We developed a mathematical model for quantifying the progress of platelet aggregation by applying the chemical kinetic theory. We established a linear inverse problem to obtain a reaction rate constant matrix which is related to the progress of aggregation. The matrix was obtained from the time series data of the numbers of small, medium, and large aggregates and their subtracted data measured by the time-resolved laser scattering method (TRLSM). The algorithm for solving the inverse problem was developed by employing the Moore-Penrose generalized inverse matrix with the singular value decomposition technique. We analyzed the experimental data with our model to investigate (1) the dependence of the ADP-induced aggregation in platelet rich plasma (PRP) on the concentration of ADP, and (2) the mechanism of aggregate formation induced by 3 different agonists, ADP, epinephrine, and collagen. The results suggested the applicability of the proposed method to quantify the progress of the platelet aggregation using classification by mechanism of aggregate formation.

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This paper presents a probabilistic evaluation of electromagnetic interference caused by portable telephones in implantable cardiac pacemakers. Based on experimental results of electromagnetic interference in the 900 MHz and 1.5 GHz band PDC(Personal Digital Cellular)system in Japan, a distribution is extracted of the maximum distances between the affected pacemaker and a portable telephone. This paper shows that the distribution is approximated as a Rayleigh distribution using statistical analysis. The interfering probability for which the maximum distance of X cm is exceeded is defined based on the product of the cumulative distribution of the Rayleigh distribution and the ratio of the affected pacemaker types to the measured ones. The interfering probabilities that exceeded the maximum distance of 15 cm for the 900 MHz and 1.5 GHz band portable telephones are 5.0×10^-4and 6.0×10^-4, respectively. The expected values, which are a product of the interfering probability and the number of measured pacemaker types for the 900 MHz and 1.5 GHz band portable telephones, are 0.210 and 0.248, respectively. The continued surge in the number of pacemaker types indicates that the expected values will continue to increase. If the immunity of the new pacemaker types in the future maintains the same level as that in the present, this paper indicates that the maximum distance of the new pacemaker types must continue to be confirmed using the electromagnetic interference test.

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It is necessary for brain-computer interfaces (BCIs) to be non-offensive devices for daily use to improve the quality of life of users, especially for the motor disabled. Some BCIs which are based on steady-state visual evoked potentials(SSVEPs), however, are unpleasant because users have to gaze at high-speed blinking light as visual stimuli. Furthermore, these kinds of BCIs may not be used as universal devices because SSVEPs are not detectable by some users. Considering these facts, we propose a novel BCI using a non-direct gazing method based on transient VEPs. This interface uses a low-speed blinking lattice pattern as visual stimuli, and users gaze at other visual targets displayed on the right and the left sides of the stimuli. The gaze direction was determined by the waveform difference of transient VEPs detected when users gazed at either target. This mechanism was established by the result of exploratory experiment that indicated transient VEPs were detected even when users did not gaze at stimuli directly and two different types of waveforms were shown depending on their gaze direction. Compared with SSVEP-based BCIs, the proposed BCI is less annoying because it uses a low-speed blinking pattern as visual stimuli and users do not have to gaze at the stimuli directly. In addition, bipolar derivation could reduce unnecessary signals and the number of responses used for signal averaging to detect transient VEPs, which led to shorter detection time of the VEPs providing this interface with acceptable speed as a BCI in terms of determining gaze direction. Experiments with 7 volunteer subjects showed a 90% accuracy rate in gaze direction judgments. The result suggests that the proposed BCI can be used as a substitute for SSVEP-based BCIs.

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Prediction of drowsiness based on an objective measure is demanded in machine and vehicle operations in which human errors may cause fatal accidents. Currently we focused on the pupil of the eye which is controlled by the autonomic nervous system, and easily observable non-invasively from the outside of the body. We employed uneventful driving simulation to induce drowsiness of human subjects, and an anti-saccade task to evaluate their cognitive and motor performance. First we confirmed that pupil diameter fluctuates with large amplitude at low frequencies when the subject is aware of his/her drowsiness as reported previously. During this period, the reaction time of anti-saccade initiation was elongated and varied. We then found that prior to this fluctuation, pupil diameter decreases gradually in most subjects, and they were not aware of sleepiness during this period. We conclude that this monotonic gradual miosis can be a reliable premonitor of drowsiness.

