• 0-Hz-IF FSK/AM Sub-Carrier Demodulator on a 6U-VME-Card

      Weitzman, Jonathan M.; GDP Space Systems (International Foundation for Telemetering, 1996-10)
      Aerospace Report No. TOR-0059(6110-01)-3, section 1.3.3 outlines the design and performance requirements of SGLS (Space Ground Link Subsystem) services. GDP Space Systems has developed a single card slot FSK (Frequency Shift Keying)/AM (Amplitude Modulation) demodulator. An application of this service is the US Air Force Satellite Command and Ranging System. The SGLS signal is tri-tone-FSK, amplitude modulated by a modified triangle wave at half the data rate. First generation FSK/AM demodulators had poor noise performance because the signal tones were filtered and processed at IF frequencies (65, 76 and 95 kHz). Second generation demodulators suffer from "threshold" due to non-linear devices in the signal path before the primary noise filtering. The GDP Space Systems demodulator uses a 0-Hz- IF topology and avoids both of these shortcomings. In this approach, the signal is first noncoherently down converted to baseband by linear devices, then it is filtered and processed. This paper will discuss the GDP 0-Hz-IF FSK/AM (SGLS) demodulator.
    • A 1,373 Year Reconstruction of Annual Precipitation for the Southern Rio Grande Basin

      Grissino-Mayer, Henri D.; Baisan, Christopher H.; Swetnam, Thomas W.; Dept. of Physics, Astronomy & Geosciences, Valdosta State University; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1977-11-10)
    • 1,4-Dioxane Remediation Using a Constructed Wetland

      Quanrud, David M.; Ward, William Jackson; Quanrud, David M.; Karpiscak, Martin; Marsh, Stuart; Hutchinson, Charles (The University of Arizona., 2008)
      This research addressed the question whether a constructed wetland system with phytoremediation could successfully uptake 1,4-Dioxane in groundwater and secondary effluent. It further addressed whether open pond storage could successfully treat wetland discharge. The project was located at the University of Arizona's Constructed Ecosystems Research Facility (CERF) in Tucson, Arizona. This two-year field study was motivated by previous laboratory studies which demonstrated the capability of plants to remediate the recalcitrant contaminant 1,4-Dioxane.The study was conducted in two open steel tanks configured to simulate constructed wetlands. The efficacy of 1,4-Dioxane uptake by cottonwood trees was tested in a side-by-side comparison utilizing planted and unplanted tanks. The sub-surface hydraulic conditions were fully characterized by bromide tracer studies. Six experiments were conducted, in which tapwater or secondary effluent was spiked with 5.2 mg/L 1,4-Dioxane and fed to the planted and unplanted (control) tank. The tank discharges were retained in separate open ponds to test if open pond storage would reduce 1,4-Dioxane content. Additional side experiments were conducted to examine the role of volatilization and UV degradation. Comparison of 1,4-Dioxane mass discharge from the planted and the control tank demonstrated an 18-48 percent uptake by the cottonwood trees. Mass balance assessments showed 1,4-Dioxane uptake efficiency was positively correlated to cottonwood transpiration rates in the planted tank. The open pond 1,4-Dioxane measurements demonstrated a 64-85 percent reduction in 1,4-Dioxane concentration due to volatilization during the initial 120 hours pond lapse time. Elimination of 1,4-Dioxane from the ponds followed first order kinetics. Field and laboratory side experiments demonstrated the potential for UV photo degradation of 1-4-Dioxane.
    • 1-D Rans Model Optimization for Turbulent Richtmyer-Meshkov Instability Experiments in the University of Arizona Vertical Shock Tube

