87 research outputs found

    Non-tuberculosis mycobacteria: Trend of isolation rate and characteristics of NTM in Cambodia during 2011–2013

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    AbstractBackgroundThe evidence of increase in the prevalence of non-tuberculosis mycobacteria (NTM) is being reported around the world. In Shanghai, China, it rose from 4% to 6% in the years between 2005 and 2008. Cambodia is one of the 22 high–tuberculosis (TB) burden countries. The NTM isolation rate among pulmonary smear-positive previously treated TB and new smear-positive non-converter at months 2 or 3 was 25% in 2011.ObjectiveTo determine the trend of the NTM isolation rate from presumptive multidrug-resistant tuberculosis (MDR-TB) cases during the period 2011–2013 and their characteristics.MethodsA retrospective cross-sectional study which included all presumptive MDR-TB patients whose samples reached two main mycobacterial culture laboratories of the National TB Program during the period 2011–2013. Each of the two samples were examined by smear microscopy with Ziehl Neelsen, cultured with Lowenstein Jensen and BACTEC MGIT 960, and identified for mycobacteria with ICA test. Possible cases were defined as a single positive NTM isolate, and definite cases were defined as two positive NTM isolates. The NTM isolation rate and the relationship of NTM and smear result were analyzed.ResultsA total of 6115 sputum samples of 3,338 patients were cultured, of which 32.3% (n=1079) of the patients have at least one positive culture with a median age of 51years (IQR: 40–62) and 59.5% were males. Out of these, 36.9% (n=398) were NTM isolates with median age of 56.5years (IQR: 46–65) and 51.0% were males. Of these, 39.7% (n=158) were defined as NTM cases. The isolation rate of NTM among culture-positive of presumptive MDR-TB patients were 26.1%, 31.5%, and 46.9% in the years 2011, 2012, and 2013, respectively. This isolation rate was strongly correlated with a grade of smear result, but not TB treatment history. The proportion of NTM by grade of smear results were 62%, 53%, 27%, 15%, and 6% among smear-negative, scanty, 1+, 2+, and 3+, respectively, and the proportion of NTM by type of TB patients was 66.7%, 53.0%, 38.5%, 34.4%, 30.9%, 29.4%, and 2.7% among pulmonary TB smear-negative previously treated cases, non-converter of new smear-positive cases, symptomatic close contacts of known MDR-TB patient, failure, HIV/TB new smear-positive, relapse, and return after default, respectively.ConclusionsThe isolation rate of NTM in Cambodia among presumptive MDR-TB patients was found to be remarkably high and increasing over the last 3years and strongly correlated with the grade of smear result. Further studies and appropriate managements should be done for those patients

    "Charged" Particle's Tunneling from Rotating Black Holes

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    The behavior of a scalar field theory near the event horizon in a rotating black hole background can be effectively described by a two dimensional field theory in a gauge field background. Based on this fact, we proposal that the quantum tunneling from rotating black hole can be treated as "charged" particle' s tunneling process in its effectively two dimensional metric. Using this viewpoint and considering the corresponding "gauge charge" conservation, we calculate the non-thermal tunneling rate of Kerr black hole and Myers-Perry black hole, and results are consistent with Parikh-Wilczek's original result for spherically symmetric black holes. Especially for Myers-Perry black hole which has multi-rotation parameters, our calculation fills in the gap existing in the literature applying Parikh-Wilczek's tunneling method to various types black holes. Our derivation further illuminates the essential role of effective gauge symmetry in Hawking radiation from rotating black holes.Comment: 15 pages, no figure; any comments are welcome

    Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm

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    The PHENIX experiement has measured the electron-positron pair mass spectrum from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions from light meson decays to e^+e^- pairs have been determined based on measurements of hadron production cross sections by PHENIX. They account for nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair yield remaining after subtracting these contributions is dominated by semileptonic decays of charmed hadrons correlated through flavor conservation. Using the spectral shape predicted by PYTHIA, we estimate the charm production cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which is consistent with QCD calculations and measurements of single leptons by PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables. Submitted to Physics Letters B. v2 fixes technical errors in matching authors to institutions. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Correlated Production of p and p^bar in Au+Au Collisions at sqrt(s_NN) = 200 GeV

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    Correlations between p and pbar's at transverse momenta typical of enhanced baryon production in Au+Au collisions are reported. The PHENIX experiment measures same and opposite sign baryon pairs in Au+Au collisions at sqrt(s_NN) = 200 GeV. Correlated production of p and p^bar with the trigger particle from the range 2.5 < p_T < 4.0 GeV/c and the associated particle with 1.8 < p_T < 2.5 GeV/c is observed to be nearly independent of the centrality of the collisions. Same sign pairs show no correlation at any centrality. The conditional yield of mesons triggered by baryons (and anti-baryons) and mesons in the same pT range rises with increasing centrality, except for the most central collisions, where baryons show a significantly smaller number of associated mesons. These data are consistent with a picture in which hard scattered partons produce correlated p and p^bar in the p_T region of the baryon excess.Comment: 420 authors from 58 institutions, 21 pages,5 figures. Submitted to Physics Letters B. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

    Reduction kinetics of Wüstite scale on pure iron and steel sheets in Ar and H<sub>2</sub> gas mixture

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    A dense and closed Wüstite scale is formed on pure iron and Mn alloyed steel after oxidation in Ar + 33 vol pct CO2 + 17 vol pct CO gas mixture. Reducing the Wüstite scale in Ar + H2 gas mixture forms a dense and uniform iron layer on top of the remaining Wüstite scale, which separates the unreduced scale from the gas mixture. The reduction of Wüstite is controlled by the bulk diffusion of dissolved oxygen in the formed iron layer and follows parabolic growth rate law. The reduction kinetics of Wüstite formed on pure iron and on Mn alloyed steel are the same. The parabolic rate constant of Wüstite reduction obeys an Arrhenius relation with an activation energy of 104 kJ/mol if the formed iron layer is in the ferrite phase. However, at 1223 K (950 °C) the parabolic rate constant of Wüstite reduction drops due to the phase transformation of the iron layer from ferrite to austenite. The effect of oxygen partial pressure on the parabolic rate constant of Wüstite reduction is negligible when reducing in a gas mixture with a dew point below 283 K (10 °C). During oxidation of the Mn alloyed steel, Mn is dissolved in the Wüstite scale. Subsequently, during reduction of the Wüstite layer, Mn diffuses into the unreduced Wüstite. Ultimately, an oxide-free iron layer is obtained at the surface of the Mn alloyed steel, which is beneficial for coating application.(OLD) MSE-
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