lunes, 15 de junio de 2009

Guisando´s People

Each spring, winged maple seeds twirl like helicopters as they glide to the ground. A seed can drift up to a kilometer on a windy day, landing on a fresh patch of earth to start its own tree. To travel so far, a seed relies on a tiny spiral of air that forms above its papery wing and provides lift, a new study shows. Such an air vortex helps moths, bats, and birds stay aloft, but its use in seeds marks a first for plants.
To make the discovery, zoologist David Lentink of Wageningen University in the Netherlands and colleagues first created an artificial maple seed in the lab. They needed something big to actually quantify the air flow patterns, so they made a seed about 10 times the size of a maple seed out of acrylic. The team then attached the seed to a robotic arm that spun it in a container of mineral oil filled with thousands of tiny glass spheres. When the fluid was lit by a laser, it illuminated the glass beads and revealed a tornado-like vortex that ran parallel to the seed's wing. The vortex, Lentink says, decreases the pressure above the seed, essentially sucking it upward to slow its decent.
But the model still wasn't the real deal, so Lentink and his colleagues built a wind tunnel, filled it with smoke, and watched as an actual maple seed rotated in midair. The team reports in today's issue of Science that the smoke patterns revealed the same tornado-like effect--also known as a leading-edge vortex--as seen in the glass bead experiment, confirming that their model was correct, ondi gana ha....and di seven and for mi Manu, Andres, Batu and Josito.

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