Thermodynamics of uranium and nitric acid extraction from aqueous solution of TBP/diluent

International Nuclear Information System (INIS)

Souza Freitas, R.F. de.

1982-06-01

A thermodynamically consistent procedure for predicting distribution equilibria for uranyl nitrate and nitric acid between an aqueous solution and 30 vol % tributyl phosphate (TBP) in a hydrocarbon diluent is studied. Experimental work is developed in order to obtain equilibrium data for the system uranyl nitrate, nitric acid, water and 30 vol % TBP in n-dodecane, at 25 0 C and 40 0 C. The theoretical equilibrium data, obtained with the aid of a computer, are compared with the experimental results. (Author) [pt

Vapor-liquid equilibria for nitric acid-water and plutonium nitrate-nitric acid-water solutions

International Nuclear Information System (INIS)

Maimoni, A.

1980-01-01

The liquid-vapor equilibrium data for nitric acid and nitric acid-plutnonium nitrate-water solutions were examined to develop correlations covering the range of conditions encountered in nuclear fuel reprocessing. The scanty available data for plutonium nitrate solutions are of poor quality but allow an order of magnitude estimate to be made. A formal thermodynamic analysis was attempted initially but was not successful due to the poor quality of the data as well as the complex chemical equilibria involved in the nitric acid and in the plutonium nitrate solutions. Thus, while there was no difficulty in correlating activity coefficients for nitric acid solutions over relatively narrow temperature ranges, attempts to extend the correlations over the range 25 0 C to the boiling point were not successful. The available data were then analyzed using empirical correlations from which normal boiling points and relative volatilities can be obtained over the concentration ranges 0 to 700 g/l Pu, 0 to 13 M nitric acid. Activity coefficients are required, however, if estimates of individual component vapor pressures are needed. The required ternary activity coefficients can be approximated from the correlations

Identification of Weak Acids and Bases by Titration with Primary Standards. A Modern Version of an Old Analytical Chemistry Experiment.

Science.gov (United States)

Thompson, Robert Q.

1988-01-01

Describes a laboratory exercise in which acid dissociation constants and molecular weights are extracted from sample data and the sample is identified. Emphasizes accurate volumetric work while bringing to practice the concepts of acid-base equilibria, activity coefficients, and thermodynamic constants. (CW)

Thermodynamic models for vapor-liquid equilibria of nitrogen + oxygen + carbon dioxide at low temperatures

Science.gov (United States)

Vrabec, Jadran; Kedia, Gaurav Kumar; Buchhauser, Ulrich; Meyer-Pittroff, Roland; Hasse, Hans

2009-02-01

For the design and optimization of CO 2 recovery from alcoholic fermentation processes by distillation, models for vapor-liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng-Robinson equation of state (EOS) and a model based on Henry's law constants, are proposed for the ternary mixture N 2 + O 2 + CO 2. Pure substance parameters of the Peng-Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to experimental binary VLE data. The Peng-Robinson EOS describes both binary and ternary experimental data well, except at high pressures approaching the critical region. A molecular model is validated by simulation using binary and ternary experimental VLE data. On the basis of this model, the Henry's law constants of N 2 and O 2 in CO 2 are predicted by molecular simulation. An easy-to-use thermodynamic model, based on those Henry's law constants, is developed to reliably describe the VLE in the CO 2-rich region.

Dissolved Divalent Metal and pH Effects on Amino Acid Polymerization: A Thermodynamic Evaluation.

Science.gov (United States)

Kitadai, Norio

2017-03-01

Polymerization of amino acids is a fundamentally important step for the chemical evolution of life. Nevertheless, its response to changing environmental conditions has not yet been well understood because of the lack of reliable quantitative information. For thermodynamics, detailed prediction over diverse combinations of temperature and pH has been made only for a few amino acid-peptide systems. This study used recently reported thermodynamic dataset for the polymerization of the simplest amino acid "glycine (Gly)" to its short peptides (di-glycine and tri-glycine) to examine chemical and structural characteristics of amino acids and peptides that control the temperature and pH dependence of polymerization. Results showed that the dependency is strongly controlled by the intramolecular distance between the amino and carboxyl groups in an amino acid structure, although the side-chain group role is minor. The polymerization behavior of Gly reported earlier in the literature is therefore expected to be a typical feature for those of α-amino acids. Equilibrium calculations were conducted to examine effects of dissolved metals as a function of pH on the monomer-polymer equilibria of Gly. Results showed that metals shift the equilibria toward the monomer side, particularly at neutral and alkaline pH. Metals that form weak interaction with Gly (e.g., Mg 2+ ) have no noticeable influence on the polymerization, although strong interaction engenders significant decrease of the equilibrium concentrations of Gly peptides. Considering chemical and structural characteristics of Gly and Gly peptides that control their interactions with metals, it can be expected that similar responses to the addition of metals are applicable in the polymerization of neutral α-amino acids. Neutral and alkaline aqueous environments with dissolved metals having high affinity with neutral α-amino acids (e.g., Cu 2+ ) are therefore not beneficial places for peptide bond formation on the primitive

Acid-base equilibria and solubility of loratadine and desloratadine in water and micellar media.

Science.gov (United States)

Popović, Gordana; Cakar, Mira; Agbaba, Danica

2009-01-15

Acid-base equilibria in homogeneous and heterogeneous systems of two antihistaminics, loratadine and desloratadine were studied spectrophotometrically in Britton-Robinson's buffer at 25 degrees C. Acidity constant of loratadine was found to be pK(a) 5.25 and those of desloratadine pK(a1) 4.41 and pK(a2) 9.97. The values of intrinsic solubilities of loratadine and desloratadine were 8.65x10(-6) M and 3.82x10(-4) M, respectively. Based on the pK(a) values and intrinsic solubilities, solubility curves of these two drugs as a function of pH were calculated. The effects of anionic, cationic and non-ionic surfactants applied in the concentration exceeding critical micelle concentration (cmc) on acid-base properties of loratadine and desloratadine, as well as on intrinsic solubility of loratadine were also examined. The results revealed a shift of pK(a) values in micellar media comparing to the values obtained in water. These shifts (DeltapK(a)) ranged from -2.24 to +1.24.

Phase equilibria and thermodynamics of the Fe–Al–C system: Critical evaluation, experiment and thermodynamic optimization

International Nuclear Information System (INIS)

Phan, Anh Thu; Paek, Min-Kyu; Kang, Youn-Bae

2014-01-01

In order to provide an efficient tool to design alloy chemistry and processing conditions for high-strength, lightweight steel, an investigation of the Fe–Al–C ternary system was carried out by experimental phase diagram measurement and a CALPHAD thermodynamic analysis. Discrepancies between previously available experimental results and thermodynamic calculations were identified. The Fe–Al sub-binary system was re-optimized in order to obtain an accurate description of the liquid phase, while Gibbs energies of solid phases were mainly taken from a previous thermodynamic modeling. Phase equilibria among face-centered cubic (fcc)/body-centered cubic (bcc)/graphite/κ-carbide/liquid phases in the Fe–Al–C system in the temperature range from 1000 to 1400 °C were obtained by chemical equilibration followed by quenching, and subsequent composition analysis using electron probe microanalysis/inductively coupled plasma spectroscopy. By merging the revised Fe–Al binary description with existing Fe–C and Al–C binary descriptions, a complete thermodynamic description of the Fe–Al–C system was obtained in the present study. The modified quasi-chemical model in the pair approximation was used to model the liquid phase, while solid solutions were modeled using compound energy formalism. A2/B2 order/disorder transition in the bcc phase was taken into account. Compared with previously known experiments/thermodynamic modeling, a better agreement was obtained in the present study, regarding the stable region of fcc and the solidification thermal peak of a ternary alloy near the liquidus temperature. The obtained thermodynamic description also reproduced various types of experimental data in the Fe–Al–C system such as isothermal sections, vertical sections, liquidus projection, etc. The solidification of various steel grades was predicted and discussed

Studies on (acid + base) equilibria in substituted (phenol + n-butylamine) systems in acetonitrile

Energy Technology Data Exchange (ETDEWEB)

Kozak, A. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Czaja, M. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Chmurzynski, L. [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland)]. E-mail: lech@chem.univ.gda.pl

2005-08-15

(Acid + base) equilibria, including molecular heteroconjugation ones, between n-butylamine and one of the following phenols: 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,5-dinitrophenol, 3-chlorophenol, 4-chlorophenol, 2,3,4,5,6-pentachlorophenol and 2,4,6-tribromophenol have been studied potentiometrically in a protophobic polar aprotic solvent, acetonitrile. Among the phenols studied, 2,5-dinitrophenol exhibited the strongest tendency towards formation of asymmetric hydrogen bonds with n-butylamine, whereas a weakest complex was formed with 2-nitrophenol. In the (n-butylamine + 2,3,4,5,6-pentachlorophenol) and (n-butylamine + 2,4-dinitrophenol) systems proton transfer reactions occurred.

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part I: Acid-base equilibria and pH buffers.

Science.gov (United States)

Persat, Alexandre; Chambers, Robert D; Santiago, Juan G

2009-09-07

We review fundamental and applied acid-base equilibrium chemistry useful to microfluidic electrokinetics. We present elements of acid-base equilibrium reactions and derive rules for pH calculation for simple buffers. We also present a general formulation to calculate pH of more complex, arbitrary mixtures of electrolytes, and discuss the effects of ionic strength and temperature on pH calculation. More practically, we offer advice on buffer preparation and on buffer reporting. We also discuss "real world" buffers and likely contamination sources. In particular, we discuss the effects of atmospheric carbon dioxide on buffer systems, namely, the increase in ionic strength and acidification of typical electrokinetic device buffers. In Part II of this two-paper series, we discuss the coupling of acid-base equilibria with electrolyte dynamics and electrochemistry in typical microfluidic electrokinetic systems.

Thermodynamic analysis and phase equilibria investigation in Pb−Zn−Ag system

Directory of Open Access Journals (Sweden)

Mitovski Aleksandra M.

2010-01-01

Full Text Available Physico-chemical processes that take place during the refining process in the extractive metallurgy of lead, are connected with ternary Pb−Zn−Ag system, which is necessary to study from the theoretical practical and aspects. Such investigation is important from production point of view, because of the phenomena that occur during desilvering of lead which is one of the important stages during lead refining process. Process of lead desilvering binds to ternary system Pb−Zn−Ag, which was the reason for numerous investigations, both from thermodynamic point of view and in terms of testing and determining the phase diagram, bearing in mind the theoretical, and practical importance of knowledge about the processes which are going in investigated system. The paper presents the results of thermodynamic analysis and investigation of phase equilibria of the Pb−Zn−Ag ternary system using the method of thermodynamic predictions and phase diagrams calculations, respectively, and the experimental results of metalography obtained by optical microscopy. Phase diagram of the vertical section Pb−Zn80Ag20 is presented, obtained by CALPHAD calculation methodology, and using PANDAT thermodynamic software, compared to experimental results obtained by DTA analysis. The results show a pronounced break in solubility, which is characteristic for the whole ternary Pb−Zn−Ag system. Also, it can be noticed that the thermodynamic properties follow the behavior of this system, which is expressed through positive deviation of Raoult’s law, pointing to the lack of lead affinity compared to the other two components in the system. The optical microscopy results of the investigated system show the following: - Sample L1 (weight% Pb = 98: the structure of the observed section shows double eutectic (Pbsol+Zn−Agsol which lies in the base of the primary crystals of lead (Pbsol - Samples L2−L5: the structure consists of a dual eutectic (Pbsol+Zn−Agsol and

Acquisition and evaluation of thermodynamic data for morenosite-retgersite equilibria at 0.1 MPa

Science.gov (United States)

Chou, I.-Ming; Seal, R.R.

2003-01-01

Metal-sulfate salts in mine drainage environments commonly occur as solid solutions containing Fe, Cu, Mg, Zn, Al, Mn, Ni, Co, Cd, and other elements. Thermodynamic data for some of the end-member salts containing Fe, Cu, Zn, and Mg have been collected and evaluated previously, and the present study extends to the system containing Ni. Morenosite (NiSO4-7H2O)-retgersite (NiSO4-6H2O) equilibria were determined along five humidity buffer curves at 0.1 MPa and between 5 and 22??C. Reversals along these humidity-buffer curves yield In K = 17.58-6303.35/T, where K is the equilibrium constant, and T is temperature in K. The derived standard Gibbs free energy of reaction is 8.84 kJ/mol, which agrees very well with the values of 8.90, 8.83, and 8.85 kJ/mol based on the vapor pressure measurements of Schumb (1923), Bonnell and Burridge (1935), and Stout et al. (1966). respectively. This value also agrees reasonably well with the values of 8.65 and 9.56 kJ/mol calculated from the data compiled by Wagman et al. (1982) and DeKock (1982), respectively. The temperature-humidity relationships defined by this study for dehydration equilibria between morenosite and retgersite explain the more common occurrence of retgersite relative to morenosite in nature.

Phase equilibria at low temperature for light hydrocarbons-methanol-water-acid gases mixtures: measurements and modelling; Equilibres de phases a basse temperature de systemes complexes CO{sub 2} - hydrocarbures legers - methanol - eau: mesures et modelisation

Energy Technology Data Exchange (ETDEWEB)

Ruffine, L.

2005-10-15

The need to develop and improve natural gas treatment processes is real. The petroleum industry usually uses separation processes which require phase equilibrium phenomena. Yet, the complexity of the phase equilibria involved results in a lack of data, which in turn limits the development of thermodynamic models. The first part of this work is devoted to experimental investigations for systems containing light hydrocarbons, methanol, water and acid gases. We present a new apparatus that was developed to measure vapor-liquid and vapor-liquid-liquid equilibria. It allowed us to obtain new phase composition data for the methanol-ethane binary system and different mixtures, and also to determine a part of the three phases equilibrium envelope of the same systems. In the second part of this work, we have developed a thermodynamic model based on the CPA equation of state. This choice may be justified by the presence of associating components like methanol, hydrogen sulfide and water in the systems. Such model is necessary for the design of gas treatment plants. Our model provides good results for phase equilibrium calculations for binaries systems without binary interaction parameter in many cases, and describes correctly the vapour-liquid and vapor-liquid-liquid equilibria for complex mixtures. (author)

A thermodynamic solution model for calcium carbonate: Towards an understanding of multi-equilibria precipitation pathways.

Science.gov (United States)

Donnet, Marcel; Bowen, Paul; Lemaître, Jacques

2009-12-15

Thermodynamic solubility calculations are normally only related to thermodynamic equilibria in solution. In this paper, we extend the use of such solubility calculations to help elucidate possible precipitation reaction pathways during the entire reaction. We also estimate the interfacial energy of particles using only solubility data by a modification of Mersmann's approach. We have carried this out by considering precipitation reactions as a succession of small quasi-equilibrium states. Thus possible equilibrium precipitation pathways can be evaluated by calculating the evolution of surface charge, particle size and/or interfacial energy during the ongoing reaction. The approach includes the use of the Kelvin's law to express the influence of particle size on the solubility constant of precipitates, the use of Nernst's law to calculate surface potentials from solubility calculations and relate this to experimentally measured zeta potentials. Calcium carbonate precipitation and zeta potential measurements of well characterised high purity calcite have been used as a model system to validate the calculated values. The clarification of the change in zeta potential on titration illustrates the power of this approach as a tool for reaction pathway prediction and hence knowledge based tailoring of precipitation reactions.

Predicting phase equilibria in one-component systems

Science.gov (United States)

Korchuganova, M. R.; Esina, Z. N.

2015-07-01

It is shown that Simon equation coefficients for n-alkanes and n-alcohols can be modeled using critical and triple point parameters. Predictions of the phase liquid-vapor, solid-vapor, and liquid-solid equilibria in one-component systems are based on the Clausius-Clapeyron relation, Van der Waals and Simon equations, and the principle of thermodynamic similarity.

Basic principles of electrolyte chemistry for microfluidic electrokinetics. Part II: Coupling between ion mobility, electrolysis, and acid-base equilibria.

Science.gov (United States)

Persat, Alexandre; Suss, Matthew E; Santiago, Juan G

2009-09-07

We present elements of electrolyte dynamics and electrochemistry relevant to microfluidic electrokinetics experiments. In Part I of this two-paper series, we presented a review and introduction to the fundamentals of acid-base chemistry. Here, we first summarize the coupling between acid-base equilibrium chemistry and electrophoretic mobilities of electrolytes, at both infinite and finite dilution. We then discuss the effects of electrode reactions on microfluidic electrokinetic experiments and derive a model for pH changes in microchip reservoirs during typical direct-current electrokinetic experiments. We present a model for the potential drop in typical microchip electrophoresis device. The latter includes finite element simulation to estimate the relative effects of channel and reservoir dimensions. Finally, we summarize effects of electrode and electrolyte characteristics on potential drop in microfluidic devices. As a whole, the discussions highlight the importance of the coupling between electromigration and electrophoresis, acid-base equilibria, and electrochemical reactions.

Applications of thermodynamic calculations to Mg alloy design: Mg-Sn based alloy development

International Nuclear Information System (INIS)

Jung, In-Ho; Park, Woo-Jin; Ahn, Sang Ho; Kang, Dae Hoon; Kim, Nack J.

2007-01-01

Recently an Mg-Sn based alloy system has been investigated actively in order to develop new magnesium alloys which have a stable structure and good mechanical properties at high temperatures. Thermodynamic modeling of the Mg-Al-Mn-Sb-Si-Sn-Zn system was performed based on available thermodynamic, phase equilibria and phase diagram data. Using the optimized database, the phase relationships of the Mg-Sn-Al-Zn alloys with additions of Si and Sb were calculated and compared with their experimental microstructures. It is shown that the calculated results are in good agreement with experimental microstructures, which proves the applicability of thermodynamic calculations for new Mg alloy design. All calculations were performed using FactSage thermochemical software. (orig.)

Applied chemical engineering thermodynamics

CERN Document Server

Tassios, Dimitrios P

1993-01-01

Applied Chemical Engineering Thermodynamics provides the undergraduate and graduate student of chemical engineering with the basic knowledge, the methodology and the references he needs to apply it in industrial practice. Thus, in addition to the classical topics of the laws of thermodynamics,pure component and mixture thermodynamic properties as well as phase and chemical equilibria the reader will find: - history of thermodynamics - energy conservation - internmolecular forces and molecular thermodynamics - cubic equations of state - statistical mechanics. A great number of calculated problems with solutions and an appendix with numerous tables of numbers of practical importance are extremely helpful for applied calculations. The computer programs on the included disk help the student to become familiar with the typical methods used in industry for volumetric and vapor-liquid equilibria calculations.

pycalphad: CALPHAD-based Computational Thermodynamics in Python

Directory of Open Access Journals (Sweden)

Richard Otis

2017-01-01

Full Text Available The pycalphad software package is a free and open-source Python library for designing thermodynamic models, calculating phase diagrams and investigating phase equilibria using the CALPHAD method. It provides routines for reading thermodynamic databases and solving the multi-component, multi-phase Gibbs energy minimization problem. The pycalphad software project advances the state of thermodynamic modeling by providing a flexible yet powerful interface for manipulating CALPHAD data and models. The key feature of the software is that the thermodynamic models of individual phases and their associated databases can be programmatically manipulated and overridden at run-time without modifying any internal solver or calculation code. Because the models are internally decoupled from the equilibrium solver and the models themselves are represented symbolically, pycalphad is an ideal tool for CALPHAD database development and model prototyping.

Acids and bases solvent effects on acid-base strenght

CERN Document Server

Cox, Brian G

2013-01-01

Acids and bases are ubiquitous in chemistry. Our understanding of them, however, is dominated by their behaviour in water. Transfer to non-aqueous solvents leads to profound changes in acid-base strengths and to the rates and equilibria of many processes: for example, synthetic reactions involving acids, bases and nucleophiles; isolation of pharmaceutical actives through salt formation; formation of zwitter- ions in amino acids; and chromatographic separation of substrates. This book seeks to enhance our understanding of acids and bases by reviewing and analysing their behaviour in non-aqueous solvents. The behaviour is related where possible to that in water, but correlations and contrasts between solvents are also presented.

(Liquid + liquid) equilibria of perfluorocarbons with fluorinated ionic liquids

International Nuclear Information System (INIS)

Martinho, S.; Araújo, J.M.M.; Rebelo, L.P.N.; Pereiro, A.B.; Marrucho, I.M.

2013-01-01

Highlights: • (Liquid + liquid) equilibria perfluorocarbons and fluorinated ionic liquids. • Non-Random Two Liquid model was successfully applied. • Thermodynamic functions that describe the solvation process were calculated. -- Abstract: In order to evaluate the feasibility of partially replace perfluorocarbons (PFCs) with fluorinated ionic liquids (FILs) in PFCs-in-water emulsions, usually used for biomedical purposes, herein the (liquid + liquid) phase equilibria of FILs containing fluorinated chains longer than four carbons with PFCs were carried out in a wide range of temperatures. With this goal in mind, two PFCs (perfluorooctane and perfluorodecalin) were selected and the (liquid + liquid) equilibria of the binary mixtures of these PFCs and FILs were studied at atmospheric pressure in a temperature range from T (293.15 to 343.15) K. For these studies, FILs containing ammonium, pyridinium and imidazolium cations and different anions with fluorocarbon alkyl chains between 4 and 8 were included. Additionally, Non-Random Two Liquid (NRTL) thermodynamic model was successfully applied to correlate the behaviour of the PFCs + FILs binary mixtures. Moreover, thermodynamic functions that describe the solvation process were calculated from the experimental data

Thermodynamic modeling of the Ce-Zn and Pr-Zn systems

International Nuclear Information System (INIS)

Wang, C.P.; Chen, X.; Liu, X.J.; Pan, F.S.; Ishida, K.

2008-01-01

In order to develop the thermodynamic database of phase equilibria in the Mg-Zn-Re (Re: rare earth element) base alloys, the thermodynamic assessments of the Ce-Zn and Pr-Zn systems were carried out by using the calculation of phase diagrams (CALPHAD) method on the basis of the experimental data including thermodynamic properties and phase equilibria. Based on the available experimental data, Gibbs free energies of the solution phases (liquid, bcc, fcc, hcp and dhcp) were modeled by the subregular solution model with the Redlich-Kister formula, and those of the intermetallic compounds were described by the sublattice model. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compound in the Ce-Zn and Pr-Zn binary systems. An agreement between the present calculated results and experimental data is obtained

Quantitative thermodynamic predication of interactions between nucleic acid and non-nucleic acid species using Microsoft excel.

Science.gov (United States)

Zou, Jiaqi; Li, Na

2013-09-01

Proper design of nucleic acid sequences is crucial for many applications. We have previously established a thermodynamics-based quantitative model to help design aptamer-based nucleic acid probes by predicting equilibrium concentrations of all interacting species. To facilitate customization of this thermodynamic model for different applications, here we present a generic and easy-to-use platform to implement the algorithm of the model with Microsoft(®) Excel formulas and VBA (Visual Basic for Applications) macros. Two Excel spreadsheets have been developed: one for the applications involving only nucleic acid species, the other for the applications involving both nucleic acid and non-nucleic acid species. The spreadsheets take the nucleic acid sequences and the initial concentrations of all species as input, guide the user to retrieve the necessary thermodynamic constants, and finally calculate equilibrium concentrations for all species in various bound and unbound conformations. The validity of both spreadsheets has been verified by comparing the modeling results with the experimental results on nucleic acid sequences reported in the literature. This Excel-based platform described here will allow biomedical researchers to rationalize the sequence design of nucleic acid probes using the thermodynamics-based modeling even without relevant theoretical and computational skills. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Thermodynamic study on salt effects on complex formation of α-, β- and γ-cyclodextrins with p-aminobenzoic acid

International Nuclear Information System (INIS)

Chibunova, E.S.; Kumeev, R.S.; Terekhova, I.V.

2015-01-01

Highlights: • Thermodynamic study on salt effects in CD/pABA complex formation was performed. • Effects of KCl, KH 2 PO 4 and K 2 SO 4 are insignificant and nonspecific. • Specific influence of KBr is caused by the ability of Br − to penetrate into CD cavity. • Coexistence of two complexation equilibria is accompanied by solvent reorganization. - Abstract: The aim of this work was to gain a deeper understanding of salt effects in the inclusion complex formation of cyclodextrins. For this purpose, thermodynamic study of complex formation of α-, β- and γ-cyclodextrins with p-aminobenzoic acid was carried out in water and solutions of KCl, KBr, KH 2 PO 4 and K 2 SO 4 (0.2 mol/kg). Stability constants were calculated from the binding isotherms obtained on the basis of 1 H NMR measurements. Enthalpy and entropy of complex formation were estimated from the van’t Hoff plots. It was found that effects of KCl, KH 2 PO 4 and K 2 SO 4 are insignificant, while the influence of KBr on complex formation of cyclodextrins with p-aminobenzoic acid is more pronounced and results in a decrease of the stability constants. Specific action of Br − is caused by the ability of these anions to penetrate into macrocyclic cavity. Coexistence of two complexation equilibria in KBr solution is accompanied by significant solvent reorganization originated from more intensive dehydration of the interacting species. This results in an increase of the enthalpy and entropy of complex formation. Manifestation of Br − effect was found to be the same in the binding of p-aminobenzoic acid with α-, β- and γ-cyclodextrins.

High temperature interdiffusion and phase equilibria in U-Mo

International Nuclear Information System (INIS)

Lundberg, L.B.

1988-01-01

Experimental data for interdiffusion and phase equilibria in the U-Mo system have been obtained over the temperature range 1400 to 1525 K as a fallout from compatibility experiments in which UO 2 was decomposed by lithium in closed molybdenum capsules. Composition-position, x-ray diffraction and microstructural data from the interdiffusion zones indicate that the intermediate phase U 2 Mo is found in this temperature range, contrary to the currently accepted equilibrium U-Mo phase diagram. The U-Mo interdiffusion data are in good agreement with published values. Inclusion of the U 2 Mo phase in a theoretical correlation of interdiffusion and phase equilibria data using Darken's equation indicate that high temperature interdiffusion of uranium and molybdenum follows the usual thermodynamic rules. Significant changes in the value of the thermodynamic based Darken factor near the U 2 Mo phase boundary on the high uranium side are indicated from both the new and published interdiffusion data. 9 refs., 10 figs., 3 tabs

Thermodynamic model for the phase equilibria of gases and brines. Example in the H{sub 2}S-H{sub 2}O-NaCl system

Energy Technology Data Exchange (ETDEWEB)

Martinez Reyes, Jose; Gonzalez Partida, Eduardo; Tinoco-Michel, Jorge A [Centro de Geociencias, Universidad Nacional Autonoma de Mexico Campo de Juriquilla, Qro., Mexico, apartado postal 76230 (Mexico); Perez, Renee J; Heidemann, Robert A [Department of Chemical and Petroleum Engineering, University of Calgary, 2500 University Drive, Calgary Alberta, T2N 1N4 (Canada)

2008-10-01

We present a thermodynamic model for the phase equilibria of gases and brines, which couples Henry's Law with the Soave-Redlich-Kwong equation of state to reproduce experimental data. In this communication we focus on the H{sub 2}S H{sub 2}O NaCl system.

In situ studies of uranium-plutonium mixed oxides. Influence of composition on phase equilibria and thermodynamic properties

International Nuclear Information System (INIS)

Strach, Michal

2015-01-01

Due to their physical and chemical properties, mixed uranium-plutonium oxides are considered for fuel in 4. generation nuclear reactors. In this frame, complementary experimental studies are necessary to develop a better understanding of the phenomena that take place during fabrication and operation in the reactor. The focus of this work was to study the U-Pu-O phase diagram in a wide range of compositions and temperatures to ameliorate our knowledge of the phase equilibria in this system. Most of experiments were done using in situ X-ray diffraction at elevated temperatures. The control of the oxygen partial pressure during the treatments made it possible to change the oxygen stoichiometry of the sample, which gave us an opportunity to study rapidly different compositions and the processes involved. The experimental approach was coupled with thermodynamic modeling using the CALPHAD method, to precisely plan the experiments and interpret the obtained results. This approach enabled us to enhance the knowledge of phase equilibria in the U-Pu-O system. (author) [fr

Stability range of MoC (hp2). II. Thermodynamic properties of generalized Lewis acid-base intermetallics

International Nuclear Information System (INIS)

Koukouvetakis, J.

1988-01-01

The γ-MoC phase with the hexagonal WC structure was prepared without the presence of metal stabilizers at temperatures below 1000 degree C. This phase was found to be thermodynamically stable at low temperatures and decomposed to Mo 2 C and graphite at 1400 K. Using equilibrium and thermodynamic data, the thermodynamic quantities of this phase were calculated. Oxide equilibration and solid-state galvanic cell experiments were used to study thermodynamic properties of binary Lewis acid-base stabilized transition-metal alloys. The activity of vanadium was determined in alloys of vanadium with platinum-group metals such as Rh, Pd, and Ir at 1000 degree C. The activities of titanium in titanium-iridium alloys and of niobium in Nb 3 Ir were determined at 1400 degree C. The ternary phase diagram of V-Pd-O at 1000 degree C was obtained. Based on the vanadium-palladium results, a partial titration curve of palladium by vanadium was constructed. The excess partial molar Gibbs free energy of vanadium at infinite dilution was found to be -36.4 kcal mol -1 at 1000 degree C. Results are in agreement with the predictions of Brewer's theory of transition-metal alloy acid-base behavior

Thermodynamic Modeling of Multi-phase Solid–Liquid Equilibria in Industrial-Grade Oils and Fats

DEFF Research Database (Denmark)

Hjorth, Jeppe Lindegaard; Miller, Rasmus L.; Woodley, John M.

2015-01-01

Compositional thermodynamic phase separation is investigated for industrial-grade vegetable oils with complex compositions. Solid–liquid equilibria have been calculated by utilizing the Margules 2-suffix activity-coefficient model in combination with minimization of the Gibb’s free energy...... of the system. On the basis of quasi-equilibrium solid-fat content (SFC) measurements, a new approach to the estimation of the interaction parameters, needed for the activity-coefficient model, has been developed. The parameters are fitted by matching the SFC of two oils at various degrees of dilution...... and isothermal temperatures. Subsequently, the parameters are successfully validated against three oils, rich in asymmetric and symmetric triacylglycerols (TAG), respectively. The new approach developed is shown to be very flexible, allowing incorporation of additional TAG and polymorphic states. It thereby...

Correlation and prediction of ion exchange equilibria on weak-acid resins by means of the surface complex formation model

International Nuclear Information System (INIS)

Horst, J.

1988-11-01

The present work summarizes investigations of the equilibrium of the exchange of protons, copper, zinc, calcium, magnesium and sodium ions on two weak-acid exchange resins in hydrochloric and carbonic acid bearing solutions at 25 0 C. The description of the state of equilibrium between resin and solution is based on the individual chemical equilibria which have to be adjusted simultaneously. The equilibrium in the liquid phase is described by the mass action law and the condition of electroneutrality using activity coefficients calculated according to the theory of Debye and Hueckel. The exchange equilibria are described by means of a surface complex formation model, which was developed by Davis, James and Leckie for activated aluminia and which has been applied to weak-acid resins. The model concept assumes the resin as a plane surface in which the functional groups are distributed uniformly. (orig./RB) [de

Acid-base behavior in hydrothermal processing of wastes. 1997 annual progress report

International Nuclear Information System (INIS)

1997-01-01

'A major obstacle to the development of hydrothermal technology for treating DOE wastes has been a lack of scientific knowledge of solution chemistry, thermodynamics and transport phenomena. The progress over the last year is highlighted in the following four abstracts from manuscripts which have been submitted to journals. The authors also have made considerable progress on a spectroscopic study of the acid-base equilibria of Cr(VI). They have utilized novel spectroscopic indicators to study acid-base equilibria up to 380 C. Until now, very few systems have been studied at such high temperatures, although this information is vital for hydrothermal processing of wastes. The pH values of aqueous solutions of boric acid and KOH were measured with the optical indicator 2-naphthol at temperatures from 300 to 380 C. The equilibrium constant Kb-l for the reaction B(OH)3 + OH - = B(OH) -4 was determined from the pH measurements and correlated with a modified Born model. The titration curve for the addition of HCl to sodium borate exhibits strong acid-strong base behavior even at 350 C and 24.1 MPa. At these conditions, aqueous solutions of sodium borate buffer the pH at 9.6 t 0.25. submitted to Ind. Eng. Chem. Res. Acetic Acid and HCl Acid-base titrations for the KOH-acetic acid or NH 3 -acetic acid systems were monitored with the optical indicator 2-naphthoic acid at 350 C and 34 MPa, and those for the HCl;Cl- system with acridine at 380 C and up to 34 MPa (5,000 psia ). KOH remains a much stronger base than NH,OH at high temperature. From 298 K to the critical temperature of water, the dissociation constant for HCl decreases by 13 orders of magnitude, and thus, the basicity of Cl - becomes significant. Consequently, the addition of NaCl to HCl raises the pH. The pH titration curves may be predicted with reasonable accuracy from the relevant equilibrium constants and Pitzer''s formulation of the Debye- Htickel equation for the activity coefficients.'

Phase diagrams and heterogeneous equilibria a practical introduction

CERN Document Server

Predel, Bruno; Pool, Monte

2004-01-01

This graduate-level textbook provides an introduction to the practical application of phase diagrams. It is intended for students and researchers in chemistry, metallurgy, mineralogy, and materials science as well as in engineering and physics. Heterogeneous equilibria are described by a minimum of theory illustrated by practical examples and realistic case discussions from the different fields of application. The treatment of the physical and energetic background of phase equilibria leads to the discussion of the thermodynamics of mixtures and the correlation between energetics and composition. Thus, tools for the prediction of energetic, structural, and physical quantities are provided. The authors treat the nucleation of phase transitions, the production and stability of technologically important metastable phases, and metallic glasses. Furthermore, the text also concisely presents the thermodynamics and composition of polymer systems.

High-temperature experimental and thermodynamic modelling research on the pyrometallurgical processing of copper

Science.gov (United States)

Hidayat, Taufiq; Shishin, Denis; Decterov, Sergei A.; Hayes, Peter C.; Jak, Evgueni

2017-01-01

Uncertainty in the metal price and competition between producers mean that the daily operation of a smelter needs to target high recovery of valuable elements at low operating cost. Options for the improvement of the plant operation can be examined and decision making can be informed based on accurate information from laboratory experimentation coupled with predictions using advanced thermodynamic models. Integrated high-temperature experimental and thermodynamic modelling research on phase equilibria and thermodynamics of copper-containing systems have been undertaken at the Pyrometallurgy Innovation Centre (PYROSEARCH). The experimental phase equilibria studies involve high-temperature equilibration, rapid quenching and direct measurement of phase compositions using electron probe X-ray microanalysis (EPMA). The thermodynamic modelling deals with the development of accurate thermodynamic database built through critical evaluation of experimental data, selection of solution models, and optimization of models parameters. The database covers the Al-Ca-Cu-Fe-Mg-O-S-Si chemical system. The gas, slag, matte, liquid and solid metal phases, spinel solid solution as well as numerous solid oxide and sulphide phases are included. The database works within the FactSage software environment. Examples of phase equilibria data and thermodynamic models of selected systems, as well as possible implementation of the research outcomes to selected copper making processes are presented.

Description of gas hydrates equilibria in sediments using experimental data of soil water potential

Energy Technology Data Exchange (ETDEWEB)

Istomin, V. [NOVATEK, Moscow (Russian Federation); Chuvilin, E. [Moscow State Univ., Moscow (Russian Federation). Dept. of Geology; Makhonina, N.; Kvon, V. [VNIIGAZ, Moscow (Russian Federation); Safonov, S. [Schlumberger Moscow Research, Moscow (Russian Federation)

2008-07-01

Analytical relationships have been developed between hydrate dissociation pressure and vapor pressure above the pore water surface. In addition, experiments have been discussed in numerous publications on the effect of narrow interconnected throats between pores on clathrate dissociation conditions in porous media. This paper presented an approach that improved upon the available thermodynamic methods for calculation of hydrate phase equilibria. The approach took into account the properties of pore water in natural sediments including three-phase equilibrium of gas-pore water-gas hydrate in a similar way as for unfrozen water in geocryology science. The purpose of the paper was to apply and adapt geocryology and soil physics method to the thermodynamic calculation of non-clathrated water content in sediments. It answered the question of how to estimate the non-clathrated water content if pore water potential was known. The paper explained the thermodynamics of water phase in porous media including the thermodynamic properties of supercooled water, the thermodynamic properties of pore water and pore ice in sediments, and the phase equilibria of pore water. The paper also discussed the quantitative techniques that were utilized for determination of unfrozen water content in sediments and its dependence on temperature variation. These included contact-saturation, calorimetric, dielectric, nuclear magnetic resonance, and others. The thermodynamic calculations of pore water phase equilibria were also presented. 30 refs., 5 tabs., 8 figs.

A Systematic Identification Method for Thermodynamic Property Modelling

DEFF Research Database (Denmark)

Ana Perederic, Olivia; Cunico, Larissa; Sarup, Bent

2017-01-01

In this work, a systematic identification method for thermodynamic property modelling is proposed. The aim of the method is to improve the quality of phase equilibria prediction by group contribution based property prediction models. The method is applied to lipid systems where the Original UNIFAC...... model is used. Using the proposed method for estimating the interaction parameters using only VLE data, a better phase equilibria prediction for both VLE and SLE was obtained. The results were validated and compared with the original model performance...

Molecular thermodynamics using fluctuation solution theory

DEFF Research Database (Denmark)

Ellegaard, Martin Dela

. The framework relates thermodynamic variables to molecular pair correlation functions of liquid mixtures. In this thesis, application of the framework is illustrated using two approaches: 1. Solubilities of solid solutes in mixed solvent systems are determined from fluctuation solution theory application......Properties of chemicals and their mutual phase equilibria are critical variables in process design. Reliable estimates of relevant equilibrium properties, from thermodynamic models, can form the basis of good decision making in the development phase of a process design, especially when access...... to relevant experimental data is limited. This thesis addresses the issue of generating and using simple thermodynamic models within a rigorous statistical mechanical framework, the so-called fluctuation solution theory, from which relations connecting properties and phase equilibria can be obtained...

An Experimental Determination of Thermodynamic Values

Science.gov (United States)

Antony, Erling; Muccianti, Christine; Vogel, Tracy

2012-01-01

Measurements have been added to an old demonstration of chemical equilibria allowing the determination of thermodynamic constants. The experiment allows the students an opportunity to merge qualitative observations associated with Le Chatelier's principle and thermodynamic calculations using graphical techniques. (Contains 4 figures.)

Density-functional study on the equilibria in the ThDP activation.

Science.gov (United States)

Delgado, Eduardo J; Alderete, Joel B; Jaña, Gonzalo A

2011-11-01

The equilibria among the various ionization and tautomeric states involved in the activation of ThDP is addressed using high level density functional theory calculations, X3LYP/6-311++G(d,p)//X3LYP(PB)/6-31++G(d,p). This study provides the first theoretically derived thermodynamic data for the internal equilibria in the activation of ThDP. The role of the medium polarity on the geometry and thermodynamics of the diverse equilibria of ThDP is addressed. The media chosen are cyclohexane and water, as paradigms of apolar and polar media. The results suggest that all ionization and tautomeric states are accessible during the catalytic cycle, even in the absence of substrate, being APH(+) the form required to interconvert the AP and IP tautomers; and the generation of the ylide proceeds via the formation of the IP form. Additionally, the calculated ΔG° values allow to calculate all the equilibrium constants, including the pK(C2) for the thiazolium C2 atom whose ionization is believed to initiate the catalytic cycle.

Boronic acid-based autoligation of nucleic acids

DEFF Research Database (Denmark)

Barbeyron, R.; Vasseur, J.-J.; Smietana, M.

2013-01-01

Abstract: The development of synthetic systems displaying dynamic and adaptive characteristics is a formidable challenge with wide applications from biotechnology to therapeutics. Recently, we described a dynamic and programmable nucleic acid-based system relying on the formation of reversible bo....... Evidence suggests that geometric and steric factors are key features for controlling the equilibria. Graphical Abstract: [Figure not available: see fulltext.]...

Impact of Thermodynamic Principles in Systems Biology

NARCIS (Netherlands)

Heijnen, J.J.

2010-01-01

It is shown that properties of biological systems which are relevant for systems biology motivated mathematical modelling are strongly shaped by general thermodynamic principles such as osmotic limit, Gibbs energy dissipation, near equilibria and thermodynamic driving force. Each of these aspects

Distribution equilibria of Eu(III) in the system: bis(2-ethylhexyl)phosphoric acid organic diluent-NaCl, lactic acid, polyaminocarboxylic acid, water

International Nuclear Information System (INIS)

Danesi, P.R.; Cianetti, C.; Horwitz, E.P.

1982-01-01

The distribution equilibria of Eu 3+ between aqueous phases containing lactic acid and N'-(2hydroxyethyl)ethylenediamine-N,N,N'-triacetic acid (HEDTA) or diethylenetriamine-N,N,N',N',N''-penetaacetic acid (DTPA) at constant ionic strength (μ = 1.0), and n-dodecane solutions of HDEHP have been studied. The formation constants of the simple Eu-lactate complexes and Eu-lactate-HEDTA mixed complex were evaluated from the k/sub d/ data. The conclusion is reached that no lactic acid is coextracted into the organic phase at tracer metal concentrations. The separation factors between Eu 3+ , Pm 3+ , and Am 3+ have been evaluated in the presence of HEDTA

The Theory of Thermodynamics for Chemical Reactions in Dispersed Heterogeneous Systems

Science.gov (United States)

Yongqiang; Baojiao; Jianfeng

1997-07-01

In this paper, the expressions of Gibbs energy change, enthalpy change, entropy change, and equilibrium constant for chemical reactions in dispersed heterogeneous systems are derived using classical thermodynamics theory. The thermodynamical relations for the same reaction system between the dispersed and the block state are also derived. The effects of degree of dispersion on thermodynamical properties, reaction directions, and chemical equilibria are discussed. The results show that the present equation of thermodynamics for chemical reactions is only a special case of the above-mentioned formulas and that the effect of the dispersity of a heterogeneous system on the chemical reaction obeys the Le Chatelier principle of movement of equilibria.

Thermodynamic foundations of applications of ab initio methods for determination of the adsorbate equilibria: hydrogen at the GaN(0001) surface.

Science.gov (United States)

Kempisty, Pawel; Strąk, Paweł; Sakowski, Konrad; Kangawa, Yoshihiro; Krukowski, Stanisław

2017-11-08

Thermodynamic foundations of ab initio modeling of vapor-solid and vapor-surface equilibria are introduced. The chemical potential change is divided into enthalpy and entropy terms. The enthalpy path passes through vapor-solid transition at zero temperature. The entropy path avoids the singular point at zero temperature passing a solid-vapor transition under normal conditions, where evaporation entropy is employed. In addition, the thermal changes are calculated. The chemical potential difference contribution of the following terms: vaporization enthalpy, vaporization entropy, the temperature-entropy related change, the thermal enthalpy change and mechanical pressure is obtained. The latter term is negligibly small for the pressure typical for epitaxy. The thermal enthalpy change is two orders smaller than the first three terms which have to be taken into account explicitly. The configurational vaporization entropy change is derived for adsorption processes. The same formulation is derived for vapor-surface equilibria using hydrogen at the GaN(0001) surface as an example. The critical factor is the dependence of the enthalpy of evaporation (desorption energy) on the pinning of the Fermi level bringing a drastic change of the value from 2.24 eV to -2.38 eV. In addition it is shown that entropic contributions considerable change the hydrogen equilibrium pressure over the GaN(0001) surface by several orders of magnitude. Thus a complete and exact formulation of vapor-solid and vapor-surface equilibria is presented.

Phase transformations and thermodynamics of aluminum-based metallic glasses

Science.gov (United States)

Gao, Changhua (Michael)

This thesis examines the thermodynamics and associated kinetics and phase transformations of the glass forming Al-Ni-Gd and Al-Fe-Gd systems. In order to fully understand the unique glass forming ability (GFA) of Al-based metallic glasses, the ternary Al-Fe-Gd and Al-Ni-Gd systems in their Al-rich corners were examined experimentally to assist in a thermodynamic assessment. The solid-state phase equilibria are determined using XRD and TEM-EDS techniques. While this work basically confirms the solid-state equilibria in Al-Fe-Gd reported previously, the ternary phase in Al-Ni-Gd system has been identified to be Al15Ni3Gd2 rather than Al16Ni 3Gd reported in the literature. DTA analysis of 24 alloys in the Al-Fe-Gd system and 42 alloys in the Al-Ni-Gd system have yielded critical temperatures pertaining to the solid-liquid transition. Based on these data and information from the literature, a self-consistent thermodynamic database for these systems has been developed using the CALPHAD technique. Parameters describing the Gibbs free energy for various phases of the Al-Gd, Al-Fe-Gd and Al-Ni-Gd systems are manually optimized in this study. Once constructed, the database is used to calculate driving forces for nucleation of crystalline phases which can qualitatively explain the phase formation sequence during crystallization at low temperatures. It was also confirmed that alloy compositions with the lowest Gibbs free energy difference between the equilibrium state and undercooled liquid state exhibit better GFA than other chemistries. Based on 250°C isothermal devitrification phase transformations of 17 Al-Ni-Gd alloys, a phase formation sequence map is constructed. Fcc-Al nanocrystals are formed first in most of the alloys studied, but eutectic crystallization of a metastable phase and fcc-Al is also observed. Addition of Al or Ni promotes fcc-Al phase formation, while increasing Gd suppresses it. The continuous heating DSC scans revealed that crystallization in Al

Dynamic data evaluation for solid-liquid equilibria

DEFF Research Database (Denmark)

Cunico, Larissa; Ceriani, Roberta; Kang, Jeong Won

The accuracy and reliability of the measured data sets to be used in regression of model parameters is an important issue related to modeling of phase equilibria. It is clear that good parameters for any model cannot be obtained from low quality data. A thermodynamic consistency test for solid...... and parameter regression. The paper will highlight the data collection, the data analysis for SLE data and the thermodynamic model performance (such as NRTL, UNIQUAC and original UNIFAC)....... studies considering the methodology proposed for SLE thermodynamic consistency tests and data from open literature and databases such as NIST-TDE®, DIPPR® and DECHEMA® are presented. The SLE consistency test and data evaluation is performed in a software containing option for data analysis, model analysis...

Prediction of phase equilibria in the In–Sb–Pb system

Directory of Open Access Journals (Sweden)

DUSKO MINIC

2008-03-01

Full Text Available Binary thermodynamic data, successfully used for phase diagram calculations of the binary systems In–Sb, Pb–Sb and In–Pb, were used for the prediction of the phase equilibria in the ternary In–Sb–Pb system. The predicted equilibrium phase diagram of the vertical Pb–InSb section was compared with the results of differential thermal analysis DTA and optical microscopy. The calculated phase diagram of the isothermal section at 300 °C was compared with the experimentally (SEM, EDX determined composition of phases in the chosen alloys after annealing. Very good agreement between the binary-based thermodynamic prediction and the experimental data was found in all cases. The calculated liquidus projection of the ternary In–Sb–Pb system is also presented.

Insight into the Am-O Phase Equilibria: A Thermodynamic Study Coupling High-Temperature XRD and CALPHAD Modeling.

Science.gov (United States)

Epifano, Enrica; Guéneau, Christine; Belin, Renaud C; Vauchy, Romain; Lebreton, Florent; Richaud, Jean-Christophe; Joly, Alexis; Valot, Christophe; Martin, Philippe M

2017-07-03

In the frame of minor actinide transmutation, americium can be diluted in UO 2 and (U, Pu)O 2 fuels burned in fast neutron reactors. The first mandatory step to foresee the influence of Am on the in-reactor behavior of transmutation targets or fuel is to have fundamental knowledge of the Am-O binary system and, in particular, of the AmO 2-x phase. In this study, we coupled HT-XRD (high-temperature X-ray diffraction) experiments with CALPHAD thermodynamic modeling to provide new insights into the structural properties and phase equilibria in the AmO 2-x -AmO 1.61+x -Am 2 O 3 domain. Because of this approach, we were able for the first time to assess the relationships between temperature, lattice parameter, and hypostoichiometry for fcc AmO 2-x . We showed the presence of a hyperstoichiometric existence domain for the bcc AmO 1.61+x phase and the absence of a miscibility gap in the fcc AmO 2-x phase, contrary to previous representations of the phase diagram. Finally, with the new experimental data, a new CALPHAD thermodynamic model of the Am-O system was developed, and an improved version of the phase diagram is presented.

Thermodynamic analysis of fatty acid esterification for fatty acid alkyl esters production

International Nuclear Information System (INIS)

Voll, Fernando A.P.; Silva, Camila da; Rossi, Carla C.R.S.; Guirardello, Reginaldo; Castilhos, Fernanda de; Oliveira, J. Vladimir; Cardozo-Filho, Lucio

2011-01-01

The development of renewable energy source alternatives has become a planet need because of the unavoidable fossil fuel scarcity and for that reason biodiesel production has attracted growing interest over the last decade. The reaction yield for obtaining fatty acid alkyl esters varies significantly according to the operating conditions such as temperature and the feed reactants ratio and thus investigation of the thermodynamics involved in such reactional systems may afford important knowledge on the effects of process variables on biodiesel production. The present work reports a thermodynamic analysis of fatty acid esterification reaction at low pressure. For this purpose, Gibbs free energy minimization was employed with UNIFAC and modified Wilson thermodynamic models through a nonlinear programming model implementation. The methodology employed is shown to reproduce the most relevant investigations involving experimental studies and thermodynamic analysis.

Thermodynamic investigations in the system U-Mo-O

International Nuclear Information System (INIS)

Chattopadhyay, G.; Kerkar, A.S.; Tripathi, S.N.

1984-01-01

Thermodynamic data on materials are required to answer some practical questions regarding chemical equilibria and also for the ultimate purpose of quantifying the relative stabilities of all possible chemical species. The present work was undertaken to determine what role molybdenum, one of the most preponderant fission products, could play in determining the state of the chemical equilibrium in the fuel fission product complex in an oxide-based nuclear reactor or in the nuclear waste disposed in ceramic or glass forms. To understand and analyze such complex systems, it is necessary to know which are the possible phases and species that are to be considered and their thermodynamic properties. In the present work attention was given to the ternary oxides of uranium and molybdenum with regard to the equilibria among the various phases. This is a prerequisite for determining the thermodynamic properties of the relevant phases. Therefore, experiments were carried out to construct the phase diagram in the region UO 2 -MoO 2 -O in a more precise manner than hitherto and, hence, to determine the free energy of formation of UMoO 5

Thermodynamic assessment of the Cu–Fe–Ni system

International Nuclear Information System (INIS)

Dreval, Liya A.; Turchanin, Mikhail A.; Agraval, Pavel G.

2014-01-01

Highlights: • The thermodynamic description of the Cu–Fe–Ni system has been updated. • The new experimental data have been used to refine thermodynamic model of the system. • The four-sublattice model has been adopted to predict the equilibria involving the ordered L1 2 phase. • A significant improvement in comparison with the previous assessments has been achieved. • The liquidus and solidus projections have been presented. -- Abstract: The thermodynamic description of the Cu–Fe–Ni system has been updated considering the newly available experimental data, as well as compatibility of the present modeling with those used for the Cu and Fe systems. All of the experimental data available in the literature have been critically reviewed, and the inconsistent information has been excluded. The thermodynamic parameters have been evaluated in order to properly describe the thermodynamic properties of the liquid phase and miscibility gap in the solid state. A significant improvement in comparison with the previous thermodynamic descriptions has been achieved. Additionally, for the ordered L1 2 phase the four-sublattice model has been adopted to predict the ternary phase equilibria involving this phase. A set of thermodynamic parameters for the phases is given

The impact of uni-univalent electrolytes on (water + acetic acid + toluene) equilibria: Representation with electrolyte-NRTL model

International Nuclear Information System (INIS)

Saien, Javad; Fattahi, Mahdi; Mozafarvandi, Maryam

2014-01-01

Highlights: • Experimental LLE data for water + acetic acid + toluene + NaCl or KCl were reported. • The salting-out effect was detected; indicating the stronger effect of NaCl. • The electrolyte-NRTL model was adequately used to correlate the phase equilibria. • A good agreement was observed between calculated and experimental tie-lines. - Abstract: The presence of salts can significantly alter the (liquid + liquid) equilibrium and extraction process. In this work, a study was conducted on the (liquid + liquid) equilibria of (water + acetic acid + toluene + sodium chloride or potassium chloride) at temperatures (288.2, 298.2 and 313.2) K. This chemical system, irrespective of salt, is frequently used in (liquid + liquid) extraction investigations. The selected salt concentrations in initial aqueous solutions were (0.9 and 1.7) mol · L −1 . The results show that salting-out effect of the salts was significant, so that an enhancement in the acetic acid distribution coefficient was achieved within (15.6 to 66.8)% with NaCl and within (2.5 to 37.6)% with KCl. Meantime, high separation factors were found at low temperatures and low solute concentrations. The electrolyte-NRTL model was satisfactorily used to correlate the phase equilibria. In this regard for each salt, the temperature dependent binary interaction parameters between components were calculated. The predicted tie-line mole fractions give root-mean square deviation (RMSD) values of only 0.0038 and 0.0045 for the systems containing NaCl and KCl, respectively

Gibbs energies of protonation and complexation of platinum and vanadate metal ions with naringenin and phenolic acids: Theoretical calculations associated with experimental values

International Nuclear Information System (INIS)

Fazary, Ahmed E.; Alshihri, Ayed S.; Alfaifi, Mohammad Y.; Saleh, Kamel A.; Elbehairi, Serag Eldin I.; Fawy, Khaled F.; Abd-Rabboh, Hisham S.M.

2016-01-01

Highlights: • The experimental thermodynamic equilibrium and stability constants of vanadium and platinum complexes involving naringin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid were determined. • The theoretical calculations of the free energy changes associated with the ligand protonation, and metal ion–ligand complex formation equilibria using density function theory calculations, providing a complete picture of the microscopic equilibria of the studied complex systems. - Abstract: The Experimental thermodynamic equilibrium (pK_a values) and stability (log β) constants of vanadium and platinum binary and mixed ligand complexes involving naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid were determined at 310.15 K in 0.16 mol·dm"−"3 KCl aqueous solutions using pH-potentiometric technique and by means of two estimation models (HYPERQUAD 2008 and Bjerrum–Calvin). The theoretical calculations of overall protonation and stability constants of the metal complex species in solution were predicted as the free energy change associated with the ligand protonation, and metal ion–ligand complex formation equilibria (species solvation/de-solvation) using ab initio and density function theory (DFT) calculations. The usage of the experimental potentiometry technique and theoretical predictions provides a complete picture of the microscopic equilibria of the studied systems (vanadium/platinum–naringenin–phenolic acid). Specifically, this theoretically DFT predications would be useful to determine the most real protonation constants of the studied bioligands in which the binding sites changes due to the ligand protonation/deprotonation equilibria. Also, the complexing capacities of vanadium and platinum towards naringenin, ferulic acid, p-coumaric acid, caffeic acid, vanillic acid, sinapic acid, and gallic acid in solutions were evaluated and discussed. From the

Development of long-lived radionuclides partitioning technology - Experimental/theoretical study of phase equilibria for multicomponent multiphase systems

Energy Technology Data Exchange (ETDEWEB)

Lee, Chul Soo; Lee, Se Il; Sim, Yeon Sik; Park, Sung Bin; Yang, Sung Oh; Park, Ji Yong [Korea University, Seoul (Korea, Republic of)

1995-08-01

In various partitioning processes, rare earth elements and actinide elements are separated from other elements in the first stage. They are then separated into rare earth groups and actinde groups. The first stage is accomplished by solvent extraction using DEHPA, by precipitation using oxalic= acid, or by cation exchange. The second stage is carried out by selective back-extraction or by selective elution using DTPA. In these processes the equilibria is governed by the concentrations of nitric acid, of solvents, and of precipitants among others. In this study various distribution coefficients in partitioning processes were experimentally determined. And thermodynamic models were proposed to calculate distribution coefficients with experimentally determined equilibrium constants. 32 refs., 11 tabs., 23 figs. (author)

Effect of temperature on acid–base equilibria in separation techniques. A review

International Nuclear Information System (INIS)

Gagliardi, Leonardo G.; Tascon, Marcos; Castells, Cecilia B.

2015-01-01

Studies on the theoretical principles of acid–base equilibria are reviewed and the influence of temperature on secondary chemical equilibria within the context of separation techniques, in water and also in aqueous-organic solvent mixtures, is discussed. In order to define the relationships between the retention in liquid chromatography or the migration velocity in capillary electrophoresis and temperature, the main properties of acid–base equilibria have to be taken into account for both, the analytes and the conjugate pairs chosen to control the solution pH. The focus of this review is based on liquid–liquid extraction (LLE), liquid chromatography (LC) and capillary electrophoresis (CE), with emphasis on the use of temperature as a useful variable to modify selectivity on a predictable basis. Simplified models were evaluated to achieve practical optimizations involving pH and temperature (in LLE and CE) as well as solvent composition in reversed-phase LC. - Highlights: • The study of theoretical principles of acid–base equilibrium has been reviewed. • The proton transfer process is often present in the analytical separation practice. • The influence of temperature on secondary chemical equilibria is examined. • The focus is laid on liquid chromatography and capillary electrophoresis. • Temperature can be a useful variable to modify selectivity under predictable basis

Experimental investigation of phase equilibria in the Zr-Cu-Ni ternary system

International Nuclear Information System (INIS)

Yang, Mujin; Wang, Cuiping; Yang, Shuiyuan; Shi, Zhan; Han, Jiajia; Liu, Xingjun

2017-01-01

The phase equilibria in the Zr-Cu-Ni ternary system are investigated combined with X-ray diffraction, electron probe micro-analysis and differential scanning calorimetry. Two isothermal sections of the Zr-Cu-Ni ternary system at 1 000 C and 1 100 C are experimentally established. Most of the binary intermetallic compounds, e.g. Zr 7 Ni 10 , ZrNi, ZrNi 5 , Zr 14 Cu 51 , and Zr 2 Cu 9 , show a remarkable ternary solubility. A new ternary compound named τ 3 (Zr 31.1-30.7 . Cu 28.5-40.3 Ni 40.4-29.0 ) is detected at 1 000 C and dissolved at 1 020 C because the nearby large liquid phase field further expands. The newly determined phase equilibria will provide important information for both thermodynamic assessment and alloy design of Zr-based metallic glass.

Calculation of α/γ equilibria in SA508 grade 3 steels for intercritical heat treatment

International Nuclear Information System (INIS)

Lee, B.J.; Kim, H.D.; Hong, J.H.

