15 research outputs found
Translational and rotational temperatures of a 2D vibrated granular gas in microgravity
We present an experimental study performed on a vibrated granular gas
enclosed into a 2D rectangular cell. Experiments are realized in microgravity.
High speed video recording and optical tracking allow to obtain the full
kinematics (translation and rotation) of the particles. The inelastic
parameters are retrieved from the experimental trajectories as well as the
translational and rotational velocity distributions. We report that the
experimental ratio of translational versus rotational temperature decreases to
the density of the medium but increases with the driving velocity of the cell.
These experimental results are compared with existing theories and we point out
the differences observed. We also present a model which fairly predicts the
equilibrium experimental temperatures along the direction of vibration.Comment: 14 pages, 11 figures, submitte
Etudes sur le mobilier Boulle, l'ébéniste de Louis XIV : quelques problÚmes d'interfaces
National audienceDans le cadre d'un programme mis en place par le musĂ©e du Louvre, dĂ©partement des objets d'art, et le C2RMF, autour de l'Ă©tude et de la restauration des mobiliers attribuĂ©s Ă l'atelier d'AndrĂ©-Charles Boulle ou Ă ses successeurs, il a Ă©tĂ© dĂ©gagĂ© plusieurs problĂšmes concernant les marqueteries mĂ©talliques et les ornements en bronze dorĂ©. Cette communication traite en premier lieu de la comprĂ©hension de la mauvaise tenue au vieillissement des collages des piĂšces de marqueterie en laitons en contradiction avec la bonne tenue des piĂšces en Ă©tain voisines. Les propriĂ©tĂ©s mĂ©caniques des assemblages laiton/colle/bois et Ă©tain/colle/bois utilisant la colle animale, notamment de poisson, ont Ă©tĂ© Ă©tudiĂ©es et la rupture prĂ©maturĂ©e de ces assemblages a pu ĂȘtre expliquĂ©e en tenant compte de la rhĂ©ologie des composants. En second lieu sont Ă©tudiĂ©es les dorures des ornements en bronze dorĂ©, grĂące Ă l'utilisation des analyses par faisceaux d'ions. Les premiers rĂ©sultats donnent une idĂ©e du procĂ©dĂ© de dorure Ă l'amalgame de mercure utilisĂ© et des Ă©paisseurs d'or appliquĂ©es, ainsi que du procĂ©dĂ© Ă©lectrolytique utilisĂ© pour les piĂšces restaurĂ©es
Rhéologie de suspensions de bulles
Un dispositif original a été développé pour fabriquer des suspensions monodisperses de bulles (diamÚtre 700”m) dans un fluide newtonien trÚs visqueux (viscosité dynamique 100Pa.s). La viscosité de ces suspensions a été mesurée dans les régimes dilué et faiblement concentré (fraction volumique en bulles comprises entre 2% et 15%) dans une géométrie Couette. La viscosité des suspensions dépend de la viscosité du fluide suspendant, de la fraction volumique en bulles et d'un nombre sans dimension (nombre capillaire) caractérisant la déformation des bulles par rapport à celle du fluide suspendant. Les résultats expérimentaux obtenus se comparent trÚs bien aux prédictions du modÚle de Frankel et Acrivos [1] dans la gamme des fractions volumiques étudiée
Rheology of calcium carbonate concentrated suspensions in the presence of plasticizer molecules
Cette Ă©tude se situe dans le contexte industriel de lâutilisation de superplastifiants pour la rĂ©alisation de bĂ©tons haute performance. Pour mieux comprendre le mode dâaction des molĂ©cules fluidifiantes nous avons utilisĂ© un systĂšme modĂšle constituĂ© de suspensions de particules de carbonate de calcium lâune commerciale et constituĂ©e de microparticules et lâautre synthĂ©tisĂ©e au LPMC et constituĂ©e de nanoparticules. LâĂ©tude a portĂ© sur cinq molĂ©cules organiques : quatre de type polymĂ©thacrylates greffĂ©s polyoxyĂ©thylĂšne (PCP) avec des longueurs de greffons diffĂ©rentes et un diphosphonate polyoxyĂ©thylĂšne : OPTIMA100. La caractĂ©risation des grandeurs pertinentes des fluidifiants comme leurs complexations vis-Ă -vis des ions ; leurs degrĂ© dâionisation, leurs tailles, leurs affinitĂ©s avec le solvant ou encore leurs capacitĂ©s dâadsorption sur les surfaces a Ă©tĂ© effectuĂ©e. Dâimportantes diffĂ©rences dâefficacitĂ© de ces fluidifiants vis-Ă -vis de la rhĂ©ologie et de la sĂ©dimentation des deux types de suspension ont Ă©tĂ© mises en Ă©vidence. Ces diffĂ©rences de comportements on Ă©tĂ© interprĂ©tĂ©es grĂące Ă la caractĂ©risation effectuĂ©e sur les fluidifiants et Ă la modĂ©lisation des forces interparticulaires.This study deals with the industrial context where the superplasticizers are used to manufacture the high performance cements. To better understand the action mode of plasticizing molecules, we used a model