Epoxy-based azo molecular glasses with four-arm architecture: Preparation,characterization and holographic recording

A series of epoxy-based azo molecular glasses with four-arm architecture was synthesized, characterized and applied to holographic recording.     

Determination of surface charge properties of PC-12 cells by electrophoresis

The electrophoretic behavior of pheochromocytoma (PC-12) cells was investigated both experimentally and theoretically. Cell mobility in aqueous media at different pHs and ionic concentrations was measured, and a model, which assumed that the cell surface contains both acidic and basic functional groups, was proposed. As a result, it was revealed that the experimental data gathered can be described satisfactorily by assuming that the cell surface contains two types of monovalent acidic functional groups and one basic functional group. The values of the dissociation constants of the acidic and basic groups are found to be close to those of acidic amino acids, which indicates that the acidic amino acids may play an important role in the surface electrical properties of PC-12 cells.     

Determination of isoniazid methanesulphonate and its metabolites in rabbit blood by high-performance liquid chromatography

A rapid and sensitive high-performance liquid chromatographic method is described for simultaneous determination of isoniazid methanesulphonate (IHMS) and its metabolites, such as isoniazid (INH) and acetylisoniazid (AcINH) in rabbit blood. According to stability studies, IHMS was most stable at pH 3-5. After acidifying the blood to pH 5.0, a suitable amount of acetonitrile was added to the supernatant for extraction and niacinamide served as an internal standard. After evaporation, the residue was reconstituted with phosphate buffer and aliquots of this solution were separated on a reversed-phase phenyl column by a mobile phase consisting of 0.25 mM tetrabutylammonium phosphate as a paired-ion reagent. UV detection was performed at 280 nm. Under these conditions, the between-run coefficients of variation of IHMS, INH and AcINH from 1 to 25 microns/ml were 4.7 +/- 2.5, 5.4 +/- 1.0 and 5.1 +/- 3.1%, respectively. Hence this sensitive, reproducible and accurate method was suitable for pharmacokinetic studies of IHMS.     

Drag on two nonuniformly structured flocs moving along the axis of a cylindrical tube

The boundary effect on the drag on two identical, nonuniformly structured flocs moving along the axis of a cylindrical tube filled with a Newtonian fluid is investigated at a small to medium larger Reynolds number. A two-layer model is adopted to simulate various possible structures of a floc, and the flow field inside is described by Darcy–Brinkman model. The results of numerical simulation reveal that a convective flow is present in the rear region of a floc when Reynolds number is on the order of 40. The presence of the tube wall and/or the porous structure of a floc has the effect of reducing that convective flow. For a fixed level of the volume-average permeability of a floc, the influence of the tube wall on the drag depends upon floc structure; the influence on a nonuniformly structured floc is more significant than that on a uniformly structured floc. The more nonuniform the floc structure, the more appreciable the deviation of the drag coefficient–Reynolds number curve from a Stokes’-law-like relation becomes. The smaller the volume-average permeability of a floc and/or the smaller the separation distance between the two flocs, the greater is the deviation, but the presence of the tube wall has the effect of reducing that deviation.     

Dual behavior of masked o-benzoquinones in intramolecular Diels-Alder reactions. Expedient synthesis of highly functionalized cis-decalins from 2-methoxyphenols

[Reaction: see text]. The potential dual behavior as dienes and dienophiles of the diene moieties of masked o-benzoquinones (MOBs) 10a-e-12a-e, generated upon oxidation of 2-methoxyphenols 1-3 with BTIB in the presence of appropriate dienols, in their intramolecular Diels-Alder (IMDA) reactions has been examined. The IMDA reactions of MOBs 10a-d, 11a,b,d, and 12a,b,d resulted in highly functionalized oxatricyclic compounds 18a-d, 19a,b,d, and 20a,b,d, respectively, with concomitant formation of cis-decalin derivatives 21a-d, 22a,b,d, and 23a,b,d in a highly regio- and stereoselective manner. However, the MOBs 10e-12e provided exclusively oxatricyclic compounds 18e-20e. The formation of cis-decalins in these IMDA reactions illustrates the dienophilic character of MOBs, in addition to their behavior as dienes. The ratio of the two cycloadducts obtained in each reaction as a result of the dual character of MOBs depends on the nature and/or position of the substituents on both the cyclohexadienone moiety and the added 2,4-dienol. The majority of the cycloadducts resulted from the diene property of MOBs in intramolecular Diels-Alder reactions smoothly underwent Cope rearrangement to furnish cis-decalins as sole products in excellent to quantitative yields that provides a short and efficient entry to polyfunctionized cis-decalins from 2-methoxyphenols. Furthermore, the variation of dienophilic and diene characters of MOBs in the IMDA reactions with the electron-donating or electron-withdrawing substituent of both cyclohexadienone moiety and the added conjugated acyclic diene or 2,4-dienol has been studied in detail.     

