Two Triterpene Synthases from Imperata cylindrica Catalyzing the Formation of a Pair of Diastereoisomers through Boat or Chair Cyclization

Imperata cylindrica is known to produce a pair of triterpenes, isoarborinol and fernenol, that exhibit identical planar structures but possess opposite stereochemistry at six of the nine chiral centers. These differences arise from a boat or a chair cyclization of the B-ring of the substrate. Herein, we report the characterization of three OSC genes from I. cylindrica. IcOSC1 and IcOSC5 were identified as isoarborinol and fernenol synthases, respectively, while IcOSC3 was characterized as a multifunctional enzyme that produces glutinol and friedelin as its major products. Mutational studies of isoarborinol and fernenol synthases revealed that the residues surrounding the DCTAE motif partially affected the conformation of the B-ring during cyclization. Additionally, the IcOSC1-W255H mutant produced the rare triterpene boehmerol. The introduced histidine residue presumably abstracted a proton from the intermediary carbocation at C18 during the 1,2-rearrangement. Expression analysis indicated that all OSC genes were highly expressed in stems.     

Characterization of the Thermo-Viscoelastic Property of Glass and Numerical Simulation of the Press Molding of Glass Lens

A measurement technique for obtaining the thermo-viscoelastic properties of glass with high accuracy is discussed. An unidirectional compression creep test was employed to measure the relaxation modulus of the glass specimens. The creep function derived from the experimental creep test is approximated by a generalized Voigt model, and then converted into a relaxation modulus expressed by a generalized Maxwell model using the Laplace transform and its inversion. Relaxation moduli and shift factors of the glass specimens BK-7 and TaF-3 were estimated according to the presented procedure, and the accuracy of the relaxation modulus was verified by a numerical demonstration using finite element analysis. A fundamental numerical simulation of the press molding of glass lenses was carried out to illustrate the validity of the thermo-viscoelastic properties obtained by the presented approach. Residual stresses under processing conditions were estimated, and the optimal conditions for residual stress minimization are discussed.     

Study on the Effects of Flow in the Volute Casing on the Performance of a Sirocco Fan

The flow at the exit from the runner blade of a centrifugal fan with forward curved blades (a sirocco fan) sometimes separates and becomes unstable. We have conducted many researches on the impeller shape of a sirocco fan, proper inlet and exit blade angles were considered to obtain optimum performance. In this paper, the casing shape were decided by changing the circumferential angle, magnifying angle and the width, 21 sorts of casings were used. Performance tests, inner flow velocity and pressure distributions were measured as well. Computational fluid dynamic calculations were also made and compared with the experimental results. Finally, the most suitable casing shape for best performance is considered.     

l-Ascorbic acid as an alternative fuel for direct oxidation fuel cells

l-Ascorbic acid (AA) was directly supplied to polymer electrolyte fuel cells (PEFCs) as an alternative fuel. Only dehydroascorbic acid (DHAA) was detected as a product released by the electrochemical oxidation of AA via a two-electron transfer process regardless of the anode catalyst used. The ionomer in the anode may inhibit the mass transfer of AA to the reaction sites by electrostatic repulsion. In addition, polymer resins without an ionic group such as poly(vinylidene fluoride) and poly(vinyl butyral) were also useful for reducing the contact resistance between Nafion membrane and carbon black used as an anode, although an ionomer like Nafion is needed for typical PEFCs. A reaction mechanism at the two-phase boundaries between AA and carbon black was proposed for the anode structure of DAAFCs, since lack of the proton conductivity was compensated by AA. There was too little crossover of AA through a Nafion membrane to cause a serious technical problem. The best performance (maximum power density of 16 mW cm⁻²) was attained with a Vulcan XC72 anode that included 5 wt.% Nafion at room temperature, which was about one-third of that for a DMFC with a PtRu anode.     

Albumin stabilizes (–)‐epigallocatechin gallate in human serum: Binding capacity and antioxidant property

(–)‐Epigallocatechin gallate (EGCg) is the major component of green tea and is known to show strong biological activity, although it can be easily oxidized under physiological conditions. In this study, we indicate that EGCg is stable in human serum and that human serum albumin (HSA) stabilizes EGCg under aerobic condition. Although EGCg is usually decomposed within 1 h in aqueous solution at neutral pH, EGCg in serum and phosphate buffer (pH 7.4) containing HSA was stable over 1 h, even at neutral and slightly alkaline pH. Under these conditions, EGCg binds to HSA non‐covalently. The sulfhydryl group acts as an antioxidant for EGCg oxidation. Incubation of EGCg with HSA is accompanied by the oxidation of a free sulfhydryl group in HSA. These results suggest that the antioxidant property and the binding capacity of HSA contribute to the stabilization of EGCg in human serum.     

Reactivity of poly(vinyl chloride) containing N-methyl dithiocarbamate toward metal ions in heterogeneous system and effect of γ-irradiation on the reactivity

The reaction of poly(vinyl chloride) containing N-methyl dithiocarbamate (PMD) with metal ions in a heterogeneous system and the effect of γ-irradiation on the reactivity were studied. PMD powder suspended in aqueous solutions did not show any reactivity toward metal ions. However, the PMD powder suspended in a methyl alcohol solution formed a chelate with various metal ions. The effects of the reaction time, pH, and the initial concentration of the metal ion were examined. PMD irradiated in methyl alcohol with γ-irradiation doses up to 28 Mrad was compared with the original PMD. The reactivity of the irradiated PMD toward the metal ions did not show any apparent decrease.     

A New Equation for Predicting the Dielectric Constant of a Mixture

The dielectric constant of a compound consisting of two different materials was simulated using the Monte Carlo and finite element methods. In the high concentration range of the higher dielectric constant material, the simulated value of the dielectric constant showed a "parallel-model"-like tendency. On the other hand, in the low concentration range of the higher dielectric constant material, the compound showed a "serial-model"-like behavior. Around 65% content of the higher dielectric constant material, it exhibited results similar to the logarithmic mixing rule. After careful consideration of these results, a new equation to predict the dielectric constant of the compound was derived. The agreement between the dielectric constant calculated by the new equation and the measured values was better than in any other case reported before.     

STORY GENERATION BASED ON DYNAMICS OF THE MIND

A story generation system based on dynamics of the mind is presented. Semantic theories until now avoided discussing a linkage of language with encyclopedic human knowledge. This paper attacks the problem of how to make clear the complicated, wide-ranging dynamics of the mind and how to connect it to language.
First, the background of this study is shown, in which our model of the mind, with both five levels along the concept formation process and eight domains according to the contents of mental activities, is surveyed.
Based on this model, then, the dynamics of mind are discussed, along an Aesop fable. A unit of data processing in the mind is called a "module," and the mental dynamics are considered as a chain activation of those modules, represented by a dynamic network. Next, a method for story generation is discussed. Propositional information of a sentence is embedded in a slot of activated, frame-structured modules, and the discourse structure of a generated story basically depends on the dynamic network. Both the chain activation and the generation processes are verified by experiments.
Lastly, residual problems of our research, a comparison with related research, and its applications are discussed.
This case study would be expected to give a basis to integrated systems for problem solving, natural language and image understandings, their generations, and intelligent robots.