekirk, a first-rate musician during that era who is largely ignored today. Perhaps due to an emphasis in American music historiography on American-born composers and particularly on orchestral works in this period, the “Second New England School” has excluded musicians like Hopekirk from its ranks. Through a historiography of the group as well as an examination of correspondence, programs, and reception, this paper reevaluates and expands the “Second New England School” by expanding its ranks beyond considerations of compositional aesthetics. By doing so, this research raises larger questions about how historiographical categories are created and about their implications.
• #### Blurring the Border: Copland, Chávez, and Pan-Americanism

Aaron Copland (1900-1990) is widely recognized for his unmistakably “American sound.” Scholarly discourse surrounding Copland’s compositional and aesthetic style focuses on various sources ranging from his studies in Paris, to European modernism, to jazz. Surprisingly, though, much of this discourse omits the considerable impact on Copland by his contemporary, the composer Carlos Chávez (1899–1978) and his native Mexico. This thesis argues that Copland’s relationship with Chávez was a driving force behind the formation of Copland’s identity as an American composer. Details of their vast correspondence reveal the significant extent and impact of their friendship and professional collaboration. Copland’s first visit to Mexico at the request of Chávez can be viewed as a catalyst for the significant period of success beginning in the 1930s with the publication of El Salón México. And while their shared philosophy that music should be accessible to the public aligned their professional and artistic goals, their compositions also bear specific similarities in style, texture, and harmonic color—notably, jagged rhythms, angular phrases, and the frequent use of quartal and quintal harmonies; such similarities are found in Copland’s Short Symphony and Statements for Orchestra and Chávez’s Horsepower Suite and Sinfonía India. This thesis thus calls for a reexamination of the significance of Copland’s and Chávez’s lifelong friendship and of modernist trends of Pan-American music in the twentieth century, all in an effort to further understand the role played by Latin American music in the development of music in the Americas.
• #### Post-World War I Navigation of Imperialism, Identity, and Nationalism in the 1919-1920 Memoir Entries of Ottoman Army Officer Taha Al-Hāshimī

Taha al-Hāshimī’s memoirs, more akin to a diary or journal, written at the time of observation, contain fascinating entries from the dynamic years 1919-20, including observations of his present and imaginings of the future, during his travels through occupied Ottoman lands in the aftermath of World War I. As a Baghdad-born, Istanbul-educated, Ottoman army officer who remained in Ottoman service through the war, al-Hāshimī offers unique perspectives which bridge many traditionally-understood divisions in historical scholarship. This work consists of a discourse and historical analysis of many of al-Hāshimī’s entries during this consequential time and place, focused on three general arguments. First, these entries reveal much about the historical trauma of the foreign conquest of Ottoman lands, as understood and experienced by a committed defender of the Empire. This sentiment is evident in al-Hāshimī’s pervasive fears of European colonial policies and in his comparisons of Syria to Algeria and Tunisia, and Iraq to unnamed British colonies in Africa. Second, these entries illustrate seemingly-conflicting and coinciding expressions of both Ottoman and Arab identification. Through both his actions and his entries, al-Hāshimī demonstrates continuity of his Ottoman identity as well as expressions of Arab identity, without predicating it on erasure or de-legitimization of his Ottoman identity. Third, al-Hāshimī’s observations of the political environment in Damascus demonstrates a multitude of nationalist activist organizations, both elite and popular, undermining Faysal’s government’s universalizing claims and dominant position in scholarship. This work supports many recent works arguing for a re-examination of this traditionally marginalized, liminal time. Rather than only a period of disruption, transition, and change, this work argues there are strong episodes of continuity amid uncertain imagined futures.
• #### Iraqi Diaspora in Arizona: Identity and Homeland in Women’s Discourse

In analyzing the collective experiences of Iraqi immigrants in displacement, facing any hardships, resettling and assimilating into their new environments, and the push factors that help form their own identity, this thesis explores the generational demarcation and the concept of the ‘reluctant immigrant’ in thinking about place attachment and displacement. Sense of belonging to the homeland is a theme in the diasporic narratives of Iraqi women. Immigrants reach out to the imagined homeland in an effort to manage the emotional trauma of exile, while diasporic imagination engages the construction of immigrant identity and political ramifications of this identity in the receiving country. This ultimately allows the individual to construct their diasporic identity in terms of their ongoing relationship with the nation-state and the intersections of class and gender in migration experiences, cultural and religious traditions, and the social struggles of fitting in and establishing a successful livelihood and state of being.
• #### Studies of Flow and Heat/Mass Transfer in Water Desalination Tower

The paper presents a concept and basic studies about a solar thermal desalination system to achieve the goal of energy efficient, low maintenance, and low-cost water and salts production, leaving no waste discharge and minimum impact on the environment. The system has three major components integrated: a glass-covered solar thermal collection space, a basin with water for evaporation, and a water vapor condensation chimney. Both clean water and salts can be collected to achieve the efficient use of land for solar energy and the maximum value of water and salt products. A preliminary experimental study has demonstrated the concept of the desalination technology with clean water collected at the solar insolation conditions of Tucson, Arizona. Further study for optimization of the coupling of solar collection area and cooling capacity (or cooling heat transfer area) for water vapor condensation will be carried out in the future. This technology is of great significance and value to the water production at arid areas where solar energy is abundant.
• #### Vision-based Upper Extremity Kinematic Analysis of Badminton Smash Hit