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To perform the instantaneous radial blood pressure measurement based on the volume-compensation method, a reference value for the servo control (V₀) has to be determined in the initial stage of the measurement. The volume-oscillometric method with a photo-plethysmography has previously been used to determine the V₀. However, an operational time by this method requires more than 30 s. In order to reduce this time and/or to reset quickly the V₀ when it suddenly changes during the measurement, we have developed a new method to determine the V₀ more quickly. In this new method, sinusoidal vibrations having a frequency of 20 Hz and an amplitude of 10 mmHg are superimposed on the cuff pressure that is increasing by the rate of 20 mmHg/s. The V₀ can be determined by detecting a mean value of the photo-plethysmographically measured arterial volume showing the maximum volume amplitude corresponding to the pressure vibration component. The validity of this method was evaluated using twenty healthy subjects by comparing with the volume-oscillometric method as a reference. The results indicated that the present method could determine the V₀ with very high accuracy: The average of the ratio of V₀ determined by these two methods was 1.002 with standard deviation of 0.012. This paper also described the effects of the levels of blood pressure, pulse rates and the circumferences of the wrists on the determination of V₀, together with the resetting of V₀ during the instantaneous blood pressure measurement when the initial V₀ was suddenly changed due to an artificial operation.

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Mechanical failure of the cemented hip stem is mainly caused by several cement mantle problems such as cement fracture. Geometries of the cement mantle and the stem are important factors of failure risks. Shape optimization, especially multi-objective optimization, is required to solve these design problems, because the cement fracture is caused by multiple factors. In this study the stem design was optimized using a genetic algorithm suitable for multi-objective optimization. A three-dimensional finite element model of the proximal femur was developed. Two objective functions, the largest maximum principal stresses of proximal and distal sections in the cement mantle, were used. The Neighborhood Cultivation Genetic Algorithm (NCGA) was introduced to minimize these two objective functions. In the results, geometry that decreases the proximal cement stress and the geometry that decreases the distal cement stress were not consistent. The distal cement stress decreased with decreasing distal stem width and decreasing proximal-lateral section width. However, it led to increase of the proximal cement stress. The method in this study can be easily applied to another calculating conditions. The multi-objective optimization with genetic algorithm is useful for shape optimization of the cemented hip stem to avoid cement fracture.

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Many researches and developments have tried to realize a μTAS in several fields, but it has not been realized yet because of a scale effect in the course of miniaturization. It is difficult to make an enough volume of flow in a micro tube. This is a bottleneck of realizing the μTAS. We have tried to apply a unique mechanism of insects to the μTAS devises. In this paper, we focused on a blood-sucking mechanism of a mosquito that can obtain blood at the rate of approximately 1.0 μl/min. To understand the structure of their pumps, we made a mosquito into many slices, and anatomized under a microscope; we also let mosquitoes feed on human blood on a glass plate. We found the following results: 1) a manner of blood sucking, 2) a power density of the pump system by an analysis of flowing red blood cells at a tip of proboscis of mosquito. We have succeeded to reveal the blood-sucking mechanism of the mosquitoes, which can be applied to micro fluid devices.

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In order to measure noninvasively living body information using photoacoustic spectroscopy(PAS), fundamental investigation regarding a high sensitivity detector was carried out by the finite element method(FEM). The mathematical model reflecting the physical mode regarding a signal generation, propagation and detection of PA signal was used, and the analysis for optimizing PA detector cell was carried out. First, in order to detect the PA signal with high sensitivity, it was shown that it is necessary to make total volume of a cell small. Next, the influence on sensitivity due to in the gap between a target sample and a detector cell was evaluated. As a result, it was shown that there is not a large influence on the detection of the PA signal, even if both degree of adhesion changes slightly. Furthermore, the sensitivity of a resonant type cell and a non-resonant type cell was compared, and it was shown that the sensitivity of the resonant type is about 9-120 times that of the non-resonant type. From these results, the conditions for achieving the PA detector cell with high sensitivity were suggested.

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Torsion movement of the left ventricle has significance in ventricle contraction and dilation. In this study, we propose methods of analyzing torsion movement of whole body and local region of left ventricle using three-dimensional images of MR Phase-contrast method. The method calculates torsion angle from average angular velocity of central axis by determining central axis from velocity field and torsion ratio from relative velocity of cross sections. In addition, we propose a method, which has no need for determining central axis, by calculating time variation of principal strain. Results showed maximum value of torsion ratio of endocardium between ventricular apex and base in the end of contraction. In addition, the result showed that torsion between cross images in the beginning of contraction and dilation is large and torsion within cross image is large in the end of contraction and dilation.

