A human lung can be simulated as an acoustic model by taking account of airways as acoustic tubes. The purpose of this study is to clarify this acoustic characteristics of the lung by calculating resonance frequencies. In the case of a particle velocity source : (1) four resonance frequencies exist under 2 000Hz, (2) these values are not affected by changing a position of the source, and (3) the particle velocity source can exist only within the 8th generation of the bronchi. On the other hand in the case of a pressure source; (1) four of five resonance frequencies exist under 2000Hz, and (2) these values are affected by changing positions of the source. Resonance frequencies in both source cases shift to lower values when the open area of the vacal cord increases and/or a velocity of air flow decreases.
Resonance frequencies are also obtained using a cast model of human bronchi. No differences between these values and calculated ones are noted except in the high frequency range around about 2000Hz.

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A new versatile stereo display system called NS-type has been developed. To measure the characteristics of binocular depth perception, standard television techniques in conjunction with special video processing have been applied in the new display in order to achieve the performance whereby the binocular parallax could easily be controlled temporally and spatially with such electric singals as brightness control.
The binocular depth cues comprise a binocular parallax and a convergence, and they occur together as a result of the lateral shift of the retinal image, depending on the depth distance and the viewing point.
The lateral shift of television pictures could be controlled by the temporal phase modulation of a video signal based on the horizontal scanning structure. The phase modulator consisted of either the fast varaible delay circuit (analog CCD) or the digital random access memory (RAM).
In this system, the stereoscopic images have been produced with the binocular parallax which was proportionate to the input signal of the spatial and temporal waveform in depth independently of image-related factors (brightness, size, density, etc.). The image has also been changed independently of the depth signal. The simplest method for the binocular vision of two television pictures has been utilized. The observer viewed two images, on two CRTs through a half-mirror and a polarizing filter placed in front of each eye and CRT, the axes of which intersected each other at a right angle.
The results of the measurement of depth perception were as follows : 1) the temporal frequency response was one of the band pass filter with a peak at 1-2 Hz; 2) the spatial frequency response was also one of the band pass filter with a peak at 1-2 cpd; and 3) the spatial responses for the horizontal and vertical gratings did not differ.
This system is not only used for the measurement of depth perception, but also is applicable to stereo-tomography.

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The electromyographic silent period can be observed preceding a reaction movement. It has been suggested that the electrical silence was attributable to the supraspinal influences. Since the electrical activities of the muscle are related to the excitability of the motoneurons in the spinal cord, the excitability of the motoneurons might be changed in the period corresponding to the appearance of the silent period. The present study has been designed to investigate variability of the excitability of the motoneurons prior to a reaction movement by means of the H-wave.
It has been observed that the change of the H-wave amplitude began with a slight decrease, and progressive increase.followed the depression period. The depression period of the H-wave appeared from 150 msec to 90 msec before the onset of the phasic discharge under the condition of the preparatory phase without the sustained contraction. Under the other condition with the sustained contraction, the depression period appeared from 120 msec to 85 msec. Thus, by application of the sustained contraction, the onset of the depression period was delayed and the duration was shortened. The results suggested that the depression period was closely related to the silent period. In other words, when the excitability of the motoneurons was lowered below the level of the EMG appearance, the silent period could be observed.

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A new instrumented-shoe has been designed for measuring independently and continuously three components of foot-to-ground forces without measuring the anterior-posterior (θ_YZ) and.medial-lateral (θ_XZ) angular motions of the lower leg relative to the floor surface during walking.A pair of force transducers are attached directly to a shoe sole at both the toe and heel to maintain the shoe's normal performance. The linearity and the reproducibility of the force transducer were tested by applying dead weight loads with variable load-acting angles to the transducer.The measurement error in each force component was better than ±3%/FS within the range of expected load-acting angles (0≤θ_YZ≤90°and|θ_XZ|≤14°). The output signals of the transducer remained unaffected by the point of application of the applied force. The dynamic characteristics were tested by comparing three comp onents of forces measured by the shoe mounted force transducers with those simultaneously recorded by a conventional force plate. A fairly good agreement between the pairs of simultaneous force recordings was obtained. The performance and the practical use of the instrumented-shoe were also evaluated through the force measurements over a variety of gait conditions including pathological gait. The instrumented-shoe is found to be accurate and useful enough in practice to be helpful to kinesiologists, rehabilitation engineers, and physical therapists in biomechanical gait studies.

