On the interpretation of solubilization results obtained from semi-equilibrium dialysis experiments

The interpretation of intramicellar solubilization data obtained from semi-equilibrium dialysis (SED) experiments is described, and methods are presented for determining equilibrium constants for the solubilization of organic species by aqueous surfactant solutions as well as activity coefficients of both the organic solute and the surfactant within the micelle. The solubilization equilibrium constant of an organic solute in an aqueous micellar solution (K) is defined as the ratio of the mole fraction of organic solute in the micellar pseudophase (X) to the concentration of the unsolubilized monomeric organic solute in the aqueous phase (c ₀). Expressions compatible with the Gibbs-Duhem equation are used to represent the concentration dependence of activity coefficients of both the solubilizate and surfactant in the micellar pseudophase; the analysis leads to calculated values of the concentrations of free and intramicellar surfactant and organic solute in both compartments of the equilibrium dialysis cell. Solubilization equilibrium constants for many amphiphiles are well correlated by the simple expressionK=K ₀(1-BX)², whereB is an empirical constant andK ₀ is the limiting value ofK asX approaches 0.     

Economic feasibility study of polyelectrolyte-enhanced ultrafiltration (PEUF) for water softening

In polyelectrolyte-enhanced ultrafiltration (PEUF), a water-soluble anionic polyelectrolyte (in this study sodium polystyrene sulfonate or PSS) is added to hard water. The calcium and magnesium bind to the polymer which has a high enough molecular weight to be rejected by an ultrafiltration membrane. The permeate is softened water. Economically, the PSS needs to be recovered from the retentate for reuse. Three methods of recovery developed in this study were addition of NaCl, Na₂CO₃ or HCl to PEUF to regenerate PSS. Of the three PEUF processes considered, NaCl/PEUF as compared to Na₂CO₃/PEUF and HCl/PEUF provided the best scheme for the water softening process. PEUF is shown in this study to be competitive with lime softening at low flow rates. The PEUF process is more expensive than ion exchange for a stream containing only hardness ions. However, PEUF becomes nearly comparable with ion exchange for a stream containing hardness ions as well as bacteria, viruses and pyrogen. The cost comparisons are based on fully continuous operations and include treatment of waste streams from each process.     

RESTRICTED LIE ALGEBRAS WITH MAXIMAL 0-PIM

In this paper it is shown that the projective cover of the trivial irreducible module of a finite-dimensional solvable restricted Lie algebra is induced from the one dimensional trivial module of a maximal torus. As a consequence, the number of the isomorphism classes of irreducible modules with a fixed p-character for a finite-dimensional solvable restricted Lie algebra L is bounded above by p ^MT(L), where MT(L) denotes the maximal dimension of a torus in L. Finally, it is proved that in characteristic p > 3 the projective cover of the trivial irreducible L-module is induced from the one-dimensional trivial module of a torus of maximal dimension, only if L is solvable.     

Differential non-destructive image current detection in a fourier transform quadrupole ion trap

Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd.     

Use of surfactants to remove water-based inks from plastic film: effect of calcium ion concentration and length of surfactant hydrophobe

Effective plastic film deinking could permit the reuse of recycled polymer to produce clear film, reduce solid waste for landfills, reduce raw material demand for polymer production, and aid process economics. In this study, the deinking of a commercial polyethylene film printed with water-based ink was studied using surfactants in the presence of hardness ions (calcium ions) at various pH levels. The electrostatic properties of ink particles in a washing bath were also investigated. Synthetic anionic surfactant or fatty acid soap in the presence of calcium ions at alkaline pH levels was found to be nearly as effective at deinking as cationic, nonionic, or amphoteric surfactants alone. However, adding calcium ions decreases the deinking effectiveness of cationic, nonionic, and amphoteric surfactants. Increasing the length of the ionic surfactant hydrophobe enhances deinking. Zeta potential measurements showed that water-based ink particles in water reach the point of zero charge (PZC) at a pH of about 3.6, above which ink particles are negatively charged, so cationic surfactant tends to adsorb better on the ink than anionic surfactant above the PZC in the absence of calcium. As the cationic surfactant concentration is varied between 0.005 and 25 mM, the zeta potential of the ink particles reverses from negative to positive owing to adsorption of cationic surfactant. For anionic surfactants, added calcium probably forms a bridge between the negatively charged ink and the negatively charged surfactant head groups, which synergizes adsorption of the surfactant and aids deinking. In contrast, calcium competes for adsorption sites with cationic and nonionic surfactants, which inhibits deinking. All the surfactants studied here disperse ink particles effectively in the washing bath above pH 3 except for the ethoxylated amine surfactant.     

Temperature hysteretic effect and its influence on colossal magnetoresistance of La0.33Nd0.33Ca0.33MnO3

Electrical resistance (R) measurements of a bulk La_0.33Nd_0.33Ca_0.33MnO₃ perovskite in magnetic fields up to 40 kOe have revealed anomalous temperature hysteretic effects both in 0 Oe and 20 kOe magnetic fields. The sharp peak observed in the R vs. T plot indicates the occurrence of metal-to-insulator (M-I) transition at a temperature of T _MI=110 K and 140 K, for cooling and warming paths, respectively. An applied magnetic field of 20 kOe reduces the resistance and shifts T _MI to 160 K and 185 K for cooling and warming, respectively. We have observed a much higher resistance in the cooling path than in the warming path leading to the hysteretic resistance ratio (R _cool/R _warm) of 200 at 110 K and 1.8 at 160 K for 0 Oe and 20 kOe, respectively. Record values of colossal magnetoresistance (CMR) have been achieved. The CMR value reaches nearly 99% in the temperature ranges of 90 K to 140 K and 90 K to 170 K for 20 kOe and 40 kOe magnetic fields in the cooling mode, respectively. The observed unusual behavior is attributed to the co-existence of La-rich and Nd-rich domains assumed to be distributed randomly in the compound.     

ac Conductivity of mixed spinel NiAl0.7Cr0.7Fe0.6O4

ac Conductivity measurements are carried out across the metal to insulator transition in NiAl_0.7Cr_0.7Fe_0.6O₄. The low frequency data is analyzed using Summerfield scaling theory for hopping conductivity. The exponent of the scaling behavior has significantly different values in the conducting and insulating regimes. The hopping frequency and the zero frequency conductivity are found to increase with temperature, slowly in the metallic regime and rapidly in the insulating regime.