染色质高级结构在基因调控中起到不可忽视的作用,染色质结构的形成与调控机制受到广泛关注。"相分离"理论近年来受到较多关注,异染色质与转录因子在其中的作用引人瞩目。但是,目前的相分离模型更关注结合因子与表观遗传性质,...染色质高级结构在基因调控中起到不可忽视的作用,染色质结构的形成与调控机制受到广泛关注。"相分离"理论近年来受到较多关注,异染色质与转录因子在其中的作用引人瞩目。但是,目前的相分离模型更关注结合因子与表观遗传性质,对DNA序列自身的作用理解尚较不充分。许多物种基因组的序列分布均具有多尺度的不均一性,仅基于Cp G岛(Cp G island,CGI)密度差异这一序列性质,就可以划分出基因、表观遗传、结构和转录性质都截然不同的高CGI密度"森林"和低CGI密度"草原"两种序列区域,体现了基因组自身的马赛克性。本文聚焦染色质结构的序列依赖性,讨论了染色质结构模型的研究进展,关注在序列几乎相同的不同细胞类型中的序列–结构关系及其功能调控,对发育、分化、衰老、疾病等多种过程的染色质结构变化进行了系统分析。针对基于序列的染色质相分离模型,对其物理驱动力进行了讨论,并在该模型的框架下基于相分离的物理特性,对温度、序列不均一性等物理因素对染色质结构可能造成的影响进行了探讨。展开更多
The oil-gas two-phase hybrid transportation technology is one of the innovative technology directions for the exploitation and transportation of marginal and deep ocean oilfields.The helical-axial multiphase pump is a...The oil-gas two-phase hybrid transportation technology is one of the innovative technology directions for the exploitation and transportation of marginal and deep ocean oilfields.The helical-axial multiphase pump is a key equipment for oil and gas extraction.At this stage,most of the research on this kind of pump focuses on the improvement of the structure and conveying performance.However,because of insufficient understanding of the flow behavior and mechanism of bubbles,it is easy to cause the gas-liquid separation.In this paper,the numerical simulation and test are combined to explore the changes in the bubble trajectory and flow structure of the helical-axial multiphase pump.The results shown that when the speed is lower than 1200 r/min,the bubble reaches the maximum volume at 1/2 of the midline of the impeller blade and it contact with the pressure surface,broken to the suction surface.When the rotation speed is higher than 1450 r/min,the number of bubbles in the impeller increases and the size decreases.The backflow occurs in the tip clearance and strength increases continuously.The research results have important significance for the theoretical design and engineering application of the helical-axial multiphase pump.展开更多
Background:High-order chromatin structure has been shown to play a vital role in gene regulation.Previously we identified two types of sequence domains,CGI(CpG island)forest and CGI prairie,which tend to spatially seg...Background:High-order chromatin structure has been shown to play a vital role in gene regulation.Previously we identified two types of sequence domains,CGI(CpG island)forest and CGI prairie,which tend to spatially segregate,but to different extent in different tissues.Here we aim to further quantify the association of domain segregation with gene regulation and therefore differentiation.Methods:By means of the published RNA-seq and Hi-C data,we identified tissue-specific genes and quantitatively investigated how their regulation is relevant to chromatin structure.Besides,two types of gene networks were constructed and the association between gene pair co-regulation and genome organization is discussed.Results:We show that compared to forests,tissue-specific genes tend to be enriched in prairies.Highly specific genes also tend to cluster according to their functions in a relatively small number of prairies.Furthermore,tissue-specific forest-prairie contact formation was associated with the regulation of tissue-specific genes,in particular those in the prairie domains,pointing to the important role of gene positioning,in the linear DNA sequence as well as in 3D chromatin structure,in gene regulatory network formation.Conclusion:We investigated how gene regulation is related to genome organization from the perspective of forest-prairie spatial interactions.Since unlike compartments A and B,forest and prairie are identified solely based on sequence properties.Therefore,the simple and uniform framework(forest-prairie domain segregation)provided here can be utilized to further understand the chromatin structure changes as well as the underlying biological significances in different stages,such as tumorgenesis.展开更多
