Specifically-language-impaired children and younger normal children matched for expressive language were presented with unfamiliar object names and referents across five experimental sessions. The objects differed in the degree to which they were associated with actions, and only certain of the object exemplars were named during presentation. Comprehension testing revealed that the specifically-language-impaired children acquired a greater number of object concepts presented in a no-action condition than the normal children. However, their extension of the names to new exemplars was more restricted and less differentiated. Several possible accounts of these findings are evaluated.

Vapour bubble collapse problems lacking spherical symmetry are solved here using a numerical method designed especially for these problems. Viscosity and compressibility in the liquid are neglected. Two specific cases of initially spherical bubbles collapsing near a plane solid wall were simulated: a bubble initially in contact with the wall, and a bubble initially half its radius from the wall at the closest point. It is shown that the bubble develops a jet directed towards the wall rather early in the collapse history. Free surface shapes and velocities are presented at various stages in the collapse. Velocities are scaled like (Δp/ρ)½ where ρ is the density of the liquid and Δp is the constant difference between the ambient liquid pressure and the pressure in the cavity. For\[\Delta p/\rho = 10^6 {\rm cm}^2/\sec^2 \approx 1\, \hbox{atm/density of water}\]the jet had a speed of about 130m/sec in the first case and 170m/sec in the second when it struck the opposite side of the bubble. Such jet velocities are of a magnitude which can explain cavitation damage. The jet develops so early in the bubble collapse history that compressibility effects in the liquid and the vapour are not important.