Search

Coronary stent placement inevitably causes mechanical damage to the endothelium, leading to endothelial denudation and in-stent restenosis (ISR). Re-endothelialization depends mainly on the migration of vascular endothelial cells (VECs) adjacent to the damaged intima, as well as the mobilization and adhesion of circulating VECs. To evaluate the combined contribution of VEC migration and adhesion to re-endothelialization under flow and the influence of stent, in vitro models were constructed to simulate various endothelial denudation scales (2 mm/5 mm/10 mm) and stent deployment depths (flat/groove/bulge). Our results showed that (1) in 2 mm flat/groove/bulge models, both VEC migration and adhesion combined completed the percentage of endothelial recovery about 27, 16, and 12%, and migration accounted for about 21, 15, and 7%, respectively. It was suggested that the flat and groove models were in favor of VEC migration. (2) With the augmentation of the injury scales (5 and 10 mm), the contribution of circulating VEC adhesion on endothelial repair increased. Taken together, endothelial restoration mainly depended on the migration of adjacent VECs when the injury scale was 2 mm. The adhered cells contributed to re-endothelialization in an injury scale-dependent way. This study is helpful to provide new enlightenment for surface modification of cardiovascular implants.

BackgroundHigh mobility group box 1 (HMGB1) and indoleamino-2, 3-dioxygenase (IDO) participate in the occurrence and development of esophageal squamous cell carcinoma (ESCC), regulate the tumor immune microenvironment, and are closely related to tumor growth and metastasis. However, the regulatory mechanism of serum HMGB1 and IDO has not been clarified and needs further exploration.MethodsBlood samples of 55 ESCC patients initially hospitalized in the Fourth Hospital of Hebei Medical University from August 2021 to January 2022 were selected as the ESCC group, and relevant clinical data were collected, and blood samples from 40 healthy people during the same period were selected as the control group. Serum HMGB1 and IDO levels were determined by ELISA, and lymphocyte subsets in peripheral blood of all subjects were detected by flow cytometry. The correlation between the expression levels of HMGB1 and IDO in ESCC cells was detected by Western blot.ResultsSerum HMGB1 and IDO levels were significantly increased in ESCC patients, and with the progression of ESCC patients, serum HMGB1 and IDO levels were also gradually increased; serum HMGB1 was significantly correlated with IDO; serum HMGB1 and IDO combined with CEA and SCC-Ag were of high value in predicting the clinical progression of ESCC patients; the absolute counts of CD4+CD28+T cells and CD8+CD28+T cells in high HMGB1 group were significantly lower than those in low HMGB1 group, while the percentage of CD4+PD-1+T cells was significantly higher than that in low HMGB1 group; the percentage and absolute counts of CD4+CD28+T cells and the absolute counts of CD8+CD28+T cells in high IDO group were significantly lower than those in the low IDO group, while the percentage of CD8+PD-1+T cells was significantly higher than that in the low IDO group; increased serum HMGB1 and IDO expression levels were closely related to poor prognosis in ESCC patients; and HMGB1 may promote IDO expression by activating NF-κB signaling pathway.ConclusionSerum HMGB1 and IDO have a synergistic effect, they inhibit immune function and promote tumor progression in ESCC patients, and also lead to poor prognosis.

Robots driven by variable stiffness actuators (VSAs) have been an important technology as they could provide intrinsic compliance for safe human-robot interaction. The internal compliance of VSA also makes it possible for the actuator to act as a torque sensor and estimate the external force. This paper presents a physical human-robot interaction control strategy for robots driven by VSA with force self-sensing. The VSA adopted in the robotic system improves the safe performance of physical human-robot interaction. The interaction force is directly estimated by measuring the internal deformation of VSA with a stiffness region control which ensures a better resolution of force estimation and avoids transgressing the limits of deformation simultaneously. Then an online estimation method for the human motion intention is developed to generate the desired trajectory based on the estimated force. The impedance control is designed to enable the robot to actively follow the desired trajectory with compliance. Under the proposed control strategy, the robot is capable of actively tracking the “motion intention” of human with the estimated interaction force, which is demonstrated through experiment studies.

This paper proposes a new kind of quasi-zero-stiffness (QZS) isolation system that has the property of low-dynamic but high-static stiffness. The negative stiffness was produced using two magnetic rings, the magnetization of which is axial. First, the force–displacement characteristic of the two coupled magnetic rings was developed and the relationship between the parameters of the magnetic rings and the stiffness of the system was investigated. Then, the dynamic response of the QZS was analyzed. The force transmissibility of the system was calculated and the effects of the damping ratio and excitation amplitude on the isolation performance were investigated. The prototype of the QZS system was developed to verify the isolation effects of the system based on a comparison with a linear vibration isolation platform. Lastly, the improvement of the QZS system was conducted based on changing the heights of the ring magnets and designing a proper non-linear spring. The analysis shows the QZS system after improvement shows better isolation effects than that of the non-improved system.

While exploring complex environments, conventional mobile robots can overcome obstacles of limited height and jumping robots can overcome obstacles several times their own size. When jumping motion and wheeled or tracked motion are combined to form a composite motion, robots have even better ability to traverse rugged terrain. Therefore, we designed a wheeled hopping robot with a novel combustion-powered actuator and carried out structural design and experimental studies. The combustion-powered actuator has a unique inlet scheme and good sealing performance and is easy to install. The jump height equation was obtained by analyzing the combustion process. With the help of orthogonal array design methods, the factors that affect the wheeled hopping robot’s jumping height were analyzed to improve its key design parameters and optimize its jumping performance. Finally, experiments were performed with the actuator and the wheeled hopping robot. When the stoichiometric ratio of the mixed fuels nears complete combustion, the combustion-powered actuator can jump 7.5 m high with a payload of 3.75 kg and its own weight of 1.25 kg, and the wheeled hopping robot can jump 4.5 m high with a payload of 6 kg. Evaluating the robot’s performance in terms of energy efficiency reveals that it has a significant jumping advantage.