US
HFCs were introduced in the 1990s to replace chemicals that had been found to erode the ozone layer
US package-delivery giant UPS and global vaccine alliance Gavi have invested $1.1 million in the Zipline project
Burundi has been mired in a year-long crisis that has killed more than 450 people and forced 270,000 to flee
Using an old mobile phone, health worker Floride Uwinkesha logs the latest local pregnancy to boost maternal health
Pilot project is slated to begin next year, with three "drone-port" buildings due for completion by 2020