Osteoblasts, the bone-forming cells, respond to various mechanical forces, such as stretch and fluid shear force in essentially similar ways. The cytoskeleton, as the load-bearing architecture of the cell, is sensitive to altered inertial forces. Disruption of the cytoskeleton will result in alteration of cellular structure and function. However, it is difficult to quantitatively illustrate cytoskeletal rearrangement because of the complexity of cytoskeletal structure. Usually, the morphological changes in actin organization caused by external stimulus are basically descriptive. In this study, fractal dimensions (D) analysis was used to quantify the morphological changes in the actin cytoskeleton of osteoblast-like cells (MC3T3-E1) under simulated microgravity using 3-D/2-D clinostats. The ImageJ software was used to count the fractal dimension of actin cytoskeleton by box-counting methods. Real-time PCR and immunofluroscent assays were used to further confirm the results obtained by fractal dimension analysis. The results showed significant decreases in D value of actin cytoskeleton, β-actin mRNA expression, and the mean fluorescence intensity of F-actin in osteoblast-like cells after 24 or 48 h of incubation under 3-D/2-D clinorotation condition compared with control. The findings indicate that 3-D/2-D clinorotation affects both actin cytoskeleton architecture and mRNA expression, and fractal may be a promising approach for quantitative analysis of the changes in cytoskeleton in different environments.

The Jiangmen Underground Neutrino Observatory (JUNO) is a multifunctional neutrino-oscillation experiment, aiming to determine the neutrino mass hierarchy and precisely measure three neutrino oscillation parameters, of which the calibration system is essential to the response of the detector. This paper presents a calibration system consisting of Remotely Operated Vehicles and Sonar Positioning System, focusing on the positioning of the Remotely Operated Vehicles. The design principles and theoretical analysis are discussed as well as specific requirements. The corresponding motion control mode is then proposed. The experiment is further performed to validate the accuracy of horizontal and vertical positioning devices. It is shown that the designed device can satisfy the harsh requirements from JUNO, including radioaction, compatibility, and magnetic effects. The speed limit (1 m/min) at the horizontal plane and positioning accuracy (30 mm/5 min) in three dimensions are also ensured, indicating the performance of the calibration system is well tested. The motion control of the positioning device in the liquid scintillator environment is finally predicted. The proposed Remotely Operated Vehicle together with the Sonar Positioning System can provide the calibration operation in JUNO.

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In this paper, sliding panels are used to increase the bending stiffness of the classic corrugated flexible skin, and the corresponding application procedure for aircraft structures is developed. After the conceptual design of the corrugated flexible skin with sliding panels is proposed, the analytical models to calculate the equivalent tensile and bending properties are investigated. At the same time, its flexibility in the corrugation direction and the load-bearing capacity (is proportional to the bending stiffness) in the direction perpendicular to corrugation are studied by numerical simulation and experiment. The application procedure is established based on geometric analysis and strain definition, and according to this procedure, the corrugated flexible skin with sliding panels is applied to the drooping leading edge to eliminate the gap on the upper skin. The results show that the corrugated flexible skin with sliding panels has more bending stiffness than the classic corrugated flexible skin in the direction perpendicular to corrugation while maintaining the deform ability in the corrugation direction, and the application procedure is effective and can be applied to other parts of the aircraft structure.

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