14,071 research outputs found
The sidereal anisotropy of cosmic rays around 3 x 10 (15) eV observed at a middle north latitude
The sidereal time variation of cosmic rays (median primary energy : 3 10 to the 15th power eV) is investigated with air shower observations at Akeno, Japan (900 m a.s.l.) which started in September 1981. Air showers are detected by a coincidence requirement on several muon detectors. The result obtained for three years is suggestive of a big semi-diurnal variation (0.37 % in amplitude). On the other hand, the diurnal variation is rather small than the semi-diurnal one. The feature of the sidereal anisotropy supposed from the present result looks quite different from that below 10 to the 14th power eV
Does mass accretion lead to field decay in neutron stars
The recent discovery of cyclotron lines from gamma-ray bursts indicates that the strong magnetic fields of isolated neutron stars might not decay. The possible inverse correlation between the strength of the magnetic field and the mass accreted by the neutron star suggests that mass accretion itself may lead to the decay of the magnetic field. The spin and magnetic field evolution of the neutron star was calculated under the hypothesis of the accretion-induced field decay. It is shown that the calculated results are consistent with the observations of binary and millisecond radio pulsars
Intrinsic spin Hall effect in platinum metal
Spin Hall effect in metallic Pt is studied with first-principles relativistic
band calculations. It is found that intrinsic spin Hall conductivity (SHC) is
as large as at low temperature, and
decreases down to at room
temperature. It is due to the resonant contribution from the spin-orbit
splitting of the doubly degenerated -bands at high-symmetry and
points near the Fermi level. By modeling these near degeneracies by effective
Hamiltonian, we show that SHC has a peak near the Fermi energy and that the
vertex correction due to impurity scattering vanishes. We therefore argue that
the large spin Hall effect observed experimentally in platinum is of intrinsic
nature.Comment: Accepted for publication in Phys. Rev. Let
Phase transition between the quantum spin Hall and insulator phases in 3D: emergence of a topological gapless phase
Phase transitions between the quantum spin Hall and the insulator phases in
three dimensions are studied. We find that in inversion-asymmetric systems
there appears a gapless phase between the quantum spin Hall and insulator
phases in three dimensions, which is in contrast with the two-dimensional case.
Existence of this gapless phase stems from a topological nature of gapless
points (diabolical points) in three dimensions, but not in two dimensions.Comment: 16 pages, 5 figure
Interspecific differences in the larval performance of Pieris butterflies (Lepidoptera: Pieridae) are associated with differences in the glucosinolate profiles of host plants
The tremendous diversity of plants and herbivores has arisen from a coevolutionary relationship characterized by plant defense and herbivore counter adaptation. Pierid butterfly species feed on Brassicales plants that produce glucosinolates as a chemical deterrent against herbivory. In turn, the larvae of pierids have nitrile specifier proteins (NSPs) that are expressed in their gut and disarm glucosinolates. Pierid butterflies are known to have diversified in response to glucosinolate diversification in Brassicales. Therefore, each pierid species is expected to have a spectrum of host plants characterized by specific glucosinolate profiles. In this study, we tested whether the larval performance of different Pieris species, a genus in Pieridae (Lepidoptera: Pieridae), was associated with plant defense traits of putative host plants. We conducted feeding assays using larvae of three Pieris species and 10 species of the Brassicaceae family possessing different leaf physical traits and glucosinolate profile measurements. The larvae of Pieris rapae responded differently in the feeding assays compared with the other two Pieris species. This difference was associated with differences in glucosinolate profiles but not with variations in physical traits of the host plants. This result suggests that individual Pieris species are adapted to a subset of glucosinolate profiles within the Brassicaceae. Our results support the idea that the host ranges of Pieris species depend on larval responses to glucosinolate diversification in the host species, supporting the hypothesis of coevolution between butterflies and host plants mediated by the chemical arms race
Single domain YBCO/Ag bulk superconductors fabricated by seeded infiltration and growth
We have applied the seeded infiltration and growth (IG) technique to the processing of samples containing Ag in an attempt to fabricate Ag-doped Y-Ba-Cu-O (YBCO) bulk superconductors with enhanced mechanical properties. The IG technique has been used successfully to grow bulk Ag-doped YBCO superconductors of up to 25 mm in diameter in the form of single grains. The distribution of Ag in the parent Y-123 matrix fabricated by the IG technique is observed to be at least as uniform as that in samples grown by conventional top seeded melt growth (TSMG). Fine Y-211 particles were observed to be embedded within the Y-123 matrix for the IG processed samples, leading to a high critical current density, Jc, of over 70 kA/cm2 at 77.3 K in self-field. The distribution of Y-211 in the IG sample microstructure, however, is inhomogeneous, which leads to a variation in the spatial distribution of Jc throughout the bulk matrix. A maximum-trapped field of around 0.43 T at 1.2 mm above the sample surface (i.e. including 0.7 mm for the sensor mould thickness) is observed at liquid nitrogen temperature, despite the relatively small grain size of the sample (20 mm diameter × 7 mm thickness)
Partial and macroscopic phase coherences in underdoped BiSrCaCuO thin film
A combined study with use of time-domain pump-probe spectroscopy and
time-domain terahertz transmission spectroscopy have been carried out on an
underdoped BiSrCaCuO thin film. It was observed that
the low energy multi-excitation states were decomposed into superconducting gap
and pseudogap. The pseudogap locally opens below K
simultaneously with the appearance of the high-frequency partial pairs around
1.3 THz. With decreasing temperature, the number of the local domains with the
partial phase coherence increased and saturated near 100 K, and the macroscopic
superconductivity appeared below 76 K through the superconductivity fluctuation
state below 100 K. These experimental results indicate that the pseudogap makes
an important role for realization of the superconductivity as a precursor to
switch from the partial to the macroscopic phase coherence.Comment: Revtex4, 4 pages, 4 figure
Quantum Spin Hall Effect and Enhanced Magnetic Response by Spin-Orbit Coupling
We show that the spin Hall conductivity in insulators is related with a
magnetic susceptibility representing the strength of the spin-orbit coupling.
We use this relationship as a guiding principle to search real materials
showing quantum spin Hall effect. As a result, we theoretically predict that
bismuth will show the quantum spin Hall effect, both by calculating the helical
edge states, and by showing the non-triviality of the Z_2 topological number,
and propose possible experiments.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev. Let
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