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The Single Chain Mean Field theory is used to link coarse-grained models of amphiphilic molecules with analytical models for membrane elasticity, where phenomenological parameters are deduced from explicit molecular models and force fields. We estimate the elastic constants based on the free energy of the amphiphilic bilayer in planar and cylindrical geometries on the example of four amphiphilic molecules that differ in length and stiffness. We study how these variations affect the equilibrium bilayer structure, the equilibrium free energy, and the elastic constants. Bending rigidities are obtained within the typical range of experimental values for phospholipid membranes in a liquid state. [ABSTRACT FROM AUTHOR]

In this paper, a coupled mechanical-chemical model is established based on the thermodynamic framework, in which the contribution of chemical expansion to free energy is introduced. The stress-dependent chemical potential equilibrium at the gas-solid interface and the stress gradient-dependent diffusion equation as well as a so-called generalized force which is conjugate to the oxidation rate are derived from the proposed model, which could reflect the influence of stresses on the oxidation reaction. Based on the proposed coupled mechanical-chemical model, a user element subroutine is developed in ABAQUS. The numerical simulation of the high temperature oxidation in the thermal barrier coating is carried out to verify the accuracy of the proposed model, and then the influence of stresses on the oxidation reaction is investigated. In thermally grown oxide, the considerable stresses would be induced by permanent volumetric swelling during the oxidation. The stresses play an important role in the chemical potential equilibrium at the gas-solid interface and strongly affect the oxidation reaction. The gradient of the stresses, however, only occurs in the extremely thin oxidation front layer, which plays a very limited role in the oxidation reaction. The generalized force could be divided into the stress-dependent and the stress-independent parts. Comparing with the stress-independent part, the stress-dependent part is smaller, which has little influence on oxidation reaction. [ABSTRACT FROM AUTHOR]

Self-propelled active particles are inherently out of equilibrium as they collect energy from their surroundings and transform it into directed motion. A recent theoretical study suggests that binary mixtures of active particles with distinct effective diffusion coefficients exhibit dynamical demixing when their diffusion coefficients differ by more than one order of magnitude. Here, we show that this difference may be reduced drastically in the presence of external fields even when the response to the field is the same for both species. We investigate this demixing as a function of the ratio of the diffusion coefficients and discuss the implications of the results for active systems. [ABSTRACT FROM AUTHOR]

We analyze the minimum electrophilicity principle of conceptual density functional theory using the framework of the finite temperature grand canonical ensemble. We provide support for this principle, both for the cases of systems evolving from a non-equilibrium to an equilibrium state and for the change from one equilibrium state to another. In doing so, we clearly delineate the cases where this principle can, or cannot, be used. [ABSTRACT FROM AUTHOR]

The coupling of the charge carriers passing through a molecule bridging two bulky conductors with local vibrational modes of the molecule gives rise to distinct features in the electronic transport properties on one hand and to nonequilibrium features in the vibrations' properties, e.g., their population, on the other. Here we explore theoretically a generic model for a molecular junction biased by an arbitrary dc voltage in the weak-coupling regime. We succinctly summarize parts of our past work related to the signature of the electron-vibration interaction on the full-counting statistics of the current fluctuations (i.e., the cumulant generating-function of the current correlations). In addition, we provide a novel account of the response to an ac field exerted on the junction (on top of the dc bias voltage); in particular, we study the nonequilibrium distribution and the displacement fluctuations of the vibrational modes. Remarkably, we find a behavior pattern that cannot be accounted for by classical forced oscillations. The calculations use the technique of nonequilibrium Green's functions and treat the electron-vibration coupling in perturbation theory, within the random-phase approximation when required. [ABSTRACT FROM AUTHOR]

Alow-temperature scanning tunneling microscopewas employed to study the differential conductance in an atomic junction formed by an adsorbed Co atom on a Cu(100) surface and a copper-covered tip.A zero-bias anomaly (ZBA) reveals spin scattering off the Co atom, which is assigned to a Kondo effect. The ZBA exhibits a characteristic asymmetric lineshape when electrons tunnel between tip and sample, while upon the tip-Co contact it symmetrizes and broadens. Through density functional theory calculations and the non-equilibrium non-crossing approximation, we showthat the lineshape broadening is mainly a consequence of the additional coupling to the tip, while non-equilibrium effects only modify the large-bias tails of the ZBA. [ABSTRACT FROM AUTHOR]

The rate of electron transfer between a molecular species and a metal, each at a different local temperature, is examined theoretically through the implementation of a bithermal (characterized by two temperatures) Marcus formalism. Expressions for the rate constant and the electronic contribution to a heat transfer mechanism which is induced by the temperature gradient between a molecule and metal are constructed. The system of coupled dynamical equations describing the electronic and thermal currents are derived and examined over diverse ranges of reaction geometries and temperature gradients. It is shown that electron transfer across the molecule-metal interface is associated with heat transfer and that the electron exchange between metal and molecule makes a distinct contribution to the interfacial heat conduction even when the net electronic current vanishes. [ABSTRACT FROM AUTHOR]

We introduce diagrammatic technique for Hubbard nonequilibrium Green functions. The formulation is an extension of equilibrium considerations for strongly correlated lattice models to description of current carrying molecular junctions. Within the technique intra-system interactions are taken into account exactly, while molecular coupling to contacts is used as a small parameter in perturbative expansion. We demonstrate the viability of the approach with numerical simulations for a generic junction model of quantum dot coupled to two electron reservoirs. [ABSTRACT FROM AUTHOR]

One of the most thrilling features of Physics is the possibility of establishing analogies between apparently distant areas. Here, we explain the parallel between a pile of grains interacting mechanically with each other, and a "pile" of superconducting vortices. In both cases the macroscopic slope of the pile is maintained by a very nonlinear avalanche process. Furthermore, both types of piles logarithmically relax in time due to "agitational" or thermal effects, aiming at a state of equilibrium. [ABSTRACT FROM AUTHOR]

The present paper aims at deriving classical expressions which permit calculation of the equilibrium constant for weakly interacting molecular pairs using a complete multidimensional potential energy surface. The latter is often available nowadays as a result of the more and more sophisticated and accurate ab initio calculations. The water dimer formation is considered as an example. It is shown that even in case of a rather strongly bound dimer the suggested expression permits obtaining quite reliable estimate for the equilibrium constant. The reliability of our obtained water dimer equilibrium constant is briefly discussed by comparison with the available data based on experimental observations, quantum calculations, and the use of RRHO approximation, provided the latter is restricted to formation of true bound states only. [ABSTRACT FROM AUTHOR]

