Scalable improvement of SPME multipolar electrostatics in anisotropic polarizable molecular mechanics using a general short‐range penetration correction up to quadrupoles

We propose a general coupling of the Smooth Particle Mesh Ewald SPME approach for distributed multipoles to a short‐range charge penetration correction modifying the charge‐charge, charge‐dipole and charge‐quadrupole energies. Such an approach significantly improves electrostatics when compared to ab initio values and has been calibrated on Symmetry‐Adapted Perturbation Theory reference data. Various neutral molecular dimers have been tested and results on the complexes of mono‐ and divalent cations with a water ligand are also provided. Transferability of the correction is adressed in the context of the implementation of the AMOEBA and SIBFA polarizable force fields in the TINKER‐HP software. As the choices of the multipolar distribution are discussed, conclusions are drawn for the future penetration‐corrected polarizable force fields highlighting the mandatory need of non‐spurious procedures for the obtention of well balanced and physically meaningful distributed moments. Finally, scalability and parallelism of the short‐range corrected SPME approach are addressed, demonstrating that the damping function is computationally affordable and accurate for molecular dynamics simulations of complex bio‐ or bioinorganic systems in periodic boundary conditions. © 2016 Wiley Periodicals, Inc.     

On second-order antidiffusive Lagrangian-remap schemes for multispecies kinematic flow models

This paper focuses on the numerical approximation of the solutions of multi-species kinematic flow models. These models are strongly coupled nonlinear first-order conservation laws with various applications like sedimentation of a polydisperse suspension in a viscous fluid, or traffic flow modeling. Since the eigenvalues and eigenvectors of the corresponding flux Jacobian matrix have no closed algebraic form, this is a challenging issue. A new class of simple schemes based on a Lagrangian- Eulerian decomposition (the so-called Lagrangian-remap (LR) schemes) was recently advanced in [4] for traffic flow models with nonnegative velocities, and extended to models of polydisperse sedimentation in [5]. These schemes are supported by a partial numerical analysis when one species is considered only, and turned out to be competitive in both accuracy and efficiency with several existing schemes. Since they are only first-order accurate, it is the purpose of this contribution to propose an extension to second-order accuracy using quite standard MUSCL and Runge-Kutta techniques. Numerical illustrations are proposed for both applications and involving eleven species (sedimentation) and nine species (traffic) respectively.     

Dynamic Aspects and Controllability of the MELiSSA Project: A Bioregenerative System to Provide Life Support in Space

Manmade ecosystems differ from their prototype biosphere by the principle of control. The Earth Biosphere is sustainable by stochastic control and very large time constants. By contrast, in a closed ecosystem such as the micro-ecological life support system alternative (MELiSSA system) developed by the European Space Agency for space exploration, a deterministic control is a prerequisite of sustainable existence. MELiSSA is an integrated sum of interconnected biological subsystems. On one hand, all unit operations in charge of the elementary functions constitutive of the entire life support system are studied until a thorough understanding and mathematical modelling. On the other hand, the systemic approach of complex, highly branched systems with feedback loops is performed. This leads to study in the same perspective, with the same degree of accuracy and with the same language, waste degradation, water recycling, atmosphere revitalisation and food production systems prior to the integration of knowledge-based control models. This paper presents the mathematical modelling of the MELiSSA system and the interface between the control strategy of the entire system and the control of the bioreactors.     

A mixed-valence polyoxovanadate(III,IV) cluster with a calixarene cap exhibiting ferromagnetic V(III)-V(IV) interactions

A series of compounds (cat)[V6O6(OCH3)8(calix)(CH3OH)] was obtained under anaerobic conditions and solvothermal reaction of VOSO4 with p-tert-butylcalix[4]arene (calix) in methanol using different types of bases (Et4NOH, NH4OH, pyridine, Et3N). All compounds contain the same polyoxo(alkoxo)hexavanadate anion [V6O6(OCH3)8(calix)(CH3OH)]- (1) exhibiting a mixed valence {VIIIVIV5O19} core with the so-called Lindqvist structure coordinated to a calix[4]arene macrocycle and cocrystallizing with the conjugated acid of the base (cat = Et4N+, NH4(+), pyridinium, Et3NH+) involved in the synthesis process. The structures have been fully established from X-ray diffraction on single crystals and the mixed valence state has been confirmed by bond valence sum calculations. The magnetic behavior of all compounds are the same because of the polyalkoxohexavanadate anion [V6O6(OCH3)8(calix)(CH3OH)]- (1) and have been interpreted by DFT calculations. Thus the V(III)...V(IV) interactions are found to be weakly ferromagnetic (<5.5 cm(-1)) while the V(IV)...V(IV) are antiferromagnetic (-17.6; -67.6 cm(-1)). The set of the coupling exchange parameters allows a good agreement with the magnetic experimental data.     

