Advanced Biomedical Engineering
Online ISSN : 2187-5219
ISSN-L : 2187-5219
Volume 6
Displaying 1-19 of 19 articles from this issue
  • Kenzo Akazawa, Tomoko Ichinose, Kakuko Matsumoto, Masayoshi Ichie, Tsu ...
    Article type: Original Paper
    2017 Volume 6 Pages 1-7
    Published: 2017
    Released on J-STAGE: January 25, 2017
    JOURNAL FREE ACCESS
    Supplementary material

    We have developed a novel electronic musical instrument with a pre-programmed score, called “Cymis,” to help the disabled enjoy playing musical pieces. In 2008, field experiments commenced at a nursing home (capacity 52 clients; average age 58.6; cerebral palsy 32 clients). The purpose of the present study was to demonstrate that Cymis is useful and effective for helping the severely disabled maintain or improve their quality of life. First, the accessibility of Cymis was revealed by the fact that 34 clients (63%) played Cymis for an average of 5.6 years. Second, each client’s progress in performance, which possibly reflects improvements of upper-limb motor control function, was examined for the longest duration of over 7 years. Among 31 clients, 13 (42%) showed progress, 17 (55%) showed no change (5 of whom showed progress initially but then regressed to their original status), and 1 (3%) revealed deterioration in condition. Third, psychological effects were measured using an original Face Scale before and after playing Cymis, for a total of 395 performances by 38 clients. Clients became happier in 208 performances (53%), showed no changes in 139 (35%), and became sadder in 48 (12%). Finally, with respect to their care plans, 19 of 52 clients (37%) selected Cymis in 2015, and this number itself implies the importance of Cymis. Basic reasons for selection were investigated by care workers’ assessments from mental and psychological perspectives. In conclusion, Cymis was useful, effective, and attractive to the disabled; it permitted them to enjoy playing music that might not otherwise be possible, and some evidence of therapeutic effect was found.

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  • Hiroyuki Tashiro, Yasuo Terasawa, Mariko Kuwabara, Koji Osawa, Takashi ...
    Article type: Original Paper
    2017 Volume 6 Pages 8-14
    Published: 2017
    Released on J-STAGE: February 17, 2017
    JOURNAL FREE ACCESS
    Supplementary material

    We have developed retinal prosthetic devices based on suprachoroidal-transretinal stimulation (STS). The effectiveness and safety of such novel devices are confirmed by in vitro and in vivo tests based on scientific knowledge. Animal testing is especially important because it demonstrates the total safety of the device. We successfully developed a long-term evaluation system with automatic stimulation and measurement of electrochemical characteristics in freely moving rabbits. This system allows evaluation of long-term safety and change in electrochemical characteristics. In addition, we conducted a pilot evaluation of the safety of STS using bullet-shaped electrodes in rabbits. No obvious injuries were observed in all examinations. However, the array moved away from the retina in a few rabbits. Visual and electrical evoked potentials (EEPs) were recorded after three-month implantation. The function of the retinal neurons around the electrode is assumed to be maintained because EEPs were observed after three-month stimulation. However, the evoked potentials become indistinct with time in some rabbits. The development of implantable recording electrode capable of long-term evaluation is necessary for assessing the function of retina exposed to electrical stimulation. Long-term safety and change in electrochemical characteristics can be confirmed easily using this system. No histological difference was observed between the active and inactive electrodes, suggesting that the amount of charge used in the study can be safely injected. The charge injection capacity (CIC) of these electrodes provides an indication of the safety threshold for STS. The electrode array should have a curvature to fit the eyeball to avoid movement of the array away from the retina. The electrode height is slightly greater compared to the sclera thickness. Accordingly, methods to enhance the CIC vs. geometrical surface area are required if the electrode height is reduced. We were able to obtain an indication of the required performance for the stimulation electrode based on the safe charge injection for STS (CIC of approximately 90 μC/cm2 in PBS) and establish a system capable of evaluating safety and durability of retinal prostheses for long-term stimulation.

