The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of ...The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions:(i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;(ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.展开更多
The computational fluid dynamics(CFD)approach can be used to obtain both internal and external characteristics of centrifugal pumps,and the variations of the hydrodynamic force,the pressure and the torque on the blade...The computational fluid dynamics(CFD)approach can be used to obtain both internal and external characteristics of centrifugal pumps,and the variations of the hydrodynamic force,the pressure and the torque on the blades acquired by the CFD are highly associated with the safety of the pumping system.Based on the CFD simulations,this paper investigates the stopping characteristics of multiple pumps with some pumps being stopped.The 3-D geometric model is built,including all 6 pumps,the valves,the pipes,the tanks and other components,and using the Realizable k-ε turbulence model.The CFD results for the operating points agree well with the results from the theoretical analysis.With some pumps being stopped,the key parameters of the operating pumps would not be stable,with a larger fluctuation;the direction of the hydrodynamic force might be opposite with more than 3 stopped pumps.For the stopped pumps,the maximum reverse values of the discharge and the rotational speed would be larger when fewer pumps are stopped,and could be more than 120%of the rated values,which is dangerous for the pumping system.The CFD results could help understanding the stopping process of multiple pump systems with some pumps being stopped.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61378083)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+1 种基金the Major Research Plan of National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110 and2013SZS03-Z01)
文摘The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions:(i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;(ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.
基金Projects supported by the National Natural Science Foundation of China(Grant Nos.51879087,51839008 and 51709087).
文摘The computational fluid dynamics(CFD)approach can be used to obtain both internal and external characteristics of centrifugal pumps,and the variations of the hydrodynamic force,the pressure and the torque on the blades acquired by the CFD are highly associated with the safety of the pumping system.Based on the CFD simulations,this paper investigates the stopping characteristics of multiple pumps with some pumps being stopped.The 3-D geometric model is built,including all 6 pumps,the valves,the pipes,the tanks and other components,and using the Realizable k-ε turbulence model.The CFD results for the operating points agree well with the results from the theoretical analysis.With some pumps being stopped,the key parameters of the operating pumps would not be stable,with a larger fluctuation;the direction of the hydrodynamic force might be opposite with more than 3 stopped pumps.For the stopped pumps,the maximum reverse values of the discharge and the rotational speed would be larger when fewer pumps are stopped,and could be more than 120%of the rated values,which is dangerous for the pumping system.The CFD results could help understanding the stopping process of multiple pump systems with some pumps being stopped.