Some systems to measure voided volume and flow rate have been developed. Clinically, urination parameters are measured using uroflowmeters that have special receivers such as cups or bowls. Since these uroflowmeters were developed for clinical use, home use is difficult and inconvenient. Many of these devices require equipment cleaning; additionally, most are too expensive for home use. To address these problems, we developed a method to measure voided volume by noncontact matrix temperature sensors that are installed under a toilet seat. The basic concept is as follows. Urine is excreted at core temperature of 37℃. The heat radiated from urine during excretion is measured by noncontact matrix temperature sensors, and the measured radiated heat is converted to urination volume. A preliminary study was conducted to estimate the voided volume using an actual toilet bowl. The noncontact matrix temperature sensors simultaneously measure the temperature of falling water at 37℃ in 16 areas using a matrix of four lines and four rows. Four noncontact matrix temperature sensors were installed at the front, rear, left and right of the underside of a toilet seat. The toilet seat equipped with the four sensors was installed on a toilet bowl. The position of the falling water was fixed at 120 mm from the front sensor. Water volumes of 100, 200 and 300 ml were passed vertically at flow rates of 10, 20, 30 and 40 ml/s. As a result, the surface of the toilet bowl was slightly heated from the heat of the falling water, and the toilet bowl retained the heat after the water had fallen. To eliminate overestimation of heat from the toilet bowl, we proposed two analytical methods: a bias temperature elimination method and a time limitation method. For all four flow rates, the variation of U with a proportional volume obtained by the time limitation method was smaller than that by the bias temperature elimination method.

Aortic wall changes dimensions and mechanical properties in response to mechanical stimulation. As these changes are driven by the cells inside the wall, and their mechanical response has been suggested to exhibit a close correlation with nuclear deformation, it is necessary to study the deformation of the aortic wall at microscopic level. Hence, we obtained 200-µm-thick slices of rabbit thoracic aortas in the circumferential-radial and longitudinal-radial planes, and stretched them in the circumferential and longitudinal directions, respectively, under a microscope. The nuclei of smooth muscle cells (SMCs) were stained with Hoechst33342. Each slice was repeatedly stretched stepwise by 4%, while the fluorescence images of the cell nuclei as well as the elastin auto-fluorescence were captured at each step. Macroscopic and microscopic stretch ratios were obtained from the fluorescence images. Local Green strain was calculated from the change in internuclear distance in a specimen stretched in the circumferential direction. The local tissue strain in the circumferential direction was 0.8 to 2.1 times the macroscopic tissue strain, indicating that the aortic wall deformation was heterogeneous at microscopic level. The shear deformation between adjacent elastic laminas was evident at specific locations, resulting in a shear strain as large as 10%. We also evaluated the relationship between tissue deformation and nuclear deformation from the change in nuclear shape in the specimen stretched in the circumferential and longitudinal directions. In the circumferential stretch, the strain calculated from the length of the nuclei was less than 70% of the macroscopic strain, suggesting that the nuclei of the SMCs are much stiffer than the cytosolic components. Some nuclei rotated noticeably in response to the stretch, and the average and maximum rotation angle was 5° and 11°, respectively, during the entire stretching process. In the longitudinal stretch, the change in nuclear length was not significant, suggesting that mechanical stimulation to the SMCs may be smaller in this direction, as reported previously. The present study shows that the deformations of both the extracellular matrix and cell nuclei are highly heterogeneous, which may have a profound effect on the vascular biology.

Measurement of instantaneous orthostatic heart rate change has been used as a screening method for care or rehabilitation for the elderly, because it allows evaluation of the autonomic nervous system. In this study, we developed a photoplethysmogram (PPG) measurement system on the forehead. The system has five sets of green light PPG sensors to measure instantaneous orthostatic pulse rate changes and is less prone to noise caused by body movement artifacts. We aimed to verify the effectiveness of the proposed method by comparing the accuracy of pulse rate measurements at the forehead and at the wrists. In the experiment, 11 young and healthy subjects were recruited, and were asked to wear an aging simulation kit during the experiment to simulate the standing-up movement of an elderly person. The pulse rates from forehead PPG, pulse rates from wrist PPG, and heart rates from electrocardiogram were measured simultaneously. The accuracy of pulse rate was evaluated by two indices: ER_b, the average of error rates for 10 s before standing up, was adopted as an index without body motion; ER_s, the average of error rates within 10 s before and after standing up and including the standing-up duration, was adopted as an index with body motion. Using these indices, statistical analyses including one-way ANOVA for contact pressures and paired t-test were conducted. For the error rates estimated from wrist PPG, a significant difference was found between ER_b and ER_s under most conditions, and ER_s was higher than ER_b. Meanwhile, for the error rates estimated from forehead PPG, no significant differences were found between ER_b and ER_s under most conditions. In addition, the ER_s was significantly different between wrist PPG and forehead PPG, especially at the center of the forehead at low contact pressure. Therefore, we confirmed that pulse rates measured by PPG placed at the center of the forehead with low contact pressure are highly accurate compared with those measured by wrist PPG. The proposed method is thus proven effective for monitoring instantaneous orthostatic pulse rate changes.

