INDEX procedures

The crystal group or Bravais lattice of an unknown crystalline material can also be obtained using SAD. This is achieved easily with polycrystalline specimens, employing the same powder pattern indexing procedures as are used in X-ray diffraction. ... 

It should be noted that italicised hyphenated prefixes which indicate structure, such as cis-. o-, m-, tert-, mixo-, N-. 0-, etc., have been ignored during the alpha-sorting routine used on this index and the group-lists, while the roman character structural prefixes iso and neo, and roman multiplying prefixes such as di, tris, tetra and hexakis, have been included in the indexing procedure. 

If this model is selected, one must then decide what variables to use for the ordinate and the abscissa. The parameters must be dose-sensitive, free of confounding variables, easily determined and preferably linear. We have evaluated this approach for estimating the bioavailability of calcium in mechanically deboned meat products (11). Typically, correlations between various bone parameters and dietary calcium are very high (r = 0.943 to 0.999). This is consistent with what others have found for similar parameters (46,47). These correlations are also similar to the those (r = 0.947 to 0.982) between the amount of calcium consumed and calcium retained (11) a good index procedure. 

The main purpose of extracting the diffraction information from any kind of diffraction pattern is to continue with stmcture solution using the extracted quantitative data. This data includes the calculated unit cell parameters obtained during the indexing procedure, s mimetry determination such as a space group or a set of possible space groups and integrated intensities for indexed reflections. 

NOTE This test is often called the Water Separation Index, Modified (WSIM) test, named after the original water separation index procedure. 

Internally IGOR uses since 1980 canonical representation of chemical reactions that is based on a linear combination B + kE (k is an integer the maximum entry of any B or E, e.g k = 10). The latter is subjected to a canonical indexing procedure by an extended version of the algorithm CANON (ref. 21,22). 

The crystal used for data coUection was transferred to an Enraf-Nonius CAD-4 diffractometer. Automatic peak search and indexing procedures yielded the same monoclinic cell as derived from the X-ray powder diffraction data and precession photographs. Testing showed that the cell was indeed primitive and that there was no superlattice present. Table 5 gives the crystal data and X-ray experimental parameters, and Table 6, the interatomic distances and angles. Positional and thermal parameters are given in Table S3 (Supporting Information)... 

The algorithm provides a probability value for each extinction symbol compatible with the lattice symmetry established by the indexing procedure. 

This can lead to problems in the indexing procedure, as for a body-centred lattice the first reflection is not the 100 but the 110. 

Now, these equations have been written with formal integration, but of course in the numerical implementation only the evaluation of the integrand at the grid points is required. Therefore, it is evident that the derivatives lyl, (Vpo)M and (Vpp)tyl can be evaluated on the grid independently of the indices pv, and so the four-index problem is decomposed into two independent two-index procedures, avoiding the potential computational bottleneck. By comparison, the resolution of the identity technique proposed by Komornicki and Fitzgerald [66] gives an approximate result in terms of a product of one two-index and two three-index quantities. 

An index should be usable with a minimum of effort on the reader s part Searching can be facilitated to some extent by proper choice of indexing procedure and arrangement of the table but it is not possible to anticipate all potential interests and needs of the readers. The primary consideration in design of the table was to assign each compound unambiguously to its position in the file so that all data and references are collected in one place, and so that the user will either find the polymer of interest direcdy or know that it is not listed. 

The indexing procedure we have just discussed has provided us with information on the unit cell, and thus the Bravais lattiee. Taking the symmetry of the diffraction pattern, the so-called Laue group (Table 10.1), into account, we ean now determine whieh reflections have to be measured, and which reflections are equivalent by symmetry. For instance. Table 10.1 shows that for the triclinic system the Laue group is 1, i.e. the diffraction pattern is centrosymmetrie and only half the reflections have to be examined for a monoclinie crystal the Laue group is 2/m, i.e. the diffraction pattern has two elements of two-fold symmetry and consequently only a quarter of the reflections are needed. In the monochnic case we have to measure all... 

The stationary phases requirements of selectivity and higher thermal stability then became more clearly defined the process of stationary-phase selection and classification became logical after the studies of McReynolds (28) and Rohrschneider (29,30) were pubUshed, both of which were based on the retention index (31). The Kovats retention index procedure and McReynolds constants are discussed in detail in the following section. Kovats retention indices today remain a widely used technique for reporting retention data, while every stationary phase developed for packed and capillary GC has been characterized by generation of its McReynolds constants. 

Kovats retention index procedure and the McReynolds and Rohrschneider constants are discussed in detail in the following sections. The Kovats index remains a widely used technique for reporting retention data, and every stationary phase developed for packed and capillary gas chromatography has been characterized by its McReynolds constants. 

Using the global index procedure, the solution approximation (12.408) can be rewritten in the following way ... 

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