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  • 1
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    The dynamics of short-scale turbulent fluctuations across low-intermediate-high-confinement transition with lower hybrid current drive in the EAST superconducting tokamak (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-02-07
    Description: Two different confinement transition discharges, the low-intermediate-high (L-I-H) and the low-intermediate-low (L-I-L) confinement transitions, respectively, have been obtained by lower hybrid current drive with lithium wall conditioning in the EAST superconducting tokamak. The dynamic features of short-scale turbulent fluctuations in the two discharges are investigated by a tangential CO 2 laser collective scattering system. It is found that the great changes of broadband fluctuations in amplitude and structure characteristics are closely related to the choice of the final transition to H-mode. These results could shed light on the understanding of the L-H transition mechanism.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Neuronal circuitry mechanism regulating adult quiescent neural stem-cell fate decision (2012)
    Nature Publishing Group (NPG)
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    Publication Date: 2012-07-31
    Description: Adult neurogenesis arises from neural stem cells within specialized niches. Neuronal activity and experience, presumably acting on this local niche, regulate multiple stages of adult neurogenesis, from neural progenitor proliferation to new neuron maturation, synaptic integration and survival. It is unknown whether local neuronal circuitry has a direct impact on adult neural stem cells. Here we show that, in the adult mouse hippocampus, nestin-expressing radial glia-like quiescent neural stem cells (RGLs) respond tonically to the neurotransmitter gamma-aminobutyric acid (GABA) by means of gamma2-subunit-containing GABAA receptors. Clonal analysis of individual RGLs revealed a rapid exit from quiescence and enhanced symmetrical self-renewal after conditional deletion of gamma2. RGLs are in close proximity to terminals expressing 67-kDa glutamic acid decarboxylase (GAD67) of parvalbumin-expressing (PV+) interneurons and respond tonically to GABA released from these neurons. Functionally, optogenetic control of the activity of dentate PV+ interneurons, but not that of somatostatin-expressing or vasoactive intestinal polypeptide (VIP)-expressing interneurons, can dictate the RGL choice between quiescence and activation. Furthermore, PV+ interneuron activation restores RGL quiescence after social isolation, an experience that induces RGL activation and symmetrical division. Our study identifies a niche cell-signal-receptor trio and a local circuitry mechanism that control the activation and self-renewal mode of quiescent adult neural stem cells in response to neuronal activity and experience.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3438284/" 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/PMC3438284/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Song, Juan -- Zhong, Chun -- Bonaguidi, Michael A -- Sun, Gerald J -- Hsu, Derek -- Gu, Yan -- Meletis, Konstantinos -- Huang, Z Josh -- Ge, Shaoyu -- Enikolopov, Grigori -- Deisseroth, Karl -- Luscher, Bernhard -- Christian, Kimberly M -- Ming, Guo-li -- Song, Hongjun -- AG040209/AG/NIA NIH HHS/ -- HD069184/HD/NICHD NIH HHS/ -- MH089111/MH/NIMH NIH HHS/ -- NS048271/NS/NINDS NIH HHS/ -- R01 AG040209/AG/NIA NIH HHS/ -- R01 HD069184/HD/NICHD NIH HHS/ -- R01 NS047344/NS/NINDS NIH HHS/ -- R01 NS048271/NS/NINDS NIH HHS/ -- R01 NS065915/NS/NINDS NIH HHS/ -- R21 ES021957/ES/NIEHS NIH HHS/ -- R56 NS047344/NS/NINDS NIH HHS/ -- England -- Nature. 2012 Sep 6;489(7414):150-4. doi: 10.1038/nature11306.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22842902" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Cell Lineage/drug effects ; Cell Proliferation/drug effects ; Dentate Gyrus/cytology/drug effects/metabolism ; Female ; GABA Modulators/pharmacology ; GABA-A Receptor Agonists/pharmacology ; GABA-A Receptor Antagonists/pharmacology ; Interneurons/cytology/drug effects/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Neural Pathways/drug effects/*physiology ; Neural Stem Cells/*cytology/drug effects/metabolism ; *Neurogenesis/drug effects ; Neuroglia/cytology/drug effects/metabolism ; Parvalbumins/metabolism ; Receptors, GABA-A/metabolism ; Signal Transduction/drug effects ; Somatostatin/metabolism ; Stem Cell Niche/drug effects/physiology ; Vasoactive Intestinal Peptide/metabolism ; gamma-Aminobutyric Acid/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 3
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    Tangential migration of glutamatergic neurons [Neuroscience] (2015)
    National Academy of Sciences
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    Publication Date: 2015-07-29
    Description: In a classic model of mammalian brain formation, precursors of principal glutamatergic neurons migrate radially along radial glia fibers whereas GABAergic interneuron precursors migrate tangentially. These migration modes have significant implications for brain function. Here we used clonal lineage tracing of active radial glia-like neural stem cells in the adult...