Individual capacity of recall memory varies greatly even among healthy young adults. Nevertheless, the difference in brain circuitry underlying varied memory capacity has yet to be fully investigated. We acquired electroencephalographic measurements from 43 healthy young adults while performing a demanding working memory task and studied the changes in regional cortical activity in relation to different levels of memory performance. The memory task involved sequentially presenting seven arrow pictures to a participant during the encoding period, who was then asked to recall the direction of one of the arrows in the sequence within the retrieval period. We divided the participants into three groups of high, intermediate, and low performance based on the weighted hierarchical grouping method. Regional brain activities were source-localized using multiple sparse priors method in the high- and low-performance groups, and group differences were determined by non-parametric permutation tests. Our findings showed that participants with higher memory performance exhibited wider distribution of cortical activity including the prefrontal and parieto-posterior cortices, whereas lower performance participants only exhibited stable activations across occipital regions. The results implied the importance of selective attention in order to attain optimal individual working memory performance. Furthermore, we suggest the potential role of the angular gyrus as an interplay between the prefrontal and posterior regions for the management of stimulus flow and signal control. Future works should focus on conducting more thorough connectivity analysis to investigate the relationship of cortical activations with individual working memory performance.

We investigated the delivery of rhodamine B and Oregon Green^®-labeled paclitaxel (OGLP) in ex vivo porcine carotid artery wall (CAW) samples after heating the reagents to 50–70℃ for 15 s. When the isolated CAW samples were placed in the heated fluorophore solutions, the penetration depth of the hydrophobic rhodamine B increased significantly compared with reference solution at 37℃. The penetration depth of OGLP also tended to increase upon heating to 70℃ for 15 s. We also studied the mechanism of this agent delivery enhancement by observing the inner surface structure and hydrophobicity of the CAW samples after heating. An expanded mesh structure at the inner surface of the heated CAW samples was observed upon heating above 70℃, and the mean hydrophobicity of the media layer also increased significantly. We hypothesize that heating at 60–70℃ for 15 s enhances the delivery of fluorophores to CAW samples as a result of an expanded mesh structure at the inner surface of the CAW, along with a simultaneous increase in hydrophobicity.

We studied the effects of interactive pressure on the delivery of hydrophobic rhodamine B to ex vivo heated artery walls to determine the optimal drug delivery conditions. The heated artery samples, which were maintained at 63℃ on the intimal surface, were prepared by heating for 15 s. Interactive pressure up to 10 atm was directly applied with a rhodamine B solution to the artery samples from the intima side over 30 s. The fluorescence brightness distribution of rhodamine B in the samples were measured microscopically to investigate the quantity and depth of drug delivery. We found a decrease in the depth of drug delivery in the heated artery samples compared with the reference artery samples. This decrease in drug delivery depth may have resulted from increased hydrophobic binding of rhodamine B at the intima because of heating. We also found a significant increase in quantity of drug delivery at a certain interactive pressure in the heated artery samples. Hematoxylin-eosin staining of cross sections of pressurized heated artery samples revealed delamination of the intima and extension of the internal elastic lamina. We hypothesize that the dependence of drug delivery quantity on the interactive pressure is attributed to morphological changes in the intima and the internal elastic lamina.

