13,361 research outputs found
Spiral-wave Dynamics Depends Sensitively on nhomogeneities in Mathematical Models of Ventricular Tissue
Every sixth death in industrialised countries occurs because of cardiac
arrhythmias like ventricular tachycardia (VT) and ventricular fibrillation
(VF). There is growing consensus that VT is associated with an unbroken spiral
wave of electrical activation on cardiac tissue but VF with broken waves,
spiral turbulence, spatiotemporal chaos and rapid, irregular activation. Thus
spiral-wave activity in cardiac tissue has been studied extensively.
Nevertheless many aspects of such spiral dynamics remain elusive because of the
intrinsically high-dimensional nature of the cardiac-dynamical system. In
particular, the role of tissue heterogeneities in the stability of cardiac
spiral waves is still being investigated. Experiments with conduction blocks in
cardiac tissue yield a variety of results: some suggest that blocks can
eliminate VF partially or completely, leading to VT or quiescence, but others
show that VF is unaffected by obstacles. We propose theoretically that this
variety of results is a natural manifestation of a fractal boundary that must
separate the basins of the attractors associated, respectively, with VF and VT.
We substantiate this with extensive numerical studies of Panfilov and Luo-Rudy
I models, where we show that the suppression of VF depends sensitively on the
position, size, and nature of the inhomogeneity.Comment: 9 pages, 5 figures
Parallel String Sample Sort
We discuss how string sorting algorithms can be parallelized on modern
multi-core shared memory machines. As a synthesis of the best sequential string
sorting algorithms and successful parallel sorting algorithms for atomic
objects, we propose string sample sort. The algorithm makes effective use of
the memory hierarchy, uses additional word level parallelism, and largely
avoids branch mispredictions. Additionally, we parallelize variants of multikey
quicksort and radix sort that are also useful in certain situations.Comment: 34 pages, 7 figures and 12 table
Photons from Nucleus-Nucleus Collisions at Ultra-Relativistic Energies
We compare the photon emission rates from hot hadronic matter with in-medium
mass shift and Quark Gluon Plasma (QGP). It is observed that the WA98 data can
be well reproduced by hadronic initial state with initial temperature MeV if the universal scaling of temperature dependent hadronic masses are
assumed and the evolution of temperature with time is taken from transport
model or (3+1) dimensional hydrodynamics. The data can also be reproduced by
QGP initial state with similar initial temperature and non-zero initial radial
velocity.Comment: Talk given in the International Nuclear Physics Conference, at the
University of California, Berkeley, USA, during July 30 - August 3, 200
Chromium-induced accumulation of peroxide content, stimulation of antioxidative enzymes and lipid peroxidation in green gram (Vigna radiata L. cv. Wilczek) leaves
Chromium (Cr)-induced oxidative damage and changes in contents of chlorophyll, protein, peroxide and malondialdehyde (MDA) and activities of enzymatic antioxidants were investigated in 4-day-old green gram (Vigna radiata L. cv. Wilczek) seedlings. Cr increased the contents of peroxide and MDA but decreased the contents of chlorophyll and proteins. Cr reduced the activities of catalase (CAT) and glutathione reductase (GR), but increased the activity of superoxide dismutase (SOD) in green gramleaves. Lipid peroxidation is considered to be an important mechanism of Cr-induced oxidative damage in green gram leaves. The peroxidation of lipids can be initiated by free radicals. The effects of Crinducedoxidative damage and increase in the contents of peroxide and MDA in green gram leaves can be minimized by pretreatment with ascorbic acid (AA) and reduced glutathione (GSH) or both
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