    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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  • 4
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    Anomalous independence of interface superconductivity from carrier density (2013)
    Springer Nature
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    Publication Date: 2013-09-24
    Description: Nature Materials 12, 877 (2013). doi:10.1038/nmat3719 Authors: J. Wu, O. Pelleg, G. Logvenov, A. T. Bollinger, Y-J. Sun, G. S. Boebinger, M. Vanević, Z. Radović & I. Božović The recent discovery of superconductivity at the interface of two non-superconducting materials has received much attention. In cuprate bilayers, the critical temperature (Tc) can be significantly enhanced compared with single-phase samples. Several explanations have been proposed, invoking Sr interdiffusion, accumulation and depletion of mobile charge carriers, elongation of the copper-to-apical-oxygen bond length, or a beneficial crosstalk between a material with a high pairing energy and another with a large phase stiffness. From each of these models, one would predict Tc to depend strongly on the carrier density in the constituent materials. Here, we study combinatorial libraries of La2−xSrxCuO4–La2CuO4 bilayer samples—an unprecedentedly large set of more than 800 different compositions. The doping level x spans a wide range, 0.15 〈 x 〈 0.47, and the measured Hall coefficient varies by one order of magnitude. Nevertheless, across the entire sample set, Tc stays essentially constant at about 40 K. We infer that doping up to the optimum level does not shift the chemical potential, unlike in ordinary Fermi liquids. This result poses a new challenge to theory—cuprate superconductors have not run out of surprises.
    Print ISSN: 1476-1122
    Electronic ISSN: 1476-4660
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 5
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    Long-Term Effects of Peatland Cultivation on Soil Physical and Hydraulic Properties: Case Study in Canada (2015)
    Soil Science Society of America (SSSA)
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    Publication Date: 2015-06-17
    Description: Organic soils are an excellent substrate for commercial lettuce ( Lactuca sativa L.) farming; however, drainage accelerates oxidation of the surface layer and reduces the water holding capacity, which is often lethal for crops that are sensitive to water stress. In this case study, we analyzed 942 peat samples from a large cultivated peatland complex (18.7 km 2 ) in southern Quebec, Canada, and demonstrated from spatial and temporal patterns that agriculture resulted in a compacted layer below the root zone. We grouped the samples based on the year in which the corresponding fields were created on the previously undisturbed peatland (cutoff years 1970, 1980, 1990, and 2000) and discovered that bulk density has continued to increase, partly due to the overburden pressure, while organic matter has continued to decline since the fields were reclaimed and drained in phases between 1955 and 2006. Saturated hydraulic conductivity ( K s ) in the upper 20 cm was remarkably lower on fields older than 10 yr ( p = 0.0973 for Wilcoxon rank test), with more samples having a K s 〈 2.0 x 10 –3 yr. Soil water available capacity (SWAC) was between approximately 5 and 33 cm on fields reclaimed after 2000, while samples from fields reclaimed before 2000 had a lower SWAC between 2 and 23 cm (groups discernable at p = 0.0203). It is possible, however, that the greatest rate of change in K s and SWAC occurred within even a year of reclamation. The results of this study call for active measures to reduce organic soil degradation such as reducing tillage and on-field traffic or following a crop rotation scheme.
    Electronic ISSN: 1539-1663
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Soil Science Society of America (SSSA)
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  • 6
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    A vanished history of skeletonization in Cambrian comb jellies (2015)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2015-07-12
    Description: Ctenophores are traditionally regarded as "lower" metazoans, sharing with cnidarians a diploblastic grade of organization. Unlike cnidarians, where skeletonization (biomineralization and sclerotization) evolved repeatedly among ecologically important taxa (for example, scleractinians and octocorals), living ctenophores are characteristically soft-bodied animals. We report six sclerotized and armored ctenophores from the early Cambrian period. They have diagnostic ctenophore features (for example, an octamerous symmetry, oral-aboral axis, aboral sense organ, and octaradially arranged ctene rows). Unlike most modern counterparts, however, they lack tentacles, have a sclerotized framework, and have eight pairs of ctene rows. They are resolved as a monophyletic group (Scleroctenophora new class) within the ctenophores. This clade reveals a cryptic history and sheds new light on the early evolution of this basal animal phylum. Skeletonization also occurs in some other Cambrian animal groups whose extant members are exclusively soft-bodied, suggesting the ecological importance of skeletonization in the Cambrian explosion.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    A thin-sheet model for global electromagnetic induction (2012)
    Oxford University Press
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    Publication Date: 2012-02-16
    Description: SUMMARY We consider the frequency domain electromagnetic (EM) induction problem in a layered spherical Earth overlain by an inhomogeneous thin sheet of finite conductance, and derive an integral equation for the secondary electric fields resulting from surface conductivity variations. The Green’s function kernel of the integral equation is singular, and must in practice be regularized for a numerical treatment. We compare two approaches: truncation of the spherical harmonic representation of the Green’s function, and projection onto a discrete spatial grid, with elements of the resulting discrete system matrix evaluated as contour integrals. In either case rotational symmetry and the fast Fourier transform (FFT) may be exploited to reduce computational costs, and Krylov space methods may be used to solve the resulting discretized integral equation efficiently. We illustrate the methods for several source field geometries. The two regularization schemes result in solutions that agree well at large scales, but exhibit substantial differences as the nominal resolution is approached. The agreement improves with increased resolution. Although the level of solution errors for the two approaches is likely comparable in an L 2 sense, the truncation approach results in Gibb’s oscillations near sharp conductivity contrasts. These may be reduced by tapering the truncated kernel, essentially equivalent to low-pass filtering the solution.