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“Metabolic indices” of blood acid-base status, such as base excess (BE) and buffer base (BB), are usually estimated by Siggaard-Andersen's nomographic method based on the measured pH of blood under preset pCO₂. Although many attempts at automating the nomogram reading have been made by numerically simulating the BE curve, the theoretical background of the hyperbolic functions of BE and BB had not been clearly presented.
On the assumption of two-compartmental model of blood in which both compartments, red. blood cells (RBC) and plasma, have linear buffer slopes of acid-base balance and the RBC membranes are selective in permeating HCO₃^- and H⁺, the relation of [HCO₃^-] and pH of plasma Phase in blood have been derived :
[HCO₃^-] =- ((1-Ht) k_p+Htk_c′) (pH-7.4) +24 (Ht (a-1-7.4b) +1)+ [BE] / (1-Ht) +Ht (a-bpH)
where Ht is hematocrit, k_p, k_c', linear buffer slopes of RBC and plasma; a, b, partition coefficients of [HCO₃^-] between plasma and RBC. Explicit hyperbolic functions of BE and BB curves have been derived analytically from this equation. The predicted and the observed curves fit fairly well using the parameter values estimated on the least square principle.
The relatively simple formulae of the blood “metabolic indices” which are directly derived from this equation can be as accurate as any of the complex computer algorithms of simulating the nomographic reading.

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The two-dimensional echocardiography for the left ventricle is widely used as a real time noninvasive diagnostic technique in clinical medicine. Cardiac information, such as volume change and wall motion of the left ventricle in the cardiac cycle, can be obtained by processing consecutive frames of echocardiograms.
This paper describes a system for computer-aided analysis of sector scan echocardiograms. The system is built of a minicomputer system, a conventional ultrasound instrument, a video tape recorder and a special interface circuit which connects them to each other. The system can record echo signals on video tape directly without using a video camera, and transfer digitized echo signals to the minicomputer. The digitized images of echocardiogram have (256, 112) pixels with 8-bit gray level. A method for tracing the boundary of the left ventricle has been made available. In this method, the boundary of the previous frame is used as a guide in searching for the new boundary of the next frame.
Some results, volume change and %-shortening, which show the quantitative information on the cardiac function, are obtainable from the detected boundaries.

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The importance of quantitative electron microscopic study of neurons and synapses has been increasingly recognized. However, this kind of neuroanatomy is very difficult and time-consuming work, and reliable methods for such studies have not yet been developed.
Proposed here is a method dealing with quantitative synaptology which treats all recorded synapses and boutons around the neuron marked with HRP, rather than a qualitative or a piecemeal quantitative study of a particular synapse and/or bouton which is not positioned in the neuron. This approach requires the development of both neuroanatomical procedures, by which a specialized whole neuronal profile is identified, and valuable specialized tools, which support gathering and analysing of a huge volume of morphometric data from a photomontage of electron micrographs, to reduce the burden of the morphologist.
The present report is concerned mainly with the computer system which has been under development in our laboratory for such morphometric synaptology. The system consists of a large sized tablet digitizer, a YHP system 45 desk top computer, hard disk drives, an X-Y plotter, and a line printer. The system is designed as a semi-automatic interactive computer system, because electron micrographs of nervous tissues have very complex textures and weak contrast. In our system, a morphologist performs the pattern recognition portion and decides what to do next in the system, and the computer functions conventionally, computing, storing and controlling. Measurement, count, and computation about morphological parameters, such as 1) cross sectional perimeter and area of a soma and boutons, 2) number of boutons and a variety of organelles, 3) contacting length of boutons, 4) classification of boutons, are made by means of the interactive method using a tablet digitizer and a menu-sheet. Further morphometric parameters, such as the S/F ratio, the covering ratio, mean values, deviation, and distribution, are computed from the quantitative data. As morphometric data are all stored in hard disks and programs for various analyses are available, we can analyse them and make a comparison between groups of neurons. In this manner, the proposed system is quite useful and efficient, and can be used as easily as a notebook, for morphometric synaptology. The system also drastically decreases the time spent on this time-consuming procedures. Some examples of morphometric measurements and analyses are also given.

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