Microemulsions as transdermal drug delivery vehicles.

Structure, dynamics and transport properties of microemulsions

We have experimentally determined the displacement of the equilibrium Grossular + 2 Kyanite + Quartz ⇆ 3 Anorthite (GASP) as a function of garnet composition in the systems Mg-Ca-Mn, Fe-Mg-Ca and Fe-Mg-Ca-Mn at 1000°C. The results were treated along with selected experimental and observational data available in the literature as well as binary parameters from other workers to obtain a set of mutually compatible binary mixing parameters of the quaternary (Fe,Mg,Ca,Mn)- aluminosilicate garnet solid solution. Attempts to determine equilibrium garnet composition in the GASP equilibrium in the Ca-Mg binary were unsuccessful due to the formation of pyroxene. Calculations of binary and ternary miscibility gaps show that the P,T,X combination required for unmixing of garnet solid solution is not realized by natural samples. The solution model was applied to account for compositional effects on Fe-Mg exchange between garnet and ortho- or clino-pyroxene. Applications of the revised thermometric formulations to selected natural assemblages yield P-T conditions which are much less sensitive to compositional effects compared to the other available formulations, and are consistent with independent constraints.

https://www.geo.arizona.edu/%7Eganguly/GtSol_CMP.pdf

Thermodynamics of aluminosilicate garnet solid solution: new experimental data, an optimized model, and thermometric applications

The thermal history of the Eastern Ghats Belt (India) as revealed by U–Pb and 40Ar/39Ar dating of metamorphic and magmatic minerals: implications for the SWEAT correlation

In the past twenty five years, microemulsions have been the focus of extensive research worldwide due to their importance in a variety of technological applications. These applications include enhanced oil recovery, combustion, cosmetics, pharmaceuticals, agriculture, metal cutting, lubrication, food, enzymatic catalysis, organic and bio-organic reactions, chemical synthesis of nanoparticles etc. The basic purpose of this review is intended to provide the most important features of microemulsions and their applications. Emphasis is placed on recent works, however, the reference list is by no means complete. In order to limit the size of the review, a more or less arbitary selection has been made with respect to examples chosen from literature. The review is started with a brief introduction and focussed with definition, structure, type, formation characteristics, stability, phase behavior and the effect of additives, pressure, temperature on the phase behavior of microemulsion. In addition, the p...

Microemulsions: an overview

Sapphirine granulite occurring as lenses in charnockite at Anantagiri, Eastern Ghat, India, displays an array of minerals which developed under different P-T-X conditions. Reaction textures in conjunction with mineral chemical data attest to several Fe-Mg continuous reactions, such as spinel+rutile+quartz+MgFe −1 =sapphirine+ilmenite cordierite=sapphirine+quartz+MgFe −1 sapphirine+quartz=orthopyroxene+sillimanite+MgFe −1 orthopyroxene+sapphirine+quartz=garnet+MgFe −1 orthopyroxene+sillimanite=garnet+quartz+MgFe −1 orthopyroxene+sillimanite+quartz+MgFe −1 =cordierite. Calculated positions of the reaction curves in P-T space, together with discrete P-T points obtained through geothermobarometry in sapphirine granulite and the closely associated charnockite and mafic granulite, define an anticlockwise P-T trajectory. This comprises a high-T/P prograde metamorphic path which culminated in a pressure regime of 8.3 kb above 950°C, a nearly isobaric cooling (IBC) path (from 950°C, 8.3 kb, to 675°C, 7.5kb) and a terminal decompressive path (from 7.5 to 4.5 kb). Spinel, quartz, high-Mg cordierite, and sapphirine were stabilized during the prograde high-T/P metamorphism, followed by the development of orthopyroxene, sillimanite, and garnet during the IBC. Retrograde low-Mg cordierite appeared as a consequence of decompression in the sapphirine granulite. Deformational structures, reported from the Eastern Ghat granulites, and the available geochronological data indicate that prograde metamorphism could have occurred at 3000±100 and 2500±100 Ma during a compressive orogeny that was associated with high heat influx through mafic magmatism. IBC ensued from P max and was thus a direct consequence of prograde metamorphism. However, in the absence of sufficient study on the spatial variation in P-T paths and the strain histories in relation to time, the linkage between IBC and isothermal decompression (ITD) has remained obscure. A prolonged IBC followed by ITD could be the consequence of one extensional mechanism which had an insufficient acceleration at the early stage, or ITD separately could be caused by an unrelated extensional tectonism. The complex cooled nearly isobarically from 2500 Ma. It suffered rapid decompression accompanied by anorthosite and alkaline magmatism at ~1400-1000 Ma.

