Now showing items 11259-11278 of 20330

    • Low-background balloon-borne direct search for ionizing massive particles as a component of the dark galactic halo matter.

      McGuire, Patrick Charles.; Bowen, Theodore; Shupe, Michael; Melia, Fulvio; Burrows, Adam; Hill, Henry (The University of Arizona., 1994)
      A dark matter (DM) search experiment was flown on the IMAX balloon payload, which tested the hypothesis that a minor component of the dark matter in the Galactic halo is composed of ionizing (dE/dx > 1 \ MeV/g/cm² or σ > 2 x 10⁻²⁰ cm²) supermassive particles (mₓ ∈ [10⁴,10¹²] GeV/c²) that cannot penetrate the atmosphere due to their low velocities (β ∈ [0.0003, 0.0025]). The DM search experiment consisted of a delayed coincidence between four ∼ 2400 cm² plastic scintillation detectors, with a total acceptance of ∼ 100 cm² sr. In order to search for ultra-slow particles which do not slow down in the IMAX telescope, the experiment contained TDCs which measured the time-delays T(i,i+1) ∈ [0.3, 14.0] μs between hits in successive counters ∼ 1% precision. Using the first 5 hours of data at float altitude (5 g/cm² residual atmosphere), we observed ∼ 5 candidate non-slowing dark matter events, consistent with the background from accidental coincidences of 4 events. This implies that the DM flux is less than 6.5 x 10⁻⁶cm⁻²s⁻¹sr⁻¹ (95% C.L.). Similar results were also obtained for particles which slow down in the counter telescope. This experiment effectively closes much of a previously unconstrained 'window' in the mass/cross-section joint parameter space for massive particles as the dominant halo DM, and implies that for certain regions of this parameter space massive particles cannot be more than one part in 10⁵ by mass of all the DM. These results can also directly constrain 'light' magnetic monopoles and neutraCHAMPs in a previously unconstrained mass region mₓ ∈ [10⁶,10⁹] GeV.
    • Low-Cost Chromatic Confocal Endomicroscope for the Diagnosis of Cervical Precancer

      Kang, Dongkyun; Kulkarni, Nachiket; Gmitro, Arthur; Barton, Jennifer (The University of Arizona., 2021)
      Cervical cancer is one of the major cancers in women living in low- and middle-income countries (LMICs). The resources needed to conduct the gold standard histopathological diagnosis, such as a trained personnel and lab equipment, are scarce in LMICs. Hence, low-cost approaches such as visual inspection with acetic acid (VIA) are used to diagnose cervical cancer. VIA and other low-cost approaches, however, often lead to overdiagnosis and overtreatment of the patient due to their low specificity. There is an unmet need for a low-cost tool that can provide both high sensitivity and specificity.This dissertation discusses the design and development of a chromatic confocal endomicroscope (CCE) that can examine the cervical tissue in vivo with a goal of aiding the diagnosis of cervical malignancy. The novelty of this device is to use longitudinal chromatic aberration to acquire cross-sectional images of the tissue without any scanning mechanisms. A custom hyperchromatic objective lens was optimally designed to focus different wavelengths of the illumination light into different depths: 500-700 nm was focused over a depth range of 110 µm. Slit apertures were used for illumination and detection, which eliminated the need for beam scanning along the slit length direction and enabled cross-sectional, two-dimensional imaging without any mechanical scanners. A custom miniature spectrometer was used to analyze the spectrum of light scattered back from the tissue and generate confocal images. The manufactured CCE device had a small form factor with an overall device diameter and length of 9 mm and 70 mm, respectively. The material cost was less than $1,500. The measured lateral and axial resolution was 2 µm and 4 µm over an axial depth of 100 µm. The CCE device was able to visualize cellular structures of human tissue, in vivo at different axial depths. Cellular nuclei of the lower lip epithelium were clearly visualized from the CCE images, which might indicate that other epithelial tissues such as the cervical epithelium can also be visualized with CCE. This might merit clinical evaluation of CCE for the diagnosis of cervical malignancy.
    • Low-Density Parity-Check Code Decoder Design and Error Characterization on an FPGA Based Framework

