code: def mason_morrow(target, throat_perimeter='throat.perimeter',
                   throat_area='throat.area'):
      r
      # Only apply to throats with an area
      ts = target.throats()[target[throat_area] <= 0]
      P = target[throat_perimeter]
      A = target[throat_area]
      value = A/(P**2)
      value[ts] = 1/(4*_sp.pi)
      return value
docs: r"""
      Mason and Morrow relate the capillary pressure to the shaped factor in a
      similar way to Mortensen but for triangles.
  
      References
      ----------
      Mason, G. and Morrow, N.R.. Capillary behavior of a perfectly wetting
      liquid in irregular triangular tubes. Journal of Colloid and Interface
      Science, 141(1), pp.262-274 (1991).