Number 137, July 19, 1993 by Phillip F. Schewe and Ben Stein
NEUTRINO LASING IN THE EARLY UNIVERSE . Some scientists believe that
a mixed dark matter (MDM) cosmology, one featuring both cold and hot dark
matter, would better explain the observed large-scale structure of the
universe than models using either cold or hot dark matter alone. Astronomers
at the Canadian Institute of Theoretical Astrophysics in Toronto suggest
that such a MDM model could be based, at least in part, on the decay of
primordial heavy neutrinos into light fermions (F) and bosons (B). In this
theory many low-energy B's are created when an initial neutrino decay triggers
subsequent decays in an exponential cascade process analogous to the stimulated
emission of light that occurs in a laser. In this case the B's are analogous
to laser photons. The colder B's can condense into a state which could
be considered cold dark matter, while the warmer B's and some of the fermions
would constitute a form of hot dark matter. (N. Kaiser, R.A. Malaney, and
G.D. Starkman, Physical Review Letters, 2 August 1993; contact Robert A.
Malaney, 416-978-8194.)
THE X-RAY EMITTING TAIL OF A PULSAR has been observed with the orbiting
Rosat telescope. The Rosat scientists believe that the tail is a pulsar-wind
nebula---consisting of relativistic particles cast off by the pulsar---which
is shaped by the movement of the nearby pulsar PSR1929 + 10 through the
interstellar medium with a proper motion of 70 km/sec. The observation
of such pulsar tails will be rare, the scientists believe, because the
pulsars must be close to our solar system and the tail must point almost
directly at us. (Q. Wang et al., Nature, 8 July 1993.)
NEAR-INFRARED IMAGES OF VENUS reveal that the lowlands are hotter by
100 K than the highlands and that the temperature above the surface falls
off with altitude at a rate of 8 K/km. The IR measurements of Venus's nightside
were recorded in February 1990 by the Galileo spacecraft on its complicated
trip toward Jupiter. In a way the infrared studies at Venus serve as a
rehearsal for the more thorough IR surveys to be conducted at Jupiter and
may also help scientists planning the future (ca. 1997) Cassini mission
to Saturn's moon Titan. (Science News, 10 July 1993.)
THE INTERNATIONAL PHYSICS OLYMPIAD took place last week in Williamsburg,
Virginia, the first time this competition among high school students has
been held in the U.S. Over 200 students from 40 countries took part in
the weeklong event, in which Zhang Junan of China and Harald Pheiffer of
Germany tied for the highest score. The Russian and Hungarian teams had
the most gold medal winners, with three each. China, the Czech Republic,
and Romania each received two golds. The lone U.S. gold medal winner was
Dean Jens of Ankeny, Iowa. (For more information, contact Randy Kaplan
at AIP, 212-661-9404.)
LEAD-CONTAINING SOLDERS are prevalent in electronic products. In an
effort to avoid the toxicity of lead, researchers at AT&T Bell Labs
have developed a new tin-zinc-silver solder that is strong, nonbrittle,
and rather good at resisting corrosion. (Science News, 17 July 1993.)
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