Desorption of InOH from indium oxides under exposure to atomic hydrogen

Species desorbing from indium oxides under exposure to atomic hydrogen (H) were observed with a quadrupole mass spectrometer. The desorption of InOH was detected at a temperature as low as 410°C, which is in contrast with the fact that, with molecular hydrogen, a much higher temperature (850°C) was required to generate InOH. Upon the interruption of H generation, the InOH signal disappeared immediately, suggesting that H is involved in the reactions leading to InOH desorption. Relevance to the low-temperature cleaning of an InP surface with H is discussed.     

Grafting of polyesters onto carbon black. VI. Copolymerization of alkylene carbonate with cyclic acid anhydride initiated by alkali metal carboxylate groups on carbon black surface

The ring-opening copolymerization of alkylene carbonate with cyclic acid anhydride was found to be initiated by carbon black containing potassium carboxylate (COOK) groups to give an alternating polymer, i.e., polyester. The polyester was propagated from COOK groups and effectively grafted from carbon black surface: e.g., the grafting ratio of polyester from ethylene carbonate (EC) and phthalic anhydride (PAn) went up to over 100%. On the other hand, the initiating activity of alkali metal carboxylate groups increased, depending on the alkali metal countercation, in the following order: COOLi < COONa < COOK < COORb < COOCs. This order was in agreement with that of increasing electropositivity of the counteraction. The activation energy of the copolymerization of EC with PAn was determined to be 26.3 kcal/mol. The rate of the copolymerization was accelerated in an aprotic solvent such as N-methyl-2-pyrrolidone. Furthermore, the effect of solvent and polymerization temperature on the grafting ratio of polyester was investigated.     

Determination of sulfur in metal sulfides by bromine water-CCl4 oxidative dissolution and modified EDTA titration

The sulfur content in metal sulfides can be determined after oxidative dissolution with bromine water-CCl₄ at 50 °C by modified EDTA titration. The sulfides were quantitatively oxidized to SO₄ ^2– without evolving H₂S, and the metal cations were removed by cation exchange on an H-type column. Sulfate was precipitated as BaSO₄, and the remaining Ba²⁺ was subsequently titrated with EDTA at pH = 10. The standard deviation for the determined sulfur in the metal sulfides, some of which can be hardly dissolved in usual mineral acid media, is about a few %. The method can be carried out with sample amounts containing as little as 1.5–2 mg sulfur. Received: 31 July 1997 / Revised: 5 January 1998 / Accepted: 9 January 1998     

Total synthesis of natural dysidiolide

Dysidiolide (1), a novel sesterterpenoid previously isolated from the Caribbean sponge Dysidea etheria de Laubenfels, inhibits the action of the protein phosphatase, cdc25A. The authors establish a novel total synthesis of natural dysidiolide (1) using intramolecular Diels-Alder reaction as the key step from optically active cyclohexenone 3. Decalin, the core structure of 1, was constructed by intramolecular Diels-Alder reaction of the diene ester generated by elimination of the phenyl sulfoxide group from sulfoxide ester 6 prepared from cyclohexenone 3. Diastereoselective methylation at C-7, alkylation at C-6, and deoxygenation of C-12 and C-24 positions gave the fully substituted bicyclic core of 1. The two side chains of the bicyclic core were further extended so as to afford natural dysidiolide (1). The total yield of this synthesis exceeds that of previous syntheses of 1.     

Ion-exchanger phase photoacoustic spectrometry for trace analysis of metal ions

Laser-induced photoacoustic spectroscopy has been applied to the determination of chromate, uranyl, and Cr(VI) and Fe(II) ions as coloured complexes that were sorbed on ion-exchanger beads. A simple photoacoustic cell has been constructed; it consisted of a fused silica glass tube and an attached cylindrical piezoelectric transducer. A pulsed laser fight at 532 or 355 nm irradiated the ion-exchanger beads that had been collected in the glass tube of the cell. Since a sample material was effectively concentrated on the ion exchanger, the sensitivity was much higher than that in the corresponding photoacoustic spectrometry in a solution state. The lowest detection limit was 0.21 ng/ml Fe for Fe(II)-DPPS (4,7-diphenyl-1,10-phenanthrolinedisulphonate) complex sorbed on QAE-Sephadex gel. Analytical characteristics of the present method are described.     

Electrophoretic phenotyping of erythrocyte enzymes.

Erythrocyte acid phosphatase (EAP), esterase D (ESD) and phosphoglucomutase (PGM) phenotypes among the erythrocyte enzyme types of blood groups are surveyed and a modified cellulose acetate membrane isoelectric focusing (CAM-IEF) method for their exploration is described. The phenotyping procedures are usually classified as either equilibrium or non-equilibrium IEF. Equilibrium IEF, which is based on differences in pI values, includes three methods: (i) a narrow pH range of carrier ampholytes, (ii) a relatively narrow pH range of carrier ampholytes containing chemical separators and (iii) immobilized pH gradient gels. Among the three methods, immobilized pH gradients provides a better resolution of isozymes. Conversely, the disadvantages of immobilized pH gradients include longer focusing times and complex gel preparations. Moreover, immobilized pH gradients are unsuitable for stain analysis because of the insensitivity of PGM1 detection. A hybrid IEF system and a commercial immobilized pH gradient dry plate have overcome these problems. However, EAP typing is extremely expensive and ESD typing is not well distinguished by hybrid IEF. As each method has both merits and demerits, the most suitable technique should be selected based on the kind of erythrocyte enzyme types and sample conditions. On the other hand, non-equilibrium IEF is a rapid method because isozymes are detected on the basis of their charge differences under non-equilibrium conditions. Moreover, the appropriate addition separators increases the charge difference and provides a good resolution within a shorter time. Addition of more separators produces a narrow pH range in the gel and takes a substantially longer time to reach the optimum pH range for charge difference.(ABSTRACT TRUNCATED AT 250 WORDS)     

Interstitial superstructures in the TaD system

Ordered deuterium arrangements and order-disorder transformations of the tantalum deuterides in the range TaD_0.50TaD_0.78 have been studied by neutron diffraction and calorimetry at temperatures between ?170 and 120°C. In addition to the disordered phase (α), three ordered phases based on the superstructures Ta₂D_1+x (β₁), Ta₄D₃, (γ), and TaD (δ) are clarified. The Ta₂D_1+x structure is a nonstoichiometric from of the Ta₂D superstructure over the rangex < 0.5. The γ-phase is formed below ?70°C near Ta₄D₃, and transforms into theβ₁and δ-phases, respectively, in the hypo and hyperstoichiometric compositions. The δ-phase that exists beyond TaD_0.75 changes to the disordered α-phase around 100°C.     

Notable deuterium effect on the electron transfer rate of myoglobin

The electron transfer reaction of wild-type myoglobin at an electrode was significantly facilitated in a D2O buffer as compared with that in an H2O buffer, with k(0)'(H2O)/k(0)'(D2O)= 0.13, while a minimal deuterium kinetic isotope effect on the myoglobin with modification at distal histidine (His-64) was observed.