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  • American Association for the Advancement of Science (AAAS)  (14)
  • Nature Publishing Group (NPG)  (8)
  • 1
    Publication Date: 2018-03-29
    Description: The Earth-Moon system likely formed as a result of a collision between two large planetary objects. Debate about their relative masses, the impact energy involved, and the extent of isotopic homogenization continues. We present the results of a high-precision oxygen isotope study of an extensive suite of lunar and terrestrial samples. We demonstrate that lunar rocks and terrestrial basalts show a 3 to 4 ppm (parts per million), statistically resolvable, difference in 17 O. Taking aubrite meteorites as a candidate impactor material, we show that the giant impact scenario involved nearly complete mixing between the target and impactor. Alternatively, the degree of similarity between the 17 O values of the impactor and the proto-Earth must have been significantly closer than that between Earth and aubrites. If the Earth-Moon system evolved from an initially highly vaporized and isotopically homogenized state, as indicated by recent dynamical models, then the terrestrial basalt-lunar oxygen isotope difference detected by our study may be a reflection of post–giant impact additions to Earth. On the basis of this assumption, our data indicate that post–giant impact additions to Earth could have contributed between 5 and 30% of Earth’s water, depending on global water estimates. Consequently, our data indicate that the bulk of Earth’s water was accreted before the giant impact and not later, as often proposed.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 2
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    American Association for the Advancement of Science (AAAS)
    In: Science
    Publication Date: 2018-08-17
    Description: We document rapid and abrupt clearings of large portions of the subtropical marine low cloud deck that have implications for the global radiation balance and climate sensitivity. Over the southeast Atlantic, large areas of stratocumulus are quickly eroded, yielding partial or complete clearing along sharp transitions hundreds to thousands of kilometers in length that move westward at 8 to 12 meters per second and travel as far as 1000+ kilometers from the African coast. The westward-moving cloudiness reductions have an annual peak in occurrence in the period from April through June. The cloud erosion boundaries reduce cloud at 10-kilometer scale in less than 15 minutes, move approximately perpendicular to the mean flow, and are often accompanied by small-scale wave features. Observations suggest that the cloud erosion is caused by atmospheric gravity waves.
    Keywords: Geochemistry, Geophysics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    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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  • 4
    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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  • 5
    Publication Date: 2015-11-28
    Description: Solar photoconversion in semiconductors is driven by charge separation at the interface of the semiconductor and contacting layers. Here we demonstrate that time-resolved photoinduced reflectance from a semiconductor captures interfacial carrier dynamics. We applied this transient photoreflectance method to study charge transfer at p-type gallium-indium phosphide (p-GaInP2) interfaces critically important to solar-driven water splitting. We monitored the formation and decay of transient electric fields that form upon photoexcitation within bare p-GaInP2, p-GaInP2/platinum (Pt), and p-GaInP2/amorphous titania (TiO2) interfaces. The data show that a field at both the p-GaInP2/Pt and p-GaInP2/TiO2 interfaces drives charge separation. Additionally, the charge recombination rate at the p-GaInP2/TiO2 interface is greatly reduced owing to its p-n nature, compared with the Schottky nature of the p-GaInP2/Pt interface.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yang, Ye -- Gu, Jing -- Young, James L -- Miller, Elisa M -- Turner, John A -- Neale, Nathan R -- Beard, Matthew C -- New York, N.Y. -- Science. 2015 Nov 27;350(6264):1061-5. doi: 10.1126/science.aad3459.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA. ye.yang@nrel.gov matt.beard@nrel.gov. ; National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA. ; National Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, CO, 80401, USA. Material Science and Engineering Program, University of Colorado, Boulder, CO, 80309, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26612947" 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: 2018-07-12
    Description: The contemporary Arctic carbon balance is uncertain, and the potential for a permafrost carbon feedback of anywhere from 50 to 200 petagrams of carbon (Schuur et al ., 2015) compromises accurate 21st-century global climate system projections. The 42-year record of atmospheric CO 2 measurements at Barrow, Alaska (71.29 N, 156.79 W), reveals significant trends in regional land-surface CO 2 anomalies (CO 2 ), indicating long-term changes in seasonal carbon uptake and respiration. Using a carbon balance model constrained by CO 2 , we find a 13.4% decrease in mean carbon residence time (50% confidence range = 9.2 to 17.6%) in North Slope tundra ecosystems during the past four decades, suggesting a transition toward a boreal carbon cycling regime. Temperature dependencies of respiration and carbon uptake suggest that increases in cold season Arctic labile carbon release will likely continue to exceed increases in net growing season carbon uptake under continued warming trends.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 7
    Publication Date: 2018-07-28
    Description: The observation and control of interweaving spin, charge, orbital, and structural degrees of freedom in materials on ultrafast time scales reveal exotic quantum phenomena and enable new active forms of nanotechnology. Bonding is the prime example of the relation between electronic and nuclear degrees of freedom. We report direct evidence illustrating that photoexcitation can be used for ultrafast control of the breaking and recovery of bonds in solids on unprecedented time scales, near the limit for nuclear motions. We describe experimental and theoretical studies of IrTe 2 using femtosecond electron diffraction and density functional theory to investigate bonding instability. Ir-Ir dimerization shows an unexpected fast dissociation and recovery due to the filling of the antibonding d xy orbital. Bond length changes of 20% in IrTe 2 are achieved by effectively addressing the bonds directly through this relaxation process. These results could pave the way to ultrafast switching between metastable structures by photoinduced manipulation of the relative degree of bonding in this manner.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 8
    Publication Date: 2018-08-28
    Description: HIV-1 intron-containing RNA expression induces innate immune activation and T cell dysfunction HIV-1 intron-containing RNA expression induces innate immune activation and T cell dysfunction, Published online: 27 August 2018; doi:10.1038/s41467-018-05899-7 Type I Interferon is thought to be a driving force for immune activation and T cell exhaustion during HIV infection. Here the authors show that intron-containing HIV RNA induces innate immune activation resulting in associated T cell dysfunction.
