Search Results - (Author, Cooperation:K. Itoh)

2018-01-27

American Physical Society (APS)

0031-9007

1079-7114

Physics

Plasma and Beam Physics

2011-01-06

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Anti-Bacterial Agents/pharmacology ; Cecum/microbiology ; Cells, Cultured ; Clostridium/growth & development/*immunology ; Colitis/immunology/pathology/prevention & control ; Colon/*immunology/metabolism/*microbiology ; Feces/microbiology ; Forkhead Transcription Factors/metabolism ; Germ-Free Life ; Immunity, Innate ; Immunoglobulin E/biosynthesis ; Interleukin-10/immunology/metabolism ; Intestinal Mucosa/*immunology/metabolism ; Intestine, Small/immunology ; Metagenome ; Mice ; Mice, Inbred A ; Mice, Inbred BALB C ; Receptors, Pattern Recognition/physiology ; Specific Pathogen-Free Organisms ; T-Lymphocytes, Helper-Inducer/immunology ; T-Lymphocytes, Regulatory/*immunology/metabolism ; Transforming Growth Factor beta/metabolism

2011-01-29

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Acetates/*metabolism ; Animals ; Bifidobacterium/genetics/*metabolism ; Cercopithecus aethiops ; Escherichia coli Infections/microbiology/*prevention & control ; Escherichia coli O157/*physiology ; Gene Expression Profiling ; Genome, Bacterial ; Mice ; Molecular Sequence Data ; Vero Cells

2018-02-26

Wiley-Blackwell

0007-0963

1365-2133

Medicine

1089-7550

AIP Digital Archive

Physics

The growth process in the initial stage of growth of Ge films on (811)Si substrate surfaces by GeH4 source molecular-beam epitaxy has been studied by in situ reflection high-energy electron diffraction observation. It has been found that a strained film by the monolayer overgrowth mode is formed initially with an epitaxial relationship of the parallel orientation, and that plate-shaped Ge islands with (811) facets are grown early in the growth, but that the predominant facet changes to {311} and the (100) planes with further growth. These growth processes are similar to those of Ge films on (100)Si surfaces reported previously. It is concluded that Ge islands with {811} facets are energetically stable in the initial stage of the island growth on the (811)Si surfaces as well as on the (100)Si surfaces.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The ion heat pulse after a sawtooth crash is studied by a time-of-flight (TOF) neutral measurement. A rapid change of the bulk ion energy distribution near the edge is observed after a sawtooth crash. The delay time is measured, and the effective measuring position is estimated by a neutral transport code. Then a transient ion thermal conductivity, χiHP, of about (7–18) m2/s is evaluated for the low confinement mode (L-mode) plasma. The simple diffusive model with constant χiHP, however, does not explain the amplitude of the pulse in the ion energy distribution. © 1996 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

Plasma turbulence and anomalous transport by the electrostatic current diffusive interchange mode are studied by the nonlinear simulation based on the magnetohydrodynamic model. The turbulence is found to have a typical characteristic of subcritical turbulence. The saturation level, as a function of the pressure gradient ∇p, is confirmed to scale like ||∇p||3/2. This nature holds independent of the ratio ||∇p||/||∇pc|| where ||∇pc||, is a critical pressure gradient against linear instability. The turbulence-driven transport is also evaluated. The simulation result confirms the theoretical prediction, which is based on the self-sustained turbulence, with respect to the nonlinear growth and damping. Both the normal cascade and inverse cascade are essential in establishing the stationary turbulent state. © 1995 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The bifurcation nature of the electrostatic structure is studied in the toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411]. Observation of bifurcation-related phenomena is introduced, such as characteristic patterns of discrete potential profiles, and various patterns of self-sustained oscillations termed electric pulsation. Some patterns of the electrostatic structure are found to be quite important for fusion application owing to their association with transport barrier formation. It is confirmed, as is shown in several tokamak experiments, that the thermal transport barrier is linked with electrostatic structure through the radial electric field shear that can reduce the fluctuation resulting in anomalous transport. This article describes in detail spatio-temporal evolution during self-sustained oscillation, together with correlation between the radial electric field and other plasma parameters. An experimental survey to find dependence of the temporal and spatial patterns on plasma parameters is performed in order to understand systematically the bifurcation property of the toroidal helical plasma. The experimental results are compared with the neoclassical bifurcation property that is believed to explain the observed bifurcation property of the CHS plasmas. The present results show that the electrostatic property plays an essential role in the structural formation of toroidal helical plasmas, and demonstrate that toroidal plasma is an open system with a strong nonlinearity to provide a new attractive problem to be studied. © 2000 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The solitary structure solution of the radial electric field Er in the tokamak plasmas is obtained. It is shown to be stable under an external power supply, like a biased electrode at the edge. The radial gradient is governed by the ion viscosity and the nonlinearlity of the perpendicular conductivity. The radial structure of Er and reduction of turbulent transport, which belong to key issues of the high confinement mode (H-Mode) [F. Wagner et al., Phys. Rev. Lett. 49, 1408 (1982)], are self-consistently determined. A bifurcation from a radially-uniform one to a solitary one occurs at a certain applied voltage, and a hysteresis is associated. © 1998 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

