Triggered seismicity is a key hazard where fluids are injected or withdrawn from the subsurface and may impact permeability. Understanding the mechanisms that control fluid injection-triggered seismicity allows its mi...Triggered seismicity is a key hazard where fluids are injected or withdrawn from the subsurface and may impact permeability. Understanding the mechanisms that control fluid injection-triggered seismicity allows its mitigation. Key controls on seismicity are defined in terms of fault and fracture strength, second-order frictional response and stability, and competing fluid-driven mechanisms for arrest. We desire to constrain maximum event magnitudes in triggered earthquakes by relating pre-existing critical stresses to fluid injection volume to explain why some recorded events are significantly larger than anticipated seismic moment thresholds. This formalism is consistent with several uncharacteristically large fluid injection-triggered earthquakes. Such methods of reactivating fractures and faults by hydraulic stimulation in shear or tensile fracturing are routinely used to create permeability in the subsurface. Microearthquakes (MEQs) generated by such stimulations can be used to diagnose permeability evolution. Although high-fidelity data sets are scarce, the EGS-Collab and Utah FORGE hydraulic stimulation field demonstration projects provide high-fidelity data sets that concurrently track permeability evolution and triggered seismicity. Machine learning deciphers the principal features of MEQs and the resulting permeability evolution that best track permeability changes – with transfer learning methods allowing robust predictions across multiple eological settings. Changes in permeability at reactivated fractures in both shear and extensional modes suggest that permeability change (Δk) scales with the seismic moment (M) of individual MEQs as Δk∝M. This scaling relation is exact at early times but degrades with successive MEQs, but provides a method for characterizing crustal permeability evolution using MEQs, alone. Importantly, we quantify for the first time the role of prestress in defining the elevated magnitude and seismic moment of fluid injection-triggered events, and demonstrate that such MEQs can also be used as diagnostic in quantifying permeability evolution in the crust.展开更多
The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensi...The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.展开更多
Two series of 5-iodo-l,2,3-triazole derivatives containing azobenzene group（s） were synthesized and their gelling properties were tested. Those containing two azobenzene groups （B series） have better gelation perf...Two series of 5-iodo-l,2,3-triazole derivatives containing azobenzene group（s） were synthesized and their gelling properties were tested. Those containing two azobenzene groups （B series） have better gelation performance than those containing one azobenzene group （A series）. The microstructure of organogels and the driving force of gelation were investigated by scanning electron microscopy and 1H NMR, respectively. It was found that π-π stacking, van der Waals interaction, and dipole-dipole interaction were the main forces of gelation. All the tested organogels are photoresponsive and those from B series are smarter than that from A series. Henry δp-δb diagrams of compounds A1, A2, and B2 were constructed on the basis of their gelation performance and the Hansen solubility parameters of related solvents. The constructed Henry δp-δh diagrams can be used to estimate the behavior of three compounds in any untested solvent.展开更多
Exosomes derived from mesenchymal stem cells(MSCs)have been confirmed to enhance cell proliferation and improve tissue repair.Exosomes release their contents into the cytoplasmic solution of the recipient cell to medi...Exosomes derived from mesenchymal stem cells(MSCs)have been confirmed to enhance cell proliferation and improve tissue repair.Exosomes release their contents into the cytoplasmic solution of the recipient cell to mediate cell expression,which is the main pathway through which exosomes exert therapeutic effects.The corresponding process of exosome internalization mainly occurs in the early stage of treatment.However,the therapeutic effect of exosomes in the early stage remains to be further studied.We report that the three-dimensional cell traction force can intuitively reflect the ability of exosomes to enhance the cytoskeleton and cell contractility of recipient cells,serving as an effective method to characterize the therapeutic effect of exosomes.Compared with traditional biochemical methods,we can visualize the early therapeutic effect of exosomes in real time without damage by quantifying the cell traction force.Through quantitative analysis of traction forces,we found that endometrial stromal cells exhibit short-term cell roundness accompanied by greater traction force during the early stage of exosome therapy.Further experiments revealed that exosomes enhance the traction force and cytoskeleton by regulating the Rac1/RhoA signaling pathway,thereby promoting cell proliferation.This work provides an effective method for rapidly quantifying the therapeutic effects of exosomes and studying the underlying mechanisms involved.展开更多
