A new dynamic model for cell-deformation-induced adenosine triphosphate （ATP） release from vascular endothelial cells （VECs） is proposed in this paper to quantify the relationship between the ATP concentration at ...A new dynamic model for cell-deformation-induced adenosine triphosphate （ATP） release from vascular endothelial cells （VECs） is proposed in this paper to quantify the relationship between the ATP concentration at the surface of VECs and blood flow-induced shear stress. The simulation results demonstrate that ATP concentration at the surface of VECs predicted by the proposed new dynamic model is more consistent with the experimental observations than those by the existing static and dynamic models. Furthermore, it is the first time that a proportional-integral-derivative （PID） feedback controller is applied to modulate extracellular ATP concentration. Three types of desired ATP concentration profiles including constant, square wave and sinusoid are obtained by regulating the wall shear stress under this PID control. The systematic methodology utilized in this paper to model and control ATP release from VECs via adjusting external stimulus opens up a new scenario where quantitative investigations into the underlying mechanisms for many biochemical phenomena can be carded out for the sake of controlling specific cellular events.展开更多
In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stres...In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stress-induced Ca^2＋ influx. It is affected both by the Ca^2＋ gradient across the cell membrane and extracellular ATP concentration on the cell surface. Meanwhile, a new static ATP release model is constructed by using published experimental data. Combining the modified intracellular calcium dynamics model with the new ATP release model, we establish a nonlinear Ca^2＋ dynamic system in vascular endothelial cells. The ATP-mediated calcium response in vascular endothelial cells subjected to shear stresses is analyzed by solving the governing equations of the integrated dynamic system. Numerical results show that the shear-stress-induced calcium response predicted by the proposed model is more consistent with the experimental observations than that predicted by existing models.展开更多
This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system...This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system consisting of a sectionalized bus arrangement with four transmission lines (TLs) and two autotransformers. The obtained results validate the model and present some of the advantages of using this type of bus protection, such as fast and safe operation, even when under adverse conditions such as current transformers (CTs) magnetic core saturation upon the occurrence of external faults.展开更多
Possibilities of synchronized oscillations in glycolysis mediated by various extracellular metabolites are investigated theoretically using two-dimensional reaction-diffusion systems, which originate from the existing...Possibilities of synchronized oscillations in glycolysis mediated by various extracellular metabolites are investigated theoretically using two-dimensional reaction-diffusion systems, which originate from the existing seven-variable model. Our simulation results indicate the existence of alternative mediators such as ATP and 1,3-bisphosphoglycerate, in addition to already known acetaldehyde or pyruvate. Further, it is also suggested that the alternative intercellular communicator plays a more important role in the respect that these can synchronize oscillations instantaneously not only with difference phases but also with different periods. Relations between intercellular coupling and synchronization mechanisms are also analyzed and discussed by changing the values of parameters such as the diffusion coefficient and the cell density that can reflect in tercellular coupling strength.展开更多
为了研究安装于电网的静止无功补偿器特性及其对电网的影响,需要对SVC进行建模并进行电磁暂态仿真,为了达到电磁暂态研究的有效性,需要建立和实际SVC设备高度一致的仿真模型。通过实际案例介绍了通过ATP仿真软件建立和实际SVC设备高度...为了研究安装于电网的静止无功补偿器特性及其对电网的影响,需要对SVC进行建模并进行电磁暂态仿真,为了达到电磁暂态研究的有效性,需要建立和实际SVC设备高度一致的仿真模型。通过实际案例介绍了通过ATP仿真软件建立和实际SVC设备高度一致模型的方法,对于应用于电网的SVC的控制方法及建模方法进行了详细的阐述,详细介绍了低电压控制、自适应增益、通过线性拟合求解触发角等功能和方法。并将所建ATP模型的仿真结果和实际装置的RTDS(real time digital power system)仿真结果进行了对比,结果表明二者的波形非常接近,表明所建ATP模型能够充分反映SVC的实际特性,对于通过ATP仿真软件进行电磁暂态研究提供了有效和可信的手段。展开更多
基金supported by NUS Academic Research Fund (R-263-000-483-112)
文摘A new dynamic model for cell-deformation-induced adenosine triphosphate （ATP） release from vascular endothelial cells （VECs） is proposed in this paper to quantify the relationship between the ATP concentration at the surface of VECs and blood flow-induced shear stress. The simulation results demonstrate that ATP concentration at the surface of VECs predicted by the proposed new dynamic model is more consistent with the experimental observations than those by the existing static and dynamic models. Furthermore, it is the first time that a proportional-integral-derivative （PID） feedback controller is applied to modulate extracellular ATP concentration. Three types of desired ATP concentration profiles including constant, square wave and sinusoid are obtained by regulating the wall shear stress under this PID control. The systematic methodology utilized in this paper to model and control ATP release from VECs via adjusting external stimulus opens up a new scenario where quantitative investigations into the underlying mechanisms for many biochemical phenomena can be carded out for the sake of controlling specific cellular events.
