主动脉瓣并非是两个瓣叶的才钙化。

An aortic valve need not be bicuspid to calcify.

youdao

这是一个有四个瓣叶的瓣膜。

This is a quadricuspid valve.

youdao

可见三个瓣叶围绕形成环。

Note there are three cusps sewn into a synthetic ring.

youdao

And it turns out that when you constructively have two p orbitals interfere, and when I say constructively, I mean they're both either positive or they're both the negative lobes, that's when you got bonding.

当两个ｐ轨道,相长干涉时，我说的相干相长，意思就是说它们要么都是,正的叶瓣要么都是负的叶瓣，这时就能成键。

麻省理工公开课 - 化学原理课程节选

So, that's going to be important later when we get to bonding, but just take note of it now, we have two nodes, or we have two lobes, excuse me, each with a separate phase.

这等到我们之后讲到成键时是非常重要的，现在先要记住，我们有两个节点，不好意思，是两个叶瓣，每个都是不同的相位。

麻省理工公开课 - 化学原理课程节选

And when we look at this, it's actually split by what's called a nodal plane, which is pointed out in light orange here on this picture, but what we just mean is that there is this whole plane that separates the two lobes where there is absolutely no electron density.

我们来看这里，实际上它被一个节面分开，在这图里用淡黄色表示，这意味着这个分开,两个叶瓣的平面上,是完全没有电子密度的。

麻省理工公开课 - 化学原理课程节选