Sorption of selenium oxyanions on TiO2 (rutile) studied by batch or column experiments and spectroscopic methods

Selenium is a known toxic element released in the environment by anthropogenic activities. The present study is devoted to the aqueous sorption behaviour of selenium oxyanions (selenate and selenite) on a reference oxide surface, namely rutile TiO(2). Batch sorption kinetics and isotherms have been studied using different physico-chemical conditions of the solution (changes of pH and ionic strength). The sorption was favoured for both anions in acidic conditions, in agreement with a surface complexation mechanism and CD-MUSIC predictions. Spectroscopic investigations of the sorbed rutile powder were also consistent with such a mechanism. EXAFS spectra confirmed that for selenite anions, an inner-sphere mechanism was the most probable process observed. Dynamic sorption experiments using a column filled with rutile powder also substantiated that a part of the surface complexes follows the inner-sphere mechanism, but also evidenced that an outer-sphere mechanism cannot be excluded, especially for selenate anions.     

Roadwise Review has limited congruence with actual driving performance of aging drivers

The Roadwise Review (RR) CD-ROM has been proposed as one way for older drivers to self-evaluate the skills that support safe driving. To better gauge the utility of RR for that purpose, further validation of RR vis-à-vis measures of driving performance is needed. We carried out this study to provide such validation. We correlated the results of the standard Useful Field of View subtest 2 (UFOV-2) and Trail Making Test (TMT) parts A and B to the corresponding RR subsections on visual information processing and visual search. We further examined the correlations between on-road performance (based on demerit points) and RR results (absolute scores and number of problems identified). The correlations between UFOV-2, TMT and the relevant RR sections ranged from .46 to .61. The correlations between demerit points and RR absolute values ranged from −.40 to .50. The correlations between demerit points and the number of problems identified by RR ranged from −.24 to .45. Using a “pass/fail” approach we also failed to find a relationship with the number of problems. These results indicate limited convergence between findings obtained with RR and actual performance using standardized approaches. Such results emphasize the importance of developing a rigorous data synthesis process before attempting knowledge translation of material aimed at older drivers.     

Reduction electrochimique de propene nitriles substitues—III alkyl(aryl)oxy-3 phenyl-3 propene nitriles Z et E

The preparation and the separation of E- and Z-isomers of 3-alkyl(aryl)oxy-3-phenylpropenenitriles are described. Configurations are assigned by nmr.In aqueous-organic media Z-isomers are more easily reduced than E-isomers. In anhydrous acetonitrile differences between E$\text{1}\text{2}$ of E- and Z-isomers are smaller or null.Polarography, cyclic voltammetry and macro-scale reductions with identification of products permit us to propose a reduction mechanism. If Taft's constant σ* of R group is negative the CC double bond is reduced with formation of 3-alkyl(aryl)oxy-3-phenylpropanenitriles. If σ* is positive the intermediate radical-anion loses RO^? ion; cinnamonitrile is formed but immediately reduced, either to in 3-phenylpropanenitrile, or to in 3,4-diphenylhexane dinitrile.It is possible to get hydrodimers while conserving OR group.     

Offset printing inks based on rapeseed and sunflower oil. Part I: Synthesis and characterization of rapeseed oil-and sunflower oil-modified alkyd resins

Two sets of alkyd resins of variable oil lengths with the required properties for offset printing ink formulations, modified by sunflower and rapeseed oil, were synthetized according to the “monoglyceride” process. The influence of the acyl composition of the modifying vegetable oil and of the oil content on alkyds’ properties was determined by detailed chemical and rheological characterization. Molecular structure, size, and molecule size distribution appeared to be linked to these two factors. A comparative study with two usual linseed oil-modified alkyds led to determination of the more appropriate alkyds for applications in offset varnishes.     

High-Temperature, High-Pressure X-ray Investigation of Dicalcium Silicate

Energy-dispersive X-ray powder diffraction experiments have been investigated at high temperature and room pressure, and at high pressure and room temperature, starting from either γ- or β-Ca₂SiO₄. High-temperature studies were performed up to 1980 K, using a versatile heating cell. The high-temperature phase transformations previously described were reexamined. Volume and linear thermal expansions were measured for each Ca₂SiO₄ polymorph, γ, β, α';_L,α';_H, and α. Volume thermal expansion increases with increasing temperature except for α';_H, whose thermal expansion tends to decrease at elevated temperature. High-pressure investigations were performed in the 0–15 GPa pressure range, using a diamond anvil cell, with silicon oil as the pressure-transmitting medium. The value of the room-pressure bulk modulus K₀ , assuming a second-order BirchMurnaghan equation of state with K'₀= 4, is 140(8) GPa for γ-Ca₂SiO₄. The γ olivine form exhibits anisotropic compression, with the c axis as the most compressible. From such in situ high-pressure X-ray investigations, the γ-→Ca₂SiO₄ phase transformation induced by cold compression is clearly evidenced and extends from 2 to about 5 GPa.     

