ISSN:0031-9228    

DOI:10.1063/1.2916122

出版商:AIP    

年代:1984

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2916075

出版商:AIP    

年代:1984

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2916076

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Might the fiery explosions from a massive nuclear war cast a cold and dark shadow over vast regions of the Earth? That gloomy possibility has been predicted by atmospheric chemists and physicists who have recently tried to quantify the environmental effects of the soot, dust and other emissions from a hypothetical nuclear exchange. The litany of known major effects from nuclear weapons—blast, fire, fallout and possibly stratospheric ozone depletion—always seemed horrible enough. Last year, Paul J. Crutzen (Max Planck Institute for Chemistry) and John W. Birks (University of Colorado) suggested that another effect might be severe enough to go on that list: the black curtain of smoke from fires initiated in a large‐scale nuclear attack. (SeePHYSICS TODAY, October 1982, page 17.) The new work now indicates that the phenomenon might be severe enough to lower temperatures over large regions of Earth below the freezing mark, even in summer, for perhaps months after a massive nuclear exchange. Richard Turco (R&D Associates), who participated in the study, has coined the phrase “nuclear winter” to describe the phenomenon.

ISSN:0031-9228    

DOI:10.1063/1.2916077

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In 1957 John Lawson at Harwell pointed out a crucial minimum requirement for the achievement of net power output from a deuterium–tritium plasma in any fusion device. No matter what the temperature, Lawson showed, a thermalized D–T plasma cannot put out more fusion power than the input power required to keep it hot unlessn&tgr;,the product of the ion density and the energy confinement time (often refered to as the confinement parameter or Lawson parameter), exceeds6×1013 sec cm−3.

ISSN:0031-9228    

DOI:10.1063/1.2916078

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Cooperative research ventures between industrial sponsors and universities are attracting increasing attention, not only because they offer benefits for both parties, but also because they promise to improve technology transfer for the nation as a whole. Yet there are risks inherent in such arrangements, as much recent press coverage suggests. This press attention reflects a concern that the needs of industrial sponsors for proprietary secrecy and other competitive advantages may undermine academic traditions of open scientific exchange. I shall examine these issues in the light of our experience with joint programs at MIT. I am not presenting MIT as a paradigm for success in this area, but we have had, perhaps, more experience with these arrangements than any other campus (see table, page 27); also, these are the arrangements with which I am most familiar. Our experiences at MIT have led me to conclude that the incentives for both parties must, from the outset, be clarified and assessed, for they are key to the evolution of a strong and healthy partnership. I shall also discuss means we have found useful for resolving areas of innate conflict between the industrial and academic perspectives, and I shall identify the kinds of conditions we have found essential for the long‐term success of these arrangements.

ISSN:0031-9228    

DOI:10.1063/1.2916079

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Speaking not as a historian but from a personal point of view, I would like to tell the story of the origin of the synchrotron as I saw it. The beginning, for me, was in the spring of 1945, when I was on the staff at Los Alamos, the wartime atomic‐bomb laboratory. The Trinity test was in preparation, and I was already thinking about what to do on my return to Berkeley—from which I was on leave—after the war ended. I had spent a great deal of time and effort before the war on the design and operation of cyclotrons, I had a reasonably good understanding of the limits on the particle energies attainable by cyclotrons, and it seemed like a worthy goal to find ways to exceed these limits. The cyclotron, as you know, is a resonance accelerator; it pushes particles to high energies by the repeated application of a moderate voltage, which must be applied at the proper instant each time the particle comes around in its circular orbit.

ISSN:0031-9228    

DOI:10.1063/1.2916080

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A key insight, gained almost accidentally during the investigation of a modest problem in a small area of physics, occasionally assumes a significance far beyond the original relevance and touches almost the entire discipline. Of such stuff is a great discovery sometimes made. A good example is the discovery of x rays by Wilhelm Ro¨ntgen. Another is the discovery of recoil‐free gamma rays by Rudolf Mo¨ssbauer, just over 25 years ago, in 1958. Like Ro¨ntgen, Mo¨ssbauer was a Bavarian. Working at the University of Heidelberg on a mundane experiment of interest only to nuclear physicists, Mo¨ssbauer happened onto an elegant effect that enables the measurement of extremely small energy shifts of nuclear gamma rays. The discovery immediately attracted widespread interest and became a technique of great usefulness for such fields as solid‐state physics, chemistry, biophysics and metallurgy, besides providing an ultrafine instrument for investigating subtle effects predicted by quantum mechanics and general relativity. That it was made while Mo¨ssbauer was still a graduate student—and earned him a Nobel prize only three years later—also made it one of the most romantic episodes in postwar physics.

ISSN:0031-9228    

DOI:10.1063/1.2916081

出版商:AIP    

年代:1984

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2916082

出版商:AIP    

年代:1984

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2916083

出版商:AIP    

年代:1984

数据来源: AIP