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  • Articles  (1,024)
  • Springer  (1,024)
  • American Institute of Physics
  • Blackwell Publishing Ltd
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  • 2010-2014  (636)
  • 2005-2009  (388)
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  • 2013  (636)
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  • Russian Journal of Physical Chemistry A  (213)
  • 64378
  • Chemistry and Pharmacology  (1,024)
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  • Articles  (1,024)
Source
Publisher
  • Springer  (1,024)
  • American Institute of Physics
  • Blackwell Publishing Ltd
  • Cell Press
  • Oxford University Press
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  • 2010-2014  (636)
  • 2005-2009  (388)
  • 1985-1989
  • 1975-1979
  • 1945-1949
Year
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Topic
  • Chemistry and Pharmacology  (1,024)
  • Nature of Science, Research, Systems of Higher Education, Museum Science
  • Economics
  • Architecture, Civil Engineering, Surveying
  • Electrical Engineering, Measurement and Control Technology
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  • 1
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    The model of a polyelectrolyte solution with explicit account of counterions within a self-consistent field theory (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: A theoretical approach to calculating the thermodynamic and structural functions of solutions of polyelectrolytes based on Gaussian equivalent representation for the calculation of functional integrals is proposed. It is noted that a new analytical result of this work is the direct assumption of counterions, along with an equation for the gyration radius of a polymer chain as a function of the concentrations of monomers and added low-molecular salt. An equation of state is obtained within the proposed model. Our theoretical results are used to describe the thermodynamic and structural properties of an aqueous solution of sodium polystyrene sulfonate with additions of NaCl.
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  • 2
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    Thermochemical study of aqueous solutions of lithium diclofenac at 293.15–318.15 K (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: The enthalpies of solution and dilution of aqueous solutions of lithium diclofenac (LiDC) are measured in the concentration range of 0.002–0.047 m at 293.15, 298.15, 308.15, and 318.5 K using an isoperibolic calorimeter. The heat capacity of solid LiDC in the temperature range of 273.15–373.15 K is determined using a DSC 204 F1 Phoenix differential scanning calorimeter (NETZSCH, Germany). The virial coefficients of the enthalpy characteristics of a water-LiDC solution are derived in terms of the Pitzer model to calculate a wide range of thermodynamic properties of both the solution and its components. Changes in these characteristics as a function of concentration and temperature are discussed.
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  • 3
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    Theoretical determinations of ionization potentials of dopamine (2013)
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    Publication Date: 2013-04-10
    Description: Adiabatic and vertical ionization potentials (IPs) of nine conformers of dopamine in the gas phase are determined using density functional theory (DFT) B3LYP, B3P86, B3PW91 methods and high level ab initio HF method with 6-311++G** basis set, respectively. And the nine stable cationic states have been found in the ionization process of dopamine. Vertical ionization potentials of nine conformers of dopamine are calculated using the older outer-valence Green’s function (OVGF) calculations at 6-311++G** basis set. Vibrational frequencies and infrared spectrum intensities of G1b and G1b + at B3LYP/6-311++G** level are discussed.
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    Isobutanol dehydrogenation on copper-containing bismuth vanadates (2013)
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    Publication Date: 2013-04-10
    Description: It is found that α, β, and Γ modifications of perovskites Bi 4 V 2 − 2 x Cu 2 x O 11 − δ (BICUVOX) exhibit different activities during catalytic transformations of isobutanol with a selectivity of isobutanal formation 85–100%. Data analysis shows that the site for the alcohol dehydrogenation reaction is the ion pair Cu 2+ -O 2− with the highest activity for a highly conductive γ-phase. It is shown that the activation energy for aldehyde formation is lower for γ-phase of the catalyst by a factor of ten than that for its α-phase. It is concluded that step-wise Arrhenius dependences without changes in the activation energy for parallel alcohol dehydrogenation and dehydration reactions are related to changes in the conducting properties of the catalyst. Step change in activity was found at temperatures of 310 and 370° and corresponds to an increase of the solid solution electric conductivity.
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  • 5
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    Equilibrium distribution of lanthanum, neodymium, and thorium between lithium chloride melt and liquid bismuth (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: The distribution of lanthanum, neodymium, and thorium between a lithium chloride melt and liquid bismuth with additions of lithium as a reducing agent are investigated at 650°C. Equilibrium values of their distribution constants are measured. It is shown that in contrast to neodymium and lanthanum, thorium cannot be extracted from bismuth into lithium chloride. This allows us to propose an efficient scheme for separating lanthanides and thorium in a system for the extraction of fuel salts in molten-salt nuclear reactors.
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  • 6
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    Rapid, one-pot synthesis of highly-soluble carbon nanotubes functionalized by L-arginine (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: Functionalization of carbon nanotubes (CNTs) is a necessary step to exploit their valuable properties. Due to having several steps and especially acid treatment, most of current methods of functionalization result in irrecoverable defects on CNTs structure. Here, multiwalled carbon nanotubes (MWCNTs) were functionalized with L-arginine in a simple, one-pot and rapid microwave-assisted technique without any acid treatment step. The CNT functionalities were analyzed with infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results confirmed the covalent functionalization of L-arginine with very low defects on CNTs. Also it is found that increase of input powers of microwave in the range 500–900 W, monotonically increase the degree of functionalization. The maximum dispersibility of MWCNT was found ∼1.03 mg/mL corresponding to 900 W irradiation. Accounting considerable low treatment time, the method may be applied for large-scale solubilization of MWCNTs in an industrial scale.
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    Effects of vacuum annealing on the particle size and phase composition of nanocrystalline tungsten carbide powders (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: The effects of the vacuum annealing temperature (400–1400°C) on the phase and chemical composition, particle size, and microstresses of the nanocrystalline powders of tungsten carbide WC with 20–60 nm particles were studied by X-ray diffraction and electron microscopy. Vacuum annealing of WC nano-powders at T ann ≤ 1400°C was accompanied by decarbonization, resulting from the interaction of carbon with the oxygen impurity. Changes in the chemical composition of the nanocrystalline powder of tungsten carbide led to changes in its phase composition. The annealing was accompanied by growth of powder particles due to the aggregation of nanoparticles and by a decrease of microstresses.
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  • 8
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    Dielectric spectroscopy of monatomic alcohols (2013)
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    Publication Date: 2013-04-10
    Description: The frequency dependences of permittivity ɛ( f ) and dielectric loss tanδ( f ) of monatomic alcohols are measured in range of frequencies f from 0.025 to 1000 kHz. Dielectric relaxation is observed in the investigated frequency range. Empirical correlation equations describing the relationships between the dielectric characteristics and physicochemical properties of monatomic alcohols are obtained.
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  • 9
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    Photoelectron spectra and electronic structure of boron difluoride β-diketonates with aromatic substituents (2013)
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    Publication Date: 2013-04-10
    Description: The electronic structure of boron difluoride chelate complexes of the acetyl acetonate type containing 4-biphenylene, 2-fluorene and 4- trans -stilbene as β-substituents is studied by means of photoelectron spectroscopy and quantum chemistry in the DFT approximation. It is established that the substituents affect the nature and sequence of the spectral bands. It is shown that calculation results corrected to the value of the Koopmans defect reproduce quite well the energy intervals between ionized states of complexes.
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  • 10
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    Physicochemical properties of magnetic fluids based on synthetic oils (2013)
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    Publication Date: 2013-04-10
    Description: A technique for synthesizing magnetic fluids based on Alkaren synthetic oil is described. The optimum synthesis conditions for the magnetite are selected, and the magnetic phase-stabilizer quantitative ratio is calculated. A magnetic fluid based on synthetic hydrocarbon oil is synthesized, and its physicochemical characteristics are determined.
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  • 11
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    Erratum to: “Interactions in L-Phenylalanine/L-Leucine/L-Glutamic Acid/L-Proline + 2 M Aqueous NaCl/2 M NaNO 3 Systems at Different Temperatures” (2013)
    Springer
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    Publication Date: 2013-04-10
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  • 12
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    Features of the kinetics of 4-nitroaniline and azoxybenzene hydrogenation in 2-propanol aqueous solutions (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: It is shown experimentally that the hydrogenation of 4-nitroaniline and azoxybenzene over a skeletal nickel catalyst in 2-propanol aqueous solutions proceeds selectively with the formation of the corresponding amines without the accumulation of side products in the bulk phase. It is concluded that during reduction, considerable participation of hydrogen bonded with active centers of a catalyst surface was observed. The competitive character of adsorption between the initial azoxybenzene and aniline formed as a result of reaction is established. It is ascertained that the character of changes in the rates of hydrogenation of nitro and azoxy groups is identical in the presence of additions of acid or base. It is demonstrated that a targeted change in the hydrogenation rates of these compounds is possible by introducing additions of acetic acid or sodium hydroxide into 2-propanol aqueous solution.
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  • 13
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    Enthalpies of dissolution of NaVO 3 · 2H 2 O in aqueous chloric acid and the standard formation enthalpy of the VO (2013)
    Springer
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    Publication Date: 2013-04-10
    Description: The enthalpies of dissolution of sodium metavanadate dihydrate in aqueous solutions of chloric acid and sodium perchlorate were measured by calorimetry at 298.15 K at ionic strengths of I = 0.3, 0.4, 0.5, 0.6, and 1.0 M. The standard formation enthalpy of the VO 2 + ion in aqueous solution was calculated from the resulting experimental data.
