14 research outputs found
Coalescence de bulles dans des fluides visqueux et génération de bulles satellites
Les procĂ©dĂ©s de bullage sont couramment utilisĂ©s dans l'industrie. On les rencontre dans les fours verriers afin d'activer le brassage mĂ©canique et amĂ©liorer les transferts thermiques. Il convient d'Ă©viter la coalescence entre les bulles produites par ces dispositifs car elle s'accompagne en gĂ©nĂ©ral de la gĂ©nĂ©ration de petites bulles dites filles qui de par leur taille restent dans la masse du liquide. Afin d'Ă©tudier les mĂ©canismes mis en jeu lors de la coalescence de deux bulles, nous avons dĂ©veloppĂ© une expĂ©rience en faisant interagir deux bulles pour les faire coalescer dans le champ d'une camĂ©ra rapide. La gĂ©nĂ©ration des bulles filles Ă l'issue de la coalescence est clairement observĂ©e. Les mĂ©canismes de production corroborer par des simulations numĂ©riques rĂ©alisĂ©es Ă l'aide de Gerris en configuration 2D-axisymĂ©trique permettent d'ĂȘtre Ă©tablis. En effet, on observe qu'aprĂšs la rupture du film, ce dernier se rĂ©tracte Ă une vitesse suffisamment rapide pour observer la crĂ©ation de couronnes gazeuses Ă la base de la crĂ©ation des bulles filles
IMGT/3Dstructure-DB and IMGT/DomainGapAlign: a database and a tool for immunoglobulins or antibodies, T cell receptors, MHC, IgSF and MhcSF
IMGT/3Dstructure-DB is the three-dimensional (3D) structure database of IMGTÂź, the international ImMunoGenetics information systemÂź that is acknowledged as the global reference in immunogenetics and immunoinformatics. IMGT/3Dstructure-DB contains 3D structures of immunoglobulins (IG) or antibodies, T cell receptors (TR), major histocompatibility complex (MHC) proteins, antigen receptor/antigen complexes (IG/Ag, TR/peptide/MHC) of vertebrates; 3D structures of related proteins of the immune system (RPI) of vertebrates and invertebrates, belonging to the immunoglobulin and MHC superfamilies (IgSF and MhcSF, respectively) and found in complexes with IG, TR or MHC. IMGT/3Dstructure-DB data are annotated according to the IMGT criteria, using IMGT/DomainGapAlign, and based on the IMGT-ONTOLOGY concepts and axioms. IMGT/3Dstructure-DB provides IMGT gene and allele identification (CLASSIFICATION), region and domain delimitations (DESCRIPTION), amino acid positions according to the IMGT unique numbering (NUMEROTATION) that are used in IMGT/3Dstructure-DB cards, results of contact analysis and renumbered flat files. In its Web version, the IMGT/DomainGapAlign tool analyses amino acid sequences, per domain. Coupled to the IMGT/Collier-de-Perles tool, it provides an invaluable help for antibody engineering and humanization design based on complementarity determining region (CDR) grafting as it precisely defines the standardized framework regions (FR-IMGT) and CDR-IMGT. IMGT/3Dstructure-DB and IMGT/DomainGapAlign are freely available at http://www.imgt.org
Hydrodynamics of heterogeneous liquid films
RevĂȘtir une surface dâun film mince permet de lui confĂ©rer de nouvelles propriĂ©tĂ©s, comme en rĂ©duire les reflets ou amĂ©liorer sa rĂ©sistance aux rayures. Une mĂ©thode pour produire ces revĂȘtements est le dĂ©pĂŽt par voie liquide : elle consiste Ă couvrir la surface avec un matĂ©riau dispersĂ© dans un liquide puis Ă le sĂ©cher. Cette mĂ©thode permet de fonctionnaliser efficacement et rapidement de grandes surfaces. Bien qu'attrayante pour lâindustrie verriĂšre, la perspective d'une fonctionnalisation par voie liquide se heurte actuellement Ă l'apparition de dĂ©fauts dans le film lors de son sĂ©chage, notamment des variations d'Ă©paisseurs sur de grandes distances. Ces imperfections dĂ©tĂ©riorent l'esthĂ©tique et les propriĂ©tĂ©s optiques de la surface. Dans cette thĂšse, nous apportons un Ă©clairage sur lâapparition de ces dĂ©fauts, en Ă©tudiant les Ă©coulements gĂ©nĂ©rĂ©s lors du sĂ©chage de films liquides de mĂ©langes binaires. En effet, l'Ă©vaporation du solvant peut induire des variations de composition qui gĂ©nĂšrent en retour des gradients de tension Ă la surface du film qui le dĂ©stabilisent. La combinaison d'expĂ©riences modĂšles, de modĂ©lisations thĂ©oriques et de simulations numĂ©riques ont permis de mettre en Ă©vidence et de dĂ©crire quantitativement plusieurs rĂ©gimes, qui correspondent aux diffĂ©rents effets limitant lâinstabilitĂ© : la pesanteur, la pression de Laplace, lâhomogĂ©nĂ©isation latĂ©rale par diffusion des composĂ©es dans le film ou au contraire la stratification