The behavior of brucite over wide ranges of temperatures and pressures is of great interest for fundamental geochemistry and geophysics. Brucite layers and their octahedral Mg(OH)6 structural units ...constitute an important structural part of layered dense magnesium hydrous silicates (DMHS), which play a major role in mineral equilibria controlling water balance in the subduction zones of the upper mantle. The ClayFF force field was originally developed for atomistic computer simulations of clays and other layered minerals and their hydrated interfaces. The crystallographic parameters of brucite at 25 °C and 1 bar were used, among several others, to develop the original ClayFF parametrization. Its new recent modification, ClayFF-MOH, can more accurately account for the bending of Mg–O–H angles in the brucite structure, and it was used here to test the applicability of this simple classical model over very wide ranges of temperature and pressure well beyond the range of its original implementation (up to 600 °C and 15 GPa). The pressure and temperature dependencies of brucite crystallographic parameters, the compressibility of the crystal lattice, the coefficients of thermal expansion, and the vibrational spectra were calculated in a series of classical molecular dynamics simulations using the ClayFF-MOH model and compared with a diverse set of available experimental data, including X-ray diffractometry, neutron scattering, IR and Raman spectroscopy. These new results demonstrated that ClayFF-MOH, as simple and approximate as it is, can be quite accurate in predicting many mineral properties at subduction zone conditions, which greatly expands the area of its applicability.
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CEKLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Viscosity and slip behavior of n-pentane in clay slit pores are studied.•Viscosity-density dependency is almost the same in 3–7 nm pores as in bulk liquid.•Slip length walls is ∼0.3nm at ...non-hydrated walls, no slip is observed at hydrated walls.•The ordering of molecules is stronger in pores with non-hydrated walls.
Shear flow of n-pentane in slit nanopores between clay surfaces is investigated by molecular dynamics simulations. Pyrophyllite and hydrated Na-montmorillonite are considered as representative examples of hydrophobic and hydrophilic clay surfaces, respectively. The viscosity-density relations and slip lengths are calculated for both pentane-clay interfaces for different pore widths. The results show that the viscosity-density dependencies for n-pentane are not changed by the confinement in pores with sizes from 3 to 7nm, compared to the bulk liquid. At the pyrophyllite-pentane interface the slip length is 0.29nm on average for all studied densities and pore sizes. However, the slip length is negligible at the montmorillonite-pentane interface, likely due to the microscopic roughness of the interface between pentane and the adsorbed water layer. The orientation analysis shows some preference for pentane molecules ordering parallel to the wall surfaces, which is stronger in pyrophyllite pores compared to the montmorillonite, suggesting an influence of the details of fluid-wall interaction on the liquid structure in nanopores.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
p50, the major core protein bound to mammalian mRNAs, has been reported to stimulate translation at low p50/mRNA ratios and
inhibit translation at high p50/mRNA ratios. This study aims to address the ...molecular mechanisms underlying these phenomena
using the in vitro assembly of 48 S preinitiation complexes from fully purified translational components in the presence or absence of p50 as
analyzed by the toeprint assay. With limited concentrations of eIF2, eIF3, and eIF4F, p50 (but not pyrimidine tract-binding
protein, which was taken for comparison) strongly stimulates formation of the 48 S preinitiation complexes with β-globin mRNA.
This stimulation is observed when just a few molecules of p50 are bound per molecule of the mRNA. When the amount of p50 in
solution is increased over some threshold p50/mRNA ratio, a remarkable repression is observed that can still be relieved by
adding more eIF2 and eIF4F. At even higher concentrations of p50, the inhibitory effect becomes irreversible. The threshold
ratio depends upon the extent of secondary structure of the 5â²-untranslated region linked to the β-globin coding region. Chemical
probing has confirmed that the binding of p50 to mRNA involves only the sugar-phosphate backbone of the mRNA leaving nucleotide
bases free for interaction with other messenger ribonucleoprotein (mRNP) components. These data are best compatible with the
functional role of p50 as a âmanagerâ of mRNA-protein interactions in mammalian mRNPs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The process of Couette flow of a hydrocarbon liquid in the slit pores has been simulated and the dynamics of the liquid molecules ordering depending on the liquid density and the slit size has been ...investigated by means of molecular dynamics. Statistical analysis of the resulting regions of ordered molecules of the hydrocarbon fluid has indicates that the wall material and the liquid viscosity affect the size of such regions.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Structured cartridges on the base of glass-fiber catalysts (GFC) are considered.•GFC structures show highest mass transfer intensity among all known catalysts.•GFCs demonstrate the ...best ratio between apparent activity and pressure drop.•Procedure for mass transfer coefficients calculation in various GFCs proposed.•Structured GFCs are especially advantageous for fast catalytic reaction.
