摘要:

Lately, for the first time, a technique for taking motion pictures of electron microscope images has been developed which is proving useful in the study of some of the effects of electrons upon matter and particularly upon colloidal crystals. Resolution of 150 to 300A is achieved and is suitable for a host of practical electron microscopical problems. Pictures are taken from outside the instrument, utilizing the radiation emitted by the fluorescent screen. Some instrument adaptation is required for adequate illumination, and precautions must be exercised against toxic x‐ray dosages.

ISSN:0021-8979    

DOI:10.1063/1.1699780

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Phenomena not seen or recorded by orthodox methods are observed on the large number of micrographs which are taken during a motion picture experiment, and reaction times as short as 0.03 sec. can be calculated. The technique is useful for investigating solid‐liquid‐solid changes both by direct observation and by recording Bragg reflections. In most cases a preliminary effect of electrons upon crystals is to drive off water. In the case of sodium chloride crystals a residual envelope is left. Inside this, small particles, both solid and liquid, are observed to move rapidly due, it is believed, to a combination of Brownian movement and convection. These gradually evaporate and diffuse through the wall. The possibility is discussed that the residual envelope is formed by contamination. Examples are also taken from bombarded, colloidal crystals of tungsten oxide.

ISSN:0021-8979    

DOI:10.1063/1.1699781

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Emissivity calculations have been carried out for nitric oxide at temperatures from 300°K to 3000°K. The results may be used, as a first approximation, at elevated total pressures.

ISSN:0021-8979    

DOI:10.1063/1.1699782

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

In the ordinary simple microscope, the same light is permitted to flow through the entire system. A more general microscope can be devised in which light of one wave‐length is permitted to flow as far as the diffraction image of the object, then light of a second wave‐length is substituted at this plane, and continues to flow through the rest of the optical system. It is shown that for such a generalized microscope, the magnification depends not only on the ordinary image‐to‐object distance ratio, but also on the ratio of wave‐lengths used. Utilizing x‐rays and visible light, this second factor is about 104diameters, and the whole magnification is of the order of 3×105. This is enough to permit one to see an atom. Apparatus has been built which realizes this theory. A most important characteristic of any such system is that a loss of phase occurs at the first diffraction image, where the wave‐length substitution takes place. This phase must be supplied by the apparatus. It is accomplished with the aid of phase shifters prepared from a large uniform mica cleavage fragment. The apparatus and the results achieved with it are described.

ISSN:0021-8979    

DOI:10.1063/1.1699783

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

At first, the description of the energy cycle of the mature tropical storm is amplified on the basis of recent upper air observations. Air particles passing through such a storm at first undergo isothermal expansion as they move toward a center. Then they ascend with release of condensation. At high levels they move outward and mix with the environment giving off heat to the surrounding colder air. Several requisites for maintenance of the observed temperature field are stated.After a discussion of previous theories of hurricane formation the proposed model is described. The initial intensification of the wind field is brought about by mass divergence at high levels that imposes a pressure reduction on the surface layers. This divergence is the result of interaction between the large‐scale disturbances of the upper air inside and outside the tropics. A solenoidal circulation is initiated that acts in the kinetic energy producing sense. But this circulation contains an internal mechanism for its own destruction and is maintained only under certain special conditions which are stated.

ISSN:0021-8979    

DOI:10.1063/1.1699784

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

Stress functions are given for forty nuclei of strain in the semi‐infinite elastic solid. The corresponding stresses have the property that the traction vanishes across the plane boundary of the solid. The nuclei are derived, by processes of superposition, differentiation and integration, from the solution of the elasticity equations for the single force in the interior of the semi‐infinite solid.

ISSN:0021-8979    

DOI:10.1063/1.1699785

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

The solution of the elasticity equations for the center of dilatation in the semi‐infinite solid is introduced into Goodier's theory of thermoelastic stress. It is shown that the problem of potential to be solved is identical with that for the solid of indefinite extent. The results are applied to the case of an expanding (or contracting) spherical inclusion embedded in an elastic body near its surface.

ISSN:0021-8979    

DOI:10.1063/1.1699786

出版商:AIP    

年代:1950

数据来源: AIP

摘要:

A method is presented for the solution of ordinary linear differential equations with constant coefficients. This method stays wholly in the time domain and obtains a general solution in a compact form including the effects of initial conditions. The differential equation as treated involves a driving function made up of the sum of terms involving the system input and its derivatives. The general solution is also given in terms of weighting functions operating on the input (in the driving function) and including outside the weighted integral, terms involving initial conditions of the input as well as the dependent variable.

ISSN:0021-8979    

DOI:10.1063/1.1699787

出版商:AIP    

年代:1950

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1699789

出版商:AIP    

年代:1950

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1699790

出版商:AIP    

年代:1950

数据来源: AIP