Insoluble anode of porous lead dioxide for electrosynthesis: preparation and characterization

Preparation of a novel type of titanium-substrate lead dioxide anode with enhanced electrocatalytic activity for electrosynthesis is described. It has been demonstrated that in the presence of a suitable surfactant in the coating solution, an adherent and mainly tetragonal form of lead dioxide is deposited on a platinized titanium surface such that the solution side of the coating is porous while the substrate side is compact. By an analysis of anodic charging curves and steady-state Tafel plots with such porous electrodes in contact with sodium sulphate solution, it has been proved that the electrochemically active area of these anodes is higher by more than an order of magnitude when compared to the area of conventional titanium-substrate lead dioxide anodes. The electrocatalytic activity is also thereby enhanced to a significant degree.

Kinetics and mechanism of anodic oxidation of chlorate ion to perchlorate ion on lead dioxide electrodes

The kinetics and mechanism of anodic oxidation of chlorate ion to perchlorate ion on titanium-substrate lead dioxide electrodes have been investigated experimentally and theoretically. It has been demonstrated that the ionic strength of the solution has a marked effect on the rate of perchlorate formation, whereas the pH of the solution does not influence the reaction rate. Experimental data have also been obtained on the dependence of the reaction rate on the concentration of chlorate ion in the solution at constant ionic strength. With these data, diagnostic kinetic criteria have been deduced and compared with corresponding quantities predicted for various possible mechanisms including double layer effects on electrode kinetics. It has thus been shown that the most probable mechanisms for anodic chlorate oxidation on lead dioxide anodes involve the discharge of a water molecule in a one-electron transfer step to give an adsorbed hydroxyl radical as the rate-determining step for the overall reaction.

NMR spectrum of pyridine-N-oxide in a thermotropic nematic phase

Absract is not available.

Cuprous oxide catalyzed air oxidation of thiosulfate and tetrathionate

Thiosulfate (S2O32−) and tetrathionate (S4O62−)are oxidized to sulfate by air at atmospheric pressure and 50–70°C in the presence of cuprous oxide (Cu2O) as catalyst. Sulfate is produced from S2O32− by series-parallel reaction paths involving S4O62− as an intermediate. The rate data obtained for air oxidation of S2O32− on Cu2O agree well with a pseudo-homogeneous first order kinetic scheme, yielding values of rate constants for series parallel reaction paths which have been used in modelling the catalyzed air oxidation of S2O32−. Air oxidation of S4O62− on Cu2O proceeds at a higher rate in the presence of S2O32− than in its absence. Cu2O is less active than Cu2S for the air oxidation of S2O32−, as shown by the rate constant values which for Cu2O catalyzed oxidation are an order of magnitude smaller than those for the Cu2S catalyzed oxidation.

Elastic properties of lead phosphomolybdate glassess

Elastic properties of lead phosphomolybdate [PbO-1bMoO3-1bP2O5] glasses have been investigated using ultrasonic velocity measurements at 10MHz. The composition dependence of elastic moduli, Poisson's ratio and the Debye temperature are found to be consistent with a structural model proposed earlier. According to this model lead acts both as a network former and as a network modifier in different composition regimes. It is suggested that the incorporation of lead into the network is accompanied by the conversion of three-connected [Image ] tetrahedra into four-connected Image tetrahedra in the network. lead; phosphorus; molybdenum

A novel combustion process for the synthesis of fine particle α-alumina and related oxide materials

Synthesis of fine particle α-alumina and related oxide materials such as MgAl2O4, CaAl2O4, Y3Al5O12 (YAG), Image , β′-alumina, LaAlO3 and ruby powder (Image ) has been achieved at low temperatures (500°C) by the combustion of corresponding metal nitrate-urea mixtures. Solid combustion products have been identified by their characteristic X-ray diffraction patterns. The fine particle nature of α-alumina and related oxide materials has been investigated using SEM, TEM, particle size analysis and surface area measurements.

Lanthanide perchlorate complexes of 4-cyano pyridine-N-oxide, 4-chloro 2-picoline-N-oxide and 4-dimethyl amino-2-picoline-N-oxide

Complexes of lanthanide perchlorates with 4-cyano pyridine-1-oxide, 4-chloro 2-picoline-1-oxide and 4-dimethyl-amino 2-picoline-1-oxide have been isolated for the first time and characterized by analysis, conductance, infrared, NMR and electronic spectra. The complexes of 4-cyano pyridine-1-oxides have the composition Ln(CyPO)6(ClO4)3. 2H2O (Ln=La, Sm, Dy and Ho); Ln(CyPO)7 (ClO4)3. 2H2O (Ln=Pr, Nd, Er and Yb); and Ln(CyPO)5 (ClO4)3. 2H2O (Ln=Gd and Tb). The complexes of 4-chloro 2-picoline-1-oxide analyse for the formulae Ln(CpicO)6 (ClO4)3 (Ln=La, Pr, Nd and Ho); and Ln (CpicO)5 (ClO4)3 (Ln=Er and Yb), and those of 4-dimethylamino 2-picoline-1-oxide for Ln(DMPicO)6 (ClO4)3 (Ln=La and Nd); Ln(DMPicO)7 (ClO4)3 (Ln=Gd, Er and Yb); and Ln(DMPicO)8 (ClO4)3 (Ln=Dy and Ho).

