anchor.diff:      integer :: r, s
       double precision :: x(3)
   
  +    call flag_timer%tic()
       do s = 1,neigh% n(1)
          r = neigh%list(s,1)
          if (solvent% species(r) == 1) then
  
positive.code:     integer :: m
      double precision :: x(3)
  
      catalytic_change = 0
      !$omp parallel do private(x, dist_to_C_sq, dist_to_N_sq) reduction(+:catalytic_change)
      do m = 1, solvent% Nmax
  
negative.code:            ! this should be solved for a single passive colloid
             if ((.not. N_type) .or. (dimer)) then
                if (.not. on_track) then
                   call flag_particles
                   call change_species
                end if
             end if
          end if
  