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Date: Thu, 23 Dec 1993 16:58:38 EST
From: KIDSPHERE Mailing List <kidsphere@vms.cis.pitt.edu>
Subject: PHYSICS NEWS UPDATE #156, 17 Dec 93 (from
 sci.research,sci.materials,sci.physics.accelerators,sci.environment,sci.geo.met
 eorology,sci.optics)
To: KIDSPHERE Subscribers <kidsphere@vms.cis.pitt.edu>

Date: 18 Dec 93 01:12:34 GMT
From: JTCHEW@lbl.gov (Ad absurdum per aspera)
Subject: PHYSICS NEWS UPDATE #156, 17 Dec 93
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PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 156  December 17, 1993

SUPERCONDUCTIVITY AT 250 K (10 F) has been reported by a
group of scientists at the Ecole Superieure de Physique et de Chemie
in Paris.  Michel Lagues and his colleagues synthesized a BiSrCaCuO
compound with a unit cell comprising eight adjacent CuO planes.
This development seems to bear out the general idea that high
temperature superconductivity happens mostly in copper-oxygen
planes and that the more such contiguous planes the better.  The
French researchers used beam epitaxy to lay down the atomic layers
one by one, a cumbersome process that would be difficult to
implement on an industrial scale.  Reports of superconductivity in
complex materials at these temperatures have been made before, only
to be withdrawn, so some scientists such as Venky Venkatesan (301-
405-7320) of the University of Maryland are skeptical.  However, in
contrast to these earlier materials, Lagues' sample remained
superconducting for weeks.  (Science, 17 Dec.)

DATA FROM TWO GREENLAND ICE PROJECTS DIFFER for
the sections of ice deposited during the Eemian period, the last
"interglacial" (warm) period prior to the current one.  Representatives
from the US-funded Greenland Ice Sheet Project 2 (GISP2) and the
European-funded Greenland Ice-core Project (GRIP) discussed their
results at the Fall Meeting of the American Geophysical Union in San
Francisco.  According to Willi Dansgaard of the University of
Copenhagen, the GRIP ice core shows that temperatures during the
Eemian fluctuated wildly, typically by 5-7 degrees Celsius over a
matter of decades.  This implies that the current interglacial period
(the Holocene), is either unusually stable or is subject to the same
fluctuations in climate.  However, Ken Taylor of the University of
Nevada reported that the GISP2 ice core does not exhibit these same
fluctuations for the Eemian period.  Both teams are trying to work out
the discrepancy, which may have been caused by distortions in the
ice. The data for the top 90% (2700 m) of the cores agree
excellently, which the researchers believe will lead to a climate model
of unprecedented accuracy stretching back to 100,000 years with
"significantly better than bi-annual resolution," according to Paul
Mayewski of the University of New Hampshire.

SUPER-INTENSE LASER FIELDS MAKE ATOMS RESISTANT
TO IONIZATION, according to computer simulations performed by
J.D. Eberly of Cornell, K.C. Kulander of Lawrence Livermore, and
others.  Contrary to the expectation that as the incident light becomes
more intense it would eject electrons from atoms more easily, very
intense fields (2 to 5 times stronger than the static electric fields
which bind electrons to the atom) actually cause the electrons to
become locked in an orbit that follows the oscillations of light's
electric field. Ironically, the atom becomes stabilized since the
electron's orbit remains fixed relative to the atom.  In hydrogen, for
example, the electron ground state, represented in a density
distribution as a single peak centered around the nucleus, would be
distorted by the intense fields into a pair of peaks, each at some
distance from the nucleus and each other.  Eberly and Kulander
believe that an experimental demonstration of this phenomenon is
likely in the near future; lasers at sufficiently high intensities exist,
but light with higher frequencies from these lasers are still needed.
(Science, 19 November 1993.)