Simultaneous description of bulk and interfacial properties of fluids by the Mie potential

The vapor-liquid equilibrium (VLE) of the Mie potential, where the dispersive exponent is constant (m = 6) while the repulsive exponent n is varied between 9 and 48, is systematically investigated by molecular simulation. For systems with planar vapor-liquid interfaces, long-range correction expressions are derived, so that interfacial and bulk properties can be computed accurately. The present simulation results are found to be consistent with the available body of literature on the Mie fluid which is substantially extended. On the basis of correlations for the considered thermodynamic properties, a multicriteria optimization becomes viable. Thereby, users can adjust the three parameters of the Mie potential to the properties of real fluids, weighting different thermodynamic properties according to their importance for a particular application scenario. In the present work, this is demonstrated for carbon dioxide for which different competing objective functions are studied which describe the accuracy of the model for representing the saturated liquid density, the vapor pressure and the surface tension. It is shown that models can be found which describe simultaneously the saturated liquid density and vapor pressure with good accuracy, and it is discussed to what extent this accuracy can be upheld as the model accuracy for the surface tension is further improved

MolMod – an open access database of force fields for molecular simulations of fluids

The MolMod database is presented, which is openly accessible at http://molmod.boltzmann-zuse.de and contains intermolecular force fields for over 150 pure fluids at present. It was developed and is maintained by the Boltzmann-Zuse Society for Computational Molecular Engineering (BZS). The set of molecular models in the MolMod database provides a coherent framework for molecular simulations of fluids. The molecular models in the MolMod database consist of Lennard-Jones interaction sites, point charges, and point dipoles and quadrupoles, which can be equivalently represented by multiple point charges. The force fields can be exported as input files for the simulation programmes ms2 and ls1 mardyn, GROMACS, and LAMMPS. To characterise the semantics associated with the numerical database content, a force field nomenclature is introduced that can also be used in other contexts in materials modelling at the atomistic and mesoscopic levels. The models of the pure substances that are included in the database were generally optimised such as to yield good representations of experimental data of the vapour–liquid equilibrium with a focus on the vapour pressure and the saturated liquid density. In many cases, the models also yield good predictions of caloric, transport, and interfacial properties of the pure fluids. For all models, references to the original works in which they were developed are provided. The models can be used straightforwardly for predictions of properties of fluid mixtures using established combination rules. Input errors are a major source of errors in simulations. The MolMod database contributes to reducing such errors.BMBF, 01IH16008E, Verbundprojekt: TaLPas - Task-basierte Lastverteilung und Auto-Tuning in der PartikelsimulationEC/H2020/694807/EU/Enrichment of Components at Interfaces and Mass Transfer in Fluid Separation Technologies/ENRICOEC/H2020/760907/EU/Virtual Materials Market Place (VIMMP)/VIMM

An AI-driven design method as basis for teaming

The product development process could benefit from a synergistic human-machine teaming, potentially shortening product development cycles and improving product performance and sustainability. However, there is a lack of available methods to achieve this goal. A technical product has to satisfy numerous requirements. Due to the variety and complexity of these requirements, the design process is challenging for human engineers. While engineers are supported by various tools (e.g. FEM) for analyzing product properties, tools for computer-aided synthesis of product properties considering the corresponding requirements are still only available in exceptional cases. However, such synthesis capabilities are necessary to qualify a computer-aided tool for productive teaming with engineers. Special methods based on artificial intelligence show a high potential for general computer-aided synthesis methods. This contribution presents an innovative approach in this direction based on topology optimization techniques

Étude de l'implication de l'acide lysophosphatidique par la production de vésicules extracellulaires vasculaires dans les dommages associés aux maladies rhumatismales auto-immunes systémiques