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    Solvent effects on kinetics of an heteroatomic nucleophilic substitution reaction in ionic liquid and molecular solvents mixtures (2013)
    Springer
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    Publication Date: 2013-12-07
    Description: Rate constants, k A , for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 2-propanol mixed with hexane, benzene, and 2-methylpropan-2-ol and 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO 4 ]) with dimethyl sulfoxide at 25°C. The obtained rate constants of the reaction in pure solvents are in the following order: 2-methylpropan-2-ol 〉 dimethyl sulfoxide 〉 2-propanol 〉 hexane 〉 benzene 〉 [Emim][EtSO 4 ]. Molecularmicroscopic solvent parameters corresponding to the selected binary mixtures were utilized to study the kinetics of a nucleophilic substitution reaction in order to investigate and compare the effects of the solvents on a chemical process. The influence of solvent parameters including normalized polarity ( E T N ), dipolarity/polarizability (π*), hydrogen bond donor acidity (α), and hydrogen bond acceptor basicity (β) on the second-order rate constants were investigated and multiple linear regressions gave much better results with regard to single parameter regressions. The dipolarity/polarizability of media has a positive effect in all mixtures regarding zwitterionic character of the reaction intermediate and the hydrogen bond acceptor basicity of the solvent by stabilizing of activated complex increases the reaction rate.
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  • 15
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    Dispersion of single-walled carbon nanotubes in alcohol-cholic acid mixtures (2013)
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    Publication Date: 2013-12-07
    Description: A procedure for dispersing single-walled carbon nanotubes (SWNTs) for the preparation of suspensions with high concentrations of individual nanotubes in various solvents was described. The most stable suspensions were obtained from a mixture of ethanol with cholic acid at an acid concentration of 0.018 mol/kg.
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  • 16
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    Structure and physicochemical properties of cation polymethine dyes in Langmuir-Blodgett films (2013)
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    Publication Date: 2013-12-07
    Description: The physicochemical properties of monomolecular layers of amphiphilic cation polymethine dyes (i.e., thia- and oxacarbocyanines) on the surface of a water subphase are studied along with the conditions of Langmuir-Blodgett (LB) film preparation. The area occupied by one dye molecule in the liquid-stretched and liquid-condensed states of a monolayer is determined. Based on a comparison of experimental and theoretically calculated areas, the nature of dye packing in monolayers is studied by means of molecular mechanics using data from conformation analysis. The spectral and luminescent properties of cationic polymethine dyes in various media are investigated. Excimer fluorescence is observed in LB films. The excimers in LB films are found to arise not from monomers but from dye dimers. A possible mechanism of their formation is considered.
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  • 17
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    Controlling the optimum surfactants concentrations for dispersing carbon nanofibers in aqueous solution (2013)
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    Publication Date: 2013-12-07
    Description: As a new nano-scale functional material, it is necessary to achieve a uniform distribution in the composites for gaining the CNFs’ excellent reinforcing effect. In this paper, CNFs were purified by the method of high temperature annealing treatment. Six surfactants, methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), sodium dodecyl sulfate (SDS), dodecylamine (DDA), N, N-dimethyl formamide (DMF) and cetyltrimethyl ammonium bromide (CTAB) were used individually and combinatorially in a certain concentration to disperse the CNFs in aqueous solution. To achieve a good dispersion of the CNFs, a method utilizing ultrasonic processing was employed. The CNFs treated by the method of high temperature annealing treatment were characterized by differential thermal analysis (DTA) and thermogravimetry analysis (TGA), and the ultrasonication-driven dispersion of CNFs in aqueous solutions were monitored by UVvis spectroscopy and transmission electron microscopy (TEM). The experiments reveal that the method of high temperature annealing treatment purified the CNFs and the maximum achievable dispersion of CNFs corresponds to the maximum UV absorbance of the solution. All results show that the surfactants mixture of MC and SDS in a certain concentration of 0.4 and 2.0 g/L has the maximum dispersion effect on CNFs in aqueous solution, the optimum concentration ratio of MC, SDS, and CNFs was 2: 10: 1.
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  • 18
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    The photocatalytic degradation of cationic surfactant from wastewater in the presence of nano-zinc oxide using Taguchi method (2013)
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    Publication Date: 2013-12-12
    Description: The photocatalytic degradation of cetyl pyridinium chloride (CPC) has been investigated in aqueous phase using ultraviolet (UV) and ZnO nanopowder. Kinetic analysis showed that the extent of surfactant photocatalytic degradation can be fitted with pseudo-first-order model and photochemical elimination of CPC could be studied by Taguchi method. Our experimental design was based on testing five factors, i.e., dosage of K 2 S 2 O 8 , concentration of CPC, amount of ZnO, irradiation time and initial pH. Each factor was tested at four levels. The optimum parameters were found to be pH 5.0; amount of ZnO 11 mg; K 2 S 2 O 8 3 mM; CPC 10 mg/L; irradiation time, 8 h.
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  • 19
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    A novel approach to the explanation the effect of microwave heating on isothermal kinetic of crosslinking polymerization of acrylic acid (2013)
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    Publication Date: 2013-12-12
    Description: The effect of microwave heating (MWH) on the isothermal kinetic of crosslinking-polymerization of acrylic acid (CPAA) was investigated. The kinetic curves of CPAA were determined in the temperature range from 303 to 328 K. By applying the model-fitting method it was revealed that the isothermal kinetics of CPAA was described by the first order chemical reaction kinetics model under the MWH and by the second order chemical reaction rate model for the conventionally heated (CH) process. The values of the reaction rate constants of CPAA are about 40 times higher for the microwave heated system than for the conventional heating. The kinetic parameters (activation energy ( E a ) and pre-exponential factor (ln A )) of the CPAA are significantly lower than the corresponding values for CH process. It was found that the increase in the reaction rate of CPAA for MWH was not a consequence of overheating neither the hot spots in the reaction system. Based on model of selective energy transfer between the reacting molecules and the heating bath a novel explanation of the established effects of MWH on the kinetics of CPAA is given. A quantized nature and value of activation energy was confirmed. The decrease in the value of activation energy of CPAA under microwave heating is explained by the increased value of energy of ground vibration level of resonant oscillator in the AA molecule (v = 1417 cm −1 ) caused by the absorption of non-thermal energy of MW field.
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    Theoretical study of structure, bonding, and aromaticity of borazyne and B-substituted borazynes (2013)
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    Publication Date: 2013-12-12
    Description: The density functional theory (DFT) is used to study the geometries, and electronic structures of triplet and singlet of borazyne and B-substituted of borazyne. The aromaticity of these systems is analyzed in the light of nucleus-independent chemical shift (NICS), average of two-center indices ( ATI ). These methods show increasing of aromaticity in deactivating groups. The relation between electron density in ring critical point (RCP) and NICS(1.0) is observed. The most important interaction in these molecules has been investigated by natural bonding orbital method (NBO).
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    Synthesis of barium and strontium carbonate crystals with unusual morphologies using an organic additive (2013)
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    Publication Date: 2013-12-12
    Description: In this paper, strontium carbonate (SrCO 3 ) and barium carbonate (BaCO 3 ) crystals were synthesized in the presence of an organic additive-hexamethylenetetramine (HMT) using two CO 2 sources. Scanning electron microscopy and X-ray powder diffractometry were used to characterize the products. The results showed that the morphologies of orthorhombic strontianite SrCO 3 transformed from branch-like to flower-like, and to capsicum-like at last, while the morphologies of BaCO 3 change from fiber-like to branchlike, and to rod-like finally with an increase of the molar ratio HMT/Sr 2+ and HMT/Ba 2+ from 0.2 to 10 using ammonium carbonate as CO 2 source. When using diethyl carbonate instead of ammonium carbonate as CO 2 source, SrCO 3 flowers aggregated by rods and BaCO 3 shuttles were formed. The possible formation mechanisms of SrCO 3 and BaCO 3 crystals obtained in different conditions were also discussed.
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    Effects of additives on the oscillations of the Briggs-Rauscher reaction (2013)
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    Publication Date: 2013-12-12
    Description: Perturbations with chemical species that have dissimilar physico-chemical properties, such as bromide ions, polyphenols or iron complexes, are often used to investigate the detailed molecular mechanism of the Briggs-Rauscher (BR) oscillating reaction. We describe in this review the effects caused by some of these species and present their mechanistic interpretations. Some new original results are also reported.
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    Thermodynamic functions of KF solubility in tributyl phosphate, dimethyl sulfoxide, N , N -dimethylacetamide and 1,4-dioxane (2013)
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    Publication Date: 2013-10-12
    Description: Based on the solubilities of potassium fluoride (KF) in some aprotic polar solvents, such as tributyl phosphate, dimethyl sulfoxide, N , N -dimethylacetamide and 1,4-dioxane at temperatures ranging from 300.87 to 359.50 K, the solubility equation with two parameters was correlated with the experimental data. The dissolution enthalpy and dissolution entropy had been calculated from the solubility data. The interactions between solute and solvent were discussed. It provided the basic data for preparation of 2,3,4,5-tetrafluorobenzoic acid.
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    Adsorption of polyacrylic acid and polyacrylamide on montmorillonite (2013)
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    Publication Date: 2013-10-12
    Description: The effect of process duration, temperature, and concentration on the adsorption of polyacrylic acid and polyacrylamide by montmorillonite is studied. It is shown that the pattern of interaction of the studied polyelectrolytes with the sorbent surface is determined by the nature of the polymers, the prevalence of acid-base sites, and the pore structure of the mineral.
