Additional Home Secretary D.R.S.Chaudhary told a news conference Sunday authorities and citizens need to be vigilant, especially in five eastern states.

VOA: standard.2009.06.21

So, we can do that by using this equation, which is for s orbitals is going to be equal to dr 4 pi r squared times the wave function squared, d r.

用这个方程,对于s轨道，径向概率分布,4πr的平方,乘以波函数的平方,这很容易理解。

麻省理工公开课 - 化学原理课程节选

"And,the President's budget for 2009 in the recovery act had the largest increase for R&D that we have seen in recent years."

VOA: standard.2009.08.31