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This paper presents an improved theoretical view of ab initio thermodynamics for polar GaN surfaces under gallium-rich conditions. The study uses density functional theory (DFT) calculations to systematically investigate the adsorption of gallium atoms on GaN polar surfaces, starting from the clean surface and progressing to the metallic multilayer. First principles phonon calculations are performed to determine vibrational free energies. Changes in the chemical potential of gallium adatoms are determined as a function of temperature and surface coverage. Three distinct ranges of Ga coverage with very low, medium, and high chemical potential are observed on the GaN(000-1) surface, while only two ranges with medium and high chemical potential are observed on the GaN(000-1) surface. The analysis confirms that a monolayer of Ga adatoms on the GaN(000-1) surface is highly stable over a wide range of temperatures. For a second adlayer at higher temperatures, it is energetically more favorable to form liquid droplets than a uniform crystalline adlayer. The second Ga layer on the GaN(0001) surface shows pseudo-crystalline properties even at a relatively high temperature. These results provide a better thermodynamic description of the surface state under conditions typical for molecular beam epitaxy and offer an interpretation of the observed growth window. [ABSTRACT FROM AUTHOR]

The study concerns the evaluation of the physicochemical and thermo-adsorptive surface properties of six commercially available mouthrinses, particularly surface tension, surface activity, partitioning coefficient, critical micellar concentration, Gibbs excesses at interfaces, surface entropy, and enthalpy. The aim was to quantify their effect on the adhesion and wettability of a model poly(methyl methacrylate) (PMMA) polymer. The adsorptive and thermal surface characteristics were derived from surface tension (γLV) vs. concentration and temperature dependences. Polymer surface wettability was characterized by the contact angle hysteresis (CAH) formalism, using the measurable advancing ΘA and receding ΘR dynamic contact angles and γLV as the input data. Further, wettability parameters: Young static angle (Θ), film pressure (Π), surface free energy (γSV) with its dispersive and polar components, work of adhesion (WA), and adhesional tension (γLV cosΘA) were considered as interfacial interaction indicators. The mouthrinse effect demonstrated the parameter's evolution in reference to the PMMA/pure water case: Θ, ΘA and ΘR↓, CAH↑, Π↓, WA↓, γSV↓, and γLVcosΘA↑. Furthermore, the variations of the surface excess ratio pointed to the formation of multilayered structures of surfactants composing the mouthrinse mixtures considered. The contact angle data allowed for the penetration coefficient and the Marangoni temperature gradient-driven liquid flow speed to be estimated. [ABSTRACT FROM AUTHOR]

Analytic profiles for periodic grain boundary grooves (PGBGs) were determined from variational theory. Variational profiles represent stationary solid-liquid profiles with abrupt, zero-thickness, transitions between adjoining phases. Variational PGBGs consequently lack tangential interfacial fluxes, the existence of which requires more realistic (non-zero) interfacial thicknesses that allow energy and solute transport. Variational profiles, however, permit field-theoretic calculations of their scaled formation free energy and thermodynamic stability, capillary-mediated chemical potentials, and their associated vector gradient distributions, all of which depend on a profile's geometry, not its thickness. Despite the fact that variational profiles are denied interface fluxes, one may, nevertheless, impute shape-dependent interface transport in the form of a profile's surface Laplacian of its presumptive chemical potential distribution due to capillarity. We compare variational surface Laplacians with residuals of the thermochemical potential measured along counterpart diffuse-interface PGBGs, simulated via phase-field with metrically-proportional profiles. Fundamentally, it is the thickness of a microstructure's interfaces and its shape that co-determine whether, and to what extent, gradients of the chemical potential excite fluxes that transport energy and/or solute. PGBGs, both variational and simulated, greatly expand the limited universe of solid-liquid microstructures suitable for steady-state thermodynamic analysis. Understanding the origin and action of these capillary-mediated interfacial fields opens a pathway for estimating and, eventually, measuring how solid-liquid interface thickness modifies the transport of energy and solute during solidification and crystal growth, and influences microstructure. [ABSTRACT FROM AUTHOR]

