Synthesis, crystal structure and magnetic property of the novel dinuclear nickel(II) complex with 4-(p-methoxyphenyl)-3,5-bis(pyridine-2-yl)-1,2,4-triazole

A novel dinuclear nickel(II) complex, [Ni₂(MOBPT)₂Cl₂(H₂O)₂]Cl₂ · 7H₂O (MOBPT = 4-(p-methoxyphenyl) −3,5-bis(pyridine-2-yl)-1,2,4-triazole), has been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction methods. The crystal structure determination shows that the dinuclear Ni₂N₈ unit is almost planer in which each Ni^II ion is coordinated by four nitrogen atoms from MOBPT equatorially and a water molecule and a chloride ion axially in a distorted octahedral geometry. Magnetic measurements reveal a relatively weak antiferromagnetic exchange in the complex.     

Optical properties of ZnO and ZnO:In nanorods assembled by sol-gel method

Self-assembled zinc oxide (ZnO) and indium-doping zinc oxide (ZnO:In) nanorod thin films were synthesized on quartz substrates without catalyst in aqueous solution by sol-gel method. The samples were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Raman-scattering spectroscopy, room-temperature photoluminescence (PL) spectra, and temperature-dependent PL spectra measurements. XRD and Raman spectra illustrated that there were no single In2O3 phase in ZnO lattice after indium doping. The PL spectra of ZnO showed a strong UV emission band located at 394 nm and a very weak visible emission associated with deep-level defects. Indium incorporation induced the shift of optical band gap, quenching of the near-band-edge photoluminescence and enhanced LO mode multiphonon resonant Raman scattering in ZnO crystals at different temperatures. Abnormal temperature dependence of UV emission integrated intensity of ZnO and ZnO:In samples is observed. The local state emission peak of ZnO:In samples at 3.37 eV is observed in low-temperature PL spectra. The near-band-edge emission peak at room temperature was a mixture of excitons and impurity-related transitions for both of two samples.     

Ruthenium-catalyzed cyclization of 3-en-1-ynyl imines with nucleophiles via tandem 5-exo-dig cyclization and nucleophilic addition

Treatment of 3-en-1-ynyl imines with TpRuPPh₃(CH₃CN)₂PF₆ catalyst (1 mol %) in DCE (50 °C, 6 h) effected catalytic cyclization with suitable nucleophiles and gave functionalized pyrroles in good yields. The reaction mechanism is proposed to proceed via (2-pyrrolyl)carbenoid intermediates derived from 5-exo-dig cyclization. This catalytic reaction works well with various nucleophiles, including water, alcohols and anilines.     

Liquid–paper interactions during liquid drop impact and recoil on paper surfaces

The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction.     

Synthesis, crystal structure and magnetic property of a new nickel selenite chloride: Ni5(SeO3)4Cl2

The new nickel selenite chloride, Ni₅(SeO₃)₄Cl₂, was obtained by high-temperature solid state reaction of NiCl₂, Ni₂O₃ and SeO₂ in a 1:2:4 molar ratio at 700 °C in an evacuated quartz tube. Its structure was established by single-crystal X-ray diffraction. Ni₅(SeO₃)₄Cl₂ crystallizes in the triclinic system, space group P-1 (No. 2) with cell parameters of a=8.076(2), b=9.288(2), c=9.376(2) Å, α=101.97(3), β=105.60(3), γ=91.83(3)° and Z=2. All nickel(II) ions in Ni₅(SeO₃)₄Cl₂ are octahedrally coordinated by selenite oxygens or/and chloride anions (([Ni(1)O₅Cl], [Ni(2)O₄Cl₂], [Ni(3)O₅Cl], [Ni(4)O₆] and [Ni(5)O₄Cl]). The structure of the title compound features a condensed three-dimensional (3D) network built by Ni(II) ions interconnected by SeO₃²⁻ anions as well as Cl⁻ anions. Magnetic property measurements show strong antiferromagnetic interaction between nickel(II) ions.     

Anomalies and curvature ofW manifolds

We study the holomorphic structure of certain complex manifolds associated withW algebras, namely, the flag manifoldsW /T andW ₁₊/T ₁₊, and the spacesW /SL(),R) andW ₁₊/GL(,R), whereT andT ₁₊ are the maximal tori inW andW ₁₊. We compute their Ricci curvature and show how the results are related to the anomaly-freedom conditions forW andW ₁₊. We discuss the relation of these manifolds with extensions of universal Teichmüller space.Supported in part by the U.S. Department of Energy, under grant DE-AS05-81ER40039Supported in part by the U.S. Department of Energy, under grant DE-FG03-84ER40168     

On error estimates of some higher order projection and penalty-projection methods for Navier-Stokes equations

Summary This paper is a continuation of our previous work [10] on projection methods. We study first existing higher order projection schemes in the semidiscretized form for the Navier-Stokes equations. One error analysis suggests that the precision of these schemes is most likely plagued by the inconsistent Neumann boundary condition satisfied by the pressure approximations. We then propose a penalty-projection scheme for which we obtain improved error estimates.This work is partially supported by NSF grant MS-8802596.