The team found levels of lead as high as thirty-two thousand parts per million in tests on some paint samples from Ecuador.

VOA: special.2009.08.31

This class will be taught on two levels.

本课程将分为两个部分。

哈佛公开课 - 幸福课课程节选

The formula tells us or absorbed based on the energy difference between the two levels that we're going between, that the electron is transitioning between.

这些公式告诉我们,或发出的光的，频率大小,是基于，电子转移的，两个能级，之间的能量差。

麻省理工公开课 - 化学原理课程节选