Now showing items 1-20 of 15814

    • Incompressible Miscible Rayleigh-Taylor Instability Experiments on the University of Arizona Linear Induction Motor Drop Tower Using Planar Laser Induced Fluorescence

      Jacobs, Jeffrey W.; Withers, Clayton James; Craig, Stuart A.; Schluntz, Justine (The University of Arizona., 2023)
      Incompressible miscible Rayleigh-Taylor instability (RTI) experiments are described that utilize the University of Arizona’s vertical Linear Induction Motor (LIM) drop tower. RTI is a buoyancy driven instability occurring at the interface between two fluids of differing densities, represented by the Atwood number, where a destabilizing acceleration causes initial perturbations along the interface to develop into characteristic spike and bubble formations. The incompressible fluid pair used in the research is a miscible combination of isopropyl alcohol solution and calcium nitrate salt solution. Experiments were conducted at Atwood numbers of 0.150 and 0.216. The experiments conducted at an Atwood number of 0.216 are used as a replication of previous research to allow comparisons to the experiments conducted at Atwood values of 0.150. The fluid solutions used in experiments conducted at the Atwood value of 0.150 have been initially mismatched in refractive index as part of an examination of possible techniques for improving imaging issues commonly experienced by miscible experiments. An acrylic tank attached to an experimental aluminum reaction plate is mounted to the LIM drop tower and filled with the two fluids in an initially stratified configuration. The reaction plate, along with the fluid tank and diagnostic equipment, is vertically raised to the top of the LIM drop tower and subsequently accelerated downward at an effective constant acceleration of approximately 11.7 g, developing the fluid instability. Acceleration is accomplished by the interaction between the LIM drop tower’s parallel set of linear induction motors and the aluminum reaction plate that is vertically constrained within the rails of the drop tower. Deceleration is accomplished with a set of permanent magnetic brakes located at the base of the LIM drop tower. Acceleration is recorded using a single axis accelerometer mounted to the experimental test sled. Imaging equipment is rigidly attached to the test sled and provides visualization from a static viewpoint of the experimental tank. Both unforced and forced experiments are conducted, where an electrically driven actuator is used to provide vertical parametric forcing of the experimental test sled. Experiments are imaged using planar laser induced fluorescence (PLIF) to visualize the instability interface. A swept 445nm laser light beam that illuminates fluorescein dye mixed into the calcium nitrate solution allows planar visualization of the instability interface and experimental images are captured using a monochrome high-speed shock-rated digital camera that documents the experimental process. Resulting images expose a single plane of the developing RTI. Postprocessing follows in which a pixel level concentration profile is obtained. The concentration profile is used to provide measurements of the mixing process. From the concentration profile, a mixing region width is extracted and subsequent measurements of the instability growth constant, α, are obtained. Two methods for calculating α are used. Calculated α values for experiments at an Atwood number of 0.150 are in the range of 0.076–0.118 and the α values for Atwood numbers of 0.216 are in the range of 0.021-0.063, depending on measurement method. Comparisons of the measured α values to α values from previous experiments are made, noting that the reported α values are higher than what might be typically expected for similar experiments. A spectral analysis to examine the prevalent wavelengths during the experiment is completed and finds that forced experiments featured earlier development of dominant wavelengths when compared to unforced experiments. An analysis of the effects of refractive index variation on image sharpness using gradient-based focus measures is performed, but considered inconclusive.
    • Experiments on the Three-Layer Richtmyer Meshkov Instability

      Jacobs, Jeffrey; Schalles, Mark David; Craig, Alex; Chan, Cholik (The University of Arizona., 2024)
      The Richtmyer-Meshkov fluid instability (RMI) can be considered a particular case of the broader Rayleigh-Taylor instability (RTI), in the situation that the fluid interface is impulsively accelerated, as is the case when such an instability is impacted by a shock wave. The study of RMI has significant applications to the research of the Internal Confinement Fusion (ICF) method of nuclear fusion, which involves the superheating of fuel contained within a capsule consisting of multiple, closely spaced layers of material each affected by the formation of such instabilities under such conditions. One important quantity studied in RMI applications is that of the growth in amplitude of the instability structures as they develop from an initial sinusoidal perturbation at the interface, and this property is the main focus of the experiments conducted for this study. The effect of placing a secondary, unperturbed interface just above the well-studied single-interface configuration is studied for its effect on the amplitude growth in the nonlinear regime of RMI. The effects of the presence of this secondary interface are considered with two different gas combinations all of varying density, with a third gas added for a second interface and studied alongside the results of the one-interface case. The gases are vertically stratified in a shock tube with the lightest gas entering at the top, the heaviest gas at the bottom, and the middle layer gas emitted through porous metal plates near where the interface is formed. Experiments are visualized by illuminating one gas seeded with particles with a light sheet from a pulsed laser, with recordings captured by a single high-speed video camera. Amplitudes are measured by defining the interface position at each frame by its maximum brightness gradient and finding its maximum vertical span. The data suggests that the presence of the second, unperturbed interface causes a decrease in amplitude growth during the nonlinear regime of the instability development. Continued research is proposed to explore the accuracy of and reasons for the observations made.
    • Platelet Activation: Association with NADPH Oxidase Expression and Reactive Oxygen Species Generation in High-Shear Environments

