Searching and matching

Complete reports of the searches and matches are formatted by the program. These can be copied to a disk file or printed. 

XRD was used to identify crystalline mineral phases in the samples. A Rigaku-Geigerflex goniometer was used (copper X-ray source, 45 kV, 35 mA, 1575 W). Samples were run in triplicate and a fourth run was conducted after tungsten was added to one of the replicates as an external standard. The data were evaluated for possible crystalline phases using the PC-based search and match program MICRO-ID (Materials Data Corp., Livermore, CA). 

Phase identification using powder diffraction data requires a comparison of several key features present in its digitized pattern with known compounds/phases. This is usually achieved by searching powder diffraction database(s) for records, which match experimentally measured and digitized pattern. Thus, a powder diffraction database or at least its subset should be available in addition to a suitable search-and-match algorithm. 

An automatic search-and-match can be done much faster, and most importantly, using multiple Bragg reflections by seeking through enormous arrays of data, which a typical database contains. The algorithms employed to conduct automatic searches vary extensively, however, parameters that are critical in any search include the following ... 

The compnter collects, stores, manipnlates, analyses and displays the spectral data. It can carry out both qualitative and qnantitative analysis as well as spectral searching and matching if the libraries are available. 

At the computer, the huge amount of information is processed and spectral searching and matching can be carried out. NMR spectra can be very complex, especially two-dimensional (2-D) experiments, and may require detailed data analysis and interpretation. Libraries can be very useful for assigning structure and identifying compounds. 

If the sample contains two or more crystalline compounds, identification becomes more complex. Here, various combinations of the more intense lines are used until a match can be found. Computer searching and matching of data greatly facilitates this task. 

Figure 10.3 Sequence information captured from the PDB illustrated for PDB complex 5hvp, HIV protease with acetyl-pepstatin. (a) The raw sequence can be used by standard sequence searching and matching tools, for example, BLAST, (b) The distance annotation permits any sequence information, for example, alignment to be focused down to the binding site sequence as defined by residues within 2,4,6, or 8 Aofthe calculated cavity, (c) PDB 3D coordinate file...

Intermediary s Role in Price Setting, Searching, and Matching... 

Results from Spectral Searching and Matching of Tobacco Types with a Reference Base Consisting of Flue-Cured, Burley, Maryland, and Dark-Fired Tobaccos... 

A. M. C. Davies, CARNAC A method of measuring composition by spectral searching and matching with Fourier vectors. Personal communications, 1990. 

Relative intensity (or area) of the peaks in the data might be completely different from what is typically observed in standard powder materials. As discussed above, that is due to the fact that the distribution of grain orientations might not be (and in most cases wiU not be) random. Although this fact greatly complicates search and match phase identification methods, this discrepancy in the observed peak intensities for a certain phase can be used to identify and in some cases quantify preferred orientation. 

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