Biomedical subjects

L Pastur

Publications and source records attributed to L Pastur.

6 recordsLinked to original sources

PubMed2004

Bistability between different localized structures in nonlinear optics.

We report the observation of different localized structures coexisting for the same parameter values in an extended system. The experimental findings are carried out in a nonlinear optical interferometer and are fully confirmed by numerical simulations. The existence of each kind of localized structure is put in relation to a corresponding delocalized pattern observed. A quantitative evaluation of the range of pump parameter allowing bistability between localized structures is given. The phenomenon reported results to be robust in parameter space.

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PubMed2004

Experimental targeting and control of spatiotemporal chaos in nonlinear optics.

We demonstrate targeting and control over spatiotemporal chaos in an optical feedback loop experiment. Different stationary target patterns are stabilized in real time by means of a two dimensional space extended perturbation field driven by an interfaced computer and applied in real space to a liquid crystal display device inserted within a control optical loop. The flexibility of the system in switching between different target patterns is also demonstrated.

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PubMed2004

Detecting local synchronization in coupled chaotic systems.

We introduce a technique to detect and quantify local functional dependencies between coupled chaotic systems. The method estimates the fraction of locally synchronized configurations, in a pair of signals with an arbitrary state of global synchronization. Application to a pair of interacting Rössler oscillators shows that our method is able to quantify the number of dynamical configurations where a local prediction task is possible, as well as in the absence of global synchronization features.

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PubMed2004

Transition to space-time chaos in an optical loop with translational transport.

We describe the transition from regular patterns to space-time chaos in an optical system with nonlocal feedback. The nonlocality introduced breaks the rotational symmetry of the system, resulting in a scenario for the transition from regular patterns to a disordered dynamics. The different regimes are characterized both in terms of spatial and temporal correlation functions, and by means of a Kahrunen-Loeve decomposition. This allows the determination of the structures participating in the dynamics, and an estimation of the active degrees of freedom versus the control parameter.

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PubMed2001

Competition of periodic and homogeneous modes in extended dynamical systems.

Despite their simple structure, spatially homogeneous modes can participate directly in pattern-formation processes. This is demonstrated by new experimental and theoretical results for thermo- and electroconvection in planar nematic liquid crystals, where two distinct homogeneous modes, twist and splay distortions of the director field, emerge. Their nonlinear excitation is due to certain spontaneous symmetry-breaking bifurcations.

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PubMed2001

Transition to spatiotemporal chaos in the fronts dynamics of a subcritical state.

The evolution of the isolated domains of a bifurcated structure in a subcritical state is experimentally studied along the hysteresis branch, up to the critical point at which a chaotic regime is found to develop. The width of the domains is unstable and the fronts dynamics exhibit a cascade of bifurcations as the constraint increases. The chaotic regime is initiated by a splitting of the isolated domains, controlled by a width-selection mechanism. Most of these results are qualitatively reproduced in a fifth-order Ginzburg-Landau model.

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