      Slepian, Marvin J; DiCaro, Michael Vincent; Singh, Aditi; Lybarger, Lonnie (The University of Arizona., 2023)
      Thromboembolic complications remain a major cause of morbidity and mortality among patients with mechanical circulatory support devices for heart failure. Mechanical circulatory support devices, including ventricular assist devices (VADs), artificial hearts, and other cardiovascular therapeutic devices, produce significant intravascular shear which leads to turbulent blood flow and enhanced thrombotic activity. Reactive oxygen species (ROS) have been implicated as inflammatory mediators of platelet activation and thrombosis. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase plays an important role in ROS production. To further evaluate the role of NADPH oxidase 4 (NOX4) and ROS in shear conditions seen in VADs, this study examined the effect of hemodynamic shear stress on NOX4 expression and subsequent production of ROS in human platelets with fluorescent immunostaining to show NOX4 localization. Additionally, this study explored the effect of hydrogen peroxide (H2O2) on shear-mediated platelet activation. Correspondingly, ROS levels were positively correlated with an increase in NOX4 expression; excess ROS most likely resulted in exacerbation of shear-mediated platelet activation. Also, H2O2 resulted in an additive effect on shear-mediated platelet activation. Our results suggest a possible link between shear-mediated activation of platelets and NOX4-induced ROS production. Shear-mediated platelet activation is a dynamic process involving multiple biologic and mechanical elements. These findings contribute to a better understanding of thrombotic complications in patients with flow-altering implantable cardiovascular devices.
    • Sizing a Space Telescope for Exoplanet Studies: A Systems Engineering Case Study

      Douglas, Ewan; Carter, Alex; Ingraham, Patrick; Chalifoux, Bandon (The University of Arizona., 2024)
      Systems Engineering is an involved and non-standardized process that can vary dramatically even within different parts of the same project. Here I present a case study for applying systems engineering techniques to an optomechanical problem for a space based telescope. This telescope is being used to study exoplanetary systems and is very similar in concept and in design specifications to the Nancy Grace Roman Space Telescope. It includes active wavefront control and a coronagraph to improve the exoplanet detection capabilities. Here I discuss the design decisions that went into determining the appropriate size for the primary mirror of the telescope. The end goal is to have a telescope primary that is sufficiently large to obtain signal to noise ratios required to detect exoplanets. The process I used here involved preliminary orbital design work for the telescope, understanding the behavior of the rest of the optics within the telescope system, the output and geometry of the target planetary systems, and balancing the desired SNR with reasonable design constraints on the size of the primary.
    • P-Glycoprotein’s Role in Anti-Retroviral Drug Delivery Across the Blood-Brain Barrier To Combat Human Immunodeficiency Virus (HIV)

      Lybarger, Lonnie; York, Larry; Diaz Fuentes, Erika; Fantry, Lori; Munoz-Rodriguez, Jose (The University of Arizona., 2023)
      HIV continues to be a significant worldwide public health concern, with millions of deaths to date and ongoing transmission in all countries. It is challenging to cure because the virus remains within stable reservoirs that evade detection by the immune system. While the available treatments for HIV are effective, there are many options that have poor penetration across the BBB (blood-brain barrier). Treating the infected immune cells found in the CNS (central nervous system) is a challenge because patients are able to have undetectable viral load tests in the blood despite having dormant HIV reservoirs elsewhere in the body. This leads to a chance for these individuals with HIV to experience a range of cognitive, motor, and/or mood issues referred to as HIV-Associated Neurocognitive Disorder (HAND). However, as shown in Figure 1, the context of awakening these reservoirs using a Trojan horse-like method specifically targeting P-glycoprotein (P-gp) in the BBB, an efflux transporter, may provide important insight into decreasing the incidence of HAND. This diagram illustrates the typical situation of an HIV-infected person receiving treatment and the role of P-gp in preventing the drug from penetrating the BBB. The diagram is adapted from Al Rihani, Sweilem B., et al. "Disease-Induced Modulation of Drug Transporters at the Blood–Brain Barrier Level." International Journal of Molecular Sciences 22.7 (2021): 3742. Print.
    • A Regression Analysis of Impostor Phenomenon and Gender and Competence Motivation