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  • Akira Toyomura, Koichi Yokosawa, Shinya Kuriki
    Article type: Original Paper
    2017 Volume 6 Pages 15-20
    Published: 2017
    Released on J-STAGE: February 25, 2017
    JOURNAL FREE ACCESS
    Supplementary material

    Bipedal locomotion requires an automatic process for rhythmic motor generation, as well as volitional and precise motor control for purposeful action. The neural substrates for these two distinct locomotion controls in humans are still unclear. This functional magnetic resonance imaging (MRI) study investigated the neural activity of the locomotor-related brain regions along with participants' lower limb behavior. Participants lay face-up in the MRI bore and moved their legs up and down at the knees under two conditions. Under the non-obstacle condition, they moved their legs while watching a point-of-view video that showed walking straight along a corridor at a constant speed. On the other hand, under the obstacle condition, the point-of-view video showed walking while avoiding obstacles in the passage. Two white markers were pasted on the soles of the participants' feet and images were captured by a video camera throughout the experiment to track the participants' lower limb movements. The horizontal fluctuation of lower limb movement was extracted offline. We assumed that the horizontal fluctuation reflected participants' volitional behavior of lower limb movement. The results showed that the obstacle condition elicited greater fluctuation of lower limb movement compared to the non-obstacle condition, and elicited brain activation in wider areas including the parietal and occipital lobes compared to the non-obstacle condition. The involvement of the parietal and occipital lobes in volitional control is consistent with findings of previous animal studies. In a correlation analysis between the signal change extracted from the locomotor-related cortical/subcortical regions and the horizontal fluctuation of the feet, activities in the cortical motor areas (primary motor cortex, premotor cortex, and supplementary motor area) showed weak but significant correlation with the fluctuation of lower limb movement. Activities in the cerebellar and mesencephalic locomotor regions showed no significant correlation, but almost constant activation irrespective of fluctuation of the lower limbs. These results suggest that the parietal, occipital cortices, and cortical motor areas are involved in volitional control.

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  • Ryohei Sakata, Megumi Nakao, Tetsuya Matsuda
    Article type: Original Paper
    2017 Volume 6 Pages 21-27
    Published: 2017
    Released on J-STAGE: March 16, 2017
    JOURNAL FREE ACCESS

    Surgery can become safer and more reliable if the conditions of the organs can be physically and quantitatively assessed through simultaneous intraoperative measurements and physical estimations of deformed organs. This study proposes a new method for estimating external forces based on local displacement of elastic bodies. Using this method, one can estimate the magnitude and position of forces not only on the forceps but also in the invisible field. Simulation studies confirmed the effectiveness of this method. The experimental results showed that partial observation of a deformed shape achieved successful estimation of the external forces.

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  • Mayuko Takano, Shinsuke Yamagishi, Takao Ohmuta, Yutaka Fukuoka, Akino ...
    Article type: Original Paper
    2017 Volume 6 Pages 28-36
    Published: 2017
    Released on J-STAGE: March 25, 2017
    JOURNAL FREE ACCESS

    In this study, we improved upon a high-input impedance monitoring device comprising capacitive sheet electrodes placed under a bed sheet, aiming to detect all ECG waves including T waves. To accomplish this, we widened the passbands for ECG and respiratory movement (RM) signals. However, because this widening may lower noise tolerance, we substituted conventional front-end buffers with buffers able to discharge DC potential. Further, the backside of the modified electrode was doubly shielded by using the electric potential of the buffer's output and ground. We also introduced a virtual midpoint circuit to realize stable ECG and independent RM measurements of the chest and abdomen with the goal to detect obstructive sleep apnea in future applications. We tested our device on seven healthy adults during a six-hour sleep experiment. In all subjects, we detected T waves and observed ECG and RM signals in supine and lateral positions. In experiments in which respiratory rate was changed at regular intervals, the RM signal was synchronized with the simultaneously measured reference signal. The sensitivity and accuracy of R waves averaged over all subjects were 93.2% and 92.9%, respectively. Both averaged sensitivity and accuracy for T waves were 94.5%, while averaged accuracy of chest and abdominal RM was 70.9% and 74.0%, respectively. The results for ECG signals indicate that our improved system is applicable to unconstrained monitoring of vital signs in adults. Although there is still room for improvement in RM measurements, the results suggest that our system may also be used to detect variations in breathing.

