Biomedical subjects

V Pérez-Muñuzuri

Publications and source records attributed to V Pérez-Muñuzuri.

17 recordsLinked to original sources

PubMed2005

Improvement of pollutant drift forecast system applied to the Prestige oil spills in Galicia Coast (NW of Spain): development of an operational system.

An integrated system named METEOMOHID, developed by MeteoGalicia in the first stage of the Prestige accident in November 2002 was used successfully in an operational form to support decision making and assist in recovering tasks. Afterwards, METEOMOHID has been enhanced with the aim of developing an operational oceanography system to be used in the NW of the Iberian Peninsula. The METEOMOHID system includes local area hydrodynamic coastal ocean modelling (MOHID), real time atmospheric forcing from a local meteorological model (ARPS). Using the available data from the Prestige crisis, a set of simulations were designed in order to reproduce the oil spill drift. The implementation of a detailed vertical resolution in the model has allowed obtaining a detailed surface dynamic, improving our knowledge of the behaviour of tarballs into the water column. Thus, the wind-driven Eckman drift, the direct dragging of the wind were detached, and the possible existence of subsurface oil was assessed. In addition, the present work evaluates the effects of introducing climatologic large scale currents in the METEOMOHID system.

Atlantic Ocean↗

PubMed2005

Noise correlation length effects on a Morris-Lecar neural network.

The role of spatially correlated stochastic perturbations on a Morris-Lecar neural network subject to an aperiodic subthreshold signal is analyzed in detail. Our results suggest that optimum signal-to-noise ratios can be obtained for two critical noise intensities due to the interplay of the subthreshold Poisson process and the correlated Gaussian forcing. For the second peak, most of the cells are periodically excited, the information transfer is enhanced, and a collective behavior develops measured in terms of the averaged activity of the network. The maximum signal-to-noise ratio increases with the correlation length, although it saturates for global coupling. It was found that there is a range of mean frequencies of the subthreshold signal that increases the signal-to-noise ratio output.

Animals↗

PubMed2002

Spiral wave meandering induced by fluid convection in an excitable medium.

An isothermal reaction-diffusion system is considered in a two-dimensional fluid medium within a gravitational field. Inhomogeneities in the concentration field of the species give rise to a fluid flow due to buoyancy forces. A two-dimensional reaction-diffusion-convection model of an excitable medium is presented. The influence of hydrodynamics on spiral wave dynamics is systematically studied. A kinematic model is also introduced to better understand the mechanisms involved here.

Journal Article↗

PubMed2001

Onset of wave fronts in a discrete bistable medium.

The transition from a standing front to a traveling front is studied in an array of symmetric bistable coupled oscillators. The mechanism leading to propagation may be understood in the context of a gluing bifurcation involving a pair of homoclinic loops. The velocity of the front shows a logarithmic dependence with the coupling strength according to this mechanism.

Journal Article↗

PubMed2001

Quasiperiodic patterns in boundary-modulated excitable waves.

We investigate the impact of domain shape on wave propagation in excitable media. Channeled domains with sinusoidal boundaries are considered. Trains of fronts generated periodically at an extreme of the channel are found to adopt a quasiperiodic spatial configuration that repeats periodically in time. The phenomenon is numerically studied in a model for a photosensitive Belousov-Zabotinsky reaction. Spatial return maps for the height and position of the successive fronts are analytically obtained, and reveal the similarity between this spatial quasiperiodicity and the temporal quasiperiodicity appearing in forced oscillators.

Journal Article↗

PubMed2001

Regular wave propagation out of noise in chemical active media.

A pacemaker, regularly emitting chemical waves, is created out of noise when an excitable photosensitive Belousov-Zhabotinsky medium, strictly unable to autonomously initiate autowaves, is forced with a spatiotemporal patterned random illumination. These experimental observations are also reproduced numerically by using a set of reaction-diffusion equations for an activator-inhibitor model, and further analytically interpreted in terms of genuine coupling effects arising from parametric fluctuations. Within the same framework we also address situations of noise-sustained propagation in subexcitable media.

Journal Article↗

PubMed2001

Wave fronts and spatiotemporal chaos in an array of coupled Lorenz oscillators.

The effects of coupling strength and single-cell dynamics (SCD) on spatiotemporal pattern formation are studied in an array of Lorenz oscillators. Different spatiotemporal structures (stationary patterns, propagating wave fronts, short wavelength bifurcation) arise for bistable SCD, and two well differentiated types of spatiotemporal chaos for chaotic SCD (in correspondence with the transition from stationary patterns to propagating fronts). Wave-front propagation in the bistable regime is studied in terms of global bifurcation theory, while a short wavelength pattern region emerges through a pitchfork bifurcation.

Journal Article↗

PubMed2001

Wave propagation in subexcitable media with periodically modulated excitability.

Wave propagation in a photosensitive, subexcitable Belousov-Zhabotinsky medium is made possible by periodic modulation of a homogeneous illumination field. The propagation can be understood in terms of an interplay between the radial expansion of the wave and the motion of its free ends as the excitability varies periodically. This description leads to a simple kinematic analysis that provides insights into the initial conditions and forcing parameters giving rise to sustained wave propagation.

Journal Article↗

PubMed1999

Comparison between the role of discontinuities in cardiac conduction and in a one-dimensional hardware model.

In real electrophysiological experiments, irregularities in the extracellular excitation spread are believed to depend on cardiac tissue microstructure. An electronic hardware model was developed to analyze this dependence by placing some inhomogeneities (slow propagation areas) in the medium. The position of such inhomogeneities is correlated with abnormal delays and irregularities measured in signal propagation.

Animals↗

PubMed1999

Colored-noise-induced chaotic array synchronization.

The effect of a time-correlated Gaussian noise on one-dimensional arrays consisting of diffusively coupled chaotic cells is analyzed. A resonance effect between the time scale of the chaotic attractor and the colored Gaussian noise has been found. As well, depending on the number of cells, coupling, and noise strength, an improvement of the synchronization or a poor synchronization between cells within the array can occur for some values of the time correlation. These nonlinear cooperative effects are studied in terms of a linear stability analysis around the uniform synchronized behavior.

Journal Article↗

PubMed1996