@article{barrios_parra_venditti_pal_2024, title={Elucidation of temperature-induced water structuring on cellulose surfaces for environmental and energy sustainability}, volume={329}, ISSN={["1879-1344"]}, url={http://dx.doi.org/10.1016/j.carbpol.2024.121799}, DOI={10.1016/j.carbpol.2024.121799}, abstractNote={Optimizing drying energy in the forest products industry is critical for integrating lignocellulosic feedstocks across all manufacturing sectors. Despite substantial efforts to reduce thermal energy consumption during drying, further enhancements are possible. Cellulose, the main component of forest products, is Earth's most abundant biopolymer and a promising renewable feedstock. This study employs all-atom molecular dynamics (MD) simulations to explore the structural dynamics of a small Iβ-cellulose microcrystallite and surrounding water layers during drying. Molecular and atomistic profiles revealed localized water near the cellulose surface, with water structuring extending beyond 8 Å into the water bulk, influencing solvent-accessible surface area and solvation energy. With increasing temperature, there was a ~20 % reduction in the cellulose surface available for interaction with water molecules, and a ~22 % reduction in solvation energy. The number of hydrogen bonds increased with thicker water layers, facilitated by a “bridging” effect. Electrostatic interactions dominated the intermolecular interactions at all temperatures, creating an energetic barrier that hinders water removal, slowing the drying processes. Understanding temperature-dependent cellulose-water interactions at the molecular level will help in designing novel strategies to address drying energy consumption, advancing the adoption of lignocellulosics as viable manufacturing feedstocks.}, journal={CARBOHYDRATE POLYMERS}, author={Barrios, Nelson and Parra, Jose G. and Venditti, Richard A. and Pal, Lokendra}, year={2024}, month={Apr} }
 @article{acosta_parra_iza_2024, title={Estudio computacional de las interacciones moleculares entre el timol y los residuos HIS41 y CYS145 presentes en el sitio activo de la proteasa 3CLpro}, url={https://doi.org/10.15446/rev.colomb.quim.v52n1.110606}, DOI={10.15446/rev.colomb.quim.v52n1.110606}, abstractNote={La proteína proteasa 3CLpro del SARS-CoV-2 es una enzima crucial para la replicación viral, convirtiéndose en un blanco terapéutico de gran importancia. El timol (2-isopropil-5-metilfenol), un compuesto natural que se encuentra en el tomillo (Thymus vulgaris), exhibe potencial actividad antiviral contra la proteasa 3CLpro. En este estudio, usando acoplamiento molecular con AutoDockTools-1.5.6, se evaluaron las energías de interacción molecular entre el timol y los residuos de aminoácidos en el sitio activo de la proteína proteasa 3CLpro. Luego, con la teoría cuántica de Átomos en Moléculas (QTAIM) y la de Interacciones no covalentes (NCI) se analizaron los tipos de interacciones moleculares entre los residuos de aminoácidos identificados y el timol. Los cálculos cuánticos se llevaron con el software Orca-5.0.3, utilizando el método DFT con el funcional M06-2X y el conjunto base aug-cc-pVDZ en fase gaseosa. Los resultados de acoplamiento molecular indican que el timol se une a la proteína 3CL con una energía de interacción igual a -3,784 kcal/mol. El análisis QTAIM indica la presencia de puntos críticos de enlace entre el timol y los residuos HIS41 y CYS145. Además, se observa la formación de un enlace de hidrógeno entre el grupo OH del timol con el residuo CYS145, lo cual es corroborado por los análisis ELF (Electron Localization Function) y NCI (Non Covalent Interactions). Finalmente, el método NCI confirma la presencia de interacciones de van der Waals con el residuo HIS41. Los resultados sugieren que el mecanismo de inhibición de la actividad de la proteína 3CLpro es controlado por interacciones moleculares tipo puente de hidrógeno e interacciones débiles.}, journal={Revista Colombiana de Química}, author={Acosta, José Gregorio González and Parra, José Gregorio and Iza, Peter}, year={2024}, month={Feb} }
 @article{parra_iza_dominguez_schott_zarate_2024, title={Unveiling the hydrophilic nature of SDS surfactant through molecular simulations: Exploring the influence of charge distribution on interfacial properties in the vacuum/SDS/water system}, url={http://dx.doi.org/10.1016/j.molliq.2024.124692}, DOI={10.1016/j.molliq.2024.124692}, abstractNote={The hydrophilicity of SDS surfactant was evaluated using different charge distributions derived from atomic charges obtained by quantum mechanical calculations. The atomic charges were determined using the Hirshfeld, CM5, CHELPG, and Merz-Kollman methods. The results indicate that the correct charge distribution in the hydrophilic group has an impact on the description of the surfactant hydrophilicity, which allows us to obtain a good estimation of the interfacial properties of the vacuum/SDS/water system. Two models of charge distribution based on the point charge model were proposed for SDS surfactant, using atomic charges computed through Quantum Mechanical calculations. The charge distributions derived from CM5, Merz-Kollman, and CHELPG atomic charges consistently predict the interfacial properties such as: area occupied per molecule, interfacial thicknesses, and radial distribution functions. Using Molecular Dynamics simulations, the ability of the charge distributions combined with nonbonded parameters of the GROMOS53A6 force field to predict the interfacial properties has the following order: CM5 > Merz-Kollman ≈ CHELPG > Hirshfeld. In contrast, the charge distributions overestimated the reduction of the interfacial tension of the vacuum/SDS/water system. Interfacial properties such as interfacial tension, area occupied per SDS molecule, and molecular interaction between the hydrophilic headgroup and water molecules were evaluated. Simulations demonstrated that the high interfacial activity of the SDS surfactant is associated with the high negative charge distribution defined for the hydrophilic headgroup of the surfactant, which enhances the ability to attract water molecules and the solvation of the hydrophilic region.}, journal={Journal of Molecular Liquids}, author={Parra, José G. and Iza, Peter and Dominguez, Hector and Schott, Eduardo and Zarate, Ximena}, year={2024}, month={May} }
