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The work is devoted to studying heat exchange processes of an ascending fluid flow in a producing well during the deposition of mechanical impurities on its walls, for example, of asphalt–paraffin deposits. A mathematical model and the results of numerical solutions of the formation of a temperature field along the wellbore are considered. It is shown that due to a change in the heat transfer coefficient in the areas of deposition of mechanical impurities, a change in the temperature gradient in a nonstationary thermal field is observed. The results obtained can be used in interpreting the data of thermodynamic studies of producing wells. [ABSTRACT FROM AUTHOR]

Results of spectral studies of fifteen Seyfert galaxies at red wavelengths based on long-term observations are presented. In this range there are lines of hydrogen Hα, [NII], [OI], and [SII]. Data on the absolute emission fluxes in the emission lines and in the continuum at the wavelength of λ = 6400 Å are presented. In order to objectively compare the examined galaxies with one another, the values of their luminosities were calculated in absolute units with the distances to these objects taken into account. [ABSTRACT FROM AUTHOR]

A theoretical investigation of the radial temperature distributions in the upward and downward flows of fluid in the borehole of a production well has been performed. The radial differences between the temperatures at the axis and wall of such a well in the cases of water and oil flows in it were determined. [ABSTRACT FROM AUTHOR]

Based on numerical modeling of thermohydrodynamic processes in the wellbore under conditions of oil degassing, the possibility of estimating the coefficient of gas solubility in oil and the well flow rate is investigated based on an analysis of temperature distribution along the wellbore. It is shown that degassing of oil in the wellbore or in a bed leads to the formation of temperature cooling anomalies, which can be used to solve certain oilfield problems. The results obtained can be used in planning field-geophysical studies and interpreting the results of temperature studies of wells during the production of live crude. [ABSTRACT FROM AUTHOR]

We study an actual problem of cleaning of conveyor belts from adhered finely divided materials in the process of operation of belt conveyors. The material remaining on the belts causes numerous problems for the conveyor transport. In the course of time, adhered particles fall into the subconveyor space, thus violating the normal operation of the conveyor. This also leads to rapid failures of the roller supports, excessive abrasion of the working surface of the belt, and hence, to a more rapid wear of the conveyor belt. The procedure of cleaning of the belts enables one to remove the indicated problems. At present, there are various types of available cleaning units. Each of these units has its own advantages and disadvantages. In most cases, this complicates the choice of the required unit. We estimate the efficiency of application of a discrete double-row scraper cleaner of the conveyor belt. Its application increases the degree of cleaning without damaging the surface of the belt due to the presence of a counterbalance clamping attachment. [ABSTRACT FROM AUTHOR]

Greedy expansions with prescribed coefficients, which have been studied by V. N. Temlyakov in Banach spaces, are considered here in a narrower case of Hilbert spaces. We show that in this case the positive result on the convergence does not require monotonicity of coefficient sequence C. Furthermore, we show that the condition sufficient for the convergence, namely, the inclusion C∈l2∖l1, can not be relaxed at least in the power scale. At the same time, in finite-dimensional spaces, the condition C∈l2 can be replaced by convergence of C to zero. [ABSTRACT FROM AUTHOR]

The data obtained by transcriptome analysis of lumbar spinal cord segments, sciatic nerve, and the respiratory diaphragm of the mice performed after a space flight on board Bion-M1 biosatellite were processed by bioinformatic methods aimed at elucidation of the regularities in hypogravity-induced transcriptome changes in various compartments of motor neurons. The study revealed abnormalities of axonal transport in spinal motor neurons provoked by weightlessness. These data agree with the results of electron microscopy examination of the spinal cord in experimental animals. In space group mice sacrificed on the landing day, the content of perinuclear ribosomes in lumbar motoneurons surpassed that in control mice or in the recovery group examined 1 week after the flight. The data corroborate our hypothesis on contribution of axonal transport disturbances into pathogenesis of hypogravity motor syndrome. They can be employed as a launching pad for further study of hypogravity-triggered motor disorder mechanisms in order to elaborate the preventive therapy against the development of hypogravity motor syndrome in space flights. [ABSTRACT FROM AUTHOR]

