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SCIENCE
Notebook

Monday, November 21, 2005; A06

Light Show Foreseen by Einstein

It is a little bit like the celestial equivalent of a terrestrial mirage. When incoming light is interrupted by a massive object such as a galaxy, space is warped and the light is bent, sometimes so radically that it appears to form a circle around the galaxy.

Einstein predicted this phenomenon, known as an Einstein ring, in a paper published in 1936, but telescopes sophisticated enough to differentiate the passing light from the glare of the galaxy did not then exist.

They do now, and a team of astronomers led by Adam Bolton of the Harvard-Smithsonian Center for Astrophysics has identified 19 instances of "gravitational lensing," or warped light. Eight are pronounced enough to be called Einstein rings.

"It happens when you have incoming light from a distant galaxy in almost perfect alignment with a foreground [closer] galaxy," Bolton said in a telephone interview. "The bending of light is sufficient to see multiple images [of the far galaxy], or even a ring."

Bolton's team sorted the optical spectra of several hundred thousand galaxies gathered by the Sloan Digital Sky Survey, looking for light signatures that, at certain frequencies, indicated possible lensing. They examined 28 with the Hubble Space Telescope, finding the 19 lensing examples.

Bolton said Einstein rings, which are "very rare," offer astronomers an opportunity to calculate the mass of an elliptically shaped foreground galaxy, composed of stars and dark matter, the invisible form of matter thought to make up most of the mass of the universe. Astronomers can indirectly observe dark matter by measuring its gravitational influence.

-- Guy Gugliotta

On Taking Anger to Heart

Extremely hostile women do not have a greater risk of heart disease than their more placid sisters, new research has found, contradicting conventional wisdom about the consequences of an angry personality for both sexes.

While men with high levels of hostility had nearly twice the risk of heart disease as men with low levels of hostility in the new study, women who were very hostile actually had a slightly lower risk of heart disease compared with women who reported little hostility, although that difference was not statistically significant, according to a paper published last week in the British Journal of Medicine.

"Hostile men, but not women, were more than twice as likely to suffer recurrent coronary heart disease events," the paper said. "Hostility may have different consequences in men and women."

The study, partly funded by the U.S. National Institutes of Health, was conducted by researchers in New York at the Mount Sinai School of Medicine, St. John's University and Columbia University Medical Center. The study tracked 206 men and women in Nova Scotia over four years and evaluated their personalities on a hostility scale. Hostility was associated with depression among both sexes, the study noted.

The researchers offered no word on the physical and emotional well-being of people who were the targets of all that rage.

-- Shankar Vedantam

Salamander's Diet Is the Dregs

Birds gotta fly. Fish gotta swim. And salamanders that live in caves where the only decent source of nutrition is bat droppings -- well, they gotta eat.

So it is that scientists have documented the first known salamander with a guano-based diet -- one of very few backboned animals dependent on feces for nutrition.

The work wasn't pretty. The researchers went deep into an Oklahoma cave system populated by thousands of gray bats that over the years had deposited piles of droppings more than six feet high. There among the guano mounds lives Eurycea spelaea , or the blind grotto salamander.

Virtually all salamanders are carnivorous, living mostly on insects, but the perpetually dark caverns of the Ozarks are mostly devoid of such life. Dante Fenolio, then at the University of Oklahoma and now at the University of Miami, led atomic isotope studies to track the source of the carbon and nitrogen in the animals, and showed that the bat droppings were the salamanders' main food group.

Consumption of feces -- known as coprophagy in respectable circles -- is not uncommon among insects. But it is relatively rare in vertebrates and most known cases are for reasons other than nutrition. Some tadpoles consume small amounts to populate their intestines with helpful bacteria, for example, and some birds use the droppings to supply a key yellow pigment for their feathers.

Bat guano is as nutritious as insects, the team found -- perhaps because bats' short intestines pass much of their diet undigested. Other cave dwellers may also depend on guano, Fenolio and colleagues suggest in the Nov. 16 issue of Proceedings of the Royal Society B. They warn that the decline of bat species in some environs may threaten such species.

-- Rick Weiss

 2005 The Washington Post Company