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La résection de second look est systématique lors de TVNIM de haut risque car elle diminue significativement le risque de récidive et de progression.

A general method to develop accurate force fields from density functional theory (DFT) computations in periodic systems is here presented. The novelty of the method consists of the inclusion of both potential energy and forces in the same fit, by using an automated procedure to balance the relative weight of the two quantities. A thorough analysis of the method capabilities is carried out by modeling the dispersion interactions of argon adsorbed in ZIF-8. While a pure energy fit leaves the parameters of some atoms kinds underdetermined, a pure forces fit gives well converged results but fails in properly reproducing the potential energy of the system. The optimal solution is found when a small contribution of forces is included in the energy fit: this allows one to fuse together the best features of the two fits, giving converged results and good reproduction of both energy and forces. The force field parameters for various DFT functionals, namely, DFT-D2, DFT-D3, vdW-DF2, and rVV10, are derived, and the corresponding isotherms are compared to experimental values. For the system here investigated, the best agreement with experiments is found for the DFT-D2 functional.

Two major improvements to the state-of-the-art Repeating Electrostatic Potential Extracted Atomic (REPEAT) method, for generating accurate partial charges for molecular simulations of periodic structures, are here developed. The first, D-REPEAT, consists in the simultaneous fit of the electrostatic potential (ESP), together with the total dipole fluctuations (TDF) of the framework. The second, M-REPEAT, allows the fit of multiple ESP configurations at once. When both techniques are fused into one, DM-REPEAT method, the resulting charges become remarkably stable over a large set of fitting regions, giving a robust and physically sound solution to the buried atoms problem. The method capabilities are extensively studied in ZIF-8 framework, and subsequently applied to IRMOF-1 and ITQ-29 crystal structures. To our knowledge, this is the first time that this approach is proposed in the context of periodic systems.

We derive a recurrence equation that relates the effective interactions among the particles adsorbed in two adjacent cages of a microporous material to the local probability distributions of cage occupancies. We show that such a relation can be used to estimate the approximate values of local partition functions, which can in turn be used as input for coarse-grained models of adsorption. After validating this theory by reproducing with good approximation the local partition functions of a lattice gas, we apply this method to the problem of adsorption of methane in all-silica zeolites DAY and ITQ-29 at various temperatures. The adsorption isotherms we obtain from the coarse-grained models built on the basis of the estimated values of the local partition functions are in very good agreement with the adsorption isotherms calculated from atomistic simulations.

An unusual water structure was found using Car–Parrinello Molecular Dynamics simulations of a slightly superhydrated Na–vermiculite clay, containing six water molecules per sodium cation, corresponding to that of recent experiments performed to detect dynamical crossovers in the adsorbed supercooled water. In our simulations we observe that water forms two closed packed hexagonal plane layers parallel to aluminosilicate sheets and linked to their surface oxygens by hydrogen bonds. The presence of these hydrogen bonds and the coordination to Na cations lying midway between the clay layers, lowers the number of water–water hydrogen bonds, thus making the closed-packed structure thermodynamically accessible. Remarkably, we have found that this structure is stable across a wide range of temperatures. At the best of our knowledge, this kind of water structure was never reported before, except for a similar hexatic phase (liquid-like, but with a local hexagonal compact symmetry) resulting from a two-dimensional model of water proposed by Vilanova and Franzese.

The results of Car–Parrinello molecular dynamics simulations of vermiculite clay at the hydration level found in the natural mineral (4 H2O per Na+) are reported. The structure and the vibrational spectrum of the aluminosilicate layer is well reproduced by the simulations. As for the structure of the Na+cations and of water molecules adsorbed in the interlayer, the ones proposed in X-ray diffraction experimental papers are not in full agreement with the results of neutron diffraction experiments found in literature, yielding only the density profile perpendicular to the aluminosilicate layers, but including hydrogens. Our calculations result in a structure of the interlayer content, which is in agreement with the neutron-diffraction density profile, and yet compatible with X-ray diffraction data. Some features of the adsorbed water resulting from the simulation are an example of incomplete cation hydration and can be of general interest.

A new force field for fast molecular dynamics simulations in flexible aluminosilicates is presented. Starting from a force field previously developed in our laboratory, an adaptation to CHARMM functional form and a subsequent optimization are performed. The obtained force field is validated checking its ability to correctly reproduce the crystallographic structures and the vibrational properties for silicalite and zeolites Na A, Ca A, Na Y, and Na X. This new force field allows the execution of large-scale simulations in a parallel environment via the most common packages available.