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  • Chinami Taki, Naruhiro Shiozawa, Tetsuya Kimura
    Article type: Original Paper
    2017 Volume 6 Pages 37-41
    Published: 2017
    Released on J-STAGE: April 03, 2017
    JOURNAL FREE ACCESS

    It has been shown that injection of a minute electrical noise to an afferent input enhances the steadiness of force output, while reducing the variability of motor unit discharge intervals. To elucidate the involvement of alpha motor neurons in this noise effect, the effect of electrical noise injection into the soleus muscle (SOL) on the excitability of the alpha motor neuron group was examined. Nine young human subjects lying supine on a bed received a minute, subthreshold electrical white-noise-like stimulation to the SOL. In each subject, a 20-min trial with noise (Noise) and another 20-min trial without noise as control (Con) were performed in random order. The H-waves and M-waves were successively elicited at 1 Hz during each trial. The results showed that the static properties (mean, standard deviation, and coefficient of variation) of H-wave and M-wave amplitude fluctuations were not different between Noise and Con conditions (p > 0.05). On the other hand, the scaling exponent α, a dynamic property of the fluctuation of H- and M-wave amplitude, decreased significantly under Noise condition in H-wave amplitude (p < 0.05), but was unchanged in M-wave amplitude (p > 0.05). These results indicate that application of electrical noise to the afferent input affects the dynamic properties of motor neuron excitability, thus supporting the notion that the motor neurons are involved in the effect of noise injection on the motor control system.

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  • Kanchi Ito, Yuki Osawa, Kenta Kaneko, Yutaka Kikuchi, Masato Odagaki
    Article type: Original Paper
    2017 Volume 6 Pages 42-47
    Published: 2017
    Released on J-STAGE: April 03, 2017
    JOURNAL FREE ACCESS

    Two different experiments utilizing the motor imagery of finger movement were conducted. We attempted to reveal the difference in corticospinal excitability between tonic contraction (TC) and rhythmic movement (RM) by transcranial magnetic stimulation (TMS). The magnetic coil was placed over the subject’s primary motor cortex to elicit motor-evoked potentials (MEPs) by TMS. We have previously shown that the MEP amplitude is modulated by the frequency of active and passive finger movements. We hypothesized that visual feedback affects the corticospinal excitability. In the present study, the subject observed both TCs and RMs, and the MEP amplitudes elicited by TMS during both tasks were analyzed to assess changes in corticospinal excitability influenced by the motor imagery. A mirror box was used to show the subject the finger movement executed by a third person as if it were his own finger movement. For the TC task, the third person performed a pinching task consisting of TC of the index finger and thumb. The subject received visual feedback of the TC in the mirror. For the RM task, the subject observed the mirror while the third person performed RM of the index finger until TMS was applied. The frequencies of finger movement were 0.5, 1, 2, 3, and 4 Hz. The resulting MEP amplitudes for the RM task at movement frequencies of 2, 3, and 4 Hz were significantly lower than that for the TC task. These results indicate that corticospinal excitability is increased by visual feedback of TC but is modulated by that of RM.

