Nonlinear characteristics of the oscillators generating alpha rhythm, which are called α-oscillators in this paper, have been studied by presenting photic stimuli of various frequencies to subjects. Monopolar recording of the EEG was taken from Oz based on 10-20 system. From power spectra of the EEG, the presence of an entrainment region of alpha rhythm has been confirmed by photic stimuli around the intrinsic alpha frequency. The α-oscillators have the following nonlinear characteristics: (1) The entrainment region is bigger for stronger photic stimuli. (2) This entrainment of alpha rhythm has hysteresis. (3) The hysteresis region below the intrinsic alpha frequency is broader than the region above it. By calculating cross spectra between the EEG and the photic input, the phase delay (phase difference) of the evoked potentials in relation to the photic stimuli has been obtained. Patterns of phase change of the evoked potentials around the intrinsic alpha frequency can be classified into the following three types. (1) Gradually changing type. (2) N-shaped type with reversal of phase. (3) Steeply changing type. As the intensity of photic stimulus declines, type of phase change shifts from type (1) to type (3) via type (2).

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Two-dimensional (2D) echocardiography has become an indispensable diagnostic tool, because it can noninvasively display an arbitrary cross-section of a heart in real time. For a better understanding of heart motion and function, however, three-dimensional (3D) views are more desirable.
This paper presents a method for reconstructing 3D left ventricular images from 2D echocardiograms. Previously reported 3D reconstructions utilized rotated long-axis cross-sections or cross-sections tilted in regular sequence. Unfortunately, the image quality of a cross-section obtained in such a regular sequence is not always good. The present method is more flexible, because any cross-section with good quality may be used. A special manipulator with four degrees of freedom has been developed, so that 3D coordinates and the orientation of an ultrasonic probe can be obtained. Echocardiograms recorded in VTR are digitized and left ventricular contours are automatically extracted. If the image quality is too poor for automatic contour extraction, the tracing of contour by hand is used. Extracted contours are placed in proper spatial relationship by taking the position and the orientation of the probe into account. Then their projections or stereo pairs are displayed. For a further refinement, wiregrid models of contour surface are developed by interpolation. Hidden line elimination, smoothing and shading are effectively applied in the manner of computer graphics. Three-dimensional regional contractility and volume changes can be quantitatively calculated.

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Many variability indices, which have been proposed to quantitatively represent both short-term variability (=STV) and long-term variability (=LTV), were analyzed mathematically and the following static property was obtained.
All of the approximate expectations for indices developed by Tarlo, Kero, Dalton, Heilbron and Cabal assumed the same formula k√1-ρσ (k: constant, ρ: correlation coefficient between the beat-to-beat interval T_i and the adjacent interval T_i+1, σ: standard deviation of T_i), and were indentical except for the constants. Those values for de Haan's and Yeh's indices were k√1-ρσ/T₀ (T₀: mean of T_i), while those for Modanlou's, Wade's, and Organ's indices were k√1-ρσ/T₀² respectively.
Hence, all of these indices represented the same quantity in essence when the mean beat-to-beat interval was constant. The expected value for de Haan's and Heilbron's LTV indices was approximately k√1+ρσ (k: constant), while those for Yeh's, Organ's, and Cabal's LTV indices essentially showed standard deviation (=σ) of T_i.
From these results, it can be concluded that measuring STV and LTV according to those formulae means evaluating ρ and σ at the same time.
Hence, there may be little significance in measuring them individually if ρ changes little. That is, it may suffice merely to measure the standard deviation (=σ) of T_i as a quantity of variability.

