From: revu@ellis.uchicago.edu (Sendhil Revuluri)
Subject: Physics News Update #103 (11/17)
Summary: Latest Physics News Update
Keywords: physics news interesting banana
Reply-To: revu@midway.uchicago.edu
Organization: University of Chicago
Date: Tue, 17 Nov 1992 23:23:59 GMT

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This is a "Physics News Update" distributed by Phillip Schewe of AIP
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Sendhil Revuluri (s-revuluri@uchicago.edu)
University of Chicago

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PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 103   November 17, 1992

DO QUARKS HAVE CONSTITUENTS?  The issue of quark
substructure can be addressed by studying the production of jets
of particles in high-energy proton-antiproton collisions.  The CDF
(Collider Detector at Fermilab) collaboration recently published
an analysis of two-jet events produced at the Tevatron collider. 
Finding no direct evidence, the researchers concluded that any
quark substructure would only become evident at energies of 1
TeV or more.  (F. Abe et al., Phys. Rev. Lett., 16 Nov.)

VORTICES IN HEAVY-FERMION SUPERCONDUCTORS
have been imaged for the first time.  In certain materials---in this
case, a uranium-platinum compound---superconductivity can occur
at temperatures below 1 K through the interactions of inner-shell
electrons which, because they are tightly bound, move as if they
were heavier than normal electrons.  Like the high-temperature
superconductors, the heavy-fermion superconductors can respond
to the presence of an external magnetic field by producing
vortices, little loops of current flowing around the magnetic flux
lines.  Studies of vortices in other superconductors indicate that
they can form a sort of "lattice" configuration.  Now a group of
scientists at AT&T Bell Labs (David J. Bishop, 908-582-3927) and
the RISO National Lab in Denmark have used neutron diffraction
to show that vortices in a heavy-fermion material, UPt3, assume an
oblique hexagonal structure.  (R.N. Kleiman et al., Phys. Rev.
Lett., 23 Nov. 1992.)

AN ANTENNA MOUNTED ON A PHOTONIC CRYSTAL has
been demonstrated by scientists at the MIT Lincoln Lab and
Bellcore.  Photonic crystals are the recently introduced structures
that reject electromagnetic radiation lying in certain frequency
ranges or "bands" in the same way that semiconductors reject
electrons in certain energy bands.  Elliott Brown of Lincoln Lab
(617-981-4713) and his colleagues built a photonic crystal-antenna
setup which can couple microwave radiation to devices on
integrated circuits.  This configuration allows integrated-circuit
devices to receive microwave radiation, or conversely, convert
electric current to microwave signals.  The configuration
traditionally used for this purpose, antennas on semiconductor
substrates, transmits only a few percent of their total power into
the air; the rest is radiated into the semiconductor.  The Lincoln
Lab-Bellcore antenna, which has a planar bow-tie geometry, has
much higher efficiency because the photonic crystal on which it is
mounted has a sizeable energy gap in the microwave region. 
(Optics & Photonics News, November 1992; also upcoming article
in "Physics News in 1992," to be published by the AIP Public
Information Division.)

THE KNOWN SHAPE OF THE MILKY WAY keeps changing
as new information comes to light.  At a recent conference
devoted to the subject, data from COBE, IRAS, Rosat, and other
sources added to or modified the traditional view of our galaxy. 
Examples include the observation of 100-light-year-wide bubbles
of hot, low-density gas and of other worm-shaped filaments of hot
gas (up to 1000 light years long) sticking up out of the galactic
plane.  Meanwhile, COBE observations of the galactic center
support an earlier assertion by Maryland astronomer Leo Blitz that
the Milky Way is not a classic pinwheel but actually a barred
spiral.  (Science, 6 Nov. 1992.)

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Sendhil Revuluri (s-revuluri@uchicago.edu)
Newsgroups: sci.physics