Changes in the structure and properties of the Ni1 –xCuxFe2O4 ferrites-spinel magnetic nanoparticles depending on the Cu ion concentration (0 ≤ x ≤ 1.0) have been studied using Mossbauer spectroscopy. It has been found that, with the increasing of the Cu ion concentration, the structure of nanoparticles changes from the structure of reverse spinel (NiFe2O4) to that of mixed spinel (CuFe2O4). It has been shown that the hydrothermal synthesis method makes it possible to obtain single-phase nanoscale particles with a very narrow size distribution and ideal magnetic ordering, which are promising for biomedical applications. The relationship between the distribution of cations on sublattices, the value of the inversion parameter, and the Cu ion concentration has been established. [ABSTRACT FROM AUTHOR]

The pulsed field gradient nuclear magnetic resonance method has been used to study self-diffusion of cyclohexane in a commercial MCM-41 material at different external gas pressures from zero to saturated vapor pressure. It is found that the effective diffusivities exhibit three different regions with increasing pressure: decrease at low pressures, a sudden drop at intermediate pressures, and increase at higher pressures. In addition, in the region of irreversible adsorption (hysteresis loop) the diffusivities are also found to differ on the adsorption and the desorption branches. A simple analytical model taking account of different molecular ensembles with different transport properties due to the complex architecture of the porous structure is developed which provides a quantitative prediction of the experimental data. The analysis reveals that the effective diffusivity is predominantly controlled by the adsorption properties of the individual mesoporous MCM-41 crystallites which, in combination with high transport rates, provide a simple instrument for fine tuning of the transport properties by a subtle variation of the external conditions. [ABSTRACT FROM AUTHOR]

Nuclear magnetic resonance has been applied to study the details of molecular motion of low-molecular-weight polar and nonpolar organic liquids in nanoporous silicon crystals of straight cylindrical pore morphology at different pore loadings. Effective self-diffusion coefficients as obtained using the pulsed field gradient nuclear magnetic resonance method were found to pass through a maximum with increasing concentration for all liquids under study. Taking account of a concentration-dependent coexistence of capillary condensed, adsorbed and gaseous phases a generalized model for the effective self-diffusion coefficient was developed and shown to satisfactorily explain the experimental results. An explicit use of the adsorption isotherm properties within the model extends its applicability to the mesoporous range and highlights the role of surface interaction for the transport of molecules in small pores. The problem of surface diffusion and diffusion of multilayered molecules is also addressed. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

At low temperatures, liquids imbibed into nanoporous materials form frozen solid cores in the interior of pores. Inbetween the cores and the pore walls, there exists a layer of nonfrozen liquid. As demonstrated here by nuclear magnetic resonance magnetization transfer and cryoporometry experiments, pools of nuclear spins that reside in those two separate domains, core and liquid layer, exchange nuclear Zeeman magnetization. This exchange is detectable in these materials thanks to the high contact area. Based on this phenomenon, we propose a new method for measuring the surface-to-volume ratio and for accessing the pore space morphology in nanoporous materials. By monitoring the magnetization transfer process, information can be obtained: (i) on the geometrical characteristics of the porous space and (ii) on the diffusivity of nuclear magnetization in the frozen phase. The diffusive transport of nuclear magnetization in the frozen core can be contributed by two mechanisms: spatial atomic/molecular diffusion and spin diffusion through nuclear dipole-dipole interaction. For the water-ice system in controlled porous glasses of known morphology, we can separate these two mechanisms to obtain an estimate of the proton diffusion coefficient of 4 × 10[sup -16] m²/s in ice at 255 K. [ABSTRACT FROM AUTHOR]

H nuclear magnetic resonance cryoporometry has been applied to study the low-temperature phase separation of the two components in a binary liquid imbibed in porous glass. The mixture of hexane and nitrobenzene was quenched below both its upper critical temperature and the freezing point of the nitrobenzene. The size distribution of phase-separated liquid domains was observed through their melting point suppression that reveals small droplets of nitrobenzene surrounded by hexane within the pores. If the bottlenecks of the porous network allow, some of these droplets coalesce and thereby completely fill parts of the network. [ABSTRACT FROM AUTHOR]

