scholarly journals Sorption hysteresis on soils and sediments: Using single-point desorption isotherms to obtain characteristic free energy values

2020 ◽  
Author(s):  
Mikhail Borisover
Keyword(s):  
Free Energy ◽  
Single Point ◽  
Soils And Sediments ◽  
Sorption Hysteresis ◽  
Desorption Isotherms

scholarly journals Sorption Hysteresis on Soils and Sediments: Obtaining Characteristic Free Energies Using "Single-Point Desorption Isotherms"

2020 ◽  
Author(s):  
Mikhail Borisover
Keyword(s):  
Free Energy ◽  
Liquid Phase ◽  
Single Point ◽  
Solute Concentration ◽  
Metastable States ◽  
Environmental Literature ◽  
Free Energies ◽  
Novel Approach ◽  
Soils And Sediments ◽  
Desorption Isotherms

<p>Sorption-desorption hysteresis (SDH) may control distributions of chemicals between diverse environmental phases, including soils and sediments. Formation of metastable states caused by pore deformation or inelastic swelling of a sorbent and their persistence during desorption were considered in the literature as one reason for "true" SDH. Such metastable states persisting during desorption lead to the lack of closure of sorption-desorption loop at non-zero sorbate concentrations, which is often observed in soil and environmental literature. Also, SDH was often characterized using single-point desorption isotherms (DIs) combining sorbed states reached during single desorption steps started from different points along a sorption isotherm (SI). The objective of this contribution is to demonstrate how the single-point DIs could be used to characterize SDH in liquid phase sorption experiments in terms of Gibbs free energy. This free energy is accumulated in some non-relaxed sorbed states belonging to DI as compared with the states of the same composition (sorbed concentration) belonging to SI. Using the literature data on SIs and single-point DIs of some polycyclic aromatic hydrocarbons and pesticides on soils and sediments, it is shown how these extra free energies could be obtained and how they could change in the selected sorbate-sorbent systems. When the extent of SDH decreases with increasing solute concentration, these additional free energies decline. They may remain constant or even increase, suggesting in the latter case that a larger work is needed to perturb a sorbent structure at higher sorbed concentrations. This paper proposes a novel approach for quantifying and understanding liquid phase SDH in the cases when a thermodynamic justification is sought, and, therefore, it advances the ability to predict the fate and activity of multiple chemicals in typical soil/sediment environments. </p><p><br></p>

scholarly journals Sorption Hysteresis on Soils and Sediments: Obtaining Characteristic Free Energies Using "Single-Point Desorption Isotherms"

2020 ◽  
Author(s):  
Mikhail Borisover
Keyword(s):  
Free Energy ◽  
Liquid Phase ◽  
Single Point ◽  
Solute Concentration ◽  
Metastable States ◽  
Environmental Literature ◽  
Free Energies ◽  
Novel Approach ◽  
Soils And Sediments ◽  
Desorption Isotherms

<p>Sorption-desorption hysteresis (SDH) may control distributions of chemicals between diverse environmental phases, including soils and sediments. Formation of metastable states caused by pore deformation or inelastic swelling of a sorbent and their persistence during desorption were considered in the literature as one reason for "true" SDH. Such metastable states persisting during desorption lead to the lack of closure of sorption-desorption loop at non-zero sorbate concentrations, which is often observed in soil and environmental literature. Also, SDH was often characterized using single-point desorption isotherms (DIs) combining sorbed states reached during single desorption steps started from different points along a sorption isotherm (SI). The objective of this contribution is to demonstrate how the single-point DIs could be used to characterize SDH in liquid phase sorption experiments in terms of Gibbs free energy. This free energy is accumulated in some non-relaxed sorbed states belonging to DI as compared with the states of the same composition (sorbed concentration) belonging to SI. Using the literature data on SIs and single-point DIs of some polycyclic aromatic hydrocarbons and pesticides on soils and sediments, it is shown how these extra free energies could be obtained and how they could change in the selected sorbate-sorbent systems. When the extent of SDH decreases with increasing solute concentration, these additional free energies decline. They may remain constant or even increase, suggesting in the latter case that a larger work is needed to perturb a sorbent structure at higher sorbed concentrations. This paper proposes a novel approach for quantifying and understanding liquid phase SDH in the cases when a thermodynamic justification is sought, and, therefore, it advances the ability to predict the fate and activity of multiple chemicals in typical soil/sediment environments. </p><p><br></p>

scholarly journals Sorption Hysteresis on Soils and Sediments: Obtaining Characteristic Free Energies Using "Single-Point Desorption Isotherms"

2020 ◽  
Author(s):  
Mikhail Borisover
Keyword(s):  
Free Energy ◽  
Liquid Phase ◽  
Single Point ◽  
Solute Concentration ◽  
Metastable States ◽  
Environmental Literature ◽  
Free Energies ◽  
Novel Approach ◽  
Soils And Sediments ◽  
Desorption Isotherms

