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Literatura académica sobre el tema "Colloides actifs"

Autor: Grafiati

Publicado: 30 de noviembre de 2024

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Artículos de revistas sobre el tema "Colloides actifs"

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Glukhov, A. F. "Распределение коллоидных частиц при одновременном действии термофореза и седиментации". Вестник Пермского университета. Физика, n.º 1 (2020): 11–16. http://dx.doi.org/10.17072/1994-3598-2020-1-11-16.

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Qu Junling, 瞿俊伶, 刘鹏 Liu Peng, 甘雪涛 Gan Xuetao y 赵建林 Zhao Jianlin. "硅基光电子芯片集成的胶体量子点有源器件（特邀）". Acta Optica Sinica 44, n.º 15 (2024): 1513011. http://dx.doi.org/10.3788/aos241121.

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DENINE, R., N. JAGER-LEZER, J. L. GROSSIORD, F. PUISIEUX y Et M. SEILLER. "Influence de la formulation d'une emulsion multiple cosmétique sur la libération des actifs encapsulés". International Journal of Cosmetic Science 18, n.º 3 (1 de mayo de 2007): 103–22. http://dx.doi.org/10.1111/j.1467-2494.1996.tb00141.x.

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Nague, Lionel Tematio, Emmanuel Mpondo, Emmanuel Nnanga Nga, Clautaire Mwebi Ekengoue y Richard Vivien Youagam. "Formulation et Fabrication des Suppositoires à Visée Antipaludique à Base du Beurre de Karité Contenant Artémisia annua Cultivé à L’ouest Cameroun". European Scientific Journal, ESJ 18, n.º 27 (31 de agosto de 2022): 204. http://dx.doi.org/10.19044/esj.2022.v18n27p204.

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Le but de la présente étude est de formuler et fabriquer des suppositoires à visée antipaludique à base de matières premières locales afin d’améliorer la prise en charge du paludisme, essentiellement chez les enfants âgés de moins de 5 ans. Pour faire cela, on a utilisé comme principe actif la poudre de feuilles et tiges sèches de Artémisia annua provenant de la Région de l’Ouest-Cameroun et comme excipient le beurre de karité en provenance de la région du Nord Cameroun puis amélioré à 4% de silice colloïdale. Les essais organoleptiques ont mis en évidence une poudre de couleur grisâtre, de saveur amère et très odorante. L’analyse granulométrique a montré que la poudre de feuilles et tiges sèches de Artémisia annua a une granulométrie allant de très fine à fineLa concentration en flavonoïdes totaux de la poudre de feuilles et tiges sèches de Artémisia annua est de 76,9 μg/ml d’équivalent de quercétine. Les suppositoires à visée antipaludique fabriqués à partir de 250mg de poudre de feuilles et tiges sèches de Artemisia annua et 1820mg de beurre de karité+4% de silice colloïdale ont suivi un contrôle pharmaceutique. Ce contrôle qualité des suppositoires à visée antipaludique contenant Artémisia annua fabriqués en utilisant le beurre de karité comme excipient a donné des valeurs des paramètres physico-chimiques en adéquation aux valeurs standards. La forme galénique issue de cette formule pourrait présenter une meilleure prise en charge thérapeutique des patients et particulièrement les enfants, au Cameroun et ailleurs en Afrique. This paper focuses on formulating and manufacturing antimalarial suppositories based on local materials in order to improve the management of malaria mainly for children under 5 years of age. Doing it, we used as active principle the powder of leaves and stems of Artemisia annua from Western Cameroon and, as an excipient, shea butter improved with 4% colloidal silica from the Northern Cameroon. The tests revealed a greyish-coloured powder with a bitter taste and a very fragrant one. The particle size analysis showed that the powder of leaves and stems of Artemisia annua has a particle size ranging from very fine to fine. The concentration of total flavonoids in the powder of leaves and stems of Artemisia annua is 76.9 μg/ml of quercetin equivalent. Antimalarial suppositories made from 250mg of Artemisia annua leaf and stem powder and 1820mg of shea butter, enhanced with 4% colloidal silica, have undergone pharmaceutical control. This quality control of Artemisia annua antimalarial suppositories, manufactured using shea butter as an excipient, gave values of the physico-chemical parameters in line with the standards values. The galenic form resulting from this formula could offer better therapeutic management of patients, particularly children, in Cameroon and elsewhere in Africa.

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Nigora, Narziyeva y Abdullayeva Nilufar Ikrombekovna. "THE EXPERIENCE OF USING A NEW PHARMACOLOGICALLY ACTIVE COMPOSITION OF NANOSTRUCTURED FLUORAPATITE IN THE TREATMENT OF EARLY MANIFESTATIONS OF INCREASED TOOTH ABRASION". European International Journal of Multidisciplinary Research and Management Studies 4, n.º 6 (1 de junio de 2024): 169–78. http://dx.doi.org/10.55640/eijmrms-04-06-25.

