One of the key problems in the concept of planetary systems origin and early evolution is solid bodies formation in the protoplanetary gas-dust disc around young stars. Dust particles interactions inside the original ...One of the key problems in the concept of planetary systems origin and early evolution is solid bodies formation in the protoplanetary gas-dust disc around young stars. Dust particles interactions inside the original fluffy dust clusters of fractal nature resulted from gravitational instability and fragmentation in the disc’s central plane areassumed as the most plausible mechanism of primary bodies set up owing to particles integration within the clusters. Follow upcollisions are regarded to be responsible for eventual growth of primary bodies to the size of planetesimals. We discuss this scenario including chemical nature of particles depending on the disc’s radial temperature distribution and phase transitions. The mathematical model is developed based on the method of penetrating particles with the account for internal structure/properties of bodies involved, complicated patterns of their interaction, and phenomenological approach to describe energy distribution in the contact zone. The model is mainly addressed to the stage of formed solid bodies collisions. The results of numerical evaluation of the model are described involving some constraints for complete or partial destruction of colliding bodies followed by either scattering of collisional fragments orpartial back accumulation.展开更多
Growing air pollution,known as"April snow",by fluffy catkins from plant flowering was frequently observed during the Spring time in China.Current efforts mainly focus on controlling catkin release,while thei...Growing air pollution,known as"April snow",by fluffy catkins from plant flowering was frequently observed during the Spring time in China.Current efforts mainly focus on controlling catkin release,while their public health and environmental impacts are unknown.Here,using culturing,microscopic and sequence methods we found that the flying catkins carry a significant amount of bio-agents(bacteria,fungal,viruses,and pollens),e.g.,up to 6.33×10^4 bacterial and 7.46×10^5 fungal cells per catkin.Abundant pollens from plants were also found riding on the flying catkins.For collected fluffy catkins,bacterial Paracoccus,Massilia,fungal Ophiocordyceps,Arthrocladiella,pollen Robina,Pickeringia,Pinus,and viral family Genomoviridae,to name a few,were found to be dominant.With infection and allergic potentials,the detected microbial structures on the fluffy catkins were different from those of local air,varying from one location to another.Being not just white pollution,flying plant fluffy catkins were discovered here also acting as a cloud of biological agents,and further actions need to be taken urgently to understand and limit their environmental and ecological consequences.展开更多
Carbon nanotubes(CNTs)hold great promise in many fields because of their unique structures and properties.However,the preparation of CNTs generally involves cumbersome equipment and time-consuming processes.Here,we re...Carbon nanotubes(CNTs)hold great promise in many fields because of their unique structures and properties.However,the preparation of CNTs generally involves cumbersome equipment and time-consuming processes.Here,we report an ultra-fast carbothermal shock(CTS)approach for synthesizing CNTs with a simple homemade setup by employing Joule heating of a carbon substrate.Carbonized silk fabric(CSF)loaded with transition metal salts in ethanol solution was used as the substrate,which was treated with a pulse voltage of 40 V for only 50 ms and then covered with uniform CNTs grown with bimetallic alloy catalyst nanoparticles(diameter:~9 nm).The temperature ramp rate is as high as 105 K/s.The as-obtained sample has a unique fluffy structure similar to the trichobothrium of spiders,endowing it versatile applications such as airflow sensors or air filters.The CTS technique presents an easy-accessible and highly efficient approach for synthesizing CNTs,which may be also applied in synthesizing other nanomaterials.展开更多
文摘One of the key problems in the concept of planetary systems origin and early evolution is solid bodies formation in the protoplanetary gas-dust disc around young stars. Dust particles interactions inside the original fluffy dust clusters of fractal nature resulted from gravitational instability and fragmentation in the disc’s central plane areassumed as the most plausible mechanism of primary bodies set up owing to particles integration within the clusters. Follow upcollisions are regarded to be responsible for eventual growth of primary bodies to the size of planetesimals. We discuss this scenario including chemical nature of particles depending on the disc’s radial temperature distribution and phase transitions. The mathematical model is developed based on the method of penetrating particles with the account for internal structure/properties of bodies involved, complicated patterns of their interaction, and phenomenological approach to describe energy distribution in the contact zone. The model is mainly addressed to the stage of formed solid bodies collisions. The results of numerical evaluation of the model are described involving some constraints for complete or partial destruction of colliding bodies followed by either scattering of collisional fragments orpartial back accumulation.
基金supported by the National Natural Science Foundation of China(Grant Nos.21725701 and 22040101)。
文摘Growing air pollution,known as"April snow",by fluffy catkins from plant flowering was frequently observed during the Spring time in China.Current efforts mainly focus on controlling catkin release,while their public health and environmental impacts are unknown.Here,using culturing,microscopic and sequence methods we found that the flying catkins carry a significant amount of bio-agents(bacteria,fungal,viruses,and pollens),e.g.,up to 6.33×10^4 bacterial and 7.46×10^5 fungal cells per catkin.Abundant pollens from plants were also found riding on the flying catkins.For collected fluffy catkins,bacterial Paracoccus,Massilia,fungal Ophiocordyceps,Arthrocladiella,pollen Robina,Pickeringia,Pinus,and viral family Genomoviridae,to name a few,were found to be dominant.With infection and allergic potentials,the detected microbial structures on the fluffy catkins were different from those of local air,varying from one location to another.Being not just white pollution,flying plant fluffy catkins were discovered here also acting as a cloud of biological agents,and further actions need to be taken urgently to understand and limit their environmental and ecological consequences.
基金the National Key Technology R&D Program of China(No.2020YFA0210702)the National Natural Science Foundation of China(No.21975141).
文摘Carbon nanotubes(CNTs)hold great promise in many fields because of their unique structures and properties.However,the preparation of CNTs generally involves cumbersome equipment and time-consuming processes.Here,we report an ultra-fast carbothermal shock(CTS)approach for synthesizing CNTs with a simple homemade setup by employing Joule heating of a carbon substrate.Carbonized silk fabric(CSF)loaded with transition metal salts in ethanol solution was used as the substrate,which was treated with a pulse voltage of 40 V for only 50 ms and then covered with uniform CNTs grown with bimetallic alloy catalyst nanoparticles(diameter:~9 nm).The temperature ramp rate is as high as 105 K/s.The as-obtained sample has a unique fluffy structure similar to the trichobothrium of spiders,endowing it versatile applications such as airflow sensors or air filters.The CTS technique presents an easy-accessible and highly efficient approach for synthesizing CNTs,which may be also applied in synthesizing other nanomaterials.
