List of sections:
Requesting the Strategy Option
The Strategy Method for Maximising Data Coverage
Examining the Results from Strategy Maximisations
Logging of the Results of Maximisations
When the 'Strategy' Option is selected, the following menu is displayed:
<Maximise Unique Data> <Maximise Acentric Pairs> <Analyse Overlaps>The first option is to determine a strategy which will maximise the unique data coverage and the second option is to determine a strategy to maximise the coverage of acentric data pairs. The third option enables an analysis of spatial overlaps for a series of oscillation angles so that a suitable oscillation angle may be selected for the data collection.<Return to Main Menu>
Note that the space group symmetry must be defined before the strategy calculation can be carried out. A check is made, where possible, that the crystal system and lattice type parameters are consistent with the space group information.
List of subsections in this section:
Maximising Unique Data or Acentric Pairs
Analysing Overlaps
<Current Set Only> <Current Set in Context>or:<Return to Main Menu>
<Current Set Only> <Current Set in Context> <In Context with MTZ>The latter will only be output if there is currently MTZ data read in and stored in the program.<Return to Main Menu>
The strategy options parameter table enables the cell division factor to be cahnged if required. Also there is a toggle value to select whether or not 'Double Segment' stategy analyses are to be carried out. By default the value is 'yes' for maximising unique data and 'no' for maximising acentric pairs. In the latter case, the double segments option may well give poorer results because of the constraint imposed on the angle ranges examined; also the calculation is more time consuming than that required in the case of maximising unique data. The default values for the toggle are reset if the program defaults are reset or a new parameters file is read in.
In all cases, any values of the rotation ranges for the current crystal set are ignored as the purpose of the strategy option is to propose suitable values for these parameters. If the first option is selected, then the strategy calculation will be carried out for the current set alone. For the other cases, the strategy option determines rotation ranges for the current set assuming the data coverage from the other sets based on their currently defined parameters and, in the third case, also including any data read from an MTZ file.
<Current Set Rotations> <Input Rotation Range>If the latter option is selected, input of a start and end angles for the rotation range is requested.<Return to Previous Menu>
Having selected the required rotation range(s), the following menu is output to enable a choice of the oscillation angles to be examined:
<Standard Oscillations> <User Selected Angles>If the first option is selected a series of five standard oscillation angles (0.5, 1.0, 1.5, 2.0, and 2.5 degrees) will be tried in sequence until 5% or more of the spots are found to be overlapped or until all five angles have been tried. If the second option is selected, the program prompts for up to five user selected oscillation angles. Input of a value of zero terminates the list.<Return to Previous Menu>
After generating the unique reflections list and predicting the reflections covering the required ranges, a progress bar is displayed showing the progress of the spatial overlaps calculation for each of the selected oscillation angles. A cancel button enables the overlaps calculation to be interrupted if it is found to be too slow or if sufficient angles have been examined. As the analysis for each angle is completed, the results of the spatial overlaps analysis are output to a table in the main input output window giving the following items:
The strategy calculations are all based on 'quick' analyses of the data. A prediction is done for all reflections within the resolution range and their 'phi' values (rotation angles) are calculated. All reflections within a given phi range are assumed to be measurable unless they are within the cusp region or would not appear on the detector i.e. no distinction is made between fully recorded and partially recorded reflections and the oscillation angle is ignored.
The strategy option also makes use of the option to divide the cell by a factor to speed up the calculations very significantly though obviously with some loss of detail (see also description of quick analyses). The cell division factor for the strategy option and any subsequent quick analyses may be set via the parameter table under the menu area displayed when the strategy option has been selected.
Two basic strategy analyses are carried out by default. These are:
For this option, the strategy calculation determines the data coverage for all possible rotation ranges in 5 degree steps an starting at all possible rotation angles again in 5 degree steps e.g. rotations of 5, 10, 15 ... 360 degrees starting from rotation angles 0, 5, 10, 15 ... 355 degrees. For each rotation range, the start angle which gives the maximum data coverage of the required type is found. The highest coverage for each rotation range and the corresponding rotation angle starting value is is presented in the results table (see 'Examining the Results') below.
