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  • 1
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    Frequency doubling and field-aligned ion streaming in a long-period poloidal pulsation (2013)
    Wiley
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    Publikationsdatum: 2013-01-03
    Beschreibung: [1]  We reexamine a long-period (10–18 min) poloidal pulsation observed by THEMIS-A in the outer dawn magnetosphere from 10:00 to 12:30 UT on 7 November 2007. The interval was originally reported by Korotova et al. (2009). Although the nonlinear compressional plasma and magnetic field perturbations observed by THEMIS-A during this interval agree well with model predictions for the linear perturbations associated with antisymmetric waves generated by the ballooning-mirror mode instability, the phase relationships between these perturbations indicates a complex frequency rather than the purely imaginary frequency that theory predicts for the outer dawnside magnetosphere. Variations in the radial plasma velocity confirm that a phase-locked north/south oscillation in the equatorial line of nodes associated with the ballooning-mirror mode waves doubles the frequency of the compressional component of the magnetic field during these pulsations. The same velocity and magnetic field perturbations exclude explanations for the frequency doubling in terms of spatial gradients sweeping back and forth across the spacecraft or drift-bounce resonances. Azimuthal electric fields associated with the pulsations generate field-aligned anisotropies in the pitch angle distributions that become more prominent with increasing ion energy due to the presence of drift-shell splitting and radial flux gradients that steepen with increasing energy. Although there was no evidence for drift-bounce interactions during this event, the role of such events in ion energization in other events and at other locations remains to be evaluated.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 2
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    First observations of foreshock bubbles upstream of Earth's bow shock: Characteristics and comparisons to HFAs (2013)
    Wiley
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    Publikationsdatum: 2013-02-27
    Beschreibung: [1]  Using multipoint in situ observations upstream of Earth's bow shock from the THEMIS mission, we present the first observations of foreshock bubbles (FBs) and compare them to observations of hot flow anomalies (HFAs). FBs are recently conceptualized kinetic phenomena that can form under the commonplace condition of a rotational discontinuity in the IMF interacting with backstreaming energetic ions in Earth's quasi-parallel foreshock. FBs may have remained elusive until now due to their many observational similarities to HFAs and the lack of coordinated multipoint measurements. Here, we introduce identification criteria for distinguishing between HFAs and FBs using in situ observations, and use them to analyze five example events that occurred on Bastille Day (14 July) and 11-12 August 2008. Three of these events satisfy the criteria for FBs and are inconsistent with multiple criteria for HFAs. The remaining two events are consistent with the traditional picture of HFAs. Furthermore, FBs involve two converging shocks, and using these events, we demonstrate their effectiveness at particle acceleration. Considering that their formation conditions are not extraordinary, FBs may be ubiquitous at collisionless, quasi-parallel shocks in a variety of astrophysical settings.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 3
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    The role of transient ion foreshock phenomena in driving Pc5 ULF wave activity (2013)
    Wiley
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    Publikationsdatum: 2013-02-01
    Beschreibung: [1]  The ion foreshock is a source of energy for magnetospheric ULF waves, but it is usually only considered effective at driving ULF waves with frequencies above the Pc5 (2–7 mHz) range. We present observations for an 8 h high speed solar wind interval on 14 July 2008 during which three distinct types of transient ion foreshock phenomena (TIFP) were observed just upstream of the dayside bow shock. We demonstrate that TIFP generate global magnetospheric Pc5 ULF waves with amplitudes as large as 10 mV/m in the electric field and 10 nT in the magnetic field. We characterize the magnetospheric ULF response to several different TIFP that occur during this interval, including the first report of the ULF response to a foreshock bubble. Using a novel spacecraft configuration, we find that the local time with the highest Pc5 wave amplitude is closely related to the location of the ion foreshock. Statistical studies of Pc5 ULF wave activity, other case studies of ULF waves driven by processes in the ion foreshock, and recent theoretical and simulation work on TIFP place these results in context: TIFP are an important energy source for Pc5 ULF waves in the magnetosphere.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 4
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    First Results from CSSWE CubeSat: Characteristics of Relativistic Electrons in the Near-Earth Environment During the October 2012 Magnetic Storms (2013)
    Wiley
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    Publikationsdatum: 2013-10-13
    Beschreibung: [1]  Measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat mission, which was launched into a highly inclined (65°) low Earth orbit (LEO), are analyzed along with measurements from the Relativistic Electron and Proton Telescope (REPT) and the Magnetic Electron Ion Spectrometer (MagEIS) instruments aboard the Van Allen Probes, which are in a low inclination (10°) geo-transfer-like orbit. Both REPT and MagEIS measure the full distribution of energetic electrons as they traverse the heart of the outer radiation belt. However, due to the small equatorial loss cone (only a few degrees), it is difficult for REPT and MagEIS to directly determine which electrons will precipitate into the atmosphere, a major radiation belt loss process. REPTile, a miniaturized version of REPT, measures the fraction of the total electron population that has small enough equatorial pitch angles to reach the altitude of CSSWE, 480 km x 780 km, thus measuring the precipitating population as well as the trapped and quasi-trapped populations. These newly available measurements provide an unprecedented opportunity to investigate the source, loss, and energization processes that are responsible for the dynamic behavior of outer radiation belt electrons. The focus of this paper will be on the characteristics of relativistic electrons measured by REPTile during the October 2012 storms; also included are long-term measurements from the Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) to put this study into context.