      Akoglu, Ali; Unal, Burak; Vasic, Bane; Bilgin, Ali; Adegbija, Tosiron (The University of Arizona., 2019)
      Low-Density Parity-Check (LDPC) codes have gained popularity in communication systems and standards due to their capacity approaching error correction performance. Among all the hard-decision based LDPC decoders, Gallager B (GaB), due to simplicity of its operations, poses as the most hardware friendly algorithm and an attractive solution for meeting the high-throughput demand in communication systems. However, GaB sufferers from poor error correction performance. In this work, we first propose a resource efficient GaB hardware architecture that delivers the best throughput while using fewest Field Programmable Gate Array (FPGA) resources with respect to the state of the art comparable LDPC decoding algorithms. We then introduce a Probabilistic GaB (PGaB) algorithm that disturbs the decisions made during the decoding iterations randomly with a probability value determined based on experimental studies. We achieve up to four orders of magnitude better error correction performance than the GaB with a 3.4% improvement in normalized throughput performance. PGaB requires around 40% less energy than GaB as the probabilistic execution results with reducing the average iteration count by up to 62% compared to the GaB. We also show that our PGaB consistently results with an improvement in maximum operational clock rate compared to the state of the art implementations. In this dissertation, we also present a high throughput FPGA based framework to accelerate error characterization of the LDPC codes. Our flexible framework allows the end user adjust the simulation parameters and rapidly study various LDPC codes and decoders. We first show that the connection intensive bipartite graph based LDPC decoder hardware architecture creates routing stress for longer codewords that are utilized in today's communications systems and standards. We address this problem by partitioning each processing element (PE) in the bipartite graph in such a way that the inputs of a PE are evenly distributed over its partitions. This allows depopulating the Loo Up Table (LUT) resources utilized for the decoder architecture by spreading the logic across the FPGA. We show that even though LUT usage increases, critical path delay reduces with the depopulation. More importantly, with the depopulation technique an unroutable design becomes routable, which allows longer codewords to be mapped on the FPGA. We then conduct two experiments on error correction performance analysis for the GaB and PGaB algorithms, demonstrate our framework's ability to reach a resolution level that is not attainable with general purpose processor (GPP) based simulations, which reduces the time scale of simulations to 24 hours from an estimated 199 years. We finally conduct the first study on identifying all possible codewords that are not correctable by the GaB for the case where a codeword has four errors. We reduce the time scale of this simulation that requires processing 117 billion codewords to 4 hours and 38 minutes with our framework from an estimated 7800 days on a single GPP.
    • Low-Dose Ketamine as a Perioperative Multimodal Regimen

      Wung, Shu-Fen; Oh, Hyun Ju; Hoch, Kristie; Rothers, Janet L. (The University of Arizona., 2020)
      Background: Postoperative opioid consumption has caused surgical complications such as postoperative nausea and vomiting (PONV), respiratory failure, and prolonged hospital stay. The culprit of the epidemic opioid crisis in the United States (U.S.) is opioid exposure after surgery. The American Society of Anesthesiologists (ASA) recommends using multimodal pain management for all surgical patients to decrease opioid consumption and its complications. Ketamine, an N-Methyl-D-aspartate (NMDA) receptor antagonist, is an effective multimodal pain regimen that decreases postoperative pain and opioid consumption without increasing risk of severe side effects. Objective: The purpose of this DNP project was to increase knowledge of ketamine as a multimodal pain regimen among the anesthesia providers and student nurse anesthetists at a regional medical center in Southern California. Design: This descriptive study includes a pre-questionnaire to assess the current knowledge of ketamine, an educational session, and a post-questionnaire after the educational session to assess increased knowledge of ketamine. Measurements: The primary measurement includes the increase in knowledge of ketamine regarding time and frequency of administration, types of surgery that can be beneficial from ketamine, and financial advantages. The secondary measurement assesses barriers to adding ketamine to current practice.
    • Low-energy collision phenomena in free jet expansions: Molecular relaxation theory and ion-molecule rate studies.

      Smith, Mark A.; Randeniya, Lakshman Kumar.; Bernath, Peter F.; Salzman, William R.; Fernando, Quintus; Buckner, Steven W. (The University of Arizona., 1990)
      Theoretical and experimental development of a new kinetic method to measure the rate coefficients of ion-molecule reactions occurring in free jet expansions below 20K is presented. The method is successfully used to determine the temperature dependences of numerous bimolecular and termolecular ion-molecule reactions over the temperature range of 0.5-20K. A new theoretical method based on the generalized Boltzmann equation is developed to calculate macroscopic flow properties of pure molecular supersonic flows. The variation of the different temperature components, hydrodynamic speed and density of the free jet as a function of distance is presented assuming a Maxwellian anisotropic distribution function. This theory facilitates the kinetic analysis and the assignment of temperatures to the chemical reactions occurring in jets. Using the Boltzmann equation, the flow properties of a mixed atomic free jet expansion are also analyzed. The method is more general than previous treatments which assume a vanishingly small mole fraction for one component of the mixture. The presence of velocity slip arising from the difference in hydrodynamic speeds of the two components complicates this treatment. Expressions for the calculation of flow properties for an atomic mixture with an arbitrary composition are presented. Temperature dependences of the termolecular association rate coefficients for the reactions of, N₂⁺ + 2N₂, O₂⁺ + 2O₂ and NO⁺ + 2NO over the temperature range of 3-15K are presented. The results are discussed in the light of statistical phase space theory. For the reactions of N₂⁺ + 2N₂ and O₂⁺ + 2O₂ excellent agreement between theory and experiment is obtained. The kinetic analysis of NO⁺ + 2NO is complicated due to the competing charge transfer reaction. The observed temperature dependence for this reaction does not agree with the predictions of the statistical theory. The ternary association rate coefficients for the reaction, Ar⁺ + 2Ar, show a strong temperature dependence at very low temperatures (0.5-2.5K). Current statistical formulations cannot predict this temperature dependence and a comprehensive model for this reaction mechanism has yet to be developed. Three distinct temperature dependences are observed for the bimolecular reactions of N₂⁺ with CH₄, O₂ and n-H₂ at temperatures below 15K. Speculations are made regarding the interaction potential energy surfaces that may lead to the observed behaviors.
    • Low-impedance CMOS optical receivers and substrate-mode holograms for optical interconnects.

