The thermodynamic properties of mixed phospholipid bilayers: a theoretical analysis

1984 ◽  
Vol 62 (8) ◽  
pp. 796-802 ◽  
Author(s):  
Maryse Mondat ◽  
A. Georgallas ◽  
D. A. Pink ◽  
M. J. Zuckermann
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Reasonable Agreement ◽  
Phospholipid Bilayers ◽  
Scanning Calorimetry ◽  
Phase Separations ◽  
Lipid Mixtures ◽  
Wide Range ◽  
Acyl Chains ◽  
Gel Phase

A theoretical model is presented with the intention of describing lateral phase separations in binary lipid mixtures in which the acyl chains of the components differ in their length. The model includes explicitly interactions between the acyl chains and between polar heads of the lipid molecules. Phase diagrams and thermodynamic properties of binary lipid mixtures were calculated using a wide range of interaction parameters. It is shown that the occurrence of immiscibility in the gel phase is related to the interactions between the polar heads of the lipid molecules. The calculated results for binary lipid mixtures are compared with the available experimental data. In particular, the calculated specific heat for dilauroyl phosphatidylcholine – distearoyl phosphatidylcholine is in reasonable agreement with experimental results obtained from differential scanning calorimetry measurements.

Experimental investigation and thermodynamic calculation in the Ag–Bi–Ni and Cu–Bi–Ni systems

2009 ◽  
Vol 24 (8) ◽  
pp. 2644-2653 ◽  
Author(s):  
Feng Gao ◽  
Cuiping Wang ◽  
X.J. Liu ◽  
Yoshikazu Takaku ◽  
I. Ohnuma ◽  
...  
Keyword(s):  
Experimental Data ◽  
Phase Equilibria ◽  
Intermetallic Compounds ◽  
Electron Probe ◽  
Reasonable Agreement ◽  
Diffusion Couples ◽  
Scanning Calorimetry ◽  
Temperatures Of Phase Transformations ◽  
Ternary Intermetallic Compound ◽  
And Diffusion

The phase equilibria at 300, 400, 500, and 600 °C in the Ag–Bi–Ni system and 300, 400, and 500 °C in the Cu–Bi–Ni system were experimentally determined by metallography and electron probe microanalysis on equilibrated alloys and diffusion couples. Differential scanning calorimetry was used to measure the temperatures of phase transformations. All the experimental results show that the solubilities of the ternary elements of the binary intermetallic compounds in the Ag–Bi–Ni system are limited. However, the binary intermetallic compounds have some solubilities of the ternary elements in the Cu–Bi–Ni system. No ternary intermetallic compound was found in the Ag–Bi–Ni and Cu–Bi–Ni systems. On the basis of the determined results, the phase equilibria in the Ag–Bi–Ni and Cu–Bi–Ni systems were thermodynamically assessed, and reasonable agreement between the calculated results and experimental data was obtained.

scholarly journals Thermodynamic description of alkali metal hydroxides over a wide range of temperatures, pressures and densities of aqueous fluids

2019 ◽  
Vol 98 ◽  
pp. 05001 ◽  
Author(s):  
Nikolay Akinfiev
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Alkali Metal ◽  
Quantum Chemical ◽  
Dissociation Constants ◽  
Thermodynamic Description ◽  
Metal Hydroxides ◽  
Alkali Metal Hydroxides ◽  
Wide Range

All available experimental data on dissociation constants of aqueous hydroxides of Na, K, and Li were critically assembled and together with quantum chemical estimations used to evaluate parameters of the AD EoS [1] for corresponding aqueous molecules NaOH(aq), KOH(aq), and LiOH(aq). Use of the proposed approach allows proper prediction of the whole set of thermodynamic properties of these hydroxides over a wide range of temperatures (0 – 800 °C), pressures (0.1 – 800 MPa) and solvent densities (0.03 – 1.1 g·cm-3).

scholarly journals Thermodynamic Properties of Aqueous Species Calculated Using the HKF Model: How Do Different Thermodynamic and Electrostatic Models for Solvent Water Affect Calculated Aqueous Properties?

