27,002 research outputs found
On scattering cross sections and durations near an isolated compound-resonance, distorted by the non-resonant background, in the center-of-mass and laboratory systems
During last 20 years there was revealed and published the phenomenon of the
appearing of the time advance instead of the time delay at the region of a
compound-nucleus resonance, distorted by the non-resonant background (in the
center-of-mass (C-) system). This phenomenon is usually accompanied by a
minimum in the cross section near the same energy. Here we analyze the cross
section and the time delay of the nucleon-nucleus scattering in the laboratory
(L-) system. In the L-system the delay-advance phenomenon does not appear. We
use and concretize the non-standard analytical transformations of the cross
section from the C-system to the L-system, obtained in our previous papers.
They are illustrated by the calculations of energy dependences of cross
sections in the L-system for several cases of nucleon elastic scattering by
nuclei 12C, 16O, 28Si, 52Cr, 56Fe and 64Ni at the range of distorted resonances
in comparison with the experimental data.Comment: 11 pages, 7 figure
Global weak solution and blow-up criterion of the general Ericksen-Leslie system for nematic liquid crystal flows
In this paper we investigate the three dimensional general Ericksen-Leslie
(E--L) system with Ginzburg-Landau type approximation modeling nematic liquid
crystal flows. First, by overcoming the difficulties from lack of maximum
principle for the director equation and high order nonlinearities for the
stress tensor, we prove existence of global-in-time weak solutions under
physically meaningful boundary conditions and suitable assumptions on the
Leslie coefficients, which ensures that the total energy of the E--L system is
dissipated. Moreover, for the E--L system with periodic boundary conditions, we
prove the local well-posedness of classical solutions under the so-called
Parodi's relation and establish a blow-up criterion in terms of the temporal
integral of both the maximum norm of the curl of the velocity field and the
maximum norm of the gradient of the liquid crystal director field
Quadruple context-free L-System mathematical tools as origin of biological evolution
It is well known that A, T, G, C annealed together early in evolution and the long stretch of DNA was found which ultimately resulted into chromosomes of different organisms. But it is unclear till date how exons, introns, conserved protein domains was formed. Using the DNA sequences of the largest known gene-family present in human genome, i.e., olfactory receptors and simplest possible quadruple context-free L-Systems, we show that conserved protein domains and intergenic regions which lies at the heart of the biological evolution started with a sixteen base-pairs stretch of DNA
Excess number of percolation clusters on the surface of a sphere
Monte Carlo simulations were performed in order to determine the excess
number of clusters b and the average density of clusters n_c for the
two-dimensional "Swiss cheese" continuum percolation model on a planar L x L
system and on the surface of a sphere. The excess number of clusters for the L
x L system was confirmed to be a universal quantity with a value b = 0.8841 as
previously predicted and verified only for lattice percolation. The excess
number of clusters on the surface of a sphere was found to have the value b =
1.215(1) for discs with the same coverage as the flat critical system. Finally,
the average critical density of clusters was calculated for continuum systems
n_c = 0.0408(1).Comment: 13 pages, 2 figure
Neutron Moderation Theory Taking into Accout the Thermal Motion of Moderating Medium Nuclei
In this paper we present the analytical expression for the neutron scattering
law for an isotropic source of neutrons, obtained within the framework of the
gas model with the temperature of the moderating medium as a parameter. The
obtained scattering law is based on the solution of the kinematic problem of
elastic scattering of neutrons on nuclei in the L-system in the general case.
I.e. both the neutron and the nucleus possess the arbitrary velocity vectors in
the L-system. For the new scattering law the flux densities and neutron
moderation spectra depending on the temperature are obtained for the reactor
fissile medium. The expressions for the moderating neutrons spectra allow
reinterpreting the physical nature of the underlying processes in the thermal
region.Comment: 26 pages, 6 figure
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