Mechanical dispersion methods

Mechanical dispersion methods are the most frequently used methods in the production of the laboratory scale liposomes. Usually two steps are included in these methods the Llm preparation anc... 

Quick-breaking foams consist of a miscible solvent system such ethanol (qv) [64-17-5] and water, and a surfactant that is soluble in one of the solvents but not in both. These foams are advantageous for topical appHcation of pharmaceuticals because, once the foam hits the affected area, the foam coUapses, deUvering the product to the wound without further injury from mechanical dispersion. This method is especially usehil for treatment of bums. Some personal products such as nail poHsh remover and after-shave lotion have also been formulated as quick-breaking foams. 

Two air-saturation systems suited for use in water treatment are shown in Figure 15 (31). Such mechanisms faciHtate the release of air that generates much finer bubbles than mechanical air dispersion methods used in mineral flotation practice. 

The PIA-investigations were carried out under dynamic vacuum (p< 10 5 mbar) and at 77 K with films cast from toluene solution onto KBr substrates. For the dispersive method [29, 30] the globar, the KBr-prism premonochromator, and the grating monochromator of a Perkin Elmer 125 lR-spcctrometer were used in the spectral range of 0.25 to 1.24 eV. The pump beam was chopped mechanically... 

Once the desired mixture of lipid components is dissolved and homogenized in organic solvent, one of several techniques may be used to disperse the liposomes in aqueous solution. These methods may be broadly classified as (1) mechanical dispersion, (2) detergent-assisted solubilization, and (3) solvent-mediated dispersion. 

The more eflicienl defoaming mechanism of spreading involves transpon of underlying liquid so that the liquid is replaced by a film of deloumcr that docs not support foam. A drop of oleic add added to water spreads at a velocity of 30 miles (48.2 kilometers) per hour. The mechanical shock to a film by such a defoamer may be considerable. In addition lo the foam-destroying aspect, spreading is also of value as a defoamer-dispersion method, particularly in viscous or poorly stirred systems. 

Probably the most popular option is mechanical dispersion, simply because the greatest number of methods that utilize it have been developed. When using mechanical means to form vesicles, the lipid solution first is dried to remove all traces of organic solvent prior to dispersion in an aqueous media. The dispersion process is the key to... 

Perhaps the simplest solvent dispersion method is that developed by Batzri and Korn (1973). Phospholipids and other lipids to be a part of the liposomal membrane are first dissolved in ethanol. This ethanolic solution is then rapidly injected into an aqueous solution of 0.16 M KC1 using a Hamilton syringe, resulting in a maximum concentration of no more than 7.5% ethanol. Using this method, single bilayer liposomes of about 25-nm diameter can be created that are indistinguishable from those formed by mechanical sonication techniques. The main disadvantages of ethanolic injection are the limited solubility of some lipids in the solvent (about 40 mM for phosphatidyl choline) and the dilute nature of the resultant liposome suspension. However, for the preparation of small quantities of SUVs, this method may be one of the best available. 

K-absorption spectrum of yttrium in YH3, which was mechanically treated in a ball planetary mill during 20 min. with angular rate of 1630 rot./min. is shown in Fig. 6 (c). This absorption spectrum, as seen from the picture, is shifted relatively to the spectrum of untreated YH3 hydride to the side of lower energies, which in accordance with the found out correlation has to testify to thermal stability of reduction of treated yttrium hydride. Actually, we determined by the method of hydrogen thermal desorption, that as a result of mechanic dispersing of this hydride its temperature of decomposition decreased more than on 300 °C (Fig. 7), i.e. the... 

One of new methods of magnesium, transition and rare-earth metals hydrides and their compounds obtaining is mechanical-chemical method. Numerous quantity of works are devoted to the improving kinetic, sorption properties of hydrides which were treated mechanically or were obtained by this method in hydrogen medium under pressure [1-7]. Great consideration is given to the influence of dispersity on phase equilibrium. At the same time the investigation of mechanical... 

From an environmental standpoint, the use of water as a solvent is desirable. Unfortunately, many of the monomers of interest are insoluble in water, but suspension polymerization offers a way to utilize water. Suspension polymerization is performed by mechanically dispersing a monomer in an incompatible solvent, most often water. The system is heterogeneous and when polymerization is complete the polymer is collected as granular beads. This method is not suitable for tacky materials, such as elastomers, as the beads will tend to clump together.31... 

The production of disperse systems is often achieved by dispersion methods in which the disperse phase is subdivided into small particles by mechanical means. Liq-... 

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