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Despite the obvious successes in the field of preventive and conservative dentistry, the prevalence of abrasion of teeth (ITP) continues to grow: during the period 1992-2004, the proportion of diseases of hard tissues of teeth with elimination properties increased from 30.9 ± 1.8% to 38.2 ± 1.3%, i.e. increased by 7.3% [1, 7-10]. Many issues related to the diagnosis and planning of an integrated approach to the provision of dental care to patients with moderate CAH have not yet been sufficiently studied and covered [2]. Biologically active calcium phosphate in gel or colloidal state is currently of increasing interest in many areas of clinical medicine related to the problem of regeneration of soft and hard tissues of the body. It has been established that the biological activity of apatite largely depends on the size of its particles or grains, and the higher the dispersion of the substance, the more pronounced it is [3]. The use of pure compounds, as well as various combinations of bioactive substances to improve properties such as adhesion, bioactivity and biocompatibility, is also very promising [4]. A promising direction of modification of calcium hydroxyapatite (HCA) from the point of view of obtaining materials with improved properties is the introduction of fluorine and silicon atoms into the structure of HCA. This transformation increases the stability of the material in the chemically active environment of the human body (due to the presence of fluoride ions) and increases its biological activity (due to the presence of silicate ions), while maintaining the inherent biocompatibility of HAP [5]. Nanotechnology is used in the study, production and use of nanostructures, devices and systems, including targeted control and modification of the shape, size, interaction and integration of their constituent nanoscale elements (1-100 nm) to obtain objects with new chemical, physical and biological properties. A number of technologies and methods. Direct transport of medicines to the focus of the pathological process can increase the effectiveness of existing drug therapies [6]. A promising direction in modern dentistry is the creation of new pharmacological agents with particle sizes of the order of 10-9 (nanoparticles) for noninvasive treatment and early prevention of dental diseases. The aim of the study was to study the effectiveness of new pharmacologically active compositions of nanostructured fluorohydroxyapatite in the treatment of early symptoms of dental hyperextension.

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de Paula-Ravagnani, Gabriela Silveira, Rolf Sundet y Carla Guanes-Lorenzi. "Leren van binnenuit: acties van therapeuten in de dagelijkse praktijk". Gezinstherapie Wereldwijd, 20 de noviembre de 2023. http://dx.doi.org/10.1007/s12440-023-00208-1.

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Tesis sobre el tema "Colloides actifs"

1

Nidhi, Vagisha. "Radiotactic colloids : towards the Decontamination Nanobots". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF052.

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Les méthodes traditionnelles de décontamination restent confrontées à des défis importants, tels que la difficulté d'accès aux espaces complexes ou confinés, la quantité élevée de déchets, etc. Il est encore nécessaire aujourd'hui d'explorer de nouvelles méthodes permettant d'atteindre des géométries complexes avec des processus de décontamination efficaces. Même si les macrorobots se révèlent utiles dans les tâches de décontamination à grande échelle, leur taille limite leur capacité à naviguer dans des environnements complexes et confinés. Les micro ou nano robots, quant à eux, pourraient traverser de tels espaces et cibler des sites de contamination spécifiques, ce qui les rendrait plus adaptés aux travaux de décontamination en milieu confinés et complexes. Dans ce contexte, cette thèse porte sur la synthèse à grande échelle et l'étude de la mobilité de colloïdes actifs, en particulier de particules Janus, susceptibles d'être utilisés comme brique dans de nouvelles méthodes de décontamination. À cette fin, différents assemblages de particules d'or sur silice (assemblage isotrope ou Janus, nanoparticules discrètes ou couche d'or continue) ont été préparés, caractérisés et comparés. Leurs mouvements 3D et 2D ont été suivis dans différents environnements. Un élément clé de ce travail a consisté en particulier à développer un dispositif microfluidique capable de générer des gradients stables d'eau oxygénée, produit de la radiolyse de l'eau. Ce dispositif s'est révélé essentiel pour l'analyse directionnelle du mouvement des différentes particule. Ces travaux ont montré que les assemblages or silice pouvaient se déplacer de manière autonome vers une source d'H₂O₂, ce qui pourrait les rendre efficaces pour cibler les sites de contamination radioactives. Nous avons également montré que des assemblages isotropes, plus simples à préparer, pouvaient également présenter un mouvement directionnel
Traditional methods of decontamination face significant challenges, such as difficulty in accessing complex or confined spaces, high amount of waste, etc. There is still a need for the development of new methods to reach complex geometries with effective decontamination processes. While macro-robots have been useful in large-scale decontamination tasks, their size limits their ability to navigate in intricate environments. Micro or nano robots, on the other hand, can traverse small, complex spaces and target specific contamination sites, making them more suitable for detailed decontamination work. In this context, this thesis studies the capacities of micro/nanoparticles to move towards contaminated spot in complex geometries, by mimicing the chemotaxism guided by H₂O₂ (product of water radiolysis). To this end, the large-scale synthesis and mobility of active colloids, in particular Janus particles is described. A set of different assemblies of gold particles on silica (isotropic or Janus assembly, discrete nanoparticles or continuous gold layer) were prepared, characterized and compared. Their movements were monitored in different environments. A key part of this work was the developement of a microfluidic device capable of generating stable hydrogen peroxide gradients. This device was essential to study the directionnal orientation of the different particles. This work showed that silica-gold assemblies could move autonomously towards a source of H₂O₂, which could make them effective for targeting radioactive contamination sites. We have also shown that isotropic assemblies, which are simpler to prepare, can also exhibit directional movement

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2

Wang, Xiaolu. "Janus Colloids Surfing at the Surface of Water". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS272/document.