      Smith, Eric D.; Demaree, Morgan Genieva; Legg-Burross, Heidi; Kersting, Nicole (The University of Arizona., 2023)
      Impostor phenomenon is a motivational construct described by an inability to internalize success, persistent self-doubt coupled with a sense of not belonging. The phenomenon is measured inconsistently, as researchers continue to use a scale based on outdated understandings of gender identity. In this thesis, I used two logistic regressions and two linear regressions to assess if a newer scale focused on competence motivation, the Self-Perception Profile for Adults is predictive of a scale historically used to measure impostor feelings of adults (Clance Impostor Phenomenon Scale). I recruited a sample of undergraduates (N = 167), which is a population that tends to have high rates of impostor-like feelings. These participants took an online survey in which they responded to scales measuring impostor-like feelings along with a scale measuring competence motivation. Using the method of scoring impostor-like feelings on a continuous was most informative. Physicality, home management, sense of humor, intelligence, and global scores of the self-perception scale were predictive of the participant’s level of impostor.
    • Development of Monitoring Tool for Managing Tospovirus Damage To Lettuce

      Carriere, Yves; Rodriguez, Shianna; Palumbo, John; Matzkin, Luciano (The University of Arizona., 2024)
      Impatiens Necrotic Spot Virus (INSV) is a recently introduced, thrips-transmitted tospovirusaffecting lettuce (Lactuca sativa) production in Yuma, Arizona. Since its discovery in Spring 2021 in Yuma, INSV has occurred every year, with incidences as high as 8% symptomatic lettuce plants at harvest during this study conducted in 2022-2023. Using RT-qPCR of lettuce plants, we detected the Tomato Spotted Wilt Virus (TSWV) in co-occurrence with INSV for the first time in Yuma in Spring 2022. However, RT-qPCR of lettuce plants and western flower thrips (Frankliniella occidentalis) populations did not detect TSWV in 2023. RT-qPCR of field-collected thrips coupled with bioassays evaluating their capacity to generate INSV symptoms in petunia leaf disks indicated that amplification of INSV primers alone can overestimate the thrips capacity to generate INSV symptoms in plants. To better evaluate the vectorial capacity of field-collected thrips, we developed a method based on amplification of primers for INSV and a reference gene in groups of individuals containing a known proportion of INSV-free thrips and thrips with empirically established positive vectorial capacity. This method was effective in detecting percentages of vector competent thrips as low as 0.5% (i.e., 1 vector competent individual out of 199 non-infected individuals). In February and March of 2023, surveys of 15 romaine lettuce fields with pairs of yellow sticky traps and transplanted petunia plants placed at the border of fields revealed that petunia plants captured a similar number of thrips as sticky traps. However, the petunia plants did not develop symptoms of INSV infection during the three weeks, even when vector competent thrips were detected on the petunia plants and in adjacent sticky traps. The proportion of vector competent thrips found in sticky traps and on petunia plants was not different. The vector manipulation hypothesis predicts a preference of non-virulent vectors for infected host plants and a preference of virulent vectors for non-infected host plants. We found that the distribution of virulent and non-virulent thrips on INSV-infected and non-infected lettuce plants in the field was consistent with this hypothesis. A key objective of this study was to determine whether INSV damage in lettuce fields at harvest can be predicted by monitoring INSV-competence in thrips and their population density early in the growing season. For each of 3 weeks of sampling, we calculated the risk of virus transmission in the 15 lettuce fields as the product of the number of thrips collected and the estimated proportion of INSV-competent thrips captured in yellow sticky traps at the border of the fields. For each of the three weeks, there was no significant positive association between the risk of virus transmission and the percentage of INSV-symptomatic lettuce plants at harvest. Sample size and the incidence of INSV infection in lettuce fields was relatively low in this study. Accordingly, more work is needed to evaluate whether the risk of virus transmission as estimated here can be used to forecast INSV damage in lettuce fields at harvest.
    • The Effects of Chronic Vaping Delta-9-Tetrahydrocannabinol (THC) in Traumatic Femur Fracture in Mice

