“…This differential equation is derived either from an Irreversible Thermodynamics treatment [6,7] of the dissipation inequality (for other applications see [8,9,10,11,12,13]), or a balance type equation for the non-convective fluxes, here the diffusion flux, is postulated in Rational Extended Thermodynamics [14,5,15]. For a purely macroscopic derivation of balance type differential equations for higher order fluxes see [16,17]. Within Rational Extended Thermodynamics it has been shown that the resulting system of field equations is symmetric hyperbolic with a convex extension [18,5,19], thereby allowing for finite speeds of disturbances only [20,21,18].…”