Methods and apparatus for protecting the thin films during chemical andor thermal edge strengthening treatment. The system of the present invention includes a particular metal-metal sealing embodied between the cap and flange of a first container or water-tight compartment, and the cap and flange of a second container. Such cell-based assays may be used to evaluate drugs or other compounds or to perform other biological studies. The two coils are located between the first and second geometrical planes of the rotor such that, when the rotor is rotating, the end zones of the rotor tongues pass opposite said at least one coil. An end of the thin plate-like member is contacted to a surface of the image bearing member toward an upstream side with respect to the rotational direction. The process is useful for alkylating the C-3 position of indoles that contain acid-sensitive substituents at the N-1 position.