Computational background

This PLOT separation allowed vapor-phase IR and mass spectral determinations to be made. Figure 7 shows a typical IR spectrum obtained from Peak X in the above FFAP chromatogram. The spectrum corresponds to a 6-sec scan with computer background correction and normalization. The spectral features correspond well with an alkyl phenolic structure and a comparison spectrum is shown in Figure 8 for 2,4-dimethylphenol eluted from the FFAP column under identical condi-... 

The background should never be subtracted prior to full pattern decomposition and full profile-based Rietveld refinement. In these cases it is approximated using various analjdical functions with coefficients, which are refined along with other parameters. Thus computed background is then added to the intensity calculated as a function of Bragg angle. 

We hope that many people from various scientific and computational backgrounds will find this book useful. 

Fig. 3.22 Computed background illumination using as a structure element a disk of radius 10 pixels and smoothed, and the measured background illumination after averaging 1200 frames (right)...

The computational background where the present CQS4 chapter will be developed does not differ abruptly from the previous CQS papers and is basically grounded in the well-known atomic shell approximation (ASA) [30-34] in order to express, within an advanced polarized promolecular framework, the quantum mechanical molecular density fimctions (DF). To obtain additional information on recent ASA application development, see for example the previous CQS chapters [12-14] and some application to describe DF for large macromolecular structures [35, 36] to see the adequate behavior for ASA DF. 

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