 @article{galarza-acosta_parra_hernández-bravo_iza_schott_zarate_castillo_mujica_2023, title={A Computational Chemistry Approach to the Molecular Design of SiO2 Nanoparticles Coated with Stearic Acid and Sodium Stearate in Ethanol Solvent.}, volume={679}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2023.132527}, DOI={10.1016/j.colsurfa.2023.132527}, abstractNote={Preparation of hydrophobic SiO2 nanoparticles (NPs) coated with different surfactants is important due to their potential application in different fields of chemistry. In this work, a combined experimental and Molecular Dynamics (MD) simulation approach, is advanced to characterize the adsorption process, in ethanol as a solvent, of stearic acid and sodium stearate on SiO2 spherical NPs with different ionization degrees (0%, 10%, and 23.3%). The main objective is to gain molecular insight into the factors involved in the preparation of hydrophobic coated NPs, which involves the intervention of ion-dipole, electrostatic, and hydrogen bond-type interactions depending on the surfactants and the nature SiO2 NPs. Our results demonstrate that the SiO2 NPs have a good affinity for ethanol solvent medium., as confirmed through the analysis of the Radial Distribution Functions (RDFs)), which indicates that hydrogen bonds are formed at a distance of ~0.192 nm between ethanol and SiO2 NPs. The presence of Na+ ions reduce the electrostatic repulsion between the -COO- and -SiO- groups in NPs with degrees of ionization of 10% and 23.3%, because it acts as a bridge and thus favors the adsorption between the silanol and carboxylic groups. The investigation of the Potentials of Mean Force (PMFs) suggests that the adsorption on these NPs, is a spontaneous process compared with the case with 0% ionization degree. The experimental coating of the NPs was studied using Atomic Force Microscopy (AFM), a technique that allows the indirect measure of the Work of Adhesion (Wadh), a key quantity to estimate the energy needed to separate the interfaces AFM tip-sample. The experimental values of Wadh for the pure SiO2 NPs and two modified SiO2 NPs correspond to 2.01 J/m2, 1.72 J/m2 and 1.43 J/m2, respectively. The main conclusion is that the interaction energies between surfactants and SiO2 NPs, estimated from MD simulations, and the Wadh obtained from AFM measurements are correlated, in the sense that the reduction in the Wadh, in a solvent-free environment, corresponds to an increment of the interaction energy in the presence of the solvent. This reduction in Wadh is also associated with the fact that the nature of the coating of the SiO2 NPs surfaces increases the NPs hydrophobicity. Our analysis provides a path for the computational design and the prediction of hydrophobicity of coated NPs, which is the main focus of our work.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Galarza-Acosta, Gabriela L. and Parra, José G. and Hernández-Bravo, Raiza and Iza, Peter and Schott, Eduardo and Zarate, Ximena and Castillo, Jimmy and Mujica, Vladimiro}, year={2023}, month={Dec}, pages={132527} }
 @article{carrillo hernández_hirota_parra_2023, title={Comportamiento de la amoxicilina en agua mediante métodos de solvatación implícita y explícita}, volume={51}, ISSN={2357-3791 0120-2804}, url={http://dx.doi.org/10.15446/rev.colomb.quim.v51n2.103567}, DOI={10.15446/rev.colomb.quim.v51n2.103567}, abstractNote={ El comportamiento molecular de la amoxicilina en agua fue explorado con solvatación implícita y explícita mediante dos estrategias que combinan diferentes técnicas de simulación molecular para evaluar el alcance de estos procedimientos. Con estas dos estrategias de cálculo computacional, la conformación molecular de la amoxicilina fue determinada en fase acuosa. En la primera estrategia se utilizó el generador de conformaciones Ballon-v1.8.2y la estabilidad de las conformaciones en agua fue evaluada utilizando la energía libre de solvatación determinada con el método de solvatación implícita SMD. En la segunda estrategia, con la dinámica molecular tipo NVT fue evaluado el arreglo espacial de esta molécula en agua y, además, la interacción molecular entre la amoxicilina y el agua fue evaluada en esta simulación. Los resultados obtenidos muestran que la conformación de la amoxicilina más estable en fase acuosa es la plegada. Además, los valores de energías de solvatación de -121,42 y -14,58 kJ/molobtenidos con solvatación implícita y dinámica molecular sugieren que esta molécula tiene una alta afinidad por el agua. Las funciones distribución radial y espacial sugieren que se forman 3 capas de solvatación alrededor de la amoxicilina y que esta molécula tiene una región altamente hidrofílica. Finalmente, la estrategia usando dinámica molecular permite obtener mejores conformaciones en equilibrio que la estrategia de simulación usando el generador de conformaciones Ballon-v1.8.2. }, number={2}, journal={Revista Colombiana de Química}, publisher={Universidad Nacional de Colombia}, author={Carrillo Hernández, Miguel Ángel and Hirota, Wilson H. and Parra, José G.}, year={2023}, month={Apr} }
 @article{parra_rodriguez_iza_zarate_schott_2023, title={Evaluation of the affinity of asphaltene molecular models A1 and A2 by the water/oil interfaces based on a novel concept of solubility parameter profiles obtained from MD simulations}, volume={376}, ISSN={0167-7322}, url={http://dx.doi.org/10.1016/j.molliq.2023.121430}, DOI={10.1016/j.molliq.2023.121430}, abstractNote={Crude oils are formed of asphaltenes that are species soluble in certain solvents such as toluene. The distribution of asphaltene models and their mixtures in water/n–heptane and water/toluene systems were explored with MD simulations. A1 and A2 asphaltene models were used for the exploration of the affinity of these compounds by the water/oil interfaces. For this, a novel concept called solubility parameter profiles was used to characterize the polarity of the regions present in water/n–heptane and water/toluene systems. Molecules of asphaltene models, n–heptane, and toluene were described with the GROMOS53A6 force field and CHELPG atomic charges, and water molecules with the SPC model. The prediction of the affinity of A1 and A2 asphaltene models at interfaces was determined using the total solubility parameter differences calculated between these species and solvent molecules. Calculated solubility parameters show a good correlation with experimental values. Total solubility parameter differences equal to Δδtotal = 3.76 MPa0.5 and Δδtotal = 0.36 MPa0.5 at the water/n–heptane interface suggest that asphaltene models have a good affinity by the water/n–heptane interface in comparison with the water/toluene interface whose values were Δδtotal = 5.82 MPa0.5 and Δδtotal = 9.94 MPa0.5 for A1 and A2 asphaltene models, respectively. It was demonstrated that the affinity of asphaltenes by a specific region of the immiscible system is controlled by the electrostatic and dispersive contributions associated with the solubility parameter profiles.}, journal={Journal of Molecular Liquids}, publisher={Elsevier BV}, author={Parra, José G. and Rodriguez, Geraldine and Iza, Peter and Zarate, Ximena and Schott, Eduardo}, year={2023}, month={Apr}, pages={121430} }