This Letter presents the results of an experimental and numerical study of a supersonic (M∞ = 7) flow past a hollow cylinder with gas-permeable porous inserts, installed along the flow. We demonstrate that it is possible to control the aerodynamic drag of the model by transferring some of the free-stream flow into the base region through gas-permeable porous inserts. The flow rate of the air directed to the base region to control the drag was regulated by heating the porous inserts with an electric glow discharge. [ABSTRACT FROM AUTHOR]

We present the data of studies on the structure, phase states, and magnetic properties of magnetic nanoparticles (MNPs) of magnesium ferrite spinel (MgFe2O4), synthesized by ultrasonic aerosols pyrolysis. Primary single-phase MNPs with an average size of 9.6, 11.5, and 14.0 nm, synthesized from precursors at concentrations of 0.06, 0.12, and 0.24 M, respectively, agglomerate into tightly aggregated spherical particles (secondary particles) with sizes of 206, 300, and 340 nm, respectively. Primary particles inside the spheres do not interact with each other and are in a superparamagnetic state. There is a layer on the surface of the particles, the magnetic structure of which differs from the structure of the inner part of the MNP; this is explained by the formation of a canted spin structure or a spin glass state in the surface layer of the MNPs. MgFe2O4 nanospheres obtained from a precursor at a concentration of 0.06 M are most promising as valid sources of heat in magnetic hyperthermia therapy. [ABSTRACT FROM AUTHOR]

An experimental study has been made of the ignition of droplets of organic coal water fuels prepared from moist waste (obtained by the flotation technique) of coal washing and used industrial oils with the use of a high-speed system of video recording of the processes proceeding in a model combustion chamber. A comparison has been made between the ignition inertias characteristics of a single droplet of organic coal water fuels, a group of three droplets, as well as of a polydisperse flow of a slurry fuel. All experiments were performed for hovering droplets (upon dehydration of the surface layer they are considered as particles) of organic coal water fuels in a model combustion chamber filled with heated air (the temperature was from 800 to 900 K). The established differences between the ignition characteristics of the slurry fuels in the three investigated schemes illustrate the possibility of prognostic evaluation of ignition characteristics of droplet aerosols of organic coal water fuels with the example of a single droplet. We present the dependences of ignition characteristics of single hovering droplets of organic coal water fuels of various component compositions on the group of diagnostic variables (temperature and flow velocity of the oxidizer, initial sizes of droplets, and concentration of the component composition). The prospects of using the obtained experimental results to optimize the performance of power-generating plants are shown. [ABSTRACT FROM AUTHOR]

Accurate structural characterization of mesoporous solids is of importance for potential applications and for better understanding of properties of natural porous materials. Among different characterization techniques, thermoporometry has several beneficial features, such as applicability to wetted and soft materials. In this review, we discuss recent advancements concerning nuclear magnetic resonance cryoporometry allowing for a notable improvement of the accuracy of this method. [ABSTRACT FROM AUTHOR]

The synthesis of an effective composite fuel from industrial wastes almost always requires mixing several components with different properties. Features of certain components can effectively compensate for the limitations of others, eventually improving the fuel as whole. We propose the optimization of the waste-derived coal-water slurry (CWS) by doping it with a small amount (2–5 wt%) of non-hydrocarbon dopants (metal-bearing powders with aluminium, iron, copper and chalk). It allows the stabilization of the combustion temperature (or even its increase), while keeping the ignition delays at the reasonable level ( ∼ 2 s at 1000 K). Doping the CWS by 2–5 wt% of chalk powder allows a radical decrease in the production of harmful exhausts (up to an order of magnitude regarding the SO 2 and 2–5 times regarding NO x ). A strong ecological effect was observed when the fuel is doped by iron powder, too. Therefore, the usage of non-organic dopants is a very promising way to prepare environmentally friendly fuel compositions with high power efficiency. [ABSTRACT FROM AUTHOR]

FeO/Fe3O4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical shape with an average size of ~20 nm. It was found that the obtained FeO/Fe3O4 nanoparticles had exchange coupling. The effect of anisotropy on the efficiency of heating (hyperthermic effect) of FeO/Fe3O4 nanoparticles by an external alternating magnetic field was examined. The specific absorption rate (SAR) of the studied nanoparticles was 135 W/g in the experiment with an external alternating magnetic field with a strength of 600 Oe and a frequency of 310 kHz. These data led to an important insight: the saturation magnetization is not the only factor governing the SAR, and the efficiency of heating of magnetic FeO/Fe3O4 nanoparticles may be increased by enhancing the effective anisotropy. Mössbauer spectroscopy of the phase composition of the synthesized nanoparticles clearly revealed the simultaneous presence of three phases: magnetite Fe3O4, maghemite γ-Fe2O3, and wustite FeO. [ABSTRACT FROM AUTHOR]

