540 research outputs found
Corrigendum: The quest for EEG power band correlation with ICA derived fMRI resting state networks
Contains fulltext :
136233.pdf (publisher's version ) (Open Access)[This corrects the article on p. 315 in vol. 7, PMID: 23805098.].2 p
Large scale numerical investigation of excited states in poly(phenylene)
A density matrix renormalisation group scheme is developed, allowing for the
first time essentially exact numerical solutions for the important excited
states of a realistic semi-empirical model for oligo-phenylenes. By monitoring
the evolution of the energies with chain length and comparing them to the
experimental absorption peaks of oligomers and thin films, we assign the four
characteristic absorption peaks of phenyl-based polymers. We also determine the
position and nature of the nonlinear optical states in this model.Comment: RevTeX, 10 pages, 4 eps figures included using eps
Scanning tunneling microscopy observations on the reconstructed Au(111) surface: Atomic structure, long-range superstructure, rotational domains, and surface defects
An Asymptomatic Case of Wolff-Parkinson-White Syndrome with Right-sided Free-wall Accessory Pathway and Left Ventricular Dysfunction
AbstractA 16-year-old girl with a known history of asymptomatic Wolff-Parkinson-White syndrome exhibited signs of left ventricular (LV) septal akinesia and LV dysfunction during routine follow-up. A 12-lead surface ECG showed pre-excitation, a predominantly negative delta wave in V1 and left axis deviation, which was consistent with the presence of a right free-wall accessory pathway. Radiofrequency ablation of the anterolateral right atrium around the local shortest atrium-to-ventricle interval created the accessory pathway block. An echocardiogram taken one month after the procedure revealed that LV septal wall motion had normalized and that LV ejection fraction had improved from 50% before the ablation to 64% after the ablation. Most previous reports of asymptomatic patients of WPW with LV septal dyskinesia and dysfunction have described right septal or posteroseptal accessory pathways. This patient reported here represents a rare case with right free-wall accessory pathway and LV dysfunction without tachycardia
Flavor SU(3) breaking effects in the chiral unitary model for meson-baryon scatterings
We examine flavor SU(3) breaking effects on meson-baryon scattering
amplitudes in the chiral unitary model. It turns out that the SU(3) breaking,
which appears in the leading quark mass term in the chiral expansion, can not
explain the channel dependence of the subtraction parameters of the model,
which are crucial to reproduce the observed scattering amplitudes and resonance
properties.Comment: RevTeX4, 4 pages, 3 figures, 2 table
Quantisation of twistor theory by cocycle twist
We present the main ingredients of twistor theory leading up to and including
the Penrose-Ward transform in a coordinate algebra form which we can then
`quantise' by means of a functorial cocycle twist. The quantum algebras for the
conformal group, twistor space CP^3, compactified Minkowski space CMh and the
twistor correspondence space are obtained along with their canonical quantum
differential calculi, both in a local form and in a global *-algebra
formulation which even in the classical commutative case provides a useful
alternative to the formulation in terms of projective varieties. We outline how
the Penrose-Ward transform then quantises. As an example, we show that the
pull-back of the tautological bundle on CMh pulls back to the basic instanton
on S^4\subset CMh and that this observation quantises to obtain the
Connes-Landi instanton on \theta-deformed S^4 as the pull-back of the
tautological bundle on our \theta-deformed CMh. We likewise quantise the
fibration CP^3--> S^4 and use it to construct the bundle on \theta-deformed
CP^3 that maps over under the transform to the \theta-deformed instanton.Comment: 68 pages 0 figures. Significant revision now has detailed formulae
for classical and quantum CP^
First principles electronic structure of spinel LiCr2O4: A possible half-metal?
We have employed first-principles electronic structure calculations to
examine the hypothetical (but plausible) oxide spinel, LiCr2O4 with the d^{2.5}
electronic configuration. The cell (cubic) and internal (oxygen position)
structural parameters have been obtained for this compound through structural
relaxation in the first-principles framework. Within the one-electron band
picture, we find that LiCr2O4 is magnetic, and a candidate half-metal. The
electronic structure is substantially different from the closely related and
well known rutile half-metal CrO2. In particular, we find a smaller conduction
band width in the spinel compound, perhaps as a result of the distinct topology
of the spinel crystal structure, and the reduced oxidation state. The magnetism
and half-metallicity of LiCr2O4 has been mapped in the parameter space of its
cubic crystal structure. Comparisons with superconducting LiTi2O4 (d^{0.5}),
heavy-fermion LiV2O4 (d^{1.5}) and charge-ordering LiMn2O4 (d^{3.5}) suggest
the effectiveness of a nearly-rigid band picture involving simple shifts of the
position of E_F in these very different materials. Comparisons are also made
with the electronic structure of ZnV2O4 (d^{2}), a correlated insulator that
undergoes a structural and antiferromagnetic phase transition.Comment: 9 pages, 7 Figures, version as published in PR
A Fermi Surface study of BaKBiO
We present all electron computations of the 3D Fermi surfaces (FS's) in
BaKBiO for a number of different compositions based on the
selfconsistent Korringa-Kohn-Rostoker coherent-potential-approximation
(KKR-CPA) approach for incorporating the effects of Ba/K substitution. By
assuming a simple cubic structure throughout the composition range, the
evolution of the nesting and other features of the FS of the underlying
pristine phase is correlated with the onset of various structural transitions
with K doping. A parameterized scheme for obtaining an accurate 3D map of the
FS in BaKBiO for an arbitrary doping level is developed. We
remark on the puzzling differences between the phase diagrams of
BaKBiO and BaPbBiO by comparing aspects
of their electronic structures and those of the end compounds BaBiO,
KBiO and BaPbO. Our theoretically predicted FS's in the cubic phase are
relevant for analyzing high-resolution Compton scattering and
positron-annihilation experiments sensitive to the electron momentum density,
and are thus amenable to substantial experimental verification.Comment: 12 pages, 7 figures, to appear in Phys. Rev.
Entropy Stable Numerical Schemes for Two-Fluid Plasma Equations
Two-fluid ideal plasma equations are a generalized form of the ideal MHD
equations in which electrons and ions are considered as separate species. The
design of efficient numerical schemes for the these equations is complicated on
account of their non-linear nature and the presence of stiff source terms,
especially for high charge to mass ratios and for low Larmor radii. In this
article, we design entropy stable finite difference schemes for the two-fluid
equations by combining entropy conservative fluxes and suitable numerical
diffusion operators. Furthermore, to overcome the time step restrictions
imposed by the stiff source terms, we devise time-stepping routines based on
implicit-explicit (IMEX)-Runge Kutta (RK) schemes. The special structure of the
two-fluid plasma equations is exploited by us to design IMEX schemes in which
only local (in each cell) linear equations need to be solved at each time step.
Benchmark numerical experiments are presented to illustrate the robustness and
accuracy of these schemes.Comment: Accepted in Journal of Scientific Computin
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