Search

We present the results of investigations of an installation aimed at the transmission of highly stable 1 PPS time signals from the hydrogen time and frequency standard over a 150 km optical fiber communication line with the use of active electronic compensation of time delays. The error (mean-square deviation) of transmission of time signals does not exceed 80 psec on the daily interval of averaging. The installation enables us to guarantee the synchronization of the time scales of remote time and frequency standards included in the primary and secondary standards of time and frequency units.

The operating principle of an optical high-resolution reflectometer running in the frequency domain (OFDR reflectometer) is examined. A mathematical model for measuring the parameters of fiber-optic systems using an OFDR reflectometer is presented. The accuracy characteristics of OFDR reflectometers are analyzed and the instrument accuracy is estimated quantitatively. Methods for calibrating OFDR reflectometers based on a distance scale are proposed and equipment for these methods is discussed.

The results are presented for the study of an installation for transmission of a highly stable frequency signal with relative instability no greater than 4·10–17 on a fiber-optic communications line over a distance of 150 km. The installation uses external modulation of laser radiation and active electronic compensation of phase noise. The installation makes it possible to provide synchronization or time scale comparison of mutually separated time and frequency standards that are a component of the highest-category time and frequency standards.

The results of international comparisons in the field of fiber-optic communication and information transmission systems, in particular, for the average power of optical radiation (COOMET PR-S6 and APMP PR-S2 projects) and chromatic dispersion in an optical fiber (EURAMET PR-S3 project), are considered. Data on comparisons as regards the length of the optical fiber (APMP PR-S8), polarization mode dispersion (COOMET PR-S9 project), and wavelength for fiber optics (COOMET PR-S8 project), all of which are now being performed, are presented.

It has been shown that, at elevated temperatures (∼350°C), the most distinct response to H2 from the thin film structure Pt/WO x /SiC is achieved at registration of change in voltage for the reverse branch of a current-voltage characteristic. Comparative studies of electric current conduction through the structure and over its surface (with deposited Pt film) have led to the conclusion that a change in properties of the Pt/WO x and WO x /SiC interfaces under action of H2 mostly determines efficiency of response of the structure in the case of “transverse” measuring geometry. In the case of a 2% concentration of H2 in air the voltage shift for the reverse branch at a current of ∼10 μA reached 5 V against 2 V on the forward branch and “planar” geometry of measurements.

Modification of biologically active cycloalkaneindoles by incorporation of a 2-trifluoromethylimidazo[1,2-a]pyridin-6-yl fragment has been proposed and performed via the interaction with 3-fluoro-2-trifluoromethylimidazo[1,2-a]pyridines in the presence of potassium hydroxide. The action of the prepared compounds on neuronal NMDA receptors has been studied by means of radioligand binding.

A method for the modification of tetrahydrocarbazoles with the 2-(5-fluoropyridin-3-yl)ethyl fragment was suggest, which consists in the reaction of 5-fluoro-3-vinylpyridine with tetrahydrocarbazoles under conditions of fluoride ion catalysis and leads to the earlier unknown 9-[2-(5-fluoropyridin-3-yl)ethyl]-2,3,4,9-tetrahydro-1H-carbazoles. Method of radioligand binding was used to study the influence of compounds synthesized on neuronal NMDA-receptors.

Bis(dialkylamides) of phosphoryl-substituted α,ω-dicarboxylic acids were synthesized and their biological activity was studied.

During the period from April to December 2011 seventeen total arthroplasties of 1 st metatarsophalangeal joint for III—IV stage deforming osteoarthrosis was performed to 11 patients (7 men, 4 women) aged 39—68 years. In 9 cases bone cement was used for implant fixation, in the rest of cases — press-fit technique. In 3 cases Goman operation was simultaneously performed on 2—3 toes, in 1 case Weil osteotomy was performed. Treatment results were assessed by AOFAS scale. Mean follow up term made up 8.6 months. Excellent and good results were achieved in 8 (72.7%) patients, satisfactory — in 2 (18.2%), poor — in 1 (9.1%) patient. Total arthroplasty of 1 st metatarsophalangeal joint is an alternative to arthrodesis and enabled to restore both joint function and stability.