Traditional batch crystallization processes encounter challenges like batch-to-batch variability, and difficulty in scale-up and achieving desired crystal size and morphology. These challenges stem from various growth mechanisms within crystallizers, influenced by operating conditions that dictate the dynamic surface structure of crystals. To overcome this, we developed a novel microscopic kinetic Monte Carlo model, which uses a specialized adsorption rate that adapts to different growth regimes by considering surface thermodynamic effects for different growth mechanisms. Specifically, the adaptive adsorption rate redefines the driving force of crystallization by considering the attachment energies of different adsorption sites (e.g., kink, adatom, and edge) and supersaturation. This approach enables seamless transitions across growth regimes. We use the lysozyme crystal system as a case study, demonstrating the model's superior predictive power in regime-to-regime transitions. Overall, the developed work provides a valuable new approach to understanding crystal morphology and predicting crystal growth rates in different growth regimes. • A new kMC model for protein crystal growth is developed. • Different adsorption sites facilitate transitions between growth regimes. • Attachment energies correlate growth mechanisms to supersaturation. • Experimental data for Lysozyme crystals validates the kMC model. [ABSTRACT FROM AUTHOR]

[Display omitted] Pressure dependence of contact angle is expected to be influenced by temperature. Nevertheless, the correlation of water contact angle with pressure is rarely investigated at high temperatures (over 100 ℃). In this work, measurements of the contact angle and interfacial tension of water in N 2 atmosphere were conducted at various pressures and temperatures (up to 17 MPa and 300 ℃). The experimental observations were elucidated based on the theory of surface thermodynamics. It was shown that the water-N 2 interfacial tension linearly decreases with increasing the pressure, and that the pressure coefficient declines as temperature rises. The pressure dependence of the water contact angle was found to be different for the low- and high-temperature regimes: the water contact angle increases below 100 ℃, whereas an inverse variation occurs over 100 ℃. According to the theoretical analysis, the pressure dependence of both the water interfacial tension and contact angle is attributed to N 2 adsorption on the surfaces of water and silicon. The variations in the water contact angle with pressure, including both the sign and magnitude, are actually the consequence of the changes of water-N 2 and Si-N 2 interfacial tensions manipulated by pressure and temperature. [ABSTRACT FROM AUTHOR]

As a fluid approaches three phase coexistence, adsorption may take place by the successive formation of two intervening wetting films. The equilibrium thickness of these wetting layers is the result of a delicate balance of intermolecular forces, as dictated by an underlying interface potential. The van der Waals forces for the two variable adsorption layers may be formulated exactly from Dzyaloshinskii-Lifshitz-Pitaevskii theory, and analytical approximations may be derived that extent well beyond the validity of conventional Hamaker theory. We consider the adsorption equilibrium of water vapor on Silver Iodide where both ice and a water layers can form simultaneously and compete for the vapor as the triple point is approached. We perform numerical calculations of Lifshitz theory for this complex system and work out analytical approximations which provide quantitative agreement with the numerical results. At the three phase contact line between AgI/water/air, surface forces promote growth of ice both on the AgI/air and the water/vapor interfaces, lending support to a contact nucleation mode of AgI in the atmosphere. Our approach provides a framework for the description of adsorption at three phase coexistence, and allows for the study of ice nucleation efficiency on atmospheric aerosols. [ABSTRACT FROM AUTHOR]

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated.