verticale de ces composĂ©s, causĂ©e par lâĂ©vaporation. Une Ă©tude indĂ©pendante a Ă©tĂ© menĂ©e sur la gĂ©nĂ©ration de trains de bulles lorsque de lâair est lentement injectĂ© dans un bain.Coating processes allow functionalizing a surface to obtain new properties, as anti-glare or anti-scratch. Amongst the various methods, wet coating, the process of spreading then drying a liquid layer containing a material of interest, is particularly appealing because of its efficiency and low cost. One key hurdle, however, is the possible apparition of defects in the film during the drying process, notably, thickness variations over large areas. These imperfections degrade the aspect and the optical properties of the surface. In this Ph.D. thesis, we shed light on the apparition of these defects, by studying the flows triggered by the evaporation in liquid films of binary mixtures. Indeed, the evaporation of the solvent can induce variations of composition which generate in return gradients of tension at the film surface which destabilize it. The combination of model experiments, theoretical modeling and numerical simulations allowed us to reveal and describe quantitatively several regimes, which correspond to the factor limiting the instability: gravity, Laplace pressure, lateral homogenization by diffusion of the compounds or by their vertical stratification due to the evaporation. An independent study has been lead on the generation of bubble trains when air is slowly injected in a bath
Hydrodynamique des films liquides hétérogÚnes
Coating processes allow functionalizing a surface to obtain new properties, as anti-glare or anti-scratch. Amongst the various methods, wet coating, the process of spreading then drying a liquid layer containing a material of interest, is particularly appealing because of its efficiency and low cost. One key hurdle, however, is the possible apparition of defects in the film during the drying process, notably, thickness variations over large areas. These imperfections degrade the aspect and the optical properties of the surface. In this Ph.D. thesis, we shed light on the apparition of these defects, by studying the flows triggered by the evaporation in liquid films of binary mixtures. Indeed, the evaporation of the solvent can induce variations of composition which generate in return gradients of tension at the film surface which destabilize it. The combination of model experiments, theoretical modeling and numerical simulations allowed us to reveal and describe quantitatively several regimes, which correspond to the factor limiting the instability: gravity, Laplace pressure, lateral homogenization by diffusion of the compounds or by their vertical stratification due to the evaporation. An independent study has been lead on the generation of bubble trains when air is slowly injected in a bath.RevĂȘtir une surface dâun film mince permet de lui confĂ©rer de nouvelles propriĂ©tĂ©s, comme en rĂ©duire les reflets ou amĂ©liorer sa rĂ©sistance aux rayures. Une mĂ©thode pour produire ces revĂȘtements est le dĂ©pĂŽt par voie liquide : elle consiste Ă couvrir la surface avec un matĂ©riau dispersĂ© dans un liquide puis Ă le sĂ©cher. Cette mĂ©thode permet de fonctionnaliser efficacement et rapidement de grandes surfaces. Bien qu'attrayante pour lâindustrie verriĂšre, la perspective d'une fonctionnalisation par voie liquide se heurte actuellement Ă l'apparition de dĂ©fauts dans le film lors de son sĂ©chage, notamment des variations d'Ă©paisseurs sur de grandes distances. Ces imperfections dĂ©tĂ©riorent l'esthĂ©tique et les propriĂ©tĂ©s optiques de la surface. Dans cette thĂšse, nous apportons un Ă©clairage sur lâapparition de ces dĂ©fauts, en Ă©tudiant les Ă©coulements gĂ©nĂ©rĂ©s lors du sĂ©chage de films liquides de mĂ©langes binaires. En effet, l'Ă©vaporation du solvant peut induire des variations de composition qui gĂ©nĂšrent en retour des gradients de tension Ă la surface du film qui le dĂ©stabilisent. La combinaison d'expĂ©riences modĂšles, de modĂ©lisations thĂ©oriques et de simulations numĂ©riques ont permis de mettre en Ă©vidence et de dĂ©crire quantitativement plusieurs rĂ©gimes, qui correspondent aux diffĂ©rents effets limitant lâinstabilitĂ© : la pesanteur, la pression de Laplace, lâhomogĂ©nĂ©isation latĂ©rale par diffusion des composĂ©es dans le film ou au contraire la stratification verticale de ces composĂ©s, causĂ©e par lâĂ©vaporation. Une Ă©tude indĂ©pendante a Ă©tĂ© menĂ©e sur la gĂ©nĂ©ration de trains de bulles lorsque de lâair est lentement injectĂ© dans un bain
