Takashi Arai

Initial Boronization of JT-60U Tokamak Using Decaborane

A decaborane-based boronization system has been installed in the JT-60U tokamak in order to reduce the influx of impurities during plasma discharges. Boronization has been performed under a glow discharge using a helium-decaborane gas mixture. The properties of the boron films deposited through boronization and the effects of boronization on the tokamak discharges were investigated. It was found that the deposition of a boron layer with high purity was achieved with few impurities other than hydrogen through boronization, and that the present boronization deposited toroidally nonuniform boron film. It was also found that the decaborane-based boronization resulted in good plasma performance similar to that of conventional boronization.

Correlation entropy and its relation to properties of liquid iron, cobalt and nickel

Abstract We present entropy calculations of liquid Fe, Co and Ni over an extended temperature range of approximately 200 K above the melting point. The theory we use is based on a systematic expansion of the entropy in terms of the partial N -particle distribution functions given first by Green for the canonical ensemble. First, we calculate the pair and triplet correlation entropies using measured diffraction data. To evaluate the triplet correlation entropy, we did not use the superposition approximation of Kirkwood in this work. Next, we calculate the self-diffusion coefficient based on Dzugutovs scaling law using the pair and triplet correlation entropies. Then we estimate the viscosity coefficient and the surface tension for these liquid metals using the Stokes–Einstein relation, the Born–Green equation and Fowlers formula for the surface tension. Predicted values of the self-diffusion coefficient, the viscosity coefficient and the surface tension are reasonable in comparison with available experimental data.

Growth of KNbO3 films by electron-cyclotron-resonance-assisted pulsed laser deposition

The (110) cut of KNbO3 piezoelectric crystal is suitable for generation of longitudinal waves, because of its high electromechanical coupling factor kt. Epitaxial (110) KNbO3 thin films have been grown on (100) MgO and (100) La-doped SrTiO3 substrates using an electron-cyclotron-resonance-assisted pulsed laser deposition (ECR-PLD) technique. In order to ascertain the effect of the ECR activation of oxygen, the X-ray diffraction pattern of a film grown by ECR-PLD is compared with that of a film grown in an oxygen atmosphere without ECR activation. As a consequence, the ECR-PLD technique is found to be notably effective for epitaxial growth of high-quality KNbO3 films. The in-plane orientation of the films is discussed and it is shown that the macroscopic in-plane structure of KNbO3 films should have a fourfold rotational symmetry. Some films grown on La-doped SrTiO3 have slightly longer (110) spacing than that of (110) orthorhombic KNbO3. This suggests that the films might be (001) tetragonal KNbO3.

Functional Fv fragment of an antibody specific for CD28: Fv-mediated co-stimulation of T cells.

The most predominant co‐stimulation pathway, which is critical for T cell activation and proliferation, is the CD28‐B7 pathway. The anti‐CD28 monoclonal antibody (mAb) also provides a co‐stimulatory signal to T cells. In order to construct a functional Fv fragment (complex of VH and VL domains) of anti‐CD28 antibody using a bacterial expression system, cDNA encoding the variable regions of immunoglobulin from 15E8 hybridoma cells was cloned and expressed in Escherichia coli. The Fv fragment was obtained as a soluble protein from the periplasmic fraction and showed a binding pattern similar to parental IgG. The Fv fragment induced proliferation of peripheral blood mononuclear cells in the presence of anti‐CD3 or anti‐CD2 mAb and enhanced anti‐tumor activity of anti‐MUC1×anti‐CD3 bispecific antibody when tested with lymphokine‐activated killer cells with T cell phenotype. Thus, the anti‐CD28 Fv fragment will be promising not only for the study of co‐stimulation, but also for cancer immunotherapy.

Pair and triplet correlation entropies based on the hard sphere solution of the Percus–Yevick equation

Abstract In this paper we have attempted to estimate the pair and triplet correlation entropies (S(2) and S(3)) of the hard sphere fluid using the Percus–Yevick approximation. The pair correlation entropies are computed from the pair correlation functions, while the triplet correlation entropies are estimated by the structure factors with the help of an analytical formula for evaluation of a change in the structure factor on application of the pressure. The calculated pair and triplet correlation entropies are consistent with those obtained by the computer simulations due to Baranyai and Evans over a wide range of thermodynamic states. The sum of the pair and triplet correlation entropies is discussed in comparison with the configurational entropy of hard spheres calculated thermodynamically from the Carnahan–Starling equation of state.

Correlation entropies of the hard sphere fluid based on the generalized mean spherical approximation due to Waisman

Abstract We have calculated the pair and triplet correlation entropies (S(2) and S(3)) of the hard sphere fluid based on the generalized mean spherical approximation (GMSA) due to Waisman. It turns out that there is no difference between the GMSA and the Percus–Yevick (PY) approximation in the entropy calculations. In the two methods S(2)s are computed from the pair correlation functions, while S(3)s are estimated by the structure factors. We did not use the Kirkwood superposition approximation for evaluation of S(3). Our results are consistent with Monte Carlo simulations over a range of thermodynamic states.

Structural modelling of liquid NaxCs1−x alloys using the reverse Monte Carlo method

The structures of liquid NaxCs1−x alloys have been modelled using the reverse Monte Carlo method on the basis of x-ray and neutron diffraction data. The partial structure factors and partial radial distribution functions obtained were consistent with previous work. The average coordination numbers and coordination number distributions for the four distinct kinds of atom pairs have been calculated over a wide range of composition. Cs forms complex clusters near 85 at.% Na, near to the maximum of the density fluctuation in these alloys.

Effective Pair Potentials Describing The Measured Structure Factor Of Expanded Caesium Near The Critical Point

Abstract Some theoretical and computational works on expanded caesium near the critical point have been reported after Winter and Hensels neutron diffraction experiments. Here we present effective pair potentials almost reproducing the observed structure data (T = 1923 K, ρ = 0.59 g/cm3). In order to obtain such effective pair potentials we use four types of reference potentials: a hard-sphere potential, a hard-sphere Yukawa potential, a Lennard-Jones potential and a pair potential derived from the pseudopotential theory. The final effective pair potentials reconstructed in this work almost equally reproduce the observed structure factor of expanded caesium at 1923 K within the accuracy of the Percus–Yevick approximation. A molecular dynamics calculation is also presented in comparison with these results.

Relation between self-diffusion coefficients and pair correlation entropies for fluids of particles interacting through inverse power potentials

Abstract The purpose of the present work is to calculate the pair and triplet correlation entropies and the self-diffusion coefficients for fluids of particles interacting through inverse power potentials and to investigate whether there is a relation between the two. Rosenfeld has proposed a semi-empirical ‘universal’ relationship for dimensionless transport coefficients in dense fluids as a function of excess entropy. The idea of configurational entropy scaling, on the other hand, has also been proposed in recent article by Dzugutov [Nature 381 (1996) 137]. We calculate the configurational entropy and self-diffusion coefficient for model liquids using a molecular dynamics method with 4th, 6th, 9th, and 12th inverse power potentials to clarify these two scaling laws.

Pair and triplet correlation entropies of the hard sphere fluid

Abstract In this paper we have calculated the pair and triplet correlation entropies of the hard sphere fluid based on the Percus–Yevick approximation and the generalized mean spherical approximation. There is no difference between the two methods in the entropy calculations. Our results are in good agreement with Monte Carlo simulations over a range of thermodynamic states.