The UASK app helps sexually assaulted college students in D.C. access a range of services, from rides to the hospital to phone numbers for counselors. The information is personalized to their school. Another version of the app, ASK, provides the same resources to non-students. Emily Jan/NPR hide caption

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In Philadelphia, some drug users are selling clean needles from needle exchange programs on the street. Researchers say the black market isn't necessarily a bad thing. ImageZoo/Corbis hide caption

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Norma Melendez, a community health worker with City Health Works, walks along Second Avenue on her way to meet a client. City Health Works is an organization that is attempting to bring an African model of health care delivery to the United States. Bryan Thomas for NPR hide caption

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A man carries old plastic containers in March 2012 through the Kibera slum in Nairobi, Kenya. Kenyans living in poverty often collect plastics that they can turn into cash by taking it to companies that recycle it. Carl de Souza/AFP/Getty Images hide caption

itoggle caption Carl de Souza/AFP/Getty Images