1998-01-01

An attempt has been made to suggest an optimum temperature for intercritical heat treatment of an SA508 grade 3 steel for nuclear pressure vessels, based on thermodynamic calculation of the α/γ phase equilibria. A thermodynamic database constructed for the Fe-Mn-Ni-Mo-Cr-Si-V-Al-C-N ten-component system and an empirical criterion that the amount of reformed austenite should be around 40 pct were used for thermodynamic calculation and derivation of the optimum heat-treatment temperature, respectively. The calculated optimum temperature, 720 C, was in good agreement with an experimentally determined temperature of 725 C obtained through an independent experimental investigation of the same steel. The agreement between the calculated and measured fraction of reformed austenite during the intercritical heat treatment was also confirmed. Based on the agreement between calculation and experiment, it could be concluded that thermodynamic calculations can be successfully applied to the materials and/or process design as an additive tool to the already established technology, and that the currently constructed thermodynamic database for steel systems shows an accuracy that makes such applications possible

Dynamic Buffer Capacity in Acid-Base Systems.

Science.gov (United States)

Michałowska-Kaczmarczyk, Anna M; Michałowski, Tadeusz

The generalized concept of 'dynamic' buffer capacity β V is related to electrolytic systems of different complexity where acid-base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton-Robinson buffers, taken as examples.

Dynamic Buffer Capacity in Acid?Base Systems

OpenAIRE

Micha?owska-Kaczmarczyk, Anna M.; Micha?owski, Tadeusz

2015-01-01

The generalized concept of ?dynamic? buffer capacity ? V is related to electrolytic systems of different complexity where acid?base equilibria are involved. The resulting formulas are presented in a uniform and consistent form. The detailed calculations are related to two Britton?Robinson buffers, taken as examples.

Vapour liquid equilibria of monocaprylin plus palmitic acid or methyl stearate at P = (1.20 and 2.50) kPa by using DSC technique

International Nuclear Information System (INIS)

Cunico, Larissa P.; Damaceno, Daniela S.; Matricarde Falleiro, Rafael M.; Sarup, Bent; Abildskov, Jens; Ceriani, Roberta; Gani, Rafiqul

2015-01-01

Highlights: • Novel VLE data for binary mixtures involving a partial acylglycerol (monocaprylin). • Use of a promising technique for measuring VLE/vapour pressure data (DSC technique). • The consistency of experimental data is analysed by a proposed methodology. • Regressed parameters are given for excess Gibbs thermodynamic models. • New regressed parameters are presented for UNIFAC to account for nonidealities. - Abstract: The Differential Scanning Calorimetry (DSC) technique is used for measuring isobaric (vapour + liquid) equilibria for two binary mixtures: {monocaprylin + palmitic acid (system 1) or methyl stearate (system 2)} at two different pressures P = (1.20 and 2.50) kPa. The obtained PTx data are correlated by Wilson, NRTL and UNIQUAC models. The original UNIFAC group contribution method is also considered and new binary interaction parameters for the main groups CH 2 , CCOO, OH and COOH are regressed, to account for the non-idealities found in these lipid systems. Established thermodynamic consistency tests are applied and attest the quality of the measured data. In terms of relevance of the selected components, system 1 can be found in the purification and deodorization steps during the production of edible oils, while, system 2 can be found in the purification steps of biodiesel. It should be noted that no such data could be found in the open literature, not only for the specific components selected but also for the combination of the classes of components considered; that is, acylglycerol plus fatty acid or fatty ester.

Fac–mer equilibria of coordinated iminodiacetate (ida ) in ternary Cu ...

Indian Academy of Sciences (India)

Unknown

Keywords. Fac–mer equilibria; CuII-iminodiacetate-imidazole/benzimidazole ternary complexes; stability constants. 1. Introduction. Mixed ligand complexes of transition metal ions with amino acids, peptides or their derivatives or analogues, and heterocyclic N-bases can serve as model compounds of bioinorganic interests ...

Binary, ternary and quaternary liquid-liquid equilibria in 1-butanol, oleic acid, water and n-heptane mixtures

NARCIS (Netherlands)

Winkelman, J. G. M.; Kraai, G. N.; Heeres, H. J.

2009-01-01

This work reports on liquid-liquid equilibria in the system 1-butanol, oleic acid, water and n-heptane used for biphasic, lipase catalysed esterifications. The literature was studied on the mutual solubility in binary systems of water and each of the organic components. Experimental results were

An Exact Method to Determine the Conductivity of Aqueous Solutions in Acid-Base Titrations

Directory of Open Access Journals (Sweden)

Norma Rodríguez-Laguna

2015-01-01

Full Text Available Several works in the literature show that it is possible to establish the analytic equations to estimate the volume V of a strong base or a strong acid (Vb and Va, resp. being added to a solution of a substance or a mix of substances during an acid-base titration, as well as the equations to estimate the first derivative of the titration plot dpH/dV, and algebraic expressions to determine the buffer β capacity with dilution βdil. This treatment allows establishing the conditions of thermodynamic equilibria for all species within a system containing a mix of species from one or from various polyacid systems. The present work shows that it is possible to determine exactly the electric conductivity of aqueous solutions for these Brønsted acid-base titrations, because the functional relation between this property and the composition of the system in equilibrium is well known; this is achieved using the equivalent conductivity λi values of each of the ions present in a given system. The model employed for the present work confirms the experimental outcomes with the H2SO4, B(OH3, CH3COOH, and H3PO4 aqueous solutions’ titration.

Statistical thermodynamics of alloys

International Nuclear Information System (INIS)

Gokcen, N.A.

1986-01-01

This book presents information on the following topics: consequences of laws of thermodynamics; Helmholtz and Gibbs energies; analytical forms of excess partial molar properties; single-component and multicomponent equilibria; phase rules and diagrams; lever rule; fermions, bosons, and Boltzons; approximate equations; enthalpy and heat capacity; Pd-H system; hydrogen-metal systems; limitations of Wagner model; energy of electrons and hols; dopants in semiconductors; derived thermodynamic properties; simple equivalent circuit; calculation procedure; multicompoent diagrams re; Engel-Brewer theories; p-n junctions; and solar cells

Analysis of the Glass-Forming Ability of Fe-Er Alloys, Based on Thermodynamic Modeling

Science.gov (United States)

Arutyunyan, N. A.; Zaitsev, A. I.; Dunaev, S. F.; Kalmykov, K. B.; El'nyakov, D. D.; Shaposhnikov, N. G.

2018-05-01

The Fe-Er phase diagram and thermodynamic properties of all its phases are assessed by means of self-consistent analysis. To refine the data on phase equilibria in the Fe-Er system, an investigation is performed in the 10-40 at % range of Er concentrations. The temperature-concentration dependences of the thermodynamic properties of a melt are presented using the model of ideal associated solutions. Thermodynamic parameters of each phase are obtained, and the calculated results are in agreement with available experimental data. The correlation between the thermodynamic properties of liquid Fe-Er alloys and their tendency toward amorphization are studied. It is shown that compositions of amorphous alloys prepared by melt quenching coincide with the ranges of concentration with the predominance of Fe3Er and FeEr2 associative groups that have large negative entropies of formation.

Extended Group Contribution Model for Polyfunctional Phase Equilibria

DEFF Research Database (Denmark)

Abildskov, Jens

of physical separation processes. In a thermodynamic sense, design requires detailed knowledge of activity coefficients in the phases at equilibrium. The prediction of these quantities from a minimum of experimental data is the broad scope of this thesis. Adequate equations exist for predicting vapor......Material and energy balances and equilibrium data form the basis of most design calculations. While material and energy balances may be stated without much difficulty, the design engineer is left with a choice between a wide variety of models for describing phase equilibria in the design......-liquid equilibria from data on binary mixtures, composed of structurally simple molecules with a single functional group. More complex is the situation with mixtures composed of structurally more complicated molecules or molecules with more than one functional group. The UNIFAC method is extended to handle...

Copper(II) 12-metallacrown-4 complexes of alpha-, beta- and gamma-aminohydroxamic acids: a comparative thermodynamic study in aqueous solution.

Science.gov (United States)

Tegoni, Matteo; Remelli, Maurizio; Bacco, Dimitri; Marchiò, Luciano; Dallavalle, Francesco

2008-05-28

A complete thermodynamic study of the protonation and Cu(II) complex formation equilibria of a series of alpha- and beta-aminohydroxamic acids in aqueous solution was performed. The thermodynamic parameters obtained for the protonation of glycine-, (S)-alpha-alanine-, (R,S)-valine-, (S)-leucine-, beta-alanine- and (R)-aspartic-beta-hydroxamic acids were compared with those previously reported for gamma-amino- and (S)-glutamic-gamma-hydroxamic acids. The enthalpy/entropy parameters calculated for the protonation microequilibria of these three types of ligands are in very good agreement with the literature values for simple amines and hydroxamic acids. The pentanuclear complexes [Cu5L4H(-4)]2+ contain the ligands acting as (NH2,N-)-(O,O-) bridging bis-chelating and correspond to 12-metallacrown-4 (12-MC-4) which are formed by self-assembly between pH 4 and 6 with alpha-aminohydroxamates (HL), while those with beta- and gamma-derivatives exist in a wider pH range (4-11). The stability order of these metallomacrocycles is beta- > alpha- > gamma-aminohydroxamates. The formation of 12-MC-4 with alpha-aminohydroxamates is entropy-driven, and that with beta-derivatives is enthalpy-driven, while with gamma-GABAhydroxamate both effects occur. These results are interpreted on the basis of specific enthalpies or entropy contributions related to chelate ring dimensions, charge neutralization and solvation-desolvation effects. The enthalpy/entropy parameters of 12-MC-4 with alpha-aminohydroxamic acids considered are also dependent on the optical purity of the ligands. Actually, that with (R,S)-valinehydroxamic acid presents an higher entropy and a lower enthalpy value than those of enantiopure ligands, although the corresponding stabilities are almost equivalent. Moreover, DFT calculations are in agreement with a more exothermic enthalpy found for metallacrowns with enantiomerically pure ligands.

A contribution to the study of mass transfer: uranium extraction from phosphoric acid

International Nuclear Information System (INIS)

Maher, A.

1985-12-01

Liquid-liquid extraction of uranium (VI) contained in phosphoric acid is examined. Synergism and thermodynamical equilibria are studied. Influence of drop size, extractant concentration and temperature on reaction kinetics are determined. The experimental study concerns extraction by HDEHP, TOPO and the mixture of both. Reaction mechanisms are interpreted [fr

Experimental and thermodynamic study of the Mg–Sn–In–Zn quaternary system

International Nuclear Information System (INIS)

Wang, Jian; Hudon, Pierre; Kevorkov, Dmytro; Chartrand, Patrice; Jung, In-Ho; Medraj, Mamoun

2014-01-01

Highlights: • Phase equilibria in the Mg-rich region of the Mg–Sn–In are determined. • Phase equilibria in the Mg-rich region of the Mg–Sn–Zn are determined. • Evaluation and thermodynamic optimization of the Mg–Sn–In–Zn quaternary system are developed. -- Abstract: Phase equilibria in the Mg-rich region of the Mg–Sn–In (at 415 °C and 330 °C), and Mg–Sn–Zn (at 300 °C) ternary systems were determined by quenching experiments, electron probe micro-analyzer (EPMA), and X-ray diffraction (XRD) techniques. The ternary isoplethal sections with constant 5 In and 10 Sn at.% of Mg–In–Sn system, and 10 Sn at.% of Mg–In–Zn system were determined by differential scanning calorimetry (DSC). No ternary compounds were found in the Mg–Sn–Zn and Mg–Sn–In isothermal sections. Critical evaluation and thermodynamic optimization of the Mg–Sn–In–Zn quaternary system were carried out using CALPHAD (Calculation of Phase Diagrams) technique. The Modified Quasichemical Model in the Pair Approximation (MQMPA) was used for modeling the liquid solution, which exhibits a high degree of short-range ordering behavior. The solid phases were modeled with the Compound Energy Formalism (CEF). All available and reliable experimental data were reproduced within experimental error limits. A self-consistent thermodynamic database was constructed for the Mg–Sn–In–Zn quaternary system, which can be used as a guide for Mg-based alloys development

Solid-phase equilibria on Pluto's surface

Science.gov (United States)

Tan, Sugata P.; Kargel, Jeffrey S.

2018-03-01

Pluto's surface is covered by volatile ices that are in equilibrium with the atmosphere. Multicomponent phase equilibria may be calculated using a thermodynamic equation of state and, without additional assumptions, result in methane-rich and nitrogen-rich solid phases. The former is formed at temperature range between the atmospheric pressure-dependent sublimation and condensation points, while the latter is formed at temperatures lower than the sublimation point. The results, calculated for the observed 11 μbar atmospheric pressure and composition, are consistent with recent work derived from observations by New Horizons.

Developing a Highly Active Blood Anticoagulant—a Heparin Complex with Glutamic Acid—by Simulating Chemical Equilibria Based on pH-Metric Data

Science.gov (United States)

Nikolaeva, L. S.; Semenov, A. N.

2018-02-01

The anticoagulant activity of high-molecular-weight heparin is increased by developing a new highly active heparin complex with glutamate using the thermodynamic model of chemical equilibria based on pH-metric data. The anticoagulant activity of the developed complexes is estimated in the pH range of blood plasma according to the drop in the calculated equilibrium Ca2+ concentration associated with the formation of mixed ligand complexes of Ca2+ ions, heparin (Na4hep), and glutamate (H2Glu). A thermodynamic model is calculated by mathematically modelling chemical equilibria in the CaCl2-Na4hep-H2Glu-H2O-NaCl system in the pH range of 2.30 ≤ pH ≤ 10.50 in diluted saline that acts as a background electrolyte (0.154 M NaCl) at 37°C and initial concentrations of the main components of ν × 10-3 M, where n ≤ 4. The thermodynamic model is used to determine the main complex of the monomeric unit of heparin with glutamate (HhepGlu5-) and the most stable mixed ligand complex of Ca2+ with heparin and glutamate (Ca2hepGlu2-) in the pH range of blood plasma (6.80 ≤ pH ≤ 7.40). It is concluded that the Ca2hepGlu2- complex reduces the Ca2+ concentration 107 times more than the Ca2+ complex with pure heparin. The anticoagulant effect of the developed HhepGlu5- complex is confirmed in vitro and in vivo via coagulation tests on the blood plasma of laboratory rats. Additional antithrombotic properties of the developed complex are identified. The new highly active anticoagulant, HhepGlu5- complex with additional antithrombotic properties, is patented.

Experimental investigation of phase equilibria in the Zr-Cu-Ni ternary system

Energy Technology Data Exchange (ETDEWEB)

Yang, Mujin; Wang, Cuiping; Yang, Shuiyuan; Shi, Zhan; Han, Jiajia; Liu, Xingjun [Xiamen Univ. (China). College of Materials and Fujian Provincial Key Lab. of Materials Genome

2017-08-15

The phase equilibria in the Zr-Cu-Ni ternary system are investigated combined with X-ray diffraction, electron probe micro-analysis and differential scanning calorimetry. Two isothermal sections of the Zr-Cu-Ni ternary system at 1 000 C and 1 100 C are experimentally established. Most of the binary intermetallic compounds, e.g. Zr{sub 7}Ni{sub 10}, ZrNi, ZrNi{sub 5}, Zr{sub 14}Cu{sub 51}, and Zr{sub 2}Cu{sub 9}, show a remarkable ternary solubility. A new ternary compound named τ{sub 3} (Zr{sub 31.1-30.7} . Cu{sub 28.5-40.3}Ni{sub 40.4-29.0}) is detected at 1 000 C and dissolved at 1 020 C because the nearby large liquid phase field further expands. The newly determined phase equilibria will provide important information for both thermodynamic assessment and alloy design of Zr-based metallic glass.

Exogenous empirical-evidence equilibria in perfect-monitoring repeated games yield correlated equilibria

KAUST Repository

Dudebout, Nicolas; Shamma, Jeff S.

2014-01-01

This paper proves that exogenous empirical-evidence equilibria (xEEEs) in perfect-monitoring repeated games induce correlated equilibria of the associated one-shot game. An empirical-evidence equilibrium (EEE) is a solution concept for stochastic games. At equilibrium, agents' strategies are optimal with respect to models of their opponents. These models satisfy a consistency condition with respect to the actual behavior of the opponents. As such, EEEs replace the full-rationality requirement of Nash equilibria by a consistency-based bounded-rationality one. In this paper, the framework of empirical evidence is summarized, with an emphasis on perfect-monitoring repeated games. A less constraining notion of consistency is introduced. The fact that an xEEE in a perfect-monitoring repeated game induces a correlated equilibrium on the underlying one-shot game is proven. This result and the new notion of consistency are illustrated on the hawk-dove game. Finally, a method to build specific correlated equilibria from xEEEs is derived.

Exogenous empirical-evidence equilibria in perfect-monitoring repeated games yield correlated equilibria

KAUST Repository

Dudebout, Nicolas

2014-12-15

This paper proves that exogenous empirical-evidence equilibria (xEEEs) in perfect-monitoring repeated games induce correlated equilibria of the associated one-shot game. An empirical-evidence equilibrium (EEE) is a solution concept for stochastic games. At equilibrium, agents\\' strategies are optimal with respect to models of their opponents. These models satisfy a consistency condition with respect to the actual behavior of the opponents. As such, EEEs replace the full-rationality requirement of Nash equilibria by a consistency-based bounded-rationality one. In this paper, the framework of empirical evidence is summarized, with an emphasis on perfect-monitoring repeated games. A less constraining notion of consistency is introduced. The fact that an xEEE in a perfect-monitoring repeated game induces a correlated equilibrium on the underlying one-shot game is proven. This result and the new notion of consistency are illustrated on the hawk-dove game. Finally, a method to build specific correlated equilibria from xEEEs is derived.

Morphology and thermodynamic characteristics of selenium-containing nanostructures based on polymethacrylic acid

Science.gov (United States)

Valueva, S. V.; Borovikova, L. N.; Vylegzhanina, M. E.; Sukhanova, T. E.

2010-09-01

The morphology and thermodynamic characteristics of nanostructures formed as a result of the reduction of the selenium ion in a selenite-ascorbate redox system in water solutions of polymethacrylic acid were studied by molecular optics and atomic-force microscopy. The dependence of the morphology of the selenium-containing nanostructures on the mass selenium-to-polymer ratio (ν) in solution was determined. It was established that a large number of macromolecules (up to 4300) is adsorbed on the selenium nanoparticles, leading to the formation of nanostructures with super-high molecular mass and an almost spherical form. It was shown that the density of the nanostructures, as calculated on the basis of the experimental data on the size and molecular mass of the nanocomposite, depends substantially on the selenium concentrations in the solution. The thermodynamic state of the solutions of nanostructures is described.

SEPARATION OF SATURED AND UNSATURATED FATTY ACIDS FROM PALM FATTY ACIDS DISTILLATES IN CONTINUOUS MULTISTAGE COUNTERCURRENT COLUMNS WITH SUPERCRITICAL CARBON DIOXIDE AS SOLVENT: A PROCESS DESIGN METHODOLOGY

Directory of Open Access Journals (Sweden)

Nélio Teixeira MACHADO

1997-12-01

Full Text Available In this work the separation of multicomponent mixtures in counter-current columns with supercritical carbon dioxide has been investigated using a process design methodology. First the separation task must be defined, then phase equilibria experiments are carried out, and the data obtained are correlated with thermodynamic models or empirical functions. Mutual solubilities, Ki-values, and separation factors aij are determined. Based on this data possible operating conditions for further extraction experiments can be determined. Separation analysis using graphical methods are performed to optimize the process parameters. Hydrodynamic experiments are carried out to determine the flow capacity diagram. Extraction experiments in laboratory scale are planned and carried out in order to determine HETP values, to validate the simulation results, and to provide new materials for additional phase equilibria experiments, needed to determine the dependence of separation factors on concetration. Numerical simulation of the separation process and auxiliary systems is carried out to optimize the number of stages, solvent-to-feed ratio, product purity, yield, and energy consumption. Scale-up and cost analysis close the process design. The separation of palmitic acid and (oleic+linoleic acids from PFAD-Palm Fatty Acids Distillates was used as a case study.

Thermodynamic modeling of CO2 mixtures

DEFF Research Database (Denmark)

Bjørner, Martin Gamel

Knowledge of the thermodynamic properties and phase equilibria of mixtures containing carbon dioxide (CO2) is important in several industrial processes such as enhanced oil recovery, carbon capture and storage, and supercritical extractions, where CO2 is used as a solvent. Despite this importance...

Constants and thermodynamics of the acid-base equilibria of triglycine in water-ethanol solutions containing sodium perchlorate at 298 K

Science.gov (United States)

Pham Tkhi, L.; Usacheva, T. R.; Tukumova, N. V.; Koryshev, N. E.; Khrenova, T. M.; Sharnin, V. A.

2016-02-01

The acid-base equilibrium constants for glycyl-glycyl-glycine (triglycine) in water-ethanol solvents containing 0.0, 0.1, 0.3, and 0.5 mole fractions of ethanol are determined by potentiometric titration at 298.15 K and an ionic strength of 0.1, maintained with sodium perchlorate. It is established that an increase in the ethanol content in the solvent reduces the dissociation constant of the carboxyl group of triglycine (increases p K 1) and increases the dissociation constant of the amino group of triglycine (decreases p K 2). It is noted that the weakening of the acidic properties of a triglycinium ion upon an increase of the ethanol content in the solvent is due to the attenuation of the solvation shell of the zwitterionic form of triglycine, and to the increased solvation of triglycinium ions. It is concluded that the acid strength of triglycine increases along with a rise in the EtOH content in the solvent, due to the desolvation of the tripeptide zwitterion and the enhanced solvation of protons.

Computed phase equilibria for burnable neutron absorbing materials for advanced pressurized heavy water reactors

Energy Technology Data Exchange (ETDEWEB)

Corcoran, E.C. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, P.O. Box 17000, St. Forces, Kingston, Ont., K7K 7B4 (Canada)], E-mail: emily.corcoran@rmc.ca; Lewis, B.J.; Thompson, W.T. [Department of Chemistry and Chemical Engineering, Royal Military College of Canada, P.O. Box 17000, St. Forces, Kingston, Ont., K7K 7B4 (Canada); Hood, J. [Atomic Energy of Canada Ltd., Sheridan Park, 2251 Speakman Drive, Mississauga, Ont., L5K 1B2 (Canada); Akbari, F.; He, Z. [Atomic Energy of Canada Ltd., Chalk River Laboratories, Chalk River, Ont., K0J 1J0 (Canada); Reid, P. [Atomic Energy of Canada Ltd., Sheridan Park, 2251 Speakman Drive, Mississauga, Ont., L5K 1B2 (Canada)

2009-03-31

Burnable neutron absorbing materials are expected to be an integral part of the new fuel design for the Advanced CANDU [CANDU is as a registered trademark of Atomic Energy of Canada Limited.] Reactor. The neutron absorbing material is composed of gadolinia and dysprosia dissolved in an inert cubic-fluorite yttria-stabilized zirconia matrix. A thermodynamic model based on Gibbs energy minimization has been created to provide estimated phase equilibria as a function of composition and temperature. This work includes some supporting experimental studies involving X-ray diffraction.

Thermodynamic analysis of chemical heat pumps

International Nuclear Information System (INIS)

Obermeier, Jonas; Müller, Karsten; Arlt, Wolfgang

2015-01-01

Thermal energy storages and heat pump units represent an important part of high efficient renewable energy systems. By using thermally driven, reversible chemical reactions a combination of thermal energy storage and heat pump can be realized. The influences of thermophysical properties of the involved components on the efficiency of a heat pump cycle is analysed and the relevance of the thermodynamic driving force is worked out. In general, the behaviour of energetic and exergetic efficiency is contrary. In a real cycle, higher enthalpies of reaction decrease the energetic efficiency but increase the exergetic efficiency. Higher enthalpies of reaction allow for lower offsets from equilibrium state for a default thermodynamic driving force of the reaction. - Highlights: • A comprehensive efficiency analysis of gas-solid heat pumps is proposed. • Link between thermodynamic driving force and equilibrium drop is shown. • Calculation of the equilibrium drop based on thermochemical properties. • Reaction equilibria of the decomposition reaction of salt hydrates. • Contrary behavior of energetic and exergetic efficiency

Experimental investigation of phase equilibria in the Co-W-V ternary system

International Nuclear Information System (INIS)

Liu Xingjun; Zhu Yihong; Yu Yan; Wang Cuiping

2011-01-01

Highlights: → Three isothermal sections of the Co-W-V ternary system at 1100 deg. C, 1200 deg. C and 1300 deg. C were determined. → No ternary compound was found in the Co-W-V ternary system. → A stable liquid miscibility gap is newly discovered in the Co-W-V ternary system. → This work is of great essence to establish the thermodynamic database for the Co-based alloys. - Abstract: The phase equilibria in the Co-W-V ternary system were experimentally investigated by optical microscopy (OM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) on the equilibrated alloys. Three isothermal sections of the Co-W-V ternary system at 1100 deg. C, 1200 deg. C and 1300 deg. C were determined, and no ternary compound was found in this system. In addition, a novel phenomena induced by the liquid phase separation in the Co-W-V alloys was firstly discovered, suggesting that a stable liquid miscibility gap exists in the Co-W-V ternary system. The newly determined phase equilibria and firstly discovered phase separation phenomena in the Co-W-V system will provide important information for the development of Co-W based alloys.

lncRNATargets: A platform for lncRNA target prediction based on nucleic acid thermodynamics.

Science.gov (United States)

Hu, Ruifeng; Sun, Xiaobo

2016-08-01

Many studies have supported that long noncoding RNAs (lncRNAs) perform various functions in various critical biological processes. Advanced experimental and computational technologies allow access to more information on lncRNAs. Determining the functions and action mechanisms of these RNAs on a large scale is urgently needed. We provided lncRNATargets, which is a web-based platform for lncRNA target prediction based on nucleic acid thermodynamics. The nearest-neighbor (NN) model was used to calculate binging-free energy. The main principle of NN model for nucleic acid assumes that identity and orientation of neighbor base pairs determine stability of a given base pair. lncRNATargets features the following options: setting of a specific temperature that allow use not only for human but also for other animals or plants; processing all lncRNAs in high throughput without RNA size limitation that is superior to any other existing tool; and web-based, user-friendly interface, and colored result displays that allow easy access for nonskilled computer operators and provide better understanding of results. This technique could provide accurate calculation on the binding-free energy of lncRNA-target dimers to predict if these structures are well targeted together. lncRNATargets provides high accuracy calculations, and this user-friendly program is available for free at http://www.herbbol.org:8001/lrt/ .

The feasibility of parameterizing four-state equilibria using relaxation dispersion measurements

International Nuclear Information System (INIS)

Li Pilong; Martins, Ilídio R. S.; Rosen, Michael K.

2011-01-01

Coupled equilibria play important roles in controlling information flow in biochemical systems, including allosteric molecules and multidomain proteins. In the simplest case, two equilibria are coupled to produce four interconverting states. In this study, we assessed the feasibility of determining the degree of coupling between two equilibria in a four-state system via relaxation dispersion measurements. A major bottleneck in this effort is the lack of efficient approaches to data analysis. To this end, we designed a strategy to efficiently evaluate the smoothness of the target function surface (TFS). Using this approach, we found that the TFS is very rough when fitting benchmark CPMG data to all adjustable variables of the four-state equilibria. After constraining a portion of the adjustable variables, which can often be achieved through independent biochemical manipulation of the system, the smoothness of TFS improves dramatically, although it is still insufficient to pinpoint the solution. The four-state equilibria can be finally solved with further incorporation of independent chemical shift information that is readily available. We also used Monte Carlo simulations to evaluate how well each adjustable parameter can be determined in a large kinetic and thermodynamic parameter space and how much improvement can be achieved in defining the parameters through additional measurements. The results show that in favorable conditions the combination of relaxation dispersion and biochemical manipulation allow the four-state equilibrium to be parameterized, and thus coupling strength between two processes to be determined.

A potentiometric study of (acid+base) equilibria in substituted 4-nitropyridine N-oxide systems in methanol and dimethyl sulfoxide

International Nuclear Information System (INIS)

Gurzynski, Lukasz; Puszko, Aniela; Makowski, Mariusz; Chmurzynski, Lech

2007-01-01

The acid dissociation constants for cationic acids conjugated with 4-nitropyridine N-oxides have been determined using potentiometric titration method. The measurements in the systems of thirteen 4-nitropyridine N-oxide derivatives were carried out in the polar amphiprotic methanol (MeOH) and in the aprotic protophilic dimethyl sulfoxide (DMSO). Likewise as in the polar aprotic protophobic solvents (acetonitrile, acetone) it was found that in MeOH for all N-oxides studied the pK a values were readily determinable, whereas in DMSO the pK a values were hardly determinable or indeterminable by using the potentiometric method. In addition, just like in our previous investigations it was revealed that the sequence of the pK a values of the cationic acids in methanol is the same as in the water and the values are lower than those determined in acetonitrile and acetone. Also, it was found that the phenomenon of cationic homoconjugation equilibria was not present in the systems involving 4-nitropyridine N-oxide derivatives in both solvents used. Furthermore, protonation energies, ΔE prot , and Gibbs free enthalpies, ΔG prot , in vacuo have been compared with acid dissociation constants (expressed as pK a MeOH values) of the protonated N-oxides determined by potentiometric titration in methanol to establish a correlation between these magnitudes

A potentiometric study of (acid+base) equilibria in substituted 4-nitropyridine N-oxide systems in methanol and dimethyl sulfoxide

Energy Technology Data Exchange (ETDEWEB)

Gurzynski, Lukasz [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Puszko, Aniela [Department of Organic Chemistry, School of Economics, Wroclaw (Poland); Makowski, Mariusz [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Chmurzynski, Lech [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland)]. E-mail: lech@chemik.chem.univ.gda.pl

2007-02-15

The acid dissociation constants for cationic acids conjugated with 4-nitropyridine N-oxides have been determined using potentiometric titration method. The measurements in the systems of thirteen 4-nitropyridine N-oxide derivatives were carried out in the polar amphiprotic methanol (MeOH) and in the aprotic protophilic dimethyl sulfoxide (DMSO). Likewise as in the polar aprotic protophobic solvents (acetonitrile, acetone) it was found that in MeOH for all N-oxides studied the pK{sub a} values were readily determinable, whereas in DMSO the pK{sub a} values were hardly determinable or indeterminable by using the potentiometric method. In addition, just like in our previous investigations it was revealed that the sequence of the pK{sub a} values of the cationic acids in methanol is the same as in the water and the values are lower than those determined in acetonitrile and acetone. Also, it was found that the phenomenon of cationic homoconjugation equilibria was not present in the systems involving 4-nitropyridine N-oxide derivatives in both solvents used. Furthermore, protonation energies, {delta}E{sub prot}, and Gibbs free enthalpies, {delta}G{sub prot}, in vacuo have been compared with acid dissociation constants (expressed as pK{sub a}{sup MeOH} values) of the protonated N-oxides determined by potentiometric titration in methanol to establish a correlation between these magnitudes.

Attractive evolutionary equilibria

NARCIS (Netherlands)

Joosten, Reinoud A.M.G.; Roorda, Berend

2011-01-01

We present attractiveness, a refinement criterion for evolutionary equilibria. Equilibria surviving this criterion are robust to small perturbations of the underlying payoff system or the dynamics at hand. Furthermore, certain attractive equilibria are equivalent to others for certain evolutionary

THE INFLUENCE OF THE SOLVENT ON THE THERMODYNAMICS OF ION ASSOCIATION

Directory of Open Access Journals (Sweden)

Vitalii Chumak

2011-03-01

Full Text Available Abstract. Some approaches which allow to divide thermodynamic functions of the ion associationprocess in two components have been developed. The first component belongs to the process, the second oneis caused by the temperature dependence of the dielectric permittivity of the solvent. The theory is confirmedby numerous examples of the ion association process of different electrolytes in the binary mixed solvents.Keywords: covalent part of the constant of ionic association, electrostatic part of the constant of ionicassociation, enthalpy of the chemical equilibria in solution, enthropy of the chemical equilibria in solution,ionic association, ionic equilibrias, the equilibrium constant.

A thermodynamic evaluation of the Fe-Nb system

International Nuclear Information System (INIS)

Srikanth, S.; Petric, A.

1994-01-01

An optimised set of thermodynamic functions consistent with the phase diagram was derived for the Fe-Nb system from information on phase equilibria and thermodynamic data available in the literature. The thermodynamic properties of the intermediate ε (Fe 2 Nb) phase were described using the sublattice model. A Redlich-Kister equation was used to describe the excess thermodynamic functions of the liquid, bcc and fcc phases. For the μ phase, the enthalpy of formation was estimated from Miedema's model. The interaction coefficients were evaluated using an optimisation procedure employing a conjugate gradient method. The phase diagram and the thermodynamic functions calculated from the evaluated parameters are in good agreement with experimental data. (orig.)

The thermodynamic assessment of the Au–In–Ga system

Energy Technology Data Exchange (ETDEWEB)

Ghasemi, M., E-mail: masoomeh.ghasemi@ftf.lth.se [Solid State Physics, Lund University, Box 118, SE-22100 Lund (Sweden); Sundman, B., E-mail: bo.sundman@gmail.com [INSTN-CEA Saclay, 91191 Gif sur Yvette (France); Fries, S.G., E-mail: suzana.g.fries@ruhr-uni-bochum.de [ICAMS, Interdisciplinary Centre for Advanced Materials Simulation, Ruhr Universitaet Bochum 44801, Bochum (Germany); Johansson, J., E-mail: jonas.johansson@ftf.lth.se [Solid State Physics, Lund University, Box 118, SE-22100 Lund (Sweden)

2014-07-05

Highlights: • The first thermodynamic assessment of the Au–In–Ga system has been presented. • Based on recent experimental results, a self-consistent database has been obtained. • A diagram of monovariant lines was calculated and invariant reactions were defined. • An isothermal section at 280 °C and two isoplethal sections were calculated. • Good agreement between the calculations and experimental results was achieved. - Abstract: The Au–In–Ga ternary phase diagram is of importance for understanding the involved thermodynamic processes during the growth of Au-seeded III–V heterostructure nanowires containing In and Ga (e.g. Au-seeded InAs/GaAs nanowires). In this work the Au–In–Ga system has been thermodynamically modeled using the CALPHAD technique based on a recent experimental investigation of the phase equilibria in the system. As a result, a set of self-consistent interaction parameters have been optimized that can reproduce most of the experimental results.

First-principles calculations, experimental study, and thermodynamic modeling of the Al-Co-Cr system.

Directory of Open Access Journals (Sweden)

Xuan L Liu

Full Text Available The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT and phase-equilibria experiments that led to X-ray diffraction (XRD and electron probe micro-analysis (EPMA measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS calculations predict a large bcc-A2 (disordered/B2 (ordered miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.

Thermodynamic properties of citric acid and the system citric acid-water

NARCIS (Netherlands)

Kruif, C.G. de; Miltenburg, J.C. van; Sprenkels, A.J.J.; Stevens, G.; Graaf, W. de; Wit, H.G.M. de

1982-01-01

The binary system citric acid-water has been investigated with static vapour pressure measurements, adiabatic calorimetry, solution calorimetry, solubility measurements and powder X-ray measurements. The data are correlated by thermodynamics and a large part of the phase diagram is given. Molar heat

Redox thermodynamic data of plutonium in acidic and carbonate media. Pu(V) stability

International Nuclear Information System (INIS)

Capdevila, H.

1992-01-01

Pu redox equilibria are studied in acidic and carbonate media in this thesis, to build a thermodynamic data bank consistent with the TDB (NEA-OECD) one and in connection with radioactive waste disposal programs. Literature is discussed and reinterpreted. The experimental method is tested with Uranium preliminary measurements. The reversible redox potentials (PuO 2 + and Pu 4+ /Pu 3+ ) are measured using the cyclic voltametric technique in perchloric media at several ionic strengths (from 0.5 to 3M) and temperatures (from 0 to 70 deg C). The Specific Interaction Theory (SIT) is used to measured activity coefficients and to extrapolate data to the standard conditions. The potentials variations versus temperature are linear in first approximation: the entropy changes are found constant from 0 to 70 deg C and the heat capacity changes are within uncertainties. The standard constant of PuO 2 + disproportionation into PuO 2 2+ and Pu 3+ is deduced from spectrophotometric measurements performed in perchloric media around pH=1 where Pu 4+ hydrolysis is discussed. The Pu non-reversible standard potentials (PuO 2 2+ /Pu 4+ for instance) are then calculated and validated with a spectrophotometric study of Pu 4+ formation from PuO 2 2+ and Pu 3+ in a 1M perchloric acidic solution. The Pu(VI/V) redox potential, activity coefficients and entropies are measured using the same technique in concentrated carbonate media. The limiting complex standard formation constants and the redox potential shifts (between acidic and carbonate media) are then discussed among the U, Np, Pu and Am actinides. A spectrophotometric study of the equilibrium between the complexes with 5 and 4 carbonate ligands allowed to measure Pu(IV) limiting complex stability at several ionic strengths. (author). 26 tabs., 46 figs., 95 refs

Experimental investigation and thermodynamic modeling of the Ga–Zr system

Energy Technology Data Exchange (ETDEWEB)

Luo, Wei [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Liu, Shuhong, E-mail: shhliu@csu.edu.cn [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Tang, Ying [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Yin, Ming [Thermal Processing Technology Center, Illinois Institute of Technology (IIT), 10 West 32nd Street, Chicago, IL 60616 (United States); Sundman, Bosse [INSTN, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France); Du, Yong [School of Material Science and Engineering, Central South University, Changsha, Hunan 410083 (China); Nash, Philip [Thermal Processing Technology Center, Illinois Institute of Technology (IIT), 10 West 32nd Street, Chicago, IL 60616 (United States); Tao, Huijin [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)

2014-02-25

Highlights: • Phase equilibria of the Ga–Zr system were investigated by experiment. • Δ{sub f}Hs for intermetallic compounds were computed via first–principles calculations. • The enthalpy of formation at 298 K for αGaZr was measured by calorimetry. • A set of self-consistent thermodynamic parameters was obtained. -- Abstract: Phase equilibria of the Ga–Zr system were investigated by experiment and thermodynamic modeling. In the experimental part, eleven alloys were prepared by melting the pure elements and annealed. Both the as-cast and annealed samples were analyzed by X-ray diffraction, optical microscopy, and scanning electron microscope. The annealed alloys were investigated by differential thermal analysis and electron probe microanalysis. In order to assist the thermodynamic modeling, the enthalpies of formation at 0 K for the GaZr{sub 2}, Ga{sub 3}Zr{sub 5}, Ga{sub 2}Zr{sub 3}, Ga{sub 4}Zr{sub 5}, αGaZr, Ga{sub 3}Zr{sub 2}, Ga{sub 5}Zr{sub 3}, Ga{sub 2}Zr and Ga{sub 3}Zr phases were computed via first-principles calculations. The enthalpy of formation at 298 K for the αGaZr was measured by high temperature reaction calorimetry. Based on the experimental phase diagram data from the present work and the literature as well as the present first-principles calculations, the Ga–Zr system was critically assessed by means of CALPHAD approach. The calculated phase diagram and thermodynamic properties agree well with the available experimental data.

Influence of the temperature on the (liquid + liquid) phase equilibria of (water + 1-propanl + linalool or geraniol)

International Nuclear Information System (INIS)

Wan, Li; Li, Hengde; Huang, Cheng; Feng, Yuqing; Chu, Guoqiang; Zheng, Yuying; Tan, Wei; Qin, Yanlin; Sun, Dalei; Fang, Yanxiong

2017-01-01

Highlights: • Ternary LLEs containing linalool and geraniol are presented. • Distribution ratios of 1-propanol in the mixtures are examined. • Influence of the temperature on the LLE is studied. • The LLE data were correlated using the NRTL and UNIQUAC models. - Abstract: Linalool and geraniol are the primary components of rose oil, palmarosa oil, and citronella oil and many other essential oils, and two important compounds used in the flavour and fragrance, cosmetic or pharmaceutical industries. Phase equilibria (LLE, VLE, solubility, etc.) and related thermodynamic properties of a mixture are essential in the processes design and control of mass transfer process. In this work, experimental (liquid + liquid) equilibria data of the systems (water + 1-propanl + linalool) and (water + 1-propanl + geraniol) are presented. The (liquid + liquid) equilibria of both systems were determined with a tie-line method at T = (283.15, 298.15 and 313.15) K under atmospheric pressure. The well-known Hand, Bachman and Othmer–Tobias equations were used to test the reliability of the experimental values. The influence of the temperature on the (liquid + liquid) phase equilibria of the mixtures, the binodal curves and distribution ratios of 1-propanl are shown and discussed. Moreover, the NRTL and UNIQUAC models were applied to fit the data for both ternary systems. The interaction parameters obtained from both models successfully correlated the equilibrium compositions. Furthermore, the ternary systems could be represented using the binary parameters of the thermodynamic model with a function of temperature.

Pierce instability and bifurcating equilibria

International Nuclear Information System (INIS)

Godfrey, B.B.

1981-01-01

The report investigates the connection between equilibrium bifurcations and occurrence of the Pierce instability. Electrons flowing from one ground plane to a second through an ion background possess a countable infinity of static equilibria, of which only one is uniform and force-free. Degeneracy of the uniform and simplest non-uniform equilibria at a certain ground plan separation marks the onset of the Pierce instability, based on a newly derived dispersion relation appropriate to all the equilibria. For large ground plane separations the uniform equilibrium is unstable and the non-uniform equilibrium is stable, the reverse of their stability properties at small separations. Onset of the Pierce instability at the first bifurcation of equilibria persists in more complicated geometries, providing a general criterion for marginal stability. It seems probable that bifurcation analysis can be a useful tool in the overall study of stable beam generation in diodes and transport in finite cavities

Attractive evolutionary equilibria

OpenAIRE

Roorda, Berend; Joosten, Reinoud

2011-01-01

We present attractiveness, a refinement criterion for evolutionary equilibria. Equilibria surviving this criterion are robust to small perturbations of the underlying payoff system or the dynamics at hand. Furthermore, certain attractive equilibria are equivalent to others for certain evolutionary dynamics. For instance, each attractive evolutionarily stable strategy is an attractive evolutionarily stable equilibrium for certain barycentric ray-projection dynamics, and vice versa.

Thermodynamic assessment of the Bi-Sn-Zn system

Czech Academy of Sciences Publication Activity Database

Vízdal, J.; Braga, M.H.; Kroupa, Aleš; Richter, K. W.; Soares, D.; Malheiros, L.F.; Ferreira, J.

2007-01-01

Roč. 31, č. 4 (2007), s. 438-448 ISSN 0364-5916 R&D Projects: GA MŠk OC 531.002 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase-equilibria * bismuth system * binary- systems Subject RIV: BJ - Thermodynamics Impact factor: 1.352, year: 2007

Experimental determination of thermodynamic equilibrium in biocatalytic transamination.

Science.gov (United States)

Tufvesson, Pär; Jensen, Jacob S; Kroutil, Wolfgang; Woodley, John M

2012-08-01

The equilibrium constant is a critical parameter for making rational design choices in biocatalytic transamination for the synthesis of chiral amines. However, very few reports are available in the scientific literature determining the equilibrium constant (K) for the transamination of ketones. Various methods for determining (or estimating) equilibrium have previously been suggested, both experimental as well as computational (based on group contribution methods). However, none of these were found suitable for determining the equilibrium constant for the transamination of ketones. Therefore, in this communication we suggest a simple experimental methodology which we hope will stimulate more accurate determination of thermodynamic equilibria when reporting the results of transaminase-catalyzed reactions in order to increase understanding of the relationship between substrate and product molecular structure on reaction thermodynamics. Copyright © 2012 Wiley Periodicals, Inc.

Thermodynamics, kinetics and process control of nitriding

DEFF Research Database (Denmark)

Mittemeijer, Eric J.; Somers, Marcel A. J.

1999-01-01

As a prerequisite for predictability of properties obtained by a nitriding treatment of iron-based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present (even) the description of thermodynamic equilibrium...... of pure iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for......, the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have...

High-pressure fluid phase equilibria phenomenology and computation

CERN Document Server

Deiters, Ulrich K

2012-01-01

The book begins with an overview of the phase diagrams of fluid mixtures (fluid = liquid, gas, or supercritical state), which can show an astonishing variety when elevated pressures are taken into account; phenomena like retrograde condensation (single and double) and azeotropy (normal and double) are discussed. It then gives an introduction into the relevant thermodynamic equations for fluid mixtures, including some that are rarely found in modern textbooks, and shows how they can they be used to compute phase diagrams and related properties. This chapter gives a consistent and axiomatic approach to fluid thermodynamics; it avoids using activity coefficients. Further chapters are dedicated to solid-fluid phase equilibria and global phase diagrams (systematic search for phase diagram classes). The appendix contains numerical algorithms needed for the computations. The book thus enables the reader to create or improve computer programs for the calculation of fluid phase diagrams. introduces phase diagram class...

Estimation of thermodynamic acidity constants of some penicillinase-resistant penicillins.

Science.gov (United States)

Demiralay, Ebru Çubuk; Üstün, Zehra; Daldal, Y Doğan

2014-03-01

In this work, thermodynamic acidity constants (pssKa) of methicillin, oxacillin, nafcillin, cloxacilin, dicloxacillin were determined with reverse phase liquid chromatographic method (RPLC) by taking into account the effect of the activity coefficients in hydro-organic water-acetonitrile binary mixtures. From these values, thermodynamic aqueous acidity constants of these drugs were calculated by different approaches. The linear relationships established between retention factors of the species and the polarity parameter of the mobile phase (ET(N)) was proved to predict accurately retention in LC as a function of the acetonitrile content (38%, 40% and 42%, v/v). Copyright © 2013 Elsevier B.V. All rights reserved.

MINTEQ, Geochemical Equilibria in Ground Water

International Nuclear Information System (INIS)

Krupka, K.M.

1990-01-01

1 - Description of program or function: MINTEQ is a geochemical program to model aqueous solutions and the interactions of aqueous solutions with hypothesized assemblages of solid phases. It was developed for the Environmental Protection Agency to perform the calculations necessary to simulate the contact of waste solutions with heterogeneous sediments or the interaction of ground water with solidified wastes. MINTEQ can calculate ion speciation/solubility, adsorption, oxidation-reduction, gas phase equilibria, and precipitation/dissolution of solid phases. MINTEQ can accept a finite mass for any solid considered for dissolution and will dissolve the specified solid phase only until its initial mass is exhausted. This ability enables MINTEQ to model flow-through systems. In these systems the masses of solid phases that precipitate at earlier pore volumes can be dissolved at later pore volumes according to thermodynamic constraints imposed by the solution composition and solid phases present. The ability to model these systems permits evaluation of the geochemistry of dissolved traced metals, such as low-level waste in shallow land burial sites. MINTEQ was designed to solve geochemical equilibria for systems composed of one kilogram of water, various amounts of material dissolved in solution, and any solid materials that are present. Systems modeled using MINTEQ can exchange energy and material (open systems) or just energy (closed systems) with the surrounding environment. Each system is composed of a number of phases. Every phase is a region with distinct composition and physically definable boundaries. All of the material in the aqueous solution forms one phase. The gas phase is composed of any gaseous material present, and structurally distinct solid forms a separate phase. 2 - Method of solution: MINTEQ applies the fundamental principles of thermodynamics to solve geochemical equilibria from a set of mass balance equations, one for each component. Because the

Membrane extraction with thermodynamically unstable diphosphonic acid derivatives

Science.gov (United States)

Horwitz, E.P.; Gatrone, R.C.; Nash, K.L.

1997-10-14

Thermodynamically-unstable complexing agents which are diphosphonic acids and diphosphonic acid derivatives (or sulphur containing analogs), like carboxyhydroxymethanediphosphonic acid and vinylidene-1,1-diphosphonic acid, are capable of complexing with metal ions, and especially metal ions in the II, III, IV, V and VI oxidation states, to form stable, water-soluble metal ion complexes in moderately alkaline to highly-acidic media. However, the complexing agents can be decomposed, under mild conditions, into non-organic compounds which, for many purposes are environmentally-nondamaging compounds thereby degrading the complex and releasing the metal ion for disposal or recovery. Uses for such complexing agents as well as methods for their manufacture are also described. 1 fig.

Stability of the n = 1 internal kink mode in equilibria with flows

International Nuclear Information System (INIS)

Aydemir, A.Y.; Waelbroeck, F.L.

1996-01-01

Stabilizing influence of mass flows, either directly or through their shearing action, on various modes is now generally recognized. Here we examine linear and nonlinear stability of the n = 1 internal kink mode in equilibria with toroidal rotation, using our nonlinear, initial-value MHD code CTD, which can be used to generate self-consistent equilibria with flows in arbitrary geometries. It is well known that equilibrium mass flows introduce complications in determination of MHD equilibria and their stability properties, such as the loss of self-adjointness and an increase in the number of conditions required to uniquely determine the equilibria. Thus, even with purely toroidal flows, an implicit statement about the equation of state is needed, in addition to a knowledge of the magnetic field and velocity profiles; rotation in an adiabatic plasma leads to a different equilibrium than, for example, in an isothermal one, with possibly quite different stability properties. We find that the expected stabilizing influence of toroidal rotation on n = 1 is generally absent in adiabatically generated equilibria in which, of all the relevant thermodynamic variables, only the specific entropy is a flux function, s = s (ψ). Fortunately, physically more relevant isothermal case where the temperature is constant on flux surfaces, T = T(ψ), has more favorable stability characteristics. On the other hand, an inconsistent but common practice of ignoring density perturbations, a benign omission for static equilibria, leads to overly optimistic results when equilibrium flows axe present, predicting stability when there may not be any. The crucial role played by the equation of state in determining equilibrium raises questions regarding the role of parallel transport in stability calculations; this and other nonideal effects, along with the role of plasma β vs. the rotational β, and nonlinear stability when the mode is pushed beyond marginality, will be discussed

Acid-base behavior in hydrothermal processing of wastes. 1998 annual progress report

International Nuclear Information System (INIS)

Johnson, K.P.; Rossky, P.J.

1998-01-01

'A new technology, hydrothermal oxidation (also called supercritical water oxidation), is being developed to treat high level nuclear wastes. Nitrates are reduced to nitrogen; furthermore, phosphates, alumina sludge, and chromium are solubilized, and the sludge is reconstituted as fine oxide particles. A major obstacle to development of this technology has been a lack of scientific knowledge of chemistry in hydrothermal solution above 350 C, particularly acid-base behavior, and transport phenomena, which is needed to understand corrosion, metal-ion complexation, and salt precipitation and recovery. The objective is to provide this knowledge with in-situ UV-vis spectroscopic measurements and fully molecular computer simulation. A major objective of the experimental studies has been to determine the equilibria for Cr(VI) up to 420 C as this is a key species to be removed from nuclear wastes. A wide range of concentrations of KOH and perchloric acid were utilized to manipulate the acid-base equilibria and to understand the effects of ion solvation and ion pairing. The second system is the equilibria between nitric acid, nitrous acid, nitrogen dioxide, nitrite and nitrate ions and oxygen. For both of these systems, chemical equilibria has not been measured previously in hydrothermal solution at these temperatures. On the theoretical side, the authors have focused on the study of the transport properties of aqueous ions in supercritical water. The motivation for these studies is two fold. First, although transport coefficients are fundamental to solution chemistry reaction rates, the behavior of such transport properties over wide ranges of density and temperature are not well established experimentally, particularly at the densities typically of interest (< 0.5 g/cc). Second, due to practical challenges, ionic association equilibria in SCW is typically accessed via measurements of conductivity followed by analysis through a theoretical model that incorporates ion

Ternary equilibria in bismuth--indium--lead alloys

International Nuclear Information System (INIS)

Liao, K.C.; Johnson, D.L.; Nelson, R.C.

1975-01-01

The liquidus surface is characterized by three binary equilibria. One binary extends from the Pb--Bi peritectic to the Pb--In peritectic. The other two extend from In--Bi eutectics, merge at 50 at. percent Bi and 30 at. percent Pb, and end at the Bi--Pb eutectic. Based on analysis of ternary liquidus contours and vertical sections, it is suggested that solidification for high lead and very high indium alloys occurs from two-phase equilibria. Solidification from all other alloys occurs from three-phase equilibria. Four-phase solidification does not occur in this system

Phase-field simulation of solidification in multicomponent alloys coupled with thermodynamic and diffusion mobility databases

International Nuclear Information System (INIS)

Zhang Ruijie; Jing Tao; Jie Wanqi; Liu Baicheng

2006-01-01

To simulate quantitatively the microstructural evolution in the solidification process of multicomponent alloys, we extend the phase-field model for binary alloys to multicomponent alloys with consideration of the solute interactions between different species. These interactions have a great influence not only on the phase equilibria but also on the solute diffusion behaviors. In the model, the interface region is assumed to be a mixture of solid and liquid with the same chemical potential, but with different compositions. The simulation presented is coupled with thermodynamic and diffusion mobility databases, which can accurately predict the phase equilibria and the solute diffusion transportation in the whole system. The phase equilibria in the interface and other thermodynamic quantities are obtained using Thermo-Calc through the TQ interface. As an example, two-dimensional computations for the dendritic growth in Al-Cu-Mg ternary alloy are performed. The quantitative solute distributions and diffusion matrix are obtained in both solid and liquid phases

Thermodynamics of dinonylnaphthalene sulfonic acid (HD)

International Nuclear Information System (INIS)

Raieh, M.A.; Aly, H.F.

1980-01-01

The effect of temperature on the extraction of the trivalent actinides Am 3+ , Cm 3+ and Cf 3+ with the liquid cation exchanger dinonylnaphtalenesulphonic acid (HD) in toluene is studied. The different thermodynamic functions of this system are determined from the experimental results. It is found that the free energy variation for the extraction of these metal ions by HD is mainly determined by the entropic terms arising from the hydration-dehydration process of the exchanged ions. (author)

Experimental investigation of phase equilibria in the Ni-Nb-V ternary system

Energy Technology Data Exchange (ETDEWEB)

Liu, Xingjun; Yang, Shuiyuan; Wang, Cuiping [Xiamen Univ. (China). Dept. of Materials Science and Engineering; Xiamen Univ. (China). Fujian Provincial Key Lab. of Materials Genome; Zhang, Xianjie; Jiang, Hengxing; Shi, Zhan [Xiamen Univ. (China). Dept. of Materials Science and Engineering

2017-09-15

The phase equilibria of the Ni-Nb-V ternary system at 1000 C and 1200 C were established using electron probe microanalysis, X-ray diffraction and differential scanning calorimetry. The results of the investigation revealed that: (1) The Nb solubility in (Ni) and σ{sup '} phases was less than 10 at.%; (2) A ternary compound τ (NiNbV) was confirmed, in which V had a large solubility; (3) A new liquid region was evident at 1200 C, but was absent at 1000 C; (4) The lattice constants of Ni{sub 3}Nb and Ni{sub 6}Nb{sub 7} phase decreased with increase in V content in the Ni{sub 3}Nb and Ni{sub 6}Nb{sub 7}. The phase equilibria of the Ni-Nb-V ternary system will contribute to its thermodynamic assessment.

The prediction and representation of phase equilibria and physicochemical properties in complex coal ash slag systems

Energy Technology Data Exchange (ETDEWEB)

E. Jak; A. Kondratiev; S. Christie; P.C. Hayes [Centre for Coal in Sustainable Development (CCSD), Brisbane (Australia)

2003-07-01

A range of problems in coal utilisation technologies, including ash slag flow in slagging gasifiers, deposit formation, slagging, fouling, fusibility tests, fluxing, blending etc, are related to the melting behaviour of the mineral matter in the coal. To assist with solving these practical issues i) thermodynamic modelling of phase equilibria, and ii) viscosity modelling studies are being undertaken at the Pyrometallurgy Research Centre (The University of Queensland, Australia) with support from the Collaborative Research Centre for Coal in Sustainable Development (CCSD). The thermodynamic modelling has been carried out using the computer system FactSage, which is used for the calculation of multi-phase slag / solid / gas / matte / alloy / salt equilibria in multi-component systems of industrial interest. A modified quasi-chemical solution model is used for the liquid slag phase. New model optimisations have been carried out, which have significantly improved the accuracy of the thermodynamic models for coal combustion processes. Viscosity modelling, using a modified Urbain formalism, is carried out in conjunction with FactSage calculations to predict the viscosities of fully liquid as well as heterogeneous, partly crystallised slags. Custom designed software packages are developed using these fundamental models for wider use by industrial researchers and engineers, and for incorporation as process control modules. The new custom-designed computer software package can be used to produce limiting operability diagrams for slag systems. These diagrams are used to describe phase equilibria and physico-chemical properties in complex slag systems. The approach is illustrated with calculations on the system SiO{sub 2}-Al{sub 2}O{sub 3}-FeO-Fe{sub 2}O{sub 3}-CaO at metallic iron saturation, slags produced in coal slagging gasifiers. 28 refs., 7 figs., 1 tab.

Statistical thermodynamics of alloys

CERN Document Server

Gokcen, N A

1986-01-01

This book is intended for scientists, researchers, and graduate students interested in solutions in general, and solutions of metals in particular. Readers are assumed to have a good background in thermodynamics, presented in such books as those cited at the end of Chapter 1, "Thermo­ dynamic Background." The contents of the book are limited to the solutions of metals + metals, and metals + metalloids, but the results are also appli­ cable to numerous other types of solutions encountered by metallurgists, materials scientists, geologists, ceramists, and chemists. Attempts have been made to cover each topic in depth with numerical examples whenever necessary. Chapter 2 presents phase equilibria and phase diagrams as related to the thermodynamics of solutions. The emphasis is on the binary diagrams since the ternary diagrams can be understood in terms of the binary diagrams coupled with the phase rule, and the Gibbs energies of mixing. The cal­ culation of thermodynamic properties from the phase diagrams is ...

A periodic point-based method for the analysis of Nash equilibria in 2 x 2 symmetric quantum games

International Nuclear Information System (INIS)

Schneider, David

2011-01-01

We present a novel method of looking at Nash equilibria in 2 x 2 quantum games. Our method is based on a mathematical connection between the problem of identifying Nash equilibria in game theory, and the topological problem of the periodic points in nonlinear maps. To adapt our method to the original protocol designed by Eisert et al (1999 Phys. Rev. Lett. 83 3077-80) to study quantum games, we are forced to extend the space of strategies from the initial proposal. We apply our method to the extended strategy space version of the quantum Prisoner's dilemma and find that a new set of Nash equilibria emerge in a natural way. Nash equilibria in this set are optimal as Eisert's solution of the quantum Prisoner's dilemma and include this solution as a limit case.

