Magnetic-type criteria

Introduction Selection of power reactors Magnetic charecteristics Design criterion and / (p characteristics of different types of reactor Application... 

In discussing various indices of aromaticity developed from different criteria (energetic, structural, magnetic), we noted correlations between indices based not only on one type of criteria, but also on different ones. Is, however, the interrelation among different criteria always clear-cut and convincing Will the aromaticity inferred from, say, a magnetic criterion be confirmed by an energetic one ... 

The material presented in Section II warrants, apparently, the conclusion that the main test of aromaticity and antiaromaticity is represented by the energetic criterion realizable within the framework of various schemes for calculating resonance energies. In most cases it correlates with structural and magnetic criteria moreover, it often accords well with a manifestation of numerous properties of compounds, which, being regarded as attributes of aromaticity, make its very concept substantially broader. Indeed, the concept of aromaticity claims an increasing number of types of compounds and requires a more and more sophisticated classification. 

These complexes and others of similar character are discussed further in Chapter 5, in which a magnetic criterion for bond type applicable to complexes of the transition elements is described. 

Complex Bond Orbitals The Magnetic Criterion for Bond Type... 

The hybrid bond orbitals discussed in the preceding chapter have been described as having only a small amount of d and / character. The bonds in many molecules and complex ions, especially those involving atoms of the transition elements, can be discussed in a simple way in terms of hybrid orbitals with a large amount of d character (and, in a few cases, / character). These bonds and a magnetic criterion for bond type are discussed in the following sections. 

Along similar lines, carbon-13 magnetic resonance has been applied to coal and to the elucidation of the character of soluble coal fractions and other coal-derived materials (Bartuska et ah, 1978 Ladner and Snape, 1978 Miknis, 1988). In fact, it is the advances in carbon-13 magnetic resonance that have brought new thoughts to the chemical nature of, and structural types in, coal. The technique brought with it the innovative solid-state techniques that allowed coal to be viewed in its natural solid state without invoking the criterion of sample solubility. This removed the need for dissolution of coal fractions and the often... 

Of all the methods available for the physical characterization of solid materials, it is generally agreed that crystallography, microscopy, thermal analysis, solubility studies, vibrational spectroscopy, and nuclear magnetic resonance are the most useful for characterization of polymorphs and solvates. However, it cannot be overemphasized that the defining criterion for the existence of polymorphic types must always be a non-equivalence of crystal structures. For compounds of pharmaceutical interest, this ordinarily implies that a non-equivalent X-ray powder diffraction pattern is observed for each suspected polymorphic variation. All other methodologies must be considered as sources of supporting and ancillary information, but cannot be taken as definitive proof for the existence of polymorphism by themselves. 

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