RESUMEN
This Letter reports on a systematic study of ß-decay half-lives of neutron-rich nuclei around doubly magic (208)Pb. The lifetimes of the 126-neutron shell isotone (204)Pt and the neighboring (200-202)Ir, (203)Pt, (204)Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden ß strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during ß decay back to stability.
RESUMEN
A ß-decaying high-spin isomer in (96)Cd, with a half-life T(1/2)=0.29(-0.10)(+0.11) s, has been established in a stopped beam rare isotope spectroscopic investigations at GSI (RISING) experiment. The nuclei were produced using the fragmentation of a primary beam of (124)Xe on a (9)Be target. From the half-life and the observed γ decays in the daughter nucleus, (96)Ag, we conclude that the ß-decaying state is the long predicted 16(+) "spin-gap" isomer. Shell-model calculations, using the Gross-Frenkel interaction and the πν(p(1/2),g(9/2)) model space, show that the isoscalar component of the neutron-proton interaction is essential to explain the origin of the isomer. Core excitations across the N=Z=50 gaps and the Gamow-Teller strength, B(GT) distributions have been studied via large-scale shell-model calculations using the πν(g,d,s) model space to compare with the experimental B(GT) value obtained from the half-life of the isomer.
RESUMEN
The gamma decay of excited states in the waiting-point nucleus (130)Cd(82) has been observed for the first time. An 8(+) two-quasiparticle isomer has been populated both in the fragmentation of a (136)Xe beam as well as in projectile fission of 238U, making (130)Cd the most neutron-rich N = 82 isotone for which information about excited states is available. The results, interpreted using state-of-the-art nuclear shell-model calculations, show no evidence of an N = 82 shell quenching at Z = 48. They allow us to follow nuclear isomerism throughout a full major neutron shell from (98)Cd(50) to (130)Cd(82) and reveal, in comparison with (76)Ni(48) one major proton shell below, an apparently abnormal scaling of nuclear two-body interactions.
RESUMEN
A new in vitro test for phototoxicity has been developed. Nine substances (eight photosensitizers and one non-photosensitizer) were screened for their ability to activate human complement in the presence of UV light, and all photosensitizers were found to be active. Complement activation was quantified by means of ELISA. In all cases activation was mediated by alternative, but not by classical, pathways. The results of a cell culture test performed with 5-methoxypsoralen suggest the existence of two different mechanisms of phototoxicity. This indicates that the battery of in vitro assays for phototoxicity prediction must contain at least two different tests.
RESUMEN
The MTT assay for cell viability and cell proliferation has been modified to improve its reproducibility and accuracy. The modified test is performed on MultiScreen filtration plates, which permits the removal of the culture medium prior to formazan solubilisation, without loss of cells or formazan crystals. A 1:1 mix of DMSO and ethanol is used as the solvent, since this has the same optical refraction index as the filters, making it possible to measure the optical densities directly on the MultiScreen plate. Data obtained in the assay method using the MultiScreen plate were compared with data from studies employing the normal flat-bottomed plate, by using cells which grow in suspension. Two cell lines were used in the study. CTLL-2, which are IL-2 dependent cells of murine T cell origin, and Jurkat E.6.1 which are IL-2 producing cells of human lymphoma origin. CTLL-2 cells and the modified MTT assay were also used for evaluating the effects of different IL-2 concentrations on cell proliferation.