Petro-tectonic Imprints in the Sapphirine Granulites from Anantagiri, Eastern Ghats Mobile Belt, India

Structural features of w/o microemulsions have been conductometrically evaluated. The radius of the water pool, the effective radius of the droplets, their number per unit volume, the effective surface area of the water pool, and the aggregation number of the surfactant and cosurfactant molecules per droplet in the oil/water interphase have been estimated. Three oils (n-heptane, n-decane, and xylene), three surfactants (CTAB, SDS, and AOT) and two cosurfactants (1-butanol and n-hexylamine) have been used; their effects on the structural properties of microemulsions have been studied at two different temperatures, 293 and 303 K, at two weight ratios of surfactant/cosurfactant, 0.33 and 0.50. The droplet radius has been found to be oil dependent and follows the order n-heptane AOT > CTAB. 1-Butanol yields greater radius than n-hexylamine with SDS and AOT, and the order is reversed with CTAB. The aggregation number of the surfactant and cosurfactant per droplet increases and decreases, respectively, with elevation of temperature. The R{sub e}/R{sub W} (ratio of the effective radius of the droplet and the radiusmore » of its water core) remains fairly constant under all situations, the average value being 1.15 {plus minus} 0.10.« less

Conductivity study of microemulsions: dependence of structural behavior of water/oil systems on surfactant, cosurfactant, oil, and temperature

Additive effects on the percolation of water/AOT/decane microemulsion with reference to the mechanism of conduction

Using the experimental data on Fe-Mg exchange between orthopyroxene and biotite of Fonarev & Konilov (1986), an orthopyroxene–biotite geothermometer is developed. The thermometer is corrected for mixing of Ti and Al in octahedral sites in biotite and also for non-ideal mixing of Fe and Mg in orthopyroxene. The thermometer is applied to several amphibolite–granulite transition facies and granulite facies rocks and also to mantle xenoliths. It yields consistent results in rocks of widely varying bulk composition, and highly magnesian mantle xenoliths. This thermometer removes the difficulty of estimating temperature in garnet-free rocks in high-grade terrains and also provides independent estimates of temperature in garnet-bearing assemblages.

An orthopyroxene–biotite geothermometer and its application in crustal granulites and mantle-derived rocks

Applications of the different formulations of garnet-clinopyroxene geothermometers to crustal granulites and particularly to metamorphosed manganese formations show a wide scatter of estimates This is primarily related to the uncertainty associated with the formulation of the activity-composition relationship in garnet solid solution besides that in the clinopyroxene solid solution The largest uncertainty appears to have resulted from the adopted Mg-Mn interaction parameter in garnet which is yet to be experimentally determined A fresh statistical regression of eleven pairs of garnet and clinopyroxene equilibrated at identical P-T conditions from a manganese formation in India yields W
 Mg-Mn
 Gt
 (=WMn-Mg) value of 1600±500 cal/mols An extension of the Ellis and Green (1979) geothermometer, known to work well in normal granulites, incorporating terms associated with the activity coefficients of the exchangeable cations, now yields consistent temperature estimation from normal granulites as well as from metamorphosed manganese formations The geothermometer, however, will not work well for garnet having XFe≥065 and clinopyroxenes containing appreciable Na, Al and/or Fe3+

P. K. Bhattacharya

Papers

Petro-tectonic Imprints in the Sapphirine Granulites from Anantagiri, Eastern Ghats Mobile Belt, India

Conductivity study of microemulsions: dependence of structural behavior of water/oil systems on surfactant, cosurfactant, oil, and temperature

Additive effects on the percolation of water/AOT/decane microemulsion with reference to the mechanism of conduction

An orthopyroxene–biotite geothermometer and its application in crustal granulites and mantle-derived rocks

Mixing behavior in quaternary garnet solid solution and an extended Ellis and Green garnet-clinopyroxene geothermometer