<p>Sorption-desorption hysteresis (SDH) may control distributions of chemicals between diverse environmental phases, including soils and sediments. Formation of metastable states caused by pore deformation or inelastic swelling of a sorbent and their persistence during desorption were considered in the literature as one reason for "true" SDH. Such metastable states persisting during desorption lead to the lack of closure of sorption-desorption loop at non-zero sorbate concentrations, which is often observed in soil and environmental literature. Also, SDH was often characterized using single-point desorption isotherms (DIs) combining sorbed states reached during single desorption steps started from different points along a sorption isotherm (SI). The objective of this contribution is to demonstrate how the single-point DIs could be used to characterize SDH in liquid phase sorption experiments in terms of Gibbs free energy. This free energy is accumulated in some non-relaxed sorbed states belonging to DI as compared with the states of the same composition (sorbed concentration) belonging to SI. Using the literature data on SIs and single-point DIs of some polycyclic aromatic hydrocarbons and pesticides on soils and sediments, it is shown how these extra free energies could be obtained and how they could change in the selected sorbate-sorbent systems. When the extent of SDH decreases with increasing solute concentration, these additional free energies decline. They may remain constant or even increase, suggesting in the latter case that a larger work is needed to perturb a sorbent structure at higher sorbed concentrations. This paper proposes a novel approach for quantifying and understanding liquid phase SDH in the cases when a thermodynamic justification is sought, and, therefore, it advances the ability to predict the fate and activity of multiple chemicals in typical soil/sediment environments. </p><p><br></p>

Environmental risk indicators for soil phosphorus status

Soil Research ◽  
2011 ◽  
Vol 49 (3) ◽  
pp. 247 ◽  
Author(s):  
P. W. Moody
Keyword(s):  
Environmental Risk ◽  
Soil Phosphorus ◽  
Single Point ◽  
Risk Indicators ◽  
Available Phosphorus ◽  
Soil P ◽  
Olsen P ◽  
Soils And Sediments ◽  
Optimum Productivity ◽  
Highly Correlated

Biologically available phosphorus (P) is divided operationally into two sources, dissolved reactive P (DRP) and bioavailable particulate P (BPP). Dilute CaCl2-extractable soil P (CaCl2-P) is considered to be the benchmark method for estimating DRP in soils, whereas P desorbed to iron-oxide impregnated filter paper (FeO-P) is the benchmark method for BPP in soils and sediments. Neither of these methods is in routine use in Australia. Selected soil P analyses were carried out on 31 diverse surface soils to develop relationships between the environmental benchmark methods and the routine soil P tests of Colwell-P, Olsen-P, and the single-point P buffer index (PBI). The index (Colwell-P/PBI) was highly correlated with CaCl2-P (r = 0.925, P < 0.001), and both Olsen-P and Colwell-P were highly correlated with FeO-P (r = 0.955 and 0.828, respectively; P < 0.001). It is suggested that these measures can be used as environmental risk indicators for soil P status. The critical values of these measures for optimum productivity were compared to the values of these measures corresponding to threshold values of currently used environmental risk indicators.

Ab Initio Free Energy Calculations at Multiple Electronic Structure Levels Made Affordable: An Effective Combination of Perturbation Theory and Machine Learning

2020 ◽  
Author(s):  
Tomas Bucko ◽  
Monika Gešvandtnerová ◽  
Dario Rocca
Keyword(s):  
Machine Learning ◽  
Free Energy ◽  
Perturbation Theory ◽  
Ab Initio ◽  
Single Point ◽  
Free Energy Calculations ◽  
Thermodynamic Quantities ◽  
Free Energies ◽  
Energy Calculations ◽  
Ab Initio Theory

<div>While free energies are fundamental thermodynamic quantities to characterize chemical reactions, their calculation based on ab initio theory is usually limited by the high computational cost. This is particularly true if multiple levels of theory have to be tested to establish their relative accuracy, if highly expensive quantum mechanical approximations are of interest, and also if several different temperatures have to be considered. We present an ab initio approach that effectively couples perturbation theory and machine learning to make ab initio free energy calculations more affordable. Starting from results based on a certain production ab initio theory, perturbation theory is applied to obtain free energies. The large number of single point calculations required by a brute force application of this approach are here significantly decreased by applying machine learning techniques. Importantly, the </div><div>training of the machine learning model requires only a small amount of data and does not need to be </div><div>performed again when the temperature is decreased.</div><div>The accuracy and efficiency of this method is demonstrated by computing the free energy of activation of the </div><div>proton exchange reaction in the zeolite chabazite. Starting from an ab initio calculation based on a semilocal</div><div>approximation of density functional theory, free energies based on significantly </div><div>more expensive non-local van der Waals and hybrid functionals are obtained with only a few tens</div><div>of additional single point calculations. In this way this work paves the route to</div><div>quick free energy calculations using different levels of theory or approximations that would be</div><div>too computationally expensive to be directly employed in molecular dynamics or Monte Carlo simulations.</div>

scholarly journals Moisture desorption isotherms of cucumber seeds: modeling and thermodynamic properties