Usage of the waste-derived fuels is a very promising way for different industrial processes. It can yield both environmental and economic benefits, but for the heat production to be effective, fuel compositions must be prepared in an intelligent way. The combustion heat of such fuels is lower than that of conventional ones, so their improvement and successful application is in our best interests. Our goal was to investigate experimentally the effect of adding a small amount of aluminium powder (particle size ∼ 10 µm) to optimize waste-derived coal-water slurry with waste petrochemicals. We show the optimal metal concentration rate (3 wt%) that provides a significant increase in the maximum combustion temperature (by more than 100°), while keeping the ignition delay time at the appropriate level. Moreover, another mode is possible, when the combustion temperature is almost independent of the temperature inside the combustion chamber. The combustion duration and underburning levels were observed, too. [ABSTRACT FROM AUTHOR]

Nanoporous silicon consisting of tubular pores imbedded in a silicon matrix has found many technological applications and provides a useful model system for studying phase transitions under confinement. Recently, a model for mass transfer in these materials has been elaborated [Kondrashova et al., Sci. Rep. 7, 40207 (2017)], which assumes that adjacent channels can be connected by 'bridges' (with probability p ) which allows diffusion perpendicular to the channels. Along the channels, diffusion can be slowed down by 'necks' which occur with probability p . In this paper we use Monte-Carlo simulations to study diffusion along the channels and perpendicular to them, as a function of p and p , and find remarkable correlations between the diffusivities in longitudinal and radial directions. For clarifying the diffusivity in radial direction, which is governed by the concentration of bridges, we applied percolation theory. We determine analytically how the critical concentration of bridges depends on the size of the system and show that it approaches zero in the thermodynamic limit. Our analysis suggests that the critical properties of the model, including the diffusivity in radial direction, are in the universality class of two-dimensional lattice percolation, which is confirmed by our numerical study. [ABSTRACT FROM AUTHOR]

This paper examines the laws of stable ignition of organic coal-water slurry containing petrochemicals (CWSP). The CWSP is based on the filter cake of coal and scavenge oil. The experiments are performed for individual CWSP particles soaring in a special set-up. The temperature and velocity of an oxidizer flow are varied between 500-1200 K, and 0.5-3 m/s. The dimensions (longitudinal and transverse) of particles range are from 0.5 mm to 5 mm. The study indicates how the shape of a fuel particle (sphere, ellipsoid, and polyhedron) influences its ignition characteristics (delay time, minimum temperature, modes, stages). Based on the experimental results, the paper explains why the surface configuration of particles influences the conditions of heat transfer with an oxidizer. The results obtained for soaring particles are compared with the results for fixed CWSP particles having different surface configurations (sphere, ellipsoid, and polyhedron). In general, the study may contribute to the expansion of the fuel resource base. The experimental data may be used for the development of the technologies of burning CWSP prepared by recycling traditional fuels. As a result of this study, several recommendations for the practical application of research results are made. [ABSTRACT FROM AUTHOR]

The paper examines the integral characteristics (minimum temperature, ignition delay times) of stable combustion initiation of organic coal-water fuel droplets (initial radius is 0.3-1.5 mm) in the oxidizer flow (the temperature and velocity varied in ranges 500-900 K, 0.5-3 m/s). The main components of organic coal- -water fuel were: brown coal particles, filter-cakes obtained in coal processing, waste engine, and turbine oils. The different modes of soaring and ignition of organic coal-water fuel have been established. The conditions have been set under which it is possible to implement the sustainable soaring and ignition of organic coal-water fuel droplets. We have compared the ignition characteristics with those defined in the traditional approach (based on placing the droplets on a low-inertia thermocouple junction into the combustion chamber). The paper shows the scale of the influence of heat sink over the thermocouple junction on ignition inertia. An original technique for releasing organic coal-water fuel droplets to the combustion chamber was proposed and tested. The limitations of this technique and the prospects of experimental results for the optimization of energy equipment operation were also formulated. [ABSTRACT FROM AUTHOR]

