Real spin-Clifford bundle and the spinor structure of space-time

By analyzing the conditions for the existence on a space-time of a global algebraic spinor field, we prove the following result, known as Geroch's theorem: A necessary and sufficient condition for to admit a spinor structure is that the orthonormal frame bundleF ₀() have a global section. Our proof, which does not use in any stage the complexification of _1,3 (the space-time Clifford algebra), is simple, requiring only the explicit construction of the algebraic spinor and the spinorial metric within _1,3 and elementary facts about associated bundles and the bundle reduction process. This is to be compared with the original proof, which uses the full algebraic topology machinery. We also clarify the relation of the covariant spinor structure and Graf'se-spinor structure.     

Synthesis of amphiphilic diacyl derivatives of 3,7-diazabicyclo[3.3.1]nonan-9-one

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Eco-friendly N–N coupling of aminofuroxans into azofuroxans under the action of electrogenerated hypohalites

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Thermal decomposition and reducibility of silica-supported precursors of Cu,Fe and Cu–Fe nanoparticles

Journal of Thermal Analysis and Calorimetry - Poly(butylene succinate) (PBS) nanocomposites filled with nanoprecipitated calcium carbonate (NPCC) were prepared via melt blending. The hybrid...     

A new and efficient method for the synthesis of 3-(2-nitrophenyl)pyruvic acid derivatives and indoles based on the Reissert reaction

The formation of 3-(2-nitrophenyl)pyruvic acid and its amide and ester derivatives – key compounds for the Reissert indole synthesis – was achieved under various reaction conditions via the acid catalyzed hydrolysis of 5-(2-nitrobenzyliden)-2,2-dimethyl-1,3-oxazolidin-4-one, which is readily available from 3-(2-nitrophenyl)oxirane-2-carboxamide. A new and highly efficient method for the synthesis of indole-2-carboxylic acid derivatives via the intramolecular reductive cyclization of o-nitrophenylpyruvic acid and its amide and ester derivatives was developed using Na₂S₂O₄ in dioxane/water at reflux.     

Ab initio evaluation of intramolecular electron transfer reactions in halobenzenes and stabilized derivatives

The potential energy surfaces for the fragmentation of the radical anions of p-nitrochlorobenzene and p- and m-chloroacetophenones were explored using first principle methods. The behavior of these compounds, stabilized by pi acceptors, is compared to that shown by the unsubstituted halobenzenes (PhX, X = F, Cl, Br, I). The presence of pi and sigma radical anions was inspected as well as the intramolecular electron transfer (intra-ET) from the pi to the sigma surface, responsible for the dissociation of these intermediates. The profiles obtained with the B3LYP functional in the gas phase and in the presence of a polar solvent are in agreement with the spectroscopic evidence and with the experimentally observed reactivity of the compounds under study. The stability of the radical anion of p-nitrochlorobenzene and the adiabatic and endothermic nature of its dissociation are explained. The order of the rate constants for dissociation m-chloroacetophenone < p-chloroacetophenone is interpreted on the basis of the differences in the adiabatic character of the intra-ET of both isomers which is ascribed to the nodal properties of their SOMOs. In the halobenzene family, the electronic factors responsible for the intra-ET are analyzed. The stabilization of the sigma surface exerted by the different halogens and its effect on the rate constants for dissociation are explained.     

Regiodirected phosphorylation of 2,2′,7,7′-tetrahydroxydinaphthylmethane

The phosphorylation of 2,2′,7,7′-tetrahydroxydinaphthylmethane was studied and the influence of molecule pre-organization on the regioselectivity of functionalization was investigated. The reactions of 2,2′,7,7′-tetrahydroxydinaphthylmethane with phosphorous amides containing 1-3 amide bonds gave oligophosphorylated derivatives differing in the number and the nature of phosphorus fragments and in the size of phosphorus rings: tetraphosphorus macrocycles containing one 24-membered and two eight-membered phosphorus rings, triphosphorus compounds containing a phosphocine ring and two acyclic phosphorus fragments, and tetraphosphorylated derivatives with four phosphorus groups in the molecule. The possibility of controlling the regioselectivity of phosphorylation by using reagents differing in the number and activity of P-N bonds was demonstrated.     

A novel equation of state for the prediction of thermodynamic properties of fluids

This work proposes a new equation of state (EOS) based on molecular theory for the prediction of thermodynamic properties of real fluids. The new EOS uses a novel repulsive term, which gives the correct hard sphere close packed limit and yields accurate values for hard sphere and hard chain virial coefficients. The pressure obtained from this repulsive term is corrected by a combination of van der Waals and Dieterici potentials. No empirical temperature functionality of the parameters has been introduced at this stage. The novel EOS predicts the experimental volumetric data of different compounds and their mixtures better than the successful EOS of Peng and Robinson. The prediction of vapor pressures is only slightly less accurate than the results obtained with the Peng-Robinson equation that is designed for these purposes. The theoretically based parameters of the new EOS make its predictions more reliable than those obtained from purely empirical forms.     

In Situ Amperometric Characterization of Liposome Suspensions with Concomitant Oxygen Reduction

Amperometry of oxygen reduction at the dropping mercury electrode (DME) was applied for in situ characterization of liposome suspensions in terms of concentration, level of polydispersity and potential range of adhesion. Liposomes prepared from egg‐phosphatidylchloline/cholesterol/dicetylphosphate in the molar ratio of 7 : 5 : 1 were suspended in phosphate‐buffered saline (PBS). Adhesion signals of single liposomes in air‐saturated suspensions were detected in the broad potential range (from ?100 to ?1200 mV vs. 0.1 M Ag/AgCl reference electrode) as transient enhacements of oxygen reduction. Measured concentration range in air‐saturated suspensions was 10⁶–10⁸ liposomes/L.     

Calculation of hfs coupling constants by the roothaan “Plus” configuration interaction method within the INDO approximation

A new set of parameters, relating hfs coupling constants to the spin densities calculated by the RHF+CI method, within the INDO approximation, is given for¹H, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F. On the whole the results, obtained for a homogeneous sample of organic radicals, are in better agreement with experimental ones, as compared with UHF method.