ISSN:0021-8979    

DOI:10.1063/1.1712890

出版商:AIP    

年代:1941

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1712891

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Carefully prepared test bars of 17S‐T aluminum alloy have been fatigued; x‐ray diffraction patterns of each specimen were taken at intervals as fatiguing progressed. Approximately thirty different test bars have been studied. Seven series of diffraction patterns, corresponding to seven different specimens, are reproduced and discussed in this paper. This study shows that (1) fatigue failure of 17S‐T aluminum is always preceded by fatigue damage which is detectable by the use of x‐ray diffraction patterns; (2) nearly all of the detectable changes occur in the last stages of fatiguing and consist of rotation of grains, introduction of strains in some of the crystallites, and fragmentation of some of the crystallites; (3) these changes do not occur when the specimen is fatigued below its endurance limit, but always occur prior to failure when it is fatigued above the endurance limit; (4) failure is probably intercrystalline rather than intracrystalline in character.

ISSN:0021-8979    

DOI:10.1063/1.1712892

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Use has been made of the radioactive properties of colloidal thorium dioxide, intravenously injected into rabbits, to study the functional capacity of the reticulo‐endothelial cells for phagocytosis. A mathematical analysis of the problem is presented which indicates that when the system is not overloaded, the foreign material should be removed from the blood according to the relationn=n0e−at+b2&agr;n0e−bt.Herea≫bandnis the number of particles remaining in the blood at any timet. Experiments on 13 rabbits substantiate this prediction. With a standard injection of 1 cc of colloidal thorium dioxide per kilogram of body weight,ndecreases according to three distinct exponential relations. The system is apparently overloaded initially, but afterndecreases to about one‐sixth its initial value (att=0), the fraction of the amount of material present that is removed in unit time increases and the rest of the curve follows the predicted relation. The fact that the system is initially overloaded was checked by the use of smaller amounts of thorium. In all cases more than 99 percent of the thorium was removed from the blood stream within 6 or 8 hours after the injection. The technique reported here should serve as a basis for testing many theories of phagocytosis now largely based on deduction.

ISSN:0021-8979    

DOI:10.1063/1.1712893

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

pH measurements on sludge of particulate carbonaceous materials and ash were made with a vacuum tube potentiometer amplifier. Dust, precipitated out of flue gas of industrial fuel burning plants through the use of the series impinger, givespH values of sludge in the range 2.5 to 5. Sludge of ash of coal used in these tests givespH values in the range 7 to 11.5, depending upon the seam and locality in which the coal is mined. The results of this study may aid the ``fingerprinting'' of dust, responsible, in part, for atmospheric pollution in American cities.

ISSN:0021-8979    

DOI:10.1063/1.1712894

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

The measured mass absorption coefficients of Allen and Wrede for H, Be, C, N, O, F, Na, Al, Si, Cl and Br have been fitted to the ``universal law''&mgr;/&rgr;=a&lgr;n+c/(1+0.048/&lgr;),by least squares, and the values ofa, n, andctabulated. The energy distribution in the continuous x‐ray spectrum in the range from 20 to 70 kv, as measured by Kirkpatrick and by Ulrey, has been recomputed, and presented graphically in a form which permits easy interpolation. The recomputation of Ulrey's data is described in some detail.

ISSN:0021-8979    

DOI:10.1063/1.1712895

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Experiments relating to mercury‐pool stroboscope tubes with external starting bands are described. Of particular interest is the unidirectional current that is found to flow in the plate circuit when grounded and its relationship to the formation of a cathode spot on the mercury cathode. Cathode‐ray oscillograms are exhibited showing the periodic nature of this current. The potential of a disconnected electrode is negative with respect to the cathode and has a value of several thousand volts. Curves of the volt‐ampere characteristics of an anode are given as a function of tube dimensions, gas pressure and other factors.

ISSN:0021-8979    

DOI:10.1063/1.1712896

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

Qualitative measurements are made on the reduction of breakdown strength of certain solid, liquid, and gaseous insulations. The observed reduction in breakdown strength is influenced by the gap length as well as the quantity of the x‐rays. Exposing a solid to air boundary to x‐rays increases the flashover voltage. A theory for this effect is offered.

ISSN:0021-8979    

DOI:10.1063/1.1712897

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

A rigorous solution of Maxwell's equations is derived for waves in a thin single‐layer coil, a concentric ground electrode being at a short distance from the coil. Simple transformer coils resemble such an ideal to a considerable degree. Any electromagnetic state of the coil propagates slowly in axial direction with such a velocity that the phase velocity along the helical conductor equals the velocity of light. The surge impedance of the coil is constant for low frequency, but decreases with higher frequency, the boundary wave‐length being determined by the insulating distances.

ISSN:0021-8979    

DOI:10.1063/1.1712898

出版商:AIP    

年代:1941

数据来源: AIP

摘要:

The object of this investigation is a study of the current distribution in or on the surface of a conductor and its associated field under the influence of a localized e.m.f. Steady‐state solutions of the field equations are found for conductors of simple geometric form. The results clarify many electromagnetic problems involving localized sources, especially in theu‐h‐fregion, for which ordinary circuit theory fails to give a satisfactory quantitative explanation. Part I treats the problem of a straight cylindrical conductor and shows the relation of the principal and complementary waves to the nature of the exciting field. A driving point impedance is calculated for the case of an external field applied over a vanishingly short section of conductor. The driving point impedance is infinite for a conductor of infinite length and perfect conductivity. Likewise the case of a conductor of finite length bounded at either end by an infinite, perfectly conducting plane is discussed. This problem bears a direct relation to that of a hollow pipe excited by a linear antenna.

ISSN:0021-8979    

DOI:10.1063/1.1712899

出版商:AIP    

年代:1941

数据来源: AIP