with respect to the real progress of the reaction because any bins which represent multiple stages of the ‘true’ re- action coordinate will require larger populations in order to give stable sampling; which will need to be crudely dealt with by setting a small γ and large N in eqn. 1. 

This paper presents a method, S-PRES, to investigate rare events in non-equilbrium and non-steady-state dy- namics. S-PRES can compute the evolution of the prob- abilities of rare events or rare states in any stochastic system with respect to time, providing that a suitable binning on the phase space can be defined. The method is based on Forward Flux Sampling with modifications to permit tracking of the ages of the configurations sampled. A version of the pruned-enriched Rosenbluth method is applied to the generation of path segments in order to achieve efficient sampling. 

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## VIII. CONCLUDING REMARKS 

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## ACKNOWLEDGMENTS 