      Kostuk, R. K.; Huang, Yang-Tung.; Palusinski, O. A.; Reagan, J. A. (The University of Arizona., 1990)
      The performance of modern VLSI systems is limited by signal transmission characteristics of electrical interconnections. Free-space optical interconnects have been suggested as a method to solve these problems. In this work, holographic optical elements (HOEs) for use as free-space interconnects and optical receivers compatible with CMOS systems are investigated. First, the switching characteristics of two basic CMOS receivers without a gain stage are investigated. A simple low-impedance load configuration for high-speed operation is introduced which requires only one photodetector to receive optical signals, and one transistor to provide a desired bias. The optimization and various operating characteristics of this receiver are discussed in detail. SPICE simulations and experimental results using discrete components demonstrate that this receiver can operate at high-frequencies with reasonable optical input power. However, the system fan-out is limited by the available optical power. In order to improve system fan-out, the basic low-impedance load CMOS receiver is extended with a simple gain stage without significantly increasing the complexity of the receivers. Addition of the gain stage is shown to improve fan-out by one order of magnitude at a fixed operating frequency. Free-space interconnects using HOEs have many advantages such as combining several optical functions into a single thin film element. However, the realization of these unique features is limited by image degradation effects due to misalignment and wavelength variations of the light source. Substrate-mode holograms (SMHs) are used to minimize these image degradation effects. Methods for recording SMHs in dichromated gelatin (DCG) are described. Techniques for fabricating SMHs and controlling the angular bandwidth are presented. Experimental results for different combinations of DCG SMHs show that these high-performance elements can function as free-space optical interconnects. In addition, highly polarization-selective substrate-mode holograms were investigated and fabricated. A demonstration of beam switching using polarization selective and non-selective elements with an electro-optic halfwave plate is also given.
    • Low-Level Arsenic Toxicity in Human Bladder Cells

      Gandolfi, A. Jay; Bredfeldt, Tiffany Gail; Gandolfi, A. Jay; Futscher, Bernard; Cherrington, Nathan; Chen, Qin; Vaillancourt (The University of Arizona., 2006)
      Arsenic is a human bladder carcinogen. Inorganic arsenic and methylated metabolites are excreted from the human body in urine. This study investigates the effects of arsenite [As(III)] and monomethylarsonous acid [MMA(III)] on human urothelial cells (UROtsa). Cytotoxicity studies found that MMA(III) was 20 times more toxic than As(III). In addition, UROtsa cells have the ability to biotransform As(III) to pentavalent and trivalent mono-methylated metabolites.To understand the mechanism of arsenic carcinogenesis, it is necessary to know which arsenicals are carcinogenic. Therefore, non-tumorigenic UROtsa cells were chronically exposed to 0.05 uM MMA(III) and monitored for signs of transformation. MMA(III)-treated cells (URO-MSC) became hyperproliferative after 12 weeks of exposure. Anchorage-independent growth was detected after 24 weeks of exposure to MMA(III). Gene array analysis conducted in URO-MSC cells after 52 weeks of exposure detected expression changes consistent with malignant transformation. Enhanced tumorigenicity in SCID mouse xenografts was also observed after 52 weeks of treatment.URO-MSC cells form squamous cell carcinoma, a histology associated with inflammation, when injected into SCID mice. Induction of cycolooxygenase-2 (COX-2) promotes proliferation, angiogenesis, and survival in cancer cells. To identify a potential mechanism of MMA(III) carcinogenesis, the effects of chronic and acute MMA(III) treatment on COX-2 expression were investigated. Western blot analysis revealed that COX-2 was induced in a time-dependent manner in URO-MSC cells. Acute MMA(III) exposure also increased COX-2 protein. To identify signal transduction pathways responsible for COX-2 induction, pharmacological inhibitors of various signaling pathways were co-administered with 0.05 uM MMA(III) and identified src and extracellular signal regulated protein kinase (ERK) activation to be responsible for COX-2 induction. Thus, MMA(III) causes ligand-independent activation of epidermal growth factor receptor (EGFR), which activates the signal cascade responsible for COX-2 expression. EGFR is elevated in URO-MSC cells. To determine if EGFR is a key mediator of URO-MSC cell tumorigenicity, inhibitors of downstream signal transduction (src, PI3K, and COX-1/-2) were found to reduce URO-MSC cell viability and growth in soft agar. Results from this work not only identify that MMA(III) can induce malignant transformation in human cells but also provides insight into the mechanism of arsenic-induced bladder cancer.
    • LOW-LOSS, HIGH PERFORMANCE HYBRID PHOTONICS DEVICES ENABLED BY ION-EXCHANGED GLASS WAVEGUIDES

