Interpolymer complexes of poly(acrylic acid) with poly(2-hydroxyethyl acrylate) in aqueous solutions

Complexes formed from poly(acrylic acid) and poly(2-hydroxyethyl acrylate) were studied in aqueous solutions by viscometric, turbidimetric, FTIR spectroscopic, and thermogravimetric analysis methods. The formation of interpolymer complexes stabilized by hydrogen bonds was observed. It was found that the compositions of these interpolymer complexes are strongly dependent on the concentration of polymers, the order of mixing the solutions, and the pH. It was demonstrated that the complexation ability of poly(2-hydroxyethyl acrylate) is relatively low compared to other known nonionic water-soluble polymers. However, it can be significantly increased via hydrophobic modification of the poly(acrylic acid) using cetyl pyridinium bromide.     

One-step, three-component synthesis of highly substituted pyridines using silica nanoparticle as reusable catalyst

One-step synthesis of ‘privileged medicinal scaffolds’, 2-amino-3,5-dicarbonitrile- 6-sulfanylpyridines, has been demonstrated via a multicomponent reaction of aldehydes, malononitrile, and thiols using silica nanoparticle (NP) as catalysts. The silica NP catalysts are very mild (nearly neutral in nature), effective, environmentally benign, and retain most of their activities after being reused for three times.     

Crystal structure of rubidium cobalticyanide

The crystal structure of Rb₃[Co(CN)₆] was determined by X-ray diffraction analysis. The crystals are monoclinic, space group P2₁/c, a = 7.163(2), b = 10.601(3), c = 8.675(3) Å, β = 107.83(2)°, V = 627.1(3) ų, Z = 2, ρ_calcd = 2.497 g/cm³, R = 0.0844, wR = 0.2090 for 769 measured reflections. The coordination polyhedron of the Co atom is the regular octahedron [Co(CN)₆]. The Rb(1) atoms are in the cavities of the octahedral structure; the Rb(2) atoms are in the cavities of the trigonal prisms, additional two atoms being more distant. All the cyano groups of the complex are in terminal positions.     

Ab initio and analytic intermolecular potentials for Ar-CF4

Ab initio calculations at the CCSD(T) level of theory were performed to characterize the Ar + CF4 intermolecular potential. Potential energy curves were calculated with the aug-cc-pVTZ basis set, and with and without a correction for basis set superposition error (BSSE). Additional calculations were performed with other correlation consistent basis sets to extrapolate the Ar-CF4 potential energy minimum to the complete basis set (CBS) limit. Both the size of the basis set and BSSE have substantial effects on the Ar + CF4 potential. Calculations with the aug-cc-pVTZ basis set, and with a BSSE correction, appear to give a good representation of the BSSE corrected potential at the CBS limit. In addition, MP2 theory is found to give potential energies in very good agreement with those determined by the much higher level CCSD(T) theory. Two model analytic potential energy functions were determined for Ar + CF4. One is a fit to the aug-cc-pVTZ calculations with a BSSE correction. The second was derived by fitting an average BSSE corrected potential, which is an average of the CCSD(T)/aug-cc-pVTZ potentials with and without a BSSE correction. These analytic functions are written as a sum of two-body potentials and excellent fits to the ab initio potentials are obtained by representing each two-body interaction as a Buckingham potential.     

There are significantly more nonegative polynomials than sums of squares

We study the quantitative relationship between the cones of nonnegative polynomials, cones of sums of squares and cones of sums of even powers of linear forms. We derive bounds on the volumes (raised to the power reciprocal to the ambient dimension) of compact sections of the three cones. We show that the bounds are asymptotically exact if the degree is fixed and number of variables tends to infinity. When the degree is larger than two, it follows that there are significantly more nonnegative polynomials than sums of squares and there are significantly more sums of squares than sums of even powers of linear forms. Moreover, we quantify the exact discrepancy between the cones; from our bounds it follows that the discrepancy grows as the number of variables increases.     

Synthesis of bicyclic quinones via 1,4-diacetoxyanthracene

1,4-Diacetoxyanthracene is introduced as a convenient intermediate for the syntheses of bicyclic quinones and diquinones.     

The synthetic potential of graphite-catalyzed alkylation

Unmodified graphite is introduced as a mild catalyst for alkylation of aromatic compounds and primary alcohols, applicable when utilization of strong Lewis acids is not feasible. The electrophilic intermediate has a significant carbocationic character and can be formed on a partially rate-limiting step.     

Associative nil-algebras and Golod groups

Non-nilpotent, finitely generated, associative nil-algebras are studied as well as their adjoint groups and Golod groups. Solutions are given to some problems in residually finite group theory, questions posed in the Kourovka Notebook included. Supported by RFBR grant No. 03-01-00356. __________ Translated from Algebra i Logika, Vol. 45, No. 2, pp. 231–238, March–April, 2006.