Number 22, February 21, 1991 by Phillip F. Schewe and Ben Stein|
CONDUCTANCE FLUCTUATIONS IN MESOSCOPIC METALS: When electrons flow through small (much less than a micron in size, but larger than atomic-sized--a size regime referred to as "mesoscopic") samples of disordered metal at low temperatures (less than 1 K) quantum effects can come into play: the wavelike electrons interfere with themselves. This results in a fluctuation in the conductance of the sample which exhibits "1/f noise," a condition in which the likelihood of a fluctuation of a certain size is inversely proportional to that size raised to some power. Shechao Feng of UCLA (213-825-8530) and Patrick Lee of MIT have shown that contrary to expectation the 1/f noise power actually increases as the temperature decreases. They also compare the current fluctuations to the speckle pattern one sees in the scattering of laser light. (Science, 8 Feb. 1991.)
FRACTAL SPACE-FILLING BEARINGS: "Is it possible to tile an infinite strip with wheels rolling on each other such that the entire area is covered with wheels?" Writing in the 24 Dec. 1990 issue of Physical Review Letters, Hans Herrmann of CEN Saclay (France) describes his model solution to this problem, which essentially amounts to the iterative process of filling the space between three touching circles with an infinite number of smaller circles. The resultant tiling pattern (studied since antiquity) has a fractal shape. Herrmann and his colleagues further require that all of the wheels are turning and that any two touching wheels turn in opposite directions. If one imagines the wheels to be mechanical bearings, Herrmann's model would entail rolling friction but not gliding friction. This property, Herrmann believes, may make his model useful not only for the study of gears but also in the study of plate tectonics and turbulence. (Physics World, Feb. 1991.)
THE DEUTERIUM-TO-HYDROGEN RATIO IS 120 TIMES HIGHER ON VENUS than on Earth. This finding by a group of astronomers from Paris, Caltech, Hawaii, and the Lowell Observatory (Barry L. Lutz, 602-774-3358) has implications for models of Venus' atmosphere. (Science 1 Feb. 1991.)
THERE ARE MORE TRANSISTORS ON EARTH THAN PEOPLE. In an article called "Quantum Mechanics in the Home," Jim Lesurf, a physicist at St. Andrews University in Great Britain, finds transistors everywhere: more than a million in personal computers, up to 1000 in a telephone, 200-300 in clock radios, 2000-3000 in dishwashers and washing machines, up to 5000 in a stereo, 10,000 in a TV, and 1000 in a VCR. (New Scientist, 19 January 1991.)
COMPUTERS IN PHYSICS CLASSROOMS are changing the way some university physics departments do business. The January/February issue of Computers in Physics features, in addition to several articles on the subject, a "Directory of Physics Courseware," a comprehensive listing of hundreds of college-level educational physics software.