18,551 research outputs found

    Radio Observations of the Supernova Remnant Candidate G312.5-3.0

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    The radio images from the Parkes-MIT-NRAO (PMN) Southern Sky Survey at 4850 MHz have revealed a number of previously unknown radio sources. One such source, G312.5-3.0 (PMN J1421-6415), has been observed using the multi-frequency capabilities of the Australia Telescope Compact Array (ATCA) at frequencies of 1380 MHz and 2378 MHz. Further observations of the source were made using the Molonglo Observatory Synthesis Telescope (MOST) at a frequency of 843 MHz. The source has an angular size of 18 arcmin and has a distinct shell structure. We present the reduced multi-frequency observations of this source and provide a brief argument for its possible identification as a supernova remnant.Comment: 5 pages, 5 figures, Accepted for publication in MNRA

    Phonon spectrum and bonding properties of Bi2_{2}Se3_{3}: Role of strong spin-orbit interaction

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    Phonon dispersions of one typical three-dimensional topological insulator Bi2_{2}Se3_{3} have been studied within density functional theory. The soft modes of two acoustic branches along the ZZ−-FF and Γ\Gamma−-FF directions within the pure local density approximation will transit to show imaginary frequency oscillating after including the spin-orbit interaction (SOI). Similar phenomenon has also been observed for Bi2_{2}Te3_{3}. Besides, we have found that the weak van der Waals forces between two Se1 layers in Bi2_{2}Se3_{3} are strengthened by turning on the SOI.Comment: 4 pages, 5 figure

    Outcomes of a remote, decentralized health center-based HIV/AIDS antiretroviral program in Zambia, 2003 to 2007

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    A cross-sectional study of patients living with HIV/ AIDS treated during 2003 to 2007 in decentralized, rural health centers in Zambia was performed to measure virological outcomes after 12 months of antiretroviral therapy and identify factors associated with virological failure. Data from 228 patients who started antiretroviral therapy >12 months prior were analyzed. In all, 93% received stavudine + lamivudine + nevirapine regimens, and median antiretroviral therapy duration was 23.5 months (interquartile range 20-28). Of the 205 patients tested for viral load, 177 (86%) had viral load <1000 copies/mL. Probability of developing virological failure (viral load >1000 copies/mL) was 8.9% at 24 months and 19.6% at 32 months. Predictors for virological failure were <100% adherence, body mass index <18.5 kg/m(2), and women <40 years old. Of those with virological failure who underwent 3 to 6 months of intensive adherence counseling, 45% obtained virological success. In a remote, resource-limited setting in decentralized health centers, virological and immunological assessments of patients on antiretroviral therapy >12 months showed that positive health outcomes are achievable
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