J.-M. P. Franosch, R. Kempter, H. Fastl, J. L. van Hemmen
Physical Review Letters (to appear)
The Zwicker tone is an auditory aftereffect. If you listen to a noise that contains all pitches of notes except for one, then switch it off, you hear the missing tone linger, even though it was never played. This auditory illusion cannot be explained by the apparatus of the ear itself, and must arise in the brain. This paper shows how some simple models of neurons in the brain can show the Zwicker effect. Understanding how the Zwicker tone works should lead to an understanding of how tinnitus, a long-term auditory phantom, occurs.
Journal article: Available to journalists on request
2) Breathing bubbles in DNA zippers
G. Altan-Bonnet, A. Libchaber, O. Krichevsky
Physical Review Letters (Print issue: April 4, 2003)
Have you ever had a zipper with a bubble? The two sides get separated for a few teeth before joining back together. Exactly the same thing can happen in DNA molecules except that in DNA, the bubbles can open and close, a process called "breathing". Physicists have now watched DNA breathing bubbles for the first time by attaching small lightbulbs to the DNA strands and watching them move. (The lightbulbs are actually fluorophores which glow back when illuminated with UV light.) The researchers see that bubbles can move along a DNA molecule with one end closing up as the other end opens. Bubbles can also get stuck in certain places and a variety of sizes of bubbles occur in DNA molecules.
Journal article: Available to journalists on request
3) Origins of solar flares
D. Hughes, M. Paczuski, R.O. Dendy, P. Helander, K.G. McClements
Physical Review Letters (Print issue: April 4, 2003)
You can think of the magnetic field beneath the photosphere of the Sun as a giant ball of yarn. Magnetic flux tubes, like loose threads, are irregularly expelled into the corona as loops anchored to the photosphere. They form the building blocks for larger scale magnetic structures such as active regions or the magnetic carpet. A solar flare is a rapid change in a strong, complicated coronal magnetic field. New simulations of these processes show that solar flares can arise as small loops of magnetic flux tubes colliding and forming a cascade of more collisions, building up to a large solar flare being ejected from the corona.
Journal article: Available to journalists on request
4) Watching bricks age
M. A.Wilson, W. D. Hoff, C. Hall, B. McKay, A. Hiley
Physical Review Letters (Print issue: March 28, 2003)
Civil engineers and materials scientists have long known that clay bricks and other fired ceramics expand as they age owing to the absorption of water from the atmosphere. In general, however, studies of moisture expansion in bricks have been limited to freshly fired bricks over short timescales. Now researchers have experimentally investigated expansion in bricks over periods extending back to Roman times, about 1900 years ago. The new theory should help in the engineering of brick structures intended to last a century or more by allowing designers to account for expansion that might otherwise lead to cracks. The studies may also be handy for archeological dating of bricks and ceramics.
Physics News Update: http://www.aip.org/enews/physnews/2003/split/630-2.html
Journal article: http://link.aps.org/abstract/PRL/v90/e125503