A new Hill-type model of skeletal muscle contraction referred to as the “SL/ST model” is proposed based on recent physiological findings: intact human skeletal muscles operate on the ascending limb (hereinafter referred to as the “as-limb”) and the descending limb (“ds-limb”) of the isometric force–length relationship; and stretch-evoked force enhancement (“ST-enhancement”) is found on the ds-limb. Dynamic behaviors differ remarkably between the two limbs. The model has two modes: a sliding filament mode (“SL mode”) and a stretch-evoked force enhancement mode (“ST mode”). The SL mode operates on the as-limb, and on the ds-limb when the muscle is shortening, while the ST mode operates when ST-enhancement occurs in the ds-limb. Transient force responses of the model to length perturbations were similar to those of frog semitendinosus muscles in vitro. Length responses to step change in load of the model suggest that the muscle is unstable and not static in SL mode on the ds-limb, while it is stable and static in SL mode on the as-limb and in ST mode on the ds-limb.

We have developed a brain-machine interface (BMI) rehabilitation system for patients with stroke and motor paralysis, which provides proprioceptive feedback upon successful generation of motor-imagery (MI)-induced event-related desynchronization (ERD) and a decrease in mu band (8–13 Hz) activity derived from hand motor imagery. This system consists of an electroencephalogram (EEG) amplifier operated using the MATLAB Simulink software; a pneumatic robotic exoskeleton to provide proprioceptive feedback to the paralyzed hand; and a tablet computer placed over the paralyzed hand to display a hand-action movie to facilitate ERD generation. The EEG amplifier was connected and synchronized via the exoskeleton and tablet computer with an Arduino microcomputer. Nine patients in the subacute stage of recovery after stroke participated in a neurofeedback training experiment, which employed the aforementioned system. During the 4 weeks of this study, the participants received 2 weeks of BMI-based or control interventions in a random and counterbalanced order, in addition to their daily conventional physiotherapy. The control intervention consisted of the same MI training as the BMI-based intervention, but the exoskeleton always provided proprioceptive feedback regardless of the ERD strength. The ERD strength in the affected hemisphere showed a desirable increase with a significant improvement of finger joint spasticity, only after the DMB-based intervention period, and not after the control intervention period. The proposed neurofeedback training can help patients with stroke and movement disorders, because increased ERD strength may lead to recovery of motor function.

We developed an excretion monitoring system equipped with non-contact temperature sensor and a semiconductor gas sensor installed under a toilet seat. The gas sensor is able to detect odors due to human excretion by transiently increasing the output. The peak amplitude and duration of the gas sensor output due to defecation were significantly greater than those due to urination. These results demonstrate the capability of the gas sensor in distinguishing whether the excretion is urination or defecation.

Simulation using computational methods is well-established for investigating mechanical and haemodynamic properties of blood vessels, however few groups have applied this technology to microvascular anastomoses. This study, for the first time, employs analytic and numeric models of sutured and coupled microarterial anastomoses to evaluate the elastic and failure properties of these techniques in realistic geometries using measured arterial waveforms. Computational geometries were created of pristine microvessels and microarterial anastomoses, performed using sutures and a coupling device. Vessel wall displacement, stress, and strain distributions were predicted for each anastomotic technique using finite element analysis (FEA) software in both static and transient simulations. This study focussed on mechanical properties of the anastomosis immediately after surgery, as failure is most likely in the early post-operative period. Comparisons were also drawn between stress distributions seen in analogous non-compliant simulations. The maximum principal strain in a sutured anastomosis was found to be 84% greater than in a pristine vessel, whereas a mechanically coupled anastomosis reduced arterial strain predictions by approximately 55%. Stress distributions in the sutured anastomoses simulated here differed to those in reported literature. This result is attributed to the use of bonded connections in existing studies, to represent healed surgical sites. This has been confirmed by our study using FEA, and we believe this boundary condition significantly alters the stress distribution, and is less representative of the clinical picture following surgery. We have demonstrated that the inertial effects due to motion of the vessel during pulsatile flow are minimal, since the differences between the transient and static strain calculations range from around 0.6–7% dependent on the geometry. This implies that static structural analyses are likely sufficient to predict anastomotic strains in these simulations. Furthermore, approximations of the shear strain rate (SSR) were calculated and compared to analogous rigid-walled simulations, revealing that wall compliance had little influence on their overall magnitude. It is important to highlight, however, that SSR variations here are taken in isolation, and that changing pressure gradients are likely to produce much greater variation in vessel wall strain values than the influence of fluid flow alone. Hence, a formal fluid-structure interaction (FSI) study would be necessary to ascertain the true relationship.

