The use of commercial devices for reducing radiofrequency field exposure has not been shown to be effective.

使用商业装置来降低射频场接触量，并无证据证明是有效的。

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The picture is a digital composite, a separate longer exposure added to an eclipse frame to capture the surrounding star field.

这幅图片是经过数码合成的，由一幅分开的长曝光照片和拍摄下周围星域的月食照片组成。

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Photos are unavoidably limited by the trade-off between depth of field, exposure time and image noise.

你必须在景深、曝光时间和噪点之间做出权衡。

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Experience in the field, or exposure to field-based operations, is desirable.

UNESCO: Vacancy : Human Resources Officer (right to education) (30/1/2012) 1CAUIS0030ST - (P-3)

At very high doses, exposure to a magnetic field can cause the muscles to twitch and some people have reported feeling dizzy or sick when moving their heads quickly around a high-field magnet.

BBC: NEWS | Health | Planned scan-limit delay welcomed

The position has afforded her considerable exposure going into the crowded field of candidates vying to succeed term-limited Mayor Michael Bloomberg.

WSJ: City Council speaker launches NYC mayoral bid