Differential Cross Section and Photon-Beam Asymmetry for the γ[over →]p → π

Differential cross sections and photon-beam asymmetries for the γ[over →]p→π^{-}Δ^{++}(1232) reaction have been measured for 0.7

Spin-density matrix elements for γp→K*0Σ+ at Eγ=1.85-3.0 GeV with evidence for the κ(800) meson exchange.

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.

Cytogenetic study of DDT on human lymphocytes in vitro.

The cytogenetic effect of DDT on human blood cultures, in vitro, was investigated. Two types of experiment were carried out: one, in which the DDT concentrations found in the culture media were similar to those found in the plasma of individuals of the Brazilian population (0.06--0.20 mug/ml); in the second experiments, doses ranging from 1 to 15 mug/ml were used. No correlation was found between DDT doses and cells with chromosomal aberrations. The Poisson test of comparison between means showed that at certain DDT concentrations (0.20, 4.05 and 8.72 mug/ml) the proportion of cells with structural aberrations was significantly greater than in the controls.

Cytogenetic study on individuals occupationally exposed to DDT.

Workers from three insecticide plants in direct contact with 2,2-bis (beta-chlorophenyl)-I,I,I,-trichloroethane (DDT) did not differ significantly in the frequencies of cells with chromosomal aberrations when compared with controls from the same plants but not in direct contact with the drug. The same was true when a group of workers from one plant was compared with a control group from the Instituto Butantan, with no history of occupational exposure to DDT. Yet, when the control group from one of the three plants, which showed high DDT plasmic levels, was added to the group in direct contact with the insecticide, the frequency of cells with chromatid aberrations was significantly higher, suggesting that DDT causes chromatid lesions. A positive correlation was found between DDT levels and times of exposure, but being in direct or indirect contact with DDT was not always correlated with the degree of contamination.

Measurement of deeply virtual compton scattering beam-spin asymmetries.

The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton (e p-->epgamma) were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range (x(B) from 0.11 to 0.58, Q2 from 1 to 4.8 GeV2, -t from 0.09 to 1.8 GeV2), the azimuthal dependence of the asymmetries is compatible with expectations from leading-twist dominance, A approximately a sinphi/(1+c cosphi). This extensive set of data can thus be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark sector.

Measurement of the N-->Delta(+)(1232) transition at high-momentum transfer by pi(0) electroproduction.

We report a new measurement of the exclusive electroproduction reaction gamma(*)p-->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the magnetic (M(1+)), electric (E(1+)), and scalar (S(1+)) multipoles in the N-->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV(2)/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E(1+)/M(1+) is small and negative, indicating strong helicity nonconservation, and the ratio S(1+)/M(1+) is negative, while its magnitude increases with Q(2).

Ensaios biológicos como testes preliminares na detecçäo de resíduos de inseticidas em frutas e hortaliças

A indicaçäo da presença de residuos de pesticidas organoclorados e organofosforados, em amostras de frutas e hortaliças, foi feita atraves de ensaios biológicos com moscas Drosophila melanogaster (Meig). Simultaneamente, procedeu-se à determinaçäo qualitativa e quantitativa dos resíduos por cromatografia gasosa. Desta maneira, foi possível comparar se os resultados observados no método de bioanálise coincidiam ou näo com os obtidos pelo método químico de cromatografia gasosa. Constatou-se que em 65% do total de 223 amostras analisadas, os resultados foram coincidentes nos dois métodos. Os resultados indicaram que, apesar das limitaçöes, os ensaios biológicos, quando utilizados como método preliminar de triagem podem prestar auxílio na pesquisa de resíduos tóxicos