Equilibrium Aspects Research Articles

Complexation between Sodium Poly(styrenesulfonate) and Alkyltrimethylammonium Bromides in the Presence of Dodecyl Maltoside.

In the present paper, the impact of dodecyl maltoside (C12G2) on the association of sodium poly(styrenesulfonate) (PSS) with dodecyl- and hexadecyltrimethylammonium bromides (DTAB and CTAB) was studied. A low amount of nonionic surfactant enhances the binding of the investigated cationic amphiphiles on PSS, reducing the cationic surfactant-to-polyanion ratio needed for charge neutralization and precipitation. This effect is more pronounced for DTAB than for CTAB due to the considerably higher free surfactant concentration of the former cationic amphiphile. The synergistic surfactant binding also affects the nonequilibrium features of PSS/CTAB association via enhancing the kinetically stable concentration range of overcharged polyion/surfactant nanoparticle dispersions. With increasing C12G2 concentration, however, an opposite effect of the uncharged additive dominates. Namely, the CTAB molecules are solubilized excessively into mixed surfactant micelles, which reduces the surface charge of the PSS/CTAB/C12G2 nanoparticles and thus destabilizes their dispersion. At appropriately large nonionic surfactant concentrations, the binding of CTAB is largely reduced, resulting in the redissolution of the precipitate. In contrast, neither the destabilization nor the resolubilization effects of the added dodecyl maltoside were observed for the PSS/DTAB system due to the much lower driving force of DTAB binding compared to CTAB. Our results clearly demonstrate that the alkyl chain length of the ionic amphiphile has a pronounced effect on both the equilibrium and nonequilibrium aspects of polyion/mixed surfactant complexation which might be further exploited in various next generation applications.

Antibody-ligand interactions for hydrophobic charge-induction chromatography: a surface plasmon resonance study.

This article describes the use of surface plasmon resonance (SPR) spectroscopy to study antibody-ligand interactions for hydrophobic charge-induction chromatography (HCIC) and its versatility in investigating the surface and solution factors affecting the interactions. Two density model surfaces presenting the HCIC ligand (mercapto-ethyl-pyridine, MEP) were prepared on Au using a self-assembly technique. The surface chemistry and structure, ionization, and protein binding of such model surfaces were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), contact-angle titration, and SPR, respectively. The influences of the surface and solution factors, e.g., ligand density, salt concentration, and solution pH, on protein adsorption were determined by SPR. Our results showed that ligand density affects both equilibrium and dynamic aspects of the interactions. Specifically, a dense ligand leads to an increase in binding strength, rapid adsorption, slow desorption, and low specificity. In addition, both hydrophobic interactions and hydrogen bonding contribute significantly to the protein adsorption at neutral pH, while the electrostatic repulsion is overwhelmed under acidic conditions. The hydrophobic interaction at a high concentration of lyotropic salt would cause drastic conformational changes in the adsorbed protein. Combined with the self-assembly technique, SPR proves to be a powerful tool for studying the interactions between an antibody and a chromatographic ligand.

Adsorption of Methylene Blue by ultrasonic surface modified chitin

HypothesisChitin is a biopolymer which can be used as a low-cost and eco-friendly material for dyes adsorption. The use of chitin for dyes removal is little investigated, due its low surface area, porosity and high crystallinity. So, an ultrasonic surface modified chitin (USM-chitin) was prepared and used for Methylene Blue (MB) adsorption. ExperimentsChitin was obtained from shrimp wastes and its surface was modified by an ultrasound-assisted treatment. USM-chitin was characterized by N2 adsorption/desorption isotherms (BET surface area, total pore volume), infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The adsorption of MB on USM-chitin was studied by kinetic, equilibrium, thermodynamic, interactions analysis, desorption and mass transfer aspects. FindingsUSM-chitin presented surface area 25 times higher than raw chitin. The porosity was increased and the crystallinity was decreased. The general order model was suitable to represent the adsorption kinetics and the Langmuir model was adequate for the equilibrium. The maximum adsorption capacity was 26.69mgg−1. The adsorption was spontaneous, favorable and exothermic. USM-chitin can be used seven times maintaining the same adsorption capacity.

