Number 163, February 4, 1994 by Phillip F. Schewe and Ben Stein
A MAGNETIC RESONANCE IMAGING SYSTEM developed by General Electric will
permit real-time MRI scans during surgery. The new system employs several
innovations; the first is the use of a pair of solenoid magnets rather
than a single magnet, enabling the part of the body under operation to
lie outside the magnet (but still subject to the high magnetic fields necessary
for MRI) in a place accessible to a surgeon. Also, the system's niobium-tin
magnet coils are kept superconducting at 10 K with a small cryocooler system
rather than with liquid helium and its attendant large pressure vessel.
High-temperature ceramic superconductors are used to connect the coils
to an external power supply. The new system is undergoing tests at the
Brigham and Women's Hospital in Boston. (Superconductivity News, 26 Jan
1994.)
A TRANSITION BETWEEN SPIRAL AND BULLS-EYE STATES has been observed in
Rayleigh-Benard convection experiments. Heating a thin fluid layer from
below will cause cells to form which exhibit patterns such as hexagons,
spirals, or bulls-eyes (target shapes). Research in this area has been
crucial in understanding pattern formation in general. Scientists at the
Weizmann Institute in Israel have been able to produce for the first time
a continuous transition (at conditions very near to the gas-liquid critical
point) between spirals and targets. Spirals and targets were even seen
to co-exist, suggesting that there might be a common physical mechanism
for producing the different patterns. Target and spiral spatio-temporal
patterns turned up in a number of chemical and biological systems. For
example, spiral electrical patterns have been measured in cardiac tissue.
(Michel Assenheimer and Victor Steinberg, Nature, 27 Jan 1994.)
THE PHYSICS JOB MARKET IS TIGHT FOR NEW PH'Ds . In 1992, for instance,
roughly 800 physics openings in the U.S. became available. Of these, 440
(representing 5.5% of the faculty) were at academic institutions; 175 were
at industrial labs (a turnover of 5%); and 180 were at national labs. Competing
for these jobs were many of the 1346 new PhDs (some of whom went abroad--see
Update 159) and a growing number of immigrant physicists from the former
Soviet Union. In the face of this physics jobs squeeze, the number of new
physics PhDs awarded each year in the U.S. has increased by 45% over the
past decade. One response to this dilemma, at Cornell University, has been
to retain some young PhDs as part-time lecturers and to reduce by a comparable
amount the number of new graduate student admissions. (Physics Today, Dec
1993.)
COBE RETIRES. Launched in November 1989, the Cosmic Background Explorer
was the first to discover fluctuations in the microwave background. A backlog
of data is still being analyzed, but the spacecraft was turned off 23 December
1993. (Sky & Telescope, March 1994.)
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