Photocatalytic activity of titania nanopowders prepared by a sol–gel process at various pHs

A strategy has been proposed to prepare photocatalytically active titania nanopowders through a sol-gel route using high-degree molecular separation upon the dilution of reagents, high water/alkoxide ratios, high reagent mixing rates, and pH effects. This strategy has been successfully used to isolate, from sols, anatase powders with high surface areas (100–310 m2/g) dependent on the pH value during the synthesis. The photocatalytic activity of titania nanopowders prepared by the sol-gel process at various pHs has been tested in photodestruction of organic dyes (Rodamine B, Methylene Blue, and Anthraquinone AcidBlue) in acid solutions. UV-radiation-induced dye destruction rates are found to depend on the surface properties (including surface area and ζ potential) and hydration specifics of the titania

Microwave-assisted hydrothermal process for the preparation of SnO from an ammoniacal Sn6O4(OH)4 suspension

SnO powder with a specific surface area of 2 m2/g has been prepared by microwave-assisted hydrothermal processing of an ammoniacal Sn6O4(OH)4 suspension. We have examined the effect of pressure rise rate in a reaction mixture on the surface morphology and photocatalytic activity of SnO. Raising the pressure has been shown to reduce the SnO synthesis time, without influencing the surface morphology of SnO or its photocatalytic activity for methyl orange photodegradation

The composition and structure of iron(III) complex compounds with salicylic acid in ethanol solution and in the solid thin film state

Owing to their properties iron(III) salicylate complexes are interest of for application in biomedicine and environmental monitoring. Recently this complex compounds also are investigated as a potential candidate for preparing Fe2O3 films by sol-gel method from ethanol film-forming solution. Relevance of the work was caused by necessity to determine the structure and composition of iron(III) salicylate complexes in ethanol solution and in the solid film state, which influence on film properties. Nowadays this information is absence in the literature. UV spectroscopy, NMR measurement, methods of isomolar series and thermal analysis were used to analyze the composition of complex in ethanol solution and in the solid state. It was found, that salicylic acid interacts with iron(III) chloride in ethanol solution promotes the formation of [FeC6H4OCOO]+ complex, where salicylate ligand behaves as bidentate ligand. After removal of the solvent from solution iron(III) chloride salicylate crystal hydrate complex of 1:1 stoichiometry was formed in solid state. Thermal decomposition of this compound led to formation α–Fe2O3

Synthesis and investigation of physico-chemical, antibacterial, biomymetic properties of silver and zinc containing hydroxyapatite

In the work we carried out microwave synthesis of modified hydroxyapatites (HA) with different content of ions. A solid solution based on HA remains a single-phase sample when the calcium ions are substituted by silver and zinc ions up to 5 % by weight (0.5 mole fraction). The microstructure parameters, morphology and the particle powders size were studied by X-ray diffraction analysis, IR spectroscopy, and scanning electron microscopy (SEM). It is shown that the modification of НA by silver (AgHA) and zinc (ZnHA) ions increases the size of its particles, the degree of crystallinity, and the pore sizes of the samples while reducing their specific surface and uniformity of their forms. Elemental analysis and distribution of elements over the surface of HA, AgHA, and ZnHA powders were performed by X-ray spectral microanalysis (RSMA). The ratio of Ca/P is within the range of 1.66-1.77 and corresponds to the ratio of Ca/P in stoichiometric HA and the HA entering bone tissue. The ability of AgHA- and ZnHA-substrates to form on their surface a calcium-phosphate layer from the simulated body fluid (SBF) at 37 °C is determined. This ability decreases in the order: in ZnHА it is less than in AgHА, but greater than in HА. The antibacterial activity of the samples was analyzed. The AgHA sample has both bactericidal and persistent bacteriostatic properties in the case of direct contact with Escherichia coli cells

Diagrammatic Monte Carlo for Correlated Fermions

We show that Monte Carlo sampling of the Feynman diagrammatic series (DiagMC) can be used for tackling hard fermionic quantum many-body problems in the thermodynamic limit by presenting accurate results for the repulsive Hubbard model in the correlated Fermi liquid regime. Sampling Feynman's diagrammatic series for the single-particle self-energy we can study moderate values of the on-site repulsion ($U/t \sim 4$) and temperatures down to $T/t=1/40$. We compare our results with high temperature series expansion and with single-site and cluster dynamical mean-field theory.Comment: 4 pages, 5 figures, stylistic change

Application of the deformation criterion of the crack growth resistance for evaluation of the pipes residual lifetime of the pipeline linear part

