Amperometric monoamine oxidase biosensors based on screen-printed graphite electrodes modified with nanostructured reduced graphene oxide (RGO) composites and cobalt nanoparticles (CoNPs) were developed to determine antidepressant drug substances: tianeptine, thioridazine, and fluoxetine. Combinations of carbon nanomaterials with metal nanoparticles (nanocomposites) along with retaining the properties of individual components, also provide a new quality of the developed devices due to their joint contribution. The nanomaterial-modifier was applied to the surface of screen-printed graphite electrodes using dropwise evaporation. Fixing of RGO on the surface of the screen-printed graphite electrodes occurs due to electrostatic interaction between RGO carboxyl groups and amine groups of the amine derivative on the platform of polyester polyol (H20–NH₂). The CoNPs were obtained electrochemically by the method of chronoamperometry at a potential E = – 1.0 V and different time of their accumulation (about 50 – 60 sec) on the electrode surface. According to the data of atomic force microscopy, the predominant size of CoNPs is (40 ± 2) and (78 ± 8) nm, depending on the time of electrochemical deposition of NPs. Data of electrochemical impedance spectroscopy show that nanocomposites RGO-chitosan/CoNPs and RGO-amine derivative on the polyester polyol (H20–NH₂)/CoNPs platform are characterized by the lowest values of the charge transfer resistance. The use of those nanocomposites modifying the electrode surface significantly improved the analytical characteristics of the developed biosensors providing a wider range of operating concentrations from 1 × 10^–4 to 5 × 10^–9 mol/liter, greater sensitivity coefficient, better correlation coefficient, and lower limit of the detectable concentrations. A possibility of using biosensors to control the quality of antidepressants upon determination of the main active substance in medicinal drugs and biological fluids is shown. The lower limit of detectable concentrations (7 – 9) × 10^–10 mol/liter is attained when using tyramine as a substrate for determination of fluoxetine, thioridazine and tianeptine, respectively.

Kinetics of Sr²⁺ sorption from potable water on clinoptilolite tuffs (CLPT) of different deposits (Honguruu (Yakutia), Holinskoe (Transbaikalia) and white Plast (Bulgaria)) is studied in detail. A technique of X-ray fluorescence analysis (XRF) is developed to determine the chemical composition of CLPT from a small sample (0.05 – 0.1 g). The emitters are prepared by pressing 10-mm tablets from the initial material added with polystyrene as a binder in a weight ratio 5:1. Reference standards (reference standards of composition) of rocks close in chemical composition to the CLPT are used for calibration. Using the empirical model of α-correction, the equations are derived to calculate the content of macro components of the sample in the «saturated» layers. To calculate the strontium content in the «intermediate» layers for the CLPT from different deposits the correction equations are derived. It is shown that the correction equation can be the same for all the CLPT used in the experiment. Kinetics of Sr²⁺ sorption on CLPT consists of 3 stages: (a) the intra-diffusion process, described by the coefficient of internal diffusion, (b) deceleration of the sorption process, described by the corresponding kinetic coefficient, and c) secondary increase in Sr²⁺ sorption which terminates when the equilibrium is reached. The results can be used to develop a mathematical model describing the dynamics of the ion-exchange process on CLPT in NH₄ form from dilute solutions.

X-ray fluorescence analysis (XRF)based on a technique of direct external standard with the use of one reference sample is traditionally used in the laboratory of microanalysis (INEOS RAS) for determination of metals in composition of novel organometallic compounds and polymers. Preparation of the samples-emitters consists in 150 – 200-fold dilution of the substances with emulsion polystyrene (PS), since the amount of substance for analysis is limited to 10 – 15 mg. With this dilution XRF analysis are carried out in the concentration range of metal from 0.005 to 0.5 %, where the analytical calibration curve is linear. Measurements of analytical lines are carried out on a VRA-30 spectrometer (CARL ZEISS JENA (Germany)), X-ray tube with Rh-anode, 40 kV, 20 mA. A possibility of automatic conduction of X-ray fluorescence analysis of organometallic compounds and polymers synthesized in INEOS RAS on a VRA-30 spectrometer using software ALPHA-VRA-30 is studied. Software package developed at the research and innovation center JSC «FORATEKS» (Ekaterinburg) is intended for automated control of the spectrometer functioning without an operator. The software provides the possibility of deducing analytical equations of multiple regression on the basis of measurements of the intensities of analytical lines from the reference sample, and calculates the content of chemical elements in the analyzed samples-emitters. Advantages of the developed software are demonstrated and the results of XRF obtained using both the developed software and the method of direct external standard are compared. The small difference between the results obtained by those methods (0.7 % (abs)) in determination of iron and zinc in organometallic compounds when the content of iron and zinc range within of 4 – 25 % proves the applicability of the software to studying new compounds. Software ALPHA-VRA-30 provides standardization of measurement conditions and lightens the work of the analyst when analyzing large batches of substances.

