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Results for DC.creator="A." AND DC.creator="G." AND DC.creator="W." AND DC.creator="Leslie" in section 11.2.6 of volume F page 1 of 2 pages. |
Integration by profile fitting
International Tables for Crystallography (2012). Vol. F, Section 11.2.6, pp. 268-271 [ doi:10.1107/97809553602060000831 ]
... background and peak regions are correctly defined, summation integration provides a method for evaluating integrated intensities that is both robust and ... by the term in equation (11.2.5.11)]. Profile fitting provides a means of improving the signal-to-noise ratio for this ... apply profile-fitting methods, the first requirement is to derive a `standard' profile that accurately represents the true reflection profile. ...
Profile fitting partially recorded reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.8, p. 271 [ doi:10.1107/97809553602060000831 ]
... fitting is applied to partially recorded reflections this leads to a systematic error in the individual intensities, but there is no ...
Estimation of overloaded reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.3, p. 271 [ doi:10.1107/97809553602060000831 ]
... pixels can simply be excluded from the profile fitting, allowing a reasonable estimate of the true intensity (except when the majority of the pixels are saturated). A knowledge of the strong intensities is essential for structure solution based on molecular replacement techniques, and so this is a very useful additional feature of profile fitting. References International ...
Elimination of peak pixel outliers
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.2, pp. 270-271 [ doi:10.1107/97809553602060000831 ]
... the feature that gives rise to the outliers affects only a small fraction of the peak pixels and gives rise to ... cooled samples. Another source of outliers is the encroachment of a strong neighbouring spot into the peak region, as discussed in ... applied to both fully recorded and partially recorded reflections, but a high [sigma] cutoff (e.g. 10-20) must be used ...
Incompletely resolved spots
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.1, p. 270 [ doi:10.1107/97809553602060000831 ]
... If adjacent spots are not fully resolved, there will be a systematic error in the integrated intensity which will be largest ... standard profiles. Secondly, when evaluating the profile-fitted intensity of a particular reflection, pixels can be omitted if they are adjacent to a pixel that is part of a neighbouring spot (rather ...
Other benefits of profile fitting
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7, pp. 270-271 [ doi:10.1107/97809553602060000831 ]
... If adjacent spots are not fully resolved, there will be a systematic error in the integrated intensity which will be largest ... standard profiles. Secondly, when evaluating the profile-fitted intensity of a particular reflection, pixels can be omitted if they are adjacent to a pixel that is part of a neighbouring spot (rather ...
Improvement provided by profile fitting weak reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.6, p. 270 [ doi:10.1107/97809553602060000831 ]
... the variance in using equation (11.2.6.21) is given by Assuming a flat background and very weak intensity, then from Poisson statistics ... is simply The ratio of the variances is thus For a typical spot profile, the right-hand side (which depends only on the shape of the standard profile) has a value of 2, showing that profile fitting can reduce ...
Profile fitting very weak reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.5, p. 270 [ doi:10.1107/97809553602060000831 ]
... of the standard profile. This shows that the intensity is a weighted sum of the individual background-corrected pixel counts (rather than a simple unweighted sum, as is the case for summation integration). Because the values of are a maximum in the centre of the spot, this will ...
Profile fitting very strong reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.4, p. 270 [ doi:10.1107/97809553602060000831 ]
Profile fitting very strong reflections 11.2.6.4. Profile fitting very strong reflections For very strong reflections, the background level is very small and equation (11.2.6.15) reduces to and the weights are given by Substituting for in (11.2.6.18) gives As pointed out by Z. Otwinowski (personal communication), this shows that for correctly weighted ...
Modifications for very close spots
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.3, pp. 269-270 [ doi:10.1107/97809553602060000831 ]
... all pixels in the measurement box that are overlapped by a neighbouring spot. This applies not only to the pixels of ... all the reflections used to form the standard profile. Consequently, a pixel should be excluded even if it is only overlapped by a neighbouring spot for one of the reflections used in ...