Novel role of the nitrite transporter NirC in Salmonella pathogenesis: SPI2-dependent suppression of inducible nitric oxide synthase in activated macrophages

Activation of macrophages by interferon gamma (IFN- ) and the subsequent production of nitric oxide (NO) are critical for the host defence against Salmonella enterica serovar Typhimurium infection. We report here the inhibition of IFN- -induced NO production in RAW264.7 macrophages infected with wild-type Salmonella. This phenomenon was shown to be dependent on the nirC gene, which encodes a potential nitrite transporter. We observed a higher NO output from IFN- -treated macrophages infected with a nirC mutant of Salmonella. The nirC mutant also showed significantly decreased intracellular proliferation in a NO-dependent manner in activated RAW264.7 macrophages and in liver, spleen and secondary lymph nodes of mice, which was restored by complementing the gene in trans. Under acidified nitrite stress, a twofold more pronounced NO-mediated repression of SPI2 was observed in the nirC knockout strain compared to the wild-type. This enhanced SPI2 repression in the nirC knockout led to a higher level of STAT-1 phosphorylation and inducible nitric oxide synthase (iNOS) expression than seen with the wild-type strain. In iNOS knockout mice, the organ load of the nirC knockout strain was similar to that of the wild-type strain, indicating that the mutant is exclusively sensitive to the host nitrosative stress. Taken together, these results reveal that intracellular Salmonella evade killing in activated macrophages by downregulating IFN- -induced NO production, and they highlight the critical role of nirC as a virulence gene.

The study of oxidation state of manganese in lead oxyhalide glasses by optical spectroscopy

Abstaract is not available.

Magnetic interactions in the oxide systems LaNi1-xMxO3 (M = Cr, Fe, or Co)

Magnetic susceptibilities of several members of the series of oxides of the general formula LaNi1-xMxO3 (M = Cr, Fe, or Co) are reported. The oxides show evidence for interesting ferrimagnetic (Cr and Co) and antiferromagnetic (Fe) interactions.

Study of surface acidity of oxide catalysts by photoacoustic spectroscopy

Photoacoustic spectroscopy has been employed to estimate quantitatively the acid sites on oxide catalysts. The technique involves the measurement of the ratio of intensities of absorption bands due to conjugate bases and acids of indicators adsorbed on the catalyst surface as a function of the amount of added n-butylamine. Basic sites in sodium-impregnated alumina samples have been examined by adsorbing phenolphthalein on these surfaces.

Growth of tin oxide single crystals in porcelain tunnel kilns

Single crystals of tin oxide have been grown under conditions obtained in oil fired porcelain tunnel kilns. It was noted that the reducing conditions in the kilns help in the growth of SnO2 crystals at much lower temperatures (1300°C). The growth seems to more pronounced in presence of silicon carbide. The crystals grow as long fibres of 0.1 to 0.5 mm dia. and 10 to 50 mm length. The crystals exhibit rutile structure and the direction of growth seems to be favoured in any one of the major axes a and c.

Stable Dispersions of Metal Oxide Nanowires and Nanoparticles in Water, Dimethylformamide and Toluene

In view of the important need to generate well-dispersed inorganic nanostructures in various solvents, we have explored the dispersion of nanostructures of metal oxides such as TiO2, Fe3O4 and ZnO in solvents of differing polarity in the presence of several surfactants. The solvents used are water, dimethylformamide (DMF) and toluene. The surfactant-solvent combinations yielding the best dispersions are reported alongwith some of the characteristics of the nanostructures in the dispersions. The surfactants which dispersed TiO2 nanowires in water were polyethylene oxide (PEO), Triton X-100 (TX-100), polyvinyl alcohol (PVA) and sodium bis(2-ethylhexyl) sulphosuccinate (AOT). TiO2 nanoparticles could also be dispersed with AOT and PEO in water, and with AOT in toluene. In DMF, PVA, PEO and TX-100 were found to be effective, while in toluene, only AOT gave good dispersions. Fe3O4 nanoparticles were held for long periods of time in water by PEO, AOT, PVA and polyethylene glycol (PEG), and by AOT in toluene. In the case of ZnO nanowires, the best surfactant-solvent combinations were found to be, PEO, sodium dodecyl sulphate (SIDS) and AOT in water and AOT, PEG, PVA, PEO and TX-100 in DMF In toluene, stable dispersions of ZnO nanowires were obtained with PEO. We have also been able to disperse oxide nanostructures in non-polar solvents by employing a hydrophobic silane coating on the surface.

Metal-insulator-semiconductor capacitors with bismuth oxide as insulator

Metal-insulator-semiconductor capacitors using aluminum Bi2O3 and silicon have been studied for varactor applications. Reactively sputtered Bi2O3 films which under suitable proportions of oxygen and argon and had high resistivity suitable for device applications showed a dielectric constant of 25. Journal of Applied Physics is copyrighted by The American Institute of Physics.