  This paper has been withdrawn by the authors due to a fatal error in the
analysis. The manuscript was submitted to Chemical Engineering Science. To
clarify the situation, we copy the main comment from an anonymous referee here:
"To my understanding, the authors analyze i = 1 ... 63 time series and
calculate their mean and standard deviation. These time series correspond to
individual, single ignition processes. Is this correct? If yes, these
processes, as Fig. 3 shows very clearly, are not stationary, and the pressure
difference (i.e., the signal) quickly decays to zero. In this case both the
mean and the standard deviation are poorly defined, for example because both
depend in a trivial fashion on the observation period T. I am not aware of any
study (including those cited by the authors) which allows for any conclusion
from such non-stationary signals. The results of Menezes and Barabasi are
strictly only valid for stationary time series, and they cannot be applied at
all in this case." We agree with this insightful comment that our data are not
stationary and the method adopted in our manuscript does not apply. We do not
see any possibility to correct this error and decide to withdraw it. We would
like to thank gratefully the referee and apologize for any inconvenience caused
by our oversight.
