8,655 research outputs found

    Acute HIV infection: the impact of anti-retroviral treatment on cellular immune responses

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    The overall value of initiating anti-retroviral therapy during the acute phase of human immunodeficiency virus type 1 (HIV-1) infection remains unclear. From a clinical perspective, the lack of data from controlled randomized clinical trials limits understanding of long-term effects of treatment on the clinical course of HIV infection. Based on available data, the impact of anti-retroviral therapy during acute infection on the immune response against HIV-1 is not particularly encouraging. Recent observations on the very early depletion of lymphocyte reservoirs in the gastrointestinal tract may partially explain the limited benefit of anti-retroviral therapy initiated during the acute phase of HIV-1 infection. This may also help to explain the dichotomy between early observations demonstrating apparent immunological benefit with early anti-retroviral treatment that were associated none the less with inability to control viral replication following treatment interruption

    The Keck/OSIRIS Nearby AGN Survey (KONA) I. The Nuclear K-band Properties of Nearby AGN

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    We introduce the Keck Osiris Nearby AGN survey (KONA), a new adaptive optics-assisted integral-field spectroscopic survey of Seyfert galaxies. KONA permits at ~0.1" resolution a detailed study of the nuclear kinematic structure of gas and stars in a representative sample of 40 local bona fide active galactic nucleus (AGN). KONA seeks to characterize the physical processes responsible for the coevolution of supermassive black holes and galaxies, principally inflows and outflows. With these IFU data of the nuclear regions of 40 Seyfert galaxies, the KONA survey will be able to study, for the first time, a number of key topics with meaningful statistics. In this paper we study the nuclear K-band properties of nearby AGN. We find that the luminosities of the unresolved Seyfert 1 sources at 2.1 microns are correlated with the hard X-ray luminosities, implying that the majority of the emission is non-stellar. The best-fit correlation is logLK = 0.9logL2-10 keV + 4 over 3 orders of magnitude in both K-band and X-ray luminosities. We find no strong correlation between 2.1 microns luminosity and hard X-ray luminosity for the Seyfert 2 galaxies. The spatial extent and spectral slope of the Seyfert 2 galaxies indicate the presence of nuclear star formation and attenuating material (gas and dust), which in some cases is compact and in some galaxies extended. We detect coronal-line emission in 36 galaxies and for the first time in five galaxies. Finally, we find 4/20 galaxies that are optically classified as Seyfert 2 show broad emission lines in the near-IR, and one galaxy (NGC 7465) shows evidence of a double nucleus.Comment: Accepted for publication in ApJ, 19 pages with 18 figure

    A z=0.9 supercluster of X-ray luminous, optically-selected, massive galaxy clusters

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    We report the discovery of a compact supercluster structure at z=0.9. The structure comprises three optically-selected clusters, all of which are detected in X-rays and spectroscopically confirmed to lie at the same redshift. The Chandra X-ray temperatures imply individual masses of ~5x10^14 Msun. The X-ray masses are consistent with those inferred from optical--X-ray scaling relations established at lower redshift. A strongly-lensed z~4 Lyman break galaxy behind one of the clusters allows a strong-lensing mass to be estimated for this cluster, which is in good agreement with the X-ray measurement. Optical spectroscopy of this cluster gives a dynamical mass in good agreement with the other independent mass estimates. The three components of the RCS2319+00 supercluster are separated from their nearest neighbor by a mere <3 Mpc in the plane of the sky and likely <10 Mpc along the line-of-sight, and we interpret this structure as the high-redshift antecedent of massive (~10^15 Msun) z~0.5 clusters such as MS0451.5-0305.Comment: ApJ Letters accepted. 5 pages in emulateapj, 3 figure

    The LWA1 Radio Telescope

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    LWA1 is a new radio telescope operating in the frequency range 10-88 MHz, located in central New Mexico. The telescope consists of 258 pairs of dipole-type antennas whose outputs are individually digitized and formed into beams. Simultaneously, signals from all dipoles can be recorded using one of the instrument's "all dipoles" modes, facilitating all-sky imaging. Notable features of the instrument include high intrinsic sensitivity (about 6 kJy zenith system equivalent flux density), large instantaneous bandwidth (up to 78 MHz), and 4 independently-steerable beams utilizing digital "true time delay" beamforming. This paper summarizes the design of LWA1 and its performance as determined in commissioning experiments. We describe the method currently in use for array calibration, and report on measurements of sensitivity and beamwidth.Comment: 9 pages, 14 figures, accepted by IEEE Trans. Antennas & Propagation. Various minor changes from previous versio

