Sol-gel preparation and optical properties of SiO2-Ta2O5 glass

Tantalum-doped silica glass was fabricated by the sol-gel process in order to obtain a glass with a high refractive index for optical use. A crack-free, clear glass rod was successfully prepared from a low-density gel and used as the core material for fabricating optical fibers. Transmission loss in the fabricated fibers was high, in the range of 10³-10⁴ dB/km, which may be caused by coloration due to the multivalency of tantalum; however, the loss was reduced by nearly one order of magnitude by heat treatment at 800 °C, that is, to 75 dB/km at a wavelength of 0.8 μm.     

Density functional calculations of dangling bonds for CN and SiN films

Hyperfine interaction constants (HFICs) of dangling bonds for CN and SiN films were calculated by density-functional theory. The averaged ¹⁴N isotropic HFICs for C dangling bonds are almost equal to those for Si dangling bonds. The anisotropic ¹⁴N HFICs calculated for C dangling bonds are larger than those for Si dangling bonds by a factor 2. The calculated results were compared with experimental results obtained by electron spin resonance and electron nuclear double resonance. It was indicated that the carbon dangling bonds are located such that they avoid N atoms in CN films.     

Photochemical deprotection of nitro-substituted benzenesulfenates via photoinduced electron transfer

The photochemical deprotection of alkyl 2,4-dinitrobenzenesulfenate or alkyl 2-nitrobenzenesulfenate was successfully achieved by addition of triethylamine, while it was unsuccessful without triethylamine. The sulfur-oxygen bond cleavage is thought to occur heterolytically in the sulfenate anion radical produced by photoinduced electron transfer with triethylamine.     

Mössbauer spectroscopic studies of ferrocene adsorbed on silica gel

Mössbauer spectra of ferrocene adsorbed on silica gel were measured in order to study the state of adsorption. Ferrocene adsorbed on silica gel tended to oxidize in air and form ferricenium ion. It is assumed that the oxidation of adsorbed ferrocene was caused by surface hydroxyls on the silica gel and O₂ in air. It was observed that ferrocene adsorbed weakly at 293 K, although the ferricenium ion adsorbed strongly at 293 K. Thus the adsorption states of ferrocene depend on the experimental condition.     

Towards the selective formation of specific isomers of fullerenes: T - and p-dependence in the yield of various isomers of fullerenes C60–C84

Systematic fractional change in the yield of various isomers of fullerenes was revealed to strongly depend on temperature of a buffer gas. A new kinetic consideration is proposed for understanding the observed temperature- and pressure-dependence of yield of fullerenes. The model consists of three competitive reactions in consideration of plausible behaviors of a precursor, (1) decomposition into smaller fragments, (2) isomerization leading to formation of a stable fullerene cage, and (3) growth into a larger carbon cluster. Arrhenius activation energy of formation of stable fullerenes was determined to be 0.8 eV for both C₆₀ and C₇₀, while a higher energy of 2.0?3.3 eV for seven different isomers of higher fullerenes ranging from C₇₆ to C₈₄. Correlation in the activation energy is noted for a series of higher fullerenes with different sizes, suggesting the existence of a specific precursor in their formation processes.     

Bounds to average interelectronic angles in Hartree-Fock theory of atoms

The average interelectronic is the expectation value of the angle thetaij (0 < or = thetaij < or = pi) subtended by the position vectors ri and rj of a pair of electrons i and j. In the Hartree-Fock theory of atoms, we point out that the angle and its subshell-pair components nl,n'l' are bounded from above and below, where n and l are the principal and azimuthal quantum numbers. The upper bounds for nl,n'l' with 0 < or = l, l' < or = 3 are 9pi/16 (=101.25 degrees), 135pi/256 (approximately 94.922 degrees), 265pi/512 (approximately 93.164 degrees), and 129pi/256 (approximately 90.703 degrees) for sp, pd, df, and sf pairs, respectively, while they are pi/2 (=90 degrees ) for the other ll' pairs, independent of n and n'. A weighted sum of these subshell-pair bounds gives an upper bound to . The lower bounds are pi/2 in all the cases.     

Determination of sulfate in river water by flow injection analysis

Sulfate ion in river water is determined by flow injection analysis at a rate of 30 samples per hour; the sulfate contents are typically less than 30 ppm. The reagent solution contains dimethylsulfonazo-III, barium chloride, potassium nitrate and chloroacetate buffer in 70% ($\text{v}\text{v}$) ethanol, and is saturated with barium sulfate. The aqueous carrier stream is also saturated with barium sulfate. The sample is filtered and treated with Amberlite IR120-B cation-exchanger before injection into the carrier stream, and the decoloration of the barium—dimethylsulfonazo-III complex by sulfate is measured at 662 nm. The calibration graph is linear over the range 0–30 μg ml^-1 for sulfate in water.     

Changes in enzymatic and membrane-adsorbing activities of sphingomyelinase from Bacillus cereus by modification with a polyethylene glycol derivative.

Sphingomyelinase (SMPLC) from Bacillus cereus was modified with a polyethylene glycol (PEG) derivative, methoxypolyethylene glycol-succinimidyl succinate (ss-PEG). The molecular weight of the ss-PEG-modified SMPLC was calculated to be approx. 150 kDa by gel-filtration whereas that of the native enzyme, was 25 kDa. By this modification, the enzyme increased its thermostability and retained its hydrolytic activity toward 2-(N-hexadecanoylamino)-4-nitrophenylphosphocholine (HNP) and sphingomyelin (SM) in the mixed micelles with the surfactants such as Triton X-100 and sodium deoxycholate (SDC). However, the activity toward liposomal SM was significantly decreased, and all the enzyme activities toward bovine erythrocytes, including membraneous SM-hydrolyzing and hemolytic activities as well as the enzyme adsorption onto the erythrocyte membranes, were completely lost.     

Emission spectrographic determination of trace elements in atmospheric particulate matter

Air containing particulate material was passed continuously for one month through a low-volume air sampler equipped with a cyclone to exclude particulates greater than 10 μm in diameter. The samples and filters were ashed in a low-temperature plasma and, after addition of In₂O₃ support, palladium internal standard and graphite buffer, the ashes were analyzed by a.c. are emission spectrometry. Standard samples were prepared from a commercial standard containing 49 elements. The procedure allows the determination of 14 trace metals (Ag, Al, Cr, Cu, Fe, Ga, Mn, Mo, Ni, Pb, Sn, Ti, V, Zn) with relative standard deviations of 1.4–15.1%. The procedure has been applied successfully to monthly determinations of the average atmospheric concentrations of these elements in Kobe City for the past three years.