Oocytes display a maternal-specific gene expression profile, which is switched to a zygotic profile when a haploid set of chromatin is passed on to the fertilized egg that develops into an embryo. The mechanism underl...Oocytes display a maternal-specific gene expression profile, which is switched to a zygotic profile when a haploid set of chromatin is passed on to the fertilized egg that develops into an embryo. The mechanism underlying this transcription reprogramming is currently unknown. Here we demonstrate that by the time when transcription is shut down in germinal vesicle oocytes, a range of general transcription factors and transcriptional regulators are dissociated from the chromatin. The global dissociation of chromatin factors （CFs） disrupts physical contacts between the chromatin and CFs and leads to erasure of the maternal transcription program at the functional level. Critical transcription factors and regulators remain separated from chromatin for a prolonged period, and become re-associated with chromatin shortly after pronuclear formation. This is followed temporally by the re-establishment of nuclear functions such as DNA replication and transcription. We propose that the maternal transcription program is erased during oogenesis to generate a relatively naive chromatin and the zygotic transcription program is rebuilt de novo after fertilization. This process is termed as the ＂erase-and-rebuild＂ process, which is used to reset the transcription program, and most likely other nuclear processes as well, from a maternal one to that of the embryo. We further show in the accompanying paper （Gao T, et al., Cell Res 2007; 17：135-150.） that the same strategy is also employed to reprogram transcriptional profiles in somatic cell nuclear transfer and parthenogenesis, suggesting that this model is universally applicable to all forms of transcriptional reprogramming during early embryogenesis. Displacement of CFs from chromatin also offers an explanation for the phenomenon of transcription silence during the maternal to zygotic transition.展开更多
Corporate restructuring has become a major component in the financial and economic environment all over the world. Industrial restructuring has raised important issues for business decisions as well as for public poli...Corporate restructuring has become a major component in the financial and economic environment all over the world. Industrial restructuring has raised important issues for business decisions as well as for public policy formulation. Since 1991, Indian industries have been increasingly exposed to both domestic and international competition and competitiveness. The companies started restructuring there operations around their core business there M ＆ A. But M ＆ A is an area of potential good and harm in corporate strategy including manufacturing industry. Therefore, an attempt has been made to analyze the security returns and to find out the net wealth increase or decrease to the shareholders of acquiring firms. In India, there are totally 58 manufacturing companies which have undergone mergers and acquisitions during 2000, 2001 ＆ 2002. Thirty percentage from the total population was taken as sample size （i.e., 17 companies out of 58）. The present study is mainly based on secondary data. The Market Model and Market Adjusted Returns Model analysis are used as tools of analysis.展开更多
The paper investigates the consensus problem of multiple nonholonomic systems. Two event-triggered control strategies, one centralized and the other distributed, are developed, which can reduce the frequency of contro...The paper investigates the consensus problem of multiple nonholonomic systems. Two event-triggered control strategies, one centralized and the other distributed, are developed, which can reduce the frequency of control updating. Under the proposed protocols, the multiple nonholonomic systems can achieve consensus, and the bound of inter-event time intervals is provided to illustrate that no Zeno behavior exists. Finally, numerical simulations are also provided to demonstrate the effectiveness of the proposed control strategies.展开更多
文摘Oocytes display a maternal-specific gene expression profile, which is switched to a zygotic profile when a haploid set of chromatin is passed on to the fertilized egg that develops into an embryo. The mechanism underlying this transcription reprogramming is currently unknown. Here we demonstrate that by the time when transcription is shut down in germinal vesicle oocytes, a range of general transcription factors and transcriptional regulators are dissociated from the chromatin. The global dissociation of chromatin factors （CFs） disrupts physical contacts between the chromatin and CFs and leads to erasure of the maternal transcription program at the functional level. Critical transcription factors and regulators remain separated from chromatin for a prolonged period, and become re-associated with chromatin shortly after pronuclear formation. This is followed temporally by the re-establishment of nuclear functions such as DNA replication and transcription. We propose that the maternal transcription program is erased during oogenesis to generate a relatively naive chromatin and the zygotic transcription program is rebuilt de novo after fertilization. This process is termed as the ＂erase-and-rebuild＂ process, which is used to reset the transcription program, and most likely other nuclear processes as well, from a maternal one to that of the embryo. We further show in the accompanying paper （Gao T, et al., Cell Res 2007; 17：135-150.） that the same strategy is also employed to reprogram transcriptional profiles in somatic cell nuclear transfer and parthenogenesis, suggesting that this model is universally applicable to all forms of transcriptional reprogramming during early embryogenesis. Displacement of CFs from chromatin also offers an explanation for the phenomenon of transcription silence during the maternal to zygotic transition.
文摘Corporate restructuring has become a major component in the financial and economic environment all over the world. Industrial restructuring has raised important issues for business decisions as well as for public policy formulation. Since 1991, Indian industries have been increasingly exposed to both domestic and international competition and competitiveness. The companies started restructuring there operations around their core business there M ＆ A. But M ＆ A is an area of potential good and harm in corporate strategy including manufacturing industry. Therefore, an attempt has been made to analyze the security returns and to find out the net wealth increase or decrease to the shareholders of acquiring firms. In India, there are totally 58 manufacturing companies which have undergone mergers and acquisitions during 2000, 2001 ＆ 2002. Thirty percentage from the total population was taken as sample size （i.e., 17 companies out of 58）. The present study is mainly based on secondary data. The Market Model and Market Adjusted Returns Model analysis are used as tools of analysis.
基金supported by the National Natural Science Foundation of China under Grant Nos.61573200and 61573199
文摘The paper investigates the consensus problem of multiple nonholonomic systems. Two event-triggered control strategies, one centralized and the other distributed, are developed, which can reduce the frequency of control updating. Under the proposed protocols, the multiple nonholonomic systems can achieve consensus, and the bound of inter-event time intervals is provided to illustrate that no Zeno behavior exists. Finally, numerical simulations are also provided to demonstrate the effectiveness of the proposed control strategies.