    Evaluation of an Extension-Delivered Resource for Accelerating Progress in Childhood Obesity Prevention: The BEPA-Toolkit

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    The Balanced Energy Physical Activity Toolkit, or the BEPA-Toolkit, supports physical activity (PA) programming via Extension in elementary schools. In a pilot study, we evaluated the effectiveness of the BEPA-Toolkit as used by teachers through Supplemental Nutrition Assistance Program Education partnerships. We surveyed teachers (n = 57) regarding their use of the kit and examined associations between teacher use of the kit and objectively measured PA of students (n = 1,103). Over 80% of responders reported that the BEPA-Toolkit provided additional opportunities for PA, and children regularly exposed to the kit were more active than those having less exposure to it. The BEPA-Toolkit may support PA opportunities in underresourced school settings

    Upper limit on spontaneous supercurrents in Sr2_2RuO4_4

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    It is widely believed that the perovskite Sr2_2RuO4_4 is an unconventional superconductor with broken time reversal symmetry. It has been predicted that superconductors with broken time reversal symmetry should have spontaneously generated supercurrents at edges and domain walls. We have done careful imaging of the magnetic fields above Sr2_2RuO4_4 single crystals using scanning Hall bar and SQUID microscopies, and see no evidence for such spontaneously generated supercurrents. We use the results from our magnetic imaging to place upper limits on the spontaneously generated supercurrents at edges and domain walls as a function of domain size. For a single domain, this upper limit is below the predicted signal by two orders of magnitude. We speculate on the causes and implications of the lack of large spontaneous supercurrents in this very interesting superconducting system.Comment: 9 page

    The Gendered Nature of Ecosystem Services

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    This is the final version. Available from Elsevier via the DOI in this record. This article assesses the extent to which our conceptualisation, understanding and empirical analysis of ecosystem services are inherently gendered; in other words, how they might be biased and unbalanced in terms of their appreciation of gender differences. We do this by empirically investigating how women and men are able to benefit from ecosystem services across eight communities in coastal Kenya and Mozambique. Our results highlight different dimensions of wellbeing affected by ecosystem services, and how these are valued differently by men and women. However, it is not just the division of costs and benefits of ecosystem services that is gendered. Using a heuristic device of the ‘ecosystem-wellbeing chain’ we explain patterns within our primary data as an outcome of gendered knowledge systems, gendered behavioural expectations, gendered access to resources and gendered institutions. We conclude that this holistic, gendered understanding of ecosystem services is important not just for how ecosystem services are conceptualised, but also for the development and implementation of sustainable and equitable policy and interventions.Natural Environment Research Council (NERC)Ecosystem Services for Poverty Alleviation (ESPA)Economic and Social Research Council (ESRC

    Product assurance technology for procuring reliable, radiation-hard, custom LSI/VLSI electronics

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    Advanced measurement methods using microelectronic test chips are described. These chips are intended to be used in acquiring the data needed to qualify Application Specific Integrated Circuits (ASIC's) for space use. Efforts were focused on developing the technology for obtaining custom IC's from CMOS/bulk silicon foundries. A series of test chips were developed: a parametric test strip, a fault chip, a set of reliability chips, and the CRRES (Combined Release and Radiation Effects Satellite) chip, a test circuit for monitoring space radiation effects. The technical accomplishments of the effort include: (1) development of a fault chip that contains a set of test structures used to evaluate the density of various process-induced defects; (2) development of new test structures and testing techniques for measuring gate-oxide capacitance, gate-overlap capacitance, and propagation delay; (3) development of a set of reliability chips that are used to evaluate failure mechanisms in CMOS/bulk: interconnect and contact electromigration and time-dependent dielectric breakdown; (4) development of MOSFET parameter extraction procedures for evaluating subthreshold characteristics; (5) evaluation of test chips and test strips on the second CRRES wafer run; (6) two dedicated fabrication runs for the CRRES chip flight parts; and (7) publication of two papers: one on the split-cross bridge resistor and another on asymmetrical SRAM (static random access memory) cells for single-event upset analysis
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