We explore thermodynamic properties of a vapor in the range of state parameters where the contribution to thermodynamic functions from bound states of atoms (clusters) dominates over the interaction between the components of the vapor in free states. The clusters are assumed to be light and sufficiently "hot" for the number of bonds to be minimized. W e use the technique of calculation of the cluster partition function for the cluster with a minimum number of interatomic bonds to calculate the caloric properties (heat capacity and velocity of sound) for an ideal mixture of the lightest clusters. The problem proves to be exactly solvable and resulting formulas are functions solely of the equilibrium constant of the dimer formation. These formulas ensure a satisfactory correlation with the reference data for the vapors of cesium, mercury, and argon up to moderate densities in both the sub- and supercritical regions. For cesium, we extend the model to the densities close to the critical one by inclusion of the clusters of arbitrary size. Knowledge of the cluster composition of the cesium vapor makes it possible to treat nonequilibrium phenomena such as nucleation of the supersaturated vapor, for which the effect of the cluster structural transition is likely to be significant. [ABSTRACT FROM AUTHOR]

Pulling a sphere and vibrating it around an equilibrium position by amplitude-modulation in the near-field of a single finite circular piston transducer is theoretically demonstrated. Conditions are found where a fluid hexane sphere (with arbitrary radius) chosen as an example, centered on the axis of progressive propagating waves and submerged in non-viscous water, experiences an attractive (steady) force pulling it towards the transducer, as well as an oscillatory force forcing it to vibrate back-and-forth. Numerical predictions for the dynamic force illustrate the theory and suggest an innovative method in designing dynamic acoustical tractor beams. [ABSTRACT FROM AUTHOR]

The problem of determining the Eckart molecule-fixed frame for an arbitrary molecule with nuclei displaced from the equilibrium positions is considered. The solution of the problem is formulated by minimizing the sum of mass-weighted squared deviations (MWSD) of the nuclei of a displaced configuration from the nuclei of the equilibrium configuration. A mathematical proof of the equivalence of Eckart conditions and the minimum of MWSD is given. It is shown that the extrema of the sum of MWSD coincide with eigenvalues of a special 4 × 4 symmetric matrix. Its minimal eigenvalue corresponds to the desired solution, and the respective eigenvector can be treated as the quaternion containing the necessary information for rotating the original coordinate system and aligning its axes with the molecule-fixed coordinate system. A detailed scheme for an efficient numerical implementation of the method is provided, and a numerical example is given. [ABSTRACT FROM AUTHOR]

We present a full quantum evaluation of the water second virial coefficient B(T) based on the Takahashi-Imada second order approximation. As the associated trace T r[e-βHAB - e-βHoAB] is performed in the coordinate representation, it does also include contribution from the whole continuum, i.e., resonances and collision pairs of monomers. This approach is compared to a Path Integral Monte Carlo evaluation of this coefficient by Schenter [J. Chem. Phys. 117, 6573 (2002)] for the TIP4P potential and shown to give extremely close results in the low temperature range (250-450 K) reported. Using a recent ab initio flexible potential for the water dimer, this new formulation leads to very good agreement with experimental values over the whole range of temperatures available. The virial coefficient is then used in the well known relation Kp(T) = -(B(T) - bM)/RT where the excluded volume bM is assimilated to the second virial coefficient of pure water monomer vapor and approximated from the inner repulsive part of the interaction potential. This definition, which renders bM temperature dependent, allows us to retrieve the 38 cm3 mol-1 value commonly used, at room temperature. The resulting values for Kp(T) are in agreement with available experimental data obtained from infrared absorption spectra of water vapor. [ABSTRACT FROM AUTHOR]

The intermetallic molecules CuSb, AgSb, and AuSb were identified in the effusive molecular beam produced at high temperature under equilibrium conditions in a double-cell-like Knudsen source. Several gaseous equilibria involving these species were studied by mass spectrometry as a function of temperature in the overall range 1349-1822 K, and the strength of the chemical bond formed between antimony and the group 11 metals was for the first time measured deriving the following thermochemical dissociation energies (D°0 , kJ/mol): 186.7 ± 5.1 (CuSb), 156.3 ± 4.9 (AgSb), 241.3 ± 5.8 (AuSb). The three species were also investigated computationally at the coupled cluster level with single, double, and noniterative quasiperturbative triple excitations (CCSD(T)). The spectroscopic parameters were calculated from the potential energy curves and the dissociation energies were evaluated at the Complete Basis Set limit, resulting in an overall good agreement with experimental values. An approximate evaluation of the spin-orbit effect was also performed. CCSD(T) calculations were further extended to the corresponding group 11 arsenide species which are here studied for the first time and the following dissociation energies (D°0 , kJ/mol): 190 ± 10 (CuAs), 151 ± 10 (AgAs), 240 ± 15 (AuAs) are proposed. Taking advantage of the new experimental and computational information here presented, the bond energy trends along group 11 and 4th and 5th periods of the periodic table were analyzed and the bond energies of the diatomic species CuBi and AuBi, yet experimentally unobserved, were predicted on an empirical basis. [ABSTRACT FROM AUTHOR]

A systematic ab initio treatment of the nitryl halides (XNO2) and the cis- and trans- conformers of the halide nitrites (XONO), where X = Cl, Br, and I, have been carried out using highly correlated methods with sequences of correlation consistent basis sets. Equilibrium geometries and harmonic frequencies have been accurately calculated in all cases at the explicitly correlated CCSD(T)-F12b level of theory, including the effects of core-valence correlation for the former. Where experimental values are available for the equilibrium structures (ClNO2 and BrNO2), the present calculations are in excellent agreement; however, the X-O distances are slightly too long by about 0.01 Å due to missing multireference effects. Accurate predictions for the iodine species are made for the first time. The vertical electronic excitation spectra have been calculated using equation-of-motion coupled cluster methods for the low-lying singlet states and multireference configuration interaction for both singlet and triplet states. The latter also included the effects of spin-orbit coupling to provide oscillator strengths for the ground state singlet to excited triplet transitions. While for ClNO2 the transitions to excited singlet states all occur at wavelengths shorter than 310 nm, there is one longer wavelength singlet transition in BrNO2 and two in the case of INO2. The long wavelength tail in the XNO2 species is predicted to be dominated by transitions to triplet states. In addition to red-shifting from X = Cl to I, the triplet transitions also increase in oscillator strength, becoming comparable to many of the singlet transitions in the case of INO2. Hence in particular, the latter species should be very photolabile. Similar trends are observed and reported for the halogen nitrites, many of which for the first time. [ABSTRACT FROM AUTHOR]

