The final four lines on page 970 were repeated on page 971. Also, the final five lines on page 973 were repeated on page 974. The following text was missing at the beginning of page 973. 5. Measuring uncertainties and comparison with known data The accuracy of the method depends on the following uncertainties.

To evaluate temperature-dependent stretching experiments of biological cells down to sub-zero temperatures in a high-frequency electric field, knowledge of the electrical parameters of the suspension is necessary. A measuring system was developed to determine the relative permittivity ε r (f , T ) and the ionic conductivity γ (f , T ) of supercooled aqueous solutions and suspensions in the frequency range 0.1-2 MHz. A parallel-plate capacitor was used in connection with an impedance analyser and a cryostat. The errors caused by the cables needed between analyser and cooled capacitor were minimized. Field homogenization within the measuring space is realized by correcting the reference potential at the guard ring. The starting capacitance at each temperature was reproduced by testing the 0 • C value after re-assembling the capacitor. Damaging of the capacitor by ice formation is prevented. For testing, a comparison was made with literature data and first measurements of supercooled aqueous solutions.

The selection of particle size distribution is based on a theoretical concept of the “close packing” of particles. The usefulness of this concept was investigated using silica as the filler in a single epoxy‐hardener system. The viscosity and settling characteristics for several particle‐size distributions and concentrations of silica fillers were studied. These studies show that significant decreases in the viscosities of casting formulations can be obtained using a two‐component filler system which permits the use of higher filler loadigs. The increase in the ratio of coarse filler to fine filler reduced the flexural strength of the castings and increased the rate of settling in the formulations. The effect of parameters other than particle size is demonstrated by the use of non‐silica fillers.

his paper presents the background and the results of T the first two years of a long-term field exposure of various types of plastic pipes in a gas-distribution system. The study is part of a program to establish the suitability of plastic pipes for gas-distribution uses. The work was initiated at Battelle in 1960 by the American Gas Association for the purpose of developing improved plastic pipe for gas-distribution service. It was soon apparent that, before an improved plastic pipe could be developed, the limitations of existing pipes had to be defined. The methods for defining these limitations ultimately became a major part of the program at Battelle. Information resulting from an earlier study at Battelle for the Thermoplastics Pipe Division, now the Plastic Pipe Institute of the Society of the Plastics Industry, Inc., indicated that the establishment of the long-term stress-rupture behavior with natural gas would be needed to demonstrate the potential use of plastic pipes for this application. This study became the major part of the laboratory work. Subsequently, however, it was deemed necessary to investigate other methods of evaluating plastic pipe that would be useful to the gas-distribution industry for detecting changes in mechanical properties. Thus, a considerable part of the program was involved in the development of test methods that could be used in defining those parameters of interest to the gas industry. A greater understanding of fatigue, permeability of the pipe, as well as resistance to impact, aging, and the effects of environments were some of the objectives of the laboratory work.Editor's Note: Actual tabular data used to construct graphs nre available from authors upon request. 111 the course of this work, the long-term stress-rupture tests with natural gas showed that the behavior with gas was essentially equal to that with water. The fatigue study showed that secondary stresses that might be encountered in the use of plastic pipe for gas distribution were not likely to be a serious factor in its long-term performance, provided the pipe was properly installed. The permeability studies demonstrated that none of the plastics currently used in the program would be expected to be eliminated as a potential material because of its permeability.About mid-1962, the activities of the A.G.A. Subcommittee on Plastic Pipe Standards revealed that several serious operational failures had occurred with plastic pipe in the gas-distribution industry. Most of these failures could be attributed to faulty installation but, in at least three serious failures, the plastics themselves appeared to be a factor. About this time, laboratory studies indicated that the fracture behavior of the pipes in the stress-rupture testing varied with both the stress-rupture life and temperature of the test. After available information on the three field-failure incidents was examined, it was concluded that the failures were aggravated by the presence of constituents other than methane in the gas. However, it was recognized t...