Magnetic properties of FexV3−xS4 (0 ≤ x ≤ 2)

The magnetic susceptibility data of Fe_xV_3?xS₄ (0 ≤ x ≤ 2) are reported in the temperature range between 4.2 and 1300 K. The behavior of the susceptibility at high temperatures changes significantly at the composition boundary x = 1.0. The magnitude of the effective magnetic moment remains unchanged at 3.2 μ_B in the composition range x < 1.0. It decreases with increasing iron content in the range > 1.0, and rapidly decreases for x close to 2.0. The c lattice parameter varies in a manner analogous to the change in magnetic moment. These phenomena suggest that metallic bonding forms between metal layers and that it becomes stronger with increasing in x. The susceptibility measurements at low temperatures show that Fe_xV_3?xS₄ is basically antiferromagnetic, although some of the Fe_xV_3?xS₄ compounds become weakly ferromagnetic after cooling in a magnetic field. The origin of the weak ferromagnetism is briefly discussed.     

Biomethylation of Arsenic in an Arsenic-rich Freshwater Environment

Arsenic circulation in an arsenic-rich freshwater ecosystem was elucidated to detect arsenic species in the river water and in biological samples living in the freshwater environment. Water-soluble arsenic compounds in biological samples were extracted with 70% methanol. Samples containing arsenic compounds in the extracts were treated with 2 mol dm³ of sodium hydroxide and reduced with sodium borohydride. The detection of arsenic species was accomplished using a hydride generation/cold trap/cryofocus/gas chromatography-mass spectrometry (HG/CT/CF/GC-MS) system. The major arsenic species in the river water, freshwater algae and fish are inorganic arsenic, dimethylarsenic and trimethylarsenic compounds, respectively. Trimethylarsenic compounds are also detected in aquatic macro-invertebrates. The freshwater unicellular alga Chlorella vulgaris, in a growth medium containing arsenate, accumulated arsenic and converted it to a dimethylarsenic compound. The water flea Daphnia magna, which was fed on arsenic-containing algae, converted it to a trimethylarsenic species. © 1997 by John Wiley & Sons, Ltd.     

Novel approach to enhance sensitivity in surface‐assisted laser desorption/ionization mass spectrometry imaging using deposited organic‐inorganic hybrid matrices

Sample pretreatment is key to obtaining good data in matrix‐assisted laser desorption/ionization mass spectrometry imaging (MALDI‐MSI). Although sublimation is one of the best methods for obtaining homogenously fine organic matrix crystals, its sensitivity can be low due to the lack of a solvent extraction effect. We investigated the effect of incorporating a thin film of metal formed by zirconium (Zr) sputtering into the sublimation process for MALDI matrix deposition for improving the detection sensitivity in mouse liver tissue sections treated with olanzapine. The matrix‐enhanced surface‐assisted laser desorption/ionization (ME‐SALDI) method, where a matrix was formed by sputtering Zr to form a thin nanoparticle layer before depositing MALDI organic matrix comprising α‐cyano‐4‐hydroxycinnamic acid (CHCA) by sublimation, resulted in a significant improvement in sensitivity, with the ion intensity of olanzapine being about 1800 times that observed using the MALDI method, comprising CHCA sublimation alone. When Zr sputtering was performed after CHCA deposition, however, no such enhancement in sensitivity was observed. The enhanced sensitivity due to Zr sputtering was also observed when the CHCA solution was applied by spraying, being about twice as high as that observed by CHCA spraying alone. In addition, the detection sensitivity of these various pretreatment methods was similar for endogenous glutathione. Given that sample preparation using the ME‐SALDI‐MSI method, which combines Zr sputtering with the sublimation method for depositing an organic matrix, does not involve a solvent, delocalization problems such as migration of analytes observed after matrix spraying and washing with aqueous solutions as sample pretreatment are not expected. Therefore, ME‐Zr‐SALDI‐MSI is a novel sample pretreatment method that can improve the sensitivity of analytes while maintaining high spatial resolution in MALDI‐MSI.     

Evidence of two dimensionality in quasi-one-dimensional cobalt oxides

The quasi-one-dimensional (Q1D) cobalt oxides A(N + 2)Co(n + 1)O(3n + 3) (A = Ca, Sr, and Ba, n = 1 - infinity) were investigated by muon-spin spectroscopy under applied pressures of up to 1.1 GPa. The relationship between the onset Néel temperature T(on)(N) and the interchain distance (d(ic)), which increases monotonically with n, is well fitted by the formula T(N)/T(N,0) = (1 - d(ic)/d(ic,o)(beta), here for T(on)(N) approximately 100 K for Ca(3)Co(2)O(6) (n = 1) and approximately 15 for BaCoCoO(3) (n = infinity at ambient P. The T(on)(N) - d(ic) curve also predicts a large dependence of Y(N) for the compounds with n > or = 5, i.e., in the vicinity of , while the compounds show only a very small effect. Indeed, our high-pressure mu(+) results show that of BaCoO(3) is enhanced by with a slope of 2.2 K(Gpa), whereas no detectable changes by P for both Ca(3)Co(2)O(6) and Sr(4)Co(3)O(9) (n = 2). This clearly confirms the role of the 2D-antiferromagnetic interaction on T(on)(N) in the Q1D cobalt oxides.     

Synthesis of anionic methylpalladium complexes with phosphine-sulfonate ligands and their activities for olefin polymerization

Reaction of diarylphosphinobenzene-2-sulfonic acids with tertially amines, followed by addition of [PdMeCl(cod)], provided anionic methylpalladium(II) complexes with bidentate phosphine-sulfonate ligands, which show high activity for copolymerization of ethylene with methyl acrylate.     

Ethylene–hexene copolymerization by heterogeneous and homogeneous Ziegler–Natta catalysts and the “comonomer” effect

Homopolymerization of ethylene and 1-hexene and their copolymerizations were compared to investigate the influence of α-olefin on the enhancement of ethylene polymerization rate (R_p), which is often referred to as the “comonomer” effect. With the two homogeneous Ziegler–Natta catalysts, Et[Ind]₂ZrCl₂/MAO and (π-C₅H₅)₂ZrCl₂/MAO (MAO = methylaluminoxane), hexene causes reduction of R_p—in other words a negative “comonomer” effect. In the case of the high activity MgCl₂ supported TiCl₃ catalysts there is a slight positive “comonomer” effect; the R_p increases by 25 to 70% with the addition of 15 mol % of hexene. The “comonomer” effects in there catalyst systems are much smaller than that observed for the classical TiCl₃ catalyst. © 1993 John Wiley & Sons, Inc.     

A new stereoselective synthesis of (±)nootkatone by means of cyclopentenone annulation

The title sesquiterpene is synthesized by means of the new cyclopentenone annulation which involves acid-treatment of IIIb. The ester group of the resulting V is transformed selectively into isopropenyl appendage of the trans configuration to the two methyl groups. Successive ring-enlargement via a dibromomethyllithium adduct X has yielded (±)nootkatone.