Overview of results from the WaterTox intercalibration and environmental testing phase II program: Part 1, statistical analysis of blind sample testing.

There is an urgent need to evaluate the presence of toxicants in waters used for human consumption and to develop strategies to reduce and prevent their contamination. The International Development Research Centre undertook an intercalibration project to develop and validate a battery of bioassays for toxicity testing of water samples. The project was carried out in two phases by research institutions from eight countries that formed the WaterTox network. Results for the first phase were reported in the special September 2000 issue of Environmental Toxicology. Phase II involved toxicity screening tests of environmental and blind samples (chemical solutions of unknown composition to participating laboratories) using the following battery: Daphnia magna, Hydra attenuata, seed root inhibition with Lactuca sativa, and Selenastrum capricornutum. This battery was also used to assess potential toxicity in concentrated (10x) water samples. Results are presented for a set of six blind samples sent to the participating laboratories over a 1-year period. Analyses were performed for each bioassay to evaluate variations among laboratories of responses to negative controls, violations of test quality control criteria, false positive responses induced by sample concentration, and variability within and between labs of responses to toxic samples. Analyses of the data from all bioassays and labs provided comparisons of false positive rates (based on blind negative samples), test sensitivities to a metal or organic toxicant, and interlaboratory test variability. Results indicate that the battery was reliable in detecting toxicity when present. However, some false positives were identified with a concentrated soft-water sample and with the Lactuca and Hydra (sublethal end-point) tests. Probabilities of detecting false positives for individual and combined toxic responses of the four bioassays are presented. Overall, interlaboratory comparisons indicate a good reliability of the battery.

Direct measurement of the pion valence-quark momentum distribution, the pion light-cone wave function squared.

We present the first direct measurements of the pion valence-quark momentum distribution which is related to the square of the pion light-cone wave function. The measurements were carried out using data on diffractive dissociation of 500 GeV/c pi(-) into dijets from a platinum target at Fermilab experiment E791. The results show that the /q&q> light-cone asymptotic wave function describes the data well for Q2 approximately 10 (GeV/c)(2) or more. We also measured the transverse momentum distribution of the diffractive dijets.

Observation of color-transparency in diffractive dissociation of pions.

We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where t(min)-->0), we find that when the per-nucleus cross section for this process is parametrized as sigma = sigma0Aalpha, alpha has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.

Effects of parents' and pediatricians' worry concerning severe gastroenteritis in early childhood on later disturbances in the child's behavior.

Probands who had been hospitalized for gastroenteritis between the ages of 2 and 5 years were studied at the ages of 8 to 12 years. More conduct problems and a tendency to excessive dependence were found (1) in probands who were severely ill by objective criteria than were others and (2) in probands whose parents were specifically worried that their child might die as a result of the illness. General worry in the parents had different consequences. Other data suggest that pediatricians, because they are no longer worried about the illness after the child is discharged, may be failing to take appropriate preventative measures at opportune moments in the years following the hospitalization.