Direct production of ultra-fine nitrides (Si3N4 and AIN) and carbides (SiC,WC and TiC) powders by the arc plasma method

A direct method of producing ultra-fine nitride and carbide powders of 20 to 40 nm by arc plasma in a controlled atmosphere (with ammonia or methane gas) is described. The powders produced were SiC, TiC, WC (+W₂C), AIN and Si₃N₄. Other nitrides and carbides may also be produced using this method. Special attention was paid to the production conditions of silicon nitride.     

Distributed memory implementation of KLIC

This paper describes external reference management and distributed unification in a distributed implementation of a concurrent logic programming language KL1. This implementation is based on the KLIC system. KLIC has a feature calledgeneric objects that enable easy modification and extension of the system without changes in the core implementation. This distributed implementation is built upon the same core and external references are represented using generic objects. Unification operations are defined as methods of generic objects. Since creation of interprocessor reference loops cannot be avoided, we studied a new unification scheme that can cope with interprocessor reference loops. We built several experimental distributed systems that all demonstrate reasonable efficiency.     

Degradation of polymers by high-speed stirring

Benzene solutions containing either poly(ethylene oxide) or poly(methyl methacrylate) or both of varying concentrations were prepared, stirred at a speed of 30,000 rpm, and the effects of concentrations of the same species or different species of polymers on the degradation of the polymers were investigated. Within experimental error little difference was observed in the [η] curves measured for each degraded polymer in spite of change in concentration. It is clear that the degradation of polymer with high-speed stirring in the concentration range 1–4% w/v is not caused by the interaction of polymer chains.     

Removal of lignin in a liquid system by an isolated fungus

The screening of a strain which could perform lignin removal was carried out. Based on taxonomic study the isolated strain (LM‐2) was identified as Penicillium sp. LM‐2 could decolorize 0.6 g dm^?3 lignin within 4 days in a shaking culture at 25 °C. The efficiency of decolorization of the lignin was over 80% in the pH range of 4.0–6.0, but was low above pH 6.2. The rise of temperature had a slight adverse effect on the lignin decolorization in the range of 25–35 °C. Lignolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase were not detected in the culture broth or within the fungal cells. The lignin was removed from the high molecular weight fraction mainly by adsorption and accumulation inside the cells. © 2001 Society of Chemical Industry     

Electric dichroism studies of the bonding of Co(III) chelate with synthetic polyelectrolytes

The interactions of bis-2-(2-pyridylazo)-1-naphthol Co(III), [Co(III) (αPAN)₂⁺], with five kinds of synthetic polyelectrolytes have been studied by spectrophotometric and transient electric dichroism measurements. The polyelectrolytes were: poly(styrene sulphonic acid) (PSS); poly(acrylic acid) (PAA); poly(l-glutamic acid) (PLG); $\text{poly}\text{(N}{}^{\mathrm{<mtext>e</mtext>}}\text{,N}{}^{\mathrm{<mtext>e</mtext>}}\text{-}\text{dicarboxylmethyl-}\text{l}\text{-lysine}$ (PDCML); and poly(l-lysine) (PLL). The equilibrium constant of the reaction:

with P = polyelectrolyte residue was determined spectrophotometrically: K₁ is > 10⁷ M^?1 (PSS); (1.4 ± 0.2) × 10⁴ M^?1 (PAA); (4.0 ± 0.4) × 10³ M^?1 (PLG); (1.4 ± 0.2) × 10⁶ M^?1 (PDCML); and < 10² M^?1 (PLL) at pH 6–8. From transient electric dichroism, the angle (ψ) between the αPAN plane and the polymer axis was determined to be 65° (PSS); 52° (PAA); 55° (PLG); and 52° (PDCML). The large K₁ and ψ values for PSS are ascribed to the hydrophobic interaction between the aromatic αPAN ring and the styrene sulphonate residues of PSS. Using stopped-flow electric dichroism measurements, rapid transfer of a bound Co(III) chelate from the PDCML to PSS chains was shown to occur.     

Iodine-initiated,solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. II. Properties of copolymer obtained by beaker-scale copolymerization

In order to elucidate the copolymerization mechanism, the properties of the copolymer obtained by the iodine-initiated copolymerization of the tetraoxane–1,3-dioxolane–methylal system have been studied using gas chromatography, microscopy, scanning electron microscopy, differential scanning calorimetry, and gel permeation chromatography. From the behavior of the thermal stability and gas chromatography of the reaction mixture, it was found that reactivity of 1,3-dioxolane with active center is larger than that of tetraoxane, i.e., more than 90% 1,3-dioxolane is consumed at an early stage of the polymerization. The results obtained by microscopy, DSC, and GPC of the copolymer suggested that the copolymerization proceeds from the surface to the center of the tetraoxane crystal as if it were a core model. It was also suggested that the heterogeniety in copolymer properties can be explained not only by heterogeneous dispersion of 1,3-dioxolane in tetraoxane crystal, but also by the difference of reactivity of 1,3-dioxolane with the active center.     

Iodine-initiated,solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. IV. Fractional dissolution of copolymer

A fractional dissolution on the oxymethylene copolymer obtained by the iodine-initiated, solid-state copolymerization of the tetraoxane–1,3-dioxolane-methylal system has been carried out using a mixed solvent which consists of tetrachloroethane, phenol, and cyclohexanol. On the fractional dissolution, the oxymethylene copolymer was divided mainly into two parts: one was the copolymer containing a larger amount of ethylene oxide unit in its main chain and having lower molecular weight; the other was copolymer containing a smaller amount of ethylene oxide unit and having a higher molecular weight. It was reasonably concluded that in this copolymerization system, the reaction proceeds from the surface to the center of the tetraoxane crystal to give a divided copolymer due to the heterogeneous properties such as copolymer composition and molecular weight.     

Production of docosahexaenoic acid by marine bacteria isolated from deep sea fish

Five bacterial strains isolated from the intestine of deep sea fish were shown to produce docosahexaenoic acid (22∶6n−3; DHA) at a level of 6.4 to 11.6% of total fatty acids when incubated in DHA-free medium. In all of the strains examined, other polyunsaturated fatty acids were barely detectable, except for eicosapentaenoic acid (20∶5n−3). A typical strain, such as T3615, produced DHA at a concentration of about 0.8 mg/L within six days of aerobic incubation at 5°C and under atmospheric pressure. The T3615 strain, belonging to the genusVibrio, is rod-shaped, Gram-negative, motile and facultatively anaerobic.     

Essence of generalized partial computation

Generalized partial computation (GPC) is a program optimization principle based on partial computation and theorem proving. Conventional partial computation methods (or partial evaluators) explicitly make use of only given parameter values to partially evaluate programs. However, GPC explicitly utilizes not only given values but also the following information: (1) logical structure of a program to be partially evaluated; (2) abstract data type of a programming language. The main purpose of this paper is to present comprehensible examples of GPC. Graphical notations, called GPC trees, are introduced to visibly describe GPC processes.