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  • Articles  (81)
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  • Articles  (81)
  • 1
    Publication Date: 2018-06-20
    Description: Journal of the American Chemical Society DOI: 10.1021/jacs.8b03755
    Print ISSN: 0002-7863
    Electronic ISSN: 1520-5126
    Topics: Chemistry and Pharmacology
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  • 2
    Publication Date: 2014-03-07
    Description: The co-evolution of a supermassive black hole with its host galaxy through cosmic time is encoded in its spin. At z 〉 2, supermassive black holes are thought to grow mostly by merger-driven accretion leading to high spin. It is not known, however, whether below z approximately 1 these black holes continue to grow by coherent accretion or in a chaotic manner, though clear differences are predicted in their spin evolution. An established method of measuring the spin of black holes is through the study of relativistic reflection features from the inner accretion disk. Owing to their greater distances from Earth, there has hitherto been no significant detection of relativistic reflection features in a moderate-redshift quasar. Here we report an analysis of archival X-ray data together with a deep observation of a gravitationally lensed quasar at z = 0.658. The emission originates within three or fewer gravitational radii from the black hole, implying a spin parameter (a measure of how fast the black hole is rotating) of a = 0.87(+0.08)(-0.15) at the 3sigma confidence level and a 〉 0.66 at the 5sigma level. The high spin found here is indicative of growth by coherent accretion for this black hole, and suggests that black-hole growth at 0.5 〈/= z 〈/= 1 occurs principally by coherent rather than chaotic accretion episodes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reis, R C -- Reynolds, M T -- Miller, J M -- Walton, D J -- England -- Nature. 2014 Mar 13;507(7491):207-9. doi: 10.1038/nature13031. Epub 2014 Mar 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, University of Michigan, Ann Arbor, Michigan 48109, USA. ; Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, California 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24598545" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2014-10-10
    Description: The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5-10 kiloelectronvolt energy band range from 10(39) to 10(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 10(40) ergs per second), which require black hole masses of 50-100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3-30 kiloelectronvolt range of 4.9 x 10(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3-10 kiloelectronvolt range of 1.8 x 10(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bachetti, M -- Harrison, F A -- Walton, D J -- Grefenstette, B W -- Chakrabarty, D -- Furst, F -- Barret, D -- Beloborodov, A -- Boggs, S E -- Christensen, F E -- Craig, W W -- Fabian, A C -- Hailey, C J -- Hornschemeier, A -- Kaspi, V -- Kulkarni, S R -- Maccarone, T -- Miller, J M -- Rana, V -- Stern, D -- Tendulkar, S P -- Tomsick, J -- Webb, N A -- Zhang, W W -- England -- Nature. 2014 Oct 9;514(7521):202-4. doi: 10.1038/nature13791.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Universite de Toulouse, UPS-OMP, Institut de Recherche en Astrophysique et Planetologie, 9, Avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France [2] CNRS, Institut de Recherche en Astrophysique et Planetologie, 9, Avenue du Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France. ; Cahill Center for Astrophysics, 1216 East California Boulevard, California Institute of Technology, Pasadena, California 91125, USA. ; MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. ; Physics Department, Columbia University, 538 West 120th Street, New York, New York 10027, USA. ; Space Sciences Laboratory, University of California, Berkeley, California 94720, USA. ; DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby, Denmark. ; Lawrence Livermore National Laboratory, Livermore, California 94550, USA. ; Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK. ; Columbia Astrophysics Laboratory, Columbia University, New York, New York 10027, USA. ; NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. ; Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada. ; Department of Physics, Texas Tech University, Lubbock, Texas 79409, USA. ; Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, Michigan 48109-1042, USA. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25297433" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2015-10-23
