ISSN:0021-8979    

DOI:10.1063/1.1707286

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707287

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707288

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707277

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The change in length of a Vinylite plastic under constant load has been measured, as well as for the succeeding recovery. The change in color of the light transmitted through crossed Polaroid plates shows large change in the birefringence. The further study is made with uniform length increments at constant temperature using Mach's method to measure the birefringence, both for stretching and recovery. The data are sufficient to give a measure of the dispersion in birefringence and of a Poisson's ratio of 0.50.

ISSN:0021-8979    

DOI:10.1063/1.1707278

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

Viscosity‐pressure‐temperature data are presented for six Pennsylvania oils which differ in chemical and physical properties at atmospheric pressure. This study is a continuation of one reported previously and employs the same apparatus and experimental method. While the pressure coefficient of viscosity increases in general with molecular weight, the relationship seems to be significant only for fractions of a narrow boiling range from a single oil. The mean temperature coefficient of viscosity, between 100° and 210°F, however, increases with molecular weight at all pressures for all the oil samples.

ISSN:0021-8979    

DOI:10.1063/1.1707279

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

Light output and screen potential data are given for zinc sulphide, calcium tungstate, willemite and several other silicate phosphors sprayed (from suspension) on Nonex glass and bombarded by electrons. The bombarding voltage range from 0.5 to 10 kilovolts is covered. The limiting potentials of willemite and other zinc silicate screens fall in the range from 6 to more than 10 kilovolts depending on the conditions of exhaust and preparation. The limiting potentials of two zinc sulphides fall in the range from 6 to 9 kilovolts while calcium tungstate has a limiting potential usually less than 5 kilovolts. Light output as a function of screen voltage over the range from 0.5 to 10 kilovolts is shown to follow a law of the form:L=Af(i)Vn,whereLis intensity of light,iis current density,Vis electron energy at the screen in kilovolts, andAis a constant. The data show thatn<2 for willemite or other zinc silicates,n=2 for sulphides, andn>2 for calcium tungstate and a fused layer of willemite. Analysis and comparison of the light output current density characteristic and the persistence characteristic shows that a definite relation exists between them in the case of silicate phosphors. The function of current density may be represented byf(i)=Ai(1−(a/(a+b))e−&agr;/Bi−(b/(a+b))e−&ggr;/Bi).The constant &agr; and &ggr; are those appearing in the persistence characteristics of the material as:L=(a/(a+b))e−&agr;t+(b/(a+b))e−&ggr;t,a formula which expresses well the persistence of silicate screens.

ISSN:0021-8979    

DOI:10.1063/1.1707280

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

Rashevsky's theory of nerve conduction has been extended to include the effects of distributed capacitance along the fiber. The simple theory of Rashevsky, based on the idea of local re‐excitation by bioelectric currents according to Blair's law of excitation, leads to a formula for the initial velocity of the nerve impulse:v=aklogA0/(A0−R),whereais the distance between Ranvier nodes,kis related to the chronaxie of the nerve,A0, is the local exciting current, andRis the threshold for excitation. This result does not depend explicitly onG, the node leakance. The present analysis gives for the initial velocity, in caseG/C»k,v=aklogA0/(A0−(R+A0&psgr;)),where &psgr; is a complicated function ofCand vanishes whenC=0. In caseG/Cis not »k, the velocity is given as the root of a transcendental equation which may be solved graphically. Formulae for the asymptotic velocity of propagation are similarly related in Rashevsky's and the present case. Empirical data necessary to check the validity of these results are as yet unavailable; the type of experiments needed to obtain these data are suggested.

ISSN:0021-8979    

DOI:10.1063/1.1707281

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

A solution of the nonlinear problem of the rate of ice formation on a long cylinder whose surface temperature is variable (but always below 0°C) is given. The first‐order correction to the steady‐state solution is evaluated and found to be small. As an example, application is made to a specific problem in freezing soil.

ISSN:0021-8979    

DOI:10.1063/1.1707282

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707283

出版商:AIP    

年代:1939

数据来源: AIP