Root, defined duration

Although the diffusion coefficient is related to the diffusion "rate/ it is difficult to define a single diffusion "rate" during diffusion because the diffusion distance is proportional not to duration, but to the square root of duration ... 

The outcome of the PQ may indicate that there are areas of weakness in the design or implementation of the application, in particular if high levels of design changes or functional failures are observed within a localized area. In such instances, it will be necessary to reconsider the adequacy of the OQ, and further testing may be required to determine the root cause of the failures. The outcome of the PQ shall further define the need to extend the PQ duration. 

---