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  • 1
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    Detection of m/q = 2 pickup ions in the plasma environment of the Moon: The trace of exospheric H2+ (2011)
    Wiley
    Details
    Publication Date: 2011-07-16
    Description: The Solar Wind Ion Detectors (SWIDs) on the Chang'E-1 spacecraft, while orbiting the Moon, occasionally observed two continuous flux peaks with energies not exceeding 8 and 4 times that of the prevailing solar wind proton energy. These form parallel curves (PCs) with an energy ratio of 2 in the energy-time spectrogram. The fluxes of the two curves are comparable, around 10−5 ∼ 10− 4 of the solar wind flux. The pitch angle distribution of PC particles is concentrated around 90°. The velocity space distribution of PC particles shows distinct double-ring feature, suggesting the existence of a pickup ion species with m/q = 2. Pickup ions from local interstellar medium, the inner sources and the lunar exosphere are investigated. We conclude that this observation may be the first in situ evidence for H2+ ions in the lunar exosphere, thus providing new insights on the evolution and fate of solar wind hydrogen in the solar system.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Fear extinction requires ASIC1a-dependent regulation of hippocampal-prefrontal correlates (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018
    Description: 〈p〉Extinction of conditioned fear necessitates the dynamic involvement of hippocampus, medial prefrontal cortex (mPFC), and basolateral amygdala (BLA), but key molecular players that regulate these circuits to achieve fear extinction remain largely unknown. Here, we report that acid-sensing ion channel 1a (ASIC1a) is a crucial molecular regulator of fear extinction, and that this function requires ASIC1a in ventral hippocampus (vHPC), but not dorsal hippocampus, mPFC, or BLA. While genetic disruption or pharmacological inhibition of ASIC1a in vHPC attenuated the extinction of conditioned fear, overexpression of the channel in this area promoted fear extinction. Channelrhodopsin-2–assisted circuit mapping revealed that fear extinction involved an ASIC1a-dependent modification of the long-range hippocampal-prefrontal correlates in a projection-specific manner. Gene expression profiling analysis and validating experiments identified several neuronal activity–regulated and memory-related genes, including 〈i〉Fos〈/i〉, 〈i〉Npas4〈/i〉, and 〈i〉Bdnf〈/i〉, as the potential mediators of ASIC1a regulation of fear extinction. Mechanistically, genetic overexpression of brain-derived neurotrophic factor (BDNF) in vHPC or supplement of BDNF protein in mPFC both rescued the deficiency in fear extinction and the deficits on extinction-driven adaptations of hippocampal-prefrontal correlates caused by the 〈i〉Asic1a〈/i〉 gene inactivation in vHPC. Together, these results establish ASIC1a as a critical constituent in fear extinction circuits and thus a promising target for managing adaptive behaviors.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Fear extinction requires ASIC1a-dependent regulation of hippocampal-prefrontal correlates (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-10-25
    Description: Extinction of conditioned fear necessitates the dynamic involvement of hippocampus, medial prefrontal cortex (mPFC), and basolateral amygdala (BLA), but key molecular players that regulate these circuits to achieve fear extinction remain largely unknown. Here, we report that acid-sensing ion channel 1a (ASIC1a) is a crucial molecular regulator of fear extinction, and that this function requires ASIC1a in ventral hippocampus (vHPC), but not dorsal hippocampus, mPFC, or BLA. While genetic disruption or pharmacological inhibition of ASIC1a in vHPC attenuated the extinction of conditioned fear, overexpression of the channel in this area promoted fear extinction. Channelrhodopsin-2–assisted circuit mapping revealed that fear extinction involved an ASIC1a-dependent modification of the long-range hippocampal-prefrontal correlates in a projection-specific manner. Gene expression profiling analysis and validating experiments identified several neuronal activity–regulated and memory-related genes, including Fos , Npas4 , and Bdnf , as the potential mediators of ASIC1a regulation of fear extinction. Mechanistically, genetic overexpression of brain-derived neurotrophic factor (BDNF) in vHPC or supplement of BDNF protein in mPFC both rescued the deficiency in fear extinction and the deficits on extinction-driven adaptations of hippocampal-prefrontal correlates caused by the Asic1a gene inactivation in vHPC. Together, these results establish ASIC1a as a critical constituent in fear extinction circuits and thus a promising target for managing adaptive behaviors.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Catching jetted tidal disruption events early in millimetre (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-20
