Physics Tip Sheet #12 - May 8, 2002
Contact: David Harris
harris@aps.org
301-209-3238
American Physical Society
1) Perfect sonic insulators
J. O. Vasseur, et al.
Physical Review E (Print issue: May 2002)
Researchers formed a square array of copper cylinders and found that they form an acoustic band-gap which will completely block a certain range of frequencies. A variation on the idea could be used to make lightweight sonic insulation.
Journal article: http://link.aps.org/abstract/PRE/v65/e056608
2) Should life be common in the universe?
C. H. Lineweaver, T M. Davis
arXiv preprint server
An argument sometimes used for the existence of life elsewhere in the universe is "if life evolved rapidly, as it did on Earth, then life must be common". The authors look at the assumptions inherent in this argument and conclude that the probability of biogenesis on Earth-like planets older than one billion years is greater than 1 in 3. This gives a value to one relevant factor in the extraterrestrial life argument but does not mean that life is necessarily common in the universe.
Preprint: http://www.arxiv.org/abs/astro-ph/0205014
3) Femtosecond light pulses
N. Zhavoronkov and G. Korn
Physical Review Letters (Print issue: May 20, 2002)
A new technique has produced single intense light pulses shorter then 4 femtoseconds (1 femtosecond=10^-15 seconds). The pulses are created using a technique called molecular phase modulation in which an initial pulse excites a molecule into some form of vibration or rotation. Then a second pulse sees the molecule's vibration or rotation as a change in refractive index, like a molecular-sized lens, which effectively focuses it to the ultra-short duration observed.
Journal article: http://link.aps.org/abstract/PRL/v88/e203901
4) Listening to DNA
D. L. Woolard, et al.
Physical Review E (Print issue: May 2002)
An experimental study has shown that the phonons (sound wave vibrations) in DNA molecules are characteristic of particular DNA sequences and can be observed using spectroscopic techniques. The authors examined the sequences, structures and dynamics of herring and salmon DNA sodium salts and concluded that the technique has potential application for obtaining DNA signatures.
Journal article: http://link.aps.org/abstract/PRE/v65/e051903
5) Left-handed materials do not make a perfect lens (two papers)
N. Garcia and M. Nieto-Vesperinas; P. M. Valanju, R. M. Walser, and A. P. Valanju
Physical Review Focus/Physical Review Letters (Print issue: May 20, 2002 and May 6, 2002)
When light refracts form one substance to another, it always bends one way. However, recent results suggested that certain (left-handed) materials could make light bend the other way. One of the possible implications of the work is that a perfect lens could be made. The result has stirred up controversy with new papers suggesting that light can only bend the usual way and even if they could bend light backwards, left-handed materials would not make a perfect lens.
Physical Review Focus: http://focus.aps.org/v9/st23.html
Journal article: http://link.aps.org/abstract/PRL/v88/e207403
Journal article: http://link.aps.org/abstract/PRL/v88/e187401
6) Single photons on demand
I. I. Smolyaninov, A. V. Zayats, A. Gungor, and C. C. Davis
Physical Review Focus/Physical Review Letters (Print issue: May 6, 2002)
Microscopic pinholes may soon allow the one-by-one transfer of photons in a way that mimics the process of a Coulomb blockade of electrons in which electrons line up on quantum dots to be released individually. The presence of one electron on a dot stops other electrons from joining it and puts a limit on the rate electrons can flow through the dot. In an optical equivalent, the authors covered a glass plate with a gold film containing cracks and gaps. They then filled the gaps with a transparent polymer. By looking at the light coming through individual gaps, they observed a maximum in the amount of light that could pass through, just as if photons in the gaps were preventing further photons from coming through.
Physical Review Focus: http://focus.aps.org/v9/st24.html
Journal article: http://link.aps.org/abstract/PRL/v88/e187402
Papers from the Physical Review series of journals are available pre-publication to journalists on request.
For media assistance with these or other physics stories, contact:
David Harris
Head of Media Relations
American Physical Society
Ph: +1 301 209 3238
Fax: +1 301 209 3264
Email: harris@aps.org
