The invention provides compounds of the formula:in salt or zwitterionic form or a pharmaceutically acceptable salt thereof, wherein R1-6, a, Z and Q are as defined in the specification. Such techniques offload specific functionality to a NIC while maintaining the bulk of the protocol processing in the host operating system. The rearranging step moves or copies the data in the memory to a part in the region storing the bit stream that has already been read. The crawler frame can be collapsible for easy transport and storage and can have a body supporting surface adjustable in height above the floor so can be adjusted for the particular user and for a particular user as the user grows to support the user at a proper height above the floor for the desired crawling action. The top and bottom layers of interconnects are patterned to avoid overlap between them, thus reducing the parasitic capacitance. When the package is produced, the connector tabs enter the lid to be adhered to the inner surface of the lid.