Synthesis of Tetrathiafulvalene-Containing Zirconium (IV) Pincers and Metallocavitands for Hosting Fullerenes

The synthesis and spectroscopic characterization of zirconium(IV) dicarboxylate 1 and metallocavitand 2 are described. Encapsulation studies of fullerenes C60 and C70 were performed using UV–Vis spectroscopy in chlorobenzene, toluene, benzene, carbon disulfide and in a mixture of toluene/dichloromethane. UV–Vis titrations have shown that the binding abilities of the hosts toward fullerene C70 are considerably higher than those obtained for fullerene C60

Le traitement de l'incertitude en gestion de crise : mise en place d'une veille stratégique du territoire

National audienceThe catastrophic events of these last years such as the catastrophe of AZF in 2001 or the various terrorist attacks made evolve the concept of risk by integrating dimensions of crisis and threat. The damages which result from this do not limit to a delimited zone but impact the whole society. The crisis organizations are destabilized by the unusual feature of these situations. The managers must anticipate these situations as soon as possible; react efficiently and in a fast way in order to avoid the consequences of the crisis. However, the decision makers need a fast, clear and structured expertise allowing reducing uncertainties related to the situation. The objective of this project is to present, after a state of the art on the crises, a methodology of decision-making aid to help the Prefects through a potential of crisis usable in vigilance and during the emergency phase.Les évènements catastrophiques de ces dernières années tels que la catastrophe d'AZF en 2001 ou les différents attentats terroristes ont fait évoluer le concept de risque en lui intégrant les dimensions de crise et de menace. Les dommages qui en découlent ne se limitent pas à une zone délimitée mais impactent la société dans son ensemble. Les organisations gestionnaires des crises sont déstabilisées en raison du caractère inhabituel de ces situations. Les gestionnaires se doivent d'anticiper au plus tôt ces situations, de réagir efficacement et de manière rapide afin d'éviter une crise. Or, les décideurs ont besoin d'une expertise rapide, claire et structurée permettant de réduire les incertitudes liées à la situation. L'objectif de ce projet est de présenter, après un état de l'art sur les situations de crise, une méthodologie d'aide à la décision permettant d'apporter de la lisibilité aux préfets à travers l'établissement d'un potentiel de crise utilisable en veille et pendant la phase d'urgence

Zirconium(IV) metallocavitands as blue-emitting materials

A series of zirconium-carboxylate metallocavitands with the general formula [(CpZr)3(μ-κ2,O′,O″CR)3(μ3-O)(μ2-OH)3]Cl (Cp = cyclopentadienyl; R = C5H4N (5), C6H7N (6), C18H14N (7), and C18H12N (8)) were synthesized in moderate to high yields (40–83%) by reacting the corresponding carboxylic acids 1–4 with Cp2ZrCl2 in a self-assembly procedure at room temperature. The metallocavitands were characterized using 1H and 13C NMR spectroscopy and by single-crystal X-ray diffraction. Complexes 7 and 8 exhibit efficient photoluminescence properties in solution. The photoluminescence peak of 7 was observed at 464 nm and that of 8 at 422 nm with respective quantum yields in solution of 87 and 65%

Analytical and practical analysis of frictional-kinetic model for dense and dilute gas-solid flows

In granular flows, when the solid volume fraction is large, the dynamic behaviour of particles becomes controlled by frictional effects. Theoretically these effects can not be taken into account in an Eulerian approach, based on the kinetic theory of granular flows, because the inter-particle contact times are long. However, in the literature several empirical models have been proposed which introduce a frictional pressure and viscosity. In the paper, these models are first compared on a simple case of sheared dense granular flows in order to analyze the individual behavior of each model. Second, the models have been implemented in an Eulerian solver and numerical simulations have been performed of an experiment of bin discharge. The results show that for large diameter, the solid mass flow rate is well predicted, while it is systematically underestimated when the ratio between the injector diameter and the diameter of particles is small

ETUDE DES SÉDIMENTS COTIERS DU CAP CORSE: RECONSTRUCTION PALÉOENVIRONNEMENTALE ET SUIVI DE LA CONTAMINATION EN ÉLÉMENTS TRACES MÉTALLIQUES AU COURS DE LA PÉRIODE HISTORIQUE

Les sédiments sont d’excellentes archives de la contamination de notre environnement. Depuis l’Antiquité, les activités humaines génèrent des aérosols anthropiques enrichis en métaux lourds (e.g. Pb, Zn, Cu, Cd, Hg) ou associés (As, Sb). Ces polluants métalliques se mélangent aux aérosols naturels (altération des roches) et leurs retombées sont incorporées dans les sols et les sédiments où ils sont préservés (Boyd, 2004). Sur des sédiments datés, une approche géochimique permet de quantifier l’apport anthropique en éléments métalliques par rapport aux sources naturelles et de reconstituer l’historique de la pollution. Les côtes méditerranéennes sont caractérisées par d’intenses échanges commerciaux, et ce depuis l’Antiquité. Nous proposons une reconstruction paléoenvironnementale ainsi qu’un suivi de la contamination anthropique au cours de la période historique pour différents sites du Cap Corse (France ; Figure 1). Cette région de Méditerranée se caractérise par une riche activité économique au cours de la période historique. Depuis le VIème siècle, la Corse a été colonisée successivement par les Grecs, les Carthaginois, les Etrusques puis par les Romains. En milieu continental, des témoins archéologiques (sépulture, oppidum, chapelle) attestent d’une occupation de cette zone sur une période assez longue. Cependant de nombreuses interrogations subsistent quant à l’importance des établissements, leurs périodes d’occupation, leurs activités économiques et leurs rapports commerciaux avec les autres cités du Cap Corse et des côtes méditerranéennes (de La Brière, 2010). Des carottes de 1 m à 1,5 m ont été prélevées à la tarière dans différents sites du Cap Corse. Les concentrations en éléments majeurs et en éléments traces métalliques ont été mesurées par spectrométrie de masse (ICP-MS), activation neutronique (INAA) et par XRF core scanner. Les datations 14C réalisées sur des macrorestes de matières végétales et charbons montrent que ces carottes couvrent toute la période historique, à l’exception de celle prélevée à Méria qui ne couvre qu’environ 300 ans. Cette carotte a également la particularité de contenir d’importantes concentrations en métaux lourds tels que le Sb (2000 ppm) et l’As (300 ppm). Cette contamination est d’origine locale et liée à la présence d’une ancienne mine d’antimoine à 2 km en amont de Méria. Afin d’obtenir un enregistrement sur les 2000 dernières années, un carottage plus long sera réalisé lors d’une nouvelle campagne de terrain. D’autres carottages seront également réalisés entre la mine et la côte actuelle afin d’observer la variation spatiale dans le but de quantifier l’impact environnemental des activités humaines locales et régionales