      Peyghambarian, Nasser; Araci, Ismail E.; Peyghambarian, Nasser; Kueppers, Franko; Norwood, Robert A. (The University of Arizona., 2010)
      Robust ion-exchanged glass waveguides exhibit low optical losses in a broad spectral range and they allow integration of several devices on the same chip due to their planar structure. Consequently, they can be a low cost alternative to semiconductors for fabricating various integrated optical devices. Two high performance photonic devices were designed and realized, demonstrating the potential of glass waveguides. The well-controlled silver-film ion-exchange process allowed the fabrication of: i) a highly sensitive biosensor based on optical absorption and, ii) a low loss hybrid electro-optic (EO) polymer modulator with a narrow coplanar electrode gap. The single-mode, channel integrated optical ion-exchange waveguide on borosilicate glass (Corning 0211) is described for broad spectral band (400-650 nm) detection and analysis of heme-containing protein films at a glass/water interface. The evanescent wave interaction is improved significantly by fabricating ion-exchange waveguides with a step-like index profile. Silver nano-particle formation is reduced in order to achieve low loss in the Soret-band (~400 nm). Unlike other surface-specific techniques (e.g. SPR, interferometry) that probe local refractive-index changes and therefore are susceptible to temperature fluctuations, the integrated optical waveguide absorption technique probes molecular-specific transition bands and is expected to be less vulnerable to environmental perturbations. The hybrid integration of phosphate glass (IOG-1) and EO polymer is realized for the first time. The critical alignment steps which are typically required for hybrid optoelectronic devices are eliminated with a simple alignment-free fabrication technique. The low loss adiabatic transition from glass to EO polymer waveguide is enabled by gray scale patterning of the novel EO polymer, AJLY. Total insertion loss of 5 dB and electrode gap of 8 μm is obtained for an optimized device design. EO polymer poling at 135 ºC and 75 V/μm is enabled by the sol-gel buffer layer.
    • Low-mass star formation and the initial mass function in young clusters

      Rieke, George H.; Luhman, Kevin Lee, 1971- (The University of Arizona., 1998)
      I have used optical and near-infrared spectroscopy and imaging to measure spectral types and luminosities for young (τ < 10 Myr), embedded (Aᵥ = 0-50), low-mass (0.1-1 M(⊙)) stars in three nearby (d < 300 pc) clusters: L1495E, IC 348, and ρ Ophiuchi. In conjunction with theoretical evolutionary tracks, I have derived the star formation history and initial mass function for each stellar population. A large number of brown dwarf candidates have been identified in the photometry, several of which are confirmed through spectroscopy. Finally, I have measured the frequency and survival times of circumstellar disks and investigated the photometric and spectroscopic properties of protostars. In § 2, I apply observational tests to the available sets of evolutionary models for low-mass stars, concluding that the calculations of D'Antona & Mazzitelli are preferred for the range of masses and ages considered here. In § 3 and § 4, I examine in detail the spectroscopic characteristics and substellar nature of two brown dwarf candidates. The study then expands to include the populations within the clusters L1495E (§ 5), IC 348 (§ 6), and ρ Ophiuchi (§ 7). In § 8, I briefly discuss the past, present, and future of scientific research related to this thesis.
    • Low-Metallicity Stars and High-Redshift Galaxies Through the Lens of Local Metal-Poor Star-Forming Regions

      Stark, Daniel P.; Senchyna, Peter Edward; Smith, Nathan; Sand, David; Kennicutt, Robert C.; Weiner, Benjamin (The University of Arizona., 2020)
      Over the last decade, unprecedented imaging campaigns and deep spectroscopy have delivered our first glimpse of galaxies in the reionization era, and the results have stymied interpretation. The prominent nebular emission in CIII], CIV, and other high-ionization lines detected in the first rest-UV spectra at these redshifts suggests that hard ionizing radiation fields are common at z>6, in striking contrast to typical star-forming systems at lower redshift. The difficulty in interpreting this emission is fundamentally tied to the lack of empirical constraints on massive stars at the very low metallicities we expect to encounter in the first billion years of the Universe. Nearby star-forming regions hosting stars and gas extending to metallicities below that of the SMC (<20% solar) represent a critical laboratory for study of such young stellar populations. In this dissertation, I first present HST/COS UV spectroscopy of HeII-emitters which reveal a clear transition from UV spectra dominated by stellar features above 20% solar metallicity to high-ionization nebular line emission at lower metallicities, tracked by a significant hardening in the inferred ionizing spectrum. I demonstrate that nebular HeII and CIV are ubiquitous among local extremely metal-poor galaxies (XMPs, <10% solar), and that CIV in particular may be an effective signpost of rapidly-assembling systems at these low metallicities in the distant Universe. I then present a new technique for locating XMPs dominated by very young stars in broadband photometry, and apply it to SDSS imaging to uncover 32 such systems at typical effective ages of tens of megayears. I demonstrate that the nebular HeII commonly encountered in such systems is inconsistent with an origin in high-mass X-ray binaries or the most massive short-lived stars, and suggest instead that this line may provide insight onto stripped stars and other uncertain products of binary evolution at very low metallicity. I also present evidence from stellar population synthesis modeling that an overabundance of massive stars or spun-up binary products are necessary to explain the strongest stellar wind features in very young systems at higher metallicities where these winds are prominent. Finally, I conclude by outlining a path forward from testing to direct calibration of models for massive stars below the metallicity of the SMC.
    • LOW-TEMPERATURE THERMOCHRONOLOGY OF THE LARAMIDE RANGES AND EASTWARD TRANSLATION OF SHORTENING IN THE SEVIER BELT, WYOMING, UTAH AND MONTANA

