The Fibonacci sequence—in which each successive number is the sum of the previous two (1, 1, 2, 3, 5, . . .)—appears all over the biological realm, describing, for example, how seeds spiral on strawberries and nautilus shells curve. Now researchers at the Chinese Academy of Sciences and their colleagues have created Fibonacci spirals in purely inorganic materials. The scientists tinkered with microstructures consisting of silver cores and silica shells. The stiff shells buckle as they harden on the compliant cores, and if the shells were encouraged into conical shapes during cooling, irregularities formed as Fibonacci spirals (photographs). The results, detailed online April 18 in Applied Physics Letters, support an old conjecture from biologists that these spirals arise as a means to minimize space or energy usage. —Charles Q. ChoiStem Cell Blood Repair
After spending years devising the right chemical cocktail, researchers from Advanced Cell Technology in Worcester, Mass., have reported growing large numbers of human embryonic stem cells called hemangioblasts. In laboratory dishes the blast cells developed tissues that resembled blood-forming stem cells as well as blood vessels. The team injected them into body parts of rodents damaged by diabetes and other injuries that impair blood flow. The hemangioblasts turned up in the unhealthy blood vessels, and mice that received them were twice as likely to survive heart injury as control mice were. Nature Methods posted the report online May 7. —JR MinkelBut It's Not Krypton, Is It?
The most Earth-like extrasolar planet yet discovered, just five times as massive as Earth, circles a red dwarf star called Gliese 581 20.5 light-years away. Planetary temperatures might range from zero to 40 degrees Celsius. “The separation between the planet and its star is just right for having liquid water at its surface,” says Stephane Udry of the Observatory of Geneva, whose team announced the finding in April. —JR Minkel