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    Features of separation on polymeric reversed phase for two classes of higher saturated fatty acids esters (2013)
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    Publication Date: 2013-10-12
    Description: The principles of sorption on polymeric reversed phase (PRP) YMS C30 for members of the two classes of esters formed by higher saturated fatty acids, i.e., lutein diesters ( I ) and triacylglycerols ( II ), are investigated. It is shown that the logarithm of the retention factor increases nonlinearly with an increase of the length of the acid radical, although the retention on PRP is higher in the case of I and lower in the case of II , compared to their retention on traditional monomeric reversed phase (MRP) Kromasil-100 5C18; however, the equivalence of the contributions to the retention of I that correspond to an identical change in acids, does not depend on the length of the hydrocarbon radical of the second acid. It is noted that the Van’t Hoff plot for PRP contains a curve break, indicating a change in the retention mechanism upon a rise in temperature.
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    Preparing hydrogenation catalysts via the simultaneous reduction of graphite oxide and platinum(IV) (2013)
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    Publication Date: 2013-10-12
    Description: The simultaneous reduction of Pt(IV) and graphite oxide is performed for the preparation of hydrogenation catalysts. It is shown that of the four studied reducing agents (formate ion, ethylene glycol, sodium borohydride, and hydrazine), only NaBH 4 and hydrazine can be used in the preparation of catalysts. It is assumed that Pt particles (≥2 nm) are fixed to the defects, vacancies, and functional groups that are formed as a result of reduction. The prepared compositions catalyze the hydrogenation of decene-1 and nitrobenzene (45°C, 1 atm H 2 ) with specific activities comparable to those in the literature.
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    A mechanism for the hydrazinolysis of benzoic acid in the presence of ion-exchange catalyst (2013)
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    Publication Date: 2013-10-12
    Description: A mechanism for the hydrazinolysis of benzoic acid via cyclic transition states is proposed on the basis of kinetic and IR spectroscopic studies.
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    Mechanism of olefin epoxidation in the presence of a titanium-containing zeolite (2013)
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    Publication Date: 2013-10-12
    Description: The effect of the nature of a solvent on the liquid-phase epoxidation of olefins with an aqueous solution of hydrogen peroxide over a titanium-containing zeolite is studied. Butanol-1, butanol-2, propanol-1, isopropanol, methanol, ethanol, water, acetone, methyl ethyl ketone, isobutanol, and tert -butanol are examined as solvents. A mechanism of olefin epoxidation with hydrogen peroxide in an alcohol medium over a titanium-containing zeolite is proposed. Epoxidation reactions involving hydrogen peroxide and different olefins are studied experimentally.
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    NiO and ZrO 2 -based catalysts in the reaction of complete methane oxidation (2013)
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    Publication Date: 2013-10-12
    Description: The reaction of complete methane oxidation over deposited catalysts (NiO/ZrO 2 and NiO/YSZ) and binary oxides NiO_ZrO 2 produced by co-precipitation, by the sol gel method, and using a bio-template (NiO content in the samples, 10.1 mol %) is investigated. It is shown that binary oxides cause methane oxidation at lower temperatures than their deposited analogue: the temperature of methane half-transformation is 470, 500, and 520°C for binary oxides, while T 50 = 570°C for NiO/ZrO 2 . Major factors affecting the activity of binary oxides in the methane oxidation reaction are determined: the dispersion of the active phase (NiO) and the availability of the second component with high mobility of the lattice oxygen.
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    Gas-chromatographic studies of the sorption thermodynamics of adamantanes on a carbon adsorbent modified with polyethylene glycol with β-cyclodextrin additives (2013)
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    Publication Date: 2013-10-12
    Description: The thermodynamic characteristics of sorption of adamantane and its derivatives on a mixed stationary phase consisting of a graphite-like solid substrate, polyethylene glycol, and β-cyclodextrin (βCD) were determined by gas chromatography. The introduction of β-CD additives to a polar polymer matrix was shown to considerably decrease the chromatographic retention of the sorbates, which is evidence of the macrocyclic effect. The presence of β-CD molecules was found to increase the selective properties of the mixed sorbent with respect to the structural isomers of adamantanes.
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    Analysis of experimental data within the statistical theory of critical phenomena (2013)
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    Publication Date: 2013-10-12
    Description: An approach devised earlier is generalized for a binodal line and used to analyze experiments on a broad set of fluids from He 4 to organic compounds. Experimental binodal lines and isothermal compressibility are described with precision for the above substances. The error characterizing the theory’s deviation from the experimental data is several times lower than in a similar analysis using the Ising model.
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    Enthalpies of Iron(III) perchlorate and Fe 3+ ion transfer from water into aqueous ethanol solvents (2013)
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    Publication Date: 2013-10-12
    Description: Thermal effects of the transfer of iron(III) perchlorate from water into aqueous ethanol solutions at 25.00 ± 0.01°C are determined calorimetrically. The enthalpies of Fe 3+ ion transfer are calculated. An increase in the enthalpies of iron(III) ion transfer upon a rise in the ethanol content in the system is observed. The Gibbs energies of Fe 3+ transfer are calculated using the linear correlation of solvation energy on the solvent and ion parameters.
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    Pulsed NMR investigation of the supercooled water-gas hydrate-gas metastable equilibrium (2013)
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    Publication Date: 2013-10-12
    Description: A method is developed for determining the thermobaric conditions of phase equilibrium in a liquid water-hydrate-gas system by means of pulsed 1H NMR. The method is founded on NMR-based measurements of the amount of liquid water phase in a sample containing gas hydrate under certain values of pressure p and temperature T . The results from investigating the p , T conditions for metastable equilibrium in a supercooled water-Freon-12 hydrate-gas system are presented. The results are in good agreement with the known literature data.
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    Viscosities of hydroxyepoxyprogesterone solutions in chloroform in a temperature range from 288 to 321 K (2013)
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    Publication Date: 2013-10-12
    Description: Based on the viscosities of HEP (11α-Hydroxy-16α, 17α-epoxyprogesterone) in chloroform from 287.65 to 321.15 K, the data of viscosities were correlated using the polynomial equation. The results showed that the model agreed very well with the experimental data.
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    Transformations of α- and β-ionones in the presence of Al 2 O 3 in a supercritical solvent in a flow reactor (2013)
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    Publication Date: 2013-10-12
    Description: The reactivity of α- and β-ionones under the supercritical conditions in a flow type reactor in the presence of Al 2 O 3 at 200–230°C was studied. α-Ionone was reduced to α-ionol, while β-ionol was unstable already at 200°C and underwent dehydration. The secondary reaction products were the corresponding megastigmatrienes.
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    Structure, hydrophobicity, and hydrothermostability of MCM-41 organo-inorganic mesoporous silicates silylated with dimethoxydimethylsilane and dichloromethylphenylsilane (2013)
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    Publication Date: 2013-10-12
    Description: Changes in the structure, hydrophobicity, and hydrothermal stability of organo-inorganic composite materials based on MCM-41 as a result of silylation with dimethoxydimethylsilane (DMODMS) and dichloromethylphenylsilane (DCMPS) were considered. Based on the data on the competitive adsorption of water and toluene it was shown, using the Weitkamp procedure, that the grafting of organosilyl groups affects the sorption properties of mesoporous materials. Hydrothermal treatment led to considerable changes in the structure and properties of the materials. The thermal stability of MCM-41 composites and changes in their hydrophilicity due to the grafting of DMODMS and DCMPS and hydrothermal treatment were studied by thermogravimetry.
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    Ca 3 (P x V 1 − x O (2013)
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    Publication Date: 2013-10-12
    Description: In this paper, Eu 3+ -doped Ca 3 (P x V 1 − x O 4 ) 2 ( x = 0.1, 0.4, 0.7) nanophosphors were synthesized in the presence of sodium dodecyl benzene sulfonate (SDBS). The products present interesting and regular morphologies under the mild conditions. For Ca 3 (P x V 1 − x O 4 ) 2 : Eu 3+ , they have the similar phase and their morphologies vary with the content ratio of P to V. Furthermore, the luminescence behavior of Eu 3+ has been investigated in this one kinds of matrices. In Ca 3 (P x V 1 − x O 4 ) 2 : Eu 3+ , the 5 D 0 - 7 F 2 emissions of Eu 3+ were the strongest, indicating that the Eu 3+ site is without inversion symmetry, the host compositions with different molar ratio of P to V have; great influence on the luminescent performance. Among those products, The value of I 615 / I 593 for Eu 3+ in Ca 3 (P 0.7 V 0.3 O 4 ) 2 host lattice is the biggest. The substitution of PO 4 3− for VO 4 3− increase the ratio of surface Eu cations as well as the value of I 615 / I 593 of Eu 3+ .
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    Evaporation of carbon atoms from the open surface of silicon carbide and through graphene cells: Semiempirical quantum-chemical modeling (2013)
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    Publication Date: 2013-10-12
    Description: The evaporation of silicon atoms during the epitaxial growth of graphene on the singular carbon and silicon faces of silicon carbide SiC was modeled by the semiempirical AM1 and PM3 methods. The analysis was performed for evaporation of atoms both from the open surface of SiC and through the surface of the formed graphene monolayers. The total activation barrier of the evaporation of the silicon atoms, their passage from the graphene cell, and further evaporation from graphene was shown to be lower than the barrier to evaporation of the silicon atom on a free surface of SiC. Passage through graphene is thus not the limiting stage of the process, but contributes significantly to the effective evaporation time.