HIGH PRESSURE VAPOR-LIQUID EQUILIBRIA OF PALM FATTY ACIDS DISTILLATES-CARBON DIOXIDE SYSTEM

Directory of Open Access Journals (Sweden)

Nélio T. MACHADO

1997-12-01

Full Text Available Vapor-Liquid equilibria of palm fatty acids distillates/carbon dioxide system has been investigated experimentally at temperatures of 333, 353, and 373 K and pressures of 20, 23, 26, and 29 MPa using the static method. Experimental data for the quasi-binary system palm fatty acids distillates/carbon dioxide has been correlated with Redlich-Kwong-Aspen equation of state. Modeling shows good agreement with experimental data. Selectivity obtained indicates that supercritical carbon dioxide is a reasonable solvent for separating saturated (palmitic acid and unsaturated (oleic+linoleic acids fatty acids from palm fatty acids distillates in a continuous multistage countercurrent column.Foi investigado experimentalmente o equilíbrio líquido-vapor para o sistema Destilado Ácido de Óleo de Palma (PFAD/Dióxido de Carbono, nas temperaturas de 333, 353 e 373 K e pressões de 20, 23, 26 e 29 MPa, usando-se o método estático. Os dados experimentais do sistema pseudo-binário PFAD/CO2 foram correlacionados com a equação de estado de Redlich-Kwong do pacote computacional ASPEN. O modelo reproduz bem os resultados experimentais. A seletividade obtida indica que o CO2 supercrítico é um solvente razoável para a separação em coluna multi-estágio e contínua, do ácido graxo saturado (ácido palmítico daqueles insaturados (ácido oleico e ácido linoleico contidos no PFAD.

HP-67 calculator programs for thermodynamic data and phase diagram calculations

International Nuclear Information System (INIS)

Brewer, L.

1978-01-01

This report is a supplement to a tabulation of the thermodynamic and phase data for the 100 binary systems of Mo with the elements from H to Lr. The calculations of thermodynamic data and phase equilibria were carried out from 5000 0 K to low temperatures. This report presents the methods of calculation used. The thermodynamics involved is rather straightforward and the reader is referred to any advanced thermodynamic text. The calculations were largely carried out using an HP-65 programmable calculator. In this report, those programs are reformulated for use with the HP-67 calculator; great reduction in the number of programs required to carry out the calculation results

Thermodynamic modeling of the Sr-Co-Fe-O system

DEFF Research Database (Denmark)

Zhang, Wei Wei; Povoden-Karadeniz, Erwin; Chen, Ming

2016-01-01

This paper reviews and assesses phase equilibria and thermodynamic properties of phases in the Sr-Co-Fe-O system, with a focus on oxides, especially the SrCo1 - xFexO3 - δ perovskite. In our work, the SrCo1 - xFexO3 - δ perovskite was modeled with a three-sublattice model, where the three...... sublattices correspond to the A, B and oxygen sites in an ABO3 perovskite, respectively. A number of other important ternary oxide phases in Sr-Co-O and Sr-Co-Fe-O were also considered. Available thermodynamic and phase diagram data were carefully assessed. A thermodynamic description of Sr-Co-O was derived...

Thermodynamic Solubility Profile of Carbamazepine-Cinnamic Acid Cocrystal at Different pH.

Science.gov (United States)

Keramatnia, Fatemeh; Shayanfar, Ali; Jouyban, Abolghasem

2015-08-01

Pharmaceutical cocrystal formation is a direct way to dramatically influence physicochemical properties of drug substances, especially their solubility and dissolution rate. Because of their instability in the solution, thermodynamic solubility of cocrystals could not be determined in the common way like other compounds; therefore, the thermodynamic solubility is calculated through concentration of their components in the eutectic point. The objective of this study is to investigate the effect of an ionizable coformer in cocrystal with a nonionizable drug at different pH. Carbamazepine (CBZ), a nonionizable drug with cinnamic acid (CIN), which is an acidic coformer, was selected to prepare CBZ-CIN cocrystal and its thermodynamic solubility was studied in pH range 2-7. Instead of HPLC that is a costly and time-consuming method, a chemometric-based approach, net analyte signal standard addition method, was selected for simultaneous determination of CBZ and CIN in solution. The result showed that, as pH increases, CIN ionization leads to change in CBZ-CIN cocrystal solubility and stability in solution. In addition, the results of this study indicated that there is no significant difference between intrinsic solubility of CBZ and cocrystal despite the higher ideal solubility of cocrystal. This verifies that ideal solubility is not good parameter to predict cocrystal solubility. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

The calculation of phase equilibria of oxide core-concrete systems

International Nuclear Information System (INIS)

Ball, R.G.J.; Mignanelli, M.A.; Barry, T.I.; Gisby, J.A.

1993-01-01

Thermodynamic models have been developed to describe the phase equilibria of oxide solutions appropriate for the understanding of the chemical interactions between nuclear reactor core debris and concrete. For this purpose, the Gibbs energy of the liquid phase is described by the inclusion of associate species and nonideal interactions between the components and associate species. Assessments of the thermodynamic and phase equilibrium data for the subsystems of the CaO-Al 2 O 3 -SiO 2 -UO 2 -ZrO 2 system have been used to obtain a thermodynamic description of the crystalline and liquid phases in good agreement with published data. The data for the subsystems have then been combined, using well established principles, to predict the phase relationships in the ternary and quaternary sytsems and in the overall quinary system. The results show that he overall system cannot properly be treated as a pseudo-ideal liquid and solid solution, as used in some computer codes which attempt to model the physics and chemistry of core-concrete interactions. The limitations of the current model are discussed. (orig.)

Experimental investigation and thermodynamic calculations of the Bi–In–Ni phase diagram

International Nuclear Information System (INIS)

Premović, Milena; Minić, Duško; Manasijević, Dragan; Ćosović, Vladan; Živković, Dragana; Dervišević, Irma

2015-01-01

Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of several vertical sections. • Calculated horizontal section, confirmed by experimental SEM–EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Bi–In–Ni system. - Abstract: Phase diagram of the Bi–In–Ni ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) analysis. Experimentally obtained results were compared with the results of thermodynamic calculation of phase equilibria based on calculation of phase diagram (CALPHAD) method and literature data. Phase transition temperatures of alloys with overall compositions along three selected vertical sections In–Bi 0.8 Ni 0.2 , x(Bi) = 0.6 and Bi–In 0.5 Ni 0.5 were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 100 °C, 300 °C and 350 °C was carried out using SEM–EDS and XRD methods. The obtained results were compared with the calculated isothermal sections of the Bi–In–Ni ternary system at corresponding temperatures. Calculated liquidus projection and invariant equilibria of the Bi–In–Ni ternary system were presented

Thermodynamic Factors Affecting UC_1-xN_xIrradiation and Synthesis

Energy Technology Data Exchange (ETDEWEB)

Lindemer, T.B.

2005-04-22

There is interest in attempting to synthesize nearly pure uranium nitride (UN) kernels for high-temperature gas-cooled reactor (HTGR) fuel. Because the proposed process involves carbothermic conversion of a urania-carbon mixture in nitrogen and because there is a complete ideal solution of uranium carbide (UC) and UN, which is written as UC{sub 1-x}N{sub x}, the practical value of x for fuel irradiation needs to be determined. Insight is to be gained by relevant thermodynamic calculations of carbide-nitride equilibria for the fuel and fission product systems. The equilibria are readily compared on the nitrogen-based Ellingham diagram, which, in turn, provides guidance in interpreting past irradiations and in synthesis of the UC{sub 1-x}N{sub x} kernels.

A periodic point-based method for the analysis of Nash equilibria in 2 x 2 symmetric quantum games

Energy Technology Data Exchange (ETDEWEB)

Schneider, David, E-mail: schneide@tandar.cnea.gov.ar [Departamento de Fisica, Comision Nacional de EnergIa Atomica. Av. del Libertador 8250, 1429 Buenos Aires (Argentina)

2011-03-04

We present a novel method of looking at Nash equilibria in 2 x 2 quantum games. Our method is based on a mathematical connection between the problem of identifying Nash equilibria in game theory, and the topological problem of the periodic points in nonlinear maps. To adapt our method to the original protocol designed by Eisert et al (1999 Phys. Rev. Lett. 83 3077-80) to study quantum games, we are forced to extend the space of strategies from the initial proposal. We apply our method to the extended strategy space version of the quantum Prisoner's dilemma and find that a new set of Nash equilibria emerge in a natural way. Nash equilibria in this set are optimal as Eisert's solution of the quantum Prisoner's dilemma and include this solution as a limit case.

D-amino acids inhibit initial bacterial adhesion: thermodynamic evidence.

Science.gov (United States)

Xing, Su-Fang; Sun, Xue-Fei; Taylor, Alicia A; Walker, Sharon L; Wang, Yi-Fu; Wang, Shu-Guang

2015-04-01

Bacterial biofilms are structured communities of cells enclosed in a self-produced hydrated polymeric matrix that can adhere to inert or living surfaces. D-Amino acids were previously identified as self-produced compounds that mediate biofilm disassembly by causing the release of the protein component of the polymeric matrix. However, whether exogenous D-amino acids could inhibit initial bacterial adhesion is still unknown. Here, the effect of the exogenous amino acid D-tyrosine on initial bacterial adhesion was determined by combined use of chemical analysis, force spectroscopic measurement, and theoretical predictions. The surface thermodynamic theory demonstrated that the total interaction energy increased with more D-tyrosine, and the contribution of Lewis acid-base interactions relative to the change in the total interaction energy was much greater than the overall nonspecific interactions. Finally, atomic force microscopy analysis implied that the hydrogen bond numbers and adhesion forces decreased with the increase in D-tyrosine concentrations. D-Tyrosine contributed to the repulsive nature of the cell and ultimately led to the inhibition of bacterial adhesion. This study provides a new way to regulate biofilm formation by manipulating the contents of D-amino acids in natural or engineered systems. © 2014 Wiley Periodicals, Inc.

Prediction of phase equilibria and thermal analysis in the Bi-Cu-Pb ternary system

Energy Technology Data Exchange (ETDEWEB)

Manasijevic, Dragan [University of Belgrade, Technical Faculty, VJ 12, 19210 Bor (Serbia); Mitovski, Aleksandra, E-mail: amitovski@tf.bor.ac.rs [University of Belgrade, Technical Faculty, VJ 12, 19210 Bor (Serbia); Minic, Dusko [University of Pristina, Faculty of Technical Sciences, 38220 Kosovska Mitrovica (Serbia); Zivkovic, Dragana; Marjanovic, Sasa [University of Belgrade, Technical Faculty, VJ 12, 19210 Bor (Serbia); Todorovic, Radisa [Institute of Mining and Metallurgy, Zeleni Bulevar 35, 19210 Bor (Serbia); Balanovic, Ljubisa [University of Belgrade, Technical Faculty, VJ 12, 19210 Bor (Serbia)

2010-05-20

The knowledge about phase diagram of the Bi-Cu-Pb ternary system is of importance in development of copper-lead based bearing materials, soldering and in refining of copper and lead. In this work, the phase diagram of the Bi-Cu-Pb ternary system was calculated by the CALPHAD method using binary thermodynamic parameters included in the COST 531 database. The results include liquidus projection, invariant equilibria and three vertical sections with molar ratio Cu:Pb = 1, Cu:Pb = 1:3 and Bi:Cu = 1. Alloys, with compositions along three predicted vertical sections, were measured using differential scanning calorimetry (DSC). The experimentally determined phase transition temperatures were compared with calculated results and good mutual agreement was noticed.

Prediction of phase equilibria and thermal analysis in the Bi-Cu-Pb ternary system

International Nuclear Information System (INIS)

Manasijevic, Dragan; Mitovski, Aleksandra; Minic, Dusko; Zivkovic, Dragana; Marjanovic, Sasa; Todorovic, Radisa; Balanovic, Ljubisa

2010-01-01

The knowledge about phase diagram of the Bi-Cu-Pb ternary system is of importance in development of copper-lead based bearing materials, soldering and in refining of copper and lead. In this work, the phase diagram of the Bi-Cu-Pb ternary system was calculated by the CALPHAD method using binary thermodynamic parameters included in the COST 531 database. The results include liquidus projection, invariant equilibria and three vertical sections with molar ratio Cu:Pb = 1, Cu:Pb = 1:3 and Bi:Cu = 1. Alloys, with compositions along three predicted vertical sections, were measured using differential scanning calorimetry (DSC). The experimentally determined phase transition temperatures were compared with calculated results and good mutual agreement was noticed.

Thermodynamic data-base for metal fluorides

Energy Technology Data Exchange (ETDEWEB)

Yoo, Jae Hyung; Lee, Byung Gik; Kang, Young Ho and others

2001-05-01

This study is aimed at collecting useful data of thermodynamic properties of various metal fluorides. Many thermodynamic data for metal fluorides are needed for the effective development, but no report of data-base was published. Accordingly, the objective of this report is to rearrange systematically the existing thermodynamic data based on metal fluorides and is to use it as basic data for the development of pyrochemical process. The physicochemical properties of various metal fluorides and metals were collected from literature and such existing data base as HSC code, TAPP code, FACT code, JANAF table, NEA data-base, CRC handbook. As major contents of the thermodynamic data-base, the physicochemical properties such as formation energy, viscosity, density, vapor pressure, etc. were collected. Especially, some phase diagrams of eutectic molten fluorides are plotted and thermodynamic data of liquid metals are also compiled. In the future, the technical report is to be used as basic data for the development of the pyrochemical process which is being carried out as a long-term nuclear R and D project.

Thermodynamic data-base for metal fluorides

International Nuclear Information System (INIS)

Yoo, Jae Hyung; Lee, Byung Gik; Kang, Young Ho and others

2001-05-01

This study is aimed at collecting useful data of thermodynamic properties of various metal fluorides. Many thermodynamic data for metal fluorides are needed for the effective development, but no report of data-base was published. Accordingly, the objective of this report is to rearrange systematically the existing thermodynamic data based on metal fluorides and is to use it as basic data for the development of pyrochemical process. The physicochemical properties of various metal fluorides and metals were collected from literature and such existing data base as HSC code, TAPP code, FACT code, JANAF table, NEA data-base, CRC handbook. As major contents of the thermodynamic data-base, the physicochemical properties such as formation energy, viscosity, density, vapor pressure, etc. were collected. Especially, some phase diagrams of eutectic molten fluorides are plotted and thermodynamic data of liquid metals are also compiled. In the future, the technical report is to be used as basic data for the development of the pyrochemical process which is being carried out as a long-term nuclear R and D project

Thermodynamic assessment of the palladium-tellurium (Pd-Te) system

International Nuclear Information System (INIS)

Gosse, S.; Gueneau, C.

2011-01-01

Among the fission products formed in nuclear fuels, the platinum-group metal palladium and the chalcogen element tellurium exhibit strong interaction. It is therefore of interest to be able to predict the chemical equilibria involving the Pd and Te fission products. A thermodynamic assessment is carried out using the Calphad (Calculation of Phase Diagram) method to investigate the behaviour of Pd-Te alloy system in nuclear fuels under irradiation and under waste disposal conditions. The Pd-Te binary description was optimized using experimental data found in literature including thermodynamic properties and phase diagram data. To validate the calculated phase diagram and thermodynamic properties, the results are compared with data from the literature. Both calculated and experimental phase diagrams and thermodynamic properties are in good agreement in the whole Pd-Te composition range. (authors)

Thermodynamic modeling of the Al-U and Co-U systems

International Nuclear Information System (INIS)

Wang, J.; Liu, X.J.; Wang, C.P.

2008-01-01

The thermodynamic assessments of the Al-U and Co-U systems have been carried out by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including thermodynamic properties and phase equilibria. Gibbs free energies of the solution phases were described by the subregular solution models with the Redlich-Kister equation, and those of the intermetallic compounds described by the sublattice models. A consistent set of thermodynamic parameters has been derived for describing the Gibbs free energies of each solution phase and intermetallic compounds in the Al-U and Co-U binary systems. The calculated phase diagrams and thermodynamic properties in the Al-U and Co-U systems are in good agreement with experimental data

Prediction of thermodynamic properties of coal derivatives

International Nuclear Information System (INIS)

Donohue, M.D.

1993-09-01

We have developed new equations of state for pure-component chain molecules. The excellent performance of complicated theories, such as the Generalized Flory Dimer (GFD) theory can be mimicked by simpler equations, if assumptions for the shape parameters are made. We developed engineering correlations based on GFD theory, using local composition theory to take into account attractive forces. During this period, we compared methods for calculating repulsive and attractive contributions to equation of state against computer simulation data for hard and square-well chains, and against experimental data from the literature. We also have studied microstructure and local order in fluids that contain asymmetric molecules. We developed a thermodynamic model for polar compounds based on a site-site interaction approach. We have shown the equivalence of various classes of theories for hydrogen bonding, and used this equivalence to derive a multiple site model for water. In addition, simple cubic equations of state have been applied to calculate physical and chemical-reaction equilibria in nonideal systems. We measured infinite dilution activity coefficients using HPLC. We also measured high pressure vapor liquid equilibria of ternary and quaternary systems containing supercritical solvents. We used FT-IR spectroscopy to examine self-association of aliphatic alcohols due to hydrogen bonding, and to investigate the hydrogen bonding in polymer-solvent mixtures

Thermodynamic reassessment of the neodymium–gold binary system

Energy Technology Data Exchange (ETDEWEB)

Moustaine, D., E-mail: mostainedris@gmail.com; Mahdouk, K.

2016-07-15

Phase relationships in Nd–Au binary system have been thermodynamically assessed by means of the CALPHAD technique through Thermo–Calc software package based on the experiment information of phase equilibria and thermodynamic properties from the published literature data. The excess Gibbs energy functions of the solution phases including liquid, fcc-A1, bcc-A2, and dhcp were formulated with Redlich–Kister polynomial functions. The two–sublattice energy model was employed to describe the Nd{sub 14}Au{sub 51} phase which exhibits a homogeneity range. The intermetallic compounds Nd{sub 2}Au, NdAu, Nd{sub 3}Au{sub 4}, Nd{sub 17}Au{sub 36}, and NdAu{sub 6} were treated as stoichiometric phases. A set of self-consistent thermodynamic parameters formulating the Gibbs energy of various phases in the Nd–Au binary system were then obtained. A much better agreement was achieved between the calculated results and the reported experimental data. - Highlights: • The Nd–Au has been re-assessed using the latest experimental results. • The intermetallic compound Nd{sub 14}Au{sub 51} was treated by a two–sublattice model. • The errors of related modelling presented in previous articles have been modified. • A self–consistent thermodynamic description of the Nd–Au system was obtained.

Thermodynamics of organic mixtures containing amines

International Nuclear Information System (INIS)

Gonzalez, Juan Antonio; Mozo, Ismael; Fuente, Isaias Garcia de la; Cobos, Jose Carlos

2006-01-01

Binary mixtures containing pyridine (PY), or 2-methylpyridine (2MPY) or 3-methylpyridine (3MPY) or 4-methylpyridine (4MPY) and an organic solvent as benzene, toluene, alkane, or 1-alkanol are investigated in the framework of DISQUAC. The corresponding interaction parameters are reported. The model describes accurately a whole set of thermodynamic properties: vapor-liquid equilibria (VLE), liquid-liquid equilibria (LLE), solid-liquid equilibria (SLE), molar excess Gibbs energies (G E ), molar excess enthalpies (H E ), molar excess heat capacities at constant pressure (C P E ) and the concentration-concentration structure factor (S CC (0)). It is remarkable that DISQUAC correctly predicts the W-shaped curve of the C P E of the pyridine + n-hexadecane system. The model can be applied successfully to mixtures with strong positive or negative deviations from the Raoult's law. DISQUAC improves the theoretical results from UNIFAC (Dortmund version). The replacement of pyridine by a methylpyridine leads to a weakening of the amine-amine interactions, ascribed to the steric effect caused by the methyl group attached to the aromatic ring. This explains that for a given solvent (alkane, 1-alkanol) H E (pyridine)>H E (methylpyridine)

Étude des équilibres thermodynamiques des réactions de gazéification en vue de l'optimisation du rapport vapeur/comburant injecté dans un gazogène souterrain Study of Thermodynamic Equilibria in Gasification Reactions So As to Optimise the Steam/Oxidizer Ratio Injected Into an Underground Gas Generator

OpenAIRE

Pirard J. P.

2006-01-01

Le but de cette étude est de déterminer sur la base des équilibres thermodynamiques des réactions de gazéification le rapport vapeur/comburant à injecter dans un gazogène fonctionnant sous pression pour optimaliser les compositions, les pouvoirs calorifiques, les rendements de gazéification et la consommation d'agent gazéifiant. The aim of this study is to determine, on the basis of the thermodynamic equilibria of gazification reactions, the steam/oxidizer ratio to be injected into a gas g...

Thermodynamic modeling of the Eu–Te and Te–Yb systems

Energy Technology Data Exchange (ETDEWEB)

Ghamri, H., E-mail: ghamri.houda@hotmail.fr; Djaballah, Y.; Belgacem-Bouzida, A.

2015-09-15

Highlights: • The Eu–Te and Te–Yb binary systems were not previously thermodynamically assessed. • The Eu–Te and Te–Yb systems were assessed by using the CALPHAD technique. • A coherent set of thermodynamic parameters was obtained for both systems. • An agreement between the calculated results and experimental data was obtained for both systems. - Abstract: In this work, thermodynamic assessments of the Eu–Te and Te–Yb binary systems were carried out by using the CALculation of PHase Diagrams (CALPHAD) method based on the available experimental data including thermodynamic properties and phase equilibria. Reasonable models were constructed for all the phases of the two systems. The liquid phases were described by the substitutional solution model with the Redlich–Kister polynomial. The three intermetallic compounds, Eu{sub 4}Te{sub 7}, Eu{sub 3}Te{sub 7} and TeYb in the two systems, were treated as stoichiometric phases, while the non-stoichiometric phase (EuTe), which has an homogeneity range, was treated by a two-sublattice model following the schema: (Eu,Te){sub 0.5}(Te){sub 0.5}. A consistent set of thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.

Experimental study and thermodynamic assessment of the ZrO2-DyO1.5 system

International Nuclear Information System (INIS)

Wang, Chong; Zinkevich, M.; Aldinger, F.; Stuttgart Univ.

2007-01-01

The phase equilibria and thermodynamic properties in the ZrO 2 -DyO 1.5 system have been studied using the experimental methods of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential thermal analysis and high temperature drop calorimetry. The tetragonal + fluorite and fluorite + C-Dy 2 O 3 phase equilibria between 1400 C and 1700 C have been determined, together with the enthalpy increments of the materials with 30 mol.% and 50 mol.% DyO 1.5 in the temperature range 200-1400 C. Furthermore, the martensitic transformation temperatures (A s ,M s ) have been measured for the samples with 1 and 2 mol.% DyO 1.5 . Finally, thermodynamic assessment has been carried out using the experimental results obtained and literature data. (orig.)

Solution thermodynamics of pyrazinamide, isoniazid, and p-aminobenzoic acid in buffers and octanol

International Nuclear Information System (INIS)

Blokhina, Svetlana V.; Ol’khovich, Marina V.; Sharapova, Angelica V.; Volkova, Tatyana V.; Perlovich, German L.

2015-01-01

Highlights: • Solubility of pyrazinamide, isoniazid, p-aminobenzoic acid were measured. • The activity coefficients of the compounds at infinite dilution were determined. • Thermodynamic functions of dissolution and solvation were calculated. - Abstract: The solubility values of pyrazinamide, isoniazid, and p-aminobenzoic acid in buffers (pH 2.0 and 7.4) and octanol were measured in the temperature range of 293.15 to 313.15 K. The dissolution Gibbs energy, enthalpy, and entropy were calculated. The dissolving process was endothermic and enthalpy-determined. The activity coefficients of the compounds at infinite dilution were determined based on the solubility data and thermophysical parameters. A positive deviation from the ideality was observed in all the solutions. A common tendency of the solubility increase with a decrease in the activity coefficients at T = 298.15 K was revealed for the investigated solute-solvent systems. The excess thermodynamic solubility functions were calculated from the temperature dependences of the activity coefficients. The solvation processes were found to have a considerable influence on the solubility of the substances in solutions studied.

Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

Energy Technology Data Exchange (ETDEWEB)

De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr [MINES ParisTech, PSL Research University, Centre de Géosciences, 35 Rue St-Honoré, 77305 Fontainebleau Cedex (France); Bertron, Alexandra; Larreur-Cayol, Steeves; Escadeillas, Gilles [University of Toulouse, UPS/INSA/LMDC, 135 Av. de Rangueil, 31077 Toulouse Cedex 04 (France)

2015-03-15

Interactions of short-chain organic acids with hydrated cement phases affect structure durability in the agro-food and nuclear waste industries but can also be used to modify cement properties. Most previous studies have been experimental, performed at fixed concentrations and pH, without quantitatively discriminating among polyacidity effects, or complexation and salt precipitation processes. This paper addresses such issues by thermodynamic equilibrium calculations for acetic, citric, oxalic, succinic acids and a simplified hydrated CEM-I. The thermodynamic constants collected from the literature allow the speciation to be modeled over a wide range of pH and concentrations. Citric and oxalic had a stronger chelating effect than acetic acid, while succinic acid was intermediate. Similarly, Ca-citrate and Ca-oxalate salts were more insoluble than Ca-acetate and Ca-succinate salts. Regarding aluminium complexation, hydroxyls, sulfates, and acid competition was highlighted. The exploration of acid mixtures showed the preponderant effect of oxalate and citrate over acetate and succinate.

Thermodynamics of ion-exchange on ferric antimonate

International Nuclear Information System (INIS)

Rawat, J.P.; Muktawat, K.P.S.

1981-01-01

A simple approach to ion-exchange equilibria on ferric antimonate has been applied. The values of selectivity coefficients for Ba 2+ , Mg 2+ , Ca 2+ and Sr 2+ have been measured using equilibrium experiments at constant ionic strength and at different temperatures from 20 to 60 0 C. The thermodynamic equilibrium constant and values of ΔG 0 , ΔH 0 and ΔS 0 are reported. (author)

Sn-In-Ag phase equilibria and Sn-In-(Ag)/Ag interfacial reactions

International Nuclear Information System (INIS)

Chen Sinnwen; Lee Wanyu; Hsu Chiaming; Yang Chingfeng; Hsu Hsinyun; Wu Hsinjay

2011-01-01

Research highlights: → Thermodynamic models of Sn-In and Sn-In-Ag are developed using the CALPHAD approach. → Reaction layer in the Sn-In-(Ag)/Ag couples at 100 deg. C is thinner than those at 25 deg. C, 50 deg. C, and 75 deg. C. → Reactions in the Sn-20 wt%In-2.8 wt%Ag/Ag couples are faster than those in the Sn-20 wt%In/Ag couples. - Abstract: Experimental verifications of the Sn-In and Sn-In-Ag phase equilibria have been conducted. The experimental measurements of phase equilibria and thermodynamic properties are used for thermodynamic modeling by the CALPHAD approach. The calculated results are in good agreement with experimental results. Interfacial reactions in the Sn-In-(Ag)/Ag couples have been examined. Both Ag 2 In and AgIn 2 phases are formed in the Sn-51.0 wt%In/Ag couples reacted at 100 and 150 deg. C, and only the Ag 2 In phase is formed when reacted at 25, 50 and 75 deg. C. Due to the different growth rates of different reaction phases, the reaction layer at 100 deg. C is thinner than those at 25 deg. C, 50 deg. C, and 75 deg. C. In the Sn-20.0 wt%In/Ag couples, the ζ phase is formed at 250 deg. C and ζ/AgIn 2 phases are formed at 125 deg. C. Compared with the Sn-20 wt%In/Ag couples, faster interfacial reactions are observed in the Sn-20.0 wt%In-2.8 wt%Ag/Ag couples, and minor Ag addition to Sn-20 wt%In solder increases the growth rates of the reaction phases.

Equilibria model for pH variations and ion adsorption in capacitive deionization electrodes.

Science.gov (United States)

Hemmatifar, Ali; Oyarzun, Diego I; Palko, James W; Hawks, Steven A; Stadermann, Michael; Santiago, Juan G

2017-10-01

Ion adsorption and equilibrium between electrolyte and microstructure of porous electrodes are at the heart of capacitive deionization (CDI) research. Surface functional groups are among the factors which fundamentally affect adsorption characteristics of the material and hence CDI system performance in general. Current CDI-based models for surface charge are mainly based on a fixed (constant) charge density, and do not treat acid-base equilibria of electrode microstructure including so-called micropores. We here expand current models by coupling the modified Donnan (mD) model with weak electrolyte acid-base equilibria theory. In our model, surface charge density can vary based on equilibrium constants (pK's) of individual surface groups as well as micropore and electrolyte pH environments. In this initial paper, we consider this equilibrium in the absence of Faradaic reactions. The model shows the preferential adsorption of cations versus anions to surfaces with respectively acidic or basic surface functional groups. We introduce a new parameter we term "chemical charge efficiency" to quantify efficiency of salt removal due to surface functional groups. We validate our model using well controlled titration experiments for an activated carbon cloth (ACC), and quantify initial and final pH of solution after adding the ACC sample. We also leverage inductively coupled plasma mass spectrometry (ICP-MS) and ion chromatography (IC) to quantify the final background concentrations of individual ionic species. Our results show a very good agreement between experiments and model. The model is extendable to a wide variety of porous electrode systems and CDI systems with applied potential. Copyright © 2017 Elsevier Ltd. All rights reserved.

Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

Science.gov (United States)

Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

2009-04-23

In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

Learning efficient correlated equilibria

KAUST Repository

Borowski, Holly P.

2014-12-15

The majority of distributed learning literature focuses on convergence to Nash equilibria. Correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However, there are no existing distributed learning algorithms that converge to specific correlated equilibria. In this paper, we provide one such algorithm which guarantees that the agents\\' collective joint strategy will constitute an efficient correlated equilibrium with high probability. The key to attaining efficient correlated behavior through distributed learning involves incorporating a common random signal into the learning environment.

Learning efficient correlated equilibria

KAUST Repository

Borowski, Holly P.; Marden, Jason R.; Shamma, Jeff S.

2014-01-01

The majority of distributed learning literature focuses on convergence to Nash equilibria. Correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However, there are no existing distributed learning algorithms that converge to specific correlated equilibria. In this paper, we provide one such algorithm which guarantees that the agents' collective joint strategy will constitute an efficient correlated equilibrium with high probability. The key to attaining efficient correlated behavior through distributed learning involves incorporating a common random signal into the learning environment.

Experimental investigation and thermodynamic calculations of the Ag–Bi–Ga phase diagram

International Nuclear Information System (INIS)

Minić, Duško; Premović, Milena; Manasijević, Dragan; Ćosović, Vladan; Živković, Dragana; Marković, Aleksandar

2015-01-01

Phase diagram of the Ag–Bi–Ga ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and x-ray powder diffraction (XRD) methods. Experimentally obtained results were compared with the results of thermodynamic prediction of phase equilibria based on calculation of phase diagram (CALPHAD) method. Phase transition temperatures of alloys with overall compositions along three selected vertical sections Ag–Bi 50 Ga 50 , Bi–Ag 50 Ga 50 and Ga–Ag 50 Bi 50 were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 200 °C was carried out using SEM-EDS and XRD methods. Obtained results were compared with the calculated isothermal section of the Ag–Bi–Ga ternary system at corresponding temperature. Calculated liquidus projection and invariant equilibria of the Ag–Bi–Ga ternary system were presented. The obtained values were found to be in a close agreement. - Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of three vertical sections Ag–Bi 50 Ga 50 , Bi–Ag 50 Ga 50 and Ga–Ag 50 Bi 50 . • Calculated horizontal section at 200 °C, confirmed by experimental SEM-EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Ag–Bi–Ga system

A thermodynamic evaluation of the Ti-Mo-C system

International Nuclear Information System (INIS)

Shim, J.H.; Oh, C.S.; Lee, D.N.

1996-01-01

A thermodynamic assessment of the Ti-Mo-C system has been made, employing a two-sublattice regular solution model for the solid solution and carbide phases and an ordinary subregular solution model for the liquid phase. A set of thermodynamic parameters describing the Gibbs energy of each individual phase in the Ti-Mo-C as well as the Ti-Mo systems was evaluated from thermochemical and phase equilibria information available in the literature through a computer-aided optimization procedure called the CALPHAD method. The comparison between the calculated and experimental results was made and practically important phase diagrams are also presented

Thermodynamic modeling of the Sr-Co-Fe-O system

DEFF Research Database (Denmark)

Zhang, Wei Wei; Povoden-Karadeniz, Erwin; Chen, Ming

2016-01-01

This paper reviews and assesses phase equilibria and thermodynamic properties of phases in the Sr-Co-Fe-O system, with a focus on oxides, especially the SrCo1 - xFexO3 - δ perovskite. In our work, the SrCo1 - xFexO3 - δ perovskite was modeled with a three-sublattice model, where the three...... sublattices correspond to the A, B and oxygen sites in an ABO3 perovskite, respectively. A number of other important ternary oxide phases in Sr-Co-O and Sr-Co-Fe-O were also considered. Available thermodynamic and phase diagram data were carefully assessed. A thermodynamic description of Sr-Co-O was derived...... using the CALPHAD approach and was further extrapolated to that of Sr-Co-Fe-O. The thermodynamic database of Sr-Co-Fe-O established in this work allows for calculating phase diagrams, thermodynamic properties, cation distribution and defect chemistry properties, and therefore enables material...

Experimental vapor-liquid equilibria data for binary mixtures of xylene isomers

Directory of Open Access Journals (Sweden)

W.L. Rodrigues

2005-09-01

Full Text Available Separation of aromatic C8 compounds by distillation is a difficult task due to the low relative volatilities of the compounds and to the high degree of purity required of the final commercial products. For rigorous simulation and optimization of this separation, the use of a model capable of describing vapor-liquid equilibria accurately is necessary. Nevertheless, experimental data are not available for all binaries at atmospheric pressure. Vapor-liquid equilibria data for binary mixtures were isobarically obtained with a modified Fischer cell at 100.65 kPa. The vapor and liquid phase compositions were analyzed with a gas chromatograph. The methodology was initially tested for cyclo-hexane+n-heptane data; results obtained are similar to other data in the literature. Data for xylene binary mixtures were then obtained, and after testing, were considered to be thermodynamically consistent. Experimental data were regressed with Aspen Plus® 10.1 and binary interaction parameters were reported for the most frequently used activity coefficient models and for the classic mixing rules of two cubic equations of state.

Belief-Based Equilibria in the Repeated Prisoners' Dilemma with Private Monitoring

OpenAIRE

V. Bhaskar; Ichiro Obara

2000-01-01

We analyze the infinitely repeated prisoners' dilemma with imperfect private monitoring and discounting. The main contribution of this paper is to construct ``belief-based'' strategies, where a player's continuation strategy is a function only of his beliefs. This simplifies the analysis considerably, and allows us to explicitly construct sequential equilibria for such games, thus enabling us to invoke the one-step deviation principle of dynamic programming. By doing so, we prove that one can...

Chemical thermodynamics. An introduction

Energy Technology Data Exchange (ETDEWEB)

Keszei, Ernoe [Budapest Univ. (Hungary). Dept. of Physical Chemistry

2012-07-01

Eminently suitable as a required textbook comprising complete material for or an undergraduate chemistry major course in chemical thermodynamics. Clearly explains details of formal derivations that students can easily follow and so master applied mathematical operations. Offers problems and solutions at the end of each chapter for self-test and self- or group study. This course-derived undergraduate textbook provides a concise explanation of the key concepts and calculations of chemical thermodynamics. Instead of the usual 'classical' introduction, this text adopts a straightforward postulatory approach that introduces thermodynamic potentials such as entropy and energy more directly and transparently. Structured around several features to assist students' understanding, Chemical Thermodynamics: - Develops applications and methods for the ready treatment of equilibria on a sound quantitative basis. - Requires minimal background in calculus to understand the text and presents formal derivations to the student in a detailed but understandable way. - Offers end-of-chapter problems (and answers) for self-testing and review and reinforcement, of use for self- or group study. This book is suitable as essential reading for courses in a bachelor and master chemistry program and is also valuable as a reference or textbook for students of physics, biochemistry and materials science.

Study of acid-base properties in various water-salt and water-organic solvent mixtures

International Nuclear Information System (INIS)

Lucas, M.

1969-01-01

Acid-base reactions have been studied in water-salt mixtures and water organic solvent-mixtures. It has been possible to find some relations between the displacement of the equilibria and the numerical value of water activity in the mixture. First have been studied some equilibria H + + B ↔ HB + in salt-water mixtures and found a relation between the pK A value, the solubility of the base and water activity. The reaction HO - + H + ↔ H 2 O has been investigated and a relation been found between pK i values, water activity and the molar concentration of the salt in the mixture. This relation is the same for every mixture. Then the same reactions have been studied in organic solvent-water mixtures and a relation found in the first part of the work have been used with success. So it has been possible to explain easily some properties of organic water-mixture as the shape of the curves of the Hammett acidity function Ho. (authors) [fr

Partial Cooperative Equilibria: Existence and Characterization

Directory of Open Access Journals (Sweden)

Amandine Ghintran

2010-09-01

Full Text Available We study the solution concepts of partial cooperative Cournot-Nash equilibria and partial cooperative Stackelberg equilibria. The partial cooperative Cournot-Nash equilibrium is axiomatically characterized by using notions of rationality, consistency and converse consistency with regard to reduced games. We also establish sufficient conditions for which partial cooperative Cournot-Nash equilibria and partial cooperative Stackelberg equilibria exist in supermodular games. Finally, we provide an application to strategic network formation where such solution concepts may be useful.

Thermodynamic functions for solubility of 3-nitro-o-toluic acid in nine organic solvents from T = (283.15 to 318.15) K and apparent thermodynamic properties of solutions

International Nuclear Information System (INIS)

Li, Xinbao; Wang, Mingju; Du, Cunbin; Cong, Yang; Zhao, Hongkun

2017-01-01

Highlights: • Solubilities of 3-nitro-o-toluic acid in nine organic solvents were determined. • The solubilities were correlated by using four thermodynamic models. • The mixing properties of solution were computed based on Wilson model. - Abstract: Separation of 3-nitro-o-toluic acid from its isomeric mixtures has essential significance in industry. In this work, by using isothermal saturation method, the solid-liquid equilibrium for 3-nitro-o-toluic acid in nine organic solvents (acetonitrile, methanol, ethanol, n-propanol, isopropanol, ethyl acetate, acetone, 1,4-dioxane and 2-butanone) were obtained experimentally within a temperature range from (283.15 to 318.15) K under atmosphere pressure of 101.2 kPa, and the solubility values of 3-nitro-o-toluic acid in these solvents were determined by a high-performance liquid chromatography. Within the studied temperature range, the mole fraction solubility of 3-nitro-o-toluic acid in selected organic solvents increased with increasing temperature. Except for ethyl acetate, the descending order of the mole fraction solubility values were as follow: 1,4-dioxane > acetone > 2-butanone > methanol > ethanol > isopropanol > n-propanol > acetonitrile. The solubility values determined for 3-nitro-o-toluic acid in the selected solvents were correlated and back calculated with the modified Apelblat equation, λh equation, Wilson model and NRTL model. The largest values of RAD and RMSD obtained with the four models were 0.67% and 4.02 × 10 −4 , respectively. In general, the four thermodynamic models were all acceptable for describing the solubility behaviour of 3-nitro-o-toluic acid in these solvents. In addition, the apparent mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration and reduced excess enthalpy were calculated. The acquired solubility data and thermodynamic studies would be very important in optimizing the separation process of 3-nitro-o-toluic acid from

Evaluation of a Mathematical Model for Single Component Adsorption Equilibria with Reference to the Prediction of Multicomponent Adsorption Equilibria

DEFF Research Database (Denmark)

Krøll, Annette Elisabeth; Marcussen, Lis

1997-01-01

An equilibrium equation for pure component adsorption is compared to experiments and to the vacancy solution theory. The investigated equilibrium equation is a special case of a model for prediction of multicomponent adsorption equilibria.The vacancy solution theory for multicomponent systems...... requires binary experimental data for determining the interaction parameters of the Wilson equation; thus a large number of experiments are needed. The multicomponent equilibria model which is investigated for single component systems in this work is based on pure component data only. This means...... that the requirement for experimental data is reduced significantly.The two adsorption models are compared, using experimental pure gas adsorption data found in literature. The results obtained by the models are in close agreement for pure component equilibria and they give a good description of the experimental data...

Equilibrium II: Acids and Bases. Independent Learning Project for Advanced Chemistry (ILPAC). Unit P3.

Science.gov (United States)

Inner London Education Authority (England).

This unit on equilibrium is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, focuses on the application of equilibrium principles to equilibria involving weak acids and bases, including buffer solutions and indicators. Level one uses Le Chatelier's…

Evaluation of Thermodynamic Models for Predicting Phase Equilibria of CO2 + Impurity Binary Mixture

Science.gov (United States)

Shin, Byeong Soo; Rho, Won Gu; You, Seong-Sik; Kang, Jeong Won; Lee, Chul Soo

2018-03-01

For the design and operation of CO2 capture and storage (CCS) processes, equation of state (EoS) models are used for phase equilibrium calculations. Reliability of an EoS model plays a crucial role, and many variations of EoS models have been reported and continue to be published. The prediction of phase equilibria for CO2 mixtures containing SO2, N2, NO, H2, O2, CH4, H2S, Ar, and H2O is important for CO2 transportation because the captured gas normally contains small amounts of impurities even though it is purified in advance. For the design of pipelines in deep sea or arctic conditions, flow assurance and safety are considered priority issues, and highly reliable calculations are required. In this work, predictive Soave-Redlich-Kwong, cubic plus association, Groupe Européen de Recherches Gazières (GERG-2008), perturbed-chain statistical associating fluid theory, and non-random lattice fluids hydrogen bond EoS models were compared regarding performance in calculating phase equilibria of CO2-impurity binary mixtures and with the collected literature data. No single EoS could cover the entire range of systems considered in this study. Weaknesses and strong points of each EoS model were analyzed, and recommendations are given as guidelines for safe design and operation of CCS processes.

MMA-EoS: A Computational Framework for Mineralogical Thermodynamics

Science.gov (United States)

Chust, T. C.; Steinle-Neumann, G.; Dolejš, D.; Schuberth, B. S. A.; Bunge, H.-P.

2017-12-01

We present a newly developed software framework, MMA-EoS, that evaluates phase equilibria and thermodynamic properties of multicomponent systems by Gibbs energy minimization, with application to mantle petrology. The code is versatile in terms of the equation-of-state and mixing properties and allows for the computation of properties of single phases, solution phases, and multiphase aggregates. Currently, the open program distribution contains equation-of-state formulations widely used, that is, Caloric-Murnaghan, Caloric-Modified-Tait, and Birch-Murnaghan-Mie-Grüneisen-Debye models, with published databases included. Through its modular design and easily scripted database, MMA-EoS can readily be extended with new formulations of equations-of-state and changes or extensions to thermodynamic data sets. We demonstrate the application of the program by reproducing and comparing physical properties of mantle phases and assemblages with previously published work and experimental data, successively increasing complexity, up to computing phase equilibria of six-component compositions. Chemically complex systems allow us to trace the budget of minor chemical components in order to explore whether they lead to the formation of new phases or extend stability fields of existing ones. Self-consistently computed thermophysical properties for a homogeneous mantle and a mechanical mixture of slab lithologies show no discernible differences that require a heterogeneous mantle structure as has been suggested previously. Such examples illustrate how thermodynamics of mantle mineralogy can advance the study of Earth's interior.

Surface current equilibria from a geometric point of view

International Nuclear Information System (INIS)

Kaiser, R.; Salat, A.

1993-04-01

This paper addresses the inverse problem of the existence of surface current MHD equilibria in toroidal geometry with vanishing magnetic field inside. Inverse means that the plasma-vacuum interface rather than the external wall or conductors are given and the latter remain to be determined. This makes a reformulation of the problem possible in geometric terms: What toroidal surfaces with analytic parameterization allow a simple analytic covering by geodesics? If such a covering by geodesics (field lines) exists, their orthogonal trajectories (current lines) also form a simple covering and are described by a function satisfying a nonlinear partial differential equation of the Hamilton-Jacobi type whose coefficients are combinations of the metric elements of the surface. All known equilibria - equilibria with zero and infinite rotational transform and the symmetric ones in the case of finite rotational transform - turn out to be solutions of separable cases of that equation and allow a unified description if the toroidal surface is parametrized in the moving trihedral associated with a closed curve. Analogously to volume current equilibria, the only continuous symmetries compatible with separability are plane, helical and axial symmetry. In the nonseparable case numerical evidence is presented for cases with chaotic behaviour of geodesics, thus restricting possible equilibria for these surfaces. For weak deviation from axisymmetry KAM-type behaviour is observed, i.e. destruction of geodesic coverings with a low rational rotational transform and preservation of those with irrational rotational transform. A previous attempt to establish three-dimensional surface current equilibria on the basis of the KAM theorem is rejected as incomplete, and a complete proof of the existence of equilibria in the weakly nonaxisymmetric case, based on the twist theorem for mappings, is given. Finally, for a certain class of strong deviations from axisymmetry an analytic criterion is

Thermodynamics of acid-base dissociation of several cathinones and 1-phenylethylamine, studied by an accurate capillary electrophoresis method free from the Joule heating impact.

Science.gov (United States)

Nowak, Paweł Mateusz; Woźniakiewicz, Michał; Mitoraj, Mariusz; Sagan, Filip; Kościelniak, Paweł

2018-03-02

Capillary electrophoresis is often used to the determination of the acid-base dissociation/deprotonation constant (pK a ), and the more advanced thermodynamic quantities describing this process (ΔH°, -TΔS°). Remarkably, it is commonly overlooked that due to insufficient dissipation of Joule heating the accuracy of parameters determined using a standard approach may be questionable. In this work we show an effective method allowing to enhance reliability of these parameters, and to estimate the magnitude of errors. It relies on finding a relationship between electrophoretic mobility and actual temperature, and performing pK a determination with the corrected mobility values. It has been employed to accurately examine the thermodynamics of acid-base dissociation of several amine compounds - known for their strong dependency of pK a on temperature: six cathinones (2-methylmethcathinone, 3-methylmethcathinone, 4-methylmethcathinone, α-pyrrolidinovalerophenone, methylenedioxypyrovalerone, and ephedrone); and structurally similar 1-phenylethylamine. The average pK a error caused by Joule heating noted at 25 °C was relatively small - 0.04-0.05 pH unit, however, a more significant inaccuracy was observed in the enthalpic and, in particular, entropic terms. An alternative correction method has also been proposed, simpler and faster, but not such effective in correcting ΔH°/-TΔS° terms. The corrected thermodynamic data have been interpreted with the aid of theoretical calculations, on a ground of the enthalpy-entropy relationships and the most probable structural effects accounting for them. Finally, we have demonstrated that the thermal dependencies of electrophoretic mobility, modelled during the correction procedure, may be directly used to find optimal temperature providing a maximal separation efficiency. Copyright © 2018 Elsevier B.V. All rights reserved.

Isotope effects on chemical equilibria

International Nuclear Information System (INIS)

Golding, P.D.

1974-01-01

The thermodynamic equilibrium constants of three deuterated substituted acetic acids are reported. The calculation of secondary isotope effects of the second kind for the three isotopic acid pairs has been accomplished by the appropriate comparison of thermodynamic equilibrium constants, and by the comparison of isotopic slopes. The effect of substituent variation on the isotope effects reported here disqualifies the simple inductive model as a legitimate description of secondary isotope effects of the second kind. The correlation of diminishing isotope effect per deuterium atom with increasing acidity is also invalidated by the present results. The syntheses of 9-thia-9,10-dihydrophenanthrene-9-oxide and thioxanthene-10-oxide are described. These compounds have been partially deuterated at their respective methylene positions. Spectral evidence indicates stereoselectivity of the methylene protons in the exchange reactions of both compounds. (author)

Thermal analysis and prediction of phase equilibria in ternary Pb-Zn-Ag system

Directory of Open Access Journals (Sweden)

Živković D.

2011-01-01

Full Text Available Ternary Pb-Zn-Ag system is typical for some physicochemical processes going on in refining phase in the extractive metallurgy of lead. Therefore, investigation of mentioned system is important from both theoretical and practical research of the phenomena occurring during the lead desilverizing process. The results of experimental investigation using differential thermal analysis (DTA and thermodynamic calculation of phase equilibria in Pb-Zn-Ag system according to CALPHAD method, in the sections with Zn:Ag mass ratio equal to 90:10, 70:30 and 50:50, are presented in this paper.

Experimental investigation and thermodynamic calculations of the Ag–Bi–Ga phase diagram

Energy Technology Data Exchange (ETDEWEB)

Minić, Duško, E-mail: dminic65@open.telekom.rs [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia); Premović, Milena [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia); Manasijević, Dragan [University of Belgrade, Technical Faculty, Bor (Serbia); Ćosović, Vladan [University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Belgrade (Serbia); Živković, Dragana [University of Belgrade, Technical Faculty, Bor (Serbia); Marković, Aleksandar [University in Priština, Faculty of Technical Science, Kos. Mitrovica (Serbia)

2015-10-15

Phase diagram of the Ag–Bi–Ga ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and x-ray powder diffraction (XRD) methods. Experimentally obtained results were compared with the results of thermodynamic prediction of phase equilibria based on calculation of phase diagram (CALPHAD) method. Phase transition temperatures of alloys with overall compositions along three selected vertical sections Ag–Bi{sub 50}Ga{sub 50}, Bi–Ag{sub 50}Ga{sub 50} and Ga–Ag{sub 50}Bi{sub 50} were measured by DTA. Liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation. Identification of coexisting phases in samples equilibrated at 200 °C was carried out using SEM-EDS and XRD methods. Obtained results were compared with the calculated isothermal section of the Ag–Bi–Ga ternary system at corresponding temperature. Calculated liquidus projection and invariant equilibria of the Ag–Bi–Ga ternary system were presented. The obtained values were found to be in a close agreement. - Highlights: • Calculated constitutive binary system based on literature data. • Experimentally determined (DTA) temperatures of phase transformations compared with analytical calculation. • Definition of three vertical sections Ag–Bi{sub 50}Ga{sub 50}, Bi–Ag{sub 50}Ga{sub 50} and Ga–Ag{sub 50}Bi{sub 50}. • Calculated horizontal section at 200 °C, confirmed by experimental SEM-EDS and XRD method. • Calculated liquidus surface projection and determined invariant reaction occurred in ternary Ag–Bi–Ga system.

Internally consistent thermodynamic data for aqueous species in the system Na-K-Al-Si-O-H-Cl

Science.gov (United States)

Miron, George D.; Wagner, Thomas; Kulik, Dmitrii A.; Heinrich, Christoph A.

2016-08-01

their experimental uncertainties. The new dataset resolves the long-standing discrepancies between thermodynamic data of minerals and those of aqueous ions and complexes, by achieving an astonishing degree of consistency between a large number of fluid-mineral equilibrium data. All of this at the expense of changing the standard state properties of aqueous species, mainly the Gibbs energy of formation. Using the same strategy, the core dataset for the system Na-K-Al-Si-O-H-Cl can be extended with additional rock-forming elements such as Ca, Mg, Fe, Mn, Ti, S, C, B. In future, the standard-state properties of minerals and aqueous species should be simultaneously optimized, to create the next-generation of fully internally consistent data for fluid-mineral equilibria. Although we employ the widely used HKF equations for this study, the same computational approach can be readily applied to any other speciation-based equation of state for multicomponent aqueous solutions.

Thermodynamic Modeling of Natural Gas Systems Containing Water

DEFF Research Database (Denmark)

Karakatsani, Eirini K.; Kontogeorgis, Georgios M.

2013-01-01

As the need for dew point specifications remains very urgent in the natural gas industry, the development of accurate thermodynamic models, which will match experimental data and will allow reliable extrapolations, is needed. Accurate predictions of the gas phase water content in equilibrium...... with a heavy phase were previously obtained using cubic plus association (CPA) coupled with a solid phase model in the case of hydrates, for the binary systems of water–methane and water–nitrogen and a few natural gas mixtures. In this work, CPA is being validated against new experimental data, both water...... content and phase equilibrium data, and solid model parameters are being estimated for four natural gas main components (methane, ethane, propane, and carbon dioxide). Different tests for the solid model parameters are reported, including vapor-hydrate-equilibria (VHE) and liquid-hydrate-equilibria (LHE...

Thermodynamic calculation on the stability of (Fe,Mn)3AlC carbide in high aluminum steels

International Nuclear Information System (INIS)

Chin, Kwang-Geun; Lee, Hyuk-Joong; Kwak, Jai-Hyun; Kang, Jung-Yoon; Lee, Byeong-Joo

2010-01-01

A CALPHAD type thermodynamic description for the Fe-Mn-Al-C quaternary system has been constructed by combining a newly assessed Mn-Al-C ternary description and a partly modified Fe-Al-C description to an existing thermodynamic database for steels. A special attention was paid to reproduce experimentally reported phase stability of κ carbide in high Al and high Mn steels. This paper demonstrates that the proposed thermodynamic description makes it possible to predict phase equilibria in corresponding alloys with a practically acceptable accuracy. The applicability of the thermodynamic calculation is also demonstrated for the interpretation of microstructural and constitutional evolution during industrial processes for high Al steels.

Potentiometric investigations of (acid+base) equilibria in (n-butylamine+acetic acid) systems in binary (acetone+cyclohexane) solvent mixtures

International Nuclear Information System (INIS)

Czaja, MaIgorzata; Kozak, Anna; Makowski, Mariusz; Chmurzynski, Lech

2005-01-01

By using the potentiometric titration method, standard equilibrium constants have been determined of acid dissociation of molecular acid, K a (HA), cationic acid, K a (BH + ), of anionic and cationic homoconjugation, K AHA - andK BHB + , respectively, and of molecular heteroconjugation, K AHB (K BHA ), in (acid+base) systems without proton transfer consisting of n-butylamine and acetic acid in binary (acetone+cyclohexane) solvent mixtures. The results have shown that both the pK a (HA) and pK a (BH + ), as well as lgK AHA - values change non-linearly as a function of composition of the solvent mixture. On the other hand, standard molecular heteroconjugation constants without proton transfer do not depend on the cyclohexane content in the mixture, i.e. on solvent polarity

Adsorption analysis equilibria and kinetics

CERN Document Server

Do, Duong D

1998-01-01

This book covers topics of equilibria and kinetics of adsorption in porous media. Fundamental equilibria and kinetics are dealt with for homogeneous as well as heterogeneous particles. Five chapters of the book deal with equilibria and eight chapters deal with kinetics. Single component as well as multicomponent systems are discussed. In kinetics analysis, we deal with the various mass transport processes and their interactions inside a porous particle. Conventional approaches as well as the new approach using Maxwell-Stefan equations are presented. Various methods to measure diffusivity, such

Quantum equilibria for macroscopic systems

International Nuclear Information System (INIS)

Grib, A; Khrennikov, A; Parfionov, G; Starkov, K

2006-01-01

Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered

Critical evaluation and thermodynamic optimization of the U-Pb and U-Sb binary systems

International Nuclear Information System (INIS)

Wang, Jian; Jin, Liling; Chen, Chuchu; Rao, Weifeng; Wang, Cuiping; Liu, Xingjun

2016-01-01

A complete literature review, critical evaluation and thermodynamic optimization of the phase diagrams and thermodynamic properties of U-Pb and U-Sb binary systems are presented. The CALculation of PHAse Diagrams (CALPHAD) method was used for the thermodynamic optimization, the results of which can reproduce all available reliable experimental phase equilibria and thermodynamic data. The modified quasi-chemical model in the pair approximation (MQMPA) was used for modeling the liquid solution. The Gibbs energies of all terminal solid solutions and intermetallic compounds were described by the compound energy formalism (CEF) model. All reliable experimental data of the U-Pb and U-Sb systems have been reproduced. A self-consistent thermodynamic database has been constructed for these binary systems; this database can be used in liquid-metal fuel reactor (LMFR) research.

Experimental and thermodynamic investigation of Al-Cu-Nd ternary system

Energy Technology Data Exchange (ETDEWEB)

Bai, W.M. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Jiang, Y. [Hunan Sushi Guangbo Testing Techniques Co. LTD, Changsha (China); Guo, Z.Y.; Zeng, L.J.; Tan, M.Y. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Meggs, C. [School of Metallurgy and Materials, The University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Zhang, L.G., E-mail: ligangzhang@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Liu, L.B., E-mail: pdc@csu.edu.cn [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China); Jin, Z.P. [School of Materials Science and Engineering, Central South University, Changsha, 410083 (China)

2017-07-01

The phase relationships in the Al–Cu-Nd ternary system at 673 K have been investigated by X-ray powder diffraction (XRD) and scanning electron microscope (SEM) with energy disperse X-ray spectroscopy (EDS) in backscattered electron imaging (BSE) modes. The existence of six ternary Stoichiometric compounds, namely τ{sub 1}-Al{sub 8}Cu{sub 4}Nd, τ{sub 2}-Al{sub 9}Cu{sub 8}Nd{sub 2}, τ{sub 3}-Al{sub 6}Cu{sub 7}Nd, τ{sub 4}-Al{sub 2.4}Cu{sub 8.6}Nd, τ{sub 5}-Al{sub 3}CuNd, τ{sub 6}-AlCuNd, have been confirmed. A complete thermodynamic description of the Al–Cu-Nd ternary system coupled with the CALPHAD method is obtained based on experimental results and first-principles calculations. The calculated phase equilibria were in agreement with the available experimental data. - Highlights: • Phase relationships in the Al-Cu-Nd system has been systematically investigated. • 9 three-phase regions and 4 two-phase regions are confirmed. • A complete thermodynamic description of the Al-Cu-Nd system is obtained. • Results of first-principle calculation consist with thermodynamic calculation.

