Kinetic description of the oxidation of hydrocarbons inhibited by sulfur-containing hydrogenated quinolines

The inhibiting effect of dithiolthione derivatives of hydrogenated quinolines (DTT) on the oxidation of various hydrocarbons (n-decane,n-decene, ethylbenzene, -carotene) was investigated. The inhibiting effect of the DTTs is greater at high temperatures (>100 °C) than that of the parent hydrogenated quinolines and weaker at moderate temperatures. The DTTs do not affect the decomposition of hydroperoxides. Probably, the introduction of a dithiolthione cycle to a hydroquinoline molecule decreases its reactivity toward O₂ and peroxide radicals, which favors the enhancement of the antioxidative activity of the DTTs at elevated temperatures.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 814–818, May, 1994.     

Study of the modulated structure of Bi2Sr2CaFe2Ox

The ceramics and single crystals of the Bi₂Sr₂CaFe₂O_x compound were synthesized. The X-ray diffraction data showed orthorhombic symmetry. The lattice parameters are equal toa=5.464 Å,b=5.453 Å,c=31.313 Å. The crystal structure is described by the primitive Bravais lattice with the possible space groups Pbmm. Pbm2 and Pb2₁m. The obtained X-ray patterns show the presence the incommensurate structural modulation with the following parameters: the modulation vector lies in the (100)-plane, the value of the wave-vector componentq _b=0.22(3). The comparison of the obtained results with data for Fe-doped Bi₂Sr₂CaCu₂O_x and Bi₂Sr₃Fe₂O_x are presented. No magnetic peculiarities of the compound were found. Mssbauer measurements of the ceramic samples indicate the presence mainly of Fe³⁺ oxidation state and Fe⁴⁺ (about 20%). The decrease of the quadrupole-splitting values for 2212Fe in comparison with Fe-doped 2212Cu was revealed that may be connected with higher symmetry of the local environment of Fe atoms in 2212Fe.     

Synthesis of 1,4-dihydropyridine derivatives having an oxy-, alkoxy-, or dimethylaminophenyl substituent in the 4 position,their antioxidant activity,and their binding to phospholipid membranes

The method of Hantzsch was used to synthesize esters and amides of 2,6-dimethyl-4-aryl-1,4-dihydropyridine-3,5-dicarboxylic acid, containing electron donor substituents in the phenyl ring. It was found that in addition to their antioxidant properties, 3,5-diamides and 4-(3,4-dioxyphenyl) derivatives have an affinity for model phospholipid membranes.Latvian Institute of Organic Synthesis, Riga, LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp, 1358–1365, October, 1996. Original article submitted June 20, 1996.     

An analog of the generalized Hardy-Littlewood problem with almost prime numbers

We obtain an asymptotic formula for the number of solutions of the equationm–(u, v)=a, wherem is an almost prime number,(u, v) is a given binary quadratic form, anda is an arbitrary fixed integer.Translated fromMatematicheskie Zametki, Vol. 59, No. 1, pp. 81–94, January, 1996.     

Dissociation kinetics of cobalt and zinc β-octabromo-meso-tetraphenyl- and β-octaethyl-meso-tetraphenylporphyrin complexes

Kinetics of solvoprotolytic dissociation of zinc and cobalt porphyrin complexes with a porphyrin macrocycle distorted to different extents (β-octaethyl-meso-tetraphenylporphyrin and β-octabromo-meso-tetraphenylporphyrin) have been studied in binary proton-donating solvents. The main factor decreasing the stability of the porphyrin complexes is the distortion of the planar structure of the macrocycle. The reactivity of the cobalt porphyrins is governed by both structural and electronic effects.     

Calculation of the structure and evaluation of the reactivity of N-methyl-N-(β-d-xylopyranosyl)-N-nitrosourea under acid-base catalysis conditions

An investigation of N-methyl-N-(-D-xyloxyl)urea (I) and its nitroso derivative (II) has been carried out in the MINDO/3 approximation by the MO-LCAO method. It has been shown that the very significant difference between the energies of molecule I in the free state and in a crystal is due to the potential energy of the crystal field and intermolecular hydrogen bonds. An analysis of the distribution of the charges on the atoms showed that the most probable site for protonation and nucleophilic attack in I and II is the carbonyl group. A picture of the changes in the electronic structure and properties of the reaction centers in I and II under model acid-base catalysis conditions has been obtained.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 596–599, September–October, 1985.     

Isolation and purification of lignoperoxidase from the mushroom <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis>

The accumulation dynamics of lignolytic enzymes in culture media of the basidiomycetes Panus tigrinus, Pleurotus ostreatus, Fomes fomentarus, and the micromycete Aspergillus terreus were studied during the incubation period. It was found that Pleurotus ostreatus is the most active producer of lignoperoxidase enzymes among the studied fungi. Gel filtration and ion-exchange chromatography were used to isolate a homogeneous enzyme with lignoperoxidase activity. The maximum activity was found at pH 2.7 and 29°C. Gel electrophoresis determined the molecular weight (44 kDa). __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 564–566, November–December, 2007.     

Condensation of Argon,Monosilane and Their Mixtures in a Pulse Free Jet

Pulse supersonic outflow of Ar, SiH₄ and Ar + SiH₄ gas mixture (where monosilane is a small admixture) was studied experimentally by the method of molecular beam mass-spectrometry. Using argon as an example we have shown that condensation processes at the quasi-stationary region of a pulse flow and within a stationary jet are similar. In the flows of pure gases clusters of argon and silane (hydrogenated silicon) and in the mixture argon – silane complexes were registered. The dependencies of the intensities of monomer and cluster ions on stagnation pressure were investigated. It was shown that in the mixture jet at low stagnation pressures the condensation process with the formation of monosilane clusters takes place and at high pressures mixed argon-silane complexes are formed. The parameters of flow transition into the regime of developed condensation were determined for pure gases and their mixture.     

Effect of rate and direction of solution flow on metal deposition in porous electrodes: The final weight and distribution of the deposit

Using an earlier-developed dynamic model for a porous flow-through electrode (PFE) with a high initial conductivity, the effect of the solution’s flow rate (0.05–10 cm/s) and direction on the final metal weight m _f and uniformity of the metal distribution in the porous matrix is studied. It is found that m _f increases with increasing flow rate. However, the dependence is nonmonotonic: it peaks at intermediate flow rates. The peak is most pronounced in the case of rear supply. At high and very low flow rates, m _f is independent of the flow direction. In the first case, the metal distribution profiles almost coincide, while in the second case they are mirror-opposite. The deposit weight correlates well with the index of uniformity of its distribution: all other factors being equal, the more uniform the deposit distribution in PFE, the larger the m _f. These effects are explained by taking into account the joint effect of profiles of cathodic polarization and concentration of metal ions in PFE.