Refinement strategies

If the risk of OOS results is disregarded, a refined strategy would be to use a flexible limit, namely < L for L = 100.56. .. 104.42, which would make the upper confidence limit CL (Xmean) coincide with the 105% specification limit (circled bold line in panel B). The OOS risk in panel B is larger than that in A for n > 4. 

Table 2. Least-squares statistical factors R, Rw and GoF of the refinement strategies. 

Final residual indices of the refinement strategies are given in Table 2. On the residual density maps shown in Figure 1, the maxima and minima do not exceed 0.2 e A-3. 

In the next section, we will demonstrate how the QM/MM refinement strategy was combined with advanced sampling techniques to resolve the ambiguous electron densities of a substrate complexed with Orf2, an aromatic prenyltransferase, and successfully clarify the relaxed substrate specificity and product regioselectivity. 

The selection of crude oil type is critical to the design and economic success of a crude oil refinery. Different crude oil types require a different refining strategy, and depending on the crude oil type, it may be easier or more difficult to achieve a specific product slate. The product slate is often determined by regional markets, unless the products are specifically earmarked for export. This also holds true for Fischer-Tropsch syncrude. 

Different refining strategies are possible, and different refinery designs are required for the refining of HTFT and LTFT syncrudes. 

D. H. Brower, A structure refinement strategy for NMR crystallography an improved crystal structure of silica-ZSM-12 zeolite from Si chemical shift tensors. /. Magn. Reson., 2008,194,136-146. 

With all of the scenarios in place, there is no doubt that petroleum and its relatives residua, heavy oil, and extra heavy oil (bitumen) will be required to produce a considerable proportion of liquid fuels into the foreseeable future. Desulfurization processes will be necessary to remove sulfur in an environmentally acceptable manner to produce environmentally acceptable products. Refining strategies will focus on upgrading the heavy oils and residua and will emphasize the differences between the properties of the heavy crude feedstocks. This will dictate the choice of methods or combinations thereof for conversion of these materials to products (Schuetze and Hofmann, 1984). 

This opens up the possibility of rigorously assigning likelihoods to the NOE assignments obtained from NOE matching, which in turn will facilitate the development iterative pose refinement strategies. 

The culpability of the accused is even greater when one takes note of the high criminal energy with which the crime was committed. The accused acted on the basis of a calculated and highly refined strategy carried out in a hidden manner that was chosen beforehand with great deliberation, involved numerous deceits and manipulations and was therefore very difficult to penetrate. (decision p. 237)... 

It is generally recognized that the best refining strategy involves the use of each potential feedstock and fraction in a way... 

As a starting model, we will use the coordinates of atoms taken from Table 6.49 together with the unit cell dimensions and all profile parameters determined from Le Bail s full pattern decomposition. They are found in the input file, Ch7Exl2a.inp for LHPM-Rietica. The powder diffraction data are located in the file Ch7Exl2 MoKa.dat on the CD. As already established in section 6.18.3 (see Figure 6.43 in Chapter 6), this model of the crystal structure is also feasible but far from complete because the observed and calculated intensities do not match well. Thus, the refinement strategy will be similar to the previous example. The least squares fit here may... 

The principles of DDM are universal and may be used in many diverse areas of powder diffraction and beyond. Future developments will be focused on studying the properties of this procedure and its efficiency in applications to different data. Various options for calculating the derivative difference minimization function and optimal refinement strategies should be subjected to methodical analysis. 

To test the validity of Rietveld based methods for QPA, the round robin organizers undertook the analysis of all eight mixtures in the Sample 1 suite using the following refinement strategy ... 

Application of total pattern fitting to X ray powder diffraction data, H. Toraya and F. Marumo, Rep. Res. Lab. Engin. Mat., Tokyo Inst. Tech., 1980, 5, 55 64 and Crystal structure refinement of alpha 813X4 using synchrotron radiation powder diffraction data unbiased refinement strategy, H. Toraya,... 

Although this method is efficient, it cannot directly tell us whether the result actually corresponds to the crystal stmcture that is being studied, since the number of mathematical solutions that minimize the gaps between the experimental pattern and the calculated one is very large. In order to properly deal with this problem, it is important to work according to a carefully planned refinement strategy. 

This method is particularly efficient [HIL 00] and has been widely implemented in the past few years. It is however necessary to have a good knowledge of the stmctures of the phases in the sample. Additionally, in this type of study, the number of refinement parameters can be very large, which means that the refinement strategy has to be carefully defined [CON 00]. 

This description clearly shows that structural refinement using the Rietveld method requires a specific refinement strategy. We have already discussed some of these aspects in Chapter 3 (see section 3.3.4). Obviously, when the objective, as in this case, is to accurately determine the stractural parameters, this refinement process must be conducted with the utmost care. 

CON 00] O CONNOR B., Influence of refinement strategy on Rietveld phase composition determinations , X-ray Anal, vol. 42, p. 204-211,2000. 

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