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Abstract: For the first time, poly(phenylene sulfones) (PPSFs) with chlorine and hydroxyl terminal groups are synthesized and tested for casting high-performance flat-sheet ultrafiltration membranes. The synthesis of PPSFs is carried out in dimethylacetamide at various ratios of 4,4'-dihydroxydiphenyl and 4,4-dichlorodiphenyl sulfone monomers. Two samples with the predominant content of hydroxyl (PPSF-ОН) and chlorine (PPSF-Cl) terminal groups are studied by NMR spectroscopy, GPC, and DSC methods. The coagulation values of polymer solutions in N-methyl-2-pyrrolidone (NMP) and the mechanical properties and hydrophilicity of polymer materials are determined. Both PPSF samples exhibit high tensile strength values at a level of 16 MPa. Using the method of precipitation of PPSF solutions in NMP with PEG-400 additives into water flat-sheet porous asymmetric membranes with a mesoporous (a pore diameter of about 7 nm) thin outer layer and fingerlike macropores in the substrate layer are obtained. An increase in the proportion of hydroxyl terminal groups enhances the hydrophilicity of the polymer. This, in turn, allows for the preparation of flat-sheet membranes from PPSF-ОН with a water permeability of 66 L/(m2h bar), which is 1.5 times higher than the water permeability of the PPSF-Cl membrane. Meanwhile, both membranes demonstrate a Blue Dextran (Mw= 70 000 g mol–1) rejection of 99.9%.

Abstract: Hollow fiber membranes originally developed in the 1960s for the reverse osmosis process have since then become widely used for diverse separation processes. The advantages of hollow fiber membranes include the low energy consumption, ease of operation and, among the most important ones, highly efficient operation in a small footprint (a large membrane area can be packed into a module unit). The production of hollow fiber membranes involves many spinning parameters to be controlled. The list of these parameters, in particular, includes the viscosity of the spinning solution, the design and geometric parameters of the spinneret, the extrusion speed of the polymer solution, the composition and temperature of the bore fluid, the type of external coagulant, the air gap distance, the draw ratio, etc. The effect of these parameters on the properties of hollow fiber membranes is reviewed. Research data pertaining to the modification of polymers, both commercially available and at the stage of their synthesis, are also presented in the context of membrane applications. In addition, the preparation of membranes using non-toxic or less toxic solvents is discussed.

The emergence of a topological transition of the polaritonic dispersion in twisted bilayers of anisotropic van der Waals materials at a given twist angle—the photonic magic angle—results in the diffractionless propagation of polaritons with deep-subwavelength resolution. This type of propagation, generally referred to as canalization, holds promise for the control of light at the nanoscale. However, the existence of a single photonic magic angle hinders such control since the canalization direction in twisted bilayers is unique and fixed for each incident frequency. Here we overcome this limitation by demonstrating multiple spectrally robust photonic magic angles in reconfigurable twisted α-phase molybdenum trioxide (α-MoO3) trilayers. We show that canalization of polaritons can be programmed at will along any desired in-plane direction in a single device with broad spectral ranges. These findings open the door for nanophotonics applications where on-demand control is crucial, such as thermal management, nanoimaging or entanglement of quantum emitters.

Abstract: Polysulfones are synthesized in aprotic dipolar solvents, such as dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide, in a wide range of molecular weights from 42 000 to 184 000 g/mol for hollow-fiber membranes spinning for the first time. Dependence of the thermal and mechanical properties of polysulfones on molecular weight characteristics is investigated. A comparison of the mechanical properties of the synthesized PSF and commercial PSF Ultrason S 6010 (BASF, Germany) and PSF-150 (JSC Institute of Plastics, Russia) shows that the synthesized polymers are not inferior to their commercial analogs and some samples even surpass them in terms of the elastic modulus and strength. According to the dynamic viscosity of spinning solutions, promising PSF samples are chosen to form porous hollow-fiber supports. It is demonstrated that the hollow-fiber supports based on PSF with a molecular weight of 110 000 g/mol have a high nitrogen permeability of 47.5 m3/(m2h bar). These supports show promise for casting composite membranes with a thin selective layer.

