Military vehicles surround a wreckage of a trolleybus, in Volgograd, Russia, Monday, December 30, 2013. A bomb blast tore through a trolleybus in the city of Volgograd on Monday morning, killing at least 10 people a day after a suicide bombing that killed at least 17 at the city's main railway station. Volgograd is about 650 kilometers (400 miles) northeast of Sochi, where the Olympics are to be held. (Photo by Denis Tyrin/AP Photo)

A participant takes part in the Bristol Park and Slide project, an interactive temporary installation by artist Luke Jerram set up in Park Street in the centre of Bristol, southwest England on May 4, 2014. Over 95,000 people applied for just 360 tickets to slide on inflatable lilos down a lubricated water slide in a town centre street. (Photo by Leon Neal/AFP Photo)

Austrian artist Erwin Wurm (R) stands next to an extra of his participation sculpture “Hose lueften, Haende hoch” (air out pants, hands high) at the garden of the Staedel Museum, in Frankfurt am Main, Germany, 06 May 2014. The series “Wurm: One Minute Sculptures” include painted or written instructions tell the person what they have to do and where for 60 seconds. The exhibition runs from 07 May to 13 July. (Photo by Arne Dedert/EPA)

In this May 4, 2014 photo, a miner holds an amalgam of mercury and gold he mined after working a 28-hour shift at an illegal gold mining process, in La Pampa, in Peru's Madre de Dios region. Thousands of artisanal gold miners sweat through the long shifts and endure, for a few grams of gold, the perils of collapsing earth, limb-crushing machinery and the toxic mercury used to bind gold flecks. (Photo by Rodrigo Abd/AP Photo)

Xie Guobiao (C), 11, tied to a pillar with a rope, cries as his grandmother (L) and younger sister look on at his home in Daohui village of Lishui, Zhejiang province May 7, 2014. Xie was diagnosed as mentally handicapped when he was young, but the family was not able to provide him with sufficient medical treatment because of poverty. At the age of six, Xie started to sneak out of his home when others were not looking, climbing on top of houses and smashing windows. Xie's family had to pay over 10,000 yuan ($1,606) in compensation to others for the damage he caused. Since then, the family has had to tie Xie up with a rope both at home and in public, they said. (Photo by William Hong/Reuters)

Rescue operations are undergoing to recover the sunken ferry MV Miraj 4 in the Megna River near Munshiganj, Bangladesh, 16 May 2014. The death toll in the Bangladesh ferry disaster rose to 26 on 16 May, including children and women and many more feared dead as the ferry, carrying more than 200 passengers on board, sunk during a storm on 15 may 2014, police authorities said. (Photo by Abir Abdullah/EPA)

A US soccer fan cheers during the FIFA World Cup 2014 group A preliminary round match between Brazil and Croatia at the FIFA Fan Fest in Copacabana, Rio de Janeiro, Brazil, 12 June 2014. Brazil won 3-1. The FIFA World Cup 2014 will take place in Brazil from 12 June to 13 July 2014. (Photo by Abedin Taherkenareh/EPA)

A flight attendant wearing a Brazil soccer team jersey demonstrates the emergency mask on an airplane travelling from Kunming to Hangzhou June 23, 2014. A Chinese airline company renovated the cabin of one of its flights then dressed the flight attendants with soccer jerseys as a way to celebrate the 2014 Brazil World Cup and hoping to attract more customers, local media reported. (Photo by Wong Campion/Reuters)