Now showing items 39014-39033 of 39116

    • X-56A Dart: Dynamically-Scaled Aircraft for Research and Testing

      Shkarayev, Sergey; Bether, Rosanna Renee; Greenberg, Phillip; Powell, Harry; Grembowski, Brianna; Drozd, Kristofer (The University of Arizona., 2015)
      The X-56A DART: Dynamically-scaled Aircraft for Research and Testing is a project where our team was tasked with creating a half-size dynamically scaled working model of the X-56A MUTT (Multi Utility Technological Testbed), a research aircraft operated by NASA and developed by Lockheed Martin. We were tasked with not only developing the exact 50% scale model, but also the creation of a straight wing version of the aircraft with the same aerodynamic characteristics. In order to accomplish this, a tail was added, the wing span and chord length investigated, and the internals and landing gear designed from scratch. For support of the internals and to absorb the loads experienced by the plane during all aspects of flight, a "stress grid" was devised and made from balsa wood, carbon fiber, and fiberglass. To solve the issue that NASA had with landing gear positioning during takeoff and because of the changing center of gravity for different planforms of the DART, a sliding track mechanism was developed for the main landing gear. Finally, construction of the straight-wing plane was started. Molds were designed and cut for the aircraft, and the fuselage was successfully constructed out of fiberglass.
    • X-ray and Infrared Diagnostics of Star Formation and Black Hole Accretion in Galaxies

      Rieke, George H; Rigby, Jane Rebecca; Rieke, George H; Strittmatter, Peter; Bechtold, Jill; Fan, Xiaohui; Green, Richard (The University of Arizona., 2006)
      Using infrared and X-ray diagnostics, we study star--formation and black hole accretion in nearby and distant galaxies.We examine diagnostics of the hardness of the ionizing field in low--redshift starburst galaxies, to constrain the initial mass function. We obtain new measurements of HeI 1.7 micron/Br 10, a physically simple diagnostic, then test ISO mid--infrared line ratios, finding them reliable. Compared to new photoionization models, the ISO ratios in 27 nearby starburst galaxies are systematically low. This argues that solar--metallicity starbursts are deficient in massive stars, or that such stars are present but highly embedded.Using Spitzer, HST, Chandra, and ground-based data, we examine the multi-wavelength (0.4--24 micron) spectral energy distributions and X-ray properties of X-ray--selected active galactic nuclei (AGN) in several deep fields: the Chandra Deep Field South, the Lockman Hole, and the extended Groth Strip. We examine the 24 micron to X-ray flux and luminosity ratios for 157 AGN at z~1; the luminosity ratios have not strongly evolved since z~0, and we find no trend with X-ray column density. This means that highly--obscured AGN do not have exceptional infrared fluxes. We examine the SEDs of 45 bright X-ray and 24 micron sources: only 22% are classified as unobscured ``type 1'' AGN; 18% are classified as ULIRG-like SEDs; and the majority are classified as obscured (``type 2'') AGN or spiral--like SEDs. This supports the picture from X-ray surveys that much of the AGN activity in the distant universe is significantly obscured. We examine why 20% of X-ray--selected AGN are optically--faint; they lie at significantly higher redshifts (median z=1.6) than most X-ray--selected AGN, and their spectra are intrinsically red. Their contribution to the X-ray Seyfert luminosity function is comparable to that of optically--bright AGN at z>1, but they do not significantly alter the redshift distribution. Lastly, we investigate why half of X-ray--selected AGN lack signs of accretion in optical spectra. We find that these ``optically--dull'' AGN have Seyfert--like mid--infrared emission, which argues that they do not have abnormally--weak UV/optical continua. The axis ratios of their host galaxies argue that extinction by host galaxies plays a key role in hiding nuclear emission lines.
    • X-Ray Crystallographic Studies of Dyrk1a, a Kinase Linked to Down Syndrome