The role of organic diluents in the aspects of equilibrium, kinetics and thermodynamic model for silver ion extraction using an extractant D2EHPA

The effects of organic diluents regarding the aspects of equilibrium data, kinetics of extraction behavior and thermodynamic model are of great importance in the extraction processes. Therefore, these effects were investigated for silver ion extraction by a liquid–liquid extraction process using D2EHPA as an extractant. Various organic diluents that have different dielectric constants like kerosene, cyclohexane, chloroform and 1-octanol were selected for use in this work. The equilibrium data of solubility and tie-lines for the ternary systems of water+D2EHPA+organic diluents exhibited type-2 LLE behavior at a temperature of 298.2K and atmospheric pressure. Moreover, the uncertainty propagation calculation was determined to validate the reliability of the data. The extraction efficiency of silver ions for each organic diluent was also investigated; maximum extraction of 94% was obtained for 1-octanol. The extraction behaviors of silver ion with D2EHPA in the different organic diluents were reported as regards their reaction stoichiometry. They were also analyzed by spectroscopic analysis. Results of the thermodynamic NRTL model were obtained and a very good correlation with the experimental LLE data was confirmed by the root-mean square deviation (rmsd) values of 1%.

Aggregation of ALS-linked FUS mutant sequesters RNA binding proteins and impairs RNA granules formation

Protein aggregate/inclusion is one of hallmarks for neurodegenerative disorders including amyotrophic lateral sclerosis (ALS). FUS/TLS, one of causative genes for familial ALS, encodes a multifunctional DNA/RNA binding protein predominantly localized in the nucleus. C-terminal mutations in FUS/TLS cause the retention and the inclusion of FUS/TLS mutants in the cytoplasm. In the present study, we examined the effects of ALS-linked FUS mutants on ALS-associated RNA binding proteins and RNA granules. FUS C-terminal mutants were diffusely mislocalized in the cytoplasm as small granules in transiently transfected SH-SY5Y cells, whereas large aggregates were spontaneously formed in ∼10% of those cells. hnRNP A1, hnRNP A2, and SMN1 as well as FUS wild type were assembled into stress granules under stress conditions, and these were also recruited to FUS mutant-derived spontaneous aggregates in the cytoplasm. These aggregates stalled poly(A) mRNAs and sequestered SMN1 in the detergent insoluble fraction, which also reduced the number of nuclear oligo(dT)-positive foci (speckles) in FISH (fluorescence in situ hybridization) assay. In addition, the number of P-bodies was decreased in cells harboring cytoplasmic granules of FUS P525L. These findings raise the possibility that ALS-linked C-terminal FUS mutants could sequester a variety of RNA binding proteins and mRNAs in the cytoplasmic aggregates, which could disrupt various aspects of RNA equilibrium and biogenesis.

Mining hidden links in social networks to achieve equilibrium

Although more connections between individuals in a social network can be identified with the development of high techniques, to obtain the complete relation information between individuals is still hard due to complex structure and individual privacy. However, the social networks have communities. In our work, we aim at mining the invisible or missing relations between individuals within a community in social networks. We propose our algorithm according to the fact that the individuals exist in communities satisfying Nash equilibrium, which is borrowed from game-theoretic concepts often used in economic researches. Each hidden relation is explored through the individual's loyalty to their community. To the best of our knowledge, this is the first work that studies the problem of mining hidden links from the aspect of Nash equilibrium. Eventually we confirm our approach's superiority from extensive experiments over real-world social networks.

Preparation of Magnetic-Activated Carbon Nanocomposite and Its Application for Dye Removal from Aqueous Solution

A nanocomposite of activated carbon and iron oxide was prepared and characterized by x-ray diffraction and scanning electron microscopy methods. The prepared magnetic nanocomposite can be separated easily from water by an external magnet. The prepared magnetic nanocomposite was used as adsorbent for removal of Bismarck Brown (B.B.) as a dye pollutant from water. The adsorption studies include both equilibrium and kinetic aspects, and the results were modeled with different equations. The obtained results indicate that the prepared magnetic nanocomposite of iron oxide and activated carbon is one of the best adsorbents for the removal of B.B. from aqueous solution.

