A mass spectrometer with a membrane interface for oil concentration monitoring in seawater

An immersion mass spectrometer with a membrane interface was used for oil detection and oil concentration measurements in seawater by measuring in situ the concentrations of three hydrocarbons: benzene, toluene, and xylene in the region of the specialized Primorsk oil loading seaport in the Gulf of Finland. The recorded mass spectra demonstrated the possibility of measuring the oil concentration in seawater and determining the grade of oil products. The use of a mass spectrometer with a membrane separator interface allows measurements of hydrocarbon concentration with high accuracy, which is currently not provided in commercially available monitors.     

Interpolyelectrolyte complexes of diblock copolymers via interaction of complementary polyelectrolyte-surfactant complexes in chloroform

We have studied the interpolyelectrolyte complexation in chloroform between polystyrene-block-poly(cetyltrimethylammonium acrylate), (PA⁻ CTA⁺), and poly(2-(methacryloyloxy)ethyldimethylethyl-ammonium dodecyl sulfate) (quaternized poly(2-(dimethylamino)ethyl methacrylate) complexed with sodium dodecyl sulfate), (PDMAEMAQ⁺ DS⁻). Turbidimetry, dynamic/static light scattering, and transmission electron microscopy show the formation of large aggregated interpolyelectrolyte complex species, which are colloidally stable in chloroform or even chloroform-soluble if the certain conditions are met. We suggest such co-assemblies to be micellar species with a core assembled from electrostatically coupled fragments of the polymeric components. The corona is built up either from a mixture of polystyrene blocks and excessive fragments of (PDMAEMAQ⁺ DS⁻) chains or from a mixture of polystyrene blocks and excessive fragments of (PA⁻ CTA⁺) blocks, depending on which polymeric component was taken in excess for the interpolyelectrolyte complexation. However, their real structures may deviate from such idealized consideration because of the non-equilibrium character of interpolyelectrolyte complexation in organic media of low polarity.     

Pressure treatment of superplastic ceramic materials

Superplasticity is defined as viscoplastic deformation of a material in a special ultra-fine-grained structural state. Modern fine ceramics with submicrometer structural components are polycrystalline materials that can exhibit superplasticity under certain temperature and rate conditions. The prospects for industrial use of the effect of superplasticity in pressure treatment of ceramics are analyzed on the basis of results of research of the last decade. It is shown that the property of superplasticity makes it possible to manufacture preforms by virtually any of the known methods of hot pressure treatment of bulk and sheet preforms.     

Discrete Superposition of Charges in a Galvanically Isolated Power Circuit when Generating Test Voltage Pulses

It has been demonstrated controlling maximum permissible current overloads and reverse currents of semiconductor power devices using a single device is practically impossible and the actual amplitude–time dependences of permissible current overloads should be determined by a computational analytical method. A new method for generating single and repeating heavy voltage sinusoidal pulses based on application of the principle of discrete superposition of charges in a galvanically isolated control circuit has been presented. A diagram of discrete superposition of charges in a galvanically isolated power circuit has been presented. Distinguishing characteristics of its determination have been shown.     

Formalization of the process of directional composition of structures of autonomous power-supply systems during design

The morphological method of synthesis of the structures of autonomous power-supply systems is presented, which is a further development of the sequential algorithms. A procedure of creating variants of the structure is given in the form of the initial information block, as well as a series of the sequentially performed operations in the formation of a tuple of electrical units with imposed restrictions being checked. The method is based on simulation of the main design rules followed by development of the design documentation. The theoretical content of the method is disclosed in the form of the initial information (axioms), rules of information processing, and logical formulas obtained as a result of applying the logical operations to the initial premises. It is recommended to use the calculation of the predicates as a mathematical basis making it possible to present the main theoretical premises of synthesis as the deductive axiomatic theory with a standard formalization. The main advantages of the proposed method are shown as specified by reduction in the time of finding of the functionally necessary structures by eliminating the need to carry out an exhaustive search for variants and using computers.     

Scattering of electrons by ionized impurities in semiconductors: quantum-mechanical approach to third body exclusion

As applied to the numerical simulation of electron transport and scattering processes in semiconductors an efficient model describing the scattering of electrons by the ionized impurities is proposed. On the example of GaAs at 77 and 300 K and Si at 300 K the dependencies of low-field electron mobility on the donor impurity concentration in the semiconductors are calculated in the framework of proposed model as well as in the framework of such most frequently used applied models as the Conwel-Weisskopf model and the Brooks-Herring one. After comparing the calculation results with the well-known experimental data it has been ascertained that the best agreement between the theory and experiment is achieved with application of the proposed model.     

Modern methods and means for nondestructive testing of the quality of power semiconductor devices

Modern methods and means for designing devices for nondestructive testing of parameters of power semiconductor devices are described. A new method for determining the junction–case thermal resistance from the transition function of a thermosensitive parameter is presented. The operating principle of a specialized digital system for controlling and displaying the vibration frequency and linear accelerations during testing of the absence of freely moving particles, short circuits, and breaks in the circuits of electrodes is presented. The function of digital filtering of a signal that is formed by the sensor–accelerometer board is considered. A new method for the formation of a single shock-current pulse is described that is based on the use of the principle of a discrete superposition of charges in the electric circuit of the secondary winding of a power pulse transformer. The principle of the formation of a test voltage pulse in a test-pulse generator of the software–hardware complex for the automatic assignment of grades, which is based on the implementation of the pulse-amplitude modulation of pulse parameters in a galvanically isolated power control loop, is presented.     

DNA Comet Giemsa Staining for Conventional Bright-Field Microscopy

This study was undertaken to evaluate the compatibility of Giemsa staining protocol with the comet assay. We showed, for the first time, that DNA comets can be visualized and analyzed using Giemsa staining. We generated DNA damage dose response curves for human peripheral blood lymphocytes exposed to X-ray radiation using the comet assay with either SybrGreen I or Giemsa stain. The dose response curves were fitted by linear regressions (R² > 0.977). The SybrGreen I results showed only ~1.2-fold higher slope coefficient (method sensitivity) compared to the Giemsa results. The unexpectedly high sensitivity of Giemsa staining for the comet assay is due to the Romanowsky-Giemsa effect, the stain photo-stability and the higher resolution of bright-field imaging compared to fluorescence imaging. Our results demonstrate that Giemsa staining can effectively be used for measuring DNA damage by the comet assay. The low cost and availability of Giemsa stain makes this method affordable for any low budget research and will facilitate new applications of the comet assay in biology and medicine.