Biomedical subjects

Zbigniew Koza

Publications and source records attributed to Zbigniew Koza.

4 recordsLinked to original sources

PubMed2006

Reaction-diffusion fronts in systems with concentration-dependent diffusivities.

We examine properties of a reaction front that forms in irreversible reaction-diffusion systems with concentration-dependent diffusivities. We study two different models of such systems and find that in the limit of a vanishingly small diffusivity of the reaction product, the reaction front dynamics enters a separate universality class, with the front width asymptotically tending to a constant value, and the reaction rate at the reaction front center diminishing with time t as t(-1/2). This behavior can be also observed in systems with nonvanishing (but small) diffusivity of the reaction product at intermediate times.

Journal Article↗

PubMed2003

A cross-platform public domain PC image-analysis program for the comet assay.

The single-cell gel electrophoresis, also known as the comet assay, has gained wide-spread popularity as a simple and reliable method to measure genotoxic and cytotoxic effects of physical and chemical agents as well as kinetics of DNA repair. Cells are generally stained with fluorescent dyes. The analysis of comets--damaged cells which form a typical comet-shaped pattern--is greatly facilitated by the use of a computer image-analysis program. Although several image-analysis programs are available commercially, they are expensive and their source codes are not provided. For Macintosh computers a cost-free public domain macro is available on the Internet. No ready for use, cost-free program exists for the PC platform. We have, therefore, developed such a public domain program under the GNU license for PC computers. The program is called CASP and can be run on a variety of hardware and software platforms. Its practical merit was tested on human lymphocytes exposed to gamma-rays and found to yield reproducible results. The binaries for Windows 95 and Linux, together with the source code can be obtained from: http://www.casp.of.pl.

Algorithms↗

PubMed2002

Asymptotic expansion for reversible A+B<-->C reaction-diffusion process.

We study long-time properties of reversible reaction-diffusion systems of type A+B<-->C by means of the perturbation expansion in powers of 1/t (inverse of time). For the case of equal diffusion coefficients we present exact formulas for the asymptotic forms of reactant concentrations and a complete, recursive expression for an arbitrary term of the expansions. Taking an appropriate limit we show that by studying reversible reactions one can obtain "singular" solutions typical of irreversible reactions.

Journal Article↗

PubMed2002

Maximal force exerted by a molecular motor.

We consider a particle diffusing in a one-dimensional periodic lattice with arbitrary transition rates between nearest-neighbor sites. We show rigorously that the ratio of the drift velocity V to the diffusion coefficient D has the upper bound 2N/d, where N is the number of nodes in an elementary cell and d denotes its length. Applying this result to a model of a molecular motor introduced by Fisher and Kolomeisky [Proc. Natl. Acad. Sci. USA 96, 6597 (1999)] we show that the so called Einstein force, which sets the lower bound for the force exerted by a molecular motor, is bounded from above by 2k(B)TN/d irrespective of the actual values of the jump rates between internal states of the motor.

Biophysical Phenomena↗