OntoMathPRO: An Ontology of Mathematical Knowledge

Doklady Mathematics - The article describes OntoMathPRO, the first Linked Open Data ontology of professional mathematical knowledge. The ontology is designed to represent mathematical concepts. The...     

Polarity,polarizability, and structure of esters. 8. Relationships in spatial structure and electrooptical characteristics of esters of benzoic acids

Average structural characteristics of esters of benzoic acids have been found by statistical treatment of crystallographic data. A general procedure has been developed for determining electrooptical parameters that are optimal for a series of molecules with C_s symmetry. In a series of methyl benzoates p-R-C₆H₄-COOCH₃, the index ellipsoid of the unsubstituted molecule is characterized by semiaxes b₁=14.89, b₂=18.74, b₃=9.27 ų; here, the b₂ axis deviates by 5° from the C-R axis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 795–801, April, 1991.     

Polarity,polarizability, and structure of esters. 6. Conformations of para-substituted phenyl chloroformates in solutions

The ellipsoid of polarizability of the chloroformate fragment ClC(O)O has principle semiaxes b₁=3.64, b₂=5.34, b₃=3.81 Å₃; the angle between b₁ and the C=0 bond is 24.5°. Aromatic chloroformates in solutions exist in conformations with cisoid position of the C=O and O-R bonds and the phenoxyl fragment in aromatic chloroformates deviates from the plane of the molecule.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2704–2708, December, 1989.The authors wish to thank S. G. Vul'fson for assistance in measuring the depolarization of Rayleigh light scattering.     

Calculation of band intensities in vibrational spectra and conformation of chloromethylformate and chloromethylacetate

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 1, pp. 70–74, July, 1988.     

Mathematical knowledge ontologies and recommender systems for collections of documents in physics and mathematics

An approach to the implementation of a recommender system based on ontologies of mathematical knowledge is presented. On the basis of a document browsed by a user, the system forms on line a list of recommendations, which include similar documents, key words, and definitions of these words from ontology and other terminological sources. The method of recommendations yields a vector representation of documents, taking into account the position of terms in the logical structure of the document and their ontological connections. On the basis of the cosine measure, a measure of proximity between documents is calculated. The order of documents in the list of recommendations is determined by values of the proximity measure. Various adaptations of the system to user scenarios aimed at the preparation of personalized recommendations are discussed.     

Polarity,polarizability, and structure of esters 7. Electronic and steric structure of clcoocclnh3-n chlorinated chloroformates

Mono-, di-, and trichloromethyl chloroformates were investigated by dipole moments, Kerr effect, and nuclear quadrupole resonance (NQR) methods. It was determined that chloromethyl chloroformate exists in solution in synclinal conformation with respect to the O-C_sp bond with COCCl dihedral angle 90±10°. The n, interaction occurring in it is close in magnitude to that in chloroalkyl formates and acetates. Dichloromethyl chloroformate exists in the crystal in the sc, ap conformation at the O-C_sp bond. In chlorinated chloroformates, the orbital n, and n, interactions are in a state of competition.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 413–417, February, 1991.     

Comparative analysis of the applicability of AM1 and CNDO/2 methods for quantitative prediction of the35Cl NQR frequencies of RC-Cl compounds

The³⁵Cl NQR frequencies of a series of RC-Cl compounds were calculated by the AM1 and CNDO/2 methods in the Townes-Dailey approximation. It was shown that neither of these methods can be directly used for the quantitative prediction of NQR frequencies, and their use in the correlation approach is only possible in narrow series. The AM1 method gives better results for saturated compounds.Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 1078–1082, May, 1992.     

Competition between n,π- and n,σ-orbital interactions in chlorinated ethers R-O-chcir 1

Using the AM-1 method, we have studied CH₂=CH-O-CHClR¹ molecules (R¹=H, Me). We have shown that the sc conformation with respect to the bond is preferred. We have systematized the¹³Cl NQR data on the degree of manifestation of the generalized anomeric effect in R-OCHClR¹ [R=Me, Ph, Vyn, R²C(=O)] molecules. We have established that enhancement of n, conjugation in the R-O fragment leads to weakening of the n, interaction in the O-C-Cl triad.Deceased.