Influence of the nutrient medium on the total lipid fatty acid composition of Actinomyces canosus

GLC was used to study the composition of endocellular fatty acids of Actinomyces canosus 89 grown on a chemically defined medium and on a complex medium to which various components were added. Total lipids of the culture contain saturated and unsaturated fatty acids, from C13 to C18, with one or two double bonds. Addition of components to the medium stimulated the biosynthesis of myristic, stearic, oleic, and linoleic fatty acids. Changes in the composition of the growth medium modify the ratio between saturated and unsaturated fatty acids of total lipids, increasing the content of unsaturated fatty acids due to a higher rate of synthesis of linoleic and oleic fatty acids. An increase in the content of unsaturated fatty acids is a positive factor because these acids are involved in important physiological functions of both this organism and other living organisms.     

Delta-Doping of Monocrystalline Semiconductors by Al and Sb Implantation Using FIB Resistless Lithography

The potential is investigated of FIB lithography for implantation delta-doping in order to produce desired arrangements of quantum wires and dots. Both raster and vector scanning are considered. The results are briefly reported of molecular-dynamics and Monte Carlo (SRIM2003) computations concerned with the scattering of low-energy Al and Sb ions from a monocrystalline-semiconductor surface. It is concluded that the ion energy should be taken within the range 100–300 eV if implantation depths of 1–5 nm are required. A formalism is derived for evaluating the ultimate resolution and the processing time of FIB implanters that use a Gaussian or a vector-scanned variable shaped beam. It is noted that the formalism can be modified to apply to IPL implanters. It is shown that an FIB implanter with an electrostatic objective can provide a lateral resolution better than 20 nm. It is also demonstrated that using a vector-scanned variable shaped beam enables one to create an experimental quantum register containing up to 10⁶ qubits.     

Selective laser sintering of steel powders to obtain products based on SAPR-models

Conclusions  

The reflectivity of alumina ceramics under intense surface heating and subsequent free cooling

The results are given of measurements of the normally hemispherical reflectivity of alumina ceramics in the semitransparency region for the wavelengths of 0.488, 0.6328, 1.15, and 3.39 μm. The measurements are performed both in the process of fast heating of ceramics in the air by concentrated radiation of a CO₂ laser with fluxes of different densities from room temperature to ～2900 K with the formation of a thin layer of melt and in the process of subsequent cooling after the heating radiation is discontinued. The heating time is approximately 2.25 s, with the density of heating radiation flux of approximately 1200 W/cm² and 1600 W/cm². It is demonstrated that the reflectivity in the process of heating depends significantly on the flux density. By the end of the heating period and under the effect of a flux of higher density, the layer of melt formed on the ceramic surface is optically infinite for reflection at all wavelengths, while no optical infinity is attained at a lower flux density. The effect of abrupt variation of the absorption coefficient during melting and solidification on the thermal-radiation characteristics is analyzed.     

Dipole-dipole interactions in nanoparticle superlattices

Nanoparticles often self-assemble into hexagonal-close-packed (hcp) structures although it is predicted to be less stable than face-centered-cubic (fcc) packing in hard-sphere models. In addition to close-packed fcc and hcp superlattices, we observe formation of nonclose-packed simple-hexagonal (sh) superlattices of nearly spherical PbS, PbSe, and gamma-Fe2O3 nanocrystals. This surprisingly rich phase diagram of monodisperse semiconducting nanoparticles is explained by considering the interactions between nonlocal dipoles of individual nanoparticles. By calculating the total electrostatic and dispersive energies, we explain stability of the hcp and sh nanoparticle superlattices, introduce the superlattice phase diagram, and predict antiferroelectric ordering in dipolar nanoparticle superlattices.     

A control system of an electromagnetic bearing

A three-loop control system for the radial electromagnetic bearing of powerful rotating machines is proposed, the working clearances in which between the stator and rotor amount to tenths of a millimeter with a rotor weight of about 1 t. In the open state, the system is unstable and has features that need to be taken into account when creating the controllers. The control system is designed in accordance with general principles typical for the systems of subordinate regulation. The problems of design of the pulse-control system and various variants of constructing the internal current loop were considered. For calculating the parameters of controllers, the method of transfer functions and z-transformation method were used. At the initial stage, the internal current loop was investigated and it was revealed that the construction of the current loop of an electromagnetic bearing with a relay controller operating in a sliding mode is the most appropriate. In accordance with the mathematical model of an electromagnetic bearing and corresponding structural diagrams, simulation models were designed in the MATLAB/Simulink software package. As a result of simulating the pulsed control system of an electromagnetic bearing, oscillograms of transient processes under control and disturbance effects were obtained. Analysis of transient processes during simulation revealed that electromagnetic bearings equipped with a three-loop control system have a high static rigidity and high operating speed. The obtained results were used in constructing a control system using the electromagnetic bearing of the gas pressurizer at the Pomarskaya compressor station.     

High-Power Electric Ship Propulsion Systems with Advanced Frequency Converters

Russian Electrical Engineering - Three types of frequency converter (FC) structures are considered as parts of high-power electric ship propulsion systems—multilevel FCs, cascade FCs, and FCs...