    Description: Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray and optical/ultraviolet flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate. Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC 043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory and more recent numerical simulations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Miller, Jon M -- Kaastra, Jelle S -- Miller, M Coleman -- Reynolds, Mark T -- Brown, Gregory -- Cenko, S Bradley -- Drake, Jeremy J -- Gezari, Suvi -- Guillochon, James -- Gultekin, Kayhan -- Irwin, Jimmy -- Levan, Andrew -- Maitra, Dipankar -- Maksym, W Peter -- Mushotzky, Richard -- O'Brien, Paul -- Paerels, Frits -- de Plaa, Jelle -- Ramirez-Ruiz, Enrico -- Strohmayer, Tod -- Tanvir, Nial -- England -- Nature. 2015 Oct 22;526(7574):542-5. doi: 10.1038/nature15708.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, The University of Michigan, 1085 South University Avenue, Ann Arbor, Michigan 48103, USA. ; SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands. ; Department of Physics and Astronomy, Universiteit Utrecht, PO Box 80000, 3508 TA Utrecht, The Netherlands. ; Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands. ; Department of Astronomy, The University of Maryland, College Park, Maryland 20742, USA. ; Department of Physics, University of Warwick, Coventry CV4 7AL, UK. ; Joint Space-Science Institute, University of Maryland, College Park, Maryland 02742, USA. ; Astrophysics Science Division, NASA Goddard Space Flight Center, MC 661, Greenbelt, Maryland 20771, USA. ; Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, Massachusetts 02138, USA. ; The Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. ; Department of Physics and Astronomy, University of Alabama, PO Box 870324, Tuscaloosa, Alabama 35487, USA. ; Department of Physics and Astronomy, Wheaton College, Norton, Massachusetts 02766, USA. ; Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK. ; Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, New York 10027, USA. ; Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26490619" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2012-08-04
    Description: Supermassive black holes (SMBHs; mass is greater than or approximately 10(5) times that of the Sun) are known to exist at the center of most galaxies with sufficient stellar mass. In the local universe, it is possible to infer their properties from the surrounding stars or gas. However, at high redshifts we require active, continuous accretion to infer the presence of the SMBHs, which often comes in the form of long-term accretion in active galactic nuclei. SMBHs can also capture and tidally disrupt stars orbiting nearby, resulting in bright flares from otherwise quiescent black holes. Here, we report on a ~200-second x-ray quasi-periodicity around a previously dormant SMBH located in the center of a galaxy at redshift z = 0.3534. This result may open the possibility of probing general relativity beyond our local universe.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reis, R C -- Miller, J M -- Reynolds, M T -- Gultekin, K -- Maitra, D -- King, A L -- Strohmayer, T E -- New York, N.Y. -- Science. 2012 Aug 24;337(6097):949-51. doi: 10.1126/science.1223940. Epub 2012 Aug 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA. rdosreis@umich.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22859817" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2015-02-24
    Description: The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Nardini, E -- Reeves, J N -- Gofford, J -- Harrison, F A -- Risaliti, G -- Braito, V -- Costa, M T -- Matzeu, G A -- Walton, D J -- Behar, E -- Boggs, S E -- Christensen, F E -- Craig, W W -- Hailey, C J -- Matt, G -- Miller, J M -- O'Brien, P T -- Stern, D -- Turner, T J -- Ward, M J -- New York, N.Y. -- Science. 2015 Feb 20;347(6224):860-3. doi: 10.1126/science.1259202.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. e.nardini@keele.ac.uk. ; Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. Center for Space Science and Technology, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. ; Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA. ; Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze, Italy. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. ; INAF, Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate (LC), Italy. ; Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK. ; Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. ; Department of Physics, Technion, Haifa 32000, Israel. ; Space Science Laboratory, University of California, Berkeley, CA 94720, USA. ; Danmarks Tekniske Universitet Space-National Space Institute, Technical University of Denmark, Elektrovej 327, 2800 Lyngby, Denmark. ; Lawrence Livermore National Laboratory, Livermore, CA 94550, USA. ; Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA. ; Dipartimento di Matematica e Fisica, Universita degli Studi Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy. ; Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA. ; Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK. ; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. ; Physics Department, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA. Eureka Scientific Inc., 2452 Delmer Street Suite 100, Oakland, CA 94602, USA. ; Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25700515" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    ISSN: 1432-1106
