This article analyzes directed lattice paths, when a boundary reflecting or absorbing condition is added to the classical models. The lattice paths are characterized by two time-independent sets of rules (also called steps) which have a privileged direction of increase and are therefore essentially one-dimensional objects. Depending on the spatial coordinate, one of the two sets of rules applie...

SUMMARY A promising new operation-coronary bypass-has been developed for the treatment of coronary heart disease. However, because of the nature of the underlying disease and the minute size of the vessels to be anastomosed, its long-range prospects are in doubt. At this point in time there is no evidence that the operation either prevents infarction or prolongs life, and great caution is urged...

I take this opportunity to record some of my own In general, the growth rate of a bacterial strain may be recollections of the work on mutation in the 1940s and within very wide limits independent of the concentration early 1950s that was so influential in the development of a given growth factor; but since at zero concentration of quantitative biology. In 1943, Luria and Delbrück the growth ra...