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981.
Tadashi Ishigaki Masahiro Yoshimura Nobuhiro Matsushita Kazuyoshi Uematsu Kenji Toda Mineo Sato 《Journal of the European Ceramic Society》2010,30(2):165-169
To synthesize various complex oxide materials and their solid solutions, we applied a novel “melt-synthesis technique” rather than conventional solid-state reaction techniques. Rapid synthesis methods to develop those double oxides have been strongly anticipated. During melt synthesis, the mixture of oxides or their precursors is melted rapidly (1–60 s) in an arc-imaging furnace using strong light radiation. A spherical molten sample with multiple homogeneously mixed cations was solidified directly on a copper hearth with rapid cooling of ca. 102 °C/s.We studied the synthesis of A2BO4 type double oxides (AA′)2BO4 (A = Sr2+, Ca2+, A′ = La3+, Gd3+, Y3+, Eu3+, B = Al) using this method. Homogeneous samples with Eu3+ dopants were synthesized using liquid phase mixing in a few seconds, which is much faster than diffusions of ions in solid phase. Red fluorescence under the irradiation of ultraviolet light (254 and 365 nm) was observed. The excitation band shifted. 相似文献
982.
Electrocatalytic reduction of O2 with dual catalysts of cobalt 1, 2, 3, 4, 8, 9, 10, 11, 15, 16, 17, 18, 22, 23, 24, 25-hexadecafluoro-29 H, 31H-phthalocyanine (CoPcF16) and MnOOH was studied in alkaline media with cyclic and rotating ring-disk electrode (RRDE) voltammetry. Cyclic voltammetric results show that CoPcF16 possesses a good catalytic activity for redox-catalyzing an apparent two-electron reduction of O2 with superoxide (O2−) as an intermediate. The combined use of CoPcF16 with MnOOH which shows a bifunctional catalytic activity toward the sequential disproportionations of the reduction intermediate and product, i.e. O2− and peroxide (HO2−), eventually enables an apparent four-electron reduction of O2 to be achieved at a positively-shifted potential in alkaline media. The possibility of utilizing the dual catalysts for the development of practical alkaline air electrodes was further explored by confining the catalysts in active carbon (AC) and carbon black (CB) matrices that are generally used as the substrate for constructing air electrodes. The RRDE voltammetric results suggest that an apparent four-electron reduction of O2 reduction can be obtained at the as-prepared carbon-based air electrode at a potential close to that at the Pt-based air electrode, and that the as-prepared electrode shows a high tolerance against methanol and glucose crossover. 相似文献
983.
Five‐Membered Cyclitol Phosphate Formation by a myo‐Inositol Phosphate Synthase Orthologue in the Biosynthesis of the Carbocyclic Nucleoside Antibiotic Aristeromycin 下载免费PDF全文
Prof. Dr. Fumitaka Kudo Takeshi Tsunoda Makoto Takashima Prof. Dr. Tadashi Eguchi 《Chembiochem : a European journal of chemical biology》2016,17(22):2143-2148
Aristeromycin is a unique carbocyclic nucleoside antibiotic produced by Streptomyces citricolor. In order to elucidate its intriguing carbocyclic formation, we used a genome‐mining approach to identify the responsible enzyme. In silico screening with known cyclitol synthases involved in primary metabolism, such as myo‐inositol‐1‐phosphate synthase (MIPS) and dehydroqunate synthase (DHQS), identified a unique MIPS orthologue (Ari2) encoded in the genome of S. citricolor. Heterologous expression of the gene cluster containing ari2 with a cosmid vector in Streptomyces albus resulted in the production of aristeromycin, thus indicating that the cloned DNA region (37.5 kb) with 33 open reading frames contains its biosynthetic gene cluster. We verified that Ari2 catalyzes the formation of a novel five‐membered cyclitol phosphate from d ‐fructose 6‐phosphate (F6P) with NAD+ as a cofactor. This provides insight into cyclitol phosphate synthase as a member of the MIPS family of enzymes. A biosynthetic pathway to aristeromycin is proposed based on bioinformatics analysis of the gene cluster. 相似文献
984.
Toshihiro?NagaoEmail author Tadashi?Fukami Yoshiharu?Horita Sadao?Komemushi Akio?Sugihara Yuji?Shimada 《Journal of the American Oil Chemists' Society》2003,80(10):975-981
An industrially available preparation of astaxanthin (Ax) from Haematococcus pluvialis contained 41.6 wt% acylglycerols and 24.9 wt% FFA in addition to 14.6 wt% Ax, which was a mixture of free and FA ester forms
(free Ax/Ax monoesters/Ax diesters=4.9∶80.3∶14.8, by mol). Enrichment of Ax by a two-step process was attempted. The first
step was hydrolysis of acylglycerols with Candida rugosa lipase: A mixture of 1.0 kg H. pluvialis cell extracts, 1.0 L water, and 50 U/g-reaction mixture of the lipase was agitated at 30°C for 42 h. The degree of hydrolysis
of acylglycerols reached 94.4%, but Ax esters were not hydrolyzed. Removal of FFA from the resulting oil layer by molecular
distillation enriched the content of Ax esters to 40.8 wt5 (named Ax40). The second step was enzymatic conversion of Ax esters
to free Ax, which successfully proceeded in the presence of ethanol (EtOH). When a mixture of 50.0 g Ax40, 8.2 g EtOH (5 molar
equiv. against FA), 58.2 mL water, and 1500 U/g-mixture of Pseudomonas aeruginosa lipase was stirred at 30°C for 68 h, the free Ax content increased to 89.3 mol%. Free Ax was efficiently recovered by precipitation
with n-hexane. The purity of Ax was thereby raised to 70.2 wt% with a 63.9% overall recovery of the initial content in the cell
extracts. 相似文献
985.
