anchor.diff:  module mod_S_curve
  +  use mod_constants
     use mod_read_parameters
  -  use mod_constants
     use mod_variables
     implicit none
  -  
  +
   contains
     !-------------------------------------------------------------------------
     ! Subroutine in order to find the result of the equation Q+ - Q- = 0
  
positive.code:     real(kind=x_precision),intent(in)                        :: T_0
      real(kind=x_precision),intent(in)                        :: rho_0
      real(kind=x_precision),intent(in)                        :: rs
      real(kind=x_precision)                      :: Scenter = 0._x_precision
  
  
      !-------------------------------------------------------------------------
  
negative.code:     E_ff                 = 6.22d20 * (rho_0 * rho)**2 * sqrt(T_0 * T)
      tau_eff              = 0.5_x_precision * sqrt(K_e * K_ff) * Sigma * Sigma_0
      nu_0                 = 2._x_precision * rs**2 * Omega_0/3._x_precision
  
  
      !-------------------------------------------------------------------------
      !Select the case for the optical depth to compute Fz
      !-------------------------------------------------------------------------
  
      optical_depth        = 1
  
     ! if (tau_eff .ge. 1.)  then
     !    optical_depth     = 1
     ! else
  