First Measurement of a Long-Lived π

The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π^{+}π^{-} atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm between the target and a 2.1 µm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, n_{A}^{L}=436_{-61}^{+157}|_{tot}, the lifetime of the 2p state is found to be τ_{2p}=(0.45_{-0.30}^{+1.08}|_{tot})×10^{-11} s, not contradicting the corresponding QED 2p state lifetime τ_{2p}^{QED}=1.17×10^{-11} s. This lifetime value is three orders of magnitude larger than our previously measured value of the π^{+}π^{-} atom ground state lifetime τ=(3.15_{-0.26}^{+0.28}|_{tot})×10^{-15} s. Further studies of long-lived π^{+}π^{-} atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.

A biopsy procedure for determining filet and predicting whole-fish mercury concentration.

Although mercury contamination of fish is a widespread phenomenon, its regional evaluation is hindered by the reluctance of permitting agencies to grant collection permits, problems in securing adequate freezer space, and time to process whole, large fish or filets. We evaluated mercury concentrations in 210 filet biopsies from 65 sites in 12 western states relative to whole-body mercury concentration in the same fish. We found a highly significant relationship (r(2) = 0.96) between biopsy and whole-fish mercury concentrations for 13 piscivorous and nonpiscivorous fish species. We concluded that relative to conventional fish-tissue sampling and analysis procedures for whole fish or filets, the biopsy procedure for mercury in fish tissue is nonlethal, less cumbersome, more likely to be permitted by fisheries agencies, and a precise and accurate means for determining both filet and whole-fish mercury concentrations.

Artificial rearing of rat pups with a protein-enriched formula.

Neonatal Long-Evans hooded rat pups were assigned to one of three groups: 1) pups normally reared, 2) pups implanted with intragastric cannulas and artificially reared with a common milk replacement formula, 3) pups implanted with intragastric cannulas and artificially reared with a protein-enriched milk formula. Daily body weights were recorded, as were the ontogeny of various reflexes. On day 18, the animals were behaviorally tested and then killed. There were no differences among the three groups in daily body weights, nor in the ontogeny of reflexive behavior. There were no differences in the wet weights of caudal brain sections, but the normally reared animals had significantly larger rostral brain sections than either artificially reared group. While cerebella of normally reared animals were significantly larger than those of the two artificially reared groups, there was a significant trend towards more normal cerebellar weights with the addition of protein in the formula of artificially reared animals. Behavioral tests indicated that the animals artificially reared have significantly different behavior than normally reared animals. However, compared to animals artificially reared using a common milk formula, animals artificially reared with additional protein in their formula behave more like normally reared animals.