Corrections officer Sgt. Charles Galaviz secures an inmate for transfer with handcuffs and shackles Jan. 24 at the Lexington Assessment and Reception Center, in Lexington, Okla. Overtime is mandatory for correctional officers in the state's prisons, which have a manpower shortage of about 33 percent and the highest inmate homicide rate in the country. Sue Ogrocki/AP hide caption

itoggle caption Sue Ogrocki/AP

Workers walk inside the LyondellBasell oil refinery in Houston in 2013. Lower oil prices are stoking fears of an economic decline in the region. Donna Carson/Reuters/Corbis hide caption

itoggle caption Donna Carson/Reuters/Corbis

More than 600 Porto city buses and taxis have been fitted with routers to provide free Wi-Fi service. It's being touted as the biggest Wi-Fi-in-motion network in the world. Sérgio Rodrigues/Veniam hide caption

itoggle caption Sérgio Rodrigues/Veniam

The sun sets as a visitor uses his mobile phone Monday during the opening day of the 2015 Mobile World Congress in Barcelona. Wall Street Journal reporter Ryan Knutson — interviewed from the conference Monday via Skype by NPR's Robert Siegel — says that for some smartphone users, Wi-Fi may be able to replace most of the functionality of a cellphone carrier. Josep Lago/AFP/Getty Images hide caption

itoggle caption Josep Lago/AFP/Getty Images

Workers stand next to a gas pipeline not far from the central Ukrainian city of Poltava in June 2014. Ukraine imports much of its gas from Russia, which is once again threatening to cut off supplies in a dispute over payments. Sergei Supinsky/AFP/Getty Images hide caption

itoggle caption Sergei Supinsky/AFP/Getty Images

Lincoln has invested hundreds of millions of dollars in revitalizing its downtown, a historic area called Haymarket, to create a more culturally vibrant urban center that is helping the city keep and attract young adults. David Schaper/NPR hide caption

itoggle caption David Schaper/NPR