RESUMEN
We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d
RESUMEN
The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of 6 x 10(19) eV, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of 4 x 10(18) eV. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.
RESUMEN
The influence of indoleacetic acid, cacodylic acid (hydroxy-dimethylarsine oxide), and amitrole (3-amino-1,2,4-triazole) on the petiole explant abscission rate was studied in three species. Indoleacetic acid increased the abscission rate in both bean (Phaseolus vulgaris L. var. Red Kidney) and Coleus (Coleus blumei Benth) at 10(-3) and 10(-4)m but had no effect on abscission in privet (Ligustrum ovalifolium). Cacodylic acid was found to stimulate abscission in explants of beans and privet, but not in Coleus. Amitrole did not stimulate abscission under any circumstance tested. In no case was the abscission rate dependent on the time at which any of the chemicals was applied. These data do not support the two-phase response of explants to applied auxin.