    Description: Relativistic jets can form from at least some tidal disruption events (TDEs) of (sub-)stellar objects around supermassive black holes. We detect the millimetre (MM) emission of IGR J12580+0134 – the nearest TDE known in the galaxy NGC 4845 at the distance of only 17 Mpc, based on Planck all-sky survey data. The data show significant flux jumps after the event, followed by substantial declines, in all six high-frequency Planck bands from 100 to 857 GHz. We further show that the evolution of the MM flux densities is well consistent with our model prediction from an off-axis jet, as was initially suggested from radio and X-ray observations. This detection represents the second TDE with MM detections; the other is Sw J1644+57, an on-axis jetted TDE at redshift of 0.35. Using the on- and off-axis jet models developed for these two TDEs as templates, we estimate the detection potential of similar events with the Large Millimeter Telescope (LMT) and the Atacama Large Millimeter/submillimeter Array (ALMA). Assuming an exposure of 1 h, we find that the LMT (ALMA) can detect jetted TDEs up to redshifts z ~ 1 (2), for a typical disrupted star mass of ~1 M . The detection rates of on- and off-axis TDEs can be as high as ~0.6 (13) and 10 (220) yr –1 , respectively, for the LMT (ALMA). We briefly discuss how such observations, together with follow-up radio monitoring, may lead to major advances in understanding the jetted TDEs themselves and the ambient environment of the circumnuclear medium.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Characterization of the Haagerup property by fibred coarse embedding into Hilbert space (2013)
    Oxford University Press
    Details
    Publication Date: 2013-09-13
    Description: We show that a finitely generated, residually finite group has the Haagerup property (Gromov's a-T-menability) if and only if one (or equivalently, all) of its box spaces admits a fibred coarse embedding into Hilbert space. In contrast, the box spaces of a finitely generated, residually finite hyperbolic group with property (T) do not admit a fibred coarse embedding into Hilbert space, but do admit a fibred coarse embedding into an p -space for some p 〉2.
    Print ISSN: 0024-6093
    Electronic ISSN: 1469-2120
    Topics: Mathematics
    Published by Oxford University Press
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  • 6
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    A systematic Chandra study of Sgr A* - I. X-ray flare detection (2015)
    Oxford University Press
    Details
    Publication Date: 2015-12-25
    Description: Daily X-ray flaring represents an enigmatic phenomenon of Sagittarius A * (Sgr A * ) – the supermassive black hole at the centre of our Galaxy. We report initial results from a systematic X-ray study of this phenomenon, based on extensive Chandra observations obtained from 1999 to 2012, totalling about 4.5 Ms. We detect flares, using a combination of the maximum likelihood and Markov Chain Monte Carlo methods, which allow for a direct accounting for the pileup effect in the modelling of the flare light curves and an optimal use of the data, as well as the measurements of flare parameters, including their uncertainties. A total of 82 flares are detected. About one third of them are relatively faint, which were not detected previously. The observation-to-observation variation of the quiescent emission has an average root-mean-square of 6–14 per cent, including the Poisson statistical fluctuation of faint flares below our detection limits. We find no significant long-term variation in the quiescent emission and the flare rate over the 14 years. In particular, we see no evidence of changing quiescent emission and flare rate around the pericentre passage of the S2 star around 2002. We show clear evidence of a short-term clustering for the Advanced CCD Imaging Spectrometer - Spectroscopy array/high energy transmission gratings 0th-order flares on time-scale of 20–70 ks. We further conduct detailed simulations to characterize the detection incompleteness and bias, which is critical to a comprehensive follow-up statistical analysis of flare properties. These studies together will help to establish Sgr A * as a unique laboratory to understand the astrophysics of prevailing low-luminosity black holes in the Universe.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Atmospheric 14C/12C changes during the last glacial period from Hulu Cave (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018
    Description: 〈p〉Paired measurements of 〈sup〉14〈/sup〉C/〈sup〉12〈/sup〉C and 〈sup〉230〈/sup〉Th ages from two Hulu Cave stalagmites complete a precise record of atmospheric 〈sup〉14〈/sup〉C covering the full range of the 〈sup〉14〈/sup〉C dating method (~54,000 years). Over the last glacial period, atmospheric 〈sup〉14〈/sup〉C/〈sup〉12〈/sup〉C ranges from values similar to modern values to values 1.70 times higher (42,000 to 39,000 years ago). The latter correspond to 〈sup〉14〈/sup〉C ages 5200 years less than calibrated ages and correlate with the Laschamp geomagnetic excursion followed by Heinrich Stadial 4. Millennial-scale variations are largely attributable to Earth’s magnetic field changes and in part to climate-related changes in the oceanic carbon cycle. A progressive shift to lower 〈sup〉14〈/sup〉C/〈sup〉12〈/sup〉C values between 25,000 and 11,000 years ago is likely related, in part, to progressively increasing ocean ventilation rates.〈/p〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Azimuthal anisotropy of the crust and uppermost mantle in northeast North China Craton from inversion of Rayleigh wave phase velocity (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-26
    Description: We imaged the azimuthal anisotropy of Rayleigh wave phase velocity (10–60 s) in northeast North China Craton using the teleseismic data recorded by a dense temporary array, and then inverted for the 3-D azimuthal anisotropy of the crust and uppermost mantle (20–110 km). The results reveal that the azimuthal anisotropy varies both horizontally and vertically. Obvious stratified azimuthal anisotropy is shown in the Central Orogenic Belt, where the fast direction is NE–SW to NNE–SSW in the depth range of 20–40 km and changes to NW–SE to NWW–SEE in the depth range of 60–110 km. In the depth range of 30–40 km, a prominent low velocity belt is shown on the southwest of Zhangjiakou-Penglai fault zone (ZPFZ) and the fast direction is subparallel to the strike of the low velocity belt. Distinct lateral variations of azimuthal anisotropy are clearly shown at 110 km. Our results provide new evidence for the existence of upwelling asthenosphere beneath the Datong volcano and support the assumption that ZPFZ may act as the channel of upwelling asthenosphere. Historical strong earthquakes ( M ≥ 6.0) mainly occurred in the transition zone between low and high velocity anomalies in the upper and middle crust. The upwelling asthenosphere may prompt the generation of large earthquake.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 9
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    Tuning the band gap and magnetic properties of BN sheets impregnated with graphene flakes (2011)
    American Physical Society (APS)
    Details
    Publication Date: 2011-11-12
    Description: Author(s): M. Kan, J. Zhou, Q. Wang, Q. Sun, and P. Jena [Phys. Rev. B 84, 205412] Published Fri Nov 11, 2011
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 10
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    Alternative reading frame selection mediated by a tRNA-like domain of an internal ribosome entry site [Biochemistry] (2012)
    National Academy of Sciences
    Details
    Publication Date: 2012-03-14
    Description: The dicistrovirus intergenic region internal ribosome entry site (IRES) utilizes a unique mechanism, involving P-site tRNA mimicry, to directly assemble 80S ribosomes and initiate translation at a specific non-AUG codon in the ribosomal A site. A subgroup of dicistrovirus genomes contains an additional stem-loop 5′-adjacent to the IRES and a short open reading frame (ORFx) that overlaps the viral structural polyprotein ORF (ORF2) in the +1 reading frame. Using mass spectrometry and extensive mutagenesis, we show that, besides directing ORF2 translation, the Israeli acute paralysis dicistrovirus IRES also directs ORFx translation. The latter is mediated by a U∶G base pair adjacent to the P-site tRNA-mimicking domain. An ORFx peptide was detected in virus-infected honey bees by multiple reaction monitoring mass spectrometry. Finally, the 5′ stem-loop increases IRES activity and may couple translation of the two major ORFs of the virus. This study reveals a novel viral strategy in which a tRNA-like IRES directs precise, initiator Met-tRNA-independent translation of two overlapping ORFs.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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