Second-order topological insulators are characterized by helical, non-spin-degenerate one-dimensional states running along opposite crystal hinges with no backscattering. Injecting superconducting pairs therefore entails splitting Cooper pairs into two families of helical Andreev states of opposite helicity, one at each hinge. Here we provide evidence for such separation via the measurement and analysis of the switching supercurrent statistics of a crystalline nanoring of bismuth. Using a phenomenological model of two helical Andreev hinge modes, we find that pairs relax at a rate comparable to individual quasiparticles, in contrast to the much faster pair relaxation of non-topological systems. This constitutes a unique telltale sign of the spatial separation of topological helical hinges.

A global trend towards miniaturization and multiwavelength performance of nanophotonic devices drives research on novel phenomena, such as bound states in the continuum and Mietronics, as well as surveys for high-refractive index and strongly anisotropic materials and metasurfaces. Hexagonal boron nitride (hBN) is one of the promising materials for future nanophotonics owing to its inherent anisotropy and prospects of high-quality monocrystal growth with an atomically flat surface. Here, we present highly accurate optical constants of hBN in the broad wavelength range of 250–1700 nm combining imaging ellipsometry measurements, scanning near-field optical microscopy and first-principles quantum mechanical computations. hBN's high refractive index, up to 2.75 in the ultraviolet (UV) and visible range, broadband birefringence of ∼0.7, and negligible optical losses make it an outstanding material for UV and visible range photonics. Based on our measurement results, we propose and design novel optical elements: handedness-preserving mirrors and subwavelength waveguides with dimensions of 40 nm operating in the visible and UV ranges, respectively. Remarkably, our results offer a unique opportunity to bridge the size gap between photonics and electronics.

Abstract—: The current state and future development of the energy industry dictate the need to use natural gas as a more environmentally friendly fossil fuel and to make a smooth transition to hydrogen energy. In this regard, adsorption at elevated pressures (>10 MPa) has been actively studied in recent decades to solve problems such as the extraction of natural gas from deep underground deposits and its further membrane purification, as well as the selection of adsorbents for the accumulation of methane and hydrogen. However, the correct determination of adsorption values at elevated pressures faces a number of problems that are not typical for moderate pressures. The main difficulties here are the correct determination of the skeletal volume of the adsorbent and the volume of the adsorbate. In the case of amorphous adsorbents, the swelling of the sample induced by sorption and its compressibility must also be taken into account. This review discusses recent advances in the description of gas adsorption at high pressures in porous media and membrane polymeric materials, including the specific conditions of contact with supercritical carbon dioxide. The paper also gives brief descriptions of the adsorption values used (net, excess, and absolute adsorption), as well as experimental methods for measuring adsorption at high pressures.

Abstract: Hydroformylation (or oxo synthesis) is currently one of the most important processes of organic synthesis. Increasing the degree of conversion of this process as well as reducing operating costs seems to be an important direction for its development. A hydroformylation membrane reactor is proposed as an in situ method for separating the catalyst and reaction mixture from the reaction products (aldehydes). This work considers the potential of application of a membrane based on polydecylmethylsiloxane (PDecMS) for a membrane reactor for the hydroformylation of 1-hexene to heptanal. To evaluate the interaction of 1-hexene and heptanal with PDecMS, the sorption of the individual substances and their mixtures at 30 up to 60°C is studied. Sorption isotherms are also obtained for a mixture containing 1-hexene and heptanal which demonstrate selective sorption of heptanal in PDecMS. The transport of 1-hexene and heptanal through a membrane based on PDecMS is studied in the vacuum pervaporation mode at 30 up to 60°C. Based on the obtained experimental data, the temperature dependences of the permeability of 1-hexene and heptanal are plotted. It is shown that the activation energy of transport through a PDecMS membrane is −11.5 kJ/mol for heptanal and −16.4 kJ/mol for 1-hexene. Extrapolation of the temperature dependence of permeability to the operating temperature of hydroformylation (130°C) at a conversion of ~80% shows that, at the permeability of heptanal of 740 mol m−2h−1bar−1and of 1-hexene, 55 mol m−2h−1bar−1, the flux of heptanal will be 37 kg m−2h−1and of 1-hexene, 5 kg m−2h−1. Thus, the permeate will be enriched with the aldehyde.

