And one -- British Prime Minister David Cameron -- even bestowed Bo, the first dog, with a bone-shaped chew toy adorned with a UK flag.

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Mr Cameron gave the family a large tapestry with an eagle and American flag design by the Rug Company, silver bracelets for daughters Sasha and Malia, and a "bone-shaped chew toy with United Kingdom flag", presumably for Bo, the family's four-year-old dog.

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The PetsCell, measuring 12.5cm (5 inches) by 7.5cm (3 inches), is shaped like a bone and is attached to the dog's collar.

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Macchiarini performed the nine-hour operation on April 9 at the Children's Hospital of Illinois after carefully creating the windpipe using stem cells from Hannah's bone marrow that were saturated over a matrix of plastic fibers shaped into a tube.

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