ISSN:0031-9228    

DOI:10.1063/1.2808150

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2808151

出版商:AIP    

年代:1995

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2808152

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In trying to understand the surprise, wonder and skepticism that have greeted the paper by David Thomson, Carol Maclennan and Louis Lanzerotti of AT&T Bell Labs in the 13 July issue ofNature, it helps to remember a few salient facts. First, the authors claim that the solar wind has components that oscillate in a coherent, stable manner. This claim contradicts the standard view that the solar wind is turbulent and possesses no long‐lived structures, other than those associated with solar rotation and structure.

ISSN:0031-9228    

DOI:10.1063/1.2808153

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have come to think that lasing requires an inversion of population between atoms in an excited state and those in a lower state: Normally the probability of absorption from the lower state equals the probability of emission from the higher state, so that the only way to have more photons coming out than going in is to start with more atoms in the upper state. It would be useful to decouple the probabilities of emission and absorption, so that one could lower the loss associated with absorption without reducing the emission.

ISSN:0031-9228    

DOI:10.1063/1.2808154

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Almost all beginning violinists generate the sound of a small woodshop when practicing low notes. Almost no professional musicians cultivate that scratchy rumble to produce definite tones of lower frequency than the violin is normally capable of. Yet such tones can be generated, and several investigators are trying to make sense of them.

ISSN:0031-9228    

DOI:10.1063/1.2808155

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The topography of the Earth is less well known than that of Mars or Venus, largely because about three‐fourths of it is hidden beneath the oceans, out of reach of direct observation by satellites. Now, however, the ocean‐floor topography of much of Earth's Southern Hemisphere has been revealed in an innovative map (see the figure on page 22), created by Walter Smith of the National Oceanographic and Atmospheric Administration and David Sandwell of Scripps Institution of Oceanography. Using the abundant gravimetric data collected by the ERS‐1 andGEOSATsatellites in combination with the few available ships' depth soundings, they have mapped the region between latitudes 30° S and 70° S with a finer resolution (better than 10 kilometers) than previously available. On the map, variations in hue represent altitude variations, or depth below sea level, as identified in the map scale, while changes in color saturation highlight the topography in light and shadow as it would appear when illuminated from longitude 0°.

ISSN:0031-9228    

DOI:10.1063/1.2808156

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

In 1987 the European Muon Collaboration, which had been scattering muons off polarized protons at CERN, shocked the particle physics community with the announcement that little or none of the proton's spin can be attributed to the spins of its three constituent quarks—two “up” quarks and one “down” quark. That report precipitated what became known as “the spin crisis.”

ISSN:0031-9228    

DOI:10.1063/1.881473

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Drop a pebble into a pond and the result is quite predictable: A circular wave expands out from the disturbance. Similarly, sound waves in the atmosphere radiate spherically from a point source. Vibrational waves in a solid medium, however, exhibit a much more intriguing behavior.

ISSN:0031-9228    

DOI:10.1063/1.881474

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Science, particularly physics, has been in a relatively privileged position in the United States since the end of World War II. Support by the government has been generous, and those of us whose careers have spanned the period since World War II have, until recently, seen research funding increasing in real terms. Our support rested on two assumptions: Science would improve the lives of the citizens, and science would make us secure in a world that seemed very dangerous because of the US‐USSR confrontation.

ISSN:0031-9228    

DOI:10.1063/1.881475

出版商:AIP    

年代:1995

数据来源: AIP