Tetrahedron Computer Methodology最新文献

The simplest versions of cluster analysis currently in use are very easy to grasp. Such a straightfoward clustering technique is explained in detail and a sample analysis covering five isomers of an organic compound is presented. Cluster analysis is normally used in conjunction with other techniques of multivariate analysis. Some examples where multivariate analysis has been applied to problem solving in Chemistry are briefly described and for an in-depth discussion of some pitfalls encountered in practical applications the reader is referred to the literature.

The PC program IGOR2 can be used to generate chemical reactions as well as structural features of molecules. The mode of operation and the practical use of IGOR2 are explained. Its application is illustrated by example runs that are described in detail. The IGOR2 program and the example data files are included on disk. The manual is included as an appendix.

The concept of WALKING on structures is proposed, and the partial ordering between a structure and a query structure (substructure) is also created by means of WALKING. Based upon the concepts above, the authors create the Heuristic-Backtracking Algorithm (HBA) of structural match with high performance. The applications of HBA in molecular graphics, synthetic planning, spectrum simulation, the representation and recognition of general structures are discussed. The source code (HBA.PAS) and executable code (HBA.COM) plus input files (DEMO∗.HBA) are included on disk.

KC Expert is a system, written in Prolog, which is an aid to solving chemical and physical problems related to the properties of the atomic elements. It consists of a limited domain natural language interface, based on a semantic grammar, to a knowledge base of the atomic elements. The knowledge base contains a data base of properties of the elements and several rules using these properties. The system can be used both in research and for instructional purposes. In this paper we discuss the development of the system, its capabilities, and planned enhancements. The executable program is included as is the Prolog source code.

The concept of Complete Synthetic Strategy (CSS) is defined. A CSS differs from most strategies found in the literature in that it provides synthesis guidelines for a complete synthesis from start to finish, that is from the target down to and including the starting materials. One CSS covers only a particular type of synthesis. In this paper the development and implementation of a CSS is outlined using the Building Block Strategy (BBS) as an example (BBS represents a convergent synthesis in which the target is made out of two structures, i.e., building blocks, coming from two starting materials). The strategy is developed under the philosophy that it is defined as generally as possible and all the intermediate chemical objects, concepts and data are derived from a minimal amount of information to be found in a chemical databank in a preprocessing stage. At RISC-Linz we have developed a chemical expert system (written in LISP) for chemical databank analysis and this was used to generate all data objects for a prototype synthetic planning system using BBS.

A set of FORTRAN subroutines for the self-consistent reaction field solvation modelling in the framework of semiempirical quantum-chemical methods is described and included on disk. These subroutines can be added to the VMS or UNIX versions of the MOPAC and AMPAC program packages. Sample calculations for 4- and 5-nitroimidazole, and comparisons with experiment, illustrate the utility of the present approach for the rationalization of condensed media phenomena.