A computational and experimental method of certification and arrangement of intra laboratory control of the methods for analysis of air environment, i.e., air of the working zone, atmosphere air and industrial emissions into the atmosphere, is developed. Note that nowadays a rather small number of standard samples (SS) of air environment (calibration gas mixtures (CGM)) is available for less than thirty substances with determined maximum permissible concentrations (MPC) (inorganic gases and light organic compounds). About 100 sources of microcflows (MF) are also developed for light organic compounds. Such a narrow set of developed SS hinders determination of the accuracy indicators on the basis of the certification experiment for the vast majority of the methods used for analysis of air samples and, in turn, keeps out of stating standards for intra-laboratory control and implementation of the procedures of operational control and control of the stability. For those techniques (in the lack of calibration gas mixtures and sources of microflows), the error characteristics are estimated usually by calculations with exception of the stability of the calibration curves and error characteristics of the individual sampling stages which are determined experimentally. The proposed method implies a conditional division of the technique into two stages: sampling and analytical stages. For the stage of sampling, the error characteristics are determined by the calculation-experimental method, for the analytical stage, by the experimental method, similar to other methods for analysis of condensed media. The possibility of arrangement of the intra-laboratory control of the analytical stage and implementation of all the algorithms of both operational and stability control, including construction of Shewhart’s control charts is shown. The proposed method makes it possible to arrange certification of the majority of similar techniques used in the sphere of state regulation of ensuring the uniformity of measurements that have not been previously certified and provided with standard samples in the form of calibration gas mixtures and sources of microflows.

The activities of the Federal Accreditation Service including cooperation with international accreditation institutions, i.e., International Laboratory Accreditation Cooperation (ILAC) and the Asia-Pacific Laboratory Accreditation Cooperation (APLAC) are reviewed. Issues regarding implementation of the system of good laboratory practice in the context of cooperation between Russia, Organization for Economic Cooperation and Development (OECD), and Slovak National Accreditation Service are considered. Information about mutual recognition agreements and bilateral arrangements of the Federal Service for Accreditation and national accreditation bodies of the foreign countries are discussed along with the results of the activities of RusAccreditation during the 1st quarter of 2018 and goals for the near future.

The use of quantitative X-ray texture analysis (QXRTA) (construction of the orientation distribution function (ODF) proceeding from the measurement of direct pole figures) and simulation of the texture formation in the framework of thermoactivation model (TA) are considered to study the features of texture formation in MA2-1pch magnesium alloy subjected to rotary swaging (RS) at 400 – 350°C. A diffuse texture consisting of basic and inclined to the pressing direction basic poles is formed in the alloy when temperature decreases and the total true deformations increase up to ε = 2.77. Model textures match experimental textures rather well when RS is provided by the action of basic ({0001} á1120), prismatic ({1010} á1120ñ) slip and twinning by the systems {1012} á1011ñ, {1011} á1012ñ, {1121} á1126ñ. Mathematical modeling of the textures also shows that the activity of the twinning systems under consideration increases in the sequence {1012} á1011ñ, {1011} á1012ñ, {1121} á1126ñ as the total deformations grow and RS temperature decreases. Those results are consistent with the previously obtained microstructural data. However, the differences in the orientation factors calculated for the initial state of the alloy and state after RS indicated to the activation of the basal slip and twinning systems under consideration, as well as to the difficulty of prismatic sliding. The obtained data are also consistent with the results of mathematical modeling of textures. At a temperature of 350°C at a total true deformation of 2.77 the basic deformation mechanisms (the basic slip and twinning by the systems {1012} á1011ñ, {1011} á1012ñ, {1121} á1126ñ) which ensure texture changes upon RS stimulate an enhance in the mechanical properties of magnesium alloy MA2-1pch bars.

