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Because of these fluctuations, estimating the annual mean concentration of radon in indoor air requires measurements of mean radon concentrations for at least three months.

鉴于这种起伏，估算室内空气中氡的年平均浓度需要对氡的平均浓度至少进行三个月的测定。

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This small area of the south east sees by far the largest concentration of air traffic, and the 18 minute window required by iFACTS is a luxury here, explained Nats General Manager Paul Haskins.

BBC: Why air traffic control still needs the human touch

But perhaps for radon concentration in the air, a radiation level of 5 to 10 picocuries per liter is about right for maximum benefit, speculates Myron Pollycove, a professor emeritus of laboratory medicine and radiology at the University of California, San Francisco.

FORBES: Magazine Article

There is an air of concentration, of quiet, mastered pleasure, and in some sense, these attributes mirror the astonishing ascendency of Japanese whisky itself, which now regularly surpasses its Scottish progenitor in international whisky awards.

WSJ: The Ascent of Japanese Whisky | The Cult of | WSJ. Magazine May 2013