In some cases it is more efficient to collect the data in two separated rotation ranges and the double rotation range analysis determines the best two ranges to use. As the computations required are much greater than for the single range analysis, the calculations are carried out within a more restricted set of ranges. The program considers a first range size from 20 to 40 degrees (in 5 degree steps) followed by a gap of 20 to 40 degrees (in 5 degree steps) before the start of the second rotation range. Starting rotation angles from 0 to 90 degrees at 15 degree intervals and total rotations from 5 to 180 degrees in 5 degree steps are considered. For a short overall rotation range, the solution selected may be for a single rather than a double range. Also, because of the more restricted sampling ranges and start rotation angles, it is possible that in some cases, the data coverage from a proposed double range may be poorer than that found for the equivalent single rotation range.
When the requested strategy calculation has been completed a new strategy results window is displayed together with the following menu:
<Quick Solution Analysis> <Full Solution Analysis> <Overlaps Analyses> <Choose Multiple Segments> <Accept a Solution>If multiple segments are selected, then the exact format of the menu will change; further details are given below. The basic options are to perform quick or full data coverage analyses on any of the solutions proposed by the strategy calculations, to make further strategy calculations based on a multi-segment analysis or to accept one of the solutions for use in data collection.<Return to Previous Menu>
List of subsections in this section:
The Strategy Results Window
Choosing Multiple Segments
Analysing the Results
Accepting a Solution
Figure 1 Example of a Strategy Results Table
For each overall rotation range, the following items are output:
If the mouse pointer is moved to the percentage coverage item, for a double rotation range, then the value will be marked by an underline and further details of the double rotation range will be displayed below the columns of results. The details show the sizes of the two rotation ranges and their corresponding start angles or, if a single range is optimum, the size of the rotation range and the start angles annotated with the message '- single range only'.
<Choose Another Segment> <Delete Multiple Segments>The first new option alows another segment may then be added if desired. This involves a further single range strategy calculation and the display of a new set of results. A solution is selected from these results (the message 'Select segment' will appear in the active strip) and the program then re-displays the original results table with the multiple segments solution section being updated with the additional segment. The second option allows the multiple segments selection to be deleted, in which case the menu will return to its original form.
If another segment is selected then the <Delete Multiple Segments> option will be replaced by the option <Delete LAst Segment>. If the maximum of five allowed segements have been selected the <Choose Another Segment> menu item will no longer be present. Thus segments up to a maximum of five may be selected or segments from the end of the multiple segments list and finally the initial single or double rotation selection may be deletes as desired.
When one of these options is selected from the menu, the user must then select one of the strategy solutions from results table (the message 'Select solution for analysis' will be displayed in the active strip). A solution is selected by using the mouse to point to the results for the required solution, when it will be highlighted, and clicking the left mouse button. Either a single range solution or a double range solution or the multiple range solution (if present) may be selected.
If a full analysis is requested, the required oscillation angle for an image needs to be input in response to a prompt in the I/O section of the results window of the form:
Oscillation angle [x.xx]:The default value displayed is the current parameter value for the crystal set in question. The number of images to be measured and the overall rotation range, adjusted to be a multiple of the oscillation angle, are output.
It should be noted that if a quick analysis is requested, then no oscillation angle is assumed and the rotation range(s) resulting from the strategy calulation are used unmodified. On returning to the main menu and performing a quick analysis for the same rotation ranges, slightly different results may be obtained as, in that case, the rotation ranges are rounded up to be a multiple of the current oscillation angle.
If the 'Overlaps Analyses' option is selected, then, after selecting the solution to be analysed, the following menu is output:
<Standard Oscillations> <User Selected Angles>If the first option is selected a series of 6 standard oscillation angles (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 degrees) will be tried. If the second option is selected, the program prompts for up to 6 user selected oscillation angles via the stretegy results input/output window. Input of a value of zero terminates the list.<Return to Previous Menu>
After generating the unique reflections list and predicting the reflections covering the required ranges, a progress bar is displayed showing the progress of the spatial overlaps calculation for each of the selected oscillation angles. A cancel button enables the overlaps calculation to be interrupted if it is found to be too slow or if sufficient angles have been examined. As the analysis for each angle is completed, the results of the spatial overlaps analysis are output to a table in the strategy results input output window giving the following items depending on whether the maximisation is for unique data or acentric pairs data:
If no solution has been accepted when the <Return to Previous Menu> item is selected from the menu, a pop-up notice will be displayed and the user has the choice of returning in spite of not having accepted a solution or cancelling the return request.
The strategy calculation results are written to the log file together with the results of any analyses carried out. The information presented is essentially the same as that described for the results window except that details are output of the rotation ranges and start angles for each of the double segment results. A note is made of any solution accepted.
