A major disadvantage of coal combustion-and characteristic of industrial cities-has been air pollution by soot, dust, ash, exhaust and large amounts of the greenhouse gas carbon dioxide.

煤炭燃烧的主要缺点——也是工业城市的特色——是烟尘、粉尘、灰渣和废气以及大量的温室气体二氧化碳污染了空气。

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The telescopes sift through the background cosmic radiation to find spots where it has been slightly perturbed as it passes through extremely hot gas, a hallmark characteristic of galaxy clusters.

南极天文台三大观测宇宙的天文台之一，旨在检测由宇宙大爆炸而产生的大量存在于微光辐射中的扭曲现象，利用天文望远镜对宇宙射线背景进行筛选，再利用星系群的特点确定一个点，即当宇宙射线穿过极热气体时会产生轻微混乱，混乱的那一刻就是所要找的那个点。

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This, in turn, causes the conductivity of the nanotubes to change-how much is a characteristic of each gas.

这样又导致了纳米管的导电性发生变化，而我们可以根据导电性变化的多少来鉴定每一种毒气。

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I could take an unknown gas and put it in and measure it and then say, wow, those are the lines that are characteristic of sodium.

我取一种未知气体，把它放到管里,然后检测它，哇，这些线是钠的特征。

麻省理工公开课 - 固态化学导论课程节选

And, furthermore, they are characteristic of the target gas element.

更进一步的说，它们是目标气体元素的特征。

麻省理工公开课 - 固态化学导论课程节选

The distinguishing characteristic is that oil and gas production slumped last year, far more than expected.

BBC: A leak in the growth pipeline