A computational study of argon in zeolite imidazolate framework-8 at various temperatures viagrand-canonical Monte Carlo (GCMC) simulations, aimed to the production of the data necessary to coarse-grain the adsorption properties of the system, is presented. Occupancy distributions and adsorption isotherms are combined to derive a thermodynamic model based on a single open ZIF-8 cage. The particular kind of confinement exerted by the ZIF-8 framework to the guest species allows a strict locality approximationto be assumed, such that for low-intermediate loadings the argon/ZIF-8 system can be represented, on a mesoscopic scale, as a set of connected cages which do exchange matter but whose respective free energies are independent of each other. Although such an approximation is quite radical and the model derived upon it very minimal, the results are in very good agreement (in most of the cases, semiquantitative) with the molecular GCMC data obtained in the selected loading range.

A computational molecular dynamics study about structural, vibrational, and dynamical properties of water adsorbed in AFI zeolite types, AlPO4-5, using a newly extended potential model and its all-silica isomorph, SSZ-24, is reported. The investigation was performed at different temperatures and for different water coverage (loading). The results of our molecular dynamics simulations allow a better comprehension of the water’s properties in these zeolites. The computed structural data agree very well with the experiments for AlPO4-5, reproducing the presence of helicoidal chains of the adsorbed water molecules, but predict a different arrangement of water molecules for SSZ-24, namely linear chains running along the channel axis. The diffusion coefficient of water at different loadings and temperature for both AlPO4-5 and SSZ-24 were computed. According to our results in the temperature range 230–300 K, the diffusivity at the highest considered loading is 1 order of magnitude smaller than in bulk water, in essential agreement with the experiment. The results of our molecular dynamics simulations allow a better comprehension of the water’s properties in these zeolites.

Correct modeling of framework flexibility plays a major role in obtaining accurate results when performing atomistic simulations of guest molecule diffusion within ZIF crystal structures. Here we present a full set of force field parameters, based on the AMBER database and on previously computed partial charges, well reproducing the ZIF-8 structural properties over a wide range of temperatures and pressures. To test our model, the self-diffusivity for sorbed carbon-dioxide is computed and is found to be in good agreement with experimental measurements. Our results are also compared to the ones obtained with other charge models and are found to be more accurate. Finally, an estimate of the influence on self-diffusion of various simulation details is given.

The behavior of water confined in nanoporous materials and, in particular, in zeolites is an important clue for understanding many various phenomena in geophysics, catalysis, and environmental science fields. In this study, the diffusion of water in zeolites Na A and NaCa A at three different loadings is studied by a classical molecular dynamics simulation technique. The results are in semiquantitative agreement with PFG NMR and QENS data, despite the good reproduction of structural and vibrational properties of the considered systems. Activation energies are in the range of those derived by the two experimental techniques. A detailed analysis of the simulated trajectories allows furnishing suggestions about the diffusion mechanism, involving a coordinated motion of water molecules and cations. Finally, the mobility of the cations, which depends strongly on the number of adsorbed water molecules and the nature of cations themselves, is investigated. The activation energies for the diffusion of the cations are too high to obtain quantitative results from MD simulations, but the observed motions can be of interest in view of the simulation of cation exchange in zeolites.

The diffusion of water in zeolites NaX and Y was investigated by quasi-elastic neutron scattering (QENS) and by a series of molecular dynamics simulations at different temperatures for different water loadings. The largest measured values of the diffusion coefficients are 1 order of magnitude smaller than in bulk water and are slightly lower in zeolite X than in zeolite Y. The dependence of the calculated diffusion coefficients versus the water content is very low at low loadings, diffusivity grows and reaches a maximum at intermediate loadings, and finally decays to smaller values when the loading approaches saturation. The reproduction of the experimental diffusion coefficient and activation energies by molecular dynamics simulations are discussed. In spite of the use of empirical potential models and classical mechanics equations, the computed activation energies are close to the experiment and the diffusion coefficients follow the same trend as the experimental ones, are of the same order of magnitude, but are overestimated, in particular in zeolite Y. Nevertheless, from these results some suggestions about the details of the diffusion mechanism may be inferred.

Recently, a possible relationship between C-Reactive Protein (CRP), a marker of underlying low-grade inflammation, and mood disorders has been proposed by some researchers. The aim of this review is to elucidate the current facts and views about CRP in mood disorders such as Depressive and Bipolar Disorders. Several studies have examined the relationship between affective disorders and CRP, but the majority of the studies in literature have been limited by retrospective, case-controlled study design, and very few studies have examined the relationship between depression and CRP in large study samples. In conclusion, the role of CRP in mood disorders is, to date, intriguing but somewhat unclear. Further prospective studies are needed to introduce the CRP in clinical settings as a marker of affective states and suicidability.

Molecular dynamics simulations of the diffusion of diatomic oscillators representing the halogen molecules and of linear flexible triatomic species modelling CO₂ and CS₂ have been carried out in the zeolite silicalite. The main purpose was to compare the performance of the random walk model to that of its “two-step’' extension in representing molecular migration inside such an interconnected 3-D pore network. The two-step model always gives a better estimate of the elements of the diffusion tensor, and also provides some interesting insight into the features of the molecular motion of the studied species. The analysis of the two-step event probabilities is also applied to assess the extent of diffusive memory in each case.