This study aims to establish a multi-segment foot model which can be applied in dynamic gait simulation. The effectiveness and practicability of this model were verified afterwards by comparing simulation results with those of previous researches. Based on a novel hybrid dynamic gait simulator, bone models were imported into automatic dynamic analysis of mechanical systems (ADAMS). Then, they were combined with ligaments, fascia, muscle and plantar soft tissue that were developed in ADMAS. Multi-segment foot model was consisted of these parts. Experimental data of human gait along with muscle forces and tendon forces from literature were used to drive the model and perform gait simulation. Ground reaction forces and joints revolution angles obtained after simulation were compared with those of previous researches to validate this model. It showed that the model developed in this paper could be used in the dynamic gait simulation and would be able to be applied in the further research.
The intracellular domain of clusters of differentiation 44 (CD44) binding to the FERM (protein 4.1-ezrin-radixin-moesin) domain of ERM (ezrin/radixin/moesin) proteins and furthermore triggering the recruitment of spleen tyrosine kinase (Syk) are very important in the process of tumor cell adhesion, migration and proliferation. At first, it was found that CD44/FERM structure was stable by observing CD44/FERM complex conformation and analyzing the interaction of interface residues both in static crystal structure and in equilibrium process. Meanwhile, unconventional immunoreceptor tyrosine-based activation motif (ITAM-like), and phosphorylation sites Y191 and Y205 were buried in FERM domain, which would hinder the phosphorylation of ERM proteins, the recruitment of Syk and subsequent signal transduction. Then, steered molecular dynamics simulation was applied to simulate the interaction between CD44 and FERM domain in the mechanical environment. The results showed that mechanical signal could induce the exposure of the ITAM-like motif and phosphorylation site Y205 by tracking and analyzing CD44/FERM complex conformational changes and the solvent-accessible surface area. This study revealed how the force regulates the activation of downstream signal through CD44 intracellular domain for the first time, and would be useful for further understanding the adhesion and migration pathway of cancer cells and the design of antitumor drugs.
The tilted supine position has been evaluated to be one of the significantly effective approaches to prevent bedsore of the patients in the bedridden state. Thus, it has deeply positive influences that in view of dynamics this study explores how the position works. Based on the anatomical theories, this study formulates the human dynamic model. Furthermore, the dynamic simulation of three usual postures in tilted supine position including lying on back, lying with one knee bent and lying with the upper and lower limb on one side lifted is carried out. Therefore, the changes of the three driving forces named as chest force, waist force and thigh force in the tilted supine position can be observed. In order to verify the validity of this simulation, this study obtains the electromyogram measurements of ectopectoralis, external obliques and thigh muscles which are respectively close to the chest, waist and thigh by conducting the human force measurements experiment. The result revealed that in terms of range and trend, the experimental data and simulation’s data were consistent. In conclusion, the changes of these muscles in the supine position movements are researched efficiently by both this experiment and the dynamic simulation. Besides, the result is crucially key to find the mechanism of human’s tilted supine position movements.
ObjectiveTo propose a path planning method for precise robot-assisted bronchial intervention. MethodsIn the MuJoCo dynamic simulation environment, a simulation model and a simulated bronchus model which could accurately represent the motion process of the robot were built. Based on the Informed RRT* algorithm, the known spatial information was used to improve the path planning method and the motion characteristics of the robot were simulated to verify the ability of the robot algorithm to reach the target position. ResultsIn the dynamic simulation environment, the robot could move as required, and could explore the target point of the planning task in a short time, and the position accuracy was improved by more than 50% compared with the existing electromagnetic navigation and other methods. ConclusionThe established simulation model can restore the motion of the robot, and the robot has the ability to move in the bronchial environment. The proposed method can precisely control the simulated robot to enter the more peripheral airway position. It has the advantages of accuracy and faster speed than traditional manual interventional surgery, and can be used for the human-machine coordinated control task of robot-assisted bronchoscopy.
In resting platelets, the 17th domain of filamin a (FLNa17) constitutively binds to the platelet membrane glycoprotein Ibα (GPIbα) at its cytoplasmic tail (GPIbα-CT) and inhibits the downstream signal activation, while the binding of ligand and blood shear force can activate platelets. To imitate the pull force transmitted from the extracellular ligand of GPIbα and the lateral tension from platelet cytoskeleton deformation, two pulling modes were applied on the GPIbα-CT/FLNa17 complex, and the molecular dynamics simulation method was used to explore the mechanical regulation on the affinity and mechanical stability of the complex. In this study, at first, nine pairs of key hydrogen bonds on the interface between GPIbα-CT and FLNa17 were identified, which was the basis for maintaining the complex structural stability. Secondly, it was found that these hydrogen bonding networks would be broken down and lead to the dissociation of FLNa17 from GPIbα-CT only under the axial pull force; but, under the lateral tension, the secondary structures at both terminals of FLNa17 would unfold to protect the interface of the GPIbα-CT/FLNa17 complex from mechanical damage. In the range of 0~40 pN, the increase of pull force promoted outward-rotation of the nitrogen atom of the 563rd phenylalanine (PHE563-N) at GPIbα-CT and the dissociation of the complex. This study for the first time revealed that the extracellular ligand-transmitted axial force could more effectively relieve the inhibition of FLNa17 on the downstream signal of GPIbα than pure mechanical tension at the atomic level, and would be useful for further understanding the platelet intracellular force-regulated signal pathway.