emissia.offline  ART 018

Physics News Update #241

(Новости Физики - бюллетень Американского Института Физики)


Бюллетень 'Physics News Update' регулярно подготавливается сотрудниками Американского Института Физики: Mr. Phillip Schewe и Mr. Ben Stein.

Бюллетень 'Physics News Update' транслируется по каналу 'sci.physics.research' c адреса (vjejjala@wam.umd.edu) Mr. Vishnu Jejjala, Университет штата Мэриленд.

С разрешения авторов-составителей, Mr. Phillip Schewe и Mr. Ben Stein и составителя е-mail версии, Mr. Vishnu Jejjala бюллетень ретранслируется петербургским образовательным сервером EDU@EMISSIA на английском языке либо в русском переводе:


The American Institute of Physics Bulletin of Physics News by Phillip F. Schewe and Ben Stein

ELECTRON BALLS: Hans Dehmelt and his colleagues at the University of Washington have imprisoned a tiny spherical drop of 1000 electrons in an atom trap. Such a miniature single-component plasma (consisting of only negative charges without any positive charges) acts like a pointlike object with an electrical charge and mass 1000 times that of an ordinary electron. Dehmelt (206-324-2018) won a Nobel Prize for his pioneering work with atom traps and has in the past monitored single electrons and positrons for months at a time. The most serious limitation to the precision of measurements of the electron's magnetism in this "geonium" atom (an "atom" consisting of the single electron and the trap, or, in a wider sense, the whole world) is the presence of a small unknown perturbation, namely the interaction between the electron and its image charge (a sort of mirror image of itself) that it induces in the electrodes of the trap. The perturbation was too small to measure for a single electron, but became detectable in the case of the 1000-electron drop. The kilo-e, as the Washington scientists refer to their electron ball, may be useful in other research areas, such as plasma physics. (Richard Mittleman et al., upcoming article in Physical Review Letters; journalists can obtain copies from AIP at physnews@aip.org)

HARVARD HAS THE BEST PHYSICS DEPARTMENT. A new study prepared by the National Research Council rates graduate programs at U.S. universities according to their scholastic quality and by the quality of their PhD preparation. Naturally, a few elite universities show up well in many categories. For example, 35 of Berkeley's 36 rated departments showed up on top-ten lists. The list of best physics departments in descending order of research quality is as follows: Harvard, Princeton, MIT and Berkeley, Caltech, Cornell, Chicago, Illinois, Stanford, and Santa Barbara. Besides ranking the departments, the NRC report provides a ledger full of data about the complexion of university physics. For example, the departments with most graduate students enrolled in Fall 1992 are as follows: MIT, 315; Illinois, 295; Berkeley, 283; and Texas, 239. The rank according to the number of PhDs granted during the period from 1987/88 to 1991/92: MIT, 196; Illinois, 174; Berkeley, 169; Texas, 156; Cornell, 142. Further facts pertaining to the top quarter (consisting of 36 universities) of the departments surveyed---greatest percentage of female PhD recipients: CUNY, 15%, followed by Harvard, Carnegie Mellon, and Indiana with 14%; the lowest female PhD output was at Princeton, with 3%. The percentage of PhDs that were minority students: CUNY at 14%, Rutgers at 9%, and MIT at 7% were high; several universities awarded no PhDs to minority students. As for PhD recipients who were US citizens or permanent residents, the highest percentages were at Berkeley (86%) Cornell (82%), Illinois (79%), and Stanford (78%); the smallest US percentages were at CUNY (25%) and Rutgers (40%). Among top- quarter departments, the median number of years for earning the PhD ranged from a low of 6.1 at Princeton to a high of 8.8 at CUNY. Mean values for other selected characteristics at top-quarter universities---total faculty members, 49; total graduate students, 150; female students, 13%; PhDs in the period 1987-1992, 85; female PhDs, 8.9%; minority PhDs, 2.9%; US PhDs, 60.8%; median years for earning PhD, 7.2. ("Research-Doctorate Programs in the United States," National Academy Press.)

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