A numerical study of the development of bulk scale-free structures upon growth of self-affine aggregates

During the last decade, self-affine geometrical properties of many growing aggregates, originated in a wide variety of processes, have been well characterized. However, little progress has been achieved in the search of a unified description of the underlying dynamics. Extensive numerical evidence has been given showing that the bulk of aggregates formed upon ballistic aggregation and random deposition with surface relaxation processes can be broken down into a set of infinite scale invariant structures called "trees". These two types of aggregates have been selected because it has been established that they belong to different universality classes: those of Kardar-Parisi-Zhang and Edward-Wilkinson, respectively. Exponents describing the spatial and temporal scale invariance of the trees can be related to the classical exponents describing the self-affine nature of the growing interface. Furthermore, those exponents allows us to distinguish either the compact or non-compact nature of the growing trees. Therefore, the measurement of the statistic of the process of growing trees may become a useful experimental technique for the evaluation of the self-affine properties of some aggregates.Comment: 19 pages, 5 figures, accepted for publication in Phys.Rev.

A mean-field kinetic lattice gas model of electrochemical cells

We develop Electrochemical Mean-Field Kinetic Equations (EMFKE) to simulate electrochemical cells. We start from a microscopic lattice-gas model with charged particles, and build mean-field kinetic equations following the lines of earlier work for neutral particles. We include the Poisson equation to account for the influence of the electric field on ion migration, and oxido-reduction processes on the electrode surfaces to allow for growth and dissolution. We confirm the viability of our approach by simulating (i) the electrochemical equilibrium at flat electrodes, which displays the correct charged double-layer, (ii) the growth kinetics of one-dimensional electrochemical cells during growth and dissolution, and (iii) electrochemical dendrites in two dimensions.Comment: 14 pages twocolumn, 17 figure

Topography reconstruction from surface plasmon resonance data.

International audienc

CRISIS-INDUCED INTERMITTENT BURSTING IN REACTION-DIFFUSION CHEMICAL-SYSTEMS

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MODELING REACTION-DIFFUSION PATTERN-FORMATION IN THE COUETTE-FLOW REACTOR

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On the tip splitting instability - I

The local destabilisation 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. It has been shown recently that the central line of a fjord follows approximately a curve normal to successive stable fingers. In this letter, we present an extensive numerical study of a minimal model of this instability for fingers growing in a wedge of angle $\theta_0$. It is shown that the form of the fjords is mainly a surface-tension–driven effect. We also infer the existence of a critical angle 60^{\circ}\le \theta_{\ab{c}} \le 90^{\circ} such that if \theta_0 < \theta_{\ab{c}}, the symmetric tip-splitting becomes unstable

SPATIOTEMPORAL PATTERNS AND DIFFUSION-INDUCED CHAOS IN A CHEMICAL-SYSTEM WITH EQUAL DIFFUSION-COEFFICIENTS

International audienceno abstrac

Proper orthogonal decomposition of DLA clusters

We use the proper orthogonal decomposition to analyze the fluctuations around the mean of DLA clusters grown in a sector. These fluctuations are described as a superposition of orthogonal modes, which appear to have very well-defined shapes. These modes are invariants of the growth, and show a strong selection phenomenon which is reflected in the large-scale structure of the branching pattern of DLA clusters. We also discuss the appearance of discrete scale invariance