[Mechanistic model for the allee effect and interference in predator population].

Simulation results obtained with an individual-based model describing spatial movement and interactions of predators and prey within a closed rectangular habitat are represented. Movement of each individual animal is determined by local conditions only, thus any collective behaviour emerges due to self-organization. It is shown that the pursuit of the prey by predators leads to the emergence of predator interference manifesting itself at the population level as the dependence of the trophic function on predator abundance (predator-dependence). The stabilizing effect of predator dependence on the dynamics of a predator-prey system has been discussed. The inclusion of prey evasion induces predators' cooperation that further distorts the functional response (the trophic function), leading to a strong Allee effect, i.e. extinction of predator population dropping below a critical threShold. Thus, we propose a simple mechanistic explanation of important but still poorly understood behavioural phenomena that underlie functioning of natural trophic systems.

[Sedimentation in the seasonal cycle of unicellular algae. Model analysis]. / Rol' osedaniia v sezonnom tsikle odnokletochnykh vodoroslei. Model'nyi analiz.

The efficiency of quick sedimentation (quicker then at normal condition) of unicellular algae at the end of seasonal cycle was studied in Okhotsk Sea. Model researches were based on the effect of competition of two algae populations. Analytical investigations of simplified variant of mathematical model and computing experiments showed that cell sedimentation and falling into the unfavorable (dark and cold) environment could be compensated by the increase in survival under these "negative" conditions. Vertical mixing of water has effect. Generally, mechanism of convective mixing is one of the factors that helps competing populations of unicellular algae to exist under conditions of changing environment.

[Blood flow in the left pulmonary veins and the regional nonuniformity of the left ventricular myocardium: an ultrasonic Doppler study]. / Potok krovi v legochnykh venakh i regionarnaia neodnorodnost' miokarda levogo zheludochka: ul'trazvukovoe dopplerovskoe issledovanie.

The paper elucidates the nature of systolic peak cleavage in pulmonary venous blood flow into the major (J) and auxiliary (J') ones. A hypothesis has been forwarded, according to which the occurrence of the peak J' is associated with the kinetics of left ventricular walls and mitral ring due to regional left ventricular myocardial heterogeneity. The paper also provides indirect evidence for this hypothesis, which has been obtained by Doppler ultrasonic study of 13 healthy individuals and 34 patients with various cardiovascular diseases. It has been found that in most cases the cleavage of the peak J was observed in patients with pronounced regional left ventricular myocardial heterogeneity (postinfarct aneurysm, dilated cardiomyopathy, Wolff-Parkinson-White syndrome, etc.).