This research examined the seismic behavior of medical equipment, which supports advanced hospital functions through shaking table testing and numerical analysis, and derived evaluation index for mitigating damage. The shaking table test observed the rocking and overturning of neonatal beds and a dialysis liquid feeding apparatus under sine waves and the building floor responses during earthquakes. The rocking and overturning damage occurred only when the casters of equipment were all locked, and the ratio between the equipment’s gravity center height (h) and leg width (b), b/h, is smaller than a certain threshold. The influence of equipment dimensions and weight on the seismic behavior was studied by parametric analysis using a distinct element method (DEM) model of equipment. The probability of damage decreased significantly when the ratio between the b/h becomes large. For the floor velocity response of 80cm/s, which is assumed for the approximate return period of 500 years and with the response amplification factor (the ground to floor response ratio) of 1.6, the probability of overturning became negligible when the b/h is 0.4 or larger. This paper also presents an analytical equation to calculate sufficient safety weights added to existing equipment for conforming to the above thresholds of b/h.

Novel artificial heart valves have been fabricated using tissue-regeneration techniques or the latest biocompatible materials. We investigated prototypes of such valves and experimentally measured how the valve size and shape influence the performance. A previous study reported that the hemodynamic performance during valve opening and closing was completely co-dependent. Combining the two performances was difficult using our fabricated semilunar valve made of a uniform thin membrane. Nevertheless, modifying the mechanical property of deformation balanced the opening and closing effectively for higher valve performance. This was achieved by adding mechanical anisotropy to the valvular cusp. This study aimed to establish how changes in mechanical property influence artificial heart-valve performance, particularly for semilunar valves whose shape is employed for atrioventricular valves as well. To add mechanical anisotropy to the valve cusp, we fabricated valvular-cusp models, with spatially periodic surface asperities using a polyurethane sheet. Its mechanical properties were identical to those of a porcine aortic valve. Further, to determine the optimal anisotropic properties of the valve cusps, sheet thickness and orientation direction of surface asperities were varied as experimental parameters. Subsequently, isotropic and fabricated anisotropic models were compared. The experiment was conducted using our fabricated in-vitro simulator under the physiological conditions of a healthy adult. Valve function was evaluated based on the international standards ISO 5840-1 and ISO 5840-2 for artificial valves. The results indicated that the functions of the valve model with anisotropic mechanical properties improved remarkably. The effective orifice area in particular, indicating valve-opening performance, was 1.5-2.0 times higher than the isotropic model with the same maximum cusp-sheet thickness. Additionally, the regurgitant fraction decreased remarkably; however, the anisotropic property did not affect its trend when cusp thickness increased. However, the thinner cusp had a lower leakage regurgitant fraction during diastole. Therefore, a combination of the anisotropic orientation on each valvular cusp and sheet-thickness distribution is effective for balancing both opening and closing performances of the valve.

All biological functions, including vision, are affected by time of day. It is known that the retinal response to visual stimuli changes according to circadian rhythms. However, the effects on visually guided behavior were poorly understood, and previous results have been inconsistent. The previous studies examined the effect of time on contrast sensitivity were also inconsistent, one reason for this could be the order effects, such as fatigue due to long measurement times. To overcome this issue, we applied a tablet PC based measurement system which made the measuring contrast sensitivity quick and easy. Observers participated in the experiment every morning, noon, evening, and night, and performed a task to detect a Gabor patch. The results showed that sensitivity improved from morning to night, and this trend was more pronounced in the mid- to high-frequency band. The improvement was reproduced even when measurements were taken once daily at random times. These results suggest that the improvement was not due to intraday learning or fatigue. We confirmed that our experimental system is useful for measuring the diurnal variation in contrast sensitivity, as it is quick and easy to use.

At facilities where the number of cases of cardiopulmonary bypass (CPB) is less than 100 per year, which accounts for 60% of the cardiac surgery facilities in Japan, it is difficult to acquire and maintain the operation technique of CPB by the open circuit. Therefore, a valve-type semi-closed extracorporeal circulation (VACC) system was devised. In the VACC, which is a closed circuit like ECMO (extracorporeal membrane oxygenation), the volume control reservoir (VR) is connected to the venous circuit via a check valve as a safety valve. The safety valve opens and closes depending on the pressure gradient between the VR which is under negative pressure and the venous circuit. As a result, the VACC can be switched between an open circuit and a closed circuit. For the purpose of improving safety in the case of air entering the venous circuit, which is the weakness of the closed circuit, water experiments to simulate an accidental venous decannulation were conducted. In the VACC, like the open circuit, when one of the two venous cannulas was decannulated, an air lock occurred. That is a phenomenon in which venous drainage and air movement are stagnant due to being obstructed by the siphon effect of a mass of air in the venous circuit. The safety valve was open when an air lock occurred, and it was easy for it to occur when the negative pressure was weaker. If a venous cannula is decannulated, the negative pressure in the venous circuit will be augmented, and then the pressure in the venous circuit will be limited to the pressure in the VR. Therefore, the suction power of a mass of air is reduced, and air movement is stagnant. As a result, an air lock occurs. When using a closed circuit, venous decannulation causes a large amount of air entering. On the other hand, the VACC can control air behavior in the venous circuit by adjusting the pressure in the VR;for example, by opening the VR to atmospheric pressure.

A conventional high-precision system for measuring microsaccadic eye movements requires a participant’s head to be fixed to maintain measurement accuracy. Therefore, it is difficult to observe microsaccades under psychologically natural situations because the contact measurement is a burden on the participant. We propose an eye-movement detection system that involves the following two methods. The first method is for non-contact measurement that combines a coarse eye position based on face detection from wide-angle images and high-precision optical eye-tracking-control information based on retro-reflected eye images from a high-speed zoom camera. The second method is for detecting microsaccades by removing the head-motion component from the eye-position information in an image in which the head motion and eye movement are mixed. Experiments using an eye model that can reproduce microsaccadic movements at any time confirmed that our system maintained high precision of the gaze-angle estimation, which enables microsaccade measure in a wider area compared with a conventional system and detected microsaccades of the eye model with 0.2-degree amplitude even when the model base moved at 20mm/s.

The present investigation aimed to identify the distinguishing effects of spontaneous laughter (SL) and aerobic exercise on autonomic nervous system (ANS) activity to develop a novel technique for indirect SL identification based on heart rate variability (HRV) under daily-living conditions. The subjects of the present investigation were ten healthy young men. The investigation consisted of three 15 min experimental periods, each following a resting period after 5h of daily-living conditions. The three experimental periods included light-intensity aerobic exercise (LAE), moderate-intensity aerobic exercise (MAE), or SL and were randomly distributed across three separate days. To induce SL, the subjects were shown comedy movies. Their ANS activity was monitored throughout the investigation period using continuous heart rate (HR) responses. Total power, low frequency (LF), and high frequency (HF) components were recorded using frequency analysis. LF and HF components were normalized to total power (nHF, nLF), and LF was then divided by HF to obtain a sympathetic activity index (LF/HF) . Instances of SL during the daily-living periods were subjectively identified using laughter intensity scores. Our results revealed a significant correlation between the effects of time and task on HR during the experimental periods (p<0.001) . HR significantly increased during LAE and MAE, but not during SL, compared with that during the resting period (p<0.05) . Temporal effects on ANS were evaluated, and no significant difference was observed between the three conditions. During daily-living conditions, ANS activity differed significantly from baseline (p<0.05) but HR did not. The present investigation revealed that SL induces similar ANS responses but different HR responses compared to aerobic exercise. These findings imply that HR responses via HRV and ANS could provide a novel means of identifying SL in daily-living conditions.