Classifications of structural

The above classification of structures is made primarily for convenience. In fact, the structures of many compounds cannot be precisely described under any of these classes, which represent limiting, or ideal cases. However, we shall use these classes to examine further the limiting types of bonding found in them. 

The possibilities for the application for neural networks in chemistry arc huge [10. They can be used for various tasks for the classification of structures or reactions, for establishing spcctra-strncturc correlations, for modeling and predicting biological activities, or to map the electrostatic potential on molecular surfaces. 

In order to examine the electronic structures of CNT it is necessary to first define the classification of structural configurations of CNT. The configuration of a CNT is constructed by enrolling a graphite sheet as illustrated in Fig. 1. That is. 

With over 600 currently known zeolites and new ones discovered every year, it is useful to have a general classification of structures endorsed by the lUPAC. In this system each structure has three letters, for example EAU for faujasites, MFI for ZSM-5 and MOR for mordenite. Within a given structure there can still be many different zeolites, as the composition may vary. 

According to Parthe et al. (1993), a standardization procedure is necessary in the presentation of the relevant data characteristic of a crystal structure (see also Parthe and Gelato 1984). A convenient description of the structure types is then possible using the Wyckoff sequence (the letters of the occupied Wyckoff sites). This allows a finer classification of structure types and offers suggestions not only for recognizing isotypic structures but also possible structural relationships like substitution, formation of vacancy or filled-in structure variants. 

Principles and types of modular series have been summarized in a book by Ferraris et al. (2004). A hierarchical classification of structure has been introduced as well as the application of modularity to structure description and modelling. The order/disorder theory has been presented as fundamental to developing a systematic theory of polytypism, dealing with structures based on both ordered and disordered stacking of one or more layers. The structures of a great number of compounds (minerals, complex oxides, salts, etc.) have been described and discussed. 

This classification reminds one of the classification of structure-insensitive (I) and structure-sensitive (II) reactions by Boudart (223). It is probably not true that all reactions of group II are structure-sensitive and vice versa, but it is to be expected that the possible candidates for structure sensitivity are indeed in group II rather than in group I of the above classification. 

It appears that the classification of structure-sensitive reactions should be expanded to separate those reactions that exhibit step (or kink) sensitivity into one group, and those that are also sensitive to the structure of the overlayer into another group. This expanded classification is shown in Table IV. 

An interesting sidelight of the organic structural classification study was that herbicidal activity could also be predicted 6). The nitrodiphenylethers could be divided into compounds which were strong herbicides and those compounds which showed little or no herbicidal activity. Both Faradaic and capacitive responses could be used to separate these classes for over half the experimental conditions examined. As was found in the classification of structure, capacitive factorial features performed somewhat better than Faradaic factorial features. It also appeared that classifications of herbicidal activity using Faradaic factorial features could be improved considerably by working at high pH and without surfactant present. The information content of Faradaic or capacitive variable effects data could be improved by variations in % ethanol. 

Survey and classification of structural domain-domain interfaces... 

In the reviews of Loeb ° and Hellner the following classification of structural types on the basis of the structure geometry of intermetallic compounds has been made ... 

Ohver N. H. S. (1996) Review and classification of structural controls on fluid flow during regional metamorphism. J. Metamorph. Geol. 14, 477—492. 

The classification of structural types can often be done more conveniently on the basis of valence electron counts. Various schemes for relating electron counts to structures have been proposed, with most proposals based on the set of rules formulated by Wade. " The classification scheme based on these rules is summarized in Table 15-7. In this table, the number of pairs of framework bonding electrons is determined by subtracting one B—H bonding pair per boron the n + 1 remaining framework electron pairs may be used in boron-boron bonding or in bonds between boron and other hydrogen atoms. 

The classification of structural variations is not easy in every arrangement there are many overlaps because of multiple substitution. Strictly speaking, only three types of ring substitution can occur in penams. 

Topological descriptors can be computed very quickly for a huge number of compounds. These descriptors are able to reproduce the intuitive classification of structural formulas. For this reason, topological descriptors are a good choice to describe the diversity of huge virtual libraries in an automated way. 

Serra, J.R., Thompson, E.D. and Jurs, P.C. (2003) Development of binary classification of structural chromosome aberrations for a diverse set of organic compounds from molecular structure. Chem. Res. Toxicol., 16, 153—163. 

For a more sensitive detection and classification of structural changes within the metastable liquid, the radial distribution function proves quite inadequate, and this had led to the development of alternative approaches. For instance, analyses in terms of the structure factor S(k) and... 

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