Porod analytical continuation

Finally the integration is carried out numerically up to smax The additional term Ap/smax in Eq. (7.25) considers the rest of the integral from smax to infinity. It results from the integration of the analytical continuation (Eq. 7.26 on p. 91) of the SAXS intensity by Porod s law. 

Porod analysis is carried out in a plot In / j (st) I Fl)vs. sf. We find the number I Fi by trial-and-error and are satisfied when the linear region becomes longest. We determine the intercept Apx = nAp and the end of the Porod region, Smax (cf. Fig. 8.11). Now we can carry out the numerical integration, again add the remainder term (Apl /smax) from the analytical continuation, and obtain... 

---