Jouer avec les dieux (notes sur la matière mythologique chez Vélasquez)

International audienceDans les tableaux mythologiques de Vélasquez, il est souvent mis l'accent sur une dimension burlesque qui ne rend peut-être pas tout à fait compte de la complexité et des nuances du dispositif mis en place par le peintre ; c'est ainsi que des œuvres comme " Le triomphe de Bacchus " ou " Mars ", trop souvent ramenées à une simple moquerie, révèlent des lignes de sens moins immédiates

Le nain, le bouffon, l'artiste : le pouvoir d'en bas dans la peinture de Vélasquez

International audienceLes nains et les bouffons occupent une place particulière dans l'œuvre de Vélasquez ; en leur rendant humanité et dignité, le peintre suscite à leur égard un regard qui diverge de celui que la société du XVIIème siècle portait globalement sur eux. Dans la perspective de cette mise en valeur de figures du bas, socialement méprisées, ils présentent plus d'un point commun avec celle de l'artiste lui-mêm

Les espaces utopiques de la peinture de Salvador Dalí

International audienceLa nature des espaces construits dans les tableaux de Salvador Dalí, que ceux-ci s'élaborent dans la perspective surréaliste (période principalement évoquée dans cet article), ou dans celle de la "mystique nucléaire" ultérieure, invite à s'interroger sur le degré d'existence ou de non-existence de ces espaces pour celui qui en est le spectateur et, par là même, sur la capacité de ce dernier à les habiter ou non de son regard

A propos des yeux et du corps dans quelques tableaux de Vélasquez

Les yeux occupent une place privilégiée dans les tableaux de Vélasquez, car ils disent plus que la simple attestation présente d'une existence passée ; ils proposent une singulière articulation de l'être et des apparences qui l'entourent, et finissent par suggérer tout un rapport de l'homme aux mondes matériel et spirituel, un rapport si profond qu'il dépasse le cadre strict de l'époque baroque

Extension of the Test-Area methodology for calculating solid-fluid interfacial tensions in cylindrical geometry

We extend the well-known Test-Area methodology of Gloor et al. [J. Chem. Phys. 123, 134703 (2005)], originally proposed to evaluate the surface tension of planar fluid-fluid interfaces along a computer simulation in the canonical ensemble, to deal with the solid-fluid interfacial tension of systems adsorbed on cylindrical pores. The common method used to evaluate the solid-fluid interfacial tension invokes the mechanical relation in terms of the tangential and normal components of the pressure tensor relative to the interface. Unfortunately, this procedure is difficult to implement in the case of cylindrical geometry, and particularly complex in case of nonspherical molecules. Following the original work of Gloor et al., we perform free-energy perturbations due to virtual changes in the solid-fluid surface. In this particular case, the radius and length of the cylindrical pore are varied to ensure constant-volume virtual changes of the solid-fluid surface area along the simulation. We apply the modified methodology for determining the interfacial tension of a system of spherical Lennard-Jones molecules adsorbed inside cylindrical pores that interact with fluid molecules through the generalized 10-4-3 Steele potential recently proposed by Siderius and Gelb [J. Chem. Phys. 135, 084703 (2011)]. We analyze the effect of pore diameter, density of adsorbed molecules, and fluid-fluid cutoff distance of the Lennard-Jones intermolecular potential on the solid-fluid interfacial tension. This extension, as the original Test-Area formulation, offers clear advantages over the classical mechanical route of computational efficiency, easy of implementation, and generality.The authors would like to acknowledge helpful discussions with A. I. Moreno-Ventas Bravo, M. M. Piñeiro, and J. M. Míguez. This work was supported by Acción Integrada España-Francia from Ministerio de Ciencia e In- novación and Picasso Project (Project Nos. FR2009-0056 and PHC PICASSO2010). Further financial support from Proyecto de Excelencia from Junta de Andalucía (Project No. P07-FQM02884), Ministerio de Ciencia e Innovación (Project No. FIS2010-14866), and Universidad de Huelva are also acknowledged

BAX: A dedicated X-Rays galaxy clusters Database

We present BAX, Base de Donn\'ees amas de galaxies X (http://webast.ast.obs-mip.fr/bax), a project aiming at building a comprehensive database dedicated to X-rays clusters of galaxies allowing detailed information retrieval. BAX provides the user with {\it basic data} published in the literature on X-rays clusters of galaxies as well as with information concerning the physical properties in the X-rays domain or at other wavelengths. BAX allows individual studies on selected clusters as well as building up homogenous samples, from known X-rays clusters for which selection criteria are chosen through web interfaces. We expect BAX to become a useful tool for astronomy community in order to optimize the cluster science return using data from both ground based facilities like MEGACAM (CFHT), VIRMOS (VLT) and space missions like XMM, Chandra and Planck.Comment: 4 pages, 1 figure. Talk given at COSPAR conference in October 2002. To be published in the COSPAR proceedings (minor change

An accurate density functional theory for the vaporliquid interface of chain molecules based on the statistical associating fluid theory for potentials of variable range for Mie chainlike fluids

