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  • 1
    Publication Date: 2016-01-20
    Description: Near a black hole, differential rotation of a magnetized accretion disk is thought to produce an instability that amplifies weak magnetic fields, driving accretion and outflow. These magnetic fields would naturally give rise to the observed synchrotron emission in galaxy cores and to the formation of relativistic jets, but no observations to date have been able to resolve the expected horizon-scale magnetic-field structure. We report interferometric observations at 1.3-millimeter wavelength that spatially resolve the linearly polarized emission from the Galactic Center supermassive black hole, Sagittarius A*. We have found evidence for partially ordered magnetic fields near the event horizon, on scales of ~6 Schwarzschild radii, and we have detected and localized the intrahour variability associated with these fields.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Johnson, Michael D -- Fish, Vincent L -- Doeleman, Sheperd S -- Marrone, Daniel P -- Plambeck, Richard L -- Wardle, John F C -- Akiyama, Kazunori -- Asada, Keiichi -- Beaudoin, Christopher -- Blackburn, Lindy -- Blundell, Ray -- Bower, Geoffrey C -- Brinkerink, Christiaan -- Broderick, Avery E -- Cappallo, Roger -- Chael, Andrew A -- Crew, Geoffrey B -- Dexter, Jason -- Dexter, Matt -- Freund, Robert -- Friberg, Per -- Gold, Roman -- Gurwell, Mark A -- Ho, Paul T P -- Honma, Mareki -- Inoue, Makoto -- Kosowsky, Michael -- Krichbaum, Thomas P -- Lamb, James -- Loeb, Abraham -- Lu, Ru-Sen -- MacMahon, David -- McKinney, Jonathan C -- Moran, James M -- Narayan, Ramesh -- Primiani, Rurik A -- Psaltis, Dimitrios -- Rogers, Alan E E -- Rosenfeld, Katherine -- SooHoo, Jason -- Tilanus, Remo P J -- Titus, Michael -- Vertatschitsch, Laura -- Weintroub, Jonathan -- Wright, Melvyn -- Young, Ken H -- Zensus, J Anton -- Ziurys, Lucy M -- New York, N.Y. -- Science. 2015 Dec 4;350(6265):1242-5. doi: 10.1126/science.aac7087. Epub 2015 Dec 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. mjohnson@cfa.harvard.edu. ; Haystack Observatory, Route 40, Massachusetts Institute of Technology, Westford, MA 01886, USA. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. Haystack Observatory, Route 40, Massachusetts Institute of Technology, Westford, MA 01886, USA. ; Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA. ; Department of Astronomy, Radio Astronomy Laboratory, 501 Campbell, University of California Berkeley, Berkeley, CA 94720-3411, USA. ; Department of Physics MS-057, Brandeis University, Waltham, MA 02454-0911. ; Haystack Observatory, Route 40, Massachusetts Institute of Technology, Westford, MA 01886, USA. National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan. Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. ; Institute of Astronomy and Astrophysics, Academia Sinica, Post Office Box 23-141, Taipei 10617, Taiwan. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. ; Academia Sinica Institute for Astronomy and Astrophysics (ASIAA), 645 N. A'ohoku Pl. Hilo, HI 96720, USA. ; Department of Astrophysics/Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen, Post Office Box 9010, 6500 GL Nijmegen, Netherlands. ; Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada. Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada. ; Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, 85748 Garching, Germany. ; James Clerk Maxwell Telescope, East Asia Observatory, 660 N. A'ohoku Place, University Park, Hilo, HI 96720, USA. ; Department of Physics, Joint Space-Science Institute, University of Maryland at College Park, Physical Sciences Complex, College Park, MD 20742, USA. ; National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan. Graduate University for Advanced Studies, Mitaka, 2-21-1 Osawa, Mitaka, Tokyo 181-8588. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA. Haystack Observatory, Route 40, Massachusetts Institute of Technology, Westford, MA 01886, USA. Department of Physics MS-057, Brandeis University, Waltham, MA 02454-0911. ; Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany. ; Owens Valley Radio Observatory, California Institute of Technology, 100 Leighton Lane, Big Pine, CA 93513-0968, USA. ; Haystack Observatory, Route 40, Massachusetts Institute of Technology, Westford, MA 01886, USA. Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany. ; Department of Astrophysics/Institute for Mathematics, Astrophysics and Particle Physics, Radboud University Nijmegen, Post Office Box 9010, 6500 GL Nijmegen, Netherlands. Leiden Observatory, Leiden University, Post Office Box 9513, 2300 RA Leiden, Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26785487" 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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  • 2
  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The proportion of random localized destructive breakdown to stable electroluminescence has been varied continuously by adjusting (1) the recipe used to fabricate dc thin-film electroluminescent devices and (2) the conditions under which they have been tested. It has been shown that neither simple geometrical artifacts nor migration effects can be responsible for localized destructive breakdown. Rather, it has been established that the experiments require an explanation based on a fundamental tendency for dc thin-film electroluminescence to be associated with a current-controlled negative differential resistance which gives rise to filamentary and sometimes destructive current concentration. It is concluded that the existence and origins of such current-controlled negative differential resistance should be tested by theoretical and materials science studies.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 2877-2884 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: It has been seen that a plasma produced by a Marshall gun can be injected into and trapped by a tokamak plasma. This trapping of a gun-injected plasma is explained in terms of a depolarization current mechanism. A model is developed that describes the slowing of a plasma beam crossing into the magnetic field of a tokamak. The slowing down time is shown to go as τs∝T3/2eL2/nbα20, where nb and Te are the density and temperature of the plasma beam and α0/L is the pitch of the field lines per unit length in the direction in which the beam is traveling. Experimental tests of this model are consistent with the scaling predictions.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Cell and Developmental Biology 3 (1987), S. 423-441 