The surface tensions (γ) of 2-diethylaminoethanol (DEAE)–tetramethylammonium glycinate ([N 1111 ][Gly]), DEAE–1-butyl-3-methylimidazolium glycinate ([Bmim][Gly]) and DEAE–1-butyl-3-methylimidazolium l -lysinate ([Bmim][Lys]) aqueous solutions were measured by using the BZY-1 surface tension meter. The temperature ranged from 303.2 K to 323.2 K. The mass fractions of DEAE and amino acid ionic liquids (AAILs) respectively ranged from 0.30 to 0.50 and 0.025 to 0.075. A thermodynamic equation was proposed to model the surface tension and the calculated results agreed well with the experiments. The effects of temperature and mass fractions of DEAE and AAILs on the surface tension were demonstrated on the basis of experiments and calculations. The surface enthalpy and surface entropy were determined and their concentration dependences were illustrated. [ABSTRACT FROM AUTHOR]

We have investigated the bulk and surface properties of the group II metal fluorides CaF2, SrF2 and BaF2 using periodic density functional theory (DFT) calculations and surface thermodynamics. Our bulk results show that the best agreement with experiment is achieved with the B3LYP and PBE functionals. We determined the relative importance of the low index surfaces in vacuum and found that an fluoride microcrystal exposes only the (111) surface in which the undercoordinated cations are sevenfold coordinated. With methods of ab initio surface thermodynamics, we analyzed the stability of different surfaces under hydrogen fluoride (HF) pressure and determined the presumable shape of the crystals with respect to different HF concentrations and temperatures. In the case of CaF2 and SrF2, the calculated shapes of the crystals agree well with TEM images of fluorolytic sol-gel synthesized nanocrystals at room temperature and high HF concentration. [ABSTRACT FROM AUTHOR]

The surface tension (γ) of 1-dimethylamino-2-propanol (DMA2P), DMA2P-monoethanolamine (MEA), and DMA2P-piperazine (PZ) aqueous solutions was measured by using the BZY-1 surface tension meter. The temperature ranged from 303.2 K to 323.2 K. The mass fractions of DMA2P, MEA and PZ respectively ranged from 0.30 to 0.50, 0.05 to 0.15 and 0.025 to 0.075. An equation was proposed to model the surface tension and the calculated results agreed well with the experiments. The surface thermodynamics including surface enthalpy and surface entropy were determined and their concentration dependence was analysed. [ABSTRACT FROM AUTHOR]

The effect of temperature on the surface tension is examined in liquid alloys that combine a positive or negative temperature coefficient with gravity limitation of the surface concentration in the surface-active metal constituent. This is a restriction that is likely to occur in alloys where the metal with lower surface tension is much denser than the other component. Since there is a surface tension increase due to diminished segregation, the resultant temperature coefficient will depend on the superposition of two independent effects. Working in the framework of Butler's thermodynamics for ideal surface phases, equations and methods of analysis are obtained to describe both effects. These developments are illustrated with alloys where the surface density is likely to attain the bulk density at certain compositions, namely the Al–Zn alloys that exhibits a negative temperature coefficient and the Sn–Bi, Ga–Bi, Ga-Pb and Cu–Pb alloys that present composition ranges with positive temperature coefficients. The specific concave down d γ /d T curves of liquid alloys are theoretically predicted. Furthermore, good estimates are obtained for systems with positive and negative temperature coefficients, except within a 50 K interval of phase transitions, or for systems showing large deviations from ideal behaviour. [Display omitted] • Surface density effect on surface tension temperature coefficients of liquid alloys. • Thermodynamic calculation of ideal temperature coefficients for liquid metal alloys. • Experimental vs. theoretically estimated surface tension temperature coefficients. [ABSTRACT FROM AUTHOR]

Hard spheres are a central and important model reference system for both homogeneous and inhomogeneous fluid systems. In this paper we present new high-precision molecular-dynamics computer simulations for a hard sphere fluid at a planar hard wall. For this system we present benchmark data for the density profile p(z) at various bulk densities, the wall surface free energy j, the excess adsorption Г, and the excess volume ve x, which is closely related to Г. We compare all benchmark quantities with predictions from state-of-the-art classical density functional theory calculations within the framework of fundamental measure theory. While we find overall good agreement between computer simulations and theory, significant deviations appear at sufficiently high bulk densities. [ABSTRACT FROM AUTHOR]

