We propose a method for the comprehensive identification of spastic and intrinsic properties of spastic knee joints using multiple pendulum tests. The stretch reflex system was modeled as a velocity feedback loop where the key component was the muscle spindle model generating the afferent signals with a constant threshold and gain of the lengthening velocity. For the comprehensive identification, multiple trajectories from one session of pendulum trials with different release angles were used as the reference trajectories that the model must reproduce. The identification was successful based on the results that the identified model represented the various features of pendulum trajectories and the simulated spastic torque closely matched the experimental EMG. The identified velocity threshold showed a remarkable correlation with the EMG duration and peak. The session-based method was effective in the identification of the spastic musculoskeletal system and the velocity threshold of the stretch reflex was suggested as a reliable and intuitive indicator of spastic severity.
A bio-check unit and health index were developed to evaluate personal health grade. The bio-check unit conducts health-related surveys and noninvasive measurements of physiological signals. Four health indices were defined such as cardiovascular index, stress index, obesity index, and management index. Programs were developed to evaluate scores of the four health indices from measured physiological signals and answers of survey questions. In order to obtain distributions of the health index scores with age, a clinical study was performed for 362 persons who visited general hospital for annual health inspection. The health index scores showed significant correlations with age. Based on the regression equation with age, five regions were divided in health index scores to classify personal health grade. The health index scores were found to identify specific diseases such as hypertension and diabetes.
The biofilm formation of Legionella pneumophila on glass was examined under nutrient water flow condition at 37°C, 40°C, and 42°C. The three-dimensional structures of 8-days biofilm were analyzed using confocal laser scanning microscopy. It was revealed that the properties of the biofilms were influenced significantly by temperature changes. Equivalent outer diameters of the microcolonies were 39µm at 37°C, 189µm at 40°C and 359µm at 42°C, respectively. The most interesting observation was that the microcolonies show areas of hollowing. The hollowness or emptiness is 37% at 37°C, 52% at 40°C and 74% at 42°C, respectively. The average number of bacteria per single colony was c.a. 1 x 105 at 37°C. Also, bacteria lengths were compared among the biofilms in liquid flow, those in static liquid and those on BCYE-α agar plate. In the liquid flow, the average bacteria length was 4.4µm at 37°C, 2.9µm at 40°C and 3.5µm at 42°C, respectively, while in the static liquid and on agar plate the lengths increased with the rise of temperature. Our experiments results on the biofilm formation of L. pneumophila will provide the basis for a better understanding of the sessile mode of life of L. pneumophila.
Ceramic articular surfaces are now widely used as total hip replacements for young and active patients. However, while the excellent tribological properties and high biocompatibility of ceramic articular surfaces prevent loosening and osteolysis, their high stiffness and low ductility occasionally result in ceramic surface fractures. Therefore, this study investigated the effect of varying the sizes of the acetabular components on the mechanical stability. Three femoral head models and 27 acetabular cup models were designed following three size parameters: ball head diameter (28, 32, and 36 mm), acetabular cup thickness (3, 4, and 5 mm), and liner thickness (9, 10, and 11 mm). For all these models, the mechanical stability was evaluated using 3D finite element analyses. Plus, the motion of the 3 femoral head models was measured in six directions using a motion study. The results showed that the maximum stress was decreased when increasing the sizes of the cup, liner, and femoral head, where the 36 mm ball head, 5 mm cup, and 11 mm liner showed the lowest maximum stress, while the 36 mm femoral head exhibited the largest range of motion. The acetabular cup stability was also shown to be affected by the stiffness of the components, where increasing the head size or thickness of the cup and liner increased the component stiffness and range of motion. Thus, the mechanical simulation demonstrated that increasing the size of the acetabular components decreased the ceramic surface stress and risk of impingement.
A MEMS based micro-actuator driven by electromagnetic force is developed to generate a micro Newton range of force for measuring the mechanical property of living cells or locally stimulating cells. The indenter consists of a probe and a couple of flexible beams with embedded electrodes. The developed device utilizes Lorentz force, which is generated by an applied electric field and a permanent magnet positioned beneath the electrodes, as its actuation power to indent a small object with the probe positioned at the midpoint of the beams. Given the magnetic force and the amount of indentation, the elastic modulus of the object of interest can be obtained. This device is a novel user-friendly micro indenter with a large deformation range, featuring high utilization potential for investigation of cell mechanics.
In this study, the mechanism of cerebral contusion was investigated using finite element analysis. A finite element human head model was constructed and used to simulate of 9 real-world fatal cerebral contusion accident cases. In these simulations, the impact velocities of the impact objects were estimated on the basis of the available information such as the regions of skull fracture and cerebral contusion. The pressure fluctuations inside the skull and the input force durations in each case were obtained using these simulations. These results show that in case of coup contusion, a negative pressure occurs on the impact side and is directly correlated with short force durations. In contrast, in case of contrecoup contusion, negative pressure occurs on the opposite side of impact and is directly correlated with long force durations. As the result, coup contusions are caused when the input force durations are short, contrecoup contusions are caused when the input force durations are long.
The purpose of this research is to develop minimally invasive medical devices by applying heated actuations of Shape Memory Alloy (SMA) transducers using a medical Ti-Ni alloy in order to enable minimal hypodermic invasive microvolume for either blood suction or drug delivery through the use of a nontoxic and minimal edged microneedle to be created in the author's laboratory. The author has focused on lymphocytes for immunotoxin and erythrocytes for the glucose level in blood. This paper reports the double-action mechanisms of the compact unit during its development and its actions by low DC inputs. Joule's heating of an SMA coil spring transducer might be useful for indenting blood vessels whose diameter is larger than the microneedle as a result of generating an indentation stroke of 2.0 mm and recovery force of 0.25 N 0.23 s following the start of moving when applied to DC 2.0 V and 0.5 A. An octagonal-pyramidal foil transducer for blood suction recovered its plane condition as before octagonal-pyramidal forming 8.3 s following the start of moving when applied to DC 1.5 V and 2.0 A.
This study aimed to predict bone fracture risk during skeletal unloading through a subject-specific finite element (FE) analysis considering heterogeneous tissue modulus. Twelve male and 14 female Institute of Cancer Research (ICR) mice (6 weeks old) were allocated into skeletal unloading and normal groups (each gender in both groups). The right hind tibia of each mouse in the skeletal unloading groups was subjected to sciatic neurectomy (denervation) and was scanned before and at 2 week after denervation using µCT. Bone volume (BV) and the distribution of Young's moduli (E) were measured from µCT images. The apparent modulus (Eapp) was calculated using the subject-specific (FE) analysis considering the heterogeneous tissue modulus derived by Hounsfield unit. At 2 weeks after denervation, the Eapp was significantly decreased in both genders (p < 0.05), and the distributions of E differed between the skeletal unloading and normal groups. However, the BV in females was significantly decreased (p < 0.05), while that in male was unchanged (p > 0.05). These results indicated that skeletal unloading reduced bone strength, leading to increased bone fracture risk.