Constituent electronic devices such as eBook reader devices may be combined to form a composite device. Inert gas having negative pressure is filled in a space outside the light emitting tube in the outer tube, and a negative high-voltage pulse is applied to the anode-side electrode at a time of start-up. More specifically, the expanding monomer used in this composition is one or more dioxiranyl tetraoxaspiro5. Thereafter, subsequent to a completed interval of a p-wave, ADIR pacing resumes to monitor ventricular response.