      Vanderah, Todd; Trejo, Joseph; Lybarger, Lonnie; Thompson, Austen (The University of Arizona., 2023)
      The growing trend of vaping delta-9-tetrahydrocannabinol (THC) has raised concerns about its potential effects on various aspects of health. Extensive research has delved into the adverse effects of tobacco smoking on wound and fracture healing in both animals and humans. Concurrently, the growing prevalence of nicotine e-cigarette use has prompted studies to explore the repercussions of e-cigarette vaping on bone health, but the potential effects of vaping THC on bone healing remain a topic of scientific inquiry. As vaping has become increasingly popular, substantial concerns have emerged regarding its potential health risks, especially among adolescents. We utilized THC vape distillate with a total THC purity of 93.4% obtained from an Arizona State Licensed Dispensary. In our study we report the effects of chronic THC vaping (18.68 mg/mL) on bone healing following a traumatic femur fracture in mice, comparing the outcomes to those of non-exposed fracture mice. We also investigated the impact of both chronic and acute vaping of THC (18.68 mg/mL), nicotine (5 mg/mL), and chronic vehicle in the absence of fracture. The analysis includes the evaluation of callus size, serum levels of bone turnover markers (OPG/TRANCE,RANKL) and bone microstructures. Radiograph imaging showed THC exposure in mice with a fracture of the femur initially resulted in a greater callus diameter 1 week post-fracture compared to non-exposed fractured mice. The diameter of the callus was reduced at 2 weeks post-fracture and sustained this characteristic through 8 weeks post-fracture as compared to controls. Micro-computed tomography (µCT) revealed a significantly smaller callus volume in the THC-exposed fracture group compared to the non-exposed fracture group at 8 weeks post-fracture. Blood serum levels were analyzed for bone molecules, OPG and TRANCE(RANKL), that are crucial signaling molecules in fracture healing and bone homeostasis. Data revealed a non-significant change in OPG serum levels between both fracture groups, THC-exposed and non-exposed. TRANCE(RANKL) serum levels showed a statistically significant increase in the chronic THC-exposed fracture group compared to non-exposed fracture group and may be why a smaller callus diameter and volume was seen since TRANCE(RANKL) levels favor bone remodeling. In the absence of fracture, whether animals were exposed acute or chronically to THC or chronically to vehicle a non-significant change was seen in OPG serum levels. Similar results were obtained with chronic or acute vaping of nicotine. Of the available serums to measure, there was a non-significant change in TRANCE(RANKL) levels in animals exposed to THC or vehicle. Studies with nicotine vaping only included serum from two animals from each cohort, therefore samples were excluded in the statistical analysis of TRANCE(RANKL) serum levels. Taken together, our data demonstrates vaping THC at 18.68 mg/mL influences fracture callus size and TRANCE(RANKL) serum levels in animals that underwent a femur fracture. In the absence of fracture, vaping THC does not appear to influence OPG or TRANCE(RANKL) serum levels. Although preliminary due to a small number of animals tested, non-fracture µCT data revealed chronic nicotine vape exposure decreased trabecular marrow and spacing, while increasing trabecular bone volume fraction (BV/TV). Additionally, µCT data of the non-fracture groups showed that acute exposure to THC or nicotine and chronic exposure to THC or nicotine resulted in elevation in cortical BV/TV when compared to chronic vehicle exposure.
    • Academic Influence on Student Perceptions of Intersecting Issues: Wild Equine

      Mars, Matthew; OConnor, Arielle; Molina, Quintin; Torres, Robert (The University of Arizona., 2023)
      Higher education and learning have a direct influence on how students perceive environmental issues. Currently, little is known about how such influence shapes student perceptions of and attitudes towards protected equine on federally regulated land. This study explores range, wildlife, veterinary, and conservation biology undergraduate and alumni student perceptions of the regulation of protected equine populations through the lenses of disciplinary moral orders and academic culture. The study used a multiple-case design to qualitatively explore the level of influence of higher education and learning on student perceptions of issues pertaining to the federal protection of wild equine. Interviews with range management, wildlife biology, veterinary, and conservation undergraduate and alumni students at a large public research university in the southwestern United States were be conducted. The current study aimed to address the gap between moral order and academic cultures, and how these influences students’ perceptions on intersecting issues within their careers following higher education.
    • Evaluating Growth of Baby Leaf Spinach with Respect to Water and Salt Balance in the Arid Southwest United States

      Sanchez, Charles; Noon, Russell; French, Andrew; Rasmussen, Craig (The University of Arizona., 2023)
      Current literature for the irrigation management of spinach focuses on full season bunching spinach with little consideration given to the much shorter season baby leaf spinach. Baby leaf spinach represents an economically valuable crop in the desert Southwest US, and therefore would benefit from greater research into data driven management strategies. To overcome the challenge of the relatively short growing season of baby leaf spinach in plotting a crop coefficient (Kc) curve, the Kc curve is plotted instead as a function of both heat units after planting (HUAP) and Normalized Difference Vegetation Index (NDVI) as opposed to days after planting (DAP) as proposed in FAO56. Utilizing in-field measurements across 9 trial sites spanning 5 years, an initial Kc (Kc-INI) value of 0.90 and a mid-season Kc (Kc-MID) value of 1.00 were calculated. Due to the rapid growth of baby leaf spinach in such a short time, further investigations with greater temporal frequency will be needed to refine the capability of utilizing NDVI as a proxy to crop evapotranspiration (ETc). Additional work in this study looked at the water and salt balance of baby leaf spinach, with it being demonstrated that diminished yields occur in soils with salinity levels in excess of 7 dS/m. Irrigation management in baby leaf spinach has many opportunities for further research, but conclusions drawn in this study demonstrated that leaching salts during the baby leaf spinach cropping season are unnecessary and could be instead deferred to other times of the year.
    • Equilibrium Thermodynamic Modeling of Arclogites: Are We There Yet? An Example From The Andean Volcanic Zone (NVZ)

