Number 197, October 5, 1994 by Phillip F. Schewe and Ben Stein|
QUARK GLUON PLASMA (QGP) is a hypothetical state of nuclear matter in
which quarks do not reside in the traditional three-quark bundles (nucleons)
or two-quark bundles (mesons) but rather mingle in an amorphous soup. Scientists
are trying to create the QGP state by colliding heavy ions together. According
to Dinesh Srivastava and Bikash Sinha, physicists at the Cyclotron Centre
in Calcutta, India, evidence for the transition from a hadron phase (nucleons
and mesons) into a QGP phase would consist of (1) an enhanced production
of strange mesons, (2) a decrease in the production of psi mesons, and
(3) an increase in the creation of photons and lepton-antilepton pairs.
Interpreting the data from a recent experiment (WA80) at CERN, one in which
single photons emanated from high-energy sulphur-gold collisions, Srivastava
and Sinha surmise that the data can best be described by a scenario in
which a plasma does indeed form, after which the plasma expands, cools,
and freezes into hadrons. (Physical Review Letters, 17 October.)
THE SHARPEST PICTURES YET OF THE LIVING HUMAN RETINA have been produced
by University of Rochester researchers, allowing scientists to see the
individual cells called cones for the first time in human patients. Presenting
their images at this week's meeting of the Optical Society of America in
Dallas, the Rochester team (contact David Williams, 716-275-8672) took
their pictures by flashing low-power yellow laser light into the dilated
pupils of patients fitted with special lenses, and captured the images
using a special electronic camera with higher sensitivity and resolution
than ordinary film. The retina, the screen-like membrane that lines the
inside of the eyeball, captures light signals and sends them to the brain.
Only 3 microns wide, cone cells detect color and facilitate daytime vision.
With current instruments, ophthalmologists can only see structures 10 microns
or larger. The ability to resolve cones in patients could aid in the treatment
of age-related macular degeneration (AMD), the leading cause of blindness
in the elderly. (University of Rochester news release.)
THE MOST ENERGETIC GAMMA BURST yet observed by the orbiting Gamma Ray
Observatory was recorded on February 17, 1994. The burst's energy was calculated
to be 25 GeV, many times more energetic than those previously measured.
Furthermore, the burst was the longest ever, lasting more than an hour.
This monster burst may have resulted from the collision of two stars. (Astronomy,
CRYSTALS THAT SHRINK ISOTROPICALLY WHEN HEATED have been devised by
Arthur Sleight at Oregon State University. Ordinarily crystals expand when
heated because the added energy serves to prize neighboring atoms further
apart. In Sleight's compound, however, a network of oxygen, vanadium, and
phosphorus atoms rearranges its internal chemical bonds so as actually
to shrink when heated from 200 C up to 800 C. The shrinkage in volume is
small, only 0.3%, but, when this network is compounded with materials that
normally expand when heated, an overall thermal stability can be achieved.
This would be advantageous, for instance, in the construction of telescope
mirrors or electronic circuits. A few previous materials have been known
to contract in one direction while expanding in another dimension. Sleight's
materials seem to be the first to contract in all directions. (New Scientist,
10 September 1994.)