Manuscript is dedicated to the cartridges on the base of micro-fibrous catalysts. Under the strong influence of external diffusion limitations, the structured cartridges with glass-fiber catalysts (GFC) demonstrate the performance at least not worse than that of the most efficient types of conventional catalysts in volumetric apparent activity, significantly exceeding them in apparent reaction rate per unit mass of the active component or per unit pressure drop, making the GFCs one of the most efficient shapes among all existing catalytic structures. The newly proposed lemniscate-shaped GFCs demonstrate the best performance among all studied systems. The intrinsic kinetics, internal and external mass transfer intensity were studied using the model reaction of toluene deep oxidation in air at Pt-containing GFC. The elaborated criterial equation provides calculation of the external mass transfer coefficient in such catalysts with acceptable accuracy. Mass transfer enhancement in GFC cartridges is explained by flexibility of fibrous supports, resulting in the change of their shape and increase of their effective external area under the influence of the moving reaction fluid. Such systems look promising for application in fast catalytic reactions, occurring under strong influence of diffusion limitations in gas, liquid and multiphase media.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Modified version of the crack compliance method is used for determination of stress intensity factor (SIF) related to narrow notches emanating from cold-expanded holes. These notches are inserted at ...different stages of low-cycle fatigue under constant external load. It is shown how residual SIF values, generated by residual stress field influence, can be separated from total experimental SIF values. Residual SIF values, obtained at different stage of low-cycle fatigue with the same stress range Δσ = 350 MPa but different stress R = –0.4 and R = –1.0, provide quantitative description of residual stress evolution near cold-expanded hole. It shown that maximal residual stress relaxation of order 20 per cent occurs at 95 lifetime per cent for both loading programs.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Fundamentals of operation of an optical fiber piezoelectroluminescent (PEL) sensor inside a polymer composite structure at its cyclic loading are considered. The optical fiber PEL-sensor is ...considered as part of the composite/sensor electromechanical system taking into account the presence of anisotropy, piezoactivity and Maxwell-Wagner relaxation of the electric fields of the sensor elements. The purpose of the optical fiber PEL-sensor is to diagnose the inhomogeneous complex volumetric deformed state of a long cylindrical area (a neighborhood along the built-in linear sensor) inside a cyclically loaded composite structure. A numerical model has been developed to solve the 3D related boundary value problem of electric elasticity for a representative fragment of the system composite/sensor in the ANSYS package. The numerical modeling of deformation and electric harmonic fields inside the representative fragment was carried out; in particular, distributions of amplitudes of these fields in elements of the structure of the optical fiber PEL sensor were found. The resonant modes are revealed, and the analysis is given of regularities of frequency dependences for the real and imaginary parts of controlling and informative transfer coefficients of the built-in fiber-optic PEL-sensor in the composite/sensor system. Additionally, graphs of frequency dependencies of tangents of mechanical loss angles for various cases of deformation of the composite/sensor system are given. Damping of the composite/sensor system is carried out as a result of the conversion of some part of the mechanical energy (transmitted from the composite to the sensor during their joint deformation) into Joule heat by the fiber-optic PEL sensor with a subsequent dispersion. The latter is caused by the direct piezoelectric effect and Maxwell-Wagner relaxation of electric fields in the sensor elements. The frequency range of deformation of the composite/sensor system is set, in which the passive vibration damping mode is most effectively implemented. It is numerically confirmed that for the extreme high-frequency case of deformation of the composite/sensor system, relaxation processes are not implemented and, as a result, solutions for the controlling and informative transfer coefficients of the PEL-sensor practically coincide with previously obtained numerical solutions that did not take into account the electrical conductivity of the sensor structure elements.
We developed a three-dimensional numerical model of a piezoelectric luminescent optical fiber sensor fixed on a composite’s plate. The computational region of the sensor is the optical fiber with two ...concentric (with 6 sectors) shells of electroluminescent and piezoelectric materials, two control electrodes on interface surfaces, such as optical fiber-electroluminophore and piezoelectric-cover. The external sensor’s cover is made in the form of a semi-elliptic cylindrical polymer shell, which rectangular base is fixed on the surface of the fiberglass plate. In the piezoelectric shell sectors, the polarization directions of the PVDF transversal-isotropic polymer piezoelectric are different and non-planar for any three sectors. Deformation of the plate causes deformation of the sensor fixed on its surface, as well as the occurrence of informative piezoelectric fields in it, thus the occurrence of informative glows of electroluminescent elements. As a result, we find the requested information about the combined deformed state of the composite plate along the length of the sensor based on the digital processing of the integral intensities of the polychrome light signals at the output of the optical fiber. In simple cases of electric and mechanical loads, we present new numerical results of simulating the distribution of non-uniform electroelastic fields in the sensor multiphase volume, the sensor’s external cover and inside fragment of the composite plate. Loading of the sensor-covering-plate system is performed by controlling electric voltage on the sensor’s electrodes and the plate’s mechanical deformation by stretching along the transverse and longitudinal axes, as well as by twisting around these axes and bending in transverse and longitudinal planes. Numerical values of the control and informative transfer coefficients of the piezoelectric luminescent optical fiber sensor are determined, which makes it possible to perform a reliable and high-precision diagnostics of complex deformations of the composite plates and design sensors of this type.
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