DATA POINTS: SHARK BITES MAN ILLUSTRATION BY MATT COLLINS Gruesome attacks provided for sensational news last summer, but 2001 actually saw a decline in the number of shark attacks worldwide compared with the number reported the previous year. Overall, the rate of attacks has risen during the past few decades because of increased human activity in the water, not because shark populations are growing. Number of unprovoked shark attacks in: 2000: 85 2001: 76 Number of fatalities in: 2000: 12 2001: 5 Fatality rate in the 1990s: 12.7% Favorite targets (percent of those attacked): Surfers: 49% Swimmers/waders: 29% Divers/snorkelers: 15% Kayakers: 6% SOURCE: International Shark Attack File, Florida Museum of Natural History of the University of Florida WWW.SCIAM.COM/NEWS BRIEF BITS Two objects thought to be neutron stars might in fact be strange quark matter stars--denser, more exotic stellar objects consisting of strange quarks in addition to the usual up and down quarks. /041202/1.html The first drafts of two rice genomes have been completed, feats that should lead to hardier and more nutritious strains of one of the world's most important foods. /040502/1.html In a clinical trial of 340 patients, St. John's wort proved to be ineffective in alleviating moderately severe depression, working no better than a placebo. /041002/1.html Despite a 98.7 percent genetic similarity, humans and chimpanzees are vastly different because of the rate of genetic activity in the brain--gene expression evolved 5.5 times faster in humans than it did in chimps. /041502/1.html

PHOTONICS Nice Threads Image: FINK RESEARCH GROUP M.I.T. AND AAAS PHOTONIC-CRYSTAL THREADS are 0.2 millimeter wide. Your clothing may someday reflect more than just your personality. Materials scientists at the Massachusetts Institute of Technology have made polymer threads coated with mirrors. They deposited a glassy substance, arsenic triselenide, onto a polymer and then rolled it up, creating a layered structure called a photonic crystal. Drawing the roll out produces long threads a few hundred microns thick that can be as reflective as gold. The fibers are more than high-tech sequins, though--the reflective properties can be adjusted by varying the diameter of the thread. Properly drawn and woven into normal fabric, the mirrored fibers could lead to wearable radiation barriers, optical bar-code tags for clothing and flexible filters for telecommunications. The April 19 Science contains the study. --Philip Yam BIOLOGY Battling Resistant Bacteria Two recent results could help fight antibiotic-resistant bacteria. Netherlands researchers report a mathematical model for determining whether hospital patients' infections stem from bacteria they carried in with them or acquired from another patient--important knowledge for evaluating infection-control strategies. The existing method demands the expensive and time-consuming step of reading the bacterium's genome. In contrast, the model analyzes several months' worth of infection-prevalence data to give spontaneous infection and transmission rates. When fed numbers from two past studies, the new technique returned rates similar to those obtained with the genetic approach. University of Rochester biologists have also developed a model that tracks antibiotic-resistant bacteria--by mimicking evolution. They generated many mutations in a 40-year-old version of a key bacterial gene and selected for variants that resisted antibiotics. The mutants they isolated were many of the same ones that emerged in people, suggesting that the model could predict how bacteria will respond to new drugs. The results already hint that resistance to the antibiotic cefepime may be forthcoming. The transmission model appears in the April 16 Proceedings of the National Academy of Sciences. The selection research is published in the March Genetics. --JR Minkel CELL BIOLOGY Gain without Pain Image: QUEST PHOTO RESEARCHERS, INC. MUSCLE FIBRILS can be energized by more mitochondria (brown spots along vertical structures). The microscopic powerhouses known as mitochondria energize all human activity--the more a cell possesses, the more stamina it has. Working out can pump up mitochondria numbers, but a study indicates that a protein apparently triggers the same effect, giving new meaning to the words "exercise supplement." Researchers at the University of Texas Southwestern Medical Center in Dallas looked at easily fatigued muscles of sedentary mice and found that an enzyme known as CaMK can boost mitochondria levels in those muscles. A mitochondria-promoting drug could help bedridden patients or people with heart and lung problems enjoy the benefits of exercise. The scientists, who described their findings in the April 12 Science, also speculate that human performance could be enhanced by altering genetic activity to make more of the protein. --Charles Choi NEAR-EARTH OBJECTS Hit or Miss Image: JPL/NASA IT'S COMING: Radar image of asteroid 1950 DA. The bad news is that the kilometer-wide asteroid 1950 DA has up to a one-in-300 chance of striking the earth--the highest risk for any known asteroid, according to NASA physicists. The 100,000-megaton explosion resulting from a strike would cause global damage. The good news is that the impact wouldn't happen until March 16, 2880. The asteroid will more likely miss us by within a few days on either side of a 20-minute collision window. Many of the factors that affect the odds are uncertain, especially the rock's axis of spin. The orientation determines the direction of the push it gets after radiating absorbed sunlight back into space. We could exploit this source of drift, called the Yarkovsky effect, to nudge space rocks out of our way, suggests Joseph N. Spitale of the University of Arizona. Covering an asteroid in chalk powder or charcoal, painting it white or even wrapping it in Mylar could all subtly change its speed. Enacted decades or centuries in advance, such a scheme could divert rocks like 1950 DA. The April 5 Science has more details. --JR Minkel MEDICAL TECH Here's Magnet in Your Eye Injecting a magnetic fluid into the eye could repair severely detached retinas. This light-sensitive layer of cells may tear away from the back of the eyeball because of disease or injury, potentially causing blindness. Doctors generally inject gas or silicone fluid to shove the retina back into place, but these methods don't always reach the bottom parts of the eye. Looking for something they could better control, chemist Judy S. Riffle of the Virginia Polytechnic Institute and her colleagues have combined tiny particles of cobalt or magnetite with a silicone-based fluid, they stated at an April meeting of the American Chemical Society. A magnetic band placed around the eye should hold the fluid against the retina at desired locations. Riffle says the group has also conducted the procedure in glass eyeballs and is set to begin in vitro toxicity testing. Animal studies could begin within a year. This approach might also work to deliver chemotherapy drugs or DNA for gene therapy. --JR Minkel BRAIN AND BEHAVIOR Double or Nothing Image: TIM FLACH STONE PLACE YOUR BETS: Your brain looks for patterns even when there aren't any. Gamblers often believe that after a string of losses they're due for a win. Scientists now think they have pinpointed areas in the brain that are partly behind this kind of false thinking. Using functional magnetic resonance imaging, investigators at Duke University found a brain region that automatically looks for patterns, real or imagined. When volunteers were shown random sequences of circles and squares, blood flow increased to the prefrontal cortex, which is located just behind the forehead and is involved in memorization during moment-to-moment activity. This brain layer reacted whenever there were violations to apparent short-term patterns in the sequences--even though subjects knew that they were random. Meanwhile researchers at the University of Michigan discovered that after losing a simple wager, volunteers were more likely to place larger, riskier bets if prompted to make another wager within a few seconds. Caps studded with electrodes revealed that when subjects learned they had won or lost wagers, electrical activity was highest in the medial frontal cortex, situated behind the prefrontal cortex. The Duke study appears online in the April 8 Nature Neuroscience; the Michigan work is in the March 22 Science. --Charles Choi