RESUMO
Resolution in scanning transmission electron microscopy (STEM) is ultimately limited by the diameter of the electron beam. The electron beam diameter is not only determined by the properties of the condenser lens system but also by electron scattering in the specimen which leads to electron-beam broadening and degradation of the resolution with increasing specimen thickness. In this work we introduce a new method to measure electron-beam broadening which is based on STEM imaging with a multi-segmented STEM detector. We focus on STEM at low electron energies between 10 and 30â¯keV and use an amorphous carbon film with known thickness as test object. The experimental results are compared with calculated beam diameters using different analytical models and Monte-Carlo simulations. We find excellent agreement of the experimental data with the recently published model by Gauvin and Rudinsky [1] for small t/λel (thickness to elastic mean free path) values which are considered in our study.
RESUMO
1.2 mega U Penicillin V potassium was given to 20 patients 2 hours (group 1) and another 19 patients 3 hours (group 2) before tonsillectomy. After the operation biological determinations of the levels of active principle were made from tonsillar tissue and serum with statistical evaluation of the results (Spearman's rank correlation). There was a significant connection between the serum and tonsillar tissue concentrations (in children and adults) in both groups. The level of the active principle in group 2 was only slightly lower than in group 1. Many of the micro-organisms responsible for tonsillitis can be influenced by the concentrations found here, so that application of Penicillin V can often be expected to have a good therapeutic effect.