      Ibanez-Mejia, Mauricio; Ascencio, Porfirio Irepan; Quade, Jay; Mallik, Ananya (The University of Arizona., 2023)
      The Northern Volcanic Zone (NVZ) in the Andes is a continental magmatic arc emplaced in >50 km-thick continental crust. In S Colombia, a Pleistocene eruption known as the Granatifera Tuff exhumed a variety of (ultra)mafic xenoliths derived from lower-crust and mantle, providing a unique opportunity to study petrologic processes operating in the roots of the Andean arc. Here, we focus on garnet-clinopyroxenite (aka ‘arclogite’) xenoliths, which are lithologies expected to drive density instabilities in arcs. These rocks consist predominantly of garnet (30-57%) and clinopyroxene (20-66%), with amphibole as an additional primary phase (10-47%) in some cases.Phase equilibria modeling of pyroxenites using free-energy minimization tools such as MELTS has been shown to be troublesome, but more recent optimizations of thermodynamic databases are yet to be tested. We used Perple_X coupled with recent thermodynamic databases and solution models to calculate pyroxenite phase equilibria to: i) test the extent to which these results agree with phase relations and partial melting conditions of pyroxenites for which experimental data exist; ii) compare the results of the pyroxenite models from the NVZ with traditional thermobarometry, to confirm previous suggestions that the Mercaderes xenoliths represent a ‘hot’ end-member of arclogite localities worldwide; and ii) better understand the petrology and density structure of the lower NVZ arc. For amphibole-free xenoliths, we constructed P-T diagrams with garnet compositional isopleths to obtain P-T conditions. For amphibole-bearing xenoliths, we created isobaric T-X(H2O) diagrams using previous P estimates, to evaluate the predicted stability of amphibole as a function of water content. For all samples, diagrams were first created assuming all iron as ferrous (FeOT) from bulk-rock XRF data. Ferrous iron was then gravimetrically determined in whole-rock aliquots using potentiometric titration, and ferric iron contents were calculated using mass balance. With these results, new phase diagrams were recalculated using appropriate Fe2O3/FeO for each, to evaluate the effects of Fe speciation in the models. Our calculation results from MIX-1G, a pyroxenite for which extensive experimental data exist in the literature, yield better agreement between recent thermodynamic databases and experimental constraints than in the past, indicating that recent optimizations of thermodynamic data are more suitable for the study of nominally anhydrous pyroxenites. For amphibole-free (anhydrous) NVZ arclogites, we found the P-T conditions of low Fe3+/Fe2+ samples to agree well with previous P-T estimates when Fe2O3 is taken into account. However, the quality of compositional isopleth intersections degrades for samples with high Fe3+/Fe2+, indicating Fe speciation is an important parameter to consider in more oxidized arclogites but that existing solution models may not yet be completely reliable handling Fe3+ in these models. Calculation results for OCA-2, an amphibole-bearing pyroxenite for which experimental data exists, shows that phase assemblages and melting could not be replicated by the model. Furthermore, results from amphibole-bearing Mercaderes pyroxenites do not predict amphibole to be stable at the P-T conditions established from equilibrium thermobarometry, therefore precluding independent verification of the accuracy of the latter. From a more general perspective, our results indicate that modeling of amphibole-bearing arclogitic cumulates remains a challenge, and thus that P-T-X modeling of amphibole bearing arclogites using existing databases should be approached with caution or altogether avoided until experimental results can be shown to be accurately replicated.
    • Environmental Injustice in Guayaquil: An Analysis of Policies and Informal Settlements in a City that is Socially Resilient

      Robison, Clare; Martinez, Ibeth; Guerrero, Eduardo; Stoker, Philip (The University of Arizona., 2023)
      Mangroves are an essential ecosystem that helps prevent climate change. Examining the history of Guayaquil, we can observe that the historian Ycaza once stated, “Guayaquil is nothing more than a mangrove with the appearance of a city.” Tracing old maps in GIS and delving into the city’s history, we find maps depicting the former locations of mangroves. Informal settlements in Guayaquil have contributed to the deforestation of mangroves and the disappearance of estuaries. Despite the constitution recognizing inalienable rights to nature, thereby establishing it as a subject of law, deforestation of ecosystems is still occurring in Guayaquil. Although policies have attempted to prevent this, they have proven ineffective. A troubling cycle persists, where individuals claim land and later seek government legalization to make the area habitable. This cycle is both expensive and environmentally detrimental. This thesis examines the patterns of deforestation and formalization of settlements, challenging urban planners and designers to implement strategies for affordable housing at various scales and advocate for alternative models.
    • Methods and Determinations of Environmental Justice Analyses in NEPA Assessments, 2016-2021

