Shin Morishita

Low-intensity pulsed ultrasound activates the phosphatidylinositol 3 kinase/Akt pathway and stimulates the growth of chondrocytes in three-dimensional cultures: a basic science study

IntroductionThe effect of low-intensity pulsed ultrasound (LIPUS) on cell growth was examined in three-dimensional-cultured chondrocytes with a collagen sponge. To elucidate the mechanisms underlying the mechanical activation of chondrocytes, intracellular signaling pathways through the Ras/mitogen-activated protein kinase (MAPK) and the integrin/phosphatidylinositol 3 kinase (PI3K)/Akt pathways as well as proteins involved in proliferation of chondrocytes were examined in LIPUS-treated chondrocytes.MethodsArticular cartilage tissue was obtained from the metatarso-phalangeal joints of freshly sacrificed pigs. Isolated chondrocytes mixed with collagen gel and culture medium composites were added to type-I collagen honeycomb sponges. Experimental cells were cultured with daily 20-minute exposures to LIPUS. The chondrocytes proliferated and a collagenous matrix was formed on the surface of the sponge. Cell counting, histological examinations, immunohistochemical analyses and western blotting analysis were performed.ResultsThe rate of chondrocyte proliferation was slightly but significantly higher in the LIPUS group in comparison with the control group during the 2-week culture period. Western blot analysis showed intense staining of type-IX collagen, cyclin B1 and cyclin D1, phosphorylated focal adhesion kinase, and phosphorylated Akt in the LIPUS group in comparison with the control group. No differences were detected, however, in the MAPK, phosphorylated MAPK and type-II collagen levels.ConclusionLIPUS promoted the proliferation of cultured chondrocytes and the production of type-IX collagen in a three-dimensional culture using a collagen sponge. In addition, the anabolic LIPUS signal transduction to the nucleus via the integrin/phosphatidylinositol 3-OH kinase/Akt pathway rather than the integrin/MAPK pathway was generally associated with cell proliferation.

Control of friction coefficient by applying electric fields across liquid crystal boundary films

Abstract Experiments are described in which friction coefficients under boundary lubrication regime are measured with a nematic liquid crystal as the lubricant. Using steel-to-steel contacts, with one of the mating surfaces coated with a thin insulating film, electric fields are applied across the liquid crystal film. A substantial decrease in the friction coefficient is observed with both d.c. and low-frequency a.c. voltages, suggesting the possibility of controlling friction by external fields.

Adaptive Vibration Control by a Variable-Damping Dynamic Absorber Using ER Fluid

This paper describes a variable-damping dynamic absorber applying Electrorheological (ER) fluid to the damping element of a conventional-type dynamic absorber. A prototype of variable-damping dynamic absorber was constructed and its performance was verified with a three-story structural model. The special ability of the present dynamic absorber is to reduce the vibration amplitude at several frequencies by a single dynamic absorber. ER fluid is functional fluid whose yield shear stress can be changed by the applied electric field strength. Because of its peculiar property, ER fluid has been applied to various mechanical components such as shock absorbers and engine mounts for vehicles, clutches, valves, etc. One of the practical ways in applying ER fluid to mechanical components may be to expand the performance of conventional mechanical components by combining ER fluid effectively with them. In this sense, this paper shows a successful application of ER fluid to a conventional-type dynamic absorber. An adaptive neural network control system composed of a forward model network for system identification and a controller network was introduced to control the variable-damping element of the dynamic absorber. The numerical simulations show good agreements with the experimental results.

Electroviscous effect of nematic liquid crystals

Abstract Liquid crystals are characterized by the orientation of their molecules, the major axis of whose direction can be controlled by an applied electric or magnetic field. In the present paper the viscosity variation of three thermotropic liquid crystals in the nematic phase having different dielectric constants is studied at varying electric field strength, shear field strength and temperature. The results show that the viscosity of liquid crystals can be varied by the applied electric field strength and that a lower temperature reduces the threshold electric field strength for the electroviscous effect to appear as well as decreasing the attainable values at higher electric field strength. In addition, the frequency of the applied electric field has little effect on electroviscosity.

ER Fluid Applications to Vibration Control Devices and an Adaptive Neural-Net Controller

This article describes several applications of electro-rheological (ER) fluid to vibra tion control actuators and an adaptive neural-net control system suitable for the controller of ER ac tuators. ER fluid is a kind of colloidal suspension, and has a notable characteristic feature in that its apparent viscosity can be controlled in response to applied electric field strength. Viscosity can be varied in a wide range and the response time is very short, as short as several milliseconds. Accord ing to previous studies, one promising application is a controllable damper. In the present article, four applications are proposed: a shock absorber system for automobiles, a squeeze film damper bearing for rotational machines, a dynamic damper for multi-degree-of-freedom structures and a vibration isolator. Furthermore, an adaptive neural-net control system, composed of a forward model network for structural identification and a controller network, was introduced for the control system of these ER actuators. As an example study of intelligent vibration control systems, an experi ment was conducted in which the ER dynamic damper was attached to a beam structure and con trolled by the present neural-net controller so that the vibration in several modes of the beam was reduced with a single dynamic damper.