We have observed the influence of an artificial macroscopic surface modification onto the ignition of droplets of the waste-derived coal water slurry with petrochemicals. Fuel composition was based on filter cake of bituminous gas-coal with inclusion of small amount of the waste oil fuel. The sizes and other parameters of the fuel droplets were chosen very close to used in typical power units. The fuel droplet surface was pierced making conical pores whose depth was more than half of the droplet radius. Changes of the ignition delay time were analysed together with features of the combustion of volatiles in vicinity of introduced macroscopic pores. The advanced mathematical model was used to clarify the contribution of the droplet surface modulation in different effects that present during the fuel ignition. It was shown that ignition delay time is decreased by up to 20% with growth of number of pores and particularly with growth of the specific surface of the droplet (by 10–20% and more). The maximal combustion temperature at the droplet center was slightly decreased after the introduction of the macro-pores. The recommendations for modification of the industrial power units to optimized ignition regime were presented. [ABSTRACT FROM AUTHOR]

In a spherically symmetric self-consistent approach (SSSA), the spin-1/2 J- J Heisenberg model on a two-dimensional square lattice is considered for two-time retarded spin-spin Green's functions. The spin excitation spectrum, ω( q), and spin gaps at symmetric points are obtained for the entire J- J diagram, i.e., for any ϕ, J = cosϕ, and J = sinϕ. The structure factor c and the correlation length ξ at finite temperature are calculated in the entire range of parameters. A radical difference in the behavior of the system in the upper, frustrated (0 ⩽ ϕ ⩽ π), and the lower, nonfrustrated (π ⩽ ϕ ⩽ 2π), regions of the diagram is demonstrated. In the latter region, there is a first-order phase transition that is unique on the phase diagram. For a weakly frustrated antiferromagnet ( J > J > 0), the results obtained are compared with the experimental dependence of ξ on temperature and doping level. A correspondence rule is proposed between frustration in a spin model and the doping of an antiferromagnet with holes. [ABSTRACT FROM AUTHOR]

Spectrograms of the Seyfert galaxy Ark 120 obtained in 1976-2013 are used to measure the radial velocities of emission features. It is assumed that these emission features with variable radial velocities are radiated by objects moving along Keplerian orbits in the gravitational field of the central body. Based on the available data, the parameters of the motion of three objects in the near-nuclear region of Ark 120 are calculated; the mass of its central body is estimated to be (1.675 ± 0.028) × 10 M. [ABSTRACT FROM AUTHOR]

Weapply dynamic mean field theory to study relaxation dynamicsfor lattice models of fluids confined in linear pores with side streamsand with ink bottle structures. Our results show several mechanismsfor how the pore structure affects the dynamics, and these are amplifiedin longer pores. An important conclusion of this work is that featuressuch as side streams and ink bottle segments can substantially slowthe equilibration of fluids confined in long pore systems where thepore lengths can be more than 100 micrometers, such as in porous silicon.This may make it difficult to properly equilibrate these systems forstates close to those where the pores should be completely filledwith liquids. The presence of trapped bubbles in the system may changethe desorption characteristics of the system and the shape of thehysteresis loops. [ABSTRACT FROM AUTHOR]

Highlights: [•] Diffusion of water in binder-containing and binderless zeolites. [•] Diffusivity enhancement in the binderless species. [•] Increase of the activation energy of long-range diffusion. [Copyright &y& Elsevier]

We have studied the filling dynamicsof model capillaries usingdynamic mean field theory for a confined lattice gas and Kawasakidynamics simulations. We have found two different scenarios for fillingof capped nanocapillaries from the vapor phase. As compared to channelswith macroscopic width, in which the filling process occurs by thedetachment of the meniscus from the cap, in mesoscopic channels thereis an alternative mechanism associated with the spontaneous condensationof the liquid close to the pore opening and its subsequent growthtoward the closed pore end. We show that these two scenarios havetotally different filling dynamics, providing an additional mechanismfor slow capillary condensation kinetics in nanoscopic objects. [ABSTRACT FROM AUTHOR]

Highlights: [•] A lattice-fluid model for solid–liquid transitions under confinement is presented. [•] Role of disorder on freezing and melting is established. [•] New routes for structural analysis using cryoporometry are suggested. [Copyright &y& Elsevier]

