Maryland hospitals are promoting hand washing among other measures to prevent patient infections. Leah-Anne Thompson/iStockphoto.com hide caption

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Leah-Anne Thompson/iStockphoto.com

The flag of the state of Arizona flies at half-staff outside University Medical Center in Tucson, Ariz., on Jan. 8. Chris Morrison/AP hide caption

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Chris Morrison/AP

Natasha Smahlei, a model, works at the Caitlin Raymond International Registry exhibit in October during the New England Business Expo at the DCU Center in Worcester, Mass. Paul Kapteyn/Courtesy of www.telegram.com hide caption

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Paul Kapteyn/Courtesy of www.telegram.com

Natasha Smahlei, a model, works at the Caitlin Raymond International Registry exhibit in October during the New England Business Expo at the DCU Center in Worcester, Mass. Paul Kapteyn/Courtesy of www.telegram.com hide caption

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Paul Kapteyn/Courtesy of www.telegram.com

In Oxford, England, people are 16 times more likely to get a particular kind of hip replacement than residents of London. Wikimedia Commons hide caption

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Wikimedia Commons

Most gases used in anesthesiology eventually end up in the atmosphere where they trap heat even more effectively than carbon dioxide. iStockphoto.com hide caption

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iStockphoto.com

A CT scan of the brain shows the cerebellum, a small portion of each temporal lobe, and the sinuses. Andrew Ciscel via Wikimedia Commons hide caption

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Andrew Ciscel via Wikimedia Commons