Search

Evolution of the morphology of cellulose solutions in N-methylmorpholine-N-oxide during coagulation with a “soft” coagulant, isobutyl alcohol, at different temperatures is considered. Using optical interferometry and transmitted and scanning electron microscopy the mechanism of phase separation of the system to form a polymer phase is studied depending on the temperature of alcohol. It is shown that, in the case of a room temperature coagulant, a heterogeneous film with a droplet texture enlarging over thickness appears along the precipitation front. At a high temperature of alcohol the coagulation of the solution occurs in two stages. At the first stage the penetration of the coagulant into the jet of spinning solution leading to the formation of vacuoles occurs. The phase separation of the solution proceeds within the vacuoles as microreactors to form a polymer-concentrated shell and a polymer-diluted phase in the vacuole cavity. At the second stage the coagulant diffuses through the vacuole shell into the bulk of the solution and causes its uniform coagulation. The process of vacuole formation is visualized. The transverse cleavage of the film is analyzed by energy dispersive X-ray spectroscopy. The difference in the content of C, N, and O atoms on the walls of vacuoles and in the region of a film with a uniform cellular morphology is established.

The kinetics of formation of a three-dimensional structure in compositions based on butyl rubber and silicon-containing hyperbranched polymethylsilsesquioxanes and MQ copolymers is studied in comparison with compositions containing common dispersed phases: carbon black and silica. Features of the chemical structure of the synthesized organosilicon polymers make it possible to treat the morphology of their elementary particles as core–shell. The role of an inorganic “core” is played by silica structures, whereas methyl shells should ensure compatibility with the carbochain matrix of the rubber. Quinol ether is used as an agent of crosslinking via double bonds of the isoprene part of the rubber. The crosslinking process is carried out in the mode of continuous heating of compositions with registration of thermal effects by differential scanning calorimetry and dynamic moduli by oscillatory rheometry. The apparent activation energies of the process of chemical crosslinking under nonisothermal conditions are calculated in terms of various models. It is shown that the apparent activation energy of crosslinking is lower for filled systems. This indicates that rubber macromolecules are partially uninvolved in chemical crosslinking as a result of adsorption and loss of relaxation mobility. The adsorption activity of fillers is estimated from a difference in the activation energies of the initial rubber and filled compositions; this parameter is the lowest for polymethylsilsesquioxanes.

A new method is developed for the production of composite fibers based on cellulose and vinyltriethoxysilane and formed from N-methylmorpholine-N-oxide solutions. Introduction of the organosilicon additive promotes the activation of cellulose pyrolysis processes, and its choice relies on the presence of a double bond in vinyltriethoxysilane, which can be opened when the temperature rises. Mixed solutions are emulsions with labile droplets of the organosilicon liquid that easily change their shape under deformation. The study of the rheological behavior of the mixed solutions of cellulose with vinyltriethoxysilane reveals an unusual character of a change in viscosity with the concentration of vinyltriethoxysilane—with a minimum at 10–15%. From joint solutions by the dry-jet wet method, composite fibers are spun in an aqueous coagulation bath at a rate of 50–70 m/min. The study of their thermal properties shows that in thermolysis vinyltriethoxysilane additives catalyze condensation processes in cellulose and lead to an increase in char yield. Using IR spectroscopy, the combined chemical transformations of cellulose and vinyltriethoxysilane at all stages of the heat treatment of composite fibers up to 1200°C are analyzed for the first time. It is found that during thermolysis the chemical interaction of vinyltriethoxysilane with cellulose occurs and carbon fibers “crosslinked” by silicon carbide fragments are formed.