Numerical model using a Volume-Of-Fluid method for the study of evaporating sessile droplets in both unpinned and pinned modes
International audienceThis article focuses on the numerical study of the evaporation of sessile dropletsusing a Volume-Of-Fluid (VOF) method in the free-software Basilisk. We con-sider pure liquid droplets forming a spherical-cap onto a smooth or rough andnon-corrosive substrate and we investigate two different modes of evaporation:the unpinned mode where the contact angle is constant and the pinned modewhere the wetting area is constant. The numerical method used to implementthe contact angle and for the reconstruction of the interface is fully described,especially for the pinned mode where we propose a new VOF implementation.In the unpinned mode, we perform parametric studies and we show the influenceof the relative humidity and the contact angle on the evaporation process. Forall the explored parameters, the simulations predict that the volume decreaseslinearly with time, which matches the signature behaviour of evaporating un-pinned droplets, irrespective of the geometrical parameters. In the pinned mode,the contact angle analysis indicates a linear decrease in time which was expectedaccording to the theory and validated with some experiments we performed
Propulsion on a superhydrophobic ratchet
International audienceLiquids in the Leidenfrost state were shown by Linke to self-propel if placed on ratchets. The vapour flow below the liquid rectified by the asymmetric teeth entrains levitating drops by viscosity. This effect is observed above the Leidenfrost temperature of the substrate, typically 200°C for water. Here we show that coating ratchets with super-hydrophobic microtextures extends quick self-propulsion down to a substrate temperature of 100°C, which exploits the persistence of Leidenfrost state with such coatings. Surprisingly, propulsion is even observed below 100°C, implying that levitation is not necessary to induce the motion. Finally, we model the drop velocity in this novel "cold regime" of self-propulsion
Coalescence de bulles dans des fluides visqueux et génération de bulles satellites
International audienceDans le but d'assurer un brassage mĂ©canique et d'accroĂźtre les transferts thermiques des dispositifs de bullage fonctionnant Ă dĂ©bit constant sont introduits dans les fours d'Ă©laboration des verres. Ces dispositifs crĂ©ent des bulles de tailles centimĂštres qui montent sous forme de train de bulles. A faible dĂ©bit, les bulles ainsi crĂ©Ă©es montent de façon rĂ©guliĂšre et sans grande interaction. Avec l'augmentation du dĂ©bit, les bulles commencent Ă interagir provoquant des coalescences. DĂšs lors que des phĂ©nomĂšnes de coalescence sont observĂ©s, un envahissement de petites bulles dans le volume du liquide est observĂ©. Il est donc important de connaĂźtre les conditions d'apparition de ces bulles et d'en comprendre l'origine. Au delĂ des intĂ©rĂȘts industriels, les mĂ©canismes provoquant l'apparition de bulles lors de la coalescence de deux bulles de grandes tailles restent des questions ouvertes en mĂ©canique des fluides
Structureâfunction relationships of the variable domains of monoclonal antibodies approved for cancer treatment
Due to their exquisite specificity for a given epitope on the target antigen, recombinant monoclonal antibodies (rmAb) can deliver âtargeted therapyâ in oncology. This review focuses on the structural bases of âantigen specificityâ to aid clinical researchers and pharmacologists in managing these new drugs. The fine structure of the Fv (Fragment variable) module (combination of VH and VL domains) from the five unconjugated antibodies currently approved for cancer treatment, namely rituximab, cetuximab, alemtuzumab, trastuzumab and bevacizumab, is presented and analysed. Co-crystal and functional studies are reviewed to define rmAb residues contributing to antigen binding site (paratope)âepitope interfaces. The genetic origin of these recombinant monoclonal antibodies, determined through the IMGT/3Dstructure-DB database and IMGT/V-QUEST (http://imgt.cines.fr), is presented, allowing the evaluation of homologies between antibodies and their closest germline human counterparts and hence their possible immunogenicity. Overall, the IMGT standards appear as a first and crucial step in the evaluation of recombinant antibodies