Modeling of interface phenomena in liquid under vibration, using the chemical model

An analysis of interface phenomena in a liquid under a vibration field is presented, based on the chemical model of vibration in a liquid. The objects studied are a bubble, a solid surface, and a linear macromolecule, in a vibrated liquid. It is concluded that many sonochemical phenomena can be realized in some different (two or more) mechanisms, and mutually stimulate. Inharmonic effects and the influence of distant neighbors are analyzed.     

Prediction of multicomponent liquid adsorption using excess quantities. II. Calculations for the liquid/solid interface

The utilization of excess quantities as the basis for a thermodynamic approach can simplify the prediction of multicomponent liquid adsorption from binary data. A new method for predicting liquid adsorption on solids is suggested, which is different from the existing equations with respect to the theoretical background and formulation. The applicability of the new model is tested with three ternary adsorption systems. The predicted surface excesses are discussed and compared with experimental ones and with those of other prediction models in the literature. The accordance between measured and predicted ternary data is convincing.     

A theoretical model for bubble formation during horizontal gas injection into liquid flow in vertical tubes

Bubble formation in flowing liquid is an important process for wastewater treatment, processing of molten metals, and biological processes. Based on a global balance of force on the bubble, this report describes a new theoretical model for bubble formation during horizontal gas injection into turbulent liquid flow in a vertical tube. This work highlights the importance of choosing the correct drag law in accordance with the bubble size. Five models for drag coefficient are compared, and of these, model III is recommended. Modified detachment criteria are applicable, depending on the liquid velocity. The new analytical model yields good predictions compared with experimental data. Based on the theoretical model, this study investigates the effects of the direction of liquid flow, liquid velocity, gas velocity, and orifice diameter on the bubble formation behavior.     

Wetting–dewetting films: The role of structural forces

The liquid wetting and dewetting of solids are ubiquitous phenomena that occur in everyday life. Understanding the nature of these phenomena is beneficial for research and technological applications. However, despite their importance, the phenomena are still not well understood because of the nature of the substrate's surface energy non-ideality and dynamics. This paper illustrates the mechanisms and applications of liquid wetting and dewetting on hydrophilic and hydrophobic substrates. We discuss the classical understanding and application of wetting and film stability criteria based on the Frumkin–Derjaguin disjoining pressure model. The roles of the film critical thickness and capillary pressure on the film instability based on the disjoining pressure isotherm are elucidated, as are the criteria for stable and unstable wet films. We consider the film area in the model for the film stability and the applicable experiments. This paper also addresses the two classic film instability mechanisms for suspended liquid films based on the conditions of the free energy criteria originally proposed by de Vries (nucleation hole formation) and Vrij–Scheludko (capillary waves vs. van der Waals forces) that were later adapted to explain dewetting. We include a discussion of the mechanisms of nanofilm wetting and dewetting on a solid substrate based on nanoparticles' tendency to form a 2D layer and 2D inlayer in the film under the wetting film's surface confinement. We also present our view on the future of wetting–dewetting modeling and its applications in developing emerging technologies. We believe the review and analysis presented here will benefit the current and future understanding of the wetting–dewetting phenomena, as well as aid in the development of novel products and technologies.     

Solvent Effect on Characteristic Vibration of IR Spectrum of 4,4'-Dibromodiphenyl Ether

The optimal geometry, IR spectrum and vibration assignment of 4,4＇-dibromodiphenyl ether（BDE-15） in gas phase were calculated via the density functional theory（DFT） at the level of B3LYP/6-3 l＋G（d）. Based on the vi- bration assignment, the calculation of vibration frequencies and intensities of 5 main vibration types of BDE-15 in 25 kinds of solvents was carried out by means of a self-consistent reaction field（SCRF） theoretical model at the level of B3LYP/6-31＋G（d） to analyze the solvent effect on the vibration of IR spectrum of BDE-15. To study the solvent ef- fect further, C--O asymmetric stretching vibration fluctuating, which is relatively acute in both vibration frequency and intensity, was selected as the characteristic vibration to establish different linear solvation energy relation（LSER） models for solvent categoring. Solvent parameters（a, /3, ~r＊）, acceptable number（AN） and quantitative structure- activity relationship（QSAR） models were established via chemical quantum parameters of solvent moleculer, which were first been introduced to investigate different solvent-solute interaction mechanisms in alcoholic and non-alcoholic solvents on molecular level. At last, a single solvent molecule was embedded in the framework of po- larizable continuum model（PCM） to validate the effect of hydrogen bonding on solvent-solute interaction in alcohol solvents. The obtained results show that 5 main vibration types of BDE-15 in different solvents have small variation range in frequency and intensity and all the vibration frequencies in solvents are lower than those in gas phase, de- creasing along with the increasing of the dielectric Constant（e） of solvents exponentially. In contrast, all the vibration intensities in solvents are greater than those in gas phase and present positive exponential trend. Twenty-five solvents were divided into two categories（non-alcoholic solvents and alcoholic solvents） by LSER. The CmO asymmetric stretching vibration was mainly reg     