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
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  • 9
    Publication Date: 2016-03-19
    Description: Expansions of a hexanucleotide repeat (GGGGCC) in the noncoding region of the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Decreased expression of C9orf72 is seen in expansion carriers, suggesting that loss of function may play a role in disease. We found that two independent mouse lines lacking the C9orf72 ortholog (3110043O21Rik) in all tissues developed normally and aged without motor neuron disease. Instead, C9orf72 null mice developed progressive splenomegaly and lymphadenopathy with accumulation of engorged macrophage-like cells. C9orf72 expression was highest in myeloid cells, and the loss of C9orf72 led to lysosomal accumulation and altered immune responses in macrophages and microglia, with age-related neuroinflammation similar to C9orf72 ALS but not sporadic ALS human patient tissue. Thus, C9orf72 is required for the normal function of myeloid cells, and altered microglial function may contribute to neurodegeneration in C9orf72 expansion carriers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Rourke, J G -- Bogdanik, L -- Yanez, A -- Lall, D -- Wolf, A J -- Muhammad, A K M G -- Ho, R -- Carmona, S -- Vit, J P -- Zarrow, J -- Kim, K J -- Bell, S -- Harms, M B -- Miller, T M -- Dangler, C A -- Underhill, D M -- Goodridge, H S -- Lutz, C M -- Baloh, R H -- GM085796/GM/NIGMS NIH HHS/ -- NS069669/NS/NINDS NIH HHS/ -- NS078398/NS/NINDS NIH HHS/ -- NS087351/NS/NINDS NIH HHS/ -- UL1TR000124/TR/NCATS NIH HHS/ -- New York, N.Y. -- Science. 2016 Mar 18;351(6279):1324-9. doi: 10.1126/science.aaf1064.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA. ; The Jackson Laboratory, Bar Harbor, ME, USA. ; Division of Biomedical Sciences, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA. ; Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA. ; Board of Governors Regenerative Medicine Institute, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA. Department of Neurology, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, CA 90048, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26989253" target="_blank"〉PubMed〈/a〉
    Keywords: Aging/immunology ; Amyotrophic Lateral Sclerosis/genetics/*immunology ; Animals ; Frontotemporal Dementia/genetics/*immunology ; Gene Knockdown Techniques ; Guanine Nucleotide Exchange Factors/genetics/*physiology ; Heterozygote ; Humans ; Lymphatic Diseases/genetics/immunology ; Macrophages/*immunology ; Mice ; Mice, Knockout ; Microglia/*immunology ; Myeloid Cells/*immunology ; Proteins/genetics/*physiology ; Rats ; Splenomegaly/genetics/immunology
    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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  • 10
    Publication Date: 2018-11-02
    Description: Many ultrafast solid phase transitions are treated as chemical reactions that transform the structures between two different unit cells along a reaction coordinate, but this neglects the role of disorder. Although ultrafast diffraction provides insights into atomic dynamics during such transformations, diffraction alone probes an averaged unit cell and is less sensitive to randomness in the transition pathway. Using total scattering of femtosecond x-ray pulses, we show that atomic disordering in photoexcited vanadium dioxide (VO 2 ) is central to the transition mechanism and that, after photoexcitation, the system explores a large volume of phase space on a time scale comparable to that of a single phonon oscillation. These results overturn the current understanding of an archetypal ultrafast phase transition and provide new microscopic insights into rapid evolution toward equilibrium in photoexcited matter.
    Keywords: Materials Science, Physics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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