Irregular arrangements of vesicles filled with excitable and precipitating chemical systems are imitated by Voronoi automata — finite-state machines defined on a planar Voronoi diagram. Every Voronoi cell takes four states: resting, excited, refractory and precipitate. A resting cell excites if it has at least one excited neighbour; the cell precipitates if a ratio of excited cells in its neigh...

The substances precipitated by CO(2) from the serum of chickens 1 or 2 years old slightly increased the activity of pure cultures of a 10 year old strain of fibroblasts, an indication that a growth-promoting substance had been obtained from the serum. The rate of growth of fibroblasts was slower in serum deprived of its globulins and the increase of the inhibiting effect of the treated serum is...

THE CLASSIC ESTIMATION OF UREA IN THE BLOOD, while not technically difficult, is time consuming, and a quicker method was sought for an emergency procedure. It has been known for many years that a solution of xanthydrol with urea forms an insoluble precipitate, dixanthylurea. Also that this precipitate dissolves in 50% sulfuric acid to give an intense yellow-colored solution which obeys Beer’s ...