Some stable hydromagnetic equilibria

Energy Technology Data Exchange (ETDEWEB)

Johnson, J L; Oberman, C R; Kulsrud, R M; Frieman, E A [Project Matterhorn, Princeton University, Princeton, NJ (United States)

1958-07-01

We have been able to find and investigate the properties of equilibria which are hydromagnetically stable. These equilibria can be obtained, for example, by wrapping conductors helically around the stellarator tube. Systems with I = 3 or 4 are indicated to be optimum for stability purposes. In some cases an admixture of I = 2 fields can be advantageous for achieving equilibrium. (author)

Long-term Nash equilibria in electricity markets

International Nuclear Information System (INIS)

Pozo, David; Contreras, Javier; Caballero, Angel; de Andres, Antonio

2011-01-01

In competitive electricity markets, companies simultaneously offer their productions to obtain the maximum profits on a daily basis. In the long run, the strategies utilized by the electric companies lead to various long-term equilibria that can be analyzed with the appropriate tools. We present a methodology to find plausible long-term Nash equilibria in pool-based electricity markets. The methodology is based on an iterative market Nash equilibrium model in which the companies can decide upon their offer strategies. An exponential smoothing of the bids submitted by the companies is applied to facilitate the convergence of the iterative procedure. In each iteration of the model the companies face residual demand curves that are accurately modeled by Hermite interpolating polynomials. We introduce the concept of meta-game equilibrium strategies to allow companies to have a range of offer strategies where several pure and mixed meta-game Nash equilibria are possible. With our model it is also possible to model uncertainty or to generate price scenarios for financial models that assess the value of a generating unit by real options analysis. The application of the proposed methodology is illustrated with several realistic case studies. (author)

Thermodynamic evaluation and optimization of the (Na+K+S) system

International Nuclear Information System (INIS)

Lindberg, Daniel; Backman, Rainer; Hupa, Mikko; Chartrand, Patrice

2006-01-01

The (Na+K+S) system is of primary importance for the combustion of black liquor in the kraft recovery boilers in pulp and paper mills. A thermodynamic evaluation and optimization for the (Na+K+S) system has been made. All available data for the system have been critically evaluated to obtain optimized parameters of thermodynamic models for all phases. The liquid model is the quasichemical model in the quadruplet approximation, which evaluates 1st- and 2nd-nearest-neighbour short-range-order. In this model, cations (Na + and K + ) are assumed to mix on a cationic sublattice, while anions (S 2- ,S 2 2- ,S 3 2- ,S 4 2- ,S 5 2- ,S 6 2- ,S 7 2- ,S 8 2- ,Va - ) are assumed to mix on an anionic sublattice. The thermodynamic data of the liquid polysulphide components M 2 S 1+n (M=Na, K and n=1-7) are fitted to ΔG=A(n)+B(n).T for the reaction M 2 S(l)+nS(l)=M 2 S n+1 (l). The solid phases are the alkali alloys, alkali sulphides, several different alkali polysulphides and sulphur. The solid solutions (Na,K) (Na,K) 2 S and (Na,K) 2 S 2 are modelled using the compound energy formalism. The models can be used to predict the thermodynamic properties and phase equilibria in the multicomponent heterogeneous system. The experimental data are reproduced within experimental error limits for equilibria between solid, liquid and gas. The ternary phase diagram of the system (Na 2 S+K 2 S+S) has been predicted as no experimental determinations of the phase diagram have been made previously

Sustainable Biocatalytic Biodiesel Production

DEFF Research Database (Denmark)

Güzel, Günduz

As part of his PhD studies, Gündüz Güzel examined the thermodynamics of reactions involved in biocatalytic biodiesel production processes, with a specific focus on phase equilibria of reactive systems. He carried out the thermodynamic analyses of biocatalytic processes in terms of phase and chemi......As part of his PhD studies, Gündüz Güzel examined the thermodynamics of reactions involved in biocatalytic biodiesel production processes, with a specific focus on phase equilibria of reactive systems. He carried out the thermodynamic analyses of biocatalytic processes in terms of phase...... and chemical equilibria as part of his main sustainable biodiesel project. The transesterification reaction of vegetable oils or fats with an aliphatic alcohol – in most cases methanol or ethanol – yields biodiesel (long-chain fatty acid alkyl esters – FAAE) as the main product in the presence of alkaline...

Phase equilibria, phases and compounds in the Ti-C system

International Nuclear Information System (INIS)

Gusev, Aleksandr I

2002-01-01

The results of experimental and theoretical investigations of the phase equilibria in the titanium-carbon system are generalised. The generalised thermodynamic characteristics of disordered titanium carbide TiC y , are reported. Peculiarities of the crystal structures of all the known and hypothetical compounds of titanium with carbon are considered in detail. The X-ray diffraction patterns which allow identification of all these compounds are presented. The phase diagrams of the Ti-C system constructed with allowance for atomic ordering of non-stoichio metric carbide, TiC y , and for the existence of the molecular cluster-like compounds Ti 8 C 12 and Ti 13 C 22 (TiC 2 ) are discussed. The bibliography includes 142 references.

Phase equilibria, phases and compounds in the Ti-C system

International Nuclear Information System (INIS)

Gusev, A.I.

2002-01-01

The results of experimental and theoretical investigations related to the phase equilibria in the titanium-carbon system are generalized. The generalized thermodynamic characteristics of the disordered titanium carbide TiC y are given. The crystal structure of all the discovered and hypothetical compounds of titanium with carbon are considered in detail. The x-ray diffraction patterns which allow one to identify all these compounds are given. The phase diagrams of the Ti-C system constructed with allowance for atomic ordering of non-stoichiometric TiC y carbide and for the existence of the compounds Ti 8 C 12 and Ti 13 C 22 (TiC 2 ) of the molecule cluster type are discussed [ru

Thermodynamic assessments of the Ag-Er and Er-Y systems

International Nuclear Information System (INIS)

Wang, S.L.; Wang, C.P.; Liu, X.J.; Tang, A.T.; Pan, F.S.; Ishida, K.

2010-01-01

The phase diagrams and thermodynamic properties in the Ag-Er and Er-Y binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, and hcp phases were described by the subregular solution model with the Redlich-Kister equation, and those of intermetallic compounds (Ag 2 Er and AgEr phases) were treated as stoichiometric compounds, and Ag 51 Er 14 phase was modeled by the sublattice model in the Ag-Er binary system. The thermodynamic parameters of the Ag-Er and Er-Y binary systems were obtained, and an agreement between the calculated results and experimental data was obtained for each binary system.

Equilibrium studies of ternary systems containing some selected transition metal ions, triazoles and aromatic carboxylic acids

Energy Technology Data Exchange (ETDEWEB)

Khalil, Mohamed Magdy; Radalla, Abd-Elatty; Qasem, Fatma; Khaled, Rehab [Beni-Suef University, Beni-Suef (Egypt)

2014-01-15

Solution equilibria of the binary and ternary complex systems of the divalent transition metal ions Cu{sup 2+}, Ni{sup 2+}, Zn{sup 2+}, and Co{sup 2+} with 1,2,4-triazole (TRZ), 3-mercapto-1,2,4-triazole (TRZSH), and 3-amino-1,2,4-triazole (TRZAM) and aromatic carboxylic acids (phthalic, anthranilic, salicylic, and 5-sulfosalicylic acid) have been studied pH-metrically at (25.0±0.1) .deg. C, and a constant ionic strength I=1x10{sup -1} mol L{sup -1} NaNO{sub 3} in an aqueous medium. The potentiometric titration curves show that binary and ternary complexes of these ligands are formed in solution. The stability constants of the different binary and ternary complexes formed were calculated on the basis of computer analysis of the titration data. The relative stability of the different ternary complex species is expressed in terms of Δ log K values, log X and R. S.% parameters. The effect of temperature of the medium on both the proton-ligand equilibria for TRZAM and phthalic acid and their metal-ligand equilibria with Cu{sup 2+}, Ni{sup 2+}, and Co{sup 2+} has been studied along with the corresponding thermodynamic parameters. The complexation behavior of ternary complexes is ascertained using conductivity measurements. In addition, the formation of ternary complexes in solution has been confirmed by using UV-visible spectrophotometry.

Jump conditions in transonic equilibria

International Nuclear Information System (INIS)

Guazzotto, L.; Betti, R.; Jardin, S. C.

2013-01-01

In the present paper, the numerical calculation of transonic equilibria, first introduced with the FLOW code in Guazzotto et al.[Phys. Plasmas 11, 604 (2004)], is critically reviewed. In particular, the necessity and effect of imposing explicit jump conditions at the transonic discontinuity are investigated. It is found that “standard” (low-β, large aspect ratio) transonic equilibria satisfy the correct jump condition with very good approximation even if the jump condition is not explicitly imposed. On the other hand, it is also found that high-β, low aspect ratio equilibria require the correct jump condition to be explicitly imposed. Various numerical approaches are described to modify FLOW to include the jump condition. It is proved that the new methods converge to the correct solution even in extreme cases of very large β, while they agree with the results obtained with the old implementation of FLOW in lower-β equilibria.

Acid-base properties of the N3 ruthenium(II) solar cell sensitizer: a combined experimental and computational analysis.

Science.gov (United States)

Pizzoli, Giuliano; Lobello, Maria Grazia; Carlotti, Benedetta; Elisei, Fausto; Nazeeruddin, Mohammad K; Vitillaro, Giuseppe; De Angelis, Filippo

2012-10-14

We report a combined spectro-photometric and computational investigation of the acid-base equilibria of the N3 solar cell sensitizer [Ru(dcbpyH(2))(2)(NCS)(2)] (dcbpyH(2) = 4,4'-dicarboxyl-2,2' bipyridine) in aqueous/ethanol solutions. The absorption spectra of N3 recorded at various pH values were analyzed by Single Value Decomposition techniques, followed by Global Fitting procedures, allowing us to identify four separate acid-base equilibria and their corresponding ground state pK(a) values. DFT/TDDFT calculations were performed for the N3 dye in solution, investigating the possible relevant species obtained by sequential deprotonation of the four dye carboxylic groups. TDDFT excited state calculations provided UV-vis absorption spectra which nicely agree with the experimental spectral shapes at various pH values. The calculated pK(a) values are also in good agreement with experimental data, within <1 pK(a) unit. Based on the calculated energy differences a tentative assignment of the N3 deprotonation pathway is reported.

Experimental Phase Equilibria Studies of the Pb-Fe-O System in Air, in Equilibrium with Metallic Lead and at Intermediate Oxygen Potentials

Science.gov (United States)

Shevchenko, M.; Jak, E.

2017-12-01

The phase equilibria information on the Pb-Fe-O system is of practical importance for the improvement of the existing thermodynamic database of lead-containing slag systems (Pb-Zn-Fe-Cu-Si-Ca-Al-Mg-O). Phase equilibria of the Pb-Fe-O system have been investigated: (a) in air at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); (b) in equilibrium with metallic lead at temperatures between 1053 K and 1373 K (780 °C and 1100 °C); and (c) at intermediate oxidation conditions for the liquid slag in equilibrium with two solids (spinel + magnetoplumbite), at temperatures between 1093 K and 1373 K (820 °C and 1100 °C). The high-temperature equilibration/quenching/electron probe X-ray microanalysis technique has been used to accurately determine the compositions of the phases in equilibrium in the system. The Pb and Fe concentrations in the phases were determined directly; preliminary thermodynamic modeling with FactSage was used to estimate the ferrous-to-ferric ratios and to present the results in the ternary diagram.

Thermodynamics of Dissolution for Crystalline Racemic Tartaric and Glutaric Acids and Isatin in KOH Aqueous Solutions at 298.15 K

Science.gov (United States)

Lytkin, A. I.; Chernikov, V. V.; Krutova, O. N.; Litvinenko, V. E.; Volkov, A. V.; Bychkova, S. A.; Skvortsov, I. A.

2018-01-01

Enthalpies of dissolution are found for crystalline racemic tartaric and glutaric acids and isatin in water and in potassium hydroxide solutions at 298.15 K via direct calorimetry. The protolytic equilibria in isatin aqueous solutions are studied at 298.15 K and ionic strengths of 0.5 (relative to potassium nitrate) by potentiometric means. Standard enthalpies of formation are calculated for racemic tartaric and glutaric acids, isatin, and the products of their dissociation in aqueous solutions.

Development of the high-temperature, solid-state, electromotive force technique to study the thermodynamics of Lewis-acid-base transition metal alloys

International Nuclear Information System (INIS)

Bullard, G.L.

1978-05-01

The basic principles of the Engel-Brewer theory of metals are summarized and illustrated. Definitions of words used to describe its fundamentals are clarified. The theory predicts the extreme stability of the Lewis-acid-base alloys. The thermodynamics of such alloys may be obtained through the use of oxide-electrolyte, electrochemical cells. Experimental techniques associated with the use of these cells are explained in detail. Much attention is given to the preparation and processing of the materials required. A selective review of the cell literature demonstrates frequent difficulty in obtaining accurate thermodynamic data. In an attempt to correct this situation, as well as to correct problems discovered in this work, the physical processes which create the cell emf are clearly identified. The fundamental understanding afforded by the resulting cell model implies the procedures used to both discover and eliminate errors. Those due to concentration overpotentials, reactive impurities in the gas phase, and interfacial reactions are carefully analyzed. The procedures used to test for and attain equilibrium in an alloy-oxide, powder compact are supported through identification of the transport processes that mediate equilibration

Development of the high-temperature, solid-state, electromotive force technique to study the thermodynamics of Lewis-acid-base transition metal alloys

Energy Technology Data Exchange (ETDEWEB)

Bullard, G.L.

1978-05-01

The basic principles of the Engel-Brewer theory of metals are summarized and illustrated. Definitions of words used to describe its fundamentals are clarified. The theory predicts the extreme stability of the Lewis-acid-base alloys. The thermodynamics of such alloys may be obtained through the use of oxide-electrolyte, electrochemical cells. Experimental techniques associated with the use of these cells are explained in detail. Much attention is given to the preparation and processing of the materials required. A selective review of the cell literature demonstrates frequent difficulty in obtaining accurate thermodynamic data. In an attempt to correct this situation, as well as to correct problems discovered in this work, the physical processes which create the cell emf are clearly identified. The fundamental understanding afforded by the resulting cell model implies the procedures used to both discover and eliminate errors. Those due to concentration overpotentials, reactive impurities in the gas phase, and interfacial reactions are carefully analyzed. The procedures used to test for and attain equilibrium in an alloy-oxide, powder compact are supported through identification of the transport processes that mediate equilibration.

Quantum equilibria for macroscopic systems

Energy Technology Data Exchange (ETDEWEB)

Grib, A [Department of Theoretical Physics and Astronomy, Russian State Pedagogical University, St. Petersburg (Russian Federation); Khrennikov, A [Centre for Mathematical Modelling in Physics and Cognitive Sciences Vaexjoe University (Sweden); Parfionov, G [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation); Starkov, K [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation)

2006-06-30

Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered.

Thermodynamic calculation on the stability of (Fe,Mn){sub 3}AlC carbide in high aluminum steels

Energy Technology Data Exchange (ETDEWEB)

Chin, Kwang-Geun [Automotive Steel Products Research Group, POSCO Technical Research Laboratories, POSCO, Jeonnam 545-090 (Korea, Republic of); School of Materials Science and Engineering, Pusan National University, Pusan, 609-735 (Korea, Republic of); Lee, Hyuk-Joong [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Kwak, Jai-Hyun [Automotive Steel Products Research Group, POSCO Technical Research Laboratories, POSCO, Jeonnam 545-090 (Korea, Republic of); Kang, Jung-Yoon [School of Materials Science and Engineering, Pusan National University, Pusan, 609-735 (Korea, Republic of); Lee, Byeong-Joo, E-mail: calphad@postech.ac.k [Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of)

2010-08-27

A CALPHAD type thermodynamic description for the Fe-Mn-Al-C quaternary system has been constructed by combining a newly assessed Mn-Al-C ternary description and a partly modified Fe-Al-C description to an existing thermodynamic database for steels. A special attention was paid to reproduce experimentally reported phase stability of {kappa} carbide in high Al and high Mn steels. This paper demonstrates that the proposed thermodynamic description makes it possible to predict phase equilibria in corresponding alloys with a practically acceptable accuracy. The applicability of the thermodynamic calculation is also demonstrated for the interpretation of microstructural and constitutional evolution during industrial processes for high Al steels.

Ternary (liquid + liquid) equilibria of {trifluorotris(perfluoroethyl)phosphate based ionic liquids + thiophene + heptane}

International Nuclear Information System (INIS)

Marciniak, Andrzej; Królikowski, Marek

2012-01-01

Highlights: ► Ternary (liquid + liquid) equilibria for 3 ionic liquid + thiophene + heptane systems. ► The influence of ionic liquid structure on phase diagrams is discussed. ► High selectivity for separation of heptane/thiophene is observed. - Abstract: Ternary (liquid + liquid) equilibria for three systems containing ionic liquids {(4-(2-methoxyethyl)-4-methylmorpholinium trifluorotris(perfluoroethyl)phosphate, 1-(2-methoxyethyl)-1-methylpiperidinium trifluorotris(perfluoroethyl)phosphate, 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate) + thiophene + heptane} have been determined at T = 298.15 K. All systems showed high solubility of thiophene in the ionic liquid and low solubility of heptane. The solute distribution coefficient and the selectivity were calculated for all systems. High values of selectivity were obtained. The experimental results have been correlated using NRTL model. The influence of ionic liquid structure on phase equilibria is discussed.

Potentiometric investigations of (acid+base) equilibria in (n-butylamine+acetic acid) systems in binary (acetone+cyclohexane) solvent mixtures

Energy Technology Data Exchange (ETDEWEB)

Czaja, MaIgorzata [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Kozak, Anna [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Makowski, Mariusz [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland); Chmurzynski, Lech [Department of General Chemistry, University of Gdansk, Sobieskiego 18, 80-952 Gdansk (Poland)]. E-mail: lech@chem.univ.gda.pl

2005-08-15

By using the potentiometric titration method, standard equilibrium constants have been determined of acid dissociation of molecular acid, K{sub a}(HA), cationic acid, K{sub a}(BH{sup +}), of anionic and cationic homoconjugation, K{sub AHA{sup -}}andK{sub BHB{sup +}}, respectively, and of molecular heteroconjugation, K{sub AHB} (K{sub BHA}), in (acid+base) systems without proton transfer consisting of n-butylamine and acetic acid in binary (acetone+cyclohexane) solvent mixtures. The results have shown that both the pK{sub a}(HA) and pK{sub a}(BH{sup +}), as well as lgK{sub AHA{sup -}} values change non-linearly as a function of composition of the solvent mixture. On the other hand, standard molecular heteroconjugation constants without proton transfer do not depend on the cyclohexane content in the mixture, i.e. on solvent polarity.

Potentiometric study on the complex equilibria between uranyl ions and 3,5-disulfosalicyclic acid in 0. 5 M NaCl0/sub 4/ medium

Energy Technology Data Exchange (ETDEWEB)

Lajunen, L H.J.; Parhi, S [Oulu Univ. (Finland)

1979-01-01

In the preceding papers on the complex equilibria between metal ions and aromatic o-hydroxycarboxylic acids, a report was presented on the equilibrium system of uranyl ions and 3-hydroxy-5,7-disulfo-2-naphthoic acid. The computer analysis showed that the data (obtained by means of emf titrations) were well explicable with two successive complexes. The present investigation was made to evaluate the formation of the U0/sub 2//sup 2 +/ complexes of 3,5-disulfosalicyclic acid in 0.5 M NaCl0/sub 4/ solution at 25/sup 0/C. In this case the computer analysis revealed the formation of more stable complexes: experimental details are given and discussed.

Simultaneous determination of thermodynamic and kinetic parameters of aminopolycarbonate complexes of cobalt(II) and nickel(II) based on isothermal titration calorimetry data.

Science.gov (United States)

Tesmar, Aleksandra; Wyrzykowski, Dariusz; Muñoz, Eva; Pilarski, Bogusław; Pranczk, Joanna; Jacewicz, Dagmara; Chmurzyński, Lech

2017-04-01

The influence of the different side chain residues on the thermodynamic and kinetic parameters for complexation reactions of the Co 2 + and Ni 2 + ions has been investigated by using the isothermal titration calorimetry (ITC) technique supported by potentiometric titration data. The study was concerned with the 2 common tripodal aminocarboxylate ligands, namely, nitrilotriacetic acid and N-(2-hydroxyethyl) iminodiacetic acid. Calorimetric measurements (ITC) were run in the 2-(N-morpholino)ethanesulfonic acid hydrate (2-(N-morpholino) ethanesulfonic acid), piperazine-N,N'-bis(2-ethanesulfonic acid), and dimethylarsenic acid buffers (0.1 mol L -1 , pH 6) at 298.15 K. The quantification of the metal-buffer interactions and their incorporation into the ITC data analysis enabled to obtain the pH-independent and buffer-independent thermodynamic parameters (K, ΔG, ΔH, and ΔS) for the reactions under study. Furthermore, the kinITC method was applied to obtain kinetic information on complexation reactions from the ITC data. Correlations, based on kinetic and thermodynamic data, between the kinetics of formation of Co 2 + and Ni 2 + complexes and their thermodynamic stabilities are discussed. Copyright © 2016 John Wiley & Sons, Ltd.

THERMODYNAMICS OF ETHANOLAMMONIUM CATIONES DISSOCIATION IN AQUEOUS SOLUTIONS

Directory of Open Access Journals (Sweden)

R. E. Khoma

2017-03-01

Full Text Available The literature data on the thermodynamics of ethanolamines onium cations dissociation have been systematized and generalized. The correlation between these cations dissociation thermodynamic functions (DH and DS and physicochemical properties (Tmp., Tbp, Pp, lgPow et al. has been revealed. There was a correlation between lipophilicity determined experimentally and calculated by QSAR. For monoethanolammonium, diethanolammonium, and their N-methyl and N-ethyl derivatives it was found dissociation thermodynamic functions to depend on bases lgPow. Acid-base dissociation of TRIS and triethanolamine onium cations does not correspond to said relationship because TRIS (primary amine, TEA (tertiary amine act differently on aqueous solutions of SO2. TEA, unlike MEA, DEA and MMEA, has a salting out effect towards sulfur dioxide because of competing hydration that promotes sulfite «onium» salts hydrolysis. TRIS promotes S(IV → S(VI sulphooxidation, in contrast to another ethanolamines. Enthalpy–enthropy compensation with isothermodynamic temperature 303 K has been recorded. The revealed correlations may be useful in developing of procedures for air sanitary cleaning from acidic gases; chemisorbents immobilized for gas and ion exchange chromatography; potentiometric methods for fluorocomplex acids determinations. The use of monoethanolamine is most promising to obtain chemisorbents because the thermodynamic functions of its onium cation acid-base dissociation are least dependent on temperature compared to other etanolammonium cations.

Axisymmetric ideal magnetohydrodynamic equilibria with incompressible flows

International Nuclear Information System (INIS)

Tasso, H.; Throumoulopoulos, G.N.

1997-12-01

It is shown that the ideal MHD equilibrium states of an axisymmetric plasma with incompressible flows are governed by an elliptic partial differential equation for the poloidal magnetic flux function ψ containing five surface quantities along with a relation for the pressure. Exact equilibria are constructed including those with non vanishing poloidal and toroidal flows and differentially varying radial electric fields. Unlike the case in cylindrical incompressible equilibria with isothermal magnetic surfaces which should have necessarily circular cross sections [G. N. Throumoulopoulos and H. Tasso, Phys. Plasmas 4, 1492 (1997)], no restriction appears on the shapes of the magnetic surfaces in the corresponding axisymmetric equilibria. The latter equilibria satisfy a set of six ordinary differential equations which for flows parallel to the magnetic field B can be solved semianalytically. In addition, it is proved the non existence of incompressible axisymmetric equilibria with (a) purely poloidal flows and (b) non-parallel flows with isothermal magnetic surfaces and vertical stroke B vertical stroke = vertical stroke B vertical stroke (ψ) (omnigenous equilibria). (orig.)

Pyroelectric Energy Harvesting: With Thermodynamic-Based Cycles

OpenAIRE

Saber Mohammadi; Akram Khodayari

2012-01-01

This work deals with energy harvesting from temperature variations using ferroelectric materials as a microgenerator. The previous researches show that direct pyroelectric energy harvesting is not effective, whereas thermodynamic-based cycles give higher energy. Also, at different temperatures some thermodynamic cycles exhibit different behaviours. In this paper pyroelectric energy harvesting using Lenoir and Ericsson thermodynamic cycles has been studied numerically and the two cycles were c...

Thermodynamic properties of minerals: Macroscopic and microscopic approaches

International Nuclear Information System (INIS)

Richet, P.; Gillet, P.; Fiquet, G.

1992-01-01

Thermodynamic modeling of experimental or natural-phase equilibria has become an integral part of petrology. In this respect, the isobaric heat capacity (C p ) has manifold importance. First, C p data constitute the basis of third-law determinations of the entropy of minerals. Second, these data are needed to calculate the variation with temperature of the entropy, the entropy, and the Gibbs free energy. As a result, it necessary to know accurately heat capacities when retrieving thermodynamic information from phase equilibria data, especially when trying to separate the effects of the enthalpies and entropies of transformation. In this paper, we broadly review the main empiricial and theoretical aspects of the heat capacity of minerals. We begin with a brief review of the three main techniques that are currently in use for determining heat capacities from 0 to 2000 K, namely, adiabatic, differential scanning (DSC), and drop colarimetry, paying attention to the experimental constraints that limit measurements to certain conditions. When minerals can be subjected at best to limited calorimetric measurements, either because of lack of gram-sized samples or of instability at high temperatures (as if often the case with high-pressure minerals), other ways have to be found for predicting standard entropies and high-temperature properties. The validity of empiricial methods of prediction of the heat capacity as a function of temperature and composition will thus be discussed

Development of a thermodynamic data base for selected heavy metals

International Nuclear Information System (INIS)

Hageman, Sven; Scharge, Tina; Willms, Thomas

2015-07-01

The report on the development of a thermodynamic data base for selected heavy metals covers the description of experimental methods, the thermodynamic model for chromate, the thermodynamic model for dichromate, the thermodynamic model for manganese (II), the thermodynamic model for cobalt, the thermodynamic model for nickel, the thermodynamic model for copper (I), the thermodynamic model for copper(II), the thermodynamic model for mercury (0) and mercury (I), the thermodynamic model for mercury (III), the thermodynamic model for arsenate.

Thermodynamic properties of an emerging chemical disinfectant, peracetic acid.

Science.gov (United States)

Zhang, Chiqian; Brown, Pamela J B; Hu, Zhiqiang

2018-04-15

Peracetic acid (PAA or CH 3 COOOH) is an emerging disinfectant with a low potential to form carcinogenic disinfection by-products (DBPs). Basic thermodynamic properties of PAA are, however, absent or inconsistently reported in the literature. This review aimed to summarize important thermodynamic properties of PAA, including standard Gibbs energy of formation and oxidation-reduction (redox) potential. The standard Gibbs energies of formation of CH 3 COOOH (aq) , CH 3 COOOH (g) , CH 3 COOOH (l) , and CH 3 COOO (aq) - are -299.41kJ·mol -1 , -283.02kJ·mol -1 , -276.10kJ·mol -1 , and -252.60kJ·mol -1 , respectively. The standard redox potentials of PAA are 1.748V and 1.005V vs. standard hydrogen electrode (SHE) at pH 0 and pH 14, respectively. Under biochemical standard state conditions (pH 7, 25°C, 101,325Pa), PAA has a redox potential of 1.385V vs. SHE, higher than many disinfectants. Finally, the environmental implications of the thermodynamic properties of PAA were systematically discussed. Those properties can be used to predict the physicochemical and biological behavior of aquatic systems exposed to PAA. Copyright © 2017 Elsevier B.V. All rights reserved.

A fresh look at the thermodynamic consistency of vapour-liquid equilibria data

International Nuclear Information System (INIS)

Wisniak, Jaime; Ortega, Juan; Fernández, Luis

2017-01-01

Highlights: • The thermodynamic consistency tests commonly used to evaluate VLE data are presented and discussed. • Advantages/disadvantages for each one of test are listed using actual examples. • All manuscripts should include information about VLE variables and test results. • In any case, the Herington test should not be used for VLE data evaluation. • Simultaneous application of several tests is recommended. - Abstract: Design of a separation unit requires real information about the phase equilibrium of the system being handled. Accurate equilibrium data allows the best design from a thermodynamic viewpoint and contributes to a better knowledge about the behaviour of fluids and their mixtures. The principles behind the concept of thermodynamic consistency are presented and discussed. The present state of the art shows that no definite test is available for insuring the quality of the measured values. The main available procedures for testing the consistency of vapour-liquid equilibrium (VLE) data at constant temperature or pressure are reviewed and analysed and recommendations provided for their proper use, for the presentation of VLE results, and also some possible means for determining their quality. Suitable examples are provided about the adequate use of the available tests and about their misuse.

M3FT-15OR0202212: SUBMIT SUMMARY REPORT ON THERMODYNAMIC EXPERIMENT AND MODELING

Energy Technology Data Exchange (ETDEWEB)

McMurray, Jake W. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Brese, Robert G. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Silva, Chinthaka M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Besmann, Theodore M. [Univ. of South Carolina, Columbia, SC (United States)

2015-09-01

Modeling the behavior of nuclear fuel with a physics-based approach uses thermodynamics for key inputs such as chemical potentials and thermal properties for phase transformation, microstructure evolution, and continuum transport simulations. Many of the lanthanide (Ln) elements and Y are high-yield fission products. The U-Y-O and U-Ln-O ternaries are therefore key subsystems of multi-component high-burnup fuel. These elements dissolve in the dominant urania fluorite phase affecting many of its properties. This work reports on an effort to assess the thermodynamics of the U-Pr-O and U-Y-O systems using the CALPHAD (CALculation of PHase Diagrams) method. The models developed within this framework are capable of being combined and extended to include additional actinides and fission products allowing calculation of the phase equilibria, thermochemical and material properties of multicomponent fuel with burnup.

(Amino acid + silica) adsorption thermodynamics: Effects of temperature

International Nuclear Information System (INIS)

Sebben, Damien; Pendleton, Phillip

2015-01-01

Highlights: • High resolution, low concentration Gly, Lys and Glu solution adsorption isotherms. • All isotherms fitted with Langmuir–Freundlich isotherm model. • Gly, Lys and Glu show exothermic adsorption processes. • Isosteric heat analyses reveal changes in interaction strength with surface coverage. - Abstract: A thorough understanding of amino acid adsorption by mineral and oxide surfaces has a major impact on a variety of industrial and biomedical applications. Little information currently exists regarding temperature effects on most of these adsorption processes. Deeper thermodynamic analyses of their multiple temperature adsorption isotherms would aid the interpretation of the interfacial interactions. Low solution concentration adsorption isotherms for glycine, lysine and glutamic acid on a silica adsorbent were generated for T = (291, 298 and 310) K. Data analysis via the Clausius–Clapeyron method yielded the isosteric heat of adsorption as a function of fractional monolayer coverage for each adsorptive. Each amino acid showed an exothermic adsorption response. Glycine and lysine experienced a greater negative effect of increased temperature compared with glutamic acid, indicating a greater number of adsorbed molecules than glutamic acid, with the former undergoing intermolecular clustering within the adsorbed phase. Isosteric heat analyses suggest ionic interactions for lysine and hydrogen bonding for glutamic acid, both weakening with increased coverage. In contrast, initial hydrogen bonding led to ionic bonding for glycine with increasing coverage

Computation of Thermodynamic Equilibria Pertinent to Nuclear Materials in Multi-Physics Codes

Science.gov (United States)

Piro, Markus Hans Alexander

Nuclear energy plays a vital role in supporting electrical needs and fulfilling commitments to reduce greenhouse gas emissions. Research is a continuing necessity to improve the predictive capabilities of fuel behaviour in order to reduce costs and to meet increasingly stringent safety requirements by the regulator. Moreover, a renewed interest in nuclear energy has given rise to a "nuclear renaissance" and the necessity to design the next generation of reactors. In support of this goal, significant research efforts have been dedicated to the advancement of numerical modelling and computational tools in simulating various physical and chemical phenomena associated with nuclear fuel behaviour. This undertaking in effect is collecting the experience and observations of a past generation of nuclear engineers and scientists in a meaningful way for future design purposes. There is an increasing desire to integrate thermodynamic computations directly into multi-physics nuclear fuel performance and safety codes. A new equilibrium thermodynamic solver is being developed with this matter as a primary objective. This solver is intended to provide thermodynamic material properties and boundary conditions for continuum transport calculations. There are several concerns with the use of existing commercial thermodynamic codes: computational performance; limited capabilities in handling large multi-component systems of interest to the nuclear industry; convenient incorporation into other codes with quality assurance considerations; and, licensing entanglements associated with code distribution. The development of this software in this research is aimed at addressing all of these concerns. The approach taken in this work exploits fundamental principles of equilibrium thermodynamics to simplify the numerical optimization equations. In brief, the chemical potentials of all species and phases in the system are constrained by estimates of the chemical potentials of the system

Underlying thermodynamics of pH-dependent allostery.

Science.gov (United States)

Di Russo, Natali V; Martí, Marcelo A; Roitberg, Adrian E

2014-11-13

Understanding the effects of coupling protein protonation and conformational states is critical to the development of drugs targeting pH sensors and to the rational engineering of pH switches. In this work, we address this issue by performing a comprehensive study of the pH-regulated switch from the closed to the open conformation in nitrophorin 4 (NP4) that determines its pH-dependent activity. Our calculations show that D30 is the only amino acid that has two significantly different pKas in the open and closed conformations, confirming its critical role in regulating pH-dependent behavior. In addition, we describe the free-energy landscape of the conformational change as a function of pH, obtaining accurate estimations of free-energy barriers and equilibrium constants using different methods. The underlying thermodynamic model of the switch workings suggests the possibility of tuning the observed pKa only through the conformational equilibria, keeping the same conformation-specific pKas, as evidenced by the proposed K125L mutant. Moreover, coupling between the protonation and conformational equilibria results in efficient regulation and pH-sensing around physiological pH values only for some combinations of protonation and conformational equilibrium constants, placing constraints on their possible values and leaving a narrow space for protein molecular evolution. The calculations and analysis presented here are of general applicability and provide a guide as to how more complex systems can be studied, offering insight into how pH-regulated allostery works of great value for designing drugs that target pH sensors and for rational engineering of pH switches beyond the common histidine trigger.

Thermodynamic assessments of the Ag-Gd and Ag-Nd systems

International Nuclear Information System (INIS)

Wang, S.L.; Wang, C.P.; Liu, X.J.; Ishida, K.

2009-01-01

The phase diagrams and thermodynamic properties in the Ag-Re (Re: Gd, Nd) binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, dhcp and hcp phases were described by the subregular solution model with the Redlich-Kister equation, and those of the intermetallic compounds (Ag 51 Gd 14 , Ag 2 Gd, AgGd, Ag 51 Nd 14 , αAg 2 Nd, βAg 2 Nd and AgNd phases) in these two binary systems were described by the sublattice model. The thermodynamic parameters of each phase in the Ag-Re (Re: Gd, Nd) binary systems were obtained, and an agreement between the calculated results and experimental data was obtained in each binary system.

Thermodynamic and Calorimetric Study of Acetylsalicylic Acid (Aspirin and Ibuprofen

Directory of Open Access Journals (Sweden)

Juan Carlos Moreno-Piraján

2011-01-01

Full Text Available Enthalpies of solution and dilution of aqueous solutions of sodium acetylsalicylic acid salt and ibuprofen salt were measured with an isoperibolic calorimeter at 293.15 K, 298.15 K, 303.15 K, 308.15 K and 318.15 K. The concentration of the electrolyte was restricted to the solubility of the salt at various temperatures and did not exceed 0.035–0.057 mol kg-1, depending on the temperature studied. The Virial coefficients were derived from Pitzer's model and the excess thermodynamic functions of both the solution and the components of the solution were calculated. An analysis of the thermodynamic characteristics of the solution in terms of concentration and temperature interval was carried out and discussed. Additionally, an analysis was performed by differential scanning calorimetry (DSC.

Thermodynamic equilibrium of hydroxyacetic acid in pure and binary solvent systems

International Nuclear Information System (INIS)

Huang, Qiaoyin; Xie, Chuang; Li, Yang; Su, Nannan; Lou, Yajing; Hu, Xiaoxue; Wang, Yongli; Bao, Ying; Hou, Baohong

2017-01-01

Highlights: • Solubility of hydroxyacetic acid in mono-solvents and binary solvent mixtures was measured. • Modified Apelblat, NRTL and Wilson model were used to correlate the solubility data in pure solvents. • CNIBS/R-K and Jouyban-Acree model were used to correlate the solubility in binary solvent mixtures. • The mixing properties were calculated based on the NRTL model. - Abstract: The solubility of hydroxyacetic acid in five pure organic solvents and two binary solvent mixtures were experimentally measured from 273.15 K to 313.15 K at atmospheric pressure (p = 0.1 MPa) by using a dynamic method. The order of solubility in pure organic solvents is ethanol > isopropanol > n-butanol > acetonitrile > ethyl acetate within the investigated temperature range, except for temperature lower than 278 K where the solubility of HA in ethyl acetate is slightly larger than that in acetonitrile. Furthermore, the solubility data in pure solvents were correlated with the modified Apelblat model, NRTL model, and Wilson model and that in the binary solvents mixtures were fitted to the CNIBS/R-K model and Jouyban-Acree model. Finally, the mixing thermodynamic properties of hydroxyacetic acid in pure and binary solvent systems were calculated and discussed.

The thermodynamics of extraction of U(VI) and Th(IV) from nitric acid by neutral phosphorus-based organic compounds

International Nuclear Information System (INIS)

Kalina, D.G.; Mason, G.W.; Horwitz, E.P.

1981-01-01

The extraction of Th(IV) and U(VI) from dilute nitric acid solution by several neutral phosphorus-based extractants has been studied as a function of temperature in the range of 0 to 50 0 C. From the variation of the distribution ratio (Ksub(d)) with temperature the thermodynamic quantities ΔG, ΔH and ΔS have been calculated for these extractions. The results of this study indicate that the steric bulk of the extractant plays a major role in determining how well Th(IV) is extracted. The size of the extractant appears to be of little or no importance in the extraction of U(VI). Similarly, the basicity of the extractant is of lesser importance in the extraction of uranyl ion relative to thorium ion. (author)

Thermodynamic evaluation and optimization of the (Na+K+S) system

Energy Technology Data Exchange (ETDEWEB)

Lindberg, Daniel [Abo Akademi Process Chemistry Centre, Abo Akademi University, Biskopsgatan 8, FI-20500 Turku (Finland)]. E-mail: Daniel.Lindberg@abo.fi; Backman, Rainer [Abo Akademi Process Chemistry Centre, Abo Akademi University, Biskopsgatan 8, FI-20500 Turku (Finland); Energy Technology and Thermal Process Chemistry, Umea University, SE-90187 Umea (Sweden); Hupa, Mikko [Abo Akademi Process Chemistry Centre, Abo Akademi University, Biskopsgatan 8, FI-20500 Turku (Finland); Chartrand, Patrice [Centre de Recherche en Calcul Thermochimique (CRCT), Ecole Polytechnique, Box 6079, Station Downtown, Montreal, Que., H3C 3A7 (Canada)

2006-07-15

The (Na+K+S) system is of primary importance for the combustion of black liquor in the kraft recovery boilers in pulp and paper mills. A thermodynamic evaluation and optimization for the (Na+K+S) system has been made. All available data for the system have been critically evaluated to obtain optimized parameters of thermodynamic models for all phases. The liquid model is the quasichemical model in the quadruplet approximation, which evaluates 1st- and 2nd-nearest-neighbour short-range-order. In this model, cations (Na{sup +} and K{sup +}) are assumed to mix on a cationic sublattice, while anions (S{sup 2-},S{sub 2}{sup 2-},S{sub 3}{sup 2-},S{sub 4}{sup 2-},S{sub 5}{sup 2-},S{sub 6}{sup 2-},S{sub 7}{sup 2-},S{sub 8}{sup 2-},Va{sup -}) are assumed to mix on an anionic sublattice. The thermodynamic data of the liquid polysulphide components M{sub 2}S{sub 1+n} (M=Na, K and n=1-7) are fitted to {delta}G=A(n)+B(n).T for the reaction M{sub 2}S(l)+nS(l)=M{sub 2}S{sub n+1}(l). The solid phases are the alkali alloys, alkali sulphides, several different alkali polysulphides and sulphur. The solid solutions (Na,K) (Na,K){sub 2}S and (Na,K){sub 2}S{sub 2} are modelled using the compound energy formalism. The models can be used to predict the thermodynamic properties and phase equilibria in the multicomponent heterogeneous system. The experimental data are reproduced within experimental error limits for equilibria between solid, liquid and gas. The ternary phase diagram of the system (Na{sub 2}S+K{sub 2}S+S) has been predicted as no experimental determinations of the phase diagram have been made previously.

Gas hydrate phase equilibria measurement techniques and phase rule considerations

International Nuclear Information System (INIS)

Beltran, Juan G.; Bruusgaard, Hallvard; Servio, Phillip

2012-01-01

Highlights: → Inconsistencies found in hydrate literature. → Clarification to the number of variables needed to satisfy and justify equilibrium data. → Application of phase rule to mixed hydrate systems. → Thermodynamically consistent format to present data. - Abstract: A brief review of the Gibbs phase rule for non-reacting systems and its correct application to clathrate hydrates is presented. Clarification is provided for a common mistake found in hydrate phase-equilibria literature, whereby initial compositions are used as intensive variables to satisfy the Gibbs phase rule instead of the equilibrium values. The system of (methane + carbon dioxide + water) under (hydrate + liquid + vapor) equilibrium is used as a case study to illustrate key points and suggestions to improve experimental techniques are proposed.

Multiple equilibria of divertor plasmas

International Nuclear Information System (INIS)

Vu, H.X.; Prinja, A.K.

1993-01-01

A one-dimensional, two-fluid transport model with a temperature-dependent neutral recycling coefficient is shown to give rise to multiple equilibria of divertor plasmas (bifurcation). Numerical techniques for obtaining these multiple equilibria and for examining their stability are presented. Although these numerical techniques have been well known to the scientific community, this is the first time they have been applied to divertor plasma modeling to show the existence of multiple equilibria as well as the stability of these solutions. Numerical and approximate analytical solutions of the present one-dimensional transport model both indicate that there exists three steady-state solutions corresponding to (1) a high-temperature, low-density equilibrium, (2) a low-temperature, high-density equilibrium, and (3) an intermediate-temperature equilibrium. While both the low-temperature and the high-temperature equilibria are stable, with respect to small perturbations in the plasma conditions, the intermediate-temperature equilibrium is physically unstable, i.e., any small perturbation about this equilibrium will cause a transition toward either the high-temperature or low-temperature equilibrium

Modeling Phase Equilibria for Acid Gas Mixtures using the Cubic-Plus-Association Equation of State. 3. Applications Relevant to Liquid or Supercritical CO2 Transport

DEFF Research Database (Denmark)

Tsivintzelis, Ioannis; Ali, Shahid; Kontogeorgis, Georgios

2014-01-01

density data for both CO2 and CO2–water and for vapor–liquid equilibrium for mixtures of CO2 with various compounds present in transport systems. In all of these cases we consider various possibilities for modeling CO2 (inert, self-associating using two-, three-, and four sites) and the possibility......The CPA (cubic-plus-association) equation of state is applied in this work to a wide range of systems of relevance to CO2 transport. Both phase equilibria and densities over extensive temperature and pressure ranges are considered. More specifically in this study we first evaluate CPA against......” for applying CPA to acid gas mixtures. The overall conclusion is that CPA performs satisfactorily; the model in most cases correlates well binary data and predicts with good accuracy multicomponent vapor–liquid equilibria. Among the various approaches investigated, the best ones are when cross association...

Trace analysis of acids and bases by conductometric titration with multiparametric non-linear regression.

Science.gov (United States)

Coelho, Lúcia H G; Gutz, Ivano G R

2006-03-15

A chemometric method for analysis of conductometric titration data was introduced to extend its applicability to lower concentrations and more complex acid-base systems. Auxiliary pH measurements were made during the titration to assist the calculation of the distribution of protonable species on base of known or guessed equilibrium constants. Conductivity values of each ionized or ionizable species possibly present in the sample were introduced in a general equation where the only unknown parameters were the total concentrations of (conjugated) bases and of strong electrolytes not involved in acid-base equilibria. All these concentrations were adjusted by a multiparametric nonlinear regression (NLR) method, based on the Levenberg-Marquardt algorithm. This first conductometric titration method with NLR analysis (CT-NLR) was successfully applied to simulated conductometric titration data and to synthetic samples with multiple components at concentrations as low as those found in rainwater (approximately 10 micromol L(-1)). It was possible to resolve and quantify mixtures containing a strong acid, formic acid, acetic acid, ammonium ion, bicarbonate and inert electrolyte with accuracy of 5% or better.

Toward Synthetic Biology Strategies for Adipic Acid Production: An in Silico Tool for Combined Thermodynamics and Stoichiometric Analysis of Metabolic Networks

DEFF Research Database (Denmark)

Averesch, Nils J. H.; Martínez, Verónica S.; Nielsen, Lars K.

2018-01-01

Adipic acid, a nylon-6,6 precursor, has recently gained popularity in synthetic biology. Here, 16 different production routes to adipic acid were evaluated using a novel tool for network-embedded thermodynamic analysis of elementary flux modes. The tool distinguishes between thermodynamically...

The Effect of CaO on Gas/Slag/Matte/Tridymite Equilibria in Fayalite-Based Copper Smelting Slags at 1473 K (1200 °C) and P(SO2) = 0.25 Atm

Science.gov (United States)

Fallah-Mehrjardi, Ata; Hayes, Peter C.; Jak, Evgueni

2018-04-01

Fundamental experimental studies have been undertaken to determine the effect of CaO on the equilibria between the gas phase (CO/CO2/SO2/Ar) and slag/matte/tridymite phases in the Cu-Fe-O-S-Si-Ca system at 1473 K (1200 °C) and P(SO2) = 0.25 atm. The experimental methodology developed in the Pyrometallurgy Innovation Centre was used. New experimental data have been obtained for the four-phase equilibria system for fixed concentrations of CaO (up to 4 wt pct) in the slag phase as a function of copper concentration in matte, including the concentrations of dissolved sulfur and copper in slag, and Fe/SiO2 ratios in slag at tridymite saturation. The new data provided in the present study are of direct relevance to the pyrometallurgical processing of copper and will be used as an input to optimize the thermodynamic database for the copper-containing multi-component multi-phase system.

DETERMINATION OF SOLID-LIQUID EQUILIBRIA DATA FOR MIXTURES OF HEAVY HYDROCARBONS IN A LIGHT SOLVENT

Energy Technology Data Exchange (ETDEWEB)

F.V. Hanson; J.V. Fletcher; Karthik R.

2003-06-01

A methodology was developed using an FT-IR spectroscopic technique to obtain solid-liquid equilibria (SLE) data for mixtures of heavy hydrocarbons in significantly lighter hydrocarbon diluents. SLE was examined in multiple Model Oils that were assembled to simulate waxes. The various Model oils were comprised of C-30 to C-44 hydrocarbons in decane. The FT-IR technique was used to identify the wax precipitation temperature (WPT). The DSC technique was also used in the identification of the onset of the two-phase equilibrium in this work. An additional Model oil made up of C-20 to C-30 hydrocarbons in decane was studied using the DSC experiment. The weight percent solid below the WPT was calculated using the FT-IR experimental results. The WPT and the weight percent solid below the WPT were predicted using an activity coefficient based thermodynamic model. The FT-IR spectroscopy method is found to successfully provide SLE data and also has several advantages over other laboratory-based methods.

Thermodynamic analysis of regulation in metabolic networks using constraint-based modeling

Directory of Open Access Journals (Sweden)

Mahadevan Radhakrishnan

2010-05-01

Full Text Available Abstract Background Geobacter sulfurreducens is a member of the Geobacter species, which are capable of oxidation of organic waste coupled to the reduction of heavy metals and electrode with applications in bioremediation and bioenergy generation. While the metabolism of this organism has been studied through the development of a stoichiometry based genome-scale metabolic model, the associated regulatory network has not yet been well studied. In this manuscript, we report on the implementation of a thermodynamics based metabolic flux model for Geobacter sulfurreducens. We use this updated model to identify reactions that are subject to regulatory control in the metabolic network of G. sulfurreducens using thermodynamic variability analysis. Findings As a first step, we have validated the regulatory sites and bottleneck reactions predicted by the thermodynamic flux analysis in E. coli by evaluating the expression ranges of the corresponding genes. We then identified ten reactions in the metabolic network of G. sulfurreducens that are predicted to be candidates for regulation. We then compared the free energy ranges for these reactions with the corresponding gene expression fold changes under conditions of different environmental and genetic perturbations and show that the model predictions of regulation are consistent with data. In addition, we also identify reactions that operate close to equilibrium and show that the experimentally determined exchange coefficient (a measure of reversibility is significant for these reactions. Conclusions Application of the thermodynamic constraints resulted in identification of potential bottleneck reactions not only from the central metabolism but also from the nucleotide and amino acid subsystems, thereby showing the highly coupled nature of the thermodynamic constraints. In addition, thermodynamic variability analysis serves as a valuable tool in estimating the ranges of ΔrG' of every reaction in the model

Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the PLLA/Dioxane/Water Ternary System for Applications in the Biomedical Field.

Science.gov (United States)

Ruggiero, Flavia; Netti, Paolo Antonio; Torino, Enza

2015-12-01

Fundamental understanding of thermodynamic of phase separation plays a key role in tuning the desired features of biomedical devices. In particular, phase separation of ternary solution is of remarkable interest in processes to obtain biodegradable and biocompatible architectures applied as artificial devices to repair, replace, or support damaged tissues or organs. In these perspectives, thermally induced phase separation (TIPS) is the most widely used technique to obtained porous morphologies and, in addition, among different ternary systems, polylactic acid (PLLA)/dioxane/water has given promising results and has been largely studied. However, to increase the control of TIPS-based processes and architectures, an investigation of the basic energetic phenomena occurring during phase separation is still required. Here we propose an experimental investigation of the selected ternary system by using isothermal titration calorimetric approach at different solvent/antisolvent ratio and a thermodynamic explanation related to the polymer-solvents interactions in terms of energetic contribution to the phase separation process. Furthermore, relevant information about the phase diagrams and interaction parameters of the studied systems are furnished in terms of liquid-liquid miscibility gap. Indeed, polymer-solvents interactions are responsible for the mechanism of the phase separation process and, therefore, of the final features of the morphologies; the knowledge of such data is fundamental to control processes for the production of membranes, scaffolds and several nanostructures. The behavior of the polymer at different solvent/nonsolvent ratios is discussed in terms of solvation mechanism and a preliminary contribution to the understanding of the role of the hydrogen bonding in the interface phenomena is also reported. It is the first time that thermodynamic data of a ternary system are collected by mean of nano-isothermal titration calorimetry (nano-ITC). Supporting

Phase equilibria basic principles, applications, experimental techniques

CERN Document Server

Reisman, Arnold

2013-01-01

Phase Equilibria: Basic Principles, Applications, Experimental Techniques presents an analytical treatment in the study of the theories and principles of phase equilibria. The book is organized to afford a deep and thorough understanding of such subjects as the method of species model systems; condensed phase-vapor phase equilibria and vapor transport reactions; zone refining techniques; and nonstoichiometry. Physicists, physical chemists, engineers, and materials scientists will find the book a good reference material.

Étude des équilibres thermodynamiques des réactions de gazéification en vue de l'optimisation du rapport vapeur/comburant injecté dans un gazogène souterrain Study of Thermodynamic Equilibria in Gasification Reactions So As to Optimise the Steam/Oxidizer Ratio Injected Into an Underground Gas Generator

Directory of Open Access Journals (Sweden)

Pirard J. P.

2006-11-01

Full Text Available Le but de cette étude est de déterminer sur la base des équilibres thermodynamiques des réactions de gazéification le rapport vapeur/comburant à injecter dans un gazogène fonctionnant sous pression pour optimaliser les compositions, les pouvoirs calorifiques, les rendements de gazéification et la consommation d'agent gazéifiant. The aim of this study is to determine, on the basis of the thermodynamic equilibria of gazification reactions, the steam/oxidizer ratio to be injected into a gas generator operating under pressure so as to optimize the compositions, the heating values, the gasification efficiencies and the consumption of gasifying agent.

Metamorphism and partial melting of ordinary chondrites: Calculated phase equilibria

Science.gov (United States)

Johnson, T. E.; Benedix, G. K.; Bland, P. A.

2016-01-01

Constraining the metamorphic pressures (P) and temperatures (T) recorded by meteorites is key to understanding the size and thermal history of their asteroid parent bodies. New thermodynamic models calibrated to very low P for minerals and melt in terrestrial mantle peridotite permit quantitative investigation of high-T metamorphism in ordinary chondrites using phase equilibria modelling. Isochemical P-T phase diagrams based on the average composition of H, L and LL chondrite falls and contoured for the composition and abundance of olivine, ortho- and clinopyroxene, plagioclase and chromite provide a good match with values measured in so-called equilibrated (petrologic type 4-6) samples. Some compositional variables, in particular Al in orthopyroxene and Na in clinopyroxene, exhibit a strong pressure dependence when considered over a range of several kilobars, providing a means of recognising meteorites derived from the cores of asteroids with radii of several hundred kilometres, if such bodies existed at that time. At the low pressures (recorders of peak conditions. The intersection of isopleths of these variables may allow pressures to be quantified, even at low P, permitting constraints on the minimum size of parent asteroid bodies. The phase diagrams predict the onset of partial melting at 1050-1100 °C by incongruent reactions consuming plagioclase, clinopyroxene and orthopyroxene, whose compositions change abruptly as melting proceeds. These predictions match natural observations well and support the view that type 7 chondrites represent a suprasolidus continuation of the established petrologic types at the extremes of thermal metamorphism. The results suggest phase equilibria modelling has potential as a powerful quantitative tool in investigating, for example, progressive oxidation during metamorphism, the degree of melting and melt loss or accumulation required to produce the spectrum of differentiated meteorites, and whether the onion shell or rubble pile

CTserver: A Computational Thermodynamics Server for the Geoscience Community

Science.gov (United States)

Kress, V. C.; Ghiorso, M. S.

2006-12-01

The CTserver platform is an Internet-based computational resource that provides on-demand services in Computational Thermodynamics (CT) to a diverse geoscience user base. This NSF-supported resource can be accessed at ctserver.ofm-research.org. The CTserver infrastructure leverages a high-quality and rigorously tested software library of routines for computing equilibrium phase assemblages and for evaluating internally consistent thermodynamic properties of materials, e.g. mineral solid solutions and a variety of geological fluids, including magmas. Thermodynamic models are currently available for 167 phases. Recent additions include Duan, Møller and Weare's model for supercritical C-O-H-S, extended to include SO2 and S2 species, and an entirely new associated solution model for O-S-Fe-Ni sulfide liquids. This software library is accessed via the CORBA Internet protocol for client-server communication. CORBA provides a standardized, object-oriented, language and platform independent, fast, low-bandwidth interface to phase property modules running on the server cluster. Network transport, language translation and resource allocation are handled by the CORBA interface. Users access server functionality in two principal ways. Clients written as browser- based Java applets may be downloaded which provide specific functionality such as retrieval of thermodynamic properties of phases, computation of phase equilibria for systems of specified composition, or modeling the evolution of these systems along some particular reaction path. This level of user interaction requires minimal programming effort and is ideal for classroom use. A more universal and flexible mode of CTserver access involves making remote procedure calls from user programs directly to the server public interface. The CTserver infrastructure relieves the user of the burden of implementing and testing the often complex thermodynamic models of real liquids and solids. A pilot application of this distributed

Determination of acid dissociation constants of warfarin and hydroxywarfarins by capillary electrophoresis.

Science.gov (United States)

Nowak, Paweł; Olechowska, Paulina; Mitoraj, Mariusz; Woźniakiewicz, Michał; Kościelniak, Paweł

2015-08-10

In this work the acid dissociation constants--pKa of warfarin and its all important oxidative metabolites have been determined by capillary electrophoresis-based methods. It has resulted in a complete description of two acid-base dissociation equilibria, yet not investigated experimentally for phase I metabolites of warfarin. The capillary electrophoresis (CE) method based on the relation between effective electrophoretic mobilities and pH has proven to be a suitable tool for pKa determination, while the spectrophotometric (CE-DAD) and the internal standard methods (IS-CE), have appeared to be promising alternative approaches. The CE-DAD approach based on the change in absorbance spectra between the acidic and basic forms is a combination between capillary electrophoresis and spectrophotometric titration, and yields very consistent values of pKa1 with CE. The IS-CE, in turn, enables an estimation of pKa1 and pKa2 from only two analytical runs, however, less accurate than CE and CE-DAD. The Debye-Hückel model has been confirmed experimentally as a good predictor of pKa values at various ionic strengths. Therefore, it has been used in determination of thermodynamic pKa1 and pKa2, referring to the zero ionic strength. The results are important from the analytical, pharmacological, and theoretical points of view. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of nature, concentration and pH of buffer acid-base system on rate determining step of the electrochemiluminescence of Ru(bpy)32+ with tertiary aliphatic amines

International Nuclear Information System (INIS)

Pastore, Paolo; Badocco, Denis; Zanon, Francesco

2006-01-01

The electrogenerated chemiluminescence (ECL) of Ru(bpy) 3 2+ (bpy 2,2'-bipyridyl) with tertiary aliphatic amines as co-reactants, was theoretically and experimentally studied as a function of the pre-equilibria involved in the ammonium proton lost and in relation to the nature of the rate determining step. Transient potential steps were used with a 3-mm glassy carbon disk electrode or carbon fiber ultramicroelectrodes array to investigate emission behavior in a variety of aqueous solution types, containing phosphate, tartrate and phthalate acid-base systems at differing pH values. The emission of Ru(bpy) 3 2+ resulting from the reaction with n-tripropylamine (TPrA), tri-isobutylamine (TisoBuA), n-tributylamine (TBuA), methyl-di-n-propylamine (MeDPrA) and triethylamine (TEtA) in varying acid-base media was interpreted on the basis of the quoted pre-equilibria, ammonium pK a being known. The nature of the rate determining steps changes depending on pH. Above pH ∼ 5 the amine neutral radical formation is the rate determining step and, is independent of pH with rate constant close to 10 3 s -1 ; below pH ∼ 5 the rate determining step becomes the deprotonation of the ammonium ion, operated by different bases present in solution. Different amines in the same acid-base system showed analogous ECL behavior, conditioned by the chosen acid base system. A single amine in different acid-base systems showed different kinetic behaviors, due to the dissociation constants of the chosen buffers. The concentration of the acid-base system also played an important role and influenced emission intensity and shape. ECL emission were simulated by finite difference methods, implementing a previously proposed mechanism by including the relevant pre-equilibria. Simulation may also give estimates of the pK a values of the ammonium ions. An ion pair formation between R 3 N· + and the mostly charged species present in solution is hypothesized to explain the contradictory experimental

Neoclassical MHD equilibria with ohmic current

International Nuclear Information System (INIS)

Tokuda, Shinji; Takeda, Tatsuoki; Okamoto, Masao.

