23,015 research outputs found

    Forbidden Ca 2 in the sun unmasked by way of Venus

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    Eleven high-dispersion spectra of Venus, taken with blue Doppler shifts have permitted the unmasking of the 7323.88A forbidden line of Ca II from terrestrial absorption. An equivalent width is obtained of 7.4 + or - 0.4mA for this line in integrated sunlight. Our value of W sub lambda is smaller than previous values and much more accurate. The HSRA solar model gives a solar calcium abundance of A sub Ca = 6.21

    Studies of the superconducting properties of Sn1-xInxTe (x=0.38 to 0.45) using muon-spin spectroscopy

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    The superconducting properties of Sn1-xInxTe (x = 0.38 to 0.45) have been studied using magnetization and muon-spin rotation or relaxation (muSR) measurements. These measurements show that the superconducting critical temperature Tc of Sn1-xInxTe increases with increasing x, reaching a maximum at around 4.8 K for x = 0.45. Zero-field muSR results indicate that time-reversal symmetry is preserved in this material. Transverse-field muon-spin rotation has been used to study the temperature dependence of the magnetic penetration depth lambda(T) in the mixed state. For all the compositions studied, lambda(T) can be well described using a single-gap s-wave BCS model. The magnetic penetration depth at zero temperature lambda(0) ranges from 500 to 580 nm. Both the superconducting gap Delta(0) at 0 K and the gap ratio Delta(0)/kBTc indicate that Sn1-xInxTe (x = 0.38 to 0.45) should be considered as a superconductor with intermediate to strong coupling.Comment: 7 pages, 6 figures, 3 table

    The 8^8B Neutrino Spectrum

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    Knowledge of the energy spectrum of 8^8B neutrinos is an important ingredient for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed approximation because of the broad alpha-unstable 8^8Be final state and recoil order corrections to the beta decay. We have measured the total energy of the alpha particles emitted following the beta decay of 8^8B. The measured spectrum is inconsistent with some previous measurements, in particular with a recent experiment of comparable precision. The beta decay strength function for the transition from 8^8B to the accessible excitation energies in 8^8Be is fit to the alpha energy spectrum using the R-matrix approach. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments, particularly for neutrino energies above 12 MeV.Comment: 15 pages, 13 figures, 4 tables, submitted to Phys. Rev. C, typos correcte

    Probing the superconducting ground state of the rare-earth ternary boride superconductors RRRuB2_2 (RR = Lu,Y) using muon-spin rotation and relaxation

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    The superconductivity in the rare-earth transition metal ternary borides RRRuB2_2 (where RR = Lu and Y) has been investigated using muon-spin rotation and relaxation. Measurements made in zero-field suggest that time-reversal symmetry is preserved upon entering the superconducting state in both materials; a small difference in depolarization is observed above and below the superconducting transition in both compounds, however this has been attributed to quasistatic magnetic fluctuations. Transverse-field measurements of the flux-line lattice indicate that the superconductivity in both materials is fully gapped, with a conventional s-wave pairing symmetry and BCS-like magnitudes for the zero-temperature gap energies. The electronic properties of the charge carriers in the superconducting state have been calculated, with effective masses m∗/me=m^*/ m_\mathrm{e} = 9.8±0.19.8\pm0.1 and 15.0±0.115.0\pm0.1 in the Lu and Y compounds, respectively, with superconducting carrier densities ns=n_\mathrm{s} = (2.73±0.042.73\pm0.04) ×1028\times 10^{28} m−3^{-3} and (2.17±0.022.17\pm0.02) ×1028\times 10^{28} m−3^{-3}. The materials have been classified according to the Uemura scheme for superconductivity, with values for Tc/TFT_\mathrm{c}/T_\mathrm{F} of 1/(414±6)1/(414\pm6) and 1/(304±3)1/(304\pm3), implying that the superconductivity may not be entirely conventional in nature.Comment: 8 pages, 8 figure

    Animal-Assisted Interventions in Health Care Settings: A Best Practices Manual for Establishing New Programs: Volunteer Manual Template

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    This document accompanies Animal-Assisted Interventions in Health Care Settings: A Best Practices Manual for Establishing New Programs (Purdue Press, 2019) and serves as a template for readers to personalize for their facility. The generic terms “ABC Health Care Facility” and “AAI Program” are intended to be replaced by the names of the reader\u27s facility and AAI program. The book can be purchased from Purdue University Press

    Optomechanical cooling of levitated spheres with doubly-resonant fields

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    Optomechanical cooling of levitated dielectric particles represents a promising new approach in the quest to cool small mechanical resonators towards their quantum ground state. We investigate two-mode cooling of levitated nanospheres in a self-trapping regime. We identify a rich structure of split sidebands (by a mechanism unrelated to usual strong-coupling effects) and strong cooling even when one mode is blue detuned. We show the best regimes occur when both optical fields cooperatively cool and trap the nanosphere, where cooling rates are over an order of magnitude faster compared to corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure

    Time-reversal symmetry breaking in noncentrosymmetric superconductor Re6Hf:further evidence for unconventional behaviour in the alpha-Mn family of materials

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    The discovery of new families of unconventional superconductors is important both experimentally and theoretically, especially if it challenges current models and thinking. By using muon spin relaxation in zero-field, time-reversal symmetry breaking has been observed in Re6Hf. Moreover, the temperature dependence of the superfluid density exhibits s-wave superconductivity with an enhanced electron-phonon coupling. This, coupled with the results from isostructural Re6Zr, shows that the Re6X family are indeed a new and important group of unconventional superconductors.Comment: 5 pages, 2 figures Accepted Physical Review B, Rapid Communicatio
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