Abstract: The permeability of n-butane and methane as well as their mixture through a PDecMS/MFFK composite membrane at reduced temperatures up to 0°C is for the first time studied in this work. According to the data of SEM, the thickness of the selective layer of PDecMS is 5 μm. It is shown that both the permeability coefficient of butane and ideal butane/methane selectivity \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\alpha }_{{{{{{{\text{C}}}_{{\text{4}}}}{{{\text{H}}}_{{{\text{10}}}}}} \mathord{\left/ {\vphantom {{{{{\text{C}}}_{{\text{4}}}}{{{\text{H}}}_{{{\text{10}}}}}} {{\text{C}}{{{\text{H}}}_{{\text{4}}}}}}} \right. \kern-0em} {{\text{C}}{{{\text{H}}}_{{\text{4}}}}}}}}}$$\end{document}increase as the temperature decreases from 60 down to 0°C. Thus, the permeability coefficient of butane is 11 400 Barrer at 0°C. It is important to emphasize that the ideal butane/methane selectivity of PDecMS/MFFK of 60 at 0°C is twofold higher than similar values for MDK and PDMS membranes (27 and 32, respectively). This is first of all associated with the difference in the values of the sorption selectivity αSof these polymers. Thus, the values of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha _{{{{{{{\text{C}}}_{{\text{4}}}}{{{\text{H}}}_{{{\text{10}}}}}} \mathord{\left/ {\vphantom {{{{{\text{C}}}_{{\text{4}}}}{{{\text{H}}}_{{{\text{10}}}}}} {{\text{C}}{{{\text{H}}}_{{\text{4}}}}}}} \right. \kern-0em} {{\text{C}}{{{\text{H}}}_{{\text{4}}}}}}}}^{{\text{S}}}$$\end{document}for PDecMS and PDMS at 0°C estimated based on the enthalpy of sorption are 170 and 95, respectively. In addition, the difference in the activation energies of diffusion of methane in PDecMS, PDMS, and MDK provides a sharper increase in the butane/methane permselectivity for PDecMS when compared to PDMS and MDK in the case of decreasing the measurement temperature. In the case of a C4H10(35 vol %)/CH4mixture, the butane/methane permselectivity of a PDecMS/MFFK membrane decreases down to 34, which is typical for all the membranes based on polysiloxanes.

Abstract: The results of chemometric analysis of the X-ray fluorescence data of biological samples are presented. Using the study of the elemental composition of the proximal tail vertebrae of mice after 30-day space flight and vivarium reference specimens as an example, the effectiveness of the application of self-modeling algorithms for identifying the element distribution in the bone matrix, inclusions, etc., is shown. The used approach eliminated residual correlations between elements from consideration and highlighted the intrinsic features of the elemental distribution in bone tissue of the tail vertebrae of mice.

Abstract: Mobility of alkaline metal cations Li+, Na+, Cs+in membranes based on polyethylene and sulfonated grafted polystyrene has been investigated by NMR relaxation technique. The kinetic curves of longitude recovery and transverse decay magnetizations of 7Li, 23Na, 133Cs nuclei were recorded. It was indicated that spin relaxation is due to interaction of nuclear quadrupole moment with electric field gradient generated by cation hydrated water molecules and sulfonate groups. The correlation times and activation energies of translational cation mobility have been calculated from spin-lattice (T1) and spin-spin (Т2) relaxation temperature dependences. Cation mobility increases in the next sequence Li+< Na+< Cs+. Diffusion coefficients calculated from NMR relaxation have been compared with macroscopic diffusion coefficients measured by pulsed field gradient NMR and impedance spectroscopy techniques. On the basis of this comparison, a model of heterogeneous membrane ionic transfer is discussed. It has been shown that membrane conductivity is restricted by ionic transfer in narrow pores with low functional group concentration.

Abstract: Formation of phases in nanocomposites of composition of carbide steels alloyed with chromium and nickel obtained as a result of mechanosynthesis in a planetary ball mill and further annealing was studied. It was shown that the structure mainly consisting of nickel-alloyed austenite and chromium-alloyed cementite is realized in composite (Fe0.80Cr0.10Ni0.10)83C17after annealing at temperatures of 700–800°C. The size of cementite grains is in the nanometer range.