      Reiners, Peter W; DeCelles, Peter G; Peyton, Sara Lynn; Reiners, Peter W; DeCelles, Peter G; Kapp, Paul; Johnson, Roy A; Zandt, George; Chase, Clement G (The University of Arizona., 2009)
      This dissertation contains two studies that investigate the Mesozoic and Cenozoic tectonics of the western USA. The first study investigates shortening in the Sevier thrust belt of northeast Utah and southwest Wyoming. Cross section restoration suggests that there was ∼8-14 km of pre-Absaroka-thrust shortening above the Jurassic Preuss salt detachment (PSD), but not below it, in the hanging wall of the Absaroka thrust. Reflection seismic data show that the Crawford thrust is not offset along the PSD, indicating that the additional shortening on the Absaroka plate was transferred east before main movement on the Crawford thrust. Integration of surface and subsurface geology suggests slip from the Willard or Lost Creek thrust was transferred several tens of kilometers east along the PSD between ∼102-90 Ma.The second study investigates the low-temperature thermochronology of the Laramide Ranges. We dated 91 borehole and surface samples from basement-cored uplifts of the Rocky Mountain foreland (Wind River, Beartooth, Bighorn and Laramie Ranges), and the Uncompahgre Uplift, using the apatite (U-Th)/He system. (U-Th)/He ages generally increase with increasing elevation. Most samples show age dispersion of tens to hundreds of Myr. Several samples show correlations between (U-Th)/He age and effective U concentration (eU = [U] + 0.235[Th]), indicating that radiation damage has affected (U-Th)/He age. Many surface and near-surface samples have (U-Th)/He ages that are older than apatite fission-track ages.Forward and inverse modeling using a radiation damage diffusion model showed that (U-Th)/He ages may be widely dispersed, and may be older than apatite fission-track ages within a fossil partial retention zone. Most samples, however, do not exhibit the predicted (U-Th)/He age-eU correlation. We show that the effects of grain size can obscure (U-Th)/He age-eU correlations. Best-fit thermal histories from the inversion of age-eU pairs were extrapolated to other elevations to create model age-elevation plots. "Too-old" (U-Th)/He ages that are not within a fossil partial retention zone are likely due to He implantation from high-eU phases. Inverse modeling of (U-Th)/He age data suggests that rapid exhumation within the Laramide province began earlier in the Bighorn Mountains (before ∼71 Ma) than the Beartooth Range (before ∼58 Ma).
    • A lower bound for the Laplacian.

      Holmberg, Gregory Peter.; Friedlander, Leonid; Ercolani, Nicholas M.; Palmer, John (The University of Arizona., 1995)
      In my dissertation I study the Dirichlet Laplacian in an unbounded Euclidean domain of dimension n, Rⁿ, and in an unbounded domain in a hyperbolic space of dimension 2, H². The basic problem is to obtain estimates from below for the spectrum of the Laplacian, σ(Δ). In the case of an Euclidean domain the spectrum is non-negative, that is the lower bound of the spectrum, λ, satisfies λ₁ ≥ 0; for a hyperbolic domain λ₁ ≥ 1/4. I establish geometric conditions under which λ₁ > 0 for an Euclidean domain and λ₁ ≥ ¼ for a hyperbolic domain. Polya established that a relevant geometric characterization that gives a lower bound for σ(Δ) is a maximal radius for a ball inscribed in the domain. On the other hand, it is known that a non-trivial lower bound for σ(Δ) cannot be proved using only the assumption that radii of all balls contained in Ω are bounded from above. Rauch's estimates of λ₁ for a domain of crushed ice gives a counterexample. Hayman obtained a lower bound for σ(Δ) in a bounded domain in Rⁿ in terms of the maximal radius of an inscribed ball. To prove this estimate he made certain geometric assumptions about the domain. In my dissertation I introduce a different condition, namely the uniform exterior cone condition. This means that there exists a solid cone of fixed shape such that for any point on the boundary, if this boundary point is the cone's vertex and the outward normal of the domain's differentiable boundary is its axis then this cone remains outside the domain. In my dissertation I prove the following Theorem: If an unbounded domain Q in Rⁿ or Ω' in H² has a differentiable boundary, contains an inscribed ball of maximal radius, and satisfies the uniform exterior cone condition then the spectrum of the Dirichlet Laplacian operating on L² functions defined on these domains is bounded from below by a positive number a in the case of an Euclidean 1 domain, and it is bounded from below by a number a' > 1/4 in the case of a hyperbolic domain. The proof of this theorem uses variational techniques and more or less follows the ideas of Hayman. I use a cocompact discrete subgroup of SL(2,R) to construct a cover of H² in the hyperbolic case.
    • Lower Metabolic Capacity in Skeletal Muscle Mitochondria From Intrauterine Growth Restricted Sheep Fetuses