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Considérant une particule isolée, la différence principale entre un colloïde actif et un colloïde passif réside dans le temps de persistance du régime balistique. La transition du régime balistique vers le régime diffusif est déterminée dans les deux cas par des coefficients de friction ou de manière équivalente par des coefficients de diffusion. Le mouvement d’une particule colloïdale passive micrométrique est diffusif lorsqu’il est observé sur des intervalles de temps d’au moins une microseconde, suffisamment longs pour que la direction de la quantité de mouvement soit rendue aléatoire par des collisions avec les molécules de solvant. A l’échelle macroscopique ces collisions se traduisent par un coefficient de friction de translation. Pour une particule colloïdale active, un mouvement diffusif est observé pour des intervalles de temps de plusieurs secondes, suffisamment longs pour que la direction d’auto-propulsion soit rendue aléatoire par la diffusion rotationnelle de la particule.Dans cette thèse, nous étudions le mouvement d’une particule colloïdale active déposée à la surface de l’eau. Des particules Janus aux propriétés catalytiques ont été préparées par dépôt de platine métal à la surface de particules de silice. La profondeur d’immersion des particules ainsi que leur orientation par rapport à la surface de l’eau ont été caractérisées et discutées en tenant compte des propriétés de mouillage non-uniformes de la surface des particules Janus. Le mouvement de particules isolées en présence de quantités variables d’eau oxygénée utilisée comme source d’énergie, a été enregistré par vidéo-microscopie optique et les trajectoires analysées en termes de déplacement carré moyen et de fonction d’auto-corrélation des vitesses. L’observation de deux types de trajectoires, rectilignes et circulaires, révèle la force effective ainsi que le couple induit par la décomposition catalytique de l’eau oxygénée à la surface de la particule Janus. Le résultat principal de ce travail est que le mouvement des particules actives confinées à l’interface persiste plus longtemps dans le régime balistique que celui de particules actives totalement immergées en solution. Ceci est dû au confinement qui réduit le nombre de degrés de liberté de rotation mais aussi aux conditions de mouillage partiel qui font apparaître des contributions supplémentaires à la friction de rotation
At the single-particle level, the main difference between active colloids and passive ones is the time scale over which the motion crosses over from ballistic to diffusive regime. In both cases, friction coefficients or equivalently diffusion coefficients determine this time scale. For instance, the motion of a passive colloid of 1m radius is diffusive when observed over lag times longer than a microsecond, once the direction of its momentum has been randomized by collisions with solvent molecules. At the macroscopic scale these collisions are accounted for by the translational friction coefficient. For an active colloid the effective diffusive behavior observed over lag times larger than few seconds results from the randomization of the direction of self-propulsion by rotational diffusion. In this thesis we investigated the motion of an active Janus colloid trapped at air-water interface. Spherical catalytic Janus colloids have been prepared through the deposition of platinum metal at the surface of silica particles. Immersion depth of the Janus colloid as well as their orientation with respect to the water surface, has been characterized and interpreted in terms of the non-uniform wetting properties of the Janus particles. The motion of the active Janus colloids in the presence of various concentration of hydrogen peroxide H2O2 as fuel was characterized by video microscopy and the trajectories analyzed through the mean square displacement and the velocity autocorrelation function. The types of trajectories, directional and circular ones that we observed in our experiments, revealed the effective force and torque induced by the catalytic decomposition of H2O2. At the water surface, active colloids perform more persistent directional motions as compared to the motions performed in the bulk. This has been interpreted as due to the loss of degrees of freedom resulting from the confinement at interface and also to the partial wetting conditions that possibly bring new contributions to the rotational friction at interface

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3

Archer, Richard. "Catalytic self-phoretic active colloids". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19453/.

