Number 20, February 5, 1991 by Phillip F. Schewe and Ben Stein
HYDROGEN REDUCTION OF RUBY may complicate the search for metallic hydrogen, which usually proceeds by placing a small sample of molecular hydrogen between the faces of a diamond anvil. Since these faces are very close together scientists sometimes add a small amount of ruby powder (Al2O3) to the hydrogen in an effort to reduce the resultant interferometric fringe pattern. Arthur Ruoff at Cornell (607-255-4161) has shown that at high pressures, hydrogen reduction of ruby produces the metal aluminum. This would confound an unambiguous measurement of metallic hydrogen. (Upcoming article in Physical Review Letters.)
EXPLOITING CHAOS RATHER THAN AVOIDING IT is the motto of a group of scientists at the Naval Surface Warfare Center in Maryland. Chaotic systems are sensitive to initial conditions: a tiny adjustment in the system may dramatically alter subsequent behavior. Conversely, it may be possible to bring some chaotic systems to heel through an active re-adjustment process. In this way the Naval scientists (William L. Ditto, 202-394-2774) recently stabilized the chaotic motions of a magnetoelastic ribbon (Physical Review Letters, 24 Dec. 1990). The theoretical groundwork for this feat was prepared by a group at the University of Maryland (Edward Ott, 301-454-3180; Phys. Rev. Lett., 12 Mar. 1990) who carried out computer simulation of chaotic systems. They believe that the control of chaos may not only be possible for physical systems, but that it may also be an important principle in biological systems as well. (Science News, 26 Jan. 1991.)
ERBIUM DOPED FIBER AMPLIFIERS (EDFA's) will soon facilitate the carrying of optical communications at gigabit rates over fiber links thousands of kilometers long. According to Emmanuel Desurvire of Columbia University, the use of erbium doping in small amounts in the optical fibers "makes it possible to distribute the gain over the fiber itself, thereby minimizing the power excursion of the signal. Such an approach makes possible virtually lossless signal transmission from one fiber network to the next." AT&T and the Japanese company KDD agreed recently to lay jointly a cross-Pacific cable capable of carrying 600,000 phone conversations simultaneously. In this case the optical signals will be amplified by EDFA's spaced every 20 to 30 miles. (Optics and Photonics, Jan. 1991.)
THE DISTANCE BETWEEN THE LARGE MAGELLANIC CLOUD and Earth has been measured more accurately than ever before. Observations of the ring of gas surrounding supernova 1987A---gas expelled by the precursor star thousands of years ago and later heated up by the supernova---using the Hubble Space Telescope to provide the angular diameter of the ring and using the International Ultraviolet Explorer satellite to provide the ring's diameter in space have resulted in an Earth-SN1987A distance calculation of 169,000 light years. This distance measurement technique may provide a better yardstick for measuring distances in the cosmos. (Physics Today, Feb. 1991.)
|