Equilibrium contact angles of liquid droplets on ideal rough solids

This work proposes a theoretical model for predicting the apparent equilibrium contact angle of a liquid on an ideal rough surface that is homogeneous and has a negligible body force, line tension, or contact angle hysteresis between solid and liquid. The model is derived from the conservation equations and the free-energy minimization theory for the changes of state of liquid droplets. The work of adhesion is expressed as the contact angles in the wetting process of the liquid droplets. Equilibrium contact angles of liquid droplets for rough surfaces are expressed as functions of the area ratios for the solid, liquid, and surrounding gas and the roughness ratio and wetting ratio of the liquid on the solid for the partially and fully wet states. It is found that the ideal critical angle for accentuating the contact angles by the surface roughness is 48°. The present model is compared with existing experimental data and the classical Wenzel and Cassie-Baxter models and agrees with most of the experimental data for various surfaces and liquids better than does the Wenzel model and accounts for trends that the Wenzel model cannot explain.     

Cellular automata models of chemical systems

This paper describes the use of kinematic, asynchronous, stochastic cellular automata to model liquid properties, solution phenomena and kinetic phenomena encountered in complex biological systems. Cellular automata models of dynamic phenomena represent in silico experiments designed to assess the effects of competing factors on the physical and chemical properties of solutions and other complex systems. Specific applications include solution behavior, separation of immiscible liquids, micelle formation, diffusion, membrane passage, first- and second-order chemical kinetics, enzyme activity and acid dissociation. Cellular automata is thus considered as providing an exploratory method for the analysis of dynamic phenomena and the discovery and understanding of new, unexpected phenomena.     

A complete nearest-neighbor force field model for C60

A force field model is developed for C(60) that features 13 force constants representing all interactions between nearest-neighboring atoms. The model is compared with, and tested against, other force field models in the literature. Force constants for C(60) are then deduced by fitting the model to the 14 known optically accessible vibrational frequencies of the molecule. Finally, the model is fitted to two existing theoretical calculations of the complete vibrational spectrum of C(60). Fair agreement is obtained with the theoretical calculations, implying that interactions with atoms other than nearest neighbors are small.     

Evaluation of Calculating the Isotonic Swelling Ratio of Emulsion Liquid Membrane by Theoretical Viscosity Models

In this study, two viscous models, the Choi‐Schwalter and Phan‐Thien‐Pham models, are used to calculate the isotonic swelling ratio of emulsion liquid membrane. The purpose is to evaluate the usefulness of calculating isotonic swelling ratios of emulsion liquid membranes by viscous models through comparing theoretical isotonic swelling ratios with experimental swelling ratios of three kinds of emulsion liquid membranes. Comparison between theoretical swelling ratios and experimental swelling ratios indicates that experimental swelling ratios are close to those calculated by the Choi‐Schwalter model, but lower than those calculated by the Phan‐Thien‐Pham viscous model. But modified Phan‐Thien‐Pham viscous models predicts reasonable values. Therefore, the method of calculating the isotonic swelling ratio of emulsion liquid membrane by theoretical viscosity models is promising.     

Cellular Automata Models of Chemical Systems

Abstract

This paper describes the use of kinematic, asynchronous, stochastic cellular automata to model liquid properties, solution phenomena and kinetic phenomena encountered in complex biological systems. Cellular automata models of dynamic phenomena represent in silico experiments designed to assess the effects of competing factors on the physical and chemical properties of solutions and other complex systems. Specific applications include solution behavior, separation of immiscible liquids, micelle formation, diffusion, membrane passage, first- and second-order chemical kinetics, enzyme activity and acid dissociation. Cellular automata is thus considered as providing an exploratory method for the analysis of dynamic phenomena and the discovery and understanding of new, unexpected phenomena.     

