Results 1 - 10 of 39847
Results 1 - 10 of 39847. Search took: 0.043 seconds
|Sort by: date | relevance|
[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] We present the general theory and implementation of the Conductor-like Screening Model according to the recently developed ddCOSMO paradigm. The various quantities needed to apply ddCOSMO at different levels of theory, including quantum mechanical descriptions, are discussed in detail, with a particular focus on how to compute the integrals needed to evaluate the ddCOSMO solvation energy and its derivatives. The overall computational cost of a ddCOSMO computation is then analyzed and decomposed in the various steps: the different relative weights of such contributions are then discussed for both ddCOSMO and the fastest available alternative discretization to the COSMO equations. Finally, the scaling of the cost of the various steps with respect to the size of the solute is analyzed and discussed, showing how ddCOSMO opens significantly new possibilities when cheap or hybrid molecular mechanics/quantum mechanics methods are used to describe the solute
[en] We investigated the interaction between polyynes (linear carbon chains) and various metal nanoparticles (Ag, Au, and Cu) to provide insight into the optical properties of metal-polyynes systems prepared by different experimental techniques. Polyynes were produced by laser ablation in deionized water, metal nanoparticles solutions, and copper chloride solution. Metal nanoparticles complexes with polyynes were analyzed by Raman, surface-enhanced Raman scattering, and UV-vis spectroscopy
[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] 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] 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