Abstract: Helfrich model of membrane bending elasticity has been most influential in establishment and development of Soft-Matter Physics of lipid bilayers and biological membranes. Recently, Helfrich theory has been extensively used in Cell Biology to understand the phenomena of shaping, fusion and fission of cellular membranes. The general background of Helfrich theory on the one hand, and the ways of specifying the model parameters on the other, are important for quantitative treatment of particular biologically relevant membrane phenomena. Here we present the origin of Helfrich model within the context of the general Gibbs theory of capillary interfaces, and review the strategies of computing the membrane elastic moduli based on considering a lipid monolayer as a three-dimensional thick layer characterized by trans-monolayer profiles of elastic parameters. We present the results of original computations of these profiles by a state-of-the-art numerical approach. [Copyright &y& Elsevier]

Highlights: [•] Surface tension of binary mixtures of alcohol/DMSO determined. [•] Surface mole fraction and surface thermodynamic parameters were calculated. [•] The surface tension data of binary mixtures were correlated with FLW, LWW and MS models. [ABSTRACT FROM AUTHOR]

Microparticle powders for nasal delivery were formulated to contain the model drug, zolmitriptan, and varying proportions of different polymers. The objective of the study was to investigate the effects of these formulative parameters on the surface chemistry of the spray-dried microparticles and their potential for adhesion to the tested substrates, porcine mucin, and nasal tissue. The polymers used were chitosans of varying ionization states and molecular weights and hydroxypropyl methyl cellulose. The surface energies of the surfaces of the microparticles were determined using contact angle measurements and the van Oss model. The theory of surface thermodynamics was applied to determine the theoretical potential for the different materials to adhere to the substrates. It was found that the drug or polymers alone, as well as the various formulations, were more likely to adhere to mucin than to nasal tissue. Further, there was a trend for higher molecular weight chitosans to adhere better to the substrates than lower molecular weight chitosans. Similarly, adhesion was improved for formulations with a higher content of polymers. These theoretical predictions may be compared with further experimental results and be of use in making informed decisions on the choice of formulations for future expensive bio-studies. [ABSTRACT FROM AUTHOR]

Abstract: Currently, great efforts are devoted to the design of drug delivery systems and many new polymers are investigated to make drug release fit the desired profiles. In this work, we investigate the formulation of colloidal aqueous suspensions based on the polymer Kollidon® SR for the oral administration of drugs. Such an investigation has never been carried out to our knowledge, as this polymer has only been used as soluble binder and film-forming agent for solid dosage forms. In this work, both the stability and redispersibility characteristics of Kollidon® SR aqueous suspensions are extensively investigated through thermodynamic and electrokinetic studies. The hydrophilic character of the polymer, and the surface charge and electrical double layer thickness play a key role in the stability of the suspensions, hence the need for a full characterization of the polymer. Kollidon® SR suspensions display a “free-layered” sedimentation determined by their hydrophilic character and their zeta potential values (indicating the electrokinetic charge on the particles). The electrostatic repulsion between the particles is responsible for the low sedimentation volume and easy redispersibility of the polymer. [Copyright &y& Elsevier]

Abstract: Equations for the chemical potentials of surface layer components are derived by accounting for the two-dimensional compressibility ɛ of adsorbed molecules having a molecular area ω that depends linearly on the surface pressure Π. The modified equations for the chemical potentials representing a generalised Butler equation, are used to derive equations of state and adsorption isotherms of surface layers both in the framework of the real two-dimensional solution theory and in the framework of the Gibbs dividing surface model. Data of surface tension, adsorption and rheological characteristics of surface layers formed from solutions of C12DMPO agree well with the theoretical models based on the assumption of intrinsic compressibility of adsorbed molecules. A good description of experimental data by the theoretical models was achieved without the consideration of surface layer compressibility in the equations for the chemical potentials. [Copyright &y& Elsevier]