1989-01-01

MHD equilibria of tokamak plasmas with neoclassical current effects (neoclassical conductivity and bootstrap current) were calculated self-consistently. Neoclassical effects on JFT-2M tokamak plasmas, sustained by ohmic currents, were studied. Bootstrap currents flow little for L-mode type equilibria because of low attainable values of poloidal beta, β J . H-mode type equilibria give bootstrap currents of 30% ohmic currents for β J attained by JFT-2M and 100% for β J ≥ 1.5, both of which are sufficient to change the current profiles and the resultant MHD equilibria. Neoclassical conductivity which has roughly half value of the classical Spitzer conductivity brings peaked ohmic current profiles to yield low safety factor at the magnetic axis. Neoclassical conductivity reduces the value of effective Z(Z eff ) which is necessary to give the observed one-turn voltage but it needs impurities accumulating at the center when such peaked current profiles are not observed. (author)

Spectroscopic and thermodynamic studies on ferulic acid - Alpha-2-macroglobulin interaction

Science.gov (United States)

Rehman, Ahmed Abdur; Sarwar, Tarique; Arif, Hussain; Ali, Syed Saqib; Ahsan, Haseeb; Tabish, Mohammad; Khan, Fahim Halim

2017-09-01

Ferulic acid is a major phenolic acid found in numerous plant species in conjugated form. It binds to enzymes and oligomeric proteins and modifies their structure and function. This study was designed to examine the interaction of ferulic acid, an active ingredient of some important medicines, with α2M, a key serum proteinase, under physiological conditions. The mechanism of interaction was studied by spectroscopic techniques such as, UV-visible absorption, fluorescence spectroscopy, circular dichroism along with isothermal titration calorimetry. Fluorescence quenching of α2M by ferulic acid demonstrated the formation of α2M-ferulic acid complex by static quenching mechanism. Binding parameters calculated by Stern-Volmer method showed that ferulic acid binds to α2M with moderate affinity of the order of ∼104 M-1. The thermodynamic signatures reveal that binding was enthalpy driven and hydrogen bonding played a major role in ferulic acid-α2M binding. CD spectra analysis suggests very little conformational changes in α2M on ferulic acid binding.

Solid phase extraction of uranium from phosphoric acid. Kinetic and thermodynamic study

Energy Technology Data Exchange (ETDEWEB)

Abdel-Magied, Ahmed Fawzy [Nuclear Materials Authority, Cairo (Egypt); Stockholm Univ. (Sweden). Dept. of Organic Chemistry

2017-07-01

There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPA-TOPO rate at MCM-41 (mass ratio 2:1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg{sup -1} min{sup -1} calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H{sub 3}PO{sub 4} is an exothermic and spontaneous process.

Complexes between ovalbumin nanoparticles and linoleic acid: Stoichiometric, kinetic and thermodynamic aspects.

Science.gov (United States)

Sponton, Osvaldo E; Perez, Adrián A; Carrara, Carlos R; Santiago, Liliana G

2016-11-15

Stoichiometric, kinetic and thermodynamic aspects of complex formation between heat-induced aggregates of ovalbumin (ovalbumin nanoparticles, OVAn) and linoleic acid (LA) were evaluated. Extrinsic fluorescence data were fitted to modified Scatchard model yielding the following results: n: 49±2 LA molecules bound per OVA monomer unit and Ka: 9.80±2.53×10(5)M. Kinetic and thermodynamic properties were analyzed by turbidity measurements at different LA/OVA monomer molar ratios (21.5-172) and temperatures (20-40°C). An adsorption approach was used and a pseudo-second-order kinetics was found for LA-OVAn complex formation. This adsorption process took place within 1h. Thermodynamic parameters indicated that LA adsorption on OVAn was a spontaneous, endothermic and entropically-driven process, highlighting the hydrophobic nature of the LA and OVAn interaction. Finally, Atomic Force Microscopy imaging revealed that both OVAn and LA-OVAn complexes have a roughly rounded form with size lower than 100nm. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermodynamic studies on the interaction of folic acid with bovine serum albumin

International Nuclear Information System (INIS)

Jha, Niki S.; Kishore, Nand

2011-01-01

Research highlights: → Thermodynamics of binding of folic acid with bovine serum albumin studied. → Effect of co-solutes on binding permitted detailed analysis of interactions. → Electrostatic interactions dominate with contribution from hydrogen bonding. → No significant conformational change in protein observed upon drug binding. - Abstract: Binding of the vitamin folic acid with bovine serum albumin (BSA) has been studied using isothermal titration calorimetry (ITC) in combination with fluorescence and circular dichroism spectroscopies. The thermodynamic parameters of binding have been evaluated as a function of temperature, ionic strength, in the presence of nonionic surfactants triton X-100, tetrabutylammonium bromide, and sucrose. The values of the van't Hoff enthalpy calculated from the temperature dependence of the binding constant agree with the calorimetric enthalpies indicating that the binding of folic acid to the BSA is a two state process without involving intermediates. These observations are supported by the intrinsic fluorescence and circular dichroism spectroscopic measurements. With increase in the ionic strength, reduction in the binding affinity of folic acid to BSA is observed suggesting predominance of electrostatic interactions in the binding. The contribution of hydrophobic interactions in the binding is also demonstrated by decrease in the binding affinity in the presence of tetrabutylammonium bromide (TBAB). The value of binding affinity in the presence of sucrose indicates that hydrogen bonding also plays a significant contribution in the complexation process. The calorimetric and spectroscopic results provide quantitative information on the binding of folic acid to BSA and suggest that the binding is dominated by electrostatic interactions with contribution from hydrogen bonding.

Development of analytical model for condensation of vapor mixture of nitric acid and water affected volatilized ruthenium behavior in accident of evaporation to dryness by boiling of reprocessed high level liquid waste at fuel reprocessing facilities

International Nuclear Information System (INIS)

Yoshida, Kazuo

2016-08-01

An accident of evaporation to dryness by boiling of high level liquid waste is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, continuous vaporing of nitric acid and water leads to increase Ru volatilization in liquid waste temperature over 120degC at later boiling and dry out phases. It has been observed at the experiments with actual and synthetic liquid waste that some amount of Ru volatilizes and transfers into condensed nitric acid solution at those phases. The nitric acid and water vapor flowing from waste tank are expected to condense at compartments of actual facilities building. The volatilized Ru could transfer into condensed liquid. It is key issues for quantifying the amount of transferred Ru through the facility building to simulate these thermodynamic and chemical behaviors. An analytical model has been proposed in this report based on the condensation mechanisms of nitric acid and water in vapor-liquid equilibria. It has been also carried out for the proposed model being feasible to formulate the activity coefficients and to review the thermodynamic properties of nitric acid solution. Practicability of the proposed analytical model has been shown successfully through the feasibility study with simulation of an experiment result. (author)

Modern Thermodynamics Based on the Extended Carnot Theorem

CERN Document Server

Wang, Jitao

2012-01-01

"Modern Thermodynamics- Based on the Extended Carnot Theorem" provides comprehensive definitions and mathematical expressions of both classical and modern thermodynamics. The goal is to develop the fundamental theory on an extended Carnot theorem without incorporating any extraneous assumptions. In particular, it offers a fundamental thermodynamic and calculational methodology for the synthesis of low-pressure diamonds. It also discusses many "abnormal phenomena", such as spiral reactions, cyclic reactions, chemical oscillations, low-pressure carat-size diamond growth, biological systems, and more. The book is intended for chemists and physicists working in thermodynamics, chemical thermodynamics, phase diagrams, biochemistry and complex systems, as well as graduate students in these fields. Jitao Wang is a professor emeritus at Fudan University, Shanghai, China.

Learning to Play Efficient Coarse Correlated Equilibria

KAUST Repository

Borowski, Holly P.; Marden, Jason R.; Shamma, Jeff S.

2018-01-01

The majority of the distributed learning literature focuses on convergence to Nash equilibria. Coarse correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However

Electrochemical dissolution of surface alloys in acids: Thermodynamic trends from first-principles calculations

DEFF Research Database (Denmark)

Greeley, Jeffrey Philip; Nørskov, Jens Kehlet

2007-01-01

A simple procedure is introduced to use periodic Density Functional Theory calculations to estimate trends in the thermodynamics of surface alloy dissolution in acidic media. With this approach, the dissolution potentials for solute metal atoms embedded in the surface layer of various host metals...

Thermodynamic modeling, energy equipartition, and nonconservation of entropy for discrete-time dynamical systems

Directory of Open Access Journals (Sweden)

Chellaboina Vijaysekhar

2005-01-01

Full Text Available We develop thermodynamic models for discrete-time large-scale dynamical systems. Specifically, using compartmental dynamical system theory, we develop energy flow models possessing energy conservation, energy equipartition, temperature equipartition, and entropy nonconservation principles for discrete-time, large-scale dynamical systems. Furthermore, we introduce a new and dual notion to entropy; namely, ectropy, as a measure of the tendency of a dynamical system to do useful work and grow more organized, and show that conservation of energy in an isolated thermodynamic system necessarily leads to nonconservation of ectropy and entropy. In addition, using the system ectropy as a Lyapunov function candidate, we show that our discrete-time, large-scale thermodynamic energy flow model has convergent trajectories to Lyapunov stable equilibria determined by the system initial subsystem energies.

Prediction of Pure Component Adsorption Equilibria Using an Adsorption Isotherm Equation Based on Vacancy Solution Theory

DEFF Research Database (Denmark)

Marcussen, Lis; Aasberg-Petersen, K.; Krøll, Annette Elisabeth

2000-01-01

An adsorption isotherm equation for nonideal pure component adsorption based on vacancy solution theory and the Non-Random-Two-Liquid (NRTL) equation is found to be useful for predicting pure component adsorption equilibria at a variety of conditions. The isotherm equation is evaluated successfully...... adsorption systems, spreading pressure and isosteric heat of adsorption are also calculated....

Isobaric (vapor + liquid) equilibria of 1-ethyl-3-methylimidazolium ethylsulfate plus (propionaldehyde or valeraldehyde): Experimental data and prediction

International Nuclear Information System (INIS)

Alvarez, Victor H.; Mattedi, Silvana; Aznar, Martin

2011-01-01

Research highlights: → We report density, refraction index, and VLE for (propionaldehyde or valeraldehyde) + [emim][EtSO 4 ]. → The Peng -Robinson + Wong -Sandler + COSMO-SAC model was used to predict density and VLE. → The densities were predicted with deviations below than 2.3%. → The experimental VLE was predicted with deviations below than 1.6%. - Abstract: This paper reports the density, refraction index, and (vapor + liquid) equilibria (VLE) for binary systems {aldehyde + 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO 4 ])}: {propionaldehyde + [emim][EtSO 4 ]} and {valeraldehyde + [emim][EtSO 4 ]}. The uncertainties for the temperature, pressure, and compositions measurements for the phase equilibria are ±0.1 K, ±0.01 kPa and ±0.0004, respectively. A qualitative analysis of the variation of the properties with changes in solvent and temperature was performed. The Peng-Robinson equation of state (PR EoS), coupled with the Wong-Sandler mixing rule (WS), is used to describe the experimental data. To calculate activity coefficients we used three different models: NRTL, UNIQUAC, and COSMO-SAC. Since the predictive liquid activity coefficient model COSMO-SAC is used in the Wong-Sandler mixing rule, the resulting thermodynamic model is a completely predictive one. The prediction results for the density and for the (vapor + liquid) equilibria have a deviation lower than 2.3% and 1.6%, respectively. The (vapor + liquid) equilibria predictions show a good description for the propionaldehyde system and only a qualitative description for the valeraldehyde system.

The heat is on: thermodynamic analysis in fragment-based drug discovery

NARCIS (Netherlands)

Edink, E.S.; Jansen, C.J.W.; Leurs, R.; De Esch, I.J.

2010-01-01

Thermodynamic analysis provides access to the determinants of binding affinity, enthalpy and entropy. In fragment-based drug discovery (FBDD), thermodynamic analysis provides a powerful tool to discriminate fragments based on their potential for successful optimization. The thermodynamic data

Thermodynamic Tuning of Mg-Based Hydrogen Storage Alloys: A Review

Science.gov (United States)

Zhu, Min; Lu, Yanshan; Ouyang, Liuzhang; Wang, Hui

2013-01-01

Mg-based hydrides are one of the most promising hydrogen storage materials because of their relatively high storage capacity, abundance, and low cost. However, slow kinetics and stable thermodynamics hinder their practical application. In contrast to the substantial progress in the enhancement of the hydrogenation/dehydrogenation kinetics, thermodynamic tuning is still a great challenge for Mg-based alloys. At present, the main strategies to alter the thermodynamics of Mg/MgH2 are alloying, nanostructuring, and changing the reaction pathway. Using these approaches, thermodynamic tuning has been achieved to some extent, but it is still far from that required for practical application. In this article, we summarize the advantages and disadvantages of these strategies. Based on the current progress, finding reversible systems with high hydrogen capacity and effectively tailored reaction enthalpy offers a promising route for tuning the thermodynamics of Mg-based hydrogen storage alloys. PMID:28788353

The Bases of Chemical Thermodynamics, Volumes 1 and 2 by Michael Graetzel and Pierre Infelta

Science.gov (United States)

van Hecke, Gerald R.

2001-09-01

Universal Publishers: Parkland, FL, 2000. Vol. 1: 298 pp. ISBN 1-58112-772-3. 25.95. Vol. 2: 300 pp. ISBN 1-58112-771-5. 25.95. Rarely does one pick up a text and find in it so many of one's favorite pedagogical devices. Graetzel and Infelta was a treat to read. The text offers many new and clever derivations of the well-worn equations of chemical thermodynamics and for this reason alone the text should be on the bookshelf of every serious teacher of thermodynamics. The writing is easy to read: not terse, but carefully worded as a thermodynamics text should be. There are no fancy sidebars or tidbits, just a straightforward presentation of material that is frankly refreshing. A brief description of the text should come next, for it consist of two volumes. You find in Volume 1 introductory material, the laws of thermodynamics, auxiliary functions, molar and partial molar quantities, gases, and component phase equilibria; in Volume 2, the energetics of chemical reactions, chemical equilibria, properties of ideal and nonideal mixtures, and an introduction to statistical mechanics. The authors make careful definitions of those slippery concepts, systems, states, and extensive and intensive variables, and use those definitions to show how the thermodynamic state of a system can be described in a minimum number of variables. A pedagogical feature that makes a hit with me is the authors' disuse of deltas. They explicitly write Ufinal - Uinitial instead of just good old DU, which really tells a reader nothing. How much better our students would understand thermodynamics if we were to ban D 's remains to be seen. The authors are consistent in their disuse of D 's except for standard expressions such as DrG°. Entropy, every beginning student's random nightmare, is introduced by the concept of arrangements available to the system. The number of arrangements can be quantified by various permutation formulas. Thank the authors for sticking with arrangements that can be

Modern thermodynamics. Based on the extended Carnot theorem

Energy Technology Data Exchange (ETDEWEB)

Wang, Jitao [Fudan Univ., Shanghai (China). Microelectronics Dept.

2011-07-01

''Modern Thermodynamics- Based on the Extended Carnot Theorem'' provides comprehensive definitions and mathematical expressions of both classical and modern thermodynamics. The goal is to develop the fundamental theory on an extended Carnot theorem without incorporating any extraneous assumptions. In particular, it offers a fundamental thermodynamic and calculational methodology for the synthesis of low-pressure diamonds. It also discusses many ''abnormal phenomena'', such as spiral reactions, cyclic reactions, chemical oscillations, low-pressure carat-size diamond growth, biological systems, and more. The book is intended for chemists and physicists working in thermodynamics, chemical thermodynamics, phase diagrams, biochemistry and complex systems, as well as graduate students in these fields. Jitao Wang is a professor emeritus at Fudan University, Shanghai, China. (orig.)

Another dimension to metamorphic phase equilibria: the power of interactive movies for understanding complex phase diagram sections

Science.gov (United States)

Moulas, E.; Caddick, M. J.; Tisato, N.; Burg, J.-P.

2012-04-01

The investigation of metamorphic phase equilibria, using software packages that perform thermodynamic calculations, involves a series of important assumptions whose validity can often be questioned but are difficult to test. For example, potential influences of deformation on phase relations, and modification of effective reactant composition (X) at successive stages of equilibrium may both introduce significant uncertainty into phase diagram calculations. This is generally difficult to model with currently available techniques, and is typically not well quantified. We present here a method to investigate such phenomena along pre-defined Pressure-Temperature (P-T) paths, calculating local equilibrium via Gibbs energy minimization. An automated strategy to investigate complex changes in the effective equilibration composition has been developed. This demonstrates the consequences of specified X modification and, more importantly, permits automated calculation of X changes that are likely along the requested path if considering several specified processes. Here we describe calculations considering two such processes and show an additional example of a metamorphic texture that is difficult to model with current techniques. Firstly, we explore the assumption that although water saturation and bulk-rock equilibrium are generally considered to be valid assumptions in the calculation of phase equilibria, the saturation of thermodynamic components ignores mechanical effects that the fluid/melt phase can impose on the rock, which in turn can modify the effective equilibrium composition. Secondly, we examine how mass fractionation caused by porphyroblast growth at low temperatures or progressive melt extraction at high temperatures successively modifies X out of the plane of the initial diagram, complicating the process of determining best-fit P-T paths for natural samples. In particular, retrograde processes are poorly modeled without careful consideration of prograde

Learning to Play Efficient Coarse Correlated Equilibria

KAUST Repository

Borowski, Holly P.

2018-03-10

The majority of the distributed learning literature focuses on convergence to Nash equilibria. Coarse correlated equilibria, on the other hand, can often characterize more efficient collective behavior than even the best Nash equilibrium. However, there are no existing distributed learning algorithms that converge to specific coarse correlated equilibria. In this paper, we provide one such algorithm, which guarantees that the agents’ collective joint strategy will constitute an efficient coarse correlated equilibrium with high probability. The key to attaining efficient correlated behavior through distributed learning involves incorporating a common random signal into the learning environment.

Multiple Equilibria in Noisy Rational Expectations Economies

DEFF Research Database (Denmark)

Pálvölgyi, Dömötör; Venter, Gyuri

with a continuous price function. However, we also construct a tractable class of equilibria with discontinuous prices that have very different economic implications, including (i) jumps and crashes, (ii) significant revisions in uninformed belief due to small changes in the market price, (iii) “upward......-sloping” demand curves, (iv) higher prices leading to future returns that are higher in expectation (price drift) and (v) more positively skewed. Discontinuous equilibria can be arbitrarily close to being fully-revealing. Finally, discontinuous equilibria with the same construction also exist in Hellwig (1980)....

Thermodynamic properties and cloud droplet activation of a series of oxo-acids

Directory of Open Access Journals (Sweden)

M. Frosch

2010-07-01

Full Text Available We have investigated the thermodynamic properties of four aliphatic oxo-dicarboyxlic acids identified or thought to be present in atmospheric particulate matter: oxosuccinic acid, 2-oxoglutaric acid, 3-oxoglutaric acid, and 4-oxopimelic acid. The compounds were characterized in terms of their cloud condensation nuclei (CCN activity, vapor pressure, density, and tendency to decarboxylate in aqueous solution. We deployed a variety of experimental techniques and instruments: a CCN counter, a Tandem Differential Mobililty Analyzer (TDMA coupled with a laminar flow-tube, and liquid chromatography/mass spectrometry (LC/MS. The presence of the oxo functional group in the α-position causes the vapor pressure of the compounds to diminish by an order of magnitude with respect to the parent dicarboxylic acid, while the CCN activity is similar or increased. Dicarboxylic acids with an oxo-group in the β-position decarboxylate in aqueous solution. We studied the effects of this process on our measurements and findings.

Acid-base properties of ceramic powders

International Nuclear Information System (INIS)

Bleier, A.

1983-01-01

This chapter addresses the fundamental aspects of potentiometric titration, electrokinetics, and conductometric titration in evaluating surface and interfacial thermodynamic behavior. Emphasizes the characterization of aqueous systems which are pertinent to the processing of ceramic powders. Attempts to clarify the role of novel analytical techniques that will increasingly contribute to the advanced characterization of ceramic powders. Evaluates recently developed acid-base and complexation concepts and their applications to the processing of oxide ceramics

Comparison of the thermodynamic properties and high temperature chemical behavior of lanthanide and actinide oxides

International Nuclear Information System (INIS)

Ackermann, R.J.; Rauh, E.G.

1977-01-01

The thermodynamic properties of the lanthanide and actinide oxides are examined, compared, and associated with a variety of high temperature chemical behavior. Trends are cited resulting from a number of thermodynamic and spectroscopic correlations involving solid phases, species in aqueous solution, and molecules and ions in the vapor phase. Inadequacies in the data and alternative approaches are discussed. The characterization of nonstoichiometric phases stable only at high temperatures is related to a network of heterogeneous and homogeneous equilibria. A broad perspective of similarity and dissimilarity between the lanthanides and actinides emerges and forms the basis of the projected needs for further study

High-pressure fluid-phase equilibria: Experimental methods and systems investigated (2000-2004)

DEFF Research Database (Denmark)

Dohrn, Ralf; Peper, Stephanie; Fonseca, José

2010-01-01

As a part of a series of reviews, a compilation of systems for which high-pressure phase-equilibrium data were published between 2000 and 2004 is given. Vapor-liquid equilibria, liquid-liquid equilibria, vapor-liquid-liquid equilibria,solid-liquid equilibria, solid-vapor equilibria, solid-vapor-l...

Thermodynamics of mixed-ligand complex formation of mercury (II) ethylenediaminetetraacetate with amino acids in solution

Energy Technology Data Exchange (ETDEWEB)

Pyreu, Dmitrii, E-mail: pyreu@mail.ru [Department of Inorganic and Analytic Chemistry, Ivanovo State University, Ermak 39, Ivanovo 153025 (Russian Federation); Kozlovskii, Eugenii [Department of Inorganic and Analytic Chemistry, Ivanovo State University, Ermak 39, Ivanovo 153025 (Russian Federation); Gruzdev, Matvei; Kumeev, Roman [Institute of Solution Chemistry, Ivanovo (Russian Federation)

2012-11-20

Highlights: Black-Right-Pointing-Pointer Stable mixed ligand complexes of HgEdta with amino acids at physiological pH value. Black-Right-Pointing-Pointer The thermodynamic and NMR data evident the ambidentate coordination mode of arginine. Black-Right-Pointing-Pointer Participation of the guanidinic group of Arg in coordination process. Black-Right-Pointing-Pointer Binuclear complexes (HgEdta){sub 2}L with the bridging function of amino acid. - Abstract: The mixed-ligand complex formation in the systems Hg{sup 2+} - Edta{sup 4-} - L{sup -}(L = Arg, Orn, Ser) has been studied by means of calorimetry, pH-potentiometry and NMR spectroscopy in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO{sub 3}). The thermodynamic parameters of formation of the HgEdtaL, HgEdtaHL and (HgEdta){sub 2}L complexes have been determined. The most probable coordination mode for the complexone and the amino acid in the mixed-ligand complexes was discussed.

Extraction equilibria of amino acids by Di (2-ethylhexyl) phosphoric acid in n-heptane solutions; Di (2-ethylhexyl) rinsan no n-heptane yoeki ni yoru aminosan no chushutsu heiko

Energy Technology Data Exchange (ETDEWEB)

Takahashi, M. [Suzuka National College of Technology, Mie (Japan); Tani, F. [Toyohashi University of Technology, Aichi (Japan); Kawai, Y. [Wako Jyunyaku Co. Ltd., Osaka (Japan); Takeuchi, H. [Nagoya University, Nagoya (Japan). Faculty of Engineering

1997-03-10

The extraction equilibria (i.e., distribution ratio) of amino acids by Di (2-ethyl hexyl) phosphoric acid in n-heptane solutions was investigated at a temperature of 298.2 K in the low pH range (of 2 to 5). The equal amount of an amino acid solution and an extracted solution with the predetermined concentration were shaken using a flask, and the concentration of amino acid in water phase was analyzed by a ninhydrin method. The concentration in organic phase was obtained by the concentration analysis in water phase and the material balance method after the amino acid is back-extracted by solution hydrochloride. The distribution ratio is in inverse proportion to the hydrogen ion concentration and in proportion to the 0.5th power of extracted agent concentration. The equilibrium constant is 0.650, 0.420, 0.320, 0.275, 0.064, and 0.040 mol{sup 0.5}/m{sup 1.5} in L-phenylalanine, L-tryptophane, L-leucine, L-methionine, glycine, and L-alanine, respectively. The equilibrium constant of the largest L-phenylalanine is 16 times as high as the smallest alanine. The extracted equilibrium constant increased as the hydrophobic property of amino acid increases. 18 refs., 10 figs., 1 tab.

Thermodynamic properties of isomeric iso-butoxybenzoic acids: Experimental and theoretical study

International Nuclear Information System (INIS)

Jakubczyk, Michał; Sporzyński, Andrzej; Emel’yanenko, Vladimir N.; Varfolomeev, Mikhail A.; Verevkin, Sergey P.

2015-01-01

Highlights: • Vapor pressures of butoxy benzoic acid derivatives were measured. • Vaporization, sublimation and fusion enthalpies were derived. • Molar enthalpies of formation were measured by calorimetry. • Thermochemical data tested for consistency using additivity rules and computations. • Simple additivity method suggested for prediction thermochemical properties. - Abstract: Standard (p° = 0.1 MPa) molar enthalpies of formation at the temperature T = 298.15 K of the 2-, 3-, and 4-iso-butoxybenzoic acids were measured using the combustion calorimetry. Standard molar enthalpies of vaporization and sublimation were derived from the vapor pressure temperature dependencies measured by the transpiration method. Molar enthalpies of the solid state phase transitions were measured by the DSC. Thermodynamic data on alkoxy substituted benzoic acids available in the literature were collected and combined with own experimental results. This data set on alkoxybenzoic acids was evaluated by using quantum-chemical and group-additivity methods

Thermodynamic properties of isomeric iso-butoxybenzoic acids: Experimental and theoretical study

Energy Technology Data Exchange (ETDEWEB)

Jakubczyk, Michał; Sporzyński, Andrzej [Faculty of Chemistry, Warsaw University of Technology, 00-664 Warszawa (Poland); Emel’yanenko, Vladimir N.; Varfolomeev, Mikhail A. [Department of Physical Chemistry, Kazan Federal University, 420008 Kazan (Russian Federation); Verevkin, Sergey P., E-mail: sergey.verevkin@uni-rostock.de [Department of Physical Chemistry, Kazan Federal University, 420008 Kazan (Russian Federation); Department of Physical Chemistry and Department, Science and Technology of Life, Light and Matter, University of Rostock, D-18059 Rostock (Germany)

2015-09-10

Highlights: • Vapor pressures of butoxy benzoic acid derivatives were measured. • Vaporization, sublimation and fusion enthalpies were derived. • Molar enthalpies of formation were measured by calorimetry. • Thermochemical data tested for consistency using additivity rules and computations. • Simple additivity method suggested for prediction thermochemical properties. - Abstract: Standard (p° = 0.1 MPa) molar enthalpies of formation at the temperature T = 298.15 K of the 2-, 3-, and 4-iso-butoxybenzoic acids were measured using the combustion calorimetry. Standard molar enthalpies of vaporization and sublimation were derived from the vapor pressure temperature dependencies measured by the transpiration method. Molar enthalpies of the solid state phase transitions were measured by the DSC. Thermodynamic data on alkoxy substituted benzoic acids available in the literature were collected and combined with own experimental results. This data set on alkoxybenzoic acids was evaluated by using quantum-chemical and group-additivity methods.

Stability of relative equilibria of three vortices

DEFF Research Database (Denmark)

Aref, Hassan

2009-01-01

Three point vortices on the unbounded plane have relative equilibria wherein the vortices either form an equilateral triangle or are collinear. While the stability analysis of the equilateral triangle configurations is straightforward, that of the collinear relative equilibria is considerably mor...

A combined experimental and computational thermodynamic study of fluorene-9-methanol and fluorene-9-carboxylic acid

International Nuclear Information System (INIS)

Oliveira, Juliana A.S.A.; Calvinho, Maria M.; Notario, R.; Monte, Manuel J.S.; Ribeiro da Silva, Maria D.M.C.

2013-01-01

Highlights: • A thermodynamic study of two fluorene derivatives is presented. • Vapour pressures and energies of combustion were measured. • Enthalpy, entropy and Gibbs energy of sublimation were derived. • Enthalpy and Gibbs energy of formation in crystal and gas phases were calculated. • Gas phase enthalpy of formation was also estimated by quantum chemical calculations. -- Abstract: This work reports an experimental and computational thermodynamic study performed on two 9-fluorene derivatives: fluorene-9-methanol and fluorene-9-carboxylic acid. The standard (p o = 0.1 MPa) molar enthalpies of formation in the crystalline phase of these compounds were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. A static method, based on a capacitance diaphragm gauge, and a Knudsen effusion method were used to perform the vapour pressure study of the referred compounds, yielding accurate determination of the standard molar enthalpies and entropies of sublimation and vaporisation. For fluorene-9-carboxylic acid, the enthalpy of sublimation was also determined using Calvet microcalorimetry. The enthalpy of fusion of both compounds was derived indirectly from vapour pressure results and directly from DSC experiments. Combining the thermodynamic parameters of the compounds studied, the standard Gibbs energy of formation in crystalline and gaseous phases were derived as well as the standard molar enthalpy of formation in the gaseous phase. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared with the experimental values

Looking for multiple equilibria when geography matters : German city growth and the WWII shock

NARCIS (Netherlands)

Bosker, Maarten; Brakman, Steven; Garretsen, Harry; Schramm, Marc

Based on the methodology of Davis and Weinstein, we look for multiple equilibria in German city growth. Bytaking the bombing of Germany during WWII as an example of a large, temporary shock, we analyze whether German city growth is characterized by multiple equilibria. In doing so, we allow for

Aluminum deoxidation equilibria and inclusion modification mechanism by calcium treatment of stainless steel melts

International Nuclear Information System (INIS)

Park, Joo Hyun; Kim, Dong Sik; Kim, Yong Hwan; Lee, Sang Beom

2005-01-01

A thermodynamic equilibrium between aluminum and oxygen along with the inclusion morphology in Fe-16%Cr stainless steel was investigated to understand the fundamentals of aluminum deoxidation technology for ferritic stainless steels. Further, the effects of calcium addition on the changes in chemistry and morphology of inclusions were discussed. The measured results for aluminum-oxygen equilibria exhibit relatively good agreement with the calculated values, indicating that the introduction of the first- and second-order interaction parameters, recently reported, is reasonable to numerically express aluminum deoxidation equilibrium in a ferritic stainless steel. In the composition of dissolved aluminum content greater than about 60 ppm, pure alumina particles were observed, while the alumino-manganese silicates containing Cr 2 O 3 were appeared at less than 20 mass ppm of dissolved aluminum. The formation of calcium aluminate inclusions after Ca treatment could be discussed based on the thermodynamic equilibrium with calcium, aluminum, and oxygen in the steel melts. In the composition of steel melt with relatively high content of calcium and low aluminum, the log(X CaO /X Al 2 O 3 ) of inclusions linearly increases with increasing the log [a Ca /a Al 2 ·a O 2 ] with the slope close to unity. However, the slope of the line is significantly lower than the expected value in the composition of steel melt with relatively low calcium and high aluminum contents

Phase equilibria in TlX-Cd(Zn)X (X-S, Se, Te) systems

International Nuclear Information System (INIS)

Gusejnov, F.Kh.; Babanly, M.B.; Kuliev, A.A.

1982-01-01

The methods of DTA, RPA and measurement of the alloys microhardness have been used to investigate the phase equilibria in the TlX-Zn(Cd)X systems. It is established that the TlZn(Cd)X 2 compounds, the presence of which is mentioned in the literature earlier, do not form in these systems. The TlSe-Zn(Cd)Se systems apply to the simple eutectic type and characterized by digenerated eutectic near the TlSe. Thermodynamical analysis of the liquidus of the TlSe-CdSe and TlTe-Zn(Cd)Te systems in approximation of the regular solutions, taking into account the dissociation of tallium chalcogenides in liquid phase, is made

Governing Influence of Thermodynamic and Chemical Equilibria on the Interfacial Properties in Complex Fluids.

Science.gov (United States)

Harikrishnan, A R; Dhar, Purbarun; Gedupudi, Sateesh; Das, Sarit K

2018-04-12

We propose a comprehensive analysis and a quasi-analytical mathematical formalism to predict the surface tension and contact angles of complex surfactant-infused nanocolloids. The model rests on the foundations of the interaction potentials for the interfacial adsorption-desorption dynamics in complex multicomponent colloids. Surfactant-infused nanoparticle-laden interface problems are difficult to deal with because of the many-body interactions and interfaces involved at the meso-nanoscales. The model is based on the governing role of thermodynamic and chemical equilibrium parameters in modulating the interfacial energies. The influence of parameters such as the presence of surfactants, nanoparticles, and surfactant-capped nanoparticles on interfacial dynamics is revealed by the analysis. Solely based on the knowledge of interfacial properties of independent surfactant solutions and nanocolloids, the same can be deduced for complex surfactant-based nanocolloids through the proposed approach. The model accurately predicts the equilibrium surface tension and contact angle of complex nanocolloids available in the existing literature and present experimental findings.

The SX Solver: A New Computer Program for Analyzing Solvent-Extraction Equilibria

International Nuclear Information System (INIS)

McNamara, B.K.; Rapko, B.M.; Lumetta, G.J.

1999-01-01

A new computer program, the SX Solver, has been developed to analyze solvent-extraction equilibria. The program operates out of Microsoft Excel and uses the built-in ''Solver'' function to minimize the sum of the square of the residuals between measured and calculated distribution coefficients. The extraction of nitric acid by tributylphosphate has been modeled to illustrate the program's use

Existence of pareto equilibria for multiobjective games without compactness

OpenAIRE

Shiraishi, Yuya; Kuroiwa, Daishi

2013-01-01

In this paper, we investigate the existence of Pareto and weak Pareto equilibria for multiobjective games without compactness. By employing an existence theorem of Pareto equilibria due to Yu and Yuan([10]), several existence theorems of Pareto and weak Pareto equilibria for the multiobjective games are established in a similar way to Flores-B´azan.

Computing Nash equilibria through computational intelligence methods

Science.gov (United States)

Pavlidis, N. G.; Parsopoulos, K. E.; Vrahatis, M. N.

2005-03-01

Nash equilibrium constitutes a central solution concept in game theory. The task of detecting the Nash equilibria of a finite strategic game remains a challenging problem up-to-date. This paper investigates the effectiveness of three computational intelligence techniques, namely, covariance matrix adaptation evolution strategies, particle swarm optimization, as well as, differential evolution, to compute Nash equilibria of finite strategic games, as global minima of a real-valued, nonnegative function. An issue of particular interest is to detect more than one Nash equilibria of a game. The performance of the considered computational intelligence methods on this problem is investigated using multistart and deflection.

Thermodynamic properties of sea air

Directory of Open Access Journals (Sweden)

R. Feistel

2010-02-01

Full Text Available Very accurate thermodynamic potential functions are available for fluid water, ice, seawater and humid air covering wide ranges of temperature and pressure conditions. They permit the consistent computation of all equilibrium properties as, for example, required for coupled atmosphere-ocean models or the analysis of observational or experimental data. With the exception of humid air, these potential functions are already formulated as international standards released by the International Association for the Properties of Water and Steam (IAPWS, and have been adopted in 2009 for oceanography by IOC/UNESCO.

In this paper, we derive a collection of formulas for important quantities expressed in terms of the thermodynamic potentials, valid for typical phase transitions and composite systems of humid air and water/ice/seawater. Particular attention is given to equilibria between seawater and humid air, referred to as "sea air" here. In a related initiative, these formulas will soon be implemented in a source-code library for easy practical use. The library is primarily aimed at oceanographic applications but will be relevant to air-sea interaction and meteorology as well.

The formulas provided are valid for any consistent set of suitable thermodynamic potential functions. Here we adopt potential functions from previous publications in which they are constructed from theoretical laws and empirical data; they are briefly summarized in the appendix. The formulas make use of the full accuracy of these thermodynamic potentials, without additional approximations or empirical coefficients. They are expressed in the temperature scale ITS-90 and the 2008 Reference-Composition Salinity Scale.

Phase equilibria in the BaUO3-BaZrO3-BaMoO3 system

International Nuclear Information System (INIS)

Kurosaki, Ken; Yamanaka, Shinsuke; Matsuda, Tetsushi; Uno, Masayoshi; Yamamoto, Kazuya; Namekawa, Takashi

2002-01-01

The phase equilibria in the pseudo-ternary BaUO 3 -BaZrO 3 -BaMoO 3 system were studied to understand the thermochemical properties of the perovskite type gray oxide phase in high burnup MOX fuel. Thermodynamic equilibrium calculation for the system was performed by using a Chem Sage program under the various oxygen potentials. Solid solutions existing in the system were treated by an ideal solution model. The present calculation results well agreed with the previous reported post irradiation examination results, showing that BaMoO 3 was scarcely included in the gray oxide phase. (author)

Stochastic Equilibria under Imprecise Deviations in Terminal-Reward Concurrent Games

Directory of Open Access Journals (Sweden)

Patricia Bouyer

2016-09-01

Full Text Available We study the existence of mixed-strategy equilibria in concurrent games played on graphs. While existence is guaranteed with safety objectives for each player, Nash equilibria need not exist when players are given arbitrary terminal-reward objectives, and their existence is undecidable with qualitative reachability objectives (and only three players. However, these results rely on the fact that the players can enforce infinite plays while trying to improve their payoffs. In this paper, we introduce a relaxed notion of equilibria, where deviations are imprecise. We prove that contrary to Nash equilibria, such (stationary equilibria always exist, and we develop a PSPACE algorithm to compute one.

Optimization of thermal systems based on finite-time thermodynamics and thermoeconomics

Energy Technology Data Exchange (ETDEWEB)

Durmayaz, A. [Istanbul Technical University (Turkey). Department of Mechanical Engineering; Sogut, O.S. [Istanbul Technical University, Maslak (Turkey). Department of Naval Architecture and Ocean Engineering; Sahin, B. [Yildiz Technical University, Besiktas, Istanbul (Turkey). Department of Naval Architecture; Yavuz, H. [Istanbul Technical University, Maslak (Turkey). Institute of Energy

2004-07-01

The irreversibilities originating from finite-time and finite-size constraints are important in the real thermal system optimization. Since classical thermodynamic analysis based on thermodynamic equilibrium do not consider these constraints directly, it is necessary to consider the energy transfer between the system and its surroundings in the rate form. Finite-time thermodynamics provides a fundamental starting point for the optimization of real thermal systems including the fundamental concepts of heat transfer and fluid mechanics to classical thermodynamics. In this study, optimization studies of thermal systems, that consider various objective functions, based on finite-time thermodynamics and thermoeconomics are reviewed. (author)

Steric and thermodynamic limits of design for the incorporation of large unnatural amino acids in aminoacyl-tRNA synthetase enzymes.

Science.gov (United States)

Armen, Roger S; Schiller, Stefan M; Brooks, Charles L

2010-06-01

Orthogonal aminoacyl-tRNA synthetase/tRNA pairs from archaea have been evolved to facilitate site specific in vivo incorporation of unnatural amino acids into proteins in Escherichia coli. Using this approach, unnatural amino acids have been successfully incorporated with high translational efficiency and fidelity. In this study, CHARMM-based molecular docking and free energy calculations were used to evaluate rational design of specific protein-ligand interactions for aminoacyl-tRNA synthetases. A series of novel unnatural amino acid ligands were docked into the p-benzoyl-L-phenylalanine tRNA synthetase, which revealed that the binding pocket of the enzyme does not provide sufficient space for significantly larger ligands. Specific binding site residues were mutated to alanine to create additional space to accommodate larger target ligands, and then mutations were introduced to improve binding free energy. This approach was used to redesign binding sites for several different target ligands, which were then tested against the standard 20 amino acids to verify target specificity. Only the synthetase designed to bind Man-alpha-O-Tyr was predicted to be sufficiently selective for the target ligand and also thermodynamically stable. Our study suggests that extensive redesign of the tRNA synthatase binding pocket for large bulky ligands may be quite thermodynamically unfavorable.

Ternary (liquid + liquid) equilibria of {bis(trifluoromethylsulfonyl)-amide based ionic liquids + butan-1-ol + water}

International Nuclear Information System (INIS)

Marciniak, Andrzej; Wlazło, Michał; Gawkowska, Joanna

2016-01-01

Highlights: • Ternary (liquid + liquid) equilibria for 3 ionic liquid + butanol + water systems. • The influence of ionic liquid structure on phase diagrams is discussed. • Influence of IL structure on S and β for butanol/water separation is discussed. - Abstract: Ternary (liquid + liquid) phase equilibria for 3 systems containing bis(trifluoromethylsulfonyl)-amide ionic liquids (1-buthyl-1-methylpiperidinium bis(trifluoromethylsulfonyl)-amide, 1-(2-methoxyethyl)-1-methylpiperidinium bis(trifluoromethylsulfonyl)-amide, {1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluorylsulfonyl)-amide) + butan-1-ol + water} have been determined at T = 298.15 K. The selectivity and solute distribution ratio were calculated for investigated systems and compared with literature data for other systems containing ionic liquids. In each system total solubility of butan-1-ol and low solubility of water in the ionic liquid is observed. The experimental results have been correlated using NRTL model. The influence of the structure of ionic liquid on phase equilibria, selectivity and solute distribution ratio is shortly discussed.

Asset pricing puzzles explained by incomplete Brownian equilibria

DEFF Research Database (Denmark)

Christensen, Peter Ove; Larsen, Kasper

We examine a class of Brownian based models which produce tractable incomplete equilibria. The models are based on finitely many investors with heterogeneous exponential utilities over intermediate consumption who receive partially unspanned income. The investors can trade continuously on a finit...... markets. Consequently, our model can simultaneously help explaining the risk-free rate and equity premium puzzles....

Temporal Asymmetry, Entropic Irreversibility, and Finite-Time Thermodynamics: From Parmenides–Einstein Time-Reversal Symmetry to the Heraclitan Entropic Arrow of Time

Directory of Open Access Journals (Sweden)

Wassim M. Haddad

2012-02-01

Full Text Available In this paper, we combine the two universalisms of thermodynamics and dynamical systems theory to develop a dynamical system formalism for classical thermodynamics. Specifically, using a compartmental dynamical system energy flow model we develop a state-space dynamical system model that captures the key aspects of thermodynamics, including its fundamental laws. In addition, we establish the existence of a unique, continuously differentiable global entropy function for our dynamical system model, and using Lyapunov stability theory we show that the proposed thermodynamic model has finite-time convergent trajectories to Lyapunov stable equilibria determined by the system initial energies. Finally, using the system entropy, we establish the absence of Poincaré recurrence for our thermodynamic model and develop clear and rigorous connections between irreversibility, the second law of thermodynamics, and the entropic arrow of time.

Phase equilibria and the thermodynamic properties of methyl and ethyl esters of carboxylic acids. 1. Methyl n-butanoate and ethyl propanoate

International Nuclear Information System (INIS)

Agafonova, Luba E.; Varushchenko, Raisa M.; Druzhinina, Anna I.; Polyakova, Olga V.

2012-01-01

Highlights: ► Heat capacities, fusion properties of CH 3 OC(O)C 3 H 7 measured by adiabatic calorimetry. ► The temperature dependence of vapour pressure determined by comparative ebulliometry. ► The thermodynamic functions derived from experiment and calculated by DFT method. ► Extending vapour pressure of moderate interval to entire region of liquid. ► An increment of the entropy of carbonyl group was defined from experimental data. - Abstract: The heat capacity of methyl n-butanoate in crystalline and liquid states was measured by vacuum adiabatic calorimetry over the temperature range from (8 to 372) K. The triple point temperature, the enthalpy and entropy of fusion, and the purity of the sample were determined. The saturated vapour pressure and the boiling temperatures were determined by comparative ebulliometry in the “atmospheric” pressure range 10.8 ⩽ (p/kPa) ⩽ 99.6. The normal boiling temperature, T n.b , and the enthalpy of vaporization at T = 298.15 K and T n.b were derived. The thermodynamic functions (absolute entropy and changes of the enthalpy, and Gibbs free energy) were derived for the solid and liquid states in the temperature range studied and for the ideal gas state at T = 298.15 K. The ideal gas heat capacities and the absolute entropies of methyl n-butanoate (MeBu) and ethyl propanoate (EtPr) were calculated by statistical thermodynamics on the basis of the molecular constants determined by the use of density functional theory on the B3LYP level. The experimental vapour pressure of MeBu and EtPr of moderate temperature intervals, Δ exp T = (59/65) K, were extended to the entire range of the liquids, Δ liq T = (364.7/345.7) K by the methods of the corresponding states law and simultaneous treatment of the pT-parameters and low-temperature heat capacities of the ideal gas and liquid, respectively. An additive contribution of the carbonyl group CO–(C, O) connected with C and O atoms was determined for calculation of the

Strong Nash Equilibria and the Potential Maimizer

NARCIS (Netherlands)

van Megen, F.J.C.; Facchini, G.; Borm, P.E.M.; Tijs, S.H.

1996-01-01

A class of non cooperative games characterized by a `congestion e ect' is studied, in which there exists a strong Nash equilibrium, and the set of Nash equilibria, the set of strong Nash equilibria and the set of strategy pro les maximizing the potential function coincide.The structure of the class

Magnetoacoustic heating and FCT-equilibria in the belt pinch

International Nuclear Information System (INIS)

Erckmann, V.

1983-02-01

In the HECTOR belt pinch of high β plasma is produced by magnetic compression in a Tokamak geometry. After compresseion the initial β value can be varied between 0.2 and 0.8. During 5 μs the plasma is further heated by a fast magnetoacoustic wave with a frequency near the first harmonic of the ion cyclotronfrequency. For the first time the β-value of a pinch plasma could be increased further from 0.34 after compression to 0.46 at the end of the rf-heating cycle. By proper selection of the final β-value the region for resonance absorption of the heating wave can be shifted. Strong heating (200 MW) has been observed in the cases, where the resonance region has been located in the center of the plasma. In deuterium discharges an increase in ion temperature is observed during the heating process, whereas the electrons are energetically decoupled, showing no temperature increase. Strong plasma losses are found in the 200 MW range after the rf-heating process. The dominant mechanisms are charge exchange collisions with neutral gas atoms. During rf-heating and the subsequent cooling phase the magnetic flux is frozen due to the high conductivity of the plasma. The observed equilibria could be identified as flux conserving Tokamak (FCT) equilibria. Based on a two-dimensional code the time-evolution of the equilibria has been calculated. The q-profiles are time-independent, with increasing β the magnetic axis of the plasma is shifted towards the outer boundary of the torus, and finally the linear relation between β and βsub(pol), which is characteristic for low-β-equilibria, is no longer valid. Thus for the first time the existence of FCT-equilibria at high β has been demonstrated experimentally together with a qualitative agreement with FCT-theory. (orig./AH) [de

Free-boundary perturbed MHD equilibria

International Nuclear Information System (INIS)

Nührenberg, C

2012-01-01

The concept of perturbed ideal MHD equilibria [Boozer A H and Nuhrenberg C 2006 Phys. Plasmas 13 102501] is employed to study the influence of external error-fields and of small plasma-pressure changes on toroidal plasma equilibria. In tokamak and stellarator free-boundary calculations, benchmarks were successful of the perturbed-equilibrium version of the CAS3D stability code [Nührenberg C et al. 2009 Phys. Rev. Lett. 102 235001] with the ideal MHD equilibrium code NEMEC [Hirshman S P et al. 1986 Comput. Phys. Commun. 43 143].

Hydrostatic Equilibria of Rotating Stars with Realistic Equation of State

Science.gov (United States)

Yasutake, Nobutoshi; Fujisawa, Kotaro; Okawa, Hirotada; Yamada, Shoichi

Stars rotate generally, but it is a non-trivial issue to obtain hydrostatic equilibria for rapidly rotating stars theoretically, especially for baroclinic cases, in which the pressure depends not only on the density, but also on the temperature and compositions. It is clear that the stellar structures with realistic equation of state are the baroclinic cases, but there are not so many studies for such equilibria. In this study, we propose two methods to obtain hydrostatic equilibria considering rotation and baroclinicity, namely the weak-solution method and the strong-solution method. The former method is based on the variational principle, which is also applied to the calculation of the inhomogeneous phases, known as the pasta structures, in crust of neutron stars. We found this method might break the balance equation locally, then introduce the strong-solution method. Note that our method is formulated in the mass coordinate, and it is hence appropriated for the stellar evolution calculations.

Isotherm, kinetic and thermodynamics study of humic acid removal process from aquatic environment by chitosan nano particle

Directory of Open Access Journals (Sweden)

Maryam Ghafoori

2016-09-01

Full Text Available Background and Aim: Humic substances include natural organic polyelectrolyte materials that formed most of the dissolved organic carbon in aquatic environments. Reaction between humic substances and chlorine leading to formation of disinfection byproducts (DBPs those are toxic, carcinogenic and mutagenic. The aim of this study was investigation of isotherms, kinetics and thermodynamics of humic acid removal process by nano chitosan from aquatic environment. Materials and Methods: This practical research was an experimental study that performed in a batch system. The effect of various parameters such as pH, humic acid concentration, contact time, adsorbent dosage, isotherms, thermodynamics and Kinetics of humic acid adsorption process were investigated. Humic acid concentration measured using spectrophotometer at wave length of 254 nm. Results: The results of this research showed that maximum adsorption capacity of nanochitosan that fall out in concentration of 50 mg/l and contact time of 90 minutes was 52.34 mg/g. Also, the maximum adsorption was observed in pH = 4 and adsorbent dosage 0.02 g. Laboratory data show that adsorption of humic acid by nanochitosan follow the Langmuir isotherm model. According to result of thermodynamic study, entropy changes (ΔS was equal to 2.24 J/mol°k, enthalpy changes (ΔH was equal to 870 kJ/mol and Gibbs free energy (ΔG was negative that represent the adsorption process is spontaneous and endothermic. The kinetics of adsorption has a good compliant with pseudo second order model. Conclusion: Regarding to results of this study, nano chitosan can be suggested as a good adsorbent for the removal of humic acids from aqueous solutions.

Determination of thermodynamic parameters of tautomerization in gas phase by mass spectrometry and DFT calculations: Keto-enol versus nitrile-ketenimine equilibria.

Science.gov (United States)

Giussi, Juan M; Gastaca, Belen; Albesa, Alberto; Cortizo, M Susana; Allegretti, Patricia E

2011-02-01

The study of tautomerics equilibria is really important because the reactivity of each compound with tautomeric capacity can be determined from the proportion of each tautomer. In the present work the tautomeric equilibria in some γ,δ-unsaturated β-hydroxynitriles and γ,δ-unsaturated β-ketonitriles were studied. The first family of compounds presents two possible theoretical tautomers, nitrile and ketenimine, while the second one presents four possible theoretical tautomers, keto-nitrile, enol (E and Z)-nitrile and keto-ketenimine. The equilibrium in gas phase was studied by gas chromatography-mass spectrometry (GC-MS). Tautomerization enthalpies were calculated by this methodology, and results were compared with those obtained by density functional theory (DFT) calculations, observing a good agreement between them. Nitrile tautomers were favored within the first family of compounds, while keto-nitrile tautomers were favored in the second family. Copyright © 2010 Elsevier B.V. All rights reserved.

Fe-solubility of Ni7S6 and Ni9S8: Thermodynamic analysis

International Nuclear Information System (INIS)

Waldner, P.

2011-01-01

Experimental data on phase equilibria have been used for thermodynamic analysis of the iron solubility of the nickel sulfides Ni 7 S 6 and Ni 9 S 8 . For both compounds, a two-sublattice approach within the framework of the compound energy formalism has been applied to perform Gibbs free energy modelling at 0.1 MPa total pressure consistently embedded in recent thermodynamic assessment studies of other iron-nickel-sulfides. The predicted maxima of iron solubility around 3 at% of Ni 7 S 6 and 5.5 at% of Ni 9 S 8 are confirmed by experimental data. The calculations of complex ternary phase relations with Fe-bearing Ni 7 S 6 and Ni 9 S 8 gain further improvement. The first internally consistent description of all thermodynamically stable phases known in the literature for the iron-nickel-sulfur system is completed.

Thermodynamic Activity-Based Progress Curve Analysis in Enzyme Kinetics.

Science.gov (United States)

Pleiss, Jürgen

2018-03-01

Macrokinetic Michaelis-Menten models based on thermodynamic activity provide insights into enzyme kinetics because they separate substrate-enzyme from substrate-solvent interactions. Kinetic parameters are estimated from experimental progress curves of enzyme-catalyzed reactions. Three pitfalls are discussed: deviations between thermodynamic and concentration-based models, product effects on the substrate activity coefficient, and product inhibition. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spectrophotometric study of the complexation equilibria of lanthanum(III) with 1,4-bis(4'-methylanilino)anthraquinone and the determination of lanthanum(III)

International Nuclear Information System (INIS)

Idriss, K.A.-R; El-Shahawy, A.S.; Sedaira, H.; Harfoush, A.A.

1985-01-01

The complexation equilibria of lanthanum(III) with 1,4-bis(4'-methylanilino)anthraquinone (Quinizarin Green) were studied spectrophotometrically in 40% V/V dimethylformamide using graphical analysis of the absorbance curves. The reaction mechanism of lanthanum with the bisarylaminoanthraquinone dye within the pH range 6 to 9.25 was demonstrated. The thermodynamic stabilities and the molar absorptivities of the complexes formed were determined. The optimum conditions for the spectrophotometric determination of La(III) with this reagent were found. (author)

Thermodynamics of pellet-cladding interaction

International Nuclear Information System (INIS)

Kyoh, Bunkei; Fuji, Kensho

1987-01-01

Equilibrium thermodynamic calculations are performed on the U-Zr-Cs-I-O system that is assumed to exist in the fuel-cladding gap of light water reactor (LWR) fuel under pellet-cladding interaction (PCI) failure condition. For this purpose a computer program called SOLGASMIX-PV for the calculation of complex multi-component equilibria is used, and the results of postirradiation examination are interpreted. The analysis of the thermodynamics of the system U-Zr-Cs-I-O indicates that cesium and iodine are assumed to be released from fuel pellet into the fuel-cladding gap as CsI, therefore, the Cs/I ratio in fuel-cladding bonding zone is one. The important condensed phases in this region are UO 2 , U 3 O 8 , Cs 2 U 2 O 7 , Cs 2 U 15 O 46 , ZrO 2 and CsI, and the major gaseous species are CsI, I 2 and I. Under this situation where Cs/I ratio is one, cesium-zirconate is not present. If, however, cesium rich phase is partially present then cesium will be associated with zirconium, possibly as Cs 2 ZrO 3 . (author)

Nash Equilibria in Fisher Market

Science.gov (United States)

Adsul, Bharat; Babu, Ch. Sobhan; Garg, Jugal; Mehta, Ruta; Sohoni, Milind

Much work has been done on the computation of market equilibria. However due to strategic play by buyers, it is not clear whether these are actually observed in the market. Motivated by the observation that a buyer may derive a better payoff by feigning a different utility function and thereby manipulating the Fisher market equilibrium, we formulate the Fisher market game in which buyers strategize by posing different utility functions. We show that existence of a conflict-free allocation is a necessary condition for the Nash equilibria (NE) and also sufficient for the symmetric NE in this game. There are many NE with very different payoffs, and the Fisher equilibrium payoff is captured at a symmetric NE. We provide a complete polyhedral characterization of all the NE for the two-buyer market game. Surprisingly, all the NE of this game turn out to be symmetric and the corresponding payoffs constitute a piecewise linear concave curve. We also study the correlated equilibria of this game and show that third-party mediation does not help to achieve a better payoff than NE payoffs.

Modelling of associating mixtures for applications in the oil & gas and chemical industries

DEFF Research Database (Denmark)

Kontogeorgis, Georgios; Folas, Georgios; Muro Sunè, Nuria

2007-01-01

Thermodynamic properties and phase equilibria of associating mixtures cannot often be satisfactorily modelled using conventional models such as cubic equations of state. CPA (cubic-plus-association) is an equation of state (EoS), which combines the SRK EoS with the association term of SAFT. For non......-alcohol (glycol)-alkanes and certain acid and amine-containing mixtures. Recent results include glycol-aromatic hydrocarbons including multiphase, multicomponent equilibria and gas hydrate calculations in combination with the van der Waals-Platteeuw model. This article will outline some new applications...... thermodynamic models especially those combining cubic EoS with local composition activity coefficient models are included. (C) 2007 Elsevier B.V. All rights reserved....

Isotope effects in ion-exchange equilibria in aqueous and mixed solvent systems

International Nuclear Information System (INIS)

Gupta, A.R.

1979-01-01

Isotope effects in ion-exchange equilibria in aqueous and mixed solvents are analyzed in terms of the general features of ion-exchange equilibria and of isotope effects in chemical equilibria. The special role of solvent fractionation effects in ion-exchange equilibria in mixed solvents is pointed out. The various situations arising in isotope fractionation in ion exchange in mixed solvents due to solvent fractionation effects are theoretically discussed. The experimental data on lithium isotope effects in ion-exchange equilibria in mixed solvents are shown to conform to the above situations. The limitations of ion-exchange equilibria in mixed solvents for isotope fractionation are pointed out. 3 tables

Thermodynamics of cosolvent action: phenacetin, salicylic acid and probenecid.

