Chemiluminescence method with potassium permanganate for the determination of organic pollutants in seawater.

A chemiluminescence method with potassium permanganate was developed for use as an indicator of organic pollutants in fresh water. This method could be applied to the determination of organic pollutants in seawater as well. However, the flow chemiluminescence method suffered from the interference of chloride ions at the same concentration of seawater because of the production of manganese dioxide in the oxidation of chloride ions with permanganate. The conditions (concentrations of potassium permanganate and sulfuric acid and sample volume, i.e. flow injection method) were chosen to minimize the interference of chloride ions. The chemiluminescence method shows a good correlation with the chemical oxygen demand method on fresh water added artificial sea salt and seawater samples. Natural seawater was analyzed by the chemiluminescence method. The results obtained were compared with those obtained by chemical oxygen demand under the alkaline condition and total organic carbon methods. The chemiluminescence method has higher sensitivity and reproducibility than the conventional chemical oxygen demand and total organic carbon methods.     

Fe-Al layered double hydroxides in bromate reduction: Synthesis and reactivity

This study presents a rare use of layered double hydroxides of Fe(II) and Al(III) (Fe-Al LDH), as reported for the first time for bromate removal from aqueous solutions. The Fe-Al LDH samples were prepared with Fe/Al molar ratios of 1-4 using a co-precipitation method at pH 7, with subsequent hydrothermal treatment at 120°C. The Fe-Al LDH (molar ratio of Fe/Al=1, 2) with a layered structure exhibited nearly complete removal of bromate from initial concentration of 100μmol/dm(3) at a wide pH range of 4.0-10.5 over a 2h reaction period; the residual bromate concentration in the solution was lower than the detection limit of 0.07μmol/dm(3) (9μg-BrO(3)(-)/dm(3)). During the reaction period, bromide was released into the solution via a reduction process. Reactivity of Fe-Al LDH with a Fe/Al molar ratio of 2 did not decrease the bromate reduction efficiency during 30days.     

In-plane mechanical behaviors of 2D repetitive frameworks with four-coordinate flexible joints and elbowed beam members

The mechanical properties of an open-framework structure constructed of joints and beam members are strongly influenced by both its geometrical configuration and joint flexibility. This paper clarifies the relationship between joint flexibility and Poisson's ratio, which is a mechanical criterion for solid deformation, and discusses two types of in-plane anisotropic structures made up of four-coordinate flexible joints and elbowed beam members. Uniaxial tensile analyses estimate the linear and nonlinear elastic properties of these frameworks by applying straightforward joint modeling with multi-rotational degrees of freedom. The numerical results show that these proposed frameworks produce a variety of deformability dependent on the joint flexibility in auxetic deformation with a negative Poisson's ratio, the folding mechanics under kinematic indeterminacy, and the transition of Poisson's ratio between the positive and negative values. The geometrical and topological aspects of the obtained mechanical behaviors are discussed.     

Simultaneous Spin-Crossover Transition and Conductivity Switching in a Dinuclear Iron(II) Coordination Compound Based on 7,7′,8,8′-Tetracyano-p-quinodimethane

The reaction of Fe(OAc)₂ and Hbpypz with neutral TCNQ results in the formation of [Fe₂(bpypz)₂(TCNQ)₂](TCNQ)₂ ( 1 ), in which Hbpypz=3,5-bis(2-pyridyl)pyrazole and TCNQ=7,7′,8,8′-tetracyano-p-quinodimethane. Crystal packing of 1 with uncoordinated TCNQ and π–π stacking of bpypz⁻ ligands produces an extended two-dimensional supramolecular coordination assembly. Temperature dependence of the dc magnetic susceptibility and heat capacity measurements indicate that 1 undergoes an abrupt spin crossover (SCO) with thermal spin transition temperatures of 339 and 337 K for the heating and cooling modes, respectively, resulting in a thermal hysteresis of 2 K. Remarkably, the temperature dependence of dc electrical transport exhibits a transition that coincides with thermal SCO, demonstrating the thermally induced magnetic and electrical bistability of 1 , strongly correlating magnetism with electrical conductivity. This outstanding feature leads to thermally induced simultaneous switching of magnetism and electrical conductivity and a magnetoresistance effect.     

