Liquid-phase oxidation of hydrogen sulfide in centrifugal bubbling apparatus

Liquid-phase oxidation of H₂S in centrifugal-bubbling apparatus in the presence of catalysts [manganese(II) chloride, cobalt phthalocyanine disulfonic acid, and a catalytic system including cobalt phthalocyanine disulfonic acid and MnCl₂] was studied.     

A mathematical model for an expanding foam

A theoretical and numerical model is presented for the shape evolution of the thin liquid films separating the gas bubbles in a foam. The motion is due to capillary action, surface tension gradients, and the overall expansion of the foam. The expansion is the result of the increase in gas content with time. Process modeling is accomplished via the solution of three coupled partial differential equations. Two time scales are included in the model: a process time and a drying or curing time. It is demonstrated that the amount of surfactant is the dominant control mechanism for the final film thickness. If sufficient surfactant is present, the films will be shown to dilate uniformly in space. A number of known features of expanding foams are reproduced by the model.     

Effective momentum transfer cross section for excess electrons in liquid argon

The momentum-transfer cross section of excess electrons Q in liquid Ar (estimated on the assumption that the characteristic energy 3eD/2μ is equal to the mean agitation energy ge) is compared with the original momentum-transfer cross section Q₁ used for the calculation of D and μ. Differences between Q and Q₁ are discussed and comparisons made between 3eD/2μ and gE.     

Generation of frustrated liquid crystal phases by mixing an achiral nematic-smectic-C mesogen with an antiferroelectric chiral smectic liquid crystal

By mixing the achiral liquid crystal HOAB, exhibiting a nematic (N)-smectic-C (SmC) mesophase sequence, with the chiral antiferroelectric liquid crystal (AFLC) (S,S)-M7BBM7, forming the antiferroelectric SmC(a)(*) phase, at least seven different mesophases have been induced which neither component forms on its own: a twist-grain-boundary (TGB(*)) phase, two or three blue phases, the untilted SmA(*) phase, as well as all three chiral smectic-C-type "subphases," SmC(alpha)(*), SmC(beta)(*), and SmC(gamma)(*). The nature of the induced phases and the transitions between them were determined by means of optical and electro-optical investigations, dielectric spectroscopy, and differential scanning calorimetry. The induced phases can to a large extent be understood as a result of frustration, TGB(*) at the border between nematic and smectic, the subphases between syn and anticlinic tilted smectic organization. X ray scattering experiments reveal that the smectic layer spacing as well as the degree of smectic order is relatively constant in the whole mixture composition range in which AFLC behavior prevails, whereas both these parameters rapidly decrease as the amount of HOAB is increased to such an extent that no other smectic-C-type phase than SmC/SmC(*) exists. By tailoring the composition we are able to produce liquid crystal mixtures exhibiting unusual phase sequences, e.g., with a direct isotropic-SmC(a)(*) transition or a temperature range of the SmC(beta)(*) subphase of about 50 K.     

A mathematical model for a copolymer in an emulsion

In this paper we review some recent results, obtained jointly with Stu Whittington, for a mathematical model describing a copolymer in an emulsion. The copolymer consists of hydrophobic and hydrophilic monomers, concatenated randomly with equal density. The emulsion consists of large blocks of oil and water, arranged in a percolation-type fashion. To make the model mathematically tractable, the copolymer is allowed to enter and exit a neighboring pair of blocks only at diagonally opposite corners. The energy of the copolymer in the emulsion is minus α times the number of hydrophobic monomers in oil minus β times the number of hydrophilic monomers in water. Without loss of generality we may assume that the interaction parameters are restricted to the cone \({\{(\alpha,\beta)\in \mathbb{R}^2\colon\,|\beta|\leq\alpha\}}\). We show that the phase diagram has two regimes: (1) in the supercritical regime where the oil blocks percolate, there is a single critical curve in the cone separating a localized and a delocalized phase; (2) in the subcritical regime where the oil blocks do not percolate, there are three critical curves in the cone separating two localized phases and two delocalized phases, and meeting at two tricritical points. The different phases are characterized by different behavior of the copolymer inside the four neighboring pairs of blocks.     

A mathematical model for blade coating of a nematic liquid crystal

The standard industrial process of blade-coating is now being used to produce new liquid crystal displays (LCDs) in which a liquid crystal and optical layers are coated onto a substrate. Motivated by this new LCD manufacturing process, we use the Ericksen-Leslie equations to develop a simple mathematical model for blade coating of a nematic liquid crystal. The direction and uniformity of the director are important factors for the performance of the displays, particularly when this alignment is 'frozen in' within optical layers. For this reason we investigate the flow and director within a liquid crystal film both after emerging from the region under a blade (the so-called 'drag-out' problem) and before entering the region under a blade (the so-called 'drag-in' problem). We restrict our attention to thin films and small director angles, and we study two particular cases in which either orientational elasticity effects or flow effects dominate the alignment of the liquid crystal. We find that there is a unique solution of the drag-out problem, whereas there may be multiple solutions of the drag-in problem. When orientational elasticity effects dominate we obtain a simple analytical solution for the director. When flow effects dominate we find that the director is uniform in the bulk of the liquid crystal, which exhibits thin orientational boundary layers near the substrate and the free surface, within which the director orientation changes rapidly from its prescribed boundary value to the flow alignment angle. These boundary layers may be potential locations for the nucleation of defects.     

