Production of dihomo-γ-linolenic acid byMortierella alpina 1S-4

The mycelial dihomo-γ-linolenic acid content of an arachidonic acid-producing fungus,Mortierella alpina 1S-4, was found to increase, with an accompanying marked decrease in its arachidonic acid content, on cultivation with sesame oil. The resultant mycelia were found to be a rich source of dihomo-γ-linolenic acid. This unique phenomenon was suggested to be due to specific repression of the conversion of dihomo-γ-linolenic acid to arachidonic acid by the oil. After fractionation of the oil with acetone into oil and non-oil fractions, it was found that the effective factor(s) was present in the non-oil fraction. In a study on optimization of the culture conditions for the production of dihomo-γ-linolenic acid byM. alpina 1S-4, a medium containing glucose, yeast extract and the non-oil fraction was found to be suitable for the production. Under the optimal conditions in a 50-1 fermentor, the fungus produced 107 mg of dihomo-γ-linolenic acid/g dry mycelia (2.17 g/l of culture broth). This value accounted for 23.1% of the total fatty acids in the lipids extracted from the mycelia. The mycelia were also rich in arachidonic acid (53.5 mg/g dry mycelia, 11.2%). Other major fatty acids in the lipids were palmitic acid (24.1%), stearic acid (7.0), oleic acid (20.1), linoleic acid (6.6) and γ-linolenic acid (4.1). On leave from Suntory Ltd.     

Copolymerizations of macromonomer prepared by addition-fragmentation chain transfer polymerization of methyl acrylate trimer

Summary An oligomer of the methyl acrylate unsaturated trimer bearing 2-carbomethoxy-2-propenyl ω-end group (M _n = 1300, M _w/M _n = 1.7, and functionality > 0.7) was copolymerized as a macromonomer (0.02 mol/L) with styrene (1.0 mol/L) in benzene at 60 °C. The amounts of monomer and macromonomer in the feed simultaneously decreased with increasing time to indicate copolymer formation, and the macromonomer was found to be as reactive as styrene toward poly(styrene) radicals. The M _ns of the copolymers were 13900–22000 depending on conversion. No resonance due to the unsaturated <ω-end group bound to the poly(styrene) chain was detected by ¹H-NMR spectroscopy, indicating that no fragmentation of adduct radical of the end group to expel the poly(methyl acrylate trimer) radical. Polymerization of ethyl methacrylate (1.0 mol/L) in the presence of the macromonomer (0.02 mol/L) resulted in a mixture of the unreacted macromonomer and homopolymer of ethyl methacrylate. No end group bound to the poly(ethyl methacrylate) was detected by ¹H-NMR spectroscopy, excluding the possibility of addition fragmentation chain transfer to the macromonomer to expel an oligomer radical of the methyl acrylate trimer. Addition of the poly(methacrylate) radical to the macromonomer is extremely slow under the present conditions of copolymerization. Received: 27 March 2003/Revised version: 30 April 2003/ Accepted: 30 April 2003 Correspondence to Bunichiro Yamada     

Temperature Dependence of KIC for High-Pressure Hot-Pressed Si3N4 Without Additives

Temperature dependence of K_IC values for Si₃N₄ bodies sintered at high pressures without additives was studied from room temperature to 1400°C. Little change in K_K was found in this range.     

Motion optimization using state-dispersion-based phase space partitions

This paper addresses a phase space partitioning problem in motion planning systems. A class of kinematic and dynamic motion planning systems, including rapid semioptimal motion-planning (RASMO), uses partitions for phase spaces in cumulative optimization criteria. In these systems, a partition results in a uniquely planned motion with a quality that is determined by a selected optimization criterion. In this paper, state-dispersion-based phase space partitioning (SDPP) that generates adaptive partitions is proposed. These partitions allow the motion planning systems to plan better motions. Uniform partitions and adaptively fixed partitions of SDPP are compared under several conditions using RASMO and a double inverted pendulum model while setting the optimality criterion of RASMO to time. The results reveal that RASMO with SDPP plans smaller time motions than those obtained with RASMO using uniform partitions.     

Redox properties of CeO2 and Pt-Rh/CeO2 studied by TAP method

Redox properties of CeO₂ and Pt-Rh/CeO₂ were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O₂. A portion of pulsed CO was oxidized to CO₂ and a portion of CO was adsorbed on the surface. Pulsing ¹⁸O₂ onto the catalyst which has surface species derived from CO, evolved CO₂ contained no ¹⁸O suggesting that the surface species will be carbonate ions.     

