The early-stage of knee osteoarthritis (OA) is usually asymptomatic. However, timely detection of osteoarthritis can prevent further cartilage degeneration via appropriate exercise prescription and behavioral change. In this article, a noninvasive method to diagnose the OA of a knee recording the knee vibroarthrographic (VAG) signals over the mid-patella during the standing movement is proposed. A method that combines empirical mode decomposition (EMD) and wavelet transform is developed to analyze the nonstationary VAG signals. The least squares support vector machine algorithm (LSSVM) that is a type of support vector machine is used to classify the knee joint VAG signals (26 normal and 25 abnormal) collected from healthy subjects and patients suffering from the knee OA using the Kellgren and Lawrence grading system III and IV (KLGS III and IV). The LSSVM classifier achieves an accuracy of 86.67% in differentiating the normal and abnormal subjects that proves the effectiveness of the autocorrelation function features and continuous wavelet transform (CWT) features. Therefore, the VAG signals can be clinically significant for the classification of healthy and OA subjects.
While rovers are of importance for Mars exploration in terms of various surveillance, surface rovers may encounter great challenges due to rough terrain and complex turbulent environment on Mars partly because aerial vehicles have difficulties to stay airborne due to the extremely low atmospheric density. Flights of surface rovers on Mars share the aerodynamic similarity with insect flights on earth in terms of low Reynolds number flow regime. Motivated by that insects can achieve remarkable flapping-wing aerodynamic performance in force production, flight stability and maneuverability under highly unsteady environments, we here proposed a bumblebee-inspired flapping-wing design for Mars surface rovers. We developed a power-efficient aerodynamic model by combining a surrogate model and a bioinspired dynamic flight simulator for hovering flight in a parametric space comprising wing shape and wing kinematics to explore feasible design points and some optimal solution with the power output minimized. Our results indicate that an enlarged wing model inspired by bumblebees is capable of sustaining hovering flight on Mars with a set of aspect ratios and wing kinematics and an optimal design point is found to correspond with a power output of 0.0509W, which may provide a novel and feasible biomimetic design for flapping-wing aerial vehicles on Mars.
Until now, numerous studies on the effects of electrical stimulation on nerve cell activation in a cell culture have been conducted. However, there are very few studies that have used the three-dimensional (3D) culture system to investigate nerve cell axonal extension. In this study, we developed a novel 3D direct current electric field (DCEF) stimulation bioreactor, which can uniformly stimulate cultured nerve cells for a long period. We observed the morphogenesis of PC12 cells using a multi photon excitation fluorescence microscope (MPM) and evaluated DCEF stimulation effects on PC12 cells axonal outgrowth. First, a DCEF stimulation bioreactor was designed using finite element analysis for uniform electric field. We, then, validated the uniform stimulation of PC12 cells using this bioreactor for 24 h. Second, we determined the optimal stimulation condition using the response surface method and adopting objective functions, such as axonal length, the ratio of axonal orientation towards the anode, and design parameters, such as the electric field strength and the duration of the stimulation. We found the optimal condition to be 43 mV/mm and 6.2 h/day for axonal length enhancement. An increase of 20.1% against the condition for the control group (Mann-Whitney’s U test, p<0.05) was obtained. In addition, the 92 % of PC12 cells were oriented toward the anode with 90 mV/mm, 24 h/day condition. However, the axonal formation was suppressed depending on the stimulation duration. Finally, we found the optimal conditions of 70 mV/mm and 7.9 h/day for achieving the enhancement of axonal extension and orientation, simultaneously.
The rapid increase in the aging population of Japan is becoming a serious social concern, and the number of elderly individuals with dementia is also increasing. The Ministry of Health, Labour and Welfare of Japan has reported that the elderly account for 4.62 million individuals, of which approximately 4 million have mild cognitive impairment (MCI). However, monofunctional disorders, such as those in individuals with MCI, can be treated, with patients recovering 44% of their abilities 2 years after treatment, thereby suggesting that early detection and treatment of dementia is important. It has been reported that individuals who walk slowly or have experienced a significant decline in walking speed with age have a higher risk of developing dementia. In this study, to study movement in individuals aged ≥ 60 years, we focused on walking, a basic activity of daily living. We proposed and evaluated novel methods to estimate cognitive function. Acceleration and angular velocity sensors were attached to the waists of 20 elderly participants who were asked to walk outdoors ordinarily for 5–10 min, during which acceleration and angular velocity were measured. The similarity, standard deviation, and period of the stride were determined from the acceleration waveform and angular velocity waveform during walking. These were used as independent variables, and multiple regression analysis was performed using the Mini-Mental State Examination (MMSE) score as a dependent variable. An MMSE score estimation equation was constructed. The relationship between the estimation formula and the actual test value was R2 = 0.773 (P <0.01), which was good. As a result of cross-validation, the root mean square (RMS) error is low and the error is neither fixed nor proportional. Using the body acceleration and angular velocity information when walking outdoors, we built a very accurate formula for estimating the MMSE score.