American Express says it is uniquely positioned to offer the service thanks to its "closed-loop" business model in which it acts as card issuer, merchant acquirer and payment processing operator.

BBC: Foursquare and Amex join forces in UK to offer discounts

The gravity-based system responded as it was designed to, circulating water and steam in a continuous loop to keep the scale-model reactor at a safe temperature automatically.

CNN: Today/Tomorrow - Helping nuclear plants keep their cool

There are many areas of overlap between biomimicry and "cradle-to-cradle" particularly in the way that ecosystems present a great model of closed loop systems in which any waste from one organism becomes the nutrient for something else.

CNN: STORY HIGHLIGHTS