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    Effect of venous wall immobilization on the thermal degradation of collagen (2013)
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    Publication Date: 2013-10-12
    Description: The results from a comparative study of the thermal denaturation of collagen in the venous walls of reference samples and samples with varicose disease are presented. Changes in the organization of collagen network of the tissue matrix are detected via thermal analysis and multiphoton microscopy with recording of the second harmonic generation (SHG). It is established that the collagen network of venous walls degrades in varicose disease. It is shown that the disordering of the tertiary structure of collagen molecules is reflected in a 40% drop in the enthalpy of protein denaturation compared to reference (Δ H D = 12.4 ± 4.9 J/g dry residue). The disorganization of fiber structures is recorded on SHG images. It is shown that upon the hydrothermal heating of sequestered samples of venous walls, the complete degradation of the tissue network occurs at 75°C. However, it is noted that upon the mechanical immobilization of samples of both types, the stability of collagen increases and complete denaturation is observed at temperatures above 84°C. It is suggested that the number of available conformations of polypeptide chains in the random coil state falls under tension, lowering Δ S D and raising the temperature of the denaturation of protein.
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    Efficiency of monolithic capillary columns in high-pressure gas chromatography (2013)
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    Publication Date: 2013-10-12
    Description: Monolithic sorbents for gas chromatography obtained in quartz capillaries are analyzed by means of kinetic curves (Poppe plots). The values for the time of a theoretical plate and the maximum number of plates are found to be strongly dependendent on the parameters of monolith synthesis, i.e., the relative amount of a monomer in the initial mixture, the temperature, and the polymerization time. Synthesis conditions are established using the kinetic curves, allowing the preparation of sorbents suitable for both performing high-rate analysis and achieving the most effective separation. It was shown that plotting kinetic curves on the basis of van Deemter curve data requires we allow for the compressibility of mobile phase.
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    Ion-molecular interactions in solutions of potassium and cadmium thiocyanates in N-methylpyrrolidone at 298.15 k, according to calorimetry and densitometry data (2013)
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    Publication Date: 2013-10-12
    Description: The heat capacity and density of KNCS-N-methylpyrrolidone (MP), Cd(NCS) 2 -MP, and KNCS-Cd(NCS) 2 -MP solutions at 298.15 K are studied by means of calorimetry and densitometry. Standard partial molar heat capacities and volumes ( $\bar C^\circ _{p,2} $ and $\bar V^\circ _2 $ ) of the studied electrolytes in MP are calculated. Standard values of heat capacity $\bar C^\circ _{p,i} $ and volume $\bar V^\circ _i $ of NCS − ions in MP at 298.15 K are determined. Values of the heat capacity and volume changes upon the formation of the three-component system KNCS-Cd(NCS) 2 -MP from binary solutions are obtained and discussed.
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    Determining the parameters of the potential of intermolecular interaction by the Zeno line (2013)
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    Publication Date: 2013-10-12
    Description: The method of determination of intermolecular interaction potential parameters by the Zeno line is proposed. The intermolecular interaction of ethane, propane, ethylene, and propylene is described using a model of site-site interactions and Karr-Konowalow potential. It is shown that the parameters of intermolecular interaction for this potential can be determined from a small number of experimental data in the single-phase area. It is noted that the final parameters allow us to describe the thermodynamic properties over a broad range of gas and liquid states with precision acceptable for practical use.
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    Solubility of esomeprazole magnesium trihydrate in alcohols at temperatures from 298.15 to 318.15 K (2013)
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    Publication Date: 2013-12-07
    Description: The solubility of esomeprazole magnesium trihydrate in methanol, ethanol, 1-propanol and 1-butanol was determined at temperatures ranging from 298.15 to 318.15 K at atmospheric pressure using gravimetrical method. The highest solubility is found in 1-butanol and lowest in ethanol. The experimental solubility data are correlated by the modified Apelblat equation. Thermodynamic properties such as dissolution enthalpy, Gibb’s energy, and entropy of mixing have been determined from the solubility data.
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    Spectroscopic and fluorescence properties of silver-dye composite nanoparticles (2013)
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    Publication Date: 2013-12-12
    Description: The aim of this work was to investigate the formation of J-aggregates of thiacyanine dye (TC, 5,5′-disulfopropyl-3,3′-dichlorothiacyanine sodium salt) in the presence of 6 nm spherical silver nanoparticles (Ag NPs) using spectrophotometric and fluorescence methods. The formation of J-aggregates was concentration dependent and characterized by the appearance of the new absorption band with the maximum at 481 nm. Spectrophotometric study of J-aggregate formation and time stability suggested that they were formed on the account of monomer form of TC. Moreover, the stability of J-aggregates increased with the lowering AgNPs concentration. The measurements of fluorescence of the NPs—dye assembly clearly indicated that the fluorescence of TC was quenched by Ag NPs on the concentration dependent manner. The spectrophotometric and fluorescence properties of NPs—dye assembly were found to be quantitatively related to the surface coverage of the dye on the Ag NPs.
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    The synthesis and optical properties of different zinc oxide nanostructures (2013)
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    Publication Date: 2013-12-12
    Description: The tetrapod-like whiskers (T-ZnO), nanoaeroplanes, nanocombs, nanobelts, bead-like nanoforms and many other forms of hexagonal zinc oxide were synthesized by the chemical deposition process (CVD). From the experimental results it can be seen that the composition of source gases and the speed of oxidation are essential to the growth of each of these morphologies of zinc oxide. By controlling the growth conditions, one novel morphology of ZnO (bead-like nanoform) has been obtained. The ZnO tetrapod-like whiskers were grown without catalysts on the walls of quartz tube. The structure and morphology of the T-ZnO was characterized. All four legs of as-grown ZnO nanotetrapods are needle-like and hexagonal shaped and grow in the ±[0001] direction. The effect of synthesis conditions on the morphology and size T-ZnO was observed. Possible mechanisms of growth were investigated. The lengths of the legs of the tetrapods range from 1 to 15 μm and diameter varying from 0.03 to 1 μm during the synthesis. In the photoluminescence spectra T-ZnO clearly shows two maxima at UV and visible regions. The oxygen impurity, particularly, oxygen flow rates mainly influences on increasing (decreasing) at PL peaks. The maximum near of 590–610 nm (∼2 eV), confirming the influence of native defects (oxygen vacancies and interstitials) on the PL intensity and optical quenching exciton peak.
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    The effect of active component distribution in a porous structure of supported catalyst (2013)
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    Publication Date: 2013-12-12
    Description: The catalytic process in supported catalyst with nonuniform distribution of active component among the pores of different size is considered. Some previous as well as new estimates are presented. The limit value of diffusivity in small pores ( D L 〈 10 −8 cm 2 /s) is established, at which the distribution can takes an effect. That is possible in the case of capillary condensation, when micro-pores are filled with liquid while macro-pores are filled with gas. Such diffusivity is also observed at configuration or surface diffusion in zeolite channels. Then the distribution may influence the pellet effectivity when the activity of active component inside zeolite crystals is higher than that on its external surface.
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    Solid-liquid phase equilibria at 50 and 75°C in the NaCl + MgCl 2 + H 2 O system and the pitzer model representations (2013)
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    Publication Date: 2013-12-12
    Description: The solubilities in the NaCl-MgCl 2 -H 2 O system were determined at 50 and 75°C and the phase diagrams were constructed on the base of experimental data. One invariant point, two univariant curves, and two crystallization zones, corresponding to sodium chloride and dihydrate (MgCl 2 · 6H 2 O) showed up in the phase diagrams of the ternary system, The mixing parameters θ Na,Mg and Ψ Na,Mg, Cl and equilibrium constant K sp were evaluated in NaCl-MgCl 2 -H 2 O system by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl and MgCl 2 β (0) , β (1) , and C φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.
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    Using the DFT-D method to describe dispersion interactions in systems of weakly-bonded Xe-aromatic molecules (2013)
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    Publication Date: 2013-07-06
    Description: The optimum version of the DFT-D class of methods (BHHLYP-D2, 6-31G*) is chosen to describe binding in a Xe-phenol system with the aim of subsequent KM/MM calculations for complex Xe-containing protein systems. It is shown that the stability of the Xe-phenol system is due to weak dispersion interactions not described in conventional approaches using the density functional. The MP2 approach using the (aug)-cc-pVTZ basis and Stuttgart pseudopotential, which yield the best reproduction of the characteristics of a Xe 2 xenon dimer, is chosen as the reference standard. It is noted that the 2010 DFT-D3 methods underestimate the binding energy by a factor of nearly three, while DFT methods without dispersion corrections do not reproduce the stability of Xe 2 and Xe-phenol systems. It is found that in the best version of calculations, BHHLYP-D2, the binding energy in Xe-phenol complex is estimated to be 2.7 kcal/mol versus the 3.1 kcal/mol found using the comparative approach. It is concluded that BHHLYP-D2 adequately reproduces the difference between the two conformers of the Xe-phenol complex and trend toward an increase in binding energy in the series of aromatic amino acids (phenylalanine, tyrosine, and tryptophan). DFT-D can also indicate the existence of excess conformers that are missing in systems according to more precise descriptions (MP2/(aug)-cc-pVTZ).
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    Combining monolithic and hollow capillary columns under conditions of two-dimensional gas chromatography (2013)
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    Publication Date: 2013-07-06
    Description: A monolithic column with the optimum structure of its monolithic layer is considered as a second dimension column under the conditions of two-dimensional gas chromatography. It is shown that despite the considerable difference between the working pressures of different columns, sample transfer from a hollow capillary column to a monolithic column is possible when a looped switching valve is used. It is found that the additional broadening of the chromatographic zone observed during sample transfer can be effectively suppressed by using an additional flow splitter. At the same time, reducing the volume of the switching valve loop is inefficient and does not allow effective separation by the monolithic column.