Abstract: In this article a method is described to prepare composite colloidal nanoparticles, consisting of a magnetic core (carbonyl iron) and a biodegradable polymeric shell [poly(butylcyanoacrylate) or PBCA]. The method is based on the so-called anionic polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) nanospheres designed for drug delivery. Interest of this investigation is based upon the fact that the heterogeneous structure of the particles can confer them both the possibility to respond to external magnetic fields and to be used as drug carriers. In order to investigate to what extent do the particles participate of this mixed properties, we compare in this work the physical characteristics (structure, chemical composition, specific surface area and surface electrical and thermodynamic properties) of the core/shell particles with those of both the nucleus and the coating material. This preliminary study shows that the mixed particles display an intermediate behavior between that of carbonyl iron and PBCA spheres. Electrophoretic mobility measurements as a function of pH and as a function of KNO3 concentration, show a great similarity between the core/shell and pure polymer nanoparticles. Similary, a surface thermodynamic study performed on the three types of particles demonstrated that the electron-donor component of the surface free energy of the solids is very sensitive to the surface composition. In fact, a measurable decrease of such component is found for core/shell particles as compared to carbonyl iron. We also analyzed the influence of the relative amounts of polymer and carbonyl iron on the characteristics of the composite particles: data on the coating thickness, the amount of polymer bound to the magnetic nuclei, the redispersibility characteristics of the suspensions and the surface electrical and thermodynamic properties, suggest that the optimal synthesis conditions are obtained for a 4/3 initial monomer/carbonyl iron weight ratio. [Copyright &y& Elsevier]

Abstract: Theoretical modelling for contact angle hysteresis carried out to date has been mostly limited to several idealized surface configurations, either rough or heterogeneous surfaces. This paper presents a preliminary study on the thermodynamics of contact angles on rough and heterogeneous surfaces by employing the principle of minimum free energy and the concept of liquid front. Based on a two-dimensional regular model surface, a set of relations were obtained, which correlate advancing, receding and system equilibrium contact angles to surface topography, roughness and heterogeneity. It was found that system equilibrium contact angles (θ ES) can be expressed as a function of surface roughness factor (δ) and the Cassie contact angle (θ C): cosθ ES = δcosθ C. This expression can be reduced to the classical Wenzel equation.: θ ES = θ W for rough but homogeneous surfaces, and the classical Cassie equation θ ES = θ C for heterogeneous but smooth surfaces. A non-dimensional parameter called surface feature factor (ω) was proposed to classify surfaces into three categories (types): roughness-dominated, heterogeneity-dominated and mixed-rough-heterogeneous. The prediction of advancing and receding contact angles of a surface is dependent on which category the surface belongs to. The thermodynamic analysis of contact angle hysteresis was further extended from the regular model surface to irregular surfaces; consistent results were obtained. The current model not only agrees well with the models previously studied by other researchers for idealized surfaces, but also explores more possibilities to explain the reported experimental results/observations that most existing theories could not explain. [Copyright &y& Elsevier]

Abstract: Surface thermodynamic functions (surface entropy, surface enthalpy, and surface composition) of dilute solutions of 2-, 3-, and 4-methylcyclohexanol in ethylene glycol were obtained using surface tension measurements at various temperatures. Surface excess values and surface mole fractions were obtained from Gibbs equation and extended Langmuir model respectively. The results show that all methylcyclohexanols are surface active in ethylene glycol. The lyophobicity of solutes decreases with increasing temperature. The presence of a maximum point in the surface entropy diagram in all systems is explained by the formation of clathrate-like solvates at the surface of these systems. [Copyright &y& Elsevier]

