Sensitive determination of tyrosine metabolites, p-hydroxyphenylacetic acid, 4-hydroxy-3-methoxyphenyl-acetic acid and 4-hydroxy-3-methoxymandelic acid, by gas chromatography-negative-ion chemical-ionization mass spectrometry. Application to a stable isotope-labelled tracer experiment to investigate their metabolism in man

A method has been established for studying the dynamic metabolism of tyrosine to its metabolites in humans using a deuterium-labelled amino acid. Phenylalanine-d5 was administered orally to human subjects (5 mg/kg) and the levels of p-hydroxyphenylacetic acid-d4, 4-hydroxy-3-methoxyphenylacetic acid-d3, and 4-hydroxy-3-methoxymandelic acid-d3 excreted into urine every hour were determined by gas chromatography-negative-ion chemical-ionization mass spectrometry. This method was also applied to some patients with depression and it was possible to detect a slight alteration in the excretion of some compounds compared with the control.     

Design of Cavities for a Short Pulse Powerful Large Orbit Gyrotron

Designs of cavities for fundamental and high harmonic operation in Large Orbit Gyrotron (LOG) are discussed. The fundamental operation allows one to use beam currents in the range from 200 A to 300 A achieve output power of the order of 9–10 MW at frequency 143.6 GHz. Mode competition calculations show that stable oscillations in the TE^1,4 mode using high beam currents are possible even with the pitch factor 1.3 which is significantly lower than the design value 1.55. For the second harmonic operation, the maximum current used for excitation of the TE^2,4 mode is 60 A and the optimum magnetic field is 7.6 T. A cavity design for fourth harmonic operation using the TE^4,4 mode is also presented.     

Asymptotic normality of a covariance estimator for nonsynchronously observed diffusion processes

We consider the problem of estimating the covariance of two diffusion-type processes when they are observed only at discrete times in a nonsynchronous manner. In our previous work in 2003, we proposed a new estimator which is free of any ‘synchronization’ processing of the original data and showed that it is consistent for the true covariance of the processes as the observation interval shrinks to zero; Hayashi and Yoshida (Bernoulli, 11, 359–379, 2005). This paper is its sequel. Specifically, it establishes asymptotic normality of the estimator in a general nonsynchronous sampling scheme.     

Nonlinear resonances and self-excited oscillations of a rotor caused by radial clearance and collision

This paper investigates oscillations in a flexible rotor system with radial clearance between an outer ring of the bearing and a casing by experiments and numerical simulations. The mathematical model considers the collisions of the bearing with the casing. The following phenomena are found: (1) Nonlinear resonances of subharmonic, super-subharmonic and combination oscillation occur. (2) Self-excited oscillation of a forward whirling mode occurs in a wide range above the major critical speed. (3) Entrainment phenomena from self-excited oscillation to nonlinear forced oscillation occur at these nonlinear resonance ranges. Moreover, this study analyzes periodic solutions of the mathematical model by the Harmonic Balance Method (HBM). As the results, the nonlinear resonances of subharmonic oscillation and its entrainment phenomenon can be explained theoretically by investigating the stability of the periodic solutions. The influence of the static force and the bearing damping on these oscillation are also clarified.     

Mechanism of alternating copolymerization of 4-hydroxy-4′-vinylbiphenyl with α-chloromaleic anhydride

The copolymerization of 4-hydroxy-4′-vinylbiphenyl (HVB) with α-chloromaleic anhydride (CMAn) was investigated in THF, 1,4-dioxane, and acetonitrile. The formation of the 1:1 charge transfer complex between HVB and CMAn was confirmed spectroscopically, and the corresponding equilibrium constant (K_eq) was determined as follows: K_eq = 0.19, 0.11, and 0.058 mol/L in THF, 1,4-dioxane, and CH₃CN, respectively. The copolymer composition is affected by the solvent, i.e., the content of HVB in the copolymer obtained in THF or 1,4-dioxane is lower than 50 mol % whereas the copolymer obtained in CH₃CN has excess of HVB units. The maximum rate of copolymerization was observed at a 1:1 initial comonomer mole ratio, irrespective of the solvent polarity. Plots of R_p/[HVB] vs. [HVB] gave a straight line with a slope and an intercept for the copolymerization in THF whereas a straight line in CH₃CN has no slope. On the basis of these results and ¹³C-NMR spectra of the copolymers, the mechanism of the predominant formation of alternating copolymers is discussed.     

Possibilistic linear regression analysis for fuzzy data

Fuzzy data given by expert knowledge can be regarded as a possibility distribution by which possibilistic linear systems are defined. Recently, it has become important to deal with fuzzy data in connection with expert knowledge. Three formulations of possibilistic linear regression analysis are proposed here to deal with fuzzy data. Since our formulations can be reduced to linear programming problems, the merit of our formulations is to be able to obtain easily fuzzy parameters in possibilistic linear models and to add other constraint conditions which might be obtained from expert knowledge of fuzzy parameters. This approach can be regarded as a fuzzy interval analysis in a fuzzy environment.     

Development of 1,3a,6a-triazapentalene-labeled enterobactin as a fluorescence quenching sensor of iron ion

1,3a,6a-Triazapentalene (TAP)-labeled enterobactin was developed as an iron ion sensor. 3-Acetylated-TAP was successfully introduced to the catechol ring of enterobactin, a well-recognized siderophore secreted by various Gram-negative bacteria. The fluorescence of TAP-labeled enterobactin decreased gradually as the amount of Fe³⁺ ion as an additive was increased, and 1.2 equiv of Fe³⁺ ion completely quenched the fluorescence. In clear contrast, when other metal ions were used, the fluorescence of TAP-labeled enterobactin remained even at 5.0 equiv.