Schematic model for the differential cross section in ion-pair formation

An analytic approximation to the differential cross section is derived for ion-pair formation in a model two-state (“turned-on Coulomb”) system. The result gives insight into the structure observed in recent experiments.     

A study of the mixing of a liquid into an elastomer

A low-melting alloy was mixed with SBR and carboxy-NBR on a rubber mill above its melting point, and changes in its state of dispersion were examined through an optical microscope. Solution of the resulting mix showed that many of the particles of alloy were of colloid size, and did not settle out. Repeated washing of the sediment with solvent could not separate all the rubber phase from the sediment, and a form of bound rubber is postulated.     

Isotope gas analysis of tritium-labelled water by means of an automatic apparatus

A procedure and an automatic apparatus designed for the radioactivity measurement of tritium-labelled water in the gaseous phase are described. The method is based on the conversion of water to hydrogen, methane and carbon monoxide in a carbon-packed quartz reactor. The reaction products are swept by hydrogen carrier gas into a piston-type counter tube. Methane is fed to the radioactive gaseous mixture, and the radioactivity of the hydrogen-methane-carbon monoxide mixture is measured in the limited proportional region. The radioactivity values are correlated with the weight of the sample taken and the results are corrected for the ‘memory effect’ obtained in the measurement of inactive water samples. The standard deviation of the procedure, characteristic of its reproducibility, is lower than ±0.5% rel. at preset number of counts.     

A mathematical model for the interactions between non-identical rough spheres, liquid bridge and liquid vapor

Investigation of the interactions between the skeleton of an unsaturated particulate material and the contained liquid involves the general interaction model consisting of a liquid bridge in contact with two rigid smooth spherical particles of unequal size and dissimilar material, at a separation determined by their actual surface roughness, and surrounded by a gas with a vapor pressure at equilibrium with the liquid. The liquid retention and capillary force of the system are related to the capillary suction, liquid-solid contact angles, filling angles, roughness of the particles, and the ratio of particle radii in normalized terms by assuming a circular arc for the shape of the liquid profile. The normalized suction is also related to the corresponding relative humidity of the pore air. The calculated equilibrium relations are shown to possess non-uniqueness, which is interpreted in terms of mechanical properties of unsaturated particulate materials. The model is able to provide new insights into the behavior of an unsaturated particulate material.     

A two-photon absorption cross section measurement in nitric oxide

We report here the measurement of a two-photon absorption cross section for the R₂₂ + S₁₂ (J″ = 9.5) [A ²Σ⁺ (ν′ = 0) - X ²Π (ν′ = 0)] transition in the gamma band system of nitric oxide by measuring the third-order susceptibility using a four-wave mixing technique. A value of σ⁽²⁾ = (1.0 ± 0.6) X 10^?38 πg(2ω₁ ? ω_f) cm⁴ s was obtained.     

Spectrophotometric errors associated with cells of circular cross section

It is shown that the use of spectrophotometric cells having circular cross sections leads to errors that depend on the absorbance, on the ratio of beam width to cell diameter, and on the distance between the center of the beam and the diameter of the cell, but that the nature and magnitude of these errors render them essentially undetectable in practical analytical work.     

Synthesis of uniform goethite nanotubes with parallelogram cross section

Uniform goethite nanotubes were synthesized from the reaction of hydrazine with Fe(III)-oleate complex immobilized in reverse micelles. The nanotubes have interesting parallelogram cross section with uniform edge dimension of as small as 7 nm. The edge dimensions and lengths of the nanotubes were easily controlled by varying the reaction conditions.     

Differential capacitance of liquid/liquid interfaces--a lattice gas model approach

A lattice gas model formalism under mean field approximation is developed for the analysis of differential capacitance pertaining to liquid/liquid interfaces. The interfacial profiles for the two solvent mole fractions are chosen and ionic charge densities are estimated by minimizing the Helmholtz free energy. The dependence of the differential capacitance on various interaction energies, electrolyte concentrations and dielectric constants is indicated. The influence of the solvent density profile is analyzed and deviations from the predictions of Gouy-Chapman theory are pointed out.     

Scale-adaptive simulation of liquid mixing in an agitated vessel equipped with eccentric HE 3 impeller

The current study presents the results of a numerical simulation of hydrodynamics in an agitated vessel equipped with an eccentric HE 3 impeller. CFD (computational fluid dynamics) simulations were carried out using ANSYS 14.0 software. Time-dependent simulations of turbulent flow were carried out using the SAS-SST (scale adaptive simulation-shear stress transport) method coupled with the SM (sliding mesh) method. The results of the calculations are presented as contours of velocity in different cross-sections of the agitated vessel, as well as profiles of components of velocity vector and turbulence kinetic energy and its dissipation rate. The iso-surface of vorticity, which shows the region of possible vortex existence, is also presented. A numerically obtained data set of impeller power number was used to calculate the averaged impeller power number. This value was compared with the experimental data with good results. The relationship between impeller position and fluctuation of the impeller power number was also analysed.     

Excess volume of mixing of some electron-donating hydrocarbons with an electron-accepting liquid 1,2,4-trichlorobenzene

The excess volume of mixing of some electron-donating aromatic hydrocarbons like benzene, toluene,p-xylene, and mesitylene with an electronaccepting liquid 1,2,4-trichlorobenzene have been measured at 30°C. The results indicate that the interaction between the components increases as the electron-donating power of the hydrocarbons increases. The V _m ^e values are related to the ionization potentials of the hydrocarbons.