Energy confinement time and heat transport in initial neutral beam heated plasmas on the large helical device

The confinement characteristics of large net-current-free plasmas heated by neutral-beam injection have been investigated in the Large Helical Device (LHD). A systematic enhancement in energy-confinement times from the scaling derived from the medium-sized heliotron/torsatron experiments have been observed, which is attributed to the edge pedestal. The core confinement is scaled with the Bohm term divided by the square root of the gyro radii. The comparative analysis using a dimensionally similar discharge in the Compact Helical System indicates gyro-Bohm dependence in the core and transport improvement in the edge region of LHD plasmas.     

Whole field measurement of temperature in water using two-color laser induced fluorescence

 A technique is described that measures the instantaneous three-dimensional temperature distribution in water using two-color laser-induced fluorescence (LIF). Two fluorescent dyes, Rhodamine B and Rhodamine 110, are used as temperature indicators. A laser light sheet scanned across the entire measurement volume excites the fluorescent dye, and an optical system involving a color beam splitter gives the intensity distribution of the individual fluorescent dyes on two separate monochrome CCD cameras. The ratio of these fluorescence intensities at each point of the image is calibrated against the temperature to eliminate the effect of the fluctuation of illuminating light intensity. A stable thermally stratified layer was measured by this system to evaluate the total accuracy of the measurement system. The random error of the measurement was ±1.4 K with 95% confidence. Measurements of thermal convection over a heated horizontal surface show temperature iso-surfaces having typical structures such as plumes, ridges and thermals. Received: 1 October 1997/Accepted: 23 March 1998     

Perfectness of Conelike *–Semigroups in ℚk

Let S be an abelian *–semigroup in ℚ^k. We give a sufficient condition for every positive definite function on S to have a unique representing measure on the dual semigroup of S (i.e. S is perfect). To characterize perfectness for any abelian *–semigroupis a challenging, but not yet generally solved problem. In this paper, we characterize the structure of involutions on an abelian *–semigroup which is a subset of ℚ^k, and show that any conelike *–semigroups in ℚ^k are perfect.     

Evaluation of reactivity for nitroxide radical trapping by correlation analysis using steric substituent parameter (ΩS)

The reactivity of nitroxide radical trapping (NRT), where stable nitroxide radicals react with transient carbon-centered radicals to form diamagnetic molecules, was evaluated. This was done with the use of the steric substituent parameter of both radicals by correlation analysis on the basis of the reactivity data determined by Ingold's group. In the case where the transient carbon-centered radicals were not resonance stabilized, the rate constant could be well correlated by using only Ω_S parameters of R₂NO⋅ and U⋅. If the transient radicals were stabilized by resonance, the parameter to estimate the amount of the resonance stabilization of U⋅ was necessary in the regression equation to evaluate the reactivity correctly. When the spin density, calculated by PM3 UHF molecular orbital calculations, was used as the resonance stabilization parameter, the rate constant could be well evaluated by a dual-parameter regression equation. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 215–221, 1998.     

Bipyridine-Modified DNA Three-Way Junctions with Amide linkers: Metal-Dependent Structure Induction and Self-Sorting

DNA three-way junction (3WJ) structures are essential building blocks for the construction of DNA nanoarchitectures. We have synthesized a bipyridine (bpy)-modified DNA 3WJ by using a newly designed bpy-modified nucleoside, U_bpy- 3 , in which a bpy ligand is tethered via a stable amide linker. The thermal stability of the bpy-modified 3WJ was greatly enhanced by the formation of an interstrand Ni^II(bpy)₃ complex at the junction core (ΔT_m=+17.7 °C). Although the stereochemistry of the modification site differs from that of the previously reported bpy-modified nucleoside U_bpy- 2 , the degree of the Ni^II-mediated stabilization observed with U_bpy- 3 was comparable to that of U_bpy- 2 . Structure induction of the 3WJs and the duplexes was carried out by the addition or removal of Ni^II ions. Furthermore, Ni^II-mediated self-sorting of 3WJs was performed by using the bpy-modified strands and their unmodified counterparts. Both transformations were driven by the formation of Ni^II(bpy)₃ complexes. The structural induction and self-sorting of bpy-modified 3WJs are expected to have many potential applications in the development of metal-responsive DNA materials.     

Experimental results of DPIS with a new RFQ

We have developed a new heavy ion production system which uses a combination of an RFQ and a laser ion source. Induced plasma by a laser shot is delivered to the RFQ without an extraction electrode. We named this new idea ‘direct plasma injection scheme (DPIS)’. In 2004, a new RFQ was built for demonstrating the capability of the DPIS. After a few months of commissioning period, we could obtain more than 60 mA of carbon beam from the RFQ. This new scheme could be applied to cancer therapy facilities and high energy nuclear physics accelerator complexes.     

Pattern-effect-free all-optical wavelength conversion using a hydrogenated amorphous silicon waveguide with ultra-fast carrier decay

Ultra-fast carrier decay, recently discovered in a hydrogenated amorphous silicon waveguide, can be exploited for pattern-effect-free all-optical signal processing based on optical Kerr nonlinearity. In this study, we utilized a 10 Gbit/s RZ-OOK data stream as a pump for degenerate four-wave mixing in a low-loss hydrogenated amorphous silicon waveguide. The propagation loss of the waveguide used was 1.0±0.2 dB/cm at 1550 nm. Unlike crystalline silicon waveguides, no noticeable difference was observed in the BER characteristics between the cases of PRBS 2(7)-1 and 2(31)-1.