Neil Johnson, a University of Miami physicist, developed this mathematical formula to predict insurgent attacks in war zones. Courtesy of Neil Johnson hide caption

itoggle caption Courtesy of Neil Johnson

This undated X-ray image from the Cleveland Clinic shows electrodes implanted in a patient's brain. The method, known as deep brain stimulation, has traditionally been used to treat diseases such as Parkinson's, but new research indicates it could be helpful for patients with obsessive-compulsive disorder. AP hide caption

itoggle caption AP

As warming temperatures drive polar bears south, they're starting to mix with brown bears much the way they did thousands of years ago. hide caption

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Kittiwake young ingest food regurgitated by their parents. USGS hide caption

itoggle caption USGS