Voltammetric study of the transfer of polyammonium ions at nitrobenzene / water interface.

The transfer of polyammonium ions, poly[(dimethylimino)-1,6-hexanediyl] (n = 140, n being the degree of polymerization) ion and poly[(dimethylimino)(2-oxo-1,2-ethanediyl)imino-alpha,omega-alkanediylimino(1-oxo-1,2-ethanediyl)(dimethylimino)-alpha',omega'-alkanediyl] ([-N+ (CH3)2CH2CONH(CH2)x NHCOCH2N+ (CH3)2(CH2)y-]n, x = 2, 3, 4, or 6, y = 3 or 6, and n = 30-130) ions, at a polarizable nitrobenzene / water interface has been studied by normal pulse voltammetry and cyclic voltammetry. Despite the polydispersity of the preparations, by normal pulse voltammetry, an S-shaped current-potential curve with a well-defined limiting current, and, by cyclic voltammetry, a pair of anodic and cathodic peak currents due to the transfer of polyammonium ions across the interface were observed within the potential window. The voltammetric behavior is described. Also, the effect of ion-pair formation of the polyammonium ions with supporting electrolyte anions in nitrobenzene- and water-phases on the half-wave or midpoint potential of the ion-transfer, and the relation between the structure of the polyammonium ions and the transfer potentials are discussed.     

High-quality two-dimensional electron gas at large scale GaN/AlGaN wafer interface prepared by mass production MOCVD systems

Basic electronic properties of two-dimensional electron gas (2DEG) formed at GaN/AlGaN hetero-interface in large-scale (100 mm) wafer made by metal organic chemical vapour deposition (MOCVD) have been reported and discussed. From conventional Hall measurements, highest electron mobility was found to be μ_e∼1680 and 9000 cm²/V s at room temperature and at ∼5 K, respectively, for sheet electron density of n_s∼8×10¹² cm⁻². In magneto-resistance (MR) measurements carried out at 1.5 K in Hall bar sample defined by photolithography and ion implantation, very clear Schubnikov de-Haas oscillations and integer quantum Hall effect were observed in diagonal (R_xx) and off-diagonal (R_xy) resistances, respectively. In addition, a good insulating nature of GaN layer is confirmed by capacitance-voltage (C-V) measurement. These results suggest the high-qualitiness of our 100 mm GaN/AlGaN high electron mobility transistor (HEMT) wafers comparable to those so far reported.     

A Fuzzy Stopping Problem with the Concept

Stimulated by Zadeh's paper (Journal of Statistical Planning and Inference,2002, 105, 233--264), we will try to consider a perceptive analysis of the optimal stopping problem. In this paper, the fuzzy perception value of the expectation of the optimal stopped reward is characterized and calculated by a new recursive equation. Also, a numerical example described by triangular fuzzy numbers is given.     

The upper limit pH in the dye-binding method for the determination of serum protein via measurements of the absorbance increase produced by protein error.

In the dye-binding method for determining the albumin concentration, the absorbance increase due to the change of the color shade by protein error of a pH indicator can be measured by a spectrophotometer. This absorbance increase is observed only in a restricted pH region, but this pH region is not theoretically studied yet. Thus, the author investigated the upper limit pH (pHUL) at which the absorbance increase occurs by the theoretical calculation, and compared these results with those obtained experimentally using four pH indicators. The pHUL is not affected by the dye or protein concentrations, or by the formation constant of the dye-protein complex; but the value changes according to the acid-dissociation constant of the dye (KD) and the ratio of the molar absorptivities of the proton-dissociated dye anion (epsilonD) and the dye-protein complex (epsilonPD). The pHUL value can be calculated by the equation, found theoretically. The calculated pHUL values of BPB, BCG, BCP and BTB were 5.1, 4.8, 6.2 and 5.5, respectively. These values correlated with the experimental results of 4.5 for BPB, 4.7 for BCG, 5.9 for BCP and 5.2 for BTB, but were not associated with the pKD values of each dye. The pHUL of these dyes did not change significantly for various dye and protein concentrations, as was expected from the thoretical calculation.     

The correlation between molecular weight and antitumor activity of galactosaminoglycan (CO-N) from Cordyceps ophioglossoides

A galactosaminoglycan (CO-N) obtained by ultrasonication from a protein-bound polysaccharide SN-C, which was isolated from Cordyceps ophioglossoides culture, has a direct cytotoxicity against tumor cells (Ohmori et al., Chem. Pharm. Bull., 37, 1019 (1989). High performance liquid chromatographic analysis revealed that CO-N shows a broad molecular weight distribution with an average molecular weight of 33000. A potent antitumor activity of CO-N was observed in the higher-molecular-weight fraction on gel filtration, and the low-molecular-weight fraction below 6600 showed a weak activity. However, the depolymerized CO-N (ca. 5500) obtained by further ultrasonication of the original CO-N still retained the antitumor activity of CO-N against Ehrlich ascitic carcinoma or MM46 solid mammary carcinoma.     

Triphenylstibine oxide–phosphorus(V) sulfide as a novel condensation catalyst system: application to the synthesis of dipeptides

Triphenylstibine oxide (Ph₃SbO) and phosphorus(V) sulfide (P₄S₁₀) synergistically catalyzed the aminolysis of N-protected amino-acids with amino-acid esters in benzene. Ph₃SbO accelerated both the initial conversion of carboxylic moieties into the corresponding thiocarboxylic moieties by P₄S₁₀ and the subsequent aminolysis of the resulting thiocarboxylic acids. Thus, dipeptides such as Z–A–A′–OEt (where Z = PhCH₂OC(O)– and A,A′ = Ala,Gly; Gly,Gly; Leu,Gly; Phe,Gly; Phe,Leu;Ser,Gly; Val,Gly, respectively) were conveniently prepared even at 35°C.     

Renormalization group analysis of the temperature dependent coupling constant in massless theory

A general analysis of finite temperature renormalization group equations for massless theories is presented. It is found that in a direction where momenta and temperature are scaled up with their ratio fixed the coupling constant behaves in the same manner as in zero temperature and that the asymptotic freedom at short distances is also maintained at finite temperature.     

Selective preconcentration of copper from aqueous solution by using kerateine gel

Summary A selective preconcentration technique for copper using the kerateine gel is described. The gel is prepared by partial oxidation of kerateine which is obtained by reducing the disulphide bonds of wool fiber. Copper is selectively adsorbed on the gel at pH 3.5. It is eluted with 3 M hydrochloric acid and is determined by atomic-absorption spectrometry. This method has been applied to the determination of copper in river water.

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Selektive Anreicherung von Kupfer aus wäßriger Lösung mit Hilfe von Keratein-Gel

Zusammenfassung Ein selektives Anreicherungsverfahren für Kupfer mit Hilfe von Keratein-Gel wurde ausgearbeitet. Das Gel wird durch teilweise Oxidation von Keratein hergestellt, das aus Wollfaser durch Reduktion der Disulfidbindungen gewonnen wird. Kupfer wird bei pH 3,5 selektiv an diesem Gel adsorbiert und kann mit 3 M Salzsäure eluiert werden. Die Bestimmung erfolgt mit Hilfe der AAS. Das Verfahren kann zur Kupferbestimmung in Flußwasser angewendet werden.