    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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  • 8
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    Xigaze forearc basin revisited (South Tibet): Provenance changes and origin of the Xigaze Ophiolite (2014)
    Geological Society of America (GSA)
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    Publication Date: 2014-10-28
    Description: Our new stratigraphic, sedimentological, and micropaleontological analysis, integrated with basalt geochemistry, sandstone petrography, and detrital-zircon U-Pb and Hf isotope data, suggests the revision of current models for the geological evolution of the Asian active margin during the Cretaceous. The Xigaze forearc basin began to form in the late Early Cretaceous, south of the Gangdese arc, during the initial subduction of the Neotethyan oceanic lithosphere under the Lhasa terrane. Well-preserved stratigraphic successions document the classical upward-shallowing pattern of the forearc-basin strata and elucidate the origin of the associated oceanic magmatic rocks. The normal mid-ocean-ridge basalt (N-MORB) geochemical signature and stratigraphic contact with the overlying abyssal cherts (Chongdui Formation) indicate that the Xigaze Ophiolite formed by forearc spreading and represents the basement of the forearc sedimentary sequence. Volcaniclastic sedimentation began with thick turbiditic sandstones and interbedded shales in the late Albian–Santonian (Ngamring Formation) followed by shelfal, deltaic, and fluvial strata (Padana Formation), with final filling of the basin by the Campanian age. Forearc sandstones do not show the classical trend from feldspatho-lithic volcaniclastic to quartzo-feldspathic plutoniclastic compositions, indicating limited unroofing of the Gangdese arc prior to collision. U-Pb age spectra of detrital zircons are unimodal with a 107 Ma peak in the lower Ngamring Formation (104–99 Ma), bimodal with a subordinate additional peak at 157 Ma in the middle Ngamring Formation (99–88 Ma), and multimodal with more abundant pre-Mesozoic ages in the upper Ngamring and Padana Formations (88–76 Ma). These three petrofacies with distinct provenances document the progressive erosional evolution of the Gangdese arc, with uplift of the central Lhasa terrane and expanding river catchments to include the central Lhasa terrane during the Late Cretaceous.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 9
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    Electromagnetic disturbances observed near the dip region ahead of dipolarization front (2016)
    Wiley
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    Publication Date: 2016-03-17
    Description: Dipolarization front (DF) is a thin magnetic structure embedded in fast flows in the magnetotail, which plays an important role in particle acceleration, flow braking, wave excitation and other related processes. Electromagnetic disturbances near the magnetic dip region in front of DFs are investigated using THEMIS observations in this paper. Strong magnetic field and electric field fluctuations, with several wave bands below and around the lower hybrid frequency, are found in an event on 21 March 2008. The properties of the wave are similar to that of magnetosonic wave. Detailed analyses show that the phase space density for ions in the perpendicular direction has a positive slope near the local Alfvén speed, which is a possible free energy source for the generation of the wave. This type of ion distribution could result from the earthward reflected ions ahead of DF, though other forming mechanism could not be fully ruled out.
    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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  • 10
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    Relevance of electrical current distribution to the forced flow and grain refinement in solidified Al-Si hypoeutectic alloy (2018)
    Springer Nature
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    Publication Date: 2018-02-20
    Description: Relevance of electrical current distribution to the forced flow and grain refinement in solidified Al-Si hypoeutectic alloy Relevance of electrical current distribution to the forced flow and grain refinement in solidified Al-Si hypoeutectic alloy, Published online: 19 February 2018; doi:10.1038/s41598-018-21709-y Relevance of electrical current distribution to the forced flow and grain refinement in solidified Al-Si hypoeutectic alloy
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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