Soldiers with the British Machine Gun Corps wear gas masks in 1916 during World War I's first Battle of the Somme. General Photographic Agency/Getty Images hide caption

Harvey Mudd President Maria Klawe often uses her longboard to get around campus and chat with students like senior Xanda Schofield. Wendy Kaufman/NPR hide caption

The Treasury Department announced this week it will pay down some of its debt for the first time in six years. Jacquelyn Martin/AP hide caption

A still from A Boy and His Atom. IBM hide caption

Violinist Rachel Barton Pine says she had her infant daughter in mind when she decided to record an album of lullabies. Andrew Eccles/Courtesy of the artist hide caption

A Customs and Border Protection officer explains to arriving international passengers at Los Angeles International Airport how to provide their fingerprints. While visitors are fingerprinted and photographed upon arrival in the U.S., they are currently not tracked upon departure. Reed Saxon/AP hide caption

In this image taken from video, South African President Jacob Zuma sits with ailing anti-apartheid icon Nelson Mandela on Monday. Mandela was hospitalized in late March with a lung infection, and in images from the visit, appeared largely unresponsive. SABC/AP hide caption

Afghan President Hamid Karzai acknowledged a report this week that the CIA has regularly been sending him money. Afghans seem to have mixed feelings. The president is shown here speaking at an event in Kabul on March 10. S. SABAWOON/EPA/Landov hide caption

Bates experienced migraines as a child. She made this painting to depict how they felt to her. Courtesy of Emily Bates hide caption

The four cuts at the top of this skull "are clear chops to the forehead," says Smithsonian forensic anthropologist Douglas Owsley. Based on forensic evidence, researchers think the blows were made after the person died. Donald E. Hurlbert/Smithsonian hide caption