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    Features of the temperature dependence for the rates of gas-phase reactions of combustion (2013)
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    Publication Date: 2013-07-06
    Description: The specific character of the dependence for the rate of most gas-phase reactions of combustion on temperature and reagent concentrations is found to be determined by the ratio of the rates of the multiplication and death of active intermediate particles. It is shown that the stepwise acceleration of the process and the transition to the combustion mode upon raising the initial temperature by 1–2 K and crossing over a critical value is due to a change in the character of the rate’s temperature dependence as a result of the sign changing from negative to positive to reflect the difference between the rates of chain branching and termination. It is concluded that this difference’s change in sign upon varying the content of reagents imposes limits on concentration.
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    Possibility of a 2D SiC monolayer formation on Mg(0001) and MgO(111) substrates (2013)
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    Publication Date: 2013-07-06
    Description: The geometrical characteristics of a 2D SiC monolayer on Mg(0001) and MgO(111) plates regarded as potential materials for growing two-dimensional silicon carbide were studied. The most favorable positions of the atoms of 2D SiC on the substrates were determined. In the 2D SiC/Mg(0001) system, unlike in 2D SiC/MgO(111), the deviation of the carbon atom from the silicon carbide monolayer was insignificant (0.08 Å). Consequently, magnesium can be used as a substrate for growing two-dimensional silicon carbide. The use of MgO(111) is not recommended because of a significant distortion of the 2D SiC surface.
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    Hydration numbers of ions in aqueous solutions of KOH, KCl, KI, and KIO 3 according to refractometric data (2013)
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    Publication Date: 2013-07-06
    Description: Ion hydration in aqueous solutions of KOH, KCl, KI, and KIO 3 was studied by refractometry. The sum of the hydration numbers of the potassium ion and each anion in these compounds and the hydration numbers of OH − , Cl − , I − , and IO 3 − anions were determined by the Lorentz-Lorenz equation at different salt concentrations. The model suggests that the polarizability of the hydrated ion is proportional to the cube of the ion radius and the volume of the hydrated ion equals the sum of the nonhydated ion and hydration shell volumes. The hydration numbers of the anions calculated by the proposed procedure increase with their radii in the sequence: OH − , Cl − , I − , and IO 3 − .
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    Thermodynamic properties of LiZr 2 (PO 4 ) 3 crystal phosphate (2013)
    Springer
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    Publication Date: 2013-07-06
    Description: The temperature dependence of the heat capacity of LiZr 2 (PO 4 ) 3 crystal phosphate is studied in an adiabatic vacuum calorimeter in the temperature range of 6 to 358 K. A phase transition caused by the transition of a low-temperature (triclinic) modification to a high-temperature (rhombohedral) modification is observed in the temperature range of 290–338 K and its standard thermodynamic characteristics are estimated and analyzed. Standard thermodynamic functions are calculated from experimental data: heat capacity, enthalpy, entropy, and Gibbs function in the range of T → 0 to 358 K. Fractal dimensionality D is calculated from the data on low-temperature (20 K ≤ T ≤ 50 K) heat capacity and the topology of the phosphate’s structure is estimated.
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    A low-parametric state equation for calculating the thermodynamic properties of substances in liquid and gaseous state (2013)
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    Publication Date: 2013-07-06
    Description: Using methods and approaches developed by the authors, a new low-parametric state equation for describing the thermal properties of normal substances is obtained that allows us to describe the thermal properties of gases, liquids, and fluids over a range of densities from the ideal gas state to the triple point, except for a critical region, with a high degree of accuracy close to that of an experiment. The caloric properties and speed of sound are calculated for argon, nitrogen, and carbon dioxide without using any caloric data except for the enthalpy of an ideal gas. It is established that the calculated values of enthalpy, heat capacity, the speed of speed of sound, etc., are in good agreement with the experimental (reliably tabulated) data.
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    Effect of the surface condition of silicas with grafted monofunctional polyfluoroalkylsilanes on the adsorption of polar molecules (2013)
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    Publication Date: 2013-07-06
    Description: Lyophobized silicas containing relatively small numbers of grafted perfluorohexyl (1.1 nm −2 ) and perfluorobutyl (1.7 nm −2 ) groups are studied by means of gas chromatography, adsorption under static conditions, and IR spectroscopy. The results are compared to those obtained by us previously for a series of samples with dense polyfluoroalkyl monolayers (≥2.0 nm −2 ). Effects related to the influence of the grafting density and the size of fluorine-containing groups on the adsorption of polar compounds and the hydrophobicity of the surface are discussed.
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    Thermodynamic properties of complex compounds of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane (2013)
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    Publication Date: 2013-07-06
    Description: The temperature dependence of the heat capacity of a complex compound of iron(II) nitrate with tris(3,5-dimethylpyrazol-1-yl)methane is studied by adiabatic calorimetry in the range of 100–300 K. A specific heat anomaly is found and localized in the temperature range corresponding to the sharp spin transition 1 A 1 ↔ 5 T 2 with hysteresis on the temperature dependence of the magnetic susceptibility. The effects of cooperative interaction are revealed on the basis of thermodynamic and magnetochemical data, using two widely used models of spin transition.
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    Inhibiting the photosensitized oxidation of anthracene and tryptophan by means of natural antioxidants (2013)
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    Publication Date: 2013-07-06
    Description: It is shown that model reactions of photosensitized oxidation of anthracene and tryptophan can be used for evaluation and comparison of antioxidant activity of various classes of compounds. Inhibition of the oxidation of substrates in the presence of the familiar antioxidants tocopherol (vitamin E), ascorbic acid (vitamin C), and mixtures of these vitamins with methionine, and in the presence of reputed antioxidants dihydroquercetin and taurine, are considered. It is concluded that all of the above compounds except for taurine have antioxidant properties; i.e., they reduce the rate constants of the photosensitized oxidation of anthracene and tryptophan. It is found that the inhibition of oxidation is associated with the interaction between antioxidants and singlet oxygen. Analysis of the kinetic dependences of the photosensitized oxidation of substrates in the presence of antioxidants reveals that a mixture of vitamins inhibits the process most efficiently, and inhibition occurs at the initial stages due to more active interaction between singlet oxygen and vitamin C
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    Calculating chemical equilibria in the heparin-Co 2+ ion-glycine system (2013)
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    Publication Date: 2013-07-06
    Description: Results from investigating interactions in the heparin-Co 2+ ion-glycine system are presented. The stoichiometry of cobalt complexes with heparin and glycine compositions CoOHHtpGly 4− and CoHepGly 3− is established.
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    Size effects in the sequential oxidation-reduction of Co nanoparticles in the Co/SiO 2 catalyst (2013)
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    Publication Date: 2013-07-06
    Description: The size effects during the oxidation-reduction treatment (ORT) of Co nanoparticles in the Co/SiO 2 catalyst were studied. The results of ORT on Co nanoparticles depended on the initial size distribution of nanoparticles; for small nanoparticles, ORT did not lead to further decrease in size. (The threshold size was obviously less than 10–15 nm.) The critical size of Co particles depended on the conditions of oxidation and reduction, i.e., the heating rate, the composition of the gas mixture, etc.
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    The mechanism of metal corrosion passivation (2013)
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    Publication Date: 2013-07-06
    Description: The main regularities of variations in the thermodynamic properties of components of cubic vanadium carbide, depending on the composition in the region of homogeneity, are investigated experimentally. It is believed that these regularities are inherent only to metal oxides. This serves as the basis for the concept that passivation during the corrosion of metals occurs due to the formation of surface metal oxide whose composition corresponds to the maximum concentration of oxygen in the region of homogeneity. The thermodynamic stimulus of corrosion is in this case reduced to almost zero.
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    Fluorescence of the lactone form of rhodamine B (2013)
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    Publication Date: 2013-07-06
    Description: A quantum-chemical investigation of spectral fluorescent properties of the lactone form of rhodamine B molecule is conducted with allowance for its interaction with polar solvent. It is shown that within the model, two emitting states emerge that can be attributed to the zwitterion and lactone forms of the rhodamine molecule based on their nature and energy. A lack of interaction between the emitting states is observed in the internal conversion channel. The rate constants of photophysical processes are estimated. The quantum yields of dual fluorescence are calculated.
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    Heat capacity and density of solutions of calcium and cadmium nitrates in N -methylpyrrolidone at 298.15 K (2013)
    Springer
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    Publication Date: 2013-07-06
    Description: The heat capacity and density of solutions of calcium and cadmium nitrates in N -methylpyrrolidone (MP) at 298.15 K are studied by calorimetry and densimetry. The obtained data are discussed in relation to certain features of solvation and complex formation in solutions of these salts. The standard partial molar heat capacities and volumes ( $\overline {C_{p^2 }^0 }$ and $\overline {V_2^0 }$ ) of the electrolytes in MP are calculated. The standard heat capacities $\overline {C_{p^i }^0 }$ and volumes $\overline {V_i^0 }$ of Ca 2+ and Cd 2+ ions in MP at 298.15 K were determined, along with the contribution from specific interactions to the values of $\overline {C_{p^i }^0 }$ and $\overline {V_i^0 }$ of Cd 2+ ions in MP solution.
