Inverse Doppler effect
The Doppler effect, heard in rising pitch of an approaching fire truck siren and seen in the reddening of light coming from galaxies moving away from Earth, has been reversed for the first time at optical frequencies of light. In a demonstration of the inverse Doppler effect, a crystal moved toward a laser beam turned its light redder — not bluer, as would be expected, an international team of scientists reports online March 6 in
. The secret to the trick is that the crystal is made of a metamaterial, a manmade substance that interacts with light in strange and counterintuitive ways. —
Anthrax coat-change decoded
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The applied science of the anthrax-letters investigation is shedding light on basic microbial genetics. Most colonies of Bacillus anthracis, the anthrax bacterium, that were grown from spores mailed in the 2001 attacks looked like plain-Jane anthrax. But some cells were funny-looking — yellow-gray, for example, or especially compact. A team of scientists has now unraveled the letters of genetic instructions for each of the four unusual cell types. Each contained DNA mutations, and in three of the four, the mutation probably led to the unusual physical appearance, the researchers report in a paper appearing March 7 in the
Proceedings of the National Academy of Sciences
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A splash of booze could help iron superconductors overcome performance anxiety. Japanese researchers found that soaking iron compounds in a variety of heated alcoholic beverages helped to trigger the emergence of superconductivity in hours, instead of the months required when these materials are exposed to open air. And the iron compounds have discriminating taste: they prefer red wine to whiskey, the scientists report in the March 7
Superconductor Science and Technology
. The alcohol itself is unlikely to be the cause of this change. Instead, other elements may prevent the iron compound molecules from lining up in the same direction, thus enhancing superconductivity. —
Stronger scent, larger turf
The size of a male red fox’s territory depends on the strength of his scent, concludes a new study analyzing how territory boundaries form and change through time. Territorial animals defend and mark their area, conveying information such as health status, sex and no-trespassing. But scientists haven’t understood how larger territory dynamics emerge from the actions of individual animals. Now mathematical modeling by British scientists reveals that the size of a single fox’s territory is proportional to two things: how long it takes the animal to walk its borders and how frequently it must refresh its scent markings. The team reports the work March 10 in
PLoS Computational Biology. —Rachel Ehrenberg