Role of fluctuations, variability and topological organization by the optimization of functioning of physical and biological systems
| Autor: | GOSAK, MARKO |
|---|---|
| Přispěvatelé: | Marhl, Marko |
| Jazyk: | slovinština |
| Rok vydání: | 2011 |
| Předmět: |
nelinearna dinamika
excitable dynamics coherence resonance koherenčna resonanca prostorsko vpete mreže nonlinear dynamics udc:530.182:577.31:517.17(043.3) stohastični procesi complex network kalcijeva signalizacija ekscitabilna dinamika calcium signalization stohastična resonanca kompleksne mreže stochastic processes spatial embedded network biological oscillator stochastic resonance biološki oscilator |
| Zdroj: | Maribor |
| Popis: | V doktorski disertaciji je preučevano in analizirano obnašanje različnih nelinearnih dinamičnih sistemov, na podlagi katerih je možno opisati delovanje številnih bioloških in fizikalnih sistemov. Ker sta za vse realne sisteme značilna prisotnost fluktuacij in heterogenost gradnikov, je tema dejavnikoma posvečena posebna pozornost. V prvem delu je dokazano, da lahko tako pravšnja intenziteta intrinzičnega šuma, ki je posledica naključnih procesov na molekularni ravni, kot pravšnja mera variabilnosti, konstruktivno vplivata na prostorsko dinamiko sklopljenih bioloških oscilatorjev. V okviru tega so izpeljani in raziskani tudi pogoji, pod katerimi je mogoče koherentno dinamiko v prostor vsiljevati z lokalnim vzpodbujevalnikom. Šum in heterogenost gradnikov lahko ključno krojita tudi obnašanje sistemov mehke snovi. V disertaciji je pokazano, da se lahko v polimersko-stabilizirani feroelektrični celici tekočega kristala manifestira pojav stohastične resonance. Ob tem je sistematično analiziran sovisen vpliv dinamičnega šuma in različnih izvorov statičnega nereda, ki so značilni za sisteme mehke snovi. Napredek pri raziskavah kompleksnih mrež, ki smo mu priča v zadnjem desetletju, je vzpodbudil raziskave različnih dinamičnih fenomenov tudi z vidika načina povezav, ki posamezne elemente povezujejo v celoto. V luči teh trendov je v drugem delu disertacije analiziran doseg šibkega vzpodbujevalnika v sistemu stohastično motenih oscilatorjev, za katerega se izkaže, da je znatno večji v primeru kompleksne topološke organiziranosti. V nadaljevanju je naslovljeno vprašanje optimalne strukture mreže, ki vodi do največje regularnosti stohastično induciranih oscilacij. V nasprotju s pričakovanji do optimalnega odziva ne vodi najučinkovitejša skalno neodvisna mreža, pač pa manj heterogena mreža, v kateri so prisotne interakcije dolgega in kratkega dosega, kar je povezano s kritičnim vedenjem v sestavi mreže. V zadnjem delu doktorske disertacije je izdelan mrežni model tkiva, sestavljenega iz gladkih mišičnih celic pljučne arterije, na podlagi katerega so razložene eksperimentalne meritve kontrakcije gladkih mišičnih celic iz zdravih in kronično obolelih podgan. Pri tem je posebna pozornost namenjena celični variabilnosti in patofiziološki vlogi topološke organiziranosti medceličnih povezav. 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. |
| Databáze: | OpenAIRE |
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