Supercapacitors have a big internal surface-area that allows a large amount of energy to be delivered rapidly and are used in some electric cars to provide a short burst of power for rapid acceleration and in hybrids to recover energy during braking.

ECONOMIST: Carbon-composite batteries

In the short run, the balance of power between the two camps will be tested at a party congress in November, which will be like a mini-parliament.

ECONOMIST: The French Socialist Party

Bear in mind that the transformation already achieved in Russia since 1991, when Boris Yeltsin came to power, is little short of miraculous, however much remains to be done.

ECONOMIST: Is Russia going wrong?

He apologised for the scale of the problems caused by the power cuts and said they would be resolved "in a relatively short period".

BBC: 'No doubts' over World Cup in SA