Orbital-optimized second-order perturbation theory (OOMP2) optimizes the zeroth order wave function in the presence of correlations, removing the dependence of the method on Hartree-Fock orbitals. This is particularly important for systems where mean field orbitals spin contaminate to artificially lower the zeroth order energy such as open shell molecules, highly conjugated systems, and organometallic compounds. Unfortunately, the promise of OOMP2 is hampered by the possibility of solutions being drawn into divergences, which can occur during the optimization procedure if HOMO and LUMO energies approach degeneracy. In this work, we regularize these divergences through the simple addition of a level shift parameter to the denominator of the MP2 amplitudes. We find that a large level shift parameter of 400 mEh removes divergent behavior while also improving the overall accuracy of the method for atomization energies, barrier heights, intermolecular interactions, radical stabilization energies, and metal binding energies. [ABSTRACT FROM AUTHOR]

In the melt polymer conformations are nearly ideal according to Flory's ideality hypothesis. Silberberg generalized this statement for chains in the interfacial region. We check the Silberberg argument by analyzing the conformations of a probe chain end-grafted at a solid surface in a sea of floating free chains of concentration φ by the self-consistent field (SCF) method. Apart from the grafting, probe chain and floating chains are identical. Most of the results were obtained for a standard SCF model with freely jointed chains on a six-choice lattice, where immediate step reversals are allowed. A few data were generated for a five-choice lattice, where such step reversals are forbidden. These coarse-grained models describe the equilibrium properties of flexible atactic polymer chains at the scale of the segment length. The concentration was varied over the whole range from φ = 0 (single grafted chain) to φ = 1 (probe chain in the melt). The number of contacts with the surface, average height of the free end and its dispersion, average loop and train length, tail size distribution, end-point and overall segment distributions were calculated for a grafted probe chain as a function of φ, for several chain lengths and substrate/polymer interactions, which were varied from strong repulsion to strong adsorption. The computations show that the conformations of the probe chain in the melt do not depend on substrate/polymer interactions and are very similar to the conformations of a single end-grafted chain under critical conditions, and can thus be described analytically. When the substrate/polymer interaction is fixed at the value corresponding to critical conditions, all equilibrium properties of a probe chain are independent of φ, over the whole range from a dilute solution to the melt. We believe that the conformations of all flexible chains in the surface region of the melt are close to those of an appropriate single chain in critical conditions, provided that one end of the single chain is fixed at the same point as a chain in the melt. [ABSTRACT FROM AUTHOR]

A wide variety of highly cooperative self-assembly processes in biological and synthetic systems involve the assembly of a large number (m) of units into clusters, with m narrowly peaked about a large size m0 > 1 and with a second peak centered about the m = 1 unassembled monomers. While very specific models have been proposed for the assembly of, for example, viral capsids and core-shell micelles of ß-casein, no available theory describes a thermodynamically general mechanism for this double peaked, highly cooperative equilibrium assembly process. This study provides a general mechanism for these cooperative processes by developing a minimal Flory-Huggins type theory. Beginning from the simplest non-cooperative, free association model in which the equilibrium constant for addition of a monomer to a cluster is independent of cluster size, the new model merely allows more favorable growth for clusters of intermediate sizes. The theory is illustrated by computing the phase diagram for cases of self-assembly on cooling or heating and for the mass distribution of the two phases. [ABSTRACT FROM AUTHOR]

We have theoretically investigated the mechanism of the acetalization reaction of acetaldehyde using the artificial force induced reaction (AFIR) method and the rate constant matrix contraction (RCMC) method. A systematic search for reaction paths by the AFIR method resulted in a reaction path network including 162 local minima and 599 transition states. By applying the RCMC method to the network, the time hierarchy of the network was revealed. Using the network and the RCMC method, the overall rate constants and the equilibrium constant including conformational entropy contributions were evaluated. The discussion demonstrates how multicomponent reactions that proceed through multiple steps are understood from their reaction path networks. [ABSTRACT FROM AUTHOR]

We have identified the dimethylamine-trimethylamine complex (DMA-TMA) at room temperature in the gas phase. The Fourier transform infrared (FTIR) spectrum of DMA-TMA in the NH-stretching fundamental region was obtained by spectral subtraction of spectra of each monomer. Explicitly correlated coupled cluster calculations were used to determine the minimum energy structure and interaction energy of DMA-TMA. Frequencies and intensities of NH-stretching transitions were also calculated at this level of theory with an anharmonic oscillator local mode model. The fundamental NH-stretching intensity in DMA-TMA is calculated to be approximately 700 times larger than that of the DMA monomer. The measured and calculated intensity is used to determine a room temperature equilibrium constant of DMA-TMA of 1.7 × 10-3 atm-1 at 298 K. [ABSTRACT FROM AUTHOR]

Abstract Ion bombardment on graphene sheets can produce atomic vacancies that can trap metal atoms. In this paper, we demonstrated that these trapped metal atoms can effectively bind other molecules with heteroatoms, making them chemisorbed to the graphene. The trapped cobalt atom can bind sarin molecule through fluorine atom with dissociation energy significantly higher than the one bonded via oxygen atom. This suggests that it can displace water molecule and therefore pledge for sarin chemisorbent in atmospheric environment. Our investigations also revealed that metallic character is enhanced upon sarin adsorption unlike the bonding of water molecule with trapped metal atom in graphene lattice which causes an opening of small (0.02 eV) band gap. Present findings can have promising application towards detecting the presence of toxic sarin molecules. Graphical Abstract Unlabelled Image Highlights • Graphene with cobalt-filled monovacancies bind sarin molecules through fluorine atoms • Sarin can displace water molecules, bonded with cobalt in graphene monovacancies • Graphene with cobalt-filled divacancies is poor chemisorbent for sarin • Sarin on cobalt in graphene monovacancy changes electronic structure of graphene [ABSTRACT FROM AUTHOR]

