Analysis of oxygen on beryllium can be routinely performed using helium-ion backscattering (RBS). However, determination of the bulk oxygen concentration by this technique is limited to about 350 atomic parts per million (appM). We have performed simultaneous RBS and particle-induced x-ray emission (PIXE) measurements to improve the detection limit for bulk oxygen. The RBS measurements allowed determination of the surface oxygen before and after in-situ sputter cleaning by argon ions in an ultra-high-vacuum system. PIXE measurements of specimens with surfaces maintained clean by sputtering permitted assessment of the concentration of oxygen in the bulk. For our geometry and detector sensitivities, 90% of the oxygen x-ray signal originated in the first 2.1 ..mu..m of the beryllium and a detection limit of 10 appM was found. 12 refs., 3 figs.

The AERIN code was written at the Lawrence Livermore National Laboratory in 1976 to compute the organ burdens and absorbed dose resulting from a chronic or acute inhalation of transuranic isotopes. The code was revised in 1982 to reflect the concepts of ICRP-30. This paper will describe the AERIN code and how it has been used at LLNL to study more than 80 cases of internal deposition and obtain estimates of internal dose. A comparison with the computed values of the committed organ dose is made with ICRP-30 values. The benefits of using the code are described. 3 refs., 3 figs., 6 tabs.

Repair deficient mutants of Chinese hamster ovary (CHO) cells are being used to identify human genes that correct the repair defects and to study mechanisms of DNA repair and mutagenesis. Five independent tertiary DNA transformants were obtained from the EM9 mutant. In these clones a human DNA sequence was identified that correlated with the resistance of the cells to CldUrd. After Eco RI digestion, Southern transfer, and hybridization of transformant DNAs with the BLUR-8 Alu family sequence, a common fragment of 25 to 30 kb was present. 37 refs., 4 figs., 3 tabs.

Substantial increases in the high-temperature creep strength of Mo-Hf alloys can be obtained by internal nitriding. The creep resistance of internally nitrided Mo-1.86 wt % Hf is more than 100 times greater than that of other commercially available molybdenum-base alloys. The HfN precipitates appear to be stable over long times at temperatures near 1600 K. Internally nitrided Mo-Hf alloys appear to be good candidates for fabrication of components of space power systems where the ratio of high-temperature strength to weight is important. They are particularly good candidates for components that can be fabricated from the lower-strength unnitrided alloy and subsequently nitrided to provide high-temperature strength.