Abstract: The surface tension, σ, of dilute solutions of cyclohexanol and cyclopentanol in ethylene glycol was measured in the temperature range between 293.15 and 323.15 K by means of the ring detachment method. The surface entropies and enthalpies were calculated. The surface excess values were obtained using the Gibbs equation. The surface tension data were analyzed using the extended Langmuir (EL) model and the surface composition were obtained from this model. It was shown that clathrate-like solvates (hydrophobic-like solvation) are forming in the dilute solution of cyclohexanol in ethylene glycol. [Copyright &y& Elsevier]

In this paper, it is shown that the symmetrically normalized activity coefficient of the solute in the bulk solution, , makes a non-negligible contribution to the standard Gibbs energy of adsorption of solute from the bulk at the surface of binary liquid mixtures, ΔadsG0. With a view to defining this change with practical purposes, we selected the pure solute and a surface pressure π of 1mNm-1 as standard states for the bulk and surface phases, respectively. Besides, we assumed availability of data in the highly dilute region, where the two-dimensional ideal equation of state holds. In this way, ΔadsG0 = -RTln. When is taken into account, Traube''s rule (that increases linearly with chain length in the water + 1-alkanol series) does not imply that ΔadsG0 increases linearly with chain length. On the contrary, together with the fact that in this series ln() increases with chain length at the same rate as , Traube''s rule implies that ΔadsG0 is constant in this series. This can be interpreted in molecular terms as indicating that in highly dilute solutions the hydrocarbon chain of alkanol molecules at the surface does not lie in or on the surface (as is implied by a linear increase in ΔadsG0 with chain length), but resides completely in the gas phase, as is now known to be true. The constancy of ΔadsG0 also explains why water + 1-alkanol systems share the same π versus curve except at high surface concentrations, where the degree of discrepancy is in any case limited by the small differences in surface tension among the pure alkanols. We conclude by using the “Extended Langmuir” model of surface behaviour to split ΔadsG0 into five distinct physically meaningful contributions. [Copyright &y& Elsevier]

The problem of the applicability of the Gibbs thermodynamics to nanosized objects is investigated. It is shown that the Gibbs surface phases method may be extended to nanoparticles if the effective surface tension (the specific excess free energy) is interpreted as a function of the particle radius. The specific surface free energy (the surface tension) for nanodroplets and nanocrystals of noble gases and aluminum was calculated using the thermodynamic perturbation theory. It has been shown that the averaged surface tension decreases with the particle size both for small droplets and for nanocrystals. [Copyright &y& Elsevier]

Biogranulation that includes anaerobic and aerobic granular sludge processes is a promising biotechnology for wastewater treatment. The formation and structure of biogranules are associated very closely with cell hydrophobicity. This paper therefore attempts to review the essential role of cell hydrophobicity in the formation of granular sludge. Cell hydophobicity could be induced by culture conditions, and in turn initiates cell-to-cell aggregation that is a crucial step towards biogranulation. In this paper, the factors that may influence cell hydrophobicity were discussed, while a thermodynamic interpretation of cell hydrophobicity was also presented. Meanwhile, a selection pressure-based inducing strategy for cell hydrophobicity was further proposed. It appears that cell hydrophobicity is a triggering force of biogranulation, and high cell hydrophobicity seems to be a prerequisite of biogranulation. However, the knowledge regarding the role of cell hydrophobicity in biogranulation process is far from complete. Some future research niches are then outlined. [Copyright &y& Elsevier]

The adhesion behaviour of Paenibacillus polymyxa bacteria on pyrite and chalcopyrite is examined by the surface thermodynamics and the extended DLVO theory approaches. In addition, the bacteria are adapted to pyrite and chalcopyrite minerals, and the adhesion behaviour of these bacteria is also investigated. The significance of acid–base interactions in adhesion is assessed. The essential parameters needed for the calculations of interaction energy between bacteria and mineral are experimentally determined. The results illustrate that the bacterial surfaces are more energetic than the mineral surfaces and the bacteria acquired acid–base surface energy component during their adaptation to mineral. The extended DLVO approach is found to be more effective in predicting the adhesion behaviour than the expectations from thermodynamic approach. The thermodynamic approach yields no bacterial adhesion on minerals and this discrepancy is the result of inadequate description of electrostatic interactions. The adhesion predictions by the DLVO approach are able to partially explain the bioflotation results of pyrite and chalcopyrite. Extended DLVO shows that on account of high bacterial surface energy, their aggregation is not feasible. But due to the hydrophobicity of pyrite and chalcopyrite, their aggregation is possible. [Copyright &y& Elsevier]

