%0 Journal Article %A Friedman, Avner %A Herrero, Miguel A. %T Extinction and positivity for a system of semilinear parabolic variational inequalities %D 1992 %@ 0022-247X %U https://hdl.handle.net/20.500.14352/57759 %X A simple model of chemical kinetics with two concentrations u and v can be formulated as a system of two parabolic variational inequalities with reaction rates v(p) and u(q) for te diffusion processes of u and v, respectively. It is shown that if pq < 1 and the initial values of u and v are “comparable” then at least one of the concentrations becomes extinct in finite time. On the other hand, for any p = q > 0 there are initial values for which both concentrations do not become extinct in any finite time. %~