Abstract: PTMSP membranes reinforced with a metal wire mesh have been fabricated and experimentally studied to increase the permeability and mechanical properties of poly(1-trimethylsilyl-1-propyne) (PTMSP) membranes in the course of thermopervaporation (TPV) removal of butanol from fermentation broths. The effect of the material wire of the mesh (stainless steel and bronze) and mesh size (30–40 μm) on the flux and separation factor in the course of thermopervaporation separation of aqueous solutions of butanol has been experimentally studied. It is shown in this work that the use of a metal wire mesh as a support instead of traditional commercial porous supports does not reduce the separation properties of a PTMSP membrane in the course of TPV removal of butanol from model fermentation mixtures. Separation modes that make it possible to obtain permeate fluxes above 1 kg m−2h−1have been found. It is shown in this work that the permeability coefficient of water through PTMSP membranes is 2.5 × 10−5mol m−2h−1kPa−1and does not depend on the temperature of the feed and thickness of the membranes.

Abstract: The main patterns of the hydration of sulfo groups, the translational mobility of water molecules, alkali metal cations, and ionic conductivity in sulfocation-exchange membranes (MSC) based on polyethylene and sulfonated grafted polystyrene have been investigated using NMR and impedance spectroscopy techniques. It has been shown that at moisture contents λ < 4 (λ is the number of water molecules per sulfo group) the H+counterions in the membranes form diaquahydrogen ions \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{{\text{H}}}_{{\text{5}}}}{\text{O}}_{{\text{2}}}^{ + }{\text{.}}$$\end{document}In the temperature range below 0°C at λ < 12, water molecules retain high mobility and do not form the ice phase. Water molecules diffusion coefficients (for the H+form, the average diffusion coefficient of water molecules and acidic protons) and first for ion-exchange systems, and the diffusion coefficients of counterions Li+, Na+, and Cs+have been measured by pulsed field gradient 1H, 7Li, 23Na, and 133Cs NMR spectroscopy. In MSC membranes in contact with water, the self-diffusion coefficients of cations increase in the Li+< Na+< Cs+series. The cation conductivity values are in the same Li+< Na+< Cs+\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \ll $$\end{document}H+sequence. The cation conductivity values calculated from the self-diffusion coefficients based on the Nernst–Einstein equation are essentially higher than the experimental values.

Abstract: The structure and properties of ultrafiltration membranes synthesized from bicomponent solutions in N,N-dimethylformamide using five commercial acrylonitrile copolymers of various compositions and molecular masses have been studied. The molecular mass characteristics of the copolymers (Mw, Mw/Mn) have been determined; the viscosity properties of dilute and concentrated solutions have been studied. It has been shown that depending on the chemical composition and molecular mass of the copolymer, the concentration dependence of the water flux is different: for copolymers with a molecular mass of Mwof 76 000–81 000 g/mol, with an increase in the copolymer concentration in solution from 12 to 16%, the water flux of the membranes decreases from 300–500 to 40–150 L/(m2h) depending on the copolymer composition. For samples with a higher molecular mass (Mw= 99 000 and 107 000 g/mol), the water flux of the membranes hardly depends on the copolymer concentration in the casting solution; it is 150 and 75 L/(m2h), respectively. The rejection factor of the membranes with a molecular mass of 40 000 g/mol for polyvinylpyrrolidone increases with increasing copolymer concentration in the casting solution regardless of the chemical composition and molecular mass of the copolymer. Scanning electron microscopy studies of the membrane structure have shown that membranes synthesized from copolymers with a higher molecular mass have a denser structure and a thicker selective layer than the respective parameters of membranes synthesized from acrylonitrile copolymers with a lower molecular mass, which are characterized by the presence of large macrovoids in the membrane matrix. These differences in the membrane structure are attributed to different viscosities of the casting solutions at identical copolymer concentrations.

Abstract: Dense membranes made of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) have been studied in thermopervaporation (TPV) separation of a butanol–water binary mixture and a real acetone–butanol–ethanol (ABE) broth. When comparing PTMSP with commercially used membranes based on polydimethylsiloxane (PDMS) in the TPV process, a significant advantage of PTMSP with respect to the butanol/water selectivity is shown. The value of the separation factor for the PTMSP membrane (114) with a thickness of 61 µm is more than ninefold higher than that of the most selective Pervap 4060 commercial membrane (Sulzer Chemtech, Switzerland). The permselectivity of PTMSP membranes with respect to the butanol/water components exceeds that of commercial membranes more than fivefold. The removal of acetone, butanol, and ethanol from real fermentation broths using PTMSP membranes in the TPV process with a porous condensation surface has been studied for the first time. It has been shown that the transport and separation characteristics of PTMSP membranes in the process of separation of real fermentation broths decline with time, while demonstrating high values of the butanol/water permselectivity (4.7).

