Hepatitis B surface antigen and its subtypes in an institution for the mentally retarded.

The prevalence of hepatitis B surface antigen (HBsAg) in 155 patients with Down's syndrome (DS) and 209 with other types of mental retardation (OMR) at Huronia Regional Centre, Orillia, Ontario was 34.8 and 5.3%, respectively.

Hepatitis B antigen: distribution of ad and ay subtypes in blood donors and hepatitis patients.

Hepatitis B antigen (HBAg) from blood donors and patients with hepatitis was tested for ad and ay subspecificity by immunodiffusion in agarose. A total of 59 sera from blood donors and 81 sera from hepatitis patients were subtyped.Subtyping of HBAg from blood donors showed ad and ay subspecificity in 64.

The oceans: growth and oxygen isotope evolution.

A study of the evolution of the oxygen-18/oxygen-16 ratio of the oceans suggests that this ratio is unlikely to have remained constant with time. Our models suiggest that early formation of the oceans is more likely than linear growth.

Sulfur Isotopes in Swaziland System Barites and the Evolution of the Earth's Atmosphere.

Sedimentary barites from the Swaziland System of South Africa (more than 3000 million years old) have sulfur-34 ratios that are enriched by only 2.5 per mil with respect to contemporary sulfides. To explain this small fractionation, it is proposed that oxygen pressure in the earth's atmosphere was very low and that local oxidation occurred in a photosynthetic layer of the ocean.

Quartz and magnetite: oxygen-18-oxygen-16 fractionation in metamorphosed biwabik iron formation.

Oxygen-18-oxygen-16 fractionation of coexisting quartz and magnetite from the Biwabik iron formation varies as a function of distance of the sample from an intrusive contact. This isotope fractionation is related to observed mineralogic variations and compared with a theoretical heat-flow model.