Synthesis and characterization of poly(oxyethylene)–poly(caprolactone) multiblock copolymers

Novel poly(oxyethylene)/poly(caprolactone) POE/PCL copolymers were synthesized by step growth polymerization of poly(ε-caprolactone) diols and poly(ethylene glycol) diacids using dicyclohexylcarbodiimide as coupling agent. The reaction was performed at room temperature and yielded multiblock copolymers with predetermined POE and PCL block lengths. The resulting copolymers were characterized by various analytical techniques including SEC, IR, ¹H NMR, DSC and X-ray diffractometry. Data showed that the properties of these polymers can be modulated by adjusting the chain lengths of the macromonomers. In particular, one or two crystalline structures can exist within the copolymers of various crystallinities. © 1998 SCI.     

Infrared study of nitrogen monoxide adsorption on palladium ion-exchanged ZSM-5 catalysts

The adsorption of NO at room temperature on a H-ZSM-5 catalyst exchanged with Pd(NH₃) ₄ ²⁺ complex and activated in oxygen at 773 K has been examined by FTIR spectroscopy. After the oxidizing treatment, the Pd tetrammine complex decomposed into Pd(II) ions and/or Pd(II) hydroxyl complexes dispersed in the zeolite channels. The subsequent adsorption of NO at room temperature led to the reduction of Pd(II) to Pd(I) entities, resulting in the formation and adsorption of NO₂ on H-ZSM-5. The Pd(I) entities were shown to adsorb NO and form mononitrosyl complexes dispersed in the zeolite porosity and characterized by a single infrared absorption band at 1881 cm^–1. The Pd(I) mononitrosyl complex was shown to reversibly coordinate water and NO₂ molecules. The resulting nitrosyl complex was characterized by a single NO vibration band at 1836 cm^–1.     

Low Breakdown Voltage Varistors by Grain Boundary Diffusion of Molten Bi2O3 in ZnO

Diffusion of molten Bi₂O₃ into the grain boundaries of sintered, alumina-doped (0.23 and 0.7 mol%) ZnO pellets resulted in varistors with breakdown voltages in the 3–5 V range and nonlinearity coefficients of 10–24. The varistors were fabricated by spreading a thin layer of Bi₂O₃ powder on the surface of ZnO pellets and heating the combination to various temperatures (860–1155°C) and different times. The highest nonlinearity coefficients (20–24) and lowest breakdown voltages (3–5 V) were recorded in samples annealed at 860°C for 35 min. Longer annealing times and/or higher temperatures resulted in progressively higher breakdown voltages. Eventually the devices became insulating, which was attributed to the formation of an insulating Bi₂O₃ layer between the grains. Separate wetting experiments have shown that the penetration of Bi₂O₃ into ZnO grain boundaries was a strong function of alumina doping —the penetration rate was decreased by a factor of 5–7 as the ZnO was doped with as little as 0.2 mol% alumina. It is this slowing down of the penetration of the ZnO grain boundaries that is believed to be critical in the development of the low breakdown voltages observed.     

Viscosimetric study of poly(vinyl alcohol)/poly(styrenesulfonic acid) miscibility in dilute aqueous solution

The miscibility of poly(vinyl alcohol) (PVA) and poly(styrenesulfonic acid) (PSSA) in dilute aqueous solutions was studied by a viscosimetric method. At a constant molecular weight of PSSA, it was found that the miscibility of both polymers increases with the molecular weight and the number of acetate groups of the PVA samples (1 and 12% unhydrolyzed sites). Moreover, this miscibility increases slightly with the total mixture concentration in the interval 1–2 g/dL. By comparison of the results of reduced viscosity of PVA/PSSA and PVA/poly(sodium styrenesulfonate) (PSSNa) mixtures, it has been deduced that the miscibility of two polymers is due mainly to intermolecular interactions between the hydroxyl and sulfonic groups of PVA and PSSA, respectively. These groups act as acceptors and donors of hydrogen bonds which are the responsible for polymers' miscibility. © 1996 John Wiley & Sons, Inc.