Water model statistical considerations

In the model of micelle proposed by Dill et al. [21], the hydrocarbon chains of the surfactants are more randomly distributed, bearing in mind statistical considerations (Fig. 4). A considerable number of hydrocarbon chains are exposed to the water at the surface. 

The observation of a system over a specific time period at atomic level causes a considerable data flood. It requires the calculation and recording of the full MD trajectory including all solvent molecules. Yet even more time consuming are analyses of the emerging data and, hence, efficient statistical methods are of utmost importance for elucidating information. Several different water models have been developed for the explicit consideration of solvation effects in MD simulations [62]. 

The choice of reference spectra is carried out, on one hand, manually from real (deterministic) spectra, with the consideration of determined spectra (nitrate, nitrite, surfactants). It is completed automatically, on the other hand, with a mathematical procedure [15] allowing the selection of the more relevant spectra for the model, able to explain by a linear combination, the shape of UV spectra of water or wastewater. This last procedure can be replaced by any advanced statistical algorithms (PCA or PLS, for example) or by commercial software (such as UVPro from Secomam). 

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