Biomedical subjects

F d'Ovidio

Publications and source records attributed to F d'Ovidio.

3 recordsLinked to original sources

PubMed2006

Coherent regimes of mutually coupled Chua's circuits.

We study the dynamical regimes that emerge from the strong coupling between two Chua's circuits with parameters mismatch. For the region around the perfect synchronous state we show how to combine parameter diversity and coupling in order to robustly and precisely target a desired regime. This target process allows us to obtain regimes that may lie outside parameter ranges accessible for any isolated circuit. The results are obtained by following a recently developed theoretical technique, the order parameter expansion, and are verified both by numerical simulations and on electronic circuits. The theoretical results indicate that the same predictable change in the collective dynamics can be obtained for large populations of strongly coupled circuits with parameter mismatches.

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PubMed2001

Synchronization of glycolytic oscillations in a yeast cell population.

The mechanism of active phase synchronization in a suspension of oscillatory yeast cells has remained a puzzle for almost half a century. The difficulty of the problem stems from the fact that the synchronization phenomenon involves the entire metabolic network of glycolysis and fermentation, and consequently it cannot be addressed at the level of a single enzyme or a single chemical species. In this paper it is shown how this system in a CSTR (continuous flow stirred tank reactor) can be modelled quantitatively as a population of Stuart-Landau oscillators interacting by exchange of metabolites through the extracellular medium, thus reducing the complexity of the problem without sacrificing the biochemical realism. The parameters of the model can be derived by a systematic expansion from any full-scale model of the yeast cell kinetics with a supercritical Hopf bifurcation. Some parameter values can also be obtained directly from analysis of perturbation experiments. In the mean-field limit, equations for the study of populations having a distribution of frequencies are used to simulate the effect of the inherent variations between cells.

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PubMed2000

Dynamical system approach to phyllotaxis

This paper presents a bifurcation study of a model widely used to discuss phyllotactic patterns, i.e., leaf arrangements. Although stable patterns can be easily obtained by numerical simulations, a stability or bifurcation analysis is hindered by the fact that the model is defined by an algorithm and not a dynamical system, mainly because new active elements are added at each step, and thus the dimension of the "natural" phase space is not conserved. Here a construction is presented by which a well defined dynamical system can be obtained, and a bifurcation analysis can be carried out. Stable and unstable patterns are found by an analytical relation, in which the roles of different growth mechanisms determining the shape is clarified. Then bifurcations are studied, especially anomalous scenarios due to discontinuities embedded in the original model. Finally, an explicit formula for evaluation of the Jacobian, and thus the eigenvalues, is given. It is likely that problems of the above type often arise in biology, and especially in morphogenesis, where growing systems are modeled.

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