Stories of Modern Science...by UPI

THREATENING IMAGES HOLD ATTENTION

Many people are finding it hard to concentrate after television viewing of reports of the aftermath of hijackings of four U.S. airlines that killed thousands of Americans on Sept. 11. Researchers from the University of Essex in England, who conducted experiments to show the link between anxiety and attention bias of threatening stimuli, say humans have an adaptive element which keeps people focused on threatening images. They say the reason people can't shift their attention back so easily is that threatening images hold people's attention much longer than non-threatening ones, especially for those who were feeling anxious before the attacks. "A delay in disengagement to threatening stimuli allows animals and humans to conduct a more detailed cognitive processing of potential threats in their environment," says Elaine Fox, Ph.D. "This attention bias might have evolved to protect us from attack by other animals centuries ago." The study on anxiety and visual attention will appear in the December issue of the Journal of Experimental Psychology.

AIR BUBBLES CAN CAUSE WATERBORNE DISEASE

Paolo Scardina, a Ph.D. candidate at Virginia Tech working with Marc Edwards has made discoveries that may help prevent outbreaks of waterborne diseases. "When you open a can of soda, bubbles form and rise to the surface," explains Edwards. "The same thing can happen in water from lakes and rivers when air bubbles are released in a 'burp' during the treatment process, pathogens and other particles can escape removal." The last treatment barrier in most drinking water treatment plants is filtration, Edwards says, and a burp of bubbles can punch holes in filters tiny holes, but large enough to let particles and pathogens escape into the water that goes out to customers. Researching the literature, Scardina noticed that serious problems often occurred at plants that experienced air bubble eruptions. In addition, to studying why bubbles form and how they punch holes in treatment plant filters, Scardina also discovered air bubbles can interfere with the first drinking water treatment process "settling" where solid particles from incoming surface water drop to the bottom of treatment tanks. "If bubbles are present at this stage, pathogens and other particles can attach to them and float on through the treatment plant," says Scardina.

ANTI-FOULING AGENT BANNED ON SHIPS

After years of pressure from environmentalists, the world's ship-owners have been put on notice to stop painting the bottoms of their vessels with the anti-fouling agent tributyl tin (TBT), New Scientist reports. The ban came at a meeting of the United Nation's London-based International Maritime Organization. The agreement gives shipping companies until January 2003 to stop using the paint, and a further five years to cover up existing TBT paint on ships' hulls. However, there is continuing concern about the effectiveness of alternatives in removing barnacles and other sea creatures, which makes ships slower and heavier. The problem with TBT-based anti-fouling paint is that it slowly leaches into the water. There it has been shown to cause sex-changes in whelks and deformation in oysters since the 1970s. While environmentalists applauded the move, the Organotin Environmental Program Association, an industry lobby, warned that banning TBT paints could cause an increase in the number of alien species that spread round the world on the hulls of ships, causing ecological havoc. It also estimates that removing TBT-based paints from the world's ships could cost up to $1 billion.

CITIES ACT LIKE ANT COLONIES

According to author Steven Johnson no one designs truly great cities they just spring up as if by magic, not because someone is directing the action, but because collectively populations figure things out, just as ants, The London Times reports. "A city seems to pulsate with its own rhythm, as if it is a living, breathing organism," Johnson says. "The superorganism of the city mirrors the superorganism of the ant colony, in which a collection of individually stupid insects somehow becomes a mesmerizing, organized whole." Both are examples of emergence, a phenomenon where the whole is much greater than the sum of its parts. In his book, "Emergence," Johnson, an American author, hopes that just as chaos was a scientific buzzword of the past century, emergence will enter the lexicon of this century. Ant colonies are remarkably similar to cities. No one choreographs the action, not even the queen ant, but ant behavior is controlled by swarm logic -- put 10,000 dumb ants together, and they become smart. They will calculate the shortest routes to food supplies sniffing out pheromone signals from other ants and Johnson says people do the same thing in cities using low-level interactions of people on the street.

( For more information, on IMAGES, call 202 336-5707; on BUBBLES, call 540 231-7236.)