Notebook
Monday, September 12, 2005
Fla. Gator Encounters Triple
The number of alligator sightings and attacks in Florida has nearly tripled in recent decades, according to a paper being published today in the journal Wilderness & Environmental Medicine.
As more Americans move to coastal communities and the country's alligator population continues to rebound, humans are increasingly encountering the once-endangered species. In Florida alone, the number of alligator attacks has risen from an annual average of five between 1948 and 1986 to an average of 14 between 1986 and 2005, said Ricky L. Langley, a medical epidemiologist at North Carolina's Department of Health and Human Services. The number of "nuisance complaints" or sightings in Florida increased from 5,000 in 1978 to nearly 15,000 in 1998.
"It's pretty much a straight line going up," Langley said in an interview, adding that Americans "just have to be more careful, and be on the lookout when they're on the water or on golf courses."
Florida leads the nation in alligator sightings; Louisiana reported 4,000 alligator encounters last year while Georgia and Texas each had about 450. Alabama followed with almost 250, and Arkansas reported just under 100 alligators in 2004.
The trend marks a sharp departure from the late 1960s, when federal officials listed the American alligator as an endangered species. U.S. alligators, which made it off the endangered species list in 1987, now number more than 3 million.
-- Juliet Eilperin
Ceres: The New Water Planet?
For years astronomers have tried to look closely at Ceres, the largest asteroid in the asteroid belt, a nearly opaque target so featureless that scientists could not even be sure of its shape.
But with the help of the Hubble Space Telescope, a team of researchers obtained enough images in enough detail to determine that Ceres is quite likely a "mini-planet" with enough gravity to make it almost spherical, and suggesting that, like Earth, it may have different layers, including a mantle composed mostly of water ice. The research was reported last week in the journal Nature.
Using Hubble's Advanced Camera for Surveys, the team tracked Ceres through its full nine-hour rotation, and with 700 pixels in each image were able to follow a "bright spot" as it moved around the asteroid, enabling them to determine its polar and equatorial axes.
Team member Lucy McFadden of the University of Maryland said scientists had thought that Ceres was homogeneous in composition because of its smooth surface and its low-density surface crust.
"But it was too round," McFadden said in a telephone interview. If it had been homogeneous, she said, centrifugal forces would have collapsed the light-density material into a more "oblate" shape -- flatter on top, swollen in the middle.
"There's something that's keeping it from collapsing on itself," McFadden said, and the likeliest suspect is water ice, which expands when it freezes. If that is so, Ceres -- only 580 miles in diameter -- may have more fresh water on it than Earth.
-- Guy Gugliotta
Backpack Makes Its Own Power
Anyone who has hiked with a backpack full of loosely packed metal gear knows from the resulting din that the contents tend to move up and down with each step.
Now a team of researchers has invented a pack that takes advantage of that annoying reality. Free to slide up and down on its frame as a person walks, it transforms the energy from that vertical motion into an electrical current strong enough to power a cell phone, an MP3 player and other devices.
The power-generating pack may someday help soldiers, campers and field researchers lighten their loads by cutting down on batteries, say Lawrence Rome and colleagues from the University of Pennsylvania and the Marine Biological Laboratory in Massachusetts.
Scientists have tried for years to capture power from the energy of walking. Incentives have only grown as the number of helpful gadgets has increased, including global positioning systems and scientific and military instruments. But the best systems until now have generated only a few hundredths of a watt.
Portable electronics are increasingly lightweight and energy efficient, but most still require a watt or so. For device-heavy hikers, that means batteries can add up to several pounds -- in some cases accounting for 25 percent of their total pack weight.
Rome's group realized from treadmill studies that a person's hips -- and any backpack along for the ride -- move up and down about 2 to 3 inches with each step. They installed a so-called pinion-gear generator that, like some "self-winding" wrist watches, can transform the energy of oscillating motion into electricity. Depending on weight, the device generates up to 7.4 watts of power -- enough to run a half-dozen or more modern gadgets, the team reported in Friday's issue of the journal Science.
-- Rick Weiss