Substrate effect on electrodeposited nanocrystalline Al-Mg alloy powders

Supersaturated dendritic Al-Mg alloy powders in globular form were produced using galvanostatic electrodeposition technique on polycrystalline Cu and Mg-substrates. The deposit produced on Cu-substrate possessed face centered cubic (fcc)-Al(Mg) phase with composition of ~ 18 at.% Mg. However, when Mg-substrate was used, initially hexagonal close packed (hcp)-Mg(Al) phase with ~ 77 at.% Mg was formed over which fcc-Al(Mg) phase with ~ 36 at.% Mg was nucleated. The results of the present study indicate that substrate crystal structure and estimated substrate-deposit lattice mismatch can influence the depositing phase and its composition but not the morphology of these powders.     

Microwave Dielectric Properties of Gallium-Doped Hexagonal Barium Titanate Ceramics

High-permittivity and low-loss ceramics with composition BaTi_0.92Ga_0.08O_2.96 have been prepared in the BaO–Ga₂O₃–TiO₂ system using the mixed-oxide route. This compound forms as the hexagonal polymorph (6 H ) of BaTiO₃ with the space group P 6₃/ mmc . The dielectric properties of dense ceramics have been studied, at microwave frequencies, with the ceramics fired at 1450°C under flowing oxygen gas; the results are a relative permittivity, ɛ_r, of ∼74 and a quality factor, Q · f _r, of ∼7815 at 5.5 GHz. The quality factor is strongly influenced by the sintering conditions (temperature and atmosphere), whereas the relative permittivity is not influenced significantly by ceramic processing for pellets ≥93% of the theoretical X-ray density. To our knowledge, this is the first report of microwave dielectric resonance in a perovskite-type BaTiO₃-based ceramic.     

Photocatalytic water splitting over ZrO2 prepared by precipitation method

ZrO₂ prepared by the precipitation method of zirconium oxychloride with various hydrolyzing agents was studied for photocatalytic water splitting reaction under UV light irradiation. The crystal structure as well surface properties were varied with the hydrolyzing agent of KOH, NH₄OH, and NH₂CONH₂. Especially, the surface area of the prepared ZrO₂ calcined at the same temperature of 750 °C for 6 h was dependent highly on the hydrolyzing agent, and thus the highest photocatalytic activity was obtained for ZrO₂ with the highest surface area when KOH was used as a hydrolyzing agent, In the presence of Na₂CO₃, the photocatalytic activity of ZrO₂ increased by 2–3 fold, which was ascribed to the physically adsorbed carbonate species on the ZrO₂ surface. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Flow of a second-order fluid over a stretching surface having power-law temperature

Summary The important physical quantities such as the coefficients of skin-friction and heat transfer are obtained from the closed-form solutions for the boundary layer equations of the flow of a second-order fluid over a stretching surface having power-law temperature.     

Molecular recognition of geometrical isomers in montmorillonite

cis-alkenes are hydrogenated preferentially followed by trans-alkenes sequentially from the mixture of geometrical isomers by the montmorillonitebipyridylpalladium(II) acetate catalyst. Such molecular recognition in montmorillonite is unusual and remarkable, and forms an advanced model to enzymes.IICT Communication No. 3187.     

Dielectric function and optical conductivity of TiOx (0.8

S Gokhale  SR Barman  DD Sarma 《Canadian Metallurgical Quarterly》1995,52(20):14526-14530

Characterization of a site-directed mutant of cytochrome b5 designed to alter axial imidazole ligand plane orientation

Mutants of cytochrome b5 were designed to achieve reorientation of individual axial imidazole ligands. The orientation of the axial ligand planes is thought to modulate the reduction potential of bis(imidazole) axially ligated heme proteins. The A67V mutation achieved this goal through the substitution of a bulkier, hydrophobic ligand for a residue, in the sterically hindered hydrophobic heme binding pocket. Solution structures of mutant and wild-type proteins in the region of the mutation were calculated using restraints obtained from 1H and 15N 2D homonuclear and heteronuclear NMR spectra and 1H-15N 3D heteronuclear NMR spectra. More than 10 restraints per residue were used in the refinement of both structures. Average local rmsd for 20 refined structures was 0.30 A for the wild-type structure and 0.38 A for the A67V mutant. The transfer of amide proton resonance assignments from wild-type to the mutant protein was achieved through overlays of 15N-1H heteronuclear correlation spectra of the reduced proteins. Side chain assignments and sequential assignments were established using conventional assignment strategies. Calculation of the orientation of the components of the anisotropic paramagnetic susceptibility tensor, using methods similar to procedures applied to the wild-type protein, shows that the orientation of the in-plane components are identical in the wild-type and mutant proteins. However, the orientation of the z-component of the susceptibility tensor calculated for the mutant protein differs by 17 degrees for the A-form and by 11 degrees for the B-form from the orientation calculated for the wild-type protein. The rotation of the z-component of the susceptibility tensor (toward the delta meso proton) is in the same direction and is of the same magnitude as the rotation of the H63 imidazole ring induced by mutation.