anchor.diff:        if(grav_type.eq.'on')then
           do nj=1,3
             HEIGHT(nj)=node_xyz(nj,np)-node_xyz(nj,1) !ARC - where to put grav reference height?
  -          G_PLEURAL=G_PLEURAL+PLEURAL_DENSITY*grav_vect(nj)*9810.d0*HEIGHT(nj) !kg
  +          G_PLEURAL=G_PLEURAL+mechanics_parameters(2)*grav_vect(nj)*9810.d0*HEIGHT(nj) !kg
          enddo
         endif
  -      Ppl=(ptrans*98.07d0)-G_PLEURAL !cmH2O->Pa
  +      Ppl=mechanics_parameters(1)-G_PLEURAL !Pa
         Pblood=prq_solution(ny,1)! Pa
         Ptm=Pblood+Ppl     ! Pa
         R0=elem_field(ne_radius_in0,ne)
  
positive.code:      elasticity_parameters(2)=0.1_dp!this is a fraction of the radius so is unitless
       elasticity_parameters(3)=0.0_dp !Not used
  else
      print *, 'Your chosen vessel type does not seem to be implemented assuming rigid'
      vessel_type='rigid'
      elasticity_parameters=0.0_dp
  endif
  
  grav_dirn=2
  
negative.code: !*calc_press_area:* Calculates new radii based on pressure area relnships
  
  subroutine calc_press_area(grav_type,grav_vect,KOUNT,depvar_at_node,prq_solution,&
      mesh_dof,vessel_type,elasticity_parameters,mechanics_type,mechanics_parameters)
  
      use indices
      use arrays,only: dp,num_nodes,num_elems,elem_field,elem_nodes,node_xyz
      use diagnostics, only: enter_exit
      character(len=60), intent(in) :: grav_type
      character(len=60), intent(in) :: vessel_type
      character(len=60), intent(in) :: mechanics_type
      real(dp), intent(in) :: grav_vect(3)
      integer,intent(in) :: KOUNT,mesh_dof
      integer,intent(in) :: depvar_at_node(num_nodes,0:2,2)
      real(dp),intent(in) ::  prq_solution(mesh_dof,2)
      real(dp),intent(in) :: elasticity_parameters(3),mechanics_parameters(2)
  
  !local variables
      integer :: nj,np,ne,ny,nn
  