Phase fluorometric method for determination of standard lifetimes

Rayleigh scatterers have long been used as standards for fluorescence lifetime determinations, but they have many drawbacks, including the well-known “color effect ’. To avoid these problems, various fiuorophores have been used as standards. Unfortunately, the lifetimes of these compounds are not agreed upon to better than 5%, and the compounds cited in the literature do not fully cover the 250–850 nm band of common fluorescence emission. We describe a multifrequency phase fluorometric method for accurately determining the lifetimes of monoexponential fluorophores (standards) without reference to another standard. Results are shown for some widely used standard fluorophores and some recently developed compounds. An Independent test of the accuracy of the method based on quenching experiments is presented. © 1988, American Chemical Society. All rights reserved

LA (IM) POSIBILIDAD DE CONSTRUIR UN CONCEPTO CIENTÍFICO DE CONSTITUCIÓN THE (IM) POSSIBILITY OF BUILDING A CIENTIFIC CONCEPT FOR CONSTITUTION

El presente trabajo analiza diversos conceptos de Constitución entregados por la doctrina, intentando responder ¿qué es una Constitución?, pregunta formulada en el siglo XIX por Lassalle. Se advierte que hay una evolución del concepto a lo largo del tiempo, pero que no es posible la elaboración de un concepto neutro y científicamente válido.<br>This work analyzes a number of concepts for Constitution, that intend to answer what is a Constitution, question that was asked by Lassalle at the XIX century. It is possible to observe that the concept does show an evolution through time, but that it is not possible to elaborate a neutral and scientific valid concept