A long and careful search for double beta decay (simultaneous emission of two electrons) appears to confirm that leptons are conserved. C. S. Wu, R. K. Bardin, P. J. Gollon and J. D. Ullman of Columbia have found 69 events that may be the kind expected if leptons are conserved—that is, events in which two electrons are emitted with two neutrinos. Meanwhile, in 1100 hours of observation, they found only one event that might be a double beta decay without neutrinos.

Besides its high-energy-physics research (PHYSICS TODAY, February, page 57) Argonne National Laboratory has strong programs in nuclear, atomic and solid-state physics, and it is building a high-flux research reactor. During a recent visit there we spoke to some of the people in charge of these programs.

George Gamow, professor of theoretical physics at the University of Colorado, died 20 Aug. after a long illness. A resident of the US since 1934 and a citizen since 1940, he was born in Odessa, Russia on 4 March 1904. He was educated in the Normal School in Odessa and at the University of Leningrad, where he received his PhD in 1928.

With the death of Otto Hahn on 28 July the world has lost one of the most significant and successful scientists of our century. His most famous discovery, the fission of the uranium nucleus, has basically changed the political and economic world picture. Perhaps this discovery and its results have been more debated than any previous scientific step forward. There has hardly ever been a scientist who has been so generally respected and loved. It would be unjust, however, when considering Otto Hahn's scientific achievements, to think only of this one great discovery, made at the age of nearly 60, although it was the conclusion and crowning of his scientific career.

On 22 May a group of the nation's most distinguished scientists—including four Nobel laureates—gathered at Columbia University to take part in a one-day symposium marking the retirement of Isidor I. Rabi. Rabi, himself a Nobel laureate, completed a career that spans nearly 40 years with Columbia.

Paul A. Flinn, a Carnegie-Mellon University professor, has received one of the two Argonne Universities Association Distinguished Appointment Awards for 1971. The award will enable Flinn, who is professor of physics and metallurgy and materials science, principal research metallurgical engineer and senior fellow at Mellon Institute of Science, to devote next year exclusively to the study of glasses and amorphous materials at Argonne National Laboratory. He will also receive a $5000 merit award.

The isomer shift in Mossbauer spectroscopy refers to changes in the resonance energy resulting from electric-monopole hyperfine interaction between the finite nuclear-charge distribution and the electron density at the nucleus. For a typical source-absorber experiment, the shifts depend on two factors: the difference in mean radii for the resonant nuclear levels and the difference in electron densities at source and absorber nuclei. Thus, any treatment of isomer shifts implicitly involves nuclear-structure considerations together with determinations of electron-charge distributions in condensed matter. For a given Mossbauer isotope, the nuclear factor is essentially constant and a determination of this quantity (by calculation or electrondensity calibration) allows observed isomer shifts to be interpreted, in principle, as relative electron densities at source and absorber. The isomer or chemical shift was first reported in 1960 by O. C. Kistner and A. W. Sunyar for the case of an «FeiOa absorber and source of Co 57 in stainless steel. This important feature of Mossbauer spectroscopy has motivated a significant amount of research during the ensuing years, and this work is authoritatively surveyed in the present volume.

Synchrotron radiation, with its remarkable properties and eminent suitability for scientific and technical applications, is having a profound effect on the many disciplines that make use of radiation in the x-ray and vacuum ultraviolet regions of the spectrum. Indeed, the rapidly increasing availability of this radiation is revolutionizing some fields and is leading to a variety of new interdisciplinary collaborations. Seeking to take advantage of this incisive tool, scientists around the world are requesting time at synchrotron radiation facilities in such large numbers that the fast-paced construction of new sources—including several in less-developed countries—has yet to bring the level of availability up to that of demand.

In May 1981, PHYSICS TODAY devoted a special issue to synchrotron radiation research. Four articles reviewed facilities, applications and the then newly developed wiggler and undulator sources. In the intervening two years there have been very significant changes in the nature and availability of synchrotron radiation sources. Five new facilities have begun operation, and a similar number of facilities already in operation have undergone major expansions. The nature of synchrotron radiation research has also changed significantly, as have our expectations. Consequently, PHYSICS TODAY will publish a series of articles describing these changes in detail.

At a number of construction sites around the world, crews are laboring in and around large circular tracks to install the accelerators and storage rings that will form the basis of new synchrotron radiation facilities. Most of the budding facilities are designed to produce synchrotron radiation, in the soft- or hard-x-ray regions, that is far brighter than available sources can provide. They are sometimes described as the "third generation." According to this rough categorization, the first generation consists of circular accelerators originally intended for other purposes: They provide synchrotron radiation to parasitic experiments or, in some cases, they have become partially dedicated to such uses. The second generation comprises facilities specifically designed to support synchrotron radiation experiments, with the radiation produced primarily as electrons or positrons curved in the field of the machines' bending magnets. The third-generation machines, by contrast, are designed to optimize the radiation that is produced as the electrons or positrons traverse devices known as wigglers and undulators. The new machines will complement existing facilities, and they will provide more opportunities for the growing user community.

Willlibald Jentschke, founder and the first director of the German Electron Synchrotron (DESY) laboratory and a former director general of CERN, died peacefully on 11 March 2002 in Göttingen, Germany.