Science.gov (United States)

Peña, M A; Escalera, B; Reíllo, A; Sánchez, A B; Bustamante, P

2009-03-01

The solubility of phenacetin, salicylic acid, and probenecid in ethanol-water and ethanol-ethyl acetate mixtures at several temperatures (15-40 degrees C) was measured. The solubility profiles are related to medium polarity changes. The apparent thermodynamic magnitudes and enthalpy-entropy relationships are related to the cosolvent action. Salicylic acid and probenecid show a single peak against the solubility parameter delta(1) of both solvent mixtures, at 40% (delta(1) = 21.70 MPa(1/2)) and 30% (delta(1) = 20.91 MPa(1/2)) ethanol in ethyl acetate, respectively. Phenacetin displays two peaks at 60% ethanol in ethyl acetate (23.30 MPa(1/2)) and 90% ethanol in water (delta(1) = 28.64 MPa(1/2)). The apparent enthalpies of solution display a maximum at 30% (phenacetin and salicylic acid) and 40% (probenecid) ethanol in water, respectively. Two different mechanisms, entropy at low ethanol ratios, and enthalpy at high ethanol ratios control the solubility enhancement in the aqueous mixture. In the nonaqueous mixture (ethanol-ethyl acetate) enthalpy is the driving force throughout the whole solvent composition for salicylic acid and phenacetin. For probenecid, the dominant mechanism shifts from entropy to enthalpy as the ethanol in ethyl acetate concentration increases. The enthalpy-entropy compensation plots corroborate the different mechanisms involved in the solubility enhancement by cosolvents. (c) 2008 Wiley-Liss, Inc. and the American Pharmacists Association

Phase equilibria and molecular interaction studies on (naphthols + vanillin) systems

International Nuclear Information System (INIS)

Gupta, Preeti; Agrawal, Tanvi; Das, Shiva Saran; Singh, Nakshatra Bahadur

2012-01-01

Highlights: ► Phase equilibria of (naphthol + vanillin) systems have been studied for the first time. ► Eutectic type phase diagrams are obtained. ► Eutectic mixtures show nonideal behaviour. ► There is a weak molecular interaction between the components in the eutectic mixtures. ► α-Naphthol–vanillin eutectic is more stable as compared to β-naphthol–vanillin. - Abstract: Phase equilibria between (α-naphthol + vanillin) and (β-naphthol + vanillin) systems have been studied by thaw-melt method and the results show the formation of simple eutectic mixtures. Crystallization velocities of components and eutectic mixtures were determined at different stages under cooling. With the help of differential scanning calorimeter (DSC), the enthalpy of fusion of components and eutectic mixtures was determined and from the values excess thermodynamic functions viz., excess Gibbs free energy (G E ), excess entropy (S E ), excess enthalpy (H E ) of hypo-, hyper- and eutectic mixtures were calculated. Flexural strength measurements were made in order to understand the non-ideal nature of eutectics. FT-IR spectral studies indicate the formation of hydrogen bond in the eutectic mixture. Anisotropic and isotropic microstructural studies of components, hypo-, hyper- and eutectic mixtures were made. Jackson’s roughness parameter was calculated and found to be greater than 2 suggesting the faceted morphology with irregular structures. The overall results have shown that there is a weak molecular interaction between the components in the eutectic mixtures and the (α-naphthol + vanillin) eutectic is more stable as compared to the (β-naphthol + vanillin) eutectic system.

Competition and equilibria in electricity markets based on two-settlement system: A conjectural variation approach

Science.gov (United States)

Watts, David

This dissertation studies electricity markets based on two-settlement systems and applies the concept of conjectural variation (CV) as a tool for representing different levels of competitiveness in the market. Some recent theoretical works are addressed to support the use of CV as a solution concept. A notion of consistency is introduced to make the level of competitiveness of the market endogenous, and allows finding consistent CV equilibria and the corresponding conditions for existence of equilibria. First, a case is studied in which firms hold exogenous levels of forward commitments. Then, backward induction and sub-game perfection are used to solve sequentially for the spot and forward market equilibrium. This allows analyzing how firms take positions in the forward market, based on considering their later impact on the spot market. It is concluded that positions taken in the forward market depend largely on firms expectations about the competitiveness of both the spot and the forward market. Forward markets are welfare enhancing even if they are not as competitive as the associated spot market as long as they are not too oligopolistie. The above formulation is used to model a dynamic scenario to analyze market stability, linking this research to Dr. Alvarado's earlier research on market stability. This brings about interesting trade offs between market power and market stability.

Sloshing-ion equilibria in the TARA endplugs

International Nuclear Information System (INIS)

Hokin, S.; Kesner, J.

1983-11-01

We have employed a modified version of the LLNL Bounce-average Fokker-Planck code to model neutral beam-produced sloshing-ion equilibria in the TARA endplugs. The questions we have addressed concern the effect of deuterium beam operation as opposed to hydrogen operation, and the advantage of using full-energy beams rather than the usual three-component beams. We find that, for the expected base case TARA operating parameters, a 40% savings in required beam power is attained by using deuterium beams rather than hydrogen beams, and that the use of full-energy beams results in an additional 26% power savings for these parameters. For higher plasma temperatures the use of full-energy beams becomes significantly advantagous. We have also investigated the equilibria of two possible alternate mirror configurations for the TARA endplugs, believed to be more stable to trapped particle modes, and report those results here

High-Temperature Phase Equilibria of Duplex Stainless Steels Assessed with a Novel In-Situ Neutron Scattering Approach

Science.gov (United States)

Pettersson, Niklas; Wessman, Sten; Hertzman, Staffan; Studer, Andrew

2017-04-01

Duplex stainless steels are designed to solidify with ferrite as the parent phase, with subsequent austenite formation occurring in the solid state, implying that, thermodynamically, a fully ferritic range should exist at high temperatures. However, computational thermodynamic tools appear currently to overestimate the austenite stability of these systems, and contradictory data exist in the literature. In the present work, the high-temperature phase equilibria of four commercial duplex stainless steel grades, denoted 2304, 2101, 2507, and 3207, with varying alloying levels were assessed by measurements of the austenite-to-ferrite transformation at temperatures approaching 1673 K (1400 °C) using a novel in-situ neutron scattering approach. All grades became fully ferritic at some point during progressive heating. Higher austenite dissolution temperatures were measured for the higher alloyed grades, and for 3207, the temperature range for a single-phase ferritic structure approached zero. The influence of temperatures in the region of austenite dissolution was further evaluated by microstructural characterization using electron backscattered diffraction of isothermally heat-treated and quenched samples. The new experimental data are compared to thermodynamic calculations, and the precision of databases is discussed.

On Nash-Equilibria of Approximation-Stable Games

Science.gov (United States)

Awasthi, Pranjal; Balcan, Maria-Florina; Blum, Avrim; Sheffet, Or; Vempala, Santosh

One reason for wanting to compute an (approximate) Nash equilibrium of a game is to predict how players will play. However, if the game has multiple equilibria that are far apart, or ɛ-equilibria that are far in variation distance from the true Nash equilibrium strategies, then this prediction may not be possible even in principle. Motivated by this consideration, in this paper we define the notion of games that are approximation stable, meaning that all ɛ-approximate equilibria are contained inside a small ball of radius Δ around a true equilibrium, and investigate a number of their properties. Many natural small games such as matching pennies and rock-paper-scissors are indeed approximation stable. We show furthermore there exist 2-player n-by-n approximation-stable games in which the Nash equilibrium and all approximate equilibria have support Ω(log n). On the other hand, we show all (ɛ,Δ) approximation-stable games must have an ɛ-equilibrium of support O(Δ^{2-o(1)}/ɛ2{log n}), yielding an immediate n^{O(Δ^{2-o(1)}/ɛ^2log n)}-time algorithm, improving over the bound of [11] for games satisfying this condition. We in addition give a polynomial-time algorithm for the case that Δ and ɛ are sufficiently close together. We also consider an inverse property, namely that all non-approximate equilibria are far from some true equilibrium, and give an efficient algorithm for games satisfying that condition.

Simulating metabolism with statistical thermodynamics.

Science.gov (United States)

Cannon, William R

2014-01-01

New methods are needed for large scale modeling of metabolism that predict metabolite levels and characterize the thermodynamics of individual reactions and pathways. Current approaches use either kinetic simulations, which are difficult to extend to large networks of reactions because of the need for rate constants, or flux-based methods, which have a large number of feasible solutions because they are unconstrained by the law of mass action. This report presents an alternative modeling approach based on statistical thermodynamics. The principles of this approach are demonstrated using a simple set of coupled reactions, and then the system is characterized with respect to the changes in energy, entropy, free energy, and entropy production. Finally, the physical and biochemical insights that this approach can provide for metabolism are demonstrated by application to the tricarboxylic acid (TCA) cycle of Escherichia coli. The reaction and pathway thermodynamics are evaluated and predictions are made regarding changes in concentration of TCA cycle intermediates due to 10- and 100-fold changes in the ratio of NAD+:NADH concentrations. Finally, the assumptions and caveats regarding the use of statistical thermodynamics to model non-equilibrium reactions are discussed.

The thermodynamic water retention capacity of solutions and gels.

Science.gov (United States)

Borchard, W; Jablonski, P

2003-01-01

The thermodynamic water retention capacity (WRC) has been defined and applied to different heterogeneous phase equilibria. This definition includes others known from the literature for testing heterogeneous systems. For the type of a real solution it is shown that at constant values of temperature and pressure the WRC is related to the difference of the chemical potential of water between the original state and the state after having applied a constraint. The dependence of WRC on concentration of a solute is predicted to be described by an e-function which has been experimentally confirmed in the literature.

A constitutive model for magnetostriction based on thermodynamic framework

International Nuclear Information System (INIS)

Ho, Kwangsoo

2016-01-01

This work presents a general framework for the continuum-based formulation of dissipative materials with magneto–mechanical coupling in the viewpoint of irreversible thermodynamics. The thermodynamically consistent model developed for the magnetic hysteresis is extended to include the magnetostrictive effect. The dissipative and hysteretic response of magnetostrictive materials is captured through the introduction of internal state variables. The evolution rate of magnetostrictive strain as well as magnetization is derived from thermodynamic and dissipative potentials in accordance with the general principles of thermodynamics. It is then demonstrated that the constitutive model is competent to describe the magneto-mechanical behavior by comparing simulation results with the experimental data reported in the literature. - Highlights: • A thermodynamically consistent model is proposed to describe the magneto-mechanical coupling effect. • Internal state variables are introduced to capture the dissipative material response. • The evolution rate of the magnetostrictive strain is derived through thermodynamic and dissipation potentials.

Study of acid-base properties in various water-salt and water-organic solvent mixtures; Etude de proprietes acides-bases dans divers melanges eau-sels et eau-solvants organiques

Energy Technology Data Exchange (ETDEWEB)

Lucas, M [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

1968-02-01

Acid-base reactions have been studied in water-salt mixtures and water organic solvent-mixtures. It has been possible to find some relations between the displacement of the equilibria and the numerical value of water activity in the mixture. First have been studied some equilibria H{sup +} + B {r_reversible} HB{sup +} in salt-water mixtures and found a relation between the pK{sub A} value, the solubility of the base and water activity. The reaction HO{sup -} + H{sup +} {r_reversible} H{sub 2}O has been investigated and a relation been found between pK{sub i} values, water activity and the molar concentration of the salt in the mixture. This relation is the same for every mixture. Then the same reactions have been studied in organic solvent-water mixtures and a relation found in the first part of the work have been used with success. So it has been possible to explain easily some properties of organic water-mixture as the shape of the curves of the Hammett acidity function Ho. (authors) [French] Nous avons envisage l'etude des reactions acides-bases dans des melanges eau-sels MX et des melanges d'eau et de solvants organiques. Les uns et les autres ont ete choisis de facon a ce que la basicite du solvant ou celle de l'anion X{sup -} soit negligeable devant celle de l'eau dans les melanges consideres. Dans un premier temps nous avons etudie dans les melanges eau-sels MX les equilibres H{sup +} + B {r_reversible} HB{sup +} et HA {r_reversible} H{sup +} + A{sup -}. On montre que connaissant la valeur de la solubilite de la base B et de l'acide HA dans le melange eau-sel considere et dans l'eau pure et celle de l'activite de l'eau dans le melange, il est possible de prevoir la valeur de la constante de l'equilibre acide-base etudiee. Dans un deuxieme temps nous avons cherche a generaliser ces resultats, lorsque l'on remplace le sel MX dans le melange avec l'eau par un solvant organique. De meme que precedemment, nous avons compare les constantes d'equilibre du type HB

Thermodynamic Investigation and Mixed Ligand Complex Formation of 1,4-Bis-(3-aminopropyl)-piperazine and Biorelevant Ligands.

Science.gov (United States)

El-Sherif, Ahmed A; Shehata, Mohamed R; Shoukry, Mohamed M; Barakat, Mohammad H

2012-01-01

Thermodynamic parameters for protonation of 1,4-bis(3-aminopropyl)-piperazine (BAPP) and its metal complexation with some divalent metal ions were determined in aqueous solution at constant ionic strength (0.1 M NaNO(3)) using a potentiometric technique. The order of -ΔG(0) and -ΔH(0) was found to obey Co(2+) Zn(2+), in accordance with the Irving-Williams order. The formation equilibria of zinc (II) complexes and the ternary complexes Zn(BAPP)L, where L = amino acid, amides, or DNA constituents), have been investigated. Ternary complexes are formed by a simultaneous mechanism. The concentration distribution of the complexes in solution was evaluated as a function of pH. Stoichiometry and stability constants for the complexes formed are reported and discussed. The stability of ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameter Δlog K.

Modulation of i-motif thermodynamic stability by the introduction of UNA (unlocked nucleic acid) monomers

DEFF Research Database (Denmark)

Pasternak, Anna; Wengel, Jesper

2011-01-01

The influence of acyclic RNA derivatives, UNA (unlocked nucleic acid) monomers, on i-DNA thermodynamic stability has been investigated. The 22 nt human telomeric fragment was chosen as the model sequence for stability studies. UNA monomers modulate i-motif stability in a position-depending manner...

Understanding Mn-Based Intercalation Cathodes from Thermodynamics and Kinetics

Directory of Open Access Journals (Sweden)

Yin Xie

2017-07-01

Full Text Available A series of Mn-based intercalation compounds have been applied as the cathode materials of Li-ion batteries, such as LiMn2O4, LiNi1−x−yCoxMnyO2, etc. With open structures, intercalation compounds exhibit a wide variety of thermodynamic and kinetic properties depending on their crystal structures, host chemistries, etc. Understanding these materials from thermodynamic and kinetic points of view can facilitate the exploration of cathodes with better electrochemical performances. This article reviews the current available thermodynamic and kinetic knowledge on Mn-based intercalation compounds, including the thermal stability, structural intrinsic features, involved redox couples, phase transformations as well as the electrical and ionic conductivity.

Influence of nature, concentration and pH of buffer acid-base system on rate determining step of the electrochemiluminescence of Ru(bpy){sub 3} {sup 2+} with tertiary aliphatic amines

Energy Technology Data Exchange (ETDEWEB)

Pastore, Paolo [Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy)]. E-mail: paolo.pastore@unipd.it; Badocco, Denis [Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy); Zanon, Francesco [Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova (Italy)

2006-07-28

The electrogenerated chemiluminescence (ECL) of Ru(bpy){sub 3} {sup 2+} (bpy 2,2'-bipyridyl) with tertiary aliphatic amines as co-reactants, was theoretically and experimentally studied as a function of the pre-equilibria involved in the ammonium proton lost and in relation to the nature of the rate determining step. Transient potential steps were used with a 3-mm glassy carbon disk electrode or carbon fiber ultramicroelectrodes array to investigate emission behavior in a variety of aqueous solution types, containing phosphate, tartrate and phthalate acid-base systems at differing pH values. The emission of Ru(bpy){sub 3} {sup 2+} resulting from the reaction with n-tripropylamine (TPrA), tri-isobutylamine (TisoBuA), n-tributylamine (TBuA), methyl-di-n-propylamine (MeDPrA) and triethylamine (TEtA) in varying acid-base media was interpreted on the basis of the quoted pre-equilibria, ammonium pK {sub a} being known. The nature of the rate determining steps changes depending on pH. Above pH {approx} 5 the amine neutral radical formation is the rate determining step and, is independent of pH with rate constant close to 10{sup 3} s{sup -1}; below pH {approx} 5 the rate determining step becomes the deprotonation of the ammonium ion, operated by different bases present in solution. Different amines in the same acid-base system showed analogous ECL behavior, conditioned by the chosen acid base system. A single amine in different acid-base systems showed different kinetic behaviors, due to the dissociation constants of the chosen buffers. The concentration of the acid-base system also played an important role and influenced emission intensity and shape. ECL emission were simulated by finite difference methods, implementing a previously proposed mechanism by including the relevant pre-equilibria. Simulation may also give estimates of the pK {sub a} values of the ammonium ions. An ion pair formation between R{sub 3}N{center_dot} {sup +} and the mostly charged species

Mathematical modeling of acid-base physiology.

Science.gov (United States)

Occhipinti, Rossana; Boron, Walter F

2015-01-01

pH is one of the most important parameters in life, influencing virtually every biological process at the cellular, tissue, and whole-body level. Thus, for cells, it is critical to regulate intracellular pH (pHi) and, for multicellular organisms, to regulate extracellular pH (pHo). pHi regulation depends on the opposing actions of plasma-membrane transporters that tend to increase pHi, and others that tend to decrease pHi. In addition, passive fluxes of uncharged species (e.g., CO2, NH3) and charged species (e.g., HCO3(-), [Formula: see text] ) perturb pHi. These movements not only influence one another, but also perturb the equilibria of a multitude of intracellular and extracellular buffers. Thus, even at the level of a single cell, perturbations in acid-base reactions, diffusion, and transport are so complex that it is impossible to understand them without a quantitative model. Here we summarize some mathematical models developed to shed light onto the complex interconnected events triggered by acids-base movements. We then describe a mathematical model of a spherical cells-which to our knowledge is the first one capable of handling a multitude of buffer reactions-that our team has recently developed to simulate changes in pHi and pHo caused by movements of acid-base equivalents across the plasma membrane of a Xenopus oocyte. Finally, we extend our work to a consideration of the effects of simultaneous CO2 and HCO3(-) influx into a cell, and envision how future models might extend to other cell types (e.g., erythrocytes) or tissues (e.g., renal proximal-tubule epithelium) important for whole-body pH homeostasis. Copyright © 2015 Elsevier Ltd. All rights reserved.

On Equilibria of the Two-fluid Model in Magnetohydrodynamics

International Nuclear Information System (INIS)

Frantzeskakis, Dimitri J.; Stratis, Ioannis G.; Yannacopoulos, Athanasios N.

2004-01-01

We show how the equilibria of the two-fluid model in magnetohydrodynamics can be described by the double curl equation and through the study of this equation we study some properties of these equilibria

The use of an MHV-2 equation of state for modeling the thermodynamic properties of refrigerant mixtures

International Nuclear Information System (INIS)

Morrison, J.D.; Barley, M.H.; Parker, I.B.

1995-01-01

This paper reports on the development and application of a thermodynamic model based on the second-order Modified Huron Vidal equation of state (MHV-2) to predict the properties of ternary mixtures of the refrigerants R32, R125, and R134a. The mixing rules of this equation of state have been used to incorporate directly an activity-coefficient model for the excess Gibbs free energy. The parameters for the activity-coefficient model have been derived from experimental VLE data for binary mixtures. This methodology has enabled the production of a thermodynamically consistent model which can be used to predict the phase equilibria of R32/R125/R134a mixtures. The input data used in the model are presented in the paper and the predictions of the model are compared with available experimental data. The model has been used to predict the behavior of ternary refrigerant blends of R32/R125/R134a in fractionation scenarios, such as liquid charging and vapor leakage, which are of direct interest to the refrigeration industry. Details of these applications and comparisons with experimental data are discussed, along with other general uses of the thermodynamic model

A unifying approach to existence of Nash equilibria

NARCIS (Netherlands)

Balder, E.J.

1997-01-01

An approach initiated in [4] is shown to unify results about the existence of (i) Nash equilibria in games with at most countably many players, (ii) Cournot-Nash equilibrium distributions for large, anonymous games, and (iii) Nash equilibria (both mixed and pure) for continuum games. A new, central

A combined variable temperature 600 MHz NMR/MD study of the calcium release agent cyclic adenosine diphosphate ribose (cADPR): Structure, conformational analysis, and thermodynamics of the conformational equilibria.

Science.gov (United States)

Javornik, Uroš; Plavec, Janez; Wang, Baifan; Graham, Steven M

2018-01-02

A combined variable temperature 600 MHz NMR/molecular dynamics study of the Ca 2+ -release agent cyclic adenosine 5'-diphosphate ribose (cADPR) was conducted. In addition to elucidating the major and minor orientations of the conformationally flexible furanose rings, γ- (C4'-C5'), and β- (C5'-O5') bonds, the thermodynamics (ΔH o , ΔS o ) associated with each of these conformational equilibria were determined. Both furanose rings were biased towards a south conformation (64-74%) and both β-bonds heavily favored trans conformations. The R-ring γ-bond was found to exist almost exclusively as the γ + conformer, whereas the A-ring γ-bond was a mixture of the γ + and γ t conformers, with the trans conformer being slightly favored. Enthalpic factors accounted for most of the observed conformational preferences, although the R-ring furanose exists as its major conformation based solely on entropic factors. There was excellent agreement between the NMR and MD results, particularly with regard to the conformer identities, but the MD showed a bias towards γ + conformers. The MD results showed that both N-glycosidic χ-bonds are exclusively syn. Collectively the data allowed for the construction of a model for cADPR in which many of the conformationally flexible units in fact effectively adopt single orientations and where most of the conformational diversity resides in its A-ring furanose and γ-bond. Copyright © 2017 Elsevier Ltd. All rights reserved.

pH-Modulated Watson-Crick duplex-quadruplex equilibria of guanine-rich and cytosine-rich DNA sequences 140 base pairs upstream of the c-kit transcription initiation site.

Science.gov (United States)

Bucek, Pavel; Jaumot, Joaquim; Aviñó, Anna; Eritja, Ramon; Gargallo, Raimundo

2009-11-23

Guanine-rich regions of DNA are sequences capable of forming G-quadruplex structures. The formation of a G-quadruplex structure in a region 140 base pairs (bp) upstream of the c-kit transcription initiation site was recently proposed (Fernando et al., Biochemistry, 2006, 45, 7854). In the present study, the acid-base equilibria and the thermally induced unfolding of the structures formed by a guanine-rich region and by its complementary cytosine-rich strand in c-kit were studied by means of circular dichroism and molecular absorption spectroscopies. In addition, competition between the Watson-Crick duplex and the isolated structures was studied as a function of pH value and temperature. Multivariate data analysis methods based on both hard and soft modeling were used to allow accurate quantification of the various acid-base species present in the mixtures. Results showed that the G-quadruplex and i-motif coexist with the Watson-Crick duplex over the pH range from 3.0 to 6.5, approximately, under the experimental conditions tested in this study. At pH 7.0, the duplex is practically the only species present.

Development of thermodynamic databases for geochemical calculations

Energy Technology Data Exchange (ETDEWEB)

Arthur, R.C. [Monitor Scientific, L.L.C., Denver, Colorado (United States); Sasamoto, Hiroshi; Shibata, Masahiro; Yui, Mikazu [Japan Nuclear Cycle Development Inst., Tokai, Ibaraki (Japan); Neyama, Atsushi [Computer Software Development Corp., Tokyo (Japan)

1999-09-01

experimental and field observations that constrain these data are consistently evaluated within this modeling framework. The accuracy of the data in SPRONS.JNC is evaluated in the present study and elsewhere by comparison of calculated equilibrium constants with their experimental counterparts at pressures and temperatures that span much of the subcritical and supercritical regions of H{sub 2}O stability. Additional experimental investigation of mineral solubilities and aqueous reactions, particularly between 0 and 100degC, are needed to further assess, and refine if necessary, the reliability of these databases. Field studies on phase equilibria in near-surface geological environments may be useful for this purpose because associated reaction times are greater than can be accommodated experimentally. The effects on mineral-solution equilibria of metastability and solid solution, and differences in the crystallinity and state of order/disorder in minerals, must be determined, however, before reliable thermodynamic properties can be retrieved from field investigations. (author)

Development of thermodynamic databases for geochemical calculations

International Nuclear Information System (INIS)

Arthur, R.C.; Sasamoto, Hiroshi; Shibata, Masahiro; Yui, Mikazu; Neyama, Atsushi

1999-09-01

experimental and field observations that constrain these data are consistently evaluated within this modeling framework. The accuracy of the data in SPRONS.JNC is evaluated in the present study and elsewhere by comparison of calculated equilibrium constants with their experimental counterparts at pressures and temperatures that span much of the subcritical and supercritical regions of H 2 O stability. Additional experimental investigation of mineral solubilities and aqueous reactions, particularly between 0 and 100degC, are needed to further assess, and refine if necessary, the reliability of these databases. Field studies on phase equilibria in near-surface geological environments may be useful for this purpose because associated reaction times are greater than can be accommodated experimentally. The effects on mineral-solution equilibria of metastability and solid solution, and differences in the crystallinity and state of order/disorder in minerals, must be determined, however, before reliable thermodynamic properties can be retrieved from field investigations. (author)

Thermodynamic assessment and the composition prediction of amorphous alloy in the Fe–B–Er alloy system

International Nuclear Information System (INIS)

Wang, S.L.; Han, J.J.; Wang, C.P.; Kou, S.Z.; Liu, X.J.

2012-01-01

Highlights: ► The thermodynamic parameters of each phase in the Fe–Er and B–Er binary systems were obtained. ► An agreement between the calculated results and experimental data was obtained in each binary system. ► The liquidus surface of Fe–B–Er system has been calculated by means of CALPHAD. ► The investigation of GFA in Fe-rich alloys in the context of Fe–B–Er liquidus surface proves the significance of calculated phase diagram in the composition design of Fe-based metallic glass. - Abstract: The phase diagrams and thermodynamic properties in the Fe–Er and B–Er binary systems have been assessed by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The thermodynamic parameters of each phase in the Fe–Er and B–Er binary systems were obtained, and an agreement between the calculated results and experimental data was obtained in each binary system. The isothermal sections at different temperatures and liquidus surface in the Fe–B–Er system have been calculated based on the binary thermodynamic data assessed in the present work. In addition, by considering that the glass formation composition of amorphous alloy is closely relative to the eutectic point in corresponding phase diagram, the investigation of glass-forming ability (GFA) in Fe-rich alloys in the Fe–B–Er liquidus surface has also been implemented in this work. The experimental result indicates that the GFA of a certain alloy is intimately relative to its location in the phase diagram, which proves that the phase diagram is an efficient tool for the composition design of Fe-based amorphous alloy.

A Tractable Disequilbrium Framework for Integrating Computational Thermodynamics and Geodynamics

Science.gov (United States)

Spiegelman, M. W.; Tweed, L. E. L.; Evans, O.; Kelemen, P. B.; Wilson, C. R.

2017-12-01

The consistent integration of computational thermodynamics and geodynamics is essential for exploring and understanding a wide range of processes from high-PT magma dynamics in the convecting mantle to low-PT reactive alteration of the brittle crust. Nevertheless, considerable challenges remain for coupling thermodynamics and fluid-solid mechanics within computationally tractable and insightful models. Here we report on a new effort, part of the ENKI project, that provides a roadmap for developing flexible geodynamic models of varying complexity that are thermodynamically consistent with established thermodynamic models. The basic theory is derived from the disequilibrium thermodynamics of De Groot and Mazur (1984), similar to Rudge et. al (2011, GJI), but extends that theory to include more general rheologies, multiple solid (and liquid) phases and explicit chemical reactions to describe interphase exchange. Specifying stoichiometric reactions clearly defines the compositions of reactants and products and allows the affinity of each reaction (A = -Δ/Gr) to be used as a scalar measure of disequilibrium. This approach only requires thermodynamic models to return chemical potentials of all components and phases (as well as thermodynamic quantities for each phase e.g. densities, heat capacity, entropies), but is not constrained to be in thermodynamic equilibrium. Allowing meta-stable phases mitigates some of the computational issues involved with the introduction and exhaustion of phases. Nevertheless, for closed systems, these problems are guaranteed to evolve to the same equilibria predicted by equilibrium thermodynamics. Here we illustrate the behavior of this theory for a range of simple problems (constructed with our open-source model builder TerraFERMA) that model poro-viscous behavior in the well understood Fo-Fa binary phase loop. Other contributions in this session will explore a range of models with more petrologically interesting phase diagrams as well as

Structure-thermodynamics-antioxidant activity relationships of selected natural phenolic acids and derivatives: an experimental and theoretical evaluation.

Science.gov (United States)

Chen, Yuzhen; Xiao, Huizhi; Zheng, Jie; Liang, Guizhao

2015-01-01

Phenolic acids and derivatives have potential biological functions, however, little is known about the structure-activity relationships and the underlying action mechanisms of these phenolic acids to date. Herein we investigate the structure-thermodynamics-antioxidant relationships of 20 natural phenolic acids and derivatives using DPPH• scavenging assay, density functional theory calculations at the B3LYP/6-311++G(d,p) levels of theory, and quantitative structure-activity relationship (QSAR) modeling. Three main working mechanisms (HAT, SETPT and SPLET) are explored in four micro-environments (gas-phase, benzene, water and ethanol). Computed thermodynamics parameters (BDE, IP, PDE, PA and ETE) are compared with the experimental radical scavenging activities against DPPH•. Available theoretical and experimental investigations have demonstrated that the extended delocalization and intra-molecular hydrogen bonds are the two main contributions to the stability of the radicals. The C = O or C = C in COOH, COOR, C = CCOOH and C = CCOOR groups, and orthodiphenolic functionalities are shown to favorably stabilize the specific radical species to enhance the radical scavenging activities, while the presence of the single OH in the ortho position of the COOH group disfavors the activities. HAT is the thermodynamically preferred mechanism in the gas phase and benzene, whereas SPLET in water and ethanol. Furthermore, our QSAR models robustly represent the structure-activity relationships of these explored compounds in polar media.

The SX Solver: A Computer Program for Analyzing Solvent-Extraction Equilibria: Version 3.0

International Nuclear Information System (INIS)

Lumetta, Gregg J.

2001-01-01

A new computer program, the SX Solver, has been developed to analyze solvent-extraction equilibria. The program operates out of Microsoft Excel and uses the built-in Solver function to minimize the sum of the square of the residuals between measured and calculated distribution coefficients. The extraction of nitric acid by tributyl phosphate has been modeled to illustrate the programs use

Two-fluid equilibria with flow

International Nuclear Information System (INIS)

Steinhauer, L.

1999-01-01

The formalism is developed for flowing two-fluid equilibria. The equilibrium system is governed by a pair of second order partial differential equations for the magnetic stream function and the ion stream function plus a Bernoulli-like equation for the density. There are six arbitrary surface function. There are separate characteristic surfaces for each species, which are the guiding-center surfaces. This system is a generalization of the familiar Grad-Shafranov system for a single-fluid equilibrium without flow, which has only one equation and two arbitrary surface functions. In the case of minimum energy equilibria, the six surface functions take on particular forms. (author)

The Pierce diode with an external circuit: II, Non-uniform equilibria

International Nuclear Information System (INIS)

Lawson, W.S.

1987-01-01

The non-uniform (non-linear) equilibria of the classical (short circuit) Pierce diode and the extended (series RLC external circuit) Pierce diode are described theoretically, and explored via computer simulation. It is found that most equilibria are correctly predicted by theory, but that the continuous set of equilibria of the classical Pierce diode at α = 2π are not observed. The stability characteristics of the non-uniform equilibria are also worked out, and are consistent with the simulations. 8 refs., 22 figs., 3 tabs

Thermodynamic Features of Benzene-1,2-Diphosphonic Acid Complexes with Several Metal Ions

Energy Technology Data Exchange (ETDEWEB)

Syouhei Nishihama; Ryan P. Witty; Leigh R Martin; Kenneth L. Nash

2013-08-01

Among his many contributions to the advancement of f-element chemistry and separation science, Professor Gregory R. Choppin’s research group completed numerous investigations featuring the application of distribution techniques to the determination of metal complexation equilibrium quotients. Most of these studies focused on the chemistry of lanthanide and actinide complexes. In keeping with that tradition, this report discusses the complex formation equilibrium constants for complexes of trivalent europium (Eu3+) with benzene-1,2-diphosphonic acid (H4BzDP) determined using solvent extraction distribution experiments in 0.2 M (Na,H)ClO4 media in the temperature range of 5 – 45 degrees C. Protonation constants for HnBzDP4-n and stoichiometry and stability of BzDP4- complexes with Zn2+, Ni2+, and Cu2+ have also been determined using potentiometric titration (at I = 0.1 M) and 31P NMR spectroscopy. Heats of protonation of HnBzDPn-4 species have been determined by titration calorimetry. From the temperature dependence of the complex Eu3+-HnBzDPn-4 equilibrium constant, a composite enthalpy (?H = -15.1 (+/-1.0) kJ mol-1) of complexation has been computed. Comparing these thermodynamic parameters with literature reports on other diphosphonic acids and structurally similar carboxylic acids indicates that exothermic heats of complexation are unique to the Eu-BzDP system. Comparisons with thermodynamic data from the literature indicate that the fixed geometry imposed by the benzene ring enhances complex stability.

Thermodynamics-based Metabolite Sensitivity Analysis in metabolic networks.

Science.gov (United States)

Kiparissides, A; Hatzimanikatis, V

2017-01-01

The increasing availability of large metabolomics datasets enhances the need for computational methodologies that can organize the data in a way that can lead to the inference of meaningful relationships. Knowledge of the metabolic state of a cell and how it responds to various stimuli and extracellular conditions can offer significant insight in the regulatory functions and how to manipulate them. Constraint based methods, such as Flux Balance Analysis (FBA) and Thermodynamics-based flux analysis (TFA), are commonly used to estimate the flow of metabolites through genome-wide metabolic networks, making it possible to identify the ranges of flux values that are consistent with the studied physiological and thermodynamic conditions. However, unless key intracellular fluxes and metabolite concentrations are known, constraint-based models lead to underdetermined problem formulations. This lack of information propagates as uncertainty in the estimation of fluxes and basic reaction properties such as the determination of reaction directionalities. Therefore, knowledge of which metabolites, if measured, would contribute the most to reducing this uncertainty can significantly improve our ability to define the internal state of the cell. In the present work we combine constraint based modeling, Design of Experiments (DoE) and Global Sensitivity Analysis (GSA) into the Thermodynamics-based Metabolite Sensitivity Analysis (TMSA) method. TMSA ranks metabolites comprising a metabolic network based on their ability to constrain the gamut of possible solutions to a limited, thermodynamically consistent set of internal states. TMSA is modular and can be applied to a single reaction, a metabolic pathway or an entire metabolic network. This is, to our knowledge, the first attempt to use metabolic modeling in order to provide a significance ranking of metabolites to guide experimental measurements. Copyright © 2016 International Metabolic Engineering Society. Published by Elsevier

Aerosol Fragmentation Driven by Coupling of Acid-Base and Free-Radical Chemistry in the Heterogeneous Oxidation of Aqueous Citric Acid by OH Radicals.

Science.gov (United States)

Liu, Matthew J; Wiegel, Aaron A; Wilson, Kevin R; Houle, Frances A

2017-08-10

A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous-phase aerosol is how the free-radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH-initiated oxidation of citric acid aerosol at high relative humidity. The reaction scheme, containing both free-radical and acid-base elementary reaction steps with physically validated rate coefficients, accurately predicts the experimentally observed molecular composition, particle size, and average elemental composition of the aerosol upon oxidation. The difference between the two reaction channels centers on the reactivity of carboxylic acid groups. Free-radical reactions mainly add functional groups to the carbon skeleton of neutral citric acid, because carboxylic acid moieties deactivate the unimolecular fragmentation of alkoxy radicals. In contrast, the conjugate carboxylate groups originating from acid-base equilibria activate both acyloxy radical formation and carbon-carbon bond scission of alkoxy radicals, leading to the formation of low molecular weight, highly oxidized products such as oxalic and mesoxalic acid. Subsequent hydration of carbonyl groups in the oxidized products increases the aerosol hygroscopicity and accelerates the substantial water uptake and volume growth that accompany oxidation. These results frame the oxidative lifecycle of atmospheric aerosol: it is governed by feedbacks between reactions that first increase the particle oxidation state, then eventually promote water uptake and acid-base chemistry. When coupled to free-radical reactions, acid-base channels lead to formation of low molecular

Electronic structure and phase equilibria in ternary substitutional alloys

International Nuclear Information System (INIS)

Traiber, A.J.S.; Allen, S.M.; Waterstrat, R.M.

1996-01-01

A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate abinitio calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr 0.5 (Ru, Pd) 0.5

Acid-base equilibrium. A thermodynamic study of formation and stability of the Bi-2223 phase

International Nuclear Information System (INIS)

Xi, Z.; Zhou, L.

1993-01-01

A general acid-base equilibrium theory was proposed to explain the formation and stability of the Bi-2223 phase based on the Lewis acid base theory and principle of metallurgical physical chemistry. The acid-base nature of oxide was defined according to the electrostatic force between cation and oxygen anion. A series of experimental facts were systematically explained based on the theory: substitution of Bi for Ca in the Pb-free 2223 phase, and the effect of substitution of the high-valent cation for Bi 3+ ; oxygen-pressure atmosphere, and the heat-schocking technique on the formation and stability of the 2223 phase. 14 refs., 2 tabs

Binding thermodynamics discriminates fragments from druglike compounds: a thermodynamic description of fragment-based drug discovery.

Science.gov (United States)

Williams, Glyn; Ferenczy, György G; Ulander, Johan; Keserű, György M

2017-04-01

Small is beautiful - reducing the size and complexity of chemical starting points for drug design allows better sampling of chemical space, reveals the most energetically important interactions within protein-binding sites and can lead to improvements in the physicochemical properties of the final drug. The impact of fragment-based drug discovery (FBDD) on recent drug discovery projects and our improved knowledge of the structural and thermodynamic details of ligand binding has prompted us to explore the relationships between ligand-binding thermodynamics and FBDD. Information on binding thermodynamics can give insights into the contributions to protein-ligand interactions and could therefore be used to prioritise compounds with a high degree of specificity in forming key interactions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Shallow-water vortex equilibria and their stability

Energy Technology Data Exchange (ETDEWEB)

Plotka, H; Dritschel, D G, E-mail: hanna@mcs.st-andrews.ac.uk, E-mail: dgd@mcs.st-andrews.ac.uk [School of Mathematics and Statistics, University of St Andrews, North Haugh, St. Andrews KY16 9SS (United Kingdom)

2011-12-22

We first describe the equilibrium form and stability of steadily-rotating simply-connected vortex patches in the single-layer quasi-geostrophic model of geophysical fluid dynamics. This model, valid for rotating shallow-water flow in the limit of small Rossby and Froude numbers, has an intrinsic length scale L{sub D} called the 'Rossby deformation length' relating the strength of stratification to that of the background rotation rate. Specifically, L{sub D} = c/f where c={radical}gH is a characteristic gravity-wave speed, g is gravity (or 'reduced' gravity in a two-layer context where one layer is infinitely deep), H is the mean active layer depth, and f is the Coriolis frequency (here constant). We next introduce ageostrophic effects by using the full shallow-water model to generate what we call 'quasi-equilibria'. These equilibria are not strictly steady, but radiate such weak gravity waves that they are steady for all practical purposes. Through an artificial ramping procedure, we ramp up the potential vorticity anomaly of the fluid particles in our quasi-geostrophic equilibria to obtain shallow-water quasi-equilibria at finite Rossby number. We show a few examples of these states in this paper.

Simulated pressure denaturation thermodynamics of ubiquitin.

Science.gov (United States)

Ploetz, Elizabeth A; Smith, Paul E

2017-12-01

Simulations of protein thermodynamics are generally difficult to perform and provide limited information. It is desirable to increase the degree of detail provided by simulation and thereby the potential insight into the thermodynamic properties of proteins. In this study, we outline how to analyze simulation trajectories to decompose conformation-specific, parameter free, thermodynamically defined protein volumes into residue-based contributions. The total volumes are obtained using established methods from Fluctuation Solution Theory, while the volume decomposition is new and is performed using a simple proximity method. Native and fully extended ubiquitin are used as the test conformations. Changes in the protein volumes are then followed as a function of pressure, allowing for conformation-specific protein compressibility values to also be obtained. Residue volume and compressibility values indicate significant contributions to protein denaturation thermodynamics from nonpolar and coil residues, together with a general negative compressibility exhibited by acidic residues. Copyright © 2017 Elsevier B.V. All rights reserved.

Evaluation of ΔGsub(f) values for unstable compounds: a Fortran program for the calculation of ternary phase equilibria

International Nuclear Information System (INIS)

Throop, G.J.; Rogl, P.; Rudy, E.

1978-01-01

A Fortran IV program was set up for the calculation of phase equilibria and tieline distributions in ternary systems of the type: transition metal-transition metal-nonmetal (interstitial type of solid solutions). The method offers the possibility of determining the thermodynamic values for unstable compounds through their influence upon ternary phase equilibria. The variation of the free enthalpy of formation of ternary solid solutions is calculated as a function of nonmetal content, thus describing the actual curvature of the phase boundaries. The integral and partial molar free enthalpies of formation of binary nonstoichiometric compounds and of phase solutions are expressed as analytical functions of the nonmetal content within their homogeneity range. The coefficient of these analytical expressions are obtained by the use either of the Wagner-Schottky vacancy model or polynomials second order in composition (parabolic approach). The free energy of formation, ΔGsub(f) has been calculated for the systems Ti-C, Zr-C, and Ta-C. Calculations of the ternary phase equilibria yielded the values for ΔGsub(f) for the unstable compounds Ti 2 C at 1500 0 C and Zr 2 C at 1775 0 C of -22.3 and 22.7 kcal g atom metal respectively. These values were used for the calculation of isothermal sections within the ternary systems Ti-Ta-C (at 1500 0 C) and Zr-Ta-C (at 1775 0 C). The ideal case of ternary phase solutions is extended to regular solutions. (author)

Uniqueness of Nash equilibria in a quantum Cournot duopoly game

International Nuclear Information System (INIS)

Sekiguchi, Yohei; Sakahara, Kiri; Sato, Takashi

2010-01-01

A quantum Cournot game whose classical form game has multiple Nash equilibria is examined. Although the classical equilibria fail to be Pareto optimal, the quantum equilibrium exhibits the following two properties: (i) if the measurement of entanglement between strategic variables chosen by the competing firms is sufficiently large, the multiplicity of equilibria vanishes, and (ii) the more strongly the strategic variables are entangled, the more closely the unique equilibrium approaches to the optimal one.

THERMODYNAMIC STUDIES ON THE CHARGE-TRANSFER ...

African Journals Online (AJOL)

... technique was employed to investigate thermodynamic parameters associated with the interaction ... KEY WORDS: Amitriptyline , chloranilic acid, thermodynamic parameters. Global Jnl Pure & Applied Sciences Vol.10(1) 2004: 147-153 ...

Isobaric (vapour + liquid) equilibria for the (1-pentanol + propionic acid) binary mixture at (53.3 and 91.3) kPa

International Nuclear Information System (INIS)

Mohsen-Nia, M.; Memarzadeh, M.R.

2010-01-01

Isobaric (vapour + liquid) equilibrium measurements have been reported for the binary mixture of (1-pentanol + propionic acid) at (53.3 and 91.3) kPa. Liquid phase activity coefficients were calculated from the equilibrium data. The thermodynamic consistency of the experimental results was checked using the area test and direct test methods. According to these criteria, the measured (vapour + liquid) equilibrium results were found to be consistent thermodynamically. The obtained results showed a maximum boiling temperature azeotrope at both pressures studied. The measured equilibrium results were satisfactorily correlated by the models of Wilson, UNIQUAC, and NRTL activity coefficients. The results obtained indicate that the performance of the NRTL model is superior to the Wilson and UNIQUAC models for correlating the measured isobaric (vapour + liquid) equilibrium data.

Thermodynamic analysis of stability in iron removal from kaolin by using oxalic acid

Directory of Open Access Journals (Sweden)

C. Ocampo-López

2013-06-01

Full Text Available The graphical representation of global stability for a system, or Pourbaix diagram, was constructed to perform a thermodynamic study of iron removal from kaolin using oxalic acid as an oxidant. To do this the free energies of formation of the oxalate complex of the system were calculated, and it was found that the more stable specie is Fe(C2O43-3, with a calculated free energy of formation of -3753.88 kcal/mol. Thermodynamic stability functions were estimated for the system as a function of pH and Eh known as potential of oxide reduction. It was built a global stability diagram for the removal system; it showed that the specie trioxalate Fe(C2O43-3 is the only oxalate in equilibrium with other compounds associated with the removal of iron in kaolin.

Thermodynamic studies on the interaction between some amino acids with some rare earth metal ions in aqueous solutions

International Nuclear Information System (INIS)

Mohamed, AbdAllah A.; Bakr, Moustafa F.; Abd El-Fattah, Khaled A.

2003-01-01

The interactions between the amino acids (glycine and L-threonine) with some rare earth metal ions (Pr 3+ , Nd 3+ , Eu 3+ , Gd 3+ , Dy 3+ , Ho 3+ and Yb 3+ ) were studied at a wide range from ionic strengths (0.07-0.32 M KNO 3 ) and temperatures (25-45 deg. C) in aqueous solutions by using Bjerrum potentiometric method. The stoichiometric and thermodynamic stability constants were calculated as well as the standard thermodynamic parameters (ΔG deg., ΔH deg. and ΔS deg. ) for all possible reactions that occur. The degree of formation (n-bar) for all studied systems was determined and discussed. The thermodynamic parameters differences (ΔΔG deg., ΔΔH deg. and ΔΔS deg. ) were calculated and discussed to determine the factors which control these complexation processes from the thermodynamic point of view

Thermodynamic and kinetic modelling of the reduction of concentrated nitric acid

International Nuclear Information System (INIS)

Sicsic, David

2011-01-01

This research thesis aimed at determining and quantifying the different stages of the reduction mechanism in the case of concentrated nitric acid. After having reported the results of a bibliographical study on the chemical and electrochemical behaviour of concentrated nitric media (generalities, chemical equilibriums, NOx reactivity, electrochemical reduction of nitric acid), the author reports the development and discusses the results of a thermodynamic simulation of a nitric environment at 25 C. This allowed the main species to be identified in the liquid and gaseous phases of nitric acid solutions. The author reports an experimental electrochemical investigation coupled with analytic techniques (infrared and UV-visible spectroscopy) and shows that the reduction process depends on the cathodic overvoltage, and identifies three potential areas. A kinetic modelling of the stationary state and of the impedance is then developed in order to better determine, discuss and quantify the reduction process. The application of this kinetic model to the preliminary results of an electrochemical study performed on 304 L steel is then discussed [fr

Exploring the evolution of standard amino-acid alphabet: When genomics meets thermodynamics

International Nuclear Information System (INIS)

Zhang, Hong-Yu

2007-01-01

One of the most intriguing aspects of life is that despite the diversified apparent shapes, similar building blocks and infrastructures, such as standard amino acids and canonical genetic codes, are shared by most life on Earth. Thus, it is challenging to explore: why nature just selects these building blocks and strategies from numerous candidates to construct life? Was this deterministic or fortuitous? Thanks to the rapid progress in genomics, bioinformatics and synthetic biology, more and more basic principles underlying life design and construction were disclosed in the past decade. However, since the origin of early life is substantially a chemical process, to understand the enigma of life origin, chemists' efforts can not be neglected. In this paper, we focus on the evolution of standard amino-acid alphabet and indicate that chemistry, especially thermodynamics, is indeed critical to understanding the forming mechanisms of amino-acid alphabet. It is revealed that nature prefers low free energy and thus ubiquitous (cheap) small amino acids when beginning to build life, which is compatible with many recent findings from genomics and bioinformatics

Two-dimensional magnetohydrodynamic equilibria with flow and studies of equilibria fluctuations

International Nuclear Information System (INIS)

Agim, Y.Z.

1989-08-01

A set of reduced ideal MHD equations is derived to investigate equilibria of plasmas with mass flow in general two-dimensional geometry. These equations provide a means of investigating the effects of flow on self-consistent equilibria in a number of new two-dimensional configurations such as helically symmetric configurations with helical axis, which are relevant to stellarators, as well as axisymmetric configurations. It is found that as in the axisymmetric case, general two-dimensional flow equilibria are governed by a second-order quasi-linear partial differential equation for a magnetic flux function, which is coupled to a Bernoulli-type equation for the density. The equation for the magnetic flux function becomes hyperbolic at certain critical flow speeds which follow from its characteristic equation. When the equation is hyperbolic, shock phenomena may exist. As a particular example, unidirectional flow along the lines of symmetry is considered. In this case, the equation mentioned above is always elliptic. An exact solution for the case of helically symmetric unidirectional flow is found and studied to determine flow effects on the magnetic topology. In second part of this thesis, magnetic fluctuations due to the thermally excited MHD waves are investigated using fluid and kinetic models to describe stable, uniform, compressible plasma in the range above the drift wave frequency and below the ion cyclotron frequency. It is shown that the fluid model with resistivity yields spectral densities which are roughly Lorentzian, exhibit equipartition with no apparent cutoff in wavenumber space and a Bohm-type diffusion coefficient. Under certain conditions, the ensuing transport may be comparable to classical values. For a phenomenological cutoff imposed on the spectrum, the typical fluctuating-to-equilibrium magnetic field ratio is found to be of the order of 10 -10

Thermodynamic stability and guest distribution of CH4/N2/CO2 mixed hydrates for methane hydrate production using N2/CO2 injection

International Nuclear Information System (INIS)

Lim, Dongwook; Ro, Hyeyoon; Seo, Yongwon; Seo, Young-ju; Lee, Joo Yong; Kim, Se-Joon; Lee, Jaehyoung; Lee, Huen

2017-01-01

Highlights: • We examine the thermodynamic stability and guest distribution of CH 4 /N 2 /CO 2 mixed hydrates. • Phase equilibria of the CH 4 /N 2 /CO 2 mixed hydrates were measured to determine the thermodynamic stability. • The N 2 /CO 2 ratio of the hydrate phase is almost constant despite the enrichment of CO 2 in the hydrate phase. • 13 C NMR results indicate the preferential occupation of N 2 and CO 2 in the small and large cages of sI hydrates, respectively. - Abstract: In this study, thermodynamic stability and cage occupation behavior in the CH 4 – CO 2 replacement, which occurs in natural gas hydrate reservoirs by injecting flue gas, were investigated with a primary focus on phase equilibria and composition analysis. The phase equilibria of CH 4 /N 2 /CO 2 mixed hydrates with various compositions were measured to determine the thermodynamic stability of gas hydrate deposits replaced by N 2 /CO 2 gas mixtures. The fractional experimental pressure differences (Δp/p) with respect to the CSMGem predictions were found to range from −0.11 to −0.02. The composition analysis for various feed gas mixtures with a fixed N 2 /CO 2 ratio (4.0) shows that CO 2 is enriched in the hydrate phase, and the N 2 /CO 2 ratio in the hydrate phase is independent of the feed CH 4 fractions. Moreover, 13 C NMR measurements indicate that N 2 molecules preferentially occupy the small 5 12 cages of sI hydrates while the CO 2 molecules preferentially occupy the large 5 12 6 2 cages, resulting in an almost constant area ratio of CH 4 molecules in the large to small cages of the CH 4 /N 2 /CO 2 mixed hydrates. The overall experimental results provide a better understanding of stability conditions and guest distributions in natural gas hydrate deposits during CH 4 – flue gas replacement.

Thermodynamics of inclusion complexes of natural and modified cyclodextrins with acetylsalicylic acid and ibuprofen in aqueous solution at 298 K

Energy Technology Data Exchange (ETDEWEB)

Castronuovo, Giuseppina, E-mail: giuseppina.castronuovo@unina.it [Department of Chemistry, University Federico II of Naples, Complesso Universitario a Monte S. Angelo, via Cintia, 80126 Naples (Italy); Niccoli, Marcella [Department of Chemistry, University Federico II of Naples, Complesso Universitario a Monte S. Angelo, via Cintia, 80126 Naples (Italy)

2013-04-10

Graphical abstract: Complexation forces acting in the association between natural and modified α- and β-cyclodextrins and acetylsalicylic acid (aspirin) or ibuprofen are examined through the analysis of the thermodynamic parameters obtained by isothermal calorimetry. Highlights: ► A calorimetric method is reported to study the association of natural and substituted cyclodextrins with acetylsalicylic acid and ibuprofen. ► The study aims to propose a hypothesis about the forces involved in the interaction. That can be useful for designing new cyclodextrins having suitable characteristics to include specific drugs. ► Enthalpic and entropic contributions on the association are discussed. The differences in the cavity dimensions of the cyclodextrins determine the values of the thermodynamic properties to be very different. - Abstract: Thermodynamic parameters for the association of natural and substituted α-, β-, and γ-cyclodextrins with acetylsalicylic acid, salicylic acid and ibuprofen have been determined by isothermal titration calorimetry. Analysis of the data shows that complexes form, all having 1:1 stoichiometry. The shape-matching between the host and guest is the factor determining the values of the thermodynamic quantities. In the case of the smallest cyclodextrin interacting with acetylsalicylic acid and salicylic acid, the parameters indicate that hydrophobic interactions play the major role. Association occurs through the shallow inclusion of the benzene ring into the cavity. In the case of substituted β-cyclodextrins, instead, inclusion of the benzene ring is deeper and the tight fitting of the guest molecule to the cavity makes the enthalpy and entropy to be both negative. Ibuprofen interacts through its isobutyl group: the values of the association constants are very high for β-cyclodextrins as determined by the large and positive entropies due to the relaxation of water molecules from the cavity and the hydration spheres of the interacting

Thermodynamics of inclusion complexes of natural and modified cyclodextrins with acetylsalicylic acid and ibuprofen in aqueous solution at 298 K

International Nuclear Information System (INIS)

Castronuovo, Giuseppina; Niccoli, Marcella

2013-01-01

Graphical abstract: Complexation forces acting in the association between natural and modified α- and β-cyclodextrins and acetylsalicylic acid (aspirin) or ibuprofen are examined through the analysis of the thermodynamic parameters obtained by isothermal calorimetry. Highlights: ► A calorimetric method is reported to study the association of natural and substituted cyclodextrins with acetylsalicylic acid and ibuprofen. ► The study aims to propose a hypothesis about the forces involved in the interaction. That can be useful for designing new cyclodextrins having suitable characteristics to include specific drugs. ► Enthalpic and entropic contributions on the association are discussed. The differences in the cavity dimensions of the cyclodextrins determine the values of the thermodynamic properties to be very different. - Abstract: Thermodynamic parameters for the association of natural and substituted α-, β-, and γ-cyclodextrins with acetylsalicylic acid, salicylic acid and ibuprofen have been determined by isothermal titration calorimetry. Analysis of the data shows that complexes form, all having 1:1 stoichiometry. The shape-matching between the host and guest is the factor determining the values of the thermodynamic quantities. In the case of the smallest cyclodextrin interacting with acetylsalicylic acid and salicylic acid, the parameters indicate that hydrophobic interactions play the major role. Association occurs through the shallow inclusion of the benzene ring into the cavity. In the case of substituted β-cyclodextrins, instead, inclusion of the benzene ring is deeper and the tight fitting of the guest molecule to the cavity makes the enthalpy and entropy to be both negative. Ibuprofen interacts through its isobutyl group: the values of the association constants are very high for β-cyclodextrins as determined by the large and positive entropies due to the relaxation of water molecules from the cavity and the hydration spheres of the interacting

The use of approximation formulae in calculations of acid-base equilibria-II: salts of mono- and diprotic acids.

Science.gov (United States)

Narasaki, H

1980-02-01

The pH of solutions of salts of mono- and diprotic acids is calculated by use of approximation formulae and the theoretically exact equations. The regions for useful application of the approximation formulae (error monoprotic acids, areas are symmetrically equal to those of the acids. For salts of diprotic acids the ranges generally depend on K(2)/K(1).

Thermodynamic modelling of acid gas removal from natural gas using the Extended UNIQUAC model

DEFF Research Database (Denmark)

Sadegh, Negar; Stenby, Erling Halfdan; Thomsen, Kaj

2017-01-01

Thermodynamics of natural gas sweetening process needs to be known for proper design of natural gas treating plants. Absorption with aqueous N-Methyldiethanolamine is currently the most commonly used process for removal of acid gas (CO2 and H2S) impurities from natural gas. Model parameters...... for the Extended UNIQUAC model have already been determined by the same authors to calculate single acid gas solubility in aqueous MDEA. In this study, the model is further extended to estimate solubility of CO2 and H2S and their mixture in aqueous MDEA at high pressures with methane as a makeup gas....

Thermodynamic consistency test procedure using orthogonal collocation and the Peng-Robinson equation of state

International Nuclear Information System (INIS)

Hamm, L.L.; Van Brunt, V.

1982-08-01

The Christiansen and Fredenslund programs for calculating vapor-liquid equilibria have been modified by replacing the Soave-Redlich-Kwong equation of state with the newly developed Peng-Robinson equation of state. This modification was shown to be a decided improvement for high pressure systems, especially in the critical and upper retrograde regions. Thermodynamic consistency tests were developed and used to evaluate and compare calculated values from both the modified and unmodified programs with reported experimental data for several vapor-liquid systems

On tokamak equilibria with a zero current or negative current central region

International Nuclear Information System (INIS)

Chu, M.S.; Parks, P.B.

2002-01-01

Several tokamak experiments have reported the development of a central region with vanishing currents (the current hole). The straightforward application of results from the work of Greene, Johnson and Weimer [Phys. Fluids 14, 671 (1971)] on a tokamak equilibrium to these plasmas leads to the apparent singularities in several physical quantities including the Shafranov shift and casts doubts on the existence of this type of equilibria. In this paper, the above quoted equilibrium theory is re-examined and extended to include equilibria with a current hole. It is shown that singularities can be circumvented and that equilibria with a central current hole do satisfy the magnetohydrodynamic equilibrium condition with regular behavior for all the physical quantities and do not lead to infinitely large Shafranov shifts. Isolated equilibria with negative current in the central region could exist. But equilibria with negative currents in general do not have neighboring equilibria and thus cannot have experimental realization, i.e., no negative currents can be driven in the central region

The Pierce diode with an external circuit. I. Oscillations about nonuniform equilibria

International Nuclear Information System (INIS)

Lawson, W.S.

1989-01-01

The nonuniform (nonlinear) equilibria of the classical (short circuit) Pierce diode and the extended (series RLC external circuit) Pierce diode are described, and the spectrum of oscillations (stable and unstable) about these equilibria are worked out. It is found that only the external capacitance alters the equilibria, though all elements alter the spectrum. In particular, the introduction of an external capacitor destabilizes some equilibria that are marginally stable without the capacitor. Computer simulations are performed to test the theoretical predictions for the case of an external capacitor only. It is found that most equilibria are correctly predicted by theory, but that the continuous set of equilibria of the classical Pierce diode at Pierce parameters (α=ω/sub pL//v 0 ) that are multiples of 2π are not observed. This appears to be a failure of the simulation method under the rather singular conditions rather than a failure of the theory

Nematic Equilibria on a Two-Dimensional Annulus

KAUST Repository

Lewis, A. H.; Aarts, D. G. A. L.; Howell, P. D.; Majumdar, A.

2017-01-01

We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.

Nematic Equilibria on a Two-Dimensional Annulus

KAUST Repository

Lewis, A. H.