An increase in the size and the number of the elements of the aircraft structures made of polymer composite materials (PCM) required the search for new energy-saving and less expensive non-autoclave technologies. The use of one of them, vacuum infusion, inevitably leads to formation of an uneven surface, thus inhibiting determination of the true thickness by standard methods, and, in turn, affects determination of the physical and mechanical properties of the material. The results of measuring density of carbon plastics by hydrostatic weighing are presented to calculate the true thickness of materials, volume content of binder and porosity. The developed method is also suitable for PCMs based on combustible reinforcing materials like organic plastics, hybrid and other materials that cannot be subjected to burning-off to determine the binder content.

Using for the solution of a problem of passing of a flat wave through a wall of an antenna radome electrodynamic model and representing wall material as multicomponent mix, assessment of influence of water on frequency radio engineering characteristics of the antenna radome system is carried out. Water, having at ultrahigh frequencies high dielectric permeability and big size of dielectric losses in comparison with radome wall material, considerably distorts the field of the falling wave at hit on a surface or in a radome wall body. As material of a wall of a radome the quartz ceramics with the time filled with air was considered. It is experimentally defined that water is in a material time in liquid state. Water was represented how the additional component which is evenly distributed on thickness in a time to quartz ceramics. The carried-out model calculations showed that introduction of water to material of a wall of a radome leads not only to reduction of level of coefficient of passing of an electromagnetic wave through a wall, but also to noticeable shifts on the frequency of radio engineering characteristics of the antenna-radome system.

Fine mesh disposable oil filters with a service life of 600 hours and more are used in aviation engines to increase the degree of oil purification. A diagnostic layer in form of a non-woven tape attached to the filter can be removed from the filter to keep up the filter in service. Information on the wear particles accumulated on the filter can be obtained each 200 h. Technique and device used for extracting wear particles from the diagnostic layer of a filter element of the type QA-07930-01 was developed. It is shown that the first flushing from the tape by the number and composition of particles is most indicative for a reliable assessment of the technical state of the engine by the parameters of the wear particles. The total time spent for analysis, including flushing, sedimentation, and treatment in an ultrasonic bath is 90 minutes. The results of assessing the technical condition of the oil system of PS-90A engines equipped with a filter element with and without a diagnostic layer are presented. The obtained data indicate that the filter element QA-07930-01 significantly improves the convenience of servicing the aircraft engines and reduces the costs of diagnostic tests.

It is shown that, growth of the layer with compressive residual stresses at advanced surface plastic deformation of smooth samples leads to an increase in the endurance limit of the notched specimens due to an increase in the compressive residual stresses in their dangerous section. The study was conducted on the specimens with outer diameter D equal to 10 and 25 mm and on a 25 mm specimen with inner diameter d = 15 mm which were subjected to air shot blasting and roll-in. Residual stresses in smooth specimens were determined by the mechanical method. Circular incisions (R = 0.3 and 0.5 mm) were applied on hardened smooth samples with a shaped cutter. Residual stresses in notched specimens were determined by a numerical method calculating the redistribution of the residual stresses upon the incision. As the diameter of the samples increases with the same strengthening surface treatment,

the depth of the layer with the compressive residual stresses increases due to an increase in the rigidity of the samples. The effect of surface hardening on the endurance limit of notched specimens was evaluated according to the criterion of the average integral residual stresses, which takes into account both the magnitude and completeness of the residual stresses. This criterion was calculated from the depth of the non-propagating fatigue crack that occurs in the surface layer in the dangerous section of the specimen during the fatigue test at the limit endurance. Fatigue tests are carried out in symmetrical cycle, the test base being 3 × 10⁶ cycles of loading. Estimation of the increment of the limit endurance of surface-hardened cylindrical specimens with semicircular notches gave the results acceptable for practice. The use of the proposed method can significantly reduce long-term and expensive fatigue tests.