      Montfort, William; Gomez Casarez, Axel Omer (The University of Arizona., 2017)
      Down syndrome (DS) is a chromosomal aberration that causes learning disability and neurodegeneration. Previous studies suggest that the overexpression of the dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) contributes to the early onset of DS symptoms. This study was conducted to find key binding interactions between DYRK1A and both AMP-PNP and the novel inhibitor DYR219. X-ray quality crystals of DYRK1A-AMPPNP and preliminary crystals of DYRK1A-DYR219 complexes were obtained. The crystal structure of the DYRK1A-AMPPNP complex was determined at a resolution of 2.7 Å. The structure identifies residues involved in the binding of AMP-PNP. Ser169, Glu239, and Leu241 form a hydrogen bond network with the ATP analogue. Asn292 and Asp307 coordinate the AMP-PNP molecule via a Mg#$ ion. Finally, a hydrophobic pocket binds the adenine ring of the AMP-PNP molecule. The structure of the DYRK1A-AMPPNP complex was compared with other DYRK1A structures to identify differences in conformation of the protein and ligand binding. ATP binding sites for various kinases from the CMGC group were also compared to identify similarities and differences in the ATP pocket. The structure of the DYRK1A-AMPPNP complex showed a distinct conformation at residue Phe170 and movement in the activation loop. Successful crystallization of the DYRK1A-DYR219 complex should result in a crystal structure and will enable detailed characterization of binding of DYR219 in the ATP pocket. These data are fundamental for the designing of new potent DYRK1A inhibitors.
    • X-ray densitometric measurement of climatic influence on the intra-annual characteristics of southwestern semiarid conifer tree rings

      Cleaveland, Malcolm Kent.; Dean, Jeffrey S.; Stokes, Marvin A.; Smiley, Terah L.; Ffolliott, Peter F.; Gay, Lloyd W. (The University of Arizona., 1983)
      Annual tree-ring width of Southwestern conifers growing on dry sites exhibits sensitivity to variation in climatically created moisture stress. Douglas-fir, ponderosa pine, and pinyon in the eastern San Juan Basin in northwestern New Mexico and southwestern Colorado were sampled at four sites to investigate covariation of climate with intra-annual anatomy. The sites possessed characteristics that created different amounts of physiological stress in trees. Increment borer samples were glued into wooden mounts and machined to approximately 1.0 mm thickness by a special router-planer. All samples were crossdated by comparing climatically controlled synchronous patterns of ring widths. Moving slit X-ray densitometry (at Forintek Canada Corporation Western Forest Products Laboratory, Vancouver, British Columbia) objectively defined the earlywood zone (large, low density cells) and latewood zone (smaller, denser cells formed late in the growing season) in each ring. The densitometer measured eight parameters for each ring: ring, earlywood, and latewood width, minimum and maximum density, and mean ring, earlywood, and latewood density. Individual radial series were standardized (i.e, transformed to indices with 1.0 mean and homogeneous variance) by fitting curves and dividing annual values by the corresponding curve values. Density series proved more difficult to standardize than widths and usually correlated more poorly among individual radii of the same data data type. Statistical characteristics of site summary density chronologies differed from width chronologies. Response functions using monthly mean temperature and total precipitation showed climate influenced all data types. Low moisture stress increased ring, earlywood, and latewood width and ring, maximum, and latewood density. High moisture stress increased minimum and early— wood density. No width or density type consistently covaried more than any other with climate. Linkage of climatic variation with density parameters differed considerably from that reported in the literature for conifers growing in wetter, cooler climates. Southwestern conifers posed unique densitometric technical difficulties. Selection of sites that caused moderate physiological stress and samples with few missing rings proved critical. Acquisition of density data required much more time and effort than optical measurement of ring width, but yielded valuable intra—annual data. Intra—annual densitometric data hold great promise for reconstruction of seasonal paleoclimate.

      MOSTACCI, DOMIZIANO VALERIO. (The University of Arizona., 1985)
      A model has been developed for calculating x-ray line emission from spherical plasmas. The main features of this method are: (1) Plasma parameters are obtained from a one-dimensional Lagrangian hydrodynamics and heat flow code. (2) Multi-frequency groups: the line structure can be reproduced with the desired accuracy by adjusting the number of frequency groups. (3) Self consistent, time dependent excited level populations and radiation fluxes: the code starts with coronal populations, calculates the ensuing radiation flux and then recalculates the populations and so on, iterating until convergence is reached. (4) Goemetrical groups of rays groups by spherical impact parameters. (5) Line broadening due to ionic thermal agitation and Doppler shift due to the net plasma flow velocity. Inclusion of the flow velocity shift would be different without the multi-frequency group treatment. The method has been applied to an aluminum target, and the results are in good agreement with previous experimental work. The total energy, summed over all lines, as well as the line intensity ratios (which are a sensitive measure of agreement with experiment) were predicted with good accuracy. The pictures that would be seen by a pinhole camera are also calculated by the code.
    • X-ray scattering effects in powdered crystal analysis

