viruses
Tim Radford
NEW SCIENCE
Bright idea
A new, man-made material could make lights that will last for 100 000 hours and cut energy costs by 80%. The material is already being tested in a set of traffic lights in Whitehall.
It produces the same light output as an electric bulb but uses only one-fifth of the power. And it could soon link small mobile phones with satellite networks.
Colin Humphreys, professor of materials science at Cambridge, says that gallium nitride is a diode that can be made to emit light in any colour, but without wasting any energy in heat. Light- emitting diodes have been used for years to show whether electric kettles are on, or to light up the keys on mobile phones.
But a new generation now control traffic lights at the corners of Marsham and Great Peter streets in London.
”Normal traffic light bulbs last six months and they are already long-life tungsten halogen bulbs,” he says.
”So every six months they change the traffic lights all over the country. The gallium nitride ones will last 10 years, so it’s a huge saving. I am told – although it’s hard to confirm this – that the energy consumption of traffic lights in this country is two medium-sized power stations. You are going to save 80% of the output of two power stations.”
The diodes – made only by two firms in the United States and one in Japan – are expensive. But they have other advantages.
”In principle all these fluorescent tubes, so long and ugly, you could replace with these tiny light-emitting diodes in any shapes you want. The actual light-emitting diode chip is a fraction of a millimetre across.
”You could replace all the electric light bulbs in the world. The other thing is, electric light bulbs last 1 000 hours. These light-emitting diodes last 100 000 hours continuously.”
His research group is about to grow its own gallium nitride to make its own diodes, and lasers powerful enough to ”write” a compact disc.
The research group also plans dramatic ways of reducing generation costs in power stations. Turbine blades in power plants are made of steel and cannot be allowed to get hotter than 550C. Jet aircraft turbine blades are made of nickel and operate at up to 750C.
If power plant turbines could be used at the same temperature, electricity generation would be 50% more efficient.
But aircraft turbine blades have to be replaced more frequently. The researchers are using computers which mimic human ways of thinking to find ways of solving the problem.
Food for thought
Dieting might slim the waistline but it could lower the brainpower as well. Experiments showed that when people responded to stimuli in tests, slimmers did worse than the well-fed.
But Michael Green of Unilever Research says this does not necessarily mean that trying to be thin makes you thick.
”This is actually to do with the psychological stresses of dieting,” he says.
”What we have found is that these effects are very closely related to dieters’ preoccupations with food, their constant thoughts of hunger, their decreased self-esteem and their increased worry about body shape,” he said.
People, like computers, have limited mental processing space, he says. If some of that space is taken up by preoccupations with food, hunger and body shape, there simply will not be enough to perform other tasks as efficiently.
”These effects are quite comparable to what you would get with anxiety and depression,” he adds.
But David Benton, a psychologist at the University of Wales, Swansea, reported a link between food and mental performance.
In a study of 832 young adult females, they were able to recall a list of words better 30 minutes after breakfast than three hours after breakfast. One theory was that breakfast supplied necessary blood glucose to the brain, and this in turn improved memory.
Finally, a use for viruses
Scientists have harnessed nature’s way of tackling antibiotic-resistant bacteria. An injection of a virus that attacks bacteria only has saved the life of a patient after all other drugs proved useless.
The technique – the use of bacteriophages or bacteria-eaters – was pioneered in the former Soviet Union at around the time of the discovery of much more swiftly effective antibiotics. Although penicillin and other such drugs changed medicine, one team in Tbilisi, Georgia, kept research into phages going to the present day.
Martin Westwell of Oxford says that phage therapy would be nature’s way of keeping ahead of the chemical arms race between humans and disease-bearing bacteria, because a virus would evolve along with its host.
”It doesn’t attack human cells at all,” he says, ”it just attacks the bacterial cell.”
A company in Seattle had taken up the technique and has just, for the first time, cured a Canadian of bacterial infection by use of a virus.
”The woman was going to die: she had an antibiotic-resistant infection and she was going to die so they used a phage therapy, a virus therapy, and it saved her life. Because the virus is a living thing, every time the bacteria take a step forward in evolution, a step forward in the arms race, the virus can take its own evolutionary step forward,” he says.
An increasing number of bacteria have become resistant to antibiotics. Other researchers are looking for other vulnerabilities in microbes that can be attacked by new drugs, and yet others are hoping to find ways to trigger swifter responses in the immune system. Phage therapy would be slow, and would depend on very accurate diagnosis of the bacterial strain.
Cosmic collisions
Death by comet or asteroid will be swift and spectacular. A stony-iron asteroid could hit the top of the atmosphere at 16km a second. As soon as it hit any air at all, it would start to slow down, and heat up dramatically.
”There will be a massive fireball, very bright light, there will be thermal radiation from the fireball, sonic booms and a shockwave as it passes through the atmosphere,” says Matthew Genge of the Natural History Museum.
”It will hit the ground. If it lands on a continent it forms a crater. Most of the damage is not from the material thrown out from the crater, which is frequently melted or vaporised into a rock gas at thousands of degrees. Most of the damage is from the shock wave generated by the impact flash.”
The shockwave generated by the monster that formed Meteor Crater in Arizona would have been capable of knocking over a brick wall 2 000km away.
A comet – just an aggregate of ice and dust – would be a different story. A comet is so weakly held together that the force required to lift a feather could splinter one.
US military spy satellites identified four or five comet ”airbursts” every year: they were caused by the arrival of fragments of comets and too high to do any harm.
However, an explosion over a crowded city such as Johannesburg would be signalled first by a brilliant flash and scorching heat.
”You would be knocked off your feet by the shockwave moving away from the explosion. Then you would be dragged back again towards the explosion as all the air rushes back in. You’re dead by then.”
Nobody is known to have died in any such disaster.
Risk experts nevertheless calculate that although collisions of the lethal kind occur only once every 10 000 years, a blast like that over a populated landscape would kill 1,5-million people.