      Limesand, Sean W.; Pendleton, Alexander; Lynch, Ronald M.; Coletta, Dawn K.; Renquist, Benjamin J.; Langlais, Paul R. (The University of Arizona., 2020)
      Placental insufficiency (PI) induced intrauterine growth restriction (IUGR) increases the risk of mortality and morbidity in both newborns and adults. PI causes a progressive, chronic, and severe decline in the maternal-fetal nutrient transport starting in mid-gestation, which results in fetal hypoxemia and hypoglycemia. Unfortunately, the decline in nutrient availability occurs concurrently with critical myogenic windows in fetal development establishing the proper complement of skeletal muscle mass in utero. Thus, IUGR fetuses are also afflicted with sarcopenia that persists into adulthood and predisposes offspring to metabolic diseases. Recent evidence indicates that the metabolic capacity of the skeletal muscle of IUGR fetuses is lowered in response to low nutrient availability. IUGR skeletal muscle adaptations to low nutrient availability includes lower protein synthesis rates as well as lower fractional glucose oxidation and amino acid oxidation rates. In the current studies, we test the hypothesis that mitochondria isolated from IUGR fetal sheep skeletal muscle have defects in both nutrient oxidation and energy production. Previous findings have linked hypoglycemia and hypoxemia to lower glucose oxidation rates in the IUGR fetus. It was postulated that pyruvate oxidation was hindered in IUGR skeletal muscle mitochondria due to the inhibition pyruvate dehydrogenase (PDH), the first step in pyruvate metabolism. However, we show PDH activity is 67% higher in IUGR skeletal muscle. Moreover, the abundance of Mitochondrial Pyruvate Carrier 2 (MPC2), the primary mitochondrial pyruvate transporter, as well as the abundances of rate-limiting Tricarboxylic Acid Cycle (TCA) enzymes, isocitrate dehydrogenase and oxoglutarate dehydrogenase, are lower in IUGR mitochondria compared to controls (P<0.05). The lower abundances of enzymes involved in substrate oxidation in IUGR fetuses are accompanied by a 47% lower complex-I mediated oxygen consumption rate (OCR) and 18% lower Complex I activity, both of which indicate impaired electron transport chain (ETC) function. Reduced pyruvate oxidation in IUGR fetal skeletal muscle is the result of concomitant decreases in pyruvate transport, TCA cycle function, and ETC function. Fetal adaptations to nutrient restriction program metabolic dysfunction in postnatal skeletal muscle in IUGR individuals. We hypothesized that mitochondria isolated from myotubes which are differentiated from 30-day old IUGR lamb satellite cells have a 44% lower complex-I mediated OCR compared to controls. The lower OCR in IUGR myotube mitochondria is associated with lower abundances of ETC Complex III and IV subunit abundances. Although the mitochondrial metabolic changes observed in IUGR myotubes differ from the metabolic changes observed in IUGR fetal skeletal muscle mitochondria, these results show the persistence of skeletal muscle mitochondrial dysfunction in IUGR individuals from birth into postnatal life.
    • Lowering the Environmental Impact Of High-κ/Metal Gate Stack Surface Preparation Processes

