8,042 research outputs found
Arrhythmias After Tetralogy of Fallot Repair
Tetralogy of Fallot is the most common cyanotic congenital heart disease, with a good outcome after total surgical correction. In spite of a low perioperative mortality and a good quality of life, late sudden death remains a significant clinical problem, mainly related to episodes of sustained ventricular tachycardia and ventricular fibrillation. Fibro-fatty substitution around infundibular resection, intraventricular septal scar, and patchy myocardial fibrosis, may provide anatomical substrates of abnormal depolarization and repolarization causing reentrant ventricular arrhythmias.
Several non-invasive indices based on classical examination such as ECG, signal-averaging ECG, and echocardiography have been proposed to identify patients at high risk of sudden death, with hopeful results. In the last years other more sophisticated invasive and non-invasive tools, such as heart rate variability, electroanatomic mapping and cardiac magnetic resonance added a relevant contribution to risk stratification.
Even if each method per se is affected by some limitations, a comprehensive multifactorial clinical and investigative examination can provide an accurate risk evaluation for every patien
Stringy Instantons as Strong Dynamics
We study the relation between stringy instantons and strong dynamics effects
in type IIB toric quiver gauge theories. By exploiting the involutive property
of Seiberg duality we relate the classical constraint on the moduli space of
the gauge theory with the stringy instanton contribution to the superpotential.
The result holds for unitary, orthogonal and symplectic gauge groups.Comment: Minor corrections, reference added, published in JHE
Tetraquarks in the 1/N expansion and meson-meson resonances
Diquarks are found to have the right degrees of freedom to describe the tetraquark poles in hidden-charm to open-charm meson-meson amplitudes. Compact tetraquarks result as intermediate states in non-planar diagrams of the 1/N expansion and the corresponding resonances are narrower than what estimated before. The proximity of tetraquarks to meson-thresholds has an apparent role in this analysis and, in the language of meson molecules, an halving rule in the counting of states is obtained
Diquark-antidiquark states with hidden or open charm
Some features and predictions of a recently proposed model based on
diquark-antidiquark bound states are illustrated. Its ability in accomodating
newly discovered charmed resonances around 4 GeV is discussed.Comment: To appear in the proceedings of the HEP2005 International Europhysics
Conference on High Energy Physics, July 21st-27th 2005, Lisboa, Portuga
Complex Grid Computing
This article investigates the performance of grid computing systems whose
interconnections are given by random and scale-free complex network models.
Regular networks, which are common in parallel computing architectures, are
also used as a standard for comparison. The processing load is assigned to the
processing nodes on demand, and the efficiency of the overall computing is
quantified in terms of the respective speed-ups. It is found that random
networks allow higher computing efficiency than their scale-free counterparts
as a consequence of the smaller number of isolated clusters implied by the
former model. At the same time, for fixed cluster sizes, the scale free model
tend to provide slightly better efficiency. Two modifications of the random and
scale free paradigms, where new connections tend to favor more recently added
nodes, are proposed and shown to be more effective for grid computing than the
standard models. A well-defined correlation is observed between the topological
properties of the network and their respective computing efficiency.Comment: 5 pages, 2 figure
Between Heaven and Hell: Perceptions of Brazil and the United States in "Brazuca" Literature
This is the published version. Copyright 2005 Johns Hopkins University Press.Brazilian emigration to the United States has increased considerably in the past three decades. Brazilian immigrants have begun using literature, music, and cinema to give expression to their experiences. After quickly discussing Brazil's shift from a land of immigration to a region of emigration, this essay introduces a number of aspects of "Brazuca" literature, and analyzes how the American experience has created changing perceptions of Brazil and the United States for this new minority group, which is a feature of their in-betweenness as immigrants
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