 @inproceedings{parra_roa_armado_2023, title={Exploration of the molecular interaction of a humic acid model with the water by means of molecular dynamics simulations}, url={http://dx.doi.org/10.54985/peeref.2303p4473663}, DOI={10.54985/peeref.2303p4473663}, abstractNote={In this work, the molecular interaction of molecular structures generated from a humic acid model called TNB with water was explored with MD simulations to explore the affinity and behavior of these species in the aqueous medium.TNB model was described with the all-atom GROMOS53A6 force field.The bonding and non-bonding parameters were obtained of the GROMACS-2019.2software package.The evaluation was realized for the functional groups -N H 2 and -COOH present in this molecular model.The spatial conformations of TNB molecule change considerably when evaluating the effect of pH on intermolecular interactions in aqueous solution.Molecular dynamics calculations showed that the acid sites of the TNB humic acid model to assess molecular interaction have low affinity for water.Results are consistent with the experimental behavior of humic acids in an aqueous solution.}, booktitle={LatinXchem 2022}, publisher={Peeref}, author={Parra, José G. and Roa, Jesús and Armado, Arnaldo}, year={2023}, month={Mar} }
 @article{figueredo_gonzález_perozo_iza_2023, title={Un procedimiento para la obtención de los espectros IR, Raman y RMN de compuestos orgánicos mediante cálculos mecánico-cuánticos con el software ORCA-5.0.3}, volume={34}, url={http://dx.doi.org/10.22201/fq.18708404e.2023.1.82742}, DOI={10.22201/fq.18708404e.2023.1.82742}, abstractNote={Este manuscrito describe un procedimiento para la estimación de los espectros IR, Raman y RMN de H1 y C13 de especies orgánicas mediante el uso de cálculos mecánico-cuánticos con la finalidad de mostrar a estudiantes universitarios la implementación de técnicas de simulación en la elucidación de sus estructuras moleculares. Los softwares Avogadro-1.2.0 (Hanwell et al., 2012) y Orca-5.0.3 (Neese, 2018) fueron utilizados para la elaboración de este procedimiento. Este estudio muestra que las frecuencias vibracionales armónicas y las intensidades de las señales estimadas para los espectros Infrarrojos fueron aceptables y en correspondencia con los valores experimentales. En cambio, las intensidades del espectro Raman presentaron desviaciones considerables que pueden atribuirse al enfoque utilizado para la estimación de las intensidades del espectro y la realización de los cálculos mecánico-cuánticos en el vacío para las moléculas seleccionadas. Finalmente, las señales de los espectros RMN de H1 y C13 fueron obtenidos con una muy buena estimación, lo cual fue corroborado con los valores de RMSE reportados.
 }, number={1}, journal={Educación Química}, publisher={Universidad Nacional Autonoma de Mexico}, author={Figueredo, José Gregorio Parra and González, José and Perozo, Elizabeth and Iza, Peter}, year={2023}, month={Jan}, pages={20–59} }
 @inproceedings{barrios_parra_lucia_venditti_pal_2023, title={Unveiling the Cellulose-Water Interaction Through Computational Simulations (2023}, booktitle={TAPPICon 2023 : Rock the Roll: Unleashing the Harmonies of the Paper Industry}, author={Barrios, N. and Parra, J.G. and Lucia, L. and Venditti, R. and Pal, L}, year={2023} }
 @inproceedings{parra_paredes_iza_2022, title={A theoretical study of the nitration of Imidazole in gas phase}, booktitle={The Royal Society of Chemistry}, author={Parra, Jose and Paredes, Myleidys and Iza, Peter}, year={2022}, month={Mar} }
 @article{hernández-bravo_miranda_parra_alvarado-orozco_domínguez-esquivel_mujica_2022, title={Experimental and theoretical study on the effectiveness of ionic liquids as corrosion inhibitors}, volume={1210}, ISSN={2210-271X}, url={http://dx.doi.org/10.1016/j.comptc.2022.113640}, DOI={10.1016/j.comptc.2022.113640}, abstractNote={An experimental and computational study, using a Density Functional Theory approach, was made about the anticorrosive effect of ionic liquids on hematite surfaces. Based on the hypothesis that adsorption is an initial step in the kinetics of corrosion, followed by electron transfer processes, adsorption energy calculations and corrosion rates are determined to investigate the effect as corrosion inhibitor of ionic liquids molecules. Several, potential descriptors of the inhibitor performance, conceptualized as an electrochemical process, based on the frontier orbital theory were used to characterize the interactions that might inhibit the corrosion, including the energies of the highest occupied (ELUMO) and lowest unoccupied (EHOMO) molecular orbitals, the energy gap between orbitals, crossed energies differences between HOMO and LUMO of the intervening chemical species and the surface, electronegativity (χ), hardness (η), and number of transferred electrons (ΔN). The main conclusion is that although the adsorption energy is a key parameter in establishing a correlation between calculated parameters and the experimental characterization of the ILs, the remaining chemical predictors also play an important role on the descriptions of activity corrosion, especially the electronegativity difference between surface and ILs, and the hardness of the IL.}, journal={Computational and Theoretical Chemistry}, publisher={Elsevier BV}, author={Hernández-Bravo, Raiza and Miranda, Alma D. and Parra, José G. and Alvarado-Orozco, Juan M. and Domínguez-Esquivel, José M. and Mujica, Vladimiro}, year={2022}, month={Apr}, pages={113640} }
 @inproceedings{parra_iza_2021, title={DFT study of the reaction of 1,3-Cyclopentadiene with MVK in certain solvents}, booktitle={XIX Mexican Meeting of Theoretical Physicochemistry}, publisher={November}, author={Parra, Jose and Iza, Peter}, year={2021} }
