MODELISATION DES SOLUTIONS AQUEUSES D’ELECTROLYTES DU TYPE 3-1 MODELLING OF AQUEOUS ELECTROLYTES SOLUTIONS OF 3-1 TYPE

Pour modéliser les coefficients d’activité des solutions aqueuses d’électrolytes du type 3-1, nous avons repris la théorie originale de Pitzer concernant l’énergie d’excès de Gibbs pour les solutions aqueusesd’électrolyte. Le modèle a été appliquépour 11 systèmes incluant des électrolytes du type 3-1. La performance de ce modèle a été comparée avec d’autres modèles existant dans la littérature. Les résultats montrent que le modèle de Pitzer peut représenter les coefficients d’activité des électrolytes dans des solutions aqueuses avec une déviation standard comparable aux autres modèles et dans la plupart des cas meilleure que les autres. To model the activity coefficients of aqueous solutions of 3-1 electrolytes, we took again the original theory of Pitzer concerning the excess Gibbs energy for the aqueous solutions ofelectrolytes. The model was applied for 11 systems including 3-1 electrolytes. The performance of this model was compared withother models existing in the literature. The results show that the model of Pitzer can represent the mean ionic activitycoefficients of 3-1 electrolytes in aqueous solutions with a standard deviation comparable with the other models and in the majority of the cases better than the others

1-Octanol/water partition coefficients of n-alkanes from molecular simulations of absolute solvation free energies

The 1-octanol/water partition coefficient is an important thermodynamic variable usually employed to understand and quantify the partitioning of solutes between aqueous and organic phases. It finds widespread use in many empirical correlations to evaluate the environmental fate of pollutants as well as in the design of pharmaceuticals. The experimental evaluation of 1-octanol/water partition coefficients is an expensive and time-consuming procedure, and thus, theoretical estimation methods are needed, particularly when a physical sample of the solute may not yet be available, such as in pharmaceutical screening. 1-Octanol/water partition coefficients can be obtained from Gibbs free energies of solvation of the solute in both the aqueous and the octanol phases. The accurate evaluation of free energy differences remains today a challenging problem in computational chemistry. In order to study the absolute solvation Gibbs free energies in 1-octanol, a solvent that can mimic many properties of important biological systems, free energy calculations for n-alkanes in the range C-1-C-8 were performed using molecular simulation techniques, following the thermodynamic integration approach. In the first part of this paper, we test different force fields by evaluating their performance in reproducing pure 1-octanol properties. It is concluded that all-atom force fields can provide good accuracy but at the cost of a higher computational time compared to that of the united-atom force fields. Recent versions of united-atom force fields, such as Gromos and TraPPE, provide satisfactory results and are, thus, useful alternatives to the more expensive all-atom models. In the second part of the paper, the Gibbs free energy of solvation in 1-octanol is calculated for several n-alkanes using three force fields to describe the solutes, namely Gromos, TraPPE, and OPLS-AA. Generally, the results obtained are in excellent agreement with the available experimental data and are of similar accuracy to commonly used QSPR models. Moreover, we have estimated the Gibbs free energy of hydration for the different compounds with the three force fields, reaching average deviations from experimental data of less than 0.2 kcal/mol for the case of the Gromos force field. Finally, we systematically compare different strategies to obtain the 1-octanol/water partition coefficient from the simulations. It is shown that a fully predictive method combining the Gromos force field in the aqueous phase and the OPLS-AA/TraPPE force field for the organic phase can give excellent predictions for n-alkanes up to C-8 with an absolute average deviation of 0.1 log P units to the experimental data

Predicting hydration Gibbs energies of alkyl-aromatics using molecular simulation : a comparison of current force fields and the development of a new parameter set for accurate solvation data

The Gibbs energy of hydration is an important quantity to understand the molecular behavior in aqueous systems at constant temperature and pressure. In this work we review the performance of some popular force fields, namely TraPPE, OPLS-AA and Gromos, in reproducing the experimental Gibbs energies of hydration of several alkyl-aromatic compounds-benzene, mono-, di- and tri-substituted alkylbenzenes-using molecular simulation techniques. In the second part of the paper, we report a new model that is able to improve such hydration energy predictions, based on Lennard Jones parameters from the recent TraPPE-EH force field and atomic partial charges obtained from natural population analysis of density functional theory calculations. We apply a scaling factor determined by fitting the experimental hydration energy of only two solutes, and then present a simple rule to generate atomic partial charges for different substituted alkyl-aromatics. This rule has the added advantages of eliminating the unnecessary assumption of fixed charge on every substituted carbon atom and providing a simple guideline for extrapolating the charge assignment to any multi-substituted alkyl-aromatic molecule. The point charges derived here yield excellent predictions of experimental Gibbs energies of hydration, with an overall absolute average deviation of less than 0.6 kJ mol(-1). This new parameter set can also give good predictive performance for other thermodynamic properties and liquid structural information

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Trihexyl(tetradecyl)phosphonium bromide:liquid density, surface tension and solubility of carbondioxide

Vapour-liquid equilibria of ionic liquid - carbon dioxide systems, as well as thermo-physical properties of the system components are very important to design and optimize various separation and reaction processes. In this work the solubility of carbon dioxide (CO2) in trihexyl(tetradecyl)phosphonium bromide([THTDP][Br]) was measured using a high-pressure sapphire cell, in pressure range of 8-22 MPa and at two temperatures, 313.2 K and 323.2 K. The thermophysical properties, namely liquid density and surface tension of the ionic liquid were determined in temperature range of 293.2-343.2 K. The densities predicted by Gardas and Coutinho model showed good agreement with the experimental data obtained in this work. The critical temperature of [THTDP][Br] was estimated using the Eotvos correlation. Moreover, these experimental and calculated data gave an opportunity to apply the Peng-Robinson equation of state (PR-EoS) in order to predict/correlate the behaviour of the studied system, ([THTDP][Br] + CO2) with satisfactory results. (C) 2012 Published by Elsevier B.V

Liquid-liquid equilibria of mixtures with ethyl lactate and various hydrocarbons

Mutual miscibility in mixtures containing ethyl lactate and various hydrocarbons (alkanes, alkenes, cyclohexane, alkyl cyclohexanes and terpenes) were explored in a range of temperatures from (273.2 to 320.9) K and at atmospheric pressure. Thus, the respective temperature-composition phase diagrams were constructed. The influence of temperature, aliphatic chain length and of double bond presence on liquid phase behavior was discussed. The obtained liquid-liquid solubility data were represented using the UNIQUAC-based model which showed to be an appropriate tool for representing the liquid-liquid behavior of (hydrocarbon + ethyl lactate) mixtures. (C) 2012 Elsevier B.V. All rights reserved