目的研究亚砷酸钠(Na As O2)对小鼠乳腺上皮细胞(NMu MG)的影响,为砷致乳腺癌机制提供理论依据。方法以小鼠乳腺上皮细胞为模型,研究亚砷酸钠对乳腺上皮细胞形态的影响;经流式细胞仪检测亚砷酸钠对小鼠乳腺上皮细胞凋亡的影响;实时定量R...目的研究亚砷酸钠(Na As O2)对小鼠乳腺上皮细胞(NMu MG)的影响,为砷致乳腺癌机制提供理论依据。方法以小鼠乳腺上皮细胞为模型,研究亚砷酸钠对乳腺上皮细胞形态的影响;经流式细胞仪检测亚砷酸钠对小鼠乳腺上皮细胞凋亡的影响;实时定量RT-PCR检测细胞周期基因P21 m RNAs表达水平。结果 Na As O2对NMu MG具有毒性效应,在一定浓度范围内,随Na As O2浓度升高,细胞形态明显改变,凋亡明显增多,且呈剂量-效应关系;细胞增殖的抑制基因P21 m RNA水平增高了18.12倍。结论亚砷酸钠可能通过上调P21基因的表达来抑制NMu MG增殖,可能是砷中毒引起乳腺癌的发生机制之一。展开更多
Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for prope...Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for proper design and construction of geogrid reinforced earth structures. Based on the calibrated model of sand and geogrid, a series of numerical pullout tests are conducted using PFC^(3D) under special considerations of particle angularity and aperture geometry of the geogrid. In this work, interface characteristics regarding the displacement and contact force developed among particles and the deformation and force distribution along the geogrid are all visualized with PFC^(3D) simulations so that new understanding on how geogrid-soil interaction develops under pullout loads can be obtained. Meanwhile, a new variable named fabric anisotropy coefficient is introduced to evaluate the inherent relationship between macroscopic strength and microscopic fabric anisotropy. A correlation analysis is adopted to compare the accuracy between the newly-proposed coefficient and the most commonly used one. Furthermore, additional pullout tests on geogrid with four different joint protrusion heights have been conducted to investigate what extent and how vertical reinforcement elements may result in reinforcement effects from perspectives of bearing resistance contribution, energy dissipation, as well as volumetric response. Numerical results show that both the magnitude and the directional variation of normal contact forces govern the development of macroscopic strength and the reinforcing effects of joint protrusion height can be attributed to the accelerated energy dissipation across the particle assembly and the intensive mobilization of the geogrid.展开更多
文摘目的研究亚砷酸钠(Na As O2)对小鼠乳腺上皮细胞(NMu MG)的影响,为砷致乳腺癌机制提供理论依据。方法以小鼠乳腺上皮细胞为模型,研究亚砷酸钠对乳腺上皮细胞形态的影响;经流式细胞仪检测亚砷酸钠对小鼠乳腺上皮细胞凋亡的影响;实时定量RT-PCR检测细胞周期基因P21 m RNAs表达水平。结果 Na As O2对NMu MG具有毒性效应,在一定浓度范围内,随Na As O2浓度升高,细胞形态明显改变,凋亡明显增多,且呈剂量-效应关系;细胞增殖的抑制基因P21 m RNA水平增高了18.12倍。结论亚砷酸钠可能通过上调P21基因的表达来抑制NMu MG增殖,可能是砷中毒引起乳腺癌的发生机制之一。
基金Projects(51278216,51478201)supported by the National Natural Science Foundation of China
文摘Geogrid has been extensively used in geotechnical engineering practice due to its effectiveness and economy. Deep insight into the interaction between the backfill soil and the geogrid is of great importance for proper design and construction of geogrid reinforced earth structures. Based on the calibrated model of sand and geogrid, a series of numerical pullout tests are conducted using PFC^(3D) under special considerations of particle angularity and aperture geometry of the geogrid. In this work, interface characteristics regarding the displacement and contact force developed among particles and the deformation and force distribution along the geogrid are all visualized with PFC^(3D) simulations so that new understanding on how geogrid-soil interaction develops under pullout loads can be obtained. Meanwhile, a new variable named fabric anisotropy coefficient is introduced to evaluate the inherent relationship between macroscopic strength and microscopic fabric anisotropy. A correlation analysis is adopted to compare the accuracy between the newly-proposed coefficient and the most commonly used one. Furthermore, additional pullout tests on geogrid with four different joint protrusion heights have been conducted to investigate what extent and how vertical reinforcement elements may result in reinforcement effects from perspectives of bearing resistance contribution, energy dissipation, as well as volumetric response. Numerical results show that both the magnitude and the directional variation of normal contact forces govern the development of macroscopic strength and the reinforcing effects of joint protrusion height can be attributed to the accelerated energy dissipation across the particle assembly and the intensive mobilization of the geogrid.
