X-ray fluorescence in some rare earth and high Z elements excited by 661.6 keV γ-rays

The K-shell X-ray fluorescence cross sections are determined experimentally for 10 elements such as Pb, Hg, Ir, W, Lu, Tm, Dy, Tb, Gd and Nd at excitation energy of 661.6 keV associated with γ-rays of ¹³⁷Cs radioisotope. The technique employed involves the measurement of total intensity of fluorescent K X-rays that follow the photoeffect absorption of a known flux of γ-rays using a well type Nal(Tl) detector. The obtained results are compared with the available theoretical values and other measured values.     

Pellet freezing of in vitro produced bovine embryos using dry ice

In vitro produced bovine embryos were frozen by pellet freezing or vitrification method. In the pellet freezing method, the embryos were cooled on the dry ice and then frozen as pellets. At warming, the pellets were immersed directly into 0.5 M sucrose. The survival rates of blastocysts frozen by the pellet freezing method were higher (P<0.01) in 40% ethylene glycol (EG) than those in the lower concentrations (20 and 30% EG). Higher survival rates of blastocysts frozen by the pellet freezing method were obtained but the development rates did not differ, as compared with those by the vitrification method. There were no significant differences between the pellet freezing and vitrification method in the frequencies of post-thaw survival of hatched blastocysts. These results demonstrate that the pellet freezing method using dry ice can be used successfully for the cryopreservation of blastocysts.     

Determination of refractory elements in U(3)O(8) by carrier distillation emission spectrography

An emission spectrographic method using carrier distillation for the determination of the refractory impurities Ta, Hf, Nb, Th, and W in uranium is described. Different carriers, such as Ga₂O₃, AgCl, AgCl + LiF, and AgCl + NaF in various proportions, were investigated: a 1% NaF + 9% AgCl mixture as carrier at 10% of total charge arced was found to be the most suitable. Spectra were excited in a d.c. arc at 12 A and were photographed with 35-sec exposures. Palladium was used as an internal standard. The lowest limits of determination lie in the range 1–10 ppm for a 100-mg charge. The precision of the method is about 16% or better.