It has been reported that increased intermittent non-Gaussian fluctuations in the instantaneous amplitude of low-frequency heart rate variability (LF-HRV) are related to high mortality risk in cardiac patients. However, little is known about the physiological origin of the amplitude modulation of LF-HRV. The purpose of this study was to clarify the relationship between amplitude modulation of LF-HRV and that of low-frequency blood pressure variability (LF-BPV). Eight normal male subjects performed movie-watching and calculation tasks in a sitting position for 40 min each while electrocardiogram and continuous blood pressure waveforms were recorded. From these signals, we calculated the instantaneous amplitude of the LF-band RR interval (RRILFamp) signal and that of the LF-band systolic blood pressure (SBP) signal (SBPLFamp) via band-pass filter and Hilbert transform. All subjects exhibited significant and relatively high positive correlation coefficients between RRILFamp and SBPLFamp in both tasks (mean Pearson correlation coefficient > 0.45). Mean coherence in the 0.01–0.05 Hz band between RRILFamp and SBPLFamp was also significant in all but one subject (mean coherence > 0.42). These results indicate a relatively high positive correlation between the amplitude modulation of LF-HRV and that of LF-BPV. We calculated the peak time lags of the cross correlation between RRILFamp and SBPLFamp in the 0.01–0.05 Hz band. A negative peak time lag implies that the amplitude modulation of LF-HRV precedes that of LF-BPV. All subjects exhibited negative peak time lag in the movie-watching task. All but one subject exhibited negative or zero peak time lag in the calculation task. These results imply that the amplitude modulation of LF-HRV precedes that of LF-BPV in the frequency range of 0.01–0.05 Hz.

Asthma is a chronic respiratory disease, in which symptoms appear or intensify suddenly, even when patients are being monitored by doctors. Continuous measurement is important to monitor a patient's breathing without missing asthma attacks. In this study, we propose a method of continuous breathing monitoring in daily life using a wearable device. There are several studies using microphones to continuously monitor breathing during activities, which show various possibilities of extracting qualitative characteristics related to asthma. Other studies on breathing measurement using accelerometers or belts have achieved breathing detection and measurement without ambient acoustic noises. Taking advantage of the breathing sound and chest movement signals, they are simultaneously acquired using a chest-mounted device, which consists of a microphone, a photoreflector, and a flexible cover. Various acoustic noises and body movements are present in the environment. Thus, acquiring these two different signals in a complementary manner makes it easier to detect breathing in daily life. For monitoring asthma, we focused on detecting the breathing phases. Most of the asthma symptoms appear during the exhalation phase. Thus, phase detection plays an important role as an asthma symptom identifier. We developed a new algorithm for breathing phase measurement using both acquired signals. The algorithm is based on the periodicity of the chest movement signal. Breathing sounds are analyzed considering their frequency characteristics. In this paper, the basic performance of the proposed device in an experimental condition which is quiet and without participant movements is examined. The results of performance evaluation confirm that the left medial side of the second intercostal space is appropriate for placing the device and studying the correlation between breathing sound amplitude and tidal volume, which implies a potential to acquire tidal volumes. The phase measurement experiment shows that chest movement can be used for estimating the breathing period. The portable system developed can measure breathing in external conditions and tracking the wearer's location. Making the system portable expands the measurable situations and facilitates an acquisition of time and location information, which is useful in identifying the causes of asthma attacks.

The purpose of this study was to demonstrate the usefulness of a small inertia sensor for quantitative classification of movement disorders based on the change in mechanical energy in patients following a stroke. We measured the sit-to-stand motion in acute stroke patients using inertial sensors in a small clinic. Three acute stroke patients and three healthy adults performed the sit-to-stand paradigm. The three-dimensional angle in the global coordinate system of the inertial sensor attached to the participant's body was then calculated. The movements of healthy adults were measured using inertial sensors and a camera motion capture system simultaneously, and only sagittal plane angles were used for the analysis, which were similar in the two devices. Subsequently, link segment models were created, and the mechanical work until seat-off was calculated. In stroke patients, the thoracic potential energy was not converted to kinetic energy, and deceleration of the thorax was greater in stroke patients than in healthy adults. Furthermore, the mean pelvic kinetic energy in stroke patients was approximately one tenth of that in healthy adults. In healthy adults, the waveforms of the angular velocities of the thorax and pelvis were synchronized. Such synchronization was not observed in the waveforms of stroke patients. A reason for the low pelvic kinetic energy in stroke patients is the fact that deceleration of the thorax by lumbar muscles does not lead to acceleration of the pelvis. The lack of synchronization of thoracic and pelvic angular velocities reduced the energy transfer efficiency. The usefulness of a small inertial sensor was demonstrated based on the evaluation of energy change efficiency during the sit-to-stand motion performed by an individual following a stroke.