The process of film formation including the initial treatment of thin layers of cellulose solutions in N-methylmorpholine N-oxide with isobutanol followed by washing with water is investigated in detail, and the structural and morphological features of the obtained films are examined. The phase state of the N-methylmorpholine N-oxide–isobutyl alcohol system is studied by differential scanning calorimetry and optical interferometry, and a diagram describing the crystalline equilibrium and allowing determination of the temperature–concentration “window” of compatibility of components is constructed. The dependence of viscosity of N-methylmorpholine N-oxide solutions in isobutanol on temperature confirms the phase composition of the system. The process of film formation is modeled by analyzing the diffusion zone of the cellulose solution–isobutyl alcohol system. The IR study of the interaction of N-methylmorpholine N-oxide containing 13.3% water with isobutanol shows that the affinity of isobutanol for water is much higher than that for N-methylmorpholine N-oxide. For this reason, when the spinning solution is brought in contact with isobutanol, the redistribution of water between the interacting components occurs and the structure of the heterogeneous gel-like complex cellulose–N-methylmorpholine N-oxide–isobutanol “is frozen,” as proved by the X-ray diffraction study of the films. Complete removal of the solvent and isolation of cellulose from this film proceed only upon subsequent washing with water. The X-ray diffraction and optical interferometry study of the effect of temperature on the interaction of a hot cellulose solution with cold isobutanol suggests that at room temperature the film obtained from solution contains inclusions of the vitrified N-methylmorpholine N-oxide. Under isothermal conditions (at a temperature of 90°С), the rate of interdiffusion grows appreciably and the solution preserves the homogeneous structure. Thus, the precipitation of cellulose from the bicomponent solvent N-methylmorpholine N-oxide–water upon contact first with isobutanol and then with water proceeds via two stages: initially the system undergoes phase separation and a concentrated solution is formed in the isobutanol-N-methylmorpholine N-oxide blend, from which cellulose precipitates upon interaction with water. When the process of primary interaction of the solution with alcohol is conducted under the conditions of compatibility of isobutanol with N-methylmorpholine N-oxide, a more homogeneous morphology of the films can be obtained.

Solid–state dissolution in N–methylmorpholine N–oxide was used to obtain solutions of mixtures derived from cellulose and various organosilicon additives, namely, tetraethoxysilane, vinyltriethoxysilane, and bis (trimethylsilyl)acetylene. Optical study of the phase composition and morphology of these solutions showed that they are two–phase emulsions with a rather broad size distribution of particles of the dispersed phase. The nature of the flow of the mixed systems in continuous and dynamic deformation when the rheological behavior is monotypic depends to a certain extent on the nature of the organosilicon additive. Dry wet–jet spinning was used to obtain composite fibers. The structure and morphology of these fibers were studied as well as their mechanical and thermal properties. Analysis of the x–ray patterns diffractograms of the cellulose and composite fibers showed that the introduction of organosilicon additives into the cellulose matrix leads to less structural ordering of the cellulose. The mechanical characteristics of the composite fibers show some decrease in the strength and deformation characteristics with an increase in the elastic modulus in comparison with the cellulose fibers. Heat treatment of the cellulose and composite fibers up to 1000°C revealed a significant increase in the mass of carbon residue, whose amount depends on the type of additive.

Replacing the aqueous coagulation bath with an alcoholic one during spinning cellulose fibers (films) from solutions in N-methylmorpholine-N-oxide leads to a radical restructuring of the hydrogen bonds net of cellulose and, as a result, to a change in the structure and properties of the resulting material. By the method of optical interferometry, it was possible to identify the intrinsic features of the interaction of the solvent and isomeric alcohols and to construct phase diagrams of binary systems describing the crystalline equilibrium. Knowledge of the phase states of the system at different temperatures renders it possible to exclude the process of solvent crystallization and conduct the spinning in pseudo-homogeneous conditions. The structure and morphology of samples were studied using X-ray diffraction and scanning electron microscopy methods for a specific coagulant. When the solution under certain conditions is coagulated at contact with alcohol, the solvent may be in a glassy state, whereas, when at coagulation in water, an amorphous-crystalline structure is formed. The structural features of cellulose films obtained by coagulation of solutions with water and alcohols help to select potential engineering or functional materials (textile, packaging, membranes, etc.), in which their qualities will manifest to the best extent.

The downtime of ball-rolling mills is largely associated with the replacement of worn rollers. In the present work, the degree and location of critical roller wear are studied: the greatest wear is observed at the flanges in the billet-capture zone. The conditions required for billet capture and successful rolling are determined analytically. Variation in roller speed during billet supply is proposed. Tests are conducted with linear and quadratic variation in roller speed. The familiar formulas for the mean deformation rate are modified for linear and quadratic variation in roller speed. Experiments are conducted on the ball-rolling mill of AO EVRAZ Nizhnetagil’skii Metallurgicheskii Kombinat (NTMK), in rolling 60-mm ШЗГsteel grinding balls on a 40–80 rolling mill. In the experiments, the roller speed is varied manually according to a specified program, with billet capture by the rollers. It is found that speed variation significantly affects the mean pressure at the instant of billet capture. Time dependences of the torque and the mean contact pressure are plotted on the basis of calculation results and experimental data. Empirical characteristics with linear and quadratic variation in roller speed are presented. The permissible agreement of the calculated and empirical results is determined. The installation of a thyristor converter is proposed, so as to decrease the roller speed before billet capture and restore the speed to the rated value in specified fashion after capture. That yields a uniform distribution of the mean contact pressure over the roller length during automatic operation of the mill in different conditions. As a result, the roller wear is decreased, without loss of mill productivity. That reduces roller consumption and the mill downtime for roller replacement.

