More than 30 years ago, the American Helicopter Society International challenged engineers to create a human-powered helicopter that could reach an altitude of at least three meters and hover for at least 60 seconds. Sikorsky Aircraft promised $20,000 to the winner. Now, they've upped the award to $250,000.

In pursuit of the elusive prize, a helicopter designed by a team of students from the University of Maryland has become the third human-powered helicopter to successfully leave the ground, and the first to be piloted by a woman.

The average washing machine uses between 40 and 45 gallons of water per load of clothes. In addition, a large amount of energy is needed to heat the water.  

However, researchers at the British company Xeros Ltd have developed a new, greener, washing-machine technology that cleans clothes using a mere cup of water and just a drop of detergent.

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