PHYSICS NEWS UPDATE A digest of physics news items prepared by Phillip F. Schewe, AIP Publ

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PHYSICS NEWS UPDATE A digest of physics news items prepared by Phillip F. Schewe, AIP Public Information Number 163 February 4, 1994 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.) CORRECTIONS. The two new intermetallic superconductors are Y-Pd-B-C and La-Ni-B-C (Update 162). The DUMAND neutrino detector seeks to observe not the low-energy neutrinos from the sun but the higher-energy neutrinos expected to come from active galactic nuclei (Update 157).


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