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    Effect of ozonation on the reactivity of lignocellulose substrates in enzymatic hydrolyses to sugars (2013)
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    Publication Date: 2013-06-17
    Description: The efficiency of pre-treatment of aspen wood with ozone for subsequent enzymatic hydrolysis into sugars is determined by the amount of absorbed ozone. The ozone absorption rate depended on the water content in the sample being ozonized and was maximum at a relative humidity of wood of ∼40%. As a result of ozone pre-treatment, the initial rate of the enzymatic hydrolysis of wood under the action of a cellulase complex increased eightfold, and the maximum yield of sugars increased tenfold depending on the ozone dose. The ozonation at ozone doses of more than 3 mol/PPU (phenylpropane structural unit of lignin) led to a decrease in the yield of sugars because of the oxidative destruction of cellulose and hemicellulose. The alkaline ozonation in 2 and 12% NaOH was inefficient because of the accompanying oxidation of carbohydrates and considerably decreased the yield of sugars.
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    Endohedral complexes of fullerene-like silica molecules with H 2 O, CH 4 , and CH 3 NH 2 molecules (2013)
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    Publication Date: 2013-06-17
    Description: The possibility of formation of (SiO 2 ) 60 @H 2 O, (SiO 2 ) 60 @CH 4 , and (SiO 2 ) 60 @CH 3 NH 2 endohedral complexes was studied by the density functional (DFT) method (B3LYP exchange correlation functional, 6-31G** basis). The penetration of these molecules into the cavity of fullerene-like silica molecules is hindered by high activation barriers, which ensures the stability of the complexes formed during the synthesis of these molecules.
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    Detection of trace amounts of Pb(II) by schiff base-chitosan-grafted multiwalled carbon nanotubes (2013)
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    Publication Date: 2013-06-17
    Description: A simple, highly sensitive, accurate and selective method for determination of trace amounts of Pb(II) in water samples is presented. A novel Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs) solid-phase extraction adsorbent was synthesized by covalently grafting a Schiff base-chitosan (S-CS) onto the surfaces of oxidized MWCNTs. The stability of a chemically (S-CS-MWCNTs) especially in concentrated hydrochloric acid which was then used as a recycling and preconcentration reagent for further uses of (S-CS-MWCNTs). The method is based on selective chelation of Pb(II) on surfactant coated C18, modified with a Schiff base-chitosan-grafted multiwalled carbon nanotubes (S-CS-MWCNTs). The retained ions were then eluted with 4 mL of 4 M nitric acid and determined by flame atomic absorption spectrometry (FAAS) at 283.3 nm for Pb. The influence of flow rates of sample and eluent solutions, pH, break-through volume, effect of foreign ions on chelation and recovery were investigated. 1.5 g of surfactant coated C18 adsorbs 40 mg of the Schiff s base which in turn can retain 15.0 ± 0.9 mg of each of the two ions. The limit of detection (3σ) for Pb(II) was found to be 3.20 ng L −1 . The enrichment factor for both ions are 100. The mentioned method was successfully applied on determination of lead in different water samples. The ions were also speciated by means of three columns system.
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    Morphological features of C 60 and C 70 microcrystals obtained from C 6 H 5 CH 3 and CCl (2013)
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    Publication Date: 2013-06-17
    Description: Fullerene C 60 and C 70 microcrystals of different morphologies obtained by crystallization from toluene and carbon tetrachloride solutions were investigated using scanning electron microscopy and diffuse reflectance IR Fourier transform spectroscopy. The obtained results are discussed with regard to the features of fullerenes clusterization processes in solutions.
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    Studying the cavities in liquid ethyleneglycol (2013)
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    Publication Date: 2013-06-17
    Description: Liquid ethyleneglycol models of 1000 molecules in a simple cell shaped as a rectangular parallelepiped are constructed using molecular dynamics at temperatures of 268 to 443 K and a system pressure maintained close to zero. The cavities (pores) in ethyleneglycol and the time and temperature dependence of their sizes are analyzed. The pores are found to arise in fluctuation in different areas of the model and to collapse rather quickly without exhibiting any dynamic connection. The radii of the largest pores are shown to grow from 1.674 to 2.174 Å formed predominantly by hydrogen and carbon atoms and appreciably depleted of oxygen atoms. It is established that the largest pores could easily accommodate argon atoms at temperatures above 385 K. The solubility of argon in ethyleneglycol is estimated as 0.1 mol % at 403 K and 0.5 mol % at 423 and 443 K.
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    Thermochemistry of solvation of 18-crown-6 ether in binary methanol-acetonitrile solvents (2013)
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    Publication Date: 2013-06-17
    Description: Heat effects of the dissolution of 18-crown-6 ether (18C6) over a wide range of compositions of mixed methanol-acetonitrile solvents are determined via calorimetry at 298.15 K. It is found that passing from methanol to acetonitrile to x AN = 0.6 mole fraction is accompanied by a sharp increase in the exothermicity of 18C6 solvation. It is concluded that a further increase in the aprotic component of a binary mixture leads to no appreciable changes in the enthalpy of solvation of the macrocycle.
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    A model p - T diagram for a ternary system with two semi-volatile and one highly volatile components (2013)
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    Publication Date: 2013-06-17
    Description: A model p-T diagram for a three-component system composed of two semi-volatile and one highly volatile components is developed. The phase equilibria and phase transitions are analyzed over a wide range of variable parameters. Isobaric T - x - y diagrams typical of real metal and salt systems with isothermal and polythermal sections are considered.
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    Stability of nickel(II) glycylglycinate complexes in aqueous solutions of dimethylsulfoxide at 298.15 K (2013)
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    Publication Date: 2013-06-17
    Description: Stability constants of nickel(II) glycylglycinate complexes in aqueous solutions of dimethylsulfoxide of variable composition (from 0.00 to 0.60 mole fractions DMSO) are determined according to potentiometry at 298.15 K and an ionic strength of 0.1 M (NaClO 4 ). It is determined that with a rise in the concentration of an organic cosolvent in solution, the stability of nickel(II) complexes with glycylglycinate ion on the whole increases, but the log K stability = f ( X DMSO ) dependences are of a critical character with a maximum of 0.3 mole fractions DMSO. It is demonstrated that the rise in the stability of complexes is related to the destabilization of ligands in the low concentration range of the organic component, while the presence of a maximum is due to the different dynamics of the solvation contributions from reagents during changes in the Gibbs energy of reaction.
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    Dependence of the thermodynamic characteristics of forms of hydrogen adsorbed on a porous nickel surface on the degree of deactivation (2013)
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    Publication Date: 2013-06-17
    Description: Thermodynamic characteristics of the adsorption equilibria of individual forms of adsorbed hydrogen are calculated using data from adsorption-calorimetric studies of liquid-phase hydrogenation in a model of a surface with discrete nonuniformity in the ideal adsorption layer approximation under conditions of liquid-phase hydrogenation. It is shown that partial deactivation raises the fraction of the molecular α form via the atomic β form of adsorbed hydrogen and increases the adsorbate-adsorbent binding energy.
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    Kinetics of the swelling of a gel of cross-linked polyvinyl alcohol during the synthesis of copper-containing composite based on it (2013)
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    Publication Date: 2013-06-17
    Description: The kinetics of processes that occur during the chemical reduction of copper in a gel of polyvinyl alcohol (PVA) are described. It is shown that we can assess the processes occurring in the polymer from changes in the degree of swelling. The effects the nature of the precursor (precursor compound) has on the conditions of reduction are analyzed. It is found that crystals of reduced copper do not change the volume of PVA gel, which has a positive effect on the mechanical stability of the resulting composite.
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    Mechanism of the catalytic ozonization of lignin in the presence of Mn(II) ions (2013)
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    Publication Date: 2013-06-17
    Description: The reaction between ozone and lignin in aqueous solutions catalyzed by Mn(II) ions is studied. The rate of destruction for aromatic structures of lignin is found to increase in the presence of Mn(II) ions. However, the greatest catalytic effect is observed upon the transformation of aliphatic acids that are difficult to oxidize with ozone. The introduction of catalyst raises the total consumption of ozone from 3 to 7 mol per each structural unit of lignin. A scheme is proposed for the transformation of phenol fragments of lignin using ozone with the participation of Mn(II) ions: at the initial stage, we observe the ozone oxidation of lignin and Mn(II) to Mn(III) ions stabilized with products of lignin oxidation and accompanied by the formation of chelate complexes, and the Mn(III) chelate complexes act as low-molecular mediators, attacking phenol structures and initiating radical processes.
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    Mechanism of crystallization of CaCO 3 in system H 2 O-CaCl 2 -Na 2 CO 3 -1,2-Bis(4-aminophenoxy)ethane- (2013)
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    Publication Date: 2013-06-17
    Description: The growth characteristics of calcium carbonate (CaCO 3 ) in the mixed systems of 1,2-bis(4-aminophenoxy)ethane- N , N , N ′, N ′-tetraacetic acid (BAPTA) and cetyltrimethyl ammonium bromide (CTAB) were studied in our experiments. The as-prepared products were characterized by scanning electron micro-scope and X-ray diffraction. Calcite and vaterite with various morphologies were contained in the BAPTA single system and the mixed systems with CTAB/BAPTA molar ratio of 1: 2 and 1: 1.25, while only calcite produced in the mixed systems with CTAB/BAPTA molar ratio of 1: 5, 1: 1, 1: 0.67 and pure CTAB system. The possible formation mechanisms of CaCO 3 produced in different solutions were discussed in the end.