A series of amides of benzodioxane-6-carboxylic and piperonylic acids have been synthesized. Biological studies showed that some of the synthesized compounds influence the central nervous system (in particular, AMPA receptors).

An accurate fiber dispersion measurement is demonstrated for different types of solid- and hollow-core photonic-crystal fibers (PCFs) using cross-correlation frequency-resolved optical gating (XFROG) with ultrashort light pulses. In the multimode regime, the XFROG technique is shown to enable a simultaneous dispersion measurement for several modes in parallel, offering a powerful fiber characterization tool for ultrafast science and metrology.

The stability of poly-α-olefin oils with molecular mass of from 500 to 1000 is investigated. It is found that the molecular mass, temperature, and introduction of various antioxidizers affect the thermo-oxidative stability of oils. It is shown that poly-α-olefin oils with antioxidizers can be used as liquid dielectrics.

The hygroscopicity of poly-α-olefin based oils is studied. Moisture saturation of all oils used in this study is reached by 60 h into the tests. The dependence of the hygroscopocity of the oils on the molecular mass of the oligomer is determined. The presence of functional additives in the oils does not greatly affect their hygroscopicity, while polar compounds (products of aging) sharply (almost twofold) increase the hygroscopicity.

Functionality and technical features of modern industrial fiber-optic sensors on Bragg gratings are considered. Feasibility to design information-measuring systems for such sensors involving the improved concept of calibration based on acetylene cavity is studied. The results of investigation regarding the design and analysis of the prototypical information-measuring system are discussed.

Propagation properties of electromagnetic waves in a medium with a negative index of refraction are investigated. A model of a physical signal that combines simultaneously qualities of both a spatially-localized beam and a wavepacket was used as the incident wave. Such a choice was necessary because of the strong frequency dispersion of metamaterials in the spectral region with a negative index of refraction. An approximate analytical solution was derived that describes the propagation dynamics of such a signal through a slab made of material showing simultaneously a negative dielectric permittivity and magnetic permeability.

The effect of cyclic heat treatments and diffusion of gold into silicon with inherent quenched-in donors on the electrical properties of the material is studied. An analysis of the data on slow cooling and quenching makes it possible to conclude that the mechanisms of transformation of quenched-in donors in the course of quenching and multi-cycle heat treatment with slow cooling are different and that there are two different acceptor states of gold atoms.

A method for stereospecific synthesis of allomargaritarin and other amination products of the natural alkaloid securinine was developed. Stereoselective nucleophilic addition of an amine at the double bond of the azobicyclooctane moiety of securinin was achieved by using ytterbium triflate as the catalyst. The biological activity of securining caused by adding pharmacophores to the molecule was shown to change experimentally.

The problem of maximization of profit in the operation of a communication network is solved as a linear programming problem of large dimensionality both with respect to the number of constraints (up to several thousands), and with respect to the number of variables (up to several millions). The original problem is reduced to a finite sequence of linear programming problems with the number of constraints lower by one order of magnitude and the number of variables up to several billions. The problems of the sequence are solved using the modified simplex method with generation of columns. The problems of maximization of profit of the owner of the upgraded network who leases channels are solved for limited capital investments and for the case of drawing up a credit, and the optimal amount of credit is determined. Solution algorithms based on the procedure of separation of variables are proposed. Numerical examples are presented.

Experimental results of studying the photoconductivity kinetics in silicon doped with either gold or sulfur are reported. The nonequilibrium charge-carrier concentration was generated by the effect of pulsed laser radiation. The time dependence of nonequilibrium conductivity was determined by contactless measurements from a variation in the reflected power of the microwave field. The long-term photoconductivity with the time constant of τ ≈ 1.6 ms at room temperature is observed in the silicon samples overcompensated with sulfur. Conventional short-term processes (τ ≈ 2–3 µs) characteristic of the centers with deep levels are observed in the silicon samples doped with gold. These differences are accounted for using the known data on the energy characteristics of the gold and sulfur levels in the silicon band gap and their charge states.

