As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stabilit...As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stability of various engineering applications.Based on the pre-peak and post-peak stages of the rock stress-strain curve,this study constructed a brittleness index BI^(*).The index quantifies the ability of rock to resist plastic deformation during the pre-peak crack growth stage and evaluates the intensity of strength drop during the post-peak softening stage.Another index,BII,was established based on the degree of pre-peak elastic energy accumulation and the instability characteristics of post-peak dissipated energy.This index reflects the essential properties of rock failure by revealing the energy evolution mechanism.Furthermore,by defining a damage variable from the energy dissipation over the entire deformation process,an index B_(D)was introduced to evaluate brittleness from the perspective of internal damage development.Triaxial compression and cyclic loading tests were conducted on rocks of different lithologies to evaluate the new index.The influences of confining pressure and lithology on rock brittleness were analyzed,along with the sensitivity analysis of various brittleness index parameters.The results indicated that the proposed brittleness indices accurately distinguish the brittleness differences among various lithologies and show effective consistency with the failure modes of specimens under different confining pressures.Meanwhile,different brittleness indices were affected by confining pressure and lithology to different degrees.The post-peak softening stage of rock played a particularly significant role in brittleness analysis.A brittleness classification system under different confining pressures and lithologies was established.The research results contribute to the enhancement and refinement of the rock brittleness evaluation system.展开更多
The deteriorated bearing capacity and nonlinear expansion deformation of weakly cemented Xiyu conglomerate under complex water environments and stress disturbances pose significant risks to the safety of stratum engin...The deteriorated bearing capacity and nonlinear expansion deformation of weakly cemented Xiyu conglomerate under complex water environments and stress disturbances pose significant risks to the safety of stratum engineering construction.In this study,to precisely comprehend the influences of pore pressure(P_(w))and stress path on the deformation characteristics,dilation behavior,and damage evolution of Xiyu conglomerate,a series of triaxial monotonic loading and cyclic loading-unloading tests were conducted on saturated Xiyu conglomerate with varied confining pressures(σ_(3))and pore pressures.The results indicate that as P_(w)increases,the secant modulus,unloading modulus,and loading modulus decrease,but increase with risingσ_(3).Additionally,P_(w)accelerates the onset of dilatancy,whereasσ_(3)delays it.Asσ_(3)increases,the peak stress,crack damage stress,and residual strength increase,while these parameters decrease with increasing P_(w).A positive correlation exists between the effective confining pressure and the effective axial stress.Furthermore,an increase in P_(w)results in a greater maximum dilation angle,which decreases with increasingσ_(3).The failure mode is mainly a tensile-shear mixed failure mode.The high pore pressure and cyclic loading stress path aggravate the deterioration of strength and failure mode of the weakly cemented Xiyu conglomerate.Finally,a new damage variable and conceptual model are proposed and discussed.The findings provide insight into the damage and failure mechanism of the Xiyu conglomerate under pore pressure and cyclic disturbance,offering a crucial experimental foundation for the design and construction of hydropower projects in the Xiyu conglomerate layer.展开更多
The complex and special mechanical properties of Xiyu conglomerate are of great significance to the construction of water conservancy and hydropower engineering.The crack characteristic stress,dilatancy behavior,and f...The complex and special mechanical properties of Xiyu conglomerate are of great significance to the construction of water conservancy and hydropower engineering.The crack characteristic stress,dilatancy behavior,and failure mechanism of Xiyu conglomerate collected from Momoke Water Control Project,southwestern China,were analyzed and discussed based on the experimental results of triaxial compression test and 3D X-ray computed tomography test.The results show that with increasing confining pressure,the deformation characteristics and all characteristic stresses increase monotonically,while