Left Void Research Articles

Dental pulp regeneration aided by blood and blood substitutes after experimentally induced periapical infection

This study was based on the hypothesis that if, after periapical infection, the pulp canal is opened maximally, then filled with whole blood and/or blood substitutes in contact with the periapical tissues, and dental pulp may regenerate. Results showed that regeneration or ingrowth of connective tissue into the root canals of these monkey teeth was not enhanced by blood and/or blood substitutes. The tissue ingrowth measured between 0.10 and 1.00 mm. and fell within this range regardless of the filling material, including those teeth left void. Overextension of the instrumentation of the root canals in this study caused widespread inflammation and, in some cases, cyst formation. The majority of the teeth developed root resorption which correlated with the presence of chronically inflamed granulation tissue. Of the teeth exhibiting root resorption, only incompletely developed cuspids showed any type of repair of the resorptive defect during the time period of this study. These cuspids, which had incomplete root formation, continued to deposit additional root length, or bridging by a calcified material was attempted, even after seven of these teeth required removal of the coronal seal in order to drain acute abscesses.

Cannery retort operation and procedure to cope with modern can‐handling methods*

SummaryIt is well known that the heat transfer properties of air or air‐steam mixtures are much inferior to those of steam and that, because of this, entrapped pockets of air in a cannery retort may lead to under‐processing and spoilage. Consequently there is a need for adequate purging or venting of air from any retort during the processing ‘come‐up’period.Following the introduction to a U.K. cannery of a high‐speed can handling system, necessitating the use of can divider plates (or layer pads) in the retort crates, this cannery experienced an outbreak of spoilage that was shown, by microbiological and can examination, to be due to under‐processing. This led to an investigation of heat distribution in the cannery retorts and of the effect on this of divider plates with varying percentages of void area. This work was extended to other canneries and various types of batch retorts.Results showed that some venting procedures in long‐standing use were not entirely satisfactory and that certain modifications were necessary, even to normally adequate procedures, when certain high‐speed can handling techniques were introduced.Graphs are presented to show quite dramatic differences in heat distribution throughout retorts when venting is inadequate.Recommendations are made for correct venting procedure and the modification necessary when divider plates are used in conjunction with high‐speed can handling systems; also regarding the area that should be left void in these divider plates. Attention is drawn to correct maintenance of retorts and retort instruments, recording equipment, etc.The effect of entrapped air during retorting on external can rusting is also discussed.

The West Pediment of the Parthenon

‘No artist will ever surpass Pheidias: progress may exist in the world, but it is not so in Art. The greatest of all sculptors will remain for ever without an equal’ (Rodin).It is agreed that the sculptures of the Western pediment represented, at the centre, the Contest of Athena and Poseidon; that this central action was terminated by two chariot groups, one on the left, the other on the right; and that beyond these were spectators. Further, it is generally accepted that a pair of figures of an old man and a maiden on the left of the central action were meant for Cecrops and one of his daughters. Immediately to the left of Cecrops, between him and the first figure in the angle of the pediment, Nointel's drawing showed a void space, and in a nearly corresponding position in the other half of the pediment the same old drawing recorded another gap (X and Y in Fig. 1). It had been supposed by many students that both spaces might have been left void intentionally; Leake and others thought that one or both would have been filled.