A convenient synthesis of diacyl sulfides using a novel sulfur transfer reagent

Various diacyl sulfides were synthesized by reaction of acyl chlorides with LiAlHSH. Reaction of glutaryl chloride with LiAlHSH afforded glutaric thioanhydride. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:633–635, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10217     

Copolymerization of 3,3,3-trifluoro-1,2-epoxypropane with N-phenylmaleimide using organozinc initiators

Novel copolymers consisting of 3,3,3-trifluoro-1,2-epoxypropane (TFEP) and N-phenylmaleimide (PMI) units were prepared by the copolymerization of TFEP with PMI initiated with an organozinc compound. Using [Zn(OCH₃)₂ · (C₂H₅ZnOCH₃)₄] as an initiator, the copolymer chains consisted mainly of TFEP-TFEP sequences. The TFEP-PMI sequence content in the copolymer chains was small. On the other hand, using (C₂H₅ZnOCH₃)₄ as an initiator, only low molecular weight copolymers were formed. Those copolymers were suggested to have block structure, poly(TFEP)-block-poly(PMI), by the ¹⁹F NMR analysis. The copolymers showed higher thermostability than poly-(TFEP).     

Ligand exchange reactions of aryl pyridyl sulfoxides with grignard reagents: Convenient preparation of 3- and 4-pyridyl grignard reagents and examination of the leaving abilities of pyridyl anions

Aryl 3- and 4-pyridyl sulfoxides undergo ligand exchange in reactions with aryl Grignard reagents to generate 3- and 4-pyridyl Grignard reagents, which, upon treatment with aldehydes or ketones, give the corresponding addition products in moderate-to-good yields. The mechanism for the exchange reaction was investigated by treating optically active 3- and 4-pyridyl p-tolyl sulfoxides with a phenyl Grignard reagent. Inversion of the configuration of the sulfur atom was the stereochemical result of the reactions. In the reactions of phenyl 2-pyridyl sulfoxide with Grignard reagents, the leaving ability of the 2-pyridyl group competes with that of the phenyl group. Both the experimental and MO calculated enthalpy values for deprotonation of α-, β-, and γ-protons of pyridine in the gas phase [1] are in accordance with the following order of the leaving abilities of aryl and pyridyl Grignard reagents: 4-PyMgBr > 3-PyMgBr » PhMgBr > p-TolMgBr > 2-PyMgBr.     

A Method for In Vitro Measurement of Oxidized Low-Density Lipoprotein in Blood,Using Its Antibody,Fluorescence-Labeled Heptapeptide and Polyethylene Glycol

Two oxidized forms of low-density lipoprotein (LDL), oxidized (Ox-LDL) and minimally modified (MM-LDL), and the immune complexes (LDL-ICs) that they form with their corresponding antibodies, play a major role in the pathogenesis of atherosclerosis. Recently, we reported that the heptapeptide KP6 (Lys-Trp-Tyr-Lys-Asp-Gly-Asp) coupled through its ε-amino group present on the N-terminal Lys to fluorescein isothiocyanate (FITC)— (FITC)KP6— binds specifically to Ox-LDL and MM-LDL, but not to native LDL. Here, to develop a novel method for measuring the levels of oxidatively modified LDL in blood, using (FITC)KP6, we analyzed the latter’s binding with MM-LDL-IC and Ox-LDL-IC. Polyacrylamide gel electrophoresis analysis revealed that (FITC)KP6 could efficiently and specifically bind to polyethylene glycol (PEG)-precipitated MM-LDL-IC and Ox-LDL-IC in a dose-dependent manner with high sensitivity in plasma and serum. Our results indicate that the above method for measuring the levels of PEG-precipitated, oxidatively modified LDL-ICs, formed by the addition of anti-Ox-LDL antibody to blood, using (FITC)KP6, can aid the diagnosis of atherosclerosis.