"Naturally,one would be concerned because with the likes of prostitutes that will be coming over, so people are bound to be more exposed to such activities such as prostitution and human trafficking."

VOA: standard.2010.05.29

All the energies are negative because it is a bound system. I start up here with n equals one.

所有能量级都是负数，因为它是一个束缚系统,在这里我从n等于1讲起。

麻省理工公开课 - 固态化学导论课程节选