Researchers studying oil-in-water emulsions practically always deal with the oil and water purified of mineral admixtures. In reality, a water/crude oil emulsion obtained from a well contains solid clay- and sand particles, which may act as surfactants. In the present work, the solid particles’ effect on the morphology and rheological behavior of heavy crude oil emulsions are studied. Water-in-oil emulsions are fluids with the weakly non-Newtonian behavior and viscosity exceeding that of the crude oil. Solid particle admixtures have practically no effect on the viscosity of these emulsions. Oil-in-water emulsions, on the contrary, are viscoplastic systems, the yield stress of which increases with silica- and clay admixture content. The transition from water emulsions to the oil ones was realized using surfactants (cetrimonium bromide, sodium dodecyl sulfate, Tween 85, and Triton X-100), the success of the phase inversion depending on the hydrophilic-lipophilic balance of a surfactant. The effective viscosity of the oil-in-water emulsions is demonstrated to depend on the shear rate and solid particle- and surfactant concentrations, this providing the opportunity to optimize the compositions of crude oil emulsions for transportation.

Carbon—silicon-carbide fibers were produced from cellulose and triethoxyvinylsilane and spun using the solid-phase NMMO-process. Scanning and transmission electron microscopy studies, energydispersive x-ray spectrometry, and x-ray structure analysis of composite carbon fibers established and identified the structure and morphology of carbon fibers that varied from an isotropic shell to regularly organized lamellae of graphite-like layers of the fiber core. Distributions of chemical elements were plotted. The nano-sized dimensions of silicon-carbide regions in the carbon fibers were determined.

In this study, explores the use of web technologies as a way to ensure that medical waste transportation is undertaken in a proper and safe way. Insofar as an incorrect waste sorting is regarded as a source of an epidemiological threat within further transportation, is proposed a synthesis of a waste sorting model. The model is based on a natural science approach to managerial decision-making. The model enables to identify and prove violations concerning medical waste sorting. Described four interconnected components of the model: an initial stage, when vaccination processes are not taking place; the vaccination is completed and medical waste is sorted according to the rules; the vaccination is completed, but the rules of medical waste sorting are violated; all the problems related to medical waste sorting are solved, so its transportation is possible.

Composite fibers were prepared by solid-state dissolution of cellulose in N-methylmorpholine-N-oxide with added tetraethoxysilane (TEOS). It was shown that adding TEOS to the cellulose matrix increased up to 16% the fiber carbon residue during heat treatment. Bonds formed between Si and C during their high-temperature treatment according to IR spectra of the composite cellulose fibers. The thermal behavior of the fibers was studied using TGA and TMA. The fiber morphology and the structure of the Si-containing additive particles were examined using SEM and TEM. The mechanical properties of carbon fibers prepared from cellulose-hydrate and composite fibers were compared.

We studied the rheological properties of heavy oil-in-water emulsions with the final goal of decreasing the high viscosity of oil in pipeline transportation. The emulsions containing 3% silica or 5% montmorillonite were stabilized by Triton X-100. All emulsions were viscoplastic media and also demonstrated viscoelasticity. At low shear stresses, emulsions are in gel-like state that was reflected by the independence of the elastic modulus from frequency. The yield stress of basic emulsion is rather low (∼1 Pa), while the introduction of solid particles leads to a remarkable increase of the yield stress. It was shown that direct transition of the rheological data for oil emulsions measured in a rotational device to capillary rheometer appeared impossible. The apparent viscosity of the samples estimated in tubes (as a model of a capillary viscometer) was not correlated with the shear viscosity measured on a rotational rheometer and overall was dependent on the tube/capillary diameter. The reason for these effects may be related to the stratified flow through a tube consisting of near-wall slippage or the existence at the stream periphery of a low-viscosity layer. This phenomenon should be taken into account in designing pipe transportation lines when viscometric data are obtained in the other conditions of flow.

