Concentrations of positively charged particles develop at the top and bottom of the cloud, but the middle region becomes negatively charged.

带正电荷的粒子集中在云团的顶部和底部，但中间区域形成的是带负电荷的粒子。

youdao

Then, that's not vertically simple because here in the middle, I have not only does top in this bottom, but I have this middle face.

这个区域不是垂直简单的,因为在中间这里，不仅有顶面有底面，我还有中间面。

youdao

So that covers the top and bottom rows of the grid, but what about the middle row?

了解顶部行和底部行之后，那么什么是中间行呢？

youdao

Basically, what the libertarians are objecting to in this case is the middle 80 percent deciding what the top ten percent are doing for the bottom ten percent.

基本上，在这个例子中，自由主义者所反对的是,由中间80%的人来决定,上层的10%，应该为底层的10%做什么。

耶鲁公开课 - 公正课程节选

Nelson's injuries destroyed all three main skin layers - the epidermis, dermis and hypodermis (the top, middle and bottom), in some places right down to the periosteum, the membrane overlying the bone.

BBC: US Army seeks new ways to treat facial skin injuries

The trend for huge celebrations has "extended socially from middle and top down to bottom" and "now we all expect these events to be big and lavish".

BBC: Why has everything become a costly milestone event?

On the right, the top and bottom buttons scroll up and down and the middle button selects.

WSJ: Watch Keeps Alerts From a Phone at Arm's Length