Для оценивания трещиностойкости труб, изготовленных из пластичной стали, использовать подходы линейной механики разрушения проблематично ввиду несоблюдения условий плоской деформации. Один из вариантов решения проблемы состоит в экстраполяции формул линейной механики разрушения для коэффициента интенсивности напряжений (КИН) на существенно нелинейную стадию деформирования с помощью функций поправки на пластичность. В работе анализируются результаты испытаний на циклическую трещиностойкость образцов из трубной стали на основе нового инженерного подхода. Получены силовые и деформационные характеристики трещиностойкости исследуемой стали. Дан анализ построенных кинетических диаграмм усталостного разрушения и диаграмм циклического упругопластического разрушения образцов, живучести труб из исследованной стали после длительной эксплуатации.To estimate the crack growth resistance of pipes made of ductile steel using a linear fracture mechanics approach is of problematic character as the conditions of plane strain are not observed. One of the ways of solution to the problem is the extrapolation of the linear fracture mechanics formulas for the stress intensity factor (SIF) on substantially nonlinear stage of deformation by means of the amendment functions on the plasticity. The results of crack growth resistance tests of samples made of pipe steel on the basis of a new engineering approach are analyzed in the paper. The force and deformation characteristics of the crack growth resistance were received. The analysis of kinetic fatigue failure diagrams and cyclic elastic-plastic fracture diagrams for specimens, crack growth life of tubes from the investigated steel after long-term use is presented. Specimen’s crack is oriented in axial and circumferential directions for study of anisotropy properties. The characteristics of a fatigue crack growth of investigated steel after long operation are discussed. The characteristics of cyclic crack growth resistance for pipe steel after long-term (over 30 years) of operation are determined experimentally: at absolute temperature T = 293 K and a critical threshold values of SIF are: Kth = 4,91 MPa, Kfc = 54,75 MPa, the values parameters of equation (6) are equal mk = 1,556, Ck = 4,0 ⋅ 10 −10. The algorithm and procedure of computational experimental evaluation of crack growth life of objects operated under cyclic elastic-plastic deformation, which is based on the use of strain approach - measuring of specimen’s width reduction, charting the cyclic elastic-plastic fracture diagram, for practical application are proposed. Graphical analysis of data according to crack growth life and service term of the tube of oil pipe line with a semi-elliptical longitudinal crack from damage is presented at various levels of pressure in the tube: 1, 2 and 3 MPa

Application of the deformation criterion of the crack growth resistance for evaluation of the pipes residual lifetime of the pipeline linear part

Для оценивания трещиностойкости труб, изготовленных из пластичной стали, использовать подходы линейной механики разрушения проблематично ввиду несоблюдения условий плоской деформации. Один из вариантов решения проблемы состоит в экстраполяции формул линейной механики разрушения для коэффициента интенсивности напряжений (КИН) на существенно нелинейную стадию деформирования с помощью функций поправки на пластичность. В работе анализируются результаты испытаний на циклическую трещиностойкость образцов из трубной стали на основе нового инженерного подхода. Получены силовые и деформационные характеристики трещиностойкости исследуемой стали. Дан анализ построенных кинетических диаграмм усталостного разрушения и диаграмм циклического упругопластического разрушения образцов, живучести труб из исследованной стали после длительной эксплуатации.To estimate the crack growth resistance of pipes made of ductile steel using a linear fracture mechanics approach is of problematic character as the conditions of plane strain are not observed. One of the ways of solution to the problem is the extrapolation of the linear fracture mechanics formulas for the stress intensity factor (SIF) on substantially nonlinear stage of deformation by means of the amendment functions on the plasticity. The results of crack growth resistance tests of samples made of pipe steel on the basis of a new engineering approach are analyzed in the paper. The force and deformation characteristics of the crack growth resistance were received. The analysis of kinetic fatigue failure diagrams and cyclic elastic-plastic fracture diagrams for specimens, crack growth life of tubes from the investigated steel after long-term use is presented. Specimen’s crack is oriented in axial and circumferential directions for study of anisotropy properties. The characteristics of a fatigue crack growth of investigated steel after long operation are discussed. The characteristics of cyclic crack growth resistance for pipe steel after long-term (over 30 years) of operation are determined experimentally: at absolute temperature T = 293 K and a critical threshold values of SIF are: Kth = 4,91 MPa, Kfc = 54,75 MPa, the values parameters of equation (6) are equal mk = 1,556, Ck = 4,0 ⋅ 10 −10. The algorithm and procedure of computational experimental evaluation of crack growth life of objects operated under cyclic elastic-plastic deformation, which is based on the use of strain approach - measuring of specimen’s width reduction, charting the cyclic elastic-plastic fracture diagram, for practical application are proposed. Graphical analysis of data according to crack growth life and service term of the tube of oil pipe line with a semi-elliptical longitudinal crack from damage is presented at various levels of pressure in the tube: 1, 2 and 3 MPa

CSP for binary conservative relational structures

We prove that whenever A is a 3-conservative relational structure with only binary and unary relations then the algebra of polymorphisms of A either has no Taylor operation (i.e. CSP(A) is NP-complete), or generates a congruence meet semidistributive variety (i.e. CSP(A) has bounded width).Comment: 9 pages, 3 figure

Preparation of composite materials based on hydroxyapatite and lactide and glycolide copolymer

Composite materials for the restoration of bone tissues based on hydroxyapatite and a copolymer of lactide and glycolide were obtained. The composition of materials at different stages of production is estimated by X-Ray diffraction method. It has been established that during the production of materials a new phase of chlorine-substituted hydroxyapatite (Ca9.7(P6O23.81)Cl2.35(OH)2.01) was formed, which promoted an increase of hydroxyapatite solubility in the composition of materials. The quantitative estimation of micro- and macroporosity of materials is given. It was found that the use of sodium chloride as the pore-forming agent delivers porosity of the composites required for use as bone substitutes