The formation and equilibria of Sr2+, Mg2+, Ca2+, Ba2+, and Y3+ (M) complexes with a mixed-chelator comprising two biodegradable chelators (GLDA, L G , 2-[bis(carboxymethyl)amino] pentanedioic acid; HIDS, L H , 2-(1,2-dicarboxyethylamino)-3-hydroxy-butanedioic acid) in an aqueous matrix was evaluated. The potentiometric measurement results (ionic strength, 0.10 M; temperature, 25 ± 0.1 °C) confirmed the formation of 1:1:1 (M:L G :L H) complexes and the experimental data sets were further used to derive the equilibrium constants for the ternary complexes. The [MHL G L H ]5− complex was the dominant ternary complex with Sr2+, Mg2+, Ca2+, and Ba2+, while Y3+ formed [M(OH) 2 L G L H ]7− as the principal ternary species. The trend in the overall formation constants of the ML mix (L mix , L G :L H = 1:1) complexes was in the order: Y3+ > Ca2+ > Mg2+ > Sr2+ > Ba2+. The ternary complexation trend was interpreted using the corresponding atomic radii and solution-phase electronegativities of the elements. The modes of interaction between the chelators and cations in the ML mix systems were subsequently deduced, and evaluated by using Gaussian 16W program. The relative stabilities of the ternary complexes (Δlog K) were interpreted by comparison with the stabilities of the corresponding binaries, with negative Δlog K values observed for all the ML mix complexes. Formation of the deprotonated ternary complexes of strontium with 2-[bis(carboxymethyl)amino]pentanedioic acid and 2-(1,2-dicarboxyethylamino)-3-hydroxy-butanedioic acid. Unlabelled Image • Mixed-chelator (L mix) comprised of two biodegradable chelators (1:1) was studied. • Complexation of Sr2+, Mg2+, Ca2+, Ba2+, or Y3+ with L mix • Protonated, deprotonated, and metal-hydroxy ternary chelate formations with L mix. • Relative stability of ternary complexes is lower than the corresponding binaries. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Regression subject to chemical equilibrium constant leads to wrong parameter values. • Wrong parameter values cause erroneous equilibrium conversion in process simulation. • We propose bilevel program for regression that leads to correct parameter values. • Illustrative single-phase dimerization using Margules and NRTL is considered. Abstract For process simulation involving chemical reactions, thermodynamically accurate model parameters for chemical equilibrium are indispensable. We demonstrate that regression subject to the well-known chemical equilibrium constant entails violation of the sufficient conditions for thermodynamic stability. As a consequence, erroneous values of the equilibrium conversion are obtained upon use of the respective parameter values in, e.g., process simulation. In order to alleviate the problem, we propose a methodology for estimating parameters subject to necessary and sufficient criteria for thermodynamic stability. In particular, we propose an extension of Mitsos et al. (2009) to parameter estimation in reactive systems; an upper-level model-experiment mismatch is minimized subject to several lower-level minimization problems (LLP), which ensure the fulfilment of the reactive tangent plane criterion (RTPC) of Smith et al. (1993), along with other desired behavior of the Gibbs free energy. A fictitious single-phase dimerization reaction employing Margules and NRTL as Gibbs free energy models illustrates the thermodynamic guarantees provided by the proposed formulation, when the conventional ones fail. Our formulation conceptually allows any type of phase equilibrium, e.g., VLLE, as well as any type of activity coefficient model. The subproblems of the bilevel algorithm pose challenges to state-of-the-art commercial solvers. [ABSTRACT FROM AUTHOR]

Abstract This paper reports FT–IR and FT–NIR spectroscopic study of hydrogen bonding between N-monosubstituted caproamides and different ethers (diethyl ether and tetrahydrofuran) in carbon tetrachloride. With increase in ether concentration increase in intensity of red-shifted band, and decrease of intensity of monomer band has been observed. The MIR and NIR spectroscopic characteristics for N H⋯O hydrogen bonded complexes and also the equilibrium constants for 1:1 complex formation are given. Further, influence of structural differences of ethers on hydrogen bonding was investigated using Taft equation. Good correlation between logarithm of formation constants and Taft steric and inductive factors has been obtained only for tetrahydrofuran in MIR range. Highlights • The FT–IR and FT–NIR characteristics of N-monosubstituted caproamide/ether complexes are given. • Influence of structural differences of monosubstituted caproamides as well as ethers on hydrogen bonding was investigated. • The comparison with other hydrogen bonded copmlexes was made. [ABSTRACT FROM AUTHOR]

Abstract Amine-basedcarbon-capture technologies have been shown to be energetically expensive and to cause significant environmental and epidemiological impacts due to their volatility. Bicarbonate formation from carbon dioxide's reaction with water has been suggested as an effective alternative for capturing CO 2 ; however, the thermodynamics of this reaction are not well understood. This study experimentally determined the equilibrium constant of sodium bicarbonate (NaHCO 3) decomposition to sodium, water, and carbon dioxide; the study also compared the equilibrium constant to theoretical calculations. Using a combination of experimentation and thermodynamic relationships, the unitless equilibrium constants of the forward and reverse reactions were calculated accurately (error <± 9% and <± 4%, respectively). Equilibrium data were calculated using enthalpy and entropy values of each component of NaHCO 3 decomposition at temperatures ranging from 25 to 155°C respectively. These results offer more data essential to optimizing NaHCO 3 use in environmentally friendly next-generation CO 2 -capture technologies. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract The photoelectric functional hierarchical materials were prepared by the simple ionic self-assembly strategy exhibits multiple stimuli-responsive switching behavior triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. Abstract The photoelectric functional hierarchical materials have been successfully prepared by the simple ionic self-assembly (ISA) strategy from the cationic ferrocenyl surfactant, 16-alkyl (ferrocenyl-methyl)ammonium bromide (Fc16AB) and the anionic alizarin red (AR). The obtained complexes exhibited multiple stimuli-responsive switching behaviour triggered by β-cyclodextrin (β-CD) inclusion, redox species, and pH. The switching mechanism corresponding to each stimulus was studied in detail. Moreover, the fluorescent intensity of binary complexes could be modulated by the concentration of Fc16AB and redox of ferrocene part. The fluorescence switching mechanism upon redox stimulus was studied in detail. Both the complexes fabrication and transition mechanisms were found to be controlled by the inclusion equilibrium and the cooperative binding of noncovalent interactions, including the electrostatic interactions, π-π stacking, and amphiphilic hydrophobic association. This work provides a deep understanding of electro-photo molecular switching device. [ABSTRACT FROM AUTHOR]

Abstract Hydrostatic pressure alters the free energy of proteins by a few kJ mol−1, with the amount depending on their partial molar volumes. Because the folded ground state of a protein contains cavities, it is always a state of large partial molar volume. Therefore pressure always destabilises the ground state and increases the population of partially and completely unfolded states. This is a mild and reversible conformational change, which allows the study of excited states under thermodynamic equilibrium conditions. Many of the excited states studied in this way are functionally relevant; they also seem to be very similar to kinetic folding intermediates, thus suggesting that evolution has made use of the 'natural' dynamic energy landscape of the protein fold and sculpted it to optimise function. This includes features such as ligand binding, structural change during the catalytic cycle, and dynamic allostery. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract In many equilibrium systems, it is customary to use a simplified, apparent equilibrium reaction instead of the complete reaction model. The resulting apparent equilibrium constants are altered or controlled by changes of the chemical system, usually modifying the total concentration of auxiliary reagents, but the variation of other parameters such the intensity of light in photo-controlled reactions, types and concentration of solvents or composition of mixed solvents, the ionic strength of the chemical media, etc. is also possible. The main goal of this work is to propose a chemical equilibrium modelling based strategy to control the conditions governing equilibrium systems in order to tune the apparent constants. Indeed, by extracting the analytic relationship between the parameters of the complete model and apparent model, the magnitude of the apparent constant(s) can be predicted. At first, a basic strategy for calculating the tunable range of apparent constants of chemical equilibria is proposed. Next, three case studies for tuning the apparent constants are investigated in detail: inclusion complexes with cyclodextrin, aqueous micellar solutions for investigating the solvent effects and the boric acid/Mannitol system that allows the tuning of the apparent protonation constant. In all examples tuning the apparent constant is possible by regulating the chemical composition. Graphical abstract Image 1 Highlights • For many equilibrium systems it is customary to use a simplified apparent, instead of a complete complex equilibrium system. • By the thermodynamic laws and equilibrium models, the exact analytic relationship between complete and apparent models of equilibrium systems can be extracted. • The extracted relationship formula determine the external parameter (s) for controlling the apparent models of equilibrium systems. • By controlling the conditions, the apparent constant of equilibrium systems could be tuned in the desired value. [ABSTRACT FROM AUTHOR]