      Philipossian, Ara; Zamani, Davoud; Shadman, Farhang; Guzman, Roberto; Raghavan, Srini; Philipossian, Ara; Shadman, Farhang (The University of Arizona., 2012)
      Hafnium based oxides and silicates are promising high-κ dielectrics to replace SiO₂ as gate material for state-of-the-art semiconductor devices. However, integrating these new high-κ materials into the existing complementary metal-oxide semiconductor (CMOS) process remains a challenge. One particular area of concern is the use of large amounts of HF during wet etching of hafnium based oxides and silicates. The patterning of thin films of these materials is accomplished by wet etching in HF solutions. The use of HF allows dissolution of hafnium as an anionic fluoride complex. Etch selectivity with respect to SiO₂ is achieved by appropriately diluting the solutions and using slightly elevated temperatures. From an ESH point of view, it would be beneficial to develop methods which would lower the use of HF. The first objective of this study is to find new chemistries and developments of new wet etch methods to reduce fluoride consumption during wet etching of hafnium based high-κ materials. Another related issue with major environmental impact is the usage of large amounts of rinsing water for removal of HF in post-etch cleaning step. Both of these require a better understanding of the HF interaction with the high-κ surface during the etching, cleaning, and rinsing processes. During the rinse, the cleaning chemical is removed from the wafers. Ensuring optimal resource usage and cycle time during the rinse requires a sound understanding and quantitative description of the transport effects that dominate the removal rate of the cleaning chemicals from the surfaces. Multiple processes, such as desorption and re-adsorption, diffusion, migration and convection, all factor into the removal rate of the cleaning chemical during the rinse. Any of these processes can be the removal rate limiting process, the bottleneck of the rinse. In fact, the process limiting the removal rate generally changes as the rinse progresses, offering the opportunity to save resources. The second objective of this study is to develop new rinse methods to reduce water and energy usage during rinsing and cleaning of hafnium based high-κ materials in single wafer-cleaning tools. It is necessary to have a metrology method which can study the effect of all process parameters that affect the rinsing by knowing surface concentration of contaminants in patterned hafnium based oxides and silicate wafers. This has been achieved by the introduction of a metrology method at The University of Arizona which monitors the transport of contaminant concentrations inside micro- and nano- structures. This is the only metrology which will be able to provide surface concentration of contaminants inside hafnium based oxides and silicate micro-structures while the rinsing process is taking place. The goal of this research is to study the effect of various process parameters on rinsing of patterned hafnium based oxides and silicate wafers, and modify a metrology method for end point detection.
    • LPCVD TUNGSTEN MULTILAYER METALLIZATION FOR VLSI SYSTEMS.

      Hamilton, Douglas; KRISHT, MUHAMMED HUSSEIN. (The University of Arizona., 1985)
      Advances in microlithography, dry etching, scaling of devices, ion-implantation, process control, and computer aid design brought the integrated circuit technology into the era of VLSI circuits. Those circuits are characterized by high packing density, improved performance, complex circuits, and large chip sizes. Interconnects and their spacing dominate the chip area of VLSI circuits and they degrade the circuit performance through the unacceptable high time delays. Multilayer metallization enables shorter interconnects, ease of design and yet higher packing density for VLSI circuits. It was shown in this dissertation that, tungsten films deposited in a cold-wall LPCVD reactor offer viable solution to the problems of VLSI multilayer interconnects. Experiments showed that LPCVD tungsten films have good uniformity, high purity, low resistivity, low stress-good adherence and are readily patterned into high resolution lines. Moreover, a multilayer interconnect system consisting of three layers of tungsten metallization followed by a fourth layer of aluminum metallization has been designed, fabricated and tested. The interlevel dielectric used to separate the metal layers was CVD phosphorus doped silicon dioxide. Low ohmic contacts were achieved for heavily doped silicon. Also, low resistance tungsten-tungsten intermetallic contacts were obtained. In addition to excellent step coverage, high electromigration resistance of interconnects was realized. Finally, CMOS devices and logic gates were successfully fabricated and tested using tungsten multilayer metallization schemes.
    • LSM1 AND RNY1: CLUES IN THE SEARCH FOR HOW RNA METABOLIC PATHWAYS CONTROL CANCER

      Parker, Roy; Luhtala, Natalie; Briehl, Margaret; Gerner, Eugene; Hurley, Laurence; Weinert, Ted (The University of Arizona., 2011)
      Carcinogenesis requires numerous alterations to gene expression to evade normal controls on cellular growth, invasion, and immortality. Traditionally, these changes have been examined in the context of deregulated transcriptional control of oncogenes and tumor suppressors. However, in recent years, research has revealed that processes outside of transcription such as RNA splicing, translation, and decay are also deregulated in cancers, sustaining tumorigenic potential. This dissertation details our investigation into the cellular functions of two RNA metabolic proteins whose human orthologs are deregulated in tumors: a putative oncogene, Lsm1, and a putative tumor suppressor, Rny1. Herein, we reveal interesting functions for these proteins that might provide insight into their roles in carcinogenesis. First, we demonstrate a role for Lsm1 over-expression in altered splicing through depletion of U6 snRNA levels. Second, we clarify the mechanism for Rny1's activity against RNA substrates and identify cis regions required for its non-catalytic role in growth inhibition. Overall, this knowledge expands our understanding of how RNA metabolism might be deregulated in cancer and could provide novel pathways to target for synthetic lethal responses in cancers with altered expression of these proteins.
    • Luciano Berio's "Sequenza XI chitarra sola": A performer's practical analysis with performance edited score

