Problem oriented transmission electron microscopy

The relative advantages and disadvantages of the variety of transmission electron microscopical techniques which can be applied to materials science problems are argued by the examination of problems from a range of different fields. The further developments which will be needed before the full potential of some of the more modern approaches can be achieved are also discussed, as are the increasing uses of ‘edge-on’ specimen preparation methods.     

Novel instabilities in the oxidation of a Nimonic alloy when YBaCuO is deposited upon it

When an YBaCuO film is deposited onto a Nimonic 80A alloy substrate using a plasma technique there is extensive inter-reaction. The microstructural and compositional relationships between the layered products in this interfacial scaling process are described using data obtained by conventional edge-on TEM techniques. Our results demonstrate the way in which the segregation of chromium to the YBaCuO overlayer dominates the scaling behaviour that is seen, despite the formation of intermediate layers which would normally have been expected to act as diffusion barriers, and highlight the potential difficulties in making well behaved electrical contacts for this superconductor.     

Electroretinographic testing in diabetics: a comparison study of the Burian-Allen and the Henkes corneal electrodes

A series of 57 diabetics underwent standard electroretinographic recordings for the purpose of testing the effect of insulin on the electroretinograms in diabetes mellitus, specifically on the oscillatory potential changes (Kozak et al., Jap. J. Ophthal. Suppl., 1979). Use of the speculum-type corneal electrode (Burian-Allen, Hansen Labs.,) produced 9 corneal abrasions in the first 28 patients in this series. However, when the technique of examination was altered by use of the Henkes-type bipolar electrode, only 2 abrasions were produced in the last 29 patients. These frequencies of abrasions are statistically different. The suggestion is made that electroretinographic tracings in diabetics the performed with the use of the Henkes bipolar low-vacuum corneal electrode (Medical Workshops, Holland).     

The analysis of a defect in ordered Ag3Mg

The high resolution image of an apparently displacive defect in the long period ordered structure of Ag₃Mg is analysed in terms of a simplified substitutional model. It is demonstrated by image simulation that the characteristics of the image could be described equally well on the basis of progressive relative substitution of Ag for Mg on two of the four sublattices in the structure.     

Determination of protein allowances in human adults from nitrogen balance data

The problem of predicting human protein requirements is examined in detail. Three methods from the literature are shown to represent a logical sequence wherin each takes into account more sources of variation than does the previous one. These are the single level method and two versions of the multiple level method, all of which assume a population response curve. A fourth method is proposed as the next step in this sequence. This method calculates a response curve for each individual and works with the individual requirements. Since each method makes fewer assumptions about the data and, therefore, about the biological situation of population protein needs, each method gives successively larger protein allowance values, while at the same time identifying the sources of variability and uncertainty in these estimates.