Regioselective allylzincation of alkenylboronate

[reaction: see text] Boryl substitution on an olefin activates the olefinic double bond toward addition of an organozinc reagent. Addition of an allylic zinc reagent to an alkenylboronate thus takes place smoothly to afford a variety of gem-zincio/boryl species. Theoretical studies with density functional calculations on the reaction pathway revealed that the reaction proceeds via a zincio-ene reaction rather than a bora-Claisen rearrangement.     

Primary processes of laser-induced selective dimer-layer removal on Si(001)-(2x1)

Excitation with nanosecond-laser pulses at fluences well below the melt threshold removes Si dimers on the Si(001)-(2x1) surface and induces atomic-Si desorption through an electronic mechanism. The rate of this photoinduced reaction depends superlinearly on the excitation intensity, and is enhanced resonantly at the photon energy where the optical transition injects holes into the dimer backbond surface-band state. The results reveal the crucial role of surface holes and their nonlinear localization in the bond rupture of Si dimers on this surface.     

Synthesis and metal-ion binding properties of monoazathiacrown ethers

Synthetic procedures for monoazathiacrown ethers were explored, and monoazatrithia-12-crown-4, monoazatetrathia-15-crown-5, and monoazapentathia-18-crown-6 were obtained in moderate yields by the reaction of bis(2-chloroethyl)amine with the appropriate dithiols in the presence of lithium hydroxide in THF. To evaluate metal-ion binding properties of the monoazathiacrown ethers by solvent extraction, lipophilic dodecyl and dodecanoyl groups were incorporated onto the monoazathiacrown ethers. The solvent extraction experiments suggested that monoazathiacrown ethers have Ag(+) and Hg(2+) selectivities and that the relative selectivity between Ag(+) and Hg(2+) depends on their nitrogen atom properties and numbers of sulfur atoms reflecting the respective affinities of nitrogen and sulfur atoms to Hg(2+) and Ag(+). An interesting ability to bind Mg(2+) was observed in the case of N-dodecyl monoazatrithia-12-crown-4.     

Hydration processes of electrolyte anions and cations on pt(111), Ir(111), Ru(001) and Au(111) surfaces: coadsorption of water molecules with electrolyte ions

Water adsorption on Pt( 111) and Ru(001) treated with oxygen, hydrogen chloride and sodium atom at 20 K has been studied by Fourier transform infrared spectroscopy, scanning tunneling microscopy and surface X-ray diffraction. Water molecules chemisorb predominantly on the sites of the electronegative additives, forming hydrogen bonds. Three types of hydration water molecules coordinate to an adsorbed Na atom through an oxygen lone pair. In contrast, water molecules adsorb on electrode surfaces in a simple way in solution. In 1 mM CuSO4 + 0.5 M H2SO4 solution on an Au(111) electrode surface, water molecules coadsorb not only with sulfuric acid anions through hydrogen bonding but also with copper, over wide potential ranges. In the first stage of underpotential deposition (UPD), each anion is accommodated by six copper hexagon (honeycomb) atoms on which water molecules dominate. At any UPD stage water molecules interact with both the copper atom and sulfuric acid anions on the Au(111) surface. Water molecules also coadsorb with CO molecules on the surface of 2 x 2-2CO-Ru(001). All of the hydration water molecules chemisorb weakly on the surfaces. There appears to be a correlation between the orientation of hydrogen bonding water molecules and the electrode potential.     

Differentiation inducing activities of isocoumarins from Hydrangea Dulcis Folium

In the course of searching for differentiation inducers against leukemic cells from plants, we have recognized the differentiation inducing activities of the methanolic extract of Hydrangea Dulcis Folium. Activity guided separation of the extract was carried out using M1 cells, and seven isocoumarins were isolated as active substances. These isocoumarins showed the activities at the concentration of 100 microM and non-cytotoxic effects even at 300 microM.     

Fluorometric determination of Ethofenprox in water by using solid-phase extraction

Ethofenprox (pesticide) exhibits a relatively strong fluorescence in the UV region. Its fluorescence properties were investigated in aqueous solution, organic solvents, and micellar media. The fluorescence intensity of Ethofenprox was enhanced by a factor of 1.2 to 2.7 in the presence of surfactants and by 1.4 in pure organic solvents without significant shift of the excitation and emission wavelengths. The conditions for solid-phase extraction of Ethofenprox from water samples were examined. Among the solid-phase extraction cartridges studied, a Sep Pak C8 with weak sorption ability was found to be the most useful due to the extremely high hydrophobicity of Ethofenprox. For the complete elution of Ethofenprox from the sorbent, an addition of 40%v/v methanol to the sample water was necessary and effective to eliminate the fluorescent impurities of the matrix. The calibration graph obtained was linear over the range of 0.03 to 2.4 mg L(-1) in 100 mL sample. The method was successfully applied to the determination of Ethofenprox in tap, well, and river waters with recoveries of 93.2-95.7%.     

Novel internal target for electron scattering off unstable nuclei

A novel internal target has been developed, which will make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. An "ion trapping" phenomenon in the electron storage ring was successfully utilized for the first time to form the target for electron scattering. Approximately 7 x 10(6) stable 133Cs ions were trapped along the electron beam axis for 85 ms at an electron beam current of 80 mA. The collision luminosity between the stored electrons and trapped Cs ions was determined to be 2.4(8) x 10(25) cm(-2) s(-1) by measuring elastically scattered electrons.     

Optical-damage-free guided second-harmonic generation in 1% MgO-doped stoichiometric lithium tantalate

Room-temperature cw second-harmonic generation from telecom wavelengths, with 30% W(-1) cm(-2) efficiency and second-harmonic power levels up to 41 mW, was achieved in buried waveguides fabricated by reverse-proton exchange in 1% MgO-doped stoichiometric lithium tantalate without any evidence of optical damage. The technology proves suitable for the realization of efficient nonlinear frequency converters and all-optical devices.     

Origin of the large polarization in multiferroic YMnO3 thin films revealed by soft- and hard-X-ray diffraction

We investigated the magnetic structure of an orthorhombic YMnO(3) thin film by resonant soft x-ray and hard x-ray diffraction. We observed a temperature-dependent incommensurate magnetic reflection below 45 K and a commensurate lattice-distortion reflection below 35 K. These results demonstrate that the ground state is composed of coexisting E-type and cycloidal states. Their different ordering temperatures clarify the origin of the large polarization to be caused by the E-type antiferromagnetic states in the orthorhombic YMnO(3) thin film.     

Novel orbital ordering induced by anisotropic stress in a manganite thin film

A novel structure of orbital ordering is found in a Nd0.5Sr0.5MnO3 thin film, which exhibits a clear first-order transition, by synchrotron x-ray diffraction measurements. Lattice parameters vary drastically at the metal-insulator transition at 170 K (= T(MI)), and superlattice reflections appear below 140 K (= T(CO)). The electronic structure between T(MI) and T(CO) is identified as A-type antiferromagnetic with a d(x2-y2) ferro-orbital ordering. The new type of antiferro-orbital ordering characterized by the wave vector (1/4 1/4 1/2) in cubic notation emerges below T(CO). The accommodation of the large lattice distortion at the first-order phase transition and the appearance of the novel orbital ordering are brought about by the anisotropy in the substrate, a new parameter for the phase control.