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This paper describes the development of the intention transmission support system, which uses the eye blink that deals with the amyotrophic lateral sclerosis (ALS) patient. ALS attacks the motor neurons, nerve cells in the brain and spinal cord that control the body's voluntary muscles. As the disease progresses, ALS patients gradually lose the use of their arms, legs, and neck muscles, ultimately becoming paralyzed. Because of that as for the ALS patient intention transmission becomes very difficult. Furthermore, many ALS patients are usually maintaining control of a motion of blink. The ALS patients can therefore use blink for communication. Eye blinks can be classified into voluntary blink and spontaneous blink. If the spontaneous blink is considered as operation of a switch, there are many incorrect inputs. Because the spontaneous blink things happen unconsciously. Therefore, the spontaneous blink is not suitable as operation of a switch. On the other hand, a voluntary blink can be used as operation of a switch. The EOG amplitude indicated that the value for the spontaneous blinks was significant difference between the spontaneous blinks and the other blinks for the duration of the EOG. In addition, the blink waveform is different from the eye movement EOG waveform. It is possible to extract a blink from an EOG waveform by the amount of change of the corneoretinal potential. Experimental measurements were performed in order to extract the voluntary blink from EOG waveforms. Two kinds of blinks, spontaneous, voluntary, and eye movement were measured for 8 men using EOG in the vertical direction to the right eyelid. As a result, all subjects were extraction rates more than 94%. We evaluate the usefulness of communication tool using voluntary blink. Therefore, we experimented on the character input. As a result, all subjects were success rates more than 88.5%. From what has been discussed above, we can conclude that voluntary blink can be used as operation of a switch.

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In this paper, an underwater shock wave propagating into a cell is analyzed by finite element method, The cell is attached on the wall in water. The fluid part and the cell part are coupled with one-dimensional viscoelastic wall. The result shows that high shear stress is generated by the shock wave in the cell membrane. The frequency of shear stress and the maximum shear stress increase when the rise time of the shock wave is short.

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When the motor unit action potential is observed with a multi-channel surface electrode, the motor unit action potential that appears in each channel will contain information on three dimensions at the position and time. However, a method of using information on three dimensions for the technique of identifying the motor unit by using template matching from the multi-channel surface electromyography has not been found. The purpose of this study is development of a motor unit identification technique that uses the grid multipoint induced surface electromyography. Therefore, we developed a technique for identifying the motor unit that applied three dimensional templates to a 7×8 channel surface electromyogram with a grid surface electrode, searched for the time and the electrode positions in which the action potential waveform that belonged in each single motor appeared, and classified it.

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We have developed control method of local density in fluid microcapsules to make use of ultrasound drug delivery system. It has been difficult to enhance the efficiency of medication because capsules solution diffuses after the injection, where motion of capsules in blood flow cannot be controlled. Then we have noticed that microcapsules are trapped by acoustic standing wave of ultrasound in water. We have applied this method to an artificial blood vessel and observed the variation of capsules density by using the software, which we have developed to detect local change of the brightness variation on echogram. The result indicated that capsules density increases in the upper course of the point where the standing wave is produced. We have also prepared another artificial blood vessel with bifurcation in it. We have recorded echogram of two lower courses after the bifurcation and evaluated the brightness average of the two regions in each course, when the standing wave is produced at a lower course near the bifurcation point. As the result, we confirmed that the density in microcapsules decreases when standing wave is put on the course, where the density increases on the other course. It shows a possibility to control microcapsules direction and to lead to an objective point in blood vessel.

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Step counters are popular for quantifying walking. However, they may not measure the number of steps taken by elderly persons. In this study, we proposed a step count algorithm based on a filter bank and threshold processing to improve the accuracy of an accelerometer-type step counter for elderly persons. The accuracy of the proposed algorithm was compared with the observed steps taken during walking. The waist acceleration signals during self-paced walking were recorded for 74 attendees (age 82.7±8.6 yr, height 148.1±7.6 cm, weight 52.3±7.8 kg) participating in gait training at a rehabilitation services center using a triaxial accelerometer. The participants walked approximately 20 m (10 m in each direction and a turning arc). After seven different band-pass filters were applied to the magnitude of the acceleration vector, a signal related to the step cycle was selected from the outputs of those filters. Then, the number of steps was estimated from this signal using a predetermined threshold. The percent error was calculated as (estimated steps-observed steps)/observed steps×100. On verifying the algorithm using the data for the 74 elderly subjects, the steps taken by 57 (77.0%) were estimated with less than 10% error. We suggest that our step count algorithm is suitable for estimating the number of steps taken by elderly persons.

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