Lysozyme requires fluctuation of the active site for the manifestation of activity

Mutations around His15 which lie far away from the active site,stimulated glycol chitin activity of lysozyme at physiologicaltemperature. Del-Argl4Hisl5 lysozyme, a mutant lysozyme whoseArgl4 and Hisl5 were deleted together, and has the highest activityamong these mutant lysozymes, had a similar binding abilityto a trimer of N-acetyl-glucosamine, a substrate analogue, relativeto native lysozyme. This suggests that the increased activitywas due to an increased k_cat in the catalysis reaction. TheH-D exchange rate of the N-1 proton in the Trp63 which is locatedin the active site cleft, was enhanced in the Del-Argl4Hisl5lysozyme, while 2-D proton NMR analysis revealed no conformationalchange around Trp63. We conclude that some sort of fluctuationat the active site might be required for the manifestation ofactivity. This theory is supported by the finding that the Del-Argl4Hisl5lysozyme showed a shift in temperature dependency of activityto lower temperatures compared with that of native lysozyme.     

Influence of reaction temperature on direct esterifications in a continuous recycling process between terephthalic acid and ethylene glycol

Simulations were carried out with a continuous recycle esterification model for the terephthalic acid–ethylene glycol (TPA–EG) system proposed previously. The influence of reaction temperatures, recycle ratios, and residence times on the oligomer characteristics was examined and the following results were obtained: (1) The main reactions proceed more under higher reaction temperatures, but the side reactions on diethylene glycol (DEG) proceed further than do the main reactions. (2) The higher residence time ratio of the first reactor to the total results in the proceeding of esterifications, which becomes remarkable as the temperature becomes high. (3) As the recycle ratio becomes high, the esterfications proceed, but in the very high degree of esterification, the tendency is reversed. (4) The characteristics of oligomer are almost the same at the same degree of esterification, independent of the reaction conditions. © 1994 John Wiley & Sons, Inc.     

Resistance to sulfur poisoning of hot gas cleaning catalysts for the removal of tar from the pyrolysis of cedar wood

In the partial oxidation of tar derived from the pyrolysis of cedar wood, the effect of H₂S addition was investigated over non-catalyst, steam reforming Ni catalyst, and Rh/CeO₂/SiO₂ using a fluidized bed reactor. In the non-catalytic gasification, the product distribution was not influenced by the presence of H₂S. Steam reforming Ni catalyst was effective for the tar removal without H₂S addition, however, the addition of H₂S deactivated drastically. In contrast, Rh/CeO₂/SiO₂ exhibited higher and more stable activity than the Ni catalyst even under the presence of high concentration of H₂S (280 ppm). On the Ni catalyst, the adsorption of sulfur was observed by XPS and Ni species was oxidized during the partial oxidation of tar. In the case of Rh/CeO₂/SiO₂, the adsorption of sulfur was below the detection limit of XPS. This can be related to the self-cleaning of catalyst surface during the circulation in the fluidized bed reactor for the partial oxidation of tar derived from cedar pyrolysis.     

Low-temperature selective reduction of NO with propene over alkaline-exchanged mordenites

Partially protonated alkaline mordenites showed higher activity per acid amount below 573 K than acidic zeolites for the selective reduction of NO with C₃H₆ in the presence of O₂, which can be related to a high concentration of NO₃ ^- species in the zeolite channels. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microstructure and Thermal Shock Resistance of Molten Glass-Coated Carbon Materials Fabricated by Interfacial Control

Carbon substrates were coated completely with a molten silicate glass, where the wettability of carbon to glass was improved by infiltration and pyrolysis of perhydropolysilazane. Microstructures of the carbon–glass interface were dependent on P n ₂ during coating. Coating at lower P n ₂ induced the formation of cristobalite at the carbon–glass interface. When the coating was performed at higher P n ₂, the glass and carbon were strongly adhered, without the formation of cristobalite. Coating at higher P n ₂ improved the thermal shock resistance of the glass layer, because crack initiation was not induced by the phase transformation of cristobalite during the cooling process. In the case of coating at higher P n ₂, an oxynitride glass layer was formed at the glass subsurface by dissolution of N₂. A porous glass subsurface layer with uniform spherical micro-pores could be produced by soaking near the glass transition temperature in a steam environment. The porous layer with fine and homogeneous microstructure acts as a thermal shock absorbing layer, so that glass-coated carbon with a porous glass layer has excellent thermal shock resistance in addition to steam oxidation resistance.