29,664 research outputs found

    Kinematics of Red Variables in the Solar Neighborhood I. Basic Data Obtained by an SiO Maser Survey

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    In order to study the streaming motions of miras in the Solar neighborhood, we newly surveyed 379 red variables in the SiO maser lines at 42.821 and 43.122 GHz with the Nobeyama 45m radio telescope. Accurate radial velocities were obtained for 229 (220 new) detected stars. The sample is selected from optical variables found by new automated surveys: the Northern Sky Variability Survey and the All Sky Automated Survey. The new sample consists of the "bluer" objects compared with those observed in the previous SiO surveys. The distances to the objects are estimated using the period-luminosity relation, and they are mostly less than 3 kpc from the Sun. The longitude-velocity diagram reveals three prominent groups of stars deviant from the circular Galactic rotation with a flat rotation curve. In addition to the Hercules group of stars which was studied before, we found two new deviant groups: one toward the Perseus arm and the other toward the Sagittarius arm. These two groups both exhibit anomalous motions toward the Galactic center, which seem to be consistent with the noncircular motions of these spiral arms found in the recent VLBI proper-motion measurements for maser gas clumps.Comment: PASJ 64 no.1 (2012 Feb. 25 issue) in press. A full version including Fig. 8a-m, and Fig. 9 are available at http://www.nro.nao.ac.jp/~lib_pub/report/data/no680.pd

    Mechanism of Ambipolar Field-Effect Carrier Injections in One-Dimensional Mott Insulators

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    To clarify the mechanism of recently reported, ambipolar carrier injections into quasi-one-dimensional Mott insulators on which field-effect transistors are fabricated, we employ the one-dimensional Hubbard model attached to a tight-binding model for source and drain electrodes. To take account of the formation of Schottky barriers, we add scalar and vector potentials, which satisfy the Poisson equation with boundary values depending on the drain voltage, the gate bias, and the work-function difference. The current-voltage characteristics are obtained by solving the time-dependent Schr\"odinger equation in the unrestricted Hartree-Fock approximation. Its validity is discussed with the help of the Lanczos method applied to small systems. We find generally ambipolar carrier injections in Mott insulators even if the work function of the crystal is quite different from that of the electrodes. They result from balancing the correlation effect with the barrier effect. For the gate-bias polarity with higher Schottky barriers, the correlation effect is weakened accordingly, owing to collective transport in the one-dimensional correlated electron systems.Comment: 21 pages, 10 figures, to appear in J. Phys. Soc. Jp

    Proton-neutron alignment in the yrast states of 66^{66}Ge and 68^{68}Ge

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    The 66^{66}Ge and 68^{68}Ge nuclei are studied by means of the shell model with the extended P+QQP+QQ Hamiltonian, which succeeds in reproducing experimentally observed energy levels, moments of inertia and other properties. The investigation using the reliable wave-functions predicts T=0, J=9 one-proton-one-neutron (1p1n1p1n) alignment in the g9/2g_{9/2} orbit, at high spins (141+14_1^+, 161+16_1^+ and 181+18_1^+) in these NZN \approx Z even-even nuclei. It is shown that a series of the even-JJ positive-parity yrast states (observed up to 261+26_1^+ for 68^{68}Ge) consists of the ground-state band and successive three bands with different types of particle alignments (two-neutron, 1p1n1p1n, two-proton-two-neutron) in the g9/2g_{9/2} orbit.Comment: 4 pages, 5 figures, to be published in Pyhs. Rev.

    Evaluation of the effects of a freeze/thaw environment on cellular glass

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    Using the evaluation criteria of water vapor permeability and conformability, a protective butylrubber/silicone conformal coating system was selected for use on Foamglas substrates in a freeze/thaw environment. The selection of a specific freeze/thaw cycle which closely models field conditions is discussed. A sampling plan is described which allows independent evaluation of the effects of conformal coatings, cycle number and location within the environmental chamber. The results of visual examination, measurement of density, modulus of rupture and Young's modulus are reported. Based upon statistical evaluation of the experimental results, it is concluded that no degradation in mechanical properties of either coated or uncoated Foamglas occurred within the duration of the test (53 freeze/thaw cycles)

    Structure of isomeric states in 66As and 67As

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    Strong residual correlations between neutrons and protons in N ~ Z systems can lead to unusual structure. Using the spherical shell model, we show that a low-excitation shape isomer can occur in the odd-odd N=Z nucleus 66As. This extends the picture of shape coexistence beyond even-even nuclei. Furthermore, it is demonstrated that in 66As and in the N=Z+1 nucleus 67As, a new type of isomer, which we term j-isomer, can be formed. The underlying mechanism for the isomerism formation is structure change in the isomeric states, which involves either an alignment of a neutron-proton pair from the high-j intruder orbitals, or a simultaneous occupation of these neutron and proton high-j orbitals.Comment: 11 pages, 2 figure

    An Estimation Method for the Emission Accounting Table of Global Agricultural Activities

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    This paper describes an estimation method to develop an emission accounting table of global agricultural activities which consists of accounting tables including agricultural commodity flows from production to consumption, GHG emissions and agricultural waste etc.. Material and monetary flows related with agricultural commodities are estimated by using reported information such as production, trade and cosumption from published statistics. In our calculation, the table covers 94 countries and 12 regions in the world from 1971 to 2000. These calculations are conducted to extract most plausible estimates which minimize differences between estimated data and reported data subjected to several constraints on the accounting systems. In our estimation, 47.4% and 72.2% of all estimated values are in 0.95-1.05% range and 0.80-1.20% range of reported value, respectvely. We found a part of outliers in the existing data was modified. We clarified that total CH4 and N2O emission is estimated to have been 2450 MtCO2eq and 131 MtCO2eq in 1971 and they are estimated to have increased to 3140 MtCO2eq and 2220 MtCO2eq in 2000

    Recombination kinetics of a dense electron-hole plasma in strontium titanate

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    We investigated the nanosecond-scale time decay of the blue-green light emitted by nominally pure SrTiO3_3 following the absorption of an intense picosecond laser pulse generating a high density of electron-hole pairs. Two independent components are identified in the fluorescence signal that show a different dynamics with varying excitation intensity, and which can be respectively modeled as a bimolecular and unimolecolar process. An interpretation of the observed recombination kinetics in terms of interacting electron and hole polarons is proposed
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