Physics Tip Sheet #44 - August 6, 2004

Contact: James Riordon
riordon@aps.org
301-209-3238
American Physical Society

Highlights of this tip sheet include a gentler way to stop heart attacks and wondering what temperature means at nanoscales.

1) A gentler way to stop heart attacks
S. Takagi et al.
Physical Review Letters, 30 July 2004
http://link.aps.org/abstract/PRL/v93/e058101
See also Physical Review Focus story

In a step towards a safer way to stop heart attacks, a team reports that applying a weak electric field across the heart can remove dangerous rotating waves in cardiac muscle without the damaging effects of standard defibrillators. The researchers' simulations show that a weak electric pulse, with an energy about 100 times less than used in standard defibrillators, could unpin pinned rotating electric waves, which are known to lead to heart attacks. If timed properly, the mild electric shock sets up a second wave that rotates in the opposite direction from the pinned wave and dislodges it, allowing it to drift away and be destroyed upon hitting the cardiac wall. The technique should work even if the exact location of the pinned wave isn't known. The authors have confirmed their ideas in a laboratory experiments on a slice of rabbit ventricle.

2) Does temperature exist at the nanoscale?
M. Hartmann et al.
Physical Review Letters (to appear)

Surprisingly, whether temperature exists at small scales depends on what temperature you're talking about, a new paper shows. The results may indicate a need for a change in the way some temperature measurements are interpreted, and could be important for understanding the thermal behavior of new nanoscale devices. The authors consider a long chain of identical particles that interact with their nearest neighbors and calculate the smallest subgroups for which temperature can be meaningfully defined. Because of quantum mechanical effects, which become important at small scales, high temperatures can exist in small regions, whereas lower temperatures exist only on larger scales, the authors found. For example, the authors calculate that for carbon nanotubes, room temperatures (about 300 Kelvin) exist on length scales of about a micrometer, while very low temperatures (about 10 K) exist only on scales larger than a millimeter.

Journal articles are available to journalists on request.

For media assistance with these or other physics stories, contact:

James Riordon
Head of Media Relations
American Physical Society
Ph: +1 301 209 3238
Fax: +1 301 209 3264
Email: riordon@aps.org