      Picard, Robert G. (The University of Arizona., 1936)
    • X-ray structures of novel intermediates in the thymidylate synthase models for chemical mechanism and conformational change

      Montfort, William R.; Arendall, William Bryan (The University of Arizona., 2001)
      The catalytic mechanism of thymidylate synthase (TS) was investigated using X-ray crystallography: four structures that yield new information about the early stages of TS action are reported. TS catalyzes the production of thymidylate (TMP), one of the four nucleotide bases of DNA, from the substrate, deoxyuridylate and cofactor, methylenetetrahydrofolate (MTF). Knowledge about the TS mechanism is important for both the medical and basic sciences. TS is the sole de novo source of TMP and it is thus a target for anti-proliferative drugs aimed at addressing cancer and other diseases marked by rapidly dividing cells. To aid this effort, past research on TS has developed two models to explain how TS works. A detailed, sequential chemical mechanism explains the methylene and hydride transfers from one cofactor to the substrate. And, a two state, dynamical model explains the conformational change that TS undergoes during its catalytic cycle. Combining these two models will lead to a fuller understanding of protein structure, function, and dynamics interrelationships. Two of the new structures contain cofactor in a heretofore unseen state, bound in the active site with its imidazolidine ring intact. Finding that this is an allowed enzyme-cofactor state indicates that ring opening and formation of the highly reactive iminium cation may occur relatively late in the methylene transfer, after preparation of the substrate; and, the reaction may perhaps be concerted. Further, details of these two structures show that protonation of the correct imidazolidine ring nitrogen (N10) may be selected by the geometry and environment imposed on the bent cofactor by TS. N5, the "wrong" ring nitrogen, is blocked and in a hydrophobic environment, while N10 is rehybridized to sp3 and its lone pair (nascent hydrogen) is pointed into an aqueous cavity trapped within the enzyme. A proposal coming from this dissertation is for a combination of the two models describing TS catalysis. The chemical mechanism model and the conformational change model both describe the same phenomena and these models should be connected and combined into one larger model to further increase our knowledge of the connections between structure, dynamics and function. The four structures reported here begin that connection process.
    • An X-ray study of silver iodide

      Nichols, Monte C., 1938- (The University of Arizona., 1962)
    • X-window based user interface and network communications for an image network

      Martinez, Ralph; Patel, Saurabh Sureshbhai, 1966- (The University of Arizona., 1992)
      Recent advances in the field of high speed computer network have opened many new applications. One such application is the transfer of color image data between geographically distributed color image databases. ImageNet is a distributed color image database system with multiple database nodes and user workstation linked by a communication network. The work presented here is the design and implementation of user-interface and communication software for a workstation. The system was emulated on the Ethernet in Computer Engineering Research Laboratory. Dedicated servers running at a database node simulate database operations. Experimental comparison between RPC with UDP and RPC with TCP was made and the use of RPC/UDP for image-transfer is investigated. The X-window user interface is user friendly. It enables users to retrieve image lists and images from remote workstations. The use of wscrawl for the remote consultation enables more than two users to participate in remote consultation from different workstations.

      Kurnick, Allen A.; Reid, Bobby L.; Anjaneyalu, Yernool Verkatarayappa, 1931- (The University of Arizona., 1962)

      Fielder, Grace; Catalano, Theresa Ann; Ruiz, Richard; Waugh, Linda (The University of Arizona., 2011)
      In this dissertation, the denaturalization of migrants in the US and Italy as represented in newspaper crime reports was identified and compared to the opposing naturalization of Italian crime organizations in Italy and Wall Street/ corporate criminals in the US. This was accomplished through careful, multidisciplinary, scientific analysis of over 100 articles taken from Italian and US newspapers of assorted political tendencies from the years 2004-2010. Quantitative and qualitative methods were combined beginning with a corpus analysis of texts from each group studied followed by a topic analysis designed to identify topics discussed in the media for each group analyzed. In addition, lexical choices were categorized as denaturalization, naturalization or derogation, and examples from texts were examined in depth to reveal linguistic (such as metaphor) strategies involved in negative or positive representation of these groups. A Critical Discourse Analysis Approach combined with Social Semiotics and grounded in Social Identity and Nationalism theories was employed to reveal an underlying racist and xenophobic ideology in both Italian and US media. Results show that in both the United States and Italy, the highlighting of migrants' lack of proficiency in the host country language as well as cultural practices functions as evidence of how migrants are different thus justifying discriminatory practices against them. The resulting categorization of migrants as "Them" serves the dominant group's purpose of staying in power. In conclusion, the author points to a need for teacher educators in the field of second language education and literacy to make it a top priority to educate teachers and students as to how discourse contains underlying ideologies and how to think critically to de-construct and de-mystify them.
    • Xenosensor Regulation of Enzymes and Transporters in Drug Exposure and Disease