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Active Janus colloids are nano to micron sized colloids, capable of propelling themselves through fluidic environments. Localised, asymmetric catalytic reactions on the colloidal bodies are used to decompose a dissolved ‘fuel’ to produce motion. Active Janus colloids have been proposed for applications in microfluidic transport. Currently active Janus colloids are restricted in their practical applications due to the randomised nature of their trajectories over time and their low yielding production methods. This thesis is focused on active Janus colloids prepared by physical vapour deposition, which utilise hemispherically coated platinum as a catalyst to decompose aqueous hydrogen peroxide. Many theories and mathematical models have been reported and are discussed in this thesis as to the precise nature of the mechanism of motion. To contribute to this discussion, active colloids were prepared with different surface functionalities on the non-catalytic section of the Janus colloids. The results indicated that the hydrophobicity of the non-catalytic face influenced the propulsive velocity of the active colloid which informs on the relationship between the fluid and the phoretic body. In an effort to produce active colloids with non-random, prescribed trajectories, the symmetry of the catalytically active layer was incrementally broken and found to introduce an additional angular velocity. The magnitude of angular velocity was controllable through production parameters. An alternative, more scalable fabrication method was developed during the course of this work. A solution based fabrication method was found to successfully produce active colloids in high concentrations which were phoretically analogous to those previously fabricated. Finally, an investigation into the effect of the active cap shape and surface coverage was conducted. Significantly, this study found that symmetrically active colloids displayed propulsive behaviour. The suggestion that asymmetry is not required for producing enhanced motion can be used to inform and simplify future fabrication methods.

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Cohen, Jack Andrew. "Active colloids and polymer translocation". Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:e8fd2e5d-f96f-4f75-8be8-fc506155aa0f.

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This thesis considers two areas of research in non-equilibrium soft matter at the mesoscale. In the first part we introduce active colloids in the context of active matter and focus on the particular case of phoretic colloids. The general theory of phoresis is presented along with an expression for the phoretic velocity of a colloid and its rotational diffusion in two and three dimensions. We introduce a model for thermally active colloids that absorb light and emit heat and propel through thermophoresis. Using this model we develop the equations of motion for their collective dynamics and consider excluded volume through a lattice gas formalism. Solutions to the thermoattractive collective dynamics are studied in one dimension analytically and numerically. A few numerical results are presented for the collective dynamics in two dimensions. We simulate an unconfined system of thermally active colloids under directed illumination with simple projection based geometric optics. This system self-organises into a comet-like swarm and exhibits a wide range of non- equilibrium phenomena. In the second part we review the background of polymer translocation, including key experiments, theoretical progress and simulation studies. We present, discuss and use a common model to investigate the potential of patterned nanopores for stochastic sensing and identification of polynucleotides and other heteropolymers. Three pore patterns are characterised in terms of the response of a homopolymer with varying attractive affinity. This is extended to simple periodic block co-polymer heterostructures and a model device is proposed and demonstrated with two stochastic sensing algorithms. We find that mul- tiple sequential measurements of the translocation time is sufficient for identification with high accuracy. Motivated by fluctuating biological channels and the prospect of frequency based selectivity we investigate the response of a homopolymer through a pore that has a time dependent geometry. We show that a time dependent mobility can capture many features of the frequency response.

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Theurkauff, Isaac. "Collective Behavior of active colloids". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10251/document.

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Nous étudions le comportement collectif d'une assemblée de colloïdes Janus, des sphères d'or de 1µm dont une moitié est recouverte de platine. Lorsqu'ils sont immergés dans une solution d'eau oxygénée, ils se déplacent à des vitesses de l'ordre de 5µm/s, contrôlable par la concentration en peroxyde. Individuellement, ces colloïdes suivent une marche aléatoire persistante ; Ils interagissent par effets phorétiques, formant des clusters dynamiques de quelques dizaines de colloïdes. Ces clusters, mobiles, échangent continuellement des colloïdes, se divisent et se fusionnent, formant une phase stationnaire. Nous avons développés ces colloïdes, ainsi qu'un système d'acquisition pour détecter et reconstituer les trajectoires des colloïdes. La taille moyenne des clusters augmente linéairement avec l'activité, définie comme la vitesse moyenne des colloïdes en dehors des clusters. La fonction densité de probabilité de la taille des clusters est une loi de puissance d'exposant -2. Nous quantifions les vitesses de translation et de rotation des clusters. Pour réaliser une étude thermodynamique, nous réalisons des expériences de sédimentation. Une transition est observée, entre une phase peu dense, un gaz parfait, dans lequel on mesure une température effective, et une phase dense à la dynamique hétérogène. L'équation d'état du système est mesurée, et une forme analytique heuristique est proposée
We study the collective behavior of an assembly of Janus Colloids. These are 1µm gold colloids with one half coated in platinum. When immersed in a peroxide bath, they self-propel, owing to diffusiophoresis and electrophoresis, moving at velocities of order 5µm/s. The velocity can be tune by adjusting the amount of peroxide in the bath. At the single particle level, the colloids undergo a persistent random walk. When in denser groups, the colloids interact through chemical and steric effects. The combination of these interactions, with the colloids activity, leads to collective effects. A dynamic cluster phase is observed, the formation of motile clusters of colloids, formed of up to 100 colloids. The clusters are in a stationary state, constantly moving, and exchanging colloids, they are also colliding, merging and breaking apart. We developed both the colloids, whose synthesis is described, and a high-throughput acquisition and analysis system. We measure the positions, and reconstruct the trajectories of thousands of colloids for a few minutes. From the trajectories, we extract statistical observables. We show that the sizes of clusters increases linearly as a function of the activity of the colloids. The probability distribution functions of sizes are power laws. As the density increases, a jamming transition is observed. The dense phase heterogeneous dynamics is characterized. We study the transition from the dense phase to a low density assembly with sedimentation experiments. The low density phase behaves as an ideal gas, allowing the definition of an effective temperature. We measure an equation of state for the system, and propose a heuristic collapse

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Sano, Masaki, Hong-ren Jiang y Daiki Nishiguchi. "Self-organization dynamics of active colloids". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179578.

