It has a half-life of approximately three years at which time it stops decaying.

它生命的一半是三年,在三年的时候，它就停止衰亡。

麻省理工公开课 - 固态化学导论课程节选

Meanwhile, his youth was going away and now this imaginary student is now thirty-three years old never had time to marry or start a normal life.

与此同时，他的青春年华也已经逝去了,现在这位设想出来的同学已经33岁了,还没有结婚也没有开始正常人的生活。

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