Power partition and energy dissipation rates are examined for a self-sustained stationary turbulence of a high-n ballooning mode in a tokamak plasma. It is found that the power to excite fluctuations is almost equally transferred to perpendicular ion motion and to parallel electron motion. The ratio of the thermalized power, which excites and sustains the turbulence, to the total power lost by energy diffusion is found to be of the order of the broken symmetry parameter, i.e., the inverse aspect ratio, a/R. The dissipation rates of the fluctuations due to the thermal conductivity, the electron viscosity, and the ion viscosity are also calculated separately. The dissipation is dominated by that associated with the thermal conductivity. The relation between the induced global flux and the microscopic dissipation is also derived. It is found that a fractional part of order a/R of the dissipated power is effective in sustaining the turbulent modes.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

The poloidal rotation velocity profiles both in low-confinement (L) and high-confinement (H) mode measured in JAERI Fusion Torus 2 Modified (JFT-2M) [Phys. Rev. Lett. 65, 1364 (1990)] are compared with H-mode models based on ion orbit loss. The profiles of poloidal rotation velocity measured in L and H modes are consistent with the calculation which consists of ion orbit loss model. The observed dependence of the thickness of the layer of high shear Er on poloidal gyroradius is explained by the radial transport of poloidal rotation velocity.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

In the discharges of the Large Helical Device [O. Motojima et al., Proceedings of the 16th Conference on Fusion Energy, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 3, p. 437], a significant enhancement of the energy confinement has been achieved with an edge thermal transport barrier, which exhibits a sharp gradient at the edge. Key features associated with the barrier are quite different from those seen in tokamaks (i) almost no change in particle (including impurity) transport, (ii) a gradual formation of the barrier, (iii) a very high ratio of the edge temperature to the average temperature, (iv) no edge relaxation phenomenon. In the electron cyclotron heating (ECH) heated discharges in the Compact Helical System [K. Matsuoka et al., in Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411], the internal electron transport barrier has been observed, which enhances the central electron temperature significantly. High shear of the radial electric field appears to suppress the turbulence in the core region and enhance the electron confinement there. © 2000 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

In this paper we present space potential profiles directly observed in a toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka et al., Proceedings, 12th International Conference on Plasma Physics and Controlled Nuclear Fusion, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411], using a 200 keV heavy ion beam probe. The potential profiles exhibit widely varied characteristics, including positive and negative polarities for electron cyclotron and neutral beam-heated plasmas, respectively. The behavior of high-energy particles in the CHS plasmas are deduced from loss cone diagrams evaluated from the observed potential profiles. © 1997 American Institute of Physics.