Our aim was to evaluate the effects of a 4-week training program using a self-powered pedaling wheelchair on brain perfusion in patients presenting with lower limb hemiparesis due to stroke, brain injury, or spinal cord injury. Our cross-sectional observational study included seven patients with lower limb hemiparesis (five men, two women; mean age, 68.3 ± 17.5 years), due to the following causes: cerebral hemorrhage (n = 1), stroke (n = 4), brain contusion (n = 1), and spinal cord injury (n = 1). The control group consisted of eight healthy participants (3 men, 5 women; mean age 62 ± 8 years). The training program consisted of five bouts of 3-min continuous pedaling per day (total, 15 min/day). The outcome variable of interest was blood flow velocity in the middle cerebral artery (time average peak [TAP], cm/s) measured using Doppler. TAP was measured at rest and after a 3-min pedaling bout, before and after the training program. In the patient group, TAP was significantly greater after the 3-min bout than at rest, both before and after the training program (p < 0.05). There was no effect of pedaling identified in the control group. In the patient group, TAP increased significantly (p < 0.05) after training, both at rest (36.9 ± 16.9 to 47.6 ± 13.8 cm/s), and after the 3-min bout (43.3 ± 13.3 to 50.5 ± 15.1 cm/s). Our pedaling wheelchair provided a safe and effective intervention to improve brain perfusion in this patient population.

Recent advances in in vivo neuroimaging have encouraged the development of noninvasive methods using near-infrared (NIR) light. The low resolution images through the skull with traditional NIR-I (700–1000 nm) were improved by the use of NIR-II (1000–1400 nm) because of reduced light scattering, weak autofluorescence, and low light absorption by intrinsic molecules such as hemoglobin and water. Nevertheless, there are few reports on the photon behaviors for this wavelength range within the brain. Using a Monte Carlo model, we analyzed the photon behaviors of NIR-II fluorescence within a heterogeneous medium that simulates the complex system of the brain and its surrounding structures. The system was modeled as a three-layered medium having optical parameters specific to skull, cerebrospinal fluid, and cortex. Photons that were assigned a weight equal to unity entered vertically through the skull surface. The weight of photons in a 100-μm depth from the cortex surface was evaluated. Quantum dots within a limited area were most efficiently excited by photons at 785 nm among three excitation wavelengths. Excitation efficiency of 670 nm against 785 nm was 93%. In the case of 488 nm, the efficiency was 73%. When quantum dots emitted fluorescence dependent on the excitation efficiency, on-axis coaxial fluorescence at 1300 nm was most efficiently detected by the image sensor. Emission efficiency of 720 nm against 1300 nm was 75%. In the case of 520 nm, the ratio was 48%. Furthermore, the angular dependence indicated more near ballistic fluorescence photons at 1300 nm than at 720 and 520 nm. Therefore, fluorescence photons at 1300 nm allow brighter and clearer imaging of vascular system in a 100-μm depth from the cortex surface using this optical system, compared with photons at 720 and 520 nm. The results obtained from this simulation are consistent with imaging data through intact mouse skull in a previous report.

The arterial baroreflex system is an important negative feedback system that controls arterial pressure (AP) within a normal range during daily activities. We have analyzed this system in anesthetized animals. Several issues need to be considered: the presence of physiological and measurement noises that interfere with the system identification, the closed-loop nature of the arterial baroreflex system, the existence of parallel feedback systems that may modify the system responses, and the presence of nonlinear responses. We opened the negative feedback loop by surgically isolating the carotid sinus baroreceptor regions from the systemic circulation. We eliminated the effects from parallel feedback systems by sectioning the aortic depressor and vagal nerves. We used a white noise approach to estimate the system characteristics under contamination of physiological and measurement noises. The arterial baroreflex system may be divided into the neural and peripheral arc subsystems. The neural arc represents the relationship between pressure inputs and efferent sympathetic nerve activity (SNA), which may be regarded as a controller subsystem. The peripheral arc represents the relationship between SNA and AP, which may be regarded as a plant subsystem. The neural arc reveals derivative characteristics whereas the peripheral arc reveals low-pass characteristics. Numerical simulations based on the analytical results indicate that the neural arc compensates for the slow peripheral arc to optimize the arterial baroreflex system in achieving both stability and quickness. Impairment of arterial baroreflex function is associated with cardiovascular diseases, and artificial activation of the arterial baroreflex system could be a device-based treatment for cardiovascular diseases associated with sympathetic hyperactivity. To improve the efficacy of such device-based therapy, we may need to understand the interactions between stimulated and non-stimulated baroreflex systems. Although static sigmoidal nonlinearity of the arterial baroreflex with threshold and saturation phenomena is well documented, dynamic nonlinearities are less understood. Further efforts are warranted to fully understand arterial baroreflex function and to apply the knowledge to the medical field.

