High school athlete Graham Hill, number 50, suffered a concussion in 2013 while playing football at Trinity Christian Academy in Addison, Texas. Courtesy of Jeffrey McWhorter hide caption

itoggle caption Courtesy of Jeffrey McWhorter

Ultrasound is often used for prenatal screening. It's just one of several prenatal screenings available to pregnant women. iStockphoto hide caption

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A polar bear walks in the Arctic National Wildlife Refuge.The Obama administration is proposing new protections in the region that would ban mining and drilling. Subhankar Banerjee/AP hide caption

itoggle caption Subhankar Banerjee/AP

As the U.S. workforce continues to become more diverse, researchers are now more than ever examining diversity and bias in the work place. iStockphoto hide caption

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When he was 59 years old, Greg O'Brien was diagnosed with early-onset Alzheimer's disease. Five years later, he is speaking publicly about his experience, even as his symptoms worsen. Courtesy of Greg O'Brien hide caption

itoggle caption Courtesy of Greg O'Brien

Allagash Brewing microbiologist and head of quality control Zach Bodah's favorite microscope picture of Brettanomyces (taken in house). The culture comes from Confluence Ale and is a blend of the Allagash house yeast and Brett yeast. Courtesy of Zach Bodah/Allagash hide caption

itoggle caption Courtesy of Zach Bodah/Allagash

An employee of the drug company Apotex, examines some Ciprofloxacin at the plant in Canada. Cipro is commonly given to travelers for diarrhea. More than 20 million Cipro doses are prescribed each year in the U.S. Getty Images hide caption

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Close-ups of a curious surface texture on Comet 67P nicknamed "goosebumps," all of them at a scale of around 3 meters and spanning areas more than 100 meters. ESA/Rosetta/MPS hide caption

itoggle caption ESA/Rosetta/MPS