Tenure, Experience, Human Capital and Wages:A Tractable Equilibrium Search Model of Wage Dynamics

We develop and estimate an equilibrium job search model of worker careers, allowing for human capital accumulation, employer heterogeneity and individual-level shocks. Wage growth is decomposed into contributions of human capital and job search, within and between jobs. Human capital accumulation is largest for highly educated workers. The contribution from job search to wage growth, both within- and between-job, declines over the first ten years of a career – the ‘job-shopping’ phase of a working life – after which workers settle into high-quality jobs using outside offers to generate gradual wage increases, thus reaping the benefits from competition between employers

DHWM: A Scheme for Managing Watermarking Keys in the Aquarelle Multimedia Distributed System

International audienceThis paper presents secure architecture and protocols for managing Intellectual Property Rights in distributed content databases in a close environment. The implementation of this architecture is cur- rently being realized in the European project AQUARELLE. Registered users will access on the Internet to high value content through secure servers. The main interest of this paper is protocols and architecture de- veloped for using watermarking technologies, with a clever and efficient key management based on the Diffie-Hellman (DH) protocol and Trusted Third Parties (TTP). This paper presents a short survey of watermarking technologies. Next Aquarelle background is specified, along with the chosen watermarking algorithm, which is convenient for the project. Next the DHWM key exchange is presented, based on the simple idea that watermarking and verification can be separated. This scheme uses the Diffie-Hellman key- exchange protocol. Next some hints on the implementation of the scheme and on its correctness are given

Synthesis of carboxylate Cp*Zr(IV) species : towards the formation of novel metallocavitands

With the intent of generating metallocavitands isostructural to species [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+), the reaction of Cp*2ZrCl2 and Cp*ZrCl3 with phenylcarboxylic acids was carried out. Depending on the reaction conditions, five new complexes were obtained, which consisted of Cp*2ZrCl(κ(2)-OOCPh) (1), (Cp*ZrCl(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2 (2), [(Cp*Zr(κ(2)-OOCPh))2(μ-κ(2)-OOCPh)2(μ(2)-OH)2]·Et2O (3·Et2O), [[Cp*ZrCl2](μ-Cl)(μ-OH)(μ-O2CC6H5)[Cp*Zr]]2(μ-O2CC6H5)2 (4), and [Cp*ZrCl4][(Cp*Zr)3(κ2-OOC(C6H4Br)3(μ3-O)(μ2-Cl)2(μ2-OH)] [5](+)[Cp*ZrCl4](-). The structural characterization of the five complexes was carried out. Species 3·Et2O exhibits host-guest properties where the diethyl ether molecule is included in a cavity formed by two carboxylate moieties. The secondary interactions between the cavity and the diethyl ether molecule affect the structural parameters of the complex, as demonstrated be the comparison of the density functional theory models for 3 and 3·Et2O. Species 5 was shown to be isostructural to the [(CpZr)3(μ(3)-O)(μ(2)-OH)3(κO,O,μ(2)-O2C(R))3](+) metallocavitands

Octahedral niobium cluster-based solid state halides and oxyhalides: effects of the cluster condensation via an oxygen ligand on electronic and magnetic properties

International audienceThe influences of an oxygen ligand on the structural, magnetic and electronic properties of octahedral niobium cluster-based oxides and oxychlorides are reported. The Nb6 metal cluster is edge-bridged by twelve inner ligands and additionally bonded to six apical ligands to form Nb6Li12La6 units (L = Cl, O) wherein oxygen and chlorine are perfectly ordered. Oxygen favours the interconnection of clusters via double Oi-a/Oa-i bridges in a similar way to the double Si-a/Sa-i bridges found in Chevrel phases based on face capped Mo6Li8La6 units. Periodic density functional theory (DFT) calculations confirm that increasing the number of inner oxygen ligands at the expense of chlorine atoms favours the 14 metal-electron (ME) count per octahedral cluster unit. It is also shown that weak interactions occur between neighbouring clusters. Indeed, magnetic measurements performed on AxNb6Cl12O2 (A = Rb, x = 0.816(8); A = Cs, x = 1) series containing 15-ME species evidence antiferromagnetic interactions at low temperatures. Broken-symmetry DFT calculations of exchange parameters within spin dimer analysis confirm the experimental results