Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in t...Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in the Qinghai-Tibet Plateau is dominated by freeze-thaw erosion.In this research,freezing–thawing process of the soil samples collected from the Qinghai–Tibet Plateau was carried out by laboratory experiments to determinate the volume variation of soil as well as physical and mechanical properties, such as porosity, granularity and uniaxial compressive strength, after the soil experiences various freeze–thaw cycles.Results show that cohesion and uniaxial compressive strength decreased as the volume and porosity of the soil increased after experiencing various freeze–thaw cycles, especially in the first six freeze–thaw cycles.Consequently, the physical and mechanical properties of the soil were altered.However, granularity and internal friction angle did not vary significantly with an increase in the freeze–thaw cycle.The structural damage among soil particles due to frozen water expansion was the major cause of changes in soil mechanical behavior in the Qinghai–Tibet Plateau.展开更多
In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential form...In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential formed by undocking the neck linker, and there are asymmetric conformational changes in the attached head formed by docking the neck linker to support the load force and bias the diffusive search to the forward direction. By performing the thermodynamic analysis, we obtain the free energy difference between forward and backward binding sites. And using the Fokker-Planck equation with two absorbing boundaries, we obtain the dependence of the ratio of forward to backward steps on the backward force. Also, within the Michaelis-Menten model, we investigate the dependence of the velocity-load relationship on the effective length of the junction between the two heads. The results show that our model can provide a physical understanding for the processive movement of kinesin.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.41401611,41301072)China Postdoctoral Science Foundation(Grant No.2014M560817,2015T81069)the Open Project Program of the State Key Laboratory of Frozen Soil Engineering(Grant No.SKLFSE201208)
文摘Extreme freeze-thaw action occurs on the Qinghai-Tibet Plateau due to its unique climate resulting from high elevation and cold temperature.This action causes damage to the surface soil structure, as soil erosion in the Qinghai-Tibet Plateau is dominated by freeze-thaw erosion.In this research,freezing–thawing process of the soil samples collected from the Qinghai–Tibet Plateau was carried out by laboratory experiments to determinate the volume variation of soil as well as physical and mechanical properties, such as porosity, granularity and uniaxial compressive strength, after the soil experiences various freeze–thaw cycles.Results show that cohesion and uniaxial compressive strength decreased as the volume and porosity of the soil increased after experiencing various freeze–thaw cycles, especially in the first six freeze–thaw cycles.Consequently, the physical and mechanical properties of the soil were altered.However, granularity and internal friction angle did not vary significantly with an increase in the freeze–thaw cycle.The structural damage among soil particles due to frozen water expansion was the major cause of changes in soil mechanical behavior in the Qinghai–Tibet Plateau.
文摘In this paper, considering the different elastic properties in the attached head and the free head, we propose a physical model, in which the free head undergoes a diffusive search in an entropic spring potential formed by undocking the neck linker, and there are asymmetric conformational changes in the attached head formed by docking the neck linker to support the load force and bias the diffusive search to the forward direction. By performing the thermodynamic analysis, we obtain the free energy difference between forward and backward binding sites. And using the Fokker-Planck equation with two absorbing boundaries, we obtain the dependence of the ratio of forward to backward steps on the backward force. Also, within the Michaelis-Menten model, we investigate the dependence of the velocity-load relationship on the effective length of the junction between the two heads. The results show that our model can provide a physical understanding for the processive movement of kinesin.
