public bool apply(reactor rec,int pa){
particle a = rec.get_particle_id(pa);
type_state old_a = a.st;
type_state new_a = end;
if (old_a != new_a)
rec.update_new_state (a, old_a, new_a);
if (unlink)
rec.all_unlink (a.id);
return true;
}
