Crossover from superdiffusive to diffusive mixing in plastically deformed solids.

We derive expressions for the effective diffusion coefficient of Richardson's pairs in plastically strained solids as a function of the pair separation distance R. We predict that a crossover from superdiffusive to diffusive mixing takes place when R becomes comparable to the coherence length of the shearing events underlying the plastic deformation. Molecular dynamics simulations on nanocrystalline and amorphous systems support this analysis, which thus provides new insight on deformation mechanisms in these systems.

Forced chemical mixing in alloys driven by plastic deformation.

Molecular dynamics simulations of forced atomic mixing in crystalline binary alloys during plastic deformation at 100 K are performed. Nearly complete atomic mixing is observed in systems that have a large positive heat mixing and in systems with a large lattice mismatch. Only systems that contained a hard precipitate in a soft matrix do not mix.

Serum IgG, IgA and IgM in asthmatic children.

Serum levels of immunoglobulins G, A and M were determined in forty-five asthmatic children and in the same number of controls. Mean IgG and IgA levels in the asthmatics were not significantly different from those in the controls. Conversely, mean IgM values in female controls and all the controls taken as a group, were significantly higher than those in their asthmatic counterparts.