 @inproceedings{parra_dominguez_iza_2021, title={Effect of NaCl on the Adsorption of SDBS Surfactant at the Water/nOctane Interface With Presence of Linear Alcohols. A Study Using MD Simulations}, booktitle={The Royal Society of Chemistry}, author={Parra, Jose and Dominguez, Hector and Iza, Peter}, year={2021}, month={Mar} }
 @article{gonzález a._parra_iza_2021, title={Exploring the hydrogen bond type interactions in organic compounds with pharmaceutical properties using molecular simulation method}, volume={11}, url={http://dx.doi.org/10.26226/morressier.616e5c2462ba8657678b1311}, DOI={10.26226/morressier.616e5c2462ba8657678b1311}, abstractNote={@LatinXChem is a virtual forum through which the community of Latin American chemists, located anywhere in the world, can share and discuss their research results and advances. More than 1200 posters from 43 countries were received in its first version, with 20 million impacts on Twitter. The second event organized by @LatinXChem will be the #LXChem2021 Conference (September 20, 2021), where posters divided into eleven categories can be discussed via Twitter.}, journal={LatinXchem 2021}, publisher={Morressier}, author={González A., José G. and Parra, José G. and Iza, Peter}, year={2021}, month={Nov} }
 @misc{parra_iza_dominguez_schott_zarate_2021, title={Final configuration of surfactants in mixed monolayer in "Effect of Triton X-100 surfactant on the interfacial activity of ionic surfactants SDS, CTAB and SDBS at the air/water interface: A study using molecular dynamic simulations"}, volume={V2}, url={https://data.mendeley.com/datasets/m66dsvpnp7}, DOI={10.17632/m66dsvpnp7.2}, journal={Mendeley Data}, author={Parra, José G. and Iza, Peter and Dominguez, Hector and Schott, Eduardo and Zarate, Ximena}, year={2021}, month={Jun} }
 @inproceedings{salas_parra_iza_zarate_schott_2021, title={Molecular Dynamics Simulations of the Molecular Interaction of Muricatacine with Phospholipids Membranes}, booktitle={The Royal Society of Chemistry}, author={Salas, Mariangeles and Parra, Jose and Iza, Peter and Zarate, Ximena and Schott, Eduardo}, year={2021}, month={Mar} }
 @article{parra_iza_dominguez_salas_2021, title={Molecular aggregation of Muricatacin in water using MD simulations}, volume={10}, url={http://dx.doi.org/10.26226/morressier.616e5c2462ba8657678b1329}, DOI={10.26226/morressier.616e5c2462ba8657678b1329}, abstractNote={@LatinXChem is a virtual forum through which the community of Latin American chemists, located anywhere in the world, can share and discuss their research results and advances. More than 1200 posters from 43 countries were received in its first version, with 20 million impacts on Twitter. The second event organized by @LatinXChem will be the #LXChem2021 Conference (September 20, 2021), where posters divided into eleven categories can be discussed via Twitter.}, journal={LatinXchem 2021}, publisher={Morressier}, author={Parra, José G. and Iza, Peter and Dominguez, Hector and Salas, Mariangeles}, year={2021}, month={Oct} }
 @article{salas_parra_iza_2021, title={Molecular dynamics simulations of the molecular interaction of muricatacin with a charged phospholipid membrane}, volume={10}, url={http://dx.doi.org/10.26226/morressier.616e5c2462ba8657678b1393}, DOI={10.26226/morressier.616e5c2462ba8657678b1393}, abstractNote={@LatinXChem is a virtual forum through which the community of Latin American chemists, located anywhere in the world, can share and discuss their research results and advances. More than 1200 posters from 43 countries were received in its first version, with 20 million impacts on Twitter. The second event organized by @LatinXChem will be the #LXChem2021 Conference (September 20, 2021), where posters divided into eleven categories can be discussed via Twitter.}, journal={LatinXchem 2021}, publisher={Morressier}, author={Salas, Mariangeles and Parra, José G. and Iza, Peter}, year={2021}, month={Oct} }
 @article{parra figueredo_iza_perozo_2021, title={Una guía para la estimación de la tensión interfasiales y el espesor de la interface de un sistema agua/hidrocarburo usando el programa gromacs-4.5.4}, volume={32}, ISSN={1870-8404 0187-893X}, url={http://dx.doi.org/10.22201/fq.18708404e.2021.3.76027}, DOI={10.22201/fq.18708404e.2021.3.76027}, abstractNote={<p class="western" lang="es-VE" align="justify">La dinámica molecular es una herramienta muy útil para estudiar los fenómenos interfaciales. Aquí se presenta un procedimiento usando el programa GROMACS-4.5.4, el cual es empleado en el laboratorio de fisicoquímica, para estimar la tensión interfacial y el espesor de película interfacial del sistema agua/n-octano con el modelo de Kirkwood-Buff y la teoría onda-capilar. En la simulación, se utilizan los tensores de presión y la tensión interfacial más aceptable fue obtenida combinando los modelos TIP3P y GROMOS53A6 para el agua y n-octano. </p>}, number={3}, journal={Educación Química}, publisher={Universidad Nacional Autonoma de Mexico}, author={Parra Figueredo, José Gregorio and Iza, Peter and Perozo, Elizabeth}, year={2021}, month={Jul}, pages={80} }
 @article{parra_iza_2020, title={Computational Theoretical study of reaction path of the unimolecular decomposition of malonic acid in the gas phase using the neb method}, volume={9}, url={http://dx.doi.org/10.26226/morressier.5f6c5f439b74b699bf390c31}, DOI={10.26226/morressier.5f6c5f439b74b699bf390c31}, journal={LatinXchem 2020}, publisher={Morressier}, author={Parra, José G. and Iza, Peter}, year={2020}, month={Sep} }
 @inproceedings{gonzalez_parra_2020, title={Computational prediction of C13 chemical shifts of benzoic acid}, booktitle={LatinXchem}, author={Gonzalez, Jose and Parra, Jose G.}, year={2020} }
 @article{parra_dominguez_aray_iza_zarate_schott_2020, title={Corrigendum to “Structural and interfacial properties of the CO<sub>2</sub>-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study” [Colloids Surf. A 578 (2019) 615](S0927775719305989)(10.1016/j.colsurfa.2019.123615)}, volume={586}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85076519435&partnerID=MN8TOARS}, DOI={10.1016/j.colsurfa.2019.124153}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, author={Parra, J.G. and Dominguez, H. and Aray, Y. and Iza, P. and Zarate, X. and Schott, E.}, year={2020} }
