Quantitative Aspects of Competition of Substitution and Addition Pathways in Chlorination of Synthetic Rubbers

The competition of substitution and addition pathways in chlorination of SKDN-N, LKN-S, SKDS-N, and NMPB synthetic rubbers in chloroform was studied.     

Research of Nanostructured Carbon Felt Materials as Electrodes of Vanadium Flow Batteries

Russian Journal of Electrochemistry - Flowing vanadium batteries are gaining great popularity in the world and are already ahead of lead-acid batteries in terms of installed capacity, but are far...     

Phosphorimetric determination of polynuclear aromatic hydrocarbons in gasoline

The possibility of determining pyrene, anthracene, and fluorene in gasoline by phosphorimetry at room temperature after the micellar extraction with sodium dodecyl sulfate was examined. It was found that the above polynuclear aromatic hydrocarbons simultaneously present in gasoline can be selectively determined by room-temperature phosphorimetry using different techniques for the excitation and population of the triplet states of luminophore (stationary and pulse excitation and triplet energy transfer). The proposed procedure was verified by gas chromatography with a mass-selective detector.     

A luminescence immunoassay test method for determining benzo[a]pyrene in natural water

A test method is developed for determining benzo[a]pyrene in natural water, based on the use of a polyethylene filter (frit) with adsorbed specific antibodies, placed within a transparent column. In passing a test solution, the analyte is adsorbed on the frit similarly to the process implemented in immunoaffinity preconcentration. The added conjugate of a labeled analyte takes the remained vacant binding sites of antibodies. Luminescent semiconductor nanoparticles (quantum dots) CdSe/ZnS, used as labels, enable visual determination under irradiation with UV light. The limit of detection for benzo[a]pyrene in water is ~0.5 ng/mL.     

Determination of Precious Metals in Geological Samples from Four Gold Ore Deposits of the North-East of Russia

Compositions of rare mineral phases containing precious metals (PMs) in samples from Natalka, Pavlik, Vetrenskoe, and Degdekan gold ore deposits (North-East of Russia) are studied by scintillation atomic emission spectrometry (SAES) and electron probe microanalysis (scanning electron microscopy and electron probe X-ray microanalysis, SEM–EPMA). The SAES method found dozens and hundreds of particles carrying gold, silver, and all platinum-group elements as native metals, intermetallides and solid solutions, arsenides, antimonites, sulfoarsenides, tellurides, selenides, etc. The variety of the elemental compositions of PM species (mineral phases) found by SAES significantly exceeds the list of minerals found previously by SEM–EPMA because of different natures of optical and X-ray spectra. The sizes of PM particles calculated by the SAES method and measured by SEM–EPMA are similar. The SAES data on the total concentrations of PMs satisfactorily agree with the results of inductively coupled plasma mass spectrometry.     

Gel-based immunoassay for non-instrumental detection of pyrene in water samples

A new qualitative immunologically based tube test for non-instrumental detection of pyrene (PYR) in water samples was developed. The method combines the pre-concentration of analyte by immunoextraction and its detection by immunoassay using Sepharose 4B-immobilized IgG-fraction of a polyclonal anti-PYR antiserum (immunoaffinity gel) and 1-pyrenebutyric acid-horseradish peroxidase conjugate (PYR-BA-HRP). The immunoaffinity gel was placed in a standard 1-ml SPE column through which a 10-ml aliquot of water sample spiked with 10% acetonitrile was passed. Following, free antibody binding sites were detected by application of PYR-BA-HRP. Four minutes after addition of the chromogenic substrate the results were visually evaluated by occurring or stayed away blue colour development for negative and positive samples, respectively. Total time for assay was about 15 min for six samples. Under optimized conditions a cut-off level for pyrene of 0.04 ng ml(-1) was found. At this defined concentration, a set of spiked samples (n=175) was analyzed and very low rates of false negatives (1.2%) and false positives (4.6%) determined which fulfils the requirement set by Commission Decision 2002/657/EC for a screening method. No interference by other PAH compounds like naphthalene, fluoranthene, phenanthrene, anthracene, and benzo[a]pyrene at a concentration of 20 ng ml(-1), i.e., 500-fold excess compared to the defined cut-off level was observed. Different water types like surface water, tap water, bottled water, and melted snow were analyzed for PYR contamination by the proposed method and results confirmed by HPLC-FLD.     

Modeling of soft phase transfer to the surface of multicomponent aluminum alloy in friction

A model for calculating the dependence of the amount of solid lubricant formed on the surface of a multicomponent aluminum alloy in friction is proposed. The constructed model is applied to analyze how the properties of the matrix and soft structural components as well as the alloy structure influence the amount of the soft phase transferred to the friction zone which provides for self-lubrication. Recommendations are given concerning the structural composition of the alloy (size and density of phase inclusions) in order to increase the thickness of formed lubricant film in specified friction modes.     

The periodic contact problem for an elastic half-space

A method of solving the periodic contact problem for a system of indentors of arbitrary shape and an elastic half-space is proposed. Different versions of the arrangement of the indentors, at one and at several levels, are considered. The results are used to analyse the effect of the parameters of the microgeometry of the characteristics of a discrete contact and the stressed state of solids possessing regular microrelief.