    ISSN: 0743-4634
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 108 (1986), S. 7124-7125 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Biology and fertility of soils 5 (1987), S. 152-157 
    ISSN: 1432-0789
    Keywords: Earthworm Casts ; “Modexi” ; Shape ; Tensile strength ; Pressure ; Aporrectodea rosea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Some physical properties of casts of the earthworm Aporrectodea rosea were examined and compared with the properties of aggregates from the bulk soil. Cast shape was quantified by three ratio methods and two mathematical spectra methods, using data obtained by two-dimensional scanning. Shapes were compared with previously published descriptions of “modexi”. The tensile strength of dry casts was measured by the indirect tension method and was found to be approximately 2.5 times greater than that of dried aggregates of similar size. Tensile strengths are used to predict that beds of casts are less compactable than beds of aggregates. From relationships between soil water content, matric potential and undrained shear strength of fresh earthworm casts, the mean pressure applied to soil as it is remoulded by passing through the earthworm gut is estimated to be 259 Pa.
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 198-198 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] HORMONE therapy is used for a wide range of disorders and the results of treatment are often dramatic. The work primarily involves the classical 'glandular' hormones that are released as circulating messenger systems because fairly large amounts of material are readily available and their target ...
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 94 (1986), S. 59-85 
    ISSN: 1573-5036
    Keywords: Cohesion ; Gossypium hirsutum ; Helianthus annuus ; Penetrometer resistance ; Pisum sativum ; Plastic failure ; Radial stress ; Root diameter ; Root growth pressure ; Soil aggregates ; Tangential stress ; Tensile stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The axial force required for penetration of soil aggregates by roots of pea (Pisum sativum cv. Greenfeast), cotton (Gossypium hirsutum cv. Sicot 3) and sunflower (Helianthus annuus cv. Hysun) seedlings was measured. Effects of aggregate size and strength on root penetration behaviour were investigated. Maximum axial root growth pressure (P x ) was estimated from the maximum axial root growth force (F max) and mean root diameter. F max, time (T max) to attainF max, andP x all increased with increase in size and strength of aggregates. A significant interactive effect of size and strength of aggregate on root diameter was observed.F max,T max and root diameter were significantly different for different plant species. Maximum penetrometer pressure (P′) was compared with the axial pressures generated during root penetration. The penetrometer probe was found to overestimate the root growth pressure by a factor of 1.8 to 3.8.P x /P′ decreased with increase in size and strength of aggregates. A theory was developed to estimate radial and tangential stresses adjacent to the soil-root interface assuming cylindrical deformation by the root in aggregates of finite size. The stresses were calculated using shear cohesion values, estimated from tensile strength measurements, and with an assumed value of soil internal friction. Radial and tangential stresses adjacent to the root axis increased with increase in dimensionless aggregate radius and aggregate strength. Tensile stress adjacent to the root axis is predicted to result in plastic failure of finite sized aggregates during root penetration.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 94 (1986), S. 43-58 
    ISSN: 1573-5036
    Keywords: Aggregate size ; Blunt probe ; Penetrometer pressure ; Plastic failure ; Plastic front ; Probe penetration ; Radial stress ; Root penetration ; Tangential stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Maximum penetrometer pressure was measured on artificial soil aggregates of finite size (2–29 mm) using blunt probes (total cone angle 60°) driven at 3 mm min−1. Maximum penetrometer pressure increased asymptotically with increase in dimensionless aggregate radius,b/a, wherea andb are the probe and aggregate radii, respectively. A theory was developed for penetration of blunt probes into soil aggregates of finite size. The theory assumed that plastic failure occurs out to a radius,R, and that beyond this only elastic straining occurs. This theory can be applied to estimate the radial and tangential stresses adjacent to a blunt probe. The estimated radial and tangential stresses increased with increase in dimensionless aggregate radius,b/a. The radius of the plastic front,R, around the probe is predicted to increase with increased aggregate size. The results also demonstrate the effect of soil shear cohesion and internal friction angle onR. The results are discussed with reference to root penetration.
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