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.     

Biofuel cell anode based on the Gluconobacter oxydans bacteria cells and 2,6-dichlorophenolindophenol as an electron transport mediator

A basic scheme of the use of the Gluconobacter oxydans bacteria cells as a biocatalyst at an anode of a biofuel cell with air-based cathode is raised up. The anode and cathode of the cell are made of graphite; 2,6-dichlorophenolindophenol serves as an electron transport mediator; and glucose is the substrate to be oxidized. The open-circuit voltage is 55 mV, for the bacteria cell, the mediator, and glucose concentrations of 3 mg/ml (raw weight), 34 mM, and 10 mM, respectively. The voltage and current of the biofuel cell loaded with an external resistance of 10 kohm are 5.6 mV and 0.56 mA. The cell’s internal resistance is 88 kohm.     

Terpolymerization of carbon monoxide, ethylene and styrene in the presence of supported palladium catalyst

Terpolymers of carbon monoxide with ethylene and styrene are synthesized in the presence of supported palladium catalyst in toluene and heptane medium for the first time. The terpolymerization rate exceeds the rate of carbon monoxide and ethylene copolymerization. The maximum terpolymer yield amounts 7.9 g per g of supported catalyst per hour or 321 g per g of palladium per hour. The influence of reaction temperature, pressure, 1.4-benzoquinone amount and co-monomers mole ratio on the yield and the composition of terpolymer have been studied. The NMR ¹³C data obtained testify to a distribution of ethylene and styrene units in terpolymer with the predominance of short blocks at equal contents of comonomer units.     

Long-term stability of long-wavelength (>1.25 µm) quantum-dot lasers fabricated on GaAs substrates

Accelerated degradation testing of long-wavelength (>1.25 µm) quantum-dot lasers made on GaAs substrates is carried out at a fixed current of 1.7 A, initial optical output of about 0.3 W, and a heat sink temperature of 60°C. No signs of degradation are revealed after testing for 450 h. The test bed is not sealed, inert gas purging is not performed, and the laser faces are not passivated.     

Two-layer turbulent flow over a rough rotating surface

A model of turbulent incompressible fluid flow over a rough surface under the action of the Coriolis force with a turbulent transfer coefficient corresponding to the Prandtl mixing length is proposed. A solution of the problem, asymptotic in the small Coriolis parameter, is presented for horizontally uniform steady-state flow. It is shown that for a small Coriolis parameter the velocity profile and the turbulent transfer coefficient can differ substantially from the limiting expressions known from Prandtl theory. The smaller the roughness coefficient, the greater the difference.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 4, pp. 61–67, July–August, 1995.     

Structural characterization of self-organized nanostructures

Self-organized nano-objects fabricated in different semiconductor systems are currently at the focus of scientific interest because of their unique electronic properties. Transmission electron microscopy and high-resolution electron microscopy have been used to study the InAs quantum dots grown by molecular-beam epitaxy (MBE) on GaAs and InP substrates. Optimal imaging conditions for visualization of quantum dots were established. Size, shape, and stability of the equilibrium island arrays were analyzed with respect to the growth conditions. Both decrease and increase of the As pressure compared to the optimal value were shown to destroy the regular arrangement of the islands. Energy benefit due to the strain relaxation in the InAs islands is likely to be the driving force for their formation. Fiz. Tverd. Tela (St. Petersburg) 40, 849–851 (May 1998) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.