system which consists of calcium carbonate particles suspensions: in one hand, commercial microparticles suspension, and in the other hand, self synthesized nanoparticles suspensions. The study focuses on the use of five organic plasticizers: four types of polymethacrylates grafted polyoxyethylene (PCP) with different lengths of grafts, and a diphosphonate polyoxyethylene (OPTIMA100).Characterization of the plasticizers relevant parameters such as their complextation with the ions, their ionization degree, their size, their affinity with the solvent and their adsorption ability on the particles surfaces was performed. Significant differences in the effectiveness of these thinners regarding to the rheology and sedimentation of the two types of suspension were identified. These discrepancies in the behavior were interpreted by means of; the characterization performed on the thinners, and modeling of interparticle forces
Rhéologie de suspensions concentrées de carbonate de calcium en présence de fluidifiant
This study deals with the industrial context where the superplasticizers are used to manufacture the high performance cements. To better understand the action mode of plasticizing molecules, we used a model system which consists of calcium carbonate particles suspensions: in one hand, commercial microparticles suspension, and in the other hand, self synthesized nanoparticles suspensions. The study focuses on the use of five organic plasticizers: four types of polymethacrylates grafted polyoxyethylene (PCP) with different lengths of grafts, and a diphosphonate polyoxyethylene (OPTIMA100).Characterization of the plasticizers relevant parameters such as their complextation with the ions, their ionization degree, their size, their affinity with the solvent and their adsorption ability on the particles surfaces was performed. Significant differences in the effectiveness of these thinners regarding to the rheology and sedimentation of the two types of suspension were identified. These discrepancies in the behavior were interpreted by means of; the characterization performed on the thinners, and modeling of interparticle forces.Cette Ă©tude se situe dans le contexte industriel de lâutilisation de superplastifiants pour la rĂ©alisation de bĂ©tons haute performance. Pour mieux comprendre le mode dâaction des molĂ©cules fluidifiantes nous avons utilisĂ© un systĂšme modĂšle constituĂ© de suspensions de particules de carbonate de calcium lâune commerciale et constituĂ©e de microparticules et lâautre synthĂ©tisĂ©e au LPMC et constituĂ©e de nanoparticules. LâĂ©tude a portĂ© sur cinq molĂ©cules organiques : quatre de type polymĂ©thacrylates greffĂ©s polyoxyĂ©thylĂšne (PCP) avec des longueurs de greffons diffĂ©rentes et un diphosphonate polyoxyĂ©thylĂšne : OPTIMA100. La caractĂ©risation des grandeurs pertinentes des fluidifiants comme leurs complexations vis-Ă -vis des ions ; leurs degrĂ© dâionisation, leurs tailles, leurs affinitĂ©s avec le solvant ou encore leurs capacitĂ©s dâadsorption sur les surfaces a Ă©tĂ© effectuĂ©e. Dâimportantes diffĂ©rences dâefficacitĂ© de ces fluidifiants vis-Ă -vis de la rhĂ©ologie et de la sĂ©dimentation des deux types de suspension ont Ă©tĂ© mises en Ă©vidence. Ces diffĂ©rences de comportements on Ă©tĂ© interprĂ©tĂ©es grĂące Ă la caractĂ©risation effectuĂ©e sur les fluidifiants et Ă la modĂ©lisation des forces interparticulaires
Viscous friction of squeezed bubbly liquid layers
International audienceShear viscosity of bubbly liquids is known to depend on both the gas volume fraction and the capillary number. Here we study the impact of confinement on their behavior by investigating the viscosity of semi-dilute bubbly liquid layers confined between two plates and characterized by a ratio of the undeformed bubble diameter to the layer thickness equal or larger than unity. For all the studied confinement ratios viscosity is shown to be smaller than the viscosity of the suspending liquid for capillary numbers larger than 0.1. Measurements of bubble deformations show that this behavior is related to bubble stretching in the direction of shear induced flow. In the limit of high capillary numbers, viscosity reaches values predicted for unconfined bubbly liquids. On the other hand, our results for smaller capillary numbers, i.e. within the range 0.001-0.1, reveal a non-monotonic variation of the viscosity as a function of the confinement ratio, exhibiting a well-defined maximum value for ratio close to 1.8. This behavior differs strongly from the reference case of unconfined bubbly liquid, and it is shown to result from both bulk and wall drag forces for the squeezed bubbles
