A process for separating a gas from a gas mixture containing an organic compound gas or vapor by a hybrid separation combining adsorption with membrane gas separation, using membranes selective for the gas over the organic compound. The following mathematical expression is satisfied where p1\u2032 denotes a period of a first pattern image at a position of the second absorption grating, and p2\u2032 denotes a substantial grating pitch of the second absorption grating, and DX denotes a dimension, in the x-direction, of an X-ray imaging area of each pixel of the FPD. Cooling air is channeled through the air channeling sub-system and into the room. Moreover, methods for preparing alternan and products resulting from them are provided.