Development of vapor phase decomposition-total-reflection X-ray fluorescence spectrometer

A total reflection X-ray fluorescence spectrometer integrated with vapor phase decomposition, VPD-TXRF, was newly developed. This instrument was designed to achieve a minimum footprint, to avoid cross contamination during operation, and to protect people and instruments from HF gas. Comparisons between analysis by VPD-TXRF and by atomic absorption spectrometry (AAS) indicated very good agreement in a wide range, from 10⁸ to 10¹² atoms/cm². The lower limits of detection (LLDs) were improved by two orders of magnitude compared with straight TXRF. For 300-mm Si wafers, the LLDs were 5×10⁸ atoms/cm² and 1×10⁷ atoms/cm² for Al and Ni, respectively. VPD-TXRF was able to perform ultra-trace analysis at the level of 10⁸ atoms/cm².     

Structural study on highly oxidized states of a water oxidation complex [RuIII(bpy)2(H2O)]2(mu-O)4+ by ruthenium K-edge X-ray absorption fine structure spectroscopy

The oxidation-induced structural change of a water-oxidizing diruthenium complex, [(bpy)(2)(H(2)O)Ru(III)(micro-O)Ru(III)(OH(2))(bpy)(2)](4+) (bpy = 2,2'-bipyridine), was investigated by means of X-ray absorption spectroscopy. Ru K-edge XANES (X-ray absorption near-edge structure) spectra from the acidic solution and solid precipitates obtained by oxidation showed that the absorption edge shifts toward higher energy with a preedge feature slightly more enhanced than those of the lower oxidation states. This indicates that the higher oxidation state has a lower symmetry due to shortening of the Ru-O bonds that originated from the water ligands. The EXAFS (extended X-ray absorption fine structure) spectra were similar to those of the lower oxidation states, whose analysis revealed the existence of short Ru-O double bonds and an almost linear Ru-O-Ru angle (169 +/- 2 degrees ). Ab initio EXAFS simulations for several possible structural models suggest that the dimeric structure is maintained during the water oxidation reaction.     

Synthesis of N-linked glycan derived from Gram-negative bacterium, Campylobacter jejuni

Recent research has revealed the presence of asparagine (Asn)-linked (N-linked) glycoproteins in certain prokaryotes. In this paper, we describe the chemical synthesis of a novel N-glycan derived from Campylobacter jejuni, a heptasaccharide composed of Asn-linked bacillosamine (Bac), repeating GalNAc, and branching Glc, namely GalNAc-α(1,4)-GalNAc-α(1,4)-[Glc-β(1,3)-]GalNAc-α(1,4)-GalNAc-α(1,4)-GalNAc-α(1,3)-Bac. The synthesis started from a Bac-acceptor, which was consecutively glycosylated with 4-O-pentafluoropropionyl (PFP) protected donors to give heptasaccharide. Reduction of azide groups was followed by debenzylation to complete the synthesis of the target oligosaccharide.     

Compressible bag model and dibaryon stars

We propose dibaryon stars on the base of the compressible bag model, in which a hadron bag responds microscopic thermal pressure of the other bags and the volume exclusion effect is considered. In general, a free bosonic point-particle matter has no pressure at zero temperature, but a condensed bosonic bag matter is able to have a finite pressure because of both the compressibility and the volume exclusion effects. We will show that the condensed dibaryon matter not only produce a very soft equation of state but can also bring the 1.44M mass star.     

Regioselective synthesis of 2,3-disubstituted 1-alkyl pyrrolo[2,3-b] quinoxalines through palladium-catalyzed Heck reaction of chalcones and evaluation of their anti-bacterial activities

The regioselective synthesis of 1-alkyl-2-aryl-3-acyl pyrrolo[2,3-b]quinoxalines through palladium-catalyzed Heck coupling reaction/heteroannulation was reported. The reaction of N-alkyl/benzyl-3-chloroquinoxaline-2-amines with chalcones catalyzed by Pd(OAc)₂ in the presence of KO^tBu, as the base, in DMSO afforded the desired products in good-to-high yields. The MIC and MBC determinations revealed that these compounds could be used in the future research works for the development of antibiotics.     

Diazadibora[1.1.1.1]m,p,m,p‐cyclophanes: Ambipolar Conjugated Macrocycles with Different B–π–N Embedded Patterns

Are different B(boron)–π–N(nitrogen) embedded patterns to bring about significant different (opto)electronic properties for the same macrocyclic molecular backbone? A series of B–π–N‐embedded alternate‐meta‐para‐linked cyclophanes 1 – 3 have been prepared and characterized as a new class of ambipolar π‐conjugated B–π–N macrocycles. The answer to the opening question is yes. These macrocycles revealed the intramolecular charge transfer in the oxidized states and the intriguing photophysical proprerties in accordance with the embedded patterns, suggesting the electronic structures are tunable by introducing multiple B–π–N moieties.     

Flow-injection photometric determination of manganese(II) based on its catalysis of the periodate oxidation of N,N'-bis(2-hydroxy-3-sulfopropyl)tolidine

A novel flow-injection spectrophotometric method has been developed for the determination of manganese(II) at sub-nanogram/ml levels. The method is based on its catalytic effect on the oxidation of N,N′-bis(2-hydroxy-3-sulfopropyl)tolidine (HSPT) by periodate. The catalytic effect of manganese(II) was enhanced by the presence of 2,2′-bipyridine as an activator. By monitoring the change in absorbance of the oxidation product of HSPT at 670 nm, manganese(II) ranging 0.02-3.0 ng ml⁻¹ could be determined with the relative standard deviations of less than 2%. The interfering ions were effectively suppressed by the addition of 2,2′-iminodiethanol and citric acid. The proposed method is directly applicable to the determination of manganese in lake and river water samples.     

ULTRAVIOLET-INDUCED DNA DAMAGE AND ITS PHOTOREPAIR IN TAIL FIN CELLS OF THE MEDAKA, Oryzias lutipes

Abstract— To study UV-induced damage and its photorepair in vivo , endonuclease-sensitive sites (ESS) induced by UV irradiation in the DNA of the tail fin of the Medaka, Oryzias latipes . were examined. Isolated fins were irradiated with UV-B, but no ESS were detected after increasing doses of UV-B up to 500 J/m². Then fins were irradiated with UV-B and fin cells were dissociated by treatment with trypsin and EDTA. Ultraviolet-B-induced ESS were detected in the epithelial cells near the tissue surface but not in the inner cells. The capacity for photo repair of both inner and outer epithelial cells and cells in fin ray was the same and was higher than that for a line of cultured cells, OL32.     

Small-angle x-ray scattering of distorted lamellar structures

Small-angle x-ray scattering (SAXS) intensity for the lamellar structure of polymeric materials has been formulated with consideration of structural defects such as the finiteness of the lamellar stack, the lamellar bend, and the paracrystalline distortions. In particular, the effects of the lamellar bend on the SAXS profile have been elucidated on the basis of Vonk'xss formula γ₁(x) – γ(x)exp(?2x/d). Here, the scattering profile due to the lamellar bend is shown to be expressed by a Cauchy function. The integral breadth is equal to 2π/d, being independent of the order of scattering. As an example of the SAXS analysis based on the theory, the characterization of the lamellar structure in the “hard” elastic polypropylene films is reported. The long period and the lamellar thickness are evaluated from the correlation function, and the distortion length and Hosemann's g factor are estimated according to the procedure presented here. On the basis of these structural parameters, the relationship between the manufacturing process and the lamellar structure of the polypropylene films is discussed. © 1993 John Wiley & Sons, Inc.