ALBERT

Description: Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A 'renoxification' process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth's surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ye, Chunxiang -- Zhou, Xianliang -- Pu, Dennis -- Stutz, Jochen -- Festa, James -- Spolaor, Max -- Tsai, Catalina -- Cantrell, Christopher -- Mauldin, Roy L 3rd -- Campos, Teresa -- Weinheimer, Andrew -- Hornbrook, Rebecca S -- Apel, Eric C -- Guenther, Alex -- Kaser, Lisa -- Yuan, Bin -- Karl, Thomas -- Haggerty, Julie -- Hall, Samuel -- Ullmann, Kirk -- Smith, James N -- Ortega, John -- Knote, Christoph -- England -- Nature. 2016 Apr 28;532(7600):489-91. doi: 10.1038/nature17195. Epub 2016 Apr 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Wadsworth Center, New York State Department of Health, Albany, New York, USA. ; Department of Environmental Health Sciences, State University of New York, Albany, New York, USA. ; Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles (UCLA), California, USA. ; Department of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, Colorado, USA. ; Department of Physics, University of Helsinki, Helsinki, Finland. ; National Center for Atmospheric Research, Boulder, Colorado, USA. ; Pacific Northwest National Laboratory, Richland, Washington, USA. ; NOAA, Earth System Research Laboratory, Chemical Sciences Division, Boulder, Colorado, USA. ; Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, USA. ; Institute for Meteorology and Geophysics, University of Innsbruck, Innsbruck, Austria. ; University of Eastern Finland, Kuopio, Finland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27064904" target="_blank"〉PubMed〈/a〉

Description: In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 +/- 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of OmegaIGM = 4.9 +/- 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short gamma-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keane, E F -- Johnston, S -- Bhandari, S -- Barr, E -- Bhat, N D R -- Burgay, M -- Caleb, M -- Flynn, C -- Jameson, A -- Kramer, M -- Petroff, E -- Possenti, A -- van Straten, W -- Bailes, M -- Burke-Spolaor, S -- Eatough, R P -- Stappers, B W -- Totani, T -- Honma, M -- Furusawa, H -- Hattori, T -- Morokuma, T -- Niino, Y -- Sugai, H -- Terai, T -- Tominaga, N -- Yamasaki, S -- Yasuda, N -- Allen, R -- Cooke, J -- Jencson, J -- Kasliwal, M M -- Kaplan, D L -- Tingay, S J -- Williams, A -- Wayth, R -- Chandra, P -- Perrodin, D -- Berezina, M -- Mickaliger, M -- Bassa, C -- England -- Nature. 2016 Feb 25;530(7591):453-6. doi: 10.1038/nature17140.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Square Kilometre Array Organisation, Jodrell Bank Observatory, SK11 9DL, UK. ; Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H29, PO Box 218, Victoria 3122, Australia. ; Australian Research Council Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia. ; Commonwealth Science and Industrial Research Organisation (CSIRO), Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, New South Wales 1710, Australia. ; International Centre for Radio Astronomy Research, Curtin University, Bentley, Western Australia 6102, Australia. ; Instituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (CA), Italy. ; Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory 2611, Australia. ; Max-Planck-Institut fur Radioastronomie (MPIfR), Auf dem Hugel 69, D-53121 Bonn, Germany. ; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK. ; National Radio Astronomy Observatory, Socorro, New Mexico, USA. ; Department of Astronomy, the University of Tokyo, Hongo, Tokyo 113-0033, Japan. ; National Astronomical Observatory of Japan, 2 Chome-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan. ; Department of Astronomical Science, SOKENDAI (Graduate University for the Advanced Study), Osawa, Mitaka 181-8588, Japan. ; Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, Hawaii 96720, USA. ; Institute of Astronomy, Graduate School of Science, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan. ; Kavli Institute for the Physics and Mathematics of the Universe (WPI), Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583, Japan. ; Department of Physics, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Kobe, Hyogo 658-8501, Japan. ; Cahill Center for Astrophysics, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, USA. ; Department of Physics, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53201, USA. ; National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Ganeshkhind, Pune 411 007, India. ; ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo, The Netherlands.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26911781" target="_blank"〉PubMed〈/a〉