 @article{parra_iza_dominguez_schott_zarate_2020, title={Effect of Triton X-100 surfactant on the interfacial activity of ionic surfactants SDS, CTAB and SDBS at the air/water interface: A study using molecular dynamic simulations}, volume={603}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2020.125284}, DOI={10.1016/j.colsurfa.2020.125284}, abstractNote={Molecular dynamics simulations were carried out to investigate the effect of TX-100 surfactant on the interfacial activity of ionic surfactants SDS, CTAB and SDBS at the air/water interface. Here, interfacial properties, molecular orientation of hydrocarbon chains of ionic surfactant and radial distribution functions between hydrophilic headgroups and water molecules at the air/water interface was evaluated by means of MD simulations. Particularly, TX-100 surfactant produces a reduction of the interfacial film thickness obtained using the water layer and increases the hydrophobic film thickness of the systems. In this investigation, we found that TX-100 surfactant present in mixed monolayers and distributed randomly on the water surface can modify the hydrophilic-lipophilic balance of the monolayer increasing the hydrophobic film thickness and reducing the adsorption of ionic surfactants at the air/water interface. Furthermore, the molecular array of these mixed monolayers obtained by the TX-100 surfactant improve the elasticity of the liquid film, which avoid the rupture of foams reducing the liquid drainage velocity of these systems. Finally, the results suggest that hydrophobic film thickness of the mixed monolayers produce by the TX-100 surfactant can reduce the diffusion of gas molecules from air phase toward the water phase, which increase the stability of foams.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Parra, José G. and Iza, Peter and Dominguez, Hector and Schott, Eduardo and Zarate, Ximena}, year={2020}, month={Oct}, pages={125284} }
 @article{aray_parra_paredes_álvarez_diaz-barrios_2020, title={Exploring the nature of the interactions between the molecules of the sodium dodecyl sulfate and water in crystal phases and in the water/vacuum interface}, volume={6}, ISSN={2405-8440}, url={http://dx.doi.org/10.1016/j.heliyon.2020.e04199}, DOI={10.1016/j.heliyon.2020.e04199}, abstractNote={The nature of the interaction between the molecules of the sodium dodecyl sulfate surfactant forming two crystal phases, one anhydrous, NaC12H25O4S and the other, NaC12H25O4S.H2O, hydrated with one water molecule for unit cell, has been studied in detail using the quantum theory of atoms in molecules and a localized electron detector function. It was found that for the anhydrous crystal, the head groups of the surfactant molecules are linked into a head-to-head pattern, by a bond path network of Na-O ionic bonds, where each Na+ atom is attached to four SO4- groups. For the hydrated crystal, in addition to these four bonds for Na+, two additional ones appear with the oxygen atoms of the water molecules, forming a bond paths network of ionic Na-O bonds, that link the Na+ atoms with the S O4- groups and the H2O molecules. Each H2O molecule is bonded to two SO4- groups via hydrogen bonds, while the SO4- groups are linked to a maximum of four Na+ atoms. The phenomenon of aggregation of the sodium dodecyl sulfate molecules at the liquid water/vacuum interface was studied using NVT molecular dynamics simulations. We have found that for surfactant aggregates, the Na+ ions are linked to a maximum of three SO4- groups and three water molecules that form Na-O bonds. Unlike hydrated crystal, each of the O atoms that make these Na-O bonds is linked to only one Na+ ion. Despite these differences, like the crystal phases, the surfactant molecules tend to form a head-to-head network pattern of ionic Na-O bonds that link their heads. The present results indicate that the clustering of anionic surfactant at the water/vacuum interface is a consequence of the electrostatic alignment of the cationic and anionic groups as occurs in the crystalline phases of sodium dodecyl sulfate.}, number={6}, journal={Heliyon}, publisher={Elsevier BV}, author={Aray, Yosslen and Parra, José G. and Paredes, Ricardo and Álvarez, Luis Javier and Diaz-Barrios, Antonio}, year={2020}, month={Jun}, pages={e04199} }
 @misc{parra_2020, title={Final configuration of surfactants in mixed monolayer in "Effect of Triton X-100 surfactant on the interfacial activity of ionic surfactants SDS, CTAB and SDBS at the air/water interface: A study using molecular dynamic simulations"}, url={https://data.mendeley.com/datasets/m66dsvpnp7/1}, DOI={10.17632/m66dsvpnp7.1}, publisher={Mendeley}, author={Parra, José G.}, year={2020}, month={Dec} }
 @inproceedings{parra_iza_dominguez_2020, title={Molecular packing of SDS surfactant at the air/water interface by means of MD simulations. An estimation of the area per molecule occupied by the SDS surfactant}, booktitle={LatinXchem}, author={Parra, Jose and Iza, Peter and Dominguez, Hector}, year={2020} }
 @misc{parra_2020, title={Reparametrization of vdW parameters between Water and CO2 force fields using solvation free energy in “Structural and interfacial properties of the CO2-in-water foams prepared with Sodium Dodecyl Sulfate (SDS): A Molecular Dynamics Simulation study”}, url={https://data.mendeley.com/datasets/78fvhhscy8/1}, DOI={10.17632/78fvhhscy8.1}, publisher={Mendeley}, author={Parra, José G.}, year={2020}, month={Nov} }
 @article{parra_aray_iza_zarate_schott_2019, title={Behavior of the SDS/1-butanol and SDS/2-butanol mixtures at the water/n-octane interface through molecular dynamics simulations}, volume={523}, url={https://doi.org/10.1016/j.chemphys.2019.04.021}, DOI={10.1016/j.chemphys.2019.04.021}, abstractNote={Interfacial properties of water/SDS+1-butanol/n-octane and water/SDS+2-butanol/n-octane systems have been determined using MD simulations with the aim of studying the molecular interactions between alcohols and SDS when are located at the water/n-octane interface. Also, interfacial properties of water/1-butanol/n-octane, water/2-butanol/n-octane and water/SDS/n-octane systems were determined to validate the used force fields. The relations of SDS/alcohol equal to 16:25, 4:5, 1:1 and 6:5 were used. The g(r)s were evaluated to determine effective interaction between the SDS and alcohol molecules at the interface. The g(r)s demonstrate that –OSO3− group present an effective interaction with the hydroxyl group of the alcohols. This indicate that hydroxyl groups can be located in the gap that exist between the –OSO3− groups of the SDS molecules. Therefore, interfacial activity of the SDS/alcohol monolayer is better, favoring the stability of the protective film and the reduction of the interfacial tension. This help to the formation and stability of the microemulsion.}, journal={Chemical Physics}, publisher={Elsevier BV}, author={Parra, José G. and Aray, Yosslen R. and Iza, Peter and Zarate, Ximena and Schott, Eduardo}, year={2019}, month={Jul}, pages={138–149} }