A method for producing cellulose-based composite fibers with the addition of tetraethoxysilane (TEOS) with a high degree of dispersion of the additive in the cellulose matrix through a “solid phase” dissolution step of the cellulose in N-methylmorpholine-N-oxide (NMMO) is proposed. Investigation of the phase state and morphological features of mixtures of cellulose solutions with TEOS additives in NMMO has shown that in the entire range of concentrations studied, the solutions are biphasic emulsions, and their dispersity and the shape of dispersed phase droplets depend on the prehistory of solution preparation. It is established that the rheological behavior of cellulose solutions with TEOS additives varies depending on the amount of the additive. A theory about a mechanism for changing the rheological behavior of cellulose solutions with TEOS is formulated. X-ray diffraction analysis, scanning and transmission microscopy and IR spectroscopy were used to characterize the structure and morphology of composite fibers. The mechanical properties of composite cellulose fibers with TEOS are investigated.

This study focuses on the preparation of carbon fiber precursors from solutions of cellulose in N-methylmorpholine-N-oxide with the addition of bis(trimethylsilyl)acetylene, studying their structural features and evaluating thermal behavior. The introduction of a silicon-containing additive into cellulose leads to an increase in the carbon yield during carbonization of composite precursors. The type of the observed peaks on the differential scanning calorimetry (DSC) curves cardinally changes from endo peaks intrinsic for cellulose fibers to the combination of endo and exo peaks for composite fibers. For the first time, coefficient of thermal expansion (CTE) values were obtained for Lyocell fibers and composite fibers with bis(trimethylsilyl)acetylene (BTMSA). The study of the dependence of linear dimensions of the heat treatment fibers on temperature made it possible to determine the relation between thermal expansion coefficients of carbonized fibers and thermogravimetric curves, as well as to reveal the relationship between fiber shrinkage and BTMSA bis(trimethylsilyl)acetylene content. Carbon fibers from composite precursors are obtained at a processing temperature of 1200 °C. A study of the structure of carbon fibers by X-ray diffraction, Raman spectroscopy, and transmission electron microscopy made it possible to determine the amorphous structure of the fibers obtained.

Recent works devoted to studying the structure and rheological properties of water/oil disperse systems have been reviewed. Contemporary understandings of crude heavy oil as a water-in-oil emulsion have been discussed. Data on the mechanism of the stabilizing effect of natural lipophilic surfactants and ultradispersed particles of different natures contained in oil have been presented. Methods that are used to improve the transport characteristics of heavy oil—in particular, the formation of low-viscosity oil-in-water emulsions—have been listed. Colloidal and rheological properties of heavy oil-in-water emulsions, which are increasingly applied for pipeline transportation of oil, have been considered.

The phase state and rheological properties of dimethyl sulfoxide (DMSO) solutions of a series of acrylonitrile-based copolymers (PAN), which were obtained by suspension polymerization and synthesized in supercritical CO2, have been studied. For PAN-DMSO (plus water) solutions, a bimodal amorphous phase equilibrium takes place at ~78°C. Comparison of the rheological behavior of homo- and copolymer solutions has shown that the presence of carboxylate ion(s) in the macromolecular chain leads to supramolecular structure formation. Small additions of non-solvent (water) enhance the viscoelasticity of the solution, whereas a large amount of water results in gel formation; beyond a certain threshold of water concentration, macroscopic phase separation takes place. Addition of carbon nanotubes into the solution does not change their phase state or rheological behavior. Application of mechanical forces to concentrated solutions may cause specific phase separation without the addition of a non-solvent.

Results of designing, at the OJSC “Power Machines,” a full-scale bench for testing a broad range of auxiliary equipment (AE) are presented. The importance of full-scale tests for improving design methods for AE is showed. The test results for some AE are interpreted graphically. It is concluded that this AE meets the consumer requirements.

The structure, phase composition and hardness of a 20X13 steel coating treated with two consecutive passes of a plasma arc are studied. It is shown that plasma treatment makes it possible to obtain martensite with a significant (30–50 %) share of permanent austenite in the structure of the local hardening zone. In this case, the hardness of the heat-strengthened blanket is 650–700 HB. The total depth of the local hardening zone with the modified structure reaches one millimeter. The study shows that a homogeneous structure with periodically changing phase composition and hardness develops in the surface layer of 20X13 steel, heat-treated plasma arc. in this case, the plasma arc must pass sequentially with a certain degree of overlap of local quenching zones. It is obvious that by adjusting the parameters of the processing conditions (the current of the plasma arc, the speed of its movement, the degree of overlap of local quenching zones), it is possible to purposefully form a certain structural-phase state of the surface layer with properties that best meet the operating conditions.