Poly(N‐acryloyl glycinamide) (PNAGA)/poly(N‐isopropyl acrylamide) (PNIPAAm) interpenetrating network (IPN) hydrogels were made by UV‐light initiated radical polymerization in two‐steps. The IPN hydrogels showed a double thermoresponsive behavior due to the combination of PNIPAAm (thermophobic) and PNAGA (thermophilic) networks. Increasing the content of the thermophobic PNIPAAm network leads to a change from a broad thermophilic volume phase transition temperature of PNAGA to a thermophilic–thermophobic‐type dual transition for the prepared IPN. Due to the double thermoresponsive character of the IPN gels, the mechanical properties are dependent upon temperature as demonstrated by performing tensile tests in water at 15 and 50 °C. Furthermore, the IPN hydrogels were characterized using turbidity measurements, SEM, and the determination of the equilibrium swelling ratio. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 539–544 The preparation and properties of a strong double thermoresponsive interpenetrating network (IPN) consisting of PNAGA and PNIPAAm hydrogels are shown. The IPNs show mechanical as well as thermoresponsive properties dependent on the temperature and weight ratio of the two networks. [ABSTRACT FROM AUTHOR]

Abstract After a critical approach to the centennial literature on Methylene Blue self-aggregation in water, accurate visible-light absorption spectra and thermodynamic equilibrium constants for the monomeric and dimeric forms of this dye in water at different temperatures were obtained by means of a novel procedure based on the Beer-Lambert equation. A thermo-solvatochromic effect was clearly detected in the monomer spectra, which we believe to be the main source of inaccuracy in all previous works. The only published explanation for this phenomenon, the existence of a colorless form of the monomer, is refuted here. Instead, a new notion has been introduced; the resonance virtual equilibrium hypothesis. According to this hypothesis the temperature-dependent absorption behavior of the monomer is provoked by the change in its electron charge distribution with the variation in the temperature-dependent dielectric constant of water. The monomer charge distribution stands between those of the virtual resonance forms, being the absorption spectrum of the monomer a composition of the theoretical spectra for the virtual mesomers, whose proportion is established by a temperature-dependent equilibrium constant. The application of this hypothesis allowed the virtual equilibrium constants and spectra for the mesomers to be evaluated with remarkable accuracy. Graphical abstract Image 1 Highlights • First accurate thermodynamic parameters for MB monomer self-aggregation in water. • Resonance virtual equilibrium hypothesis to understand MB monomer thermo-solvatochromism. • Flawless Visible light absorption spectra for MB monomeric resonance forms and MB dimer. [ABSTRACT FROM AUTHOR]

Highlights • Isobaric VLE data for systems including diethanolamine, p-cresol, m-cresol were measured at 20.0 kPa. • The VLE data were well correlated by Wilson, NRTL and UNIQUAC models and chemistry theory's model. • The excess Gibbs free energy data for binary systems were calculated by the NRTL model. • The equilibrium constants for binary systems were obtained and the reaction thermodynamic parameters were predicted. Abstract Isobaric vapour–liquid equilibrium (VLE) data for two binary systems of p-Cresol (PC) + diethanolamine (DEA) and m-Cresol (MC) + DEA were measured at 20.0 kPa. The Herington area method was used to check the binary VLE data, and the results showed good thermodynamic consistency. Meanwhile, the Wilson, NRTL, UNIQUAC models and the chemistry theory proposed by Dolezalek were used to correlate the VLE data. The binary energy interaction parameters for activity models, and reaction equilibrium constants for chemistry theory were obtained. With help of the parameters obtained in this work, the NRTL model was used to predict the VLE data of the two binary systems at the pressure of 8.33 kPa. The predictive results were compared with the literature's data. At same time, the excess Gibbs free energy for the two binary systems, and infinite dilution activity coefficients for MC and PC in DEA were estimated. The calculated results showed that the DEA had slightly stronger interaction with PC than MC. [ABSTRACT FROM AUTHOR]

Methylcyclohexane dehydrogenation to toluene and hydrogen (MTH) is an important reaction for H2 energy based systems. Hence, it is important to have a reliable equation for the dependence of the reaction equilibrium constant on temperature. A number of such equations have been proposed in the literature, but it is unclear which of them is more accurate in representing the equilibrium of methylcyclohexane dehydrogenation to toluene. To resolve this uncertainty, we analyzed their validity based on existing experimental data. Experimentally derived equilibrium constants were found to be generally bigger than those calculated by classical thermodynamics at 300-400 °C and 3, 10, and 15 bar. Equilibrium constants calculated based on tabulated free energy of the reaction, were closer to the experimental values than those based on standard heat capacities of the reacting materials. Part of the deviation is caused by the non-ideality of the reacting components at these conditions, which is reflected by their calculated compressibility factors. The equilibrium conversions calculated based on the proposed equilibrium constants have been compared to those obtained in a set of methylcyclohexane to toluene reactions carried out in continuous flow packed bed and membrane reactors and this comparison revealed that only the experimentally derived equilibrium constants provide reasonable results. [ABSTRACT FROM AUTHOR]

