Effect of the chemical species of arsenic on sensitivity in graphite furnace atomic absorption spectrometry.

The sensitivity of graphite furnace atomic absorption spectrometry (GFAAS) to arsenobetaine (AB) was 1.3-times higher than to inorganic As. In order to understand the mechanism underlying this observation, the atomization processes for both chemical species were investigated in terms of the enthalpy change (DeltaH) during the atomization process in GFAAS. The enthalpy change of AB was slightly lower than that of inorganic As, which suggested that AB was atomized more efficiently than was inorganic As. Moreover, it was observed that some co-existing organic materials enhanced the analytical sensitivity of inorganic As. The sensitivity difference between inorganic As and AB depended upon the mechanisms of their atomization processes.     

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.     

Estimation of growth rate in unidirectionally solidified multicrystalline silicon by the growth-induced striation method

Multicrystalline silicon was grown by unidirectional solidification method using the accelerated crucible rotation technique. The application of the accelerated crucible rotation technique in unidirectional solidification method induced growth striations across the axial direction of the grown crystal. This striation pattern was observed from carbon concentration distribution, obtained by using Fourier transform infrared spectroscopy. The generated striation pattern was found to be weak and discontinuous. Some striations were absent, probably due to back melting, caused during each crucible rotation. From the growth striations and applied time period in crucible rotation, the growth rate was estimated by using Fourier transformation analysis.     

Preparation of poly(amino‐amide) particles complexed with ZnO particles using silane coupling agents

Poly(amino‐amide) particles were prepared by reacting 4,4′‐diphenyldicarbonyl chloride and 3,3′‐diaminobenzidine using a precipitation polymerization method with ultrasonic irradiation. The resulting particles had a narrow size distribution with an average diameter of 334 nm and showed excellent dispersion stability in water. The particles obtained were then modified with silane coupling agents (GPES) by reacting the amino groups of the poly(amino‐amide) particles with the epoxide rings of the GPES molecules in N,N‐dimethylformamide or N‐methylpyrrolidone using di‐n‐butyltin dilaurate as a catalyst. The amount of GPES covalently bonded to the poly(amino‐amide) particles was found to depend strongly on the reaction solvent and catalyst used. The resulting particles showed a narrow size distribution and the connections among the particles were not observed. On the other hand, the particles before and after modification showed different thermal properties and dispersion stability in water. The GPES‐modified aromatic polyamide particles were then complexed with ZnO particles with an average diameter of about 20 nm in aqueous acetic acid solution. It was found that the surface of the aromatic polyamide particles was covered with ZnO particles via hydrolysis reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4908–4918, 2009     

Security number of grid-like graphs

The security number of a graph is the cardinality of a smallest vertex subset of the graph such that any attack on the subset is defendable. In this paper, we determine the security number of two-dimensional cylinders and tori. This result settles a conjecture of Brigham et al. [R.C. Brigham, R.D. Dutton, S.T. Hedetniemi, Security in graphs, Discrete Appl. Math. 155 (2007) 1708-1714].     

Study of buried Si(1 1 1)-5 × 2-Au by surface X-ray diffraction

The structure of buried Si(1 1 1)-5 × 2-Au capped with amorphous Si was investigated using surface X-ray diffraction. It was found that the 5 × 2 structural periodicity is kept under the amorphous Si from the in-plane measurement. Furthermore, the intensity variation along the fractional-order rod indicates that Au atoms are located almost on the same plane.     

Spontaneous emulsification at oil–water interface by tetraalkylammonium chloride

Water droplets were formed spontaneously at the interface of the 2-nitrophenyloctyl ether and aqueous phases on the oil phase side when the oil contained tetraalkylammonium chloride without surfactants. The droplets, less than some micrometers in diameter, gathered at the interface. The number density of the droplets was proportional to the concentration of tetraethylammonium chloride, and hence this salt should be responsible for the formation of the droplets as a surfactant. When positive voltage was applied to the aqueous phase against the oil, the droplets departed from the interface toward the oil bulk. The droplets should be negatively charged by chloride. The adsorption model of the salt was suggested, in which chloride is immobilized at the interface on the aqueous side electrostatically with tetraethylammonium ion on the oil side.     

Azacalix[4]arene tetramethyl ether with inherent chirality generated by substitution on the nitrogen bridges

The first inherently chiral azacalix[4]arene has been prepared by introducing three benzyl groups onto the nitrogen bridges. The highly enantioenriched compound was easily obtained via a moderately enantioselective cyclization followed by a simple crystallization procedure. NMR and X-ray crystallographic studies revealed that easy access to the enantiomer was permitted by the non-racemizable 1,3-alternate conformation in solution, up to 110 °C, as well as by the preferential crystallization of a racemic compound.     

Nucleophilic substitution reaction at an sp carbon of vinyl halides with an intramolecular thiol moiety: synthesis of thio-heterocycles

This article presents a full account of intramolecular vinylic substitution reactions of bromoalkenes having an acetylthio moiety, which give sulfur-containing heterocycles such as dihydrothiophene, tetrahydrothiopyran, and 2-alkylidenethietane derivatives. The reaction pathways of the substitution reactions were investigated by theoretical and experimental studies.