    Print ISSN: 0148-0227
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 5
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    A non-storm time enhancement of relativistic electrons in the outer radiation belt (2013)
    Wiley
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    Publikationsdatum: 2013-12-03
    Beschreibung: ABSTRACT [1]  Despite the lack of a geomagnetic storm (based on the Dst index), relativistic electron fluxes were enhanced over 2.5 orders of magnitude in the outer radiation belt in 13 hours on January 13-14, 2013. The unusual enhancement was observed by MagEIS, onboard the Van Allen Probes; REPTile, onboard the Colorado Student Space Weather Experiment (CSSWE); and SST, onboard THEMIS. Analyses of MagEIS phase space density (PSD) profiles show a positive outward radial gradient from 4 〈 L 〈 5.5. However, THEMIS observations show a peak in PSD outside of the Van Allen Probes’ apogee, which suggest a very interesting scenario: wave-particle interactions causing a PSD peak at ~ L* = 5.5 from where the electrons are then rapidly transported radially inward. This letter demonstrates, for the first time in detail, that geomagnetic storms are not necessary for causing dramatic enhancements in the outer radiation belt.
    Print ISSN: 0094-8276
    Digitale ISSN: 1944-8007
    Thema: Geologie und Paläontologie , Physik
    Publiziert von Wiley im Namen von American Geophysical Union (AGU).
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  • 6
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    Electromagnetic energy conversion at reconnection fronts (2013)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2013-09-28
    Beschreibung: Earth's magnetotail contains magnetic energy derived from the kinetic energy of the solar wind. Conversion of that energy back to particle energy ultimately powers Earth's auroras, heats the magnetospheric plasma, and energizes the Van Allen radiation belts. Where and how such electromagnetic energy conversion occurs has been unclear. Using a conjunction between eight spacecraft, we show that this conversion takes place within fronts of recently reconnected magnetic flux, predominantly at 1- to 10-electron inertial length scale, intense electrical current sheets (tens to hundreds of nanoamperes per square meter). Launched continually during intervals of geomagnetic activity, these reconnection outflow flux fronts convert ~10 to 100 gigawatts per square Earth radius of power, consistent with local magnetic flux transport, and a few times 10(15) joules of magnetic energy, consistent with global magnetotail flux reduction.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Angelopoulos, V -- Runov, A -- Zhou, X-Z -- Turner, D L -- Kiehas, S A -- Li, S-S -- Shinohara, I -- New York, N.Y. -- Science. 2013 Sep 27;341(6153):1478-82. doi: 10.1126/science.1236992.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Planetary and Space Sciences and Institute of Geophysics and Planetary Physics, University of California Los Angeles, Los Angeles, CA 90095-1567, USA. vassilis@ucla.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24072917" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 7
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    Electron acceleration in the heart of the Van Allen radiation belts (2013)
    American Association for the Advancement of Science (AAAS)
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    Publikationsdatum: 2013-07-28
    Beschreibung: The Van Allen radiation belts contain ultrarelativistic electrons trapped in Earth's magnetic field. Since their discovery in 1958, a fundamental unanswered question has been how electrons can be accelerated to such high energies. Two classes of processes have been proposed: transport and acceleration of electrons from a source population located outside the radiation belts (radial acceleration) or acceleration of lower-energy electrons to relativistic energies in situ in the heart of the radiation belts (local acceleration). We report measurements from NASA's Van Allen Radiation Belt Storm Probes that clearly distinguish between the two types of acceleration. The observed radial profiles of phase space density are characteristic of local acceleration in the heart of the radiation belts and are inconsistent with a predominantly radial acceleration process.