2017-01-16

We study planar nematic equilibria on a two-dimensional annulus with strong and weak tangent anchoring, in the Oseen–Frank theoretical framework. We analyze a radially invariant defect-free state and compute analytic stability criteria for this state in terms of the elastic anisotropy, annular aspect ratio, and anchoring strength. In the strong anchoring case, we define and characterize a new spiral-like equilibrium which emerges as the defect-free state loses stability. In the weak anchoring case, we compute stability diagrams that quantify the response of the defect-free state to radial and azimuthal perturbations. We study sector equilibria on sectors of an annulus, including the effects of weak anchoring and elastic anisotropy, giving novel insights into the correlation between preferred numbers of boundary defects and the geometry. We numerically demonstrate that these sector configurations can approximate experimentally observed equilibria with boundary defects.

Thermodynamic and structural properties in complexing media

International Nuclear Information System (INIS)

Di Giandomenico, M.V.

2007-10-01

Protactinium is experiencing a renewal of interest in the frame of long-term energy production. Modelling the behaviour of this element in the geosphere requires thermodynamic and structural data relevant to environmental conditions. Now deep clayey formation are considered for the disposal of radioactive waste and high values of natural sulphate contents have been determined in pore water in equilibrium with clay surface. Because of its tendency to polymerisation, hydrolysis and sorption on all solid supports, the equilibria constants relative to monomer species were determined at tracer scale (ca. 10 - 12 M) with 233 Pa. The complexation constants of Pa(V) and sulphate ions were calculated starting from a systematic study of the apparent distribution coefficient D in the system TTA/Toluene/H 2 O/Na 2 SO 4 /HClO 4 /NaClO 4 and as a function of ionic strength, temperature, free sulphate, protons and chelatant concentration. First of all, the interaction between free species H + , SO 4 - , Na + leads to the formation of HSO 4 - and NaSO 4 - , for which concentrations depend upon the related thermodynamic constants. For this purpose a computer code was developed in order to determine all free species concentration. This iterative code takes into account the influence of temperature and ionic strength (SIT modelling) on thermodynamic constants. The direct measure of Pa(V) in the organic and aqueous phase by g-spectrometry had conducted to estimate the apparent distribution coefficient D as function of free sulphate ions. Complexation constants have been determined after a mathematical treatment of D. The extrapolation of these constants at zero ionic strength have been realized by SIT modelling at different temperatures. Besides, enthalpy and entropy values were calculated. Parallelly, the structural study of Pa(V) was performed using 231 Pa. XANES and EXAFS spectra show unambiguously the absence of the trans di-oxo bond that characterizes the other early actinide

Numerical calculation of axisymmetric non-neutral plasma equilibria

International Nuclear Information System (INIS)

Spencer, R.L.; Rasband, S.N.; Vanfleet, R.R.

1993-01-01

Efficient techniques for computing axisymmetric non-neutral plasma equilibria are described. These equilibria may be obtained either by requiring global thermal equilibrium, by specifying the midplane radial density profile, or by specifying the radial profile of ∫n dz. Both splines and finite-differences are used, and the accuracy of the two is compared by using a new characterization of the thermal equilibrium density profile which gives a simple formula for estimating the radial and axial gradient scale lengths of thermal equilibria. It is found that for global thermal equilibrium 1% accuracy is achieved with splines if the distance between neighboring splines is about two Debye lengths while finite differences require a grid spacing of about one-half Debye length to achieve the same accuracy

Thermodynamics of antibody-antigen interaction revealed by mutation analysis of antibody variable regions.

Science.gov (United States)

Akiba, Hiroki; Tsumoto, Kouhei

2015-07-01

Antibodies (immunoglobulins) bind specific molecules (i.e. antigens) with high affinity and specificity. In order to understand their mechanisms of recognition, interaction analysis based on thermodynamic and kinetic parameters, as well as structure determination is crucial. In this review, we focus on mutational analysis which gives information about the role of each amino acid residue in antibody-antigen interaction. Taking anti-hen egg lysozyme antibodies and several anti-small molecule antibodies, the energetic contribution of hot-spot and non-hot-spot residues is discussed in terms of thermodynamics. Here, thermodynamics of the contribution from aromatic, charged and hydrogen bond-forming amino acids are discussed, and their different characteristics have been elucidated. The information gives fundamental understanding of the antibody-antigen interaction. Furthermore, the consequences of antibody engineering are analysed from thermodynamic viewpoints: humanization to reduce immunogenicity and rational design to improve affinity. Amino acid residues outside hot-spots in the interface play important roles in these cases, and thus thermodynamic and kinetic parameters give much information about the antigen recognition. Thermodynamic analysis of mutant antibodies thus should lead to advanced strategies to design and select antibodies with high affinity. © The Authors 2015. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.

Heading in the right direction: thermodynamics-based network analysis and pathway engineering.

Science.gov (United States)

Ataman, Meric; Hatzimanikatis, Vassily

2015-12-01

Thermodynamics-based network analysis through the introduction of thermodynamic constraints in metabolic models allows a deeper analysis of metabolism and guides pathway engineering. The number and the areas of applications of thermodynamics-based network analysis methods have been increasing in the last ten years. We review recent applications of these methods and we identify the areas that such analysis can contribute significantly, and the needs for future developments. We find that organisms with multiple compartments and extremophiles present challenges for modeling and thermodynamics-based flux analysis. The evolution of current and new methods must also address the issues of the multiple alternatives in flux directionalities and the uncertainties and partial information from analytical methods. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Nonequilibrium thermodynamics and energy efficiency in weight loss diets

Directory of Open Access Journals (Sweden)

Fine Eugene J

2007-07-01

Full Text Available Abstract Carbohydrate restriction as a strategy for control of obesity is based on two effects: a behavioral effect, spontaneous reduction in caloric intake and a metabolic effect, an apparent reduction in energy efficiency, greater weight loss per calorie consumed. Variable energy efficiency is established in many contexts (hormonal imbalance, weight regain and knock-out experiments in animal models, but in the area of the effect of macronutrient composition on weight loss, controversy remains. Resistance to the idea comes from a perception that variable weight loss on isocaloric diets would somehow violate the laws of thermodynamics, that is, only caloric intake is important ("a calorie is a calorie". Previous explanations of how the phenomenon occurs, based on equilibrium thermodynamics, emphasized the inefficiencies introduced by substrate cycling and requirements for increased gluconeogenesis. Living systems, however, are maintained far from equilibrium, and metabolism is controlled by the regulation of the rates of enzymatic reactions. The principles of nonequilibrium thermodynamics which emphasize kinetic fluxes as well as thermodynamic forces should therefore also be considered. Here we review the principles of nonequilibrium thermodynamics and provide an approach to the problem of maintenance and change in body mass by recasting the problem of TAG accumulation and breakdown in the adipocyte in the language of nonequilibrium thermodynamics. We describe adipocyte physiology in terms of cycling between an efficient storage mode and a dissipative mode. Experimentally, this is measured in the rate of fatty acid flux and fatty acid oxidation. Hormonal levels controlled by changes in dietary carbohydrate regulate the relative contributions of the efficient and dissipative parts of the cycle. While no experiment exists that measures all relevant variables, the model is supported by evidence in the literature that 1 dietary carbohydrate, via its

Black hole thermodynamics based on unitary evolutions

International Nuclear Information System (INIS)

Feng, Yu-Lei; Chen, Yi-Xin

2015-01-01

In this paper, we try to construct black hole thermodynamics based on the fact that the formation and evaporation of a black hole can be described by quantum unitary evolutions. First, we show that the Bekenstein–Hawking entropy S BH may not be a Boltzmann or thermal entropy. To confirm this statement, we show that the original black hole's ‘first law’ may not simply be treated as the first law of thermodynamics formally, due to some missing metric perturbations caused by matter. Then, by including those (quantum) metric perturbations, we show that the black hole formation and evaporation can be described effectively in a unitary manner, through a quantum channel between the exterior and interior of the event horizon. In this way, the paradoxes of information loss and firewall can be resolved effectively. Finally, we show that black hole thermodynamics can be constructed in an ordinary way, by constructing statistical mechanics. (paper)

Determination of thermodynamic parameters for enolization reaction of malonic and metylmalonic acids by using quartz crystal microbalance

Directory of Open Access Journals (Sweden)

Minoru Yoshimoto

2016-06-01

Full Text Available We investigated the process of a bromination reaction of malonic acid and methylmalonic acid in the Belousov-Zhabotinsky reaction by using a quartz crystal microbalance (QCM. The process involves an enolization reaction as a rate-determining step. We found that, in the step, the variation of Br2 concentration induced an exactly quantitative shift of a resonant frequency of the QCM, based on the change of the surface mass on the QCM and the solution viscosity and density. This new finding enabled us to estimate the reaction rate constants and the thermodynamic parameters of the enolization reaction due to a QCM measurement. The values measured by the QCM were in good agreement with those measured by a UV-spectrophotometer. As a result, we succeeded to develop a new measurement method of a nonlinear chemical reaction.

Investigation of mono/competitive adsorption of environmentally relevant ionized weak acids on graphite: impact of molecular properties and thermodynamics.

Science.gov (United States)

Moustafa, Ahmed M A; McPhedran, Kerry N; Moreira, Jesús; Gamal El-Din, Mohamed

2014-12-16

The thermodynamics of adsorption and competitive interactions of five weak acids on a graphite surface was assessed in alkaline solutions. Adsorption of the acids in mono- and multicompound solutions followed their Freundlich isotherms which suggest a diversity of graphite adsorption sites as confirmed by the presence of carboxylic and phenolic groups observed on graphite surfaces. Thermodynamic calculations assigned the formation of the negatively charged assisted hydrogen bond (-CAHB) between ionized solutes and adsorbent surface groups as the possible adsorption mechanism. However, the similar pKa values of current acids resulted in comparable free energies for -CAHB formation (ΔG(-CAHB)) being less than solvation free energies (ΔGSolv). Thus, additional ΔG is supplemented by increased hydrophobicity due to proton exchange of ionized acids with water (ΔΔG Hydrophobicity). Adsorption capacities and competition coefficients indicated that ΔΔG Hydrophobicity values depend on the neutral and ionized acid Kow. Competitive adsorption implies that multilayer adsorption may occur via hydrophobic bonding with the CH3 ends of the self-assembled layer which affects the acid adsorption capacities in mixtures as compared to monocompound solutions. The determination of adsorption mechanisms will assist in understanding of the fate and bioavailability of emerging and classical weak acids released into natural waters.

CO_2 capture from flue gas using clathrate formation in the presence of thermodynamic promoters

International Nuclear Information System (INIS)

Kim, Soyoung; Choi, Sung-Deuk; Seo, Yongwon

2017-01-01

Tetrahydrofuran (THF) as a water-soluble sII clathrate former, cyclopentane (CP) as a water-insoluble sII clathrate former, and tetra n-butyl ammonium chloride (TBAC) as a water-soluble semiclathrate former were used to investigate their thermodynamic promotion effects on clathrate-based CO_2 capture from simulated flue gas. The phase equilibria of CO_2 (20%) + N_2 (80%) + promoter clathrates at different promoter concentrations revealed that the presence of THF, CP, and TBAC could significantly reduce the clathrate formation pressure. THF solutions provided the highest gas uptake and steepest CO_2 concentration changes in the vapor phase, whereas TBAC solutions showed the highest CO_2 selectivity (∼61%) in the clathrate phase. CP solutions exhibited a slower formation rate, but their final gas uptake and CO_2 selectivity in the clathrate phase were comparable to the THF solutions. Raman spectroscopy confirmed the enclathration of both CO_2 and N_2 in the clathrate cages and a structural transition due to the inclusion of promoters in the clathrate phase. The overall experimental results indicate that TBAC is a viable thermodynamic promoter for clathrate-based CO_2 capture from simulated flue gas, considering the lower pressure requirement for clathrate formation, higher CO_2 enrichment in the clathrate phase, non-toxicity, and non-volatility. - Highlights: • Clathrate-based CO_2 capture was investigated in the presence of thermodynamic promoters. • THF, CP, and TBAC demonstrated a significant thermodynamic promotion for CO_2 (20%) + N_2 (80%) clathrates. • The highest gas uptake was observed for the THF (5.6 mol%) solution. • TBAC solutions showed the highest CO_2 selectivity in the clathrate phase (∼61%). • Raman spectroscopy confirmed the guest gas enclathration and clathrate structure.

Thermodynamic activity-based intrinsic enzyme kinetic sheds light on enzyme-solvent interactions.

Science.gov (United States)

Grosch, Jan-Hendrik; Wagner, David; Nistelkas, Vasilios; Spieß, Antje C

2017-01-01

The reaction medium has major impact on biocatalytic reaction systems and on their economic significance. To allow for tailored medium engineering, thermodynamic phenomena, intrinsic enzyme kinetics, and enzyme-solvent interactions have to be discriminated. To this end, enzyme reaction kinetic modeling was coupled with thermodynamic calculations based on investigations of the alcohol dehydrogenase from Lactobacillus brevis (LbADH) in monophasic water/methyl tert-butyl ether (MTBE) mixtures as a model solvent. Substrate concentrations and substrate thermodynamic activities were varied separately to identify the individual thermodynamic and kinetic effects on the enzyme activity. Microkinetic parameters based on concentration and thermodynamic activity were derived to successfully identify a positive effect of MTBE on the availability of the substrate to the enzyme, but a negative effect on the enzyme performance. In conclusion, thermodynamic activity-based kinetic modeling might be a suitable tool to initially curtail the type of enzyme-solvent interactions and thus, a powerful first step to potentially understand the phenomena that occur in nonconventional media in more detail. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:96-103, 2017. © 2016 American Institute of Chemical Engineers.

Solid–liquid equilibrium and thermodynamic research of 3-Thiophenecarboxylic acid in (water + acetic acid) binary solvent mixtures

International Nuclear Information System (INIS)

Liu, Xiang; Liang, Mengmeng; Hu, Yonghong; Yang, Wenge; Shi, Ying; Yin, Jingjing; Liu, Yan

2014-01-01

Highlights: • The solubility was measured in (water + acetic acid) from 283.15 to 338.15 K. • The solubility increased with increasing temperature and water contents. • The modified Apelblat equation was more accurate than the λh equation. - Abstract: In this study, the solubility of 3-thiophenecarboxylic acid was measured in (water + acetic acid) binary solvent mixtures in the temperature ranging from 283.15 to 338.15 K by the analytical stirred-flask method under atmospheric pressure. The experimental data were well-correlated with the modified Apelblat equation and the λh equation. In addition, the calculated solubilities showed good agreement with the experimental results. It was found that the modified Apelblat equation could obtain the better correlation results than the λh equation. The experiment results indicated that the solubility of 3-thiophenecarboxylic acid in the binary solvents increased with increasing temperature, increases with increasing water contents, but the increments with temperature differed from different water contents. In addition, the thermodynamic properties of the solution process, including the Gibbs energy, enthalpy, and entropy were calculated by the van’t Hoff analysis. The experimental data and model parameters would be useful for optimizing the process of purification of 3-thiophenecarboxylic acid in industry

Thermodynamic Study of the Interaction of Bovine Serum Albumin and Amino Acids with Cellulose Nanocrystals.

Science.gov (United States)

Lombardo, Salvatore; Eyley, Samuel; Schütz, Christina; van Gorp, Hans; Rosenfeldt, Sabine; Van den Mooter, Guy; Thielemans, Wim

2017-06-06

The interaction of bovine serum albumin (BSA) with sulfated, carboxylated, and pyridinium-grafted cellulose nanocrystals (CNCs) was studied as a function of the degree of substitution by determining the adsorption isotherm and by directly measuring the thermodynamics of interaction. The adsorption of BSA onto positively charged pyridinium-grafted cellulose nanocrystals followed Langmuirian adsorption with the maximum amount of adsorbed protein increasing linearly with increasing degree of substitution. The binding mechanism between the positively charged pyridinum-grafted cellulose nanocrystals and BSA was found to be endothermic and based on charge neutralization. A positive entropy of adsorption associated with an increase of the degree of disorder upon addition of BSA compensated for the unfavorable endothermic enthalpy and enabled formation of pyridinium-g-CNC-BSA complexes. The endothermic enthalpy of adsorption was further found to decrease as a function of increasing degree of substitution. Negatively charged cellulose nanocrystals bearing sulfate and/or carboxylic functionalities were found to not interact significantly with the BSA protein. To investigate in more detail the role of single amino acids in the adsorption of proteins onto cellulose nanocrystals, we also studied the interaction of different types of amino acids with CNCs, i.e., charged (lysine, aspartic acid), aromatic (tryptophan, tyrosine), and polar (serine) amino acids. We found that none of the single amino acids bound with CNCs irrespective of surface charge and that therefore the binding of proteins with CNCs appears to require larger amino acid sequences that induce a greater entropic contribution to stabilize binding. Single amino acids are thus not adsorbed onto cellulose nanocrystals.

Study of uranium(VI) speciation in phosphoric acid solutions and of its recovery by solvent extraction

International Nuclear Information System (INIS)

Dartiguelongue, Adrien

2014-01-01

Because small amounts of uranium are present in phosphate rocks, wet phosphoric acids may contain up to 300 ppm of uranium(VI). Therefore, such acids are a cost-effective unconventional source of this metal. Its recovery is a challenge for metallurgical firms which must develop reliable and selective solvent extraction processes. Such processes need to know the chemical equilibria involved in the extraction process, the speciation of uranium and its thermodynamics in solution. These two last points have been investigated in this work. Firstly, the most probable species of uranium(VI) in phosphoric acid solutions have been selected thanks to a detailed review of the literature. Then, a thermodynamic model founded on an equation of state for electrolytes has been built according these hypotheses. It has been validated with speciation data coming from original ATR-IR spectroscopy measurements. Finally, the composition of the aqueous phosphoric acid solutions and the activity coefficients obtained have been combined with a chemical model of uranium(VI) extraction into an organic phase containing a synergistic mixture of bis(2-ethylhexyl)phosphoric acid (D2EHPA) and tri-n-octylphosphine oxide (TOPO) in order to represent the variation of the distribution coefficient of uranium(VI) with H 3 PO 4 concentration. This model had been previously developed at Chimie ParisTech at a given concentration of H 3 PO 4 (i.e., 5,3 mol/L), but in the present study we have tested its validity in an extended range of phosphoric acid concentrations (i.e., 1-7 mol/L) and improved it. (author)

Experimental investigation of thermodynamic properties of binary mixture of acetic acid + n-butanol and acetic acid + water at temperature from 293.15 K to 343.15 K

Science.gov (United States)

Paul, M. Danish John; Shruthi, N.; Anantharaj, R.

2018-04-01

The derived thermodynamic properties like excess molar volume, partial molar volume, excess partial molar volume and apparent volume of binary mixture of acetic acid + n-butanolandacetic acid + water has been investigated using measured density of mixtures at temperatures from 293.15 K to 343.15.

Investigation of Degradation Mechanisms of LSCF Based SOFC Cathodes — by CALPHAD Modeling and Experiments

DEFF Research Database (Denmark)

Zhang, Weiwei; Barfod, Rasmus

cathodes, investigation of the La-Sr-Co-Fe-O system using computational thermodynamics and designed key experiments was carried out in this work. The first part of the research work was devoted to establish a self-consistent thermodynamic database of relevant components (La-Sr-Co-Fe-O) using the CALPHAD...... (CALculation of PHAse Diagrams) approach. Published thermodynamic databases and experimental data related to the La-Sr-Co-Fe-O system were critically reviewed. The thermodynamic descriptions of the La-Co-O, Sr-Co-O and La-Sr-Co-O systems were further improved in order to construct the present thermodynamic...... database for LSCF, while new thermodynamic modeling of the Co-Fe-O, Sr-Co-Fe-O and La-Sr-Co-Fe-O systems was performed in this work. Calculated phase equilibria in LSCF as functions of composition, temperature, oxygen partial pressure are discussed by comparing with experimental data. Based...

New investigation of phase equilibria in the system Al-Cu-Si.

Science.gov (United States)

Ponweiser, Norbert; Richter, Klaus W

2012-01-25

The phase equilibria and invariant reactions in the system Al-Cu-Si were investigated by a combination of optical microscopy, powder X-ray diffraction (XRD), differential thermal analysis (DTA) and electron probe micro analysis (EPMA). Isothermal phase equilibria were investigated within two isothermal sections. The isothermal section at 500 °C covers the whole ternary composition range and largely confirms the findings of previous phase diagram investigations. The isothermal section at 700 °C describes phase equilibria only in the complex Cu-rich part of the phase diagram. A new ternary compound τ was found in the region between (Al,Cu)-γ(1) and (Cu,Si)-γ and its solubility range was determined. The solubility of Al in κ-CuSi was found to be extremely high at 700 °C. In contrast, no ternary solubility in the β-phase of Cu-Al was found, although this phase is supposed to form a complete solid solution according to previous phase diagram assessments. Two isopleths, at 10 and 40 at.% Si, were investigated by means of DTA and a partial ternary reaction scheme (Scheil diagram) was constructed, based on the current work and the latest findings in the binary systems Al-Cu and Cu-Si. The current study shows that the high temperature equilibria in the Cu-rich corner are still poorly understood and additional studies in this area would be favorable.

New 3,4-diaminobenzoic acid Schiff base compounds and their complexes: synthesis, characterization and thermodynamics.

Science.gov (United States)

Mohammadi, Khosro; Niad, Mahmood; Jafari, Tahereh

2014-03-25

Some new tetradentate Schiff base ligands (H3L) were prepared via condensation of 3,4-diaminobenzoic acid with 2-hydroxybenzaldehyde derivatives, such as 3,4-bis((E)-2,4-dihydroxybenzylideneamino)benzoic acid (H3L(1)), 3,4-bis((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (H3L(2)) and 3,4-bis((E)-5-bromo-2-hydroxybenzylideneamino)benzoic acid (H3L(4)). Additionally, a tetradentate Schiff base ligand 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (H3L(3)) and its complexes were synthesized. Their metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were prepared in good yields from the reaction of the ligands with the corresponding metal acetate. They were characterized based on IR, (1)H NMR, Mass spectroscopy and UV-Vis spectroscopy. Also, the formation constants of the complexes were measured by UV-Vis spectroscopic titration at constant ionic strength 0.1M (NaClO4), at 25 °C in dimethylformamide (DMF) as a solvent. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

A Numerical Algorithm to find All Scalar Feedback Nash Equilibria

NARCIS (Netherlands)

Engwerda, J.C.

2013-01-01

Abstract: In this note we generalize a numerical algorithm presented in [9] to calculate all solutions of the scalar algebraic Riccati equations that play an important role in finding feedback Nash equilibria of the scalar N-player linear affine-quadratic differential game. The algorithm is based on

Molecular Structure-Based Methods of Property Prediction in Application to Lipids: A Review and Refinement

DEFF Research Database (Denmark)

Cunico, Larissa; Hukkerikar, Amol; Ceriani, Roberta

2013-01-01

The paper is a review of the combined group contribution (GC)–atom connectivity index (CI) approachfor prediction of physical and thermodynamic properties of organic chemicals and their mixtures withspecial emphasis on lipids. The combined approach employs carefully selected datasets of different...... dependent, have been developed. For mixtures, properties related to phase equilibria aremodeled with GE-based models (UNIQUAC, UNIFAC, NRTL, and combined UNIFAC-CI method). The col-lected phase equilibrium data for VLE and SLE have been tested for thermodynamic consistency togetherwith a performance...... evaluation of the GE-models. The paper also reviews the role of the databases andthe mathematical and thermodynamic consistency of the measured/estimated data and the predictivenature of the developed models....

Evaluation of thermodynamic data on zirconium and hafnium halides and oxyhalides by means of transport experiments

International Nuclear Information System (INIS)

Dittmer, G.; Niemann, U.

1987-01-01

A consistent set of thermodynamic data for zirconium and hafnium halides, oxides and oxyhalides was achieved. It was found that formation enthalpies of gaseous compounds could be derived from solubility measurements together with theoretical estimations and a revision of literature data. Free energy functions were calculated employing statistical mechanics. Data for liquid and solid compounds were obtained via sublimation and vaporization data. Chemical equilibria of zirconium and hafnium with halogens are discussed. 51 refs.; 16 figs.; 14 tabs

Predicting Microstructure Development During HighTemperature Nitriding of Martensitic Stainless SteelsUsing Thermodynamic Modeling

OpenAIRE

Tschiptschin, André Paulo

2002-01-01

Thermodynamic calculations of the Fe-Cr-N System in the region of the Gas Phase Equilibria have been compared with experimental results of maximum nitrogen absorption during nitriding of two Martensitic Stainless Steels (a 6 mm thick sheet of AISI 410S steel and green powder compacts of AISI 434L steel) under N2 atmospheres. The calculations have been performed combining the Fe-Cr-N System description contained in the SGTE Solid Solution Database and the gas phase for the N System contained i...

Potentiometric investigation of acid dissociation and anionic homoconjugation equilibria of substituted phenols in dimethyl sulfoxide[Substituted phenols; Acid-base equilibria; Dimethyl sulfoxide (DMSO); Potentiometry

Energy Technology Data Exchange (ETDEWEB)

Czaja, Malgorzata; Kozak, Anna; Makowski, Mariusz; Chmurzynski, Lech. E-mail: lech@chemik.chem.univ.gda.pl

2003-10-01

Standard acidity constants, K{sub a}{sup DMSO} (HA), expressed as pK{sub a}{sup DMSO} (HA) values, and anionic homoconjugation constants, K{sup DMSO}{sub AHA{sup -}}, (in the form of lg K{sup DMSO}{sub AHA{sup -}} values) have been determined for 11 substituted phenol-phenolate systems a polar protophilic aprotic solvent, dimethyl sulfoxide (DMSO) with a potentiometric titration. A linear relationship has been determined between lg K{sup DMSO}{sub AHA{sup -}} and pK{sub a}{sup DMSO} (HA). The tendency towards anionic homoconjugation in these systems increases with increasing pK{sub a}{sup DMSO} (HA) that is with declining phenol acidity. The pK{sub a}{sup DMSO} (HA) are correlated with both pK{sub a}{sup W} (HA) water and other polar non-aqeous solvents.

Thermodynamic modeling of complex systems

DEFF Research Database (Denmark)

Liang, Xiaodong

after an oil spill. Engineering thermodynamics could be applied in the state-of-the-art sonar products through advanced artificial technology, if the speed of sound, solubility and density of oil-seawater systems could be satisfactorily modelled. The addition of methanol or glycols into unprocessed well...... is successfully applied to model the phase behaviour of water, chemical and hydrocarbon (oil) containing systems with newly developed pure component parameters for water and chemicals and characterization procedures for petroleum fluids. The performance of the PCSAFT EOS on liquid-liquid equilibria of water...... with hydrocarbons has been under debate for some vii years. An interactive step-wise procedure is proposed to fit the model parameters for small associating fluids by taking the liquid-liquid equilibrium data into account. It is still far away from a simple task to apply PC-SAFT in routine PVT simulations and phase...

Stability and attractive basins of multiple equilibria in delayed two-neuron networks

International Nuclear Information System (INIS)

Huang Yu-Jiao; Zhang Hua-Guang; Wang Zhan-Shan

2012-01-01

Multiple stability for two-dimensional delayed recurrent neural networks with piecewise linear activation functions of 2r (r ≥ 1) corner points is studied. Sufficient conditions are established for checking the existence of (2r + 1) 2 equilibria in delayed recurrent neural networks. Under these conditions, (r + 1) 2 equilibria are locally exponentially stable, and (2r + 1) 2 — (r + 1) 2 — r 2 equilibria are unstable. Attractive basins of stable equilibria are estimated, which are larger than invariant sets derived by decomposing state space. One example is provided to illustrate the effectiveness of our results. (general)

Thermodynamic properties and atomic structure of Ca-based liquid alloys

Science.gov (United States)

Poizeau, Sophie

To identify the most promising positive electrodes for Ca-based liquid metal batteries, the thermodynamic properties of diverse Ca-based liquid alloys were investigated. The thermodynamic properties of Ca-Sb alloys were determined by emf measurements. It was found that Sb as positive electrode would provide the highest voltage for Ca-based liquid metal batteries (1 V). The price of such a battery would be competitive for the grid-scale energy storage market. The impact of Pb, a natural impurity of Sb, was predicted successfully and confirmed via electrochemical measurements. It was shown that the impact on the open circuit voltage would be minor. Indeed, the interaction between Ca and Sb was demonstrated to be much stronger than between Ca and Pb using thermodynamic modeling, which explains why the partial thermodynamic properties of Ca would not vary much with the addition of Pb to Sb. However, the usage of the positive electrode would be reduced, which would limit the interest of a Pb-Sb positive electrode. Throughout this work, the molecular interaction volume model (MIVM) was used for the first time for alloys with thermodynamic properties showing strong negative deviation from ideality. This model showed that systems such as Ca-Sb have strong short-range order: Ca is most stable when its first nearest neighbors are Sb. This is consistent with what the more traditional thermodynamic model, the regular association model, would predict. The advantages of the MIVM are the absence of assumption regarding the composition of an associate, and the reduced number of fitting parameters (2 instead of 5). Based on the parameters derived from the thermodynamic modeling using the MIVM, a new potential of mixing for liquid alloys was defined to compare the strength of interaction in different Ca-based alloys. Comparing this trend with the strength of interaction in the solid state of these systems (assessed by the energy of formation of the intermetallics), the systems with

Spectrophotometric study of the complexation equilibria of uranium(VI) with 1,4-bis(4'-methylanilino)anthraquinone and determination of uranium(VI)

International Nuclear Information System (INIS)

Idriss, K.A.; Seleim, M.M.; Abu-Bakr, M.S.; Sedaira, H.

1985-01-01

The reaction of U(VI) with 1,4-bis(4'-methylanilino)anthraquinone (quinizarin green) in water-dimethylformamide medium was investigated spectrophotometrically. The complexation equilibria in solution were demonstrated. The study of the reaction in presence of equimolar concentrations or in solutions containing metal or ligand excess gave evidence for the formation of complexes with stoichiometric ratios of UO 2 :L = 1:1 and 1:2 in dependence on the pH of the medium. Their thermodynamic stabilities and the values of their molar absorption coefficients were determined. The optimum conditions for spectrophotometric determination of U(VI) with this reagent were found. (author)

Effect of backbone chemistry on hybridization thermodynamics of oligonucleic acids: a coarse-grained molecular dynamics simulation study.

Science.gov (United States)

Ghobadi, Ahmadreza F; Jayaraman, Arthi

2016-02-28

In this paper we study how varying oligonucleic acid backbone chemistry affects the hybridization/melting thermodynamics of oligonucleic acids. We first describe the coarse-grained (CG) model with tunable parameters that we developed to enable the study of both naturally occurring oligonucleic acids, such as DNA, and their chemically-modified analogues, such as peptide nucleic acids (PNAs) and locked nucleic acids (LNAs). The DNA melting curves obtained using such a CG model and molecular dynamics simulations in an implicit solvent and with explicit ions match with the melting curves obtained using the empirical nearest-neighbor models. We use these CG simulations to then elucidate the effect of backbone flexibility, charge, and nucleobase spacing along the backbone on the melting curves, potential energy and conformational entropy change upon hybridization and base-pair hydrogen bond residence time. We find that increasing backbone flexibility decreases duplex thermal stability and melting temperature mainly due to increased conformational entropy loss upon hybridization. Removing charges from the backbone enhances duplex thermal stability due to the elimination of electrostatic repulsion and as a result a larger energetic gain upon hybridization. Lastly, increasing nucleobase spacing decreases duplex thermal stability due to decreasing stacking interactions that are important for duplex stability.

Thermodynamics

CERN Document Server

Fermi, Enrico

1956-01-01

Indisputably, this is a modern classic of science. Based on a course of lectures delivered by the author at Columbia University, the text is elementary in treatment and remarkable for its clarity and organization. Although it is assumed that the reader is familiar with the fundamental facts of thermometry and calorimetry, no advanced mathematics beyond calculus is assumed.Partial contents: thermodynamic systems, the first law of thermodynamics (application, adiabatic transformations), the second law of thermodynamics (Carnot cycle, absolute thermodynamic temperature, thermal engines), the entr

Thermodynamic properties of aqueous solutions with citrate ions. Compressibility studies in aqueous solutions of citric acid

International Nuclear Information System (INIS)

Apelblat, Alexander; Korin, Eli; Manzurola, Emanuel

2013-01-01

Highlights: • Over a wide range of concentrations and temperatures sound velocities were measured in aqueous solutions of citric acid. • Compressibility properties of citric acid solutions are thermodynamically characterized. • Changes in the structure of water when citric acid is dissolved are discussed. -- Abstract: Sound velocities in aqueous solutions of citric acid were measured from 15 °C to 50 °C in 5 °C intervals, within the 0.1 mol · kg −1 to 5.0 mol · kg −1 concentration range. These sound velocities served to evaluate the isentropic and isothermal compressibilities, the apparent molar compressibilities, the isochoric thermal pressure coefficients, changes of the cubic expansion coefficients with pressure at constant temperature, the changes of heat capacities with volume and hydration numbers of citric acid in aqueous solutions

Effect of medium acidity on the thermodynamics and kinetics of the reaction of pyridoxal 5'-phosphate with isoniazid in an aqueous solution

Science.gov (United States)

Gamov, G. A.; Zavalishin, M. N.; Usacheva, T. R.; Sharnin, V. A.

2017-05-01

Thermodynamic characteristics of the formation of the Schiff base between isoniazid and pyridoxal 5'-phosphate in an aqueous solution at different pH values of a medium are determined by means of spectrophotometry and calorimetric titration. The process kinetics is studied spectrophotometrically, and the reaction rate constants for the formation of the imine at different acidities of a medium are determined. Biochemical aspects of the binding of pyridoxal 5'-phosphate into stable compounds are discussed.

Computation of Stackelberg Equilibria of Finite Sequential Games

DEFF Research Database (Denmark)

Bosanski, Branislav; Branzei, Simina; Hansen, Kristoffer Arnsfelt

2015-01-01

The Stackelberg equilibrium is a solution concept that describes optimal strategies to commit to: Player~1 (the leader) first commits to a strategy that is publicly announced, then Player~2 (the follower) plays a best response to the leader's choice. We study Stackelberg equilibria in finite...... sequential (i.e., extensive-form) games and provide new exact algorithms, approximate algorithms, and hardness results for finding equilibria for several classes of such two-player games....

Combined thermodynamic study of nickel-base alloys. Progress report

International Nuclear Information System (INIS)

Brooks, C.R.; Meschter, P.J.

1981-01-01

Achievements during this period are the following: (1) initiation of a high-temperature study of the Ni-Ta system using the galvanic cell technique, (2) emf study of high-temperature thermodynamics in the Ni-Mo system, (3) measured heat capacity data on ordered and disordered Ni 4 Mo, (4) heat capacities of Ni and disordered Ni 3 Fe, and (5) computer correlation of thermodynamic and phase diagram data in binary Ni-base alloys

Thermodynamic and Kinetic Study of Zinc bis-(Dipalmithyl Dithiophosphate Activity as Anti-Corrosion Additive-Fatty Acid Based Through Potentiodynamic Polarization Technique

Directory of Open Access Journals (Sweden)

Komar Sutriah

2016-08-01

Full Text Available Zinc bis-(dipalmithyl dithiophosphate (ZDTP16 is one product variant of zinc dialkyl dithiophosphate (ZDTP-fatty acid based having function as corrosion inhibitor. By using 3% of effective dose for the application, its effectiveness of ZDTP16 corrosion inhibition will achieve 97% and it will be able to decrease Cu metal corrosion rate from 0.152 to 0.004 mm per year. Thermodynamic and kinetic parameter verification indicates the decreasing of spontaneity and corrosion rate by existence of ZDTP16 inhibitor. Gibbs free energy transition corrosion of Cu metal in electrolyte medium is measured in corrosion simulator increased from +85.22 to +91.77 kJ mol-1, while its activation energy increased from +16.66 to +33.68 kJ mol-1. Morphology observation of Cu metal substrate surface using SEM-EDX shows that the adsorption of ZDTP16 at substrate surface is able to protect surface from corrosion indicated by the existence of Zn, P, S, and C constituents representing composer atoms of ZDTP16, and the decreasing of Cl- corrosive constituent at substrate surface.

On Pure and (approximate) Strong Equilibria of Facility Location Games

DEFF Research Database (Denmark)

Hansen, Thomas Dueholm; Telelis, Orestis A.

2008-01-01

We study social cost losses in Facility Location games, where n selfish agents install facilities over a network and connect to them, so as to forward their local demand (expressed by a non-negative weight per agent). Agents using the same facility share fairly its installation cost, but every...... agent pays individually a (weighted) connection cost to the chosen location. We study the Price of Stability (PoS) of pure Nash equilibria and the Price of Anarchy of strong equilibria (SPoA), that generalize pure equilibria by being resilient to coalitional deviations. For unweighted agents on metric...

Generic Model-Based Tailor-Made Design and Analysis of Biphasic Reaction Systems

DEFF Research Database (Denmark)

Anantpinijwatna, Amata

systems have a broad range of application, such as the manufacture of petroleum based chemicals, pharmaceuticals, and agro-bio products. Major considerations in the design and analysis of biphasic reaction systems are physical and chemical equilibria, kinetic mechanisms, and reaction rates. The primary...... contribution of this thesis is the development of a systematic modelling framework for the biphasic reaction system. The developed framework consists of three modules describing phase equilibria, reactions and mass transfer, and material balances of such processes. Correlative and predictive thermodynamic......Biphasic reaction systems are composed of immiscible aqueous and organic liquid phases where reactants, products, and catalysts are partitioned. These biphasic conditions point to novel synthesis paths, higher yields, and faster reactions, as well as facilitate product separation. The biphasic...

Kinetic and thermodynamic studies of a novel acid protease from Aspergillus foetidus.

Science.gov (United States)

Souza, Paula Monteiro; Aliakbarian, Bahar; Filho, Edivaldo Ximenes Ferreira; Magalhães, Pérola Oliveira; Junior, Adalberto Pessoa; Converti, Attilio; Perego, Patrizia

2015-11-01

The kinetics of a thermostable extracellular acid protease produced by an Aspergillus foetidus strain was investigated at different pH, temperatures and substrate concentrations. The enzyme exhibited maximal activity at pH 5.0 and 55°C, and its irreversible deactivation was well described by first-order kinetics. When temperature was raised from 55 to 70°C, the deactivation rate constant increased from 0.018 to 5.06h(-1), while the half-life decreased from 37.6 to 0.13h. The results of activity collected at different temperatures were then used to estimate, the activation energy of the hydrolysis reaction (E*=19.03kJ/mol) and the standard enthalpy variation of reversible enzyme unfolding (ΔH°U=19.03kJ/mol). The results of residual activity tests carried out in the temperature range 55-70°C allowed estimating the activation energy (E(*)d=314.12kJ/mol), enthalpy (311.27≤(ΔH°d≤311.39kJ/mol), entropy (599.59≤ΔS(*)d≤610.49kJ/mol K) and Gibbs free energy (103.18≤ΔG(*)d≤113.87kJ/mol) of the enzyme irreversible denaturation. These thermodynamic parameters suggest that this new protease is highly thermostable and could be important for industrial applications. To the best of our knowledge, this is the first report on thermodynamic parameters of an acid protease produced by A. foetidus. Copyright © 2015 Elsevier B.V. All rights reserved.

High-pressure phase equilibria in the (carbon dioxide + 1-hexanol) system

International Nuclear Information System (INIS)

Secuianu, Catinca; Feroiu, Viorel; Geana, Dan

2010-01-01

(Vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) data for the (carbon dioxide + 1-hexanol) system were measured at (293.15, 303.15, 313.15, 333.15, and 353.15) K. Phase behaviour measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between (0.6 and 14.49) MPa. The Soave-Redlich-Kwong (SRK) equation of state (EOS) with classical van der Waals mixing rules (two-parameters conventional mixing rule, 2PCMR), was used in a semi-predictive approach, in order to represent the complex phase behaviour (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behaviour is reasonably well predicted.

Numerical computation of FCT equilibria by inverse equilibrium method

International Nuclear Information System (INIS)

Tokuda, Shinji; Tsunematsu, Toshihide; Takeda, Tatsuoki

1986-11-01

FCT (Flux Conserving Tokamak) equilibria were obtained numerically by the inverse equilibrium method. The high-beta tokamak ordering was used to get the explicit boundary conditions for FCT equilibria. The partial differential equation was reduced to the simultaneous quasi-linear ordinary differential equations by using the moment method. The regularity conditions for solutions at the singular point of the equations can be expressed correctly by this reduction and the problem to be solved becomes a tractable boundary value problem on the quasi-linear ordinary differential equations. This boundary value problem was solved by the method of quasi-linearization, one of the shooting methods. Test calculations show that this method provides high-beta tokamak equilibria with sufficiently high accuracy for MHD stability analysis. (author)

Thermodynamics of axial substitution and kinetics of reactions with amino acids for the paddlewheel complex tetrakis(acetato)chloridodiruthenium(II,III).

Science.gov (United States)

Santos, Rodrigo L S R; van Eldik, Rudi; de Oliveira Silva, Denise

2012-06-18

The known paddlewheel, tetrakis(acetato)chloridodiruthenium(II,III), offers a versatile synthetic route to a novel class of antitumor diruthenium(II,III) metallo drugs, where the equatorial ligands are nonsteroidal anti-inflammatory carboxylates. This complex was studied here as a soluble starting prototype model for antitumor analogues to elucidate the reactivity of the [Ru(2)(CH(3)COO)(4)](+) framework. Thermodynamic studies on equilibration reactions for axial substitution of water by chloride and kinetic studies on reactions of the diaqua complexes with the amino acids glycine, cysteine, histidine, and tryptophan were performed. The standard thermodynamic reaction parameters ΔH°, ΔS°, and ΔV° were determined and showed that both of the sequential axial substitution reactions are enthalpy driven. Kinetic rate laws and rate constants were determined for the axial substitution reactions of coordinated water by the amino acids that gave the corresponding aqua(amino acid)-Ru(2) substituted species. The results revealed that the [Ru(2)(CH(3)COO)(4)](+) paddlewheel framework remained stable during the axial ligand substitution reactions and was also mostly preserved in the presence of the amino acids.

Thermodynamic characterization of bio-fuels: Excess functions for binary mixtures containing ETBE and hydrocarbons

International Nuclear Information System (INIS)

Segovia, Jose J.; Villamanan, Rosa M.; Martin, M. Carmen; Chamorro, Cesar R.; Villamanan, Miguel A.

2010-01-01

European energy policy is promoting the use of bio-fuels for transportation. Bioethers and bioalcohols are used as blending agents for enhancing the octane number. They make gasoline work harder, help the engine last longer and reduce air pollution. They also cause changes in the fuel properties. Development of renewable fuels needs both knowledge of new thermodynamic data and improvement of clean energy technologies. In this context, the use of ethanol of vegetable origin in its manufacture process, increases the interest of ETBE or bio-ETBE as an oxygenated additive. A complete study of the behaviour of ETBE + hydrocarbons mixtures is presented. Some experimental data concerning vapor-liquid equilibria and heats of mixing were determined in our laboratory. All the techniques have a high accuracy. The data were reduced by well-known models, such as NRTL and used to model the thermodynamic properties.

Prediction of vapour-liquid equilibria for the kinetic study of processes based on synthesis gas

Energy Technology Data Exchange (ETDEWEB)

Di Serio, M.; Tesser, R.; Cozzolino, M.; Santacesaria, E. [Naples Univ., Napoli (Italy). Dept. of Chemistry

2006-07-01

Syngas is normally used in the production of a broad range of chemicals and fuels. In many of these processes multiphase reactors, gas-liquid or gas-liquid-solid are used. Kinetic studies in multiphase systems are often complicated by the non-ideal behaviour of reagents and/or products that are consistently partitioned between the liquid and the vapour phase. Moreover, as often kinetic data are collected in batch conditions for the liquid phase, activity coefficients of the partitioned components can consistently change during the time as a consequence of changing the composition of the reaction mixture. Therefore, it is necessary, in these cases, to known the vapor-liquid equilibria (VLE) in order to collect and to interpret correctly the kinetic data. The description of phase equilibria, at high pressures, is usually performed by means of an EOS (Equation of State) allowing the calculation of fugacity coefficients, for each component, in both phases and determining the partition coefficients but the EOS approach involves the experimental determination of the interaction parameters for all the possible binary system of the mixture. For multicomponent mixtures a complete experimental determination of vapourliquid equilibria is very hard, also considering the high pressure and temperatures used. Some predictive group contribution methods have been recently developed. In this paper, we will describe in detail the application of these methods to the methanol homologation, as an example, with the scope of determining more reliable kinetic parameters for this reaction. (orig.)

Thermodynamic calculation of Al-Gd and Al-Gd-Mg phase equilibria checked by key experiments

International Nuclear Information System (INIS)

Groebner, J.; Kevorkov, D.; Schmid-Fetzer, R.

2001-01-01

The binary Al-Gd and the ternary Al-Gd-Mg systems were calculated using the Calphad method. It is demonstrated that previous interpretation of ternary liquidus temperatures below 700 C must be related to other phase equilibria. The actual ternary liquidus temperatures are much higher, up to some 600 C above the previous interpretation in literature. They are widely governed by the high-melting compounds Al 2 Gd and Al 3 Gd with liquidus surfaces stretching far into the ternary system. A small number of key experiments in this work confirmed the calculated liquidus temperature and the phase relations. The available experimental data in literature fit excellently with the calculation in the binary Al-Gd system. In the ternary Al-Gd-Mg system, which is shown in several sections of the phase diagram, a good agreement can be observed too, considering the necessary reinterpretation of the liquidus temperatures suggested by Rokhlin et al. Ternary solubilities were not found experimentally. The ternary compound Al 4 GdMg (τ) forms in a ternary peritectic reaction at 761 C. (orig.)

Physicochemical Profiling of α-Lipoic Acid and Related Compounds.

Science.gov (United States)

Mirzahosseini, Arash; Szilvay, András; Noszál, Béla

2016-07-01

Lipoic acid, the biomolecule of vital importance following glycolysis, shows diversity in its thiol/disulfide equilibria and also in its eight different protonation forms of the reduced molecule. In this paper, lipoic acid, lipoamide, and their dihydro derivatives were studied to quantify their solubility, acid-base, and lipophilicity properties at a submolecular level. The acid-base properties are characterized in terms of six macroscopic, 12 microscopic protonation constants, and three interactivity parameters. The species-specific basicities, the pH-dependent distribution of the microspecies, and lipophilicity parameters are interpreted by various intramolecular effects, and contribute to understanding the antioxidant, chelate-forming, and enzyme cofactor behavior of the molecules observed. © 2016 Wiley-VHCA AG, Zürich.

Institutions, Equilibria and Efficiency

DEFF Research Database (Denmark)

Competition and efficiency is at the core of economic theory. This volume collects papers of leading scholars, which extend the conventional general equilibrium model in important ways. Efficiency and price regulation are studied when markets are incomplete and existence of equilibria in such set......Competition and efficiency is at the core of economic theory. This volume collects papers of leading scholars, which extend the conventional general equilibrium model in important ways. Efficiency and price regulation are studied when markets are incomplete and existence of equilibria...... in such settings is proven under very general preference assumptions. The model is extended to include geographical location choice, a commodity space incorporating manufacturing imprecision and preferences for club-membership, schools and firms. Inefficiencies arising from household externalities or group...... membership are evaluated. Core equivalence is shown for bargaining economies. The theory of risk aversion is extended and the relation between risk taking and wealth is experimentally investigated. Other topics include: determinacy in OLG with cash-in-advance constraints, income distribution and democracy...

Benzimidazole acrylonitriles as multifunctional push-pull chromophores: Spectral characterisation, protonation equilibria and nanoaggregation in aqueous solutions

Science.gov (United States)

Horak, Ema; Vianello, Robert; Hranjec, Marijana; Krištafor, Svjetlana; Zamola, Grace Karminski; Steinberg, Ivana Murković

2017-05-01

Heterocyclic donor-π-acceptor molecular systems based on an N,N-dimethylamino phenylacrylonitrile benzimidazole skeleton have been characterised and are proposed for potential use in sensing applications. The benzimidazole moiety introduces a broad spectrum of useful multifunctional properties to the system including electron accepting ability, pH sensitivity and compatibility with biomolecules. The photophysical characterisation of the prototropic forms of these chromophores has been carried out in both solution and on immobilisation in polymer films. The experimental results are further supported by computational determination of pKa values. It is noticed that compound 3 forms nanoaggregates in aqueous solutions with aggregation-induced emission (AIE) at 600 nm. All the systems demonstrate spectral pH sensitivity in acidic media which shifts towards near-neutral values upon immobilisation in polymer films or upon aggregation in an aqueous environment (compound 3). The structure-property relationships of these functional chromophores, involving their spectral characteristics, acid-base equilibria, pKa values and aggregation effects have been determined. Potential applications of the molecules as pH and biomolecular sensors are proposed based on their pH sensitivity and AIE properties.

Field line diversion properties of finite β-helias equilibria

International Nuclear Information System (INIS)

Hayashi, Takaya; Schwenn, Ulrich; Strumberger, Erika.

1992-01-01

The diversion properties of the magnetic field outside the last closed magnetic surface of a Helias stellarator configuration are investigated for finite pressure equilibria. The results indicate that a divertor concept which has been developed from the diversion properties of the corresponding vacuum field can be maintained for finite pressure equilibria. Cross-field particle transport is simulated by a simplified scrape-off layer (SOL) model. (author)

submitter Modeling the thermodynamics and kinetics of sulfuric acid-dimethylamine-water nanoparticle growth in the CLOUD chamber

CERN Document Server

Ahlm, L; Schobesberger, S; Praplan, A P; Kim, J; Tikkanen, O -P; Lawler, M J; Smith, J N; Tröstl, J; Acosta Navarro, J C; Baltensperger, U; Bianchi, F; Donahue, N M; Duplissy, J; Franchin, A; Jokinen, T; Keskinen, H; Kirkby, J; Kürten, A; Laaksonen, A; Lehtipalo, K; Petäjä, T; Riccobono, F; Rissanen, M P; Rondo, L; Schallhart, S; Simon, M; Winkler, P M; Worsnop, D R; Virtanen, A; Riipinen, I

2016-01-01

Dimethylamine (DMA) has a stabilizing effect on sulfuric acid (SA) clusters, and the SA and DMA molecules and clusters likely play important roles in both aerosol particle formation and growth in the atmosphere. We use the monodisperse particle growth model for acid-base chemistry in nanoparticle growth (MABNAG) together with direct and indirect observations from the CLOUD4 and CLOUD7 experiments in the cosmics leaving outdoor droplets (CLOUD) chamber at CERN to investigate the size and composition evolution of freshly formed particles consisting of SA, DMA, and water as they grow to 20 nm in dry diameter. Hygroscopic growth factors are measured using a nano-hygroscopicity tandem differential mobility analyzer (nano-HTDMA), which combined with simulations of particle water uptake using the thermodynamic extended-aerosol inorganics model (E-AIM) constrain the chemical composition. MABNAG predicts a particle-phase ratio between DMA and SA molecules of 1.1–1.3 for a 2 nm particle and DMA gas-phase mixing ratio...

Introduction to supercritical fluids a spreadsheet-based approach

CERN Document Server

Smith, Richard; Peters, Cor

2013-01-01

This text provides an introduction to supercritical fluids with easy-to-use Excel spreadsheets suitable for both specialized-discipline (chemistry or chemical engineering student) and mixed-discipline (engineering/economic student) classes. Each chapter contains worked examples, tip boxes and end-of-the-chapter problems and projects. Part I covers web-based chemical information resources, applications and simplified theory presented in a way that allows students of all disciplines to delve into the properties of supercritical fluids and to design energy, extraction and materials formation systems for real-world processes that use supercritical water or supercritical carbon dioxide. Part II takes a practical approach and addresses the thermodynamic framework, equations of state, fluid phase equilibria, heat and mass transfer, chemical equilibria and reaction kinetics of supercritical fluids. Spreadsheets are arranged as Visual Basic for Applications (VBA) functions and macros that are completely (source code) ...

Ideal MHD beta-limits of poloidally asymmetric equilibria

Energy Technology Data Exchange (ETDEWEB)

Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

1981-05-01

The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in ..beta../sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is ..beta../sub critical/ approx. = 6.5%.

Ideal MHD beta-limits of poloidally asymmetric equilibria

International Nuclear Information System (INIS)

Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

1981-05-01

The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in β/sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is β/sub critical/ approx. = 6.5%

A general approach to the testing of binary solubility systems for thermodynamic consistency. Consolidated Fuel Reprocessing Program

Science.gov (United States)

Hamm, L. L.; Vanbrunt, V.

1982-08-01

The numerical solution to the ordinary differential equation which describes the high-pressure vapor-liquid equilibria of a binary system where one of the components is supercritical and exists as a noncondensable gas in the pure state is considered with emphasis on the implicit Runge-Kuta and orthogonal collocation methods. Some preliminary results indicate that the implicit Runge-Kutta method is superior. Due to the extreme nonlinearity of thermodynamic properties in the region near the critical locus, and extended cubic spline fitting technique is devised for correlating the P-x data. The least-squares criterion is employed in smoothing the experimental data. The technique could easily be applied to any thermodynamic data by changing the endpoint requirements. The volumetric behavior of the systems must be given or predicted in order to perform thermodynamic consistency tests. A general procedure is developed for predicting the volumetric behavior required and some indication as to the expected limit of accuracy is given.

Thermodynamics and Structure of Actinide(IV) Complexes with Nitrilotriacetic Acid

Energy Technology Data Exchange (ETDEWEB)

Bonin, L.; Guillaumont, D.; Jeanson, A.; Den Auwer, C.; Moisy, Ph. [CEA Marcoule, DEN, DRCP, SCPS, F-30207 Bagnols Sur Ceze (France); Grigoriev, M. [RAS, AN Frumkin Inst Phys Chem and Electrochem, Moscow 119991 (Russian Federation); Berthet, J.C. [CEA Saclay, DSM, IRAMIS, URA 331, Serv Chim Mol, CNRS, F-91191 Gif Sur Yvette (France); Hennig, C.; Scheinost, A. [Forschungszentrum Dresden Rossendorf, Inst Radiochem, D-01314 Dresden (Germany)

2009-05-15

Nitrilotriacetic acid, commonly known as NITA (N(CH{sub 2}CO{sub 2}H){sub 3}), can be considered a representative of the polyamino-carboxylic family. The results presented in this paper describe the thermodynamical complexation and structural investigation of An(IV) complexes with NTA in aqueous solution. In the first part, the stability constants of the An(IV) complexes (An = Pu, Np, U, and Th) have been determined by spectrophotometry. In the second part, the coordination spheres of the actinide cation in these complexes have been described using extended X-ray absorption fine structure spectroscopy and compared to the solid-state structure of (Hpy){sub 2}[U(NTA){sub 2}].H{sub 2}O. These data are further compared to quantum chemical calculations, and their evolution across the actinide series is discussed. In particular, an interpretation of the role of the nitrogen atom in the coordination mode is proposed. These results are considered to be model behavior of polyamino-carboxylic ligands such as diethylenetriamine pentaacetic acid, which is nowadays the best candidate for a chelating agent in the framework of actinide decorporation for the human body. (authors)

Mathematical Model for Multicomponent Adsorption Equilibria Using Only Pure Component Data

DEFF Research Database (Denmark)

Marcussen, Lis

2000-01-01

A mathematical model for nonideal adsorption equilibria in multicomponent mixtures is developed. It is applied with good results for pure substances and for prediction of strongly nonideal multicomponent equilibria using only pure component data. The model accounts for adsorbent...

Experimental study and thermodynamic modelling of methane clathrate hydrate dissociation conditions in silica gel porous media in the presence of methanol aqueous solution

International Nuclear Information System (INIS)

Hashemi, Hamed; Javanmardi, Jafar; Zarifi, Mojdeh; Eslamimanesh, Ali; Mohammadi, Amir H.

2012-01-01

Highlights: ► Phase equilibria of hydrates of methane in confined silica gel pores are reported. ► Dissociation data in the presences of methanol aqueous solution are also measured. ► A thermodynamic model is developed for prediction of the obtained data. ► Acceptable agreement is found between the obtained data and the predicted results. - Abstract: In this work, the phase equilibria of clathrate hydrates of methane in the presence of pure water and 0.035 mass fraction of methanol aqueous solution in confined silica gel pores with (10 and 15) nm mean diameters are measured and reported. A thermodynamic model is also developed for prediction of the obtained experimental hydrate dissociation data. The Valderrama–Patel–Teja (VPT-EoS) equation of state (EoS) accompanied with the non-density dependent (NDD) mixing rules coupled with a previously developed activity model are applied to evaluate the fugacity of the species present and the activity coefficient of water in methanol aqueous solution. Acceptable agreement between the reported data and the predicted results using the proposed model and an existing method reported in the literature demonstrates the reliability of the presented model.

Thermodynamics of mixtures containing alkoxyethanols. XXVIII: Liquid-liquid equilibria for 2-phenoxyethanol + selected alkanes

Energy Technology Data Exchange (ETDEWEB)

Alonso, Victor; Garcia, Mario [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Gonzalez, Juan Antonio, E-mail: jagl@termo.uva.es [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain); Garcia De La Fuente, Isaias; Cobos, Jose Carlos [G.E.T.E.F., Grupo Especializado en Termodinamica de Equilibrio entre Fases, Departamento de Fisica Aplicada, Facultad de Ciencias, Universidad de Valladolid, E-47071 Valladolid (Spain)

2011-07-10

Highlights: {yields} LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. {yields} UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. {yields} For the latter mixtures, UCST increases with the size of the alkyl group attached. {yields} Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.

Thermodynamics of mixtures containing alkoxyethanols. XXVIII: Liquid-liquid equilibria for 2-phenoxyethanol + selected alkanes

International Nuclear Information System (INIS)

Alonso, Victor; Garcia, Mario; Gonzalez, Juan Antonio; Garcia De La Fuente, Isaias; Cobos, Jose Carlos

2011-01-01

Highlights: → LLE coexistence curves were determined for mixtures of 2PhEE with alkanes. → UCST values are higher for n-alkane systems than for solutions with cyclic alkanes. → For the latter mixtures, UCST increases with the size of the alkyl group attached. → Alkoxyethanol-alkoxyethanol interactions are enhanced by aromatic group in cellosolve. - Abstract: The coexistence curves of the liquid-liquid equilibria (LLE) for systems of 2-phenoxyethanol (2PhEE) with heptane, octane, cyclohexane, methylcyclohexane or ethylcyclohexane have been determined by the method of the critical opalescence using a laser scattering technique. All the curves show an upper critical solution temperature (UCST), have a rather horizontal top and their symmetry depends on the relative size of the mixture compounds. UCST values are higher for systems with linear alkanes than for solutions including cyclic alkanes. For these mixtures, the UCST increases with the size of the alkyl group attached to the cyclic part of the molecule. It is shown that interactions between alkoxyethanol molecules are stronger when the hydroxyether contains an aromatic group. Data are used to determine the critical exponent for the order parameter mole fraction. Values obtained are consistent with those provided by the Ising model or by the renormalization group theory.

