THE ULTRA STRUCTURE OF INSECT SURFACES BY SCANNING ELECTRON MICROSCOPY
A recent development in microscopy certain to be of great interest to entomologists is the Scanning Electron Microscope. This machine overcomes the difficulties of studying solid surfaces with a standard light microscope and the problems of the extremely small limits of penetration of the electron microscope. This new microscope focuses a stream of electrons into a beam as small as 1 μ in diameter which moves over the surface of the specimen in a regular pattern, causing secondary radiations to emerge from the surface of the specimen. These are collected by a very sensitive detector and converted to an image similar to that produced by a television tube.
Abstract In situ composites can be obtained either by unidirectional eutectic solidification or by unidirectional solid- state decomposition. Techniques in the latter category are dealt with in this review. The solid-state growth methods may be classified, according to the state of the starting material, into (a) eutectoid decomposition, (b) discontinuous precipitation, or (c) growth from the noncrystalline state. Common to the three processes is the duplex microstructure which occurs, permitting alignment during growth in a temperature gradient. The author reviews the theory of the transformation, the experimental techniques, and the empirical parameters which have been reported in the literature. Emphasis is placed upon the relationships between interphase spacing and growth rate, and upon the potential discrepancies between growth rate and pulling rate.