Tissue expanders and their methods of use. Thus, the emulsion can be appropriately used in the temporary inhibition of contraction of gastrointestinal tract for, for example, observation of gastrointestinal tract by an endoscope. Concavities are formed in the outer surface of the dielectric at positions corresponding to the crimp connection portion of the inner contact The concavities control the characteristic impedance of the coaxial connector. Direct methanol fuel cell incorporating these cathodes are also disclosed.