h i g h l i g h t sLaminar burning velocities of ammonia/air flames at high pressures are evaluated. Maximum value of laminar burning velocity of ammonia/air flame is about 7 cm/s. Laminar burning velocity decreases with the increase in the pressure. Markstein length increases with the increase in equivalence ratio. Markstein lengths at high pressure are lower than those at 0.1 MPa. a b s t r a c tAmmonia is expected to be useful not only as a hydrogen-energy carrier but also as a carbon-free fuel. In order to design an ammonia fueled combustor, fundamental flame characteristics of ammonia must be understood. However, knowledge of the characteristics of ammonia/air flames, especially at the high pressures, has been insufficient. In this study, the unstretched laminar burning velocity and the Markstein length of ammonia/air premixed flames at various pressures up to 0.5 MPa were experimentally clarified for the first time. Spherically propagating premixed flames, which propagate in a constant volume combustion chamber, were observed using high-speed schlieren photography. Results indicate that the maximum value of unstretched laminar burning velocities is less than 7 cm/s within the examined conditions and is lower than those of hydrocarbon flames. The unstretched laminar burning velocity decreases with the increase in the initial mixture pressure, tendency being the same as that of hydrocarbon flames. The burned gas Markstein length increases with the increase in the equivalence ratio, the tendency being the same as that of hydrogen/air flames and methane/air flames. The burned gas Markstein lengths at 0.1 MPa are higher than those at 0.3 MPa and 0.5 MPa. However, the values of burned gas Markstein length at 0.3 MPa and 0.5 MPa are almost the same. In addition, numerical simulations using CHEMKIN-PRO with five detailed reaction mechanisms which are presently applicable for the ammonia/air combustion were also conducted. However, qualitative predictions of unstretched laminar burning velocity using those reaction mechanisms are inaccurate. Thus, further improvements of reaction mechanisms are essential for application of ammonia/air premixed flames.

Ammonia is a carbon-free fuel and its application to internal combustion engines is expected. However, few studies on ammonia flames, especially at high pressures, have been carried out because ammonia has not been considered to be a fuel owing to its lower combustion intensity. Most of NOx, which is formed by ammonia combustion, is considered to be the fuel NOx. The objectives of this study were to investigate the fundamental characteristics of NOx experimentally, such as NO emission and chemiluminescence of ammonia/air flames not only at the atmospheric pressure but also under high pressures and to explore NO formation/reduction mechanisms using numerical simulation. Experiments were carried out using a nozzle-type burner. NH2 ammonia  band spectra were observed, and it was clarified that the color of ammonia flame is mainly determined by the NH2 ammonia  band and H2O spectra. Burned gas was sampled from ammonia flame stabilized at the burner. The mole fraction of NO decreased with the increase in equivalence ratio at atmospheric pressure. Reaction flow analysis was performed, and it was clarified that the decrease in the mole fraction of NO for rich mixtures was caused by NHi (i = 2, 1, 0). High pressure experiments were performed using a high pressure combustion test facility for stoichiometric ammonia flame. Consequently, the decrease in the mole fraction of NO was experimentally observed and its tendency was found to qualitatively agree with the results of the numerical simulation. It was clarified that the third body reaction of OH + H + M  H2O + M plays an important role in the reduction of the mole fraction of NO at high pressure.

