Steady vortical flow around a finite plate

An explicit solution for a layer of fluid with constant vorticitysurrounding a thin plate of finite length is obtained usingelementary conformal mapping methods. In the limit of largeplate length the behaviour of the solution near the ends ofthe plate tends to that of the previously known solution fora semi-infinite plate. Contour dynamics is used to investigatethe stability of the steady solutions.     

Effect of Cation/Anion Co‐doping on the Photocatalytic Performance of Na3SbO(PO4)2

Silver/copper‐nitrogen co‐doped Na₃SbO(PO₄)₂ were prepared by solid state/ion exchange methods. The materials were characterized by powder XRD, SEM‐EDS, TG analysis, as well as FT‐IR and UV/Vis diffuse reflectance spectroscopy. All the doped materials crystallize in orthorhombic lattice with space group P2₁2₁2₁. The infrared spectra of the samples gave characteristic bands corresponding to PO₄ and SbO₆ groups. The bandgap energy of all the samples was deduced from their UV/Vis DRS profiles. The bandgap energy of doped materials decreased substantially. Visible‐light‐induced photocatalytic oxidation of the methyl violet (MV) and methylene blue (MB) was examined. The influence of cation, anion, and co‐doping on the photoactivity of Na₃SbO(PO₄)₂ was studied. The Ag⁺ and nitrogen co‐doped Na₃SbO(PO₄)₂ exhibited the highest photocatalytic activity among the materials investigated.     

Determination of trace concentrations of elements in high purity tellurium by radio frequency glow discharge optical emission spectrometer (RF-GDOES)

A method was established for the determination of trace impurities in high purity tellurium (Te) 99.9999 (6N) by radio frequency glow discharge optical emission spectrometry (RF-GDOES). The optimized parameters are power, argon pressure, pre-integration time, analysis time and selection of wavelength. Nine elements Se, Ca, Mg, Si, Fe, Cr, Cu, Ni and Pb were analysed in 6N Te, out of which only three elemental peaks (Se, Ca, and Mg) were detected and the remaining six elements ( Si, Fe, Cr, Cu, Ni and Pb) were below detection levels. Finally, the method was evaluated by the analysis of the above traces using inductively coupled plasma mass spectrometry (ICP-MS) and was found to be satisfactory. The detection limits for most of the elements were below 10 ng/g and R.S.D. was around 10%, which indicated that this method could fully satisfy the requirements for the trace analysis in high purity Te metal.     

Highly regio-, chemo- and diastereoselective synthesis of oxa-bridged spirocycles: a novel observation of reverse selectivity

The reverse regio- and diastereoselectivities are observed between the reactions involving 5- and 6-membered-ring cyclic carbonyl ylide dipoles with alpha-methylene ketones. A mild catalytic route to synthesize spirocyclic systems with high regio-, chemo- and diastereoselectivities is described.     

Characterization, conductivity and photocatalytic studies of AHfM(PO4)3 (A = Na and Ag; M = Ti and Zr) powders synthesized by sol–gel method

Materials belonging to NASICON family of compositions NaHfM(PO₄)₃ and AgHfM(PO₄)₃ (M = Ti and Zr) are prepared by sol–gel and ion exchange methods, respectively. Ethylene glycol is used as a gelating agent. All the compositions are characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, ³¹P MAS NMR, UV–Vis DRS, XPS and energy dispersive spectral methods. All these phosphates are crystallized in rhombohedral lattice with space group $R\overline{3} c$ R 3 ¯ c . These compounds exhibit characteristic PO₄ vibrational modes in their FT-IR spectra. The ³¹P MAS NMR gave broad signals indicating distribution of chemical environments around P ion. The dc and ac conductivity of AgHfM(PO₄)₃ (M = Ti and Zr) are higher compared to their sodium containing compounds. The Cole–Cole plots of impedance show semicircles between 373 and 623 K. The variation of dc conductivity with temperature follows the Arrhenius equation. The photocatalytic activity of all the samples was studied against methylene blue decomposition using sun light. AgHfM(PO₄)₃ (M = Ti and Zr) have shown higher photoactivity than the sodium containing Nasicons.