Thermodynamics-based models of transcriptional regulation with gene sequence.

Science.gov (United States)

Wang, Shuqiang; Shen, Yanyan; Hu, Jinxing

2015-12-01

Quantitative models of gene regulatory activity have the potential to improve our mechanistic understanding of transcriptional regulation. However, the few models available today have been based on simplistic assumptions about the sequences being modeled or heuristic approximations of the underlying regulatory mechanisms. In this work, we have developed a thermodynamics-based model to predict gene expression driven by any DNA sequence. The proposed model relies on a continuous time, differential equation description of transcriptional dynamics. The sequence features of the promoter are exploited to derive the binding affinity which is derived based on statistical molecular thermodynamics. Experimental results show that the proposed model can effectively identify the activity levels of transcription factors and the regulatory parameters. Comparing with the previous models, the proposed model can reveal more biological sense.

Stability of black holes based on horizon thermodynamics

Directory of Open Access Journals (Sweden)

Meng-Sen Ma

2015-12-01

Full Text Available On the basis of horizon thermodynamics we study the thermodynamic stability of black holes constructed in general relativity and Gauss–Bonnet gravity. In the framework of horizon thermodynamics there are only five thermodynamic variables E, P, V, T, S. It is not necessary to consider concrete matter fields, which may contribute to the pressure of black hole thermodynamic system. In non-vacuum cases, we can derive the equation of state, P=P(V,T. According to the requirements of stable equilibrium in conventional thermodynamics, we start from these thermodynamic variables to calculate the heat capacity at constant pressure and Gibbs free energy and analyze the local and global thermodynamic stability of black holes. It is shown that P>0 is the necessary condition for black holes in general relativity to be thermodynamically stable, however this condition cannot be satisfied by many black holes in general relativity. For black hole in Gauss–Bonnet gravity negative pressure can be feasible, but only local stable black hole exists in this case.

Nash Equilibria in Symmetric Games with Partial Observation

DEFF Research Database (Denmark)

Bouyer, Patricia; Markey, Nicolas; Vester, Steen

2014-01-01

We investigate a model for representing large multiplayer games, which satisfy strong symmetry properties. This model is made of multiple copies of an arena; each player plays in his own arena, and can partially observe what the other players do. Therefore, this game has partial information...... and symmetry constraints, which make the computation of Nash equilibria difficult. We show several undecidability results, and for bounded-memory strategies, we precisely characterize the complexity of computing pure Nash equilibria (for qualitative objectives) in this game model....

An NMR and ab initio quantum chemical study of acid-base equilibria for conformationally constrained acidic alpha-amino acids in aqueous solution

DEFF Research Database (Denmark)

Nielsen, Peter Aadal; Jaroszewski, Jerzy W.; Norrby, Per-Ola

2001-01-01

The protonation states of a series of piperidinedicarboxylic acids (PDAs), which are conformationally constrained acidic alpha -amino acids, have been studied by C-13 NMR titration in water. The resulting data have been correlated with theoretical results obtained by HF/6-31+G* calculations using...

Recent progress in the relative equilibria of point vortices — In memoriam Hassan Aref

DEFF Research Database (Denmark)

Beelen, Peter; Brøns, Morten; Krishnamurthy, Vikas S.

2013-01-01

Hassan Aref, who sadly passed away in 2011, was one of the world's leading researchers in the dynamics and equilibria of point vortices. We review two problems on the subject of point vortex relative equilibria in which he was engaged at the time of his death: bilinear relative equilibria...

Variational-moment method for computing magnetohydrodynamic equilibria

International Nuclear Information System (INIS)

Lao, L.L.

1983-08-01

A fast yet accurate method to compute magnetohydrodynamic equilibria is provided by the variational-moment method, which is similar to the classical Rayleigh-Ritz-Galerkin approximation. The equilibrium solution sought is decomposed into a spectral representation. The partial differential equations describing the equilibrium are then recast into their equivalent variational form and systematically reduced to an optimum finite set of coupled ordinary differential equations. An appropriate spectral decomposition can make the series representing the solution coverge rapidly and hence substantially reduces the amount of computational time involved. The moment method was developed first to compute fixed-boundary inverse equilibria in axisymmetric toroidal geometry, and was demonstrated to be both efficient and accurate. The method since has been generalized to calculate free-boundary axisymmetric equilibria, to include toroidal plasma rotation and pressure anisotropy, and to treat three-dimensional toroidal geometry. In all these formulations, the flux surfaces are assumed to be smooth and nested so that the solutions can be decomposed in Fourier series in inverse coordinates. These recent developments and the advantages and limitations of the moment method are reviewed. The use of alternate coordinates for decomposition is discussed

Critical thermodynamic evaluation and optimization of the Fe–B, Fe–Nd, B–Nd and Nd–Fe–B systems

International Nuclear Information System (INIS)

Van Ende, Marie-Aline; Jung, In-Ho

2013-01-01

Highlights: ► Complete critical evaluation of all available phase diagram and thermodynamic data for the Fe–Nd–B system for the first time. ► Thermodynamic database of optimized model parameters has been developed. ► Gibbs energies of binary and ternary solid and liquid phases were properly described. ► All reliable thermodynamic and phase diagram data were properly reproduced. ► Liquidus projection of the Fe–Nd–B system is properly predicted for the first time. - Abstract: All experimental data on phase equilibria and thermodynamic properties of the Fe–B, Fe–Nd and Nd–B binary and Fe–Nd–B ternary systems in literature were reviewed and critically examined. A set of optimized model parameters for all solid stoichiometric compounds, solid solutions and liquid phase was built to reproduce all available reliable thermodynamic properties and phase diagram data within experimental error limits. The solid solutions were modeled using the Compound Energy Formalism. The Modified Quasichemical Model in the pair approximation was used to describe the thermodynamic properties of the liquid solution accurately. The database of the model parameters can be used, along with the software for Gibbs energy minimization, to calculate any type of phase diagram section. Unexplored liquidus projection of the Fe–Nd–B ternary system was predicted from the thermodynamic models and optimized parameters.

Control Algorithms Along Relative Equilibria of Underactuated Lagrangian Systems on Lie Groups

DEFF Research Database (Denmark)

Nordkvist, Nikolaj; Bullo, F.

2008-01-01

We present novel algorithms to control underactuated mechanical systems. For a class of invariant systems on Lie groups, we design iterative small-amplitude control forces to accelerate along, decelerate along, and stabilize relative equilibria. The technical approach is based upon a perturbation...

Control algorithms along relative equilibria of underactuated Lagrangian systems on Lie groups

DEFF Research Database (Denmark)

Nordkvist, Nikolaj; Bullo, Francesco

2007-01-01

We present novel algorithms to control underactuated mechanical systems. For a class of invariant systems on Lie groups, we design iterative small-amplitude control forces to accelerate along, decelerate along, and stabilize relative equilibria. The technical approach is based upon a perturbation...

Thermodynamics of the ternary systems: (water + glycine, L-alanine and L-serine + di-ammonium hydrogen citrate) from volumetric, compressibility, and (vapour + liquid) equilibria measurements

International Nuclear Information System (INIS)

Sadeghi, Rahmat; Gholamireza, Afsaneh

2011-01-01

The apparent molar volumes and isentropic compressibility of glycine, L-alanine and L-serine in water and in aqueous solutions of (0.500 and 1.00) mol . kg -1 di-ammonium hydrogen citrate {(NH 4 ) 2 HCit} and those of (NH 4 ) 2 HCit in water have been obtained over the (288.15 to 313.15) K temperature range at 5 K intervals at atmospheric pressure from measurements of density and ultrasonic velocity. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated amino acids have been obtained and their variations with temperature and their transfer properties from water to aqueous solutions of (NH 4 ) 2 HCit have also been obtained. The results have been interpreted in terms of the hydration of the amino acids. In the second part of this work, water activity measurements by the isopiestic method have been carried out on the aqueous solutions of {glycine + (NH 4 ) 2 HCit}, {alanine + (NH 4 ) 2 HCit}, and {serine + (NH 4 ) 2 HCit} at T = 298.15 K at atmospheric pressure. From these measurements, values of vapour pressure, osmotic coefficient, activity coefficient and Gibbs free energy were obtained. The effect of the type of amino acids on the (vapour + liquid) equilibrium of the systems investigated has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. Furthermore, the thermodynamic behaviour of the ternary solutions investigated has been studied by using the semi-ideal hydration model and the linear concentration relations have been tested by comparing with the isopiestic measurements for the studied systems at T = 298.15 K.

Native characterization of nucleic acid motif thermodynamics via non-covalent catalysis

Science.gov (United States)

Wang, Chunyan; Bae, Jin H.; Zhang, David Yu

2016-01-01

DNA hybridization thermodynamics is critical for accurate design of oligonucleotides for biotechnology and nanotechnology applications, but parameters currently in use are inaccurately extrapolated based on limited quantitative understanding of thermal behaviours. Here, we present a method to measure the ΔG° of DNA motifs at temperatures and buffer conditions of interest, with significantly better accuracy (6- to 14-fold lower s.e.) than prior methods. The equilibrium constant of a reaction with thermodynamics closely approximating that of a desired motif is numerically calculated from directly observed reactant and product equilibrium concentrations; a DNA catalyst is designed to accelerate equilibration. We measured the ΔG° of terminal fluorophores, single-nucleotide dangles and multinucleotide dangles, in temperatures ranging from 10 to 45 °C. PMID:26782977

Cocrystals of a 1,2,4-thiadiazole-based potent neuroprotector with gallic acid: solubility, thermodynamic stability relationships and formation pathways.

Science.gov (United States)

Surov, Artem O; Churakov, Andrei V; Proshin, Alexey N; Dai, Xia-Lin; Lu, Tongbu; Perlovich, German L

2018-05-30

Three distinct solid forms, namely anhydrous cocrystals with 2 : 1 and 1 : 1 drug/acid ratios ([TDZ : GA] (2 : 1), [TDZ : GA] (1 : 1)), and a hydrated one having 1 : 1 : 1 drug/acid/water stoichiometry ([TDZ : GA : H2O] (1 : 1 : 1)), have been formed by cocrystallization of the biologically active 1,2,4-thiadiazole derivative (TDZ) with gallic acid (GA). The thermodynamic stability relationships between the cocrystals were rationalized in terms of Gibbs energies of the formation reactions and further verified by performing a set of competitive and exchange mechanochemical reactions. Interestingly, competitive grinding in the presence of the structurally related vanillic acid led to the formation of a new polymorphic form of the [TDZ : Vanillic acid] (1 : 1) cocrystal, which was promoted by gallic acid. The mechanochemical method was also applied to elucidate the alternative pathways of the [TDZ : GA : H2O] (1 : 1 : 1) cocrystal formation. Direct cocrystallization of TDZ with GA monohydrate was found to proceed much faster than the reaction of TDZ and anhydrous GA in the presence of an acetonitrile/water mixture, which may indicate the presence of a transitional stage. According to dissolution studies, the [TDZ : GA : H2O] (1 : 1 : 1) cocrystal was ca. 6.6 times more soluble than the parent 1,2,4-thiadiazole at pH 2.0 and 25.0 °C. The apparent two-step dehydration behavior of the [TDZ : GA : H2O] (1 : 1 : 1) cocrystal monohydrate was clarified by analyzing the intermolecular interactions of water molecules with the crystalline environment derived from solid state DFT calculations.

The Al-rich region of the Al-Mn-Ni alloy system. Part II. Phase equilibria at 620-1000 oC

International Nuclear Information System (INIS)

Balanetskyy, S.; Meisterernst, G.; Grushko, B.; Feuerbacher, M.

2011-01-01

Research highlights: → Phase equilibria in the Al-rich region of the Al-Mn-Ni alloy system were studied at 1000, 950, 850, 750, 700, 645 and 620 deg. C by means of SEM, TEM, powder XRD and DTA. → Three ternary thermodynamically stable intermetallics, the φ-phase (Al 5 Co 2 -type, hP26, P63/mmc; a = 0.76632(16), c = 0.78296(15) nm), the κ-phase (κ-Al 14.4 Cr 3.4 Ni l.1 -type, hP227, P63/m; a = 1.7625(10), c = 1.2516(10) nm), and the O-phase (O-Al 77 Cr 14 Pd 9 -type, Pmmn, oP650,: a = 2.3316(16), b = 1.2424(15), c = 3.2648(14) nm), as well as three ternary metastable phases, the decagonal D 3 -phase with periodicity about 1.25 nm, the Al 9 (Mn,Ni) 2 -phase (Al 9 Co 2 -type, P1121/a, mP22; a = 0.8585(16), b = 0.6269(9), c = 0.6205(11) nm, β = 95.34(10) o ) and the O 1 -phase (basecentered orthorhombic, a ∼ 23.8, b ∼ 12.4, c ∼ 32.2 nm) were revealed. → The existence of a thermodynamically stable R-phase of stoichiometry Al 60 Mn 11 Ni 4 , reported earlier in literature, was not confirmed in the present study. - Abstract: Phase equilibria in the Al-rich region of the Al-Mn-Ni alloy system were studied at 1000, 950, 850, 750, 700, 645 and 620 o C. Three ternary thermodynamically stable intermetallics, the φ-phase (Al 5 Co 2 -type, hP26, P6 3 /mmc; a = 0.76632(16), c = 0.78296(15) nm), the κ-phase (κ-Al 14.4 Cr 3.4 Ni l.1 -type, hP227, P6 3 /m; a = 1.7625(10), c = 1.2516(10) nm), and the O-phase (O-Al 77 Cr 14 Pd 9 -type, Pmmn, oP650,: a = 2.3316(16), b = 1.2424(15), c = 3.2648(14) nm), as well as three ternary metastable phases, the decagonal D 3 -phase with periodicity about 1.25 nm, the Al 9 (Mn,Ni) 2 -phase (Al 9 Co 2 -type, P112 1 /a, mP22; a = 0.8585(16), b = 0.6269(9), c = 0.6205(11) nm, β = 95.34(10) o ) and the O 1 -phase (base-centered orthorhombic, a ∼ 23.8, b ∼ 12.4, c ∼ 32.2 nm) were revealed. Their physicochemical behaviour in the Al-Mn-Ni alloy system was studied.

Study of thermodynamic and acoustic behaviour of nicotinic acid in binary aqueous mixtures of D-lactose

Science.gov (United States)

Sharma, Ravi; Thakur, R. C.

2017-07-01

In the present study, the thermodynamic properties such as partial molar volumes, partial molar expansibilities, partial molar compressibilities, partial molar heat capacities and isobaric thermal expansion coefficient of different solutions of nicotinic acid in binary aqueous mixtures of D-lactose have been determined at different temperatures (298.15, 303.15, 308.15, 313.15) K. Masson's equation is used to interpret the data in terms of solute-solute and solute-solvent interactions. In the present study it has been found that nicotinic acid behaves as structure maker in aqueous and binary aqueous mixtures of D-lactose.

Institutions, Equilibria and Efficiency

DEFF Research Database (Denmark)

Competition and efficiency is at the core of economic theory. This volume collects papers of leading scholars, which extend the conventional general equilibrium model in important ways. Efficiency and price regulation are studied when markets are incomplete and existence of equilibria in such set...... in OLG, learning in OLG and in games, optimal pricing of derivative securities, the impact of heterogeneity...

Solid formation in piperazine rate-based simulation

DEFF Research Database (Denmark)

Gaspar, Jozsef; Thomsen, Kaj; von Solms, Nicolas

2014-01-01

of view but also from a modeling perspective. The present work develops a rate-based model for CO2 absorption and desorption modeling for gas-liquid-solid systems and it is demonstrated for the piperazine CO2 capture process. This model is an extension of the DTU CAPCO2 model to precipitating systems....... It uses the extended UNIQUAC thermodynamic model for phase equilibria and thermal properties estimation. The mass and heat transfer phenomena is implemented in a film model approach, based on second order reactions kinetics. The transfer fluxes are calculated using the concentration of the dissolved...

Hard and soft acids and bases: atoms and atomic ions.

Science.gov (United States)

Reed, James L

2008-07-07

The structural origin of hard-soft behavior in atomic acids and bases has been explored using a simple orbital model. The Pearson principle of hard and soft acids and bases has been taken to be the defining statement about hard-soft behavior and as a definition of chemical hardness. There are a number of conditions that are imposed on any candidate structure and associated property by the Pearson principle, which have been exploited. The Pearson principle itself has been used to generate a thermodynamically based scale of relative hardness and softness for acids and bases (operational chemical hardness), and a modified Slater model has been used to discern the electronic origin of hard-soft behavior. Whereas chemical hardness is a chemical property of an acid or base and the operational chemical hardness is an experimental measure of it, the absolute hardness is a physical property of an atom or molecule. A critical examination of chemical hardness, which has been based on a more rigorous application of the Pearson principle and the availability of quantitative measures of chemical hardness, suggests that the origin of hard-soft behavior for both acids and bases resides in the relaxation of the electrons not undergoing transfer during the acid-base interaction. Furthermore, the results suggest that the absolute hardness should not be taken as synonymous with chemical hardness but that the relationship is somewhat more complex. Finally, this work provides additional groundwork for a better understanding of chemical hardness that will inform the understanding of hardness in molecules.

Acid-Base Equilibria of Some N-Substituted Thiophene-2-Carboxamidoximes in Non-Aqueous Media

OpenAIRE

DÜRÜST, Nedime

2002-01-01

The protonation constants of the amino nitrogens of some N-substituted thiophene-2-carboxamidoximes have been determined in acetic acid by means of potentiometric titration with perchloric acid. pKa values of the title compounds were interpreted on the basis of structural effects due to the substituents and the main skeleton.

Thermodynamics of mixed-ligand complex formation of zinc nitrilotriacetate with amino acids and dipeptides in solution

International Nuclear Information System (INIS)

Pyreu, Dmitrii; Gruzdev, Matvey; Kumeev, Roman; Gridchin, Sergei

2014-01-01

Highlights: • Stable mixed ligand complexes of ZnNta with amino acids and dipeptides. • Histamine-like coordination mode of His in the complex ZnNtaHis. • Glycine-like coordination of Lys and Orn in the complexes ZnNtaL and ZnNtaHL • NH 2 , CO-coordination mode of GlyGly in the complex ZnNtaGG. • NH 2 , N − or NH2, N − , COO-coordination modes of GlyGly in the complex ZnNtaGGH −1 . - Abstract: The isothermal calorimetry, pH-potentiometric titration and 1 H and 13 C NMR methods has been used to study the mixed-ligand complex formation in the systems Zn 2+ –Nta 3– –L − (L = His, Orn, Lys, GlyGly, AlaAla) in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO 3 ). The thermodynamic parameters of formation of the mixed complexes have been determined. The relationship between the probable coordination modes of the complexone and amino acid or dipeptide molecules in the mixed-ligand complex and the thermodynamic parameters has been discussed

Thermodynamics of mixed-ligand complex formation of zinc nitrilotriacetate with amino acids and dipeptides in solution

Energy Technology Data Exchange (ETDEWEB)

Pyreu, Dmitrii, E-mail: pyreu@mail.ru [Department of Inorganic and Analytic Chemistry, Ivanovo State UniversityErmak 39, Ivanovo 153025 (Russian Federation); Gruzdev, Matvey; Kumeev, Roman [G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo (Russian Federation); Gridchin, Sergei [Ivanovo State University of Chemistry and Technology, Ivanovo (Russian Federation)

2014-10-20

Highlights: • Stable mixed ligand complexes of ZnNta with amino acids and dipeptides. • Histamine-like coordination mode of His in the complex ZnNtaHis. • Glycine-like coordination of Lys and Orn in the complexes ZnNtaL and ZnNtaHL • NH{sub 2}, CO-coordination mode of GlyGly in the complex ZnNtaGG. • NH{sub 2}, N{sup −} or NH2, N{sup −}, COO-coordination modes of GlyGly in the complex ZnNtaGGH{sub −1}. - Abstract: The isothermal calorimetry, pH-potentiometric titration and {sup 1}H and {sup 13}C NMR methods has been used to study the mixed-ligand complex formation in the systems Zn{sup 2+}–Nta{sup 3–}–L{sup −} (L = His, Orn, Lys, GlyGly, AlaAla) in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO{sub 3}). The thermodynamic parameters of formation of the mixed complexes have been determined. The relationship between the probable coordination modes of the complexone and amino acid or dipeptide molecules in the mixed-ligand complex and the thermodynamic parameters has been discussed.

Development of a thermodynamic data base for selected heavy metals; Entwicklung einer thermodynamischen Datenbasis fuer ausgewaehlte Schwermetalle

Energy Technology Data Exchange (ETDEWEB)

Hageman, Sven; Scharge, Tina; Willms, Thomas

2015-07-15

The report on the development of a thermodynamic data base for selected heavy metals covers the description of experimental methods, the thermodynamic model for chromate, the thermodynamic model for dichromate, the thermodynamic model for manganese (II), the thermodynamic model for cobalt, the thermodynamic model for nickel, the thermodynamic model for copper (I), the thermodynamic model for copper(II), the thermodynamic model for mercury (0) and mercury (I), the thermodynamic model for mercury (III), the thermodynamic model for arsenate.

The free energy of Maxwell-Vlasov equilibria

International Nuclear Information System (INIS)

Morrison, P.J.; Pfirsch, D.

1989-10-01

A previously derived expression for the energy of arbitrary perturbations about arbitrary Vlasov-Maxwell equilibria is transformed into a very compact form. The new form is also obtained by a canonical transformation method for solving Vlasov's equation, which is based on Lie group theory. This method is simpler than the one used before and provides better physical insight. Finally a procedure is presented for determining the existence of negative-energy modes. In this context the question of why there is an accessibility constraint for the particles, but not for the fields, is discussed. 16 refs

Thermodynamic and structural basis for electrochemical response of Cu–Zr based metallic glass

International Nuclear Information System (INIS)

Zhang, Chunzhi; Qiu, Nannan; Kong, Lingliang; Yang, Xiaodan; Li, Huiping

2015-01-01

Highlights: • Thermodynamic and structural basis for electrochemical response were proposed. • La improves the corrosion resistance by inhibition of the selective dissolution. • Corrosion of the MG responses well with thermodynamic and structural parameters. - Abstract: Cu–Zr based metallic glasses were prepared by hyperquenching strategy to explore the thermodynamic and structural basis for electrochemical response. The thermodynamic parameters and the local atomic structure were obtained. Corrosion resistance in seawater was investigated via potentiodynamic polarization curve. The results indicate that increasing thermodynamic parameter values improves the corrosion resistance. The topological instability represented by the nearest neighbor atomic distance yields same tendency as the corrosion resistance with La addition

Model-supported selection of distribution coefficients for performance assessment

International Nuclear Information System (INIS)

Ochs, M.; Lothenbach, B.; Shibata, Hirokazu; Yui, Mikazu

1999-01-01

A thermodynamic speciation/sorption model is used to illustrate typical problems encountered in the extrapolation of batch-type K d values to repository conditions. For different bentonite-groundwater systems, the composition of the corresponding equilibrium solutions and the surface speciation of the bentonite is calculated by treating simultaneously solution equilibria of soluble components of the bentonite as well as ion exchange and acid/base reactions at the bentonite surface. K d values for Cs, Ra, and Ni are calculated by implementing the appropriate ion exchange and surface complexation equilibria in the bentonite model. Based on this approach, hypothetical batch experiments are contrasted with expected conditions in compacted backfill. For each of these scenarios, the variation of K d values as a function of groundwater composition is illustrated for Cs, Ra, and Ni. The applicability of measured, batch-type K d values to repository conditions is discussed. (author)

Recovery of Acrylic Acid Using Calcium Peroxide Nanoparticles: Thermodynamics and Continuous Column Study

Directory of Open Access Journals (Sweden)

B. S. De

2018-03-01

Full Text Available The thermodynamic parameters (DGº, DHº, and DSº for adsorption of acrylic acid on CaO2 nanoparticle were estimated in the temperature range of 300.15 – 313.15 K, which helps to evaluate the feasibility of adsorption process, nature of adsorption process, and affinity of adsorbent toward solute molecule. A dynamic adsorption study in a fixed-bed column was performed using CaO2 nanoparticle for the recovery of acrylic acid from aqueous stream. The breakthrough curves of adsorption system were obtained for different process variables, such as initial acrylic acid concentration (2882–7206 mg L–1, flow rate (5–9 mL min–1, and bed height (10–20 cm. The bed-depth service time model, Thomas model, Yoon-Nelson model, and deactivation kinetic model were applied to the experimental data to predict the column performance. The data were in good agreement with the deactivation kinetic model. The presented results may be useful for the design of adsorption system using nanoparticles, which can be further extended to other systems.

Reactive Distillation for Esterification of Bio-based Organic Acids

Energy Technology Data Exchange (ETDEWEB)

Fields, Nathan; Miller, Dennis J.; Asthana, Navinchandra S.; Kolah, Aspi K.; Vu, Dung; Lira, Carl T.

2008-09-23

The following is the final report of the three year research program to convert organic acids to their ethyl esters using reactive distillation. This report details the complete technical activities of research completed at Michigan State University for the period of October 1, 2003 to September 30, 2006, covering both reactive distillation research and development and the underlying thermodynamic and kinetic data required for successful and rigorous design of reactive distillation esterification processes. Specifically, this project has led to the development of economical, technically viable processes for ethyl lactate, triethyl citrate and diethyl succinate production, and on a larger scale has added to the overall body of knowledge on applying fermentation based organic acids as platform chemicals in the emerging biorefinery. Organic acid esters constitute an attractive class of biorenewable chemicals that are made from corn or other renewable biomass carbohydrate feedstocks and replace analogous petroleum-based compounds, thus lessening U.S. dependence on foreign petroleum and enhancing overall biorefinery viability through production of value-added chemicals in parallel with biofuels production. Further, many of these ester products are candidates for fuel (particularly biodiesel) components, and thus will serve dual roles as both industrial chemicals and fuel enhancers in the emerging bioeconomy. The technical report from MSU is organized around the ethyl esters of four important biorenewables-based acids: lactic acid, citric acid, succinic acid, and propionic acid. Literature background on esterification and reactive distillation has been provided in Section One. Work on lactic acid is covered in Sections Two through Five, citric acid esterification in Sections Six and Seven, succinic acid in Section Eight, and propionic acid in Section Nine. Section Ten covers modeling of ester and organic acid vapor pressure properties using the SPEAD (Step Potential

A spreadsheet-coupled SOLGAS: A computerized thermodynamic equilibrium calculation tool. Revision 1

Energy Technology Data Exchange (ETDEWEB)

Trowbridge, L.D.; Leitnaker, J.M. [Oak Ridge K-25 Site, TN (United States). Technical Analysis and Operations Div.

1995-07-01

SOLGAS, an early computer program for calculating equilibrium in a chemical system, has been made more user-friendly, and several ``bells and whistles`` have been added. The necessity to include elemental species has been eliminated. The input of large numbers of starting conditions has been automated. A revised spreadsheet-based format for entering data, including non-ideal binary and ternary mixtures, simplifies and reduces chances for error. Calculational errors by SOLGAS are flagged, and several programming errors are corrected. Auxiliary programs are available to assemble and partially automate plotting of large amounts of data. Thermodynamic input data can be changed on line. The program can be operated with or without a co-processor. Copies of the program, suitable for the IBM-PC or compatibles with at least 384 bytes of low RAM, are available from the authors. This user manual contains appendices with examples of the use of SOLGAS. These range from elementary examples, such as, the relationships among water, ice, and water vapor, to more complex systems: phase diagram calculation of UF{sub 4} and UF{sub 6} system; burning UF{sub 4} in fluorine; thermodynamic calculation of the Cl-F-O-H system; equilibria calculations in the CCl{sub 4}--CH{sub 3}OH system; and limitations applicable to aqueous solutions. An appendix also contains the source code.

On the uniqueness of fully informative rational expectations equilibria

OpenAIRE

Peter DeMarzo; Costis Skiadas

1998-01-01

This paper analyzes two equivalent equilibrium notions under asymmetric information: risk neutral rational expectations equilibria (rn-REE), and common knowledge equilibria. We show that the set of fully informative rn-REE is a singleton, and we provide necessary and sufficient conditions for the existence of partially informative rn-REE. In a companion paper (DeMarzo and Skiadas (1996)) we show that equilibrium prices for the larger class of quasi-complete economies can be characterized as r...

Coexistence of equilibria in a New Keynesian model with heterogeneous beliefs

International Nuclear Information System (INIS)

Agliari, Anna; Pecora, Nicolò; Spelta, Alessandro

2015-01-01

The recent macroeconomic literature has been stressing the importance of considering heterogeneous expectations while addressing monetary policy. In this paper we consider a standard New Keynesian model, described by a two-dimensional nonlinear map, to analyze the bifurcation structure when agents have heterogeneous expectations and update their beliefs based on past performance. Depending on the degree of reactivity of the monetary policy to inflation and output deviations from the target equilibrium, different kind of dynamics may occur. We find that multiple equilibria and complicated dynamics, associated to codimension-2 bifurcations, may arise even if the monetary policy is set to respond more than point for point to inflation, as the Taylor principle prescribes. We show that if the monetary policy accommodates for a sufficient degree of output stabilization, complicated dynamics can be avoided and the number of coexisting equilibria reduces.

A note on relative equilibria in a rotating shallow water layer

KAUST Repository

Ait Abderrahmane, Hamid

2013-05-08

Relative equilibria of two and three satellite vortices in a rotating shallow water layer have been recorded via particle image velocimetry (PIV) and their autorotation speed was estimated. This study shows that these equilibria retain the fundamental characteristics of Kelvin\\'s equilibria, and could be adequately described by the classical idealized point vortex theory. The same conclusion can also be inferred using the experimental dataset of Bergmann et al. (J. Fluid Mech., vol. 679, 2011, pp. 415-431; J. Fluid Mech., vol. 691, 2012, pp. 605-606) if the assigned field\\'s contribution to pattern rotation is included. © 2013 Cambridge University Press.

Density, refraction index and vapor–liquid equilibria of N-methyl-2-hydroxyethylammonium butyrate plus (methyl acetate or ethyl acetate or propyl acetate) at several temperatures

International Nuclear Information System (INIS)

Alvarez, V.H.; Mattedi, S.; Aznar, M.

2013-01-01

Highlights: ► Densities, refraction indices and VLE were measured for ester + m-2-HEAB mixtures. ► V E , apparent molar volumes and thermal expansion coefficients were calculated. ► Peng–Robinson EoS + Wong–Sandler mixing rule + COSMO-SAC predicted the data. -- Abstract: This paper reports the densities, refraction indices, and vapor liquid equilibria for binary systems ester + N-methyl-2-hydroxyethylammonium butyrate (m-2-HEAB): methyl acetate (1) + m-2-HEAB (2), ethyl acetate (1) + m-2-HEAB and propyl acetate (1) + m-2-HEAB (2). The excess molar volumes, deviations in the refraction index, apparent molar volumes, and thermal expansion coefficients for the binary systems were fitted to polynomial equations. The Peng–Robinson equation of state, coupled with the Wong–Sandler mixing rule, is used to describe the experimental data. Since the predictive activity coefficient model COSMO-SAC is used in the Wong–Sandler mixing rule, the resulting thermodynamic model is a completely predictive one. The prediction results for the density and for the vapor–liquid equilibria have a deviation lower than 1.0% and 1.1%, respectively

The Effect of Learning Based on Technology Model and Assessment Technique toward Thermodynamic Learning Achievement

Science.gov (United States)

Makahinda, T.

2018-02-01

The purpose of this research is to find out the effect of learning model based on technology and assessment technique toward thermodynamic achievement by controlling students intelligence. This research is an experimental research. The sample is taken through cluster random sampling with the total respondent of 80 students. The result of the research shows that the result of learning of thermodynamics of students who taught the learning model of environmental utilization is higher than the learning result of student thermodynamics taught by simulation animation, after controlling student intelligence. There is influence of student interaction, and the subject between models of technology-based learning with assessment technique to student learning result of Thermodynamics, after controlling student intelligence. Based on the finding in the lecture then should be used a thermodynamic model of the learning environment with the use of project assessment technique.

Critical evaluation and thermodynamic optimisation of the Si-RE systems: Part II. Si-RE system (RE = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y)

International Nuclear Information System (INIS)

Kim, Junghwan; Jung, In-Ho

2015-01-01

Highlights: • The (Si-RE) (RE = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) systems have been reviewed. • The thermodynamic optimization of the (Si-RE) systems have been performed. • Systematic changes and similarities in the (Si-RE) systems were found. • The systematic approach resolved inconsistencies in the experimental data. • The systematic approach was used to assess the unexplored phase diagrams. - Abstract: A critical evaluation and optimisation of all available phase diagrams and thermodynamic data of the (Si-RE) (RE = Gd, Tb, Dy, Ho, Er, Tm, Lu and Y) systems was conducted to obtain reliable thermodynamic functions of all the phases in the system. In the thermodynamic modelling, a systematic analysis involving the similarity and periodicity observed in the lanthanide series was applied to resolve inconsistencies in the experimental data and to estimate the unknown thermodynamic properties and phase equilibria data. In particular, the phase diagrams and thermodynamic properties of (Si-Tm) and (Si-Lu) systems which are rarely investigated can be predicted from this approach. Systematic trends in thermodynamic properties of solid and liquid phases and phase diagram of the entire (Si-RE) systems were summarized

Stackelberg equilibria and horizontal differentiation

OpenAIRE

Lambertini, Luca

1993-01-01

This paper proposes a taxonomy of the Stackelberg equilibria emerging from a standard game of horizontal differentiation à la Hotelling in which the strategy set of the sellers in the location stage is the real axis. Repeated leadership appears the most advantageous position. Furthermore, this endogenously yields vertical differentiation between products at equilibrium.

Thermodynamics of the ternary systems: (water + glycine, L-alanine and L-serine + di-ammonium hydrogen citrate) from volumetric, compressibility, and (vapour + liquid) equilibria measurements

Energy Technology Data Exchange (ETDEWEB)

Sadeghi, Rahmat, E-mail: rahsadeghi@yahoo.co [Department of Chemistry, University of Kurdistan, Sanandaj (Iran, Islamic Republic of); Gholamireza, Afsaneh [Department of Chemistry, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

2011-02-15

The apparent molar volumes and isentropic compressibility of glycine, L-alanine and L-serine in water and in aqueous solutions of (0.500 and 1.00) mol . kg{sup -1} di-ammonium hydrogen citrate {l_brace}(NH{sub 4}){sub 2}HCit{r_brace} and those of (NH{sub 4}){sub 2}HCit in water have been obtained over the (288.15 to 313.15) K temperature range at 5 K intervals at atmospheric pressure from measurements of density and ultrasonic velocity. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated amino acids have been obtained and their variations with temperature and their transfer properties from water to aqueous solutions of (NH{sub 4}){sub 2}HCit have also been obtained. The results have been interpreted in terms of the hydration of the amino acids. In the second part of this work, water activity measurements by the isopiestic method have been carried out on the aqueous solutions of {l_brace}glycine + (NH{sub 4}){sub 2}HCit{r_brace}, {l_brace}alanine + (NH{sub 4}){sub 2}HCit{r_brace}, and {l_brace}serine + (NH{sub 4}){sub 2}HCit{r_brace} at T = 298.15 K at atmospheric pressure. From these measurements, values of vapour pressure, osmotic coefficient, activity coefficient and Gibbs free energy were obtained. The effect of the type of amino acids on the (vapour + liquid) equilibrium of the systems investigated has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. Furthermore, the thermodynamic behaviour of the ternary solutions investigated has been studied by using the semi-ideal hydration model and the linear concentration relations have been tested by comparing with the isopiestic measurements for the studied systems at T = 298.15 K.

Thermodynamic properties and low-temperature X-ray diffraction of vitamin B{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Knyazev, A.V., E-mail: knyazevav@gmail.com; Smirnova, N.N.; Shipilova, A.S.; Shushunov, A.N.; Gusarova, E.V; Knyazeva, S.S.

2015-03-20

Highlights: • Temperature dependence of heat capacity of vitamin B{sub 3} has been measured by precision adiabatic vacuum calorimetry. • The thermodynamic functions of the vitamin B{sub 3} have been determined for the range from T → 0 to 346 K. • The thermodynamic analysis of reactions involving nicotinic acid was made. • The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion. - Abstract: In the present work temperature dependence of heat capacity of vitamin B{sub 3} (nicotinic acid) has been measured for the first time in the range from 5 to 346 K by precision adiabatic vacuum calorimetry. Based on the experimental data, the thermodynamic functions of the vitamin B{sub 3}, namely, the heat capacity, enthalpy H°(T) – H°(0), entropy S°(T) – S°(0) and Gibbs function G°(T) – H°(0) have been determined for the range from T → 0 to 343 K. The value of the fractal dimension D in the function of multifractal generalization of Debye’s theory of the heat capacity of solids was estimated and the character of heterodynamics of structure was detected. The thermodynamic parameters Δ{sub f}S°, Δ{sub f}G° at T = 298.15 K and p = 0.1 MPa have been calculated. The thermodynamic analysis of reactions involving nicotinic acid was made. The low-temperature X-ray diffraction was used for the determination of coefficients of thermal expansion.

Aquatic chemistry of acid deposition

Energy Technology Data Exchange (ETDEWEB)

Stumm, W; Sigg, L; Schnoor, J L

1987-01-01

The occurrence of acid precipitation in many regions of the Northern hemisphere is a consequnece of human interference in the cycles that unite land, water and atmosphere. The oxidation of carbon, sulfur and nitrogen, resulting mostly from fossil fuel burning, rivals oxidation processes induced by photosynthesis and respiration and disturbs redox conditions in the atmosphere. The paper discusses oxidation-reduction reactions, particularly those involving atmospheric pollutants that are important in the formation of acid precipitation. Topics covered are: a stoichiometric model of acid rain formation; sulfur dioxide and ammonia adsorption; acid neutralizing capacity. The paper concludes that explanations of simple chemical equilibria between gases and water aid our understanding of how acidifying gases become dissolved in cloud water, in droplets of falling rain, or in fog. Rigorous definitions of base- or acid-neutralizing capacities are prerequisites to measuring and interpreting residual acidity in dry and wet deposition and for assessing the disturbance caused by the transfer of acid to terrestrial and aquatic ecosystems. 20 references.

Determination of 3D Equilibria from Flux Surface Knowledge Only

International Nuclear Information System (INIS)

Mynick, H.E.; Pomphrey, N.

2001-01-01

We show that the method of Christiansen and Taylor, from which complete tokamak equilibria can be determined given only knowledge of the shape of the flux surfaces, can be extended to 3-dimensional equilibria, such as those of stellarators. As for the tokamak case, the given geometric knowledge has a high degree of redundancy, so that the full equilibrium can be obtained using only a small portion of that information

Establishment of data base files of thermodynamic data developed by OECD/NEA. Pt. 1. Thermodynamic data of Np and Pu

International Nuclear Information System (INIS)

Yoshida, Yasushi; Sasamoto, Hiroshi

2004-01-01

Thermodynamic data base for compounds and complexes of actinides and fission products specialized in modeling requirements for safety assessments of radioactive waste disposal systems are being developed by NEA TDB project of OECD/NEA. In this project, relevant data bases for compounds and complexes of Np and Pu were published in 2001. JNC established the data base files available for geochemical calculation codes using these Np and Pu published data. And this procedure for establishment and contents of data base files are described in this report. These data base files were prepared as the formats of major geochemical codes PHREEQE, PHREEQC, EQ3/6 and Geochemist's workbench. Additionally modification for data in the thermodynamic data base files which had been already published by JNC was also done. This procedure and revised data bases are shown in the appendix of this report. (author)

Nash Equilibria in Symmetric Graph Games with Partial Observation

DEFF Research Database (Denmark)

Bouyer, Patricia; Markey, Nicolas; Vester, Steen

2017-01-01

We investigate a model for representing large multiplayer games, which satisfy strong symmetry properties. This model is made of multiple copies of an arena; each player plays in his own arena, and can partially observe what the other players do. Therefore, this game has partial information...... and symmetry constraints, which make the computation of Nash equilibria difficult. We show several undecidability results, and for bounded-memory strategies, we precisely characterize the complexity of computing pure Nash equilibria for qualitative objectives in this game model....

Tautomeric and Microscopic Protonation Equilibria of Anthranilic Acid and Its Derivatives.

Science.gov (United States)

Zapała, Lidia; Woźnicka, Elżbieta; Kalembkiewicz, Jan

2014-01-01

The acid-base chemistry of three zwitterionic compounds, namely anthranilic (2-aminobenzoic acid), N -methylanthranilic and N -phenylanthranilic acid has been characterized in terms of the macroconstants K a1 , K a2 , the isoelectric point p H I , the tautomerization constant K z and microconstants k 11 , k 12 , k 21 , k 22 . The potentiometric titration method was used to determine the macrodissociation constants. Due to the very poor water solubility of N -phenylanthranilic acid the dissociation constants p K a1 and p K a2 were determined in MDM-water mixtures [MDM is a co-solvent mixture, consisting of equal volumes of methanol (MeOH), dioxane and acetonitrile (MeCN)]. The Yasuda-Shedlovsky extrapolation procedure has been used to obtain the values of p K a1 and p K a2 in aqueous solutions. The p K a1 and p K a2 values obtained by this method are 2.86 ± 0.01 and 4.69 ± 0.03, respectively. The tautomerization constant K z describing the equilibrium between unionized form ⇌ zwitterionic form was evaluated by the K z method based on UV-VIS spectrometry. The method uses spectral differences between the zwitterionic form (found at isoelectric pH in aqueous solution) and the unionized form (formed in an organic solvent of low dielectric constant). The highest value of the K z constant has been observed in the case of N -methylantranilic acid (log 10 K z  = 1.31 ± 0.04). The values of log 10 K z for anthranilic and N -phenylanthranilic acids are similar and have values of 0.93 ± 0.03 and 0.90 ± 0.05, respectively. The results indicate that the tested compounds, in aqueous solution around the isoelectric point pH I , occur mainly in the zwitterionic form. Moreover, the influence of the type of substituent and pH of the aqueous phase on the equilibrium were analyzed with regard to the formation and the coexistence of different forms of the acids in the examined systems.

Non-existence of Normal Tokamak Equilibria with Negative Central Current

International Nuclear Information System (INIS)

Hammett, G.W.; Jardin, S.C.; Stratton, B.C.

2003-01-01

Recent tokamak experiments employing off-axis, non-inductive current drive have found that a large central current hole can be produced. The current density is measured to be approximately zero in this region, though in principle there was sufficient current-drive power for the central current density to have gone significantly negative. Recent papers have used a large aspect-ratio expansion to show that normal MHD equilibria (with axisymmetric nested flux surfaces, non-singular fields, and monotonic peaked pressure profiles) can not exist with negative central current. We extend that proof here to arbitrary aspect ratio, using a variant of the virial theorem to derive a relatively simple integral constraint on the equilibrium. However, this constraint does not, by itself, exclude equilibria with non-nested flux surfaces, or equilibria with singular fields and/or hollow pressure profiles that may be spontaneously generated

Thermodynamic assessment of the rhodium-ruthenium-oxygen (Rh-Ru-O) system

Science.gov (United States)

Gossé, S.; Bordier, S.; Guéneau, C.; Brackx, E.; Domenger, R.; Rogez, J.

2018-03-01

Ruthenium (Ru) and rhodium (Rh) are abundant platinum-group metals formed during burn-up of nuclear fuels. Under normal operating conditions, Rh and Ru accumulate and predominantly form metallic precipitates with other fission products like Mo, Pd and Tc. In the framework of vitrification of high-level nuclear waste, these fission products are poorly soluble in molten glasses. They precipitate as metallic particles and oxide phases. Moreover, these Ru and Rh rich phases strongly depend on temperature and the oxygen fugacity of the glass melt. In case of severe accidental conditions with air ingress, oxidation of the Ru and Rh is possible. At low temperatures (T 1422 K for rhodium sesquioxide and T > 1815 K for ruthenium dioxide), they may decompose into (Rh)-FCC or (Ru)-HCP metallic phases and radiotoxic volatile gaseous species. A thermodynamic assessment of the Rh-Ru-O system will enable the prediction of: (1) the metallic and oxide phases that form during the vitrification of high-level nuclear wastes and (2) the release of volatile gaseous species during a severe accident. The Calphad method developed herein employs a thermodynamic approach in the investigation of the thermochemistry of rhodium and ruthenium at high temperatures. Current literature on the thermodynamic properties and phase diagram data enables preliminary thermodynamic assessments of the Rh-O and Ru-O systems. Additionally, select compositions in the ternary Rh-Ru-O system underwent experimental tests to complement data found in literature and to establish the phase equilibria in the ternary system.

Thermodynamics of Bi2O3-SiO2 system

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Onderka B.

2017-01-01

Full Text Available Thermodynamic properties of the liquid Bi2O3-SiO2 solutions were determined from the results of the electrochemical measurements by use of the solid oxide galvanic cells with YSZ (Yttria-Stabilized-Zirconia electrolyte. Activities of Bi2O3 in the solutions were determined for 0.2, 0.3, 0.4, and 0.5 SiO2 mole fractions in the temperature range 1073-1293 K from measured electromotive force (e.m.f of the solid electrolyte galvanic cell: Bi, Bi2O3-SiO2 | YSZ | air (pO2 = 0.213 bar Additionally, heat capacity data obtained for two solid phases 6Bi2O3•SiO2 and 2Bi2O3•3SiO2 were included into optimization of thermodynamic properties of the system. Optimization procedure was supported by differential thermal analysis (DTA data obtained in this work as well as those accepted from the literature. Using the data obtained in this work, and the information about phase equilibria found in the literature, binary system Bi2O3-SiO2 was assessed with the ThermoCalc software.

Binding of phenazinium dye safranin T to polyriboadenylic acid: spectroscopic and thermodynamic study.

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Ankur Bikash Pradhan

Full Text Available Here, we report results from experiments designed to explore the association of the phenazinium dye safranin T (ST, 3,7-diamino-2,8-dimethyl-5-phenylphenazinium chloride with single and double stranded form of polyriboadenylic acid (hereafter poly-A using several spectroscopic techniques. We demonstrate that the dye binds to single stranded polyriboadenylic acid (hereafter ss poly-A with high affinity while it does not interact at all with the double stranded (ds form of the polynucleotide. Fluorescence and absorption spectral studies reveal the molecular aspects of binding of ST to single stranded form of the polynucleotide. This observation is also supported by the circular dichroism study. Thermodynamic data obtained from temperature dependence of binding constant reveals that association is driven by negative enthalpy change and opposed by negative entropy change. Ferrocyanide quenching studies have shown intercalative binding of ST to ss poly-A. Experiments on viscosity measurements confirm the binding mode of the dye to be intercalative. The effect of [Na⁺] ion concentration on the binding process suggests the role of electrostatic forces in the complexation. Present studies reveal the utility of the dye in probing nucleic acid structure.

Intermediates and Generic Convergence to Equilibria

DEFF Research Database (Denmark)

Marcondes de Freitas, Michael; Wiuf, Carsten; Feliu, Elisenda

2017-01-01

Known graphical conditions for the generic and global convergence to equilibria of the dynamical system arising from a reaction network are shown to be invariant under the so-called successive removal of intermediates, a systematic procedure to simplify the network, making the graphical conditions...

Thermodynamics of T cell receptor – peptide/MHC interactions: progress and opportunities

Science.gov (United States)

Armstrong, Kathryn M.; Insaidoo, Francis K.; Baker, Brian M.

2013-01-01

αβ T cell receptors (TCR) recognize peptide antigens presented by class I or class II major histocompatibility complex molecules (pMHC). Here we review the use of thermodynamic measurements in the study of TCR-pMHC interactions, with attention to the diversity in binding thermodynamics and how this is related to the variation in TCR-pMHC interfaces. We show that there is no enthalpic or entropic signature for TCR binding; rather, enthalpy and entropy changes vary in a compensatory manner that reflects a narrow free energy window for the interactions that have been characterized. Binding enthalpy and entropy changes do not correlate with structural features such as buried surface area or the number of hydrogen bonds within TCR-pMHC interfaces, possibly reflecting the myriad of contributors to binding thermodynamics, but likely also reflecting a reliance on van’t Hoff over calorimetric measurements and the unaccounted influence of equilibria linked to binding. TCR-pMHC binding heat capacity changes likewise vary considerably. In some cases the heat capacity changes are consistent with conformational differences between bound and free receptors, but there is little data indicating these conformational differences represent the need to organize commonly disordered CDR loops. In this regard, we discuss how thermodynamics may provide additional insight into conformational changes occurring upon TCR binding. Finally, we highlight opportunities for the further use of thermodynamic measurements in the study of TCR-pMHC interactions, not only for understanding TCR binding in general, but for understanding specifics of individual interactions and the engineering of T cell receptors with desired molecular recognition properties. PMID:18496839

Phase Behavior of Aqueous NA-K-MG-CA-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

Energy Technology Data Exchange (ETDEWEB)

M.S. Gruszkiewiez; D.A. Palmer; R.D. Springer; P. Wang; A. Anderko

2006-09-14

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems.

Measurement and modeling of high-pressure (vapour + liquid) equilibria of (CO{sub 2} + alcohol) binary systems

Energy Technology Data Exchange (ETDEWEB)

Gutierrez, Jorge E.; Bejarano, Arturo [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Fuente, Juan C. de la, E-mail: juan.delafuente@usm.c [Departamento de Ingenieria Quimica y Ambiental, Universidad Tecnica Federico Santa Maria, Avda. Espana 1680, Valparaiso (Chile); Centro Regional de Estudios en Alimentos Saludables, Blanco 1623, Valparaiso (Chile)

2010-05-15

An apparatus based on a static-analytic method assembled in this work was utilized to perform high pressure (vapour + liquid) equilibria measurements with uncertainties estimated at <5%. Complementary isothermal (vapour + liquid) equilibria results are reported for the (CO{sub 2} + 1-propanol), (CO{sub 2} + 2-methyl-1-propanol), (CO{sub 2} + 3-methyl-1-butanol), and (CO{sub 2} + 1-pentanol) binary systems at temperatures of (313, 323, and 333) K, and at pressure range of (2 to 12) MPa. For all the (CO{sub 2} + alcohol) systems, it was visually monitored to insure that there was no liquid immiscibility at the temperatures and pressures studied. The experimental results were correlated with the Peng-Robinson equation of state using the quadratic mixing rules of van der Waals with two adjustable parameters. The calculated (vapour + liquid) equilibria compositions were found to be in good agreement with the experimental values with deviations for the mol fractions <0.12 and <0.05 for the liquid and vapour phase, respectively.

Human Brain Networks: Spiking Neuron Models, Multistability, Synchronization, Thermodynamics, Maximum Entropy Production, and Anesthetic Cascade Mechanisms

Directory of Open Access Journals (Sweden)

Wassim M. Haddad

2014-07-01

Full Text Available Advances in neuroscience have been closely linked to mathematical modeling beginning with the integrate-and-fire model of Lapicque and proceeding through the modeling of the action potential by Hodgkin and Huxley to the current era. The fundamental building block of the central nervous system, the neuron, may be thought of as a dynamic element that is “excitable”, and can generate a pulse or spike whenever the electrochemical potential across the cell membrane of the neuron exceeds a threshold. A key application of nonlinear dynamical systems theory to the neurosciences is to study phenomena of the central nervous system that exhibit nearly discontinuous transitions between macroscopic states. A very challenging and clinically important problem exhibiting this phenomenon is the induction of general anesthesia. In any specific patient, the transition from consciousness to unconsciousness as the concentration of anesthetic drugs increases is very sharp, resembling a thermodynamic phase transition. This paper focuses on multistability theory for continuous and discontinuous dynamical systems having a set of multiple isolated equilibria and/or a continuum of equilibria. Multistability is the property whereby the solutions of a dynamical system can alternate between two or more mutually exclusive Lyapunov stable and convergent equilibrium states under asymptotically slowly changing inputs or system parameters. In this paper, we extend the theory of multistability to continuous, discontinuous, and stochastic nonlinear dynamical systems. In particular, Lyapunov-based tests for multistability and synchronization of dynamical systems with continuously differentiable and absolutely continuous flows are established. The results are then applied to excitatory and inhibitory biological neuronal networks to explain the underlying mechanism of action for anesthesia and consciousness from a multistable dynamical system perspective, thereby providing a

Thermodynamic estimation: Ionic materials

International Nuclear Information System (INIS)

Glasser, Leslie

2013-01-01

Thermodynamics establishes equilibrium relations among thermodynamic parameters (“properties”) and delineates the effects of variation of the thermodynamic functions (typically temperature and pressure) on those parameters. However, classical thermodynamics does not provide values for the necessary thermodynamic properties, which must be established by extra-thermodynamic means such as experiment, theoretical calculation, or empirical estimation. While many values may be found in the numerous collected tables in the literature, these are necessarily incomplete because either the experimental measurements have not been made or the materials may be hypothetical. The current paper presents a number of simple and relible estimation methods for thermodynamic properties, principally for ionic materials. The results may also be used as a check for obvious errors in published values. The estimation methods described are typically based on addition of properties of individual ions, or sums of properties of neutral ion groups (such as “double” salts, in the Simple Salt Approximation), or based upon correlations such as with formula unit volumes (Volume-Based Thermodynamics). - Graphical abstract: Thermodynamic properties of ionic materials may be readily estimated by summation of the properties of individual ions, by summation of the properties of ‘double salts’, and by correlation with formula volume. Such estimates may fill gaps in the literature, and may also be used as checks of published values. This simplicity arises from exploitation of the fact that repulsive energy terms are of short range and very similar across materials, while coulombic interactions provide a very large component of the attractive energy in ionic systems. Display Omitted - Highlights: • Estimation methods for thermodynamic properties of ionic materials are introduced. • Methods are based on summation of single ions, multiple salts, and correlations. • Heat capacity, entropy

Solubility of perfumery and fragrance raw materials based on cyclohexane in 1-octanol under ambient and high pressures up to 900 MPa

International Nuclear Information System (INIS)

Domanska, Urszula; Morawski, Piotr; Piekarska, Maria

2008-01-01

The (solid + liquid) phase equilibria (SLE) of binary mixtures containing 1-octanol and fragrance raw materials based on cyclohexane were investigated. The systems {1-octanol (1) + cyclohexyl carboxylic acid (CCA), or cyclohexyl acetic acid (CAA), or cyclohexyl acetate (CA), or 2-cyclohexyl ethyl acetate (2CEA), or 2-cyclohexyl ethanol (2CE)(2)} have been measured by a dynamic method in wide range of temperatures from (220 to 320) K and ambient pressure. For all systems SLE diagrams were detected as eutectic mixtures with complete miscibility in the liquid phase. The experimental data were correlated by means of the Wilson and NRTL equations, utilizing parameters derived from the (solid + liquid) equilibrium. The root-mean-square deviations of the solubility temperatures for all calculated data are dependent upon the particular system and the particular equation used. Additionally, the SLE in binary mixture that contain {1-octanol (1) + CCA (2)} has been measured under very high pressures up to about 900 MPa at the temperature range from T = (303.15 to 353.15) K. The thermostatted apparatus for the measurements of transition pressures from the (liquid + solid) state was used. The freezing and melting temperatures at a constant composition increase monotonously with pressure. The high pressure experimental results obtained at isothermal conditions (p-x) were interpolated to more convenient T-x diagram. Data of the (pressure + temperature) composition relation at the high pressure (solid + liquid) phase equilibria was correlated by the polynomial based on the Yang model. The basic thermodynamic properties of pure substances viz. the melting point, enthalpy of fusion, enthalpy of solid-solid phase transition, and glass transition, have been determined by the differential scanning calorimetry (DSC)

Temperature effect on the acid-base behaviour of Na-montmorillonite.

Science.gov (United States)

Duc, Myriam; Carteret, Cédric; Thomas, Fabien; Gaboriaud, Fabien

2008-11-15

We report a study of the acid-base properties of Na-montmorillonite suspensions at temperatures from 25 degrees C to 80 degrees C, by continuous and batch potentiometric methods, combined with analysis of the dissolved and readsorbed species. The batch titration curves reveal that the dissolution processes of Na-montmorillonite and silica-rich secondary phases are increasingly predominant, respectively at acid and basic pH, and according to the temperature. The continuous titration curves are less affected by these side reactions. In the absence of a common intersection point, the thermodynamic analysis of the curves was based on the shift of the PZNPC with the ionic strength. This shift was not significantly altered by the temperature, by comparison with the dissociation product of water in the same conditions. Therefore we concluded that protonation-deprotonation of the dissociable sites at the edges of the clay platelets is not significantly temperature dependent.

Ballooning mode second stability region for sequences of tokamak equilibria

International Nuclear Information System (INIS)

Sugiyama, L.; Mark, J.W.K.

A numerical study of several sequences of tokamak equilibria derived from two flux conserving sequences confirms the tendency of high n ideal MHD ballooning modes to stabilize for values of the plasma beta greater than a second critical beta, for sufficiently favorable equilibria. The major stabilizing effect of increasing the inverse rotational transform profile q(Psi) for equilibria with the same flux surface geometry is shown. The unstable region shifts toward larger shear d ln q/d ln γ and the width of the region measured in terms of the poloidal beta or a pressure gradient parameter, for fixed shear, decreases. The smaller aspect ratio sequences are more sensitive to changes in q and have less stringent limits on the attainable value of the plasma beta in the high beta stable region. Finally, the disconnected mode approximation is shown to provide a reasonable description of the second high beta stability boundary

Gyrokinetic magnetohydrodynamics and the associated equilibria

Science.gov (United States)

Lee, W. W.; Hudson, S. R.; Ma, C. H.

2017-12-01

The gyrokinetic magnetohydrodynamic (MHD) equations, related to the recent paper by W. W. Lee ["Magnetohydrodynamics for collisionless plasmas from the gyrokinetic perspective," Phys. Plasmas 23, 070705 (2016)], and their associated equilibria properties are discussed. This set of equations consists of the time-dependent gyrokinetic vorticity equation, the gyrokinetic parallel Ohm's law, and the gyrokinetic Ampere's law as well as the equations of state, which are expressed in terms of the electrostatic potential, ϕ, and the vector potential, A , and support both spatially varying perpendicular and parallel pressure gradients and the associated currents. The corresponding gyrokinetic MHD equilibria can be reached when ϕ→0 and A becomes constant in time, which, in turn, gives ∇.(J∥+J⊥)=0 and the associated magnetic islands, if they exist. Examples of simple cylindrical geometry are given. These gyrokinetic MHD equations look quite different from the conventional MHD equations, and their comparisons will be an interesting topic in the future.