Vpliv fluktuacij, variabilnosti in topološke organiziranosti fizikalnih in bioloških sistemov na optimizacijo njihovega delovanja : doktorska disertacija

english
slovenian

doktorska dela

2011

Univerza v Mariboru, Fakulteta za naravoslovje in matematiko

The doctoral thesis is dedicated to the analysis and examination of various nonlinear dynamical systems, which can be used for the description of functioning of numerous physical and biological systems. Special attention is devoted to intrinsic fluctuations and structural diversity, a common feature of all real-life systems. In the first part it is shown that a suitable intensity of internal noise, originating from random processes on the mesoscopic scale, as well as a proper level of structural variability, lead to a coherent spatial dynamics in an ensemble of coupled biological oscillators. Furthermore, via an analytical treatment the necessary conditions under which coherent periodic waves can be triggered by localized pacemaker activity are derived. Due to their extreme susceptibility, functioning of soft matter systems can also be substantial affected by noise and quenched disorder. In view of that it is revealed that stochastic resonance can be realized in a polymer-stabilized ferroelectric liquid crystal cell, whereby combined effects of dynamical noise and different origins of static disorder are systematically analyzed. In the last decade, together with the advances in the network science, the interplay between network structure and dynamics has attracted a great deal of attention in connection with a variety of processes. Along these lines the second part of the doctoral thesis is devoted to the analysis of the outreach of localized pacemaker activity in a system of noisy oscillators. It is shown that a complex interaction topology substantially improves the dissemination of localized rhythmic activity. Furthermore, the question of optimal network organization that warrants the most regular noise induced oscillations is addressed. It turns out, in contrast with our expectations, that the greatest response is not achieved when oscillators are connected in the most effective scale free network. Instead, the best global response is achieved if oscillators form a less heterogeneous network in which long as well as short range connections are present. It is revealed that the existence of an optimal network topology is linked with the critical point of the network structure. In the last part, a spatial network model of the pulmonary artery is developed, which provides a theoretical explanation for the experimentally measured contraction responses in tissues form normoxic and chronic hypoxic rats. A particular interest is devoted to variability of smooth muscle cells and to the pathophysiological role of the topology of intercellular communication pathways.

08.08.2023