Ionic conduction in CuxAg1−xBrTe solid solutions

The ionic conduction of cation substituted CuBrTe, Cu_xAg_1−xBrTe solid solutions, is investigated in the temperature range between 100 and 400 K. The change of electrical conductivities with temperature in the range of 0.94≤x<1 shows the characteristics of second-order rather than first-order phase transitions. The replacement of Cu with the Ag cation in Cu_xAg_1−xBrTe leads to an increase in conductivity especially in the β and γ-phases.     

Direct electron transfer with glucose oxidase immobilized in an electropolymerized poly( N-methylpyrrole) film on a gold microelectrode

Direct electron transfer between active glucose oxidase (GOD) and a gold electrode was obtained when GOD was immobilized in poly(N-methylpyrrole) electrochemically prepared on the gold electrode. When electropolymerization was accomplished at 50 °C, after glucose addition, the cyclic voltammograms showed an increased oxidation peak at ca. ?0.45 V vs. Ag/AgCl. This potential corresponds to the oxidation potential for FADH₂. Although the GOD becomes much less selective, a glucose-dependent current response is obtained.     

A first high enantiocontrol of an asymmetric tertiary carbon center attached with a fluoroalkyl group via Rh(I)-catalyzed conjugate addition reaction

Treatment of fluoroalkylated electron-deficient olefins with various boronic acids in the presence of a catalytic amount of Rh(I) coordinated with (S)-BINAP in toluene/H₂O at the reflux temperature for 3 h gave the corresponding conjugate addition products with high enantioselectivity in high yields.     

Characterization and quantification of fluoxymesterone metabolite in horse urine by gas chromatography/mass spectrometry

Fluoxymesterone, an anabolic steroid with the 17alpha-methyl,17beta-hydroxy group, has been developed as an oral formulation for therapeutic purposes. However, it is also used illegally in racehorses to enhance racing performance. In this study, we detected 9alpha-fluoro-17,17-dimethyl-18-norandrostane-4,13-dien-11beta-ol-3-one by gas chromatography/mass spectrometry (GC/MS), which has not been reported as a fluoxymesterone metabolite so far in horse. It was synthesized for use as a reference standard, and characterized on the basis of (1)H NMR and (13)C NMR spectra, as well as GC/MS EI mass spectra of TMS derivatives. It was excreted as the main metabolite in horse urine, and its reference standard could be synthesized easily. Therefore, this metabolite could be a useful target for a doping test of fluoxymesterone in racehorses.     

Regio-selective cyanation of (Z)-(1,2-dibromo-2-arylvinyl)triisopropylsilane with suppression of halogen elimination

Highly regio-selective cyanation of vicinal (Z)-dibromoalkenyl silanes was achieved by a vinylic Rosenmund-von Braun reaction, significantly suppressing side-production of alkyne. The alkyne was generated by a halogen elimination side-reaction that is an intrinsic problem in metal-activation of vicinal dihaloalkenes. We have studied to overcome the problem, and finally found the combination of CuCN and O = PPh₃ in toluene solvent effectively controlled the production of byproducts. The resultant single isomer has significance in potentially application as a multi-tunable synthetic scaffold.     

High-Pressure Synthesis of Fully Occupied Tetragonal and Cubic Tungsten Bronze Oxides

A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K₃W₅O₁₅ (K_0.6WO₃). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of R_W=3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice. The asymmetric nature of the tetragonal tungsten bronze K_xWO₃-K_0.6−yBa_yWO₃ phase diagram implies that superconductivity for x≤0.45 originates from the lattice instability because of potassium deficiency. A cubic perovskite KWO₃ phase was also identified as a line phase—in marked contrast to Na_xWO₃ and Li_xWO₃ with varying quantities of x (<1). This study presents a versatile method by which the solubility limit of tungsten bronze oxides can be extended.     

Comparative Study of the Determination of Parabens in Shampoos by Liquid Chromatography with Amperometric and Coulometric Detection

The simultaneous determination of four para‐hydroxybenzoic acid esters (parabens) in shampoos was studied by liquid chromatography (LC) with amperometric (LC‐AD) and coulometric (LC‐CD) detection. The parabens were separated on an ODS C18 reversed column by isocratic elution with a mobile phase based on methanol‐0.1 M acetic acid (60 : 40%, v/v) with 0.02 M NaClO₄ at a flow rate of 0.8 mL min^?1. The limit of detection (S/N>3) for the analytes was in the 15–25 pg (injected mass) range at an applied potential of 1.20 V vs. Ag/AgCl using the LC‐AD and in the 2–3 pg range at a potential of 0.790 V vs. Pd using the LC‐CD. The peak ratio of the internal standard peak (IS: 4‐hydroxybenzoic acid sec‐butyl ester) versus the analyte peak was found to be related to the amount injected from 0.1 ng to 100ng (r=0.996–0.999) with the LC‐AD and from 0.050 ng to 100 ng range (r=0.999–1.000) with the LC‐CD. The relative standard deviation (RSD, n=10) was comprised between 1.8 to 3.5% by LC‐AD ( 5 ng injected) and between 2.0 to 2.4% by LC‐CD (0.5 ng injected). The determination of four most used parabens in ten different shampoos was successfully realized.     

Degradation of hydroxymaleimide in 2-propanol by irradiation of energetic heavy ions (II)—N2-saturated system

Hydroxymaleimide was irradiated in N₂-saturated 2-propanol solutions by high-energy heavy ions over a wide range of LET values. The differential G-values of the degradation of hydroxymaleimide by irradiation with the heavier ions were lower than those of the lighter ions for the same LET value. An opposite result obtained in the air-saturated system. The degradation efficiency was 1.5 times higher, when the dose rate was 1/10 times lower. When irradiated at an LET value lower than 8 eV/nm, the G-values converged to a value less than that obtained by γ-irradiation.     

Peierls mechanism of the metal-insulator transition in ferromagnetic hollandite K2Cr8O16

Synchrotron x-ray diffraction experiment shows that the metal-insulator transition occurring in a ferromagnetic state of a hollandite K(2)Cr(8)O(16) is accompanied by a structural distortion from the tetragonal I4/m to monoclinic P112(1)/a phase with a √2×√2×1 supercell. Detailed electronic structure calculations demonstrate that the metal-insulator transition is caused by a Peierls instability in the quasi-one-dimensional column structure made of four coupled Cr-O chains running in the c direction, leading to the formation of tetramers of Cr ions below the transition temperature. This provides a rare example of the Peierls transition of fully spin-polarized electron systems.