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-24 ◽  
Author(s):  
George D. Miron ◽  
Allan M. M. Leal ◽  
Alina Yapparova
Keyword(s):  
Experimental Data ◽  
Dielectric Properties ◽  
Thermodynamic Properties ◽  
Elevated Temperatures ◽  
Rock Interaction ◽  
Water Solvent ◽  
Wide Range ◽  
Temperature And Pressure ◽  
The Impact ◽  
Aqueous Species

Thermodynamic properties of aqueous species are essential for modeling of fluid-rock interaction processes. The Helgeson-Kirkham-Flowers (HKF) model is widely used for calculating standard state thermodynamic properties of ions and complexes over a wide range of temperatures and pressures. To do this, the HKF model requires thermodynamic and electrostatic models of water solvent. In this study, we investigate and quantify the impact of choosing different models for calculating water solvent volumetric and dielectric properties, on the properties of aqueous species calculated using the HKF model. We identify temperature and pressure conditions at which the choice of different models can have a considerable effect on the properties of aqueous species and on fluid mineral equilibrium calculations. The investigated temperature and pressure intervals are 25–1000°C and 1–5 kbar, representative of upper to middle crustal levels, and of interest for modeling ore-forming processes. The thermodynamic and electrostatic models for water solvent considered are: Haar, Gallagher and Kell (1984), Wagner and Pruß (2002), and Zhang and Duan (2005), to calculate water volumetric properties, and Johnson and Norton (1991), Fernandez and others (1997), and Sverjensky and others (2014), to calculate water dielectric properties. We observe only small discrepancies in the calculated standard partial molal properties of aqueous species resulting from using different water thermodynamic models. However, large differences in the properties of charged species can be observed at higher temperatures (above 500°C) as a result of using different electrostatic models. Depending on the aqueous speciation and the reactions that control the chemical composition, the observed differences can vary. The discrepancy between various electrostatic models is attributed to the scarcity of experimental data at high temperatures. These discrepancies restrict the reliability of the geochemical modeling of hydrothermal and ore formation processes, and the retrieval of thermodynamic parameters from experimental data at elevated temperatures and pressures.

Calculation of Enthalpy and Entropy From Experimentally Measurable Quantities

2016 ◽  
Author(s):  
Shane Coogan ◽  
Klaus Brun ◽  
Sarah Simons ◽  
Brandon Ridens ◽  
Rainer Kurz
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
Specific Volume ◽  
Input Data ◽  
Equations Of State ◽  
Volume Data ◽  
Specific Heats ◽  
Wide Range ◽  
Work Input ◽  
Enthalpy And Entropy

In the design and testing of gas compressors, the correct determination of the thermodynamic properties of the gas, such as enthalpy, entropy, and specific volume from pressure, temperature, and composition, plays an important role. Due to the wide range of conditions encountered, pressure, specific volume and temperature (p-v-T) equations of state (EOS) are used to determine the isentropic or polytropic efficiency, the work input, and capacity of a compressor configuration. However, accurate equations of state may be lacking for some more complicated gas mixtures. Experimentally determined thermodynamic state information is more accurate and is needed to validate, correct, or supplant existing equations of state. The methodology for calculating enthalpy and entropy from experimental data is presented including the full step-by-step derivation from first principles. The thermodynamic relations or calculus properties used in each step of the derivation are clearly identified to provide traceability and encourage verification. Results are presented in three forms to match all possible tabulation formats of temperature, pressure, and volume data. Calculation methods for other useful but unmeasured thermodynamic properties such as the specific heat at constant pressure and the ratio of specific heats are also given. The methodology is demonstrated in two examples. The first is a verification case where REFPROP, an equation of state software, is used to generate input data, and the enthalpy and entropy values calculated from the input data are shown to match those given directly by REFPROP. The second is a practical demonstration where the methodology is used with actual experimental data.

Reduced Time Approach to Curing Kinetics, Part II: Master Curve from Nonisothermal Data

1994 ◽  
Vol 67 (2) ◽  
pp. 314-328 ◽  
Author(s):  
G. D. Shyu ◽  
T. W. Chan ◽  
A. I. Isayev
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Kinetic Data ◽  
Master Curve ◽  
Curing Kinetics ◽  
Reference Temperature ◽  
Scanning Calorimetry ◽  
Kinetic Information ◽  
Wide Range ◽  
Curing Kinetic