Escherichia coli cultured under different carbon and nitrogen conditions was measured for growth and surface thermodynamics to examine the impact of C/N ratio on E. coli growth and its surface thermodynamics. Among the three carbon sources, glucose grown cultures had the greatest specific growth rate (0.67 and 0.44 h−1 with ammonia and nitrate serving as the nitrogen source, respectively, and no carbon or nitrogen limitation), and yielded the least hydrophilic surface (31.49 and 22.23 mJ m−2 of the total interfacial free energy of interaction); propionate grown cultures had the greatest stoichiometric yield coefficient (0.61 and 0.49 g biomass per g substrate), lipopolysaccharide production efficiency (0.161 and 0.149 g per g biomass), and yielded the most hydrophilic surface (46.32 and 39.32 mJ m−2 of the total interfacial free energy of interaction). For the same carbon source, ammonia-grown cultures yielded a greater specific growth rate, growth yield and lipopolysaccharide production efficiency, and a more hydrophilic surface than nitrate grown cultures. In carbon-limited cultures, a smaller specific growth rate and lipopolysaccharide production efficiency and greater growth yield were observed as compared with cultures grown with no carbon and nitrogen limitation. In addition, under carbon-limited growth, the cells exhibited a less hydrophilic surface. When nitrogen was the limiting factor, E. coli displayed a smaller specific growth rate and growth yield, greater lipopolysaccharide production efficiency and a more hydrophilic surface as compared with cultures grown with no carbon and nitrogen limitation. [Copyright &y& Elsevier]

A rigorous theoretical model is presented which describes the equilibrium behaviour of a surfactant mixtures at liquid/fluid interfaces. The theory describes mixtures of surfactants with different molar areas and accounts for the non-ideality of the surface layer. The theoretical results are in good agreement with experimental data and support the idea of additivity of the interaction parameters in the surface layer. The rigorous equation of state is transformed into simple relationships for the description of the adsorption behaviour of mixed surfactant systems. The model requires surface tensions of the single surfactant systems or the adsorption isotherms to construct the isotherm of the mixture while no extra interaction parameters between the different compounds are assumed. The model is tested with a number of literature data, such as mixed sodium alkyl sulfates, mixtures of betaine homologues BHB12 with BHB16, non-ionic surfactant mixtures, and anionic-nonionic mixtures (1-butanol with BHB12, and oxethylated decanol (C10EO5) with sodium dodecyl sulfate). The agreement between experimental data and the theoretical calculations is excellent. This approach can be especially important for practical applications of surfactant mixtures for which experimental data are scarce. [Copyright &y& Elsevier]

• Thermodynamics of surfaces. • Modified Eötvös surface tension equation. • Table of surface thermodynamics. Many thermodynamic properties, such as entropy, lattice energy, and so forth, correlate with some function of formula volume. We here report on a recently rediscovered modified Eötvös equation which relates surface tension values to molar Gibbs surface energies, surface entropies and surface enthalpies. The resulting thermodynamic values are valuable in understanding molecular configurations of surfaces. The molar surface entropy, Δ s , in what may be considered to be a Trouton surface entropy, is roughly constant at 20 J K−1 mol−1 compared with the Trouton entropy of (80–100) J K−1 mol−1 for evaporation at the boiling point of liquids. Weakly-bonded molecular liquids like alkanes have a relatively large molar surface entropy, Δ s ≅ 25 J K−1 mol −1, suggesting a loss in order on surface formation, while the rather smaller molar surface entropy, Δ s ≅ 13 J K−1 mol −1, for the hydrogen-bonded alcohols indicates that the surface molecules are quite strongly bound to that surface. [ABSTRACT FROM AUTHOR]

