How cells accomplish cell size homeostasis is a fascinating topic, and several cell size regulation mechanisms were proposed: timer, sizer, and adder. Recently the adder model has received a great deal of attention. A...How cells accomplish cell size homeostasis is a fascinating topic, and several cell size regulation mechanisms were proposed: timer, sizer, and adder. Recently the adder model has received a great deal of attention. Adder property was also found in the DNA replication cycle. This paper aims to explain the adder phenomenon both in the division-centric picture and replication-centric picture at the molecular level. We established a self-replication model, and the system reached a steady state quickly based on evolution rules. We collected tens of thousands of cells in the same trajectory and calculated the Pearson correlation coefficient between biological variables to decide which regulatory mechanism was adopted by cells. Our simulation results confirmed the double-adder mechanism. Chromosome replication initiation and cell division control are independent and regulated by respective proteins.Cell size homeostasis originates from division control and has nothing to do with replication initiation control. At a slow growth rate, the deviation from adder toward sizer comes from a significant division protein degradation rate when division protein is auto-inhibited. Our results indicated the two necessary conditions in the double-adder mechanism: one is balanced biosynthesis, and the other is that there is a protein trigger threshold to inspire DNA replication initiation and cell division. Our results give insight to the regulatory mechanism of cell size and instructive to synthetic biology.展开更多
最大功率点跟踪控制（Maximum Power Point Tracking,MPPT）技术可以使光伏系统工作在最大功率点处,从而提高光伏系统的发电效率。本文首先对光伏MPPT算法进行了分类及其性能进行比较,针对传统变步长算法存在跟踪死区,导致光伏系统的启...最大功率点跟踪控制（Maximum Power Point Tracking,MPPT）技术可以使光伏系统工作在最大功率点处,从而提高光伏系统的发电效率。本文首先对光伏MPPT算法进行了分类及其性能进行比较,针对传统变步长算法存在跟踪死区,导致光伏系统的启动性能和跟踪性能变差的缺陷。本文提出一种基于自适应变步长模糊控制实现最大功率点跟踪算法,即用模糊控制语言实现功率开关管的控制。结果表明该方法相比传统的扰动观察法能够快速、准确跟踪到最大功率点,具有较好的动态和稳态性能,提高了光伏系统输出功率的效率,降低跟踪过程中的能量损失,最后,总结目前模糊控制算法在光伏系统MPPT中的应用情况。展开更多
The molecular mechanisms of organ size control and regulation remain one of the major unsolved mysteries of development biology. Almost a decade ago, the discovery of the Hippo signaling pathway in Drosophila shed som...The molecular mechanisms of organ size control and regulation remain one of the major unsolved mysteries of development biology. Almost a decade ago, the discovery of the Hippo signaling pathway in Drosophila shed some light on this puzzling issue. The Hippo signaling pathway is highly conserved in both invertebrates and vertebrates, and plays critical roles in animal development. It controls organ size and growth by inhibiting cell proliferation and by promoting apoptosis. Malfunction of the Hippo signaling pathway leads to cancer development and tumorigenesis. Although the core of the signaling pathway is well understood, the upstream inputs and downstream transcriptional regulation are still obscure to us. In this review, we summarize the current understanding of the mechanism and the function of the Hippo signaling pathway and compare its differences between flies and mammals. We underline the crosstalk between the Hippo signaling pathway and other signaling pathways, and the possible roles of the Hippo pathway in stem cell proliferation and self-renewal.展开更多
文摘How cells accomplish cell size homeostasis is a fascinating topic, and several cell size regulation mechanisms were proposed: timer, sizer, and adder. Recently the adder model has received a great deal of attention. Adder property was also found in the DNA replication cycle. This paper aims to explain the adder phenomenon both in the division-centric picture and replication-centric picture at the molecular level. We established a self-replication model, and the system reached a steady state quickly based on evolution rules. We collected tens of thousands of cells in the same trajectory and calculated the Pearson correlation coefficient between biological variables to decide which regulatory mechanism was adopted by cells. Our simulation results confirmed the double-adder mechanism. Chromosome replication initiation and cell division control are independent and regulated by respective proteins.Cell size homeostasis originates from division control and has nothing to do with replication initiation control. At a slow growth rate, the deviation from adder toward sizer comes from a significant division protein degradation rate when division protein is auto-inhibited. Our results indicated the two necessary conditions in the double-adder mechanism: one is balanced biosynthesis, and the other is that there is a protein trigger threshold to inspire DNA replication initiation and cell division. Our results give insight to the regulatory mechanism of cell size and instructive to synthetic biology.
文摘最大功率点跟踪控制（Maximum Power Point Tracking,MPPT）技术可以使光伏系统工作在最大功率点处,从而提高光伏系统的发电效率。本文首先对光伏MPPT算法进行了分类及其性能进行比较,针对传统变步长算法存在跟踪死区,导致光伏系统的启动性能和跟踪性能变差的缺陷。本文提出一种基于自适应变步长模糊控制实现最大功率点跟踪算法,即用模糊控制语言实现功率开关管的控制。结果表明该方法相比传统的扰动观察法能够快速、准确跟踪到最大功率点,具有较好的动态和稳态性能,提高了光伏系统输出功率的效率,降低跟踪过程中的能量损失,最后,总结目前模糊控制算法在光伏系统MPPT中的应用情况。
基金supported by the grants from the National Natural Science Foundation of China(No.30971646)the National Basic Research Program of China(973 Program No. 2010CB912100)+2 种基金the National Key Basic Research and Development Program of China(No.2011CB915502)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XDA01010406)L.Z.is the scholar of the Hundred Talents Program of the Chinese Academy of Sciences
文摘The molecular mechanisms of organ size control and regulation remain one of the major unsolved mysteries of development biology. Almost a decade ago, the discovery of the Hippo signaling pathway in Drosophila shed some light on this puzzling issue. The Hippo signaling pathway is highly conserved in both invertebrates and vertebrates, and plays critical roles in animal development. It controls organ size and growth by inhibiting cell proliferation and by promoting apoptosis. Malfunction of the Hippo signaling pathway leads to cancer development and tumorigenesis. Although the core of the signaling pathway is well understood, the upstream inputs and downstream transcriptional regulation are still obscure to us. In this review, we summarize the current understanding of the mechanism and the function of the Hippo signaling pathway and compare its differences between flies and mammals. We underline the crosstalk between the Hippo signaling pathway and other signaling pathways, and the possible roles of the Hippo pathway in stem cell proliferation and self-renewal.
