Number 117, March 8, 1993 by Phillip F. Schewe and Ben Stein
HEALTHY AND DISEASED HEARTS display distinctly different patterns in
the time intervals between heartbeats, a new experiment shows. For the
healthy heart, the intervals are arranged in a complex fashion even over
tens of thousands of heartbeats, with a long interval-short interval pattern
emerging on all time scales, regardless of whether the 1st and 2nd, or
1st and 1000th, intervals are being compared. No such pattern exists for
the severely diseased hearts studied in the experiment; the lengths of
the intervals for the diseased hearts fluctuate in a manner reminiscent
of a random walk. Physicians may one day be able to use information of
this nature as an aid in diagnosing patients. (C.-K. Peng (617-353-9460)
et al., Physical Review Letters, 1 March 1993.)
THE EXTREME ULTRAVIOLET EXPLORER (EUVE) , launched by NASA in June, has
yielded its first images. Among them are a couple of surprises: white dwarfs
vary with unexpected diversity in the EUV wavelength range and at least
seven sources outside the Milky Way were detected; this was surprising
because scientists did not expect that the EUV could penetrate the interstellar
medium so well. Also recorded were the first EUV images of the Moon and
the Cygnus loop, the gaseous shell created from a supernova explosion that
is colliding with the interstellar medium. Future EUVE investigations will
look at the atmospheres of cool stars and compare them to the extensively
studied corona of our Sun. (Science, 26 February 1993.)
MANIPULATING BEAMS OF ATOMS with techniques normally used for beams
of light is becoming more common. The high electric fields available in
intense laser light and the advent of submicron machining have facilitated
the development of a variety of atom beam splitters, lenses, mirrors, and
interferometers. One example: a laser beam, channeled through a dielectric
medium by total internal reflection, will exhibit an "evanescent field,"
an exponentially-decaying light field in the vacuum just outside the medium.
This light has been used to reflect atoms. According to Martin Sigel and
Jurgen Mlynek of the University of Konstanz in Germany, if this or other
atom mirror designs could be employed to make a cavity for containing standing
or traveling atom waves, then it might be possible to store cold atoms
(useful in the search for Bose condensation) or even to produce coherent
atom beams. (Physics World, Feb. 1993.)
SUPERMOLECULAR CHEMISTRY is a new field in which scientists design complex
structures---perhaps even molecular-scale computer-related components such
as diodes and transistors---from molecules that spontaneously assemble
themselves in liquid solution and perform their function through intermolecular
interactions. An example of such "wetware" is a supermolecular
structure in which a ringlike molecule shuttles between a pair of molecular
sites along a polyether "string." Researchers are attempting
to control the shuttling between molecular sites (at a rate so far of hundreds
of times per second) so that it could function as a switch that stores
information. Researchers are also working on lipid-based "molecular
wires" that can conduct electricity in solution and may be used to
interlink supermolecular switches. (Science, 12 February 1993.)
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