      López-Hoffman, Laura; Binford-Walsh, Alexander Joseph; Miller, Marc L.; Fehmi, Jeffrey S. (The University of Arizona., 2023)
      Since 1994, Federal agencies have been responsible for identifying and addressing disproportionately high and adverse impacts on environmental justice (EJ) populations, including minority and low-income populations. EPA defines environmental justice as the “fair treatment and meaningful involvement of all people regardless of race, color, national origin or income with respect to the development, implementation and enforcement of environmental laws, regulations and policies.” The environmental assessment process of the National Environmental Policy Act (NEPA) has been a primary regulatory process through which EJ analyses have been performed. We evaluated NEPA EJ analyses from a random sample of 100 Final Environmental Impact Statements (FEISs) completed between 2016 and 2021 to determine the specific methods and determinations of the analyses. We developed a coding rubric and classified documents according to metrics evaluating the EJ methods and determinations. We detected no consistent method used to identify EJ populations, with 28 different minority threshold combinations and 30 different low-income threshold combinations described. Twenty-seven FEISs did not conduct an EJ demographic analysis and thirty-four FEISs provided a page or less of EJ-related text. The results of this study show a need for defined EJ methods and improved regulatory guidance. Agencies may find the results of this study practically helpful when developing overall EJ guidance, and information regarding the demographic analysis process and specific mitigation measures may be helpful to EIS preparers at the project-level.
    • Variation in Water Use Strategies of Riparian Velvet Mesquite

      Hu, Jia; Gillespie, Collin; Scott, Russell; Quanrud, David (The University of Arizona., 2023)
      In the semi-arid to arid Sonoran and Chihuahuan deserts, mesquite trees are fixtures across the landscape occupying diverse habitats. Mesquite plays a pivotal ecological role, influencing hydrological processes and contributing to the overall biodiversity of the region. This is especially true in riparian areas, where an understanding of the adaptive water use strategies they employ is essential to understanding the ecohydrology of these important ecosystems. This study investigates the water use strategies of riparian mesquite trees (Prosopis velutina) in southern Arizona across two water years. We explore the impact of age, size, and density of mesquite stands on source water use, with a focus on understanding how these trees access both deep groundwater and shallow soil moisture. We found that despite differences in stand characteristics (e.g. mature, young thicket, and thinned thicket), riparian P. velutina opportunistically used both deep and shallow water sources, depending on the time of year. We also examined leaf water potential to assess seasonal water stress, and found increasing water stress over the growing season, even after the onset of monsoon rains. Despite differences in monsoon precipitation over the study period, leaf water potential remained similar between the two years, suggesting the significance of winter precipitation preceding drier monsoons. The study highlights the anisohydric strategy of riparian P. velutina, emphasizing carbon assimilation over water loss and opportunistic patterns in source water use.
    • Habitat Selection by Desert Sucker and Black Bass Throughout the Year: Insights from Radio Telemetry

      Bonar, Scott A.; Gahl, Kaitlyn; Bauder, Javan M.; Merritt, David M. (The University of Arizona., 2023)
      The Verde River Watershed in Arizona provides crucial habitat for native and introduced fish species, particularly in mid-level perennial streams. However, increasing human and environmental pressures pose a risk to these environments. With an increased likelihood of habitat degradation, it is important to identify and protect habitat features essential for fishes inhabiting these streams. I conducted radio telemetry surveys to assess habitat use and selection by two common fish species in two wilderness tributaries of the Verde River: Wet Beaver Creek and West Clear Creek. I tracked 23 Desert Sucker Catostomus clarkii and 19 Black Bass Micropterus spp. in West Clear Creek, and 38 Desert Sucker and 43 Black Bass in Wet Beaver Creek for one year. I developed habitat selection models by comparing features used by fish to available stream features. My analysis revealed that Desert Sucker generally selected deep moving waters and Black Bass generally selected deep low velocity areas. Both fish often utilized areas with cobble substrate, canopy cover, and instream cover. Our results highlight the importance of stream features such as velocity, depth, and substrate in habitat selection. Furthermore, I demonstrate the effectiveness of radio telemetry tracking in remote wilderness locations. These findings provide valuable insights into habitat selection by Verde River Watershed fishes, which can inform conservation efforts and management strategies.
    • Cryptic Biodiversity of Arid-Land Fungi: Fungal Associates of Biocrusts, Lichens and Plants

