Surface treatment of silicon carbide using TiO2(IV) photocatalyst

Silicon carbide (SiC) and diamond were decomposed to CO(2)(g) by the photocatalysis with TiO(2) at room temperature, although the decomposition rate of diamond was very slow. According to the XPS spectra of Si2p on the SiC surface, SiO(2) was simultaneously formed on the surface by the TiO(2) photocatalysis. The thickness of the SiO(2) formed on the SiC surface during the photocatalytic oxidation for 1 h was estimated to be about 40 A from the depth profile of the XPS spectra using Ar etching. The SiC surface was oxidized by the TiO(2) photocatalysis even under the condition without a direct contact with the TiO(2). This indicates that the photocatalytic oxidation of the SiC occurs due to active oxygen species photogenerated on the TiO(2) surface, but not by hole produced in the valence band of the TiO(2). Moreover, a remote surface treatment system using the quartz beads coated with TiO(2) was developed for the SiC surface oxidation. Consequently, the TiO(2) photocatalysis will be very useful for the surface treatment of SiC such as photopatterning without defects and damage to the substrate because the photocatalytic reaction is carried out under mild conditions.     

Structural and spectroscopic characterization of a diruthenium o-dioxolene complex possessing a singly occupied molecular orbital delocalized over the entire molecule, [Ru2(3,6-DTBDiox)4]-

Chemical oxidation of [Ru2(6+)(3,6-DTBCat)4]2- affords [n-Bu4N][Ru2(3,6-DTBDiox)4].acetone (2.acetone). The oxidized species was characterized by X-ray crystallographic analysis and EPR, and the delocalization of the unpaired electron over the entire molecule was indicated. This example showed that the utilization of redox-active ligands into a Ru2 complex expanded the degree of freedom in the electronic structure. DFT calculations support this view, and the spin population was estimated to be approximately 18% and 82% for the Ru2 core and the four dioxolene ligands, respectively.     

Graphs with small boundary

For a pair of vertices x and y in a graph G, we denote by d_G(x,y) the distance between x and y in G. We call x a boundary vertex of y if x and y belong to the same component and d_G(y,v)?d_G(y,x) for each neighbor v of x in G. A boundary vertex of some vertex is simply called a boundary vertex, and the set of boundary vertices in G is called the boundary of G, and is denoted by B(G).In this paper, we investigate graphs with a small boundary. Since a pair of farthest vertices are boundary vertices, |B(G)|?2 for every connected graph G of order at least two. We characterize the graphs with boundary of order at most three. We cannot give a characterization of graphs with exactly four boundary vertices, but we prove that such graphs have minimum degree at most six. Finally, we give an upper bound to the minimum degree of a connected graph G in terms of |B(G)|.     

Optical measurements on semiconductor microcrystal beams generated by gas evaporation

We have developed a simple measurement method for measuring the optical spectra of free microcrystals, by combining the time-resolved and space-resolved spectroscopies with the gas evaporation method. The structure of the obtained spectra and their time- and space-dependencies indicate well the quantum-confinement effects of carriers and excitons in free semiconductors microcrystals.     

Determination of fructosyl amino acids and fructosyl peptides in protease-digested blood sample by a flow-injection system with an enzyme reactor.

A flow-injection system with an enzyme reactor was proposed for the measurement of fructosyl amino acids and fructosyl peptides in protease-digested blood samples. A fructosyl-amino acid oxidase (FAOX-TE) and two fructosyl-peptide oxidases (FPOX-CE and FPOX-CET) were covalently immobilized onto an inert support. They were used as the enzyme reactor in a FIA system with a hydrogen peroxide electrode. In particular, the FPOX-CET reactor possessed high selectivity for the detection of fructosyl valine (FV) and fructosyl valyl histidine (FVH) and an excellent operational stability. The proposed FIA system with the FPOX-CET reactor responded linearly to the concentration of FV over the dynamic range of 7.8 x 10(-6) to 5.8 x 10(-4) M. The present method could be successfully applied to the assay of FV and FVH in the protease-digested blood samples.     

On-line liquid chromatography and circular dichroism detection of stereo-isomers of alpha-tocopherol derivatives generated by an electrochemical reaction

The electrochemical oxidation of (+/-)-alpha-tocopherol on a porous graphite electrode was performed in the presence of methanol, and successive separation and detection of the products were performed by an on-line liquid chromatography/mass spectrometry system. Three products were identified, one of which was determined to be alpha-tocopheryl quinone, because its m/z was 469 [M+Na](+). The other two products showed identical mass and UV spectra, and were suspected to be diastereomers of 9-methoxy-alpha-tocopheron, because their molecular weights were m/z 483 [M+Na](+), and also because it is known that the chemical oxidation of alpha-tocopherol by benzoyl peroxide or N-bromosuccinimide in the presence of methanol should provide 9-methoxy-alpha-tocopheron. To confirm that these two compounds were diastereomers, a circular dichroism detector was used. The signs of both peaks detected by the circular dichroism detector at 230 nm were opposite. In addition to observations of identical mass and ultraviolet spectra, these results indicated that the two products were diastereomers of 9-methoxy-alpha-tocopheron, whose stereochemistry is different at the newly generated chiral center of the 9-position. The on-line use of a circular dichroism detector with an electrochemical cell/liquid chromatography system may expand the utility of the system to study the metabolism of a chiral drug.     

Synthesis of n-alkyl-n-(1-hydroxyperoxyalkyl)nitrosamines by oxygenation of lithiated dialkylnitrosamines

N-Alkyl-N(1-hydroperoxyalkyl)nitrosamines were synthesized from N,N-dialkylnitrosamines by lithiation with lithium diisopropylamide, followed by oxygenation with oxygen in good yields.     

Polymerisation von Methylmethacrylat mit dem Benzoin-Pyridin-CCl4-Systemen. Substituenten- und L?sungsmittel-Effekte

Ohne Zusammenfassung