A Small-sized Variable-damping Mount using Magnetorheological Fluid

This paper deals with an application study of a magnetorheological (MR) fluid to a small-sized variable-damping mount for precision equipment of automobiles. MR fluids are a class of functional fluids with a controllable yield stress due to the applied magnetic field strength. A typical MR fluid is a suspension where pure iron particles of 1-20 mm diameter are dispersed in a liquid such as mineral or silicone oil, at a concentration of 20-40 vol%. A variable-damping mount filled with an MR fluid is combined with a magnetic coil at the bottom, and its performance is investigated experimentally and its damping mechanism is estimated analytically.

Optimal design of an engine mount using an enhanced genetic algorithm with simplex method

This study provides an analysis of the applications of optimization routines for designing fluid mounts. After summarizing the concept of fluid mounts and their dynamic characteristics, we review the importance of the notch and resonance peak that occur in dynamic stiffness of fluid mounts. Fluid mounts are tuned for specific application so that their notch frequency coincides with the disturbance frequency, by selecting the proper parameters for the mount. Additionally, the mount parameters are selected such that the notch remains as deep (close to zero) as possible and the resonance peak is kept as short as possible. The notch depth and resonance peak present opposing requirements for the selection of mount parameters in the sense that lowering one will result in increasing the other. Using a bond graph model, this study will evaluate the effect of various parameters on the mount notch depth and resonance peak height characteristics. The results show that different parameters can have a varying effect on the notch frequency and depth, as well as the resonance frequency and peak height. The results of the study are extended by examining the effectiveness of two different optimization methods—namely, the Enhanced Genetic Algorithm (EGA) and Sequential Quadratic Programming (SQP)—for selecting the combination of parameters that can yield the deepest notch and shortest resonance peak. Using two different design cases, the study shows that SQP exhibits much more sensitivity to the initial conditions that are selected for the mount parameters than EGA. Both methods, however, are able to converge to an optimal solution within the constraints that are selected for the parameters. For both cases, EGA is able to converge to the set of parameters that provide a deep notch and a short resonance peak.

Acquisition of Local Neighbor Rules in the Simulation of Pedestrian Flow by Cellular Automata

Cellular Automata is applied to model the pedestrian flow, in which the local neighbor rules implemented to each person in the crowd are determined automatically in the process of simulation. The collision patterns in the visible area settled around each person is introduced, and each person walks around just avoiding the collision patterns. As the simulation proceeds along the time step, various collision patterns are observed. By being informed the collision patterns to all the pedestrians simultaneously, the pedestrian begins to flow quite smoothly and the column formation is observed.

In vitro stability of open wedge high tibial osteotomy with synthetic bone graft.

It has been predicted that significant stress will be applied to the plate and lateral cortical hinge of an osteotomy site when early full weight bearing is commenced after an open wedge high tibial osteotomy. We hypothesized that the stress concentration on the plate or at the lateral cortical hinge would be reduced by inserting bone substitutes into the osteotomy gap. Two different types of tibia model were investigated: Group A, fixation with TomoFix with the osteotomy site left as an open space; and Group B, two beta-TCP wedges are inserted into osteotomy site and fixed with TomoFix. Stress at five points was measured using strain gauges. Specimens were mounted onto a testing machine with an FTA (femoro-tibial angle) of 170 degrees . Cyclic load tests and an ultimate load test were then performed. The mean stress on the plate was measured at 15.5+/-1.8Mpa in Group A. On the other hand, this value in Group B was only 9.52+/-2.1Mpa and this was a significant difference (P<0.01). The mean stress on the lateral hinge in Groups A and B was 3.31+/-0.5 and 2.49+/-0.2, respectively which was also a significant difference (P<0.05). The mean maximum breaking load in Group A was 2500+/-280N and in Group B 4270+/-420N which was a significant difference (P<0.01). Hence, for OWHTO procedures, the use of beta-TCP wedges and TomoFix is thus likely to improve the initial axial and possibly rotational stability at the osteotomy site in comparison with methods that leave the osteotomy gap open.

Development of 400kN magnetorheological damper for a real base-isolated building

A 400kN magnetorheological damper (MR damper) for a real base-isolated building was developed and its dynamic characteristics were verified by experimental tests. The MR damper has 950mm (+/-475mm) stroke and by-pass flow potion. A new type of Magneorheological fluid is also developed in order to apply to the MR damper. MR fluid had a property of the settlement of particles in dampers. Authors developed a new MR fluid, which keeps the particles in the fluid adequately enough for usual use of MR damper. Analytical model was discussed in this paper. The force by the bingham visco-plastic model was compared with the results of experimental tests. It was found that this analytical model is useful to predict the capacity of the MR damper.