Spectrofluorometric determination of thallium(III) with pyrogallol red and 3,4,5,6-tetrachlorofluorescein

Summary A spectrofluorophotometric determination of thallium(III) is proposed. It is based on the enhancement of the fluorescence reaction of 3,4,5,6-tetrachlorofluorescein (TCF) with Pyrogallol Red (PR) by thallium(III) in the presence of Swanol (AM 301, lauryldimethyl aminoacetic acid betain) as an amphoteric surfactant. The method was found to be suitable for the determination of thallium(III) down to 4.0 g in 10.0 ml by measuring the difference in the relative fluorescence intensities of a TCF/PR/thallium(III) solution and a TCF/PR solution. The recovery test in artificial urine was satisfactory (96±2%).     

Reactions of 2-amino-, 2-alkylamino-, and 2-piperidino-1-azaazulenes with aryl and chlorosulfonyl isocyanates

Reaction of 2-amino-1-azaazulene with phenyl isocyanate gave 3-phenyl-2H-3,4-dihydro-1,3,4a-triazabenz[5,4-a]azulene-2,4-dione. Reactions of 2-alkylamino-1-azaazulenes with aryl isocyanates gave 2-(N-ethyl-N′-arylureido)-1-azaazulenes initially, which rearranged to N-aryl-2-alkylamino-1-azaazulene-3-carboxamides and successive reaction with another molar amount of aryl isocyanate furnished uracil-fuzed 1-azaazulenes. Reaction of 2-piperidino-1-azaazulene with aryl isocyanate gave N-aryl-2-piperidino-1-azaazulene-3-carboxamide. Reaction of 2-(substituted amino)-1-azaazulenes with chlorosulfonyl isocyanate gave 3-cyano- and 3-chloro-2-(substituted amino)-1-azaazulenes.     

Partially nanowire-structured TiO2 electrode for dye-sensitized solar cells

Partially nanowire-structured TiO₂ was prepared by a hydrothermal processing followed by calcination in air. The hydrogen titanate powder as-synthesized was calcined at 300 °C for 4 h to obtain the partially nanowire-structured TiO₂. A dye-sensitized solar cell (DSC) with a film thickness of 5.6 μm, fabricated using the partially nanowire-structured TiO₂ showed better performance than using a fully nanowire-structured TiO₂ or a conventional equi-axed TiO₂ nanopowder. The short-circuit current density (J_SC), the open-circuit voltage (V_OC), the fill factor (FF) and the overall efficiency (η) are 11.9 mA/cm², 0.754 V, 0.673 and 6.01 %, respectively. The effects of one-dimensional nanostructure and electron expressway concept are discussed.     

Sintering behavior and apatite formation of diopside prepared by coprecipitation process

Sintering behavior and bioactivity of diopside, CaMgSi₂O₆, prepared by a coprecipitation process were examined for its biomedical applicability. As-prepared powder was synthesized by adding aqueous ammonia to an ethanol solution containing Ca(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O, and Si(OC₂H₅)₄ and characterized by means of TG–DTA, XRD, and TG–MS. The dried powder was X-ray amorphous and crystallized into diopside at 845.5 °C. The glass network formation by SiO₄ tetrahedra was almost completed below 800 °C. The bioactivity of the diopside prepared by sintering the compressed powder at 1100 °C for 2 h was evaluated by immersion of the sintered body in a simulated body fluid (SBF) at 36.5 °C. Leaf-like apatite particles were found to be formed on the surface of the sintered body and grew with passage of soaking time. This apatite-forming behavior in the SBF is related to the dissolution of Ca(II) ions from the sintered body in the early stage of immersion. Thus, diopside prepared by the coprecipitation process using the metal alkoxide and the metal salts was found to have an apatite-forming ability.     

Alternative spectrophotometric determination of niobium and tantalum with o-hydroxyhydroquinonephthalein in cationic surfactant micellar media

Summary The alternative and simultaneous spectrophotometric determination of niobium and tantalum was examined by using the colour development between o-hydroxyhydroquinonephthalein (Qnph) and niobium or tantalum in the presence of hexadecyltrimethylammonium chloride (HTAC) in strong acidic media. Beer's law was obeyed up to 10.0 g of niobium and up to 18.0 g of tantalum in a final volume of 10.0 ml. The apparent molar absorption coefficients for niobium and tantalum were 2.18×10⁵ and 2.09×10⁵ l mol^–1 cm^–1 with Sandell's sensitivities of 0.00042 g/cm² niobium at 520 nm and 0.00085 g/cm² tantalum at 510 nm, respectively. The alternative assay of niobium and tantalum was possible by using two methods: Method A — masking method with oxalic acid, Method B — acid adjusting-method using 50% sulfuric acid. These methods were 2–6-times more sensitive than other methods.Application of xanthene derivatives in analytical chemistry. Part XC. Part LXXXIX see ref [1]     

Isolation and stereostructures of neocitreoviridinol and epineocitreoviridinol

Both neocitreoviridinol and epineocitreoviridinol with a 2,5-dioxabicyclo[2.2.1]-heptane ring have been isolated as new metabolises of $\text{Penicillium citreo-viride}$ B., and their stereostructures have also been elucidated on the basis of their spectral data coupled with molecular mechanics calculations. In addition, a promising synthetic intermediate for neocitreoviridinol has been made.     

