Primary dose in photon beams with lateral electron disequilibrium.

It is shown that in narrow monoenergetic photon beams under conditions of lateral electron disequilibrium, primary absorbed dose P(r) is a simple function of beam radius r: P(r) = P lambda.(1 - e(-gamma.r)), where P lambda is the primary dose in broad beams for which complete lateral electron equilibrium exists, and gamma depends on photon energy and absorbing medium. This formula was evaluated using Monte-Carlo-generated data for the primary dose in water from monoenergetic photons in the energy range from 2 to 8 MeV. The primary dose was studied in beams of radii 0.006 cm less than r less than 5.0 cm and within the depth interval 0.5 cm less than or equal to d less than or equal to 24 cm. It was concluded that the saturation equation above provides an accurate description of the primary dose from monoenergetic photon beams, as judged by comparison with Monte Carlo results.

Abnormal hemoglobins in the Silk Road region of China.

A review is presented of the occurrence of 24 abnormal hemoglobins (13 alpha-chain variants and 11 beta-chain variants) in populations in the Silk Road area of Northwestern China. Most frequently occurring were Hb D-Punjab [beta 121(GH4)Glu----Gln] in Uygurs, Kazaks, and Khalkhas, Hb G-Taipei [beta 22(B4)Glu----Gly] in persons of the Han nationality, and Hb G-Coushatta [beta 22 (B4)Glu----Ala] in the Uygurs, Kazaks, Hans, and related nationalities. The data suggest that these variants likely originated in Central Asia, in the Han nationality of China, and in the minorities of northern China, respectively. Other variants occurred at considerably lower frequencies and were imported from other countries or arose as independent mutations. Two variants [Hb Tashikuergan or alpha 19(AB1)Ala----Glu; Hb Tianshui or beta 39(C5) Gln----Arg] were observed for the first time. The data from this study of the many variants support the movements of various populations in this area, as reported in numerous historical documents.