Second, once sleep is fully obtained, there is an increase of carbon dioxide and a decrease of oxygen in the blood that persists during NREM.

第二，一旦完全进入睡眠状态，非快速眼动期间血液中的二氧化碳增加，氧气减少。

youdao

However, we now know that since oxygen levels were much lower in the Mesozoic than we assumed, there was much less plant life for sauropods to eat than we thought.

然而我们现在知道了，由于中生代空气的含氧量比我们想象的要低得多，所以蜥脚类动物可食用的植物也比我们想象的要少得多。

youdao

The higher one climbs, the less oxygen there is in the air.

爬得越高，空气中的氧气就越少。

youdao

Well, if you get the combustion chamber hot enough, in point of fact, there are some reactions between nitrogen and the oxygen.

如果燃烧室的温度足够高的话，实际上在氮气和氧气之间,会发生一些反应。

麻省理工公开课 - 固态化学导论课程节选

I mean, if the energy is lower to occupy a smaller volume, then if I have this room and a bunch of molecules of oxygen, and nitrogen and what have you in the air, and there are weak attractions between them, why don't they all just sort of glum together and find whatever volume they like.

我的意思是，如果占据小的体积会使能量降低，如果我有这样一个空间,和一些氧气，氮气和其他空气中有的气体，并且分子之间还有微弱的相互作用，为什么他们不黏在一起,然后占据他们所想要占据的体积。

麻省理工公开课 - 热力学与动力学课程节选

Anglers say the sudden drop in water levels mean that there is not enough oxygen in the water for the fish.

BBC: dead fish

There are also different oxygen isotopes in this meteorite than in younger Martian meteorites.

FORBES: Meteorite Shows Evidence Of Water On Ancient Mars

Air tests overnight suggested there may be oxygen levels of about 20 percent in the area where the miners are thought to be, Stickler said.

CNN: Camera lowered into mine cavity shows 'survivable space'