Steady shear viscosity of semi-dilute bubbly suspensions
International audienceThe steady shear viscosity of bubbly suspensions is known to depend upon the suspending fluid viscosity, the bubble volume fraction and a dimensionless number (the capillary number) accounting for the deformability of the bubbles under a viscous stress. However, experimental data on bubbly suspensions in the literature are scarce and present two main shortcomings: (i) the studied systems are polydisperse, which leads to arbitrariness in the definition of a capillary number, and (ii) there is a lack of data for capillary numbers of order unity, where bubbles are slightly deformable. This leads to the absence of clear conclusion on the relevance of the existing theoretical models. In order to make significant progress, an original device is designed to produce monodisperse suspensions of bubbles in a highly viscous Newtonian fluid. The steady shear viscosity of the bubbly suspensions is measured in the dilute and semi-dilute concentration regimes (volume fraction of bubbles between 2% and 18%) using a Couette geometry with a 20-bubbles-wide gap, for capillary numbers ranging between 0.01 and 10. The new obtained data are shown to be much more accurate than data previously reported in the literature. Experimental data are in very good agreement with the model of Frankel and Acrivos (1970), originally developed for dilute suspensions, in the whole range of studied volume fractions
Adsorption de polyélectrolytes en relation avec la rhéologie d'une suspension de carbonate de calcium
Les fluidifiants utilisĂ©s dans lâindustrie cimentaire permettent dâaugmenter la fraction volumique en particules de la suspension afin d'accroĂźtre les propriĂ©tĂ©s mĂ©caniques du bĂ©ton tout en conservant une maniabilitĂ© satisfaisante lors de sa mise en Ćuvre. Notre Ă©tude est centrĂ©e sur le mode dâaction du fluidifiant. Dans ce but nous Ă©tudions la rhĂ©ologie d'une suspension modĂšle de particules minĂ©rales de carbonates de calcium. Les fluidifiants analysĂ©s sont des polyĂ©lectrolytes formĂ©s dâun squelette mĂ©thacrylate sur lequel sont greffĂ©es des chaines polyoxyĂ©thylĂšne (POE) de diffĂ©rentes longueurs : quatre molĂ©cules de longueurs de chaines diffĂ©rentes sont Ă©tudiĂ©es. Nous prĂ©senterons une Ă©tude de lâinfluence, sur la rhĂ©ologie de suspensions de particules de CaCO3, de la longueur des chaĂźnes de POE et de leurâaffinitĂ© avec le solvant. Ces mesures sont effectuĂ©es sur deux types de particules: des nanoparticules synthĂ©tisĂ©es au laboratoire et des microparticules obtenues par broyage. Sur ces derniĂšres de trĂšs fortes fractions volumiques (jusqu'Ă 64%) ont pu ĂȘtre utilisĂ©es. On met en Ă©vidence diffĂ©rents types de comportement rhĂ©o-Ă©paississant qui apparaĂźssent avec lâajout de fluidifiant et avec la diminution de la contrainte seuil. Par ailleurs des mesures de taille par diffusion de lumiĂšre et de turbiditĂ©, ont mis en Ă©vidence une micellisation du fluidifiant par augmentation du pH ou d'ions CO3- -, que nous avons corrĂ©lĂ© avec le comportement rhĂ©ologique. Nous discuterons Ă©galement ces rĂ©sultats Ă l'aide d'un modĂšle de forces d'interactions interparticulaires en prĂ©sence de polyĂ©lectrolyt
Discontinuous shear thickening in the presence of polymers adsorbed on the surface of calcium carbonate particles
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Renal cell carcinoma with leiomyomatous stroma in tuberous sclerosis complex: a distinct entity
International audienceRenal cell carcinoma with leiomyomatous stroma (RCCLS) is an emerging entity frequently associated with tuberous sclerosis complex (TSC). We described herein a series of RCCLS in TSC patients at pathological and cytogenetic levels. Three male patients with TSC and RCCLS were identified between 2000 and 2019 at the University Hospital of Rennes. Histologically, the architecture was tubulo-papillary with thick bundles of smooth muscle cells. The tumor cells showed clear cytoplasm with eosinophilic globules. The immunohistochemical profile was identical with an intense positivity of CK7, CAIX, and CD10 and a heterogeneous positivity of CK20. SDHB was low but positive and TFE3 was not expressed. Comparative genomic hybridization (CGH) did not show any quantitative chromosome abnormality. No recurrence was observed with a median follow-up of 4 years. RCCLS in TSC patients has morphological, immunohistochemical, and cytogenetic distinct features that could constitute a distinct entity and a sentinel manifestation for the diagnosis of TSC