SARS-CoV-2 infection has become an urgent public health concern worldwide, severely affecting our society and economy due to the long incubation time and high prevalence. People spare no effort on the rapid development of vaccine and treatment all over the world. Amongst the numerous ways of tackling this pandemic, some approaches using extracellular vesicles (EVs) are emerging. In this review, we summarize current prevalence and pathogenesis of COVID-19, involving the combination of SARS-CoV-2 and virus receptor ACE2, endothelial dysfunction and micro thrombosis, together with cytokine storm. We also discuss the ongoing EVs-based strategies for the treatment of COVID-19, including mesenchymal stem cell (MSC)-EVs, drug-EVs, vaccine-EVs, platelet-EVs, and others. This manuscript provides the foundation for the development of targeted drugs and vaccines for SARS-CoV-2 infections.

Objectives: The objective of this study is to evaluate the efficacy of autocross-linked hyaluronic acid (HA) compared with intrauterine device (IUD) for preventing intrauterine adhesions (IUAs) in infertile patients after hysteroscopic adhesiolysis. Materials and Methods: A randomized clinical trial (ChiCTR-IOR-16007746). Upon completion of adhesiolysis, 3 ml of HA gel was placed into the uterine cavity in Group A; 3 ml of HA gel and an IUD were placed in Group B; and only an IUD was placed in Group C. A second hysteroscopic examination was performed in all patients at approximately 1 month postoperatively for the evaluation of IUA. The primary outcome measure was the effective rate of IUA prevention based on the American Fertility Society (AFS) scoring system. Results: Eighty-nine women were randomly distributed into two groups for intention to treat with 30 patients in Group A, 24 patients in Group B, and 35 patients in Group C. Patients were scored and stratified into three degrees and were enrolled using the simple random sampling method. The three groups were well balanced. There were no significant differences in age, endometrial thickness, the previous number of pregnancy, and the distribution of adhesion categories across mild, moderate, and severe between the three groups. The effective rate of IUA prevention, the AFS score after therapy, and the percentage improvements of Chinese score and AFS score before and after surgery were statistically significant difference between Groups A and C. The clinical pregnancy rate in Group A was higher than those in Groups B and C, but the difference was not statistically significant. Conclusion: HA gel has an advantage over an IUD in reducing IUA recurrence and decreasing adhesions.

A virtual prototype model of S195 diesel engine was established by using CAD, finite element analysis based on virtual prototype technology and dynamics theory of flexible multibody systems to study the kinetic discipline of the crank-rod mechanism,vibration of cylinder block caused by inertia force and the balance problem of inertia force.The rigid body and flexible body simulation were compared.The interaction force between components could be determined by flexible multibody dynamics analysis of the crankshaft system under the real working condition. The simulation results are accordant with those in true working state of S195 diesel engine. This research provides a feasible advanced method for design and development of diesel engine.

This article briefly describes the composite materials and their excellent physical and chemical properties, the application of resin-based composite materials in the coal mine are emphatically introduced; and the application of rubber-based, cement-based composite materials in coal mine are briefly introduced, pointed out that the development and application of composite materials in coal production in China has great potential and broad development prospects.