Abstract The adsorption of herbicides belonging to the group of halogenated phenoxyacids on the activated carbon was studied. They are differentiated in terms of quantity and type of functional groups (such as chloride, bromide, fluoride) and their position on an aromatic ring. The experimental equilibrium data were analyzed using adsorption isotherm equations taking into account energetic heterogeneity of the adsorption systems. The calculated concentration profiles from the kinetic data were discussed applying two diffusion models, MOE, f-MOE and multi-exponential equations. The dependences between the properties of adsorbates, adsorption uptake and rate were analyzed. The adsorption affinity of pesticides was correlated with adsorbate hydrophobicity, character of functional group, molecular structure. The applicability of kinetic models and equations was investigated; the assumptions of the models were analyzed with regard to consistency with adsorption mechanism. Similarity of adsorption mechanism was found for all adsorbates confirmed by similarity of kinetic curves and corresponding distributions of rate coefficients. The differences in kinetic profiles were attributed to differentiation of herbicide's molecules - number and type of functional groups and their positions on aromatic ring. Graphical abstract Image 1 Highlights • Strong influence of adsorbate structure and properties on adsorption. • Significant impact of energetic heterogeneity of systems. • Adsorption processes are very slow - developed internal structure of adsorbent. • Kinetic can be described by the FOE/SOE/MOE and f-MOE equations. • The best optimization results gives the multi-exponential equation. [ABSTRACT FROM AUTHOR]

Nebulization of enantiomerically mixed serine solutions, followed by ion deflection and gentle on‐line protonation, is used to isolate and characterize the strongly preferred homochiral neutral serine octamer (Ser8). The separation of the nebulization and ionization steps and the use of the enantiomeric l‐serine ion (l‐d3Ser)8H+ as a soft protonating agent ensured that neutral (d‐Ser)8 was characterized without interference from serine octamer ((d‐Ser)8H+) ions. MS/MS experiments showed that the ionized neutral octamer and the protonated octamer formed directly by ESI have the same structures. Experiments in which the temperature of the heated transfer tube was varied indicate dissociation of the neutral octamer to the dimer. Field‐free nebulization of racemic serine forms the separate homochiral species with very high chiral selectivity. We suggest that the homochiral preference is a property of (d‐Ser)8 and that the preference observed earlier for (d‐Ser)8H+ is simply an expression of this feature of the neutral cluster. Neutral serine octamer: Nebulization coupled with gentle on‐line protonation and MS analysis is used to isolate and characterize the neutral serine octamer (Ser8). Ser8 was transmitted from the nebulizer into the ionization region while any residual protonated octamer was deflected. Nebulized near‐racemic serine solutions exhibited homochiral preference for the octamer, which is proposed to be the origin of the homochiral preference observed in Ser8H+. [ABSTRACT FROM AUTHOR]

In this study, the removal of mercury (II) ions from aqueous solutions by dried biomass of Phragmites australis was investigated in the batch system. The biomass was characterized by Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray fluorescence (ED-XRF), Brunauer-Emmett-Teller (BET) surface area techniques (BET). Inductively Coupled Plasma Atomic Emission Spectrophotometer (ICP-OES, Spectro Blue) was used to analyze Hg(II) concentration and obtained data in batch experiments indicated that Hg (II) was rapidly adsorbed and such adsorption reached equilibrium within 60 min. The initial pH of the solution was effective parameter for Hg (II) biosorption. The biosorption kinetics was in better good fit with pseudo-second order kinetics and the results obtained from the batch experiments were conformed better with the Langmuir isotherm model than Freundlich and D-R isotherm models. The maximum Hg (II) biosorption capacity of P.australis was 20.0 ± 0.4 mg/g. The availability of other metal ions affected mercury biosorption. Adsorption/desorption studies demonstrated that the adsorbed Hg (II) could be desorbed effectively with a 0.1 M ethylenediamine tetra-acetic acid (EDTA) solution. The biosorption capacity of the regenerated biosorbent could still be maintained at 72% at the fifth adsorption-desorption cycle. Consequently, it can be said that P. australis can be used as an applicable, cost-efficient, nature friendly biosorbent for treating wastewater. [ABSTRACT FROM AUTHOR]

Abstract This paper deals with modelling and reconstruction of strain fields, relying upon data generated from neutron Bragg-edge measurements. We propose a probabilistic approach in which the strain field is modelled as a Gaussian process, assigned a covariance structure customised by incorporation of the so-called equilibrium constraints. The computational complexity is significantly reduced by utilising an approximation scheme well suited for the problem. We illustrate the method on simulations and real data. The results indicate a high potential and can hopefully inspire the concept of probabilistic modelling to be used within other tomographic applications as well. [ABSTRACT FROM AUTHOR]

The ethyl ester of levulinic acid, ethyl levulinate is a completely bio-based chemical made from levulinic acid, which is a hydrolysis product of cellulose and bio-ethanol. The very precise kinetics of levulinic acid esterification with ethanol was studied in an isothermal batch reactor in the presence of homogeneous (H2SO4) and heterogeneous catalysts (cation exchange resin Smopex-101). The temperature interval of the experiments was 50-70 °C. A kinetic model was proposed for both kinds of catalysts, adopting equilibrium rate expressions in any case. The different role of the catalyst used was considered separately, while a unique equilibrium constant was assumed for each system. The kinetic parameters were successfully determined by non-linear regression analysis. The model gave a very good description to the experimental data. The heterogeneous catalyst was used to demonstrate the feasibility of continuous operation in isothermal fixed bed reactors. The catalyst showed a good stability and high conversions of levulinic acid were obtained in the laboratory-scale fixed bed reactor. The model was able to predict both dynamic and steady-state experimental data. [ABSTRACT FROM AUTHOR]

Abstract We consider the notion of equilibration for an isolated quantum system exhibiting Anderson localization. The system is assumed to be in a pure state, i.e., described by a wave-function undergoing unitary dynamics. We focus on the simplest model of a 1D disordered chain and we analyse both the dynamics of an initially localized state and the dynamics of quantum states drawn at random from the ensemble corresponding to the minimum knowledge about the initial state. While in the former case the site distribution remains confined in a limited portion of the chain, the site distribution of random pure state fluctuates around an equilibrium average that is delocalized over the entire chain. A clear connection between the equilibration observed when the system is initialized in a fully localized state and the amplitude of dynamical fluctuations of a typical random pure state is established. [ABSTRACT FROM AUTHOR]

A study of the reaction mechanism and thermodynamic modeling of pentavalent vanadium V(V) extraction from NaVO 3 -H 2 SO 4 -H 2 O solutions using Di-(2-ethylhexyl) phosphoric acid (D2EHPA or HA) extractant was carried out. The effects of initial pH of the solution, extractant concentration, and temperature on the extraction of V(V) were examined. The stoichiometry of the extraction reaction was determined using the slope analysis method. The extracted species was shown to be VO 2 A. A thermodynamic modeling approach was proposed for the prediction of equilibrium concentrations and pH of the system based on the known initial concentrations and process temperature. In the presented approach, the non-ideality of both aqueous and organic phases was taken into account. The activity coefficients of all organic components were calculated using UNIQUAC-NRF model, while the Electrolyte-UNIQUAC-NRF model was employed to calculate the activity coefficients of ions in aqueous phase. The equilibrium constant of the extraction reaction and the unknown parameters of the models were adjusted through the regression of experimental data at 25 °C, 35 °C, and 45 °C. Adjusted parameters were used for the prediction of equilibrium vanadium concentration in organic phase and equilibrium pH of the aqueous phase. Both of regressed and predicted values were in very good agreement with the experimental data. Moreover, calculated standard molar enthalpy of the reaction indicated the endothermicity of extraction reaction between VO 2 + and D2EHPA. [ABSTRACT FROM AUTHOR]