The aim of this study was to measure maximum isometric force under two different conditions: active and passive conditions. The electromyograms (EMGs) were also measured. The elbow flexors of healthy subjects were studied. Six healthy subjects took part in this study. The isometric maximum force and the EMGs of the elbow flexors were measured under two contrasting conditions. The first was a standard isometric measurement in which a subject actively pulled a fixed wire using their elbow flexor at 100% effort (active). In the second case, the subject tried to keep their elbow at 90 degrees of flexion for as long as possible against external forces produced by an electric motor (passive). The highest force values were extracted during the isometric phase when the elbow angles were kept constant. Hence, the elbow angles were also monitored by an electric goniometer in the later measurement. The passive condition resulted in higher forces than the active condition in 4 of 6 subjects. For a subject who showed different maximum forces under the two conditions, the mean (standard deviation) measured maximum forces under active and passive conditions were 285.2 (11.0) N and 300.2 (14.1) N, respectively (p < 0.01). For the EMG, there were no significant differences between the two conditions. In conclusion, the passive condition used in this study enhanced isometric maximum forces compared to that obtained under standard isometric conditions.

During walking, arm and leg swings in healthy people are closely coupled temporally by interlimb coordination. A split-belt treadmill contains two belts that can be driven at different velocities, and is used to demonstrate the adaptability of human bipedal locomotion. Previous studies focusing on the use of split-belt treadmills in patients with neurological disorder demonstrated the existence of impaired temporal limb coordination in such patients, but the influences of neural and nonneural factors on interlimb coordination could not be examined separately. Further, the influence of limiting one joint of an arm on temporal coupling was unclear. The purpose of this study was to clarify the influences of limiting one arm joint and the corresponding compensation by the unlimited arm. Ten healthy young adults walked on a double-belt treadmill equipped with force sensors, during a tied-belt period (velocity of both belts = 0.9 m/s, 3 min) followed by a split-belt period (belt velocities = 0.9 m/s and 1.8 m/s, 6 min). The following experimental conditions were studied: slow side restrained, fast side restrained, and unrestrained (NR). A non-flexible bandage-type restraint limited the elbow extension to 20°. The correlations between the trajectories of arm and leg swings were analyzed using a Vicon motion capture system. The correlation coefficients between the restraint arm swing and slow- or fast-side leg swing were significantly lower in the restraint conditions compared to other condition in both tied-belt and split-belt periods. In particular, the anti-phase swing of the ipsilateral arm and leg and the in-phase swing of the contralateral arm and leg decreased. These results suggest that elbow limitation inhibits interlimb temporal coordination. The unrestrained arm swing increased in spatial amplitude, but maintained higher temporal coupling with the leg. Non-neural factors are expected to cause reduction of interlimb coordination in individuals having neurological disorders and joint limitations.

Electrodes that output electric current as conduction current are widely used to stimulate nerves and cardiac cells in human body. We designed a photoelectric dye-coupled polyethylene film for use as a thin film device to stimulate nerve cells by electric potential changes. The aim of this study was to measure its photoresponsive properties and to record in vitro biological response. When measured using a Kelvin probe system, the photoelectric dye-coupled film showed rapid rise and fall of surface electric potential in response to light-on-and-off. Light-evoked surface electric potential of the dye-coupled film increased in response to increasing light intensity. In vitro biological response to the dye-coupled film was assessed in isolated rat retinal tissues using a multielectrode array recording system. As positive control, electroretinogram-like waves were recorded in response to light from normal rat retinal tissue placed with the inner retinal surface at the bottom of the multielectrode array dish. In contrast, no light-elicited wave was recorded from degenerative retinal tissue isolated from retinal dystrophic Royal College of Surgeons (RCS) rats. When the dye-coupled film was simply overlaid on the degenerative retinal tissue with the inner retinal surface placed at the bottom of the multielectrode array dish, electroretinogram-like waves were elicited in response to light projected from the bottom. Plain polyethylene film without photoelectric dye coupling was used as negative control, and did not yield light-elicited response when placed on the degenerative retinal tissue. For detailed recordings of action potential spikes high-passed at 100 Hz, a nylon mesh anchor was placed on top of the preparation to ensure close contact between the multielectrode array and the retinal tissue with or without the dye-coupled film. In this experimental setting, the degenerative retinal tissue alone showed spontaneous action potential spikes as numerous small trivial amplitudes in the background noise, while the degenerative retinal tissue overlain with the dye-coupled film showed action potential spikes with increased amplitude in response to light against the background of spontaneous spikes. This study confirmed that the photoelectric dye-coupled polyethylene film is able to stimulate degenerative retinal tissue that has lost photoreceptor cells, and may function as a novel type of retinal prosthesis. Electric potential changes, probably as displacement current or capacitive current, may be an alternative approach to stimulate nerves in human body.

