A preconditioned domain decomposition algorithm for the solution of the elliptic Neumann problem

A new preconditioned conjugate gradient (PCG)-based domain decomposition method is given for the solution of linear equations arising in the finite element method applied to the elliptic Neumann problem. The novelty of the proposed method is in the recommended preconditioner which is constructed by using cyclic matrix. The resulting preconditioned algorithms are well suited to parallel computation.     

Synthesis and some conversions of 6-methyl- and 1,6-dimethyl-5-nitro-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidines

Using a modification of the Biginelli reaction, we have synthesized 6-methyl- and 1,6-dimethyl-5-nitro-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidines. We have studied some of their chemical conversions involving the methyl group on the C₍₆₎ atom, the nitrogen atoms of the pyrimidine ring, and the phenyl substituent.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 3, pp. 388–392, March, 1993.     

Sigma complexes in the pyrimidine series. 2. σ Complexes of 5-nitropyrimidine and methoxy-substituted 5-nitropyrimidines with the acetone anion

The corresponding σ complexes of the Meisenheimer type, viz., anions of the potassium salts of 6H-5-nitro-6-acetonylpyrimidines, were obtained and isolated in the reaction of 5-nitro-, 5-nitro-4-methoxy-, 5-nitro-2-methoxy-, and 5-nitro-2,4-dimethoxypyrimidines with acetone in the presence of potassium hydroxide. The structures of the complexes were proved by means of the PMR, IR, and UV spectra. It is shown that the acetone anion in all cases adds to the methoxy-unsubstituted position of the pyrimidine ring, whereas nucleophilic attack takes place at the C₄ atom when the 2 and 4 positions are free. See [1] for communication 1. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 239–242, February, 1980.     

σ-Complexes in the pyrimidine series. 13. Reaction of 7- and 5-methoxyfuroxano-[3,4-d]pyrimidines with some C-nucleophiles

We have studied the reaction of isomeric 7-and 5-methoxyfuroxano[3,4-d]pyrimidines with carbanions of some CH acids. We have shown that regardless of the position of the substituent in the pyrimidine ring, nucleophilic attack occurs regioselectively at the C₍₇₎ atom. As a result, we have obtained the products of substitution at the methoxy group, and also anionic complexes and covalent adducts.For Communication 12 see [1].Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kiev 253660. Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 34, No. 1, pp. 112–119, January, 1998.     

GENETIC VARIATIONS AND LINOLENIC ACID INDUCED CHANGES IN THE ORIENTATION PATTERN OF CHLOROPHYLL a IN THYLAKOID MEMBRANES

Abstract Orientation pattern of the Q_y absorption and emission dipoles of chlorophyll a were studied in wild type Scenedesmus obliquus and in mutants deficient in chlorophyll b and carotenoids. Fluorescence polarization ratio at –140°C and linear dichroism at 25°C were measured in whole cells and thylakoids aligned in polyacrylamide gel. Unlike normal thylakoids, mutants displayed fluorescence polarization ratios significantly lower than 1.0 and showed a negative LD signal around 672 nm, indicating the tendency of the Q_y dipoles to tilt out from the membrane plane. Such an orientation pattern can also be artificially induced by treating normal thylakoids with linolenic acid.     

Electrophilicity of 5-benzylidene-1,3-dimethylbarbituric and -thiobarbituric acids

The kinetics of reactions of acceptor-stabilized carbanions 2a-m with benzylidenebarbituric and -thiobarbituric acids 1a-e has been determined in a dimethyl sulfoxide solution at 20 degrees C. Second-order rate constants were employed to determine the electrophilicity parameters E of the benzylidenebarbituric and -thiobarbituric acids 1a-e according to the correlation equation log k(20 degrees C) = s(N + E). With E parameters in the range of -10.4 to -13.9, the electrophilicities of 1a-e are comparable to those of analogously substituted benzylidenemalononitriles.