      Arnold, A. Elizabeth; Marand, Mariam; Orbach, Marc; Baltrus, David A. (The University of Arizona., 2023)
      Organisms in arid and semi-arid lands face environmental challenges such as heat and drought, high salinity and low organic content of soils, and intense ultraviolet radiation. Despite these challenges, dryland environments are some of the most biologically diverse ecosystems in the world: plants that inhabit these ecosystems have evolved unique ways to combat these challenges through distinctive adaptations and, in some cases, symbiotic associations that enhance their resilience. Little work has been done to characterize the fungal lineages that occur as cryptic symbionts of plants in dryland environments. This thesis focuses specifically on characterizing fungi that occur within photosynthetic structures – leaves, lichen thalli, and biological soil crusts – collected from arid and semi-arid environments. In my first chapter I characterize fungi associated with biological soil crusts in the southwestern United States, focusing on their responses to disturbance at the Santa Rita Experimental Range in Arizona. In my second chapter, I contribute novel data regarding culturable endophytes of lichens and plants in southwestern Africa, and place these into a global context by relating their diversity and composition to climate variables across three continents. Taken together, my work showcases the diversity of fungi that exists within these ecosystems and provides insight into how the distributions of fungi and their hosts may shift in response to changes, such as those associated with land-use, disturbance, and ultimately, climate change.
    • Economical Smartphone-Integrated and Automated High Tunnel Greenhouse System on the Navajo Nation

      Kacira, Murat; Bethke, Calder; Giacomelli, Gene A.; Hooks, Triston (The University of Arizona., 2023)
      The Navajo Nation has a lack of access to nutritious and fresh produce-based food. High tunnel greenhouses have become more popular for leafy greens and other fresh produce. However, it can be challenging and time-consuming to produce crops without environmental controls for optimal crop quality and yield. This project demonstrated an economical smart-phone integrated and environmentally controlled greenhouse system to improve greenhouse management, therefore making a high tunnel greenhouse on the Navajo Nation more data accessible, productive, and engaging for the user. This was done by controlling the air temperature in the aerial environment and irrigation with a sensor-based feedback control using low-cost microcontrollers, radio transmission, and Wi-Fi, and by providing the owner via smartphone with greenhouse environmental data and notifications. The system was able to keep the greenhouse within 11 K of the outside temperature, and was an improvement over natural ventilation in providing a more favorable environment for crop production, especially during periods of low wind.
    • Combined / Layered Normalization Effectively Removes Systematic Errors in Small Untargeted Lipidomics Studies

      Hallmark, Brian; Snider, Justin; Wang, Qiuming; Chilton, Floyd; Zhang, Hao (The University of Arizona., 2023)
      Untargeted lipidomics is a powerful approach for studying the lipidomes of biological samples and determining how lipid profiles change under different conditions. Liquid chromatography-mass spectrometry (LC-MS) is an essential analytical tool that has advanced over the past ten years to drive the development of untargeted lipidomics. However, systematic errors, such as batch effects, temporal drift, and lipid concentration variation, pose a significant challenge in LC-MS-based lipidomics analysis and data normalization to account for these errors is an essential data processing step before downstream statistical analysis and visualizations. While a number of different normalization methods have been presented in the literature, more recent developments have focused on computational approaches for large clinical and epidemiological studies. Most of these normalization methods haven't been evaluated or compared in studies with small sample sizes. To examine this, we designed a small (n=50 samples) experiment with biological and technical duplicates (pooled quality control samples) to mimic the systematic errors that typically occur in untargeted lipidomics studies. Internal standards, principal component analysis (PCA), and Kullback-Leibler (KL) divergence-based scores were used to evaluate normalization performance. We found that Total Intensity Normalization (TI) and the Probabilistic Quotient Normalization (PQN) successfully removed drift and concentration variation, while Bridge Sample Normalization (BRDG) and Median Run Normalization (MED) eliminated the batch effect. We developed the combined and layered normalization strategies based on the function of the systematic error removal for TI, PQN, BRDG, and MED. All combined and layered normalizations effectively improved the overall performance of error removal. In particular, MED-combined/layered normalizations achieved optimal performance with the minimal unique biological information change among all investigated methods. PQN&MED is a robust normalization strategy for small sample size lipidomics data with batch effect, drift, and lipid concentration variation. In conclusion, it is necessary to detect specific systematic errors in the data before determining which normalization methods should be applied. Although decreasing data variance due to systematic errors is critical, it is also important to quantify the biological information alternation after normalization. Thus, running multiple biological and technical duplicates is recommended in small studies with multiple batches to evaluate the selected normalization methods. A validated normalization approach from that procedure can significantly reduce errors and enhance the reproducibility in limited-size untargeted lipidomics studies.
    • Vibratory Stimulation At Hip Vs. Ankle Muscles: Investigating Dynamic Balance Recovery Outcomes Due To Stochastic Stimulation In Healthy Young Adults And Older Adults

