ISSN:0031-9228    

DOI:10.1063/1.2806667

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881788

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881791

出版商:AIP    

年代:1997

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.881789

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

After decades of looking in vain, astronomers have finally found the optical and x‐ray “afterglow” of a gamma‐ray burster (GRB), together with a fuzzy object that may well be its parent galaxy. Of the several thousand GRBs that have been recorded by orbiting gamma detectors since the early 1970s, the one detected by the Italian‐Dutch BeppoSAX satellite on 28 February is the first, and so far the only one, for which a transient or persistent counterpart has been identified at any other wavelength.

ISSN:0031-9228    

DOI:10.1063/1.881761

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Twelve years ago, Richart Slusher and his colleagues at AT&T Bell Labs produced light whose noise was below the vacuum quantum fluctuations, at least in part of the signal. Since then, researchers have been trying to squeeze the uncertainties out of other systems as well. So far they have succeeded in quieting a classical mechanical oscillator and both classical and nonclassical states of a vibrating, trapped ion. Now comes a report of squeezed phonons: By striking a crystal with a femtosecond laser pulse, a group at the University of Michigan believes it has excited an acoustic mode whose variance falls below the standard quantum limit. So far, the noise has been reduced by only 0.01&percent; (the earliest experiments on optical squeezing yielded 20&percent;), but just the concept of squeezed phonons has intrigued many observers.

ISSN:0031-9228    

DOI:10.1063/1.881762

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

What can be done with radioactive waste? This extremely difficult question has not really been answered anywhere in the world; yet it must be answered. Like death and taxes, radioactive waste is with us—it cannot be wished away. This special, five‐article issue ofPHYSICS TODAYreviews the technical problems and risks, outlines the reasons why the basic question posed above has not been answered and suggests some possible new approaches that could enable us to make progress.

ISSN:0031-9228    

DOI:10.1063/1.881792

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Exposure to radioactivity is not a new phenomenon: Jewelry workers painting luminous dials on watches in the 1920s were exposed to radium, a naturally occurring radioactive element, until its dangers were identified; in recent decades, homeowners have worried about radon, a naturally occurring radioactive gas that can adversely affect both their health and the resale value of their homes. Today, we must worry as well about the enormous quantities of anthropogenic radioactive materials that have accumulated as waste in this country and worldwide since the 1940s, largely because of the nuclear weapons programs and nuclear power plants. Some of the anthropogenic material is still valuable—for example, as fuel for nuclear reactors. Vast amounts of it, however, consist of waste. Radioactive waste, by definition, is unneeded material that contains unstable elements that decay by emitting alpha, beta or gamma emissions. This article describes the sources of this waste, the types of waste that are of concern and the amounts estimated to be present in the US.

ISSN:0031-9228    

DOI:10.1063/1.881763

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this sixth decade of the nuclear age, the US and many other nations face daunting technical challenges to the disposal of nuclear waste. There are many contributing factors, not the least of which are the sheer volumes of waste and the great number of chemical and physical forms in which it exists at defense and civilian sites both here and abroad. (See figure 1, for example, and see also John Ahearne's article on page 24.)

ISSN:0031-9228    

DOI:10.1063/1.881764

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Although it is arguably for the benefit of society, the translation of basic nuclear processes into technological achievements produces nuclear wastes that can become environmental hazards if they are not properly cared for. Light‐element fusion, heavy‐element fission and radioactive decay have provided us with nuclear weapons, nuclear power plants and nuclear medicine. But they all produce radioactive materials that are unusable, no longer needed, or unwanted. Ultimately, these materials require long‐term isolation from the biosphere.

ISSN:0031-9228    

DOI:10.1063/1.881765

出版商:AIP    

年代:1997

数据来源: AIP