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F Sastre

Publications and source records attributed to F Sastre.

6 recordsLinked to original sources
PubMed2006

Thermodynamic and structural properties of confined discrete-potential fluids.

The thermodynamic and structural behaviors of confined discrete-potential fluids are analyzed by computer simulations, studying in a systematic way the effects observed by varying the density, temperature, and parameters of the potentials that characterize the molecule-molecule interactions. The Gibbs ensemble simulation technique for confined fluids [A. Z. Panagiotopoulos, Mol. Phys. 62, 701 (1987)] is applied to a fluid confined between two parallel hard walls. Two different systems have been considered, both formed by spherical particles that differ by the interparticle pair potential: a square well plus square shoulder or a square shoulder plus square well interaction. These model interactions can describe in an effective way pair potentials of real molecular and colloidal systems. Results are compared with the simpler reference systems of square-shoulder and square-well fluids, both under confinement. From the adsorption characterization through the use of density profiles, it is possible to obtain specific values of the interparticle potential parameters that result in a positive to negative adsorption transition.

Journal Article↗
PubMed2001

Stochastic analog to phase transitions in chaotic coupled map lattices.

Stochastic dynamical systems are shown to exhibit the same order-disorder phase transitions that have been found in chaotic map lattices. Phase diagrams are obtained for diffusively coupled two-dimensional (2D) lattices, using two stochastic maps and a chaotic one, for both square and triangular geometries, with simultaneous updating. We show how the use of triangular geometry reduces (or even eliminates) the reentrant behavior found in the phase diagrams for the square geometry. This is attributed to the elimination (via frustration) of the antiferromagnetic clusters common to simultaneous updating of square lattices. We also evaluate the critical exponents for the stochastic maps in the triangular lattices. The strong similarities in the phase diagrams and the consistency between the critical exponents of one stochastic map and the chaotic one, evaluated in an early work by Marcq et al. [Phys. Rev. Lett. 77, 4003 (1996); Phys. Rev. E 55, 2606 (1997)] suggest that the "sign-persistence," defined as the probability that the local map keeps the sign of the local variable in one iteration, plays a fundamental role in the presence of continuous phase transitions in coupled map lattices, and is a basic ingredient for models that belong to this weak Ising universality. However, the fact that the second stochastic map, which has an extremely simple local dynamics, seems to fall in the 2D Ising universality class, suggests that some minimal local complexity is also needed to generate the specific correlations that end up giving non-Ising critical behavior.

Journal Article↗
PubMed1995

Generic model for the localization of the cerebral cortex and preoperative multimodal integration in epilepsy surgery.

In cerebral cortex neurosurgery and particularly in epilepsy surgery, the recognition of individual cortical anatomic landmarks is necessary for presurgical evaluation and planning. To overcome the classical great variability in the superficial aspect of the human cerebral cortex, we have developed an original generic description of the cerebral cortex in a three-dimensional structure. The result is a generic model matching the cortical topography of each brain regardless of inter- and intra-individual variability. In this model, sulcal roots (fundi) are separated by more or less superficial annectent gyrus, and buried by operculization during the gyrification. This original generic model of the cerebral cortex enabled us to develop a mathematical methodology for the construction of a structural representation of the cortical topography from a T1-weighted three-dimensional MR image. This program can provide automatic detection and recognition of the main cortical sulci.

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PubMedDate not supplied

[Electroconvulsive therapy in Parkinson disease. Description of three cases].

Electroconvulsive therapy (ECT) has demonstrated to be useful in psychiatric patients with parkinsonism as well as patients with Parkinson's disease (PD) without associated psychopathology. We prospectively evaluated three patients with PD and major depression in whom ECT proved to be efficacious. These patients experimented a marked improvement measured by the Unified Parkinson's Rating Scale (UPDRS). In two cases the ECT allowed for a reduction in their drug treatment, and in one case complex fluctuations disappeared. In the two patients who continued with ECT fortnightly, the improvement observed inicially has remained. Since ECT has shown a good tolerance, we conclude that this therapy should be considered as an alternative approach for PD patients with a poor answer to conventional treatment.

Antiparkinson Agents↗