Stretching more than half a billion kilometers, the ion tail that Comet Hyakutake flaunted when it passed near the sun in 1996 is the longest ever recorded and suggests that otherwise invisible comets could be detected by searching for their tails. (p. 228)

Two novel tests for prostate cancer may help physicians catch this disease earlier and with far fewer false alarms. (p. 228)

As the federal government proposes phasing out the gasoline additive MTBE, scientists explore ways to remove this potential carcinogen from drinking-water supplies that it has tainted throughout the nation. (p. 229)

The blue whale, bottlenose dolphin, Weddell seal, and elephant seal cut diving energy costs 10 to 50 percent by simply gliding downward. (p. 230)

In social exchanges, monkeys and people often appear to act according to the principle that "one good turn deserves another." (p. 231)

By altering the chemical structures of dyelike molecules called chromophores, researchers have created tiny, low-voltage devices for converting electronic signals into light waves. (p. 231)

Social and psychological forces sway the course of manic depression. (p. 232)

For preventing heart disease, diets that control insulin are all the buzz. (p. 236)

People began to manage herds of wild goats at least 10,000 years ago in western Iran. (p. 235)

Some early human ancestors appear to have walked on all fours using their knuckles, much as chimpanzees do. (p. 235)

Pristine fragments of a meteorite that fell January 18 in the frozen Yukon and that remained frozen until they were delivered to a NASA laboratory may reveal much about the earliest days of the solar system. (p. 235)

Supermassive black holes and the galaxies they inhabit appear to grow up together. (p. 235)

Researchers working with mice are trying to fashion an HIV vaccine by using a weakened rabies virus to bring an HIV glycoprotein to the attention of the immune system. (p. 239)

A microbial odd couple—the brucellosis pathogen and a nitrogen-fixer for plants—need the same gene to settle into their hosts long-term. (p. 239)

Researchers have engineered a strain of stressed-out mice by knocking out one gene. (p. 239)

Egypt's public health service inadvertently spread hepatitis C while treating patients for schistosomiasis, a common parasitic disease, with injections of antischistomal medications. (p. 239)

People with asthma have more acidic lungs than do people who don't have the disease, a finding that may prompt the development of novel asthma treatments aimed at restoring the normal pH value of the lungs. (p. 239)

Using gene chips to study the activity of thousands of genes simultaneously, researchers showed that a common cancer of white blood cells—diffuse large B-cell lymphoma—is in fact two distinct diseases. (p. 239)