      Toosizadeh, Nima; Elali, Karam; Laksari, Kaveh; Arellano, Christopher (The University of Arizona., 2023)
      Human balance is a complex mechanism that involves sensory units, muscular reflexes, and central nervous system control. Among older adults, falls represent a significant source of traumatic injuries, with tripping as the primary cause [1]. Research has underscored the association between proprioceptive deficits and compromised balance recovery [2]. Recent studies suggest that proprioceptive signals from proximal musculature associated with the hip joint initiate the recovery response, while distal proprioception associated with the ankle joint completes the recovery step [3]. These conclusions pivot on the assumption that the onset of muscle activity is intrinsically tied to proprioceptive performance. Yet, to gain a deeper understanding of the specific contributions of ankle versus hip proprioceptive areas to balance control, a methodology enabling direct manipulation of proprioceptive performance is necessary. Stochastic vibratory stimulation (SVS) applied to lower extremities has shown promise in impacting upright balance sway. This impact arises from the mechanical vibration of muscles, which increases the excitement of type Ia afferents in spindles. This enhanced excitement is postulated to influence both short-latency reflex mechanisms and long-latency feedback to the central nervous system [4].The primary goal of these studies was to identify how modifications in proprioceptive information originating from ankle and hip muscles impact balance recovery. By manipulating proprioceptive performance in joint muscles using SVS, we investigated the distinct contributions of ankle and hip proprioception in balance recovery within two phases. The first phase was healthy young participants aged between 18 and 30. We recruited 20 participants and categorized them into two groups: ankle stimulation (n=10) and hip stimulation (n=10). In the second phase, we recruited 24 older adults aged 65 and above. They were asked to visit twice for a complete participation, on one day, they would undergo ankle stimulation, and on another day, they would undergo hip stimulation. All participants underwent treadmill perturbations with varying levels of vibration and speed randomly, and were assessed for balance recovery outcomes, including reaction time, recovery step length, and full recovery time. The results and subsequent discussion of this study unveiled notable findings. For younger adults, ankle SVS emerged as a significant factor influencing reaction time and recovery step length (p<0.002). In contrast, hip SVS primarily affected the time required for full recovery, displaying a 61.4% increase at 40 Hz and a remarkable 99.7% increase at 80 Hz during slow speeds. Similarly, for fast speeds, full recovery time experienced a 30.8% increase at 40 Hz and a 29.2% increase at 80 Hz SVS (p=0.019). As hypothesized, the main finding of this study was that local SVS on ankle and hip muscles significantly influence recovery performance among healthy young adults. Within our sample, SVS caused a negative impact on the balance recovery performance, which was observed as a delayed reaction time when the stimulation was applied to the ankle muscles. However, findings from phase II balance recovery studies among older adults indicate that vibratory stimulation to the hip joint affects reaction time, unlike the ankle joint, which remains unaffected by the stimulation. These observations provide further support for the notion that in older adults, the deterioration of proprioceptive signals stems from nerve cell death and the demyelinating process associated with aging [5, 6] . Current findings demonstrated the role of ankle and hip muscle proprioceptive information in balance recovery. Our next step is to test SVS on older adults who are at high risk of fall. Our hypothesis is that SVS improves balance recovery by enhancing the proprioceptive afferent signal. This is based on our previous work showing that SVS can improve upright standing balance and timed up-and-go test among high fall risk older adults [7, 8]. This will ultimately guide us to engineer an easy-to-use sleeve/device that would help high fall risk older adults in performing strenuous tasks.
    • Machine learning analysis of streamflow recession patterns across climates in the contiguous United States

      Troch, Peter A.; Haugen, Hannah; Gupta, Hoshin V.; Bennett, Andrew; Kim, Minseok; Bauser, Hannes (The University of Arizona., 2023)
      Streamflow recession analysis has received substantial attention over the past decades. Such analysis strives to understand what controls low flow dynamics. Most studies use a power law relationship between streamflow and its time derivative and these variables are typically plotted on log-log scale to reveal the parameters of the power law. The exponent shows up in such plots as the slope of the central tendency of the point cloud. Recently, this procedure has been questioned, as individual recessions typically have slopes that are higher than the slope of the point cloud. To reconcile these two viewpoints, a machine learning method for catchment-scale recession analysis has been introduced that successfully integrates point clouds and individual event trajectories. The machine learning model demonstrated the existence of an attractor in phase space to which long individual recessions converge. In order to test the limits of this new approach and see how it performs under different circumstances, we applied the same methodology to a selection of catchments representing the variation in climate across the contiguous United States (CONUS). Several catchments were found to have potentially valid attractors in the modeled point cloud. Models for catchments with out-of-phase precipitation with significant snow cover struggled to capture the hysteresis in the observed point cloud, while still sometimes performing well on individual summer events. Arid, highly seasonal catchments performed poorly in the analysis. This work reveals the importance of out-of-phase precipitation and snow fraction on the success of the methodology, provides a reference point for the variety of behaviors that might be expected when conducting recession analysis on a range of climates, and further emphasizes the importance of careful recession selection criteria, especially in catchments outside of the standard humid, mild seasonality climates traditionally focused on in such recession analysis work.