International Tables for Crystallography (2012). Vol. F, Section 11.2.6, pp. 268-271 [ doi:10.1107/97809553602060000831 ]
... background and peak regions are correctly defined, summation integration provides a method for evaluating integrated intensities that is both robust and ... by the term in equation (11.2.5.11)]. Profile fitting provides a means of improving the signal-to-noise ratio for this ... apply profile-fitting methods, the first requirement is to derive a `standard' profile that accurately represents the true reflection profile. ...
Profile fitting partially recorded reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.8, p. 271 [ doi:10.1107/97809553602060000831 ]
... fitting is applied to partially recorded reflections this leads to a systematic error in the individual intensities, but there is no ...
Estimation of overloaded reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.3, p. 271 [ doi:10.1107/97809553602060000831 ]
... pixels can simply be excluded from the profile fitting, allowing a reasonable estimate of the true intensity (except when the majority of the pixels are saturated). A knowledge of the strong intensities is essential for structure solution based on molecular replacement techniques, and so this is a very useful additional feature of profile fitting. References International ...
Elimination of peak pixel outliers
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.2, pp. 270-271 [ doi:10.1107/97809553602060000831 ]
... the feature that gives rise to the outliers affects only a small fraction of the peak pixels and gives rise to ... cooled samples. Another source of outliers is the encroachment of a strong neighbouring spot into the peak region, as discussed in ... applied to both fully recorded and partially recorded reflections, but a high [sigma] cutoff (e.g. 10-20) must be used ...
Incompletely resolved spots
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7.1, p. 270 [ doi:10.1107/97809553602060000831 ]
... If adjacent spots are not fully resolved, there will be a systematic error in the integrated intensity which will be largest ... standard profiles. Secondly, when evaluating the profile-fitted intensity of a particular reflection, pixels can be omitted if they are adjacent to a pixel that is part of a neighbouring spot (rather ...
Other benefits of profile fitting
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.7, pp. 270-271 [ doi:10.1107/97809553602060000831 ]
... If adjacent spots are not fully resolved, there will be a systematic error in the integrated intensity which will be largest ... standard profiles. Secondly, when evaluating the profile-fitted intensity of a particular reflection, pixels can be omitted if they are adjacent to a pixel that is part of a neighbouring spot (rather ...
Improvement provided by profile fitting weak reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.6, p. 270 [ doi:10.1107/97809553602060000831 ]
... the variance in using equation (11.2.6.21) is given by Assuming a flat background and very weak intensity, then from Poisson statistics ... is simply The ratio of the variances is thus For a typical spot profile, the right-hand side (which depends only on the shape of the standard profile) has a value of 2, showing that profile fitting can reduce ...
Profile fitting very weak reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.5, p. 270 [ doi:10.1107/97809553602060000831 ]
... of the standard profile. This shows that the intensity is a weighted sum of the individual background-corrected pixel counts (rather than a simple unweighted sum, as is the case for summation integration). Because the values of are a maximum in the centre of the spot, this will ...
Profile fitting very strong reflections
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.4, p. 270 [ doi:10.1107/97809553602060000831 ]
Profile fitting very strong reflections 11.2.6.4. Profile fitting very strong reflections For very strong reflections, the background level is very small and equation (11.2.6.15) reduces to and the weights are given by Substituting for in (11.2.6.18) gives As pointed out by Z. Otwinowski (personal communication), this shows that for correctly weighted ...
Modifications for very close spots
International Tables for Crystallography (2012). Vol. F, Section 11.2.6.3, pp. 269-270 [ doi:10.1107/97809553602060000831 ]
... all pixels in the measurement box that are overlapped by a neighbouring spot. This applies not only to the pixels of ... all the reflections used to form the standard profile. Consequently, a pixel should be excluded even if it is only overlapped by a neighbouring spot for one of the reflections used in ...
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