The esterification of nopol with acetic acid to produce nopyl acetate using sulfuric acid as homogeneous catalyst was studied. The reactions were carried out in a batch reactor, at different temperatures (50, 60, 70 and 80 °C), catalyst concentrations (0.0184, 0.0275, 0.0367 and 0.0480 mol L-1) and molar ratio of acetic acid to nopol (1: 1, 1:2, 1:3 and 1: 4); the chemical equilibrium composition was measured at those reaction conditions. It was found that the equilibrium composition is a weak function of temperature, equilibrium conversion was 63, 68, 71 and 75% at 50, 60, 70 and 80°C, respectively. The reaction was described with a simple power-law model with a second-order kinetic model for both the forward and the backward reaction, using concentration and activities which were predicted by the Universal Functional group Contribution (UNIFAC) method for considering non-ideal behavior of the liquid phase. The forward reaction rate and the equilibrium constants increased with temperature; the relation of the pre-exponential factor with the catalyst amount was evaluated. The activation energy and pre-exponential factor estimated for the forward reaction using the kinetic model based on concentration, were respectively, 28.08 kJ mol-1 and 11126 L mol-1 h-1 with a concentration of catalyst of 0.0275 M. Using the kinetic model based on activities, the forward reaction rate constant was 28.56 kJ·mol-1 and the kfo, act was 33860 L mol-1 h-1. The enthalpy (34.90 kJ mol-1) and the entropy (0.12 kJ mol-1 K-1) of reaction were determined using van't Hoff equation. [ABSTRACT FROM AUTHOR]

The monitoring of the non-interfacial phenomena of mass transport and homogeneous chemical reactions by combining spectroscopic and electrochemical methods is examined. The spectroelectrochemical study of a charge transfer process is addressed, considering the possibilities that the electro-consumed species is regenerated in solution by means of a first-order chemical reaction or that the diffusivity of the oxidized and reduced species differ from each other significantly. Novel closed-form explicit analytical expressions for the concentration profiles and the absorbance response of all the species for any voltammetric technique are deduced, taking into account the two main working arrangements: the normal-beam and parallel-beam modes. The analytical solutions are particularized to double potential step chronoamperometry and to cyclic voltammetry. The corresponding chronoabsorptometric and voltabsorptometric responses in parallel-mode are proven to provide additional information with respect to electrochemical-only measurements, as well as insights into the solution regions next to the interface where the concentration changes and equilibrium disruption take place. With this theory the absorptometric response can be related to the physicochemical dynamics of the redox system and optimum configuration and conditions for the study of diffusion and reaction layers, the species diffusion coefficients and the chemical kinetic and equilibrium constants can be established. [ABSTRACT FROM AUTHOR]

Enthalpies of high-pressure phase transitons in ZrSiO 4 were measured by high-temperature drop-solution calorimetry. The enthalpies for the zircon-reidite transition in ZrSiO 4 and for dissociation of reidite to cotunnite-type ZrO 2  + SiO 2 stishovite were obtained to be 27.5 ± 3.3 and 50.3 ± 3.0 kJ/mol, respetively, at 298 K. By thermal relaxation method, low-temperature isobaric heat capacities of ZrSiO 4 reidite and cotunnite-type ZrO 2 were measured, giving standard entropies at 298 K of 77.29 ± 0.04 and 49.10 ± 0.04 J/mol·K, respectively. Combining the measured enthalpies and entropies with other available thermophysical data, the transition boundaries in ZrSiO 4 were calculated. The calculated zircon-reidite transiton boundary is consistent with that by in situ high-pressure expreiments by Ono et al. (2004a) within the errors. The calculated dissociation boundary of reidite has a smaller slope than that by high-pressure quench expreiments by Tange and Takahashi (2004). The equilibrium zircon-reidite transition pressure is calculated to be 8 GPa at 298 K, which is by 12–15 GPa lower than the transition pressures observed by room-temperature static compression experiments. Our results suggest that zircon transforms to reidite and dissociates into the two phases at 330 and 610 km depths, respectively, along the normal mantle geotherm. Combining the calculated phase relations with kinetics estimated from the first principles calculation may provide some insights to P, T conditions which reidites found in impact ejecta layers and craters experienced. [ABSTRACT FROM AUTHOR]

Efficient waste-load allocation plays a critical role in improving water quality. In this paper, a Pigovian tax-based waste-load allocation problem generalized from a prototype in the Tuojiang River basin is proposed. To control water quality and resolve the conflicts between dischargers, a Pigovian tax-based equilibrium strategy for waste-load allocation is designed to provide an optimization method for water quality management that fully considers the Stackelberg game between the environmental regulators and the river system dischargers. The successful application of this model to the Tuojiang River basin demonstrates its practicality and efficiency. Sensitivity analyses under different tax rate settings are given to provide the environmental regulators with insights into the impacts of a Pigovian tax policy on the discharger’s BOD removal decisions, as well as to identify the waste-load allocation trade-offs between costs and equity. Compared to conventional models, the proposed method has the ability to reduce pollutants and achieve equitable waste-load allocations. The results demonstrated that as the proposed method can encourage dischargers to improve emissions performance, it could be of significant assistance to environmental decision making. [ABSTRACT FROM AUTHOR]

This discussion article summarizes all protonation and stability constants data found in the literature for nonprotein l-norleucine amino acid and its metal complexes. The results of approximately 18 published articles discussing the protonation and complexation equilibria of l-norleucine using different techniques and software were presented to comprehend the data on the grounds of modern aspects of l-norleucine complex chemistry. [ABSTRACT FROM AUTHOR]

