Новости науки и техники в "Scientific American"

FOUR-WINGED DINOSAURS AND THE DAWN OF FLIGHT

The ancestors of birds may have taken to the air on four wings and a prayer. Paleontologists have recovered from deposits in Liaoning, China, dinosaur fossils that exhibit evidence of flight feathers on their hindlimbs as well as their forelimbs. The specimens are said to represent a long-sought intermediate stage in the evolution of birds from flightless theropod dinosaurs, and could breathe new life into the theory that protobirds glided between trees before developing powered, flapping flight.

STONES SELF-ORGANIZE INTO CIRCLES

It sounds like the stuff of science fiction: stones arranging themselves into perfect circles or elaborate labyrinths. But it turns out the forces behind these mysterious patterns, which are commonly found in many polar and high alpine environments, are much more pedestrian - simple cyclic freezing and thawing of the surrounding ground.

BONE MARROW STEM CELLS REACH BRAIN AND ACCLIMATE

A new study underscores the promise of adult stem cells for changing into other useful cell types. The results reveal that transplanted bone marrow cells can migrate to a recipient's brain and transform into neurons.

THE REALITY OF RACE

Race doesn't exist, the mantra went. The DNA inside people with different complexions and hair textures is 99.9 percent alike, so the notion of race had no meaning in science. At a National Human Genome Research Institute (NHGRI) meeting five years ago, geneticists were all nodding in agreement. Then sociologist Troy Duster pulled a forensics paper out of his briefcase. It claimed that criminologists could find out whether a suspect was Caucasian, Afro-Caribbean or Asian Indian merely by analyzing three sections of DNA.

ULTRAPOWERFUL X-RAYS REVEAL HOW BEETLES REALLY BREATHE

Even the most up-to-date biology textbooks, if they address insect respiration, now need revision. With the help of a high-energy particle accelerator, researchers have documented insects breathing in a manner never before thought possible. The x-ray video technology used to conduct the examinations could have applications in robotics and medicine.

ASK THE EXPERTS: WHY DO CATS PURR?

Leslie A. Lyons, an assistant professor at the School of Veterinary Medicine at the University of California, Davis, explains.