an matrix.</span>
         J = JacobianMtrx(this,X,Xn)

         <span class="comment">%------------------------------------------------------------------</span>
         <span class="comment">% Compute the determinant of the jacobian.</span>
         detJ = detJacobian(this,X,Xn)

         <span class="comment">%------------------------------------------------------------------</span>
         <span class="comment">% Compute strain-displacement matrix.</span>
         [B,detJ] = BMatrix(this,X,Xn)

       