      Jacobs, Jeffrey W.; Holt, Brason; Little, Jesse C.; Chan, Cholik (The University of Arizona., 2020)
      In this study, a comparison of experimental and computational results for the Richtmyer-Meshkov instability in a shock tube at the University of Arizona with a diffuse interface is carried out. Two turbulence models, the K-L-a and K-L-a-V models, are used to obtain the computational data using 1D simulations. The models are optimized for a new set of membraneless experiments performed in the University of Arizona vertical shock tube. The varied parameters are L_0, the initial turbulent length scale, and α_b, the Rayleigh-Taylor bubble growth parameter. One parameter, the Richtmyer-Meshkov growth exponent θ, was adjusted from a value of 0.25 to 0.5 to match the experimental setup. The experiments used to calibrate these models used membranes to initially separate the two gases in the shock tube. The presence of a membrane affects the development of the fluid instability and turbulence. However, the model has an option to model a diffuse interface. It was therefore desired to determine if this model can accurately model the membraneless experiments by utilizing this diffuse interface modeling. Many different optimization parameter pairs were tested and the goodness of fit to the experimental data was calculated. The diagnostic metrics used to evaluate the goodness of fit were the width of the turbulent mixing region and the turbulent kinetic energy (TKE) over time. Experimental data with both high and low amplitude initial perturbations were used. The best fits for each of these metrics are presented. It was found that the parameters that provided the best fits for these experiments did not match the model defaults. When α_b is not changed from its default value of 0.06, it was found that the model fits the data well before reshock, but overpredicts the post-reshock growth of both mixed width and TKE. Better fits were found when α_b was able to vary over a range of [0.02,0.06] and L_0 was varied as well. For the best fits, the values of α_b were not the same for the high and low amplitude cases. The best fit values of α_b did agree when comparing mixed width and TKE in the high amplitude case, but not for the low amplitude case. A value of α_b=0.025 was found to work for all metrics fairly well. Although this did not provide the best fit overall, it did provide a reasonable fit for both the low and high amplitude cases. It should be, however, expected that there is a relationship between α_b and the amplitude of the initial perturbation.
    • 1-O-Acetylgeopyxin A, a derivative of a fungal metabolite, blocks tetrodotoxin-sensitive voltage-gated sodium, calcium channels and neuronal excitability which correlates with inhibition of neuropathic pain

      Zhou, Yuan; Cai, Song; Gomez, Kimberly; Wijeratne, E M Kithsiri; Ji, Yingshi; Bellampalli, Shreya S; Luo, Shizhen; Moutal, Aubin; Gunatilaka, A A Leslie; Khanna, Rajesh; et al. (BMC, 2020-05-11)
      Chronic pain can be the result of an underlying disease or condition, medical treatment, inflammation, or injury. The number of persons experiencing this type of pain is substantial, affecting upwards of 50 million adults in the United States. Pharmacotherapy of most of the severe chronic pain patients includes drugs such as gabapentinoids, re-uptake blockers and opioids. Unfortunately, gabapentinoids are not effective in up to two-thirds of this population and although opioids can be initially effective, their long-term use is associated with multiple side effects. Therefore, there is a great need to develop novel non-opioid alternative therapies to relieve chronic pain. For this purpose, we screened a small library of natural products and their derivatives in the search for pharmacological inhibitors of voltage-gated calcium and sodium channels, which are outstanding molecular targets due to their important roles in nociceptive pathways. We discovered that the acetylated derivative of the ent-kaurane diterpenoid, geopyxin A, 1-O-acetylgeopyxin A, blocks voltage-gated calcium and tetrodotoxin-sensitive voltage-gated sodium channels but not tetrodotoxin-resistant sodium channels in dorsal root ganglion (DRG) neurons. Consistent with inhibition of voltage-gated sodium and calcium channels, 1-O-acetylgeopyxin A reduced reduce action potential firing frequency and increased firing threshold (rheobase) in DRG neurons. Finally, we identified the potential of 1-O-acetylgeopyxin A to reverse mechanical allodynia in a preclinical rat model of HIV-induced sensory neuropathy. Dual targeting of both sodium and calcium channels may permit block of nociceptor excitability and of release of pro-nociceptive transmitters. Future studies will harness the core structure of geopyxins for the generation of antinociceptive drugs.
    • 1. Anionic additions to glycosyl iodides 2. Neutral addition of alcohols to glycosyl iodides 3. Glycosyl iodides in solid phase oligosaccharide synthesis

      Gervay, Jacquelyn; Hadd, Michael Joseph (The University of Arizona., 1998)
      The usefulness of glycosyl iodides in carbohydrate chemistry has been demonstrated. Both anionic and neutral nucleophiles have been shown to react readily with glycosyl iodides as the glycosyl donor. High yields and stereoselectivity were obtained along with short reaction times. Anionic nucleophiles gave β glycosides selectively, whereas neutral nucleophiles gave α glycosides in the presence of tetrabutylammonium iodide. Initial investigation of the applicability of these glycosidation conditions to solid phase oligosaccharide synthesis has been accomplished.
    • 1. Development of a novel ELISA for the testing of glycobioconjugates as anti-HIV agents 2. Synthesis of potential inhibitors of the HIV entry mechanism 3. Probing the secondary structural characteristics of oligosaccharides utilizing circular dichroism