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  • Xuan Li, Tadao Matsunaga, Yuji Suda, Takashi Sawai, Yoichi Haga
    Article type: Original Paper
    2017 Volume 6 Pages 48-52
    Published: 2017
    Released on J-STAGE: April 03, 2017
    JOURNAL FREE ACCESS

    Bronchoscopic diagnosis of peripheral lung cancer with ground-glass opacity (GGO) is difficult because GGO lesions cannot be visualized using currently available radial probe endobronchial ultrasound. Therefore, a forward-looking single fiber scanning optical coherence tomography (OCT) probe with a local observation function has been developed to achieve precise sampling. The new OCT probe is only 1 mm in diameter. The probe is composed of a patterned electroplated copper coil fabricated on a polyimide tube using non-planar photofabrication technique, and an optical fiber having a permanent magnetic tube with a diameter of 0.5 mm. When an electrical alternating current is supplied to the coil, the permanent magnet vibrates electromagnetically with the optical fiber. To increase the fiber vibration amplitude, a micro gradient-index (GRIN) lens is set in front of the tip of the optical fiber. Using the micro GRIN lens, the output beam is focused, and the scanning range is enlarged. The view angle becomes approximately 45°, and image resolution becomes approximately 60 μm. The structure of grating was successfully imaged using the new OCT probe. Further improvements and animal experiments are necessary to determine the clinical application of the probe.

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  • Mikie Nakabayashi, Yumie Ono
    Article type: Original Paper
    2017 Volume 6 Pages 53-58
    Published: 2017
    Released on J-STAGE: May 11, 2017
    JOURNAL FREE ACCESS

    Diffuse correlation spectroscopy (DCS) is an emerging optical technique for noninvasive measurement of hemodynamics of living tissues. Using emitter and detector optical probes attached to the body surface, DCS estimates the mean speed of blood flow in the tissue, through which the emitted near-infrared light propagates (blood flow index: BFI). The advantage of DCS is that the mean blood flow in deeper tissues such as muscle layers can be measured noninvasively. To investigate the sensitivity of DCS in detecting the physiological changes of blood flow in deep and shallow tissues, we measured the blood flow speed in 14 healthy participants during a reactive hyperemia test and skin temperature changes. In the reactive hyperemia test, blood flow returned to the steady state faster in deep tissues than in shallow tissues, and temperature-dependent reallocation of local blood flow in shallow and deep tissues was clearly observed. These results demonstrate that DCS can measure the differences in physiological blood flow dynamics in deep and shallow tissues, suggesting the potential use of DCS to noninvasively quantify changes at microcirculation level in both shallow and deep tissue layers.

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  • Mariko Kuwabara, Hiroyuki Tashiro, Yasuo Terasawa, Koji Osawa, Takashi ...
    Article type: Original Paper
    2017 Volume 6 Pages 59-67
    Published: 2017
    Released on J-STAGE: May 31, 2017
    JOURNAL FREE ACCESS
    Supplementary material

    Development of direct neural interface (DNI) including visual prostheses absolutely requires confirmation of their long-term safety and stability. Functional evaluation by electrically evoked potentials (EEPs) is effective in this regard, although the recording system must be stable for chronic use. In addition, control of anesthetic depth is important for stable recording of the evoked potentials. The purpose of this study was to develop a chronically implanted electrode capable of recording visual evoked responses safely during repeated anesthesia over long periods, which would allow more effective safety evaluations of not only visual prostheses but also DNI. We developed two types of electrodes, and implanted them into rabbits. A general screw electrode was used for comparison with the novel electrodes. Structurally, the newly developed platinum (Pt) ball-tip screw electrode consisted of a plastic screw with smoothly surfaced Pt balls on the tip. The depth of implantation into the brain was adjustable via a threaded insert installed in the skull. The newly developed platinum/iridium (Pt/Ir) ball-tip planar multi-electrode array (MEA) comprised Pt/Ir ball electrodes placed in a two-dimensional lattice pattern, which was implanted just beneath the skull. These electrodes recorded variations in visual evoked potentials (VEPs) in response to 20 J flash stimuli over a period of 48 weeks. After 48 weeks of implantation, the ability of the electrodes to continue recording EEPs was confirmed (500 µA, 500 µs, cathodic first biphasic). During the recording of VEPs and EEPs, stable anesthesia was maintained with isoflurane (end-tidal 2.4%). The depth of anesthesia using isoflurane could be adjusted safely, and allowed stable recording of evoked potentials throughout the long-term study. However, stable recording using the general screw electrode was possible only for a short period. We also obtained stable latency and N1 amplitude readings over the 48 weeks using the newly developed electrodes, and successfully recorded EEPs after the 48-week period. These results suggest that the novel electrodes work well over the entire duration of the study, and may allow assessment of long-term safety and stability of not only visual prostheses, but also other devices utilizing brain machine interfaces or direct neural interfaces.

