An information system that comprises a data source that transmits a data item to a group of database instances using a packet-switched communication protocol in which retransmission of the data item to a data base instance is independent from reception of an acknowledgement to the transmitted data item from the database instance. The compounds have the following structure :including stereoisomers, pharmaceutically acceptable salts and prodrugs thereof, wherein X, Y, R1 and R2 are as defined herein. The flutter shutter image may be preceded and following by a continuous shutter image. A first mask, extending in a first direction, is formed over the first electrically conductive layer and then trimmed so that those portions of the first electrically conductive layer and the memory material layer not covered by the first mask are removed. The rocking mechanism portion swings the backrest portion and the seat portion about a rocking center, and the rocking center is apart or different from the reclining center. One feature of the invention is to form a first mask pattern having low wettability over a conductive layer, form a second mask pattern having high wettability over the conductive layer using the first mask pattern as a mask, and form a mask pattern for etching the conductive layer by removing the first mask pattern.