Emulsions artificial

SDS emulsion of linoleic acid Linoleic acid micelle oxidation induced by AAPH monitored hy conjugated diene (234 nm) Not specific, influenced by physical micelle properties of emulsion, not real oil-in-water emulsion, artificial inducer, inappropriate substrate Pryor cf a/. (1988, 1993)... 

Sedimentation FFF has been used for the fractionation of polystyrene, latex beads, emulsions, artificial blood, viruses, and aqueous colloids, liposomes, albumin spheres, and DNA. Thermal FFF has been applied to different types of synthetic polymers. A recent development in FFF has been the increase of separation speed to allow fractionation on a minute scale instead of hours. 

Medical appHcations of PFC emulsions for organ perfusion and intravenous uses have received much attention in recent years. The first commercial blood substitute (Fluosol DA 20%, trademark of the Green Cross Corp.) employed perfluorodecalin, and improved, second generation products based on this PFC, or perfluorooctylbromide, are now under development (20,21). The relatively high oxygen dissolving capabiHty of PFCs undedies these appHcations (see Blood, artificial). 

Regardless of the cause, the mainstay of treatment for dry eye is artificial tears. Artificial tears augment the tear film topically and provide relief. If a patient uses artificial tears more than four times daily, recommend a preservative-free formulation. Preservative-free formulations are also appropriate if the patient develops an allergy to ophthalmic preservatives. Artificial tears are available in gel, ointment, and emulsion forms that provide a longer duration of relief and may allow for less frequent instillation. Ointment use is appropriate at bedtime.30... 

Anti-inflammatory agents may be used in conjunction with artificial tears. The only approved agent is cyclosporine emulsion. Administered topically, it is thought to act as a partial immuno-modulator suppressing ocular inflammation, but the exact mechanism is unknown. Cyclosporine emulsion increases tear production in some patients. Fifteen minutes should elapse after instillation of cyclosporine before artificial tears are instilled.31 Use of topical corticosteroids for short periods (e.g., 2 weeks) may suppress inflammation and ocular irritation symptoms. No topical corticosteroid is approved for this indication, however.30... 

The rubber may be natural, in which case the latex is produced by the rubber tree. Latex of the main synthetic rubbers is produced by the technique of emulsion polymerisation. The term latex has been broadened in recent years and a general definition is now a stable dispersion of a polymeric substance in an aqueous medium . Latices may be classified as natural (from trees and plants), synthetic (by emulsion polymerisation) and artificial (by dispersion of the solid polymer in an aqueous medium). They may also be classified according to the chemical nature of the polymer, e.g., SBR, nitrile, polychloroprene, etc. 

Artificial control of the monomer concentrations is possible by changing the monomer feed methods, which includes multishot, stage feed (19), and continuous feed. A multishot emulsion polymerization is expected to form multilayered particles if the monomers are chosen properly. When the layers are sufficiently thin, the particles exhibit unique thermal and mechanical properties. The stage feed system is shown in Figure 11.1.6. It makes it possible to produce particles having gradient composition of different monomer units. 

PE), usually present in the ratio of approximately 3 1 and making up about 90% of the total weight of the lecithin phospholipids (Table 9.1). It is known that the two main phospholipids account for most of the stabilization and emulsification activity of the lecithin, but it is thought that minor components such as sphingomyelin and phosphatidic acid also play some as yet undefined role in the process. It might be emphasized here that the natural mixture of components is more effective at stabilizing emulsions than any of the major components in either purified or synthetic form, alone or in artificial admixtures. 

Liquid membranes of the water-in-oil emulsion type have been extensively investigated for their applications in separation and purification procedures [6.38]. They could also allow extraction of toxic species from biological fluids and regeneration of dialysates or ultrafiltrates, as required for artificial kidneys. The substrates would diffuse through the liquid membrane and be trapped in the dispersed aqueous phase of the emulsion. Thus, the selective elimination of phosphate ions in the presence of chloride was achieved using a bis-quaternary ammonium carrier dissolved in the membrane phase of an emulsion whose internal aqueous phase contained calcium chloride leading to phosphate-chloride exchange and internal precipitation of calcium phosphate [6.1]. 

CONCENTRATED GAS-IN-LIQUID EMULSIONS IN ARTIFICIAL MEDIA. I. DEMONSTRATION BY LASER-LIGHT SCATTERING... 

This section contains a general description of the principles by which the Coulter Model N4 Sub-Micron Particle Analyzer, used in this study to characterize artificial gas-in-water emulsions (see Section 10.4), determines sample particle size. The measuring principles are based on the theory of Brownian motion and photon correlation spectroscopy (ref. 464,465 see also Sections 10.2 and 10.4). 

The surfactant mixture used (CAV-CON Filmix 3) is identical to that used to form the artificial gas-in-water emulsions described in Chapter 9, where the concentrated emulsion particles observed were all above 0.3 pm in diameter (which is the lower detection limit of the laser-based flow cytometer instrument) and therefore did not include the co-existing micelles. 

In conclusion, it is possible to prepare concentrated gas-inwater emulsions using various surfactant mixtures. The artificial, surfactant-stabilized microbubbles produced apparently undergo a cyclical process of microbubble formation/coalescence/fission/dis-appearance, where the end of each cycle is characterized by a collapse of the gas microbubbles into large micellar structures — only to re-emerge soon after as newly formed, gas microbubbles. This cyclical microbubble process is promoted by prior mechanical agitation of, and hence entrapment of macroscopic gas bubbles in, these saturated surfactant solutions. 

Still another factor favoring the formation of coarse gas-inliquid emulsions, as demonstrated in Chapter 10, is that all the surfactants employed were nonionic. This feature results in weaker repulsive interactions among the (polar, but uncharged) head groups in the surfactant monolayer surrounding each artificial... 

Vol. 19 Stable Gas-in-Liquid Emulsions Production in Natural Waters and Artificial Media Second Edition By J.S. D Arrigo... 

Stable gas-in-liquid emulsions, as found in natural waters or when modeled from natural micro bubbles using artificial media, are basically coated microbubbles and represent one more example of self-assembly in science. 

The surfactant-coated microbubbles described in this book range in size from nanoscale (i.e., submicron) to mesoscale (i.e., microns or micrometers), and fall into two categories. First, surfactant-stabilized natural microbubbles ( 0.5-100 pm in diameter), also referred to as dilute gas-in-liquid emulsions, are reviewed and analyzed in Chapters 1-8 of the book. Second, the synthetic or artificially coated microbubbles (from submicron to a few micrometers in diameter), also referred to as concentrated gas-in-liquid emulsions or as lipid-coated microbubbles, are described and their properties examined in detail in Chapters 9-15. 

The surface or interfacial phenomena associated with colloidal systems such as emulsions and foams are often studied by means of experiments on artificially prepared flat surfaces rather than on the colloidal systems themselves. Such methods provide a most useful indirect approach to the various problems involved. 

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