XPS and XAES study for oxidation of V/Cu(100) and V,Na/Cu(100) surfaces

Oxidation states of vanadium overlayers ( 0.1 to 2.0 ML) on a Cu(100) surface with and without sodium on the surface were investigated by XPS and XAES. The vanadium overlayers gave a V₂O₃-like surface oxide after exposure up to 600 L O₂, showing a chemical shift of the V2p_3/2 peak by 3.5 eV without coverage dependence. The surface vanadium oxide was easily oxidized further to V⁵⁺ to give a chemical shift of 5.5 eV after addition of sodium atoms on the oxide and heating at 530 K for 5 min. The high oxidation state was interpreted by a mixing of vanadium oxide and oxidized sodium. This mixing is affirmed by spectral changes showing a separation of sodium ions from the oxide during the formation of sodium acetate by adsorption of acetic acid.     

Conversion of arsenobetaine to dimethylarsinic acid by arsenobetaine-decomposing bacteria isolated from coastal sediment

Arsenobetain [(CH₃)₃As⁺CH₂COO^-]-containing growth media (1/5 ZoBell 2216E and solution of inorganic salts) were inoculated with two bacterial strains, which were isolated from a coastal sediment and identified as members of the Vibro-Aeromonas group, and incubated under aerobic and anaerobic conditions. Arsenobetaine was converted to a metabolite only under aerobic conditions. This arsenic metabolite was identified as dimethylarsinic acid [(CH₃)₂AsOOH] by hydride generation/cold trap/GC MS/SIM analysis and high-performance liquid-chromatographic behaviour. The conversion pattern shown by these arsenobetaine-decomposing bacteria (that is, arsenobetaine → dimethylarsinic acid) was fairly different from that shown by the addition of sediment itself as the source of arsenobetaine-decomposing micro-organisms (that is, arsenobetaine → trimethylarsine oxide → inorganic arsenic). This result suggests to us that various micro-organisms, including the arsenobetaine-decomposing bacteria isolated in this study, participate in the degradation of arsenobetaine in marine environments.     

Stereo- and regioselective methods for the synthesis of three consecutive asymmetric units found in many natural products

Regio- and stereoselective methods are described for the synthesis of compounds possessing the stereochemistry of type $\text{1a}$, $\text{1b}$, $\text{1c}$, and $\text{1d}$ from the aldehyde $\text{2}$.     

Silicon-wire-based ultrasmall lattice filters with wide free spectral ranges

Using silicon-on-insulator-based silicon-wire waveguides with submicrometer cross sections, we constructed ultrasmall channel-dropping lattice filters for 1.5-microm infrared systems. The waveguide's low-loss bends with 2.5-microm radius reduce the total length of the filter to less than 100 microm and enlarge the free spectral range to more than 80 nm. The measured spectra show fine channel-dropping characteristics, and the results agree well with numerical predictions. Moreover, we have succeeded in tuning the dropping wavelength by adjusting the lengths of the delay lines.     

Further studies on the structure of polysaccharides from the lichen Flavoparmelia caperata (L.) Hale

A water-soluble polysaccharide called PC-2 was previously isolated from Flavoparmelia caperata (L.) Hale and assigned to alpha(1-3)(1-4)glucan. However, PC-2 separated into three components, PC-2A, PC-2B, and PC-2C (a single peak in HPLC, respectively) on further purification. Methylation analysis and (1)H- and (13)C-NMR spectroscopic studies suggested that PC-2A is composed of repeating units of [alpha-D-Glc1-3](3), : [alpha-D-Glc1-4](2), while PC-2B and PC-2C are partly branched galactoglucomannans consisting of (1-3)- and (1-4)-linked alpha-D-glucopyranosyl units as the main chain. In addition we confirmed that the polysaccharide fraction PB-2 from the lichen of the same genus, Flavoparmelia baltimorensis (Gyelink & Foriss) Hale, is identical to PC-2 based on the chemical and spectroscopic data.     

Facile intramolecular cyclization in oxidative coupling of acetylenes linked to 1,3-positions of benzene: strained [12]metacyclophanedienetetrayne system

Oxidative coupling of ethynylpropellane linked to 1,3,5-position of a benzene core 3b did not give the cage dimer 2 but the dimer 4 having a strained [12]metacyclophanedienetetrayne system. The spectral and structural features of the novel ring system were revealed for the simple dibenzo derivative 6, which was also prepared efficiently by the intramolecular cyclization of the open-chain precursor.     

Total synthesis and assignment of the double-bond position and absolute configuration of (-)-pyrinodemin A

[structure: see text] The first asymmetric total synthesis of a structurally novel cis-cyclopent[c]isoxazolidine alkaloid, (-)-pyrinodemin A (3), which exhibits potent cytotoxicity, has been accomplished through a highly diastereoselective intramolecular nitrone-olefin cycloaddition reaction as the key step. Thus, it has been found that the hitherto unknown absolute configuration of pyrinodemin A is as indicated in the structural formula 3.     

Bipolar reverse osmosis membrane for separating mono-and divalent ions

Bipolar reverse osmosis membranes that have both negatively and positively charged layers have been prepared to enhance the selectivity towards mono- and divalent ions in respect of both cations and anions. Positively charged layers are formed on low pressure reverse osmosis membranes having negative charge (NTR-7410 and 7450) by an adsorption method using polyethyleneimine (PEI) or a quaternary ammonium polyelectrolyte (QAP). These layers attach to the membrane's dense layer, which is made of sulfonated polyether sulfone. The selectivity of mono- and divalent ions is proven by experimental results for single electrolytes (NaCl, Na₂SO₄ and MgCl₂). Although negatively charged membranes repulse divalent anions more strongly than cations and monovalent anions, bipolar reverse osmosis membranes reject both divalent cations and divalent anions better than monovalent ions. An optimal preparation method for bipolar membranes showing selectivity towards mono- and divalent ions were developed. The bipolar membranes showed good ion selectivity for artificial sea water.     

X-ray and UV photoelectron-spectroscopic studies of pyridine adsorbed on evaporated nickel and palladium in the temperature range 140–385 k

The states of pyridine adsorbed on evaporated nickel and palladium films have been investigated as a function of temperature in the range 140–385 K by means of X-ray and UV photoelectron spectroscopy. At ～ 140 K, pyridine “N-bonded” on the metal surfaces gives C 1s and N 1s peaks whose binding energies are very close to those for condensed pyridine and “N-bonded” pyridine on pre-oxidized nickel. The high-lying valence orbitals, 2b₁ (π) and 1a₂ (π) + 7a₁ (n), of pyridine show shifts similar to those for the “N-bonded” molecule on pre-oxidized nickel. At ～ 290 K, “π-bonded” pyridine shows large shifts in the C 1s and N 1s peaks and in the high-lying valence orbitals, as observed for “π-bonded” benzene on nickel. The assignments of the adsorbed states are supported by work-function change data. A large proportion of pyridine converts from the “N-bonded” to the “π-bonded” form between 220 and 290 K. Formation of “α-pyridyl” is suggested at ～ 375 K on nickel.