the dilation angle and dilatancy index decrease,and exponential function model can accurately describe the evolution rule of dilatancy index with confining pressure.While the porosity is negatively correlated with confining pressure.The failure modes of Xiyu conglomerate include axial tensile cracks,shear cracks,local cross cracks and cracks around gravel.With increasing confining pressure,the failure modes transform from tension cracks to shear cracks.A non-associated micromechanical damage model considering pressure dependent matrix presenting tension-compression asymmetry is proposed and applied to Xiyu conglomerate with pores and a large number of gravels.By comparing numerical calculations and experimental results,the proposed micromechanical plastic damage model is able to describe the mechanical behavior of Xiyu conglomerate.展开更多
Background: De novo lipogenesis (DNL) is a critical event for the development of tumors, in the present work,we revealed the role of propofol in colorectal cancer (CRC) cell proliferation. Methods: Western blotting (W...Background: De novo lipogenesis (DNL) is a critical event for the development of tumors, in the present work,we revealed the role of propofol in colorectal cancer (CRC) cell proliferation. Methods: Western blotting (WB), Real-timePCR, and luciferase combined with chromatin immunoprecipitation (ChIP) were used to identify the mechanismunderlying propofol-modulated cell proliferation in CRC cells. Results: Herein, we showed that propofol suppressedcell proliferation, which was attributed to the inhibition of DNL characterized by reduced fatty acid synthase (FASN),acetyl-coA carboxylase alpha (ACCA), and stearoyl-coA desaturase-1 (SCD1) expression. Mechanically, propofolstimulation decreased sterol regulatory element-binding proteins-1c (SREBP-1c) mature and nuclear translocation,which further decreased SCD1 transactivation confirmed by luciferase and ChIP analysis, while no significantdifference in total SREBP1c was observed. What’s more, supplementation of Monounsaturated fatty acid (MuFA)could reverse the inhibitory effect of propofol on cell proliferation. Conclusion: Taken together, these resultssuggested propofol modulated cell proliferation is dependent on SREBP1c-mediated DNL.展开更多
基金support from the National Natural Science Foundation of China(Grant Nos.12072102 and 12102129).
文摘As a critical mechanical characteristic of rock,brittleness significantly influences fracture modes and damage evolution processes.Accurate quantitative evaluation of brittleness is essential for ensuring the stability of various engineering applications.Based on the pre-peak and post-peak stages of the rock stress-strain curve,this study constructed a brittleness index BI^(*).The index quantifies the ability of rock to resist plastic deformation during the pre-peak crack growth stage and evaluates the intensity of strength drop during the post-peak softening stage.Another index,BII,was established based on the degree of pre-peak elastic energy accumulation and the instability characteristics of post-peak dissipated energy.This index reflects the essential properties of rock failure by revealing the energy evolution mechanism.Furthermore,by defining a damage variable from the energy dissipation over the entire deformation process,an index B_(D)was introduced to evaluate brittleness from the perspective of internal damage development.Triaxial compression and cyclic loading tests were conducted on rocks of different lithologies to evaluate the new index.The influences of confining pressure and lithology on rock brittleness were analyzed,along with the sensitivity analysis of various brittleness index parameters.The results indicated that the proposed brittleness indices accurately distinguish the brittleness differences among various lithologies and show effective consistency with the failure modes of specimens under different confining pressures.Meanwhile,different brittleness indices were affected by confining pressure and lithology to different degrees.The post-peak softening stage of rock played a particularly significant role in brittleness analysis.A brittleness classification system under different confining pressures and lithologies was established.The research results contribute to the enhancement and refinement of the rock brittleness evaluation system.
基金This work was supported by the Central University Basic Research Fund of China(B230201059and No.B240201155)the water science and technology special fund of Xinjiang Uygur Autonomous Region(No.XSKJ-2023-30)funded by China Power Construction Group research project(Grant No.DJ-HXGG-2023-16).
