Index of content:
Volume 12, Issue 7, July 1941
12(1941); http://dx.doi.org/10.1063/1.1769896View Description Hide Description
A useful fifth‐degree equation is derived for the d.c. behavior of the string galvanometer; it contains seven parameters, three for the (symmetric) magnetic field, three for the (elastic)suspension, and one for the length of the string. Examples and a discussion are given concerning the practical use of this equation.
12(1941); http://dx.doi.org/10.1063/1.1769897View Description Hide Description
A speed control for the air‐driven ultracentrifuge based on a stroboscopic principle is described. The pressure of the air driving the centrifuge is automatically decreased or increased according as the centrifuge tends to accelerate or decelerate. The speed of the centrifuge can be maintained constant within less than one revolution a second.
Electrical Bombardment of Biological Materials II. An Electron Tube for the Production of Homogeneous Beams of Cathode Rays from Ten to One Hundred Kilovolts12(1941); http://dx.doi.org/10.1063/1.1769898View Description Hide Description
An apparatus is described for irradiation of biological and chemical materials in vacuum with electron beams of intensities varying between 10−6 and 10−10 coulomb per square centimeter and of energies ranging between 10 and 100 kv. The beam can be easily adjusted and scanned for homogeneity. Through an arrangement of stops, a large number of targets can be conveniently irradiated in a relatively short period.
12(1941); http://dx.doi.org/10.1063/1.1769899View Description Hide Description
A current integrator employing a neon bulb has been used; it is found to require no correction of any kind, and to be independent of power supply fluctuations. The lowest current for which the integrator can be considered reliable is 0.05 microampere. Currents up to 30 microamperes have been integrated properly, and it is believed that currents up to 200 microamperes could be integrated by a similar circuit.