609 research outputs found

    High Spatial Resolution X-Ray Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

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    Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222127, in the supernova remnant IC443 reveal an ~5′′^{\prime\prime}-radius ring-like structure surrounding the pulsar and a jet-like feature oriented roughly north-south across the ring and through the pulsar's location at 06h^{\rm h}17m^{\rm m}5.200s^{\rm s} +22∘^{\circ}21′^{\prime}27.52′′^{\prime\prime} (J2000.0 coordinates). The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar, (2) the non-thermal spectrum and morphology of the surrounding nebula are consistent with a pulsar wind and, (3) the spectrum at greater distances is consistent with thermal emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic: There is no evidence either spectrally or morphologically for a bow shock or contact discontinuity; the nearly circular ring is not distorted by motion through the ambient medium; and the shape near the apex of the nebula is narrow. Comparing this observation with previous observations of the same target, we set a 99% confidence upper limit to the proper motion of CXOU J061705.3+222127 to be less than 44 mas/yr (310 km/s for a distance of 1.5 kpc), with the best-fit (but not statistically significant) projected direction toward the west.Comment: Accepted for publication in the Astrophysical Journa

    Trypanosoma brucei poly(A) binding protein I cDNA cloning, expression, and binding to 5 untranslated region sequence elements

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    Abstract Poly(A) binding protein I (PABPI) is a highly conserved eukaryotic protein that binds mRNA poly(A) tails and functions in the regulation of translational efficiency and mRNA stability. As a first step in our investigation of the role(s) of mRNA poly(A) tails in posttranscriptional gene regulation in Trypanosoma brucei, we have cloned the cDNA encoding PABPI from this organism. The cDNA predicts a protein homologous to PABPI from other organisms and displaying conserved features of these proteins, including four RNA binding domains that span the N-terminal two-thirds of the protein. Comparison of northern blot data with the cDNA sequence indicates an unusually long 3% untranslated region (UTR) of approximately three kilobases. The 5% UTR contains both A-rich and AU repeat regions, the former being a ubiquitous property of PABPI 5' UTRs. T. brucei PABPI, expressed as a glutathione-S-transferase fusion protein, bound to RNA comprised of its full length 5% UTR in UV cross-linking experiments. This suggests that PABPI may play an autoregulatory role in its own expression. Competition experiments indicate that the A-rich region, but not the AU repeats, are involved in this binding

    Inflammatory monocytes expressing tissue factor drive SIV and HIV coagulopathy

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    Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. http://www.sciencemag.org/about/science-licenses-journal-article-reuseThis is an article distributed under the terms of the Science Journals Default LicenseIn HIV infection, persistent inflammation despite effective antiretroviral therapy is linked to increased risk of noninfectious chronic complications such as cardiovascular and thromboembolic disease. A better understanding of inflammatory and coagulation pathways in HIV infection is needed to optimize clinical care. Markers of monocyte activation and coagulation independently predict morbidity and mortality associated with non-AIDS events. We identified a specific subset of monocytes that express tissue factor (TF), persist after virological suppression, and trigger the coagulation cascade by activating factor X. This subset of monocytes expressing TF had a distinct gene signature with up-regulated innate immune markers and evidence of robust production of multiple proinflammatory cytokines, including interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and IL-6, ex vivo and in vitro upon lipopolysaccharide stimulation. We validated our findings in a nonhuman primate model, showing that TF-expressing inflammatory monocytes were associated with simian immunodeficiency virus (SIV)-related coagulopathy in the progressive [pigtail macaques (PTMs)] but not in the nonpathogenic (African green monkeys) SIV infection model. Last, Ixolaris, an anticoagulant that inhibits the TF pathway, was tested and potently blocked functional TF activity in vitro in HIV and SIV infection without affecting monocyte responses to Toll-like receptor stimulation. Strikingly, in vivo treatment of SIV-infected PTMs with Ixolaris was associated with significant decreases in D-dimer and immune activation. These data suggest that TF-expressing monocytes are at the epicenter of inflammation and coagulation in chronic HIV and SIV infection and may represent a potential therapeutic target.This study was supported by the NIH Intramural Research Program, National Institute of Allergy and Infectious Diseases, and Bench-to-Bedside award R01HL117715-10S1 (to I.S. and I.P.). Part of this project has been also funded with federal funds from the National Cancer Institute, NIH, under contract no. HHSN261200800001E. The NHP study has also been funded in part with federal funds from the NIH (R01 HL123096 and RO1 HL117715 to I.P., R01 AI119346 to C.A., and R01AI104373 to R.M.R.).info:eu-repo/semantics/publishedVersio

    Chemical Fabrication Used to Produce Thin-Film Materials for High Power-to- Weight-Ratio Space Photovoltaic Arrays

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    The key to achieving high specific power (watts per kilogram) space solar arrays is the development of a high-efficiency, thin-film solar cell that can be fabricated directly on a flexible, lightweight, space-qualified durable substrate such as Kapton (DuPont) or other polyimide or suitable polymer film. Cell efficiencies approaching 20 percent at AM0 (air mass zero) are required. Current thin-film cell fabrication approaches are limited by either (1) the ultimate efficiency that can be achieved with the device material and structure or (2) the requirement for high-temperature deposition processes that are incompatible with all presently known flexible polyimide or other polymer substrate materials. Cell fabrication processes must be developed that will produce high-efficiency cells at temperatures below 400 degrees Celsius, and preferably below 300 degress Celsius to minimize the problems associated with the difference between the coefficients of thermal expansion of the substrate and thin-film solar cell and/or the decomposition of the substrate
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