Badminton is one of the fastest sports in the world. Athletes’ body rotations introduce a lot more complexities for studying badminton. The goal of this work is to develop a series of analysis including designing MATLAB programs and acquire kinematics data of badminton sport to help badminton players improve their skills. To validate these analyses are consistent with what badminton coaches teach athletes, interviews are conducted with coaches at the collegiate level to set commonly agreed “coaching points”. A full body marker setup is applied to this study while the markers are hand-made to reduce the weight and improve accuracy. 6 badminton players in different skill levels are brought in for data collecting. Subjects are asked to perform a smash motion as a return of a high and long badminton serving. Smashing data was captured by an eight-camera Vicon Motion Capture System (Nexus 1.8.5), and one video camera. Analyses were programmed by MATLAB to examine coaching points: speed and acceleration of shuttlecock and racket, contact point on racket net surface, coefficient of momentum transfer, coefficient of restitution, the angle between racket surface direction, racket moving direction, and angular velocity contributions from body parts. The results indicate the experiments and analysis are successful. Most of the ”coaching points” are proved by comparing kinematic quantities from players. These kinematic quantities can be applied as indicators to show the skill level of a player. With further development of this research, the coaching system can provide a series of dynamic analysis and lively visualized feedback to the athlete.
• #### Time-Resolved Planar Particle Image Velocimetry of the 3-D Multi-Mode Richtmyer Meshkov Instability

An experimental investigation of the Richtmyer-Meshkov instability (RMI) is carried out using a single driver vertical shock tube. A diffuse, stably stratified membrane-less interface is formed between air and sulfur hexafluoride (SF6) gases (Atwood number, $A = \frac{\rho_1 - \rho_2}{\rho_1+\rho_2} \approx0.67$) via counterflow, where the light gas (air) enters the tube from the top of the driven section, and the heavy gas (SF$_6$) enters from the bottom of the test section. A perturbation is imposed at the interface using voice coil drivers that cause a vertical oscillation of the column of gases. This oscillation results in the Rayleigh-Taylor unstable growth of random modes present at the interface, and gives rise to Faraday waves which invert with half the frequency of the oscillation. The interface is initially accelerated by a Mach 1.17 (in air) shock wave, and the development of the ensuing mixing layer is investigated. The shock wave is then reflected from the bottom of the apparatus, where it interacts with the mixing layer a second time (reshock). The experiment is initialized with two distinct perturbations - high amplitude experiments where the shock wave arrives at the maximum excursion of the perturbation, and low amplitude experiments where it arrives near its minimum. Time resolved Particle Image Velocimetry (PIV) is used as the primary flow diagnostic, yielding instantaneous velocity field estimates at a rate of 2 kHz. Measurements of the growth exponent $\theta$, where the mixing layer width $h$ is assumed to grow following $h(t) \approx t^\theta$, yield a value of $\theta\approx 0.51$ for high amplitude experiments and $\theta\approx0.45$ for low amplitude experiments following the incident shock wave when estimated using the width of the mixing layer approximated by the width of the turbulent kinetic energy containing region. Following interaction with the reflected shock wave, $\theta \approx 0.33$ for high amplitude experiments, and $\theta \approx 0.50$ for low amplitude experiments. It is observed that the low amplitude experiments grow faster than the high amplitude experiments following reshock, likely owing to the presence of steeper density gradients present in the relatively less developed mixing layer. $\theta$ is also estimated using the decay of turbulent kinetic energy for experiments where dissipation is significant. Theta estimates using both methods are found to be in good agreement for the high amplitude case following the incident shock, with $\theta\approx0.51$. $\theta \approx 0.46$ is found following reshock, which is larger than the value found when fitting $\theta$ to width data. Low amplitude experiments do not exhibit significant dissipation, and a value of $\theta \approx 0.68$ is found for low amplitude experiments following the incident shock, and $\theta \approx 0.62$ following reshock. Persistent anisotropy is a commonly observed phenomenon in the RMI mixing layer, owing to the stronger velocity perturbation components in the streamwise direction following the passage of a shock wave. High amplitude experiments are observed to reach a constant anisotropy ratio (defined as the ratio of streamwise to spanwise turbulent kinetic energy, or TKX/TKY), an indication of self-similarity, shortly following the passage of the incident shock wave with value of $\approx 1.8$. Low amplitude experiments do not reach a constant value during the experimental observation window, suggesting that the flow is still evolving even after a second shock interaction. Examination of the spanwise average anisotropy tensor reveals asymmetry in the anisotropy for low amplitude experiments, with the heavy gas exhibiting a slightly larger degree of anisotropy. The high amplitude experiments exhibit transitional outer Reynolds numbers ($Re\equiv\frac{h\Dot{h}}{\nu} > 10^4$) using the criterion proposed by Dimotakis shortly following the passage of the initial shock wave, while the low amplitude experiments largely remain below this threshold. Following reshock, both sets of experiments are elevated to $Re \approx 10^5$, which is a strong indication that mixing transition should occur and an inertial range will form. However, extended length scale analysis proposed by Zhou that accounts for the temporal evolution of scales which are a prerequisite for the formation of an inertial range indicates that neither high or low amplitude experiments have entered a transitional regime even following reshock. Furthermore, the $\theta \approx 0.5$ growth of the outer length scale in these experiments suggests that transition will not occur even if longer observation windows were possible. The lack of an inertial range is evident in spectral analysis of the mixing region.