Number 16, January 10, 1991 by Phillip F. Schewe and Ben Stein
IN BALLISTIC ELECTRON EMISSION MICROSCOPY (BEEM) , an elaboration of scanning tunneling microscopy (STM), electrons (with sufficient energy) from the probe behave ballistically and are able to penetrate a sample consisting of a thin metal film and beneath it a thin semiconductor layer. The measured current provides information about atomic details of the metal-semiconductor boundary; this should help in the design of electronic devices. By using an even higher voltage than is needed to image the boundary layer, scientists at Cornell University (Robert A. Buhrman, 607-255-3732) found that they could inscribe lines (8.5 nm wide) in the boundary layer without disturbing the outer surface of the metal layer above. (Science News, Jan. 5.)
THE FAR SIDE OF THE MOON , impossible to see from the Earth, was recently photographed by the Galileo spacecraft on its way toward Jupiter. New information about the mineralogical composition of the far side's crust was recorded and pictures revealed the largest impact basin yet seen on the moon, more than 2000 km in diameter and so deep that is may have penetrated through the crust to the moon's mantle. (Eos, January 1, 1991.)
SELF ORGANIZED CRITICALITY is the name for the tendency in many large interactive systems to evolve toward a critical state in which a minor event can lead to a chain reaction or catastrophe. According to Brookhaven scientist Per Bak (516-282-3798), the global properties of some composite systems---such as earthquake faults, sandpiles, the stock market, or weather fronts---cannot be understood by studying only parts of the system and that "self organized criticality is the only model or mathematical description that has led to a holistic theory of dynamical systems." Computer modeling has revealed that one characteristic of self organized criticality is a manifestation of a power-law relation; for example, the rate of earthquakes with an energy E is proportional to E raised to a certain power. (Scientific American, January 1991.)
THE LARGE HADRON COLLIDER (LHC) has received the endorsement of the European Committee for Future Accelerators as the best next step in particle physics for Europe. LHC, which would be built in the tunnel of the existing LEP electron-positron collider at CERN, is designed to provide proton-proton collisions at 8 TeV per beam. (Cern Courier, December 1990.) The CERN Council, which governs CERN's activities, will study the LHC proposal further. CERN Director General Carlo Rubbia has said that the LHC can be built sooner (by as early as 1998) and for far less money than the SSC and that its more intense beam will make up for the fact that its maximum energy is lower than SSC's 20 TeV per beam.
WOMEN RECEIVED 8% OF THE PHYSICS PHD's in America in 1988/89, the most recent period sampled in a report issued by the AIP. Of the 1112 doctorates granted in 88/89 39% went to foreign citizens. Among the total of 13,361 physics graduate students that year, 4610 listed condensed matter physics as their research subfield, while particle physics had the second highest number with 1605. (Contact Susanne Ellis, AIP Education and Employment Statistics Division, 212-661-9404.)
|
