Transmission synchronization and bandwidth adjustment in a broadcast system are described. The header 40 calls each stub in appropriate order, installing the stub in a loader region 42, executing the stub and then removing it. An immiscible liquid, such as an oil, is included to control loading of process materials, facilitate mixing and reconstitution of dried reagents, limit evaporation, control heating of reaction materials, concentrate solid support materials to prevent clogging of fluid connections, provide minimum volumes for fluid transfers, and to prevent process materials from sticking to chamber surfaces.