Blow-up Metastability Random perturbations BLOW-UP ECUACIONES EN DERIVADAS PARCIALES ESTOCASTICAS Explosions GIBBS MEASURES LOSS NETWORKS MEDIDAS DE GIBBS METAESTABILIDAD METASTABILITY PIROGOV-SINAI PROCESOS ESTOCASTICOS REDES DE PERDIDA STOCHASTIC PARTIAL DIFFERENTIAL EQUATIONS STOCHASTIC PROCESSES Stochastic differential equations Cardiopatia Domain of attraction Doppler echocardiography Gibbs measures Linear equations Lq dimensions Metastabilities Partial differential equations Random processes Reaction diffusion equations Stable equilibrium Stochastic partial differential equation