      Gervay-Hague, Jacquelyn; McReynolds, Kathrine Dawn (The University of Arizona., 1999)
      AIDS, or acquired immunodeficiency syndrome, is caused by the human immunodeficiency virus (HIV). HIV is a retrovirus that is capable of rapid genetic mutation, which makes the virus and the disease difficult to treat. Several drug therapies are currently available, in the form of viral enzyme inhibitors. Other inhibitors of the viral entry and replication process are being investigated to enhance the drug therapy arsenal. Our research has focused on the development of HIV entry inhibitors. We are working towards the development of novel carbohydrate-based agents that are capable of binding the gp120 protein on the viral surface, such that viral entry into an uninfected host cell is prevented. In order for our research to progress, a qualitative method by which our synthetic compounds could be evaluated for gp120 binding was sought. We have developed a unique ELISA (enzyme-linked immunosorbent assay) that indicates whether or not a compound has binding affinity for the viral protein. A TIRF (total internal reflection fluorescence) microscopy method, has been developed as part of a collaborative effort with the laboratories of Professors Saavedra and O'Brien, to assess active compounds for quantitative equilibrium binding constants to gp120. We have synthesized several carbohydrate-based molecules targeted to one or more of the binding sites on the surface of gp120; the galactosylceramide site, the V3 loop, and the CD4 binding site. Utilizing both the ELISA and TIRF methods, we have succeeded in probing the binding profile of gp120. Circular dichroism studies have also been employed to evaluate the secondary structural characteristics of oligomeric carbohydrate materials. Molecules with helical properties have potential as CD4 binding site inhibitors. The long term goals of this project involve the synthesis and gp120 binding evaluation of novel carbohydrate-based materials to serve as entry inhibitors of the HIV replication process. A possible application of this project lies in the development of compounds capable of binding to more than one site on the protein. A variation of this goal involves the tethering of various compounds with specificities to different sites on gp120, for the purpose of inhibiting multiple binding sites on the protein.
    • 1. Mechanistic studies on the formation of glycosyl iodides 2. Synthesis of amino sugars via glycosyl iodides

      Gervay, Jacquelyn; Nguyen, Truc Ngoc, 1972- (The University of Arizona., 1998)
      The synthesis of oligosaccharides remains a challenging task. In our studies, we applied glycosyl iodides to the synthesis of oligosaccharides. The mechanism of formation of glycosyl iodides from anomeric acetates of glucose, galactose and mannose, and 1,2 and 1,6 anhydro sugars were investigated by NMR. Glycosyl iodides were then applied in glycosidation studies and specifically in the synthesis of a precursor to the trisaccharide of Lewis x, a blood group antigen.
    • 1. Synthesis of C-glycoside sulfones via oxirane-thirane exchange 2. Preparation of sialic acid derivatives amenable to solid-phase synthesis 3. Conformational analysis of complex polysaccharides

      Gervay, Jacquelyn; Flaherty, Terrence Michael (The University of Arizona., 1997)
      As part of a program directed toward the synthesis of novel glycosyl transferase inhibitors possessing a sugar-CH₂-SO₂-CH₂-SO₂-CH₂-nucleoside structure, β-C-glycoside sulfones have been prepared with high stereoselectivity. Both glucose and fucose derivatives were prepared. Sulfur incorporation was achieved by free radical addition of thiolacetic acid to exocyclic glycals. As part of a program directed toward the preparation of amide-linked sialic acid oligomers, a strategy was developed for the synthesis of sialic acid derivatives possessing either a free amine or a free acid functionality. Solution phase coupling of these monomers using standard peptide coupling techniques resulted in the synthesis of (1 → 5)-amide linked sialic acid dimers. As part of a program directed toward the identification of novel helical structures, the solution phase conformation of the polylactone of colominic acid was examined by NMR and molecular modeling. The two structures generated from molecular modeling that were consistent with the NOE data were both helical.