科学家通过广泛使用的调查问卷方式，测量了具有代表性的年龄超过65岁的1766个人血液中的维生素d的含量。
Scientists measured blood levels of the vitamin in a representative sample of 1, 766 people over 65 and assessed their mental functioning with a widely used questionnaire.
然而，设法测量灾难对人们健康的影响的一个难题是研究不能有代表性的提供幸存者以往健康状况的信息。
However, a problem in trying to measure the impact of disasters on people's health is that studies typically have no information on what survivors' health was like before the experience.
目的通过对成都某几个氡气观测实验室以及代表性建筑物的氡浓度测量，分析氡浓度的时间变化特点和垂直变化特点。
Objective To analyze the temporal and spatial variations of radon concentration by measuring in some LABS and typical buildings in Chengdu.
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