5,029 research outputs found
The inferior caval vein draining into the left atrial cavity : a rare case
The inferior vena cava (IVC) draining into the left atrium (LA) is exceedingly rare in the setting of the usual atrial arrangement (situs solitus). This article describes a patient with this unique anomaly, and its repair.peer-reviewe
Polarization and light curve variability: the "patchy shell" model
Recent advances in early detection and detailed monitoring of GRB afterglows
have revealed variability in some afterglow light curves. One of the leading
models for this behavior is the patchy shell model. This model attributes the
variability to random angular fluctuations in the relativistic jet energy.
These an-axisymmetric fluctuations should also impose variations in the degree
and angle of polarization that are correlated to the light curve variability.
In this letter we present a solution of the light curve and polarization
resulting from a given spectrum of energy fluctuations. We compare light curves
produced using this solution to the variable light curve of GRB 021004 and we
show that the main features in both the light curve and the polarization
fluctuations are very well reproduced by this model. We use our results to draw
constraints on the characteristics of the energy fluctuations that might have
been present in GRB 021004.Comment: 10 pages, 2 figures, Final version to appear in ApJ
Superconducting Volume Fraction in Overdoped Regime of La_2-x_Sr_x_CuO_4_: Implication for Phase Separation from Magnetic-Susceptibility Measurement
We have grown a single crystal of La_2-x_Sr_x_CuO_4_ in which the Sr
concentration, x, continuously changes from 0.24 to 0.29 in the overdoped
regime and obtained many pieces of single crystals with different x values by
slicing the single crystal. From detailed measurements of the magnetic
susceptibility, chi, of each piece, it has been found that the absolute value
of chi at the measured lowest temperature 2 K, |chi_2K_|, on field cooling
rapidly decreases with increasing x as well as the superconducting (SC)
transition temperature. As the value of |chi_2K_| is regarded as corresponding
to the SC volume fraction in a sample, it has been concluded that a phase
separation into SC and normal-state regions occurs in a sample of
La_2-x_Sr_x_CuO_4_ in the overdoped regime.Comment: 4 pages, 3 figures, ver. 2 has been accepted in J. Phys. Soc. Jp
Magnetic Phase Diagram of the Hole-doped CaNaCuOCl Cuprate Superconductor
We report on the magnetic phase diagram of a hole-doped cuprate
CaNaCuOCl, which is free from buckling of CuO
planes, determined by muon spin rotation and relaxation. It is characterized by
a quasi-static spin glass-like phase over a range of sodium concentration
(), which is held between long range antiferromagnetic
(AF) phase () and superconducting phase where the system is
non-magnetic for . The obtained phase diagram qualitatively agrees
well with that commonly found for hole-doped high-\tc cuprates, strongly
suggesting that the incomplete suppression of the AF order for is an
essential feature of the hole-doped cuprates.Comment: 5 pages, submitted to Phys. Rev. Let
Energy Injection Episodes in Gamma Ray Bursts: The Light Curves and Polarization Properties of GRB 021004
Several GRB afterglow light curves deviate strongly from the power law decay
observed in most bursts. We show that these variations can be accounted for by
including refreshed shocks in the standard fireball model previously used to
interpret the overall afterglow behavior. As an example we consider GRB 021004
that exhibited strong light curve variations and has a reasonably well
time-resolved polarimetry. We show that the light curves in the R-band, X-rays
and in the radio can be accounted for by four energy injection episodes in
addition to the initial event. The polarization variations are shown to be a
consequence of the injections.Comment: 4 pages, 2 figures. To appear in ApJ
Muon spin relaxation studies of incommensurate magnetism and superconductivity in stage-4 LaCuO and LaSrCuO
This paper reports muon spin relaxation (MuSR) measurements of two single
crystals of the title high-Tc cuprate systems where static incommensurate
magnetism and superconductivity coexist. By zero-field MuSR measurements and
subsequent analyses with simulations, we show that (1) the maximum ordered Cu
moment size (0.36 Bohr magneton) and local spin structure are identical to
those in prototypical stripe spin systems with the 1/8 hole concentration; (2)
the static magnetism is confined to less than a half of the volume of the
sample, and (3) regions with static magnetism form nano-scale islands with the
size comparable to the in-plane superconducting coherence length. By
transverse-field MuSR measurements, we show that Tc of these systems is related
to the superfluid density, in the same way as observed in cuprate systems
without static magnetism. We discuss a heuristic model involving percolation of
these nanoscale islands with static magnetism as a possible picture to
reconcile heterogeneity found by the present MuSR study and long-range spin
correlations found by neutron scattering.Comment: 19 pages, 15 figures, submitted to Phys. Rev. B. E-mail:
[email protected]
Boson-fermion model beyond mean-field approximation
A model of hybridized bosons and fermions is studied beyond the mean field
approximation. The divergent boson self-energy at zero temperature makes the
Cooper pairing of fermions impossible.The frequency and momentum dependence of
the self- energy and the condensation temperature of initially
localized bosons are calculated analytically. The value of the boson
condensation temperature is below which rules out the
boson-fermion model with the initially localized bosons as a phenomenological
explanation of high-temperature superconductivity. The intra-cell
density-density fermion-boson interaction dominates in the fermion self-energy.
The model represents a normal metal with strongly damped bosonic excitations.
The latter play the role of normal impurities.Comment: 16 pages, Latex, 5 figures available upon reques
- …