Joint deformation of two elastic layers is considered, one of them being a coating applied to the surface of another thicker layer. It is assumed that slippage is absent in the plane of layer contact. External load is normal to the coating surface and unchanging in width. In the absence of lateral loading, the junction can be considered a two-layer beam and described by the equations of the plane elasticity using the asymptotic method. The required functions, normal and tangential stresses, and also the components of the displacement of an arbitrary point of the beam and coating are expanded in power series of the small parameter (accepted as a half thickness of the corresponding layer). In contrast to the known asymptotic expansions, an alternative asymptotic method is proposed in which all the required functions are asymptotically equivalent, i.e., expanded in asymptotic series of the same structure. When all positive powers of the small parameter are present in the series, the asymptotic algorithm leads to the appearance of two independent recurrent systems of linear equations, which greatly simplifies their solution. In each approach for one elastic layer the algorithm generates five indefinite functions of the longitudinal coordinate. Due to a rapid convergence of the asymptotic series, the first asymptotic approximation is used to construct the mathematical model of the deformation of a beam-to-coating coupling. Ten indefinite functions of the coordinate x provide fulfilling of eight conditions of continuity of the stress-strain state in the linkage depth, two functions remaining indefinite. Equilibrium equations (a system of two linear differential equations of the sixth order) are derived for them proceeding from the principle of minimum potential energy of deformation and corresponding boundary conditions (that can be realized both in static and kinematic variants). Numerical results are obtained in static approximation for two types of surface loading — steady and sinusoidally varying — along the length of the coating. An emphasis is made on the necessity of allowing for tangential stresses when studying the stress state of the coating as they can be rather significant upon bending.

The goal of this study is to develop a mathematical model of the transition of the structural material from elastic state to elastoplastic state upon tension. The model is based on a modified three-parameter transition operator from one mathematical function to another. A procedure of the mathematical approximation of the transition and corresponding algorithm, which provides a generalized canonical description of the transition, regardless of the form of the functions that characterize the system behavior before and after the transition are presented. The technique is used to describe the transition of two structural materials from the elastic to elastoplastic state upon tension of the samples. Initial sections of the tension diagram are described using three empirical parameters. The role of each of them — maximum permissible relative deformation, transition rate and asymmetry of the transition — are determined. Statistical interpretation of the elastoplastic transition is developed and substantiated. Mathematical expressions for the integral probability function and probability density functions that provide numerical statistical estimation of the degree of change in the state of the structural elements of the material during loading are derived. Analytical description of the initial part of the tension diagram of the material can be used to rearrange the diagrams when modeling deformation processes in conditions of reversible elastoplastic loading.

A design of the device for studying plastic compression of long cylindrical specimens under conditions of a linear stress state is presented. The device is developed to study the properties of metals under plastic deformation in conditions of nonmonotonic loading. The goal of getting the accurate experimental data entails the necessary of carrying out tests using one long-length cylindrical sample, with the calculated length being more than five diameters. To prevent flexure of the long-length sample upon compression, the support conical sectors made by cutting truncated cone shaped blank into 6 or 8 equal parts with a central longitudinal hole having a diameter equal to the diameter of the test sample are used. The sectors are coupled by two pairs of semirings. A transcendental equation is obtained for determination of the taper angle of those sectors on the basis of kinematic analysis of the mobile links. This angle depends on the total weight of the sectors and sliding friction coefficients in the corresponding kinematic pairs of the device. For the considered device, the taper angle of the sectors is 36°. This device is designed and manufactured for compression testing of the samples with a diameter of 16.5 mm and a gaged length of 135 mm. Samples from steel 45 are tested with a goal of the flow curve construction and experimental verification of the strain diagrams under conditions of cyclic tensile-compression. Comparison of the calculated and experimental data proved the satisfactory accuracy of the stress determination, which makes it possible to recommend this device as a testing tool to be used in mechanical laboratories of the universities and research institutes.