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  • Tetsuo Sato, Haruka Dejima, Makito Haruta, Satoshi Kamikawa, Hitomi Na ...
    Article type: Original Paper
    2017 Volume 6 Pages 68-75
    Published: 2017
    Released on J-STAGE: June 24, 2017
    JOURNAL FREE ACCESS

    In this study, we used a small implantable complementary metal–oxide–semiconductor (CMOS) imaging device developed by our research group to estimate the blood flow changes by focusing on the movement of red blood cells in the captured movements. Conventional methods for determining blood flow velocity have limitations in that variation occurs due to manual measurement. Therefore, we developed a novel technique to measure blood flow in the brain. This method involves calculating the changes of selected pixels using a normalized cross-correlation coefficient. Using this cross-correlation method, we analyzed a mouse cerebral infarction model to detect changes in brain activity. The results of analysis showed that the average velocity of blood flow upstream of the infarction site decreased while the velocity in blood vessel parallel to the infarction increased after occlusion was induced. These results thus confirmed that the new method can detect blood velocity changes, suggesting the feasibility of the cross-correlation method for estimating blood flow velocity.

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  • Andrey Grushnikov, Kazuma Kikuchi, Yoshimi Matsumoto, Takeo Kanade, Ya ...
    Article type: Original Paper
    2017 Volume 6 Pages 76-82
    Published: 2017
    Released on J-STAGE: July 08, 2017
    JOURNAL FREE ACCESS

    In recent years, a rapid increase in bacterial strains resistant to modern antibiotics has been observed. This alarming rise in drug-resistant organisms has emphasized the importance of identifying new effective antimicrobial agents. Since traditional approaches for drug susceptibility testing are time-consuming and labor-intensive, more efficient methods are urgently needed. Here, we report an automatic image analysis system for drug susceptibility testing that provides results within 3 hours using a drug susceptibility testing microfluidic (DSTM) device. The device consists of five sets of four microfluidic channels prepared by soft lithography. The channels are in close proximity to allow simultaneous observations. The antimicrobial agent and bacterial suspension to be tested are added to the channel and incubated for 3 hours. Previously, microscopic images of the DSTM device were analyzed manually by an expert to evaluate the susceptibility of a strain. In this work, we present an automatic computer vision algorithm for processing images and performing analysis. The algorithm enhances the quality of the input image, detects cells in each channel, extracts a variety of cell-related characteristics, and estimates drug susceptibility using a pre-trained support vector machine. We address the issue of overlapping cells by incorporating a graph-based cell separation algorithm. The minimum concentration of a drug for which the proposed method predicted susceptibility represents the minimum inhibitory concentration (MIC). The novel method was implemented as a standalone application and tested on a dataset containing images of 101 clinically isolated strains of Pseudomonas aeruginosa incubated in the presence of five different drugs. The estimated MICs correlated well with the results obtained using the conventional broth microdilution method.

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  • Kazuhiko Yamashita, Emi Anzai, Tomoko Yamashita, Yuji Ohta, Mitsuru Sa ...
    Article type: Original Paper
    2017 Volume 6 Pages 83-87
    Published: 2017
    Released on J-STAGE: October 13, 2017
    JOURNAL FREE ACCESS

