External boundary effects on simultaneous diffusion and reaction processes

External boundaries influence the spatial and temporal structure of evolution of dynamic systems governed by reaction-diffusion equations. Critical limits, i.e. thresholds for explosive growth or onset of diffusion dominated decay, are found to be caused by the presence of the boundary and to depend on: (i) the position of the boundary, where the density is assumed to be zero at any instant of time; (ii) the mutual weights (coefficients) and powers of the nonlinear reaction and diffusion processes; (iii) the initial spatial distribution