LHCb prospects for full energy and beyond (incl. upgrades)

The LHCb experiment is running at the Large Hadron Collider to study CP violation and rare decays in the beauty and charm sectors. The physics potential is given for five key observables sensitive to new physics in nominal conditions. The motivation and the strategy of the upgrade envisaged for 2016 is presented with the expected performance for an integrated luminosity of 50 1/fb.Comment: 5 pages, 2 figures, Proceeding of the HCP2010 conferenc

Thermooxidative aging of polydicyclopentadiene in glassy state

Thermal aging of thin films of unstabilized polydicyclopentadiene (pDCPD) at several temperatures ranging from 120 to 30 C was investigated by means of carbonyl build up by FTIR with ammonia derivatization, double bond titration, mass uptake measurement, hydroperoxides titration by iodometry and DSC coupled with sulfur dioxide treatment. In the temperature range under investigation, pDCPD is in glassy state and it oxidizes faster than common polymers oxidized at rubbery state (e.g. polydienic elastomers). Using the kinetic analysis, these results were ascribed to increased initiation rate due to catalyst residues, some possible intramolecular processes favoring propagation, or a very low termination rate of oxidation radical chains because of the control of termination reactions by macroradical diffusion

Chose, concept et molécularisme autour de la proposition des Principles de Russell

à paraître dans Soyons logiques (ed. Moktefi)The early Russell (Principles of Mathematics, 1903) believed there is nothing essentially linguistic about propositions and viewed language as a mere psychological contingency. Then it should be possible to conceive of propositions in such a way that logical relationships are not dependent on linguistic forms. Here we examine such a contention for simple propositions, i.e. that do not involve embedded propositions or their nominalized counterparts. We discuss the construction of such a proposition from its building blocks: things, concepts and predicates or relations. Many problems already occur and the semantic chemistry is fraught with specific difficulties.Sur les difficultés fondamentales et les fondements mal assurés d'un molécularisme de la proposition platonicienne des Principles de Russell, avant même d'en venir à des considérations plus élaborées comme celles liées aux paradoxes, qui concernent le modèle dans la nature même de ses objets et non dans leur utilisation mal régulée. Russell en était certes conscient : "les propositions sont des complexes d'une certaine sorte mais je ne sais pas décrire cette sorte de complexité que les propositions ont et que les autres complexes n'ont pas". Sa construction ne permettait pas davantage d'expliquer les propriétés des propositions, dont leur vérité ou (plus encore) leur fausseté. La construction de la molécule sémantique pose des problèmes spécifiques, différant fondamentalement de ceux de la chimie sur deux points au moins : l'absence de substrat géométrique et le caractère orienté de l'assemblage

Controlled Cavitation in Microfluidic Systems

We report on cavitation in confined microscopic environments which are commonly called microfluidic or lab-on-a-chip systems. The cavitation bubble is created by focusing a pulsed laser into these structures filled with a light-absorbing liquid. At the center of a 20 µm thick and 1 mm wide channel, pancake-shaped bubbles expand and collapse radially. The bubble dynamics compares with a two-dimensional Rayleigh model and a planar flow field during the bubble collapse is measured. When the bubble is created close to a wall a liquid jet is focused towards the wall, resembling the jetting phenomenon in axisymmetry. The jet flow creates two counter-rotating vortices which stir the liquid at high velocities. For more complex geometries, e.g., triangle- and square-shaped structures, the number of liquid jets recorded correlates with the number of boundaries close t

Oxidation of unvulcanized, unstabilized polychloroprene: A kinetic study

Thermal oxidation in air at atmospheric pressure, in the 80-140 °C temperature range and in oxygen at 100 °C in the 0.02-3 MPa pressure range, of unvulcanized, unstabilized, unfilled polychloroprene (CR) has been characterized using FTIR and chlorine concentration measurement. The kinetic analysis was focused on double bond consumption. A mechanistic scheme involving unimolecular and bimolecular hydroperoxide decomposition, oxygen addition to alkyl radicals, hydrogen abstraction on allylic methylenes, alkyl and peroxyl additions to double bonds and terminations involving alkyl and peroxy radicals was elaborated. The corresponding rate constants were partly extracted from the literature and partly determined from experimental data using the kinetic model derived from the mechanistic scheme in an inverse approach. Among the specificities of polychloroprene, the following were revealed: The rate of double bond consumption is a hyperbolic function of oxygen pressure that allows a law previously established for the oxidation of saturated substrates to be generalized. CR oxidation is characterized by the absence of an induction period that reveals the instability of hydroperoxides. The kinetic analysis also reveals that peroxyl addition is faster than hydrogen abstraction but slower in CR than in common hydrocarbon polydienes

Journées de réflexions sur l'exploitation et la gestion des ressources en eau du Sénégal

Depuis 1980, l'ORSTOM a entrepris un vaste programme de recherches multidisciplinaires sur les fleuves Sénégal et Gambie, dont les objectifs principaux consistent à chiffrer tout le long de ces 2 axes les mouvements et la migration de l'eau et de matières dissoutes ou particulaire

Water clustering in polychloroprene

Water sorption has been studied gravimetrically for polychloroprene rubber samples, first at a fixed hygrometric ratio (98% HR) and several temperatures (25, 40, 60 and 80 °C) for samples of 1.8 and 3.8 mm thickness (Constant Temperature and Hygrometry, CTH experiments), then at fixed temperature (40 °C) and several hygrometric ratios ranging from 0 to 95% HR on samples of 0.1 mm thickness (DVS experiments). CTH experiments reveal an abnormal sorption behavior: after an apparently fickian transient period, the water absorption continues at almost constant rate, no equilibrium is observed after more than 2500 h, whatever the temperature. DVS experiments reveal a very low Henry's solubility but the formation of clusters at water activities higher than 40%. The water diffusivity is almost independent of activity below 50% HR and decreases rapidly when activity increases above 50%. Contrary to CTH experiments, equilibrium is reached in DVS and the difference is not simply linked to the well-known effect of sample thickness on diffusion rate. The results allow hypotheses such as hydrolysis or osmotic cracking to explain the abnormal sorption phenomenon to be rejected. It is suggested that clusters could be polymer-water complexes having a linear/branched structure able to grow without phase separation that could explain the reversibility of sorption-desorption cycles. The difference of behavior between thin 0.1 mm and thicker 1.8 or 3.8 mm samples could be due to an effect of swelling stresses