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We have used high-resolution magnetic birefringence to study very dilute mixtures of the nonionic surfactant pentaethylene glycol mono-dodecyl-ether (C12E5) in water at fields to H=18 T. The induced refractive index anisotropy Δn shows distinct H dependencies in the Lα-lamellar and L3-‘‘sponge’’ phases, and demonstrates that these are separated by a two-phase coexistence region. In the L3 phase and for surfactant concentrations γ[bar_over_tilde:_approx._equal_to]0.02 (the vicinity of the Lα phase terminus), we observe a sharp change in the magnitude and H dependence of Δn. A quantitative analysis shows this to be consistent with a crossover from a highly-connected ‘‘symmetric sponge’’ to a droplet or ‘‘asymmetric sponge’’ structure as a function of γ, a result previously suggested by neutron scattering and electrical conductivity measurements [R. Strey, R. Schomacker, D. Roux, F. Nallet, and U. Olssen, J. Chem. Soc. Faraday Trans. II 86, 2253 (1990)]. Finally, for γ>=0.02 and at large H, we present evidence of a field-induced transformation of the L3 structure. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

To characterize the granulation rate processes in the kneading section of the twin screw granulator, separate experiments were conducted using exclusively conveying elements as the baseline in addition to different configurations of kneading elements. The configuration parameters examined were the length of the kneading section, the advance angle, and the angle direction. Granule size, shape and liquid distribution were measured. Two main rate processes were observed (1) breakage and layering, and (2) Shear elongation and layering. Breakage was dominant in the 90° configuration while shear elongation dominated in the 30° reverse configurations, with other configurations giving some combination of the two rate processes. The distinct three-dimensional (3-D) shape characteristics of granules obtained from each configuration were crucial in elucidating the dominant granulation rate process in each case. The proposed granulation mechanisms explain the events leading to particular granule attributes, but more importantly provide insight into future optimization of twin screw granulation process. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4100-4115, 2013 [ABSTRACT FROM AUTHOR]

The effect of pH on the precipitation of soy protein between pH 4 and 6.8 was investigated. Precipitation between pH 5.7 and 6.8 gave a binary liquid-liquid separation in which a protein-rich secondary liquid phase containing between 20 - 30 wt % protein of 80 - 99% purity in glycinin formed as droplets of 1 - 10 µm. The droplets could be coalesced upon centrifugation to form a homogeneous bottom liquid layer. The high-protein concentration phase was stable (did not precipitate or crystallize) for up to several months when stored at 4°C. Stable high-protein liquid phases have not previously been reported. In the pH region for which liquid-liquid separation occurred (pH 6.15 to 5.35), the droplet-size distribution was controlled by nucleation and growth. No drop breakage, and little or no drop coalescence was observed. Mixer speed and geomeotry did not have a large effect on the size of the protein-rich droplets in suspension. Nucleation occurred in two separate bursts at pH 6.15 and pH 5.85. followed by growth of the new nuclei as pH was decreased. Thus, the drop-size distribution was monomodal between 6.15 and 5.85, and bimodal between pH 5.85 and 5.35. At pH 5.6 and below, protein precipitated as amorphous material which intertwined with and bound primary particles into aggregates. These agglomerates grew with decreasing pH, particularly below pH 5.35, as more protein precipitated with amorphous material acting as a binder. The addition of NaCl prevented the liquid-liquid separation at higher pH. Instead solid precipitates of a different morphology were formed at low-pH only. [ABSTRACT FROM AUTHOR]

This paper reports an x-ray diffraction study of structures and restacking transitions within the B phases of heptyloxybenzylidene-heptylaniline. The system evolves from a hexagonal close-packed structure, through intermediate orthorhombic and monoclinic phases, to a simple hexagonal structure. The monoclinic phase has a temperature-dependent shear which transforms the system from orthorhombic to hexagonal. The latter three phases exhibit a single-q⃗ sinusoidal modulation of the molecular layers., Engineering and Applied Sciences

We have used x-ray specular reflection to study the structure of the air–liquid-crystal interface of the lyotropic liquid crystal formed from binary mixtures of cesium perfluoro-octanoate (CsPFO) and water. In the isotropic phase the surface is coated with a monolayer of CsPFO separated by layers of water from one or more smectic bilayers of CsPFO. As for the case of thermotropic liquid crystals, the isotropic-to-nematic phase transition has no effect on the surface structure, and as the temperature is lowered towards the nematic–to–smectic-A transition temperature, the number of surface-induced smectic layers increases dramatically (e.g., approximately 100 layers were observed). Theoretical modeling of the reflectivity excludes the possibility that the surface bilayers are arrays of micelles. X-ray scattering from critical smectic short-range order in the bulk, studied by tuning the spectrometer away from the specular condition, indicates that the scattering is fundamentally different from short-range smectic order in thermotropic systems., Engineering and Applied Sciences

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]

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.