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A new circuit unit for the analysis and the synthesis of the chaotic behaviours in a fractional-order Liu system is proposed in this paper. Based on the approximation theory of fractional-order operator, an electronic circuit is designed to describe the dynamic behaviours of the fractional-order Liu system with α = 0.9. The results between simulation and experiment are in good agreement with each other, thereby proving that the chaos exists indeed in the fractional-order Liu system. 相似文献
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剪应力信号转导是目前细胞生物力学的研究热点之一。Ca^2+作为一种第二信使在剪应力信号转导中扮演了重要角色,钙信号转导是通过胞内自由Ca^2+浓度变化来实现的。胞内Ca^2+浓度的大小不仅依赖于细胞承受剪应力的大小,同时依赖于细胞外ATP的浓度。本文采用剪应力诱发内皮细胞分泌ATP的时变模型,通过对平行平板流动腔中的ATP浓度场进行数值模拟,分析了剪应力对培养内皮细胞表面ATP浓度的影响。结果表明,剪应力诱发的ATP分泌明显影响细胞表面附近ATP的浓度;剪应力、对流和扩散效应、ATP的水解作用共同决定了细胞外表面附近ATP的浓度。这一结果提示,剪应力大小并非剪应力信号转导过程中的唯一决定因素;剪应力的作用、激动剂的浓度改变共同参与了剪应力信号转导。 相似文献
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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. 相似文献
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