49,942 research outputs found
Three Dimensional Simulation of Gamma Ray Emission from Asymmetric Supernovae and Hypernovae
Hard X- and -ray spectra and light curves resulting from radioactive
decays are computed for aspherical (jet-like) and energetic supernova models
(representing a prototypical hypernova SN 1998bw), using a 3D energy- and
time-dependent Monte Carlo scheme. The emission is characterized by (1) early
emergence of high energy emission, (2) large line-to-continuum ratio, and (3)
large cut-off energy by photoelectric absorptions in hard X-ray energies. These
three properties are not sensitively dependent on the observer's direction. On
the other hand, fluxes and line profiles depend sensitively on the observer's
direction, showing larger luminosity and larger degree of blueshift for an
observer closer to the polar () direction. Strategies to derive the degree
of asphericity and the observer's direction from (future) observations are
suggested on the basis of these features, and an estimate on detectability of
the high energy emission by the {\it INTEGRAL} and future observatories is
presented. Also presented is examination on applicability of a gray effective
-ray opacity for computing the energy deposition rate in the aspherical
SN ejecta. The 3D detailed computations show that the effective -ray
opacity cm g reproduces the
detailed energy-dependent transport for both spherical and aspherical
(jet-like) geometry.Comment: 24 pages, 13 figures. Figure 7 added in the accepted version. ApJ,
644 (01 June 2006 issue), in press. Resolution of figures lower than the
published versio
Topological fault-tolerance in cluster state quantum computation
We describe a fault-tolerant version of the one-way quantum computer using a
cluster state in three spatial dimensions. Topologically protected quantum
gates are realized by choosing appropriate boundary conditions on the cluster.
We provide equivalence transformations for these boundary conditions that can
be used to simplify fault-tolerant circuits and to derive circuit identities in
a topological manner. The spatial dimensionality of the scheme can be reduced
to two by converting one spatial axis of the cluster into time. The error
threshold is 0.75% for each source in an error model with preparation, gate,
storage and measurement errors. The operational overhead is poly-logarithmic in
the circuit size.Comment: 20 pages, 12 figure
A Topological Framework for the Computation of the HOMFLY Polynomial and Its Application to Proteins
Polymers can be modeled as open polygonal paths and their closure generates
knots. Knotted proteins detection is currently achieved via high-throughput
methods based on a common framework insensitive to the handedness of knots.
Here we propose a topological framework for the computation of the HOMFLY
polynomial, an handedness-sensitive invariant. Our approach couples a
multi-component reduction scheme with the polynomial computation. After
validation on tabulated knots and links the framework was applied to the entire
Protein Data Bank along with a set of selected topological checks that allowed
to discard artificially entangled structures. This led to an up-to-date table
of knotted proteins that also includes two newly detected right-handed trefoil
knots in recently deposited protein structures. The application range of our
framework is not limited to proteins and it can be extended to the topological
analysis of biological and synthetic polymers and more generally to arbitrary
polygonal paths.Comment: 20 pages, 7 figure
Investigation of Thermodynamic Properties of Cu(NH3)4SO4.H2O, a Heisenberg Spin Chain Compound
Detailed experimental investigations of thermal and magnetic properties are
presented for Cu(NH3)4SO4.H2O, an ideal uniform Heisenberg spin half chain
compound. A comparison of these properties with relevant spin models is also
presented. The temperature dependent magnetic susceptibility and specific heat
data has been compared with the exact solution for uniform Heisenberg chain
model derived by means of Bethe ansatz technique. Field dependent isothermal
magnetization curves are simulated by Quantum Monte Carlo technique and
compared with the corresponding experimental ones. Specific heat as a function
of magnetic field (up to 7T) and temperature (down to 2K) is reported.
Subsequently, the data are compared with the corresponding theoretical curves
for the infinite Heisenberg spin half chain model with J=6K. Moreover, internal
energy and entropy are calculated by analyzing the experimental specific heat
data. Magnetic field and temperature dependent behavior of entropy and internal
energy are in good agreement with the theoretical predictions
Preliminary investigation on auto-thermal extrusion of ground tire rubber
Ground tire rubber (GTR) was processed using an auto-thermal extrusion as prerequisite to green reclaiming of GTR. The reclaimed GTR underwent a series of tests: thermogravimetric analysis combined with Fourier-transform infrared spectroscopy (TGA-FTIR), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and static headspace and gas chromatography-mass spectrometry (SHS-GC-MS) in order to evaluate the impact of barrel heating solution (with/without external barrel heating) on reclaiming process of GTR. Moreover, samples were cured to assess the impact of reclaiming heating solution on curing characteristics and physico-mechanical properties. Detailed analysis of the results indicated that the heat supplied by the machinery was replaced by energy generated due to the high shearing phenomenon, what significantly influenced energy consumption and hereby lowered processing costPostprint (published version
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