Abstract Nonisothermal curing kinetic data obtained from differential scanning calorimetry (DSC) for a rubber compound are corrected for the effects of temperature lag between the DSC sample and furnace. The method of Eder and Janeschitz-Kriegl, which is based on experimental data alone without reference to any kinetic model, is used for these corrections. A method is presented for shifting the corrected nonisothermal curing kinetic data with respect to an arbitrarily chosen reference temperature to obtain a master curve. The method is based on experimental data alone without assuming any specific form of kinetic model. When the isothermal curing kinetic data for the same material are shifted with respect to the same reference temperature, a master curve is also obtained which basically overlaps the corresponding master curve from nonisothermal data. It follows that nonisothermal DSC measurements provide the same curing kinetic information as isothermal ones, only over a wider range of temperatures. The shift factors obtained from experimental data alone are compared with the corresponding values calculated from a kinetic model with an Arrhenius type of temperature dependence. This serves as a means of model evaluation. It is concluded that the kinetic model is good at describing isothermal curing kinetic data. But it yields reliable curing kinetic information over a narrower range of temperatures than nonisothermal data alone without resort to any model. The Arrhenius extrapolation of the limited isothermal data to a wide range of temperatures is quite good.

Ab initio study of the anharmonic properties of dipole moment functions of ammonia and the oxonium ion

1988 ◽  
Vol 53 (10) ◽  
pp. 2175-2190 ◽  
Author(s):  
Petr Pracna ◽  
Zdeněk Havlas
Keyword(s):  
Experimental Data ◽  
Dipole Moment ◽  
Ab Initio ◽  
Reasonable Agreement ◽  
Ab Initio Study ◽  
Transition Moments ◽  
Wide Range ◽  
Moment Functions ◽  
Vibrational Bands ◽  
Electronic Ground

Ab initio SCF electric dipole moment functions of the electronic ground states of ammonia and the oxonium ion are determined over a wide range of vibrational coordinates. The dipole moment functions are used within the framework of the nonrigid invertor Hamiltonian to evaluate transition moments for various types of vibrational bands. Reasonable agreement with experimental data for ammonia is achieved by scaling the dipole moment function. Several new transition moments for combination and hot bands are predicted.

Estimation of the Thermodynamic Properties of Unbranched Hydrocarbons

1999 ◽  
Vol 121 (1) ◽  
pp. 45-50 ◽  
Author(s):  
H. He ◽  
M. Metghalchi ◽  
J. C. Keck
Keyword(s):  
Experimental Data ◽  
Heat Capacity ◽  
Free Energy ◽  
Simple Model ◽  
Thermodynamic Properties ◽  
Statistical Thermodynamic ◽  
Wide Range ◽  
On Line ◽  
Kinetic Calculations ◽  
Good Agreement

A simple model has been developed to estimate the sensible thermodynamic properties such as Gibbs free energy, enthalpy, heat capacity, and entropy of unbranched hydrocarbons over a wide range of temperatures. The model is based on statistical thermodynamic expressions incorporating translational, rotational, and vibrational motions of the atoms. A relatively small number of parameters are needed to calculate the thermodynamic properties of a wide range of molecules. The calculated results are in good agreement with the available experimental data for unbranched hydrocarbons. The model can be used to make estimates for molecules whose properties have not been measured and is simple enough to be easily programmed as a subroutine for on-line kinetic calculations.

LIQUIDUS THERMO-BAROMETER FOR THE MODELING OF MAGNETITE — MELT EQUILIBRIUM

2018 ◽  
pp. 71-80
Author(s):  
N. S. Aryaeva ◽  
E. V. Koptev-Dvornikov ◽  
D. A. Bychkov
Keyword(s):  
Experimental Data ◽  
Liquidus Temperature ◽  
Vertical Structure ◽  
Maximum Error ◽  
Silicate Melt ◽  
System Of Equations ◽  
Wide Range ◽  
Basaltic Melts ◽  
Multidimensional Statistics

A system of equations of thermobarometer for magnetite-silicate melt equilibrium was obtained by method of multidimensional statistics of 93 experimental data of a magnetite solubility in basaltic melts. Equations reproduce experimental data in a wide range of basalt compositions, temperatures and pressures with small errors. Verification of thermobarometers showed the maximum error in liquidus temperature reproducing does not exceed ±7 °C. The level of cumulative magnetite appearance in the vertical structure of Tsypringa, Kivakka, Burakovsky intrusions predicted with errors from ±10 to ±50 m.

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

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