Polyethylene Disks Research Articles

Study of Antistatic Agent on Plastics by Ellipsometry

The recovery processes of thickness, refractive index and surface conductivity of the antistatic agent layer formed on a polyethylene disk incorporated with the antistatic agent 0.5 phr homogeneously are measured. In thirteen days after moulding the disk, the thickness of the surface layer is 685Å, the refractive index is 1.575 and the surface conductivity is 2.2×10-12\\mho. Even if the antistatic agent layer is removed by washing, the thickness and the refractive index recover up to 621Å and 1.575 in two days respectively. The surface conductivity recovers from 4.2×10-16\\mho to 2.2×10-12\\mho in twenty four days also. The diffusion, the surface concentration, the evaporation of the antistatic agent, and the interaction of the antistatic agent with the absorbed water are discussed.

A Measurement of the Neutronic Interaction Between Two Cylindrical Moderators

The stationary interaction parameter between the plane surfaces of two identical, cylindrical, polyethylene disks has been measured with the pulsed neutron method. It was shown that it is possible to overcome the delay effect caused by the flight of the neutrons in the gap between the moderators through the insertion was varied between 0.06 and 0.77; the resulting values of the interaction was varied between 0.06 and 0.77; the resulting values of the interaction parameter varied from 0.93 to 0.24. Two different thicknesses of the disks were employed; one assembly gave decay constants from 10 000 to 17 000 sec−1 and the other assembly yielded values in the range 17 000 to 40 000 sec−1. Although full equilibrium of the neutron distribution was not reached in all cases for the last series, the two series show a general agreement. A calculation based on a zero’th-order Bessel function as radial distribution and (cos θ)/π as angular distribution of the neutrons leaving the interacting surfaces gives a too-large interaction parameter for all separation distances. However, the overestimate is small when the surfaces are close together.

The pulsed neutron method applied to the interaction between moderators

The possibility of using the pulsed neutron method to study two interacting moderators has been investigated. The decay constants have been measured in a system consisting of two polyethylene discs separated along the symmetry axis. The experiments cover a range in decay constants from 10,000 to 40,000 s −1. It is found that m all the experiments, with the exception of those in the limits zero and infinite separation distance, the decay constants are drifting in time. Therefore they cannot, within the scope of the experiments in this article, be looked upon as discrete modes or reliable pseudomodes. This behaviour has been confirmed by a qualitative theoretical investigation. The result can be extended to include all experiments with the pulsed neutron method applied to moderators containing cavities or having concave boundaries. A method to eliminate the drifting effect through the incorporation of absorbers in the cavities is suggested.

Cold Pressing of Polyethylene Disks. A New Technique

Techniques for the preparation of polyethylene disks for the cesium iodide range were proposed recently in notes of May and Schwing (1) as well as Smethurst and Steele (2). Both techniques apply heat to obtain translucent disks. Some disadvantages may result from heating during work with substances of low mp or with easily decomposed [Table I] organics. For this reason we were in need of a highly linear polyethylene which would produce translucent disks at room temperature without application of heat. It has been found, that Vestolen A 120 powder of the Chemical Works Huls (Western Germany) satisfies our demands fully. The data for this highly linear polyethylene in Table I were supplied by CWH.

The Use of Polyethylene Disks in the Far Infrared Spectroscopy of Solids

The Use of Polyethylene Disks in the Far Infrared Spectroscopy of Solids

Neutron dose measurements by an attenuation technique.

A technique was developed for finding the RBE dose-rate and average energy of stray neutron radiation. Neutron energies can be measured by applying the fact that the spatial variation of a thermal flux formed in a moderating material is a function of the fast flux energy distributions. An attenuation curve is plotted using polyethylene disks as neutron absorbers and a BF/sub 3/ counter as the detector. Several curves are preserted, including relaxation length vs. energy, relaxation length vs. dose-rate per unit neutron flux, and the calibration curve of relaxation length vs. doserate per court per min. The system is compared to the double moderator dosimeter of DePangher. (auth)

Some local factors affecting iridic lipid infiltration in hypercholesteremic rabbits.

The influence of various factors affecting the deposition of lipid and cholesterol in the iris of rabbits fed cholesterol and cottonseed oil was studied. It was observéd that this deposition could be increased by the intraocular implantation of either normal aortic tissue or polyethylene discs. In an additional study, it was found that intermittent exposure of the eyes of cholesterol-fed rabbits to intense light also provoked an earlier and more intense iris deposition of lipid and cholesterol than was observed in the eyes of similarly fed rabbits kept either in absolute darkness or under ordinary laboratory conditions. It was postulated that the factor responsible for the greater iridic deposition observed in all these experimental animals was the iridic vasodilatation effected by these experimental measures.

A multiple-unit plastic container for processing unmounted sections.

The use of polyethylene containers eliminates many disadvantages of those made of glass. A container consisting of 35 individual units (baskets) mounted vertically in a polyethylene disk 43½4 inches in diameter and 1½8 inch thick was a very successful substitute for glass baskets when used in Schneider's (1952) shaker-staining method. Each basket was made from a 2-inch length of 56-inch outside diameter and ½-inch inside diameter polyethylene tubing, with its bottom end closed by a fused-in circular piece of 100-mesh nickel screen. The baskets were inserted through tight holes bored in the disk by a No. 10 cork borer. The multiple-unit assembly was fitted with a handle made of polyethylene rods. Staining was the same as that obtained in glass baskets and polyethylene was found to resist the usual histological reagents at temperatures below 70 °C.