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X-ray scattering data of a three-component lamellar phase composed of oil (octane), water and a non-ionic surfactant (C12E5) are shown for various surfactant concentrations as well as oil/water volume ratios, in order to study the periodicity of the layers as well as the effect of structural symmetry on their interactions and organization of the layers. The data are fitted with a recently proposed model which takes into account the geometry and the fluctuations of these repeated structures and gives a good fit for a highly fluctuating non-charged and non-oriented lamellar phase. The variation of the exponent η which characterizes the quasi-long range order indicates that the structure is more ordered for the most symmetrical system: i.e.for an oil/water ratio of 1.

Granular γ-Al2O3 support and 8 wt % CuO/γ-Al2O3 catalyst were synthesized by a sol−gel granulation method. The pore structure, crush strength, hardness, and elasticity of these sol−gel-derived catalysts were studied and compared with similar commercial catalysts prepared by non-sol−gel methods. Alumina and CuO-coated alumina granular particles prepared by different methods have different macro- and microstructure. The sol−gel-derived granular γ-alumina and CuO-coated γ-alumina granular particles have a structure defined by compact packing of uniform, nanosized γ-alumina crystallites. They are characterized by a more uniform pore size distribution and larger surface area as compared to similar commercial samples with a structure defined by packing of aggregates consisting of nonuniform γ-alumina crystallites. Because of the differences in the macro- and microstructure, the sol−gel-derived granular samples offer higher crush strength and greater hardness than the commercial samples.

The unsaturated flow of liquid through packed beds of large particles was studied using six different liquids, all with contact angles greater than 90° on the bed packing (wax spheres of 9, 15 and 19.4 mm diameter). The liquidflow was discrete in nature, as drops for low flow rates and rivulets for high flow rates. For unsaturated liquid flows, the actual percolation velocity, not superficial velocity, should be used to characterize the flow. The percolation velocity did not vary with packed‐bed depth, but was a strong function of liquid flow rate, liquid and particle properties. Effects of liquid and particle properties (but not flow rate) are well captured by a simple correlation between the liquid‐particle fiction factor and Reynolds number based on actual percolation velocities. Liquid dispersion, characterized by the maximum dispersion angle, varies significantly with liquid and particle properties. The tentative correlation suggested here needs further validation for a wider range of conditions.

In this work, the coalescence of deformable granules in wet granulation processes is modelled. The model accounts for both the mechanical properties of the granules and the effect of the liquid layer at the granule surface. It is an extension to the model of Ennis et al. (1991) to include the possibility of granule plastic deformation during collisions. The model is written in dimensionless groups such as viscous and deformation Stokes numbers and the ratio of granule dynamic yield strength to granule Young's modulus (Yd/E*). These variables are bulk parameters of the powder‐binder mixture and also functions of the process intensity. The model gives the conditions for two types of coalescence–type I and type II. Type I coalescence occurs when granules coalesce by viscous dissipation in the surface liquid layer before their surfaces touch. Type II coalescence occurs when granules are slowed to a halt during rebound, after their surfaces have made contact. The model explains some of the trends observed in the literature, are preliminary validation of the coalescence criterion with drum granulation data is encouraging. An extension is also made to the case of surface dry granules, where liquid is squeezed to the surface during granule deformation.

Aspergillus oryzae ACM 4996 was grown on an artificial gel-based substrate and on steamed wheat bran during solid-state fermentations in 18.7 L rotating drum bioreactors. For gel fermentations fungal growth decreased as rotational speed increased, presumably due to increased shear. For wheat bran fermentations fungal growth improved under agitated compared to static culture conditions, due to superior heat and mass transfer. We conclude that the effects of operational variables on the performance of SSF bioreactors are mediated by their effects on transport phenomena such as mixing, shear, heat transfer, and mass transfer within the substrate bed. In addition, the substrate characteristics affect the need for and the rates of these transport processes. Different transport phenomena may be rate limiting with different substrates. This work improves understanding of the effects of bioreactor operation on SSF performance. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 63: 383–391, 1999.

A model for particle transport in a flighted horizontal rotary dryer is developed in this paper. Mathematical principles applied to the current study are in the areas of differential calculus and analytical geomentry. In contrast to the conventional approaches which are either based on mpirical/semi-empirical correlations or obtained from the investieation of single particle trajectories, this paper develops rigorous mathematical analysis of the transport of bulk solids. A variety of important issues in rotary drying, such as axial flowrate of solids, retention time distribution and solid holdup are addressed and treated by using non-traditional methods. Since the model takes dimension, number and geometry of flights into account, it possesses the following two haracteristics : (1) it is not only useful in the study of rotary drying dynamics, but lso applicable to other processes employing flighted rotating cylinders (such as granulation drumsand crushers) and (2) based on the model, an optimal drum configuration can be designed by using optimisation techniques. The model can be incorporated within a distributed arameter dryer model developed previously to form a more rigorous integrated dynamic model. A heoretical foundation for optimal flight design by using the current model is explained.A pilot scale perspex rotary dryer equipped with a video camera has been constructed and used for model validation. Raw sugar was handled in the experiments. Particle transport was observed and measured by using a flow visualisation technique supplemented with traditional sampling methods. A significant model quality improvement has been observed through a comparative study between the newly developed model and conventional ones.

