Effect of the Microstructure of Copper Films on the Damping of Oscillating Quartz Resonators*

An electrochemical procedure is described which allows the preparation of copper films of various crystallinity. Impedance spectra recorded for copper loaded quartz resonators were analysed in terms oft he lumped-element circuit of the Butterworth-Van Dyke type to obtain their electrical and mechanical properties. Plots of the damping resistance versus film thickness indicate that the film's dissipation factor is significantly smaller in the case of disordered films with a finer crystallinity (10—100nm) than in the case of more ordered structures having a grain size between 600—1500nm. This observations states, that the finely structured copper phase behaves more rigid than the coarse material. The suggested explanation relates this effect to energy losses which occur during oscillation at the phase boundary of the grains by wearless internal friction. No contributions to the damping from surface roughness were observed for films thicker 0.5pm. Thus, the damping of the quartz oscillator caused by different degrees of surface roughness of the generated copper films was of secondary importance, compared with the effect of the crystallinity

Anionic synthesis of [1,4-poly(diene)-b-syndiotactic poly(methyl methacrylate)] diblock copolymers: 7Li NMR study of the intermediate reaction of lithium poly(diene) anion with 1,1-diphenylethylene

The end-capping with 1,1-diphenylethylene (DPE) of living 1,4-poly(diene) lithiated anions prepared in cyclohexane (Chx) and toluene is a major but poorly controlled step in the synthesis of syndiotactic poly(methyl methacrylate) (sPMMA) containing block copolymers. The kinetics of the reaction have been studied by means of 7Li NMR not only in Chx and toluene but also in their mixtures with polar solvents, since the solvent polarity must be increased for MMA to be predominantly converted into sPMMA. Although the addition of a polar solvent (tetrahydrofuran (THF), diethyl ether) to Chx and toluene is known to increase the reactivity of living polymeric anions, contaminating lithium salts, such as lithium hydroxide, slow down the end-capping reaction even when 10 vol.-% polar solvent is added. Moreover, the polymeric diphenylalkyllithium anions are unstable in 1/9 (v/v) THF/Chx mixture, as a result of the nucleophilic attack of THF. On the basis of all these observations, new experimental conditions are proposed for improving the control of the anionic block copolymerization of 1,3-dienes and MMA to yield 1,4-poly(diene) and sPMMA containing block copolymers

Protocoles d'accord pour la gestion d'une grille de calcul dynamique

Nous présentons un système de gestion de grilles de calcul dynamique où les ressources fédérées sont mises à disposition par différentes institutions. Au sein d'un domaine, les ressources peuvent interagir de façon synchrone. Les interactions entre ressources de domaines distincts sont asynchrones. Une machine ou un domaine peut joindre et quitter la grille à tout moment, de manière délibérée, ou suite à une défaillance. Nous proposons une solution tolérante aux défaillances qui exploite cette structure hiérarchique pour résoudre les problèmes d'évolution de la composition de la grille et de placement des tâches avec équilibrage de charge. Chaque service est la composition d'un protocole synchrone et d'un protocole d'accord asynchrone qui est toujours une déclinaison du problème fondamental du Consensus. Nous définissons l'insensibilité aux suspicions erronées, une métrique inédite pour comparer des protocoles de Consensus utilisant des détecteurs de défaillances "Losange S".We present a middleware for dynamic grids where the federated resources are provided by different institutions. Within a domain, the resources interact in a synchronous manner. Interactions between resources belonging to different domains are asynchronous. Every machine or domain can join or leave the grid at any time; due to failures, or on purpose. We propose a fault-tolerant solution which takes advantage of this hierarchical structure to solve the grid membership problem and the load-balanced task allocation problem. Each service is the composition of a synchronous protocol and an asynchronous agreement protocol which is always a variation of the fundamental Consensus problem. We define the "insensitivity to erroneous suspicions"; a new metric to compare different Consensus protocols based on Diamond S failure detectors.RENNES1-BU Sciences Philo (352382102) / SudocRENNES-INRIA Rennes Irisa (352382340) / SudocSudocFranceF

Synthesis and properties of carboxy‐functionalized poly(3‐alkylthienylenes)

The synthesis of a new type of, and doping mechanism in, “self exchange” or “self‐doping” conducting polymers based on 3‐(ω‐carboxyalkyl)thiophenes (with n = 4‐14) is examined (see figure). The properties of the polymers are different to that of those based on the corresponding sulphonic acids due to the lower acidity of the carboxylic acid function