Informal use of decision theory to improve radiological patient management

Six radiologists reviewed 50 urograms to determine whether arteriography or needle aspiration should be recommended for evaluation of a space-occupying renal lesion. In addition to their usual decision methods, they were encouraged to think about the problem from a decision theory viewpoint. No computations were required. It was found that even informal, non-numerical application of decision theory resulted in improved outcomes; further improvement was noted with explicit use of numerical methods.     

Effect of Grinding on Flaw Geometry and Fracture of Glass

Fracture mechanics is combined with fracture surface analysis to analyze brittle failure of glass bars which were tested relative to the direction of grinding. Grinding essentially produces two sets of flaws from which failure occurs. In the most severe set, formed basically parallel to the grinding direction, the ratio of the average depth ( a ) to the half-width ( b ) is 0.5. In the less severe set, formed perpendicular to the grinding direction, the average a / b ratio is 1.6. In both sets the most severe flaws are generally associated with a particularly deep grinding groove or gouge. The strength reduction resulting from testing perpendicular to the grinding direction results from the larger flaw size and slightly higher stress-intensity factor resulting from the greater ellipticity of the flaws formed parallel to the grinding grooves and perpendicular to the tensile axis. Detailed analysis of these 2 sets of flaws causing failure of appropriately oriented specimens shows that (1) the fracture mirror radius, r , occurs at a constant stress-intensity level independent of flaw geometry; (2) unsymmetric fracture mirrors result from unsymmetric, irregular flaws leading to unsymmetric stress-intensity distributions; (3) is constant for semielliptical flaws; and (4) fracture energy calculated from an expression including mirror constants, the flaw-to-mirror size ratio, and the flaw geometry agrees with measured values over a wide range of a / b values.     

Amplified migration inhibition effect

Upon exposure to specific antigen in tissue culture, sensitive lymphocytes released macrophage migration inhibition factor and other lymphokines into the supernatant culture medium. Migration of peritoneal macrophages from nonsensitive animals was inhibited in the presence of such supernatants. However, with previous techniques it was found that an inhibitory effect was present at only low low titers (less than 10(2)). It is therfore of great interest that by increasing cellular density, the total number of cells being kept constant, inhibitory activity can be amplified by a factor as great as 10(10). This amplification was observed only when lymphocytes and macrophages were loosely packed, as by spontaneous sedimentation in a conical test tube. The effect was abolished by dispersing the cell suspension in a flat-bottomed flask or, alternatively, by shaking the test tube so that intimate prolonged intercellular contact was prevented.     

The effects of CO2 on the components of breathing pattern

Experiments were performed on 12 rabbits in 4 experimental groups: A. breathing spontaneously; B. nonparalysed and ventilated by means of a pump driven by the integrated phrenic nerve activity; C. paralysed and ventilated as mentioned above; D. like in the group C, but subjected to bilateral vagotomy. The relationships were investigated between the chosen basic parameters describing the rhythm and depth of respiration in steady states during exposure to hypercapnic mixtures. A high correlation was found between the amplitude of the integrated phrenic nerve activity and the time of inspiration which is modified by the afferent activities from the lungs and thorax TI and TE seem to be controlled by different mechanisms, and the contribution of TE to the control of the cycle duration is greater than that of TI.