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The lattice and radiation conductivities have been determined for commercial mould fluxes in glassy and partially crystalline states as functions of the degree of crystallinity to confirm whether or not more crystallisation of mould fluxes is always effective in slow cooling in continuous casting. Lattice conductivities, refractive indices and absorption/extinction coefficients were measured on glassy and partially crystallised samples from commercial mould fluxes. The lattice conductivities of mould fluxes increased with increasing the degree of crystallinity at temperatures around 773 K and more prominent increase was observed where the degree of crystallinity exceeded about 20 %, which would be due to the contact between crystal grains precipitated. However, fluxes having higher degrees of crystallinity showed negative temperature coefficients in the lattice conductivities, particularly at higher temperatures, and thus there was a case where the lattice conductivities decreased with increasing the degree of crystallinity at higher temperatures. On the other hand, the radiation conductivities tended to decrease with increasing the degree of crystallinity and became almost constant where the degree of crystallinity exceeded about 15 %. As a consequence of this, more crystallisation does not always lead to slow cooling in continuous casting: the degree of crystallinity should be controlled to be about 15 % where the partially crystalline phase exists around 773 K.KEY WORDS: lattice conductivity; radiation conductivity; mould flux; crystallisation; hot wire method. air gap i.e., a thermal resistance, at the mould/flux interface 2) due to the fact that the density of the crystalline phase is greater than that of the glass.Thus, the degree of crystallinity of the flux film is a key factor in the control of horizontal heat flux. Consequently, when casting slabs of MC steel, it is customary to use a mould flux which gives a film with a high degree of crystallinity to reduce the horizontal heat transfer. However, when casting round billets, it is important to minimise the shrinkage of the flux film to support the billet and in this case it is necessary to use a flux giving a glassy film.3) The heat transfer is reduced by introducing transition metal oxides, which increases the absorption coefficient a and thus decreases l R . Paradoxically, l L increases as the degree of crystallinity increases because of the increased packing density and regularity in crystal structure but the enhancement of the total heat transfer across the mould flux by these effects would be much smaller than the decrease in the heat transfer due to (i) pore and air gap formations and (ii) the reduction of l R . The present work primarily focuses on qualitative investigation about the effect of crystallisation on lattice and radiation conductivities for mould fluxes. From such a viewpoint, several attempts have been made to measure values of l L of silicates in liquid and solid states, [4][5][6][7][8][9][10] suggesting that more crystallised samp...

Tapes japonica lysozyme (TJL) is classified as a member of the recently established i-type lysozyme family. In this study, we solved the crystal structure of TJL complexed with a trimer of N-acetylglucosamine to 1.6 Å resolution. Based on structure and mutation analyses, we demonstrated that Glu-18 and Asp-30 are the catalytic residues of TJL. Furthermore, the present findings suggest that the catalytic mechanism of TJL is a retaining mechanism that proceeds through a covalent sugar-enzyme intermediate. On the other hand, the quaternary structure in the crystal revealed a dimer formed by the electrostatic interactions of catalytic residues (Glu-18 and Asp-30) in one molecule with the positive residues at the C terminus in helix 6 of the other molecule. Gel chromatography analysis revealed that the TJL dimer remained intact under low salt conditions but that it dissociated to TJL monomers under high salt conditions. With increasing salt concentrations, the chitinase activity of TJL dramatically increased. Therefore, this study provides novel evidence that the lysozyme activity of TJL is modulated by its quaternary structure.A known bacteriolytic enzyme, lysozyme (EC 3.2.1.17), is widely distributed throughout the animal and plant kingdom. Several types of lysozyme have been described to date as follows: chicken, goose, bacteria, plant, and phage. Recently, there has been increasing interest in a new type of lysozyme, i.e. invertebrate-type (i-type) 4 lysozyme. The existence of this new type of lysozyme was proposed as early as 1975 (1). A lysozyme composed of 123 amino acids (13.8 kDa) was recently isolated from the marine bivalve Tapes japonica and was shown to be an i-type lysozyme (2). This was the first lysozyme to be identified as an i-type lysozyme based on determination of the complete amino acid sequence at the protein level. Furthermore, several lysozymes have been identified, including those from the following organisms: two coastal bivalves belonging to the genus Mytilus (3), four deep-sea bivalves belonging to the genera Bathymodiolus and Calyptogena (3), a bivalve belonging to Chamys islandica (4, 5), and a starfish belonging to Asterias rubens (6). In 2002, alignment and phylogenic analyses using six bivalve lysozymes suggested that i-type lysozymes form a monophyletic family (7). The tertiary structures of representative lysozymes from chickens (8), geese (9), bacteria (10), plants (11), and phages (12) have already been determined but that of the i-type lysozymes has not. Because the primary sequences of i-type lysozymes are not homologous to those of any other types of lysozyme, the tertiary structure cannot be constructed. Interestingly, the lytic activity of bivalve lysozymes has been shown to be very sensitive to the ionic strength of a solution. With increasing salt concentrations, oyster and blue mussel lysozyme activity against Micrococcus lysodeikticus was activated and increased until exposure to a 0.1 M salt solution had been reached; at higher salt concentrations, lysozymatic activity t...

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