Several recent studies have demonstrated that dietary DAG oil rich in 1,3-species suppresses the postprandial increase of
serum TAG level and decreases body fat accumulation, compared with TAG oil. To clarify the mechanisms underlying the beneficial
effects of DAG, we investigated the metabolic features of DAG in the small intestine with regard to the digestion pathway
in the lumen and the TAG-synthesis pathway in the mucosa. When intraduodenally infused as an emulsion, TAG was digested to
1,2-DAG, 2-MAG, and FFA, whereas 1,3-DAG was digested to 1(3)-MAG and FFA. When assessed by the incorporation of [1-14C]linoleic acid in lipids, the mucosal TAG-synthesis was significantly reduced by DAG infusion compared with TAG infusion.
However, the mucosal 1,3-DAG synthesis was remarkably increased in the DAG-infused rats. The total amount of mucosal 1,3-DAG
was also increased (4.5-fold) after DAG infusion compared with that after TAG infusion. Next, we examined the synthesis pathway
of 1,3-DAG. In cultures of the everted intestinal sacs, 1,3-DAG production required the presence of 1-MAG, suggesting that
the 1,3-DAG synthesis was due to acylation of 1(3)-MAG in the DAG-infused rats. Furthermore, measurements of DAG acyltransferase
activity indicated that 1,3-DAG was little utilized in TAG synthesis. These findings suggest that features of 1,3-DAG digestion
and assimilation in the intestine may be responsible for the reduction of the postprandial serum TAG level by dietary DAG. 相似文献
986.
Hiroaki Takadama Hyun-Min Kim Tadashi Kokubo Takashi Nakamura 《Journal of the American Ceramic Society》2002,85(8):1933-1936
The process of apatite formation on the surface of Na2 O–SiO2 glass in a body environment was investigated, mainly by X-ray photoelectron spectroscopy, as a function of soaking time in a simulated body fluid (SBF). The glass was found to release Na+ ions via exchange with H3 O+ ions in the SBF to form Si—OH groups on its surface. These Si—OH groups induced apatite formation indirectly, by forming calcium silicate and amorphous calcium phosphate. The formation of the calcium silicate and amorphous calcium phosphate is attributed to electrostatic interactions between the Si—OH groups on the glass surface and the calcium and phosphate ions in the SBF. 相似文献
987.
988.
Rajiv Asthana Mrityunjay Singh Hua‐Tay Lin Tadashi Matsunaga Toshihiro Ishikawa 《International Journal of Applied Ceramic Technology》2013,10(5):801-813
SiC fiber‐bonded ceramics, SA‐Tyrannohex®, (SA‐THX) with perpendicular and parallel fiber orientations were brazed using Ag‐, Ni‐ and Pd‐base brazes, and four Si–X (X: Ti, Cr, Y, Ta) eutectics. Outcomes were variable, ranging from bonded joints through partially bonded to un‐bonded joints. Prominent Ti‐ and Si‐rich interfaces developed with Cusil‐ABA, Ticusil, and Copper‐ABA and Ni‐ and Si‐rich layers with MBF‐20. Stress rupture tests at 650 and 750°C on Cusil‐ABA‐bonded joints revealed a temperature‐dependent behavior for the perpendicular joints but not for the parallel joints with failure occurring at brazed interface. Higher‐use temperatures can be targeted with eutectic Si–Ti and Si–Cr alloys. 相似文献
989.
Hiroaki Sobagaki Tadashi Yano Kenjiro Hashimoto Yoshinobu Nayatani 《Color research and application》1999,24(6):439-456
The structure of the color-appearance model CIECAM97s is examined. The problems with its chromatic-adaptation transform, called the Bradford transform, are discussed in detail. The contradictions existing between the measures at various stages of CIECAM97s are described, which are ea-eb, saturation s, chroma C, and colorfulness M. The main contradictions are (1) the inversion of chromatic components between test and reference colors at different measures; and (2) the similarity between chroma and colorfulness found in the experiments done under different adapting illuminances. The structural problems in CIECAM97s are clarified by comparing its predictions with those using CIECAT94LAB, which consists of the CIE chromatic-adaptation transform published in 1994 and the CIELAB formula. © 1999 John Wiley & Sons, Inc. Col Res Appl, 24, 439–456, 1999 相似文献
990.