Use of transition elements to enhance sensitivity for selenium determination by graphite-furnace atomic-absorption spectrophotometry combined with solvent extraction with the APDC-MIBK system

A microanalytical method for the measurement of selenium in waters and biological materials by a flameless atomic-absorption technique has been developed. The ammonium pyrrolidinedithiocarbamate-methyl isobutyl ketone extraction system is used for separation from interfering materials such as large amounts of alkali and alkaline earth metal salts and mineral acids. The atomic-absorption sensitivity for selenium is found to be enhanced to a large extent by co-extraction of some transition metal ions. Copper(II) has been used successfully as such an additive to diminish the volatility of selenium in the graphite furnace during the ashing step of the atomization cycle. When the aqueous phase/organic solvent volume ratio is 5 and the volume injected into the graphite furnace is 20 mul, the sensitivity for selenium is 0.3 ng/ml for 1% absorption. The relative standard deviation is ca. 2%. Interference by other metal ions is prevented by masking with EDTA. The method has been applied satisfactorily for the determination of minute amounts of selenium in waters and various biological materials.     

New organosols of nickel sulfides,palladium sulfides,manganese sulfide,and mixed metal sulfides and their use in preparation of semiconducting polymer-metal sulfide composites

Organosols of NiS, PdS, and MnS in N,N-dimethylformamide were prepared by reaction of the metal acetate with H₂S. Organosols of mixed-metal sulfides (Zn _x Cd_1–x S, Hg _x Cd_1–x S, Hg _x Cu_1–x S, Cd _x Mn_1–x S, Hg _x Mn_1–x S, Hg _x Cd_1–x S, and Mn _x Zn_1–x S) were similarly obtained by reaction of mixtures of the metal salts with H₂S. The organosol of Zn_0.5Cd_0.5S contained particle with two particle size distributions centered at 6.5 nm and 29 nm, as revealed by Ar laser-scattering analysis. The metal sulfides are recovered by addition of Et₂O to the organosols. Zn _x Cd_1–x S thus obtained shows magnetic susceptibility in the range 0.5×10^–6–2.3×10^–6 emug^–1 depending on thex value. Addition of polymers to the organosols affords semiconducting films of metal sulfide-polymer composites.     

Cu(I) catalyst in DMF: an efficient catalytic system for the synthesis of furans from 2-(1-alkynyl)-2-alken-1-ones

The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride.     

Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Stereocontrolled approaches to 9(0)-methanoprostacyclin

A stable PGI₂ analog (methanoprostacyclin $\text{2}$) was synthesized starting from 5-norbornene-2,3-dicarboxylic anhydride.     

Effects of various triamines on cell-free polypeptide synthesis of Escherichia coli and on growth of its polyamine auxotrophs

The effects of various synthetic triamines having a general structure, H2N(CH2)xNH(CH2)yNH2, where x = 2-5 and y = 2-8 (abbreviated, x-y; with 3-4 being spermidine itself), on poly(U)-directed polypeptide synthesis of Escherichia coli and on growth of its polyamine-requiring mutants were examined in comparison with those of spermidine. Except for 2-2 and 2-3, all of the triamines stimulated more or less polypeptide synthesis at suboptimal Mg2+ concentrations, but the Mg2+ concentration required for the maximal stimulatory effect was different for each triamine. The degree of maximal stimulation caused by 3-3 (norspermidine), 4-4 (homospermidine), or 4-5 was nearly comparable with that by spermidine. The acetylspermidines were inactive, however, they inhibited the spermidine-stimulated polyphenylalanine synthesis. Many of the triamines examined reduced the ratio of leucine to phenylalanine incorporation into polypeptides during poly(U)-directed translation, and the degree of this effect did not necessarily correspond with that of the stimulatory effect. Moreover, 2-4, 2-5, 3-3 and 4-4 could stimulate the growth of a polyamine auxotroph of E. coli, MA 261, as effectively as did spermidine. However, 3-3 was the only triamine which could fully replaced spermidine in promoting growth of a mutant strain, KK 101, which is more dependent on polyamines than MA 261. Thus, these results demonstrated that some synthetic triamines were as active as spermidine in eliciting these effects, and also that there were some differences among these effects in the structural requirement for triamine.