2015 ◽  
Vol 37 (3) ◽  
pp. 218-225 ◽  
Author(s):  
Paulo Cesar Corrêa ◽  
Maycon Fagundes Teixeira Reis ◽  
Gabriel Henrique Horta de Oliveira ◽  
Ana Paula Lelis Rodrigues de Oliveira ◽  
Fernando Mendes Botelho
Keyword(s):  
Free Energy ◽  
Relative Humidity ◽  
Thermodynamic Properties ◽  
Moisture Content ◽  
Gibbs Free Energy ◽  
Content Increase ◽  
Statistical Parameters ◽  
Thermodynamic Relation ◽  
Differential Enthalpy ◽  
Desorption Isotherms

Hygroscopic equilibrium curves or sorption isotherms are important in order to define dehydration limits of the product, estimate moisture content alterations under environment conditions and to acquire moisture content values for safe storage. This work aimed to determine desorption isotherms of cucumber seeds stored at different temperature (10, 20, 30, 40 and 50 ºC) and relative humidity (0.11 to 0.96) and the thermodynamic properties of this process. Mathematical models were fitted to experimental data in order to represent the agricultural products hygroscopicity. Net isosteric heat of desorption was performed based on the Clausius-Clapeyron thermodynamic relation and Gibbs free energy through the Van't Hoff equation. Based on statistical parameters, Modified Henderson model was the one that best represented hygroscopicity of cucumber seeds. Equilibrium moisture content of cucumber seeds decreased with temperature increment at a constant value of relative humidity. Differential enthalpy values, representing the energy required to remove moisture from the cucumber seeds, ranged from 2923 to 2469 kJ. kg-1. Values of differential entropy and Gibbs free energy decreased with moisture content increase. Enthalpy-entropy compensation theory is valid for the sorption of cucumber seeds, in which the water sorption mechanism in cucumber seeds can be considered to be enthalpy controlled.

scholarly journals Predicting folding free energy changes upon single point mutations

2012 ◽  
Vol 28 (5) ◽  
pp. 664-671 ◽  
Author(s):  
Zhe Zhang ◽  
Lin Wang ◽  
Yang Gao ◽  
Jie Zhang ◽  
Maxim Zhenirovskyy ◽  
...  
Keyword(s):  
Free Energy ◽  
Single Point ◽  
Point Mutations ◽  
Single Point Mutations ◽  
Folding Free Energy

scholarly journals Protein-Protein Interactions: Insight from Molecular Dynamics Simulations and Nanoparticle Tracking Analysis

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5696
Author(s):  
Wei Lim Chong ◽  
Koollawat Chupradit ◽  
Sek Peng Chin ◽  
Mai Mai Khoo ◽  
Sook Mei Khor ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Free Energy ◽  
Protein Binding ◽  
Protein Interactions ◽  
Binding Free Energy ◽  
Single Point ◽  
Md Simulations ◽  
Nanoparticle Tracking Analysis ◽  
Buffer Solution ◽  
Dynamics Simulations

Protein-protein interaction plays an essential role in almost all cellular processes and biological functions. Coupling molecular dynamics (MD) simulations and nanoparticle tracking analysis (NTA) assay offered a simple, rapid, and direct approach in monitoring the protein-protein binding process and predicting the binding affinity. Our case study of designed ankyrin repeats proteins (DARPins)—AnkGAG1D4 and the single point mutated AnkGAG1D4-Y56A for HIV-1 capsid protein (CA) were investigated. As reported, AnkGAG1D4 bound with CA for inhibitory activity; however, it lost its inhibitory strength when tyrosine at residue 56 AnkGAG1D4, the most key residue was replaced by alanine (AnkGAG1D4-Y56A). Through NTA, the binding of DARPins and CA was measured by monitoring the increment of the hydrodynamic radius of the AnkGAG1D4-gold conjugated nanoparticles (AnkGAG1D4-GNP) and AnkGAG1D4-Y56A-GNP upon interaction with CA in buffer solution. The size of the AnkGAG1D4-GNP increased when it interacted with CA but not AnkGAG1D4-Y56A-GNP. In addition, a much higher binding free energy (∆GB) of AnkGAG1D4-Y56A (−31 kcal/mol) obtained from MD further suggested affinity for CA completely reduced compared to AnkGAG1D4 (−60 kcal/mol). The possible mechanism of the protein-protein binding was explored in detail by decomposing the binding free energy for crucial residues identification and hydrogen bond analysis.

Sign in / Sign up

Export Citation Format

Share Document