    kva = dexp((Vm - Vtheta_dhpr)/sigma_v_dhpr)/(1.d0 + dexp((Vm - Vtheta_dhpr)/sigma_v_dhpr))  ![unitless]
    kvi = 1.d0 - (1.d0/(1.d0+EXP((Vm+21.5d0)/4.5d0)) + 0.27d0/(1.d0 + EXP((30.d0-Vm)/8.d0))) ![unitless]
