摘要:

The study of nuclear magnetic resonance or nuclear induction, a recent field of research for which F. Bloch and E. M. Purcell have been awarded the Nobel Prize, has been carried out by a variety of techniques. The usual approach has been to observe the nuclear resonance of an ensemble of nuclear moments in a large static magnetic field as a function of a slow change in this field. Meanwhile, a small radio‐frequency field is applied continuously to the nuclear sample in a direction perpendicular to the large field. An alternative method to this steady state or “slow passage” technique is one by which the radio‐frequency energy is applied to the sample in the form of short, intense pulses, and nuclear signals are observed after the pulses are removed. The effects which result can be compared to the free vibration or “ringing” of a bell, a term often applied to the free harmonic oscillations of a shocked inductive‐capacitive (LC) circuit. The circuit is first supplied with electrical energy from some source, and the supply of energy is suddenly removed. The LC circuit then remains for a time in the “excited state”, and the energy is gradually dissipated into heat, mostly in the circuit resistance. Similarly the atom or nucleus in the excited state can store energy for a time before it is completely dissipated, and in the case discussed here, the free oscillation or precession of an ensemble of nuclear spins in a large static field provides the ringing process.

ISSN:0031-9228    

DOI:10.1063/1.3061075

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

Our understanding of the plastic behavior of solids has lagged well behind the knowledge gained in other branches of solid state physics. Electrical, thermal, elastic, magnetic, and optical properties are explained in terms of a few basic concepts such as the vibrations of atoms and the motion and spin of electrons. We understand fairly well what happens to the atoms and electrons when, for example, a metal absorbs heat or light or carries current in an electric or magnetic field. It is considerably more difficult, however, to discover what basic atomic mechanisms operate when a metal fractures or deforms plastically. Nevertheless the problems of strength and plasticity are highly important technologically and become more so with the increasing importance of jet engines, gas turbines, and other devices that require materials to withstand large forces at high temperatures.

ISSN:0031-9228    

DOI:10.1063/1.3061039

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3061040

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3061042

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3061048

出版商:AIP    

年代:1953

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3061050

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The special committee of scientists appointed last April to evaluate the functions and operations of the National Bureau of Standards has recommended that steps be taken to enlarge the bureau's basic programs relating to the accurate determination of physical constants, properties of materials, standards and standard practices, and testing and evaluation procedures. These programs, the group indicated, are all “essential services for our industrial society” which must be expanded if the nation's needs are to be met.

ISSN:0031-9228    

DOI:10.1063/1.3061052

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The third annual session of the Summer School for Theoretical Physics, which is located near Les Houches in the French Alps, was held from July 6 to August 29, 1953. As in preceding years there were thirty students, half of them French and most of the others from nearby European countries. Represented this year were Belgium, Germany, Great Britain, Italy, Sweden, Turkey, Ireland, Portugal, Egypt, and China.

ISSN:0031-9228    

DOI:10.1063/1.3061054

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

The Renaissance Society of the University of Chicago is planning, as one of its regular art exhibitions, a display illustrating artistic form in the scientific research laboratory. The exhibit will be composed of specimens, apparatus, photographs, models, records, and the like (including working demonstrations), all of which are to be indigenous to the laboratory though they will be selected by a group of artists solely on the basis of intrinsic form.

ISSN:0031-9228    

DOI:10.1063/1.3061055

出版商:AIP    

年代:1953

数据来源: AIP

摘要:

A List of forty‐seven contracts with universities and private research institutions for unclassified physical research has been made public by the Atomic Energy Commission.

ISSN:0031-9228    

DOI:10.1063/1.3061059

出版商:AIP    

年代:1953

数据来源: AIP