L'acide lysophosphatidique (LPA) est un lipide bioactif qui est formé dans le sang par l'autotaxine. Le LPA est un médiateur important du système vasculaire, notamment par sa modulation de l'immunité et de l'inflammation. Plusieurs espèces moléculaires de LPA existent en fonction de leur acide gras. Les espèces moléculaires de LPA ont des affinités différentes pour les récepteurs aux LPA. Il en résulte que les espèces moléculaires de LPA peuvent avoir des effets différents, même si elles ciblent une même cellule. Parmi ses nombreux effets, le LPA induit l'activation des plaquettes et est le seul activateur endogène connu des globules rouges (GR). L'activation des plaquettes et des GR induit la libération de vésicules extracellulaires (EV). Les EV de plaquettes (PEV) et les EV de GR (REV) ont des effets pro-inflammatoires et sont des acteurs importants de la coagulation. Le LPA est connu pour promouvoir la pathophysiologie de la polyarthrite rhumatoïde (PAR), une maladie rhumatismale auto-immune systémique (MRAS). Les patients touchés par les MRAS comme la PAR ou le lupus érythémateux disséminé (LED) présentent une inflammation vasculaire importante et sont plus à même de développer des maladies cardiovasculaires comme l'athérosclérose. Les maladies cardiovasculaires sont la première cause de mortalité chez ces patients. Le LPA et les EV promeuvent tous deux l'inflammation vasculaire et le développement de maladies cardiovasculaires. Ils sont également impliqués dans la coagulation. L'hypothèse à l'origine des travaux de cette thèse est que le LPA via l'activation des GR peut promouvoir l'inflammation vasculaire et participer aux dommages vasculaires associés aux MRAS comme l'athérosclérose et la thrombose. Dans cette thèse, nous avons d'abord étudié l'action des principales espèces moléculaires de LPA trouvées dans le plasma sur les GR. Par des approches de cytométrie en flux à haute sensibilité, nous avons montré que certaines espèces moléculaires de LPA induisent l'exposition de la phosphatidylsérine (PS) par les GR et la libération de REV PS⁻ et PS⁺ similaire à celles trouvées dans le plasma de patients LED. Cependant, d'autres espèces moléculaires de LPA inhibent l'activation des GR. J'ai établi les principales voies de signalisation impliquées dans l'activation et l'inhibition des GR. De plus, nous avons mis en évidence que, même si elle est possible dans le plasma, l'activation des GR par le LPA dépend de son environnement. Notre deuxième focus était centré les potentielles associations entre l'autotaxine et les EV avec le risque de thrombose et le développement de l'athérosclérose chez des patients LED. Nous avons montré que l'autotaxine n'était pas augmentée ni associée avec l'activité de la maladie chez les patients LED. Et bien que les patients LED présentaient des quantités très importantes de PEV et de REV, elles n'étaient pas associées avec l'activité de la maladie. Cependant, les quantités de REV PS⁺ sont associées avec un risque plus élevé de thrombose chez les patients SLE. De plus, le groupe de patients avec des quantités élevées de REV PS⁺ présentait également des concentration d'autotaxine plasmatique plus élevées. Le travail présenté dans cette thèse approfondit la compréhension de l'effet du LPA sur l'activation des GR et leur libération de REV. Il met également en évidence l'implication potentielle du LPA et des REV dans les thromboses associées aux patients MRAS.The lysophosphatidic acid (LPA) is a bioactive lipid which is formed by autotaxin in blood. LPA is an important mediator in the vascular system mainly through its modulation of immunity and inflammation. Several LPA species exist depending on the fatty acid. LPA species varies in their affinity for the LPA receptors, which means that LPA species may have different effects, even if they target a same cell. Among its numerous biological actions, LPA induces platelet activation and is the only known endogenous activator of red blood cells (RBCs). Both platelet and RBC activation lead to the liberation of extracellular vesicles (EVs). Platelet EVs (PEVs) and RBC EVs (REVs) are the two main populations of EVs found in blood. Both PEVs and REVs have been described as pro-inflammatory mediators and are important actors of the coagulation. LPA is a known promoter of the pathophysiology of rheumatoid arthritis (RA), a systemic autoimmune rheumatic disease (SARD). Patients affected by SARDs such as RA and systemic lupus erythematosus (SLE) present high vascular inflammation and are more prone to develop cardiovascular diseases for instance atherosclerosis. Cardiovascular diseases are the first cause of mortality for these patients. LPA and EVs are two mediators which promotes vascular inflammation and the development of cardiovascular diseases. Also, both are pro-coagulant factors. The hypothesis driving this thesis is that LPA through the activation of RBCs promotes vascular inflammation and participate to the vascular damages associated with MRAS patients such as atherosclerosis and thrombosis. In this thesis, we first focused our interest to study the action of major blood LPA species on RBCs. Through high sensitivity flow cytometry, we found that some LPA species induces the exposition of phosphatidylserine (PS) by RBCs and the liberation of PS⁻ and PS⁺ REVs similar to those found in the plasma of LED patients. However, other species were inhibitors of RBC activation. We have established the main LPA's signaling pathways involved in the activation and inhibition as well that even if it is possible in the plasma, RBC activation by LPA is affected by the environment. Our second focus was on the potential associations of autotaxin and EVs with thrombotic risk and the development of atherosclerosis in SLE patients. We found that autotaxin were not elevated in SLE patients nor associated with the disease activity. Even though, SLE patients presented high quantities of PEVs and REVs, they were not associated with the disease activity. However, we showed that the quantities of PS⁺ REVs were associated with a higher risk of thrombosis in SLE patients. Moreover, the group of patients with high quantities of PS⁺ REVs also presented higher quantities of plasmatic autotaxin. The work presented in this thesis brings a better understanding of LPA impact on RBC activation and REV liberation. It also highlights the potential implication of both LPA and REVs in thrombosis associated with SARD patients

Mass Transfer through Vapor-Liquid Interfaces Studied by Non-Stationary Molecular Dynamics Simulations

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The Cost of Prediction

This paper examines a looming reproducibility crisis in the core of the hard sciences. Namely, it concentrates on molecular modeling and simulation (MMS), a family of methods that predict properties of substances through computing interactions on a molecular level and that is widely popular in physics, chemistry, materials science, and engineering. The paper argues that in order to make quantitative predictions, sophisticated models are needed which have to be evaluated with complex simulation procedures that amalgamate theoretical, technological, and social factors – leading to problems with reproducibility. Thus, for methodological reasons, the predictive success causes a reproducibility problem