Removal of Evans Blue and Yellow thiazole dyes from aqueous solution by Mg-Al-CO3 Layered Double Hydroxides as anion-exchanger

Mg-Al-CO3 Layered double hydroxide (LDH) was prepared by co-precipitation method at constant pH, and subsequently used to remove Evans Blue (EB) and Yellow thiazole (YT) dyes from aqueous solutions.The obtained material was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), thermal analysis and BET. The kinetic and equilibrium aspects of sorption of the anionic dyes from aqueous solution by Mg-Al-CO3 were investigated in batch mode. The sorption kinetic data were found to be consistent with the pseudo-second-order model. Data for YT and EB sorption by Mg-Al-CO3 were fitted better by the Langmuir equation than by the Freundlich equation based on the determination coefficient values R2. The maximum adsorption capacities of 222.2 mgg-1 for Yellow thiazole and 107.5 mgg-1 for Evans blue. The thermodynamic parameters including Gibbs free energy ( G°), standard enthalpy change ( H°), and standard entropy change ( S°) for the process were calculated. The negative  G° value indicates the spontaneity of the removal process.

Multiphase equilibrium flash with salt precipitation in systems with multiple salts

A new methodology for determining simultaneous chemical and phase equilibrium of mixtures of light gases and aqueous electrolyte solutions with the potential for multiple salt deposition is proposed. The novel aspects of this new approach include, but are not limited to (1) a novel tearing algorithm for determining equilibrium ion solubility limits, (2) rigorous proof that the proposed tearing algorithm generates a Cauchy sequence and is therefore guaranteed to converge to the correct equilibrium ion solubility limits (3) and a unique formulation of the combined chemical and multi-phase equilibrium flash problem that accounts for salt deposition but decouples the chemical and phase equilibrium aspects of the flash.Examples from real EOR and CO2 sequestration applications are presented. Results clearly show that the proposed numerical approach is reliable, robust, and efficient and can be used to determine salt deposition in multi-phase flash problems. Several geometric illustrations and numerical details are used to elucidate key points of the proposed approach.

Mercury removal from aqueous solution by dried biomass of indigenous Vibrio parahaemolyticus PG02: Kinetic, equilibrium, and thermodynamic studies

In this study, for the first time the potential use of dried Vibrio parahaemolyticus PG02 to remove mercury from synthetic effluent was investigated by considering equilibrium, kinetic, and thermodynamic aspects. The results indicated that Hg2+ biosorption was best described by the pseudo-second order model. In addition, it was found that intraparticle diffusion was not the sole rate-limiting step. The ion-exchange mechanism was a predominant biosorption mechanism in the first 15 min of contact. The Langmuir isotherm better described the equilibrium data of Hg2+ biosorption than the Freundlich isotherm. According to this model, the maximum biosorption capacity was found to be 9.63 × 10−4 mol g−1 at optimum conditions (pH = 6.0 and temperature =35 °C).

Karyopherin-Centric Control of Nuclear Pores Based on Molecular Occupancy and Kinetic Analysis of Multivalent Binding with FG Nucleoporins

Intrinsically disordered Phe-Gly nucleoporins (FG Nups) within nuclear pore complexes exert multivalent interactions with transport receptors (Karyopherins (Kaps)) that orchestrate nucleocytoplasmic transport. Current FG-centric views reason that selective Kap translocation is promoted by alterations in the barrier-like FG Nup conformations. However, the strong binding of Kaps with the FG Nups due to avidity contradicts rapid Kap translocation in vivo. Here, using surface plasmon resonance, we innovate a means to correlate in situ mechanistic (molecular occupancy and conformational changes) with equilibrium (binding affinity) and kinetic (multivalent binding kinetics) aspects of Karyopherinβ1 (Kapβ1) binding to four different FG Nups. A general feature of the FxFG domains of Nup214, Nup62, and Nup153 is their capacity to extend and accommodate large numbers of Kapβ1 molecules at physiological Kapβ1 concentrations. A notable exception is the GLFG domain of Nup98, which forms a partially penetrable cohesive layer. Interestingly, we find that a slowly exchanging Kapβ1 phase forms an integral constituent within the FG Nups that coexists with a fast phase, which dominates transport kinetics due to limited binding with the pre-occupied FG Nups at physiological Kapβ1 concentrations. Altogether, our data reveal an emergent Kap-centric barrier mechanism that may underlie mechanistic and kinetic control in the nuclear pore complex.