Modeling of neutron activation process with Americium Beryllium source. Application to the activation of fluorspar samples

This paper shows the mathematical models which represent the phenomena that occur in a neutron activation process. These phenomena are, on the one hand, the neutron flux decreases with the distance between the neutron source and the sample, and on the other hand, the attenuation of the gamma rays originating from the sample activated on its way to the detector position. The development of the mathematical model has been divided into two parts. Firstly, the phenomena are shown separately. Secondly, the phenomena are shown together. Finally, this model is fitted to the neutron activation of a fluorspar sample, and the influence of the two phenomena as defined above can be seen.     

The vibrational group frequency of the N-O* stretching band of nitroxide stable free radicals

The group frequency of the N-O radical stretching vibration has received scant attention in the literature. The few existing treatments of the vibrational spectroscopy of nitroxides are incomplete at best and potentially misleading to workers in the field. To close this gap in the available knowledge, the existing literature on the vibrational spectra of nitroxide stable free radicals is critically reviewed with particular reference to the wavenumber position of the N-O stretching vibration, nu(N-O). Poor evidentiary bases for the assignment nu(N-O) were found in many instances. Ab initio Density Field Theory calculations using a model chemistry of UB3LYP at the 6-311++G(d,p) level were performed to obtain a theoretical band position of nu(N-O) for comparison with the published data. Large discrepancies between the theoretical and experimental values were found for the radical 3-carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxyl, which currently sets the lower limit of the accepted wavenumber range of nu(N-O), as well as for the nitronyl and iminyl nitroxides. The wavenumber position of nu(N-O) was found to occur in the range 1450-1420cm(-1) for 5-membered cyclic nitroxides and 1395-1340cm(-1) for 6-membered cyclic and acyclic nitroxides. In nitronyl nitroxides, the symmetric stretching vibration occurs in the region 1470cm(-1), but coupling to other modes makes specific band assignments problematic for the nitronyl nitroxide group.     

Polymer Alloys—Their Structure,Morphology, and Properties

Polymeric materials with novel properties for new technological applications are increasingly obtained by combining existing polymers, while the synthesis of new monomers has receded into the background. These polymer combinations or “alloys” (polyblends) are characterized by their chemical composition, the conformation of the chain molecules, and the morphology, i.e. the state of order at supramolecular level. Multiphase constitution is a typical characteristic of these substances, with a decisive influence on their macroscopic properties. The morphology of multiphase polymer alloys can be controlled to a limited extent via the chemical composition of their components when homopolymers are mixed in the melt or as dispersions. Graft copolymerization, on the other hand, makes it possible to achieve the desired morphology at a given chemical composition. Furthermore, transprent two-phase polymer alloys can be obtained under certain conditions. In multiphase polymers the reduction of stress without fracture, caused by mechanical loading will be treated using models. Certain combinations of properties such as hardness and toughness are connected with the coexistence of disperse and continuous phases. Equilibrium thermodynamical criteria for liquid mixtures wil be used to explain demixing phenomena in polymers. In the last few years it has become possible to determine the chain conformation experimentally using neutron scattering.     

