We have measured the velocity of propagation of the 3 He A -B interface as a function of temperature and pressure for the 3 He-^ initially in a hypercooled state. Velocities as high as 67 cm/s have been observed. Nucleation of the B phase occurred at greatly different temperatures in two different regions of the experimental cell.

Experiments aimed at comparing crossbred and purebred boars were reviewed. These experiments showed that crossbred boars matured sexually more quickly than corresponding purebred boars: they exhibited greater testis weight, large ejaculate volume and had better semen quality. Young crossbred boars were more aggressive sexually and achieved a higher conception rate, particularly on first service. Differences between the two types of boars for litter size and weight were generally small and variable in direction. Growth rate, feed efficiency and carcass characteristics of progeny of purebred and crossbred boars were generally similar. In addition, there was little evidence that use of crossbred sires had any effect on variability of pig performance.

No abstract