A hemoconcentrator is installed as a part of cardiopulmonary bypass to concentrate the blood by removing excess water and unnecessary electrolytes from the blood diluted with myocardial protection fluid. The hemoconcentrator must remove water from diluted blood efficiently and quickly and remove proinflammatory cytokines and other unwanted molecules, without losing useful proteins such as albumin. Especially, the pore diameter and diameter distribution of the innermost surface greatly affect the pure water permeability and sieving coefficient of the solutes. In this study, the pore structure of the inner surface of the membrane was observed, and pore measurement of hollow fiber hemoconcentrator membranes was attempted using a scanning probe microscope (SPM). The samples studied were commercially available hemoconcentrator membranes PUREMA A and B (JMS Co. Ltd., Japan) having asymmetric structures. A SPM was used using the dynamic force microscopy (DFM), cyclic contact mode. The deep and tortuous pore structure on the inner surface of the hemoconcentrator membrane was observed for the first time using DFM. The pores had an elliptical shape, elongated in the longitudinal direction. When the elliptical area on the inner surface of the hemoconcentrator membrane was larger, pure water permeability was higher, showing a correlation between the elliptical area and membrane functions. The mean major pore diameters and minor pore diameters as well as the equivalent pore diameter calculated from the tortuous capillary pore model were consistent. Using DFM, the three-dimensional tortuous capillary pores at the inner surface of a hollow fiber hemoconcentrator membrane could be studied, and pore diameter and distribution could be measured by image analysis. The results were supported by the tortuous capillary pore model. In the future, we need to clearly show the further superior innovations or creative/ingenious techniques related to this study. Further the state of new findings which contribute to development of a new hemoconcentrator and other semipermeable membranes will help to increase the value of this paper. This study is one of the key studies to achieve the targeted function for the transport phenomena through semipermeable membranes including hemoconcentrator.

This paper describes the designing of a fourth order low-pass filter (LPF) for portable ECG application. The proposed filter is designed by cascading one P-biquad and one N-biquad to form a fourth order filter. It is self-compensated and provides a 0 dB gain. It also acquires the same input and output common mode voltages, which helps to produce higher order filters. It consumes power of 7.2 nW with a supply voltage of 1.2 V. Dynamic range of 68.1 dB with noise of 61.2 µVrms is obtained. The proposed filter is designed for a cut-off frequency of 230 Hz, suitable for ECG application. With 100 Hz frequency and 100 mV_pp ac amplitude, HD₃ of 71 dB is achieved. The circuit is simulated in cadence software using Silterra 130 nm CMOS technology. Compared with other state-of-the-art designs, this novel LPF provides the largest dynamic range and the best figure of merit (FOM).

Cells sense the mechanical properties of their surrounding environment and activate intracellular signaling pathways that play important roles in cell survival, proliferation, differentiation, and migration. Migration of cells into an injury site is crucial for repair after injury and requires cytoskeletal reorganization and remodeling of focal adhesions that connect the cytoskeleton to the extracellular matrix. Thus, it is possible that a directional cyclic stretch stimulation of cells may facilitate the wound healing process and establish ordered tissue formation. Here, we investigated the effects of directional cyclic uniaxial stretch on wound repair processes of monolayer epithelial-like cells that was scratch wounded. We controlled the direction of scratched wound in cell tissue to be i) perpendicular to the stretch direction (perpendicular stretch), ii) parallel to the direction of the zero normal strain in the substrate θ₀ (～60º) (oblique stretch), and iii) parallel to stretch direction (parallel stretch). We found that cyclic stretching perpendicular to the scratched wound direction did not improve cell migration, whereas oblique stretching, by which cells were induced to align in the zero normal strain direction θ₀, significantly facilitated cell migration for wound closure even though the migration direction was varied. We further found that cell migration for wound closure was improved most efficiently by cyclic stretching parallel to the wound direction, which facilitated polymerization of actin cytoskeleton aligning in the migration direction and vinculin–actin interactions. These results indicate that cell migration for wound healing is significantly influenced not only by the normal strain applied to cells but also by shear strain under cyclic strain fields, and cells for wound healing preferentially migrate to the direction in which both the normal and shear strains applied to them become smaller.

