757 research outputs found
Phase Diagram of Lattice-Spin System RbCoBr
We study the lattice-spin model of RbCoBr which is proposed by Shirahata
and Nakamura, by mean field approximation. This model is an Ising spin system
on a distorted triangular lattice. There are two kinds of frustrated variables,
that is, the lattice and spin. We obtain a phase diagram of which phase
boundary is drawn continuously in a whole region. Intermediate phases that
include a partial disordered state appear. The model has the first-order phase
transitions in addition to the second-order phase transitions. We find a
three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice
ferrimagnetic state does not appear when the lattice is not distorted.Comment: 5 pages, 4 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn.
Vol.75 (2006) No.
Generarized Cubic Model for BaTiO-like Ferroelectric Substance
We propose an order-disorder type microscopic model for BaTiO-like
Ferroelectric Substance. Our model has three phase transitions and four phases.
The symmetry and directions of the polarizations of the ordered phases agree
with the experimental results of BaTiO. The intermediate phases in our
model are known as an incompletely ordered phase, which appears in a
generalized clock model.Comment: 6 pages, 4figure
Quantum fluctuation induced ordered phase in the Blume-Capel model
We consider the Blume-Capel model with the quantum tunneling between the
excited states. We find a magnetically ordered phase transition induced by
quantum fluctuation in a model. The model has no phase transition in the
corresponding classical case. Usually, quantum fluctuation breaks ordered phase
as in the case of the transverse field Ising model. However, in present case,
an ordered phase is induced by quantum fluctuation. Moreover, we find a phase
transition between a quantum paramagnetic phase and a classical diamagnetic
phase at zero temperature. We study the properties of the phase transition by
using a mean field approximation (MFA), and then, by a quantum Monte Carlo
method to confirm the result of the MFA.Comment: 7 pages, 6 figures, corrected some typo
Application of a novel method for subsequent evaluation of sinusoids and postsinusoidal venules after ischemia-reperfusion injury of rat liver
Although several intravital fluorescence microscopic studies demonstrated that microcirculatory derangement is induced during liver ischemia-reperfusion, these data were obtained from randomly selected microvascular areas and microvessels, Repeated observation of the identical microvessels has not been performed yet. Using a specially designed cover glass, it is now possible to relocate desired sites of observation repeatedly over the whole reperfusion time, The aim of this study was to determine the impact of reperfusion time on hepatic microvascular perfusion state. Twenty minutes of ischemia induced a significant decrease in sinusoidal perfusion rate (29.1 +/- 10.2%) as compared with baseline values (98.0 +/- 0.3%). At 30, 60, and 120 min of reperfusion, the percentage of perfused sinusoids recovered to 62.8 +/- 6.6, 67.5 +/- 5.7, and 77.2 +/- 5.4%. The number of stagnant leukocytes in the same sinusoids was 6.2 +/- 1.9/lobule at baseline and increased to 22.3 +/- 3.6/lobule at 120 min of reperfusion. The number of leukocytes adhering within postsinusoidal venules was 53.5 +/- 12.5/mm(2) before ischemia and increased to 414.2 +/- 62.5/mm(2) at 120 min of reperfusion. We have demonstrated that during 120 min of reperfusion, there was a steady increase in both sinusoidal and venular leukocyte adhesion along with an attenuation of the initially severely depressed sinusoidal perfusion. a no-reflow phenomenon at an early phase of reperfusion and subsequent reflow were proven
Segmented scintillation detectors with silicon photomultiplier readout for measuring antiproton annihilations
The Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA)
experiment at the Antiproton Decelerator (AD) facility of CERN constructed
segmented scintillators to detect and track the charged pions which emerge from
antiproton annihilations in a future superconducting radiofrequency Paul trap
for antiprotons. A system of 541 cast and extruded scintillator bars were
arranged in 11 detector modules which provided a spatial resolution of 17 mm.
Green wavelength-shifting fibers were embedded in the scintillators, and read
out by silicon photomultipliers which had a sensitive area of 1 x 1 mm^2. The
photoelectron yields of various scintillator configurations were measured using
a negative pion beam of momentum p ~ 1 GeV/c. Various fibers and silicon
photomultipliers, fiber end terminations, and couplings between the fibers and
scintillators were compared. The detectors were also tested using the
antiproton beam of the AD. Nonlinear effects due to the saturation of the
silicon photomultiplier were seen at high annihilation rates of the
antiprotons.Comment: Copyright 2014 American Institute of Physics. This article may be
downloaded for personal use only. Any other use requires prior permission of
the author and the American Institute of Physics. The following article
appeared in Review of Scientific Instruments, Vol.85, Issue 2, 2014 and may
be found at http://dx.doi.org/10.1063/1.486364
Thermally-induced magnetic phases in an Ising spin Kondo lattice model on a kagome lattice at 1/3-filling
Numerical investigation on the thermodynamic properties of an Ising spin
Kondo lattice model on a kagome lattice is reported. By using Monte Carlo
simulation, we investigated the magnetic phases at 1/3-filling. We identified
two successive transitions from high-temperature paramagnetic state to a
Kosterlitz-Thouless-like phase in an intermediate temperature range and to a
partially disordered phase at a lower temperature. The partially disordered
state is characterized by coexistence of antiferromagnetic hexagons and
paramagnetic sites with period . We compare the results
with those for the triangular lattice case.Comment: 4 pages, 2 figure
- …