For decades, ever since the mile was timed, no one broke the four minute barrier.

数十年来，自从开始一英里跑计时以来，没有人突破四分钟界限。

哈佛公开课 - 幸福课课程节选

Some form what are called megakaryocytes which become platelets, which are responsible for clotting, for forming a barrier if your circulatory system gets injured so you don't bleed.

还有一些类型的细胞称为巨核细胞,生成有凝血作用的血小板,在你的循环系统受损时形成止血屏障

耶鲁公开课 - 生物医学工程探索课程节选

The problem it solves for the cell is how to do I make a barrier around myself to define what's in me and what's outside of me when most of what's around me and what's in me is water.

它为细胞解决的问题是,当我体外和体内大部分都是水情况下,我怎样在自己周围设置一个界线,来区分什么是体内的,什么是体外的

耶鲁公开课 - 生物医学工程探索课程节选