Osmium-187/osmium-186 in manganese nodules and the cretaceous-tertiary boundary

As a result of the radioactive decay of rhenium-187 (4.6 x 10(10) years) the osmium-187/osmium-186 ratio changes in planetary systems as a function of time and the rhenium-187/osmium-186 ratio. For a value of the rhenium-187/osmium-186 ratio of about 3.2, typical of meteorites and the earth's mantle, the present-day osmium-187/osmium-186 ratio is about 1. The earth's continental crust has an estimated rhenium-187/osmium-186 ratio of about 400, so that for a mean age of the continent of 2 x 10(9) years, a present-day osmium-187/osmium-186 ratio of about 10 is expected. Marine manganese nodules show values (6 to 8.4) compatible with this expectation if allowance for a 25 percent mantle osmium supply to the oceans is allowed. The Cretaceous-Tertiary boundary iridium-rich layer in the marine section at Stevns Klint, Denmark, yields an osmium-187/osmium-186 ratio of 1.65, and the one in a continental section in the Raton Basin, Colorado, is 1.29. The simplest explanation is that these represent osmium imprints of predominantly meteoritic origin.     

"Baby Doe" regs thrown out by court

On April 14, 1983, federal district court judge Gerhard Gesell overturned, as "arbitrary and capricious," a Department of Health and Human Services regulation that required hospitals to post notices concerning the illegality of denying life-saving care to handicapped infants and encouraged anyone with knowledge of such a case to report it to HHS via a telephone hotline. This article reviews the evolution and implementation of the HHS regulation, the legal challenge to it, and the judge's ruling.     

Isotopic Composition of Cellulose from C3, C4, and CAM Plants Growing Near One Another

Cellulose from plants having crassulacean acid metabolism was enriched in deuterium but not in oxygen-18 in relation to cellulose from C(3) and C(4) plants growing in the same area, indicating that the deuterium enrichment is due to isotopic fractionation during biochemical reactions rather than during evapotranspiration. Hydrogen and oxygen stable isotope ratios of cellulose from the plants in this restricted area showed more variability than that observed in samples collected across an entire continent. Biological factors appear to be as important as environmental factors in determining the isotope ratios of plant cellulose.     

Single-cell proteins

Both photosynthetic and nonphotosynthetic microorganisms, grown on various carbon and energy sources, are used in fermentation processes for the production of single-cell proteins. Commercial-scale production has been limited to two algal processes, one bacterial process, and several yeast and fungal processes. High capital and operating costs and the need for extensive nutritional and toxicological assessments have limited the development and commercialization of new processes. Any increase in commercial-scale production appears to be limited to those regions of the world where low-cost carbon and energy sources are available and conventional animal feedstuff proteins, such as soybean meal or fish meal, are in short supply.     

Mutants of Rhizobium japonicum with Increased Hydrogenase Activity

Some strains of Rhizobium japonicum can use hydrogen as an energy source for growth under microaerophilic conditions. Mutant strains have been selected that use hydrogen in the presence of high partial pressures of oxygen. The mutants contain more hydrogenase than the parent strain, both as free-living cells and as bacteroids in nitrogen-fixing soybean root nodules.