Understanding the dynamics of soil respiration,microbial carbon use efficiency(CUE),and temperature sensitivity(Q_(10))in response to exogenous organic matter(EOM)input,soil aggregate size,and incubation temperature i...Understanding the dynamics of soil respiration,microbial carbon use efficiency(CUE),and temperature sensitivity(Q_(10))in response to exogenous organic matter(EOM)input,soil aggregate size,and incubation temperature is crucial for predicting soil carbon cycling responses to environmental changes.In this study,these interactions were investigated by 180-day incubation of soil aggregates supplemented with EOM at various temperatures(5°C,15°C and 25°C).The results reveal an‘L-shaped’trend in soil respiration on the time scale across all treatments,characterized by initial rapid declines followed by stability.EOM input and higher temperatures significantly enhance respiration rates.Notably,the respiratory rates of soil aggregates of different sizes exhibit distinct patterns based on the presence or absence of EOM.Under conditions without the addition of EOM,larger aggregates show relatively lower respiration rates.Conversely,in the presence of EOM,larger aggregates exhibit higher respiratory rates.Furthermore,Q_(10)decreases with increasing aggregate size.The relationship between Q_(10)and the substrate quality index(SQI)supports the carbon quality temperature(CQT)hypothesis,highlighting SQI’s influence on Q_(10)values,particularly during later incubation stages.Microbial CUE decreases with EOM input and rising temperatures.Meanwhile,aggregate size plays a role in microbial CUE,with smaller aggregates exhibiting higher CUE due to enhanced nutrient availability.In conclusion,the intricate interplay of EOM input,aggregate size,and temperature significantly shapes soil respiration,microbial CUE,and Q_(10).These findings underscore the complexity of these interactions and their importance in modeling soil carbon dynamics under changing environmental conditions.展开更多
The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings.We proposed a solution for reducing background radiation from time-resol...The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings.We proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint(TSP)measurement in a hypersonic flow with Ma=6.5 and T_(0)=3525 K.The TSP was applied on an inlet ramp model,and the images were taken by a high-speed camera at 2 kHz under a modulated excitation.The strong background radiation led to a low signal-to-noise ratio and significant errors for the first half of the 130-ms test duration.Accordingly,three noise reduction methods were developed and evaluated based on temporal reconstruction,spatial reconstruction and robust principal component analysis(RPCA),respectively.The RPCA method showed the best performance that successfully recovered high-quality TSP data for a majority of test duration(t≥40 ms).展开更多
The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inhere...The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inherent limitation,that is,the spreading angle cannot be controlled independently,rather by the jet volume flow rate and internal geometry.Accordingly,two types of fluidic oscillators based on the master-slave design are developed in current study to decouple this correlation.In both designs,the master layer inherits the similar oscillation mechanisms of a sweeping jet,and the slave layer resembles a steady jet channel.The difference between the two designs is that Design A has a short diverging exit in the slave layer,but Design B adds a long interaction chamber in the exit channel to intensify flow instability.The external flow fields and governing oscillation properties of these two designs are experimentally explored with time-resolved Particle Image Velocimetry(PIV),while the internal flow dynamics and driving oscillation mechanisms are numerically investigated.By fixing the total volume flow rate,the jet spreading angle of Design A can be increased smoothly from 0°to above 100°by increasing the proportion of master layer’s flow rate from 0 to 100%.For Design B,the control authority of the master layer is significantly enhanced by adding the interaction chamber in the slave layer.In addition,the added chamber causes notable jet oscillation even when the master layer has none input.展开更多
基金Derek Elsworth acknowledges the support from a Gledden Visiting Fellowship from the Institute of Advanced Studies at the University of Western Australia,Australia,and the G.Albert Shoemaker Endowment at Pennsylvania State University,USA.
