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[en] The fundamentals of the theory of formation of surface complexes (or the surface complexation theory, SCT), which is used in processing the results of studies on the equilibria in multicomponent ion exchange sorption systems, are outlined. The advantage of the theory is the use of the sorption characteristics of binary ion exchange systems for the description and calculation of multicomponent equilibria with allowance for the medium pH value. The solutions to some problems of nonlinear sorption dynamics theory obtained using the description of multicomponent equilibria in the framework of the SCT model are considered. Experimental data on the concentration distributions of components in frontal and displacement chromatograms are compared with the results of corresponding numerical calculations using various sets of parameters of the SCT model (including versions with allowance for the effect of complexation reactions in the mobile phase).
[en] Repetitive plasma discharges developed in saline solutions have been investigated using fast, intensified charge coupled detector imaging techniques. The images show that synchronously pulsed multielectrode configurations tend to develop intense, transient plasma regions somewhat randomly in both space and time on short (10 μs) time scales, even though they appear to be stationary on longer (tens of milliseconds) time scales. Evidence for the production of both strongly ionized and weakly ionized plasmas is also presented
[en] Modern trends in studies of solutions of surfactant mixtures are discussed. The emphasis is placed on thermodynamic and molecular-statistical modelling of the phase behaviour and self-assembly patterns. The methods for prediction of properties of mixed micellar solutions based on the data for solutions of individual surfactants and the methods for calculation of the size, shape and composition distribution of micelles using the quasichemical models that take into account the molecular characteristics of components are analysed. Recent studies of surfactant solutions using computer experiments are surveyed. Theoretical approaches to the description of self-assembly phenomena in solutions of amphiphilic polymers and of their mixtures with low-molecular-mass surfactants are discussed.
[en] Physical and chemical methods for the synthesis of nanoparticles of complex organic compounds (mechanical grinding, laser ablation, solvent replacement, reduction in solution, ion association, etc.) are analyzed. Emphasis is placed on a method that employs supercritical fluids and on cryochemical synthesis. Physicochemical properties of nanoparticles of organic compounds and the prospects of their use are considered.
[en] Thermo-dependence of electrodiffusional measurements of wall velocity gradient has been studied in a fully developed turbulent channel flow. In isothermal conditions, the direct thermo-compensation can be provided using the measurements of thermo-dependence of molecular diffusivity and viscosity. The simultaneous transient and steady-state limiting diffusion current measurements open the possibility for in situ compensation of thermal effects in electrodiffusional flow diagnostics at non-isothermal conditions where the local temperature gradients are presented. The feasibility of the proposed method of thermo-compensation has been confirmed experimentally for the case of local heating of the solution by means of pulse hot-wire technique
[en] Gas discharge initiation of chemical processes in electrolyte solutions is considered. Data on the types of chemical transformations in plasma-solution systems are presented. The processes of generation of primary reactive species in solutions under gas discharge and the key routes for their further reactions are analysed. The prospects for practical application of plasma-solution systems in solving technological and environmental problems are considered.
[en] The crystal structure of phenolic acid decarboxylase from B. pumilus strain UI-670 has been determined and refined at 1.69 Å resolution. The enzyme is a dimer, with each subunit adopting a β-barrel structure belonging to the lipocalin fold. The decarboxylation of phenolic acids, including ferulic and p-coumaric acids, to their corresponding vinyl derivatives is of importance in the flavouring and polymer industries. Here, the crystal structure of phenolic acid decarboxylase (PAD) from Bacillus pumilus strain UI-670 is reported. The enzyme is a 161-residue polypeptide that forms dimers both in the crystal and in solution. The structure of PAD as determined by X-ray crystallography revealed a β-barrel structure and two α-helices, with a cleft formed at one edge of the barrel. The PAD structure resembles those of the lipocalin-fold proteins, which often bind hydrophobic ligands. Superposition of structurally related proteins bound to their cognate ligands shows that they and PAD bind their ligands in a conserved location within the β-barrel. Analysis of the residue-conservation pattern for PAD-related sequences mapped onto the PAD structure reveals that the conservation mainly includes residues found within the hydrophobic core of the protein, defining a common lipocalin-like fold for this enzyme family. A narrow cleft containing several conserved amino acids was observed as a structural feature and a potential ligand-binding site
[en] Understanding of spatial and temporal behaviour of interacting species or reactants in ecological or chemical systems has become a central issue, and rigorously determining the formation of patterns in models from various mechanisms is of particular interest to applied mathematicians. In this paper, we study a bimolecular autocatalytic reaction–diffusion model with saturation law and are mainly concerned with the corresponding steady-state problem subject to the homogeneous Neumann boundary condition. In particular, we derive some results for the existence and non-existence of non-constant stationary solutions when the diffusion rate of a certain reactant is large or small. The existence of non-constant stationary solutions implies the possibility of pattern formation in this system. Our theoretical analysis shows that the diffusion rate of this reactant and the size of the reactor play decisive roles in leading to the formation of stationary patterns
[en] Adaptive dampers are an interesting solution for conjugating the necessity of controllable devices and low power consumption. Magneto-rheological fluids (MRF) can be profitably employed in adaptive dampers because of the significant variation of fluid parameters with magnetic field properties. This paper focuses on the design process of an innovative rotational MR damper specifically created to be placed in the front-wheel suspension of a compact car. The advantages of the rotational damper and the definition of the optimal design are described. The proposed damper significantly reduces several key problems associated with MR devices: the quantity of fluid required, the sedimentation of ferromagnetic particles in the suspension and the abrasion of the seals. In fact, with this solution, low average working pressure, low flow velocity through valves, a wide range of variable damping characteristics, and high durability of the damper can be achieved. Thanks to this innovative component, different new architectures for adaptive suspension systems can be developed to have a planar distribution of the suspension components with a consequent space optimization and size reduction in the vertical direction