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Sano, Masaki, Hong-ren Jiang y Daiki Nishiguchi. "Self-organization dynamics of active colloids". Diffusion fundamentals 20 (2013) 17, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13541.

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Semeraro, Enrico Federico. "Interactions effectives et dynamiques en systèmes actifs de colloïdes autopropulsés". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV017/document.

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L’objectif de ce projet était l’étude systématique des interactions, de la microstructure et de la dynamique de suspensions de colloïdes qui imitent les mouvements de systèmes auto-propulsés (actifs), au moyen de techniques de diffusion : diffusion des rayons X aux (ultra) petits angles (USAXS/SAXS) et spectroscopie de corrélation de photons X (XPCS).À la différence des colloïdes passifs conventionnels (particules browniennes), les colloïdes actifs sont des systèmes hors équilibre faits d’objets auto-propulsés. Ces systèmes montrent une dynamique fascinante qui s’apparente aux mouvements de volée d'oiseaux, d’essaim d’insectes, etc.Les micro-organismes mobiles sont des exemples types de colloïdes actifs, notamment certaines variétés de bactéries, ou les colloïdes de type Janus caractérisé par une composition asymétrique de leur surface qui peux engendrer une propulsion, l’auto-diffusiophorèse. Les thèmes principaux de cette thèse sont les interactions inter-particule, les interactions particule-solvant et les dynamiques phorétiques des systèmes actifs.En premier lieu, la structure et la mobilité de la bactérie Escherichia coli ont été étudiées au moyen de SAXS/USAXS . Comme projet secondaire, l’obtention de données couvrant une très large gamme de vecteur de diffusion (q) a permis de dériver un modèle structural multi-échelle de la bactérie, en combinant les caractéristiques de colloïdes (corps cellulaire), de membranes (enveloppe cellulaire) et de polymères (flagelles). Ce modèle a été affiné au moyen de mesures complémentaires de diffusion de neutrons aux petits angles (SANS) sur des suspensions de la bactérie E. coli en variant le contraste externe (remplacement isotopique partielle du solvant) afin d’aboutir à une détermination quantitative de la densité électronique des membranes et des distances entre membranes.Ces bactéries ont ensuite été utilisées comme éléments actifs en mélange avec des colloïdes passifs de silice de taille sub-micrométrique, pour comprendre comment la présence de bactéries actives mobiles affecte les interactions effectives et la dynamique des colloïdes passifs. Des mesures USAXS et XPCS simultanées ont permis de déduire les propriétés statiques et hydrodynamiques de ces colloïdes passifs. Les données suggèrent que les bactéries actives se comportent comme un fluidifiant pour les colloïdes passifs, en réduisant leurs interactions attractives et en augmentant leur dynamique ; réciproquement, ces derniers sont affectés par la solution tampon et par la présence de bactéries augmente la viscosité environnante effective.Enfin, les mouvements phorétiques de colloïdes de silice et de type Janus (silice partiellement recouvert de nickel) suspendus dans un mélange de 3-methylpyridine (3MP) + eau/eau lourde pendant la séparation de phase liquide-liquide ont été investigués par USAXS et XPCS. Les mouvements des colloïdes sont fortement corrélés à la dynamique de la séparation de phase du fait de l’absorption préférentielle de 3MP à la surface de silice. Les colloïdes de silice montrent une dynamique advective avec une diffusion amélioré en direction des microdomaines riches en 3MP, évoquant la dynamique des systèmes auto-propulsés, jusqu’à l’aboutissement de la séparation de phase. Les suspensions de colloïdes de type Janus ont un comportement beaucoup plus complexe, la dynamique étant fortement corrélée aux interactions asymétriques avec le solvant. Cette dynamique est soit augmentée soit supprimée en fonction de la concentration en 3MP qui modifie aussi la micro-structure du système. Au lieu que les colloïdes de silice migrent vers la phase riche en 3MP, les colloïdes de type Janus agissent comme des tensioactifs en se plaçant à l’interface.Cette thèse démontre l’intérêt des techniques de diffusion pour explorer les propriétés des systèmes actifs et examiner leur comportement en thermodynamique hors équilibre afin de compléter les informations obtenues par observations microscopique
This project aimed to systematically investigate the interactions, microstructure and dynamics in suspensions of colloidal particles that mimic active motions, using (Ultra) Small- Angle X-ray Scattering (USAXS/SAXS) and X-ray Photon Correlation Spectroscopy (XPCS). As opposed to the conventional passive colloids (Brownian particles), active colloids are non-equilibrium systems consisting of self-propelled particles that display many fascinating dynamics, such as streaming, swarming, flocking, etc. in appropriate media. Practical examples of active systems are motile microorganisms, such as some species of bacteria, or synthetic Janus colloids – characterized by an asymmetric chemical composition of their surface – that can induce a propulsion mechanisms, like self-diffusiophoresis. The foci of this thesis are on interparticle interactions, particle-medium interactions and the phoretic dynamics in active systems.Firstly, the structure and motility of Escherichia coli bacteria were investigated by combined USAXS and SAXS methods. As an offshoot, the scattering data spanning a broad scattering vector (q)-range permitted the derivation of a multiscale structural model by combining colloidal (cell-body), membrane (cell-envelope) and polymer (flagella) features. This model was further refined by contrast-variation Small Angle Neutron Scattering (SANS) measurements on E. coli suspensions at three match points and the full contrast which allowed the determination of the membrane electron-density and the inter-membrane distances on a quantitative scale.These bacteria were then used as active component in a mixture with micron-sized passive silica colloids, with the aim of investigating how the effective interactions and dynamics of passive colloids are affected by the presence and the motility of active E. coli. Both static and hydrodynamic information were obtained via the simultaneous use of USAXS and XPCS techniques. Data suggested active bacteria act as a fluidizing agent in such systems, reducing attractive interactions and enhancing the dynamics of passive colloids, which, at the same time, are affected by the buffer and more viscous environment due to the bacterial presence.Finally, the phoretic motions of micron-sized silica colloids and half-coated silica/nickel Janus colloids suspended in a mixture of 3-methylpyridine (3MP) and water/heavy water undergoing liquid-liquid phase separation were investigated using USAXS and XPCS. Due to the preferential wetting of 3MP on the silica surface, the motion of the colloids is strongly correlated to the dynamics of phase separation.Silica colloids displayed advective motion with enhanced diffusion toward the 3MP-rich phase reminiscent of self-propelled motion until the phase separation is completed. Suspensions of Janus colloids showed a much richer scenario, where colloid dynamics are strongly influenced by the asymmetric interactions with the solvent. The dynamics of Janus colloids were either enhanced or suppressed depending on the 3MP concentration, which, concurrently, affected the microstructure of the system. As opposed to the partitioning in 3MP-rich phase in the case of silica colloids, Janus particles behave like surfactants at the interface.The thesis demonstrates the ability of studying active systems by means of scattering methods and probe their behaviour in the thermodynamic limit and complement the information derived from direct microscopy observations

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Ibrahim, Yahaya. "Phoretic self-propulsion of chemically active colloids". Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723473.

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Harrer, Christian, Igor Gazuz, Thomas Voigtmann y Matthias Fuchs. "Driven motion of colloids in active microrheology". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-179429.

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Más fuentes

Libros sobre el tema "Colloides actifs"

1

Tung, Clarion K. Studies of Polymers, Active Colloids, and Proteins. [New York, N.Y.?]: [publisher not identified], 2016.

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2

1942-, Pugh Robert J. y Bergström Lennart 1959-, eds. Surface and colloid chemistry in advanced ceramic processing. New York: M. Dekker, 1994.

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Müller, Rainer H. Colloidal carriers for controlled drug delivery and targeting. Boca Raton: CRC Press, 1990.

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F, Tadros Th. Self-organized surfactant structures. Weinheim: Wiley-VCH, 2011.

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1942-, Lindman Björn, Olofsson G, Stenius Per, Aniansson Gunnar 1924-1984 y Scandinavian Symposium on Surface Chemistry (8th : 1984 : Lund, Sweden), eds. Surfactants, adsorption, surface spectroscopy, and disperse systems. Darmstadt: Steinkopff, 1985.

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Müller, Rainer H. Colloidal carriers for controlled drug delivery and targeting: Modification, characterization, and in vivo distribution. Stuttgart: Wissenschaftliche Verlagsgesellschaft, 1991.

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Kim, Derek Doowon. Structure and Property Correlations of Surface-Active Agents in the Control of Colloidal Behavior in Home/Personal Care and Biochemical Systems. [New York, N.Y.?]: [publisher not identified], 2021.

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Meunier, Jacques. Physics of Amphiphilic Layers: Proceedings of the Workshop, Les Houches, France February 10-19, 1987. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987.

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Park, Kinam. Biodegradable hydrogels for drug delivery. Lancaster, PA: Technomic Pub., 1993.

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K, Poon W. C., Andelman D. 1955- y Scottish Universities Summer School in Physics (59th : 2004 : Edinburgh, Scotland), eds. Soft condensed matter physics in molecular and cell biology. New York: Taylor & Francis, 2006.

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Capítulos de libros sobre el tema "Colloides actifs"

1

Pismen, Len. "Active Colloids". En Active Matter Within and Around Us, 43–64. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-68421-1_3.

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Ostinato, Mattia, Antonio Ortiz-Ambriz y Pietro Tierno. "The Synchronous to Exchange Transition in Magnetically Driven Colloidal Dimers". En Topics in Applied Physics, 69–80. Cham: Springer International Publishing, 2024. http://dx.doi.org/10.1007/978-3-031-58376-6_7.

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AbstractNumerical simulations are used to investigate the collective dynamics of an ensemble of driven paramagnetic colloidal particles confined between two plates. The particles are subjected to an external precessing field and, depending on the field frequency and cell thickness, they can assemble into rotating dimers, up and down binary crystals or dynamic states characterized by particle exchange between nearest dimers. We characterize the transition between the synchronous and the exchange state by measuring the fraction of “active” particles, namely colloids that do not stroboscopically recover their original place in a Voronoi cell. We find that the relaxation time decreases algebraically with the reduced frequency and that the transition displays signatures of an absorbing phase transition.

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Mestre, Francesc Sagués. "Emerging Concepts in Active Matter". En Colloidal Active Matter, 115–38. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-5.

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Mestre, Francesc Sagués. "Modeling Active Fluids". En Colloidal Active Matter, 139–86. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-6.

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Mestre, Francesc Sagués. "Concepts and Models for Dry Active Matter". En Colloidal Active Matter, 187–206. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-7.

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Mestre, Francesc Sagués. "Particle-based Active Systems". En Colloidal Active Matter, 23–70. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-3.

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Mestre, Francesc Sagués. "Fundamental Concepts: Isotropic and Anisotropic Colloidal Suspensions". En Colloidal Active Matter, 3–22. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-2.

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Mestre, Francesc Sagués. "Introduction". En Colloidal Active Matter, 1–2. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-1.

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Mestre, Francesc Sagués. "Protein-based Active Fluids". En Colloidal Active Matter, 71–114. Boca Raton: CRC Press, 2022. http://dx.doi.org/10.1201/9781003302292-4.

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Borzenkov, Mykola y Orest Hevus. "Colloidal Properties of Surface Active Monomers". En SpringerBriefs in Materials, 23–37. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08446-6_2.

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Actas de conferencias sobre el tema "Colloides actifs"

1

Aydin, Koray. "Colloidal crystal engineering for programmable and stimuli-responsive optical metasurfaces and metamaterials". En Active Photonic Platforms (APP) 2024, editado por Ganapathi S. Subramania y Stavroula Foteinopoulou, 81. SPIE, 2024. http://dx.doi.org/10.1117/12.3028200.

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Lhuillier, Emmanuel, Tung Hu Dang, Adrien Khalili, David Darson, Pierre Potet y Angela Vasanelli. "Nanophotonics applied to the design of nanocrystal based infrared sensor". En CLEO: Applications and Technology, JM4D.3. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/cleo_at.2024.jm4d.3.

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It's fascinating to witness the significant progress achieved in leveraging colloidal nanocrystals as a viable platform for infrared optoelectronics. Their adaptability as a spin-coatable resist with infrared photoactive properties has spurred developments that transcend mere material advancements and delve deeply into advanced device design. A standout accomplishment in the infrared domain is the development of infrared cameras utilizing nanocrystal thin films as their active layers. This marks a paradigm shift in infrared imaging, challenging the long-held focus on high-quality monocrystalline thin films. The emergence of nanocrystal films, despite being highly polycrystalline, enables the fabrication of cost-effective sensors that are beginning to rival established technologies like InGaAs, especially in the short-wave infrared.Among potential materials, HgTe1 stands out as the most versatile platform, capable of spanning the entire infrared spectrum from visible wavelengths for the most confined forms to THz2 frequencies for bulk-like particles. In this presentation, I will begin by reviewing recent advancements in transitioning HgTe nanocrystal films from single-pixel sensors to high-quality imagers34.However, achieving such imagers marks just the beginning of the journey. One key challenge revolves around the interaction between light and matter. The polycrystalline nature, while enabling cost-effective sensors, does come with a trade-off – reduced mobility compared to bulk films, limiting the efficiency of charge collection. Therefore, introducing processes to focus light on a film thickness within which transport remains efficient becomes critical. In the latter part of the presentation, I will demonstrate how the incorporation of nanophotonic structures can introduce new functionalities such as actively reconfigurable spectral responses5 and the extension of the device's spectral response into the mid-infrared range.The broad spectral tunability of HgTe nanocrystals also positions them favorably for thermal imaging. However, in this spectral range, the entire device architecture needs a reevaluation compared to visible wavelengths. Notably, the transparent conductive oxide layers typically used as electrodes exhibit weak transmission characteristics, necessitating alternative designs for transparent and conductive electrodes. Here, I will illustrate how the utilization of exalted transmission effects can enhance the design of high-performance mid-infrared sensors.6Schematic illustrating transformation of nanocrystal solution into an infrared focal plane array and finally exemple of image obtained with the imager

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Callegari, Agnese, Alessandro Magazzù, Andrea Gambassi y Giovanni Volpe. "Optical Trapping and Critical Casimir Forces". En Optical Manipulation and Its Applications. Washington, D.C.: Optica Publishing Group, 2023. http://dx.doi.org/10.1364/oma.2023.am4d.4.

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Critical Casimir forces between colloidal particles act at distances reaching often hundreds of nanometers. Keeping colloids at such distances is a major experimental challenge. Here, we review how optical tweezers help quantitatively in studying critical Casimir forces acting on particles in suspensions.

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Toga, Shinji y Takatsune Narumi. "Flow Induced Crystallization of Colloidal Dispersion". En ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-14021.

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In this study, we have examined a crystallization effect of colloidal dispersion induced by the various elongational flows. Extremely strong electrostatic repulsion makes a crystal structure called ‘colloid crystal’. A colloid crystal has hundreds of nano-meters in grating scale and it reflects the visible light due to the Bragg diffraction. It has the potential to become different photonic devices such as an inexpensive photonic device and a planar laser source, but it requires the evolution of the process of making a single-crystal with external stimulus. The methods using flow operation described in this study are expected to the crystallization action of a colloidal dispersion. In the experiment, 2 types of the flow have been examined. The flows have a contraction or an expansion part between two parallel plates separated by 0.1 mm gap and it cause deformations of a contraction or an extension for the colloid. We have evaluated the crystallization effects by a spectroscopic observation of visible-lights reflection on the flow region. As a result, while expansion flows have no crystallization effect, contraction flows have shown it.

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Mehdi, Muhammad Muntazir, Muhammad Zakir, Paulina Taba y S. Rida Zahra Naqvi. "Evaporation of drops containing active colloids". En PROCEEDINGS OF 5TH INTERNATIONAL CONFERENCE ON SUSTAINABLE INNOVATION IN ENGINEERING AND TECHNOLOGY 2023, 020002. AIP Publishing, 2024. http://dx.doi.org/10.1063/5.0164468.

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Kakadjian, Sarkis, Jarrett Kitchen, Amanda Flowers, John Vu, Amanuel Gebrekirstos y Otman Algadi. "Successfully Optimizing Breakers in Polyacrylamides for Slickwater and High-Viscosity Fluids". En SPE Annual Technical Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/206279-ms.

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Abstract Polyacrylamide-based friction reducers (FR's) - including viscosifying polyacrylamides, which are designed to decrease proppant settling by increasing molecular weight and/or active material in the FR - are used extensively in high-rate fracture stimulations. However, because polyacrylamides are difficult to break, there have been concerns about how these materials impact fracture conductivity and formation permeability. This study presents the effect of conventional and novel oxidative breakers over the viscosity and colloidal size distribution of the broken polymers. Breakers tested include conventional persulfates, perborates and patent pending peroxides, all of which generate free radicals to degrade partially hydrolyzed polyacrylamides (PHPAs). Breakers were tested at bottomhole temperatures encountered in the Permian, Bakken, Haynesville and Eagle Ford. Changes to PHPA viscosity were determined using vibrational viscometers. Size distributions and percentage of the broken colloidal PHPA were determined by dynamic light scattering. This method can measure sizes down to 0.6 nanometers, which is within the range of even the smallest pore-throat sizes in shales. Light scattering revealed surprising anomalies in breaker performance. When aged at temperatures typical of the Permian, each of the tested breakers at each of the varied concentrations caused similar levels of viscosity reduction but different size distributions. Some breakers had the unwanted effect of narrowing the colloidal size fractions to the lower end of the spectrum. At these small sizes, colloids are more likely to overlap with segments of the pore throat distribution in some shales, which could inhibit production. In addition, when the FR was aged at the higher temperatures encountered in the Bakken, Eagle Ford and Haynesville, some breakers were not able to uniformly break the PHPA. In these cases, FR's without breakers delivered superior performance. The results clearly demonstrate that breakers may not always have the desired effect of increasing the formation's permeability. In fact, depending on the type of breaker and the concentration, they can often have detrimental effects that ultimately hinder production.

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Kays, Joshua y Allison M. Dennis. "Development of a biodegradable and non-toxic near infrared optically active quantum dot (Conference Presentation)". En Colloidal Nanoparticles for Biomedical Applications XV, editado por Marek Osiński y Antonios G. Kanaras. SPIE, 2020. http://dx.doi.org/10.1117/12.2545020.

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Zhou, Xuemao. "Identifying the Orientation of Active Janus Colloids in Dilute Limit". En 2023 2nd International Conference on Futuristic Technologies (INCOFT). IEEE, 2023. http://dx.doi.org/10.1109/incoft60753.2023.10425399.

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Ghosh, Ambarish y Souvik Ghosh. "Strategies for active colloidal manipulation with plasmonic tweezers (Conference Presentation)". En Optical Trapping and Optical Micromanipulation XVI, editado por Kishan Dholakia y Gabriel C. Spalding. SPIE, 2019. http://dx.doi.org/10.1117/12.2529415.

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Schmidt, Falko, Benno Liebchen, Hartmut Löwen y Giovanni Volpe. "Light-driven Assembly and Optical Manipulation of Active Colloidal Molecules". En Optical Manipulation and Its Applications. Washington, D.C.: OSA, 2019. http://dx.doi.org/10.1364/oma.2019.at1e.4.

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