Despite extensive research on neurological disorders, unanswered questions remain regarding the molecular mechanisms underpinning the course of these diseases, and the search continues for effective biomarkers for early diagnosis, prognosis, or therapeutic intervention. These questions are especially acute in the study of spinal cord injury (SCI) and neurodegenerative diseases. It is believed that the changes in gene expression associated with processes triggered by neurological disorders are the result of post-transcriptional gene regulation. microRNAs (miRNAs) are key regulators of post-transcriptional gene expression and, as such, are often looked to in the search for effective biomarkers. We propose that cerebrospinal fluid (CSF) is potentially a source of biomarkers since it is in direct contact with the central nervous system and therefore may contain biomarkers indicating neurodegeneration or damage to the brain and spinal cord. However, since the abundance of miRNAs in CSF is low, their isolation and detection is technically difficult. In this review, we evaluate the findings of recent studies of CSF miRNAs as biomarkers of spinal cord injury (SCI) and neurodegenerative diseases. We also summarize the current knowledge concerning the methods of studying miRNA in CSF, including RNA isolation and normalization of the data, highlighting the caveats of these approaches and possible solutions. [ABSTRACT FROM AUTHOR]

This article discusses the atomization of composite liquid fuels. A large group of injectors is considered. A comparative analysis of the atomization characteristics (droplet sizes and velocities, jet opening angles) and the influence of the fuel characteristics (density, viscosity, component composition) and the process parameters (the ratio of the fuel–air mass flow rates, the features of the jet formation) has been carried out. Finally, the most effective types of injectors, which provide for the necessary characteristics of fuel atomization for its combustion, have been determined. The most favorable conditions for the applicability of each type of atomization have been formulated. Possible mechanisms of secondary fragmentation of droplets of composite fuels have been analyzed: those resulting from mutual collisions of droplets in the flux and from the interaction with a solid surface as well as those resulting from thermal overheating in the presence of a phase boundary or a large gradient of component volatility. A conclusion is made about the need of using a synergistic effect of primary and secondary atomization of fuel suspension droplets. [ABSTRACT FROM AUTHOR]

Abstract: Diffusion properties of carbon dioxide-expanded toluene in bulk and confined to nanoporous glasses have been assessed using pulsed field gradient technique of NMR. In the bulk phase the diffusivity of toluene is found to increase significantly with increasing carbon dioxide content. The same dependence is observed in the mesoporous glass with large pore size, but with lower absolute values resulting from the tortuosity of the porous matrix. In contrast, in the porous glass with small pore size, strong confinements lead to different behavior due to an altered equilibrium phase composition in the pore space affecting the mass transfer rates. [Copyright &y& Elsevier]

Abstract: The pulsed field gradient technique of NMR (PFG NMR) is applied for exploring molecular diffusion in different specimens of zeolite NaCaA, notably in samples containing “hierarchical” pore systems where the micropores are traversed by mesopores. Choosing ethane (capable of permeating both micro- and mesopores) and cyclohexane (unable to penetrate the micropores) as guest molecules and varying purposefully the accessibility and mobility in the mesopores by temperature variation and pore blocking, the diffusivities in the two pore spaces are measured separately from each other. It is shown that the presence of the mesopores may give rise to dramatically enhanced intracrystalline diffusivities while a blockage of the mesopores reduces the intracrystalline diffusivities by an order of magnitude. [Copyright &y& Elsevier]

Possible orbits for the motion of a region in the gravitational field of the central body of the galaxy NGC 4151 are presented. The region is manifest through its line emission, observed in the red wing of the H α, P β, and other broad lines. We carried out a computer selection of all Keplerian orbits for which the measured radial velocities of the emission-line region could be observed. We used radial-velocity data obtained by us at the Fesenkov Astrophysical Institute, as well as data from the literature. The computation results can be used to determine the mass range for the central body of NGC 4151 that provides the best agreement with the observational data: (61-65)× 10 M. Suitably designed monitoring of active galactic nuclei can be used to verify these results, and to carry out similar analyses for other Seyfert galaxies. [ABSTRACT FROM AUTHOR]