文摘Triggered seismicity is a key hazard where fluids are injected or withdrawn from the subsurface and may impact permeability. Understanding the mechanisms that control fluid injection-triggered seismicity allows its mitigation. Key controls on seismicity are defined in terms of fault and fracture strength, second-order frictional response and stability, and competing fluid-driven mechanisms for arrest. We desire to constrain maximum event magnitudes in triggered earthquakes by relating pre-existing critical stresses to fluid injection volume to explain why some recorded events are significantly larger than anticipated seismic moment thresholds. This formalism is consistent with several uncharacteristically large fluid injection-triggered earthquakes. Such methods of reactivating fractures and faults by hydraulic stimulation in shear or tensile fracturing are routinely used to create permeability in the subsurface. Microearthquakes (MEQs) generated by such stimulations can be used to diagnose permeability evolution. Although high-fidelity data sets are scarce, the EGS-Collab and Utah FORGE hydraulic stimulation field demonstration projects provide high-fidelity data sets that concurrently track permeability evolution and triggered seismicity. Machine learning deciphers the principal features of MEQs and the resulting permeability evolution that best track permeability changes – with transfer learning methods allowing robust predictions across multiple eological settings. Changes in permeability at reactivated fractures in both shear and extensional modes suggest that permeability change (Δk) scales with the seismic moment (M) of individual MEQs as Δk∝M. This scaling relation is exact at early times but degrades with successive MEQs, but provides a method for characterizing crustal permeability evolution using MEQs, alone. Importantly, we quantify for the first time the role of prestress in defining the elevated magnitude and seismic moment of fluid injection-triggered events, and demonstrate that such MEQs can also be used as diagnostic in quantifying permeability evolution in the crust.
基金The authors thank the National Key R&D Program of China(2016YFB0301100)National Natural Science Foundation of China(51571043)+1 种基金Graduate Research and Innovation Foundation of Chongqing,China(Grant No.CYB18004)Fundamental Research Funds for the Central Universities(Nos.2018CDJDCL0019,cqu2018CDHB1A08 and 2018CDGFCL0005).
文摘The strain hardening is an effective mode of enhancing mechanical properties in alloys.In this work,the strain hardening behaviors of Mg-xY(x=1,2,and 3 wt%)after extrusion process was investigated using uniaxial tensile tests.Results suggest that the Mg-xY alloys are composed ofα-Mg with a little amount of Mg24Y5 phase.The average grain size reduces from 19.8μm to 12.2μm as the Y content adds from 1 wt%to 2 wt%.Nevertheless,when Y content reaches 3 wt%,the grain size reaches to 12.9μm,which is close to that of Mg-2Y.The strain hardening rate decreases from 883 MPa to 798 MPa at(σ-σ0.2)=40 MPa,and Mg-2Y and Mg-3Y have the similar strain hardening response.Moreover,Mg-1Y shows an obvious ascending stage after the steep decreasing stage,which is mainly caused by the activation of twinning.The strain hardening behavior of Mg-xY is explained based on understanding the roles of the deformation mechanisms via deformation microstructure analysis and Visco-Plastic Self Consistent(VPSC)model.The variation of strain hardening characteristics with increasing Y content is related to the effects of grain size and texture.
基金Acknowledgements This work was supported by the Natural Science Foundation of Tianjin （No. 15JCYBJC20100）.
文摘Two series of 5-iodo-l,2,3-triazole derivatives containing azobenzene group（s） were synthesized and their gelling properties were tested. Those containing two azobenzene groups （B series） have better gelation performance than those containing one azobenzene group （A series）. The microstructure of organogels and the driving force of gelation were investigated by scanning electron microscopy and 1H NMR, respectively. It was found that π-π stacking, van der Waals interaction, and dipole-dipole interaction were the main forces of gelation. All the tested organogels are photoresponsive and those from B series are smarter than that from A series. Henry δp-δb diagrams of compounds A1, A2, and B2 were constructed on the basis of their gelation performance and the Hansen solubility parameters of related solvents. The constructed Henry δp-δh diagrams can be used to estimate the behavior of three compounds in any untested solvent.
基金supported by the National Natural Science Foundation of China(Grant Nos.12232017,12222212,and 12072339)the National Science and Technology Major Project(J2019-V-0006-0100).
文摘Exosomes derived from mesenchymal stem cells(MSCs)have been confirmed to enhance cell proliferation and improve tissue repair.Exosomes release their contents into the cytoplasmic solution of the recipient cell to mediate cell expression,which is the main pathway through which exosomes exert therapeutic effects.The corresponding process of exosome internalization mainly occurs in the early stage of treatment.However,the therapeutic effect of exosomes in the early stage remains to be further studied.We report that the three-dimensional cell traction force can intuitively reflect the ability of exosomes to enhance the cytoskeleton and cell contractility of recipient cells,serving as an effective method to characterize the therapeutic effect of exosomes.Compared with traditional biochemical methods,we can visualize the early therapeutic effect of exosomes in real time without damage by quantifying the cell traction force.Through quantitative analysis of traction forces,we found that endometrial stromal cells exhibit short-term cell roundness accompanied by greater traction force during the early stage of exosome therapy.Further experiments revealed that exosomes enhance the traction force and cytoskeleton by regulating the Rac1/RhoA signaling pathway,thereby promoting cell proliferation.This work provides an effective method for rapidly quantifying the therapeutic effects of exosomes and studying the underlying mechanisms involved.
