Existence of linear Pfaff systems with lower characteristic set consisting of countably many segments in the space <Emphasis Type="Italic">R</Emphasis><Superscript>3</Superscript>

We prove the existence of a completely integrable Pfaff system ∂x/∂t _i = A _i (t)x, x ∈ R _n , t = (t ₁, t ₂, t ₃) ∈ R ₊³, i = 1, 2, 3, with infinitely differentiable bounded coefficient matrices and with lower characteristic set being the union of countably many segments in the space R ³.     

2,5-diphenyl-3,4-bis[p-(phenylethynyl)phenyl]cyclopentadienone and product of its Diels-Alder homocondensation

A new monomer of the ABA type, 2,5-diphenyl-3,4-bis[p-(phenylethynyl)phenyl]-cyclopentadienone, was synthesized. The Diels-Alder homocondensation of the monomer resulted in a highly branched polyphenylene (M _w=160000), readily soluble in organic solvents. The polymer obtained is thermally stable up to 600 °C (in argon atmosphere) and has a glass transition of 280°C. The structure of the monomer and polymer was confirmed by¹H NMR,¹³C NMR, IR Fourier, and Raman Fourier spectroscopy. Max-Planck-Institut für Polymerforschung, Ackermann-Weg, 10, Mainz, Deutschland. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 953–958, May, 1999.     

Molecular characteristics of aqueous solutions of biologically active disubstituted derivatives of fullerene C60

The study of the degree of association of biologically active disubstituted fullerene derivatives at different substance concentrations in an aqueous solution using the diffusion method showed that the nature of substituents exerts the strongest effect on the degree of association of the fullerene derivatives.     

Power and lasing threshold for longitudinally pumped lasers with intracavity raman self-conversion

A method is developed for calculating the power and lasing threshold for longitudinally pumped lasers with intracavity Raman conversion. The theoretical analysis is based on equations for the powers of light beams in the cavity. Expressions for the power and lasing threshold of a Raman laser with self-conversion as functions of the parameters of the active medium, cavity, and pumping, taking into account the overlap of all the interacting beams, are derived and analyzed.     

Formation of Rechargeable Films on Platinum in Sulfuric Acid Solutions of Isopolytungstates

Two types of redox processes, with the formation of (a) dissolved reduced forms of tungstates and (b) solid products, occur on a platinum electrode in metastable long-lived true solutions of isopolytungstates (pH 0.5) in the hydrogen adsorption region. The solid products accumulate on the platinum surface as crystalline films capable of reversible recharging. Basic parameters of the films are determined using cyclic voltammetry, x-ray diffractometry, and scanning tunneling microscopy. Based on a spectrophotometric analysis of solutions, redox conversions, observed in the hydrogen range of potentials, are referred to dissolved hepta- and decatungstates present in the system.     

Effect of the addition of indium to alumina-platinum catalysts on the dehydrogenation of higher n-paraffins

Conclusions The addition of 0.2–4.0% indium to alumina-platinum catalysts with 0.05–0.5% platinum suppresses the acidic function of the support, increases catalyst selectivity relative to normal monoolefins, and, in contrast to lithium, increases activity in the dehydrogenation of normal dodecane. The maximum activity is found for catalysts with 1–2% indium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2089–2094, September, 1982.     

Michael condensation of 3-arylidene-3H-pyrrol-2-ones and 3-arylidene-3H-furan-2-ones with cyclohexanone

The Michael condensation in the series of 5-aryl-3-arylidene-3H-pyrrol-2-ones and 5-aryl-3-arylidene-3H-furan-2-ones, containing an activated C=C bond, with cyclohexanone was investigated. It was shown that the condensation products were 1,5-dicarbonyl compounds containing a heterocyclic fragment. The enolization of one of the oxo groups, leading to the formation of hydroxypyrrole or hydroxyfuran structures, was demonstrated by the spectral data. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 823–827, June, 2007.     

Functional polymer colloids with ordered interior

Polymer colloids with internal ordering were synthesized using hydrolytic condensation of octadecyl-dimethyl(3-trimethoxysilylpropyl)ammonium chloride (ODMACl) and a mixture of ODMACl and the trisodium salt of the triacetic acid N-(trimethoxysilylpropyl)ethylenediamine (TANED). The structure and morphology of these colloids were studied with small-angle X-ray scattering, transmission electron microscopy, nuclear magnetic resonance, sedimentation in ultracentrifuge; and other methods. When polymer colloids are obtained from a single precursor (ODMACl), their local structure, molecular weight characteristics, and morphology strongly depend on the reaction conditions, while lamellar ordering remains nearly unaffected. Use of a mixture of cationic and anionic silanes (ODMACl and TANED) as precursors in hydrolytic condensation results in novel zwitterionic copolymer colloids with two-dimensional hexagonal packing. Interaction of the ODMACl quaternary ammonium groups with the three carboxy groups of TANED leads to replacement of sodium and chloride ions and formation of gegenions, resulting in a molar ratio ODMACl:TANED = 3:1 (each TANED molecule contains three carboxy groups). Due to their ordered interior, polyODMACl (PODMACl) and PODMACl-TANED colloids can be used as templates for controlled positioning of nanoparticles within these colloids. For example, lamellar ordering controls Pt nanoparticle formation within PODMACl colloids providing Pt nanoparticle alignment within the lamellar structure. Loading of PODMACl-TANED colloids with iron salts followed by pH increase results in the formation of iron oxide nanoparticles located within PODMACl-TANED cylinders.     

Esterification of n-Butanol with Acetic Acid in the Presence of H3PW12O40 Supported on Mesoporous Carbon Materials

The adsorption of H₃PW₁₂O₄₀ (HPA) from methanol solutions on mesoporous carbon supports (multiwall carbon nanotubes (CFC-3) and CFC modified with nitrogen atoms (N-CFC)) was studied. It was found that up to 10 wt % HPA was irreversibly adsorbed on the surface of CFC. This character of adsorption is indicative of the strong interaction of the adsorbate (HPA molecules) with coal surface groups (carboxylic, lactone, etc.) to form intermolecular hydrogen bonds with -electron interactions. It was found that N-containing surface centers affected the adsorption of HPA on N-CFC. The acid and catalytic properties of HPA/CFC systems in the esterification reaction of n-butanol with acetic acid were studied ([BuOH]/[HOAc] = 1 : 15 mol/mol; 80°C). It was found that the strength of proton centers, which was determined as proton affinity, decreased upon supporting HPA. The HPA/CFC-3 systems most actively catalyzed the reaction. The catalytic activity of HPA/N-CFC depended on the nature of N-containing groups at the support surface, and it decreased with concentration of pyridine-like structures.     

A mixed-valence bis(diarylamino)stilbene: crystal structure and comparison of electronic coupling with biphenyl and tolane analogues

The E-4,4'-bis[di(p-anisyl)amino]stilbene cation is a class-III mixed-valence species with electronic coupling comparable to that in its biphenyl-bridged analogue, whereas its tolane-bridged analogue belongs to class II.