Background: abT cells have a wide distribution of CD3 membrane density. The aim of this article was to evaluate the significance of the CD3 differential expression on T cell subsets. Analysis was performed on healthy donors and renal transplant patients by flow cytometry. The results obtained are: (1) CD3 expression was widely distributed (CV 5 38.3 6 3.1 to 43 6 2.3%). (2) The CD4, CD8, CD45 and forward scatter were similarly distributed. (3) The diversity of CD3 expression was directly related to the clonotypes: c9, non c9 from cdT cells and Vb clonotype from abT cells (e.g., Vb3FITC 7,980 6 1,628 Vb8PE: Vb20-FITC 11,768 6 1,510). (4) Using a computer simulation, we could confirm differential kinetics of T cell activation according to the initial parameters. Finally, in vitro activation was significantly higher on Vb8 and Vb9 (high CD3) compared with Vb2 and Vb3 (low CD3, P 5 0.040-0.0003).
Résumé -Discussion sur les mécanismes d'agglomération entre particules d'hydrate dans les émulsions eau dans huile -Le bouchage des conduites lors de la formation des hydrates de gaz dans les émulsions eau dans huile peut être appréhendé par l'augmentation de la fraction volumique effective de la suspension de particules d'hydrate. Cette augmentation est due à un processus d'agglomération qui se produit pendant la phase de formation des hydrates. Deux mécanismes d'agglomération présentés dans la littérature sont discutés. Le premier est le mécanisme d'agglomération induit par contact pour lequel le processus de cristallisationagglomération est le résultat du contact entre une goutte d'eau et une particule d'hydrate. Le second est le mécanisme d'agglomération limité par le cisaillement pour lequel la compétition entre force hydrodynamique et force adhésive est considérée. Il est proposé de réunir ces deux mécanismes dans un modèle unifié afin de prédire l'évolution de la viscosité de la suspension d'hydrate pendant la formation. Un tel modèle repose sur un modèle de bilan de population dans lequel le noyau d'agglomération est associé au mécanisme d'agglomération induit par contact et le noyau de fragmentation est associé au mécanisme d'agglomération limité par le cisaillement.
Abstract -Discussion of Agglomeration Mechanisms between Hydrate Particles in Water in
International audienceThe goal of this work is to quantify the Van der Waals interactions in systems involving gas hydrates. Gas hydrates are crystalline compounds that are often encountered in oil and gas industry, where they pose problems (pipeline plugging. etc.) and represent opportunities (energy resources. gas transport, etc.). We focus on methane hydrate, which is the most common one. and calculate its Hamaker constant. Two methods are used and lead to results in good agreement. The Hamaker, microscopic, approach gives a first estimate of the Hamaker constant of 4.59 x 10(-21) J for the hydrate-water-hydrate system. The Lifshitz, macroscopic, method used in combination with the Kramers-Kronig relationship gives a value of 8.25 x 10(-21) J. The Hamaker constant is also computed for three phases systems (gas hydrate clathrate and liquid water with ice, dodecane, quartz, sapphire, Teflon, metals). The interaction potential in different geometrical configurations is then calculated by a hybrid method and various cases of practical interest are studied
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