2,718 research outputs found
Models of Meson-Baryon Reactions in the Nucleon Resonance Region
It is shown that most of the models for analyzing meson-baryon reactions in
the nucleon resonance region can be derived from a Hamiltonian formulation of
the problem. An extension of the coupled-channel approach to include
channel is briefly described and some preliminary results for the
excitation are presented.Comment: Latex 13 pages; to appear in the Proceedings of Workshop on the
Physics of excited nucleons (NSTAR2004), Grenoble (France), March 24-27, 200
Magnetic and Electronic Phase Diagram and Superconductivity in the Organic Superconductors k-(BEDT-TTF)2X
The magnetic susceptibility of the organic superconductors -(h8 or
d8-ET), Cu(NCS) and Cu[N(CN)]Br has been studied. A
metallic phase below 37 38 K for Cu[N(CN)]Br and
46 50 K for Cu(NCS) has an anisotropic temperature
dependence of the susceptibility and the charge transport. Partial
charge-density-wave or charge fluctuation is expected to coexist with the
metallic phase instead of the large antiferromagnetic fluctuation above
. The phase diagram and the superconductivity of -(ET)
are discussed in connection with this phase.Comment: 5 pages, 4figures, REVTeX, references are corrected, accepted for
pubication in Phys. Rev.
Dynamical Coupled-Channels Effects on Pion Photoproduction
The electromagnetic pion production reactions are investigated within the
dynamical coupled-channels model developed in {\bf Physics Reports, 439, 193
(2007)}. The meson-baryon channels included in this study are , , , and the , and resonant components
of the channel. With the hadronic parameters of the model determined
in a recent study of scattering, we show that the pion photoproduction
data up to the second resonance region can be described to a very large extent
by only adjusting the bare helicity amplitudes, while the
non-resonant electromagnetic couplings are taken from previous works. It is
found that the coupled-channels effects can contribute about 10 - 20 % of the
production cross sections in the (1232) resonance region, and can
drastically change the magnitude and shape of the cross sections in the second
resonance region. The importance of the off-shell effects in a dynamical
approach is also demonstrated. The meson cloud effects as well as the
coupled-channels contributions to the form factors are found
to be mainly in the low region. For the magnetic M1
(1232) form factor, the results are close to that of the Sato-Lee Model.
Necessary improvements to the model and future developments are discussed.Comment: Corrected version. 14 pages, 10 figure
Weak localization and spin splitting in inversion layers on p-type InAs
We report on the magnetoconductivity of quasi two-dimensional electron
systems in inversion layers on p-type InAs single crystals. In low magnetic
fields pronounced features of weak localization and antilocalization are
observed. They are almost perfectly described by the theory of Iordanskii,
Lyanda-Geller and Pikus. This allows us to determine the spin splitting and the
Rashba parameter of the ground electric subband as a function of the electron
density.Comment: Accepted for publication in Phys. Rev. B, 4 page
Double and single pion photoproduction within a dynamical coupled-channels model
Within a dynamical coupled-channels model which has already been fixed from
analyzing the data of the pi N -> pi N and gamma N -> pi N reactions, we
present the predicted double pion photoproduction cross sections up to the
second resonance region, W< 1.7 GeV. The roles played by the different
mechanisms within our model in determining both the single and double pion
photoproduction reactions are analyzed, focusing on the effects due to the
direct gamma N -> pi pi N mechanism, the interplay between the resonant and
non-resonant amplitudes, and the coupled-channels effects. The model parameters
which can be determined most effectively in the combined studies of both the
single and double pion photoproduction data are identified for future studies.Comment: Version to appear in PRC. 16 pages, 13 figure
Disentangling the dynamical origin of P11 Nucleon Resonances
We show that two almost degenerate poles near the threshold and
the next higher mass pole in the partial wave of scattering
evolve from a single bare state through its coupling with , and
reaction channels. This finding provides new information on
understanding the dynamical origins of the Roper and
resonances listed by Particle Data Group. Our results for the resonance poles
in other partial waves are also presented.Comment: Improved version, accepted Phys. Rev. Let
Dynamical coupled-channels analysis of 1H(e,e'pi)N reactions
We have performed a dynamical coupled-channels analysis of available
p(e,e'pi)N data in the region of W < 1.6 GeV and Q^2 < 1.45 (GeV/c)^2. The
channels included are gamma^* N, pi N, eta N, and pi pi N which has pi Delta,
rho N, and sigma N components. With the hadronic parameters of the model
determined in our previous investigations of pi N --> pi N, pi pi N reactions,
we have found that the available data in the considered W < 1.6 GeV region can
be fitted well by only adjusting the bare gamma^* N --> N^* helicity amplitudes
for the lowest N^* states in P33, P11, S11 and D13 partial waves. The
sensitivity of the resulting parameters to the amount of data included in the
analysis is investigated. The importance of coupled-channels effect on the
p(e,e' pi)N cross sections is demonstrated. The meson cloud effects, as
required by the unitarity conditions, on the gamma^* N --> N^* form factors are
also examined. Necessary future developments, both experimentally and
theoretically, are discussed.Comment: 14 pages, 11 figures. Version to appear in PR
Significance of myocardial tenascin-C expression in left ventricular remodelling and long-term outcome in patients with dilated cardiomyopathy
Aim Dilated cardiomyopathy (DCM) has a variety of causes, and no useful approach to predict left ventricular (LV) remodelling and long-term outcome has yet been established. Myocardial tenascin-C (TNC) is known to appear under pathological conditions, possibly to regulate cardiac remodelling. The aim of this study was to clarify the significance of myocardial TNC expression in LV remodelling and the long-term outcome in DCM. Methods and results One hundred and twenty-three consecutive DCM patients who underwent endomyocardial biopsy for initial diagnosis were studied. Expression of TNC in biopsy sections was analysed immunohistochemically to quantify the ratio of the TNC-positive area to the whole myocardial tissue area (TNC area). Clinical parameters associated with TNC area were investigated. The patients were divided into two groups based on receiver operating characteristic analysis of TNC area to predict death: high TNC group with TNC area ≥2.3% (22 patients) and low TNC group with TNC area <2.3% (101 patients). High TNC was associated with diabetes mellitus. Comparing echocardiographic findings between before and 9 months after endomyocardial biopsy, the low TNC group was associated with decreased LV end-diastolic diameter and increased LV ejection fraction, whereas the high TNC group was not. Survival analysis revealed a worse outcome in the high TNC group than in the low TNC group (P < 0.001). Multivariable Cox regression analysis revealed that TNC area was independently associated with poor outcome (HR = 1.347, P = 0.032). Conclusions Increased myocardial TNC expression was associated with worse LV remodeling and long-term outcome in DCM
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