Engineers who invented a bra that converts into a gas mask and Irish police officers who mistakenly wrote tickets to "Driver's Licence" have all won spoof IgNobel prizes.

The IgNobels - a play on the name of the Nobel prizes awarded every October from Stockholm and Oslo - are given out by the Harvard-based humour magazine Annals of Improbable Research.

Prizes also went to Zimbabwe for issuing banknotes that ranged in value from one Zimbabwean cent to 100 trillion Zimbabwean dollars, to Mexican scientists who made diamonds out of tequila, and to the leaders of four Icelandic banks that suffered spectacular collapses.

The Public Health prize went to Elena Bodnar of Hinsdale, Illinois and colleagues who designed and patented a bra that can be quickly converted into a pair of gas masks, one for the brassiere wearer and one to be given to some needy bystander.

Ireland's police won the literature prize for writing more than 50 traffic tickets to a frequent visitor and speeder named Prawo Jazdy. In Polish, this means "driver's licence".

Pathologist Stephan Bolliger and colleagues at the University of Bern in Switzerland won for a study they did to determine whether an empty beer bottle does more or less damage to the human skull than a full one in a bar fight.

"Both suffice in breaking the human skull. However, the empty ones are more sturdy," Mr Bolliger said by email.

This is because the pressure of the beer, aided by carbonation, makes a full beer bottle explode quickly.

The economics prize went to managers at Kaupthing Bank, Landsbanki, Glitnir Bank and Central Bank of Iceland "for demonstrating that tiny banks can be rapidly transformed into huge banks, and vice versa".

Donald Unger of California was honoured for a lifelong experiment in which he cracked the knuckles of his left hand but never his right for more than 60 years to prove that cracking your knuckles does not cause arthritis.

Other winners included farmers who showed that naming your cows makes them give more milk, researchers who used panda droppings to break down household trash, and a scientist who calculated why pregnant women do not fall over.

- Reuters