      Patterson, Thomas R.; Wuestemann, Gerd, 1967- (The University of Arizona., 1998)
      The Sequenza XI per chitarra sola is a recent work of great significance for the guitar repertoire. Written by one of the most accomplished living composers, the Sequenza XI is also part of a series of works that demonstrates the state of instrumental composing in the 20th century. This study examines elements of the composition in regard to their significance for the performer. It also discusses problems in the execution of the piece and attempts to outline ways in which to overcome these problems. After discussing possible revisions with the composer, the author has included an edited version of the score as part of this study. The Sequenza XI is clearly linked to other works in the series of Sequenzas through their common concept of integrated development. Berio's musical language often includes a very personal approach to tonality as well as a preference for meaningful virtuosity. A particularly effective compositional technique in the Sequenza XI is Berio's layering of sounds. The composer has a unique and individual understanding of lyricism in music that determines musical material and shapes structures. It is this lyricism that is often difficult to understand. Finally, the Sequenza XI was written as a challenge to the technical possibilities of the guitar. Furthermore, it was co-commissioned and written for Eliot Fisk, a performer with unusual physical and technical ability. For that reason, I have created the attached critical edition of the score of the Sequenza XI, making the work more approachable for the majority of guitarists.
    • Luigi Rinaldo Legnani: His life and position in European music of the early nineteenth century, with an annotated performance edition of selections from 36 Capricci per Tutti I Tuoni Maggiori E Minori, Opus 20.

      James, Douglas Goff; Patterson, Thomas; Hirst, Grayson; Asia, Daniel (The University of Arizona., 1994)
      Luigi Legnani (1790-1877) was an important guitarist/composer of the early nineteenth century Italian Romantic school. In addition, he was also a highly skilled singer, violinist, and luthier. Legnani's guitar compositions represent the logical next step after Giuliani; fully evocative of the operatic vocal style characterized by Rossini, and technically adventurous in much the way Paganini's compositions were for the violin, although not to the same degree. His contributions to guitar literature form an important link in the chain of compositional and technical development during the nineteenth-century. This study is in two parts. The first will present as concise a biography as possible, particularly regarding Legnani's concert itineraries, contributions to guitar construction, and relationship with Paganini. An examination of little-known contemporary reviews of his performances will serve as a means of both documenting his concertizing and developing a concept of Legnani's performance style. The second part, an annotated performance edition of selections from Legnani's most famous composition, 36 Capricci per tutti i tuoni maggiori e minori, opus 20, will provide a basis for the understanding and successful performance of Legnani's music by modern guitarists. In conclusion, Legnani's unique contributions to both guitar composition and construction are reevaluated, and an up-to-date list of compositions appended.
    • Luisa Capetillo y Patrícia Galvão-Voces de la Transición: Negociación y Reconstrucción de la Condición Femenina

      Bezerra, Kátia da Costa; González Morales, Zuleima; Gutiérrez, Laura G.; Morales, Mónica; Harden, Faith; Bezerra, Kátia da Costa (The University of Arizona., 2015)
      Este trabajo examina la manera en que durante momentos de transición política se establece un proceso de desestabilización de las relaciones de género y de la condición femenina por parte de voces marginalizadas. Específicamente, esta disertación tiene como objetivo percibir el modo en que durante períodos de transición política se crea un ambiente propicio para polemizar y resistir de manera crítica las relaciones de poder, problematización que ocasiona la abertura de un espacio de negociación de los discursos que limitan la identidad de género. Dicho proceso de negociación es entendido por medio de un renovado performance de género establecido por ciertas mujeres, performance que incluye tanto su producción literaria como la reconstrucción de lo femenino a través de sus propias experiencias como mujeres y de sus cuerpos. Para realizar este análisis se estudian los casos particulares de Puerto Rico y Brasil a finales del siglo XIX y comienzos del siglo XX a través de las figuras de Luisa Capetillo (1879-1922) y de Patrícia Galvão (1910-1962). Por un lado, se examinan algunos de los ensayos publicados por Luisa Capetillo en sus libros Ensayos libertarios (1907), Mi opinión sobre las libertades, derechos y deberes de la mujer (1911) e Influencias de las ideas modernas (1916). Por otro lado, se analizan algunas de las crónicas publicadas por Patrícia Galvão en su columna "A mulher do povo" (1931) las cuales aparecen en el periódico panfletario O homem do povo. Para identificar el proceso paulatino de desestabilización y reconstrucción visual de lo femenino como parte de la negociación de género que ambas mujeres entablan, en el presente trabajo se observan algunas fotografías que tienen tanto a Luisa Capetillo como a Patrícia Galvão como protagonistas. Por tanto, este trabajo se apoya en las teorías desarrolladas por teóricos como Michel Foucault, Judith Butler, Richard Schechner e Irit Rogoff de manera que podamos entender el modo en que los dicursos hegémonicos intentan estructurar la categoría identitaria de género a través de dispositivos de poder, e igualmente, la forma en que esos discursos pueden llegar a ser transgredidos por medio del fenómeno de performance.
    • THE LUMINESCENCE OF CHROMIUM COMPLEXES

      De Armond, Marvin Keith, 1935- (The University of Arizona., 1963)