• Temperature coefficient of the surface tension of liquid metal alloys. • Thermodynamic expression for the temperature coefficient. • Factors contributing to positive temperature coefficients. • Experimental versus theoretical temperature coefficients for the liquid metal alloys Ag–Bi, Ag–Pb, Ag–Sn, Cu–In and Cu–Sn. ga1 The atypical increase of surface tension when the temperature of a liquid alloy increases, is addressed using Butler's thermodynamic model for an ideal surface phase. A rigorous expression for this temperature coefficient at fixed bulk alloy composition, requiring only pure-metal density and surface tension data and no arbitrary simplifying assumptions, is worked out. This theoretical development predicts the occurrence of positive temperature coefficients whenever a combination involving large difference of pure-metal surface tensions, temperatures close to the alloy melting point and molar surface area of the surface-active metal larger than that of the other component, is met. The proposed method is applied to the alloys Cu–Sn, Cu–In, Ag–Bi, Ag–Pb and Ag–Sn for which experimentally measured positive temperature coefficients have been reported. An acceptable agreement between theoretical and experimental values is documented. This theoretical approach predicts a negative temperature coefficient of the surface tension at fixed surface-phase composition, which is in fact the typical behaviour for this dependence. It is concluded that the temperature and composition ranges over which a certain binary alloy may exhibit positive temperature coefficient of the surface tension can be established beforehand using the proposed methodology. [ABSTRACT FROM AUTHOR]

• Surface tensions and viscosities of DMA2P-AEP/DAMP aqueous solutions were measured. • Thermodynamics equations were applied to model the surface tensions and viscosities. • Surface thermodynamics including surface entropy and surface enthalpy were deduced. • Viscosity activation energy was estimated based on the viscosity. The surface tensions (γ) and viscosities (η) of 1-dimethylamino-2-propanol (DMA2P) − 1-(2-aminoethyl)piperazine (AEP) and DMA2P − 1,5-diamino-2-methylpentane (DAMP) were measured and correlated. According to the CO 2 capture temperature from the thermal power plant flue gas (around 313 K), the experimental temperatures were selected to be 303.2 K, 313.2 K and 323.2 K. The mass fractions of DMA2P ranged from 0.300 to 0.500, and those for activators (AEP and DAMP) ranged from 0.050 to 0.150. Temperature and composition dependences of γ and η were demonstrated on the basis of experiments and calculations. The activation energy (E a) was estimated from the temperature dependence of viscosity. Analytical formulations of surface entropy (S S) and surface enthalpy (H S) were deduced from the analytical equation of γ. S S and H S were calculated and their variations with respect to mass fraction were analyzed. [ABSTRACT FROM AUTHOR]

The surface tension and viscosity values of N-methyldiethanolamine (MDEA) aqueous solutions promoted by tetramethylammonium arginate ([N1111][Arg]) were measured and modeled. The experimental temperatures were 303.2 to 323.2 K. The mass fractions of MDEA (wMDEA) and [N1111][Arg] (w[N1111][Arg]) were 0.300 to 0.500 and 0.025 to 0.075, respectively. The measured surface tension and viscosity values were satisfactorily fitted to thermodynamic models. With the aid of experimentally viscosity data, the activation energy (Ea) and H2S diffusion coefficient (DH2S) of MDEA-[N1111][Arg] aqueous solution were deduced. The surface entropy and surface enthalpy of the solutions were calculated using the fitted model of the surface tension. The quantitative relationship between the calculated values (surface tension, surface entropy, surface enthalpy, viscosity, activation energy, and H2S diffusion coefficient) and the operation conditions (mass fraction and temperature) was demonstrated. [ABSTRACT FROM AUTHOR]