Fig. (9) (z) curve simulations for biological specimens mounted on fused quartz and sapphire substrates. (A) V(z) curve for a kidney-derived cell mounted on a fused quartz substrate. The thickness of the cell was found to be 3 μm; (B) V(z) curve for a HeLa cell adherent on a sapphire substrate. The thickness of the cell was determined to be 5.27 μm.