 @article{parra_aray_rodríguez_perozo_2019, title={Distribución del 1-butanol y 2-butanol en los sistemas agua/n-octano y agua/Dodecil ´Sulfato de Sodio (SDS)/n-octano usando dinámica molecular. Parte II. Uso de las herramientas gmx-density y gmx-densmap}, volume={11}, ISSN={1390-5384}, url={http://dx.doi.org/10.18272/aci.v11i2.1289}, DOI={10.18272/aci.v11i2.1289}, abstractNote={En este trabajo, la distribución de las moléculas de 1-butanol y 2-butanol en los sistemas agua/n-octano y agua/SDS/n-octano fue determinada usando las herramientas gmx-density y gmx-densmap del programa gromacs con la finalidad de complementar a nivel computacional el comportamiento experimental estos co-surfactantes cuando están localizados en la región interfacial de estos sistemas. Los modelos de energía potencial GROMOS53A6 y SPC fueron utilizados para describir a las moléculas de 1-butanol, 2-butanol, SDS y agua, respectivamente. Estos modelos fueron capaces de predecir las propiedades interfaciales del sistema agua/n-octano y el área por molécula del Dodecil Sulfato de Sodio en la interfaz agua/n-octano de forma consistente. Finalmente, los perfiles y mapas de densidad demuestran que las moléculas de alcohol y SDS coexisten en la región interfacial del sistema agua/n-octano favoreciendo la estabilidad de la monocapa de surfactante y la película interfacial. viewed = 671 times}, number={2}, journal={ACI Avances en Ciencias e Ingenierías}, publisher={Universidad San Francisco De Quito}, author={Parra, José Gregorio and Aray, Yosslen R. and Rodríguez, Geraldine and Perozo, Elizabeth}, year={2019}, month={Jun} }
 @article{parra_domínguez_aray_iza_zarate_schott_2019, title={Structural and interfacial properties of the CO2-in-water foams prepared with sodium dodecyl sulfate (SDS): A molecular dynamics simulation study}, volume={578}, ISSN={0927-7757}, url={http://dx.doi.org/10.1016/j.colsurfa.2019.123615}, DOI={10.1016/j.colsurfa.2019.123615}, abstractNote={Structural characteristics, interfacial distribution and molecular interactions of the components of the CO2(gas)/SDS/water/SDS/CO2(gas) systems as a function of the CO2(gas)/water interface coverage by the SDS surfactant to different amounts of the CO2 were studied with molecular dynamics simulations and the NVT ensemble. Initially, the repulsive nonbonding parameter between the water oxygen and CO2 oxygen was adjusted to improve the prediction of the solvation free energy, solubility of the CO2 gas in water and the behavior of the CO2(gas)/SDS/water/SDS/CO2(gas) systems at molecular level. Our results show that the stability of the studied foams can be improved incrementing of the vapor/water interface coverage with the SDS surfactant and the amount of CO2 in the system. With the highest interface coverage, the sulfate group has a molecular array more compact at the interface. Furthermore, CO2 gas have a reduction of the diffusion across of the hydrocarbon chains to the water layer with an increment of the number of CO2 molecules in the system, indicating a behavior more hydrophobic of the CO2 gas. The tendencies obtained of the simulations are consistent with the reported experimental results.}, journal={Colloids and Surfaces A: Physicochemical and Engineering Aspects}, publisher={Elsevier BV}, author={Parra, José G. and Domínguez, Héctor and Aray, Yosslen and Iza, Peter and Zarate, Ximena and Schott, Eduardo}, year={2019}, month={Oct}, pages={123615} }
 @inproceedings{parra_2017, title={Affinity of asphaltene models of Venezuelan crude oils to water/oil interfaces. A molecular dynamics study}, booktitle={4th International Conference on Materials Science, ICMS 2017}, author={Parra, J.G.}, year={2017}, month={Oct} }
 @article{díaz_parra_coll_2017, title={Computational study of one-step polar Diels–Alder reactions using the NEB method for the minimum energy paths search}, volume={43}, ISSN={0892-7022 1029-0435}, url={http://dx.doi.org/10.1080/08927022.2017.1287910}, DOI={10.1080/08927022.2017.1287910}, abstractNote={Abstract The Nudged Elastic Band (NEB) method is an algorithm to search the minimum energy path (MEP), which has been successfully applied for studying several processes that involve solid-state models; however, it has not been widely tested in discrete molecular systems. Performing density functional theory calculations, this method was employed in NWChem to find the MEP of reactions between cyclopentadiene and cyano-substituted ethylenes. Results suggest that the reaction mechanism is concerted in all systems. Also, kinetics and thermodynamics analysis were done: With respect to experimental data, energetic parameters are computed better at the M06-2X/6-31++G** level; entropy and frequency factors were poorly predicted. This is a simple methodology, where the NEB method is evaluated to find the MEP in some prototypical Diels–Alder reactions.}, number={8}, journal={Molecular Simulation}, publisher={Informa UK Limited}, author={Díaz, Miguel A. and Parra, José G. and Coll, David S.}, year={2017}, month={Feb}, pages={644–655} }
 @article{aray_parra_jiménez_paredes_martiz_samaniego_cornejo_ludena_paredes_2017, title={Exploring the effect of the O-(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation}, volume={17}, ISSN={1472-7978 1875-8983}, url={http://dx.doi.org/10.3233/JCM-160659}, DOI={10.3233/JCM-160659}, abstractNote={Using molecular dynamics simulations a systematic study of the binding energy per cross sectional area for the 21 water/n-alkane (hexane, octane, decane, dodecane and tetradecane) interfaces was performed. The effect of the Sodium p-(122 heptylnonyl) benzene sulfonate surfactant, on the adhesion forces of the water/n-hydrocarbon (decane, undecane, dodecane, and 23 tetradecane) interfaces was studied. Scanning of the binding energy per area against n-alkanes shows that the magnitude of this 24 parameter for the surfactant tail-alkane interactions at the interface systematically increases with the chain length of the alkane, 25 whereas it shows a maximum at undecane for the water-surfactant head interactions at the interface. This maximum of head 26 adhesion forces thus agrees with the reported minimum value of the interfacial tension at undecane for the p-(1-heptylnonyl) 27 benzene sulfonate, suggests that for the water/alkane interface it is this trend in surfactant head adhesion at the interface that 28 defines that interfacial tension minimum value. 29}, number={1}, journal={Journal of Computational Methods in Sciences and Engineering}, publisher={IOS Press}, author={Aray, Yosslen and Parra, José Gregorio and Jiménez, Doris Marianela and Paredes, Ricardo and Martiz, Alejandro and Samaniego, Samantha and Cornejo, Mauricio and Ludena, Eduardo V. and Paredes, Cecilia}, editor={Ruette, Fernando and Sierralta, Anibal and Sánchez, Morella and Luiggi, NeyEditors}, year={2017}, month={Mar}, pages={39–53} }
