# Search articles

## Low-density Approximation in the Theory of Creation the Electron-positron Plasma from Vacuum in Strong Laser Fields

Kinetic description of the vacuum creation of the electron-positron plasma under action of the strong electromagnetic fields is considered in two simplest approximations. The results are compared with the numerical solution of the relevant kinetic equation. It allows to select the regions of effectiveness of the introduced methods and to analyse some features of the obtained analytical solutions.

## The Influence of Monogaloidosubstitution on the Structure and Dynamics of Sixmember Cyclic Compounds

The structure and vibrational states of monosubstituted cyclic compounds (monogaloidosubstituted of benzene, benzoquinone, gammapyrone and tiopiron) by density functional DFT / b3LYP 6-311G ** and 6-311+** are simulated. Vibrational states are interpreted.

## Recovery of Models of Time-delay Systems from Short Experimental Time Series

Time-delay systems reconstructed from short and noisy time series is conducted by the specialized method based on utilizing of driven system with the structure similar to the structure of the studied object. To show the efficiency of this approach, parameters were reconstructed for radiophysical chaotic generator and for the model of biological system.

## Application of Thin Film Structures Based on Amorphous Silicon for pH Measurements in Solutions

Formation possibility of pH-sensor based on amorphous silicon thin films is shown. The principle of sensor operation is similar to the ionselective field effect transistor. Change of the investigated solution pH leads to change of depletion width and conductivity of amorphous silicon thin film structure.

## Calculation of Field Amplitude Distribution of Ultrasonic Wave Beam in Moving Media

The results of acoustical (ultrasonical) wave beam amplitude distribution modeling in free space and in application of moving media are presented. The propagation of ultrasonical wave has been considered in x-y coordinate plane for infinitive plate radiator restricted on x – axis. The shift of ultrasonical beam field for different distributions of moving media velocity projections in the plane of wave propagation is considered.

## About the Definition of a Nonlinear Inductance in Static and Dynamic Regimes

The integral relations and integral-differential equations that take into account the influence of the magnetic shields (magnetic) inductance have been obtained. The non-linear magnetic materials with hysteresis and without it, and approximation of nonlinear materials and inductors have been considered. It is shown that for hysteresis we should use the nonlinear equation for the magnetization. The establishment of oscillations in a chain with the simplest approximation of a nonlinear inductance are reviewed.

## Surface Acoustic Wave Propagation in Two-dimensional Phononic Crystal on Piezoelectric Substrate

Using finite element method analysis of surface acoustic wave (SAW) propagation in the phononic crystal in a form of periodic lattice from nickel pillars, located on a piezoelectric substrate of Y + 128°-cut LiNbO3, has been conducted. Amplitude and phase characteristics of SAW propagation through said structure have been numerically studied and the change in the formed stopbands width and center frequency, related with geometric parameters of the phononic crystal changing, was analyzed. The numerical results were compared with the experimental measurements.

## Analysis by Finite Element Method of Integral Antenna of RFID Tag at 5.5–6.5 GНz

Numerical analysis effective integral antenna of acoustoelectronic RFID tag was accomplished. Optimal parameters of the antenna compatible with interdigital transducer on a range of 5.5–6.5 GHz were obtained.

## Methods for Enhancing Emissive Ability of the Carbon Nanotubes

The analysis of papers devoted to study of the emission properties of the carbon nanotubes and to revealing ways for the control of these properties has been performed. Five main methods for enhancing emissive ability of the carbon nanotubes have been singled out.

## Structural-dinamics Models and Spectral Identification of Monohydroxysubstituted Flavone

On based of the calculations for parameters of adiabatic potential by method DFT/b3LYP are proposed the structural-dinamics models for monohydroxyflavones. The indications of spectral identification are revealed.

## Instanton for the Maxwell–Einstein Equations

In this article instanton solution for the Maxwell–Einstein equations is investigated. Equations for the field of instanton and metrics are derived. Metrics of pseudoeuclidean space which is corresponding to transition between degenerate classical vacua of problem and is connected with presence at the space infinity divergent and convergent spherical electromagnetic waves is studied. An expression of the instanton is received and it’s size is found. Value of pseudoeuclidean action is calculated.

## Using of Method Spectrometric Analysis for Detection Microorganisms

This article presents data on the development of a new tool and method for detection of dangerous infectious diseases agents, which is based on spectrometric analysis. A device for detection of mentioned agents and software for analysis of results have been developed. This device allows to carry out non-specific and specific detection of pathogens with 30 minutes.

## Dispersion Characteristic Calculation of Photonic Crystal Fiber Guided Modes

Dispersion characteristic of photonic crystal fiber guided mode is calculated. Numerical modeling based on the Maxwell equation for magnetic components for field of the photonic crystal is obtained. It is shown, that slot photonics crystal waveguides can be used to tailor dispersion.

## Influence of Water and Biology Active Media on Silicon Nanostructures

The obtained results of comparative study of solubility, optical properties and morphology of silicon nanoparticles and nano porous Si before, during and after interaction with distilled water and the biology active medium- yeast (Saccharomycetes cereviseae) show the significant dependence of the interaction between water and BAM on structure of the researched materials.

## Methodological Aspects and Structure Modelling and Predicting the Behaviour of Nanocomposite Materials in QuantumWise

Methodological aspects and structure modelling and predicting the behaviour of nanocomposite materials in QuantumWise are discussed.

## The Effect of Illumination on Conformation of Polyelectrolyte Molecules During Adsorption onto Semiconductor Substrate

The analytical model describing the influence of illumination of semiconductor substrate during polyelectrolyte adsorption onto it, which results in different deposited organic layer thickness, was suggested. The both changes of non-equilibrium charge carriers concentrations and surface charge density under illumination of semiconductor were considered, which allows one to explain changing of adsorbed layer thickness due to molecule conformation changes because of their electrostatic interaction with photosensitive substrate.

## Comparative Experimental Investigations of Backward Diffuse Light Scattering of Test Objects

The results of measurements of the spectral characteristics of the light scattering on test objects with different types of spectroscopic instruments were compared, backward diffuse scattering spectra, which were obtained with an integrating sphere and with the help of the illuminating and receiving optical fibers located at a short distance, were considered, the features of the spectral characteristics, which were determined by the parameters of the object, and the differences, which were caused by a method of recording of the spectrum, were identified in the scientific work.

## Kinetics of Diffusion-limited Elongation of DNA Fragments

The numerical model of the elongation kinetics of the single-stranded DNA has been proposed and studied. The proposed model is based on the principles of the phenomenological modelling and implemented as diffusion cellular automata. The analytical and numerical estimates of the elongation reaction rate for different concentrations of nucleotides has been obtained. The possibility of nucleotide binding delays with reducing the concentration of one of the nucleotides in the solution is shown.

## Study of Stochastic Andronov – Hopf Bifurcation in the Oscillator by a Numerical Method

We investigate soft Andronov – Hopf bifurcation in the Van der Pol self – sustained oscillator, which is under the influence of additive Gaussian white noise. To determine the bifurcation used numerical solution of the Fokker – Planck – Kolmogorov equation. The results are compared with the data of numerical integration of stochastic equations. Demonstrated the existence of a bifurcation interval calculated theoretically in [6].

## Reception of Ultrashort Radio Pulses Propagating in a Dispersion Medium

Signal spectrum detection algorithm of ultrashort radio pulses sequence propagating in a dispersion medium is developed. Technical implementation of detection device is considered.