deletions | additions       diff --git a/Background estimation.tex b/Background estimation.tex  index e3e5c9a..08f21ee 100644  --- a/Background estimation.tex  +++ b/Background estimation.tex 
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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 threshold above which the distribution is exponential.   It is possible to use a different threshold thresholds  for each photon stream passing a tuple \href{https://docs.python.org/2/tutorial/datastructures.html#tuples-and-sequences}{tuple}  as \verb|tail_min_us| (instead of a scalar). For an ALEX measurement the tuple needs to have 5 values   corresponding to thresholds for the 5 photon streams. The list of photon   streams for a \verb|Data| object can be found in the \verb|ph_streams|   attribute (in the present example \verb|d.ph_streams|).   Finally, it  is possible to use a heuristic estimation of the threshold using   \verb|tail_min_us='auto'|. For more details refer to the   \href{http://fretbursts.readthedocs.org/en/latest/data_class.html#fretbursts.burstlib.Data.calc_bg}{\texttt{calc\_bg} documentation}.