The influence of the operating parameters of electric arc heat treatment of the surface layer of graphite flake cast iron type CП-61 on the structure, microhardness of structural components and the size of the hardening zone is studied. It is shown that controlling the arc power, its speed and the degree of overlap of local hardening zones allows purposefully forming modified structural States with properties most suitable for specific operating conditions in the surface working layer of cast iron. Overlapping of local hardening zones allows purposefully forming modified structures with suitable properties for specific operating conditions in the surface working layer of cast iron rolls. According to the research results, regularities of formation of the structure and phase composition and properties of the surface layer of cast iron type CП-61 under the influence of electric arc heat treatment were obtained. Control of parameters of the processing mode (power and speed of the arc, the degree of overlap of local hardening zones) allows you to purposefully form modified structures with suitable properties for specific operating conditions in the surface working layer of cast iron.

Blends based on polystyrene and first- and third-generation carbosilane dendrimers with dimethyl(2-phenylethyl)silyl)propyl terminal groups are studied. For the same chemical structure of the outer layer, a change in the radii of nanoparticles from 0.9 to 2.0 nm entails a sharp decline in the rate of their mass transfer to the polymer bulk. Dendrimers of the first and third generations are characterized by substantially different compatibilities with polystyrene. It is assumed that this effect is associated with an increase in the energy of interaction between dendrimers. When dendrimers of the first generation are introduced into polystyrene, the viscosity, glass-transition temperature, and storage modulus decrease, while the filling of polystyrene with dendrimers of the third generation insignificantly affects these characteristics of the polymer.

This research investigates polystyrene mixtures with nanosized surface-modified particles, i.e., molecular silicasol, silsesquioxane, and first-generation carbosilane dendrimer. Three types of similarly sized particles with the same type of surface layer possess different chemical structures and rigidities of the cores. The latter is defined not by the numerical value of the elastic modulus but is based on the concept of molecular mobility of the chemical bonds that form the core. The phase and rheological behaviour as well as the relaxation and dielectric properties of the systems were investigated. The viscosity and the glass transition temperature of the systems decrease with increasing filler content but do not depend on the core rigidity of the particles. However, the molecular structure of the core of a hybrid nanoparticle defines both its own elastic modulus and the elastic modulus of the whole composite as well as affects the rate and activation energy of the segmental motion in the polymer. The characteristics of the composite depend on the core rigidity of the nanoparticles if the correlation radius of the physical characteristic is comparable to or less than the nanoparticle radius. The organic surface layer of nanoparticles serves both as a compatibilizer of the polymer-nanoparticle system and as a peculiar type of a “solvent” in the polymer matrix.

There has been studied the effect of heat input plasma hardening steels process 0.9 C-Cr-Si, 1 C and 1.7 C-Cr-Ni-Mo on the structure, the depth of hardening and the hardness of the local area. It is shown that a graded structure is formed along the depth of the zone with regularly changing dispersion and microhardness. There have been specified the dependences, allowing to operate the structural state and performance properties of the hardening zone, ensuring their optimum ratios for different wear conditions. © Published under licence by IOP Publishing Ltd.

Comb-like polymethylsiloxanes consisting of a silsesquioxane backbone and dimethylsiloxane side chains were synthesized by means of the “grafting to” method using a linear polyfunctional matrix [SiMe(ONa)O]n and monofunctional oligomers (CH3)3Si[OSi(CH 3)2]nOCOCH3. The effects of architecture of the synthesized methylsiloxane polymers on their physicochemical properties, rheology, and behavior at the air–water interface were studied and compared with those for the linear analogue – polydimethylsiloxane.

Comparative studies of the structure and thermal behavior of cellulose and composite precursors with additives of silyl-substituted acetylene and alkoxysilanes were carried out. It is shown that the introduction of silicon-containing additives into the cellulose matrix influenced the thermal behavior of the composite fibers and the carbon yield after carbonization. Comparison of the activation energies of the thermal decomposition reaction renders it possible to determine the type of additive and its concentration, which reduces the energy necessary for pyrolysis. It is shown that the C/O ratio in the additive and the presence of the Si&ndash, C bond affected the activation energy and the temperature of the beginning and the end of the pyrolysis reaction.

