In one general aspect, an instrument for measuring characteristics of particles suspended in a fluid is disclosed. A responding node then sends a response message to the requesting node including a referral message comprising at least one referred node that is expected to have the requested data, based on knowledge of the referred node’s previous incoming and outgoing data transfers. The filter wheel supports UV filters and non-UV glass that can be selectively aligned with the illuminators. An incoming ion stream enters the aperture region so as to be controlled by the quadrupole field. The PVR also creates an index for indexing the enhanced file-state data so that, when the broadcast data is rendered, the correct file-state data can be located and rendered at the appropriate time with the broadcast data.