Synthesis and characterization of biodiesel fuel based of esters of tall oil fatty acids

Synthesis of esters from tall oil fatty acids and lower aliphatic alcohols is studied, and characteristics of the products as substitutes or components of diesel fuel are determined.     

Asymptotic model of active resonance absorber of acoustic vibrations in a closed region

Novosibirks. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 44–55, November–December, 1994.     

Acoustic resonance associated with vibrations of an array of plates in a subsonic flow

The acoustic resonance effect occurring in the vibrations of an array of profiles (cascade) in a gas flow has been studied by a number of authors [1–8]. Relying on assumptions of a heuristic nature [1, 2, 7, 8] and using rather crude models [4, 6], they have derived criteria governing the acoustic resonance regimes and given the effect a certain physical interpretation. However, many problems of a physical bearing with regard to the quantitative and qualitative principles of the effect have been left unresolved. For a more complete and rigorous solution of the problem the author has previously [9, 10] analyzed the natural modes of a gas flowing past an array of plates It was determined that in the array domain the vibrational modes of the gas are localized in the vicinity, of the array and the eigenvalues are determined by the characteristic dimensions of the interstitial channel (as an open resonator). Also, the eigenfrequences were determined for the gas in the flow plane with the array absent [9]. Under spatial periodic conditions, such that the flow in the plane can be considered as a certain model of flow in an annular duct, these eigenfrequencies concurred with those obtained earlier in [1, 2, 4–6]. The results of [9, 10] are used in the present study as a basis for investigating certain laws and relations governing the unsteady aerodynamic characteristics of arrayed profiles in or close to regimes such that the gas can execute natural vibrations in the array domain and in an annular duct in the absence of the array.Novosibirsk. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 139–144, September–October, 1972.     

Effect of π-Extended Substituents on Photophysical Properties of BODIPY Dyes in Solutions

Four boron-dipyrrine (BODIPY) based dyes with π-extended substituents in 8-position of dipyrrin ligand have been synthesized and characterized. Photophysical properties of the obtained compounds have been investigated in different individual solvents. Deposits of solvent polarity and viscosity were evaluated. BODIPY with 8-biphenyl substituent was found to be the fluorescent molecular rotor in contrast to more extended substituents. The complex nature of solvent-solute interactions leads to the poor applicability of standard multiparameter approaches to BODIPY solvatochromic properties. Fluorescence intensity was found to increase in case of solvent polarity growth, it is not typical for BODIPY. Taking that into account the BODIPY with π-extended substituents could be used for fluorescence viscosity measurements, and as the fluorescent media polarity indicators in analytical chemistry and biochemistry.     

Electron spin resonance with g eff ≈ 4.2 in YBa2Cu3O6.35. Model of chain copper-oxygen fragments

Systematic measurements are made of ESR spectra with g ≈ 4.2 in YBa₂Cu₃O_6+y compounds with various doping indices y. Temperature dependences of the spectrum intensity show that the ground states of the centers are singlet and the energies of the excited states M _S = ±1 correspond to 8?11 K. In general, the intensity of the ESR spectra varies with time and depends on the sample preparation technology. The most probable models for the paramagnetic centers studied are considered to be chain fragments of copper ions of variable valence. General laws governing the energy structure of these centers are described.     

Desulfurization of tall oil pitch

Method for desulfurization of tall oil pitch is suggested. The method is based on successive treatments with hydrogen peroxide, sulfuric acid, and aqueous solutions of acetonitrile. As a result, the total content of sulfur was reduced from 3800 to 220 ppm. The fuel characteristics of the desulfurized pitch were determined. The purified pitch can be used in the conventional areas of its application, in which restrictions are imposed on the total content of sulfur.     

Identification of the La6F37 cubooctahedral clusters in mixed crystals (BaF2)1 ? x(LaF3)x by the electron paramagnetic resonance method

The electron paramagnetic resonance (EPR) spectra of mixed crystals (BaF₂)_{1 − x} (LaF₃) _x (x = 0, 0.001, 0.002, 0.005, 0.010, 0.020) doped with Ce³⁺ ions (0.1%) are investigated at a frequency v ≈ 9.5 GHz in magnetic fields up to 1.45 T at temperatures T = 10 and 15 K. The EPR spectrum of “pure” barium fluoride BaF₂ (x = 0) is characterized by a single Ce³⁺-F⁻ center with tetragonal symmetry (i.e., the O center with g _‖ = 2.601 and g _⊥ = 1.555). For a lanthanum trifluoride concentration x ≠ 0, the spectrum exhibits new lines due to the presence of the clusters containing Ce³⁺ and La³⁺ ions. The intensity of EPR signals from the O centers decreases rapidly as the lanthanum trifluoride concentration x increases. The lines attributed to a paramagnetic center with tetragonal symmetry and strongly anisotropic g factors (i.e., the K center with g _‖ = 0.725 and g _⊥ = 2.52) are separated in the complex EPR spectrum with the use of the angular dependence of the EPR signal intensity measured for the samples with x ≥ 0.002. This center is identified as a cubooctahedral cluster of the La₆F₃₇ type in which one of the La³⁺ ions is replaced by the Ce³⁺ ion. Original Russian Text ? L.K. Aminov, I.N. Kurkin, S.P. Kurzin, I.A. Gromov, G.V. Mamin, R.M. Rakhmatullin, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 11, pp. 1990–1993.