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The mechanical behavior of vascular walls has been analysed by using a homogeneous, incompressible and curvilinearly orthotropic thick cylinder model based on the finite deformation theory.
First, for the deformation of vascular tissues, an existence of a (pseudo) strain energy density function has been assumed. The difference between the circumferential and radial stress components and the difference between the axial and radial stress components were expressed in two sets of series, the coefficients of which were determined from the pressure-volume and the force-volume relationships obtained experimentally. The strain energy density function and the stresses in the vascular wall were obtained accurately from the series just determined. The stress-strain relation of the vascular wall element was also derived in a simple manner.
The method proposed here is different from the works so far reported on the following points: (1) The differences of the stress components are not assumed as the specific form such as an exponential function or a polynomial, so that the results are accurate over the full range of the experimental data. (2) The expressions of the strain energy density function, the stress components in the wall and the stress-strain relation of the wall element are derived analytically, so that they may be determined by a simple calculation without using numerical integrations and/or iterative calculations.

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Localization of potential sources in the brain from the superficial potential distribution data, measured through surface electrodes, is one of the most promissing techniques to be used for clinical diagnosis of neurological diseases and even for the studies of the information processing mechanism of the brain. In order to get a reliable estimation for the dipole location and orientation, care has to be taken in many stages of the analysis.
In this paper we discuss and conclude (i) that electric pulse stimuli and click sounds are suitable for use in the dipole localization tests, because they can generate fairly confined potential distributions in the brain with rather short latencies; (ii) that the number of A/D converter resolution levels have little affect on the final accuracy of the data, when an averaging procedure is used for the data with fairly poor signal to noise ratio; (iii) that the amplitude measurement of waves with particular latencies requires suitable compensation of the base line instability, which could be realized via noise cancellation through linear prediction procedures; (iv) that the modeling accuracy of the 3-layered spherical model is practically acceptable for the dipole localization analyses, except for the data measured through electrodes attached close to the eyes, ears and the chin, especially when the orientation of the dipole source is pointing at those positions. These results are numerically obtained through the finite element method with an inhomogeneous model.
Finally, experimental data obtained by electrical stimulation of the median nerve are analyzed to get reasonable estimates for the dipole position along the sensory pathways in the brain.

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Postoperative deep body temperature rhythms in fifteen patients undergoing aorto-coronary bypass surgery (group I), and in seven patients undergoing non-cardiac major surgery (group II) have been studied. Analysis was made by Halberg's least squares method. Temperature rhythms of both groups were found to be greatly deviated from those under normal conditions. In group I, 2 patients showed ultradian rhythm, 3 patients, circadian rhythm, and 8 patients, infradian rhythm. In 2 patients, the rhythm could not be classified. In group II, 4 patients showed ultradian rhythm, 2 patients, circadian and 1 patient, infradian rhythm. The period of the rhythm cycle of group I (33.0±15.4 hours) was longer (P<0.05) than that of group II (19.5±8.0 hours). The variance of the mesor of group I (8.4°C) was larger (P<0.01) than that of group II (0.5°C). The variance of the amplitude of body temperature in group I (18.5°C) was also larger (P<0.05) than that of group II (2.6°C). As for acrophase, no significant difference was found between the two groups (14°30'±5°45' in group I, 9°54'±4°48' in group II). It took 6.0±1.3 days after surgery for temperature rhythm to return to 24-hour cycle in group I. On the other hand it took 3.8±1.6 days in group II, indicating speedier recovery of the 24-hour rhythm than group I (P<0.01). It was concluded that the cardiac surgery group showed greater temperature rhythm disturbance compared with the non-cardiac surgery group.

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A new inductive plethysmograph has been developed for non-invasive respiratory monitoring. This device consists of two coils of insulated wire sewn onto elastic bondages that encircle the rib cage and abdomen, and electronic circuits for detecting the deviation of the oscillation frequency caused by the change in the length of the coils. The deviation is nearly proportional to tidal volume, and is converted into voltage change by phase locked loop. The static accuracy of the device is tested by comparing its output with that of a hot wire flowmeter. The difference between the two outputs is within ±10% for normal respiration, but the output of the device shows saturation when tidal volume exceeds 2l. The movement of the body does not have much effect on the accuracy.

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