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.     

A pitch-synchronous analysis of hoarseness in running speech

A method of pitch-synchronous acoustic analysis of hoarseness requiring a voice sample of only four fundamental periods is presented. This method calculates a noise-to-signal (N/S) ratio, which indicates the depth of valleys between harmonic peaks in the power spectrum. The spectrum is calculated pitch synchronously from a Fourier transform of the signal, windowed through a continuously variable Hanning window spanning exactly four fundamental periods. A two-stage procedure is used to determine the exact duration of the four fundamental periods. An initial estimate is obtained using autocorrelation in the time domain. A more precise estimate is obtained in the frequency domain by minimizing the errors between the preliminary calculated power spectrum and the predicted spectrum spread of a windowed harmonic signal. Analysis of synthesized voices showed that the N/S ratio is sensitive to additive noise, jitter, and shimmer, and is insensitive to slow (8 Hz) modulation in fundamental frequency and amplitude. An analysis of pre- and postoperative voices of six patients with benign laryngeal disease showed that the N/S ratio for vowel /u/ in running speech consistently improved after surgery for all subjects, in agreement with their successful therapeutic results.     

Circular dichroism in ferroelectric and antiferroelectric liquid crystals

Liquid crystal induced circular dichroism (LCICD) measurements were made to investigate the pretransitional phenomena in the S_A phase just above the S_A-S*_C and S_A-S*_CA phase transitions of both the first and the second order. The pretransitional LCICD in S_A was observed in the second order phase transition to S*_c and S*_cA, suggesting the existence of a dynamic helical structure in S_A. Such behaviour disappears when the transition is of the first order. It seems that the handedness of the dynamic helix in S_A is the same as that in S*_c even when the lower temperature phase is S*_cA. This is explained as a result of a dominant contribution of ferroelectric soft mode.     

Polarization gradient cooling effect in the outer potential field

Received: 15 January 1998/Final version: 15 June 1998     

Vinca alkaloids. XXXII. Microbiological conversions of vindoline, a major alkaloid from Vinca rosea L

Vindoline, a major alkaloid from Vinca rosea _L was subjected to microbiological conversion using Streptomyces cultures. Several new metabolites were isolated and their structures elucidated.     

Evidence for muon neutrino oscillation in an accelerator-based experiment

We present results for nu(mu) oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced nu(mu) beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy-dependent disappearance of nu(mu), which we presume have oscillated to nu(tau). The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).     

Time-resolved study of intramolecular charge transfer fluorescence in 1,2,3,4-tetrachloro-11H-isoindolo-[2, 1-a]-benzimidazol-11-one

Fluorescent properties of 1,2,3,4-tetrachloro-11H-isoindolo-[2,1-a]-benzimidazol-11-one (TCIB) in various organic solutions are described. Detailed investigation of the fluorescence from the solutions revealed that it was ascribable to the electronic transition from the lowest singlet excited state of an isolated molecule to its ground state, though the fluorescence spectrum was broad and structureless and the Stokes’ shift was about 1 eV. The absorption peak of TCIB was relatively insensitive to change in solvent polarity, whereas its fluorescence peak shifted to the red with an increase in the polarity. This finding suggests that the dipole moment of the molecule in the ground state is almost zero, and that the excited state has a non-zero dipole moment, which coincides with the predicted semiempirical molecular orbital calculation. Fluorescence quantum efficiency decreased with increase of solvent polarity. The efficiency was reduced by a factor of 39 in going from n-hexane solution to acetonitrile solution. The radiative rate constant also decreased with increase of solvent polarity. However, its reduction was very moderate; the reduction factor was only 2.5 for acetonitrile solution as compared with n-hexane solution. This finding indicates that the emitting state of the title compound is influenced by a solvent-dependent non-radiative mechanism, for which solvent-sensitive intersystem-crossing deactivation is tentatively proposed.     

π-Face-selective hetero Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide. An excellent trapping reagent for thioaldehydes and thioketones

Hetero Diels-Alder reactions of 3,4-di-tert-butylthiophene 1-oxide (1) with thioaldehydes and thioketones take place exclusively, except the reaction with thiobenzophenone, at the syn-π-face of 1 with respect to the SO bond. The π-face selectivity was explained in terms of the extent of conformational changes of 1 that are brought about in the process to the transition states.