    Objectives: Foot problems are common in the elderly and are associated with impaired lower limb muscle strength, reduced balance function, and foot pain. We investigated the effect of foot care on these parameters as well as on medical costs in 32 community-dwelling elderlies (mean age 75.3 ± 6.1 years). They were divided into two groups based on pre-intervention fall risk assessed by lower limb muscle strength. In this study, we examined the impact of foot care intervention on medical costs by conducting an analysis on the medical costs of the subjects who had been compensated by the National Health Insurance or by the medical care system for those aged over 75 years.
    Measurements: Lower limb muscle strength was evaluated by measuring toe-gap force and knee-gap force. Balance capability was evaluated by the trajectory of the length and area of center of pressure (COP) and pressure ratio of toe contact with the ground. Medical costs were compared before and after intervention.
    Results: Significant increases in toe-gap force and knee-gap force were observed after foot care intervention. Post-intervention toe-gap force and knee-gap force were significantly lower in the foot pain group than in the foot pain-free group. The toe-gap force and knee-gap force in both groups improved significantly after foot care intervention. The subjects who had pain in their feet were significantly more likely to belong to the higher fall risk group. There was a reduction in medical costs for the group of the over-75 group.
    Conclusion: In community-dwelling elderly, foot care improves lower limb muscle strength and balance, which are associated with falls, and reduces medical costs.

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  • Kanae Hashimoto, Akiyoshi Hashimoto, Masumi Kishimoto, Kosuke Sugawara ...
    Article type: Research Letter
    2017 Volume 6 Pages 88-94
    Published: 2017
    Released on J-STAGE: October 24, 2017
    JOURNAL FREE ACCESS

    Background and Objective: Acute vasoreactivity testing using inhaled nitric oxide (NO) is performed to determine the treatment strategy in patients with pulmonary hypertension. Operators of the test are exposed to NO and nitrogen dioxide (NO2) to the same extent during the test procedure, but the safety zone for operators in the catheterization laboratory is unclear. This study aimed to clarify the safety zone for operators during the NO inhalation test. Methods: The mask was placed on the examination table in the catheterization laboratory. NO was added using the INOvent® (INO-Therapeutics, LLC), which was attached to an oxygen line and delivered NO to the mask. During simulated NO inhalation tests (n = 10) in a catheterization laboratory, NO and NO2 concentrations were measured at nine specified locations: at the mask outflow port (E0); 25 cm (E25) and 50 cm (E50) from the mask outflow port; heights of 25 cm (A25) and 50 cm (A50) above E0 and E25; and a height of 25 cm (B25) below E0 and E25. During NO inhalation testing conducted in 5 patients, concentrations of NO and NO2 were measured at E0 and E25A50. The Steel-Dwass and Student t-tests were used to perform intergroup analyses. Results: NO-E0A25 (0.00 ± 0.00 ppm), NO-E25A25 (0.01 ± 0.10 ppm), NO-E0A50 (0.00 ± 0.00 ppm), and NO-E25A50 (0.00 ± 0.00 ppm) were significantly lower than NO-E0 (17.01 ± 0.22 ppm), NO-E25 (4.06 ± 0.47 ppm), and NO-E50 (1.90 ± 0.39 ppm) (p < 0.01, all comparisons). NO2 concentrations were less than 0.1 ppm at all nine locations. NO and NO2 concentrations were not affected by room temperature (20, 24, or 28℃) or the flow rate of oxygen (15 or 10 L/min). During NO inhalation testing in patients, NO-E25A50 (0.20 ± 0.45 ppm) was significantly lower than NO-E0 (7.20 ± 2.39 ppm, p < 0.01); however, no significant difference in the NO2 concentration was seen between NO2-E0 (0.220 ± 0.179 ppm) and NO2-E25A50 (0.180 ± 0.205 ppm). Conclusions: An operator safety zone in NO vasoreactivity testing is a zone >25 cm in all directions from the mask for NO inhalation. The concentrations of NO and NO2 to which an operator is exposed in the clinical setting are within the permissible exposure limits defined by the National Institute for Occupational Safety and Health.