Stability of a dispersion of particles covered by a charge-regulated membrane: effect of the sizes of charged species

The influence of the sizes of charged species on the stability of a colloidal dispersion is investigated theoretically. We consider the case where a particle comprises a rigid core and an amphoteric, charge-regulated membrane layer, which simulates biocolloids and particles covered by artificial membranes. A modified Poisson-Boltzmann equation, which takes the sizes of all the charged species into account, is adopted to describe the electrical field. The effects of other key parameters such as electrolyte concentration, pH, and the valence of counterions on the behavior of a dispersion are also examined. We show that the larger the effective size of the counterions, the greater the stability ratio, which is consistent with experimental observations in the literature.     

Studies on the thermotropic liquid crystalline polymer. VII. Synthesis and properties of photocrosslinkable poly(ether-ester) containing cinnamic group

A series of semi-aromatic poly(ether-ester)s containing cinnamic group was prepared from 4,4′-diacrylic acid-α,ω-phenoxyalkanes with diols in the presence of diphenylchlorophosphate (DPCP) and pyridine as a catalyst and solvent. The phase behavior of these polymers was studied by differential scanning calorimetry (DSC), optical polarizing microscopy equipped with a heating stage, and wide-angle x-ray diffraction (WAXD). All of the poly(ether-ester)s, except P3 , show nematic or smectic thermotropic liquid crystalline behaviour under optical polarizing microscopic observation. These polymers can undergo photocrosslinking reaction upon heating, as examined by IR, solubility, and DSC analysis. © 1993 John Wiley & Sons, Inc.     

Charge transport properties of tris(8-hydroxyquinolinato)aluminum(III): why it is an electron transporter

The charge transport properties of mer-tris(8-hydroxyquinolinato)aluminum(III) (mer-Alq), which is the most widely used electron transport material in OLED, were investigated by quantum chemistry calculations within the framework of the charge hopping model and Marcus electron transfer theory. Internal reorganization energies of 0.276 and 0.242 eV were calculated by the DFT-B3LYP method employing a 6-31 G* basis set for the electrons lambdai(e) and holes lambdai(h), respectively. The relative distances and orientations of Alq molecules in amorphous film were simulated by those in the beta-phase. The intermolecular charge-transfer integrals, Hda(h) and Hda(e), along all 14 hopping pathways were then calculated by the Koopmans Theorem in conjunction with the Hartree-Fock method employing a 6-31 G* basis set as well as by the direct coupling method. The results showed that there were some Hda(e) that were 1 order of magnitude larger than any Hda(h), because hopping pathways with effective overlaps of LUMOs can occur and, thus, large Hda(e). On the other hand, effective overlap of HOMO was absent in all pathways, resulting in a relatively small Hda(h). This difference in the magnitudes of Hda(e) and Hda(h) would predict a 2 orders of magnitude difference in the electron-transfer rate constants and account for the observed 2 orders of magnitude difference in the mobilities of electrons and holes.     

Charge stabilization in nonpolar solvents

While the important role of electrostatic interactions in aqueous colloidal suspensions is widely known and reasonably well-understood, their relevance to nonpolar suspensions remains mysterious. We measure the interaction potentials of colloidal particles in a nonpolar solvent with reverse micelles. We find surprisingly strong electrostatic interactions characterized by surface potentials, |ezeta|, from 2.0 to 4.4 k(B)T and screening lengths, kappa(-1), from 0.2 to 1.4 microm. Interactions depend on the concentration of reverse micelles and the degree of confinement. Furthermore, when the particles are weakly confined, the values of |ezeta| and kappa extracted from interaction measurements are consistent with bulk measurements of conductivity and electrophoretic mobility. A simple thermodynamic model, relating the structure of the micelles to the equilibrium ionic strength, is in good agreement with both conductivity and interaction measurements. Since dissociated ions are solubilized by reverse micelles, the entropic incentive to charge a particle surface is qualitatively changed from aqueous systems, and surface entropy plays an important role.     

Two-temperature dilute-acid prehydrolysis of hardwood xylan using a percolation process

This article outlines some of the factors influencing the choice of a suitable reactor for using immobilized biocatalysts. We have concentrated on biochemical engineering parameters of immobilized biocatalysts, which are important with respect to their application in industrial processes.