Imbricin,an Antifungal Antibiotic of Non-Medical Application: Preparation,Physicochemical Properties,Structural Features,and Industrial and Agricultural Uses (Review)

Published data on the preparation, physicochemical properties, and structural features of imbricin, an antifungal antibiotic of non-medical application, were systematically described. Directions of practical application of imbricin in various areas of industry and agriculture were summarized.     

Mass Spectrometric Analysis of Microcystins from Cyanobacterial Biomass: Optimization of the Sample Preparation Procedure

The sample preparation procedure for determination of microcystins from biomass by the LC–MS method was optimized. Treatment of freeze-dried biomass samples with acetonitrile prior to the main extraction was effectively used for decreasing the amount of protein-like matrix compounds in extracts. Use of acetonitrile–water mixtures during the main ultrasound-assisted extraction allowed increasing the total microcystins amount in the resultant extracts compared to the traditional extraction using 75% methanol.     

Solubilization of prothionamide with micelles of an amphiphilic acrylic acid oligomer with thiohexyl terminal groups and preparation of postoperative cavity filling formulations

An amphiphilic oligomer was prepared by telomerization of acrylic acid in the presence of n-hexyl mercaptan. The structure, molecular weight, critical micelle concentration, and ζ-potential of the oligomer, and also its particle-size distribution in aqueous solution were determined. The product allows solubilization of prothiondamide antituberculosis drug. A procedure was suggested for preparing a filling formulation containing prothionamide for filling postoperative cavities in connective tissue.     

Structure and Thermal Stability of Nanostructured Precursor Powders of Copper(I) Sulfide and Selenide

The hydrochemical precipitation method at 298 and 333 K with, respectively, thiocarbamide and sodium selenosulfate was used to obtain nanostructured powders of copper sulfide with formula composition Cu₂S, which are composed of globules 200–500 nm in diameter, formed by 70–100-nm particles, and copper(I) selenide, composed of crystallites with polyhedral shape, sizes of 80 to 500 nm, and a formula composition Cu_1.84Se. An X-ray diffraction analysis revealed the orthorhombic Cu₂S structure (space group no. 39-Abm2) with unit cell parameters a = 1.182 nm, b = 2.705 nm, and c = 1.343 nm. Powders of Cu_1.84Se copper selenide have a cubic structure (space group Fm3m) with lattice constant a = 0.5693 nm. A thermal analysis demonstrated that the chemically precipitated Cu₂S and Cu_1.84Se powders have a stable elemental composition up to 200–240°C. An intense oxidation of the samples begins at a temperature exceeding 250°C and is accompanied by a sharp decrease in their content of sulfur (selenium) and by an increase in the content of oxygen.     

Low-Temperature Plasma-Chemical Deposition of Nanocomposite Antifriction Molybdenum Disulfide (Filler)–Silicon Oxide (Matrix) Coatings

It was demonstrated experimentally that the spatial separation of two processes of chemical vapor deposition, one of which provides synthesis of filler (MoS₂) nanoparticles and the other yields the matrix (SiO₂) of the nanocomposite coating, performed ina common reactor, enables an independent control over two process rates and makes it possible to widely vary the composition of the films deposited in this way. The deposition was performed in a double-zone vertical tubular quartz reactor. Molybdenum disulfide particles were produced by pyrolysis of aerosols of ammonium thiomolybdate solutions in dimethylformamide in the upper zone of the reactor, and the plasma-chemical deposition of a nanocomposite coating occurred in the lower zone into which MoS₂ nanoparticles were transported by the gas flow and tetraethoxysilane was delivered. It was shown that the nanocomposite coatings composed of molybdenum disulfide (filler) and silicon oxide (matrix) possess improve the antifriction properties as compared with the matrix (SiO₂ layers), these properties being determined by the relative amounts of MoS₂ nanoparticles in the layer and by their average size.     

Preparation of Ultramicroporous Materials by Fluidized-Bed Pyrolytic Deposition of Carbon in Pores of a Carbon Matrix

Samples of microporous materials were prepared by pyrolytic deposition of carbon from divinyl in a fluidized bed reactor onto carbon supports obtained from coconut and pine nut shells. The influence exerted on the adsorption capacity for CO2 by the divinyl pyrolysis temperature (in the range 600–750°С) and degree of densification (in the range 6–22%) was studied. Carbon deposition conditions ensuring the specific surface area (S_BET) lower than 5 m2 g^–1 at the adsorption capacity for СО₂ higher than 1 mmol g^–1 for both samples were found.     

Degradation of physicomechanical properties of epoxy nanocomposites with carbon nanotubes upon heat and humidity aging

The dependence of the physicomechanical properties of epoxy nanocomposites subjected to heat and humidity aging on the type of covalently functionalized carbon nanotubes and on the uniformity of their distribution in the epoxy matrix was studied. Two types of carbon nanotubes were used: those modified with carboxy and amide groups. The elastic modulus, bending deflection, and ultimate bending strength for the initial epoxy nanocomposites with carbon nanotubes and for those subjected to heat and humidity aging were determined. The epoxy binders modified with carboxylated carbon nanotubes are more resistant to the action of aging factors. The presence of aggregates of carboxylated carbon nanotubes in the epoxy matrix positively influences the preservation of physicomechanical properties of the composite subjected to heat and humidity aging. Microscopic examination revealed structural features of the epoxy nanocomposite and their effect on the resistance of the composite to the heat and humidity aging.     

Aggregatively stable suspensions of micrometer powders of doped barium cerate for electrophoretic deposition of thin-film coatings of solid-oxide fuel cells

Potentialities of the method of electrophoretic deposition of thin-film coatings based on micrometer powders of multidoped barium cerate BaCe_0.8Sm_0.19Cu_0.01O_3–δ (BCSCuO) and BaCe_0.89Gd_0.1Cu_0.01O_3–δ (BCGCuO) were considered. Micrometer powders of BCSCuO and BCGCuO were produced by the methods of solid-phase and citrate-nitrate syntheses, respectively. The dispersity, fraction composition, and electrokinetic potential of nonaqueous suspensions of these powders and the electrokinetic parameters of the electrophoretic deposition process were examined. An ultrasonic treatment and ultracentrifugation produced aggregatively stable suspensions of BCGCuO and BCSCuO micrometer particles in a mixed (70/30 vol %) isopropanol–acetyl acetone medium. These suspensions are characterized by high positive values of the zeta potential (+24 and +28 mV, respectively). Thin film coatings of the electrolyte materials BCSCuO and BCGCuO, which are of interest for the technology of medium-temperature solid-oxide fuel cells, were produced by the electrophoretic deposition onto a dense model cathode.     

Distribution of Zinc Oxide Nanocrystals in a Polymer Film

The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter.     

Effect of gas environment parameters on operation efficiency of chemical absorbents of carbon dioxide

Effect of main characteristics of the gas medium on the absorbing properties of alkaline chemical absorbents is demonstrated. The following gas flow parameters were examined as variables: carbon dioxide content of the gas flow within the range 0.2–5.0 vol %, gas humidity of 25–90 rel %, and pressure in the zone of the chemisorption process in the range from 2 to 6 MPa. As objects of study served mixed chemical absorbents based on calcium, sodium, and lithium hydroxides.