Biomedical subjects

Gonzalo Izús

Publications and source records attributed to Gonzalo Izús.

4 recordsLinked to original sources

PubMed2005

Anomalous nonequilibrium Ising-Bloch bifurcation in discrete systems.

We investigate the self-organization of two-dimensional activator-inhibitor discrete bistable systems in the neighborhood of a nonequilibrium Ising-Bloch bifurcation. The system exhibits an anomalous transition--induced by discretization--whose signature is the coexistence of Ising and Bloch walls for selected values of the spatial coupling. After curvature reduction of Bloch walls, coexistence gives rise to a unique and striking spatiotemporal dynamics: Bloch walls drive the motion and Ising walls play the role of "extended defects" oriented along the background grid directions. Strong enough external noise asymptotically restores the scenario found in the continuum limit.

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PubMed2003

Synchronization of vectorial noise-sustained structures.

The synchronization of vectorial, noise-sustained structures in nonlinear optical systems is discussed. In particular, the analysis is made for nondegenerate optical parametric oscillators with walk off. The interplay between walk off and noise fluctuations leads to the formation of noise-sustained transverse patterns in both the signal and idler fields. Despite the fact that both patterns are stochastic macroscopic structures driven by independent sources of noise, their correlation grows with time, finally leading to a spatially distributed time synchronization of noise-sustained structures. A physical explanation of this phenomenon is found by analyzing the linear instability process and the existence of exact nonlinear solutions that show the same correlation.

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PubMed2003

Noise-sustained structures in differential-flow reactors with autocatalytic kinetics.

We have studied the formation of noise-sustained structures in a differential-flow reactor with cubic autocatalytic kinetics (the Gray-Scott model). In this system the interplay between advection, diffusion, reaction, and noise fluctuations leads to the formation of noise-sustained patterns in the key species. Numerical integration in one and two spatial dimensions shows that the structures are nonlocally cross correlated. Near threshold, the observed correlation is related to the properties of the convectively unstable critical modes.

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PubMed2002

Polarization coupling and pattern selection in a type-II optical parametric oscillator.

We study the role of a direct intracavity polarization coupling in the dynamics of transverse pattern formation in type-II optical parametric oscillators. Transverse intensity patterns are predicted from a stability analysis, numerically observed, and described in terms of amplitude equations. Standing wave intensity patterns for the two polarization components of the field arise from the nonlinear competition between two concentric rings of unstable modes in the far field. Close to threshold a wavelength is selected leading to standing waves with the same wavelength for the two polarization components. Far from threshold the competition stabilizes patterns in which two different wavelengths coexist.

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