A structurally coated silica can be prepared by spraying and mixing a pyrogenic silica with water and a coating agent in a suitable mixing vessel, then milling and then conditioning the product. The apparatus may include a cutter for removing a portion of cover material from a hard book cover assembly. The first pit string P1 and the second pit string P2 are adapted so that the gaps between pits constituting those strings in accordance with address information are equal to, or less than, the width of the pits measured in a radial direction of the disk. The minute ventilation of the subject may be decreased or increased from the baseline level by decreasing or increasing a parameter that changes minute ventilators.