Results 1 - 10 of 37087
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[en] Classification and analysis of pipelines and pipeline fittings according to the material of their fabrication and sphere of application used during hydrotransportation of solid loose materials through pipelines have been considered. (author)
[en] The effect the initial structure of a two-component reaction powder mixture has on the dynamics of its isothermal homogenization is investigated. Relations for determining the duration of homogenization are obtained. A technique for calculating kinetic parameters is proposed.
[en] Highlights: → Irreversible thermodynamics establishes form of multicomponent diffusion coefficients. → Phenomenological coefficients and thermodynamic factors affect sign of diffusion coefficients. → Negative diagonal elements of diffusion coefficients matrix can occur in non-ideal mixtures. → Eigenvalues of the matrix of Fickian diffusion coefficients may not be all real. - Abstract: The form of multicomponent Fickian diffusion coefficients matrix in thermodynamically stable mixtures is established based on the form of phenomenological coefficients and thermodynamic factors. While phenomenological coefficients form a symmetric positive definite matrix, the determinant of thermodynamic factors matrix is positive. As a result, the Fickian diffusion coefficients matrix has a positive determinant, but its elements - including diagonal elements - can be negative. Comprehensive survey of reported diffusion coefficients data for ternary and quaternary mixtures, confirms that invariably the determinant of the Fickian diffusion coefficients matrix is positive.
[en] A model based on experimentally determined potentials and peak height and half-width components was suggested for voltammetric peaks. The possibility of mathematical describing both individual voltammetric signals of Tl(1) and Cd(2) and signals in the simulation of outlines for mixtures and in an analysis of experimentally found curves was demonstrated
[en] Characteristic features of the synthesis of molecularly imprinted polymer systems used as sorbents for separation of complex mixtures into components are discussed. The data about the molecules imprinted in monoliths of various natures and shapes are integrated. Examples of application of new-generation separating media are discussed. Data on the utilization of the molecular imprinting principle for the fabrication of supermacroporous monolithic cryogels specific to particular molecules, which is important for the design of smart biomaterials, are analyzed. The bibliography includes 293 references
[en] A process is described for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached
[en] Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed
[en] The structure of colloidal crystals, determined by scattering methods, is discussed. Charge-stabilized particles are considered briefly. The phase behaviour and crystal structures of 'hard-sphere' sterically-stabilized particles are described in more detail. Both one-component suspensions and binary mixtures of different-sized spheres are considered. (author). 9 refs.; 2 figs
[en] We consider the most feasible ways to significantly improve the sensitivity of spectroscopic methods for detection and measurement of trace concentrations of greenhouse gas molecules in the atmosphere. The proposed methods are based on combining light fluxes from a number of spectral components of the specified molecule on the same photodetector, taking into account the characteristic features of the transmission spectrum of devices utilizing multipath interference effects.