Model-Free Unraveling of Supported Nanoparticles Plasmon Resonance Modes

Plasmonics of Ag, Au, and Zn nanoparticles supported on Al2O3(0001), TiO2(110), and ZnO(0001) substrates has been probed by surface differential reflectivity spectroscopy (SDRS) during vapor deposition growth. Parallel and perpendicular interfacial susceptibilities (ISs), or “optical thicknesses”, which characterize only the dielectric response of the film, are derived from experimental spectra in p- and s-polarization using an inversion procedure based on Kramers–Kronig transform. The consistency of the approach is checked against sum rules. Plasmonic contributions are unraveled by decomposing ISs into damped oscillators and identified with the help of dielectric simulations of truncated supported spheres or spheroids. Beyond the common Drude behavior of Ag, Au, and Zn, the comparison between the three metals demonstrates the paramount role of interband transitions in the ISs profiles. While gold and silver show free electron plasmon modes, zinc exhibits polarization modes of bound electrons. However, despite those differences, the resonant modes that are identified herein are universal for supported particles. Particle shape, equilibrium aspect ratio, image field, polydispersity, and interface-induced damping are discussed by analyzing changes in frequencies, oscillator strengths, and broadenings. Deposit-induced band gap absorption for semiconductor substrate and switches from growth to coalescence regimes are evidenced. Static and dynamic coalescence are characterized by power law exponents as a function of particle size. Therefore, the unique framework that is proposed opens strong prospects in the optical characterization of growth, metal/semiconductor interfaces, and gas adsorption.

Removal of Methyl Violet Dye from Aqueous Solution by sf Platanus Carpinifolia Tree Leaves as Highly Efficient Sorbent: Multivariate Optimization, Isotherm Modeling, and Kinetic Studies

This study introduces a novel and highly efficient biosorbent called Platanus Carpinifolia tree leaves to remove Methyl violet from aqueous solution. A Box-Behnken design of experiment based on three main factors (initial concentration ( C d ), sorbent amount (S), and pH) through the response surface methodology approach was chosen to model the removal efficiency (R%) of Methyl violet. The optimum conditions were found from the obtained model as C d = 500 mg/L and S = 0.11 g/L with no pH significant influences. Langmuir, Freundlich, and Temkin isotherms were applied to scrutinize the equilibrium aspect of biosorption by fitting the adsorption experimental data with isotherms. The adsorbent's maximum capacity uptake ( q max ) was obtained to be 555.5 mg/g from the Langmuir model, which has shown better description of the equilibrium process. Kinetic of biosorption was studied with making use of the pseudo-first order and pseudo-second order models along with intra-particle diffusion. The results showed that the adsorption process behaves in accordance with the pseudo-second order model, and intraparticle diffusion is not solely the rate-limiting step. Regarding the thermodynamical investigation, Δ G°, ΔH ○ , and ΔS°respectively, were predicted to be 1.96, 37.34 kJ/mol, and 132 J/mol. This implies that chemisorption is the predominant portion of adsorption mechanism.

EFFECT OF ELECTROLYTES ON THE TEMPERATURE PROFILE OF SALINE EXTRACTIVE DISTILLATION COLUMNS

The effect of electrolytes in the temperature profile of saline extractive distillation columns is analyzed using a Newton–Raphson based program (acronym GKTM) with a new increase-bystep technique and applied to the system 1-propanolwater-LiNO3. In addition, the E-NRTL model is examined in order to validate its capability of making accurate predictions of phase equilibrium behavior and its suitability for simulation of extractive distillation columns. Special aspects of the phase equilibrium of mixed solvents electrolyte systems are analyzed. These particular features determine the special temperature profile in these cases.

