Biomedical subjects

R Botet

Publications and source records attributed to R Botet.

18 recordsLinked to original sources

PubMed2001

Scaling laws in magneto-optical properties of aggregated ferrofluids.

Since statistically isotropic fractal aggregates of particles are a particular case of self-organized critical systems, we describe formally field-induced behaviors of aggregated ferrofluids as responses of regular at-equilibrium critical systems at the critical point to the small field conjugated to its order parameter. This leads us to expect some general scaling laws, which are checked numerically on two examples: the magnetic susceptibility and the magneto-optical linear dichroism of two-dimensional aggregated ferrofluids. This is performed by numerical simulations of such an aggregating system under weak magnetic field applied in the plane of the aggregates.

Journal Article↗

PubMed2001

Universal fluctuations in heavy-ion collisions in the Fermi energy domain.

We discuss the scaling laws of both the charged fragments multiplicity n fluctuations and the charge of the largest fragment Z(max) fluctuations for Xe + Sn collisions in the range of bombarding energies between 25A MeV and 50A MeV. We show at E(lab) > or similar to 32 MeV/A the transition in the fluctuation regime of Z(max) which is compatible with the transition from the ordered to disordered phase of excited nuclear matter. The size (charge) of the largest fragment is closely related to the order parameter characterizing this process.

Journal Article↗

PubMed2000

Universal features of the order-parameter fluctuations: reversible and irreversible aggregation

We discuss the universal scaling laws of order-parameter fluctuations in any system in which a second-order critical behavior can be identified. These scaling laws can be derived rigorously for equilibrium systems when combined with a finite-size scaling analysis. The relation between the order parameter, the criticality, and the scaling law of fluctuations has been established, and the connection between the scaling function and the critical exponents has been found. We give examples in out-of-equilibrium aggregation models such as the Smoluchowski kinetic equations, or at-equilibrium Ising and percolation models.

Journal Article↗

PubMed2000

Molecular-dynamics simulation of two-dimensional thermophoresis

A numerical technique is presented for the thermal force exerted on a solid particle by a gaseous medium between two flat plates at different temperatures, in the free molecular or transition flow. This is a two-dimensional molecular-dynamics simulation of hard disks in a inhomogeneous thermal environment. All steady-state features exhibited by the compressible hard-disk gas are shown to be consistent with the expected behaviors. Moreover the thermal force experienced by a large solid disk is investigated, and compared to the analytical case of cylinders moving perpendicularly to the constant temperature gradient for an infinite Knudsen number and in an infinite medium. We show precise examples of how this technique can be used simply to investigate more difficult practical problems, in particluar the influence of nonlinear gradients for large applied differences of temperature, of proximity of the walls, and of smaller Knudsen numbers.

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PubMed1996