Measurements of the intensity and spectrum of light scattered by bend mode director fluctuations near the smectic-A to nematic phase transition of cyanobenzylidene octyloxyaniline are presented and analyzed. The longitudinal correlation length in the nematic phase appears to diverge (T- T)-0.75 and the data are consistent with the jähnig-Brochard scalilng function up to q∥ = 10. The bend viscosity diverges as (T - T) -0.5 when correction for beckground and Arrhenius temperature dependence are included.

A high-resolution calorimetric study of methylbutylphenyloctyloxybiphenyl carboxylate (8OSI) has been carried out near the smectic-C to hexatic smectic-I transition. The excess heat capacity peak ΔCl, is large but clearly rounded over a 300 mK range. The ΔCp data and previously published Co order parameter data can be fit simultaneously using a phenomenological equation of state with a temperature independent tilt field H. Interpretation of the underlying effective critical exponents α = 0.47 and β = 0.077 is not clear, but one possibility is that the SmC-SmI transition in the limit H → 0 would be weakly first-order.

The role of symmetry in determining classical or non-classical behavior at structural phase changes is compared with phase changes in liquid crystals. Structural transitions in the smectic B phase of liquid crystals are also discussed.

A regime map of granule growth behavior is proposed based on granule deformation during collision and the granule liquid content measured as the maximum pore saturation. The granule deformability on collision is represented by a deformation number, which is a ratio of granule impact energy to the plastic energy absorbed per unit strain. Granule growth regimes such as steady growth, induction, nucleation, crumb, and slurry are defined. This regime map qualitatively explains the uariatiom in granulation behauior. Laboratoly drum granulation experiments were used to test the regime map. Experiments were peqformed in a 0.3‐m‐dia. drum using three sizes of glass ballotini (19, 31, and 60 μm) with water and glycerol as liquid binders. Increasing granule yield stress by decreasing particle size and increasing binder viscosity caused the system to move from steady growth to induction behauior as predicted by the regime map. Preliminary validation with literature data was also encouraging. More work, howeuer, is required to better quantify the boundaries between different growth regimes and to investigate the effect of process agitation intensiq. This regime map has great potential to help design and control granulation systems, because it is based on properties of the powder/binder qstem that can be measured or estimated without peqforming any granulation tests.

In this paper, we report results from synchrotron X-ray scattering studies of thefluid/hexactic/solid phases and phase transitions in both very thick and very thin, freely suspended films of tilted hexatic liquid crystals. Contrary to the thick film case, the higher Fourier coefficients describing the bond orientational order are suppressed in very thin films. This suppression is consistent with a two-dimensional bond orientational order parameter,?6, rather than the three-dimensional bond orientational order parameter found in very thick films. For a film containing twently-three (23) smectic layers we find that?6 is two-dimensional whereas the positional order in the crystallineSJ phase is three-dimensional. We present an analysis of the thick film data in terms of the three-dimensionalXY-model and a new mean field theory model which incorporates explicitly the quasi two-dimensional nature of bulk smectic phases.

We have used light scattering to study nematic elastic constantsK2 andK3 in the alkyl-cyanobiphenyl (n CB) system. As the average alkyl chain lengthn increases, the temperature range of the nematic phase decreases and the system approaches a tricritical point. Our data are analyzed to determine the parallel and perpendicular correlation lengths and critical exponents for smectic short-range order. We find a continuous decrease in the critical exponentsv? andv? as the tricritical point, which occurs at ?9.1 CB, is approached. There is also a significant decrease in the magnitude of the parallel correlation length at a fixed reduced temperature.

We have carried out a comprehensive x-ray scattering study of the nematic to smecticA transition in the alkylbenzoate (nCB) and thiosulfate $$\bar nS5$$ series. By changing the aliphatic chain lengthn (CnH2n+1) in these series, crossovers from critical to tricritical behavior are induced. We observe a smooth progression of effective exponents from the set,y?1.5,v??0.80, andv??0.67 toy=1.1,v?=0.6, andv?=0.5 for the critical and tricritical regions respectively. In both cases the exponents are close to, but in disagreement with, values expected from current theoretical models. We conclude on an empirical basis that the varied exponents reported in the literature for other systems reflect the critical to tricritical crossover.

Some recent experiements that have been carried out at M.I.T. provide results that illustrate the effect of thermal fluctuations on order-disorder phase transitions.

We report birefringence measurements of the nematic order parameter of the lyotropic liquid crystal formed by aqueous solution of cesium perfluoro-octanoate (CsPFO). For a mole fraction x = 0.035 of CsPFO the first order jump at the nematic-isotropic transition is about twice that in a sample with x = 0.025. The results are analyzed using a Landau-de Gennes model.

We measured the intensity and the spectrum of light scattered by the nematic liquid crystal p-methoxybenzylidene p-n-butylaniline as a function of temperature. The measurements yield the temperature dependence of the amplitude and dynamics of orientational fluctuations in the ordered phase. We analyze the results in terms of the two theories of normal modes of liquid crystals, and examine the extensions required to make the macroscopic elastic theory consistent with experiment.