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reeves, G D -- Spence, H E -- Henderson, M G -- Morley, S K -- Friedel, R H W -- Funsten, H O -- Baker, D N -- Kanekal, S G -- Blake, J B -- Fennell, J F -- Claudepierre, S G -- Thorne, R M -- Turner, D L -- Kletzing, C A -- Kurth, W S -- Larsen, B A -- Niehof, J T -- New York, N.Y. -- Science. 2013 Aug 30;341(6149):991-4. doi: 10.1126/science.1237743. Epub 2013 Jul 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Space Science and Applications Group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. reeves@lanl.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23887876" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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  • 8
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    Severe malaria is associated with parasite binding to endothelial protein C receptor (2013)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2013-06-07
    Beschreibung: Sequestration of Plasmodium falciparum-infected erythrocytes in host blood vessels is a key triggering event in the pathogenesis of severe childhood malaria, which is responsible for about one million deaths every year. Sequestration is mediated by specific interactions between members of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family and receptors on the endothelial lining. Severe childhood malaria is associated with expression of specific PfEMP1 subtypes containing domain cassettes (DCs) 8 and 13 (ref. 3), but the endothelial receptor for parasites expressing these proteins was unknown. Here we identify endothelial protein C receptor (EPCR), which mediates the cytoprotective effects of activated protein C, as the endothelial receptor for DC8 and DC13 PfEMP1. We show that EPCR binding is mediated through the amino-terminal cysteine-rich interdomain region (CIDRalpha1) of DC8 and group A PfEMP1 subfamilies, and that CIDRalpha1 interferes with protein C binding to EPCR. This PfEMP1 adhesive property links P. falciparum cytoadhesion to a host receptor involved in anticoagulation and endothelial cytoprotective pathways, and has implications for understanding malaria pathology and the development of new malaria interventions.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3870021/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3870021/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Turner, Louise -- Lavstsen, Thomas -- Berger, Sanne S -- Wang, Christian W -- Petersen, Jens E V -- Avril, Marion -- Brazier, Andrew J -- Freeth, Jim -- Jespersen, Jakob S -- Nielsen, Morten A -- Magistrado, Pamela -- Lusingu, John -- Smith, Joseph D -- Higgins, Matthew K -- Theander, Thor G -- G0901062/Medical Research Council/United Kingdom -- R01 AI047953/AI/NIAID NIH HHS/ -- R01 AI47953/AI/NIAID NIH HHS/ -- U19 AI089688/AI/NIAID NIH HHS/ -- Medical Research Council/United Kingdom -- England -- Nature. 2013 Jun 27;498(7455):502-5. doi: 10.1038/nature12216. Epub 2013 Jun 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre for Medical Parasitology, Department of International Health, Immunology & Microbiology, University of Copenhagen and Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark. lturner@sund.ku.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23739325" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Animals ; Antigens, CD/*metabolism ; Blood Coagulation ; Brain/blood supply ; CHO Cells ; Cell Adhesion ; Cell Line ; Cricetinae ; Endothelial Cells/metabolism ; Erythrocyte Membrane/metabolism ; Humans ; Inflammation/complications/parasitology/pathology ; Malaria, Falciparum/complications/*parasitology/*pathology ; Microcirculation ; Plasmodium falciparum/chemistry/*metabolism/pathogenicity ; Protozoan Proteins/chemistry/metabolism ; Receptors, Cell Surface/*metabolism
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 9
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    PfSETvs methylation of histone H3K36 represses virulence genes in Plasmodium falciparum (2013)
    Nature Publishing Group (NPG)
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    Publikationsdatum: 2013-07-05