文摘The deteriorated bearing capacity and nonlinear expansion deformation of weakly cemented Xiyu conglomerate under complex water environments and stress disturbances pose significant risks to the safety of stratum engineering construction.In this study,to precisely comprehend the influences of pore pressure(P_(w))and stress path on the deformation characteristics,dilation behavior,and damage evolution of Xiyu conglomerate,a series of triaxial monotonic loading and cyclic loading-unloading tests were conducted on saturated Xiyu conglomerate with varied confining pressures(σ_(3))and pore pressures.The results indicate that as P_(w)increases,the secant modulus,unloading modulus,and loading modulus decrease,but increase with risingσ_(3).Additionally,P_(w)accelerates the onset of dilatancy,whereasσ_(3)delays it.Asσ_(3)increases,the peak stress,crack damage stress,and residual strength increase,while these parameters decrease with increasing P_(w).A positive correlation exists between the effective confining pressure and the effective axial stress.Furthermore,an increase in P_(w)results in a greater maximum dilation angle,which decreases with increasingσ_(3).The failure mode is mainly a tensile-shear mixed failure mode.The high pore pressure and cyclic loading stress path aggravate the deterioration of strength and failure mode of the weakly cemented Xiyu conglomerate.Finally,a new damage variable and conceptual model are proposed and discussed.The findings provide insight into the damage and failure mechanism of the Xiyu conglomerate under pore pressure and cyclic disturbance,offering a crucial experimental foundation for the design and construction of hydropower projects in the Xiyu conglomerate layer.
基金supported by National Natural Science Foundation of China(Nos.12102129 and 12072102)the Water Science and Technology Special Fund of Xinjiang Uygur Autonomous Region(No.XSKJ-2023-30)+1 种基金the Central University Basic Research Fund of China(Nos.B220202014 and B230201059)the Key Laboratory of Safe Mining of Deep Metal Mines,Ministry of Education(No.DM2022B01)。
文摘The complex and special mechanical properties of Xiyu conglomerate are of great significance to the construction of water conservancy and hydropower engineering.The crack characteristic stress,dilatancy behavior,and failure mechanism of Xiyu conglomerate collected from Momoke Water Control Project,southwestern China,were analyzed and discussed based on the experimental results of triaxial compression test and 3D X-ray computed tomography test.The results show that with increasing confining pressure,the deformation characteristics and all characteristic stresses increase monotonically,while the dilation angle and dilatancy index decrease,and exponential function model can accurately describe the evolution rule of dilatancy index with confining pressure.While the porosity is negatively correlated with confining pressure.The failure modes of Xiyu conglomerate include axial tensile cracks,shear cracks,local cross cracks and cracks around gravel.With increasing confining pressure,the failure modes transform from tension cracks to shear cracks.A non-associated micromechanical damage model considering pressure dependent matrix presenting tension-compression asymmetry is proposed and applied to Xiyu conglomerate with pores and a large number of gravels.By comparing numerical calculations and experimental results,the proposed micromechanical plastic damage model is able to describe the mechanical behavior of Xiyu conglomerate.
基金supported by Zhuhai Science and Technology Plan Project in the Field of Social Development(2320004000157)National Natural Science Foundation of China(82072215,82272219)+1 种基金Shenzhen Science and Technology Program(JCYJ20210324134602006)Natural Science Foundation of Guangdong Province(2214050001873).
文摘Background: De novo lipogenesis (DNL) is a critical event for the development of tumors, in the present work,we revealed the role of propofol in colorectal cancer (CRC) cell proliferation. Methods: Western blotting (WB), Real-timePCR, and luciferase combined with chromatin immunoprecipitation (ChIP) were used to identify the mechanismunderlying propofol-modulated cell proliferation in CRC cells. Results: Herein, we showed that propofol suppressedcell proliferation, which was attributed to the inhibition of DNL characterized by reduced fatty acid synthase (FASN),acetyl-coA carboxylase alpha (ACCA), and stearoyl-coA desaturase-1 (SCD1) expression. Mechanically, propofolstimulation decreased sterol regulatory element-binding proteins-1c (SREBP-1c) mature and nuclear translocation,which further decreased SCD1 transactivation confirmed by luciferase and ChIP analysis, while no significantdifference in total SREBP1c was observed. What’s more, supplementation of Monounsaturated fatty acid (MuFA)could reverse the inhibitory effect of propofol on cell proliferation. Conclusion: Taken together, these resultssuggested propofol modulated cell proliferation is dependent on SREBP1c-mediated DNL.
