Biomedical subjects

J Elezgaray

Publications and source records attributed to J Elezgaray.

10 recordsLinked to original sources

PubMed2004

Selection rules for the tip-splitting instability.

The local destabilization of a Saffman-Taylor viscous finger occurs by a splitting of its tip and results in the formation of two branches separated by a fjord. The accumulation of such instabilities leads to complex patterns. In this paper we present a detailed analysis of a dynamical model that accounts for the selection of both the width and the orientation of the fjords growing in a wedge of angle theta(0). It is shown that the selection rules have a dynamical origin and are related to the existence of attracting sets that disappear in the absence of surface tension. We also infer the existence of a critical angle theta(c)=60 degrees such that if theta(0)<theta(c), the symmetric tip-splitting becomes unstable.

Journal Article↗

PubMed2002

Exploring the natural conformational changes of the C-terminal domain of calmodulin.

Several experimental results suggest that the Ca2+-loaded C-terminal domain of calmodulin (or some of its mutants) exhibits conformational changes triggered solely by thermal fluctuations. The time scales involved are in the 10(-6)-10(-3) s range. Here we develop a theoretical method to explore this type of motions based on a modified version of molecular dynamics algorithm where the secondary structure motifs are held fixed. In this version, increasing the temperature enhances the sampling of conformations with locally fixed secondary structures. From the temperature dependence of the transition rate between various conformational states, we obtain characteristic times that are consistent with those observed experimentally.

Algorithms↗

PubMed2000

Dense branching morphology in electrodeposition experiments: characterization and mean-field modeling

Dense branching morphologies (DBM) obtained in thin gap electrodeposition cells are characterized by a dense array of branches behind a flat advancing envelope. In this Letter, we show the existence in DBM of a new (porous) phase, qualitatively different from a (compact) metal deposit. The local porosity inside the branches is found to be much more robust than geometric characteristics such as the width or the distance between branches. This fact seems to be unreported in previous modeling of DBM. A mean-field model is proposed that displays overall features observed in the experiments, such as concentration profiles, front velocity, and branched internal structure.

Journal Article↗

PubMed2000

Internal structure of dense electrodeposits

We report experimental investigations of the structure of dense patterns obtained during electrochemical deposition of copper in thin cells. The deposit correlation function reveals the periodic structuration of the patterns but shows that the primary spacing is not steady during the growth and that moreover it is not simply related to the diffusion length. Another measurable quantity is the occupancy ratio of the fingers in the cell. Its variation as a function of the experimental parameters is interpreted from specific properties of electrochemical growth. The results are discussed with respect to the well-known behavior of cellular solidification fronts.

Journal Article↗

PubMed1998

Modeling large-scale dynamics of proteins.

We study a dynamical model for the large-scale motions of bovine pancreatic trypsin inhibitor in vacuum. The model is obtained by projecting Newton equations onto some set of anharmonic modes. We compare the statistics of the so-obtained trajectories with those obtained by standard techniques, and conclude that our dynamical model is able to reproduce fairly well the average properties of the large-scale motions of this protein. Moreover, it allows for time steps one order of magnitude larger than the standard ones.

Aprotinin↗

PubMed1996