Electronic Resource

1089-7674

AIP Digital Archive

Physics

Coupled oscillation of the radial electric field, the heating power, and the plasma temperature in helical systems is analyzed. This oscillation is caused by the influence of the radial electric field on the direct loss of injected fast ions. The damped oscillations of the radial electric field, temperature and fast-ion loss are predicted. Conditions for the occurrence of the mode and the oscillation frequency are discussed.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Interfilament contact in Nb3Sn wires made by the internal-tin-diffusion process causes excess hysteresis loss beyond the intrinsic magnetic hysteresis loss of the filaments. In analogy with eddy-current and proximity-effect coupling losses, the excess contact loss can be reduced by decreasing the twist-pitch length of the filaments in the wire. One consequence of interfilament contact is that volume magnetization measurements are strongly dependent on sample length below about one twist pitch. We define a characteristic length whose reciprocal is equal to the sum of the reciprocals of the sample length and the twist pitch. Hysteresis loss is a universal function of characteristic length for different sample lengths and twist pitches. We discuss several experimental parameters for the magnetic determination of hysteresis loss.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Cubic Laves phase alloy YFe2 forms four types of hydrides, YFe2Hx: β1, β2 (hexagonal) of 1.2〈x〈1.6, γ (hexagonal) of 2.8〈x〈3.45, and δ (orthorhombic) of 3.7〈x. The β1 and β2 hydrides are formed in the hydrogen absorption below and above 500 K. The deuterides YFe2Dx have been prepared by deuterium absorption at various temperatures for YFe2 powders of diameters less than 0.3 mm. The formed samples are mixtures of main and extra deuteride phases. The x-ray and magnetization measurements in a magnetic field of 10.6 kOe showed five types of ferromagnetic deuterides with Curie temperatures of about 100 K (δ1), 300 K (δ2), 380 K (γ), 300–380 K (β1), and 540 K (amorphous). The extrapolated values of magnetization at 0 K are 3.5μB/YFe2Dx. The crystal structures are as follows: δ1, hexagonal, a=0.57 nm, c=2.74 nm; δ2, cubic, a=0.79 nm; γ, hexagonal, a=0.56 nm, c=2.63 nm; and β, hexagonal (a=0.53 nm, c=0.87 nm)–(a=0.51 nm, c=0.82 nm). © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Theoretical analysis of the output performance of a transverse discharge pumped neon Penning laser (585.3 nm) using a mixture of Ne/H2 is described. The validity of the kinetic model is confirmed by comparing the results to the experimental discharge and laser performance. It is theoretically shown that the optimum mixing ratio of the Ne/H2 mixture is 1:2.5, and the optimum operating pressure is about 56 Torr. The model also predicts that the intrinsic efficiency reaches a peak of 8.5×10−6 at an excitation rate of 0.5 MW/cm3 under the optimum mixing ratio and operating pressure conditions. At excitation rates in excess of 0.5 MW/cm3 the laser output power is slowly increasing and then saturates due to electron collisional quenching of the upper laser level. The laser power extraction is increased by laser injection seeding in order to rapidly build up the lasing. The improved intrinsic efficiency is about two times higher than without the injection seeding. The improved specific laser output is 8 W/cm3, therefore, a discharge volume of 125 cm3 will be able to generate the peak laser power reaching 1 kW. This power value is sufficient to obtain the same treatment effect as the gold vapor laser used in photodynamic therapy. Moreover, by fitting this model to the experimental results of the laser output energy with a Ne/D2 mixture, it is shown that the Penning ionization rate constant of H2 is larger than that of D2. © 1995 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Magnetization and Mössbauer measurements were performed for PuNi3 type alloys Y(Fe1−xCox)2.9 and their hydrides. The composition dependencies of magnetization, Curie temperature, and average hyperfine field of 57Fe in the alloys show a maximum near x=0.5, and those in hydrides decrease with increasing x. This behavior suggests that the magnetic moments of iron and cobalt are nearly the same, except for cobalt rich alloys. Numerical fitting using a Stoner theory with a parabolic band was performed. It was assumed that the alloys and hydrides are ferromagnets of 3d-band-hole with incomplete saturation. It was shown that both the exchange energy kθ and Fermi energy ε0 decrease with substitution of cobalt for iron, and that the difference in the composition dependencies of kθ/ε0 in alloys and hydrides leads to different composition dependencies of the magnetization and Curie temperature. It was shown that ε0 and kθ decrease with hydrogenation, but kθ/ε0 increases to lead magnetization increase only in YFe3. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An ordered structure with the double periodicity in a 〈111〉 direction has been found by in situ reflection high-energy electron diffraction observation in the initial stage of Ge films grown on (100)Si and (811)Si substrate surfaces by GeH4 gas source molecular beam epitaxy. The ordered structure is formed on {111} planes parallel to the side planes of 〈011〉 steps on {811} facets of Ge growing islands on both substrates. The formation is observed at substrate temperatures of 300–700 °C and is considered to result from solid phase reactions at the interfaces during growth.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The Bi-(Pb)-Sr-Ca-Cu-O superconductor was fabricated into tapes with a Cu sheath. Measurements of magnetization and critical current density Jc in magnetic fields up to 23 T were made for them. The magnetization measurement revealed that, at 4.2 K, these tape specimens had excellent Jc -H(magnetic field) characteristics, while at 77 K, the flux pinning force in them was reduced to zero above 0.3 T due to the flux creep. In the resistive Jc measurement at 4.2 K, these tape specimens showed Jc of ∼7000 A/cm2 at 23. The Jc -H curve showed a slight peak effect, indicating the peak over 30 T.

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