ABSTRACTA new design of electron beam gun for welding in open space has been developed. The gun design is based on the application of triode emission system with improved quality of electron beam formation. This provides increased specific power of the beam and, as a result, the high capability to increase the penetration depth of welded joints. To reduce the dimensions of the gun and increase its service reliability, the high-voltage insulation has been provided applying metal-ceramic heat-resistant welded-brazed vacuum-tight components. The original technologies for their manufacture have been developed. The performed tests of the new gun design have proved the possibility of its application under open space conditions.

A new design of electron beam gun for welding in open space has been developed. The gun design is based on the application of triode emission system with improved quality of electron beam formation. This provides increased specific power of the beam and, as a result, the high capability to increase the penetration depth of welded joints. To reduce the dimensions of the gun and increase its service reliability, the high-voltage insulation has been provided applying metal-ceramic heat-resistant welded-brazed vacuum-tight components. The original technologies for their manufacture have been developed. The performed tests of the new gun design have proved the possibility of its application under open space conditions.

A comparison of the results of a study of visual acuity obtained using an eye chart and a chart projector at different distances with a demonstration of various optotypes was performed. It is determined that, depending on the visometry version, the results of visual acuity testing can vary significantly. For example, when using an image projector at a visual acuity range below 0.1 and a distance closer than 5.0 m, overestimation was observed. It has been established that to assess the dynamics of visual functions it is better to use the same method for studying visual acuity from a constant distance. A calculation method is proposed that allows one to obtain an exact value of visual acuity of less than 0.1 using a chart projector, provided that the distance from the screen is taken into account.

Membranes are widely used in modern technology. The demand for different types of membranes and membrane processes is increasing every year. This review summarizes the current state of the art and prospects of membrane science developments including membrane materials for gas separation, pervaporation, and pressure-driven membrane processes; ion-exchange, hybrid, and track-etched membranes; membranes for electrochemical sensors; and mathematical modeling of membrane separation processes and ion and water transport in membrane systems. Studies aimed at improving the selectivity and performance of membranes and their stability are surveyed. New approaches to the synthesis and modification of membranes as well as their advanced applications are discussed.

The problem of producing high-current electron beams with relatively small lateral sizes and small velocity spread is more than a hundred years old. The continuous improvement of near-ultraviolet electromagnetic radiation sources (lasers with harmonics generators) allows significantly improving the parameters of existing electron guns. This paper discusses some problems in the development of electron guns with photocathodes and considers possible ways of using laser photocathodes in the electron guns designed at the Budker INP SB RAS.

The efficiency of coherent multichannel beam combining under focusing through a turbulent medium on a target in the cases of phase conjugation and target irradiation in the feedback loop is investigated numerically in various approximations. The conditions of efficient focusing of multichannel radiation on the target are found. It is shown that the coherent beam combining with target irradiation in the feedback loop, which does not require a reference beam and wavefront measurements, is as good as the phase conjugation approach in the efficiency of focusing. It is found that the main effect of focusing is provided by properly chosen phase shifts in the channels, whereas taking into account local wavefront tip tilts weakly affects the result.

Based on numerical simulations, self-focusing of conventional and vortex optical beams produced by femtosecond pulses in air is comparatively analysed. It is shown that, other things being equal, in the case of self-focusing of vortex beams, a significantly higher concentration of energy is observed in the focal spot. As a consequence, there also arises a significant broadening of the space - time spectrum of the focused vortex beam as compared with the vortex-free self-focusing regime. The azimuthal instability of the vortex structure at small initial perturbations of the wave front leads to filamentation of radiation at distances greater than is usually the length of self-focusing.

Methods of synthesis of metal nanoparticles and metal/polymer nanocomposites including ion-exchange materials are considered. The effect of the composition and size of nanoparticles on their catalytic activity is analyzed. Attention is focused on the composites used in catalytic processes, namely, catalytic membranes and ion-exchange systems. The problems associated with the removal of dissolved oxygen from water by means of such composites are discussed. The bibliography includes 225 references.

