On a vibration problem of antiplane strain (shear) of orthotropic non-homogeneous prismatic shell-like bodies

Vibration problem of an antiplane strain (shear) of orthotropic non-homogeneous prismatic shell-like bodies is considered when the shear moduli depending on the body projection (i.e. on a domain lying in the plane of interest) variables may vanish on a part of the boundary of the projection.     

Using Plasma-Activated High Performance Fibers with Nanocrystalline Structure in Producing New Reinforced Composite Materials

A multifilament wet-pull-out method for estimation of physicochemical interaction between the fiber and the matrix in composite materials reinforced with high-strength high-modulus polyethylene fiber has been proposed. Controlled parameters are fiber capillary rise h and pull-out force F. The method allows one to estimate the wettability and multifilament fiber impregnation with the liquid matrix and measure fiber capillary rise and the joint strength after curing process finished. The multifilament wet-pull-out method considers a total interaction between the matrix and filaments in a complex fiber or yarn. It is the advantage of this method in comparison with the tests of individual monofilament. The method makes it possible to model the real operating conditions of CM.     

Temperature-induced iron oxidation in bafertisite Ba2Fe${}_{4}^{2+}$Ti2(Si2O7)2O2(OH)2F2: X-ray diffraction and Mössbauer spectroscopy study

The high-temperature behavior of bafertisite was studied by combination of techniques in order to characterize the temperature-induced iron oxidation associated with deprotonation of an octahedral layer. The chemical formula of bafertisite from Darai-Pioz alkaline complex (Tajikistan) determined by electron-microprobe analyzes and Mössbauer spectroscopy is Ba _2.11(Fe\({}_{2.70}^{2+}\)Fe\({}_{0.17}^{3+}\)Mn _1.09Zr _0.04Na _0.03) (Ti _1.96Nb _0.07)(Si ₂ O ₇)₂ O ₂(OH _1.29 O _0.65 F _0.06)F ₂. In situ high-temperature powder X-ray diffraction revealed abrupt shift of reflections to the high-angle region and reduction of their intensity at T >?525 ^°C. The Mössbauer spectroscopy studies indicated that the crystal structure of bafertisite contains Fe in octahedral sites as predominantly ferric ions with Fe ³⁺/ ΣFe =?0.06, whereas bafertisite annealed at T =?600 ^°C has Fe in the same position with Fe ³⁺/ ΣFe up to 0.39. The differential scanning calorimetry and thermogravimetric analyzes reveal the occurrence of a broad exothermic effect at T ～ 537 ^°C associated with the mass loss corresponding to deprotonation. Since in the studied sample of bafertisite, Fe ²⁺ apfu strongly prevails over OH apfu, the stoichiometric (charged-balanced) high-temperature oxidized modification cannot be obtained. In the paper, the high-temperature behavior of bafertisite is discussed and compared to that of astrophyllite.     

Bisphenylene homologues of BINOL-based phosphoramidites: synthesis, stereostructure, and application in catalysis

Bis-ortho- and bis-meta-phenylene homologues of BINOL-based N,N-dimethylphosphoramidites were prepared from the corresponding diols by treatment with hexamethyltriaminophosphane. Phosphoramidites derived from bulkier secondary amines were synthesized by 5-phenyl-1H-tetrazole-promoted amine exchange. All the phosphoramidites were obtained as single diastereomers. Their configurations at the C(naphthyl)-C(phenyl) axes were determined by vibrational circular dichroism (VCD) spectroscopy. Preliminary testing of the ligands in copper-catalyzed conjugate addition of diethylzinc to acyclic enones and nitrostyrene gave the corresponding products in up to 74% ee.     

Aqueous two-phase systems containing N-vinylpyrrolidone: Experimental results and correlation/prediction

Experimental results are presented for the liquid–liquid equilibrium of a ternary system (N-vinylpyrrolidone + sodium sulfate + water) and three quaternary systems composed of (N-vinylpyrrolidone + poly(vinylpyrrolidone) + sodium sulfate + water) at 25 °C. The quaternary systems differ in the number averaged molecular mass of the poly(vinylpyrrolidones). That molecular mass was between about 4 000 and 140 000. The experimental results are described with a semi-empirical model (VERS model) for the excess Gibbs energy.     