The phase state and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions in toluene and cyclohexane are studied. Samples of poly(1-trimethylsilyl-1-propyne) have the same backbone structure (cis-trans configuration ratio) but different molecular masses. Phase diagrams of these systems are derived via optical interferometry. It is found that they have an upper critical mixing temperature (UCMT) whose value exceeds the boiling points of the individual solvents. The two solvents exhibit limited solubility with respect to the studied polymer, and this parameter decreases with an increase in the molecular mass of the polymer. In the transition from dilute to concentrated solutions, the pattern of the rheological behavior changes from Newtonian to pseudoplastic. The concentration dependences of the zero-shear-rate viscosity of the solutions are typical for flexible-chain polymers. The viscous behavior of the poly(1-trimethylsilyl-1-propyne)-solvent system can be described through a single generalized viscosity-concentration relationship if dimensionless reduced values that take into account the contribution of the molecular mass, the nature of the solvent, and the pattern of intermolecular interactions in the solutions are used as the argument and the function.

In this work the possibility of forming nanocomposite materials based on polyethylene oxide and hybrid organo-inorganic “core-shell” systems known as molecular silicasols with a modified external layer is studied. The chemical structure of a particle shell similar to the polymer matrix monomeric unit allows one to decrease the surface tension on the disperse phase-disperse medium interface. The level of compatibility of the components and its influence on the molecular weight of the polymer matrix was estimated based on interferometry and viscometry data, as well as an analysis of the concentration dependence of MFI, dielectric, and mechanical properties of the composites.

Investigations of the process of submerged-arc surfacing show that the experimental values of the thermal process of penetration of the parent metal at low values of current and surfacing speed are approximately half the values obtained in theoretical investigations. The addition of a correction to the well-known Rykalin procedure results in calculated values with an error not higher than 10% and can be used to determine the area of the penetration zone of the parent metal in submerged-arc surfacing in the surfacing current range of 400–1000 A and the surfacing speed range of 5–10 m/h.

The rheological properties of MQ copolymer melts are investigated under steady-state shear flow and dynamic oscillatory shear within a wide temperature range. The MQ copolymers are highly branched polycyclic compounds (densely crosslinked nanosized networks) incapable of further intermolecular interactions. The samples have identical chemical compositions, but their detailed molecular structures are different. The polymers under consideration show Newtonian behavior in a wide shear-stress range. The values of viscosity vary considerably with the molecular structure of the copolymers. The generalized frequency dependence of complex dynamic modulus components is constructed with the use of the temperature-frequency superposition method. In a first approximation, the viscoelastic behavior of the materials is satisfactorily described by the Maxwell model with a single relaxation time. In this respect, the studied materials are similar to micellar colloids. The relaxation spectra of the copolymers distinguished by narrow distributions are calculated.

A derivation of the conjugation criterion for a rotating disc is reported. Characteristics of conjugate heat transfer on a single disc and in a cavity formed by two discs, one rotating and the other stationary, are analysed.

We present the results from a 3D numerical calculation aimed at analyzing the thermal state of the steam-cooled segment of the flow path of a double-flow intermediate-pressure cylinder used in a steam turbine for ultrasupercritical steam conditions. It is shown that the circumferential nonuniformity of metal temperature on the end-face surfaces of disks and on the rotor surface may be disregarded when the turbine runs at the nominal frequency of rotation.

A multifunctional instrument for measuring viscoelastic characteristics of polymeric materials is described. The operational principle of this instrument is based on the method of mechanical Fourier spectrometry. An incoming signal represents white noise that, like an outgoing signal, is expanded into a Fourier series in frequency. The use of a highly sensitive displacement transducer and a high-precision electromagnetic actuator makes it possible to collect spectral functions in a broad frequency range with a fair level of reliability. For the tests of flowable media, deformation is performed so that the test sample is compressed between two plane-parallel plates. In the tests of rubbery and solid samples, loading is accomplished via a three-point bending procedure or deformation of a membrane. The instrument makes it possible to perform tests on small samples (a volume less than 0.25 μl) and solid films with a thickness of 10–300 μm. The interval of complex elastic-modulus measurements ranges from 10 Pa to 50 MPa in the regime of a rheometer and from 10 kPa to 100 GPa in the regime of a solid-body spectrometer. The frequency interval is 0–1 Hz, and the temperature interval ranges from −100 to +300°C under the isothermic regime or under scanning at a heating rate from 0.1 to 10 K/min. Examples of the experimental results are presented.

