Nonlinear Model of Blood Flow Through Stenosed Coronary Arteries

Blood flow and pulse wave propagation in the blood vessels are usually studied on the incompressible linearized axsymmetric Navier-Stokes equations (Womersley model) coupled with linear and nonlinear viscoelastic equations for the vessel walls. A brief review of the nonlinear models is given. Blood flow and wave propagation through the stenosed artery terminated by a viscoelastic chamber with different resistivity and compliance has been considered. The material parameters of the wall corresponded to healthy elastic and degenerated compliant human arteries. Both 2d linearized and 1d nonlinear models have been applied for numerical solution of the problem. The computational results for the pressure P(t), flow U(t) and diameter d(t) oscillations have been compared to the measurement data. It is shown that the dynamics of the fluid-filled vessels with healthy elastic walls is satisfactory described by the linearized equations while for the age-related degenerative walls, stenosed or diluted vessels the nonlinear models are preferable

The purpose and peculiarities of testing

In the process of teaching in general and teaching foreign languages in particular we need to pay attention to many aspects: how effective the methods and techniques used in the process are, how well the learners know the new material, what should be changed, what should be discussed in detail. It is a test that helps assess the existing situation. However, there are different attitudes to testing. There are some opinions that tests do not do any good, but only create additional stress for students. In addition, it is said that in most cases guessing of the right answer takes place, instead of demonstrating the real knowledge. This article will try to understand what testing is, how appropriate it is in the process of teaching foreign languages, what kinds of tests exist

Mathematical modeling of bioactive arterial wall

Biological tissues and their artificial substitutes are composed by different fibers and possess complex viscoelastic properties. Here the most popular 3-element and 5-element rheological models of human soft tissues as viscoelastic bodies are considered accounting for the time delay between the load and mechanical respond of the material.The obtained data compared to the experimental curves got on the vessel wall and heart tissues

Mechano-Electric Feedbacks in a New Model of the Excitation-Contraction Coupling in Human Cardiomyocytes

The study is aimed to develop a new human cardiomyocyte model, which describes electromechanical coupling and mechano-electric feedbacks. The combined electromechanical model (TP+M) links the TP06 electrophysiological model of the human cardiomyocyte with our earlier developed model of the myocardium mechanical activity and its calcium regulation. In the TP+M model, we tried to maintain principal features of calcium transients and action potentials during the twitches typical for the human cardiomyocytes. The developed TP+M model allows simulating several basic classic phenomena such as load-dependent relaxation and length-dependence of isometric twitches and respective changes in action potential duration. We have also simulated some age-dependent changes in the electrical and mechanical activity in the human cardiomyocytes. © 2018 Creative Commons Attribution.The work was carried out within the framework of the IIP UrB RAS themes (Nos. AAAA-A18-118020590031-8, АААА-А18-118020590134-6) and was supported by Act 211 Government of the Russian Federation, contract № 02.A03.21.0006, and by RFBR (18-01-00059 - single cell modeling; 18-015-00368 – ageing simulation)

Bacterial Carriage of Pathogenic Antibiotic-resistant Staphylococci Among Conditionally Healthy Infants and Preschool-age Children

Staphylococci are related to opportunistic microorganisms and are part of normal human microflora. However, there are varieties that can cause pyoinflammatory diseases in organisms with weakened immune status. In the event of an inadequate therapeutic approach, they are preserved in the body, and the person becomes a bacterial carrier and a source of dissemination of pathogenic microorganisms. The formation of antibiotic resistance also plays a significant role in the emergence of bacterial carriage. The situation is especially serious in organized children’s groups, where children are in close contact with one another. Thus, the study of the prevalence rate of antibiotic resistance among pathogenic strains of staphylococci in children’s groups is topical and worthy of attention. The purpose of this work is to identify carriers of pathogenic and antibiotic resistant staphylococci isolated from the microflora of the oral cavity of preschool children considered healthy. The results of the research can prove useful in practical healthcare and, particularly, in pediatric practice. Keywords: staphylococci, pathogenic cocci, bacterial carriage, antibiotic resistance, infant morbidity rat