Mass spectrometric identification and characterization of a new long-term metabolite of metandienone in human urine

Anabolic-androgenic steroids are some of the most frequently detected drugs in amateur and professional sports. Doping control laboratories have developed numerous assays enabling the determination of administered drugs and/or their metabolic products that allow retrospectives with respect to pharmacokinetics and excretion profiles of steroids and their metabolites. A new metabolite generated from metandienone has been identified as 18-nor-17beta-hydroxymethyl,17alpha-methyl-androst-1,4,13-trien-3-one in excretion study urine samples providing a valuable tool for the long-term detection of metandienone abuse by athletes in sports drug testing. The metabolite was characterized using gas chromatography/(tandem) mass spectrometry, liquid chromatography/tandem mass spectrometry and liquid chromatography/high-resolution/high-accuracy (tandem) mass spectrometry by characteristic fragmentation patterns representing the intact 3-keto-1,4-diene structure in combination with typical product ions substantiating the proposed C/D-ring structure of the steroid metabolite. In addition, structure confirmation was obtained by the analysis of excretion study urine specimens obtained after administration of 17-CD(3)-labeled metandienone providing the deuterated analogue to the newly identified metabolite. 18-Nor-17beta-hydroxymethyl,17alpha-methyl-androst-1,4,13-trien-3-one was determined in metandienone administration study urine specimens up to 19 days after application of a single dose of 5 mg, hence providing an extended detection period compared with commonly employed strategies.     

Interface controlled electronic charge inhomogeneities in correlated heterostructures

For heterostructures of ultrathin, strongly correlated copper-oxide films and dielectric perovskite layers, we predict inhomogeneous electronic interface states. Our study is based on an extended Hubbard model for the cuprate film. The interface is implemented by a coupling to the electron and phonon degrees of freedom of the dielectric oxide layer. We find that electronic ordering in the film is associated with a strongly inhomogeneous polaron effect. We propose to consider the interfacial tuning as a powerful mechanism to control the charge ordering in correlated electronic systems.     

Mesoporous TiO2 microspheres with improved efficiency for photooxidation of volatile organic compounds

Research on Chemical Intermediates - Mesoporous hierarchical TiO2 microspheres have been prepared using titanium alkoxide and crown ether as a structure-directing agent in combination with a small...     

Centers and Uniform Isochronous Centers of Planar Polynomial Differential Systems

For planar polynomial vector fields of the form

$$\begin{aligned} (-y+X(x,y))\dfrac{\partial }{\partial x}+(x+Y(x,y))\dfrac{\partial }{\partial y}, \end{aligned}$$

where X and Y start at least with terms of second order in the variables x and y, we determine necessary and sufficient conditions under which the origin is a center or a uniform isochronous centers.

     

Liposomal Form of Tetra(Aryl)Tetracyanoporphyrazine: Physical Properties and Photodynamic Activity In Vitro

Tetra(aryl)tetracyanoporphyrazines are the promising group of dyes for photodynamic therapy of tumors with unique combination of photosensitizer properties and sensitivity of fluorescence parameters to the environment viscosity. However, in vivo application of such hydrophobic photosensitizers requires using of drug carriers ensuring efficient delivery to the tumor site. The present study is focused on obtaining liposomes loaded with tetrakis(4-benzyloxyphenyl)tetracyanoporphyrazine and examining their properties depending on lipid composition. An efficient loading of the dye and a high long-term stability were proved for the liposomes composed of phosphatidylcholine with cholesterol and phosphatidylglycerol. This can be explained by the presence of negatively charged lipids in the bilayer and, as a consequence, a high value of the surface potential. A high rate of cellular uptake and a strong photoinduced toxicity give the prerequisites for the further use of the liposomal form of the photosensitizer for photodynamic therapy of tumors.