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Environmental scanning refers to the many methods and resources that continuing professional educators use to assess their internal and external surroundings and the forces at work within the health, social, and political contexts to help them to identiy current and potential learning needs. This article describes the general techniques and sources available for environmental scanning, the advantages and disadvantages of scanning, a checklist for evaluating the quality and usefulness of documents that might be used, and a perspective on the ethics of scanning. Scanning provides apractical and systematic means of using data that is available to improve the continuing professional education effort.

If information technology is to enhance dermatology, physicians must adapt to new uses and forms oflanguage previouslyunconsidered and must adopt new methods and standards of communication. The American Academy of Dermatology (AAD) celebrated its fiftieth anniversary by presenting the 1988 Congress on Technology. The Congress focused on three technologic perspectives: educational applications, clinical practice, and medical information systems (medical informatics). This article considers these issues and offers highlights of the AAD Congress on Technology.

Dermatologists were shown digitized images of skin lesions compressed by Joint Photographic Expert Group (JPEG) and fractal image format (FIF) algorithms and asked to make a diagnostic assessment and rate the image quality in displaying the features necessary for that assessment. Dermatologists performance in the diagnostic assessment was not affected by the level of compression (up to 40×) using either algorithm, but ratings of image quality for all compressed images were significantly lower than for uncompressed images and for the original photographic slides. There were no significant differences in dermatologists' performance or ratings between the two compression algorithms.

The preparation of tree radicals from lead tetraethyl and tetramethyl has been described by Paneth and Hofeditz* and, having fully confirmed their work with the former compounds we sought, at the commencement of this investigation, to apply a simi1ar technique to an analogous problem : the preparation of atomic hydrogen by the thermal dissociation of metallic hydrides. preliminary experiments on the dissociation of certain of the more accessible hydrides showed, however, that those of sulphur, selenium, tellurium, arsenic, antimony and tin, under the conditions employed, failed to yield hydrogen which was capable of removing even the most sensitive metallic mirror—such a mirror, we had been able to show, disappears quickly and completely when atomic hydrogen is present. It is really not surprising that the hydrogen from these compounds is inactive since the accepted accommodation coefficients of the elements involved are relatively low. In this respect, the hydrides of lead and bismuth promised greater success. Hitherto, the hydrides of lead and bismuth have been obtained only in minute quantities, and have been characterized entirely by circumstantial evidence, hence it was necessary to discover means whereby they might be prepared on a larger scale. Bismuth hydride, as it proved, did not present much difficulty ; the yields from the dissolution of a magnesium-bismuth alloy in acid, although email, sufficed for our purposes. On the other hand, the results accruing from the whole of our work on the lead compound are so meagre, and so dependent on inexplicable circumstances, as to leave a sense of uncertainty regarding the nature of the traces of lead-carrying body produced in the operations, Neither the dissolution of the magnesium alloy, nor the reduction of lead salts by magnesium gave the hydride, whilst a change of the alloying metal to lithium, the use of which in these preparations is new, resulted in the merest trace of a very impure, volatile lead compound from 20 gm. of the alloy, and was without promise of yielding either a pure product or a sufficient quantity. About fifty experiments with the oscillating are, sometimes in its original form* and sometimes, modified so as to reduce the by products contaminating the lead-containing condensate, agreed down to the minutest detail with the recorded observations of Paneth and Norring, but, incidentally, gave uselessly small fields, they found the presence of carbon to be a condition essential to the appearance of lead in the effluent gases, and of this there can be no question. That our lithium contained carbon, whereas our magnesium was practically free from it is also significant in this connection.