Now,he thinks short is better. "I've gotten researchers telling me that you don't realize is how long someone can have a high level of concentration.

VOA: standard.2010.03.26

They move from regions of high concentration to regions of low concentration by this natural flow down a concentration gradient.

从高浓度区域,向低浓度区域流动,顺浓度梯度流动

耶鲁公开课 - 生物医学工程探索课程节选