Science notes

Giving new meaning to phrase 'power suit'

It may not be long before your portable CD player, PDA, or digital watch is powered by its case instead of a battery.

Scientists at the University of California at Berkeley say they have developed a way to make low-cost solar cells that could be painted onto surfaces or easily layered within them. The discovery could lead to many more uses for solar cells.

"The beauty of this is that you could put solar cells directly on plastic, which has unlimited flexibility," says team leader A. Paul Alivisatos, a UC Berkeley chemist. "This opens up all sorts of new applications, like putting solar cells on clothing."

They convert only about 1.7 percent of the light striking them into electricity, researchers concede. But they say that unlike other methods of making plastic solar cells, this approach holds the promise of achieving at least 10 percent efficiency – comparable with that of commercial solar cells.

The team began by producing tiny rods of cadmium selenide, which convert sunlight to electricity. The rods measured 7 nanometers (7 billionths of a meter) across and were 60 nanometers long. The researchers suspended these rods in a plastic semiconductor sandwiched between two electrodes. The solar-cell sandwich is about 200 nanometers thick – one-thousandth of the thickness of a human hair – and produces 0.7 volts, about half the voltage of a flashlight battery.

The project is described in the current issue of the journal Science.

To most people, earthquakes are sudden events that can crumble buildings in seconds. Geophysicists have uncovered another kind of quake, however, that continues for weeks, and no one feels a thing. First reported in 1995 by Japanese researchers, these slow quakes now have been detected in the Pacific Northwest. Even more intriguing, researchers say, is that they occur with almost clock-like regularity.

This week a team headed by Meghan Miller at Central Washington University reports that eight of these slow quakes have occurred in the Pacific Northwest since 1992, including one that began on Feb. 7. Over that time, they found that a new quake is triggered every 14 months, give or take a week. This regularity, she says, suggest that slow quakes help ease strain in areas where one crustal plate slides under another.

Researchers note that it's unclear what kind of effect these slow quakes have on the overall quake hazard in the region. But, they say, they're working on it.

Planetary scientists have the green light from NASA to begin building a probe to orbit Mercury. Known as Messenger, the craft will orbit the first rock from the sun for a year, gathering data on its crust, core, atmosphere, and magnetic field.

Engineers at the Applied Physics Lab at Johns Hopkins University in Baltimore note that one of the biggest challenges will be keeping the spacecraft's instruments cool. The sun is 11 times brighter at Mercury than it is at Earth. The $286 million Messenger craft is scheduled for launch in March 2004 and will take up its orbit in 2009.