The co-contamination of ciprofloxacin (CIP) with metal ions results in alteration of CIP mobility, antimicrobial activity and distribution/development of the antibiotic-resistance genes. In this study, the stability of five CIP-Me complexes [Me = Al(III), Co(II), Cu(II), Fe(III), Mg] was investigated in the presence of humic substances (HS) at two temperatures 18 ± 2 °C and 4 ± 1 °C for seven days period. The most stable complexes were CIP-Al, CIP-Cu, and CIP-Co with the stability constants ( K ) at 18 °C 35.5 ± 1.4 11.5 ± 1.5 and 11.7 ± 1.5 respectively. At lower temperature (4 °C), the stability constants decreased: 1-fold for CIP-Al, 14-fold for CIP-Co and 2-fold for CIP-Cu. The presence of humic substances decreased the stability of complexes. The chemical reactions of Fe 3+ in water at circumneutral pH resulted in stability alteration. The formation of CIP-Mg complexes at lower temperatures and in the presence of HS was limited. In ultrapure water, CIP-Me complexes exhibit higher toxicity towards Gram-negative Enterobacter aeruginosa (ranged between 0.125 and 0.5 μg/ml). However, the presence of HS reduced the antimicrobial activity of CIP-Me complexes by at least 2-fold. Gram-positive representative, Bacillus subtilis was not affected by the presence of metal ions and/or HS. The toxicity toward B. subtilis for the complexes was equal to toxicity of CIP alone (MIC = 0.25 μg/ml). This suggested the different susceptibility to CIP and its complexes. [ABSTRACT FROM AUTHOR]

In this paper, a new method for phase equilibrium calculations at constant temperature, volume and moles (VTN flash) is presented. The problem is formulated as an unconstrained minimization of the Helmholtz free energy with respect to mole numbers. Volume is a dependent variable and its dependence on mole numbers is taken into account by solving a nonlinear equation (the volume balance equation) for pressure at each iteration level. By analyzing the block structure of the Hessian matrix in the constrained minimization of the Helmholtz free energy with respect to mole numbers and volume (used in previous approaches), it is shown that the Hessian in the proposed method has a higher implicitness level and Newton iterations converge faster (in terms of number of iterations). The calculation framework is similar to that in flash calculations at pressure and temperature specifications (PT flash). A combined successive substitution - Newton method is used, with mole numbers or natural logarithms of equilibrium constants as independent variables. The iterations in the VTN flash are “PT-like” (for a sequence of pressures converging to the pressure at which the volume specification is met) and the number of iterations required for convergence is comparable to that of the PT flash performed at the final pressure. The proposed method is tested for several mixtures of various complexities and proved to be rapid and robust. For vapor-liquid equilibrium, the convergence is obtained starting from the ideal equilibrium constants, even very close to phase boundaries and at near-critical conditions. Existing codes for PT flash calculations can be easily modified to incorporate the new method for VTN flash calculations. [ABSTRACT FROM AUTHOR]

Herein, hybrid Cu/Ni-based hexagonal rods were obtained through a competing reaction of dimethylglyoxime with copper acetate and nickel acetate. Using Cu2+ to intervene the coordination equilibrium between Ni2+ and dimethylglyoxime, the length of the rods was altered; moreover, the coordination environments were investigated by adjusting the concentration of Cu2+ and replacing the solvent. The decomposition products porous NiO and CuO/NiO were directly employed as SC electrodes. The CuO/NiO electrode delivered higher specific capacitance and energy with more excellent energy deliverable ability and better cycling stability than the pristine NiO electrode. After 2000 continuous cycles, the capacitance retention of the as-synthesized CuO/NiO electrode was 87.9%. The maximum specific capacitance and energy delivery efficiency of the CuO/NiO electrode were 344 F g−1 and 93.5%, respectively, at a current density of 0.625 A g−1. The better performance of the hybrid sample was mainly due to higher surface area, lower charge-transfer resistance, and possible synergistic effect. Furthermore, MgO/NiO nanoparticles were synthesized and compared to confirm the existence of a synergistic effect. [ABSTRACT FROM AUTHOR]

There are large discrepancies existing in equilibrium Mg isotope fractionation calculations and experimental investigations for cases related to mineral vs. solution. To clarify this confusing issue, a newly designed cluster-model-based quantum chemistry method, i.e., volume variable cluster model (VVCM), is used to provide equilibrium Mg isotope fractionation factors between Mg-bearing carbonates (calcite, aragonite, dolomite and magnesite), amorphous calcium carbonates (ACCs), brucite and aqueous species (i.e., Mg 2+ (aq) , MgHCO 3 + (aq) and MgOH + (aq) ). We find that local configuration sampling of aqueous species is essential to provide precise fractionations between mineral and solution. The phonon-based periodic boundary method is also used for several minerals and it obtains very similar fractionations with VVCM results. Our results are very close to those of Pinilla et al. (2015) although via completely different approaches. Both of them have included the effect of local configuration disorder. However, both of them are significantly different from some of experimental results for cases of carbonates vs. solutions. The existence of various Mg-bearing species in fluids of experiments, the direct incorporation of hydrated Mg 2+ into the solids, the Mg 2+ concentration effect, and the existence of intermediate precursors (e.g., ACCs) are several possible causes for the mismatches. Relative to coexisting aqueous Mg 2+ , we find that ACCs will enrich heavy Mg isotopes, i.e., ~1.45‰ at 25 °C, agreeing with previous experimental estimation. Equilibrium Mg isotope fractionation factors between brucite and solutions are also predicted. Besides, we applied VVCM to predict the Mg isotope fractionations between high-temperature phases, i.e., forsterite, diopside, enstatite, tremolite and spinel. The predicted β factors are in the order of spinel > tremolite > diopside > enstatite > forsterite. This study provides a base for understanding the accumulating Mg isotope data. [ABSTRACT FROM AUTHOR]

Together with increasing world population, developing technology and rapid industrialization process bring about environmental pollution. Nowadays, cleaning environment from industrial wastes and pollutants is of utmost importance. Some organic materials, produced by the majority of textile waste, cause environmental pollution. Many dyestuffs, which are hazardous for environment, can be released to environment by industrial organizations without having any precaution. Textile dyestuffs, being above certain concentrations, can cause poisoning of aquatic organisms. Dyestuffs can be classified as following: Anionic: Direct, acid and reactive dyes Cationic: Basic dyes Nonionic: Disperse dyes It can be said that most problematic group of dyes used in the textile industry is the group of reactive dyes. Analyzing performed studies shows that these views are supported. Today, adsorption techniques are gaining ground due to efficiency in removal of too stable pollutants. Adsorption is, economically, a reasonable method and we can say that it provides formation of high quality products. With the development of industry search for materials, to be used as adsorbent for removal of factory wastes and water-soluable dyestuffs from water, accelerates. In our study, from natural adsorbents diatomite(Çaldıran/VAN) is used as an adsorbent material. The removal of natural red and basic blue from aqueous solution using diatomite, was investigated with respect to the adsorbent dose (0,02 g), initial concentration (20-140 mg/L), temperature (between 25 and 450C), on batch adsorption were studied as a function of contact time. The lineer Langmuir, Freundlich and Temkin adsorption equations were applied to describe the equilibrium isotherms. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (ΔH0), Gibbs free energy (ΔG0) and entropy (ΔS0) shoved spontaneous and endothermic in nature of adsorption for both of adsorbents. [ABSTRACT FROM AUTHOR]