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  • Ryoichiro Shiraishi, Yoshiyuki Sankai
    Article type: Original Paper
    2017 Volume 6 Pages 95-101
    Published: 2017
    Released on J-STAGE: November 18, 2017
    JOURNAL FREE ACCESS

    This paper proposes a specific method of balance control learning at a half-rising posture using an assistive system for improving the pulling chair movement, and reports a case study of a quadriplegic wheelchair user. The system provides informatics-based biofeedback and user weight support. It does not require attaching any equipment or sensor to the user's body. Although our participant was able to transfer from a wheelchair to a chair, she was not able to pull a chair until the desired position. We analyzed the physical kinematics and kinetics during pulling chair movement and developed a balance control learning method that enables the user to move the center of gravity (COG) backward when assuming a deep half-rising posture. We conducted an experiment on a quadriplegic participant once a week for four weeks. Before learning, the participant was not able to realize the pulling chair movement even though a lot of time was provided. However, after learning, the participant could move the COG backward when attempting to realize the half-rising posture, and pull a chair completely. This case proved our hypothesis that a half-rising posture with backward shifting of the center of pressure is effective in improving the pulling chair movement. Through the experiment, we achieved proof of concept of the proposed learning method and the first case study of successful application of the method.

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  • Yuji Ishioka, Nur Elina Binti Zulkifli, Kenji Shiba
    Article type: Original Paper
    2017 Volume 6 Pages 102-109
    Published: 2017
    Released on J-STAGE: November 18, 2017
    JOURNAL FREE ACCESS

    Transcutaneous energy transmission systems (TETS), which use electromagnetic induction to wirelessly transfer energy, have been widely used as energy transmission systems for artificial hearts. TETS help to improve the patient's quality of life and reduce the risk of infection caused by percutaneous connections. However, to provide protection against the established adverse health effects caused by electromagnetic induction, it is necessary to quantify the amount of energy absorbed by biological tissues. In this study, we sought to analyze the specific absorption rate (SAR) and the internal electric field E of human biological tissues surrounding an air-core coil transcutaneous energy transmission transformer. We used four types of human biological tissue models with different genders, ages, weights, heights, and body sizes, at a frequency of 0.9 MHz. Each tissue model consisted of dry skin, wet skin, fat, muscle, and cortical bone tissue. A primary coil was placed on the surface of the dry skin tissue, while the secondary coil was embedded between the wet skin and fat tissues. The transmission power was 15 W, and the load resistance was 38.4 Ω. The simulation data was obtained using the FEKO electromagnetic simulator. The results showed that the SAR and E for adult models (male and female) were well below the limits specified by ICNIRP for both general public and occupational exposure. For children, the SAR and E exceeded the ICNIRP general public exposure limits but remained below the limits prescribed by ICNIRP for occupational exposure. These results show that it is safe to transmit 15 W of energy in an adult.

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  • Toshitaka Yasuda, Midori Fukiwake, Kenji Shimokasa, Yasuhiro Mine
    Article type: Original Paper
    2017 Volume 6 Pages 110-121
    Published: 2017
    Released on J-STAGE: December 01, 2017
    JOURNAL FREE ACCESS

    The present study proposes control target for the motion of an active self-feeding spoon by analyzing skilled spoon motions reflecting the grasping actions of healthy people eating specific foods. We measured spoon motions in terms of time (t), rotational (θ) and azimuthal angles (φ) while five healthy participants ate soup, malt balls, firm tofu, pudding, and yogurt. We developed a wireless angle measurement spoon with which to evaluate changes in the inclination angles (IAs) of the spoon and the correlation between θ and φ during scooping and transporting spoon motions. A negative θ value indicates that the surface of the spoon bowl has rotated toward the participant. A negative φ value indicates that the tip of the spoon bowl has rotated downward. After observing eating actions and measuring IAs (θ, φ, t), we examined the correlation between θ and φ using the coefficient of determination R2 with a second-order curve regression (2OCR) model. R2 of the scooping action exceeded 0.55 while that of the transporting action was less than 0.25. We found the effects of food type on the grasping action as follows. For soup, the scooping and transporting times were longer than those for the other foods. The spoon was rotated negatively to avoid spilling soup and malt balls at the end of scooping and at the start of transporting. Firm tofu and pudding required cutting and scooping actions. The grasping action of food at the end of transporting affected the IAs (θ, φ). The correlation R of the relationship between the 2OCR model for pudding (R2 = 0.79, highest among food types) and the 2OCR models for other foods exceeded 0.94. We suggest the control target of the active self-feeding spoon as follows: set IAs (θ, φ, t) at the start and end of scooping and transporting actions to avoid spillage induced by the inertial force of foods and to facilitate putting food into the mouth. IAs (θ, φ, t) during the scooping and transporting actions were applied to the 2OCR models for pudding (highest R2) and liquid food.

