The center's distance learning program uses puppets to teach children in classrooms in forty-four American states.

VOA: special.2009.09.23

So, for example, if I have a sodium ion over here, and I have a chloride ion over here, where the distance from center to center r I'm denoting as r, this is nucleus to nucleus separation.

所以，比如这有一个钠离子，和一个氯离子，它们中心与中心间的距离,我把它设为，这是原子核和原子和的间距。

麻省理工公开课 - 固态化学导论课程节选

The Ghanaians took part from a distance learning center in Accra.

VOA: special.2009.11.12