Equilibrium and Kinetic Aspects in the Sensitization of Monolayer Transparent TiO2Thin Films with Porphyrin Dyes for DSSC Applications

Free base, Cu(II) and Zn(II) complexes of the 2,7,12,17-tetrapropionic acid of 3,8,13,18-tetramethyl-21H,23H porphyrin (CPI) in solution and bounded to transparent monolayer TiO2nanoparticle films were studied to determine their adsorption on TiO2surface, to measure the adsorption kinetics and isotherms, and to use the results obtained to optimize the preparation of DSSC photovoltaic cells. Adsorption studies were carried out on monolayer transparent TiO2films of a known thickness. Langmuir and Frendlich adsorption constants of CPI-dyes on TiO2monolayer surface have been calculated as a function of the equilibrium concentrations in the solutions. The amount of these adsorbed dyes showed the accordance with Langmuir isotherm. Kinetic data on the adsorption of dyes showed significantly better fits to pseudo-first-order model and the evaluated rate constants linearly increased with the grow of initial dye concentrations. The stoichiometry of the adsorption of CPI-dyes into TiO2and the influence of presence of coadsorbent (chenodeoxycholic acid) have been established. The DSSC obtained in the similar conditions showed that the best efficiency can be obtained in the absence of coadsorbent with short and established immersion times.

망간슬래그의 비소에 대한 수착특성 연구

비소의 오염은 다양한 자연적 또는 인위적 원인들로 인하여 발생할 수 있다. 비소의 자연상 다양한 화학종 중 3가와 5가 형태로 대부분 존재하고, 비소의 거동은 Al, Fe, Mn 산화물 등에 의해 영향을 받는다. 이에 본 연구는 Mn, Si, Ca 등의 성분이 많이 포함된 망간슬래그를 이용한 비소 수착특성을 규명하기 위해 수행되어졌다. 망간슬래그의 수착제로서의 주요한 특성을 조사하고 평형론과 반응 속도론 실험을 통해 비소 화학종별 수착양상을 고찰하였다. 망간슬래그의 비표면적은 <TEX>$4.04m^2/g$</TEX>, 전위차 적정법에 의해 측정된 영전하점(point of zero salt effect, PZSE)은 7.73으로 측정되었다. pH 4, 7, 10의 조건으로 두 비소 화학종의 수착반응에 대한 평형실험 결과 3가 비소보다 5가 비소가 수착량이 더 컸으며 망간슬래그와의 친화력이 더 높은 것으로 나타났다. 3가 비소는 pH 7에서, 5가 비소는 pH 4에서 수착량이 가장 높게 나타났는데 이는 pH에 따른 두 비소 화학종의 존재형태와 망간슬래그의 표면전하 간 상호작용에 기인한 것이다. 수착반응은 3가 비소와 5가 비소 모두 2시간 이내에 최대 수착량에 도달하였고, 반응속도 실험결과를 다양한 반응속도 모델들에 모사하였을 때, 유사이차(pseudo-second-order)와 포물선(parabolic) 모델이 가장 적합한 모델로 조사되었다. Arsenic contamination may be brought about by a variety of natural and anthropogenic causes. Among diverse naturally-occurring chemical speciations of arsenic, trivalent (As(III), arsenite) and pentavalent (As(V), arsenate) forms have been reported to be the most predominant ones. It has been well known that the behavior of arsenic is chiefly affected by aluminum, iron, and manganese oxides. For this reason, this study was initiated to evaluate the applicability of manganese slag (Mn-slag) containing high level of Mn, Si, and Ca as an efficient sorbent of arsenic. The main properties of Mn-slag as a sorbent were investigated and the sorption of each arsenic species onto Mn-slag was characterized from the aspects of equilibrium as well as kinetics. The specific surface area and point of zero salt effect (PZSE) of Mn-slag were measured to be <TEX>$4.04m^2/g$</TEX> and 7.73, respectively. The results of equilibrium experiments conducted at pH 4, 7 and 10 suggest that the sorbed amount of As(V) was relatively higher than that of As(III), indicating the higher affinity of As(V) onto Mn-slag. As a result of combined effect of pH-dependent chemical speciations of arsenic as well as charge characteristics of Mn-slag surface, the sorption maxima were observed at pH 4 for As(V) and pH 7 for As(III). The sorption of both arsenic species reached equilibrium within 3 h and fitting of the experimental results to various kinetic models shows that the pseudo-second-order and parabolic models are most appropriate to simulate the system of this study.

