Restless atoms responsible for ageing

How do computers grow old with time? Why does the car refuse to start? The answer, say scientists from Vienna, lies in atoms that can get pretty much wild. The behaviour of atoms has come to light for the first time by the use of cutting edge technology that uses X-ray sources called electron synchrotrons.

The scientists term the behaviour wild because the atoms are restless and they jump within a solid. The restless atoms are responsible for ageing, and therefore, loss of specific material properties. The research team used the European Synchrotron Radiation Facility in France, which creates special X-rays of exceptional intensity and quality.

They observed the movement of atoms in a copper-gold alloy and discovered how far and in what directions atoms jumped and how temperature affected their movement.

The temperature where atoms start hopping depends on the material. They found at 270°C, atoms of the alloy changed position about once per hour. If the temperature was increased by 10°C, the jump rate doubled. It halved when the temperature was decreased 10°C, said Michael Leitner, of the research team, in the study published online in Nature Materials in July.

“The only way to stop atoms from jumping would be to lower the temperature,” said Leitner.

One could also modify the material and observe the movement. Take for instance aluminium, said Leitner, which is rather soft. “Anyone who has crushed a beer can knows that. When mixed with copper and other elements, and kept at a given high temperature, aluminium is much harder.” Does that mean it will last forever?

“The initial heat treatment makes the material hard, but subsequent high temperatures make it soft. We need to know more about atomic diffusion to understand what goes on,” he said.

Indrajit Bose
Down To Earth Feature Service

Smallest dinosaur in North America

Small dinosaurs are big these days. Researchers recently announced the discovery of a tiny prototype of a Tyrannosaurus from China. Now paleontologists are reporting the smallest dinosaur ever found in North America.

The animal, Fruitadens haagarorum, had a body length of about 30 inches and weighed an estimated two pounds.

Fossils dating from the late Jurassic period were excavated in Colorado in the 1970s and kept at the Natural History Museum of Los Angeles County, where they have now been studied and described by Richard J Butler, of the Bavarian State Collection for Paleontology in Germany, and colleagues.

Fruitadens is also the smallest ornithischian dinosaur ever found. Ornithischians, one of the two main groups of dinosaurs, generally ate plants, and “plant eaters require a fairly large gut,” said Luis M Chiappe, director of the museum’s Dinosaur Institute and a co-author of a paper describing the finding in The Proceedings of the Royal Society B: Biological Sciences. The small size of Fruitadens and an absence of grinding wear on its teeth, Chiappe added, suggest it probably supplemented its diet with small animals and insects.

Fruitadens is one of a subgroup of ornithischians that survived for more than 100 million years. Chiappe said that dinosaur species became morphologically more specialised in evolution but that Fruitadens was “conventional and unspecialised.” That, he said, may be why the subgroup survived for so long: Species like it were better able to adapt.

Henry Fountain, NYT News Service