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  • Takumi Hase, Soichiro Ishigaki, Kazuki Shibusawa, Sakuya Hamanaka, Yuk ...
    Article type: Original Paper
    2017 Volume 6 Pages 122-128
    Published: 2017
    Released on J-STAGE: January 06, 2018
    JOURNAL FREE ACCESS

    Microfluidic devices are powerful bioapplication tools for cellular experiments in particular, as they can regulate physical and chemical parameters such as the flow rate, shear stress, oxygen, and molecular concentrations in a culture medium to mimic physiological and pathological microenvironments in vitro. However, as cell cultures take place in enclosed spaces, culture samples have to be removed repeatedly to monitor cell-derived metabolites and proteins in order to maintain the cellular microenvironment. We report a simple method for obtaining surface enhanced Raman scattering (SERS) spectra through self-assembly of a nanoparticle monolayer on polydimethylsiloxane (PDMS), which is commonly used in highly biocompatible microfluidic devices. Silica nanoparticles were stabilized as a hexagonal close packed structure on an O2 plasma-processed PDMS membrane, and was coated with silver using vapor deposition to create an SERS plate. When this SERS plate was installed in a microfluidic device, the nanoparticles did not peel off even after long-term fluid immersion. The SERS spectra exhibited stable SERS generation and an enhancement factor of more than 1.5 × 106 of the Raman signals from rhodamine 6G compared to the signals without nanoparticles. The SERS spectra of lactate and ATP were obtained, and Raman shifts due to the different masses of 12C- and 13C-lactate were observed, suggesting that the proposed method can be applied to determine the cellular metabolic flux in microfluidic devices. We also obtained cell membrane-derived SERS spectra by culturing murine mammary carcinoma 4T1 cells directly on the nanoparticle membrane. PDMS has high biocompatibility and is often used for fabricating microfluidic devices. Through tight binding of the nanoparticles to the O2 plasma-treated PDMS, the chemical reaction products or the metabolites from cells can be measured for a long duration, while maintaining the microenvironment. We anticipate that this technology can be utilized as a useful tool for analyzing cellular metabolic functions and imaging cellular distributions without staining in various pathological models created in microfluidic devices.

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  • Ryunosuke Kodera, Shigehito Tanahashi, Atsuhiko Iijima, Yoshinobu Maed ...
    Article type: Research Letter
    2017 Volume 6 Pages 129-133
    Published: 2017
    Released on J-STAGE: December 29, 2017
    JOURNAL FREE ACCESS

    We investigated why movement of the human eye enables us to swiftly find a target symbol out of many alternatives. To this end, we obtained experimental gaze step data, defined as the distance between two serial gaze positions, on a monitor screen. The frequency distribution of this data approximately follows a power-law distribution. Using this frequency distribution, we constructed a network model to replicate the gaze step dynamics, in which the vertices (or nodes) and the paths between two vertices correspond to the gaze positions (tremors or drifts) and the gaze steps (saccades), respectively. The constructed network has the features of a small-world network. We suggest, therefore, that there is a physiological mechanism in visual search, which reduces the size of the physically wide search area. Such eye movement can find the target symbol in a relatively short time proportional to the logarithm of the number of symbols on the screen.

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