Synthesis of CuO---Al2O3---SiO2 glasses from the sol-gel method and properties

The synthesis of CuO---Al₂O₃---SiO₂ glasses by the sol-gel method was investigated and the thermal expansion of bulk glasses was measured. Phase separation was observed in these glasses and apparently consisted of a copper-rich dispersed phase and a network former-rich matrix phase. The low thermal expansion coefficient of these glasses was governed by the matrix phase.     

Wake properties of a single gas bubble in three-dimensional liquid-solid fluidized bed

Experiments were performed to investigate the wake properties of a single gas bubble in a three-dimensional liquid-solid fluidized bed via a video camera moving at the same speed as the bubble. The solids holdup in the fluidized bed varied up to around 10%. The bubble size varied from 5 to 20 mm with corresponding bubble Reynolds numbers ranging from 1000 to 6500. The bubble was observed to have two types of wake configurations depending on the bubble size: the asymmetric/helical vortex wake for small bubbles and the symmetric wake for large bubbles. The bubble shape and relative rise velocity in the fluidized bed can be well-represented by correlations developed for single bubbles in liquid media, although the bubble shape in liquid-solid media is slightly more flattened compared to that in liquid media. The bubble rocking frequency was found to be independent of particle properties and to correspond in magnitude to the vortex shedding frequency in a two-dimensional liquid-solid fluidized bed. The average primary wake size in three dimensions is comparable to that in two dimensions.     

Level-rank duality of WZW models in conformal field theory

We consider the decomposition of the conformal blocks under the conformal embeddings. The case (â is an affine extension of the abelian subalgebra of the central elements ofgl(lr)) is studied in detal. The reciprocal decompositions of -modules induce a pairing between the spaces of conformal blocks of and Wess-Zumino-Witten models on the Riemann sphere. The completeness of the pairing is shown. Hence it defines aduality between two spaces.Dedicated to Professor Masahisa Adachi on his 60th birthday     

Conformation of dithia[3.3]- and [2.2] azuleno(2,6)pyridinophanes

Four azuleno(2,6)pyridinophanes (1–4) were synthesized and their conformations were found by NMR spectroscopy to be very similar to those of the corresponding azulenometacyclophanes. A transverse conformational change was observed for [2.2](5,7)azuleno(2,6)pyridinophane.     

Thermal cis—trans isomerization of bis(diamine) cobalt(III) and chromium(III) complexes in a solid phase

Thermal cis—trans isomerization of the simple bis(diamine) complexes [MX₂(aa or bb)₂]X · HX · n H₂O and the mixed bis(diamine) complexes [MX₂(aa)(bb)]X · HX · n H₂O was investigated in a solid phase, where M = Co(III) or Cr(III) ion, X = Cl or Br, aa and bb are one of the diamines selected from ethylenediamine (en), d, l-1,2-propane-diamine (pn), d,l-2,3-butanediamine (dl-bn), d,l-1,2-cyclohexanediamine (chxn), 1,3-propanediamine (ln) and d,l-2,4-pentanediamine (ptn), and n = 0–2. The information obtained may be summarized as follows. (1) The features of isomerization are considerably dependent upon the kind of metal ions, halide ions and diamines contained in the complexes. (2) Trans-cis isomerization was identified in the simple bis(diamine) complexes containing en, pn, dl-bn or chxn which can form five-membered chelate rings with metal ions, whereas cis-trans isomerization was detected in the simple bis(diamine) complexes containing tn or ptn which forms six-membered rings; all the mixed bis(diamine) complexes isomerize from trans to cis even when they have a combination of five- and six-membered chelate rings. (3) The cobalt(III) complexes isomerize in a temperature range of dehydration and/or dehydrohalogenation with activation energies of about 100 kJ mole⁻¹, whereas the chromium(III) complexes usually isomerize in the anhydrous state and the activation energies amount to as much as 150–190 kJ mole⁻¹. (4) “Aquation-anation” and “bond rupture” were proposed for the isomerization of the cobalt(III) and the chromium(III) complexes, respectively.     

Determination of L-3,4-dihydroxyphenylalanine in blood by high-performance liquid chromatography after solvent extraction

The use of high-performance liquid chromatography combined with solvent extraction for sample purification is described for the determination of L-3,4-dihydroxyphenylalanine in blood plasma. It is extracted into n-hexanol via complexation of its catechol moiety with diphenyl borate and ion-pair formation of its carboxylic group with tetrapentylammonium ion in an alkaline buffer. Under optimal extraction conditions, L-3,4-dihydroxyphenylalanine and 3,4-dihydroxybenzylamine used as an internal standard are extracted from blood plasma by a simple procedure and in a short time and then separated by reversed-phase ion-pair chromatography. The analytical recovery (100.8%) and reproducibility (coefficient of variation = 2.3% for n = 6) from plasma samples are good enough for routine analysis. L-3,4-Dihydroxyphenylalanine levels in blood can be monitored by this method after oral intake of the substance.     

Fast matrix digestion with hot ethanolic alkali plus pyrogallol for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and coplanar polychlorinated biphenyls analysis in biological samples

The efficiency of hot alkaline digestion of a sample matrix was investigated for determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (CoPCBs) in biological samples. Results of recovery tests of octachlorodibenzofuran (OCDF) after spiking into lean tuna showed degradation of OCDF and the production of a large quantity of lower-chlorinated dibenzofurans (LoCDFs) when the sample was digested with hot ethanolic KOH. However, it was also confirmed that pyrogallol (PG) prevented dechlorination of OCDF. The accuracy of the hot alkaline digestion method with PG was demonstrated by analyzing PCDD/Fs-spiked lean tuna. The proposed method is more suitable than conventional versions for the determination of dioxins in biological samples in terms of savings in time, adequate digestion of matrix and high degree of recovery of internal standards.     

Preparation, characterization, and cycloaddition reaction of the heterocumulenes attached directly to azulenes. An efficient strategy for the preparation of azulene-substituted heterocycles

Preparation and cycloaddition reaction of novel azulene-substituted N-sulfinylamines 1 and 2 are reported. The influence of the -NSO group on the UV-vis and NMR spectra of the azulene ring to which it is bonded is discussed. X-ray crystal analysis of 1 revealed the syn-configuration and the twisted structure of the N-sulfinylamine moiety. The synthetic utility of 1 and 2 have been explored by the cycloaddition reaction to afford novel azulene-substituted heterocycles under high-pressure conditions. We also described herein the synthesis and some properties of related 2-azulenylisothiocyanate.     

Efficient preparation of 2-azulenylboronate and Miyaura-Suzuki cross-coupling reaction with aryl bromides for easy access to poly(2-azulenyl)benzenes

This paper describes an efficient preparation of 2-azulenylboronate (6) starting from 2-iodoazulene by halogen-metal exchange reaction using n-BuLi and subsequent quenching with 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane. The boronate 6 has been found to undergo Pd-catalyzed Miyaura-Suzuki cross-coupling reaction with a range of aryl bromides including aromatic poly bromides utilizing Pd₂(dba)₃-P(t-Bu)₃ as a catalyst and establishes a strategy to produce novel poly(2-azulenyl)benzenes, some of which are found to be insoluble in common organic solvents, however. The redox behavior of 2-arylazulenes and poly(2-azulenyl)benzenes was examined by cyclic voltammetry (CV) and compared with those of 6-azulenylbenzene derivatives reported previously.