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  • 1
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Since the start of the Large Helical Device (LHD) experiment, various attempts have been made to achieve improved plasma performance in LHD [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. Recently, an inward-shifted configuration with a magnetic axis position Rax of 3.6 m has been found to exhibit much better plasma performance than the standard configuration with Rax of 3.75 m. A factor of 1.6 enhancement of energy confinement time was achieved over the International Stellarator Scaling 95. This configuration has been predicted to have unfavorable magnetohydrodynamic (MHD) properties, based on linear theory, even though it has significantly better particle-orbit properties, and hence lower neoclassical transport loss. However, no serious confinement degradation due to the MHD activities was observed, resolving favorably the potential conflict between stability and confinement at least up to the realized volume-averaged beta 〈β〉 of 2.4%. An improved radial profile of electron temperature was also achieved in the configuration with magnetic islands, minimized by an external perturbation coil system for the Local Island Divertor (LID). The LID has been proposed for remarkable improvement of plasma confinement like the high (H) mode in tokamaks, and the LID function was suggested in limiter experiments. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental test of the radial force balance equation was done in the Compact Helical System Heliotron/Torsatron [S. Okamura et al. Nucl. Fusion 39, 1337 (1999)]. A radial electric field is measured with a heavy ion beam probe, while plasma rotation and drift velocity of fully ionized carbon are measured with charge exchange spectroscopy. The two measurements agree with each other to within 10% of the radial electric field in a wide range of electron densities of 0.3–2.0×1019 m−3. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The experimentally optimized magnetic field configuration of the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)], where the magnetic axis is shifted inward by 15 cm from the early theoretical prediction, reveals 50% better global energy confinement than the prediction of the scaling law. This configuration has been investigated further from the viewpoints of high energy particle confinement and magnetohydrodynamic (MHD) stability. The confinement of high energy ions is improved as expected. The minority heating of ion cyclotron range of frequency was successful and the heating efficiency was improved by the inward shift. The confinement of passing particles by neutral beam injection was also improved under low magnetic field strength, and there could be obtained an almost steady high beta discharge up to 3% in volume average. This was a surprising result because the observed pressure gradient exceeded the Mercier unstable limit. The observed MHD activities became as high as beta but they did not grow enough to deteriorate the confinement of high energy ions or the performance of the bulk plasma, which was still 50% better than the scaling. According to these favorable results, better performance would be expected by increasing the heating power because the neoclassical transport can also be improved there. © 2002 American Institute of Physics.
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  • 6
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In neutral-beam-injection (NBI) heated plasmas of the Compact Helical System (CHS) heliotron/torsatron [K. Matsuoka et al., Plasma Physics and Controlled Nuclear Fusion Research, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 441], inward turbulent particle flux is observed at a particular radial location near the plasma edge. The observed reversal of the particle flux is connected to the change in the cross-phase between electron density and poloidal electric field fluctuations. This phenomenon is observed in the parameter regime of low collisionality at the electron temperature Te〉15 eV, electron density ne〈3×1018 m−3, which approximately corresponds to the effective collision frequency normalized by the transit frequency of a circulating particle ν*(approximately-less-than)1. The large inward particle flux ((approximately-greater-than)1×1020 m−2 s−1) correlates with the positive shear of the radial electric field Er′ ((approximately-greater-than)1×106 V m−2), but does not have clear correlation with the radial electric field Er and the curvature Er″. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 611-614 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Semiconductor detectors based on natural diamonds have been installed on the Large Helical Device (LHD) heliotron to measure the energy distribution of charge exchange fast neutral particles from different viewing angles. Advantages of a natural diamond detector (NDD) are (1) very compact size, (2) relatively easy handling, and (3) high energy resolution. Although NDDs are sensitive to visible light, vacuum ultraviolet, and soft x rays, unfavorable pulses produced by such radiation were greatly reduced by choosing an appropriate stainless steel shield in this experiment. In LHD, the time-resolved energy distribution of counter-going beam ions and ion cyclotron range of frequency-produced energetic ions have been successfully obtained by means of an NDD. The performance of NDDs as a neutral particle analyzer and its good suitability to LHD plasmas were demonstrated throughout this work. © 2001 American Institute of Physics.