On-line monitoring of composite nanoparticles synthesized in a pre-industrial laser pyrolysis reactor using Laser-Induced Breakdown Spectroscopy

Laser-Induced Breakdown Spectroscopy (LIBS) was employed for on-line and real time process monitoring during nanoparticle production by laser pyrolysis. Laser pyrolysis has proved to be a reliable and versatile method for nanoparticle production. However, an on-line and real time monitoring system could greatly enhance the process optimization and accordingly improve its performances. For this purpose, experiments aiming at demonstrating the feasibility of an on-line monitoring system for silicon carbide nanoparticle production using the LIBS technique were carried out. Nanosecond laser pulses were focused into a cell through which part of the nanoparticle flux diverted from the production process was flowed for LIBS analysis purposes. The nanoparticles were vaporized within the laser-induced plasma created in argon used as background gas in the process. Temporally-resolved emission spectroscopy measurements were performed in order to monitor nanoparticle stoichiometry. Promising results were obtained and on-line Si/C_x stoichiometry was successfully observed. These results put forward the possibility of real time correction of the nanoparticle stoichiometry during the production process.     

Reversible pH-triggered encapsulation and release of pyrene by adsorbed block copolymer micelles

The well-established ability of copolymer micelles to encapsulate and release hydrophobic molecules has been investigated following their adsorption onto silica particles. Here, a pH-responsive copolymer, poly(2-(dimethylamino)ethyl methacrylate)- b-poly(2-(diethylamino)ethyl methacrylate) (PDMA(106)- b-PDEA(25)), has been used to study the formation and dissociation of adsorbed micelles through pH variation. This copolymer behaves as free unimers in aqueous solutions below pH 8 and forms micelles 29 nm in hydrodynamic diameter above this pH. Encapsulation and release of a model hydrophobic compound (pyrene) by in situ adjustment of the solution pH has been compared for both free and adsorbed micelles using fluorescence spectrophotometry, epifluorescence microscopy, and zeta potential measurements. At basic pH values, pyrene is solubilized within the cores of micelles adsorbed on silica particles: addition of acid leads to micelle dissociation and release of the pyrene into the bulk aqueous solution. Micelle adsorption does not appear to hinder the extent of pyrene uptake/release. Moreover, this pH-responsive behavior is both reversible and reproducible over multiple pH cycles.     

Understanding lead chemistry from topological insights: the transition between holo- and hemidirected structures within the [Pb(CO)n]2+ model series

In this contribution, we focus to the currently unknown [Pb(CO)(n)](2+) model series (n=1 to 10), a set of compounds which allows us to investigate in-depth the holo- and hemidirectional character that lead complexes can exhibit. By means of DFT computations performed using either relativistic four-component formalisms coupled to all-electron basis sets for [Pb(CO)](2+), [Pb(OC)](2+) and [Pb(CO)(2)](2+), or scalar relativistic pseudopotentials for higher n values, the structure and the energetics of these species are investigated. The results are complemented by Constrained Space Orbital Variations (CSOV) and Electron Localization Function (ELF) comprehensive analyses in order to get better insights into the poorly documented chemical fundamentals of the Pb(2+) cation. Whereas the discrimination between holo- and hemidirected structures is usually done according to the geometry, we here provide a quantitative indicator grounded on (V(Pb)), the mean charge density of the valence monosynaptic V(Pb) ELFic basin associated to the metal cation. Free-enthalpy relying discussions show, moreover, that those gas-phase complexes having n=7, 8 or 9 may be experimentally instable and should dissociate into [Pb(CO)(6)](2+) and a number of CO ligands. According to second-order differences in energy, it is anticipated that the n=3 or 6 structures should be the most probable structures in the gas phase. Gathering all data from the present theoretical study allows us to propose some concepts that the versatile structural chemistry of Pb(2+) complexes could rely on.     

Preparation and study of new poly-8-hydroxyquinoline chelators for an anti-Alzheimer strategy

Fourteen different ligands have been synthesized with two covalently linked 8-hydroxyquinoline motifs that favor metal complexation. These bis-chelators include different bridges at the C2 positions and different substituents to modulate their physicochemical properties. They can form metal complexes in a ratio of one ligand per metal ion with Cu II and Zn II, two metal ions involved in the formation of amyloid aggregates of the toxic Abeta-peptides in the Alzheimer disease. The apparent affinity of all bis-8-hydroxyquinoline ligands for Cu II and Zn II are similar with logK Cu II approximately 16 and logK Zn II approximately 13 and are 10,000 times more efficient than for the corresponding 8-hydroxyquinoline monomers. Their strong chelating capacities allow them to inhibit more efficiently than the corresponding monomers the precipitation of Abeta-peptides induced by Cu II and Zn II and also to inhibit the toxic formation of H2O2 due to copper complexes of Abeta. The best results were obtained with a one-atom linker between the two quinoline units. X-ray analyses of single-crystals of Cu II, Zn II or Ni II complexes of 2,2'-(2,2-propanediyl)-bis(8-hydroxyquinoline), including a one-atom linker, showed that all heteroatoms of the bis-8-hydroxyquinoline ligand chelate the same metal ion in a distorted square-planar geometry. The Cu II and Zn II complexes include a fifth axial ligand and are pentacoordinated.     

固体氧化物燃料电池阳极材料Sm1-xSrxCrO3(0≤x≤0.1)的合成及电化学性能

Sm1-xSrxCrO3;电导率;极化电阻;固体氧化物燃料电池