    Keywords: Auditory cortex ; Single units ; Rhesus monkey ; Behavioral state ; Anesthetic state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Auditory-evoked responses in single neurons from rhesus monkey auditory cortex were measured under four relatively well defined behavioral and physiological conditions: (1) monkey awake and performing a simple auditory reaction time task; (2) monkey awake but not performing a task (State A); (3) monkey in a drowsy or Stage 1 sleep state (State B); and (4) monkey anesthetized with a short-acting nonbarbiturate anesthetic. For most units studied the response evoked by the auditory stimulus was greater in the performance condition than in the nonperformance condition. Similarly, evoked activity was usually greater in State A than in State B. Finally, evoked responses under anesthesia were usually weaker than those obtained in the unanesthetized animal. Some exceptions were noted in each case. Differences in response patterns and in rate versus intensity functions of neurons were also found to be associated with the behavioral and physiological state of the preparation. No significant changes in unit spontaneous activity associated with changes in behavioral or physiological condition were observed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three subtypes, as defined byHindIII restriction endonuclease (RE) analysis patterns [17], of bovine herpesvirus 1 (BHV 1) were used to inoculate seronegative, BHV 1-free cattle. These included: infectious bovine rhinotracheitis virus (IBRV), subtype 1.1; infectious pustular vulvovaginitis virus (IPPV) isolate K22, subtype 1.2b; and IPVV isolate FI, subtype 1.2a. Nasal, vaginal, and buffy coat samples were taken for virus isolation from each animal. RE analysis was done on virus isolates collected during acute infection, after reactivation from latency, and after reactivation followed by superinfection with a subtype of BHV 1 that differed from the primary inoculation virus. Changes occurred in the BHV1 genome after only 1 passage in the host animal, and varied from tissue to tissue within the same animal. Viruses reactivated from latency also displayed genome variability. Only animals that received IPVV as the primary inoculation virus were successfully superinfected. After superinfection, cattle shed both superinfecting and reactivated viruses, and genome variability was observed. These data suggest that the application of RE analysis in diagnostic and epidemiologic studies of BHV 1 is limited to analysis between types and subtypes, and is not applicable for the examination of isolates from within a BHV 1 subtype.
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  • 9
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A cocultivation method was used to establish a cytocidal bovine immunodeficiency-like virus (BIV) infection in primary fetal bovine lung (FBL) cell cultures. Cultures were monitored for virus production using radial immunodiffusion and agar gel immunodiffusion. Pelleted virus and detergent (CHAPS)-solubilized infected cell lysates from BIV-infected cell cultures were compared as sources of antigen for Western blots. Pelleted virus preparations from FBL-BIV cell cultures produced the best antigen for Western blot. Sheep and goats were inoculated with BIV and serum antibody responses were monitored up to 1 year post inoculation (PI). Sera from experimentally infected cattle, sheep, and goats reacted in Western blot assay with BIV viral induced polypeptides gp 110, p 72, p 55, p 50, gp 42, p 38, p 26, p 24, p 18, p 15, and p 13. Antibodies to p 26 were detected as early as 2 weeks PI in cattle, sheep, and goats. Antibodies to gp 110 were detected by 4 to 6 weeks PI in cattle, and by 9 months PI in sheep and goats. Antibodies to BIV proteins were still evident in cattle sera 2 1/2 years PI, and in sheep and goat sera 1 year PI.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We inoculated plaque-purified bovine herpesvirus type 1 (BHV 1), strain K22, subtype BHV 1.2b, intravenously into susceptible cattle. Five months later, we reactivated latent virus with dexamethasone and then super-infected the same cattle intranasally and intravaginally with a different plaquepurified BHV1, strain Cooper, subtype BHV 1.1. After a second dexamethasone treatment four months later, reactivated viruses were isolated and examined with restriction endonucleases. We showed that both virus subtypes were reactivated, proving that 2 different strains of an alphaherpesvirus can establish latency in the same tissue in the host animal.
    Type of Medium: Electronic Resource
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