Biomedical subjects

S Khrapak

Publications and source records attributed to S Khrapak.

3 recordsLinked to original sources

PubMed2006

Superdiffusion and viscoelastic vortex flows in a two-dimensional complex plasma.

Viscoelastic vortical fluid motion in a strongly coupled particle system has been observed experimentally. Optical tracking of particle motion in a complex plasma monolayer reveals high grain mobility and large scale vortex flows coexistent with partial preservation of the global hexagonal lattice structure. The transport of particles is superdiffusive and ascribed to Lévy statistics on short time scales and to memory effects on the longer scales influenced by cooperative motion. At these longer time scales, the transport is governed by vortex flows covering a wide spectrum of temporal and spatial scales.

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PubMed2004

Experimental determination of dust-particle charge in a discharge plasma at elevated pressures.

The charge of dust particles is determined experimentally in a bulk dc discharge plasma in the pressure range 20-100 Pa. The charge is obtained by two independent methods: one based on an analysis of the particle motion in a stable particle flow and another on an analysis of the transition of the flow to an unstable regime. Molecular-dynamics simulations of the particle charging for conditions similar to those of the experiment are also performed. The results of both experimental methods and the simulations demonstrate good agreement. The charge obtained is several times smaller than predicted by the collisionless orbital motion theory, and thus the results serve as an experimental indication that ion-neutral collisions significantly affect particle charging.

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PubMed2002

Universal scaling in complex (dusty) plasmas.

The structural and dynamical properties of three-dimensional isotropic complex plasmas are investigated kinetically within the framework of a dissipative Yukawa model. A modified Coulomb coupling parameter is proposed whose value alone determines the location of the complex plasma melting line. This implies that the phase transition has a universal scaling at the kinetic level. In detail, our molecular dynamics investigations show that the system dynamics is universal (but different) in the limits of high as well as low-frictional dissipation, while in the intermediate case it depends considerably on the dissipation rate. Issues such as the influence of the interaction strength on the single particle diffusion constant and the applicability of dynamical criteria for freezing are discussed.

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