Number 207, December 15, 1994 by Phillip F. Schewe and Ben Stein|
COPPERLESS PEROVSKITE SUPERCONDUCTORS have been devised by a collaboration
of physicists at IBM Zurich and Hiroshima University. Perovskite, a class
of ceramic crystal (e.g., MgSiO3) in which three chemical elements combine
in the ratio 1:1:3 to form a layered cubic structure, is prominent in the
Earth's mantle. It became even more famous when over the past eight years
a series of superconducting perovskites were discovered. The superconductivity
in these compounds appears to reside in planar networks of copper and oxygen
and scientists have wondered whether copper was crucial. Copper may well
be special but now ruthenium-oxygen planes seem to carry superconductivity
too. The Hiroshima-IBM material, a Sr-Ru-O compound, only becomes superconducting
at 0.93 K, but the researchers believe that by studying the new "ruthenate"
materials we will learn more about the higher-temperature cuprate materials.
(Y. Maeno et al., Nature, 8 December 1994.)
A GLOBAL SEA LEVEL RISE has been detected by the TOPEX/Poseidon satellite.
Speaking at last week's meeting of the American Geophysical Union in San
Francisco, scientists from the U.S.-French project announced that the average
ocean height had risen 3 mm each year since late 1992. The rise may be
due to a longterm trend such as an increase in the melting of glaciers,
or to a shorter-term phenomenon such as El Nino effects in the Pacific.
If the latter, then sea levels would shortly decline again. The TOPEX/Poseidon
satellite, launched in August 1992, views the face of the ocean with carefully
timed radar beams. Designed to study ocean currents, the craft has been
able to monitor sea levels because of a higher than expected accuracy in
altimetry. (Science News, 10 December 1994.)
THE HIGHEST ENERGY ACCELERATOR BEAM in the world is at CERN, where lead
ions achieve energies as high as 35 TeV. The Tevatron at Fermilab still
possesses beams with the highest energy per nucleon, 900 GeV, but CERN's
lead ions (each consisting of 208 nucleons) have more total energy. CERN
researchers hope that collisions involving their lead ions will provide
the first tangible evidence for quark-gluon plasma, the hypothetical state
of matter in which quarks do not necessarily configure themselves into
the conventional groupings of two quarks (mesons) and three quarks (baryons).
(CERN press release, November 21, 1994.)
THE ABANDONED SSC SITE may be used for various geoscience projects,
such as the study of subsurface fluid flow, particularly as it applies
to the preservations of aquifers. The partially completed SSC tunnel is
22.5 km long and proceeds through sedimentary strata---shale and chalk---similar
to those found underneath many Midwestern cities. A meeting at LBL was
convened in September 1994 to discuss the matter. (Eos, Nov. 29.)
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