Vladimir Lisy

Brownian Motion of Charged Particles Driven by Correlated Noise in Magnetic Field

Analytical solutions of the generalized Langevin equation have been found for the time correlation functions describing the motion of a charged Brownian particle in an external magnetic field when the thermal random force in weakly viscoelastic fluids is exponentially correlated in the time. To obtain a correct description at short times, inertial effects are included into the consideration. The found mean square displacement of the particle motion across the field contains a term proportional to the time, a constant term, and exponentially decaying contributions. The solution for a particle trapped in a harmonic well is also found.

Inverse geometric approach for the simulation of close-to-circular growth. The case of multicellular tumor spheroids

We demonstrate the power of genetic algorithms to construct a cellular automata model simulating the growth of 2D close-to-circular clusters, revealing the desired properties, such as the growth rate and, at the same time, the fractal behavior of their contours. The possible application of the approach in the field of tumor modeling is outlined.

Intrinsic viscosity of PVP polymers in extremely diluted solutions

In conventional viscometry studies an additional treatment of data is necessary in order to obtain the expected linear dependence of the reduced viscosity on concentration in extremely diluted polymer solutions. This work reports on the direct measurements of this dependence using a new Couette-type viscometer. The values of intrinsic viscosity and Huggins coefficient of the studied poly(N-vinyl-2-pyrrolidone) (PVP) water solution notably differ from the previous results obtained by the traditional capillary viscometers. From the obtained data the parameters used in the bead-spring theories of polymer universal behavior, such as the gyration radius and the longest relaxation time are calculated.

Simple Derivation of the First Cumulant for the Rouse Chain

Abstract A simple analytic expression for the first cumulant of the dynamic structure factor of a polymer coil in the Rouse model is derived. The obtained formula is exact within the usual assumption of the continuum distribution of beads along the chain. It reflects the contributions to the scattering of light or neutrons from both the internal motion of the polymer and its diffusion, and is valid in the whole region of the wave-vector change at the scattering.