The dc volume resistivity of plasticized PVC

A study has been made of the dc volume resistivity of plasticized PVC using a guarded-electrode system in a sensitive vibrating capacitor–electrometer circuit. Transient effects were found to be pronounced in all but the least plasticized compositions, and the behavior in general was non-Ohmic. The resistivity decreases with plasticizer concentration and with temperature; an Arrhenius-type relationship is observed and resistivity undergoes an inflection at the glass transition temperature. The mechanism of conduction appears to be electrolytic rather than charge injection or semiconduction.     

Recovery of heterokaryons at high cell densities following isolation using irreversible biochemical inhibitors

The selection of heterokaryons using irreversible biochemical inhibitors provides an effective method for isolating fusion products between any types of cultured cells. One weakness of the technique is that the surviving heterokaryons can only be obtained at low culture densities, making their analysis cumbersome. This report describes the use of Ficoll-sodium diatrizoate gradients to partially separate viable from nonviable cells and characterizes the effects of initial plating density and medium volume on heterokaryon survival. The combined result of optimizing these parameters increases cell rescue and permits heterokaryons to attach at densities of 60,000 cells/cm 2 instead of 600 cells/cm 2. These modifications substantially improve the ease of using irreversible biochemical inhibitors to isolate purified populations of heterokaryons.     

Silicon diode detectors used in radiological physics measurements. Part II: Measurement of dosimetry data for high-energy photons

Initial calibration of a linear accelerator requires physics instruments to measure accurately central axis depth-dose and off-axis data, both in and out of the beam. These data for an 8- MeV unit were first measured using film, a Farmer 0.6-cm3 ion chamber, a 0.3-cm3 ion chamber, and a 0.1-cm3 silicon diode. Both small probes and film gave a high response compared to the Farmer probe, which has a uniform energy response. Measurements with the diode interfaced to an X-Y recorder required only a fraction of the time required with the chambers, minimizing error due to change in machine output, and permitted resolution of isodose lines in the penumbra. However, corrections required at points in depth due to nonuniform energy response of the unshielded diode were laborious. Construction of a partially shielded diode which duplicates the response of the Farmer probe eliminated the necessity for corrections, permitting rapid accumulation of a wide range of depth-dose and off-axis data.     

The high-temperature oxidation of cobalt-21 wt.% chromium-3 vol.% Y2O3 alloys

Alloys of Co-21 wt. % Cr-3 vol. % Y ₂ O ₃ have been prepared by a mechanical alloying method, and oxidized in oxygen at 100 Torr in the temperature range 900–1200°C. The general effects of the dispersed oxide phase are similar to those reported for nickel-base alloys: the selective oxidation of chromium to form a continuous protective Cr ₂ O ₃ scale is promoted; the rate of growth of Cr ₂ O ₃ is reduced compared to dispersoid-free alloys; the adhesion of the Cr ₂ O ₃ is greatly improved; and the scale-forming reaction is probably at the scale-metal interface in the alloys containing the dispersoid, whereas it is at the scale-oxygen interface in dispersoid-free alloys. This last point has not been positively demonstrated. The improvement in adhesion is of particular significance, since the scales on cobalt-base alloys are prone to spallation, and it has been possible to study the mechanism of adhesion in more detail. It appears that in dispersoid-free material the metal recedes from the scale-metal interface, leaving the scale supported on the tops of metal peaks but this does not happen in the alloy containing the dispersoid, either because the growth direction of the scale has been changed, or because of changes in the substrate grain size. In general, the observations support the model proposed in an early study for the oxidation of Ni-20 wt.% Cr alloys containing oxide dispersions.This work has been supported by the Naval Air Systems Command under Contract No. N00019-71-C-0079.     

Experimental study of surface channel in insulated-gate field-effect transistor

A simple experimental technique is described for measuring the effective channel length and the surface-channel drift mobility in the insulated-gate field-effect transistor. Experimental results are presented for p channel transistors made in 8 ? cm silicon.