A positive allosteric modulator of AMPA receptors has been designed using computer-aided molecular modeling techniques. It possessed a record high experimentally confirmed potency in the picomolar concentration range and belongs to a new type of bivalent AMPA receptor ligands containing bicyclo[3.3.1]nonane scaffold. The suggested structure could serve as a basis for further optimization and development of drugs for the treatment of neurodegenerative diseases, cognition enhancement, and improvement of memory.

The state and problems involved in achieving the uniformity of measurements in the field of fiber-optic information transmission systems and their components are considered. Possible approaches to the solution of these problems and the basic methods and techniques that have been developed in Russia up to this point are analyzed.

A solution to the problem of motion of a projectile in the bore of a pneumatic line launcher equipped with a fast-acting valve of large clear opening is obtained. The results are represented in the user-friendly graphical form and include a variety of the gasdynamic and design parameters of the launcher that influence the projectile velocity. The calculated data are in good agreement with data of multiparametric experiments.

The influence of high-temperature annealings followed by cooling under different conditions on changes in the specific resistance and photoconductivity relaxation time in silicon and on the formation of the acceptor state of gold, when gold diffused from a layer vacuum-deposited on the surface, was studied in experiments including sequences of processes conducted using various temperatures, cooling conditions, and surface states. The experimental data are analyzed based on the concept of changes in the state of impurities present in silicon and in the corresponding dynamic and static force fields.

Dimebon in low concentrations potentiated activity of AMPA-receptors in rat cerebellar Purkinje neurons, while memantine produced only an insignificant potentiation in a small group of these cells. In cortical neurons of rat brain memantine efficiently blocked NMDA-induced currents in dimebon-insensitive neurons. By contrast, its effect was far weaker in neurons, where the blocking action of dimebon on NMDA-receptors was most pronounced. It was hypothesized that the differences in the effects of memantine and dimebon are determined by their interaction with different sites of NMDA-receptors.

The problem of using electric insulating oils in underwater oil production equipment is examined. The results of comparative studies of the physicochemical and insulating properties and thermooxidative stability of domestic and foreign oils of this class are presented.

Data are presented on the effect of long-term high-temperature heat treatment (750°C, 200 h; 950°C, 50 h; and 1050°C, 50 h) preceding Au diffusion on the acceptor behavior of Au in n-type Czochralski silicon. Detailed studies of Au diffusion reveal that the impurity gettering process depends strongly on the heat treatment conditions. The results are interpreted in terms of oxygen precipitation in Si.

The equations of thermally stimulated currents were derived for an exponential heating profile. The applicability of this approach was checked using experimental data for Si〈P,Au〉. The ionization energies of two trap levels in Si〈P,Au〉 were determined to be 0.25 and 0.40 eV.

Data are presented on the electrical activity of Au in Czochralski Si heat-treated and diffusion-doped under various conditions. The results are interpreted in terms of force fields responsible for changes in the concentration of electrically active centers. Long-term heat treatment between 700 and 1050°C is shown to have a significant effect on the acceptor behavior of Au in diffusion-doped Si. The concentration of Au acceptors is sensitive to the surface condition in the course of heat treatment: a tungsten coating increases the Au concentration in the bulk of diffusion-doped Si.

A study has been made on the effects of purification on the electrical installation of transformer oil. There is scope for improving the quality of oil made in accordance with GOST 10121 to reach the level corresponding to oils T–750 and T–1500. Oils of T–750 type may be made by completing the treatment of transformer oil with selective purification.

This paper reports results of experiments on initiation and development of detonation in cylindrical charges of a porous explosive by overdriven detonation products of a gas mixture C2H2 + 2.5 O2. Explosive charges with a bulk density of about 1 g/cm3 in fragile shells were studied. For PETN and RDX charges, the critical initial pressure of the gas mixture at which detonation initiation still occurs is determined and the pressures acting immediately on the charge are given. For PETN, critical initial pressures and initiation delays were measured for the first time for charges with particles of various diameters. The obtained dependence characterizes the following abnormal property of porous charges: there is an optimum particle size for which the explosive sensitivity is maximal. Streak records of self‐luminosity for typical initiation modes are given. Mass velocity profiles in initiation waves at different depth of the charge are obtained using an electromagnetic procedure.