The rheological properties of high-generation carbosilane dendrimers carrying different kinds of terminal groups are studied. It is shown that the nonlinear viscoelastic behavior of dendrimers and the high-temperature relaxation transition in dendrimers are interrelated and result from the reversible breakdown of the supramolecular structure formed by the system of contacts of exterior shells of dendrimers. The strength of the supramolecular structure is dependent on the specific interaction of terminal groups of dendrimers and their mobility. The dendrimers under study demonstrate the dualism of macromolecule-particle properties: They behave as both polymer melts and colloidal systems.

Data on the direction and speed of liquid metal flows in the pool in consumable electrode arc welding (surfacing) are scarce and contradicting and relate mainly to the process without the effect of...

For the first time the composite fibers based on cellulose with additives of vinyltriethoxysilane (VTEOS) have been obtained. The choice of the additive was justified by the chemical structure of the VTEOS, namely the Si-C links content and the low C/O ratio. Composite fibers were prepared from solid phase pre-solutions of cellulose with VTEOS in N-methylmorpholine-N-oxide (NMMO). An investigation of the rheological behavior of the filled cellulose solutions with VTEOS showed a slight effect of the additive on the viscosity properties of the system. Introduction of 5% of VTEOS to cellulose does not lead to significant structural changes and, as a result, mechanical properties of the fibers. The thermal behavior of composite fibers differs from cellulose fibers.

The article covers results of clinical and roentgenologic data analysis. The data were obtained in the study that covered 447 pneumoconiosis patients, 75 of which were subjected to high resolution CT. If compared to chest X-ray, high resolution CT helps more precise forecast of further course in pneumoconiosis.

Particle motion and deposition are modelled numerically on an infinite transversely streamlined cylinder subjected to force factors of a non-turbulent nature.

The general relativistic equations for a homogeneous istoropic metric of the most general form are considered. It is concluded that an event horizon is a possible alternative to a cosmological singularity for “usual” matter. This conclusion is illustrated by the case of a flat spatial universe.

Results of diagnosis of thyroid nodes in 404 patients are analyzed. Ultrasonic examination and US-assisted puncture biopsy were carried out before operations. Their results were compared with ones of morphologic study performed after surgery. Solitary nodes were diagnosed in 171 (42.3%) patients, multiple--in 233 (57.7%). The most specific ultrasonic symptoms of different forms of thyroid nodes were revealed. Thyroid cancer is imaged as hypoechogenic node with clear and unclear contour, heterogeneous structure, multiple zones of hyperechogenicity and calcification. Adenomas are presented as isoechogenic homogenic nodes with clear border and cystic cavities. Colloid nodes picture is the same. Rathen often different morphologic forms of nodes are similar, thus ultrasonic examination permits to detect morphologic structure of nodes hypothetically only. Sensitivity of puncture biopsy for goiter, adenomas and cancer was 87.1, 92.9 and 69.7% respectively. Cancer was not diagnosed before surgery in 30.3% cases when colloid goiter or adenomas were suspected. In these cases small cancer was located amidst colloid nodes and didn't differ by ultrasonic symptoms. Diagnosis of malignant tumor in nodular goiter was highly precise. Morphologic form of cancer was verified cytologically in majority of cases.

Post-Einstein theory of gravitation (PETG) is suggested. The PETG equations for a Robertson‐Walker cosmological model are obtained. It is shown that in PETG and in some other theories a ‘dynamical’ Universe cannot be realized as the configuration of a ‘common’ matter.

Fractionation of type B. Cl. botulinum toxin, a protein complex, was carried out; as a result, 3 fractions, alpha, beta, and gamma, were isolated in a pure form, alpha-fraction, or neurotoxin, is highly toxic (5-10.10(7) LDm per 1 mg of protein), beta-fraction showed hemagglutinating activity (64-128 HAU per 1 mg of protein), gamma-fraction was not biologically active. The molecular weight of alpha and gamma-fractions was 150,000. All these fractions had antigenic properties. alpha-fraction was serologically specific. beta- and gamma-fractions showed incomplete serologic identity.