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Your search keyword '"Litster, J. D."' showing total 145 results
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145 results on '"Litster, J. D."'

143. Growth rates of ibuprofen crystals grown from ethanol and aqueous ethanol.

Author

Rashid, A., White, E. T., Howes, T., Litster, J. D., and Marziano, I.

Subjects
*IBUPROFEN, *CRYSTAL growth, *ETHANOL, *CRYSTALLIZATION, *REFRACTIVE index, *LASER beam scattering
Abstract

To quantify the crystallization of racemic ibuprofen [2-(4-isobutyl-phenyl)-propionic acid] from aqueous ethanol it is necessary to know the growth rate kinetics. Growth rates were measured by adding SPG (size proportional growth) seed crystals to an isothermal non-nucleating batch crystallization and sampling during the batch. The supersaturation was measured by refractive index and the crystal size by laser light scattering (Malvern). To ensure the batch was non-nucleating the supersaturation was kept within the narrow secondary MZ (metastable zone). Measurements were made at three temperatures, 10, 25 and 40 °C. The growth rate was proportional (first order kinetics) to the solution supersaturation, expressed in mass ratio of ibuprofen to ethanol units. Despite the narrow MZ, the initial growth rates were substantial (up to 1 µm/min). Temperature has a large effect on growth rate with an activation energy of 13.7 kj/mol. The water content affects the growth rate coefficient differently depending on the temperature. [ABSTRACT FROM AUTHOR]

Published
2012
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145. Light-scattering studies of the monomer-dimer states of gramicidin A.

Author

Rondelez F and Litster JD

Subjects
Dimethyl Sulfoxide, Dioxanes, Light, Macromolecular Substances, Methanol, Scattering, Radiation, Solvents, Gramicidin
Abstract

Measurements of the intensity and autocorrelation function of ligh quasielastically scattered by gramicidin A indicate that the molecules exist as dimers in methanol and dioxane and monomers in dimethyl sulfoxide when solute concentrations range from 18 to 50 mg/ml. This gives further evidence that gramicidin A can dimerize in low-polarity media such as the hydrocarbon part of the membrane bilayers.

Published
1979
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