We determine the values of the stress intensity factor at the crack tip depending on the location of circular holes used to simulate pores and compare the results of theoretical calculations with the experimental data.

Visible and IR absorption spectra are studied for copper phthalocyanin (CuPc)-polyyimide composites. The composite films are obtained by vacuum codeposition of CuPc, pyromellitedianhydride, and diaminodiphenyloxide followed by temperature-induced imidization. On the basis of IR spectra it is shown that in the prepared composites imidization occurs over the whole CuPc concentration range (10–90%). From the visible spectra it is found that CuPc is deposited mainly in the form of a-microcrystals, which are destroyed during imidization to produce noncrystalline molecular aggregates. Subsequent heat treatment (320–350°C) gives rise to CuPc β-microscrystals.

Experimental results on the acceleration of inert spherical particles(30–170 µm in diameter) by gas detonation waves in tubes with nozzles are presented. It is shown that divergent nozzles increase the particle velocity by up to40%. Laser visualization was applied to obtain streak records of particle motion.

The occurrence of changes in impurity accumulation after a long-term annealing preceding the in-diffusion of impurities is shown experimentally. Atoms of Au as acceptors affecting the resistivity and photoconductivity decay time were used as indicators in studies of these changes.

The neuroprotective action of hybrid structures based on fullerene C60 with attached proline amino acid has been studied. Hybrid structures contained natural antioxidant carnosine or addends with one or two nitrate groups. It has been shown that all studied compounds had antioxidant activity and decreased the concentration of malondialdehyde in homogenates of the rat brain. Compound 1, which contained the antioxidant carnosine, has been found to be the most effective antioxidant. All compounds except IV and V inhibited the activity of monoamine oxidase B, while compounds I-IV increased the activity of monoamine oxidase A. All investigated compounds inhibited glutamate-induced Ca2+ uptake into synaptosomes of the rat brain cortex. Compound III, containing two nitrate groups, has been found to be the most effective inhibitor. This compound caused a significant increase of the currents of AMPA receptors (AMPA, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid).

The effect of derivatives of arachidonic and docosahexaenoic acids on AMPA receptors in Purkinje cells from the rat cerebellum was studied using the patch-clamp electrophysiological method. It was shown that derivatives of arachidonic acid-arachidonoyl dopamine and docosahexaenoic acid-docosahexaenoyl dopamine and ester of docosahexaenoic acid with ethylene glycol in nanomolar concentrations effectively potentiated the ionic currents caused by activation of AMPA receptors of kainic acid. Ester of docosahexaenoic acid with nitroethylene glycol blocked AMPA receptors, and anandamide (ethanolamide of arachidonic acid) was not effective. A behavioral test showed that docosahexaenoyl dopamine in doses of 0.1-20 mg/kg had no effect on the learning and memory abilities of the animals tested.

SAMP 10 mice with genetically determined senescence (senescence-accelerated mouse prone 10) aged 16 months demonstrated (in comparison to 3-months old animals of the same strain) the following traits typical of old animal: behavior and memory deficiency, exploratory behavior impairment, and elevated level of anxiety. Dimebon administered for a long period of time with drinking water (1.5 mg/kg over 5 months) produced a positive action upon behavior and memory of 16-months-old SAMP 10 mice, optimized exploratory behavior in the open field test, diminished anxiety in elevated plus maze test, and improved retrieval of passive avoidance reaction.

A theory of signal shaping is proposed for semiconductor investigation by the method of photodeflection spectroscopy with pulse excitation that would take account of the influence of charge carrier recombination on the temperature distribution in the specimen. Quantitative computations are performed for silicon that demonstrate the change in PDS signal amplitude and shape when taking account of bulk carrier recombination. It is shown that taking account of the influence of bulk recombination discloses the possibility of obtaining additional quantitative information about the charge carrier lifetime in the specimen.