 @inproceedings{parra_2017, title={Molecular dynamics simulations to study synergism between SDS/1- butanol and SDS/2-butanol mixtures located at the interfacial region of water/noctane system}, booktitle={4th International Conference on Materials Science, ICMS 2017}, author={Parra, J.G.}, year={2017} }
 @article{comportamiento del sds localizado en la región interfacial del sistema agua/n-octano. un estudio usando dinámica molecular_2016, url={http://dx.doi.org/10.18272/aci.v8i1}, DOI={dx.doi.org/10.18272/aci.v8i1}, journal={Avances en ciencias e ingenierias}, year={2016}, month={Dec} }
 @article{parra_aray_2016, title={Comportamiento del SDS localizado en la región interfacial del sistema agua/n-octano. Un estudio usando dinámica molecular}, url={https://doi.org/10.18272/aci.v8i14.279}, DOI={10.18272/aci.v8i14.279}, abstractNote={En este trabajo, usando dinámica molecular se determinaron las propiedades interfaciales y el comportamiento del Dodecil Sulfato de Sodio (SDS) ubicado en la región interfacial de los sistemas vacío/agua y agua/n-octano. La tensión interfacial fue estimada con el modelo propuesto por Kirkwood y Buff [23]. A su vez, los espesores de película interfacial fueron determinados usando los criterios 10-90 y 90-90. Además, el área por molécula fue estimado con la variación de la presión superficial en función de la concentración del surfactante. En los sistemas vacío/SDS/agua, el área por molécula del SDS fue obtenida con dos procedimientos diferentes. Los valores fueron 53.3 Ã…2 y 54.3 Ã…2, respectivamente. Para los sistemas agua/n-octano y agua/SDS/n-octano, los espesores de película interfacial aumentan en función del número de moléculas de surfactantes presentes en la región interfacial. Los resultados obtenidos son consistentes con datos medidos por experimentación.}, journal={ACI Avances en Ciencias e Ingenierías}, author={Parra, José Gregorio and Aray, Yosslen R.}, year={2016}, month={Jul} }
 @article{parra_aray_2016, title={Comportamiento del SDS localizado en la región interfacial del sistema agua/n-octano. Un estudio usando dinámica molecular}, volume={8}, ISSN={2528-7788 1390-5384}, url={http://dx.doi.org/10.18272/aci.v8i1.279}, DOI={10.18272/aci.v8i1.279}, abstractNote={En este trabajo, usando dinámica molecular se determinaron las propiedades interfaciales y el comportamiento del Dodecil Sulfato de Sodio (SDS) ubicado en la región interfacial de los sistemas vacío/agua y agua/n-octano. La tensión interfacial fue estimada con el modelo propuesto por Kirkwood y Buff [23]. A su vez, los espesores de película interfacial fueron determinados usando los criterios 10-90 y 90-90. Además, el área por molécula fue estimado con la variación de la presión superficial en función de la concentración del surfactante. En los sistemas vacío/SDS/agua, el área por molécula del SDS fue obtenida con dos procedimientos diferentes. Los valores fueron 53.3 Å2 y 54.3 Å2, respectivamente. Para los sistemas agua/n-octano y agua/SDS/n-octano, los espesores de película interfacial aumentan en función del número de moléculas de surfactantes presentes en la región interfacial. Los resultados obtenidos son consistentes con datos medidos por experimentación.}, number={14}, journal={Avances en Ciencias e Ingeniería}, publisher={Universidad San Francisco De Quito}, author={Parra, José Gregorio and Aray, Yosslen R.}, year={2016}, month={Dec} }
 @article{exploring the effect of the o-(1-heptylnonyl) benzene sulfonate surfactant on the nature of the linear hydrocarbons/water interface by means of an atomistic molecular dynamics simulation_2016, volume={17}, url={http://content.iospress.com/articles/journal-of-computational-methods-in-sciences-and-engineering/jcm659}, DOI={DOI: 10.3233/JCM-160659}, number={1}, journal={Journal of Computational Methods in Sciences and Engineering}, year={2016}, month={Dec}, pages={39–53,} }
 @inproceedings{parra_rodriguez_2015, title={Behavior of certain asphaltene models in different organic solvents by computational techniques}, booktitle={IV Venezuelan Congress of Science, Technology and Innovation within the framework of the LOCTI and PEII}, author={Parra, J.G. and Rodriguez, G.}, year={2015}, month={Dec} }
 @inproceedings{parra_aray_2015, title={Determination of the lateral diffusion of asphaltene models in water/n-heptane and water/toluene by molecular dynamics}, booktitle={IV Venezuelan Congress of Science, Technology and Innovation within the framework of the LOCTI and PEII}, author={Parra, J.G. and Aray, Y.R.}, year={2015}, month={Dec} }
 @article{parra_aray_alcala_rodriguez_2014, title={Effect of sodium dodecyl sulfate (SDS) on interfacial film thickness and molecular orientation of water in water/1-pentanol and water/1-hexanol systems}, volume={9}, number={1}, journal={Faraute de Ciencias y Tecnolog ıa}, author={Parra, J.G. and Aray, Y.R. and Alcala, J.A. and Rodriguez, G.}, year={2014}, pages={5–11} }
 @article{explorando el comportamiento de los alcoholes 1-butanol y 2-butanol ubicados en la región interfacial de los sistemas n-hexano/agua, ciclohexano/agua y tolueno/agua mediante dinámica molecular_2014, url={http://www.redalyc.org/articulo.oa?id=93333720001}, journal={Avances en Química}, year={2014} }
 @article{parra_aray_2014, title={Exploring the behavior of 1-butanol and 2-butanol alcohols located in the interfacial region of the n-hexane/water, cyclohexane/water and toluene/water systems through molecular dynamics,Explorando el comportamiento de los alcoholes 1-butanol y 2-butanol ubicados en la región interfacial de los sistemas n-hexano/agua, ciclohexano/agua y tolueno/agua mediante dinámica molecular}, volume={9}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85018779217&partnerID=MN8TOARS}, number={3}, journal={Avances en Quimica}, author={Parra, J.G. and Aray, Y.R.}, year={2014}, pages={87–96} }
