GCSE History AQA B : modern world history

Es un recurso para la preparación del examen del General Certificate Secondary Education (GCSE) que reúne una serie de características que ayudan a clarificar el contenido de las unidades temáticas. Estas características son: fuentes históricas; problemas historiográficos sobre el tema; y un apartado para expresar la opinión personal sobre importantes debates de un asunto histórico. También, se incluye otro recuadro que permite hacer averiguaciones propias sobre hechos históricos; y por último, un esquema con los principales temas y problemas de cada período con identificación de los puntos clave para su comprensión, y un resumen sobre un tema específico con argumentos a favor y en contra.SCBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín, 5 - 3 planta; 28014 Madrid; Tel. +34917748000; [email protected]

Pooled biological specimens for human biomonitoring of environmental chemicals: Opportunities and limitations

Biomonitoring has become the ‘gold standard’ in assessing chemical exposures, and plays an important role in risk assessment. The pooling of biological specimens – combining multiple individual specimens into a single sample – can be used in biomonitoring studies to monitor levels of exposure and identify exposure trends, or to identify susceptible populations in a cost-effective manner. Pooled samples provide an estimate of central tendency, and may also reveal information about variation within the population. The development of a pooling strategy requires careful consideration of the type and number of samples collected, the number of pools required, and the number of specimens to combine per pool in order to maximize the type and robustness of the data. Creative pooling strategies can be used to explore exposure-outcome associations, and extrapolation from other larger studies can be useful in identifying elevated exposures in specific individuals. The use of pooled specimens is advantageous as it saves significantly on analytical costs, may reduce the time and resources required for recruitment, and in certain circumstances, allows quantification of samples approaching the limit of detection. In addition, use of pooled samples can provide population estimates while avoiding ethical difficulties that may be associated with reporting individual results