Index of content:
Volume 12, Issue 5, May 1941
12(1941); http://dx.doi.org/10.1063/1.1769874View Description Hide Description
12(1941); http://dx.doi.org/10.1063/1.1769875View Description Hide Description
A study has been made of the characteristic effects of the inert gas, and of variations in the dimensions of the cathode, on the minimum pressure at which the Schuler discharge may be started and maintained. Partially closing the open end of the cathode was found to have a very beneficial effect. An interesting example of rotating anode spots, observed incidentally, is also described.
12(1941); http://dx.doi.org/10.1063/1.1769876View Description Hide Description
The magnets used in the new University of Illinois mass spectrograph are described. Included is a discussion of the advantages and disadvantages of single casting cores as compared to the usual built‐up multiple section type of core. Core designs for mass spectrographic purposes and possible limitations as to size are suggested. Plots showing the experimental and theoretical fringing flux distributions for Armco iron, and also the general stray field distribution around the larger magnet, are included.
12(1941); http://dx.doi.org/10.1063/1.1769877View Description Hide Description
A sensitive differential manometer used in the recording of small differential pressures is described. This instrument responds to pressure differences as small as 0.00003 cm of mercury and as rapid as 80 cycles per second. The moving element is a rectangular glass mirror 0.010 inch thick and approximately 0.060 inch×0.080 inch, supported on a glass shaft 0.007 inch in diameter. Motion is supplied by a thin rubber diaphragm approximately 0.003 inch thick. Included in recordings made with the aid of this instrument are wave forms originating in the human neck and finger, also pressure changes in a glass cell enclosing a tracheal breathing insect.
12(1941); http://dx.doi.org/10.1063/1.1769878View Description Hide Description
This paper discusses the operation and characteristics of electrostatic photo‐multipliers, using the Western Electric D‐159076 photo‐multiplier as an example to illustrate specific points. The following subjects are discussed: description of operation, advantages and applications, typical operating conditions, variation of sensitivity with voltage, hum due to ripple in power supply, effect of unequal voltage division, output impedance, linearity of response and fluctuation noises.
12(1941); http://dx.doi.org/10.1063/1.1769879View Description Hide Description
An improved design for fixed angle quantity type rotors is presented in which the holes are drilled at 10° to the axis of rotation and the Lusteroid tubes containing the centrifugate are individually sealed by means of tapered plugs. The advantages of this design are (a) increased capacity for a given diameter rotor, (b) prevention of tube collapse at all speeds and (c) more efficient concentration of materials in solution. Some charts illustrating differential sedimentation and concentration of proteins are given.