Scientists may have come up with a new explanation for how a woman's biological clock works. (p. 163)

A new analysis of brains from a variety of mammal species indicates that frontal-cortex expansion has occurred in all primates, not just in people, as scientists have traditionally assumed. (p. 163)

Astronomers unveiled the deepest visible-light portrait of the universe ever taken, a million-second-long exposure by the Hubble Space Telescope that includes near-infrared images of what appear to be the most-distant galaxies known. (p. 164)

By shutting down a signaling molecule on cancerous cells, scientists have found a way to slow multiple myeloma and fibrosarcoma, tests in animals show. (p. 164)

Researchers have created a fuel cell that breaks down organic matter in wastewater and, in the process, generates small amounts of electricity. (p. 165)

Nutrition research supports the ancient notion that a diet rich in meat contributes to the development of gout, a form of arthritis common in men. (p. 165)

Scientists have genetically engineered a butterfly for the first time, putting a jellyfish protein into a tropical African species so that its eyes fluoresce green. (p. 166)

The controversial strategy of screening embryos to produce donors for siblings raises hopes and presents new ethical dilemmas. (p. 168)

President Bush recently unveiled an ambitious plan for a manned mission to Mars, using the moon as a testing area and stepping-stone, but for many planetary scientists the moon is a desirable destination in and of itself. (p. 170)

Needing tiny radioactive sources to calibrate medical scanners with ever-sharper vision, an Australian team dipped tiny balls the size of candy sprinkles into a radioactive liquid. (p. 173)

Irradiating bundles of carbon nanotubes can lead to tougher fibers. (p. 173)

Newly discovered strains of bacteria have developed a metabolic shortcut for eating away iron with great efficiency. (p. 173)

Oceanographic data gathered across the North Pacific in 1985 and again in 1999 indicate that the deepest waters there have been heating up. (p. 173)

Contrary to much anthropological thought, the genus Paranthropus showed as much dietary and behavioral flexibility as ancient Homo species did between 3 million and 1 million years ago. (p. 174)

The magnetic characteristics of rocks and debris excavated from Pompeii reveal the changing temperatures of the volcanic ash cloud that smothered the Italian city in A.D. 79. (p. 174)

Two anti-inflammatory drugs for rheumatoid arthritis—methotrexate and etanercept—work better together than either does individually. (p. 174)

Recurring exposure to soot particles from diesel exhaust fumes reduces the immune system's capacity to fend off infection, tests on rodents indicate. (p. 174)

(p. 175)