The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithel...The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithelial morphogenesis.We review here the advantages of Drosophila as a model genetic organism, the morphogenesis of the epithelial structures of the posterior gut, and what is known about the genetic requirements to form these structures.In overview, primordia are patterned by expression of hierarchies of transcription factors; this leads to localized expression of cell signaling molecules, and finally, to the least understood step: modulation of cell adhesion and cell shape. We describe approaches to identify additional genes that are required for morphogenesis of these simple epithelia, particularly those that might play a structural role by affecting cell adhesion and cell shape.展开更多
In order to improve the dynamic response bandwidth of three-stage electro-hydraulic servo valve,a new method,speed-feedback control is presented in this paper.The construction and principle of three-stage electro-hydr...In order to improve the dynamic response bandwidth of three-stage electro-hydraulic servo valve,a new method,speed-feedback control is presented in this paper.The construction and principle of three-stage electro-hydraulic servo valve are explained,and the mathematical model of three-stage electro-hydraulic servo valve is built in frequency domain.Experimental and simulation results show that the bandwidth compared with proportional control is improved under speed-feedback control.Moreover,the research results play an important role in developing high performance three-stage electro-hydraulic servo valve.展开更多
文摘The posterior gut of the Drosophila embryo, consisting of hindgut and Malpighian tubules, provides a simple,well-defined system where it is possible to use a genetic approach to define components essential for epithelial morphogenesis.We review here the advantages of Drosophila as a model genetic organism, the morphogenesis of the epithelial structures of the posterior gut, and what is known about the genetic requirements to form these structures.In overview, primordia are patterned by expression of hierarchies of transcription factors; this leads to localized expression of cell signaling molecules, and finally, to the least understood step: modulation of cell adhesion and cell shape. We describe approaches to identify additional genes that are required for morphogenesis of these simple epithelia, particularly those that might play a structural role by affecting cell adhesion and cell shape.
基金Ministry of Science and Technology of China(No.2006BAF01B12-03)
文摘In order to improve the dynamic response bandwidth of three-stage electro-hydraulic servo valve,a new method,speed-feedback control is presented in this paper.The construction and principle of three-stage electro-hydraulic servo valve are explained,and the mathematical model of three-stage electro-hydraulic servo valve is built in frequency domain.Experimental and simulation results show that the bandwidth compared with proportional control is improved under speed-feedback control.Moreover,the research results play an important role in developing high performance three-stage electro-hydraulic servo valve.
