A hemolysis gene (hlx) which lyses sheep erythrocytes on blood agar plates when expressed in Escherichia coli was cloned from Vibrio cholerae. The cloned gene is predicted to encode a polypeptide of 92 amino acid residues with a deduced molecular mass of 10,451. E. coli transformed with this gene lysed sheep, goose, horse and chicken erythrocytes but not those of guinea pig and human. The hlx gene was observed in classical- and El Tor-biotype V. cholerae O1, V. cholerae non-O1, and V. mimicus, but not in V. parahaemolyticus.
Sibilant /s/, one of unvoiced sounds, is believed to be produced by flow turbulence provoked by the impingement of a jet to anterior teeth. Although it would be possible that the impingement of a jet as well as pressure fluctuations behind the anterior teeth associated with flow turbulence make anterior teeth vibrate, whereby contributing to the production of sibilant /s/, no studies have focused on this aspect. The present study is designed to investigate the possibility that the vibration of teeth contributes to the production of sibilant /s/. A morphologically simplified model of an oral cavity is fabricated. An air is steadily delivered at 45 L/min to the model to produce aeroacoustic sounds. Sound and vibration of teeth (obstacle wall) are measured simultaneously with a microphone and the Michelson interferometer. The spectrum analysis showed two peaks in the sound at 1,300 and 3,500 Hz, and one peak in the wall vibration at 3,500 Hz. An association of the peak at 3,500 Hz between the sound and wall vibration suggested that this sound is produced as a result of wall vibration. Experiments exhibited a decrease in the sound amplitude with an increase in thickness (rigidity) of teeth (obstacle wall). Those results demonstrated potential of the proposed method for exploring the production mechanism of sibilant /s/ and possibility of the contribution of teeth vibration to the production of sibilant /s/.
In order to understand the contribution of teeth vibration to the production of sibilant/s/, the pre-sent study was designed to develop a method of simultaneously measuring aeroacoustic sounds and the vibration of an obstacle. To measure the vibration without disturbing flow, the Michelson interferometer was employed. The flow channel, which had an obstacle wall inside of it, was fabricated such that it morphologically mimicked the simplified geometry of the oral cavity. Given airflows at a flow rate of 7.5 × 10–4 m3/s from the inlet, aeroacoustic sounds were generated. A spectrum analy-sis of the data demonstrated two prominent peaks in the sound at 1,300 and 3,500 Hz and one peak in the wall vibration at 3,500 Hz. The correlation in peak frequencies between the sound and wall vibration suggests that the sound at 3,500 Hz was induced by the wall vibration. In fact, the sound amplitude at 3,500 Hz decreased when the obstacle wall was thickened, which increased its rigidity (p < 0.05, t-test). The experimental results demonstrate that the developed techniques are capable of measuring aeroacoustic sound and obstacle wall vibration simultaneously, and suggest the potential to pave the way for detailed analysis of the production of sibilant sounds /s/
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