ISSN:0031-9228    

DOI:10.1063/1.2405499

出版商:AIP    

年代:1900

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.1325179

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Twenty‐five years after the discovery of the tau lepton(&tgr;±),its neutrino(&ngr;&tgr;)has at long last been detected. At a Fermilab seminar in July, Byron Lundberg of the international DONUT (Direct Observation of Nu Tau) collaboration reported that five months of exposing a photographic‐emulsion target to an intense neutrino beam from the Tevatron had netted four identifiable&ngr;&tgr;interactions.

ISSN:0031-9228    

DOI:10.1063/1.1325185

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The trillion or so neurons in our brains are input‐output devices. Feeding each neuron with information is a tree‐like body of fine filaments called dendrites, whose trunk originates at the neuron's cell body or soma. Also attached to the soma is the axon, which carries the processed information to other cells—mostly the dendrites of other neurons via junctions called synapses.

ISSN:0031-9228    

DOI:10.1063/1.1325186

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Superconducting wire is a central part of many of the applications devised for high‐temperature superconductors in the 15 years following their discovery. With transition temperaturesTcabove the boiling temperature of liquid nitrogen (77 K), these superconductors have the potential to provide cheap, low‐loss wires capable of carrying large currents. The technological realization of this potential has been difficult, however, due in part to the anisotropic character of the ceramic high‐Tcmaterials. Although single crystals of high‐Tcsuperconductors have high critical current densities—the figure of merit in wire applications—polycrystalline wires suffer from significantly reduced current‐carrying ability.

ISSN:0031-9228    

DOI:10.1063/1.1325187

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Experiments designed to probe differences between matter and antimatter using low‐energy antiprotons have been on hold since CERN shut down its Low‐Energy Antiproton Ring (LEAR) in December 1996. But the progress made at LEAR motivated the construction at CERN of a $5 million new facility, the Antiproton Decelerator (AD) (see PHYSICSTODAY, March 1996, page 17; November 1996, page 9; and May 1997, page 19). The photo shows the dipole (red) and quadrupole (blue) magnets in a section of the new ring. Antiprotons enter from the transfer line on the right.

ISSN:0031-9228    

DOI:10.1063/1.1325188

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

It is little appreciated, even in William Lanouette's excellent biography, that Leo Szilard worked as a professional inventor during most of his scientific career, constantly filing patent applications that covered an astonishingly large range of novel ideas.

ISSN:0031-9228    

DOI:10.1063/1.1325189

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The recent achievement of compact blue‐emitting gallium nitride semiconductor lasers is likely to have far‐reaching technological and commercial effects. The lasers' short wavelengths—around 400 nm, half that of gallium arsenide‐based lasers—permit higher spatial resolution in applications such as optical storage and printing. And the high photon energy will open up new applications for these inexpensive, compact light sources. An aesthetic satisfaction with these devices stems from finally extending the existing and mature semiconductor laser technology for the near‐infrared and red to encompass the “new frontier” blue and near‐ultraviolet regions, thereby bridging the entire visible spectrum. At the same time, there are significant research opportunities arising from a plethora of poorly understood microscopic issues in the underlying material system, which include such fundamental properties as charge control, transport, and formation of optical gain for stimulated emission.

ISSN:0031-9228    

DOI:10.1063/1.1325190

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

At the end of the 20th century, a large “science gap” still exists between Latin America and the developed countries of the North. One major reason for this disparity is economic: Poor economic conditions in most Latin American countries have seriously restricted their capability to invest in science and technology. However, the rich natural resources of the region—including oil, copper, nickel, cobalt, and other minerals—provide a solid economic base, and many countries are following the examples of Brazil, Mexico, and Argentina in recognizing that scientific research and technological development are necessary to achieve social and cultural progress. At present, prospects look good for growth in science and technology during the next century.

ISSN:0031-9228    

DOI:10.1063/1.1325191

出版商:AIP    

年代:1900

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.1325192

出版商:AIP    

年代:1900

数据来源: AIP