A method of starting up a gas phase polymerization reactor, comprising controlling an amount of hydrocarbon absorbed in a polymer seedbed during startup to avoid formation of agglomerates or sheeting on an interior wall of the reactor. The coatings are typically thin coatings, such as thin film coatings. The present invention includes the use of a compound described above in order to prepare a medicament effective in the prevention or treatment of bacterial infections. The second stages are arranged such that an output of a second stage defines a primary input of an another second stage, with the output of the second stage of the last pair crossing over the output of the first stage of the last pair and defining a primary input of the first stage of the first pair, thereby defining a closed loop.