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Biomedical subjects

P Woafo

Publications and source records attributed to P Woafo.

11 recordsLinked to original sources
PubMed2006

Synchronization in a ring of four mutually coupled van der Pol oscillators: theory and experiment.

We investigate different states of synchronization in a ring of four mutually coupled van der Pol oscillators. The stability analysis and numerical simulation are performed to determine the suitable coupling parameters leading to high-quality synchronization. The consequences of parameter mismatch are also highlighted. Experimental realization is then used to show the existence of complete and partial synchronization.

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PubMed2006

Intercellular waves propagation in an array of cells coupled through paracrine signaling: a computer simulation study.

A linear chain of cells is considered in which calcium (Ca2+) fluctuations within a cell are described by a simple minimal model. Cells are coupled together by bidirectional paracrine signaling via calcium oscillations. Two typical zones of propagation are observed: a transition zone and a regular zone. The transition zone exhibits the same phenomena that can be observed in single cells, pairs or triplets of cells. Within the regular zone, simple periodic oscillations of calcium propagate and the Ca2+ signal is similar from one cell to another (same amplitude and same frequency). But, the signals are separated by a slight phase shift characterizing the propagation of Ca2+ waves due to the type of coupling used. We also consider the colonization of the lattice by the abnormal oscillations of sick cells.

Animals↗
PubMed2004

Synchronized states in a ring of mutually coupled self-sustained electrical oscillators.

We investigate in this paper different states of synchronization in a ring of mutually coupled self-sustained electrical oscillators. The good coupling parameters leading to complete and partial synchronization or disordered states are calculated using the properties of the variational equations of stability. A stability map showing domains of synchronization to an external excitation locally injected in the ring is also obtained. In both cases, the numerical simulation validates and complements the results of the analytical investigation.

Journal Article↗
PubMed2003

Dynamics of solitary blood waves in arteries with prostheses.

We analyze the behavior of blood waves interacting with a prosthesis following the Yomosa nonlinear wave theory extended to include the spatial variation of the arterial radius and wall rigidity. When the prosthesis is short or when its characteristics are close to those of the host artery, the amplitude of the blood solitary wave increases just proximal to the prosthesis and then decreases to a magnitude smaller than the normal value in a healthy vessel. In the presence of an extended prosthesis, we derive the reflection and transmission coefficients at the interfaces, and we thereby obtain the optimal characteristics for an ideal prosthesis. Our results agree qualitatively with known experimental and numerical studies.

Animals↗
PubMed2003

Transitions from spatiotemporal chaos to cluster and complete synchronization states in a shift-invariant set of coupled nonlinear oscillators.

We study the spatiotemporal dynamics of a ring of diffusely coupled single-well Duffing oscillators. The transitions from spatiotemporal chaos to cluster and complete synchronization states are particularly investigated, as well as the Hopf bifurcations to instability. It is found that the underlying mechanism of these transitions relies on the motion of the representative points corresponding to the system's nondegenerated spatial transverse Fourier modes in the parametric Strutt diagram. A scaling law is used to demonstrate that the compact interval of the scalar coupling parameter values leading to cluster synchronization broadens in a square-power-like fashion as the number of oscillators is increased. The analytical approach is confirmed by numerical simulations.

Journal Article↗
PubMed2003

Optimization and stability boundaries for the synchronization of semiconductor lasers with external optical feedback.

We perform a stability and optimization analysis for the synchronization of unidirectionally coupled external-cavity semiconductor lasers. Using rigorous stability criteria, we qualitatively derive the boundaries of the high-quality synchronization basin. The underlying influence of Hopf bifurcations on the stability of the synchronization manifold is also investigated.

Journal Article↗
PubMed2002

Generalized correlated states in a ring of coupled nonlinear oscillators with a local injection.

In this paper, we study the spatiotemporal dynamics of a ring of diffusely coupled nonlinear oscillators. Floquet theory is used to investigate the various dynamical states of the ring, as well as the Hopf bifurcations between them. A local injection scheme is applied to synchronize the ring with an external master oscillator. The shift-invariance symmetry is thereby broken, leading to the emergence of generalized correlated states. The transition boundaries from these correlated states to spatiotemporal chaos and complete synchronization are also derived. Numerical simulations are performed to support the analytic approach.

Journal Article↗
PubMed2002

Stability and optimal parameters for continuous feedback chaos control.

We investigate the conditions under which an optimal continuous feedback control can be achieved. Chaotic oscillations in the single-well Duffing model, with either a positive or a negative nonlinear stiffness term, are tuned to their related Ritz approximation. The Floquet theory enables the stability analysis of the control. Critical values of the feedback control coefficient fulfilling the optimization criteria are derived. The influence of the chosen target orbit, of the feedback coefficient, and of the onset time of control on its duration is discussed. The analytic approach is confirmed by numerical simulations.

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