Changes in luminescence of semiconductor colloidal quantum dots CdSe@CdS by replacement of hydrophobic ligands with 1-thioglycerol

Luminescent properties of CdSe@CdS colloidal quantum dots upon replacement of hydrophobic stabilizing ligands with water-soluble 1-thioglycerol have been studied. The data obtained have made it possible to optimize the ligand replacement procedure and significantly decrease the loss of the fluorescence quantum yield of the resulting hydrophilic quantum dots.     

Experimental study of gasification of vacuum residue in metal melt by alternating reactor feeding with carbonaceous feedstock and oxidant

Processes occurring in a metal melt during plasma-assisted melt gasification of carbonaceous feedstock have been studied in the mode of alternating feeding the reactor with the carbonaceous feedstock and oxidant. Vacuum residue was used as an oxygen-free carbonaceous material, and air and steam were used as an oxidant. The results of the study show that by alternating the carbonaceous-feedstock pyrolysis step and the step of carbon oxidation in the metal melt, it is possible to produce synthesis gas with any desired H₂/CO ratio.     

The relationship between self-organization and membrane effects of aqueous dispersion systems of the thyroliberin oligopeptide

The relationship between rearrangement of the dispersed phase inducing considerable changes in the pH and nonmonotonic concentration dependences of membrane effects in aqueous systems of the endogenous regulatory peptide, thyroliberin (thyrotropin-releasing hormone), in 10^–3–10^–16 mol/L concentration range was demonstrated for the first time. The membrane structure modification in the 10^–13–10^–16 mol/L range was found to be due to accumulation of nanoassociates, while the oppositely directed pronounced structural changes in the 10^–6–10^–12 mol/L range may be associated with the coexistence and rearrangement of dispersed phases of various nature (domains and associates) whose action on membrane lipid components is regulated in this concentration range by the correlated changes in the dispersed phase parameters and pH.     

Supercomputer technologies for structural-kinetic study of mechanisms of enzyme catalysis: A quantum-chemical description of aspartoacylase catalysis

The results of modeling of the complete catalytic cycle of aspartoacylase-catalyzed N-acetylaspartate hydrolysis by the combined quantum mechanics/molecular mechanics method and with the use of umbrella sampling replica-exchange molecular dynamics simulations are reported. It has been shown that the decrease in the high-energy barriers of rate-limiting stages is achieved through the preceding equilibrium stages, such as proton transfer and conformational changes. General features of the catalytic behavior of enzymes have been formulated.     

Ammonolysis of magnesiothermic tantalum powders

Tantalum nitrides are synthesized by ammonolysis of a mesoporous magnesiothermic tantalum powders. The effect of specific surface area of the powders and synthesis temperature on product composition is shown. Nitrogen content in the ammonolysis product of tantalum powder with a specific surface area of 56 m² g^–1 corresponds to oxynitride TaON exposed to 600°C for 1 h. The specific surface area of the oxynitride is 35 m² g^–1.     

Complexation of uranium(VI) and europium(III) with new polydentate pincer ligands in aqueous systems

Coordination of uranyl ion with new polydentate ligands derived from amino acids and extraction of uranium(VI) and europium(III) from aqueous salt solution into poly(ethylene glycol) phase with the use of new polydentate pincer ligands has been studied.     

Production and characteristics of substituted lanthanum niobate LaNb<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>W<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4 + δ</Subscript>

Solid solutions LaNb_1–x W _x O_{4 + δ} (x = 0.02–0.10, Δx = 0.02) were investigated, which crystallize in the monoclinic system (space group I2/c) at room temperature and undergo a phase transition into the tetragonal modification with increasing temperature. The stability of various modifications was analyzed by high-temperature X-ray powder diffraction analysis. The electrical conductivity of sintered samples was studied by impedance spectroscopy. Insertion of tungsten into the niobium sublattice leads to an increase in the conductivity of the solid solutions.     

Crystal structure of 9-(5,5-dimethyl-2,4,5,6-tetrahydro-1<Emphasis Type="Italic">H</Emphasis>-phenalen-2-yl)-5,5,9-trimethyl-5,6,8,9-tetrahydrocyclopenta[<Emphasis Type="Italic">a</Emphasis>]phenalen-10(4<Emphasis Type="Italic">H</Emphasis>)-one

The structure of 9-(5,5-dimethyl-2,4,5,6-tetrahydro-1H-phenalen-2-yl)-5,5,9-trimethyl-5,6,8,9-tetrahydrocyclopenta[а]phenalen-10(4H)-one was determined by X-ray crystallography. The intermolecular interaction energies were calculated by the atom-atomic approach for the crystal structure. The character of the crystal structure and the structural subclass were established.     

Direct Analysis of Natural Waters by Electron Spray Ionization and High-Resolution Time-of-Flight Mass Spectrometry Detection. Determination of Pesticides of Various Classes

The possibility of directly determining 36 pesticides (derivatives of urea, triazines, triazoles, imidazoles, carbamates, triazinones, benzamides, and pyridazinones and organophosphorus pesticides) by electrospray ionization with high-resolution quadrupole time-of-flight mass spectrometry in natural waters is demonstrated. A significant matrix effect is observed in the determination of pesticides in natural waters, and the use of the standard addition method is proposed for their determination in test samples, both undiluted and diluted with deionized water. The analytical range of the analytes was 0.5–50 ng/mL. The relative standard deviation of the results does not exceed 10%; the time required for the analysis is 10–15 min.