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  • 8
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The Large Helical Device (LHD) is the largest helical machine with superconducting coils. Key diagnostics issues for LHD are: (a) capability for multidimensional measurements because of the nonaxisymmetric toroidal plasma; (b) measurements of the electric field; (c) cross check of fundamental parameters using different methods; (d) advanced measurements appropriate for steady-state operation; and (e) a satisfactory data acquisition system. The design and research and development of plasma diagnostics were carried out taking these issues into consideration. As a result, the present status of diagnostics is described: diagnostics for LHD operation, fundamental diagnostics for plasma performance, diagnostics for physics subjects, innovative diagnostics and diagnostics for long-pulse operation. The LHD experiment started in March, 1998. Since then, the development of diagnostics has kept pace with the experimental campaigns. © 2001 American Institute of Physics.
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  • 9
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary Background CX-659S, a newly discovered anti-inflammatory compound, exerts inhibitory effects against acute contact hypersensitivity responses (CHRs) induced by picryl chloride (PC), oxazolone and dinitrochlorobenzene. The murine model of chronic CHR induced by repeated application of PC is known to mimic many, if not all, events occurring within the lesional skin of patients with atopic dermatitis (AD). Objectives To investigate the ability of CX-659S to inhibit PC-induced chronic CHR in mice. Methods The protective and curative effects of CX-659S were tested on PC-treated ears of BALB/c mice, and were compared with those of prednisolone. Effects were quantified by measurements of ear thickness, serum IgE and cytokine mRNA expression. Results Both protectively applied and curatively applied CX-659S significantly inhibited increases in ear thickness and total serum IgE. Inhibition was dose-dependent. Although protectively applied prednisolone showed similar activities to CX-659S against chronic CHR, curatively applied prednisolone did not affect the serum IgE level despite inhibiting increases in ear thickness and inflammatory cell infiltration. Consistent with these results, CX-659S reduced mRNA expression of interleukin (IL)-4 and IL-10 but not of interferon (IFN)-γ, whereas prednisolone inhibited not only mRNA expression of IL-4 and IL-10 but also that of IFN-γ in the ear lesion. In contrast to prednisolone, CX-659S did not show any side-effect such as atrophy, alopecia or telangiectasia. Conclusions CX-659S is the first promising compound having inhibitory activities against chronic CHR accompanied by a diminishing effect on elevated serum IgE, without any other side-effect. Therefore, CX-659S may be a promising candidate for management of patients with recurring AD who require long-term therapy.
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  • 10
    ISSN: 1432-2277
    Keywords: Key words Metalloproteinases ; Coronary arteriosclerosis ; Cardiac allografts ; Nonhuman primates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are important in any process of tissue remodeling. However, there is no report evaluating their expression in cardiac allografts in human or nonhuman primates. Heterotopic cardiac transplantation was performed on Japanese monkeys. Subjects were treated with chimeric anti-human lymphocyte function-associated antigen-1 monoclonal antibody for 2 weeks. Heart grafts were harvested at days 1–95 (n = 7). Native monkey hearts were used as controls (n = 2). We examined expression of MMP-2, MMP-9, TIMP-1, and TIMP-2 using immunohistochemistry and in situ reverse transcriptase polymerase chain reaction (RT-PCR). In the myocardium, the expression of MMP-2 was increased in the spindle-shaped cells of acutely rejected myocardial interstitium and prior to the presence of mononuclear cell infiltration at days 1–41. TIMP-1 and 2 expression was enhanced in association with the progression of fibrosis at days 40–95. In the coronary arteries of chronically rejected allografts, enhanced MMP and decreased TIMP expression was observed in both thickened intima and media at days 40–95. The medial MMP mRNA expression was observed before the development of intimal thickening occurred at days 7–28. MMPs are critical for the progression of acute and chronic rejection, and TIMP predominance plays important roles in fibrosis in association with acute rejection. Expression of MMPs and TIMPs is a sensitive indicator of acute and chronic cardiac rejection.
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