How Heterogeneity Shapes Vilfredo Pareto’s Social Equilibrium

The current idea of the ‘representative agent’ cannot be readily applied to Vilfredo Pareto’s analysis, which is predicated on the heterogeneity of individuals. Indeed, recognition of the importance of heterogeneity leads Pareto to introduce statistical equilibrium as a complement to the theoretical equilibrium that results from a balance of economic forces. The purpose of this paper is to highlight the implications of Pareto’s views on heterogeneity for the study of political economy and to draw attention to the largely Italian literature that stresses Pareto’s anticipation of aspects of statistical equilibrium developed in the physical sciences.

Electron transfer reactions associated with ethyl viologen-β-cyclodextrin complexation: equilibrium and kinetic aspects

Formation of the complex of ethyl viologen in its cationic (Ev+•) and neutral (Ev∘) forms with β-cyclodextrin (β-CD) was investigated by means of voltammetric technique in buffer solution of pH 7.00. The number of βCD (n or m) per viologen species (Ev+•) or (Ev∘), bonding equilibrium constants as well as bonding rate constants was calculated. The calculated values of $$K_{\text{eq}}^{(1)}$$ and $$K_{\text{eq}}^{ ( 2)}$$ (pertaining to the bonding of Ev+• and Ev∘ with βCD) are 13.6 M–n and 2.1 × 103 M−m , respectively, whereas the calculated values of n and m are 0.54 and 1.25, respectively. The bimolecular rate constant for the Ev∘−βCD inclusion complex formation is 3.03 × 103 M−1s−1. These results are supported by the simulation of the experimental cyclic voltammograms. This study also highlights the significance of the proposed electrochemical method as compared to earlier studies on viologen-Cyclodextrin systems.

Multi-staging for extraction of cesium from nitric acid by a single liquid–liquid countercurrent centrifugal extractor with Taylor vortices

Fission products that emit considerable decay heat and radioactivity, such as 137Cs, have a large impact on waste management. Small and high-performance extractor is desirable for separating such nuclei. In this study, we implemented the continuous extraction of Cs from nitric acid in a single liquid–liquid countercurrent centrifugal extractor with Taylor Vortices by calix[4]arene-bis(t-octylbenzo-crown-6)(BOBCalixC6) as an extractant with trioctylamine(TOA) as a suppressant and with 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB) as a phase modifier. Because of slow extraction kinetics of this process, extraction with multiple theoretical stages by just replacing conventional extractors into the single centrifugal extractor is difficult. Hence, we improved the dispersion of organic phase by an inner rotor made of lipophilic epoxy resin and elevating the solution temperature to lower the viscosity. Higher temperature was not appropriate from the aspect of chemical equilibrium in this process, but extraction with multiple theoretical stages was found to be possible.

Convective‐scale responses of a large‐domain, modelled tropical environment to surface warming

AbstractThis article explores the response of convective‐scale atmospheric characteristics to surface temperature through the lens of large‐domain, cloud‐system‐resolving model experiments run at radiative convective equilibrium. We note several features reminiscent of the response to surface warming in atmospheric general circulation models. These include an increase in the rain rate that is smaller than the modelled increase in precipitable water, a systematic decrease in sensible heating and an increase in clear‐sky cooling. However, in contrast to climate models, we note that tropospheric relative humidity increases and column‐integrated water vapour increases at the rate anticipated from the Clausius–Clapeyron relationship, but only when compared with the troposphere mean temperature rather than surface temperature. Also shown are results elucidating the changes in the vertically integrated water budget and the distribution of high precipitation rates shifting toward higher rates. Moist static energy distributions are analyzed and, from these, clouds are implicated in effecting the final equilibrium state of the atmosphere. The results indicate that, while there are aspects of the tropical equilibrium that are represented realistically in current general circulation model climate‐change experiments, there are potentially influential local interactions that are sufficiently important as to alter the mean response of the tropical water and energy balance to changes in sea‐surface temperature. Convection is shown to dictate the equilibrium state across all scales, including those unresolved in climate models, rather than only responding to surface‐induced changes.