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    Determining the thermodynamic melting parameters of sulfamethoxazole, trimethoprim, urea, nicodin, and their double eutectics by differential scanning calorimetry (2013)
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    Publication Date: 2013-07-06
    Description: The literature data on the thermodynamic melting characteristics of sulfamethoxazole, urea, trimethoprim, and nicodin are analyzed for individual compounds. Their enthalpies and melting points, either individually or in the composition of eutectics, are found by means of DSC. The entropies of fusion and the cryoscopic constants of individual compounds are calculated.
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    Molecular interactions in a surfactant-water-polyacrylamide system, according to densimetry, viscometry, conductometry, and spectroscopy data (2013)
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    Publication Date: 2013-07-06
    Description: Molecular interactions in a surfactant-polyacrylamide-water system are investigated. It is established that the interactions affect such physicochemical parameters of the system as viscosity, density, surface tension, conductivity, and critical micelle concentration. It is shown that in a polyacrylamide-water system, raising the polyacrylamide concentration to 0.02% causes conformational changes in its macromolecule.
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    Preparation and characterization of sulfur-modified mesoporous titania photocatalyst (2013)
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    Publication Date: 2013-07-06
    Description: Sulfur-modified mesoporous titania (S-MTiO 2 ) was investigated as a potential photocatalyst under visible light. The photocatalyst was prepared by template method using thiourea and tetrabutyl titanate (Ti(OC 4 H 9 ) 4 ) as precursors and Pluronic P123 as template. The photoabsorbance of as-prepared photocatalyst was measured by UV-vis absorption spectroscopy, which confirmed the extension of absorption into the visible region. The microstructure of S-MTiO 2 was characterized using X-ray diffraction (XRD) and N 2 adsorption-desorption measurements. The micro crystal of the S-doped photocatalyst consisted of anatase phase and no significant influence on the nature of crystal formation. X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of C in the prepared photocatalyst in addition to S. The photo-catalytic performance was studied by photodegradation methyl orange (MO) in water under visible light irradiation. The calcination temperature and the doping content influenced the photoactivity.
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    Rheological and volumetric properties of aqueous solutions of anionic polymer surface-active substances (2013)
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    Publication Date: 2013-07-06
    Description: The kinematic viscosity and density of diluted aqueous solutions of polymer anionic surface-active substances (ASASes) is studied in the temperature range of 298.15 to 323.15 K. The intrinsic viscosities, Huggins constants, apparent activation energies of viscous flow, and partial molar volumes at infinite dilution are determined for these systems. IR spectra of the investigated ASASes are obtained. The conformations of ASAS macromolecules in solution are corrected, based on an analysis of experimental data.
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    Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K (2013)
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    Publication Date: 2013-07-06
    Description: The interaction between L -phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L -phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.
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    Epitaxial assembly of graphene on face (0001) of silicon carbide: Modeling by semiempirical methods (2013)
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    Publication Date: 2013-09-03
    Description: The epitaxial growth of graphene on silicon face (0001) of silicon carbide is simulated using the semiempirical methods of quantum chemistry. The experimental conditions for the epitaxial growth of graphene on SiC, at which the probability of seams and similar defects appearing is reduced to a minimum, are formulated. Possible ways of the emergence of reconstructions of the singular carbon and silicon SiC faces during the synthesis of graphenes are investigated as a test of the approach’s efficiency. It is noted that simulation reproduces the reconstruction periods experimentally determined for both faces, and yields the most likely atomic arrangements in cases where the experimental formula of the superstructure allows different versions of such arrangements.
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    Properties of conducting films of electrophoretic concentrates of silver and gold nanoparticles in AOT surfactant (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Liquid concentrates of silver and gold nanoparticles with 1–2 M metal concentrations were isolated by electrophoresis in a capacitor-type cell from AOT reverse micellar solutions in n -decane. The electrophoretic concentrates and the starting micellar solutions were characterized by nonaqueous electrophoresis, transmission electron microscopy, photon correlation spectroscopy (dynamic light scattering), and spectrophotometry. The hydrodynamic diameter of silver and gold nanoparticles was 13.2 and 8.6 nm, respectively; the ζ-potential was 70 and 13 mV. The drying of the concentrates on glass and silicon substrates and subsequent treatment with a 30% solution of water in ethanol gave mirror conducting Ag, Au, Ag-Au, and Au/Ag films containing on the average 80% metal and 20 wt % AOT. The film structure, morphology, and composition were studied by scanning electron microscopy (SEM) and energy dispersion analysis (EDX).
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    Simulating the conditions for the formation of graphene and graphene nanowalls by semiempirical quantum chemical methods (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: A “substrate-surface graphene island” is simulated by semiempirical quantum chemical methods for different substrates. It is established that such systems with various island sizes correspond to graphene growth on corresponding substrates when CVD is used. Carbon atoms can be incorporated into the island from either the side of the substrate or the side of the CVD reactor exposed to it. It is shown for a wide range of island sizes that the best configuration with respect to the substrate is the structure of a carbon nanowall oriented perpendicular to the substrate. It is emphasized that a transition to this configuration is possible in reality only if CVD is plasma-stimulated when there is a strong near-electrode field near the surface, and the preliminary scission of the carbon carrier material occurs simultaneously in the CVD reactor volume.
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  • 83
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    Mechanism of the conductivity and sensor response of nanostructured In 2 O 3 +ZnO films (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: The conductivity and sensor properties of mixed nanostructured In 2 O 3 +ZnO metal oxide systems with different component ratios are investigated. It is found that maximum sensor sensitivity in detecting hydrogen and CO in composite films containing 15 and 80 wt % In 2 O 3 considerably exceeds the sensitivity of individual oxides. A mechanism of the sensor action, which is largely determined by the dependency of the paths of conductivity in a composite metal-oxide film on its composition, is proposed. It is established that the main factors determining the conductivity and sensor sensitivity of In 2 O 3 + ZnO composite are modifications in the electron structure of crystals (mainly by In 2 O 3 ) during the formation of composites, electron transfer from In 2 O 3 to ZnO, and the catalytic activity of ZnO. It is shown in particular that ZnO effectively catalyzes the reaction of hydrogen dissociation and, in contact with In 2 O 3 , favors the chemical sensibilization of the sensor response of such mixed metal oxide systems in detecting H 2 and CO.
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  • 84
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    Inhibiting the combustion of air-methane mixtures (2013)
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    Publication Date: 2013-09-03
    Description: It is found that additives containing i -C 4 H 8 , CO 2 , CF 3 H, and CF 4 effectively inhibit the ignition and combustion of air-methane mixtures of any composition at atmospheric pressure, evidence of the branched-chain character of methane combustion. The reason for the great distinction between the efficiency of inhibiting methane and hydrogen combustion by trifluoromethane is found. The synergism in the joint effect of the abovementioned additives is revealed and taken advantage of. It is shown that the effect is inherent to the branched-chain mechanism.
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  • 85
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    Initial stage of the epitaxial assembly of graphene from silicon carbide and its simulation by semiemprical quantum chemical methods: Carbon face (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: The epitaxial growth of graphene on a singular carbon face of silicon carbide is simulated by semiempirical quantum chemical methods. It is shown that the main regularities of the growth of graphene on such a face, i.e., the sequence of surface reconstructions with a short spatial period (2 × 2) → (3 × 3) → graphene, are exhibited naturally during the analysis of various paths of graphene assembly and seeking the most probable path.
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  • 86
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    Simulating the synthesis and thermodynamic characteristics of the desolvation of lanthanide borohydride tris -Tetrahydrofuranates (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Lanthanide borohydride tris -tetrahydrofuranates (Ln(BH 4 ) · 3THF, where THF is tetrahydrofuran and Ln is La, Nd, Sm, Gd, Er, Yb, and Lu) is synthesized via the exchange reaction of lanthanide(III) chloride and sodium borohydride in THF. It is found that synthesis proceeds according to a stepwise mechanism and the product of the reaction (lanthanide borohydride) initiates the process. The two-step character of the desolvation of Ln(BH 4 ) 3 · 3THF under steady-state conditions in the temperature range of 300 to 400 K is determined through X-ray phase and chemical analyses, tensiometry, and gas volumetry. It is established that one mole and then two moles of THF are removed from the initial sample at the first and second steps, respectively. Equations for barograms are obtained and the thermodynamic characteristics of desolvation of Ln(BH 4 ) 3 · 3THF under study are calculated. Gibbs energy values of the stages of process are determined semi-empirically. The law of its change for the entire series of Ln(BH 4 ) 3 · 3THF is determined with the emergence of the tetrad effect.
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  • 87
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    The densities and viscosities of aqueous solutions of glycine and glycylglycine containing carbohydrates and structural properties of the ternary systems (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Apparent molar volumes, V ϕ for glycine (Gly) and glycylglycine (Gly-Gly) in aqueous D(+)-glucose and sucrose solutions have been determined from solution density, ρ measurements at 298.15, 303.15, 308.15, and 313.15 K as a function of the concentration of solutes (Gly and Gly-Gly). The standard partial molar volume, V ϕ 0 , transfer volume, ΔV ϕ(tr) 0 , for Gly and Gly-Gly from water to aqueous carbohydrate solutions, partial molar expansibility, E ϕ 0 , and hydration number, n H of solute have been calculated. The viscosity data have been analyzed by means of Jones-Dole equation to obtain A - and B -coefficients, free energy of activation of viscous flow per mole of solvent, Δμ 1 0# , and solute, Δμ 2 0# , enthalpy, Δ H 0# , and entropy of activation, Δ S 0# of viscous flow were evaluated. The behavior of these parameters has been interpreted in terms of solute-solute and solute-solvent interactions.
