Correction to This Article
A March 12 Science Notebook item incorrectly referred to millipedes as insects. Although, like insects, millipedes belong to the phylum Arthropoda, they are in the class Diplopoda, not Insecta.


A flying wind turbine, which is essentially a tethered gyrocopter flying as a kite, uses spinning propellers to generate both lift and electricity. The electricity runs down the tether to be used on the ground.
A flying wind turbine, which is essentially a tethered gyrocopter flying as a kite, uses spinning propellers to generate both lift and electricity. The electricity runs down the tether to be used on the ground. (Illustration By Ben Shepard)
Monday, March 12, 2007

Renewable Energy Up in the Air

A study by Australian, American and Canadian scientists suggests that high-altitude wind power could provide a major source of renewable energy in years to come.

Their paper -- in the March 1 edition of the journal IEEE Transactions on Energy Conversion -- provides detailed technical specifications for a prototype flying wind turbine that could generate far more energy than a ground-based turbine.

The authors, led by Sydney-based University of Technology professor B.W. Roberts, wrote that jet stream winds have 10 to 100 times the energy of winds close to the ground.

"This is the highest power density for a large renewable energy resource anywhere on earth," they wrote.

The flying wind turbine they described amounts to a tethered gyrocopter flying as a kite, whose spinning blades would generate both lift and electricity. The lift keeps the gyrocopter in the air and the electricity is transmitted down the tether to be used on the ground.

Carnegie Institution senior scientist Ken Caldeira, one of the study's co-authors, wrote in an e-mail that the paper "makes it clear that there is a case to be made that these kind of aircraft could be a major piece of the solution to the climate problem -- just tapping into 1 percent of the energy in high altitude winds would be enough to power all of civilization."

-- Juliet Eilperin

New Millipedes Found in Caves

Ten thousand years ago, two species of millipede disappeared into the cool and damp of caves along the Grand Canyon. Two weeks ago, scientists announced they had discovered their descendants.

The discoverers figured the newly found arthropods probably represent distinct species, as they were found on opposite sides of the Colorado River. Detailed study revealed they are something rarer, a previously unknown genus of the insects.

They have a markedly different shape to their gonopods, the modified legs the males use in reproduction, which warrants putting them in a category of their own, said William A. Shear, a biologist at Hampden-Sydney College in Virginia. In biological parlance, the millipedes are "relicts" -- survivors of a previously large natural community.

They presumably lived in leaf litter when northern Arizona was a wetter and more hospitable place, at the end of the last ice age. As the climate changed, they sought refuge in the caves. They were already blind and unpigmented, so they fit in well with other denizens of the dark. Today, they survive on vegetation that periodically washes into the caves during flash floods, and on bacteria and fungi.

Their closest living relatives are cave-dwelling millipedes found in Texas. However, one of their discoverers, J. Judson Wynne, of Northern Arizona University and the U.S. Geological Survey, did not rule out that relatives may survive in Arizona slot canyons with water and trees.

Wynne discovered the millipedes over the past two years in ecological surveys with Kyle Voyles, of the Bureau of Land Management. The species are not yet named.

-- David Brown

Dinosaur Genomes Rather Small

Dinosaurs were the largest creatures ever to walk the Earth, but some had genetic signatures no bigger than those of modern hummingbirds, a study found.

Researchers at Harvard University and the University of Reading in England estimated the size of dinosaur genomes by examining fossilized bones and extrapolating from known relationships between the sizes of cells in living organisms and the size of their genomes. They found that a class of carnivorous dinosaurs known as theropods, such as Tyrannosaurus rex and velociraptor, had very small genomes similar in size to those of modern birds. In contrast, ornithischians, such as stegosaurus and triceratops, had bigger genomes, about the size of those of today's lizards and crocodiles.

The research, published last week in the journal Nature, shows that the smaller genomes typically associated with birds evolved in dinosaurs as long as 250 million years ago and not with the emergence of modern birds 110 million years ago. Smaller genomes can be lumped in with other dinosaur traits once thought to be characteristic only of modern birds, including feathers, nesting and parental care.

"If you take the dinosaurs and you fit that into what people have hypothesized about avian genomes, we get a richer picture of how avian genomes have evolved, but also [learn] that some of our current ideas are wrong," said Chris Organ, at Harvard. "For example . . . small genome size is not directly associated with flight, which previously was sort of the dominant going theory."

-- Christopher Lee

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