      Cherrington, Nathan J.; Merrell, Matthew David; Cherrington, Nathan J.; Gandolfi, A. Jay; Zhang, Donna D.; Smith, Catharine L.; Chen, Qin M. (The University of Arizona., 2011)
      A large and varied array of xenobiotics (foreign chemicals) enters into our bodies every day. In order to prevent toxicity resulting from xenobiotic accumulation, the body has developed a complex and integrated network of enzymes and transporters to promote and control the metabolism and excretion of drugs and other compounds. Drug metabolizing enzymes are classified as oxidative (Phase I) or conjugative (Phase II), and generally result in increased hydrophilicity of their substrates. Drug transporters actively route xenobiotics into (Phase 0) or out of (Phase III) the cells. The expression of the proteins involved in drug metabolism and transport are coordinately regulated by xenosensing transcription factors, including the constitutive androstane receptor, the pregnane X receptor, the aryl hydrocarbon receptor, and Nrf2. Through the activation of these xenosensors, chemical exposure itself induces the processes which help to remove the xenobiotics from the body. The liver is the major organ of drug metabolism in the body. Chronic hepatic diseases impact the activity of xenosensors and the expression of their enzyme and transporter gene targets. Nonalcoholic fatty liver disease (NAFLD) is the most prevalent liver disease in the United States, affecting 20-30% of the populations. This profoundly underdiagnosed disease has significant effects on hepatic gene expression and may increase the risk of adverse drug reactions and xenobiotic toxicity in affected patients. This manuscript presents original research which contributes to our understanding of xenosensor function in the contexts of chemical exposure and liver disease. Manuscripts in this dissertation investigate 1) the induction profile and mechanisms of the experimental therapeutic agent oltipraz, 2) the xenosensor-regulated mechanisms of induction of the drug transporter ABCC3, 3) the impact of NAFLD on the expression of major drug metabolizing enzymes, and 4) the utility of altered drug disposition as a biomarker for NAFLD progression. The findings of these studies highlight the clinical importance of xenosensor activation and the potential pharmacological and toxicological consequences of hepatic disease.
    • Xerophytic Cucurbita seed proteins

      Kuttan, Girija R. (The University of Arizona., 1978)

      Hartman, John H.; MOWERY, JEREMY DALE (The University of Arizona., 2016)
      XOS is an Everything as a Service operating system designed for the modern 1 cloud that uses the OpenStack platform. XOS makes it easy to create and deploy new cloud services. For this project I developed two new services for XOS, the first a tutorial service that is used as a framework for the current tutorial documentation for XOS, and a OpenVPN service that allows operators to create new VPNs using OpenVPN. The OpenVPN service is the subject of this document, it provides an easy to use interface for creating secure VPN servers and adding clients to VPNs. The benefit of using a VPN is security. All computers connected to a VPN can communicate privately and securely in isolation2. In many situations this is useful, such as database servers that should be isolated from a larger network. Future plans for the OpenVPN service are to support replication across multiple sites, adding entire slices as clients to a VPN, and adding an entire service as a client to a VPN. The research for this thesis came primarily from understanding XOS to create the tutorial service, and from understanding OpenVPN and its security requirements including managing a Public Key Infrastructure.
    • Y chromosome polymorphisms and the peopling of the Americas

      Hammer, Michael F.; Vuturo Brady, Jennifer Ann, 1966- (The University of Arizona., 1996)
      Polymorphisms at four paternally-inherited loci (DYS287, SPY1, DYS199 and DXYS156) were surveyed in twenty-seven populations (n = 997) world-wide to trace the origins of Native Americans. One of the haplotypes (6) is found at relatively high frequencies in all seven Native American populations representing two of the major linguistic divisions in the New World. The same haplotype was found at low frequencies in Siberian Eskimos and was absent from eleven other Asian populations. A second haplotype (7) was present at high frequencies in all the Native American and several Siberian populations. It was present at moderate frequencies in European populations and at low frequencies in several Asian populations. These data best support the hypothesis of a single male-mediated migration wave for the early peopling of the Americas, although a multi-wave hypothesis is not rejected.