Evoked response elicited by electrical stimulation to a human eye has been studied for the purpose of application to the routine clinical testing in ophthalmology.
In this paper, in order to investigate the retinal origin of AC-EER (Electrically Evoked Response by Alternate Current stimulus), the influence of the condition of visual cells in the stimulated retina in discussed using seven characteristics parameters which are calculated from the AC-EER and its power spectrum.
These parameters obtained from 14 normal subjects and those from 12 patients with pigmentary retinal dystrophy are also analized by method of principal component analysis.
The results obtained in this study are as follows,
1. The AC-EER and its power spectrum are influenced not only by the disease with dysfunctional visual cells in the electrically stimulated retina, but also by the state of adaptation.
2. The α band in the power spectrum of the AC-EER reflects these influences remarkably.

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The purpose of this study was to identify a bicycle-human system during moderate exercise. Four male subjects performed pedalling exercises on an electrically controlled ergometer which had a feedback loop to maintain the power value given by the other computer. Work load was varied for 9.6 sec as a pseudorandom binary sequence (dt=0.05 sec, 6 bit, 3 cycle) which enable us to calculate the frequency response and the transfer function of the system, after dead time correction. Three trials were performed with a set load of 40-80, 80-120, and 40-120W, respectively. The transfer function could be described as the fourth-order rational function when calculated by least squares on time domain as follows:
G(jω)=[0.46-0.0030(jω)+0.00098(jω)²-0.0000024(jω)³+0.00000052(jω)⁴]/[1.0+0.018(jω)+0.0050(jω)²+0.000013(jω)³+0.0000031(jω)⁴]
The parameters of these transfer functions had no significant differences among the subjects nor the work load settings (p>0.05). The characteristics of Bode diagrams showed the resonance on the average to be approximately 2.2 and 6.4Hz. The resonance of 6.4Hz was unstable. It is necessary for identification of a human body system to design a control system that tracks rapid changes of work load.

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A new theory for measuring compliance of the aorta in vivo has been developed, utilizing the changes in transthoracic electrical impedance and aortic pressure with an induced change in volume of the aorta. Based on this theory, blood injection method and intra-aortic balloon inflation method were devised and compared. As a result, the blood injection method was thought to be more reliable comparing the two methods. “IABP MONITOR” developed by the authors' laboratory was useful for measuring compliance of the aorta adopting these methods.

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Integrated electromyograms (IEMGs) are often used as an index of muscle force in rehabilitation medicine, physical education and many other fields, but the reliability of IEMG is low because of its great variance. In this study the authors analyzed the relation between variance of IEMG and spacing of electrodes to seek a measurement method of IEMG with variance as small as possible. We examined human biceps brachii and found that the narrower the spacing of electrodes, the smaller the variance of IEMG. Thus, to obtain reliable IEMG results, electrode spacing should be kept as narrow as practical. We also analyzed the relation in light of an EMG generation model. The results of this analysis suggested that the reason for the small variance of IEMG is the brevity of motor unit action potentials detected by narrowly spaced electrodes.

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A piezoelectric vibrometer was developed for measuring contact compliances of a soft material. In general. the heavy device for measuring contact compliance has an influence on the results when it is placed on a soft material. The transducer developed here, which is very different from conventional electrodynamic vibrometers, is designed to operate with a piezoelectric disk employed as a driver unit. Therefore, it is so small and light that it is convenient for handling. The characteristics of the vibration mode and the contact compliance of a foam rubber and a geratinized one were studied experimentally and theoretically when the piezoelectric vibrometer was placed on them. The actual values measured in experiments were consistent with the results obtained with theoretical analysis.

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In order to investigate the mechanics of serum leakage from expanded polytetrafluoroethylene (EPTFE) vascular prosthesis, we carried out computer simulation of the percolation processes of liquid into the layer in which long round rods or fibers are distributed randomly. The simulation model employed in the present work is as follows. Many circles are generated randomly on the finite plane by avoiding to overlap each other. The plane is then divided into Delaunay triangles. Starting from the state that one side of the plane is exposed to the liquid, the liquid fronts take steps forward with the criteria depending on the distance between two neighbouring circles, the surface tension of the liquid T and the inside pressure of the liquid p.
From the simulation for many cases, liquid leakage from the layer was noticed for small values of d_c=T/p and vice versa. Moreover, the following facts became clear for the maximum value of d_c, d_m, even with which the liquid leakage takes place.
(i) d_m² is inversely proportional to the density of the circles σ.
(ii) When the circle diameter a is below 1μm, d_m does not change noticeably. It is, however, going to decrease above 1μm and the change of d_m with a becomes insignificant again, and then d_m approaches to the value around 1/√σ.
(iii) When a=0, 2d_m=(1.2-1.3)×1/√σ.
Considering these results, the minimum blood pressure for serum leakage from EPTFE vascular prosthesis was estimated to be approximately 140mmHg. This value of the pressure is consistent with the experience of Blalock-Taussig shunt operations using EPTFE vascular prosthesis.

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This paper describes an advanced ECG inverse solution method with an automatic search algorithm for the expansion points which estimates simultaneously the epicardial potentials and the path of a single moving dipole. First, the initial expansion points were calculated from the measured torso surface potentials using the multipole expansion and moving electrical center methods. Second, the torso surface potentials were estimated during the forward processing with these points using the boundary integral equation relating the torso surface potentials to the epicardial ones. The optimum expansion points were then determined with the simplex method so as to minimize the potential residues between the measured and the estimated torso surface potentials. Thus the epicardial potentials were estimated with a mode expansion and the path of the single moving dipole was determined by linking the optimum expansion points. The validity of this method was examined with an animal experimental system consisting of an isolated canine heart and a cylindrical torso model under normal beats condition and ST elevation produced by a freezing injury. The results are as follows: 1) The average correlation coefficient between measured and estimated epicardial potentials was 0.567 for all the normal QRS, 0.725 during the middle portion of the QRS, and 0.765 for the injured ST elevation. 2) The peak value reproduction ratio of the potentials ranged from 30 to 85 percent for the QRS inverse solution and 85 percent for the ST elevation. 3) The estimated potential distributions fairly agreed with the measured ones, except during the breakthrough period. 4) The average size of the estimated ST elevation was 60 percent of the measured one, and the peak value locations agreed completely with the measured ones. In conclusion, this method can be expected to have sufficient accuracy and supply useful information for the diagnosis of cardiac abnormalities.

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It is now widely accepted that various biological systems produce deterministic chaos. In this research, a chaotic response of a squid giant neuron and an alpha wave in MEG are examined by a dimensional analysis. It is shown that the neural response and the alpha wave have the fractal dimension of 1.7 and that of 4.7, respectively.

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