A healthy gypsy moth caterpillar on a leaf. Outbreaks of gypsy moths damage roughly 1 million acres of forest in the U.S. each year. Michael Grove/Science/AAAS hide caption

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The brain "seems to be specialized in alerting us to things that are emotionally important to us — either positive or because they're scary," a scientist says. iStockphoto.com hide caption

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A convoy of Walmart trucks waited to enter New Orleans on Sept. 1, 2005, after the city was battered by Hurricane Katrina. Government agencies said the massive storm taught them that big-box retailers need to be an integral part of hurricane preparation and relief efforts. Nicholas Kamm/AFP/Getty Images hide caption

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This image shows the above-normal water temperature in the Pacific Ocean during the December 1997 El Nino. Green-blue colors represent normal temperatures; dark red indicates hotter water. NOAA hide caption

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The P-3B NASA research aircraft, seen on the tarmac at Baltimore Washington International Airport on June 28, will gather data as it flies spirals over six ground stations in Maryland. Paul E. Alers/NASA hide caption

itoggle caption Paul E. Alers/NASA

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

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Dr. Donald Brown, left, gives 14-year-old Kelly Kent a dose of Gardasil, a vaccine for the human papillomavirus in 2006. The group that advises the U.S. government on vaccination recommendations is now starting to take costs for vaccines like Gardasil into consideration as vaccine prices rise. Charles Rex Arbogast/AP hide caption

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Eve offers Adam the fruit in the garden of Eden in Theatrum Biblicum, a drawing by Johann Fischen (circa 1650). Sex lets a species evolve faster to rapidly adapt to a new environment, researchers say. Hulton Archive/Getty Images hide caption

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An image believed to be that of a hole-punch cloud. Scientists say airplanes create these patterns when they fly through certain types of clouds. The water in the clouds can turn to rain or snow and fall to the ground. H. Raab/Vesta/Wikimedia Commons hide caption

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This image from April 27 shows a series of tornadoes forming over Alabama and Mississippi. Captured from a satellite orbiting located at a fixed location above Earth, images like these help track trends in weather patterns. Another set of polar-orbiting satellites are useful for long-term forecast predictions. NASA Earth Observatory hide caption

itoggle caption NASA Earth Observatory

This tornado touched down near Chickasha, Okla., on May 24. In addition to being tracked by the existing NEXRAD radar system, this storm was also being monitored by an experimental radar system that provided more precise information about the tornado's behavior and path. Heather Mosher/Courtesy National Weather Service/NOAA hide caption

itoggle caption Heather Mosher/Courtesy National Weather Service/NOAA