Computer cell counting experiments were performed in order to examine the consequences of over- or under-counting. The three-dimensional reaggregate culture laboratory environment for cell counting was used as a model for computer simulation. The laboratory environment for aggregate and cell sizes, numbers and spatial placement in gelatin blocks was mimicked in the computer setup. However, in the computer, cell counting was set to be either ideally unbiased, or deliberately biased in regard to over- or under-counting so as to compare eventual results when using the various cell counting methods. It was found that there was no effect of the cell counting methods used in determining whether there was a significant difference in cell number between two experimental groups. In addition, it was found that under the conditions of these simulations, the optical dissector method behaved similarly, on the average, as the ideal method of counting cell centers and in both of those cases, the average ratio between actual cell number in a flask and estimated number was close to 1.00.
We have analyzed 370 000 pictures taken in the 30-inch hydrogen bubble chamber exposed to the 5.5-GeV/c separated K~ beam 1 at the Argonne zero-gradient synchrotron (ZGS). Light particle contamination in the beam was £5% when calculated from a r scan of the film. A Cerenkov counter operated during the exposure indicated the same high purity. About 5000 two-prong events with an associated A decay have been found. After kinematic analysis, these yielded 328 fits to the final state A77 + TT"" and 89 fits to 2°77 + 7r~.When more than one hypothesis produced a fit to a given event, a x 2 probability cut was used to exclude all fits having a probability 5 times less than that for the best fit. After this selection, all events fitting the hypothesis ATT + 77~ with a \ 2 probability >1% were classified as ATT + TT~ events. Of the remaining events, all those fitting the Z°Tf + 7r~ hypothesis with a X 2 probability >1% were classified as £°7r + 77~" events. These criteria yield a rather pure sample of the four-constraint AIT + IT~ final state. 2 The two-constraint fits to S°7r + 7r"~ have some (unknown) contamination from the A7T + ir~n° events, but this uncertainty is not important for the present results. Because of the high-beam purity, contamination due to events originating from pions can be neglected. 3 The Dalitz plot and the mass-squared projection for the events classified as ATI + IT~ are shown in Fig.
The results described in this paper were obtained from an analysis of bubble-chamber pictures of K~p interactions at incident momenta of 4.1 and 5.5 GeV/c. This paper reports the results on quasi-two-body final states, which are observed to be predominantly peripheral. In the final states Ap, Aw, A<£, and FI* + (1385)TT", the exchange mechanisms were investigated in terms of the density-matrix formalism. In general, vector-meson exchange appeared to be dominant, and in particular the decay distributions of the Yi* + (l385)w~ final state were in good agreement with the predictions of the Stodolsky-Sakurai model. Several reactions show small backward peaks expected from baryon exchange. The prediction of the independent quark model and other symmetry schemes that the forward cross sections for Ap° and Aw production should be equal is well satisfied by the present data. We also report measurements of the properties of various resonant states. We find a mass and width for the Fi*(1695) of M =1700=b20 MeV, F=130db25 MeV. The dominant decay mode is Ax + , but limits are placed on other possible channels.
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