This stem cell which is reproduced still has the potential to undergo asymmetric division but this one does not.

新生成的干细胞,仍然有潜能进行不对称分裂,但定向祖细胞就不行

耶鲁公开课 - 生物医学工程探索课程节选

You can't have slaves without wealth, because you got to feed them at the very least, and no matter how wicked a master you are, dead slaves are no good to you.

养奴隶没钱是不行的,因为不管你有多恶劣,也得供给他们生存的食物,死人是毫无用处的

耶鲁公开课 - 古希腊历史简介课程节选