Abstract: Pulsed field gradient NMR has been applied to investigate water diffusion in Na+-form zeolites beta and LTA if, in addition to the micropores, the intracrystalline space is traversed by a network of mesopores. In zeolite beta, the presence of the mesopores is found to enhance the rate of molecular diffusion by a factor of 3. The measurements with mesoporous zeolite LTA yield diffusivities which reproduce the order of magnitude of the diffusivities found in previous studies with genuine microporous specimens. [Copyright &y& Elsevier]

The distributions of phase saturations, pressure, and temperature in a porous medium of nonuniform permeability are studied by numerical modeling of nonisothermal two-phase filtration of oil and water with the Joule-Thomson effect and adiabatic effect taken into account. It is shown that the presence of nonuniformity in the near-well zone of the reservoir results in nonmonotonic angular and radial distributions of temperature and phase saturations. During oil and water filtration, there is transition from negative to positive temperature anomalies or vice versa, depending on the ratio of the reservoir permeabilities and the presence of a segment on which the angular temperature distribution in the well is nonuniform. [ABSTRACT FROM AUTHOR]

The results of studying the pore size distribution of mesoporous silicon by NMR cryoporosimetry are described. These data are compared with the results obtained by adsorption methods. [ABSTRACT FROM AUTHOR]

Abstract: Resistometry and electron microscopy were used to study Ni65Al35 and Ni56Al34Co10 (at.%) alloys prepared by the method of accelerated melt spinning. Ribbon samples were studied during and after different heating–cooling cycles or different isothermal holding conditions at temperatures of up to 780°C. A method was proposed for improvement of the heat resistance of the supersaturated β solid solution and stabilization of the reversibility of the high-temperature martensitic transformation in alloys of the Ni–Al system. This method consists in a partial replacement of nickel by cobalt, accelerated melt spinning, and short-time stabilization annealing in the low-temperature range of the B2 austenite. [Copyright &y& Elsevier]

Abstract: We record the probability distribution of molecular displacements (i.e., the distribution of the lengths of the diffusion paths) of guest molecules in nanostructured SBA-15 silica by means of pulsed field gradient (PFG) NMR. Two different morphologies of SBA-15 were studied, namely isolated fibers and bundles. The guest molecules (nitrobenzene) are applied in excess so that, by measurement below the bulk freezing point but above the freezing point in the nanopores, the space between the host particles becomes inaccessible for notable mass transfer, and the range of molecular displacements, as observed in the experiments, is determined by the nanopores and the shape of the individual particles. The measurements clearly reflect the 1-D channel architecture of SBA-15. Over the displacements traced in the experiment (5μm) there is a distinct difference in the time dependence of the coefficients characterizing diffusion anisotropy. Diffusion measurements with the isolated fibers (embedded in the frozen guest phase surrounding the host particles) reveal increasing transport resistance with increasing observation time, acting both parallel and perpendicular to the channel direction. By contrast, in the bundles diffusivity in the channel direction remains constant while the rate of displacements perpendicular to this direction increases. These dependencies may be rationalized by the different sample morphologies. [Copyright &y& Elsevier]

Abstract   In this contribution, we review the results of our experimental studies on diffusion of guest molecules in mesoporous solids using pulsed field gradient (PFG) NMR technique. Having unique potentials to non-invasively probe the microscopic diffusion processes in pores, this method may provide quintessential information on the character of molecular propagation for different pore morphologies and fluid phase state. In particular, different modes of molecular diffusion in partially filled pores may be separately probed and the overall diffusion process could be analyzed taking account of the details of the inter-phase coexistence. In addition to the dynamic properties, some information concerning the distribution of guest molecules within the porous matrix may also be obtained. [ABSTRACT FROM AUTHOR]

Abstract   Supercritical fluids are an essential constitute of modern chemical industry. However, their optimal use in processes involving porous solids is rather limited due to our poor knowledge about their transport properties under confinements. By using the non-invasive pulsed field gradient NMR method, we directly assessed molecular diffusivities of n-pentane in mesopores at sub- and supercritical temperatures. The obtained results ultimately point out that criticality in pores occurs at lower temperatures than in the bulk liquid surrounding the porous solid. The data on molecular diffusivities and pore density may be self-consistently quantified using simple gas-kinetic arguments. [ABSTRACT FROM AUTHOR]