Synthesis and Nonlinear Optical Susceptibility of Cyanine Dye J-Aggregate Doped Silica Film (I)

We synthesized thin silica films doped with condensed J aggregates of pseudisocyanine dyes (PIC) as a material for nonlinear optical devices by simple sol-gel processing and spincasting. The sol and the silica films were characterized with UV-visible absorption spectroscopy, fluorescence spectroscopy and fluorescence microscopy. The films contain plenty J aggregates, and are optically transparent and stable at room temperature. J aggregation dependence on dye concentration in the sol and spin speed during spincasting were investigated. It was found that dye condensation in the sol solution and fast spinning promote the formation of J aggregates in the films. Because of the high third order nonlinear susceptibility around 10^–7 esu, the films are expected to be useful for non-linear optical devices.     

Asymmetry measurement of the polarized Σ+p elastic scattering and the hyperon-nucleon spin-orbit interaction

In order to study the hyperon-nucleon spin-orbit interaction, asymmetries of the polarized Σ⁺ elastic scattering on protons have been measured. The polarized hyperons were produced through the p(π⁺, K⁺) Σ⁺ reaction in a liquid-scintillator active target, and tracks of Σ⁺p scattering events were recorded with a newly developed track detector named SCITIC (scintillating track image camera). Although analyses of 10 times more data with more sophisticated data-taking systems and more elaborated analyzing tools are under way, data from an early stage of this experiment indicate a large Σ⁺p spin-orbit interaction in contrast to the case of the small ΛN spin-orbit interaction. Received: 27 May 2002 / Accepted: 23 July 2002 / Published online: 19 November 2002 RID="a" ID="a"e-mail: nakai@post.kek.jp Communicated by Th. Walcher     

Local Whittle likelihood estimators and tests for non-Gaussian stationary processes

In this paper, we propose a local Whittle likelihood estimator for spectral densities of non-Gaussian processes and a local Whittle likelihood ratio test statistic for the problem of testing whether the spectral density of a non-Gaussian stationary process belongs to a parametric family or not. Introducing a local Whittle likelihood of a spectral density f _θ (λ) around λ, we propose a local estimator [^(q)] = [^(q)] (l){\hat{\theta } = \hat{\theta } (\lambda ) } of θ which maximizes the local Whittle likelihood around λ, and use f_{[^(q)] (l)} (l){f_{\hat{\theta } (\lambda )} (\lambda )} as an estimator of the true spectral density. For the testing problem, we use a local Whittle likelihood ratio test statistic based on the local Whittle likelihood estimator. The asymptotics of these statistics are elucidated. It is shown that their asymptotic distributions do not depend on non-Gaussianity of the processes. Because our models include nonlinear stationary time series models, we can apply the results to stationary GARCH processes. Advantage of the proposed estimator is demonstrated by a few simulated numerical examples.     

Numerical schemes for random ODEs with affine noise

Numerical schemes for random ordinary differential equations, abbreviated RODEs, with an affine structure can be derived in a similar way as for affine control systems using Taylor expansions that resemble stochastic Taylor expansions for Stratonovich stochastic differential equations. The driving noise processes can be quite general, such as Wiener processes or fractional Brownian motions with continuous sample paths or compound Poisson processes with piecewise constant sample paths, and even more general noises. Such affine-Taylor schemes of arbitrarily high order are constructed here. It is shown how their structure simplifies when the noise terms are additive or commutative. A derivative free counterpart is given and multi-step schemes are derived too. Numerical comparisons are provided for various explicit one-step and multi-step schemes in the context of a toggle switch model from systems biology.     

Synthesis of poly(ethynylplatinumporphyrin) and its application as an oxygen pressure-sensitive paint

5-(4-Trimethylsilyethynylphenyl)-10,15,20-triphenylplatinumporphyrin was synthesized and copolymerized with trimethylsilylpropyne to give a new high-molecular-weight porphyrin polymer. The polymer formed a smooth and tough coating on many types of surfaces. The coating showed a strong blue luminescence from the platinumporphyrin residue which was quenched in the presence of oxygen. The relationship of the luminescence intensity vs oxygen pressure displayed a remarkably high pressure sensitivity in the low oxygen pressure area, which was ascribed to the high oxygen permeability of the polymer.