Mechano-calcium and mechano-electric feedbacks in the human cardiomyocyte analyzed in a mathematical model

Experiments on animal hearts (rat, rabbit, guinea pig, etc.) have demonstrated that mechano-calcium feedback (MCF) and mechano-electric feedback (MEF) are very important for myocardial self-regulation because they adjust the cardiomyocyte contractile function to various mechanical loads and to mechanical interactions between heterogeneous myocardial segments in the ventricle walls. In in vitro experiments on these animals, MCF and MEF manifested themselves in several basic classical phenomena (e.g., load dependence, length dependence of isometric twitches, etc.), and in the respective responses of calcium transients and action potentials. However, it is extremely difficult to study simultaneously the electrical, calcium, and mechanical activities of the human heart muscle in vitro. Mathematical modeling is a useful tool for exploring these phenomena. We have developed a novel model to describe electromechanical coupling and mechano-electric feedbacks in the human cardiomyocyte. It combines the 'ten Tusscher-Panfilov' electrophysiological model of the human cardiomyocyte with our module of myocardium mechanical activity taken from the 'Ekaterinburg-Oxford' model and adjusted to human data. Using it, we simulated isometric and afterloaded twitches and effects of MCF and MEF on excitation-contraction coupling. MCF and MEF were found to affect significantly the duration of the calcium transient and action potential in the human cardiomyocyte model in response to both smaller afterloads as compared to bigger ones and various mechanical interventions applied during isometric and afterloaded twitches. © 2020 The Author(s).Russian Foundation for Basic Research, RFBR: 18‑01‑00059The work was carried out within the framework of the IIP UrB RAS themes (Nos. AAAA‑A18‑118020590031‑8, AAAA‑A18‑118020590134‑6) and was supported by RFBR (18‑01‑00059) and by Act 211 Government of the Russian Federation, contract No. 02.A03.21.0006

Transmural cellular heterogeneity in myocardial electromechanics

Myocardial heterogeneity is an attribute of the normal heart. We have developed integrative models of cardiomyocytes from the subendocardial (ENDO) and subepicardial (EPI) ventricular regions that take into account experimental data on specific regional features of intracellular electromechanical coupling in the guinea pig heart. The models adequately simulate experimental data on the differences in the action potential and contraction between the ENDO and EPI cells. The modeling results predict that heterogeneity in the parameters of calcium handling and myofilament mechanics in isolated ENDO and EPI cardiomyocytes are essential to produce the differences in Ca2+ transients and contraction profiles via cooperative mechanisms of mechano-calcium-electric feedback and may further slightly modulate transmural differences in the electrical properties between the cells. Simulation results predict that ENDO cells have greater sensitivity to changes in the mechanical load than EPI cells. These data are important for understanding the behavior of cardiomyocytes in the intact heart. © 2017, The Physiological Society of Japan and Springer Japan.Japan Society for the Promotion of Science, JSPS: 16K1287

Resource-saving factor in the development of Russian cities

The purpose of the article is to identify the problems of Russian cities and urban-type settlements from the standpoint of their historical and economic development. Using the methodology of economic, statistical and retrospective analysis, it was revealed that along with the growth of large cities in recent years, there has been a tendency towards a reduction in small settlements, which is associated with a decrease in industrial production. The result of this is the active development of urban processes, leading to the concentration in large cities of the scientific, technical and intellectual and production potential of the regions, their transformation into self-sufficient centers for the development of territorial socio-economic locations. The result of the study is the substantiation of the need to create new methodological approaches to the development and placement of productive forces, planning of urban areas, solving problems of energy and resource supply of territories on the basis of achieving their ecological and economic efficiency. The concept of the decisive role of the resource-saving factor in the process of urbanization of territories is substantiated. It was revealed that the approach to the analysis and modeling of the city economy when considering it as a "quasi-corporation" involves the formation of an integrated reproduction system based on increasing the efficiency of the use of territory resources, which translates the process of planning the development of the urban environment into the category of business process technologies