Dear mailing list, we recently published a paper where we broke with the "Sayers & Bunker 1988 - Paradigm" to apply normalization as consistently as possible between samples and standards when performing linear combination fitting: http://pubs.acs.org/doi/abs/10.1021/acs.est.5b03096. There, we showed that for known mixtures of phosphorus standards the LCF of P K-edge XANES spectra delivers better results when changing the base-line and normalization parameters of the sample (in defined ranges, using the software /R/). I'm writing to the mailing list of several reasons: 1) A reviewer explicitly asked to contact Bruce Ravel so that the new insight could be implemented in ATHENA, 2) I was trying to combine my code with ATHENAs way of LCF before publishing the code. Unfortunately, I have not been able to resolve that a combination of both approaches results in large numbers of LCF procedures (sometimes Million or Billion). So many procedures are not fittable in reasonable time, maybe because my code is slow or maybe because /R/ isn't fast enough (or just the nlsLM-function that I'm using for LCF). I'm stuck and maybe programming in Perl would be a better choice (never programmed in Perl, yet)? Maybe a different kind of fitting algorithm would be faster?, 3) When using the nlsLM-function to perform LCF in /R/, I also have to provide portions of the standards before starting the fit. I used the same approach as ATHENA, dividing 1 by the number of standards so that every standard has the same portion. However, when playing with the code I realized that changing the starting portion can have an impact on the fitting result. Has this been observed or tested before by anyone else? How do you, in general, justify using the same starting portion for every standard? 4) Some minor question about LCF in ATHENA: a) Could the standards (the columns) in the output .csv-file after LCF be sorted alphabetically?, b) Does LCF in ATHENA sometimes produce negative numbers of a portion because the weight of any "last" standard in a set is always calculated by "1-sum(portions_of_other_standards)" (could it be this? https://github.com/bruceravel/demeter/blob/master/lib/Demeter/LCF.pm#L375-L3...). To mimic "all samples sum to one" from ATHENA and to not produce negative portions, we used all LCF results which have a residual "absolute(1-sum(portions_of_all_standards)) < 0.0005"; maybe this is of interest also for ATHENA? Cheers, Florian