The beta decay of the radioactive members of the mass-eight and -twelve triads has been studied with a spiral-orbit spectrometer having a 1.3% resolution. The end point, half-life and log-ft values respectively are: for N{sup 12}, 16.37 {+-} 0.06 MeV, 11.43 {+-} 0.05 milliseconds, and 4.17; for B{sup 12}, 13.40 {+-} 0.05 MeV, 20.6 {+-} 0.2 msec and 4.11; for B{sup 8}, 14 MeV (broad), 0.75 {+-} 0.02 sec, and 5.72; and for Li{sup 8}, 13 Mev (broad), 0.87 {+-} 0.01 sec, and 5.67. The mass excesses in millimass units are: for N{sup 12}, 22.48 {+-} 0.06; for B{sup 12}, 18.19 {+-} 0.06; for B{sup 8}, 27.08 {+-} 0.13; and for Li{sup 8}, 24.97 {+-} 0.09. The shapes of the Kurie function for the mirror pairs indicate positron and electron transitions to the same levels of the daughter nuclide, with greater percentages in the positron branches relative to the ground-state transitions because of the higher energy available. The Li{sup 8} and B{sup 8} shapes are consistent with the shape of the alpha spectrum following the decay of the Be{sup 8} daughter. Less than 1% of the Li{sup 8} transition and less than 5% of the B{sup 8} transition go to …

Plutonium, thermally cycled through the low-temperature allotropic transformations, exhibited extensive physical damage. The physical damage was greater than that reported for any other metal or alloy. The extent of physical damage was determined by measurements of fluid displacement and the dimensional changes. The internal porosity was examined metallographically. Physical damage varied considerably, depending on the cycling conditions and the characteristics of the metal (particularly inclusions and casting imperfections). Observations showed that increasing the specimen size produced a greater decrease in density as a function of the number of cycles. The degree of void formation was directly proportional to volume change associated with the phase transformation. Other variables such as the length-diameter ratio (constant diameter) had little or no influence on the amount of physical damage. The dimensional growth was both radial and longitudinal. The tensile strength and the yield strength of tensile specimens cycled ten times between the gamnna and alpha phases were decreased to an average of 30,000 and 26,000 psi, respectively. (auth)