Data demonstrating the potential of NMR methods in studying the formation of transport channels, the mechanisms of ion-polymer matrix interaction, the mobility and diffusion of ions and molecules in polymer electrolytes are analyzed and generalized. Ion-exchange membranes with polymer matrices of various chemical types are considered. The translational mobilities of ions measured by pulsed field gradient NMR are compared with the data on ionic conductivity acquired by impedance spectroscopy methods. Attention is focused on the possibilities of NMR methods in studying the state of ions and molecules in electrolytes and also their diffusional mobility on different spatial scales. Based on the NMR data, the mechanisms of ion transport in ion-exchange perfluorinated membranes are proposed. The bibliography includes 182 references.

We present the results of experiments on the interaction of nanosecond laser radiation at 532 and 1064 nm with nanostructured silicon carbide thin films of different polytypes. We have found the effect of optical intensity limiting at both wavelengths. The intensity of optical limiting at l = 532 nm (Icl [?] 106 W cm-2) is shown to be an order of magnitude less than that at l = 1064 nm (Icl [?] 107 W cm-2). We discuss the nature of the nonlinearity, leading to the optical limiting effect. We have proposed a method for determining the amount of linear and two-photon absorption in material media.

The phasing of a multichannel laser beam by means of an iterative stochastic parallel gradient (SPG) algorithm has been numerically and experimentally investigated. The operation of the SPG algorithm is simulated, the acceptable range of amplitudes of probe phase shifts is found, and the algorithm parameters at which the desired Strehl number can be obtained with a minimum number of iterations are determined. An experimental bench with phase modulators based on lithium niobate, which are controlled by a multichannel electronic unit with a real-time microcontroller, has been designed. Phasing of 16 cw laser beams at a system response bandwidth of 3.7 kHz and phase thermal distortions in a frequency band of about 10 Hz is experimentally demonstrated. The experimental data are in complete agreement with the calculation results.

The results of 3D simulations of the laboratory Ne-like Ge x-ray laser in RFNC-VNIIEF are in good agreement with the experimental data. Calculations show that considerable rise of brightness and transverse coherence length can be achieved under half-cavity conditions.

This paper considers the theoretical bases of the vectorial-algebraic method developed and applied in Russia for the time-series analysis of vector values – wind, currents and ice drift – and presents examples of the analysis of measurement data. The vectorial-algebraic approach allows the initial information to be significantly compressed and adequately describe the vector time-series of full-scale and model data restricted by a set of statistical characteristics in the invariant form. The methodology was used in the MyOcean Project (FP7).

Abstract: The sizes of supramolecular density fluctuations in gels and solid films obtained during formation of iodine inclusion compounds in an aqueous solution of poly(vinyl alcohol) are studied via small-angle X-ray scattering. It is shown that, in the case of iodine-containing poly(vinyl alcohol) samples prepared through drying of iodine-containing gels, several diffraction peaks that are related to the long-range order in the packing of structural fragments manifest themselves. The presence of the peaks indicates periodic density fluctuations in the packing of polymer chains with a period of 1.34 nm and a coherence length of 18.0 × 0.5 nm. The equidistance of peaks in units of scattering-vector modulus makes it possible to suggest the formation of layered systems, that is, systems with a single well-defined repeat period, during gel drying. Wet samples of the iodine-containing gel based on poly(vinyl alcohol) do not reveal any ordering. Heterogeneities in the structure of iodine-free gels may be regarded as voluminous structures with free cavities that survived after the extraction of iodine. These cavities in gels may be again filled with iodine or other complementary molecules.

Abstract: The spectral theory of symmetric viscoelastic fluids with arbitrary anisotropy, which is based on the generalized Maxwell relaxation law, is developed. A feature of the proposed approach is the use of a spectral (canonical) representation of tensors that describe the anisotropic properties of fluids. Simple special cases of the spectra of viscosity and relaxation-time tensors are considered. The orientation dynamics of anisotropic fluids is discussed. A theory of generation of eigenmodes that are related to stress relaxation is developed. On the basis of the spectral theory, the possibility of the existence of soft (zero energy) modes in anisotropic fluids with deep anisotropy is considered. The proposed theory opens up new alternatives for classifying anisotropic fluids.

