ISSN:0031-9228    

DOI:10.1063/1.2811486

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2811488

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2811490

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Last August, in the dark of the Antarctic winter, more than 100 scientists descended to the southern tip of the globe, some to monitor the stratosphere from airplanes flying high above Antarctica, others to sample it with balloons and remote sensing equipment from ground stations on the continent. The massive assault was an urgent effort to determine the cause of the ozone hole—the depletion of ozone in the lower stratosphere that has occurred with increasing severity each spring since the mid‐1970s. After analyzing their data, these scientists reconvened last May in Snowmass, Colorado, to present for the first time all the details of their findings. The extensive new data leave no doubt that man‐made chlorofluorocarbons are primarily responsible for the ozone hole. They elucidate more clearly than ever before the unique wintertime meteorological conditions that allow chlorine compounds from these CFCs to destroy virtually all the ozone in the lower stratosphere over the Antarctic: The ice clouds that form in the dry, frigid stratosphere seem to facilitate chemical reactions that free chlorine atoms from those compounds in which they are normally trapped. The freed chlorine atoms can then ravage the ozone. Although this general hypothesis was gaining wide support even before the recent expedition, the new data put it on firmer grounds and allow the specialists to start filling in the details.

ISSN:0031-9228    

DOI:10.1063/1.2811491

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2811492

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Is there really a “fifth force”? Since Purdue particle theorist Ephraim Fischbach and his colleagues dusted off the 80‐year‐old data of Roland von Eo¨tvo¨s three years ago, pointing out that this classic test of the equivalence principle hinted that all was not well with Newtonian gravity, a broad array of physicists have been investigating the possible existence of a force weaker than gravity, with a finite macroscopic range. A lonely band of geophysicists had been gathering evidence of such a force in Australian mine shafts since 1981. (SeePHYSICS TODAY, October 1986, page 17.) But the jury is still out.

ISSN:0031-9228    

DOI:10.1063/1.2811493

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Noncrystalline condensed matter presents contemporary physics with a number of basic questions. Traditional solid‐state physics has emphasized the study of periodic systems, whose energy levels may be labeled by the wavevector. The concept of reciprocal space, or of allowed wavevector values, therefore provides a convenient and consistent framework for describing electronic, vibrational and magnetic properties of crystalline solids in terms of energy bands. In a nonperiodic system, the concept of a wavevector is not valid. The need for a fundamental concept that might be useful in the study of nonperiodic systems therefore forces us to focus attention on structural configurations in real space.

ISSN:0031-9228    

DOI:10.1063/1.881123

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

In 1930 solid‐state physics did not exist. The very term was unknown; nor was there any intellectual or social entity to which the term could have applied. Certainly there flourished a number of specialties—for example, the electron theory of metals—that would eventually fall within the field of solid‐state physics. However, there was no feeling that physicists who studied solids should be distinguished as a group from those who studied gas spectra, for instance, or nuclear reactions. Thirty years later the situation had entirely changed. The term “solid‐state physics” not only was familiar in 1960, but could be attached to a number of institutions: university chairs, journals, research groups and even buildings devoted entirely to the subject.

ISSN:0031-9228    

DOI:10.1063/1.881124

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2811494

出版商:AIP    

年代:1988

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2811495

出版商:AIP    

年代:1988

数据来源: AIP