update.328 (fwd)

[Jim Choate <ravage@ssz.com>]

Forwarded message:
>From physnews@aip.org Wed Jul  2 19:12:35 1997
Date: Wed, 2 Jul 97 11:02:31 EDT
From: physnews@aip.org (AIP listserver)
Message-Id: <9707021502.AA12498@aip.org>
To: physnews-mailing@aip.org
Subject: update.328

PHYSICS NEWS UPDATE                         
The American Institute of Physics Bulletin of Physics News
Number 328 July 2, 1997    by Phillip F. Schewe and Ben Stein

THE MARS PATHFINDER spacecraft arrives July 4 at its
destination where, after firing retrorockets and deploying a
parachute and numerous airbags, it will bounce to a halt on what
was probably an ancient floodplain.  After this, its missionary
rover will venture forth to taste rocks and make movies. The
local weather forecast calls for blue skies and wispy clouds with a
small chance of a dust storm (currently 600 miles to the south),
in which case the sky will be pink. In September another craft,
the Mars Global Surveyor, will take up orbit around Mars.  (For
the latest update, view the JPL website: mpfwww.jpl.nasa.gov/)

STORING AN OPTIMUM AMOUNT OF INFORMATION IN A
PHOTON or any other quantum particle is possible even in the
presence of noise, researchers have concluded (B. Schumacher et
al., Physical Review A, July 1997; A.S. Holevo, upcoming in
IEEE Transactions on Information Theory).  A photon has many
different quantum states, each of which can be made to represent a
different digit.  Furthermore, one can store many digits
simultaneously in a single photon by putting it into a combination
or "superposition" of many states.  However, quantum mechanics
prevents a measuring device from perfectly distinguishing between
all these different states.  Previously, physicists discovered that the
maximum amount of information that can be read from a photon
can be no greater than the amount of entropy, or disorder, it
acquires when a range of quantum states is created to represent
different digits.  Now, the researchers show that this upper limit can
be reached, even in a noisy environment, by utilizing several
strategies, such as employing only those quantum states that are
most distinguishable.  These findings provide insights into how little
energy is required to store a message.  (For more details, go to
www.aip.org/physnews/preview; Ben Schumacher, Kenyon
College, 614-427-5832)

HOLLOW NANOPARTICLE LUBRICANTS, consisting of
fullerene-like tungsten disulfide balls, have performed well in
friction and durability tests, and may be superior to other solid-state
lubricants, which usually come in powdered form.  The 100-nm
WS2 balls (much smaller than conventional powder grains, microns
across) are nested like some carbon nanotubes, but flexible.  This,
their chemical inertness, and the tendency to roll rather than slide
when pushed, should make the nanoparticles a good lubricant at the
micron scale, or as an additive in other lubricants. Scientists
working at the Weizmann Institute and at the Center for
Technological Education in Israel are now able to make gram
amounts of the lubricant.  (L. Rapoport et al., Nature, 19 June
1997.)

ONE MEASURE OF A NATION'S SCIENTIFIC STRENGTH is
the number of papers it generates and the citations those papers
receive.  For the period 1992-96, these were the top  producers of
papers in a select set of journals: US (1.3 million), UK (300,000),
Japan (281,000), and Germany (259,000).  Ranked according to
citations per paper, the order becomes Switzerland (5.66), US
(5.03), Netherlands (4.46), Sweden (4.38), and UK (4.19).
The EU nations lumped together and the US each have a 36% share
of total citations.  The general trend these past 15 years has been for
the US citation rate to remain high but for its citation share to give
ground to the EU and to Asian/Pacific nations.  (ISI ScienceWatch,
May/June; also Nature, 5 June 1997.)