anchor.diff:  
     sigma_E = PTread_d(config, 'sigma_E', loc=params_group)
     sigma_N = PTread_d(config, 'sigma_N', loc=params_group)
  +
  +  N = rho * ( L(1)*L(2)*L(3) - int(N_enzymes*4*pi/3*(2*sigma_N**3 + sigma_E**3)) )
   
     ! solvent index first, colloid index second, in solvent_colloid_lj
     epsilon(:,1) = PTread_dvec(config, 'epsilon_E', 3, loc=params_group)
  
positive.code:   colloids% force_old = colloids% force
  
    call h5fflush_f(hfile%id, H5F_SCOPE_GLOBAL_F, error)
    write(*,*) 'Running for', equilibration_loops, '+', N_loop, 'loops'
  
    call main%tic()
  
negative.code: 
    L = PTread_ivec(config, 'L', 3, loc=params_group)
    rho = PTread_i(config, 'rho', loc=params_group)
  
    T = PTread_d(config, 'T', loc=params_group)
    link_d = PTread_dvec(config, 'link_d', 2, loc=params_group)
  