3,270 research outputs found

    Binary to binary-coded-decimal converter Patent

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    Binary to binary-coded decimal converter using single set of logic circuits notwithstanding number of shift register decade

    Tests of Lorentz violation in muon antineutrino to electron antineutrino oscillations

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    A recently developed Standard-Model Extension (SME) formalism for neutrino oscillations that includes Lorentz and CPT violation is used to analyze the sidereal time variation of the neutrino event excess measured by the Liquid Scintillator Neutrino Detector (LSND) experiment. The LSND experiment, performed at Los Alamos National Laboratory, observed an excess, consistent with neutrino oscillations, of νˉe{\bar\nu}_e in a beam of νˉμ{\bar\nu}_\mu. It is determined that the LSND oscillation signal is consistent with no sidereal variation. However, there are several combinations of SME coefficients that describe the LSND data; both with and without sidereal variations. The scale of Lorentz and CPT violation extracted from the LSND data is of order 101910^{-19} GeV for the SME coefficients aLa_L and E×cLE \times c_L. This solution for Lorentz and CPT violating neutrino oscillations may be tested by other short baseline neutrino oscillation experiments, such as the MiniBooNE experiment.Comment: 10 pages, 10 figures, 2 tables, uses revtex4 replaced with version to be published in Physical Review D, 11 pages, 11 figures, 2 tables, uses revtex

    Shell-model calculations of neutrino scattering from 12C

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    Neutrino reaction cross-sections, (νμ,μ)(\nu_\mu,\mu^-), (νe,e)(\nu_e,e^-), μ\mu-capture and photoabsorption rates on 12^{12}C are computed within a large-basis shell-model framework, which included excitations up to 4ω4\hbar\omega. When ground-state correlations are included with an open pp-shell the predictions of the calculations are in reasonable agreement with most of the experimental results for these reactions. Woods-Saxon radial wave functions are used, with their asymptotic forms matched to the experimental separation energies for bound states, and matched to a binding energy of 0.01 MeV for unbound states. For comparison purposes, some results are given for harmonic oscillator radial functions. Closest agreement between theory and experiment is achieved with unrestricted shell-model configurations and Woods-Saxon radial functions. We obtain for the neutrino-absorption inclusive cross sections: σˉ=13.8×1040\bar{\sigma} = 13.8 \times 10^{-40} cm2^2 for the (νμ,μ)(\nu_{\mu},\mu^{-}) decay-in-flight flux in agreement with the LSND datum of (12.4±1.8)×1040(12.4 \pm 1.8) \times 10^{-40} cm2^2; and σˉ=12.5×1042\bar{\sigma} = 12.5 \times 10^{-42} cm2^2 for the (νe,e)(\nu_{e},e^{-}) decay-at-rest flux, less than the experimental result of (14.4±1.2)×1042(14.4 \pm 1.2) \times 10^{-42} cm2^2.Comment: 19 pages. ReVTeX. No figure

    Search for π0νμνˉμ\pi^0 \to \nu_{\mu}\bar\nu_{\mu} Decay in LSND

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    We observe a net beam-excess of 8.7±6.38.7 \pm 6.3 (stat) ±2.4\pm 2.4 (syst) events, above 160 MeV, resulting from the charged-current reaction of νμ\nu_{\mu} and/or νˉμ\bar\nu_{\mu} on C and H in the LSND detector. No beam related muon background is expected in this energy regime. Within an analysis framework of π0νμνˉμ\pi^0 \to \nu_{\mu}\bar\nu_{\mu}, we set a direct upper limit for this branching ratio of Γ(π0νμνˉμ)/Γ(π0all)<1.6×106\Gamma(\pi^0 \to \nu_\mu \bar\nu_\mu) / \Gamma(\pi^0 \to all) < 1.6 \times 10^{-6} at 90% confidence level.Comment: 4 pages, 4 figure

    Pneumococcal Gene Complex Involved in Resistance to Extracellular Oxidative Stress

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    Streptococcus pneumoniae is a Gram-positive bacterium which is a member of the normal human nasopharyngeal flora but can also cause serious disease such as pneumonia, bacteremia, and meningitis. Throughout its life cycle, S. pneumoniae is exposed to significant oxidative stress derived from endogenously produced hydrogen peroxide (H2O2) and from the host through the oxidative burst. How S. pneumoniae, an aerotolerant anaerobic bacterium that lacks catalase, protects itself against hydrogen peroxide stress is still unclear. Bioinformatic analysis of its genome identified a hypothetical open reading frame belonging to the thiol-specific antioxidant (TlpA/TSA) family, located in an operon consisting of three open reading frames. For all four strains tested, deletion of the gene resulted in an approximately 10-fold reduction in survival when strains were exposed to external peroxide stress. However, no role for this gene in survival of internal superoxide stress was observed. Mutagenesis and complementation analysis demonstrated that all three genes are necessary and sufficient for protection against oxidative stress. Interestingly, in a competitive index mouse pneumonia model, deletion of the operon had no impact shortly after infection but was detrimental during the later stages of disease. Thus, we have identified a gene complex involved in the protection of S. pneumoniae against external oxidative stress, which plays an important role during invasive disease.

    Resistance to the antimicrobial agent fosmidomycin and an FR900098 prodrug through mutations in the deoxyxylulose phosphate reductoisomerase gene (dxr)

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    There is a pressing need for new antimicrobial therapies to combat globally important drug-resistant human pathogens, including Plasmodium falciparum malarial parasites, Mycobacterium tuberculosis, and Gram-negative bacteria, including Escherichia coli. These organisms all possess the essential methylerythritol phosphate (MEP) pathway of isoprenoid biosynthesis, which is not found in humans. The first dedicated enzyme of the MEP pathway, 1-deoxy-d-xylulose 5-phosphate reductoisomerase (Dxr), is inhibited by the phosphonic acid antibiotic fosmidomycin and its analogs, including the N-acetyl analog FR900098 and the phosphoryl analog fosfoxacin. In order to identify mutations in dxr that confer resistance to these drugs, a library of E. coli dxr mutants was screened at lethal fosmidomycin doses. The most resistant allele (with the S222T mutation) alters the fosmidomycin-binding site of Dxr. The expression of this resistant allele increases bacterial resistance to fosmidomycin and other fosmidomycin analogs by 10-fold. These observations confirm that the primary cellular target of fosmidomycin is Dxr. Furthermore, cell lines expressing Dxr-S222T will be a powerful tool to confirm the mechanisms of action of future fosmidomycin analogs
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