She said physicians even used to stick ping pong balls into peoples' lungs in an attempt to starve the lung of oxygen, to kill the bacteria.

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Napolitano responded that Tsarnaev's departure did "ping" in the homeland security screening system, but she noted that because the FBI's investigation in 2011 found no suspicious activity, there was no reason to follow up.

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She had a narrow lead over the incumbent, Jean Ping of Gabon, through the first three rounds and reached the required two-thirds majority with 37 votes in the fourth round.

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