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  • 88
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    Synthesis of co-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: The conditions of synthesis of cobalt-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays were correlated with their texture characteristics. The main factors governing the texture properties of the material were shown to be the montmorillonite content in natural clay, the calcination temperature, and the type of hydrolyzing agent and OH − : Me n + ratio during the preparation of the modifying solution.
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  • 89
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    Features of the temperature and concentration dependences of the contraction of aqueous solutions of ethanol (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Temperature and concentration dependences of the contraction of aqueous solutions of ethanol are studied. It is shown that at a molar concentration of x = 0.077, the curves of the temperature dependences of contraction intersect at one point that is interpreted as the singular point of a water-ethanol solution. To reveal the role of intermolecular forces of attraction, our results are compared to the behavior of contraction for hard-sphere mixtures with varying ratios of their radii. The change in the total volume of the solution induced by the formation of hydrogen bonds is analyzed in detail.
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  • 90
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    Theoretical investigations on electronics structure and chemical bonding on iridathiabenzene and iridaoxabenzene (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: The electronic structure and properties of the iridathiabenzene and iridaoxabenzene isomers have been investigated using the hybrid density functional mpw1pw91 theory. The energetic aspect shows that trans - ortho -isomer is the most stable isomer. This is compatible with principles of minimum energy and minimum polarizability. Molecular orbital analysis shows a linear correlation between hardness and anisotropic polarizability values for Iridathiabenzene and iridaoxabenzene isomers. The structural and natural bond analysis (NBO) results illustrate electronic delocalization in these rings. Also, the study of non linear optical properties of these molecules indicate a good correlation between β tot and E (HOMO) for iridathiabenzene. The results from natural bond orbital (NBO) analysis have provided insights into Ir—ligand, P—H apical and P—H basal bonding.
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    Enthalpies of formation of acetyl radicals (2013)
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    Publication Date: 2013-09-03
    Description: The database on the enthalpies of formation (Δ f H ○ ) of aliphatic acetyl radicals of the RC·(O) type is analyzed and extended. Δ f H ○ values are estimated for the first time for three compounds on the basis of experimental data. The data were analyzed using the additive group approach with the determination and correction of parameters. Good correspondence between the Δ f H ○ (RC·(O)) values calculated according to parameters with experimental data is observed.
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  • 92
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    Mechanism of the protonation of azulenes in aqueous solutions of acids (2013)
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    Publication Date: 2013-09-03
    Description: In aqueous solutions of strong acids (H 2 SO 4 , H 3 PO 4 , and HCl) containing azulene, the fast reversible protonation of azulene is accompanied by the slow formation of a disperse dark violet dye insoluble in acids, alcohol, and heptane. On the basis of the kinetic specifics of this reaction and the nonlinear (nearly reciprocal quadratic) dependence of the concentrations ratio of their cationic and neutral forms on the Hammett acidity function known for azulene and 14 of its derivatives, azulene is shown not to be a Hammett base. A mechanism for the reversible reactions of the azulenium cation is proposed that considers supramolecular dimers to be the basic state of azulene and its derivatives. The scheme includes reactions of the unstable intermediate π complexes formed from the dimers and hydrated hydrogen cations; the complexes quickly dissociate in the opposite direction and react with the hydrated protons to yield azulenium cations and unstable molecules that induce polymerization of the dimers.
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  • 93
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    Complexation study of cryptand 222 with lanthanum(III) cation in binary mixed non-aqueous solvents (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Conductometric titrations have been performed in some binary solvent solutions of acetonitrile (AN), 1,2-dichloroethane (DCE), ethylacetate (EtOAc) and methylacetate (MeOAc) with methanol (MeOH), at 288, 298, 308, and 318 K to give the complex stability constant and the thermodynamic parameters for the complexation of lanthanum(III) cation with 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]-hexacosane (cryptand 222). The stability constant of the resulting 1:1 complex at each temperature was determined from computer fitting of the conductance-mole ratio data. The results revealed that, the stoichiometry and the stability order of (cryptand 222 · La) 3+ complex changes with the nature and also the composition of the solvent system. A non-linear relationship was observed between the stability constant (log K f ) of (cryptand 222 · La) 3+ complex versus the composition of the binary mixed solvents. Thermodynamically, the complexation of lanthanum(III) cation with the cryptand 222, is mainly entropy governed and the values of these parameters are influenced by the nature and composition of the binary mixed solvent solutions.
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    Dynamics of CO hydrogenation for bimetallic Co-Fe/Carrier catalysts (2013)
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    Publication Date: 2013-09-03
    Description: Bimetallic catalysts based a Co-Fe/carrier system are prepared via the consecutive and combined deposition of metals on Al 2 O 3 and MgO · Al 2 O 3 . The dynamics of CO hydrogenation at 300°C is studied.
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  • 95
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    Characteristics of atomic vibrational motion in a one-component defective crystal (2013)
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    Publication Date: 2013-09-03
    Description: Vibrations of atoms in a defective argon crystal are considered. Frequencies are calculated in the harmonic approximation and Mie and Einstein approximations. The vibrations are calculated for a set of local clusters differing in the position of a vacancy at different distances from a selected atom. Probabilities for these clusters are calculated within a quasichemical approximation of the lattice gas model. It is shown that when combined contributions from lateral interactions and vibrational motions are allowed for in the free crystal energy, there is an increase in the lattice constant upon a rise in temperature in all approximations. It is found that the frequencies calculated using the Mie model become closer to the frequency distribution in the harmonic approximation as the degree of crystal defectiveness increases.
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    Non-isothermal decomposition kinetics of diosgenin (2013)
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    Publication Date: 2013-09-03
    Description: The thermal stability and kinetics of isothermal decomposition of diosgenin were studied by thermogravimetry (TG) and Differential Scanning Calorimeter (DSC). The activation energy of the thermal decomposition process was determined from the analysis of TG curves by the methods of Flynn-Wall-Ozawa, Doyle, Šatava-Šesták and Kissinger, respectively. The mechanism of thermal decomposition was determined to be Avrami-Erofeev equation ( n = 1/3, n is the reaction order) with integral form G (α) = [−ln(1 − α)] 1/3 (α = 0.10–0.80). E a and log A [s −1 ] were determined to be 44.10 kJ mol −1 and 3.12, respectively. Moreover, the thermodynamics properties of Δ H ≠ , Δ S ≠ , and Δ G ≠ of this reaction were 38.18 kJ mol −1 , −199.76 J mol −1 K −1 , and 164.36 kJ mol −1 in the stage of thermal decomposition.
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    UV spectroscopy of methanofullerene derivatives with different degrees of substitution (2013)
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    Publication Date: 2013-09-03
    Description: Compounds from the series of methanofullerenes with different degrees of functionalization were studied by UV spectroscopy. As the number of substituents increased, a hypsochromic shift of the characteristic absorption bands took place and the optical density of the solutions of the compounds at characteristic maxima decreased. A similar dependence was also noted for the ratio of the optical densities of the 258 and 329 nm bands typical for fullerene ( A 258 / A 329 ). An exponential dependence of the molar absorption coefficients of metanofullerenes on the degree of functionalization of the fullerene nucleus was found.
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    Effect of thermomechanical processing on the thermal stability of amorphous Fe-B alloys (2013)
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    Publication Date: 2013-09-03
    Description: Results from investigating the effect of thermomechanical processing on the thermal stability of amorphous Fe-B alloys are presented. It is shown that the combined thermomechanical processing of amorphous alloys raises the temperature of intense crystallization onset by 80 K for binary alloys; by 20–50 K, for multicomponent alloys. The greater expansion of the thermal stability interval of binary alloys relative to multicomponent alloys is explained by the presence of alloying dopants such as molybdenum, nickel, and silicon that inhibit the diffusion of boron and thus hinders nucleation and the growth of the crystalline phase. The enhanced thermal stability of amorphous alloys induced by thermomechanical processing is explained by the reduction in size of amorphous-phase frozen crystallization centers and by the formation of a nanostructured state.
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    Structure and properties of magnetic composite sorbents based on hypercrosslinked polystyrenes (2013)
    Springer
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    Publication Date: 2013-09-03
    Description: Magnetic composite sorbents based on microporous and biporous hypercrosslinked polystyrenes (HCPs) with inclusions of iron oxide nanoparticles were studied by X-ray diffraction and differential thermal analysis. In microporous composites, the size of impregnated magnetite nanoparticles was less than ∼6 nm, the nanocomposites remaining optically transparent. Biporous HCPs (with micro- and macropores) had larger nanoparticles (∼16 nm). The sorption studies revealed that composite magnetic sorbents, as well as the starting hypercrosslinked polystyrenes, are effective adsorbents with high capacity for many compounds including toxic and physiologically active compounds.
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    Heat capacity and thermodynamic functions of manganite ferrites NdM I MnFeO 5 (M I = Li, Na) in the range of 298–673 K (2013)
    Springer
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    Publication Date: 2013-04-18
    Description: The heat capacities of the new manganite ferrites NdM I MnFeO 5 (M I = Li, Na) are investigated in the range of 298.15–673 K by dynamic calorimetry. It is found that in the investigated temperature range, C p ○ ∼ f ( T ) curves exhibit λ-shaped effects at 348 and 473 K for NdLiMnFeO 5 , and at 423 K for NdNaMnFeO 5 , corresponding probably to phase transitions of the second kind. Equations describing the experimentally obtained C p ○ ∼ f ( T ) curves are derived, and the temperature dependences of the investigated compounds’ thermodynamic functions, S ○( T ), H ○( T ) − H ○(298.15), and Φ xx ( T ), are calculated.
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