 @inproceedings{parra_aray_2014, title={Exploring the interfacial properties of the n-octane/SDS/ water/SDS/n-octane system by molecular dynamics}, booktitle={III Venezuelan Congress of Science, Technology and Innovation within the framework of LOCTI and PEII}, author={Parra, J.G. and Aray, Y.}, year={2014}, month={Nov} }
 @inproceedings{parra_rodriguez_cazar_torres_2014, title={Molecular interactions between amino-g and water using continuous solvation and molecular dynamics methods}, booktitle={Fifth congress of Theoretical and Computational Physicochemistry}, author={Parra, J.G. and Rodriguez, G. and Cazar, D. and Torres, J.}, year={2014} }
 @inproceedings{parra_2013, title={Molecular dynamics simulation of C12E2 and C12 E5 surfactants located at the vacuum/water interface}, booktitle={II Venezuelan Congress of Science, Technology and Innovation within the framework of the LOCTI and PEII}, author={Parra, J.G.}, year={2013}, month={Nov} }
 @inproceedings{parra_aray_2013, title={Molecular dynamics simulation of sodium dodecyl sulfate surfactant located at the vacuum/water interface}, booktitle={VIII National Congress and 2nd. International Research Congress of the University of Carabobo}, author={Parra, J.G. and Aray, Y.}, year={2013}, month={Nov} }
 @inproceedings{parra_aray_2012, title={Simulation of the n-hexane/1-butanol/water system using molecular dynamics}, booktitle={IV Congress of Theoretical and Computational Physicochemistry.}, author={Parra, J.G. and Aray, Y.}, year={2012}, month={Nov} }
 @article{aray_hernández-bravo_parra_rodríguez_coll_2011, title={Exploring the Structure–Solubility Relationship of Asphaltene Models in Toluene, Heptane, and Amphiphiles Using a Molecular Dynamic Atomistic Methodology}, volume={115}, ISSN={1089-5639 1520-5215}, url={http://dx.doi.org/10.1021/jp204319n}, DOI={10.1021/jp204319n}, abstractNote={The solubility parameters, δ, of several asphaltene models were calculated by mean of an atomistic NPT ensemble. Continental and archipelago models were explored. A relationship between the solubility parameter and the molecule structure was determined. In general, increase of the fused-rings number forming the aromatic core and the numbers of heteroatoms such as oxygen, nitrogen, and sulfur produces an increase of the solubility parameter, while increases of the numbers and length of the aliphatic chains yield a systematic decrease of this parameter. Molecules with large total carbon atom number at the tails, n(c), and small aromatic ring number, n(r), exhibit the biggest values of δ, while molecules with small n(c) and large n(r) show the smallest δ values. A good polynomial correlation δ = 5.967(n(r)/n(c)) - 3.062(n(r)/n(c))(2) + 0.507(n(r)/n(c))(3) + 16.593 with R(2) = 0.965 was found. The solubilities of the asphaltene models in toluene, heptane, and amphiphiles were studied using the Scatchard-Hildebrand and the Hansen sphere methodologies. Generally, there is a large affinity between the archipelago model and amphiphiles containing large aliphatic tails and no aromatic rings, while continental models show high affinity for amphiphiles containing an aromatic ring and small aliphatic chains.}, number={42}, journal={The Journal of Physical Chemistry A}, publisher={American Chemical Society (ACS)}, author={Aray, Yosslen and Hernández-Bravo, Raiza and Parra, José G. and Rodríguez, Jesús and Coll, David S.}, year={2011}, month={Sep}, pages={11495–11507} }
 @article{predicción del volumen molar y la entalpía molar de vaporización de moléculas orgánicas usando variables determinadas mediante el modelo de apantallamiento tipo conductor (cosmo)_2011, url={http://www.redalyc.org/articulo.oa?id=93321324004}, journal={Avances en Química}, year={2011} }
 @article{parra_aray_2011, title={Prediction of Molar Volume and Molar Enthalpy of Vaporization of organic molecules using variables determined by the COSMO model}, volume={6}, number={3}, journal={Avances en Quımica}, author={Parra, J.G. and Aray, Y.R.}, year={2011}, pages={79–88} }
 @article{parra_aray_2011, title={Relationship between the cohesive energy density of hydrocarbons, linear alcohols and aromatic compounds with the nonbonding free energy density estimated by solvation methods}, volume={6}, number={2}, journal={Faraute de Ciencias y Tecnologıa}, author={Parra, J.G. and Aray, Y.R.}, year={2011}, pages={12–21} }
 @article{parra_guaregua_aray_2010, title={Estimation of the Solubility Parameter of models of fractions A1 and A2 of asphaltenes through molecular dynamics}, volume={5}, number={1}, journal={Faraute de Ciencias y Tecnolog ıa}, author={Parra, J.G. and Guaregua, J. and Aray, Y.R.}, year={2010}, pages={68–76} }
 @inproceedings{parra_2010, title={Relationship between the solubility parameter and the non-bonding free energy density of some solvents estimated using the C-PCM solvation method}, booktitle={VII National Congress and 1st. International Research Congress of the University of Carabobo}, author={Parra, J.G.}, year={2010} }
 @inproceedings{parra_2009, title={A1 and A2 of asphaltenes through molecular dynamics}, booktitle={IX Venezuelan Congress of Chemistry and I International Congress of the Venezuelan Society of Chemistry (SVQ)}, author={Parra, J.G.}, year={2009} }
 @inproceedings{parra_roldan_2009, title={Study of the solubility of models of fractions
A1 and A2 of asphaltenes through molecular dynamics}, booktitle={IX Venezuelan Congress of Chemistry and I International Congress of the Venezuelan Society of Chemistry (SVQ)}, author={Parra, Jos´e G. and Roldan, Angelesmary}, year={2009} }
 @inproceedings{parra_galvis_2008, title={Estimation of the interaction energies of asphaltene fractions models on dolomite (001) and magnesite (100) surfaces by molecular dynamics}, booktitle={VI Research Congress of the University of Carabobo}, author={Parra, J.G. and Galvis, G.}, year={2008}, month={Oct} }
 @inproceedings{parra_guaregua_2005, title={Correlation between the molecular structure of surfactants and their lipophilic-hydrophilic character (HLB)}, booktitle={VII Venezuelan Congress of Chemistry of the Venezuelan Chemistry Society}, author={Parra, J.G. and Guaregua, J.}, year={2005} }