It must be noted that sand is a 'particulate matter' (PM) and is recognized as such when measuring levels of the many different components that make up air pollution.

需要说明的是，沙子，是一种颗粒物质(PM)。测量空气污染物的不同组成成分含量等级时，它被归为颗粒物质。

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These films can be used to make a new type of loudspeaker that works by heating and cooling the air, rather than bouncing up and down to vibrate the air directly.

这样制成的薄膜可以被用来制造一种新型扩音器，这种扩音器通过加热和冷却空气工作，而不再是直接通过往复运动使空气产生振动效果。

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Make up, perfume and skincare products used after the expiry date carry a risk of irritation and infection, Debenhams said. This is due to air and bacteria infiltrating the products.

由于空气和细菌渗透原因，化妆品、香水和护肤品在截止日期后使用会有带有刺激性和感染的风险，德本汉姆公司说。

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More speed on the ground may make up for less in the air.

ECONOMIST: Air travel: After Concorde | The

High petrol prices and the desire to clean up our air quality make them the smart choice.

ENGADGET: UK's first fuel cell-powered black cab hits the streets of London

When Whirlpool set up factories to make refrigerators, air-conditioners, washing machines and microwave ovens in China in 1994, it assumed that it was racing against other foreigners.

ECONOMIST: Infatuation��s end