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M A Tsyganov

Publications and source records attributed to M A Tsyganov.

At least 19 recordsLinked to original sources
PubMed2004

Half-soliton interaction of population taxis waves in predator-prey systems with pursuit and evasion.

In this paper, we use numerical simulations to demonstrate a half-soliton interaction of waves in a mathematical model of a "prey-predator" system with taxis when of two colliding waves, one annihilates and the other continues to propagate. We show that this effect depends on the "ages" or, equivalently, "widths" of the colliding waves. In two spatial dimensions we demonstrate that the type of interaction, i.e., annihilation, quasisoliton, or half-soliton, depends not only on curvature and width of the colliding waves, but also on the angle of the collision. When conditions of collision are varying in such a way that only a part of a wave survives the collision, then "taxitons," compact pieces of solitary waves, may form, which can exist for a significant time.

Adaptation, Physiological↗
PubMed2004

Pursuit-evasion predator-prey waves in two spatial dimensions.

We consider a spatially distributed population dynamics model with excitable predator-prey kinetics, where species propagate in space due to their taxis with respect to each other's gradient in addition to, or instead of, their diffusive spread. Earlier, we have described new phenomena in this model in one spatial dimension, not found in analogous systems without taxis: reflecting and self-splitting waves. Here we identify new phenomena in two spatial dimensions: unusual patterns of meander of spirals, partial reflection of waves, swelling wave tips, attachment of free wave ends to wave backs, and as a result, a novel mechanism of self-supporting complicated spatiotemporal activity, unknown in reaction-diffusion population models.

Adaptation, Physiological↗
PubMed2003

Quasisoliton interaction of pursuit-evasion waves in a predator-prey system.

We consider a system of partial differential equations describing two spatially distributed populations in a "predator-prey" interaction with each other. The spatial evolution is governed by three processes: positive taxis of predators up the gradient of prey (pursuit), negative taxis of prey down the gradient of predators (evasion), and diffusion resulting from random motion of both species. We demonstrate a new type of propagating wave in this system. The mechanism of propagation of these waves essentially depends on the taxis and is entirely different from waves in a reaction-diffusion system. Unlike typical reaction-diffusion waves, which annihilate on collision, these "taxis" waves can often penetrate through each other and reflect from impermeable boundaries.

Animals↗
PubMed1999

Spatiotemporal irregularity in an excitable medium with shear flow.

We consider an excitable medium moving with relative shear, subjected to a localized disturbance that in a stationary medium would produce a pair of spiral waves. The spiral waves so created are distorted and then broken by the motion of the medium. Such breaks generate new spiral waves, and so a "chain reaction" of spiral wave births and deaths is observed. This leads to a complicated spatiotemporal pattern, the "frazzle gas" [term suggested by Markus et al., Nature (London) 371, 402 (1994)], which eventually fills the whole medium. In this paper, we display and interpret the main features of the pattern.

Journal Article↗
PubMed1995

Structure of open promoter complexes with Escherichia coli RNA polymerase as revealed by the DNase I footprinting technique: compilation analysis.

Footprinting data for 33 open promoter complexes with Escherichia coli RNA polymerase, as well as 17 ternary complexes with different regulators, have been compiled using a computer program FUTPR. The typical and individual properties of their structural organization are analyzed. Promoters are subgrouped according to the extent of the polymerase contact area. A set of alternative sequence elements that could be responsible for RNA polymerase attachment in different promoter groups is suggested on the basis of their sequence homology near the hyperreactive sites. The model of alternative pathways used for promoter activation is discussed.

Alternative Splicing↗
PubMed1993

Instability of waves formed by motile bacteria.

Many motile chemotactic bacteria (for instance, Escherichia coli) inoculated at some point in a semisolid nutrient medium can form circular expanding population waves. The formation of these motile structures is due to chemotaxis. The circular waves originate from an expanding bacterial lawn (a parent population). The regular shape of these waves results from the isotropic distribution of freely diffusible nutrient molecules which are also attractants. In this paper we show that the regular shape of the bacterial population waves can be spontaneously disturbed. As this takes place arc-shaped population waves ('bursts') are formed. It was found that initially the mean length of the cells forming the bursts was greater than that of the parent cell population. But then it decreased resulting in a value characteristic of the parent population.

Cell Division↗
PubMed1992

pH track of expanding bacterial populations.

A method of pH distribution measurements in agar nutrient media containing expanding bacterial populations is described. It is based on measuring pH microsamples taken at different points of the media. The sample volume was 10 microliters. A pH sensitive field effect transistor was used as a measuring electrode. Acidification was found to occur in glucose media, while alkalization occurred in the media containing peptone.

Bacteriological Techniques↗
PubMed1991

Formation of demarcation zones when bacterial population waves are drawn together.

Many motile bacteria (for instance, Escherichia coli) inoculated at some point in a semisolid nutrient medium can form population waves: bands or rings. The formation of these motile structures is due to chemotaxis. The population waves when they are drawn together can form two types of non-motile structures. Firstly, the population waves can collide. Secondly, in certain conditions, the waves can slow down and stop without coming into contact directly with each other. In this way demarcation zones are formed. The mechanism of the occurrence of the demarcation zones has been unknown. In this paper we show that formation of these zones is due to lack of nutrients (which at the same time act as attractants) within the narrow gap between individual bacterial populations.

Cell Movement↗