A new Helmholtz free energy density functional is presented to predict the vapor-liquid interface of chainlike molecules. The functional is based on the last version of the statistical associating fluid theory for potentials of variable range for homogeneous Mie chainlike fluids (SAFT-VR Mie). Following the standard formalism, the density functional theory (SAFT-VR Mie DFT) is constructed using a perturbative approach in which the free energy density contains a reference term to describe all the short-range interactions treated at the local level, and a perturbative contribution to account for the attractive perturbation which incorporates the long-range dispersive interactions. In this first work, we use a mean-field version of the theory in which the pair correlations are neglected in the attractive term. The SAFT-VR Mie DFT formalism is used to examine the effect of molecular chain length and the repulsive exponent of the intermolecular potential on density profiles and surface tension of linear chains made up to six Mie (lr6) segments with different values of the repulsive exponent of the intermolecular potential. Theoretical predictions from the theory are compared directly with molecular simulation data for density profiles and surface tension of Mie chainlike molecules taken from the literature. Agreement between theory and simulation data is good for short-chain molecules at all thermodynamic conditions of coexistence considered. Once the theory has proven that is able to predict the interfacial properties, and particularly interfacial tension, the SAFT-VR Mie DFT formalism is used to predict the interfacial behavior of two new coarse-grained models for carbon dioxide and water recently proposed in the literature. In particular, the theoretical formalism, in combination with the coarse-grained models for carbon dioxide and water, is able to predict the interfacial properties of these important substances in a reasonable way.The authors thank helpful discussions with Carlos Avendaño andJosé Matías Garrido. We also acknowledge Centro de Supercom-putación de Galicia (CESGA, Santiago de Compostela, Spain) andMCIA (Mésocentre de Calcul Intensif Aquitain) of the Universitésde Bordeaux and Pau et Pays de l’Adour (France), for providingaccess to computing facilities and Ministerio de Economía, In-dustria y Competitividad through Grant with reference FIS2017-89361-C3-1-P co-financed by EU FEDER funds. Further financialsupport from Junta de Andalucía and Universidad de Huelva isalso acknowledged. J.A., J.M.M., and F.J.B. thankfully acknowl-edge the computer resources at Magerit and the technical supportprovided by the Spanish Supercomputing Network (RES) (ProjectQCM-2018-2-0042)

Density functional theory for the description of spherical non-associating monomers in confined media using the SAFT-VR equation of state and weighted density approximations

As a first step of an ongoing study of thermodynamic properties and adsorption of complex fluids in confined media, we present a new theoretical description for spherical monomers using the Statistical Associating Fluid Theory for potential of Variable Range (SAFT-VR) and a Non-Local Density Functional Theory (NLDFT) with Weighted Density Approximations (WDA). The well-known Modified Fundamental Measure Theory is used to describe the inhomogeneous hard-sphere contribution as a reference for the monomer and two WDA approaches are developed for the dispersive terms from the high-temperature Barker and Henderson perturbation expansion. The first approach extends the dispersive contributions using the scalar and vector weighted densities introduced in the Fundamental Measure Theory (FMT) and the second one uses a coarse-grained (CG) approach with a unique weighted density. To test the accuracy of this new NLDFT/SAFT-VR coupling, the two versions of the theoretical model are compared with Grand Canonical Monte Carlo (GCMC) molecular simulations using the same molecular model. Only the version with the “CG” approach for the dispersive terms provides results in excellent agreement with GCMC calculations in a wide range of conditions while the “FMT” extension version gives a good representation solely at low pressures. Hence, the “CG” version of the theoretical model is used to reproduce methane adsorption isotherms in a Carbon Molecular Sieve and compared with experimental data after a characterization of the material. The whole results show an excellent agreement between modeling and experiments. Thus, through a complete and consistent comparison both with molecular simulations and with experimental data, the NLDFT/SAFT-VR theory has been validated for the description of monomers.This work was sponsored by the ERC advanced grant Failflow (27769). This financial support is gratefully acknowledged. This work was supported by Acción Integrada España-Francia from Ministerio de Ciencia e Innovación and Picasso Project (Project Nos. FR2009-0056 and PHC PI- CASSO2010). F.J.B. would like to acknowledge financial support from Ministerio de Ciencia e Innovación (Project No. FIS2010-14866), Junta de Andalucía, and Universidad de Huelva. C. Malheiro would like to acknowledge the ISIFOR Carnot institute for her mobility grant

Effect of dispersive long-range corrections to the pressure tensor: The vapour-liquid interfacial properties of the Lennard-Jones system revisited

We propose an extension of the improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264–6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, rc = 2.5, 3, 4, and 5σ . In addition, we have also considered cutoff distances rc = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long- range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.The authors would like to acknowledge helpful discus- sions with J. M. Míguez, L. G. MacDowell, and M. M. Piñeiro. This work was supported by Ministerio de Ciencia e Innovación (MICINN, Spain) (Grant No. FIS2010-14866) and by Ministerio de Economía y Competitividad (MINECO) (Grant No. FIS2013-46920-C2-1-P). Further financial sup- port from Junta de Andalucía and Universidad de Huelva is also acknowledged

Adsorption and interfacial phenomena of a Lennard-Jones fluid adsorbed in slit pores: DFT and GCMC simulations

Confinement of fluids in porous media leads to the presence of solid–fluid (SF) interfaces that play a key role in many different fields. The experimental characterisation of SF interfacial properties, in par- ticular the surface tension, is challenging or not accessible. In this work, we apply mean-field density functional theory (DFT) to determine the surface tension and also density profile of a Lennard-Jones fluid in slit-shaped pores for realistic amounts of adsorbed molecules. We consider the pore walls to interact with fluid molecules through the well-known 10-4-3 Steele potential. The results are com- pared with those obtained from Monte Carlo simulations in the Grand Canonical Ensemble (GCMC) using the test-area method. We analyse the effect on the adsorption and interfacial phenomena of volume and energy factors, in particular, the pore diameter and the ratio between SF and fluid–fluid dispersive energy parameters, respectively. Results from DFT and GCMC simulations were found to be comparable, which points to their reliability.The authors would like to acknowledge helpful discussions with A. I. Moreno-Ventas Bravo. We also acknowledge Centro de Supercomputación de Galicia (CESGA, Santiago de Compostela, Spain) and MCIA (Mésocentre de Calcul Intensif Aquitain) of the Universités de Bordeaux and Pau et Pays de l’Adour (France), for providing access to computing facilities