Non-equilibrium electric surface phenomena

Non-equilibrium aspects of traditional electrokinetic phenomena (electrophoresis, electroosmosis, streaming potential, sedimentation potential), electrostatic interaction of particles and new electrokinetic phenomena are considered. The significance of non-equilibrium electric surface phenomena for many major areas of modern colloid science (characterization of colloids, membrane science, transport phenomena and separation, particle interaction and coagulation) is established.The study of non-equilibrium electric surface phenomena is connected with the validation of the standard electrokinetic model (SEM), the development of a non-standard model and the development of an extensive programme of disperse system characterization based on integrated electrokinetic investigations. Experimental and theoretical studies of systems with a smooth, non-porous impermeable surface (mica in Anderson's experiments, and quartz microcapillaries with a molecule-smooth surface in Churaev's experiments) have shown that usually there are no significant difficulties in interpreting electrokinetic investigations despite the possible anomaly in the water structure near the surface and the possibility of maximum shear stress (yield stress), i.e. the anomalous viscosity and decreased dissolving power with respect to ions. However, systems which do not satisfy the conditions of the SEM are widely distributed, owing to the porosity, roughness or permeability of the boundary layer of the surface of the solid body which simultaneously belongs to the solid and liquid phases. In this layer, enclosed between the outer Helmholtz plane and the slipping plane, the motion of the liquid strongly slows down and the tangential flow of ions is characterized purely by the mobility which is close to the normal. Thus, a general property of a non-standard electrokinetic model is the presence of an anomalous (additional) surface conductivity in excess of the surface conductivity determined according to Bikerman's equation based on the ζ -potential alone.Confidence in modelling the electrokinetic phenomena has grown with the development of methods for modifying the surface such that its properties approach those of the SEM (Bijsterbosch and co-workers; Saville and co-workers).Extension of the particle characterization concept requires the measurement of both the mobile charge and the electrokinetic charge and from this an estimate of the thickness of the additional conductivity zone can be made. With the additional measurement of a titratable charge, it is possible to estimate the ion distribution between the dense and diffuse parts of the double layer (DL) and to estimate the decreased mobility of ions in the Stern layer or in the immobilized part of the DL.Quantitative laws governing the interaction of particles and corresponding to the non-standard model substantially differ from the traditional laws described by the DVLO theory as applied to the SEM. This is also true for adsorption properties which are characterized without sufficient reason by means of the ζ-potential. Therefore both the development of models of interaction and adsorption of ions, allowing for the non-standard electrokinetic model, and the extension of the particle characterization programme to integrated investigations of electric surface phenomena are required.Further generalization of the theory of electrokinetic phenomena is achieved. In addition to the surface charge another variety of surface force can be the origin of the electrokinetic phenomena.     

An efficient method for computing excess free energy of liquid

We present a new theoretical method for efficient calculation of free energy of liquid. This interaction entropy method allows one to compute entropy and free energy of liquid from standard single step MD (molecular dynamics) simulation directly in liquid state without the need to perform MD simulations at many intermediate states as required in thermodynamic integration or free energy perturbation methods. In this new approach, one only needs to evaluate the interaction energy of a single (fixed) liquid molecule with the rest of liquid molecules as a function of time from a standard MD simulation of liquid and the fluctuation of distribution of this interaction energy is then used to calculate the interaction entropy of the liquid. Explicit theoretical derivation of this interaction entropy approach is provided and numerical calculations for the benchmark liquid water system were carried out using three different water models. Numerical analysis of the result was performed and comparison of the computational result with experimental data and other theoretical results were provided. Excellent agreement of calculated free energies with the experimental data using TIP4P model is obtained for liquid water.     

Comparison of different retention models in normal- and reversed-phase liquid chromatography with binary mobile phases

The dependence on mobile phase composition of the retention of selected test analytes in different normal- and reversed-phase chromatographic systems is studied. The aim of this study is to compare the performance of six valuable retention models reported in the literature with a new empirical equation, which is first introduced in this study. All of these models are compared for different thin-layer chromatographic and high-performance liquid chromatographic systems by use of three criteria: the sum of the squared differences between the experimental and theoretical data, approximation of the standard deviation, and the Fisher test.     

Statistical tests for the selection of the optimum parameters set in models describing response surfaces in reversed-phase liquid chromatography

Summary An appropriate procedure based on statistical criteria is suggested for the determination of the optimum set of model parameters for a given chromatographic system. The criteria employed are the t-ratio test, the rate of change in the sum of squares of residuals, the standard error of the fit, the F-test, and the C_P-test. The suggested procedure has been evaluated using two different models, one based on partition and the other on adsorption mechanisms, which describe the combined effect of pH and organic modifier content on the retention of ionogenic solutes in reversed-phase liquid chromatography. It is shown that all the criteria give almost converged results and therefore we may simply use the F-test, which seems to be the most sensitive and reliable criterion excluding any personal judgement. It is also found that the retention models tested show a different behavior towards their simplification. In particular, the use of a reduced equation of the partition model, selected on the basis of the suggested procedure, is necessary for the prediction of meaningful retention surfaces, whereas the decrease in the number of the adjustable parameters in the adsorption model offers only noise reduction and fitting simplicity, because no version of this model predicts abnormal retention surfaces.