The Senate chamber is laid out in four concentric semicircles, with adjacent desks almost touching on the crowded Democratic side, and the desks of the much smaller Republican minority spaced loosely apart.

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The canals that ring the city in tight concentric circles are lined with 3, 000 of them, moored to centuries-old stone quays.

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Equipped with a flat underside and cupped upper shell that resembles a skewed dome, they are etched with faint concentric lines that recall growth spurts.

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On the right edge, the power button continues to use the concentric metallic finish found on other RAZR devices, with the volume rocker matching the plastic of the handset's shell.

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But they did see concentric grooves left by what they think was a drill with a tiny stone bit.

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He plans to cut a series of concentric circles into the surface of a piece of diamond, a material with one of the highest refractive indices known.

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Their model consists of two concentric steel cylinders, three metres high and 80 centimetres in diameter, filled with molten sodium.

BBC: Planet Earth