Vigor tests for evaluation of crambe (Crambe abyssinica Hochst) seed quality

The aim of this study was adapting the methodology of the accelerated aging test (AA) and electrical conductivity test (EC) to evaluate seed quality of crambe, as well as verifying enzymatic activity in relation to vigor differences. Crambe seed lots, cv. FMS Brilhante, were evaluated by the AA test, for periods of 0, 24, 48, 72 and 96 h, at 42 °C, with and without NaCl saturated solution; and the EC test, by soaking seeds into deionized water (mL) in the ratios of 25/25, 25/50, 50/50 and 50/75 (seed/water) for 2, 4, 6, 8, 10, 12, 14, 16 and 18 h. The electrophoretic profile for isozymes esterase, superoxide dismutase, catalase, isocitrate lyase, alcohol dehydrogenase and malate dehydrogenase was evaluated on polyacrylamide gel (7.5%). The AA test conducted at 42 °C, for 96 h, was efficient to detect differences on seed quality levels; however, the EC test was not suitable to evaluate vigor of those seeds. The bands stained for isozymes esterase, superoxide dismutase and catalase were evident for the more vigorous seeds; and the bands for isozymes isocitrate lyase and alcohol dehydrogenase were less evident for the less vigorous seeds. For enzyme malate dehydrogenase enzyme intensity of bands was similar

Precision measurement of the Ξb−\Xi^-_b baryon lifetime

International audienceA sample of $pp$ collision data, corresponding to an integrated luminosity of 5.5 fb$^{-1}$ and collected by the LHCb experiment during Run 2, is used to measure the ratio of the lifetime of the $\Xi^-_b$ baryon to that of the $\Lambda^0_b$ baryon, $r_{\tau}\equiv\tau_{\Xi^-_b}/\tau_{\Lambda^0_b}$. The value ${r_{\tau}^{\rm Run\,2}=1.076\pm0.013\pm0.006}$ is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain ${r_{\tau}^{\rm Run\,1,2} = 1.078\pm0.012\pm0.007}$. Multiplying by the world-average value of the $\Lambda^0_b$ lifetime yields $\tau_{\Xi^-_b}^{\rm Run~1,2} = 1.578\pm0.018\pm0.010\pm0.011$ ps, where the uncertainties are statistical, systematic, and due to the limited knowledge of the $\Lambda^0_b$ lifetime. This measurement improves the precision of the current world average of the $\Xi^-_b$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions