Bibliographies thématiques / Surfactant aggregate

Littérature scientifique sur le sujet « Surfactant aggregate »

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Publié le 18 mai 2024

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Articles de revues sur le sujet "Surfactant aggregate"

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Veldhuizen, R. A., S. A. Hearn, J. F. Lewis et F. Possmayer. « Surface-area cycling of different surfactant preparations : SP-A and SP-B are essential for large-aggregate integrity ». Biochemical Journal 300, no 2 (1 juin 1994) : 519–24. http://dx.doi.org/10.1042/bj3000519.

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Surface-area cycling is an in vitro procedure for the conversion of large into small surfactant aggregates. In this procedure a tube containing a surfactant suspension is rotated end-over-end at 37 degrees C so that the surface area of the suspension changes twice each cycle. We have utilized this method to study the mechanisms involved in aggregate conversion. Several different surfactant preparations were analysed: (1) bovine natural surfactant, a sucrose-gradient-purified material containing surfactant phospholipid and surfactant-associated proteins (SP-) SP-A, SP-B and SP-C; (2) bovine lipid-extract surfactant, which contains the surfactant phospholipids and SP-B and SP-C; (3) mixtures of dipalmitoyl phosphatidylcholine and phosphatidylglycerol (7:3, w/w) reconstituted with one or more surfactant proteins. Aggregate conversion was measured by phosphorus analysis of a 40,000 g supernatant (small aggregate) and pellet (large aggregates) before and after surface-area cycling. Surface-area cycling of lipid extract surfactant or lipids plus SP-B or SP-C resulted in rapid aggregate conversion. Lipids alone were not converted. Only a small percentage of purified natural surfactant was converted into small aggregates. Addition of SP-A to lipid extract surfactant could inhibit aggregate conversion of this material, but this was only observed when an additional 1% (w/w) of SP-B was added to the lipid extract. It is concluded that SP-A is important for large-aggregate integrity. It appears that SP-A acts in conjunction with SP-B. The presence of SP-B and/or SP-C is required for aggregate conversion; it is proposed that this reflects the necessity for lipid adsorption in aggregate conversion.
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Veldhuizen, R. A., J. Marcou, L. J. Yao, L. McCaig, Y. Ito et J. F. Lewis. « Alveolar surfactant aggregate conversion in ventilated normal and injured rabbits ». American Journal of Physiology-Lung Cellular and Molecular Physiology 270, no 1 (1 janvier 1996) : L152—L158. http://dx.doi.org/10.1152/ajplung.1996.270.1.l152.

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Alveolar surfactant can be separated into two subtypes; large aggregates and small aggregates. Large aggregates represent the surface active form of surfactant and are the metabolic precursors of small aggregates. Previous studies examined the mechanism by which large aggregates are converted into small aggregates in vitro. We used intratracheal injection of radiolabeled large aggregates in rabbits to probe the aggregate conversion in vivo. After this injection, animals were mechanically ventilated for 60 min. After the animals were killed, the lungs were lavaged, and the percentage of radiolabel present in the small aggregate fraction was determined. Our results showed that ventilation resulted in aggregate conversion and that increases in tidal volume, but not in respiratory rate, correlated with increased conversion. Aggregate conversion in rabbits with acute lung injury correlated significantly with severity of injury. We conclude that a change in surface area (i.e., respiration) is necessary for aggregate conversion in vivo and that the ventilation strategy can affect this conversion. Furthermore, increased aggregate conversion in injured lungs might contribute to increased small-to-large aggregate ratios in these lungs compared with normal lungs.
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Paul, Nawal K., Tyler Mercer, Hussein Al-Mughaid, D. Gerrard Marangoni, Michael J. McAlduff, Kulbir Singh et T. Bruce Grindley. « Synthesis and properties of multiheaded and multitailed surfactants based on tripentaerythritol ». Canadian Journal of Chemistry 93, no 5 (mai 2015) : 502–8. http://dx.doi.org/10.1139/cjc-2014-0342.

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The surface and self-assembly properties of a family of multiheaded, multitailed surfactants based on a tripentaerythritol backbone are described. Critical aggregation concentrations of these unusual surfactant systems have been determined from surface tension measurements; aggregate sizes in the presence and absence of a small amount of added electrolyte have been obtained via dynamic light scattering, and the morphologies of the aggregates were examined from electron microscopy measurements. In general, when compared to conventional ionic and two-headed surfactants (and other recently synthesized pentaerythritol derived surfactants from this group), these multiheaded surfactants exhibited some unusual trends in their aggregation behaviour and interesting aggregate structures in aqueous solution, as a function of alkyl chain length.
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Chavez-Martinez, E. H., E. Cedillo-Cruz et H. Dominguez. « Adsorption of metallic ions from aqueous solution on surfactant aggregates : a molecular dynamics study ». Condensed Matter Physics 24, no 2 (2021) : 23601. http://dx.doi.org/10.5488/cmp.24.23601.

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Metallic ion adsorption on surfactant aggregates were studied with Molecular dynamics simulations. Using ionic salts, such as lead sulfate (PbSO4) and aluminum sulfate [Al2(SO4)3], adsorption of lead and aluminum were investigated at different salt concentrations and different surfactant aggregates (micelles) sizes. The micelles were constructed with spherical shapes composed of sodium dodecyl sulfate (SDS) anionic surfactants. The electrostatic interactions between the positive ions and the negative SDS headgroups promote capture of the metal particles on the aggregate surface. Metal adsorption was analyzed in terms of radial density profiles, partial pair distribution functions and adsorption isotherms. It is showed that SDS micelles adsorb better lead than aluminum ions regardless of the size of the aggregates and salt concentrations.
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Ikegami, Machiko, Thomas R. Korfhagen, Jeffrey A. Whitsett, Michael D. Bruno, Susan E. Wert, Kazuko Wada et Alan H. Jobe. « Characteristics of surfactant from SP-A-deficient mice ». American Journal of Physiology-Lung Cellular and Molecular Physiology 275, no 2 (1 août 1998) : L247—L254. http://dx.doi.org/10.1152/ajplung.1998.275.2.l247.

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Mice that are surfactant protein (SP) A deficient [SP-A(−/−)] have no apparent abnormalities in lung function. To understand the contributions of SP-A to surfactant, the biophysical properties and functional characteristics of surfactant from normal [SP-A(+/+)] and SP-A(−/−) mice were evaluated. SP-A-deficient surfactant had a lower buoyant density, a lower percentage of large-aggregate forms, an increased rate of conversion from large-aggregate to small-aggregate forms with surface area cycling, increased sensitivity to inhibition of minimum surface tension by plasma protein, and no tubular myelin by electron microscopy. Nevertheless, large-aggregate surfactants from SP-A(−/−) and SP-A(+/+) mice had similar adsorption rates and improved the lung volume of surfactant-deficient preterm rabbits similarly. Pulmonary edema and death caused by N-nitroso- N-methylurethane-induced lung injury were not different in SP-A(−/−) and SP-A(+/+) mice. The clearance of125I-labeled SP-A from lungs of SP-A(−/−) mice was slightly slower than from SP-A(+/+) mice. Although the absence of SP-A changed the structure and in vitro properties of surfactant, the in vivo function of surfactant in SP-A(−/−) mice was not changed under the conditions of these experiments.
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Veldhuizen, R. A., Y. Ito, J. Marcou, L. J. Yao, L. McCaig et J. F. Lewis. « Effects of lung injury on pulmonary surfactant aggregate conversion in vivo and in vitro ». American Journal of Physiology-Lung Cellular and Molecular Physiology 272, no 5 (1 mai 1997) : L872—L878. http://dx.doi.org/10.1152/ajplung.1997.272.5.l872.

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Within the alveolar space pulmonary surfactant is converted from the surface active large aggregates (LA) to the inactive small aggregates (SA). This conversion is affected by a change in surface area, lung injury, breathing pattern, and protease activity. This study examined the effect of N-nitroso-N-methylurethane-induced acute lung injury on aggregate conversion in mechanically ventilated and spontaneously breathing rabbits. Both the in vitro surface area cycling techniques and the in vivo technique of intratracheally injecting radiolabeled LA were used for analyzing aggregate conversion. Mechanical ventilation of injured lungs resulted in increased aggregate conversion and increased surfactant aggregate ratios compared with controls. Spontaneously breathing injured animals had aggregate conversion and aggregate ratios that were not significantly different from controls. In vitro aggregate conversion was slower for LA obtained from injured animals compared with normal animals. We conclude that the mechanical stress of mechanical ventilation results in increased aggregate conversion and aggregate ratios. Furthermore, in vitro conversion of isolated LA does not necessarily reflect the conversion of aggregates within the alveoli.
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Madsen, Jens, Gunna Christiansen, Lise Giehm et Daniel Otzen. « Release of Pharmaceutical Peptides in an Aggregated State : Using Fibrillar Polymorphism to Modulate Release Levels ». Colloids and Interfaces 3, no 1 (26 mars 2019) : 42. http://dx.doi.org/10.3390/colloids3010042.

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Traditional approaches to achieve sustained delivery of pharmaceutical peptides traditionally use co-excipients (e.g., microspheres and hydrogels). Here, we investigate the release of an amyloidogenic glucagon analogue (3474) from an aggregated state and the influence of surfactants on this process. The formulation of peptide 3474 in dodecyl maltoside (DDM), rhamnolipid (RL), and sophorolipid (SL) led to faster fibrillation. When the aggregates were subjected to multiple cycles of release by repeated resuspension in fresh buffer, the kinetics of the release of soluble peptide 3474 from different surfactant aggregates all followed a simple exponential decay fit, with half-lives of 5–18 min and relatively constant levels of release in each cycle. However, different amounts of peptide are released from different aggregates, ranging from 0.015 mg/mL (3475-buffer) up to 0.03 mg/mL (3474-DDM), with 3474-buffer and 3474-RL in between. In addition to higher release levels, 3474-DDM aggregates showed a different amyloid FTIR structure, compared to 3474-RL and 3474-SL aggregates and a faster rate of degradation by proteinase K. This demonstrates that the stability of organized peptide aggregates can be modulated to achieve differences in release of soluble peptides, thus coupling aggregate polymorphism to differential release profiles. We achieved aggregate polymorphism by the addition of different surfactants, but polymorphism may also be reached through other approaches, including different excipients as well as changes in pH and salinity, providing a versatile handle to control release profiles.
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Veldhuizen, R. A. W., K. Inchley, S. A. Hearn, J. F. Lewis et F. Possmayer. « Degradation of surfactant-associated protein B (SP-B) during in vitro conversion of large to small surfactant aggregates ». Biochemical Journal 295, no 1 (1 octobre 1993) : 141–47. http://dx.doi.org/10.1042/bj2950141.

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Pulmonary surfactant obtained from lung lavages can be separated by differential centrifugation into two distinct subfractions known as large surfactant aggregates and small surfactant aggregates. The large-aggregate fraction is the precursor of the small-aggregate fraction. The ratio of the small non-surface-active to large surface-active surfactant aggregates increases after birth and in several types of lung injury. We have utilized an in vitro system, surface area cycling, to study the conversion of large into small aggregates. Small aggregates generated by surface area cycling were separated from large aggregates by centrifugation at 40,000 g for 15 min rather than by the normal sucrose gradient centrifugation. This new separation method was validated by morphological studies. Surface-tension-reducing activity of total surfactant extracts, as measured with a pulsating-bubble surfactometer, was impaired after surface area cycling. This impairment was related to the generation of small aggregates. Immunoblot analysis of large and small aggregates separated by sucrose gradient centrifugation revealed the presence of detectable amounts of surfactant-associated protein B (SP-B) in large aggregates but not in small aggregates. SP-A was detectable in both large and small aggregates. PAGE of cycled and non-cycled surfactant showed a reduction in SP-B after surface area cycling. We conclude that SP-B is degraded during the formation of small aggregates in vitro and that a change in surface area appears to be necessary for exposing SP-B to protease activity.
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Liu, Z., D. A. Edwards et R. G. Luthy. « Nonionic Surfactant Sorption onto Soil ». Water Science and Technology 26, no 9-11 (1 novembre 1992) : 2337–40. http://dx.doi.org/10.2166/wst.1992.0731.

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Experiments in batch soil/aqueous systems were conducted to evaluate the sorption onto soil of four nonionic surfactants. At bulk solution surfactant concentration less than the respective critical micelle (aggregate) concentration (CMC or CAC), sorption can be assessed using a surface tension technique and can be characterized with a Freundlich isotherm. At bulk solution surfactant concentrations equal to or greater than the critical concentration, sorption of the micelle-forming surfactants can be assessed by a spectrophotometric technique with an azo dye and had a constant value; sorption of the lamellae-forming surfactant can be assessed by a chemical oxidation technique and, however, appeared to be an increasing function of the surfactant dose.
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VELDHUIZEN, Ruud A. W., Li-Juan YAO, Stephen A. HEARN, Fred POSSMAYER et James F. LEWIS. « Surfactant-associated protein A is important for maintaining surfactant large-aggregate forms during surface-area cycling ». Biochemical Journal 313, no 3 (1 février 1996) : 835–40. http://dx.doi.org/10.1042/bj3130835.

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Alveolar surfactant can be separated into two major subfractions, the large surfactant aggregates (LAs) and the small surfactant aggregates (SAs). The surface-active LAs are the metabolic precursors of the inactive SAs. This conversion of LAs into SAs can be studied in vitro using a technique called surface-area cycling. We have utilized this technique to examine the effect of trypsin on aggregate conversion. Our results show that trypsin increases the conversion of LAs into SAs in a concentration- and time-dependent manner. Immunoblot analysis revealed that surfactant-associated Protein A (SP-A) was the main target of trypsin. To examine further the role of SP-A in aggregate conversion, we tested the effect of Ca2+ and mannan on this process. The absence of Ca2+ (1 mM EDTA) and the presence of mannan both increased the formation of SAs. Electron microscopy revealed that highly organized multilamellar and tubular myelin structures were present in samples that converted slowly to SAs. We concluded that SP-A is important for maintaining LA forms during surface-area cycling by stabilizing tubular myelin and multilamellar structures.
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Thèses sur le sujet "Surfactant aggregate"

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Mrinmay, Jha. « Physico-chemical studies on soft matter : behaviour of surfactant aggregate and biodegradable polymer systems ». Thesis, University of North Bengal, 2015. http://ir.nbu.ac.in/handle/123456789/1526.

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Mousseau, Fanny. « Le surfactant pulmonaire, une barrière déterminante de la réponse des cellules à l'exposition aux nanoparticules ». Thesis, Sorbonne Paris Cité, 2017. http://www.theses.fr/2017USPCC125/document.

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Les particules fines émises par l'activité humaine sont la cause de diverses pathologies pulmonaires et cardiaques. Les particules de taille inférieure à 100 nm, appelées nanoparticules, sont particulièrement nocives car une fois inhalées, elles peuvent atteindre les alvéoles pulmonaires, lieux des échanges gazeux. Dans les alvéoles, les nanoparticules entrent d'abord en contact avec le surfactant pulmonaire. Ce fluide biologique tapisse les cellules épithéliales des alvéoles sur une épaisseur de quelques centaines de nanomètres et est composé de phospholipides et de protéines, les phospholipides étant assemblés sous forme de vésicules et corps multi-lamellaires. Dans ce travail, nous avons sélectionné des nanoparticules modèles de nature différente connues pour leur toxicité cellulaire (latex, oxydes métalliques, silice). Leur interaction avec un fluide pulmonaire mimétique administré aux prématurés (Curosurf®) a été étudiée en détail par microscopie optique et électronique, et par diffusion de la lumière. Nous avons mis en évidence que cette interaction est non spécifique et d'origine électrostatique. La diversité des structures hybrides obtenues entre particules et vésicules témoigne cependant de la complexité de cette interaction. En contrôlant cette interaction, nous avons formulé des particules couvertes d’une bicouche supportée de Curosurf® qui possèdent des propriétés remarquables de stabilité et de furtivité en milieu biologique.Dans une seconde partie, nous avons étudié le rôle du surfactant pulmonaire sur l’interaction entre particules et cellules épithéliales alvéolaires (A459). A l'aide d'expériences de biologie cellulaire réalisées in vitro, nous avons observé que la présence de surfactant diminue de manière significative le nombre de particules internalisées par les cellules. Dans le même temps, nous avons constaté une augmentation importante de la viabilité cellulaire. Une conclusion majeure de notre travail concerne la mise en évidence du rôle protecteur joué par le surfactant pulmonaire dans les mécanismes d'interaction des nanoparticules avec l'épithélium alvéolaire
Particulate matter emitted by human activity are the cause of various pulmonary and cardiac diseases. After inhalation, nanoparticles (ie particles smaller than 100 nm) can reach the pulmonary alveoli, where the gas exchanges take place. In the alveoli, the nanoparticles first encounter the pulmonary surfactant which is the fluid that lines the epithelial cells. Of a few hundreds of nanometers in thickness, the pulmonary fluid is composed of phospholipids and proteins, the phospholipids being assembled in multilamellar vesicles. In this work, we considered model nanoparticles of different nature (latex, metal oxides, silica). Their interaction with a mimetic pulmonary fluid administered to premature infants (Curosurf®) was studied by light scattering and by optical and electron microscopy. We have shown that the interaction is non-specific and mainly of electrostatic origin. The wide variety of hybrid structures found in this work attests however of the complexity of the phospholipid/particle interaction. In addition, we succeeded in formulating particles covered with a Curosurf® supported bilayer. These particles exhibit remarkable stability and stealthiness in biological environment. In a second part, we studied the role of the pulmonary surfactant on the interactions between nanoparticles and alveolar epithelial cells (A459). With cellular biology assays, we observed that the number of internalized particles decreases dramatically in presence of surfactant. At the same time, we found a significant increase in the A459 cell viability. Our study shows the importance of the pulmonary surfactant in protecting the alveolar epithelium in case of nanoparticle exposure
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Kjellin, Mikael. « Structure-Property Relationships of Surfactants at Interfaces and Polyelectrolyte-Surfactant Aggregates ». Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3299.

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The first part of this thesis is concerned with thestructure-property relationships in nonionic surfactantsystems. The main aim was to investigate how the surfactantstructure influences the adsorption at interfaces andinteractions between surfactant coated interfaces.Particularly, the effect of the structure of the surfactantheadgroups was investigated. These were sugar-based headgroupwith varying size and flexibility and poly(ethylene oxide)based headgroups with or without an additional amide or estergroup. The hydrophobic part of the surfactant consisted mostlyof straight alkyl chains, except for one type of poly(ethyleneoxide) based surfactant with a dehydroabietic hydrophobe.

The main technique that was used is the surface forcetechnique, with which the forces acting between two adsorbedsurfactant layers on hydrophilic or hydrophobic surfaces can bemeasured. These forces are important for e.g. the stability ofdispersions. The hydrophilic surfaces employed were glass andmica, whereas the hydrophobic surfaces were silanized glass andhydrophobized mica. The adsorption behavior on hydrophilicsurfaces is highly dependent on the type of headgroup andsurface, whereas similar results were obtained on the two typesof hydrophobic surfaces. To better understand how the surfaceforces are affected by the surfactant structure, measurementsof adsorbed amount and theoretical mean-field latticecalculations were carried out. The results show that the sugarsurfactant layers and poly(ethylene oxide) surfactant layersgive rise to very different surface forces, but that the forcesare more similar within each group. The structure-propertyrelationships for many other physical properties have beenstudied as well. These include equilibrium and dynamicadsorption at the liquid-vapor interface, micelle size, micelledynamics, and wetting.

The second part in this thesis is about the aggregationbetween cationic polyelectrolytes and an anionic surfactant.The surface force technique was used to study the adsorption ofa low charged cationic polyelectrolyte on mica, and theaggregation between the adsorbed polyelectrolyte with theanionic surfactant. The aggregation in bulk was studied withturbidimetry, small angle neutron scattering (SANS), and smallangle x-ray scattering (SAXS). An internal hexagonal aggregatestructure was found for some of the bulk aggregates.

Keywords:nonionic surfactant, sugar surfactant,poly(ethylene oxide), amide, ester, polyelectrolyte, SDS,hydrophobic surface, glass surface, mica, adsorption,aggregation, micelle size, surface forces, wetting, dynamicsurface tension, NMR, TRFQ, SANS, SAXS, mean-field latticecalculations.

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Renoncourt, Audrey. « Study of supra-aggregates in catanionic surfactant systems ». [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976351714.

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Singh, Pankaj Kumar. « Dispersion of nanoparticulate suspensions using self-assembled surfactant aggregates ». [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001182.

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Voisin, David. « Polyelectrolyte surfactant aggregates and their deposition on macroscopic surfaces ». Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251089.

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Lam, Viet Duy. « Structure of Rod-like Polyelectrolyte-Surfactant Aggregates in Solution and in Adsorbed Layers ». Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/69.

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Polyelectrolyte-surfactant aggregates (PES) have diverse sets of properties, which could be controlled by a wide range of parameters, both within the aggregates themselves and the surrounding environment. The large portfolio of applications amplifies the need to understand them. A particular system of polyelectrolyte-surfactant aggregate, polycetyltrimethyl vinylbenzoate, denoted pC16TVB, which self-assembles in aqueous solution, is the main focus of the thesis. Its structure is the product of the balance between surfactant head groups – polyelectrolyte charge groups electrostatic interactions and surfactant tails – polyelectrolyte backbone hydrophobic interactions. At neutral solution pH, the structure is one of a core-shell cylinder, with the shell consisting of surfactant heads. The surfactant tails point toward the core center, while the polyelectrolyte also resides in the core, but remains close to the core-shell interface for charge neutralization. As the pH drops to 1.0, the balance is disrupted with the hydrophobic interaction being increasingly dominant while electrostatic interaction is reduced, and the structure transforms into a more commonly seen string-of-pearl, in which the polymer chain connects a series of spherical surfactant micelles. The solution properties are impacted accordingly, becoming viscoelastic while solubilizing 10 times more hydrophobic molecules. Treating the pC16TVB aggregate as a whole, its adsorption onto oxide nanoparticles surfaces has been analyzed, extended from a previous flat surface adsorption work. Aided by hydrophobic dyes as molecular trackers, the adsorbed thickness has been proven to be a function of the surface curvature, with less curve surface adsorbs more material. The dye loading remains intact after the adsorption, enabling the use of the aggregate as a delivery vehicle for hydrophobic materials in aqueous solution. The resulting adsorption of pC16TVB aggregate onto SiO2 surfaces has a core-shell sphere structure. Unlike for flat surfaces, in which the adsorption mechanism has been shown previously to consist of two main steps, with some dissociated surfactant molecules adsorbing head first via electrostatic attraction with the surface to create hydrophobic anchor points for further aggregate adsorption, the high bending energy cost and the low aggregate concentration (relative to the total sphere surface area) suspend the adsorption after the initial surfactant adsorption step
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Chagas-Silva, Fatima Aparecida das. « Novos materiais funcionais organo-híbridos baseados em óxidos metálicos e diimidas aromáticas ». Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-10092012-094158/.

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O uso e estudo de materiais híbridos para desenvolver novos materiais com qualidades superiores para aplicações em fotônica, sensores e áreas afins é um desafio para o químico. Neste contexto deve-se especular sobre as propriedades de associação de materiais orgânicos e inorgânicos para alcançar novas e melhores propriedades. Neste estudo, os óxidos metálicos (óxidos de cério em particular), uma classe especial entre nanopartículas inorgânicas, foram selecionados para explorar as suas aplicações com uma classe, também especial de compostos orgânicos, sendo no nosso estudo as Naftaleno Diimidas. Óxido de cério é um semicondutor, com uma “bandgap” larga, conhecido por sua capacidade catalítica e por sua simples manipulação para preparar filmes finos e nanopartículas. Derivados de Naftaleno Diimidas são conhecidos por sua superior atividade eletroquímica comparáveis aos dos Paraquat (metilviologênio), mas com amplitude maior de aplicações fotoquímicas. Foram sintetizadas Naftaleno Diimidas carregados positivamente e negativamente com propriedades surfactantes. Após a caracterização detalhada das Naftaleno Diimidas, incluindo auto-associação e interação com moléculas de surfactantes, a interação com nanopartículas de óxido de cério foram determinadas. As Naftaleno Diimidas interagiram de forma especial com nanopartículas de óxido de cério conferindo ausência de atividade hidrolítica e um comportamento fotocrômico singular. Propõe-se que o corante orgânico se adsorve nas ranhuras das nanopartículas e, além disso forma dímeros estáveis que têm importância para as novas fotoatividades observadas.
The use and study of hybrid materials is a challenge for the chemist to develop materials having new and superior qualities for applications in photonics, sensors and related areas. In this context one has to speculate on the properties of the organic and inorganic partners to achieve better and new properties. In this study the metal oxides (in particular Cerium Oxides), a special class among inorganic nanoparticles were selected to exploit their applications with an also special class of organic compounds the Naphthalene Diimides. Cerium Oxide is a wide bandgap semiconductor well known for its catalytic capabilities and for its simple manipulation to prepare thin films and nanoparticles. Naphthalene Diimides derivatives are known for their superior lectrochemical activities comparable to those of Paraquat (Methyl Viologen) but with larger amplitude of photochemical applications. Positively and negatively charged, surfactant like, Naphthalene Diimides, were synthesized. After detailed characterization of the Naphthalene Diimides including selfassociation and interaction with surfactant molecules, the interaction with Cerium Oxide nanoparticles was determined. Naphthalene Diimides interacted in a special manner with Cerium Oxide nanoparticles rendering hydrolytic inertness and novel photochromic behavior. The organic dye is proposed to adsorb in the crevices of the particles and furthermore forming stable dimers that accounts for the new photoactivities observed
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Li, Yan. « A study of surfactant aggregates (a) in the presence of neutral polymers, and (b) as potential lubricants ». Thesis, University of Salford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244844.

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Shen, Licheng. « Investigation of the removal and recovery of metal cations and anions from dilute aqueous solutions using polymer-surfactant aggregates ». Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:33afa911-3ffb-484e-8db5-b6843928f175.

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Dilute metallic ion treatment (< 10 mg/L) remains a challenge in water purification and resource recovery. A novel and inexpensive treatment process that employs polymer-surfactant aggregates (PSAs) has been developed and applied to remove and recover dilute metallic ions, such as Cr3+, Rh3+, Cd2+, Fe(CN)6 3- and CrO42-, from industrial process and effluent. At the heart of this process is a material that comprises a colloidal structure of polymers and surfactants, named a polymer-surfactant aggregate (PSA), that trap metallic ions. The ion loaded PSAs then coalesce and settle out. The flocs are then treated separately by acid-base wash to recover the ions in a concentrated salt and regenerate the polymer and surfactant. The regenerated polymer and surfactant can then be recycled without a deterioration of removal ability in the next cycle. This process is simple, uses low energy, and generates little material loss or discharge. The thesis is divided into three main parts: fundamentals, cation treatment and anion treatment. First, the mechanism of formation of PSAs and their interactions with metallic ions are investigated using surface tension and electrical conductivity measurements. Both measurements reveal that the PSA is formed by surfactant monomers binding to the oppositely charged polymer chains and forming micelle-like aggregates via hydrophobic and electrostatic forces. These aggregates, like micelles, can bind to the oppositely charged metallic ions, but the surfactant concentration required is a few orders of magnitude lower than that required for micelle formation. The resulting nano-size PSA has a large surface area to volume ratio, and can effectively treat dilute aqueous streams. Each PSA consists of positive and negative charges. Within a near charge neutralisation range, they can quickly self-flocculate to simultaneously remove metallic ions and settle the flocs out of aqueous solutions. Correlating the removal efficiency of ions with surface tension and electrical conductivity measurements, the results suggest that the PSA is indeed responsible for removing the ions from the streams. Based on the fundamentals, a PSA process consisting of three stages (removal, recovery and recycle) is developed to treat metal cations in dilute streams. At the removal stage, polymer and surfactant (i.e. removal agent) are used to form PSAs and trap 99% of 0.1 mM metal ions into flocs. At the recovery stage, a small amount of acid solution is added to leach out 95% of the trapped metal ions into a concentrated salt, and then using a base solution to completely dissolve and regenerate the removal agent. After that, the removal agent are recycled in the next cycle without the need for any make-up, and little deterioration of removal ability is found. The same three-stage process is also applied to recover dilute metallic anions. As the targeted ions are negatively charged, the charge of polymer and surfactant used and the order of acid-base wash are reversed as compared with the cation treatment process. The PSA process is robust under different conditions, e.g. pH, temperature, salinity and organic contaminants. Such a sustainable process thus has potential applications for the efficient removal and recovery of dilute metallic ions during process effluent water treatment.
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Livres sur le sujet "Surfactant aggregate"

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1931-, Christian Sherril Duane, et Scamehorn John F. 1953-, dir. Solubilization in surfactant aggregates. New York : M. Dekker, 1995.

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Aveyard, Bob. Surfactants. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198828600.001.0001.

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Characteristically, surfactants in aqueous solution adsorb at interfaces and form aggregates (micelles of various shapes and sizes, microemulsion droplets, and lyotropic liquid crystalline phases). This book is about the behaviour of surfactants in solution, at interfaces, and in colloidal dispersions. Adsorption at liquid/fluid and solid/liquid interfaces, and ways of characterizing the adsorbed surfactant films, are explained. Surfactant aggregation in systems containing only an aqueous phase and in systems with comparable volumes of water and nonpolar oil are each considered. In the latter case, the surfactant distribution between oil and water and the behaviour of the resulting Winsor systems are central to surfactant science and to an understanding of the formation of emulsions and microemulsions. Surfactant layers on particle or droplet surfaces can confer stability on dispersions including emulsions, foams, and particulate dispersions. The stability is dependent on the surface forces between droplet or particle surfaces and the way in which they change with particle separation. Surface forces are also implicated in wetting processes and thin liquid film formation and stability. The rheology of adsorbed films on liquids and of bulk colloidal dispersions is covered in two chapters. Like surfactant molecules, small solid particles can adsorb at liquid/fluid interfaces and the final two chapters focus on particle adsorption, the behaviour of adsorbed particle films and the stabilization of Pickering emulsions.
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Christian, Sherril D., et John F. Scamehorn. Solubilization in Surfactant Aggregates. Taylor & Francis Group, 2020.

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Solubilization in Surfactant Aggregates. Taylor & Francis Group, 2020.

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Christian, Sherril D., et John F. Scamehorn. Solubilization in Surfactant Aggregates. Taylor & Francis Group, 2019.

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Christian, Sherril D., et John F. Scamehorn. Solubilization in Surfactant Aggregates. Taylor & Francis Group, 2020.

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Christian, Sherril D., et John F. Scamehorn. Solubilization in Surfactant Aggregates. Taylor & Francis Group, 2020.

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Chapitres de livres sur le sujet "Surfactant aggregate"

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Bharti, Bhuvnesh. « Surfactant Adsorption and Aggregate Structure at Silica Nanoparticles ». Dans Adsorption, Aggregation and Structure Formation in Systems of Charged Particles, 47–61. Cham : Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07737-6_4.

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Dong, J., G. Mao et R. M. Hill. « Atomic Force Microscopy Study of Trisiloxane Surfactant Aggregate Structures at the Solid-Liquid Interface ». Dans ACS Symposium Series, 2–16. Washington, DC : American Chemical Society, 2003. http://dx.doi.org/10.1021/bk-2003-0861.ch001.

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Clint, John H. « Dispersions of surfactant aggregates ». Dans Surfactant Aggregation, 173–91. Dordrecht : Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-2272-6_8.

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Kunitake, Toyoki. « Syntheses, Aggregate Morphologies, and Applications of Membrane-Forming Amphiphiles ». Dans Surfactants in Solution, 727–44. Boston, MA : Springer US, 1986. http://dx.doi.org/10.1007/978-1-4615-7981-6_14.

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Rosenholm, J. B., et C. Jolicoeur. « Thermodynamic Analysis of the Breakdown of w/o -Microemulsion Aggregates due to Changes in the Composition of the Solvent ». Dans Surfactants in Solution, 89–101. Boston, MA : Springer US, 1989. http://dx.doi.org/10.1007/978-1-4615-7990-8_4.

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Kunitake, Toyoki. « Structural Relationships between Monomeric Surfactants and Their Aggregates ». Dans Modern Trends of Colloid Science in Chemistry and Biology, 34–54. Basel : Birkhäuser Basel, 1985. http://dx.doi.org/10.1007/978-3-0348-6513-5_2.

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Brackman, Josephine C., et Jan B. F. N. Engberts. « Interactions Between Water-Soluble Nonionic Polymers and Surfactant Aggregates ». Dans ACS Symposium Series, 337–49. Washington, DC : American Chemical Society, 1994. http://dx.doi.org/10.1021/bk-1994-0578.ch024.

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Johansson, Jan. « Harnessing the Self-Assembling Properties of Proteins in Spider Silk and Lung Surfactant ». Dans Amyloid Fibrils and Prefibrillar Aggregates, 455–70. Weinheim, Germany : Wiley-VCH Verlag GmbH & Co. KGaA, 2013. http://dx.doi.org/10.1002/9783527654185.ch21.

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Klyachko, Natalia L., et Andrey V. Levashov. « Surfactant Aggregates as Matrix Nanocontainers for Proteins (Enzymes) Entrapment and Regulation ». Dans ACS Symposium Series, 156–70. Washington, DC : American Chemical Society, 2008. http://dx.doi.org/10.1021/bk-2008-0986.ch009.

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Szönyi, S., A. Cambon, H. J. Watzke, P. Schurtenberger et E. Wehrli. « Multicomponent Vesicular Aggregates (MCVA) : Spontaneous Vesiculation of Perfluorinated Single-Chain Surfactant Mixtures ». Dans Springer Proceedings in Physics, 198–201. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-84763-9_39.

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Actes de conférences sur le sujet "Surfactant aggregate"

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Christesen, Steven D., Stephanie M. Garlick et Fred R. Longo. « Microemulsion Aggregation Numbers Determined by Time-Resolved Luminescence ». Dans Laser Applications to Chemical Analysis. Washington, D.C. : Optica Publishing Group, 1990. http://dx.doi.org/10.1364/laca.1990.wb3.

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The time-resolved luminescence technique developed by Infelta et. al. 1 has been used to measure the aggregation numbers (number of surfactant molecules per aggregate) for microemulsions containing cetyltrimethylammonium bromid (CTAB) and cetyltrimethylammonium chloride (CTAC) as surfactants. Microemulsions are transparent dispersions of two immiscible liquids (e.g. oil and water) stabilized by an emulsifier comprising a surfactant and cosurfactant (Figure 1). The microemulsion aggregates typically have radii of 100-500 Angstroms. Microemulsions are being studied for possible use in decontamination of toxic organophosphorus compounds.
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Coscia, Benjamin, Andrea Browning, Jeffrey Sanders et Mat Halls. « Molecular simulation as a tool for the design of biosurfactant-based cosmetic formulations ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/jdlz5827.

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There is growing consumer-driven demand in the cosmetic industry to replace petroleum-based surfactants with environmentally friendly alternatives. Biologically derived surfactants, or biosurfactants, are a promising class of molecules which may be suitable towards this end. However, separate from challenges in producing these materials which have been increasingly addressed throughout the last decade, formulations built around these new surfactants must perform competitively compared to existing formulations. There are a number of subclasses of biosurfactant molecules and modifications which can be made to those. The cosmetic science community is in need of lucid design principles for reformulating existing products using this set of ingredients. We believe that this presents an optimization challenge which molecular simulation is well-equipped to solve. In this work, we demonstrate how physics-based molecular simulation paired with chemistry-oriented informatics software can aid in the prospective design of new formulations. Simulation trivializes the enumeration of possible formulation compositions, allowing us to systematically study and gain a molecular-level understanding of surfactant aggregates at a variety of conditions. We test aqueous mixtures of four different types of biosurfactants at various concentrations and pH and present our analysis of aggregate size, shape and composition as well as solution properties such as viscosity and diffusivity.
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Marliere, Claire, Vincent Miralles, Claire Morgand, Virginie Rome, Aymerick Le Bris, Chloé Guilloteau, Tiphaine Courtaud et David Rousseau. « Surfactant-Polymer Compatibility in Bulk and Static Conditions vs. Confined and Under Flow Conditions ». Dans SPE Conference at Oman Petroleum & Energy Show. SPE, 2022. http://dx.doi.org/10.2118/200074-ms.

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Abstract The objective of surfactant-polymer (SP) formulation design is to simultaneously achieve ultra-low interfacial tension and good mobility ratio. However, in some cases, the presence of both polymer and surfactant can cause compatibility issues leading to a cloudy or even demixing solution. Until now, those observations were made in bulk conditions but the assessment of this behavior has not been studied in confined and under flow conditions. Three SP compatibility cases were selected using the same SP formulation and playing on the brine salinity (low, medium and high). Bulk and kinetic studies based on solubility, viscosity and cryo-TEM were performed prior to monophasic injections carried out in a transparent micromodel representing a 2D rock porous medium and in a coreflood rig with a 3D outcrop rock. The observation in micromodel was performed using an optical microscope under polarized light to visualize the physical structure of the SP formulations. The pressure drop along the core was monitored during coreflood experiments to measure the mobility reduction entailed by the injected solution. In bulk conditions it is shown that increasing the solution salinity leads, after a few to several days depending on the solution's volume, to a degradation of the SP compatibility or even demixing. This behavior can be attributed to depletion effects. In this case, depletion is due to the formation of surfactant vesicles (hundreds of namometers in size) that tend to aggregate in the presence of polymer molecules. As expected, injection of the compatible SP solution (at low salinity) in the 2D porous medium micromodel and in the outcrop rock led to an easy in-depth transport, namely mobility reduction compatible with the viscosity of the solution. More interestingly, the same formulation at higher salinity exhibited a deposit of SP aggregates having a crystalline structure when injected in the micromodel. However, this formulation at high salinity did not show any issue in terms of mobility reduction when injected in the outcrop rock as the mobility reduction stabilized rapidly at a value close to the relative viscosity of the solution. These results highlight that the presence of a demixing phase does not always induce propagation issues in cores and that some cloudy SP solutions could be injected without causing any pressure increase. The objective of this study was to correlate the bulk behavior of SP formulations showing respectively good and poor compatibilities with their performance in confined and under flow conditions. It has been proved that a poor compatibility in bulk does not always induce transport issues when the solution is injected in porous medium, despite the deposit of structured aggregates in some pores.
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Bello, Ayomikun, Alexander Rodionov, Anastasia Ivanova et Alexey Cheremisin. « Experimental Investigation and Molecular Dynamics of the Fluid-Fluid Interactions Between Binary Surfactant Systems for EOR ». Dans GOTECH. SPE, 2024. http://dx.doi.org/10.2118/219237-ms.

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Abstract This work aims to explore the properties and interactions between binary surfactant systems. We employed a methodology comprising experimental analysis, mathematical modeling, and molecular dynamics simulations. In the experimental study, we examined eight individual surfactants and six binary surfactant systems at various ratios to determine their critical micelle concentrations (CMCs), using reservoir oil and performing experiments at reservoir conditions. Then, Rubingh's Regular Solution Theory (RST) was applied to evaluate interactions within the binary surfactant mixtures. Finally, using molecular dynamics simulations, we characterized the microscopic interactions to comprehend how hydrophilic and hydrophobic parts of the surfactants interact with surrounding media, and how they self-assemble into aggregates such as micelles or bilayers. The key findings of our work showed that the occurrence of synergism or antagonism in lowering the CMC of binary surfactant mixtures depend on both the concentration of the individual surfactant and the type of surfactant used. Nevertheless, we noted a prevalent synergistic phenomenon in all binary surfactant systems, notably influenced by the concentration of the non-ionic surfactant. Increased concentrations of non-ionic surfactants notably enhanced synergistic interactions, fostering lowered CMC values when combined with anionic, cationic, and zwitterionic surfactants. On the other hand, an excessive concentration of cationic surfactants demonstrated relatively ‘weak’ synergistic effects, attributed to their comparatively smaller hydrophobic tail. Moreover, the formation of mixed micelles in binary surfactant systems led to a more negative free energy of micellization, thereby achieving synergistic effects between surfactants and resulting in lower CMC values. This emphasizes the crucial role of surfactant concentration in achieving synergistic outcomes within mixed systems. Generally, binary surfactant systems demonstrated lower CMC values compared to single surfactants, suggesting the potential for their use at lower concentrations to achieve desired interfacial and recovery outcomes, thereby reducing operational costs.
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Gutierrez, Gustavo, Juan Catan˜o et Oscar Perales-Perez. « Development of a Magnetocaloric Pump Using a Mn-Zn Ferrite Ferrofluid ». Dans ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-13784.

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Magnetic fluids or ferrofluids are colloidal dispersions of magnetic nanoparticles in a liquid carrier. These nanoparticles have a specific size range in order to remain suspended in the liquid, about 3 to 15 nm. In this range Brownian motion (thermal molecular motion in the liquid) keeps the particles from settling out. Because magnetic particles tend to aggregate, and aggregates sediment faster than single particles, the particles are coated with a stabilizing dispersing agent. The surfactant must be matched to the carrier type and must overcome the attractive Van der Waals and magnetic forces between the particles to prevent agglomeration even when a strong magnetic field is applied to the ferrofluid. A device that can pump a fluid with no moving mechanical parts represents a very encouraging alternative since such device would be practically maintenance free. A magnetocaloric pump achieves this purpose by providing a pressure gradient to a ferrofluid placed inside a magnetic field while experiencing a temperature change. If the temperature change is produced by extracting heat out of an element that needs refrigeration, coupling this heat via a heat pipe with the magnetocaloric pump will result in a completely passive cooling system. For applications near ambient temperature the ferrofluid must have specific characteristics such as low Curie temperature, high pyromagnetic coefficient, high thermal conductivity and low viscosity. This work presents the detailed description of the synthesis of ferrofluids composed of Mn-Zn ferrite nanoparticles and the characterization of its magnetic and thermal properties. Different composition of Mn-Zn ferrites nanoparticles were produce and evaluated. This ferrite ferrofluid was compared with commercially available magnetite ferrofluid in a magnetocaloric pump prototype. Results of saturation magnetization, pyromagnetic coefficient, Curie temperature, particle size, viscosity and pressure increment inside the magnetocaloric pump are presented.
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Chen, Shaohua, Ming Han, Abdulkareem AlSofi et Alhasan Fuseni. « Non-Ionic Surfactant Formulation with Ultra-Low Interfacial Tension at High-Temperature and High-Salinity Conditions ». Dans SPE Conference at Oman Petroleum & Energy Show. SPE, 2022. http://dx.doi.org/10.2118/200273-ms.

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Abstract Non-ionic alkyl polyglucoside (APG) surfactants have been considered as eco-friendly, nontoxic and biodegradable surfactants. In this study, the physicochemical properties of two APG surfactants under high-temperature and high-salinity conditions were evaluated. The effectiveness of the surfactants as imbibition agents on improving oil production in carbonate reservoirs was investigated. A formulation with ultra-low interfacial tension (IFT) was introduced and the mechanisms resulting in such low IFT were probed and discussed. Two APG surfactants were studied. Compatibility was evaluated by the transparency in brine solutions after aging. IFT was measured with the formulations of surfactant/additives. The morphology of network formed by surfactant/additives was observed via scanning electron microscope (SEM). The static adsorption of the APGs onto carbonate powder was determined by total organic carbon (TOC) analyzer. The contact angle of oil droplet on surface of carbonate core was measured in surfactant solution. The oil production via spontaneous imbibition of water in carbonate core was obtained using Amott cell. An imbibition simulation model was validated by the experimental results using UTCHEM simulator. Both surfactants APG-1 and APG-2 exhibited excellent compatibility with the simulated high salinity water at reservoir temperature. They also demonstrated low static adsorption on carbonate reservoir. The surfactant containing larger hydrophobic carbons (APG-1) showed more incremental oil production potential than the other one bearing shorter hydrophobic chain (APG-2). At a concentration of 0.2 wt%, APG-1 yielded a low IFT in the order of 10-2 mN/m and an ultra-low IFT in the order of 10-3 mN/m was obtained upon addition of a small amount of additives. SEM pictures indicated that APG-1 and the additives synergistically generated a more compact structure via interaction between hydrophobic moieties of the chemicals compared to the aggregated structure formed by APG-1 alone. Such an effect could eventually lead to a decrease in IFT between oil and water. APG-1 slightly altered the wettability of carbonate core surface toward water-wet. The experimental results of spontaneous imbibition tests showed an oil production of 28% and 21% by APG-1 and APG-2, respectively. After parameter tuning, the yielded curves from numerical simulation by UTCHEM simulator perfectly matched the experimental data. A new APG-based formulation was designed with an ultra-low IFT resulting in a much more compact amphiphilic structure along the oil-water interface. This study shows a great potential of APG surfactants and the relevant derivative formulations in improving oil production application for high-temperature and high-salinity carbonate reservoirs.
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Quan, Glen Lelyn, Kentaro Matsumiya, Michiaki Araki, Yasuki Matsumura et Yoshihiko Hirata. « The role of sophorolipid as carrier of active substances ». Dans 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/hnkx3869.

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Sophorolipid is a glycolipid-type biosurfactant, produced from natural sources by fermentation with a nonpathogenic yeast Starmerella bombicola. Its structure is composed of 2 hydrophilic parts, a sophorose unit, a glucose disaccharide glycosically linked to a hydroxyl fatty acid. Its structure spontaneously forms a vesicle of about 100 nm in an aqueous solution, which is similar to that of liposomes used as drug delivery systems and transdermal absorption promoters. It can be expected to have an effect of promoting permeation of active substances such as lactoferrin. Lactoferrin is an iron-binding glycoprotein having a molecular weight of about 80 kDa, and is most abundant in breast milk in the living body. Since it is also present in amniotic fluid that protects the mother and fetus, it is important to study the physiological relationship between skin and lactoferrin. The transdermal administration of lactoferrin with sophorolipid was verified, followed by the investigation protein-surfactant interactions between bovine lactoferrin and sophorolipid. Structural changes were further observed using spectroscopic, microscopic and biochemical methods under weakly acidic and neutral pH conditions. From particle size analysis by dynamic light scattering, microscopic observation by cryo-SEM, and digestion pattern observation by enzyme treatment, it was confirmed that bovine lactoferrin and sophorolipid interact with each other to form a sheet and nanometer-sized coagulation at pH 5.0 and 7.0 forming an aggregate, which was considered to be due to the self-organizing structure characteristic of sophorolipid. It can be concluded that sophorolipid has a potential of being a transport carrier of active substances, which can have vast applications not only in cosmetics but in drug delivery systems as well. Biosurfactants and biopolymers: Between interactions, orthogonality and mutual
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Kamel, Ahmed H. « Rheological Characteristics of Surfactant-Based Fluids : A Comprehensive Study ». Dans ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86044.

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Surfactant-based fluids, SB fluids exhibit complex rheological behavior due to substantial structural change caused by the molecules self-assembled colloidal aggregation. Various factors affect their rheological properties. Among these factors, surfactant concentration, shear rate, temperature, and salinity are investigated. One of the most popular surfactants, Aromox® APA-T viscoelastic surfactant (VES) is examined. The study focuses on four different concentrations (1.5%, 2%, 3%, and 4%) over a shear rate ranging from 0.0526 sec−1 to 1944 sec−1 using Bohlin rheometer. For salinity effects, two brine solutions are used; 2 and 4% KCl while for temperature effects, a wide range from ambient temperature of 72°F up to 200°F is covered. The results show that SB fluids exhibit a complex rheological behavior due to its unique nature and the various structures form in the solution. In general, SB fluids at all concentrations exhibit a non-Newtonian pseudo-plastic shear thinning behavior. As the surfactant concentration and/or shear increases, a stronger shear thinning behavior can be seen. Increasing solution salinity promotes formation of rod-like micelles and increases its flexibility. Salinity affects micelles’ growth and their rheological behavior is very sensitive to the nature and structure of the added salt. Different molecular structures are formed; spherical micelles occur first and then increased shear rate and/or salinity promotes the formation of rod-like micelles. Later, rod-like micelles are aligned in the flow direction and form a large super ordered structure of micellar bundles or aggregates called shear induced structure (SIS). Different structures implies different rheological properties. Likewise, rheology improves with increasing temperature up to 100°F. Further increase in temperature reverses the effects and viscosity decreases. However, the effects of temperature and salinity diminish at higher shear rates. Furthermore, a rheology master curve is developed to further understand the rheological behavior of SB fluids and correlate rheological properties to its microscopic structure.
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Guetni, Imane, Claire Marlière et David Rousseau. « Chemical EOR in Low Permeability Sandstone Reservoirs : Impact of Clay Content on the Transport of Polymer and Surfactant ». Dans SPE Western Regional Meeting. SPE, 2021. http://dx.doi.org/10.2118/200784-ms.

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Abstract Application of chemical enhanced oil recovery (C-EOR) processes to low-permeability sandstone reservoirs (in the 10-100 mD range) can be very challenging as strong retention and difficult in-depth propagation of polymer and surfactant can occur. Transport properties of C-EOR chemicals are particularly related to porous media mineralogy (clay content). The present experimental study aimed at identifying base mechanisms and providing general recommendations to design economically viable C-EOR injection strategies in low permeability clayey reservoirs. Polymer and surfactant injection corefloods were conducted using granular packs (quartz and clay mixtures) with similar petrophysical characteristics (permeability 70-130 mD) but having various mineralogical compositions (pure quartz sand, sand with 8 wt-% kaolinite and sand with 8 wt-% smectite). The granular packs were carefully characterized in terms of structure (SEM) and specific surface area (BET). The main observables from the coreflood tests were the resistance and residual resistance factors generated during the chemical injections, the irreversible polymer retention and the surfactant retention in various injection scenarios (polymer alone, surfactant alone, polymer and surfactant). A first, the impact of the clay contents on the retention of polymer and surfactant considered independently was examined. Coreflood results have shown that retention per unit mass of rock strongly increased in presence of both kaolinite and smectite, but not in the same way for both chemicals. For polymer, retention was about twice higher with kaolinite than with smectite, despite the fact that the measured specific surface area of the kaolinite was about 5 times less than that of the smectite. Conversely, for surfactant, retention was much higher with smectite than with kaolinite. Secondly, the impact of the presence of surfactant on the polymer in-depth propagation and retention was investigated in pure quartz and kaolinite-bearing porous media. In both mineralogies, the resistance factor quickly stabilized when polymer was injected alone whereas injection of larger solution volumes was required to reach stabilization when surfactant was present. In pure quartz, polymer retention was shown, surprisingly, to be one order of magnitude higher in presence of surfactant whereas with kaolinite, surfactant did not impact polymer retention. The results can be interpreted by considering adsorption-governed retention. The mechanistic pictures being that (a) large polymer macromolecules are not able to penetrate the porosity of smectite aggregates, whereas surfactant molecules can, and (b) that surfactant and polymer mixed adsorbed layers can be formed on surfaces with limited affinity for polymer. Overall, this study shows that C-EOR can be applied in low permeability reservoirs but that successful injection strategies will strongly depend on mineralogy.
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Ewbank, Conrado Gerard, John Clements, Max Deluge, Rodrigo Balloni Rabelo, Rafael Sobral Dezotti et Roger Pezzuol Dallaqua. « Development and Evaluation of Asphaltene Inhibitors for Offshore Brazilian Crudes ». Dans Offshore Technology Conference Brasil. OTC, 2023. http://dx.doi.org/10.4043/32761-ms.

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Abstract Asphaltene deposition has been an extremely critical flow assurance challenge in the Oilfield industry and the chemical treatment with continuous asphaltene inhibitors injection has been one of the best solutions for operators to face this challenge preventively, especially in the offshore market where it has the presence of extreme application conditions. This study focuses on optimizing the selection of the best chemicals and dosages of asphaltene inhibitors in Brazilian offshore crudes quickly and effectively. Combinations of different techniques and surfactants (non-ionic and polymeric surfactants) were evaluated in this study. To determine the best solution to be used for these systems, studies were carried out through the colloidal characterization both of asphaltenes in petroleum and of the effect of additives on the asphaltene deposition mechanism using LUMiSizer (Dispersion Analyzer), an equipment that enables extremely effective techniques, with high sensitivity and fast response time, applied for different Brazillian Offshore crude oils To determine the kinetics of destabilization and a tendency of asphaltene aggregate formation, data were acquired from LUMISizer, confirming the minimization of aggregate growth in more stable systems. Results also indicate the existence of a minimum effective concentration, suggesting a minimum dosage that promotes coating in the flakes formed, so that the steric barrier is effective in the curvature of the growth and deposition of asphaltenes. The LUMiSizer was used to rank the efficiency of different inhibitors and dispersants for a specific oil. Such results are even more informative than just saying whether an inhibitor is suitable or not.
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