Yukio Kumagai

Audio signal storing apparatus having a function for converting speech speed

The speed of an input speech is changed without any change of the pitch of the input speech. Raw data of a speech are stored so that the speed of the speech can be modulated continuously on the basis of the raw data of the speech. In the speech speed conversion method, a speech speed conversion process for the input speech is carried out in a period designated when speech speed conversion is needed, which the speech speed conversion is not carried out in the other period. Further, in the speech speed conversion apparatus having a unit for inputting a speech, a speech speed conversion unit for changing the speed of the input speech, and a unit for supplying the output of the speech speed conversion unit as an output speech to listeners ears, the apparatus further includes a speech speed conversion switch, and a unit for outputting a speech while changing the speech speed of the input speech in a period in which the speech speed conversion switch is turned on, but for outputting a speech without any change of the input speech in the other period in which the speech speed conversion switch is turned off.

Unshielded fetal magnetocardiography system using two-dimensional gradiometers

We performed fetal magnetocardiography (fMCG) measurements in an unshielded hospital environment to demonstrate our developed fMCG system using two-dimensional (2D) gradiometers based on low-T c superconducting quantum interference devices. The subjects were 25 pregnant women, including two subjects with twin pregnancies, or 27 fetuses, in this study. The 2D gradiometer was optimized for fMCG measurements and detected both the axial second-order gradient and planar-first-order gradient of a magnetic field. Depth of the fetal heart was also measured by using ultrasonography before fMCG measurement. As a result, the QRS peaks of the fMCG waveform were detected in real time for 15 cases including early fetal gestational periods as 24 and 25 weeks. Moreover, the P and T waves were also detected in some cases by averaging. These results demonstrate that the developed unshielded fMCG system can detect fMCG waveforms in an unshielded hospital environment.

Demonstration of Unshielded Fetal Magnetocardiography System Using Two-Dimensional Gradiometers

We performed fetal magnetocardiography (fMCG) measurements in an unshielded hospital environment to demonstrate our developed fMCG system using two-dimensional (2D) gradiometers based on low-T c superconducting quantum interference devices. The subjects were 25 pregnant women, including two subjects with twin pregnancies, or 27 fetuses, in this study. The 2D gradiometer was optimized for fMCG measurements and detected both the axial second-order gradient and planar-first-order gradient of a magnetic field. Depth of the fetal heart was also measured by using ultrasonography before fMCG measurement. As a result, the QRS peaks of the fMCG waveform were detected in real time for 15 cases including early fetal gestational periods as 24 and 25 weeks. Moreover, the P and T waves were also detected in some cases by averaging. These results demonstrate that the developed unshielded fMCG system can detect fMCG waveforms in an unshielded hospital environment.

Note: Unshielded bilateral magnetoencephalography system using two-dimensional gradiometers

Magnetoencephalography (MEG) noninvasively measures neuronal activity with high temporal resolution. The aim of this study was to develop a new type of MEG system that can measure bilateral MEG waveforms without a magnetically shielded room, which is an obstacle to reducing both the cost and size of an MEG system. An unshielded bilateral MEG system was developed using four two-dimensional (2D) gradiometers and two symmetric cryostats. The 2D gradiometer, which is based on a low-T(c) superconducting quantum interference device and wire-wound pickup coil detects a magnetic-field gradient in two orthogonal directions, or ∂/∂x(∂(2)B(z)/∂z(2)), and reduces environmental magnetic-field noise by more than 50 dB. The cryostats can be symmetrically positioned in three directions: vertical, horizontal, and rotational. This makes it possible to detect bilateral neuronal activity in the cerebral cortex simultaneously. Bilateral auditory-evoked fields (AEF) of 18 elderly subjects were measured in an unshielded hospital environment using the MEG system. As a result, both the ipsilateral and the contralateral AEF component N100m, which is the magnetic counterpart of electric N100 in electroencephalography and appears about 100 ms after the onset of an auditory stimulus, were successfully detected for all the subjects. Moreover, the ipsilateral P50m and the contralateral P50m were also detected for 12 (67%) and 16 (89%) subjects, respectively. Experimental results demonstrate that the unshielded bilateral MEG system can detect MEG waveforms, which are associated with brain dysfunction such as epilepsy, Alzheimers disease, and Down syndrome.

Control system for readout electronics of multi-channel magnetocardiographs using high-temperature DC superconducting quantum interference devices

We aimed to develop a control system for multichannel magnetocardiography (MCG) based on a high-temperature DC superconducting quantum interference device (high-Tc SQUID). To create this system, we used one oscillator as an AC bias controller to operate a multichannel high-Tc SQUID. To optimize the SQUID parameters (such as the AC bias, offset voltage), two new control sequences based on a cross-correlation method and a fast Fourier transform method were developed. Using the AC bias controller and the sequences, the typical white noise level of the SQUID was about 50–60 fT Hz-1/2 around 100 Hz. Multichannel MCG signals were detected clearly in the system with the SQUIDs. We conclude that our control system with one oscillator and new protocols can reliably operate a multichannel SQUID.