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Non-homogeneous random walks, subdiffusive migration of cells and anomalous chemotaxis
This paper is concerned with a non-homogeneous in space and non-local in time
random walk model for anomalous subdiffusive transport of cells. Starting with
a Markov model involving a structured probability density function, we derive
the non-local in time master equation and fractional equation for the
probability of cell position. We show the structural instability of fractional
subdiffusive equation with respect to the partial variations of anomalous
exponent. We find the criteria under which the anomalous aggregation of cells
takes place in the semi-infinite domain.Comment: 18 pages, accepted for publicatio
Halo Formation in Spheroidal Bunches with Self-Consistent Stationary Distributions
A new class of self-consistent 6-D phase space stationary distributions is
constructed both analytically and numerically. The beam is then mismatched
longitudinally and/or transversely, and we explore the beam stability and halo
formation for the case of 3-D axisymmetric beam bunches using particle-in-cell
simulations. We concentrate on beams with bunch length-to-width ratios varying
from 1 to 5, which covers the typical range of the APT linac parameters. We
find that the longitudinal halo forms first for comparable longitudinal and
transverse mismatches. An interesting coupling phenomenon - a longitudinal or
transverse halo is observed even for very small mismatches if the mismatch in
the other plane is large - is discovered.Comment: 3 pages, 3 figures; presented at European Particle Accelerator
Conference, Stockholm, Sweden (June 22-26, 1998
Optical nonlinearity and light-induced structural transformations in gallium nanoparticles
We report that gallium nanoparticles, prepared by light-assisted self-assembly, show a nonlinear response to low-power optical excitation. Reversible reflectivity changes of several percent are induced as the result of light-induced structural transformations in the meta
On the kinetic equation approach to pair production by time-dependent electric field
We investigate the quantum kinetic approach to pair production from vacuum by
time-dependent electric field. Equivalence between this approach and the more
familiar S-matrix approach is explicitly established for both scalar and
fermion cases. For the particular case of a constant electric field exact
solution for kinetic equations is provided and the accuracy of low-density
approximation is estimated.Comment: 8 pages, 4 figure
Memory Effects in Turbulent Dynamo: Generation and Propagation of Large Scale Magnetic Field
We are concerned with large scale magnetic field dynamo generation and
propagation of magnetic fronts in turbulent electrically conducting fluids. An
effective equation for the large scale magnetic field is developed here that
takes into account the finite correlation times of the turbulent flow. This
equation involves the memory integrals corresponding to the dynamo source term
describing the alpha-effect and turbulent transport of magnetic field. We find
that the memory effects can drastically change the dynamo growth rate, in
particular, non-local turbulent transport might increase the growth rate
several times compared to the conventional gradient transport expression.
Moreover, the integral turbulent transport term leads to a large decrease of
the speed of magnetic front propagation.Comment: 13 pages, 2 figure
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