Belief network models of land manager decisions and land use change.

A two-stage model of land use change is described, which is driven by the types of decisions that land managers make when changing their broad styles of use. The first stage uses decision modelling techniques to assess if a manager is currently satisfied with the present situation, when compared to various potential alternatives. If this evaluation indicates satisfaction, it is assumed that the present land use will continue. However, if it indicates dissatisfaction, Belief Network techniques are used to estimate, in more detail, both how dissatisfied the manager is and whether the costs of changing, from the present use to a potentially better one, will be out-weighed by the anticipated benefits. The proposed models can use a variety of cost and benefit criteria (e.g. financial, social and ecological). The approach is illustrated with a case-study of the factors that might influence changes from farming to forestry in marginal upland areas of the UK.

Divalent metal ion mediated interaction of proteins with negatively charged membranes. A model study employing molecular mechanics.

Previous molecular mechanics calculations on the effect of Ca(II) and Mg(II) ions on the conformation of the 18-23 loop of bovine prothrombin [Maynard et al. 1988, Int. J. Peptide Protein Res. 31, 137-149] are extended to include the effect of a model phospholipid head group methyl[L-seryl] phosphate. Whereas the conformation of the Gla-21 Pro-22 amide bond remains decidedly trans in the absence of the model head group, in its presence, the cis Ca(II) ion induced (but not Mg(II] form is significantly lowered in relative energy. The low energy Ca(II) structures establish a coordination sphere with more ligands than do the low energy Mg(II) ion structures.

Organochlorine pesticide residues in human milk samples from women living in Northwest and Northeast Mississippi, 1973-75.

Organochlorine pesticide analyses were performed on human milk samples obtained from 34 women living in the Mississippi Delta, a high pesticide usage area, and from six women living in Starkville, Mississippi, a low pesticide usage area. Nine women collected samples before and after their babies had nursed so that fat levels and sigma DDT levels could be compared on whole milk and milk fat bases. sigma DDT values were independent of collection time if calculated on a milk fat basis, but not if calculated on a whole milk basis. Thus, the most consistent indicator of DDT residues were values calculated on a milk fat basis. Residue levels for p,p'-DDE, p,p'-DDT, and sigma DDT were significantly different (P less than 0.01) in samples from the two areas. Residues of o,p'-DDT, beta-BHC, and oxychlordane in milk samples from women living in the high pesticide usage area also were significantly different (P less than 0.05). A mean value of 19.17 ppm sigma DDT, found in the milk fat of samples from the high pesticide usage area, is the highest ever reported. Samples from the low pesticide usage area contained a mean level of 2.36 ppm sigma DDT.

DDT residues in air in the Mississippi delta, 1975.

In a previous publication the authors reported on 88 percent decrease in sigma DDT (DDT plus metabolities) in air between 1972 and 1974 in the Mississippi Delta. This period was the first two years after the use of DDT was banned in the United States. The present report shows an additional 36 percent decrease in sigma DDT levels in air between 1974 and 1975. Thus in the past three years sigma DDT in air has decreased by 92 percent, a much more rapid decrease than had been expected.

Insecticide exposure of mothers and newborns in a rural agricultural area.

Pregnant women in a rural agricultural area were found to have levels of residues of chlorinated hydrocarbon insecticides in their serum which were comparable to those found in occupationally exposed men. Cord blood of offspring also had significant residue levels. Residues were higher in blacks and in mothers living in rural areas where exposure was more intense. In newborns no signs or symptoms compatible with acute chlorinated hydrocarbon poisoning were found. Despite the lack of DDT use during most of the study period, over 90% of the mothers. 84% of the black newborns, and 45% of the white newborns demonstrated evidence of recent DDT exposure.