Evolution of lower-hybrid-driven current during the formation of an internal transport barrier

Evolution of the lower-hybrid(LH)-driven current profile was measured during the formation of an internal transport barrier (ITB) in a reversed magnetic shear discharge. As the ITB developed, the initially centrally peaked LH-driven current profile gradually turned hollow and was sometimes accompanied by an off-axis peak in the electron temperature profile. These observations indicate the concentration of LH power deposition to the ITB for this case as a result of nonlinear coupling between the LH waves and the target plasma.     

Extremely low vertical-emittance beam in the accelerator test facility at KEK

Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance.     

Estimating the amplitude of measurement noise present in chaotic time series

We propose a method for estimating the amplitude of measurement noise present in chaotic time series. This method is based on the evaluation of initial errors for a given time series and for a new one synthesized by adding an adequate amount of noise to the given one. The method is valid over a much wider range of noise levels than the previous methods are because it is not based on the detail of dynamical structure which generates the data. In addition, it is possible to check if the method is valid for the given data prior to its application. To confirm the effectiveness of the method we show the results of numerical experiments and apply the method to chaotic data obtained from an electrochemical experiment. (c) 1999 American Institute of Physics.     

Single-molecule fluorescence imaging of the remote TiO2 photocatalytic oxidation

The remote TiO2 photocatalytic oxidation reaction of single dyes has been investigated by the single-molecule fluorescent imaging technique. The present results suggest that the active oxygen species (Ox) is most probably the .OH radical, which is generated from the photodecomposition of H2O2 by UV light. The analyses of the number, intensity, and spectrum of individual fluorescence spots at the single-molecule level also indicate that unoxidized and oxidized dyes exist during the bleaching processes of single dyes.     

Highly effective synthetic methods for substituted 2-arylbenzofurans using [3,3]-sigmatropic rearrangement: short syntheses of stemofuran a and eupomatenoid 6

A new and efficient synthesis of 2-arylbenzofurans has been achieved via a route involving acylation and subsequent [3,3]-sigmatropic rearrangement of oxime ethers. Its synthetic utility is demonstrated by a short synthesis of stemofuran A and eupomatenoid 6 in which no procedure for protection of the phenolic hydroxyl groups is needed. [reaction--see text]     

Palladium-indium iodide-mediated allylation and propargylation of glyoxylic oxime ether and hydrazone: the role of water in directing the diastereoselective allylation

Allylation and propargylation of glyoxylic oxime ether in the presence of a catalytic amount of palladium(0) complex and indium(I) iodide were studied. Excellent diastereoselectivities in allylation were achieved in the presence of water, although low diastereoselectivities were observed in the absence of water. Propargylation of glyoxylic oxime ether proceeded with good diastereoselectivities in the presence of LiBr or LiCl.     

Magnetic penetration depth measurements of Pr2-xCexCuO4-delta films on buffered substrates: evidence for a nodeless gap

We report measurements of the inverse squared magnetic penetration depth, lambda(-2)(T), in Pr(2-x)Ce(x)CuO(4-delta) (0.115< or =x < or =0.152) superconducting films grown on SrTiO3 (001) substrates coated with a buffer layer of insulating Pr2CuO4. lambda(-2)(0), T(c), and normal-state resistivities of these films indicate that they are clean and homogeneous. Over a wide range of Ce doping, 0.124< or =x < or =0.144, lambda(-2)(T) at low T is flat: it changes by less than 0.15% over a factor of 3 change in T, indicating a gap in the superconducting density of states. Fits to the first 5% decrease in lambda(-2)(T) produce values of the minimum superconducting gap in the range of 0.29< or =Delta(min)/k(B)T(c)< or =1.01.