The governance of imported 2019-nCov infections:What can be learned from China’s experience?

Delta and Omicron variants of 2019-nCoV are still spreading globally,and many imported infections have been identified in China as well.In order to control the spread chain from imported to local,China has implemented the dynamic Covid-zero policy.In this article we summarized China’s governance models and practices of fighting potential imported infections in two directions.One targets at international travelers,which can be outlined as four lines of defense:customs epidemic prevention,quarantine upon arrival,relevant laws and regulations,and community tracking.The other is against other vectors potentially carrying 2019-nCoV,which can be outlined by three lines of defense:customs epidemic prevention,disinfection and personal protection,and information management.However,there are still some challenges that are yet to be addressed,such as illegal immigration,accidental occupational exposure to 2019-nCoV,etc.China’s experience indicates that no country can stay safe during the global pandemic as long as there are local outbreaks in other countries,and active prevention and control measures based on science and a complete set of laws and regulations are still necessary at current stage.What’s more,accountable government commitment and leadership,strengthened health and social governance systems,and whole society participation are required.It is suggested that the global community continue to closely cooperate together and take active rather than passive actions to block the potential imported 2019-nCoV from causing local spreading.

Structural design and mechanical responses of closely spaced super-span double tunnels in strongly weathered tuff strata

This paper presents a study of closely spaced double tunnels in Taizhou,China.One is Xiabei Mountain No.2 four-line super-span high-speed railway tunnel(HRT),and the other is Xiabei Mountain double-line large-span subway tunnel(ST).The excavation spans of HRT and ST are 26.3 and 14 m,respectively.The two tunnels are located at different levels,and their separating distance is 17.2 m.Due to the short construction period,the HRT excavation was completed earlier than ST.The structural design of the HRT,taking account of the disturbance by the ST construction,was analyzed by a numerical simulation.It was found that the“yielding principle”design was more feasible than the“resistance principle”design when considering the safety and durability of the HRT secondary lining.The mechanical responses of the HRT during ST construction were comprehensively monitored and analyzed,including the vault settlement,horizontal convergence,surrounding rock pressure,and the internal stress in shotcrete and steel arch.Results show that the longitudinal influence range of the ST construction on the HRT was approximately 0.6–1.1 times the ST outer diameter;the disturbance was mainly generated in the ST upper bench excavation;and the final axial force of the HRT shotcrete was approximately 9–16 times that of the steel arch,which indicated that the shotcrete was the main bearing structure.The safety status of the HRT was assessed based on the monitoring data,and the minimum safety factors of the HRT shotcrete and steel arch were 1.61 and 1.89,respectively.Parametric studies were performed to show how the lining stress of HRT was affected by the relative angle,pillar width,ST excavation method and excavation footage.Finally,the design and construction optimization were proposed according to the monitoring data and parameter analysis results.This study might provide practical reference for similar projects.

A low-cost and high-strength basalt/carbon fiber reinforced polymer improved by imitating tree-root micro/nano aramid short fiber

The high-strength Basalt Carbon Fiber Reinforced Polymer(BCFRP)composites had been manufactured by guiding Imitating Tree-root Micro/Nano Aramid Short Fiber(ITMNASF)into the interlayer of Basalt Fiber(BF)and Carbon Fiber(CF)plies to form thin interleaving,and various mass proportions of IT-MNASF were designed to discuss the reinforcing effect on the BCFRP heterogeneous composites.The results of three points bending tests showed that flexural strength and energy absorption of 4wt%IT-MNASF reinforced BCFRP heterogeneous composites had been improved by 32.4%and 134.4%respectively compared with that of unreinforced specimens.The 4wt%IT-MNASF reinforced BCFRP specimens showed both a greater strength and a lower cost(reduced by 31%around)than that of plain CFRP composites.X-ray micro-computed tomography scanning results exhibited that the delamination-dominated failure of plain BCFRP composites was changed into multi-layer BF and CF fabrics damage.The reinforcing mechanism revealed that the introduced IT-MNASF could construct quasi-vertical fiber bridging,and it was used as"mechanical claws"to grasp adjacent fiber layers for creating a stronger mechanical interlocking,and this effectively improved resin-rich region and interfacial transition region at the interlayers.The simple and effective IT-MNASF interleaving technique was very successful in low-cost and high-strength development of BCFRP heterogeneous composites.

Constructing flexible fiber bridging claws of micro/nano short aramid fiber at interlayer of basalt fiber reinforced polymer for improving compressive strength with and without impact

The high-performance Basalt Fiber Reinforced Polymer(BFRP)composites have been prepared by guiding Micro/Nano Short Aramid Fiber(MNSAF)into the interlayer to improve the resin-rich region and the interfacial transition region,and the flexible fiber bridging claws of MNSAF were constructed to grasp the adjacent layers for stronger interlaminar bond.The lowvelocity impact results show that the MNSAF could improve the impact resistance of BFRP composites.The compression test results demonstrate that the compressive strength and the residual compressive strength after impact of MNSAF-reinforced BFRP composites were greater than those of unreinforced one,exhibiting the greatest 56.2% and 73.3% increments respectively for BFRP composites improved by 4wt%MNSAF.X-ray micro-computed tomography scanning results indicate that the“fiber bridging claws”contributed to better mechanical interlocking to inhibit the crack generation and propagation under impact and compression load,and the original delamination-dominated failure of unreinforced BFRP composites was altered into sheardominated failure of MNSAF-reinforced BFRP composites.Overall,the MNSAF interleaving might be an effective method in manufacturing high-performance laminated fiber in industrial production.

Generation of gene-target dogs using CRISPR/Cas9 system

Dear Editor,Dogs(Canis familiaris)serve as human companions and are raised to herd livestock,aid hunters,guard homes,perform police and rescue work,and guide the blind.Dogs exhibit close similarities to humans in terms of metabolic,physiological,and anatomical characteristics,and thus are ideal genetic and clinical models to study human diseases(Tsai et al.,2007).Gene target technology is a powerful tool to create new strains of animals with favorable traits.However,thus far,gene-target dogs have not been developed due to their unique species-specific reproductive characteristics,which limits the applications of dogs especially in the field of biomedical research.Recently,clustered regularly interspaced short palindromic repeats(CRISPRs)/CRISPR-associated(Cas)9 system was applied to edit specific genes with a high efficiency(Cong et al.,2013;Mali et al.,2013).Here we attempt to explore the feasibility of producing gene knockout(KO)dogs by using this technology.Beagle dog,the most widely used breed in biomedical research,was used as our animal model.Myostatin(MSTN)was chosen as the first gene of interest.