deletions | additions       diff --git a/background-estimation.tex b/background-estimation.tex  index 031eb4d..1cd8e7e 100644  --- a/background-estimation.tex  +++ b/background-estimation.tex 
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\label{sec:bg_calc}  The first step of smFRET analysis involves estimating the background level.   For example, to compute the background every 30s, 30 s,  using a minimal timestamp delay threshold of 2 ms for all the photon streams we execute:   \begin{verbatim} 
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\href{http://fretbursts.readthedocs.org/en/latest/background.html}  {\texttt{background} module}). The second argument, \verb|time_s|, is the   \textit{background period} (section~\ref{sec:bg_intro}) and the third argument   is the timestamp delay  threshold above which the distribution is exponential. It is possible to use different thresholds   for each photon stream passing a   \href{https://docs.python.org/2/tutorial/datastructures.html#tuples-and-sequences}{tuple}