End‐functionalization of polystyrene by malto‐oligosaccharide generating aggregation‐tunable polymeric reverse micelle

This article describes that glucose, maltose, maltotriose, maltotetraose, maltopentaose, and maltohexaose ( a , b , c , d , e , and f , respectively) were introduced into the initiating chain‐end of polystyrene (PSt) through the 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐mediated radical polymerization. A series of glycoconjuaged TEMPO‐adducts, 1a–f , was synthesized and used as the initiators for the polymerization of styrene (St) for 6 h at 120 °C to afford the end‐functionalized PSt's with the acetyl saccharides, 2a–f , in the yields of 37–43%. For 2a–f obtained by the polymerizations using the [St]/[ 1 ] of 125, 250, and 500, the number‐average molecular weights determined by size exclusion chromatography (SEC), M_n,SEC's, were 4800–6300, 8800–10,600, and 18,400–25,200, respectively, which fairly agreed with the predicted values. The end‐functionalized PSt's with saccharides, 3a–f , which were obtained from the deacetylation of 2a–f using sodium methoxide in dry THF, formed the polymeric reverse micelles consisting of a saccharide‐core and a PSt‐shell in chloroform and toluene. The static laser light scattering (SLS) measurements provided the average molar mass of the aggregates in toluene, M_w,SLS's, which ranged from 7.50 × 10⁴ to 1.77 × 10⁵ for 3a , from 1.90 × 10⁵ to 4.93 × 10⁵ for 3b , from 4.41 × 10⁵ to 7.21 × 10⁵ for 3c , from 5.85 × 10⁵ to 8.51 × 10⁵ for 3d , from 7.55 × 10⁵ to 8.53 × 10⁵ for 3e , and from 8.54 × 10⁵ to 9.26 × 10⁵ for 3f . The aggregation numbers, N_agg's, which were calculated from the M_w,SLS's, were from 7 to 24 for 3a , from 20 to 37 for 3b , from 34 to 89 for 3c , from 39 to 116 for 3d , from 41 to 145 for 3e , and from 31 to 146 for 3f . It was confirmed that the aggregation property, such as the M_w,SLS or N_agg values, was strongly related to the polymerization degrees of St (DP's) or the number of the glucose residues (n's) for 3a–f . © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4864–4879, 2006     

A microscopic time scale approximation to the behavior of the local slope on the faceted surface under a nonuniformity in supersaturation

The morphological stability of a growing faceted crystal is discussed. We argue that the interplay between nonuniformity in supersaturation on a growing facet and anisotropy of surface kinetics derived from the lateral motion of steps leads to a faceted instability. Qualitatively speaking, as long as the nonuniformity in supersaturation on the facet is not too large, it can be compensated for by a variation of step density along the facet, and the faceted crystal can grow in a stable manner. The problem can be modeled as a Hamilton-Jacobi equation for height of the crystal surface. The notion of a maximal stable region of a growing facet is introduced for microscopic time scale approximation of the original Hamilton-Jacobi equation. It is shown that the maximal stable region keeps its shape, determined by profile of the surface supersaturation, with constant growth rate by studying large time behavior of solution of macroscopic time scale approximation. A quantitative criterion for the facet stability is given.     

In vivo NMR T2 relaxation of experimental brain tumors in the cat: a multiparameter tissue characterization.

Experimental gliomas (F98) were inoculated in cat brain for the systematic study of their in vivo T₂ relaxation time behavior. With a CPMG multi-echo imaging sequence, a train of 16 echoes was evaluated to obtain the transverse relaxation time and the magnetization M(0) at time T = 0. The magnetization decay curves were analyzed for biexponentiality. All tissues showed monoexponential T₂, only that of the ventricular fluid and part of the vital tumor tissue were biexponential. Based on these NMR relaxation parameters the tissues were characterized, their correct assignment being assured by comparison with histological slices. T₂ of normal grey and white matter was 74 ± 6 and 72 ± 6 msec, respectively. These two tissue types were distinguished through M(0) which for white matter was only 0.88 of the intensity of grey matter in full agreement with water content, determined from tissue specimens. At the time of maximal tumor growth and edema spread a tissue differentiation was possible in NMR relaxation parameter images. Separation of the three tissue groups of normal tissue, tumor and edema was based on T₂ with T_2(normal) < T_2(tumor) < T_2(edema). Using M(0) as a second parameter the differentiation was supported, in particular between white matter and tumor or edema. Animals were studied at 1–4 wk after tumor implantation to study tumor development. The magnetization M(0) of both tumor and peritumoral edema went through a maximum between the second and third week of tumor growth. T₂ of edema was maximal at the same time with 133 ± 4 msec, while the relaxation time of tumor continued to increase during the whole growth period, reaching values of 114 ± 12 msec at the fourth week. Thus, a complete characterization of pathological tissues with NMR relaxometry must include a detailed study of the developmental changes of these tissues to assure correct experimental conditions for the goal of optimal contrast between normal and pathological regions in the NMR images.