Visual Interpretation Compared with Caliper and Computerized Measurements in Experimental Vessel Stenosis

To explain visual interpretation errors on angiograms, visual interpretation, caliper measurement, and computerized measurement of cine film were compared using each of 10 graphic models and 10 acrylic models with “stenotic vessels”. Stenosis > 40% was overestimated and stenosis < 40% underestimated by visual interpretation. In caliper measurement, stenosis > 40% at exposure of 90 kV was greatly overestimated by a degree similar to the estimation by visual interpretation, and stenosis > 40% at exposures of 74 kV and 58 kV was slightly overestimated. In computerized measurement, the estimation was consistent with the actual degree of stenosis. Therefore, visual interpretation was not reliable for estimation, and computerized measurement was indispensable for estimation of vessel stenosis. Moreover, we consider the most common cause of error in visual interpretation to be optical illusions.

Micro Auger analysis using a field emission source

The use of a high brightness field emission source holds clear promise in the area of micro Auger analysis of surfaces. The high current density and small probe diameter obtainable from the field emitter (30 n A into 300Ǻ, for example) offer the possibility of recording Auger spectra from areas less than 300Ǻ, as previously demonstrated . Furthermore, the ultra high vacuum technology necessary for a reliable field emission source, is wholly compatible with the type of vacuum experimental vessel customary in surface analysis applications.We describe here results obtained with an HB50A Auger Microprobe in which an environmental cell, introduced on a bellows movement into the experimental vessel, permits heating to 800°C in an atmosphere of 0.1 torr of gas. The sample under study was pure polycrystalline iron.This was reacted with methane at 750°C in situ for 12 hours. The carbon resulting from cracked methane, dissolved in the iron to such an extent that, on cooling to 600˚C, precipitation occured. Figure 1 shows an SEM image of a characteristic precipitate, recorded with the sample held at 600˚C at a magnification of 2,000 X.

Experiments with mice and fleas

We need a fuller understanding of the feeding habits of fleas on rodents, both to help in the study of the epidemiology of plague and also in carrying out laboratory experiments on the same subject. In an earlier paper (Buxton, 1938) I described a ‘synthetic mouse hole’ in which I kept a rodent with a population of fleas (Xenopsylla cheopis) under controlled conditions of climate and feeding for periods of many days; with this I obtained some measure of the progeny which resulted under a variety of conditions. There was evidence that the mouse ate a number of the fleas, and I never controlled this variable, which was erratic and sometimes very large. We attempted to avoid the destruction of the fleas by feeding them on a baby mouse, which was changed at intervals, so that there was always one in the experimental vessel. In a postscript to the above paper it was shown that the baby mouse does not consume the fleas, almost all of which are alive when the experiment has lasted a week; in that period the adult mouse may eat about half or more of the fleas. Further experiments are in progress on the factors which determine the destruction of fleas by the mouse, and on the proportion of fleas which are actually found on the mouse under different conditions of temperature and so forth. In the present note, I shall confine myself to studying the baby mouse, as a host of X. cheopis. All the experiments here described were carried out between 1937 and 1939, though it has not till now proved possible to tabulate and consider the results. The execution of the work was in the hands of Mr S. Smith, whose help is acknowledged.