Abstract: Cobalt ferrite nanoparticles are synthesized in hybrid micelles of poly[styrene-block-(ethylene oxide)] and sodium dodecyl sulfate in water at room temperature. The nanoparticles are prepared by the chemical precipitation method via the exchange reaction between iron and cobalt salts with sodium dodecyl sulfate and the redox reaction under the action of an aqueous solution of methylamine. As evidenced by small-angle X-ray scattering, transmission electron microscopy, and ferromagnetic resonance examination, cobalt ferrite nanoparticles occurring in hybrid micelles of the block copolymer and sodium dodecyl sulfate are polydisperse (their size is 0.3–50 nm) and ferromagnetic.

Abstract: Data are presented on some structure parameters of mesoscale turbulence mechanisms playing a significant role in the troposphere-stratosphere exchange in the tropical tropopause layer and in the lower stratosphere. The data are obtained in the framework of the international aircraft AMMA experiment in Burkina Faso (West Africa) in August 2006.

Abstract: The properties of a mathematical programming problem that arises in finding a stable (in the sense of Tikhonov) solution to a system of linear algebraic equations with an approximately given augmented coefficient matrix are examined. Conditions are obtained that determine whether this problem can be reduced to the minimization of a smoothing functional or to the minimal matrix correction of the underlying system of linear algebraic equations. A method for constructing (exact or approximately given) model systems of linear algebraic equations with known Tikhonov solutions is described. Sharp lower bounds are derived for the maximal error in the solution of an approximately given system of linear algebraic equations under finite perturbations of its coefficient matrix. Numerical examples are given.

Abstract: This review surveys the results of studies performed at the Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, and devoted to the design of poly[(1-trimethylsilyl)-1-propyne]-based membranes intended for liquid-liquid separation as applied to the pervaporation recovery of organic products from fermentation broths (preparation of bioethanol and biobutanol) and the nanofiltration separation of organics. The effects of synthesis conditions, molecular-mass characteristics, and chain microstructure on the properties of membranes have been studied. It has been shown that membranes based on poly[(1-trimethylsilyl)-1-propyne], which is prepared with TaCl5/Al(i-Bu)3 and NbCl5 catalysts, possess good chemical resistance under the conditions of separation of fermentation broths. With the use of poly[(1-trimethylsilyl)-1-propyne], it has been shown for the first time that membranes for the nanofiltration of organic media may be designed on the basis of glassy polymers with a high fraction of the unrelaxed free volume.

By using the TRANS code, we performed three-dimensional calculations of amplified spontaneous emission (ASE) in X-ray lasers on the 3p--3s transition in Ne-like Ge (l = 19.6 nm) and Ti (l = 2.6 nm) operating in the transient regime upon irradiation of a flat target by a high-power picosecond laser pulse focused into a line with one or two nanosecond prepulses. The hydrodynamics and population kinetics of the active medium of X-ray lasers were calculated by using the SS-9M code. The pulse duration, the gain, the spatial structure of the laser beam and the type of influence of a 'travelling' pump wave on the ASE brightness obtained in calculations are in agreement with the experimental data. The use of the 'travelling pump wave' leads not only to the increase in the ASE brightness but also considerably reduces its angular divergence.

The paper presents peculiarities of organization and performance of activities on disposition of the high level activity radwaste repository located at the radwaste disposal site of the Russian Research Center “Kurchatov Institute” in Moscow. The process of the radwaste extraction from the repository is described in comparison with similar activities in other old repositories. Tools and equipment used for the radwaste extraction from the repository are listed. Conventional construction machines equipped with a hydraulic hammer or a clamshell were used for destruction of the concrete-encased radwaste mass and extraction of low-level radwaste. Intermediate- and high-level radwaste was extracted by remotely controlled robots operating inside the shielding structure. Gamma visor was used for detection of high-level radwaste or fragments in the mass concrete being destroyed and for pointing remotely controlled robots accordingly. The paper describes peculiarities of radiation monitoring in the course of operations on disposition of the repository. For rapid detection of changes in radiation conditions in the working areas, there was used a gamma locator with on-line transmission of its data to a PC and their processing. The same measuring and extraction equipment were used for remediation of high-level radwaste repository at the Gas Plant complexes.