Absorption of shocked benzene

Abstract

We used absorption spectroscopy to observe decomposition of benzene (C₆H₆) subjected to the passage of strong shock waves generated by projectile impact. These measurements were made using a recently developed double-beam, double-pass, fiber-optic-coupled apparatus. Near 13 GPa, we observe absorption throughout most of the visible region, with strong absorption occurring for wavelengths below 400 nm. The absorption is most likely due to a combination of molecular absorption and Mie scattering from carbon particles formed as a result of shock decomposition.     

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.     

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].     

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.     

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.     

Novel macroscopic BC3 honeycomb sheet

We have successfully grown a uniform BC₃ honeycomb sheet with high crystalline quality over the entire macroscopic area of the NbB₂ (0001) surface by carbon-substituted technique in a boron honeycomb. This is the first macroscopic uniform sheet of single-crystal BC₃ with a monolayer thickness. So far, only BC₃ micro-crystals with radii of a few nanometres were produced. The properties of the sheet have been investigated by using XPS, AES, LEED, STM, ARUPS and HREELS. All the experimental data and the theoretical calculations, which are concerning with atomic structure, chemical concentration, and phonon structure, indicated that the uniform BC₃ honeycomb sheet was grown in an epitaxial manner to the substrate lattice.     

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.     

Theory of the steady-state current of a redox couple at interdigitated array electrodes of which pairs are insulated electrically by steps

The possibility of constructing an interdigitated array electrode (IDA) with a submicrometre gap is proposed in which adjacent microband electrodes are separated from each other by an insulated step. Then the IDA is an assembly of protrusive and hollow microband electrodes. The unit model of the IDA consisted of half of the lower (hollow) microband electrode, an insulated step and half of the upper (protrusive) microband electrode with a finite thickness on the step. The boundary value problem involving the two-dimensional Laplace equation is presented for redox cycling at the IDA under diffusion control and is solved numerically by a boundary element method. The steady-state current was computed as a function of the height of the step and the thickness of the upper electrode. It was larger than the current at the ordinary IDA, partly because the true electrode area was larger than the area of the ordinary IDA. The current varied linearly with the logarithm of the step height. It was expressed by a simple approximate equation in order to facilitate prediction of its numerical value.     

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.