基金the National Natural Science Foundation of China(No.10472027) the NUS Academic Research Fund(No.R-263-000-483-112)
文摘In consideration of the mechanism for shear-stress-induced Ca^2＋ influx via ATP（adenosine triphosphate）-gated ion channel P2X4 in vascular endothelial cells, a modified model is proposed to describe the shear-stress-induced Ca^2＋ influx. It is affected both by the Ca^2＋ gradient across the cell membrane and extracellular ATP concentration on the cell surface. Meanwhile, a new static ATP release model is constructed by using published experimental data. Combining the modified intracellular calcium dynamics model with the new ATP release model, we establish a nonlinear Ca^2＋ dynamic system in vascular endothelial cells. The ATP-mediated calcium response in vascular endothelial cells subjected to shear stresses is analyzed by solving the governing equations of the integrated dynamic system. Numerical results show that the shear-stress-induced calcium response predicted by the proposed model is more consistent with the experimental observations than that predicted by existing models.
文摘This paper presents a modeling of a high-impedance bus differential protection logic using the ATP (Alternative Transients Program) MODELS language. The model is validated using ATP simulations on an electrical system consisting of a sectionalized bus arrangement with four transmission lines (TLs) and two autotransformers. The obtained results validate the model and present some of the advantages of using this type of bus protection, such as fast and safe operation, even when under adverse conditions such as current transformers (CTs) magnetic core saturation upon the occurrence of external faults.
文摘Possibilities of synchronized oscillations in glycolysis mediated by various extracellular metabolites are investigated theoretically using two-dimensional reaction-diffusion systems, which originate from the existing seven-variable model. Our simulation results indicate the existence of alternative mediators such as ATP and 1,3-bisphosphoglycerate, in addition to already known acetaldehyde or pyruvate. Further, it is also suggested that the alternative intercellular communicator plays a more important role in the respect that these can synchronize oscillations instantaneously not only with difference phases but also with different periods. Relations between intercellular coupling and synchronization mechanisms are also analyzed and discussed by changing the values of parameters such as the diffusion coefficient and the cell density that can reflect in tercellular coupling strength.
文摘为了研究安装于电网的静止无功补偿器特性及其对电网的影响,需要对SVC进行建模并进行电磁暂态仿真,为了达到电磁暂态研究的有效性,需要建立和实际SVC设备高度一致的仿真模型。通过实际案例介绍了通过ATP仿真软件建立和实际SVC设备高度一致模型的方法,对于应用于电网的SVC的控制方法及建模方法进行了详细的阐述,详细介绍了低电压控制、自适应增益、通过线性拟合求解触发角等功能和方法。并将所建ATP模型的仿真结果和实际装置的RTDS(real time digital power system)仿真结果进行了对比,结果表明二者的波形非常接近,表明所建ATP模型能够充分反映SVC的实际特性,对于通过ATP仿真软件进行电磁暂态研究提供了有效和可信的手段。
