ISSN:0031-9228    

DOI:10.1063/1.2995304

出版商:AIP    

年代:1979

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2995269

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

X‐ray crystallography provides information on the average structure of protein molecules. The images of atoms have always been broadened, but until the last few years this broadening was generally attributed to inaccuracies in the structure determination, lattice disorder and purely thermal vibration. Most crystallographers were skeptical about interpreting the temperature factors as structural motion. A typical small globular protein has a molecular weight of 20 000 a.m.u. and a diameter of 30–40 A˚.

ISSN:0031-9228    

DOI:10.1063/1.2995270

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Earlier this year observations of a close pair of visible astronomical sources previously identified with a quasar candidate from low‐resolution radio data appeared to indicate that the pair is actually a single object doubled by the effect of a “gravitational lens.” More recent radio observations make some difficulties for the hypothesis, but do not necessarily rule it out. The exact nature of the object(s) is thus still uncertain.

ISSN:0031-9228    

DOI:10.1063/1.2995271

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

In recent months, the 20‐armed Shiva laser system at the Lawrence Livermore Laboratory has attained a significant milestone on the road to the development of a laser‐fusion reactor. The Livermore group has reported that with target pellets of classified design Shiva has driven the deuterium–tritium fuel inside the pellets to between 50 and 100 times its liquid density. (With unclassified ablative targets they report achieving 10 to 20 times liquid density.) One hundred times liquid density is only an order of magnitude short of the densities that will be needed to achieve “scientific break‐even.” This goal, namely the release of as much fusion energy as the lasers deliver to the target (or the somewhat more modest goal of thermonuclear ignition), may well be achieved by Nova, the next generation laser system at Livermore, on which construction began in May.

ISSN:0031-9228    

DOI:10.1063/1.2995272

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The birds and bees do it and—yes—even bacteria in the seas do it. Species of all these organisms synthesize tiny crystals of magnetite. The demonstration of a direct link between this magnetic material and an orientational response for at least the simplest of these organisms—bacteria—has suggested the tantalizing possibility that the magnetic material found in the abdomen of honey bees and near the skull of pigeons may play a similar guidance role. Recent studies on the bacteria have identified the magnetic particles as crystals of magnetite that fall in the narrow size range for single domains—an optimal configuration.

ISSN:0031-9228    

DOI:10.1063/1.2995273

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Just about twenty years ago, at the Christmas, 1959, meeting of The American Physical Society at Cal Tech, Richard P. Feynman gave a delightful talk, “There's Plenty of Room at the Bottom.” He said at first that he imagined that experimental physicists must often look with envy at men like Heike Kamerlingh Onnes, who opened the field of low temperatures, which seems to be bottomless—one can go down and down, or Percy Bridgman who, in designing a way to obtain high pressure, opened up another new field—in which one can go up and up. Attainment of ever higher vacuum, he said, was a continuing development of the same kind. He then went on to say that he wanted “to describe a field, in which little has been done, but in which an enormous amount can be done in principle.” This was the field of miniaturization, the problem of manipulating and controlling things on a small scale.

ISSN:0031-9228    

DOI:10.1063/1.2995274

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A field such as microstructure science, which draws its practitioners and their techniques from a wide range of disciplines, needs a national center where research workers from different backgrounds can come together, where appropriate experimental equipment can be concentrated, and which can serve as an information resource for the nation's research community. Without such a center for microstructure research, a very noticeable gap was opening up between university research on the one hand and the accomplishments of industrial laboratories on the other, due mainly to the expensive equipment and the interdisciplinary nature of microstructure science and engineering. The National Science Foundation, sensing the widening gap, established a national facility for university research in this field in 1977. Currently housed in temporary quarters at Cornell University, in Ithaca N.Y., the facility is due to move its operations to a new laboratory on the Cornell campus in 1981. The purpose of this “focussed” facility is to stimulate university research by providing an equipment base for visiting scientists from other universities, as well as for resident Cornell scientists, who could not otherwise afford programs in microstructure research.

ISSN:0031-9228    

DOI:10.1063/1.2995275

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Extensive work on the fabrication of thin‐film microstructures began in the early 1960's when it became apparent that thousands or even millions of circuits could potentially be integrated into a single piece of silicon less than a centimeter on a side. In the years since, the potential has been realized, as one can see from figure 1, and has produced the well‐known dramatic growth of the microelectronics industry. The same technologies that make large‐scale integrated circuits possible also make possible a variety of other devices of scientific and technological interest, including magnetic bubble devices, high‐speed computer switching circuits based on the Josephson effect, surface acoustic‐wave devices, integrated optical circuits, Josephson microbridges and zone‐plate lenses for focusing soft x rays.

ISSN:0031-9228    

DOI:10.1063/1.2995276

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The scientific and technological achievements in the three decades following the invention of the transistor are unprecedented in the history of science. Accompanying and supporting this sparkling series of inventions and discoveries is a new industrial revolution that is still in the making. Microelectronics has achieved apparently miraculous results in both consumer and industrial products and services. A remarkable feature of these achievements has been that in almost every case, the microelectronic products have become steadily cheaper in an otherwise inflationary economy. Two major reasons for this deflationary effect are marketplace competition and the ever‐increasing capability to produce microstructures. The ability to construct thousands of devices already connected in a digital circuit and to build the circuit in the area used for a single device a decade earlier (see, for example, figure 1) can serve as a general example of the effect of microstructure capability on microelectronics.

ISSN:0031-9228    

DOI:10.1063/1.2995277

出版商:AIP    

年代:1979

数据来源: AIP