390 research outputs found
Periodic Oscillations of Josephson-Vortex Flow Resistance in Oxygen-Deficient Y1Ba2Cu3Ox
We measured the Josephson vortex flow resistance as a function of magnetic
field applied parallel to the ab-planes using annealed Y1Ba2Cu3Ox intrinsic
Josephson junctions having high anisotropy (around 40) by oxygen content
reduction. Periodic oscillations were observed in magnetic fields above 45-58
kOe, corresponding to dense-dilute boundary for Josephson vortex lattice. The
observed period of oscillations, agrees well with the increase of one fluxon
per two junctions (\textit{=}\textit{/2Ls}), may correspond
to formation of a triangular lattice of Josephson vortices as has been reported
by Ooi et al. for highly anisotropic (larger than 200) Bi-2212 intrinsic
Josephson junctions.Comment: 5 pages, 4 figure
A Multi-band Photometric Study of Tidal Debris in A Compact Group of Galaxies: Seyfert's Sextet
In order to investigate the properties of the prominent tidal debris feature
extending to the northeast of the compact group of galaxies Seyfert's Sextet,
we analyzed multi-band (U, B, V, VR, R, I, J, H and K') photometric imaging
data and obtained the following results: 1) The radial surface brightness
distribution of this tidal debris in Seyfert's Sextet (TDSS) in each band
appears to be well approximated by an exponential profile. 2) The observed B-V
color of TDSS is similar to those of dwarf elliptical galaxies in nearby
clusters. 3) Comparing the spectral energy distribution (SED) of TDSS with
theoretical photometric evolution models and with the SED of the stars in the
outer part of HCG 79b, we find that its SED is comparable to that of a
10 Gyr-old stellar population with solar metallicity, similar to the stellar
population in the outer part of HCG 79b. This suggests that TDSS consists of
stars that may have been liberated from HCG 79b by strong galaxy interactions,
not a pre-existing dwarf galaxy previously thought.Comment: 9 pages, included 6 figures (5 PS files and 6 EPS files), emulateapj
LaTeX, Publications of the Astronomical Society of Japan, 2002, 54, No.1, in
pres
Применение криптографических методов шифрования информации
Необходимость технических средств защиты диктуется тем, что Интернет – это источник информации, за который никто не несет ответственности, и вероятность получения из него недостоверной, оскорбительной, пиратской или запрещенной по другим причинам информации весьма велика.The need for technological protection measures dictated by the fact that the Internet - a source of information for which no one is responsible, and the probability of getting out of it inaccurate, abusive, pirated or illegal for other reasons information is very high
In-situ epitaxial growth of superconducting La-based bilayer cuprate thin films
We investigate the epitaxial growth of bilayer cuprate La2CaCu2O6+\delta
using pure ozone as an oxidant, and find that even the crystal with parent
composition without cation substitution can show metallic behavior with the aid
of epitaxial strain effect. The hole concentration is controlled simply by
excess-oxygen doping, and the films grown under the optimum conditions exhibit
superconductivity below 30 K. This is the first result on the superconductivity
of bilayer La2CaCu2O6+\delta induced purely by the excess oxygen.Comment: 5 pages, 3 figures, To appear in Phys. Rev. B, Rapid Communication
Macroscopic quantum tunneling in a d-wave high-Tc superconductor
There is a wide recognition that Josephson-junction-like structures intrinsic
to the layered cuprate high temperature superconductors offer an attractive
stage for exploiting possible applications to new quantum technologies. On the
other hand the low energy quasiparticle excitations characteristically present
in these d-wave superconductors may easily destruct the coherence required.
Here we demonstrate for the first time the feasibility of macroscopic quantum
tunneling in the intrinsic Josephson junctions of a high temperature
superconductor, and find it to be characterized by a high classic-to-quantum
crossover temperature and a relatively weak quasiparticle dissipation.Comment: 4 pages, 3 figures, Ver. 2, Added referenc
Observation of Spin-Dependent Charge Symmetry Breaking in Interaction: Gamma-Ray Spectroscopy of He
The energy spacing between the ground-state spin doublet of He(1,0) was determined to be keV, by measuring
rays for the transition with a high efficiency germanium
detector array in coincidence with the He He
reaction at J-PARC. In comparison to the corresponding energy spacing in the
mirror hypernucleus H, the present result clearly indicates the
existence of charge symmetry breaking (CSB) in interaction. It is
also found that the CSB effect is large in the ground state but is by one
order of magnitude smaller in the excited state, demonstrating that the
CSB interaction has spin dependence
On the Hidden Order in URuSi --- Antiferro Hexadecapole Order and its Consequences
An antiferro ordering of an electric hexadecapole moment is discussed as a
promising candidate for the long standing mystery of the hidden order phase in
URuSi. Based on localized -electron picture, we discuss the
rationale of the selected multipole and the consequences of the antiferro
hexadecapole order of symmetry. The mean-field solutions and
the collective excitations from them explain reasonably significant
experimental observations: the strong anisotropy in the magnetic
susceptibility, characteristic behavior of pressure versus magnetic field or
temperature phase diagrams, disappearance of inelastic neutron-scattering
intensity out of the hidden order phase, and insensitiveness of the NQR
frequency at Ru-sites upon ordering. A consistency with the strong anisotropy
in the magnetic responses excludes all the multipoles in two-dimensional
representations, such as . The expected azimuthal angle
dependences of the resonant X-ray scattering amplitude are given. The
-type antiferro quadrupole should be induced by an in-plane
magnetic field along , which is reflected in the thermal expansion and
the elastic constant of the transverse mode. The
-type [-type] antiferro quadrupole is also induced by
applying the uniaxial stress along direction [ direction]. A
detection of these induced antiferro quadrupoles under the in-plane magnetic
field or the uniaxial stress using the resonant X-ray scattering provides a
direct redundant test for the proposed order parameter.Comment: 10 pages, 10 figures, 5 table
The optical afterglows and host galaxies of three short/hard gamma-ray bursts
Short GRBs are commonly thought to originate from the merging of double
compact object binaries but direct evidence for this scenario is still missing.
Optical observations of short GRBs allow us to measure redshifts, firmly
identify host galaxies, characterize their properties, and accurately localize
GRBs within them. Multiwavelength observations of GRB afterglows provide useful
information on the emission mechanisms at work. These are all key issues that
allow one to discriminate among different models of these elusive events. We
carried out photometric observations of the short/hard GRB 051227, GRB 061006,
and GRB 071227 with the ESO-VLT starting from several hours after the explosion
down to the host galaxy level several days later. For GRB 061006 and GRB 071227
we also obtained spectroscopic observations of the host galaxy. We compared the
results obtained from our optical observations with the available X-ray data of
these bursts. For all the three above bursts, we discovered optical afterglows
and firmly identified their host galaxies. About half a day after the burst,
the optical afterglows of GRB 051227 and GRB 061006 present a decay
significatly steeper than in the X-rays. In the case of GRB 051227, the optical
decay is so steep that it likely indicates different emission mechanisms in the
two wavelengths ranges. The three hosts are blue, star forming galaxies at
moderate redshifts and with metallicities comparable to the Solar one. The
projected offsets of the optical afterglows from their host galaxies centers
span a wide range, but all afterglows lie within the light of their hosts and
present evidence for local absorption in their X-ray spectra. We discuss our
findings in light of the current models of short GRB progenitors.Comment: Accepted for publication by A&A. 11 pages, 9 figures; v2: minor
changes and new version of Fig.
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