Magnetocardiography (MCG) is an effective modality for clinical application and health monitoring due to non-contact measurement and mapping of heart activity at high spatial resolution. A superconducting quantum interference device (SQUID) magnetometer is usually used for measuring MCG signals. However, a SQUID magnetometer has high running cost due to the liquid helium. Moreover, measuring MCG signals inside a magnetically shielded room (MSR) can be costly. Therefore, we developed a 64-channel magneto-impedance (MI) sensor system that does not require an MSR. However, the MCG measurement has very high noise level without an MSR. In this paper, we discuss the signal processing techniques of various noise reduction methods to decrease very loud noises. In particular, we investigated three spatial filter conditions that decrease correlated noises among the 64-channel signals to achieve a high peak value of MCG signals. By using a spatial filter that uses the average of the circumference channels and gradient, the distortion of MCG signals can be reduced. The average reduction in amplitude of the R wave as a result of using a spatial filter was 4.5 pT. Furthermore, the signal to noise ratio (SNR) of the P wave was 29.1 dB, while that of the R wave was 42.3 dB, and clear MCG signals were obtained when using the spatial filter that uses the average of the circumference channels and the gradient. Finally, we successfully measured the MCG signals without an MSR.

Percutaneous extracorporeal circulation therapies such as apheresis and hemodialysis are commonly used in intensive care units, hemodialysis centers, and clinically settings. In these treatments, there is always a possibility of continuous bleeding from the puncture site. Since the blood flow in these therapies is high, a hemorrhagic shock may be caused by severe blood loss, and - in the worst case - this may even lead to the patient's death. Therefore, it is important to continuously monitor blood leakage during the treatment. Typical procedures include the electrode method and the blood absorbance method, but their function may be affected by leakage of colored chemicals used, or by sweat or light. In this study, we developed a blood leakage determination module based on the chromaticity of a color sensor. Since the method is specifically sensitive to the red color, it can detect blood leakage. We performed experiments to verify the effectiveness of the proposed method and compared this new procedure with the existing ones, and we confirmed that the proposed method correctly detected blood leakage. Moreover, we investigated the blood detection capability of our new procedure and found that it could be applied to detect hematocrit levels within the range of 2% to 64%. We developed a multicolor sensor module and established a blood leakage detection method to meet the conditions that we had set as our goal. Our study confirmed that the proposed method did not cause malfunction due to leakage of chemical or presence of obstacle in the light path, while the traditional methods did. We also evaluated its performance and found that our method was able to detect blood leakage within the hematocrit range of 2% to 64%.

To evaluate muscle function accurately, it is necessary to simultaneously measure electromyogram (EMG) and mechanomyogram (MMG). We have developed an MMG/EMG hybrid transducer system that can simultaneously measure displacement-MMG (dMMG) and EMG, and reported that the dMMG and EMG measurements reflect muscle strength during dynamic exercise. The analysis of dMMG and EMG in our previous studies only calculated the total power spectrum obtained from discrete Fourier transform (DFT). Using this method of analysis, however, it is difficult to present information on muscle contraction in real time during exercise because of high computational cost due to huge amount of computation by DFT. In the present study, we propose a simplified method to evaluate muscle contraction during dynamic exercise by directly processing dMMG and EMG in the time domain. We adapted the dMMG/EMG data during recumbent bicycle pedaling obtained in our previous study to perform time-domain analysis. The novel time-domain analysis yielded equivalent results as those of previous analysis, and reflected muscle contraction during dynamic exercise. In addition, because dMMG and EMG by the proposed analysis increased with load increase during prolonged pedaling, it may be suitable for real-time monitoring of muscle function. The proposed method not only accurately measures muscle function during dynamic exercise in real time but also has a significantly lower computational cost.