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The hydrodynamic properties of rigid fractal aggregates have been investigated by considering their motion in shear flow in the Stokesian dynamics approach. Due to the high fluid viscosity and small particle inertia of colloidal systems, the total force and torque applied to the aggregate reach equilibrium values in a short time. Obtaining equilibrating(More)
We present the stochastic approach of the polarization state of an electromagnetic wave traveling through randomly twisted optical fiber. We treat the case of the weak randomness. When the geometric torsion of the fiber is distributed as a Gaussian law, we can write explicitly the Fokker-Planck equation for the Stokes parameters of the wave, and find the(More)
Surface-enhanced Raman scattering (SERS) from a self-affine surface is shown to be very large. A theory is developed expressing this SERS in terms of the eigenmodes of a self-affine surface; the theory successfully explains the observed SERS from cold-deposited thin films that are known to have a self-affine structure. Spatial distributions of local fields(More)
Nonlinear optical phenomena on rough self-affine metal surfaces are theoretically studied. Placing nonlin-early polarizable molecules on such surfaces results in strong enhancement of optical nonlinearities. A quasi-static approximation is used to calculate local-enhancement factors for the second and third harmonic generation , degenerate four-wave mixing,(More)
We report small-angle x-ray scattering experiments on aqueous dispersions of colloidal silica with a broad monomodal size distribution (polydispersity, 14%; size, 8 nm). Over a range of volume fractions, the silica particles segregate to build first one, then two distinct sets of colloidal crystals. These dispersions thus demonstrate fractional(More)
We present experiments and numerical simulations to investigate the collective behavior of submicrometer-sized particles immersed in a nematic micellar solution. We use latex spheres with diameters ranging from 190 to 780 nm and study their aggregation properties due to the interplay of the various colloidal forces at work in the system. We found that the(More)
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(More)
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(More)
We apply the recent exact theory of multiple electromagnetic scattering by sphere aggregates to statistically isotropic finite fractal clusters of identical spheres. In the mean-field approximation the usual Mie expansion of the scattered wave is shown to be still valid, with renormalized Mie coefficients as the multipolar terms. We give an efficient method(More)
We present a framework for the stochastic features of the polarization state of an electromagnetic wave propagating through the optical medium with both deterministic (controlled) and disordered birefringence. In this case, the Stokes parameters obey a Langevin-type equation on the Poincaré sphere. The functional integral method provides for a natural tool(More)