Figure B2.2.

Confocal coordinate system modeling an apical dome. Periclines are the red curves corresponding to the v coordinate and anticlines correspond to the u coordinate. The curved boundary of the surface is represented by the curve v = 6, which is under tension produced by internal pressure. The singularity of the system is marked by an asterisk. The curves (u, v) coincide with stress trajectories dictated by the Lamé-Maxwell equations on a surface subjected to compression. In this case, the v curves are the compression trajectories. The singularity corresponds to the unique region on the surface at which growth rates are nearly zero, meaning that stresses are also almost null at this point.