文摘染色质高级结构在基因调控中起到不可忽视的作用,染色质结构的形成与调控机制受到广泛关注。"相分离"理论近年来受到较多关注,异染色质与转录因子在其中的作用引人瞩目。但是,目前的相分离模型更关注结合因子与表观遗传性质,对DNA序列自身的作用理解尚较不充分。许多物种基因组的序列分布均具有多尺度的不均一性,仅基于Cp G岛(Cp G island,CGI)密度差异这一序列性质,就可以划分出基因、表观遗传、结构和转录性质都截然不同的高CGI密度"森林"和低CGI密度"草原"两种序列区域,体现了基因组自身的马赛克性。本文聚焦染色质结构的序列依赖性,讨论了染色质结构模型的研究进展,关注在序列几乎相同的不同细胞类型中的序列–结构关系及其功能调控,对发育、分化、衰老、疾病等多种过程的染色质结构变化进行了系统分析。针对基于序列的染色质相分离模型,对其物理驱动力进行了讨论,并在该模型的框架下基于相分离的物理特性,对温度、序列不均一性等物理因素对染色质结构可能造成的影响进行了探讨。
基金supported by the National Natural Science Foundation of China(Grant Nos.51969014,51609113)supported by the China Postdoctoral Science Foundation(Grant No.2018M633651XB)+2 种基金the Natural Science Foundation of Gansu(Grant No.20JR5RA456)the Outstanding Young Talents Funding Scheme of Gansu province(Grant No.20JR10RA204)the Hong liu Outstanding Young Talents Funding Schemeof Lanzhou University of Technology.
文摘The oil-gas two-phase hybrid transportation technology is one of the innovative technology directions for the exploitation and transportation of marginal and deep ocean oilfields.The helical-axial multiphase pump is a key equipment for oil and gas extraction.At this stage,most of the research on this kind of pump focuses on the improvement of the structure and conveying performance.However,because of insufficient understanding of the flow behavior and mechanism of bubbles,it is easy to cause the gas-liquid separation.In this paper,the numerical simulation and test are combined to explore the changes in the bubble trajectory and flow structure of the helical-axial multiphase pump.The results shown that when the speed is lower than 1200 r/min,the bubble reaches the maximum volume at 1/2 of the midline of the impeller blade and it contact with the pressure surface,broken to the suction surface.When the rotation speed is higher than 1450 r/min,the number of bubbles in the impeller increases and the size decreases.The backflow occurs in the tip clearance and strength increases continuously.The research results have important significance for the theoretical design and engineering application of the helical-axial multiphase pump.
基金the National Natural Science Foundation of China(Nos.21927901,21821004 and 21873007)the National Key R&D Program of China(No.2017YFA0204702).
文摘Background:High-order chromatin structure has been shown to play a vital role in gene regulation.Previously we identified two types of sequence domains,CGI(CpG island)forest and CGI prairie,which tend to spatially segregate,but to different extent in different tissues.Here we aim to further quantify the association of domain segregation with gene regulation and therefore differentiation.Methods:By means of the published RNA-seq and Hi-C data,we identified tissue-specific genes and quantitatively investigated how their regulation is relevant to chromatin structure.Besides,two types of gene networks were constructed and the association between gene pair co-regulation and genome organization is discussed.Results:We show that compared to forests,tissue-specific genes tend to be enriched in prairies.Highly specific genes also tend to cluster according to their functions in a relatively small number of prairies.Furthermore,tissue-specific forest-prairie contact formation was associated with the regulation of tissue-specific genes,in particular those in the prairie domains,pointing to the important role of gene positioning,in the linear DNA sequence as well as in 3D chromatin structure,in gene regulatory network formation.Conclusion:We investigated how gene regulation is related to genome organization from the perspective of forest-prairie spatial interactions.Since unlike compartments A and B,forest and prairie are identified solely based on sequence properties.Therefore,the simple and uniform framework(forest-prairie domain segregation)provided here can be utilized to further understand the chromatin structure changes as well as the underlying biological significances in different stages,such as tumorgenesis.
