A method for providing frame start indication that includes receiving a data transfer via a channel in a memory system. In one embodiment, the warning system comprises a visibility measuring device. This allows the content that can be used on a given user terminal to be tried out on another user terminal without the latter user having recourse to the steps of searching for the content in question. Second, the brackets are provided with a vertical member which engages the shelves. The poly is particularly useful for the fabrication of fluid separation membranes.