Nuclear multifragmentation time scale and fluctuations of the largest fragment size.

Distributions of the largest fragment charge, Zmax, in multifragmentation reactions around the Fermi energy can be decomposed into a sum of a Gaussian and a Gumbel distribution, whereas at much higher or lower energies one or the other distribution is asymptotically dominant. We demonstrate the same generic behavior for the largest cluster size in critical aggregation models for small systems, in or out of equilibrium, around the critical point. By analogy with the time-dependent irreversible aggregation model, we infer that Zmax distributions are characteristic of the multifragmentation time scale, which is largely determined by the onset of radial expansion in this energy range.

Three-dimensional simulations of a vertically vibrated granular bed including interstitial air.

We present a numerical study of the effect of interstitial air on a vertically vibrated granular bed within one period of oscillation. We use a three-dimensional molecular-dynamics simulation including air phenomenologically. The simulations are validated with experiments made with spherical glass beads in a rectangular container. After validation, results are reported for a granular column of 9000 grains and approximately 50 layers deep (at rest), agitated with a sinusoidal excitation with maximal acceleration 4.7g at 11.7 Hz. We report the evolution of density, granular temperature, and coordination number within a vibration cycle, and the effect of interstitial air on those parameters. In three-dimensional computer simulations we found that the presence of interstitial air can promote the collective motion of the granular material as a whole.

The role of interparticle forces in colloidal aggregates: local investigations and modelling of restructuring during filtration.

Industrial solid-liquid separation processes, such as pressure filtration or membrane processes, involve the application of pressure to suspensions. In response, some water is extracted, the suspension volume is reduced, and the dispersed aggregates start to form a network. In recent works, we aimed to make a prediction for the response of aggregates to stress which occurs during a filtration. We chose model systems made of aggregated silica nanoparticles. Some of these systems offer a strong resistance to applied stresses, and retain their permeability; others yield and collapse. We used small angle neutron scattering by which we can locally quantify the particle distribution withi the network to determine the processes by which particles reorganise during collapse: we found that reordering processes at the scale of 1 to 10 particle diameters control the course of collapse and the loss of permeability. Finally we constructed a numerical model for describing the processes by which colloidal aggregates are compressed. This model predicts that the response of such networks to pressure follows some scaling laws, which depend only on the elastic vs. dissipative nature of interparticle bonds.

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.

Development of monofixation syndrome in congenital esotropia.

Fifty patients with 8 prism diopters or less of esotropia after the last surgery were studied. Forty-nine percent of those straightened before 12 months of age and 41% of those straightened between 13-24 months developed the M.S. Only one of the 22 patients straightened after the age of two developed the M.S. Although D.V.D. and overaction of the inferior oblique muscles were associated findings, neither precluded the development of the M.S. Those patients without M.S. had a higher incidence of subsequent exotropia and manifest D.V.D.

Sclerodermiform linear atrophy after the use of intralesional steroids for periorbital hemangiomas: a review of complications.

A 1-year-old girl developed a linear atrophy 3 months after a second injection of intralesional steroids for a periorbital hemangioma, followed by spontaneous resolution of the atrophy within 13 months. Reported and potential complications of intralesional steroids for periorbital hemangiomas are reviewed.