The viruses hMPV, PIV-1, PIV-2 and PIV-3 were quantified by LightMix assays (TIB MOLBIOL, Berlin, Germany). The virus controls of the NATRVP-2 are purified intact virus particles that have been ...

The principle of the PIV measurement technique relies on the physical definition of velocity as a differential quotient. The trajectory of many tracer particles which follow the flow faithfully can be ...