    Beschreibung: The variant antigen Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1), which is expressed on the surface of P. falciparum-infected red blood cells, is a critical virulence factor for malaria. Each parasite has 60 antigenically distinct var genes that each code for a different PfEMP1 protein. During infection the clonal parasite population expresses only one gene at a time before switching to the expression of a new variant antigen as an immune-evasion mechanism to avoid the host antibody response. The mechanism by which 59 of the 60 var genes are silenced remains largely unknown. Here we show that knocking out the P. falciparum variant-silencing SET gene (here termed PfSETvs), which encodes an orthologue of Drosophila melanogaster ASH1 and controls histone H3 lysine 36 trimethylation (H3K36me3) on var genes, results in the transcription of virtually all var genes in the single parasite nuclei and their expression as proteins on the surface of individual infected red blood cells. PfSETvs-dependent H3K36me3 is present along the entire gene body, including the transcription start site, to silence var genes. With low occupancy of PfSETvs at both the transcription start site of var genes and the intronic promoter, expression of var genes coincides with transcription of their corresponding antisense long noncoding RNA. These results uncover a previously unknown role of PfSETvs-dependent H3K36me3 in silencing var genes in P. falciparum that might provide a general mechanism by which orthologues of PfSETvs repress gene expression in other eukaryotes. PfSETvs knockout parasites expressing all PfEMP1 proteins may also be applied to the development of a malaria vaccine.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3770130/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3770130/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jiang, Lubin -- Mu, Jianbing -- Zhang, Qingfeng -- Ni, Ting -- Srinivasan, Prakash -- Rayavara, Kempaiah -- Yang, Wenjing -- Turner, Louise -- Lavstsen, Thomas -- Theander, Thor G -- Peng, Weiqun -- Wei, Guiying -- Jing, Qingqing -- Wakabayashi, Yoshiyuki -- Bansal, Abhisheka -- Luo, Yan -- Ribeiro, Jose M C -- Scherf, Artur -- Aravind, L -- Zhu, Jun -- Zhao, Keji -- Miller, Louis H -- 250320/European Research Council/International -- Z01 AI000241-27/Intramural NIH HHS/ -- ZIA AI000241-31/Intramural NIH HHS/ -- England -- Nature. 2013 Jul 11;499(7457):223-7. doi: 10.1038/nature12361. Epub 2013 Jul 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Key Laboratory of Molecular Virology & Immunology, Unit of Human Parasite Molecular and Cell Biology, Institut Pasteur of Shanghai, Shanghai 200031, China. lbjiang@ips.ac.cn〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23823717" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): DNA-Binding Proteins ; Drosophila Proteins ; Erythrocytes/cytology/metabolism/parasitology ; *Gene Silencing ; Genes, Protozoan/genetics ; Histones/chemistry/*metabolism ; Introns/genetics ; Lysine/metabolism ; Malaria Vaccines/genetics ; Methylation ; Plasmodium falciparum/*genetics/metabolism/*pathogenicity ; Promoter Regions, Genetic/genetics ; Protozoan Proteins/genetics/*metabolism ; RNA, Long Noncoding/genetics ; Transcription Factors ; Transcription Initiation Site ; Virulence/genetics ; Virulence Factors/*genetics
    Print ISSN: 0028-0836
    Digitale ISSN: 1476-4687
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von Nature Publishing Group (NPG)
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  • 10
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    Climate change. Hell and high water: practice-relevant adaptation science (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publikationsdatum: 2013-11-10
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moss, R H -- Meehl, G A -- Lemos, M C -- Smith, J B -- Arnold, J R -- Arnott, J C -- Behar, D -- Brasseur, G P -- Broomell, S B -- Busalacchi, A J -- Dessai, S -- Ebi, K L -- Edmonds, J A -- Furlow, J -- Goddard, L -- Hartmann, H C -- Hurrell, J W -- Katzenberger, J W -- Liverman, D M -- Mote, P W -- Moser, S C -- Kumar, A -- Pulwarty, R S -- Seyller, E A -- Turner, B L 2nd -- Washington, W M -- Wilbanks, T J -- New York, N.Y. -- Science. 2013 Nov 8;342(6159):696-8. doi: 10.1126/science.1239569.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24202163" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Climate Change ; *Disaster Planning ; *Floods ; Research/*organization & administration ; United States
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Publiziert von American Association for the Advancement of Science (AAAS)
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