Preparation of a polyacetylene composite with single-walled carbon nanotubes and study of its electrochemical properties

A composite consisting of single-walled carbon nanotubes (2.4 wt %) covered by polyacetylene has been prepared. Polyacetylene synthesized directly on single-walled carbon nanotubes is a defectless long-chain polymer composed of trans and cis units with a sufficient length (60% trans and 40% cis isomers). An appreciable acceleration of the lithium ion intercalation-deintercalation corresponds to an increase in the conductivity of the composite material near the percolation threshold. The polyacetylene layer on single-walled carbon nanotubes plays the role of an electrochemically active ion-conductive membrane suitable for the transport of Li⁺ cations to the surface of nanotubes.     

Cation Distribution and Interatomic Interactions in Oxides with Heterovalent Isomorphism: III. Complex Aluminates LnCaAlO4 (Ln = Y,La, Nd,Gd, Ho,Er, Yb)

The heterovalent isomorphism of Ln³+⁺ and Ca^{2 +} cations in stoichiometric LnCaAlO₄ oxides was studied. The X-ray diffractometry of the intensity of Laue background modulations revealed a positive short-range order in Ln^{3 +} and Ca^{2 +} distribution over points of one structural site common for both ions, which results in formation of stable Ln³⁺-Ca²⁺ couples in adjacent nine-coordinate oxygen polyhedra. The degree of order and the interchange energy estimated in the quasichemical approximation depend both on the effective cationic charges and on the number of unpaired f electrons of the lanthanide atom.     

Intermolecular hydrogen bond and its spectroscopic manifestations in formation of small water complexes

Ab initio calculations of small water(H ₂ O) _n , n=2–7, complexes and the experimental evidence available are compared. The results obtained are used as a basis for a theoretical investigation into the water molecule association through hydrogen bonding and its spectroscopic manifestations. Basic structural and spectroscopic trends are established as the complex increases in size. Siberian Physicotechnical Institute at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 87–91, September 1999.     

Modeling the compositions of slime waters in the tailing dumps of the Central and Krasnorechensk concentrating mills at the Dal’negorsk district in the positive temperature range

The paper describes the physicochemical modeling of slime water formation in the dried tailing dumps of the Central and Krasnorechensk concentrating mills in the positive temperature range. The Eh and pH parameters of the equilibrium solutions, quantitative element compositions of the latter, and the compositions of the crystallizing hypergene and technogenic minerals were determined. The modeling was carried out on the basis of the averaged chemical compositions of the tailings. The resulting data point to a possible hydrosphere pollution with slime waters containing elements of sulfide ores and enclosing rocks, which may occur over the entire considered temperature range, both before hypergene mineral deposition and after that.     

Pretreatment-free immunochromatographic assay for the detection of streptomycin and its application to the control of milk and dairy products

A rapid pretreatment-free immunochromatographic assay was developed for the control of the streptomycin (STR) content in milk and dairy products. The assay is based on the competition between an immobilized STR–protein conjugate and STR in a sample to be tested for the binding to monoclonal anti-STR antibodies conjugated to colloidal gold during the flow of the sample along a membrane strip with immobilized reactants. It is possible to improve the cut-off level of positive and negative samples distinguished by a change in the molar STR to protein ratio in the immobilized conjugate. The cut-off level (500 ng mL⁻¹) thus achieved corresponds to the stated MRL of STR in milk and dairy products. For STR concentrations in the range of 16–250 ng mL⁻¹ its content can be quantitatively measured based on the degree of binding of a colloidal gold label in the test strip zone with the immobilized STR–protein conjugate. The duration of the assay is 10 min. The selected sizes of membrane pores and colloidal gold particles allow the assay to be carried out at room temperature without additional reactants and pretreatment. The applicability of the assay for milk, whole milk, sour clotted milk, and kefir with different fat content (from 0.5% to 6%) was confirmed. The results of quantitative immunochromatographic assay show good correlation with traditional ELISA (r was equal to 0.935 and 0.940 for the series tested).     

Physicochemical modeling of the impact of tailings dumps in the Kavalerovskii tin-ore district of the Russian far east on the hydrosphere

Physicochemical modeling was applied to determine Eh and pH parameters of anthropogenic mineral formation in the Kavalerovskii mining district, study crystallization of supergene minerals from solution, examine the qualitative and quantitative ion compositions of solutions, estimate the role of supergenesis in the pollution of surface and ground water, and assess environmental situation in the district.     

Photocatalytic activity of TiO2-MO x composites in the reaction of hydrogen generation from aqueous isopropanol solution

The photocatalytic activity of the composites TiO₂-MO _x (M = Ni, Cu, Zn, Fe, Cr) was studied in the reaction of hydrogen generation from aqueous alcoholic suspensions under UV light. The samples modified by the oxides of the metals capable of being reduced from oxides under photocatalytic conditions showed a high catalytic activity. The studied modifiers were divided in three groups in terms of their effect of the photocatalytic activity of TiO₂: activating (NiO, CuO), inhibiting (Fe₂O₃), and indifferent (ZnO, Cr₂O₃).     

Investigation of the amplifying properties of a krypton gas discharge plasma

The characteristics of a gas discharge in krypton (at a pressure of several atmospheres), used as a medium for lasers based on excimer transitions in the VUV region, have been calculated. It is shown that, to achieve the threshold values of excimer concentration, a high preionization level and the shape of the applied voltage pulse are important factors. It has been found that the shape of the excimer emission pulse is determined, to a large extent, by stepwise processes with the participation of electrons and by the relaxation time of the electron energy.