A recording and reproducing apparatus for recording data to and reproducing data from a hologram recording medium is provided. The shield has an end surface that extends between an outer surface and an inner surface of the shield and has such hardness and is designed with a convex curvature of such a radius that one part of the broken sawchain that comes to an external location during operation of the saw can slide around the end surface in an essentially unhindered manner in a direction towards the inner surface. The polymers are also expected to be useful in a variety of medical applications. In a case where a transmission timing timer for the second group has expired, the mobile station stops uplink transmissions in the cells constituting the second group for which the transmission timing timer has expired. The metal substrate has a second coefficient of thermal expansion that nominally matches the first coefficient of thermal expansion of the cell. The contact hole is formed in an etching step of reducing ion energy and an oxygen flow rate as an etching depth progresses, thereby suppressing the damage layer formed on the base.