基金supported by the National Natural Science Foundation of China(31971532 and 32171648).
文摘Understanding the dynamics of soil respiration,microbial carbon use efficiency(CUE),and temperature sensitivity(Q_(10))in response to exogenous organic matter(EOM)input,soil aggregate size,and incubation temperature is crucial for predicting soil carbon cycling responses to environmental changes.In this study,these interactions were investigated by 180-day incubation of soil aggregates supplemented with EOM at various temperatures(5°C,15°C and 25°C).The results reveal an‘L-shaped’trend in soil respiration on the time scale across all treatments,characterized by initial rapid declines followed by stability.EOM input and higher temperatures significantly enhance respiration rates.Notably,the respiratory rates of soil aggregates of different sizes exhibit distinct patterns based on the presence or absence of EOM.Under conditions without the addition of EOM,larger aggregates show relatively lower respiration rates.Conversely,in the presence of EOM,larger aggregates exhibit higher respiratory rates.Furthermore,Q_(10)decreases with increasing aggregate size.The relationship between Q_(10)and the substrate quality index(SQI)supports the carbon quality temperature(CQT)hypothesis,highlighting SQI’s influence on Q_(10)values,particularly during later incubation stages.Microbial CUE decreases with EOM input and rising temperatures.Meanwhile,aggregate size plays a role in microbial CUE,with smaller aggregates exhibiting higher CUE due to enhanced nutrient availability.In conclusion,the intricate interplay of EOM input,aggregate size,and temperature significantly shapes soil respiration,microbial CUE,and Q_(10).These findings underscore the complexity of these interactions and their importance in modeling soil carbon dynamics under changing environmental conditions.
基金supported by the National Natural Science Foundation of China(Grants 11725209 and 11872038)and funding from Gas Turbine Research Institute of Shanghai Jiao Tong University.
文摘The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings.We proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint(TSP)measurement in a hypersonic flow with Ma=6.5 and T_(0)=3525 K.The TSP was applied on an inlet ramp model,and the images were taken by a high-speed camera at 2 kHz under a modulated excitation.The strong background radiation led to a low signal-to-noise ratio and significant errors for the first half of the 130-ms test duration.Accordingly,three noise reduction methods were developed and evaluated based on temporal reconstruction,spatial reconstruction and robust principal component analysis(RPCA),respectively.The RPCA method showed the best performance that successfully recovered high-quality TSP data for a majority of test duration(t≥40 ms).
基金financial support from the National Natural Science Foundation of China(Nos.12072196 and 11702172)Science and Technology Commission of Shanghai Municipality(No.19JC1412900)+1 种基金Aeronautics Power Foundation(No.6141B09050393)Key Laboratory of Aerodynamic Noise Control(No.ANCL20190106)extended to this study。
文摘The fluidic oscillator is an instrument that can continuously generate a spatially sweeping jet entirely based on its internal geometry without any moving parts.However,the traditional fluidic oscillator has an inherent limitation,that is,the spreading angle cannot be controlled independently,rather by the jet volume flow rate and internal geometry.Accordingly,two types of fluidic oscillators based on the master-slave design are developed in current study to decouple this correlation.In both designs,the master layer inherits the similar oscillation mechanisms of a sweeping jet,and the slave layer resembles a steady jet channel.The difference between the two designs is that Design A has a short diverging exit in the slave layer,but Design B adds a long interaction chamber in the exit channel to intensify flow instability.The external flow fields and governing oscillation properties of these two designs are experimentally explored with time-resolved Particle Image Velocimetry(PIV),while the internal flow dynamics and driving oscillation mechanisms are numerically investigated.By fixing the total volume flow rate,the jet spreading angle of Design A can be increased smoothly from 0°to above 100°by increasing the proportion of master layer’s flow rate from 0 to 100%.For Design B,the control authority of the master layer is significantly enhanced by adding the interaction chamber in the slave layer.In addition,the added chamber causes notable jet oscillation even when the master layer has none input.
