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Diffusion and aggregation process in biological physics: prionic diseases and random walks with memory

Grant number: 07/04220-4
Support type:Regular Research Grants
Duration: October 01, 2007 - September 30, 2009
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal Investigator:Marco Antonio Alves da Silva
Grantee:Marco Antonio Alves da Silva
Home Institution: Faculdade de Ciências Farmacêuticas de Ribeirão Preto (FCFRP). Universidade de São Paulo (USP). Ribeirão Preto , SP, Brazil


In this project we will study two problems: prionic diseases and non-Markovian random walks. Specifically, with prions we will study the incubation time distributions starting from existent experimental data for cattle and hamsters. Recently, we obtained an important result, showing that a simple mean field model of purely autocatalytic kinetics can reproduce experimental data; in that same work we introduced an automaton cellular model that gave qualitatively good results. However, those models do not possess the minimum ingredients for generalization of the results, because they do not reproduce "microscopically" the topology of the aggregation phenomenon. In this work we propose models, similar to epidemic models, which can be solved with Dynamic Monte Carlo, whose kinetics can generate aggregates. In these more general models we will analyse the importance of the autocatalytic term in the prionic reactions. For random walks with memory, we showed recently that loss of old memory above certain limit leads to Markovian behaviour. Differently, in recent memory loss it appears anomalous diffusion in a region of negative feedback, which can explain repetitive behaviours just as in the Alzheimer disease. We got experimentally (computational simulation), a complete phase diagram for that system. In this work we intend to find analytical results in order to define rigorously the observed transitions. Another objective is to analyse big systems (~10**8) with Monte Carlo simulation for several memory profiles. (AU)

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
FERREIRA, A. S.; CRESSONI, J. C.; VISWANATHAN, G. M.; ALVES DA SILVA, MARCO ANTONIO. Anomalous diffusion in non-Markovian walks having amnestically induced persistence. Physical Review E, v. 81, n. 1, 1 JAN 2010. Web of Science Citations: 12.
FELISBERTO, M. L.; PASSOS, F. S.; FERREIRA, A. S.; DA SILVA, M. A. A.; CRESSONI, J. C.; VISWANATHAN, G. M. Sudden onset of log-periodicity and superdiffusion in non-Markovian random walks with amnestically induced persistence: exact results. European Physical Journal B, v. 72, n. 3, p. 427-433, DEC 2009. Web of Science Citations: 3.
DA SILVA‚ M.A.A.; VISWANATHAN‚ GM; FERREIRA‚ AS; CRESSONI‚ JC. Spontaneous symmetry breaking in amnestically induced persistence. Physical Review E, v. 77, n. 4, p. 040101, 2008.

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