Dear Editor Targeted genome-editing tools are very important and efficient for plant functional genomics research, especially when proper mutants are not available. CRISPR/Cas9-based genome edit- ing is a recently dev...Dear Editor Targeted genome-editing tools are very important and efficient for plant functional genomics research, especially when proper mutants are not available. CRISPR/Cas9-based genome edit- ing is a recently developed powerful technology derived from the bacterial clustered regularly interspaced short palindromic repeats （CRISPR）/CRISPR-associated （Cas） defense system,展开更多
Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted accord...Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted according to the local traffic density in its vision and its current velocity. The numerical simulation results show that the maximum traffic capacity of the improved model under the same parameters is greater than that of the Nagel-Schreckenberg model, and is closer to the measured data. In addition, the traffic flow and vehicle velocity under different meteorological conditions are simulated by using the improved model, and the synchronized flow phenomenon consistent with the actual traffic is reproduced. Meanwhile, the results show that under the same parameters, when the traffic density is equal to 0.3, the traffic flow of the improved model increases by about 11% compared with the original model, and when the traffic density increases to 0.6, the traffic flow increases by about 27%. .展开更多
The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportio...The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were studied.The size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring(FBRM)technique,and the influencing factors of aggregation and breakage kinetics of CPB were discussed.The results indicate that influenced by both internal and external factors,the paste kinetics evolution covers the dynamic phase and the stable phase.Increasing the mass content or the cement-tailings ratio can accelerate aggregation kinetics,which is advantageous for the rise of average floc size.Besides,the admixture and high shear can improve breaking kinetics,which is beneficial to reduce the average floc size.The chord length resembles a normal distribution somewhat,with a peak value of approximate 20μm.The particle disaggregation con-stant(k_(2))is positively correlated with the agitation rate,and k_(2) is five orders of magnitude greater than the particle aggregation constant(k1).The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.展开更多
Precisely designing atomic metal-nitrogen-carbon(M-N-C)catalysts with asymmetric diatomic configurations and studying their structure–activity relationships for oxygen reduction reaction(ORR)are important for zinc-ai...Precisely designing atomic metal-nitrogen-carbon(M-N-C)catalysts with asymmetric diatomic configurations and studying their structure–activity relationships for oxygen reduction reaction(ORR)are important for zinc-air batteries(ZABs).Herein,a dualatomic-site catalyst(DASC)with CoN_(3)S-MnN_(2)S_(2) configuration was prepared for the cathodes of ZABs.Compared with Co-N-C(Mn-free)and CoMn-N-C(S-free doping),CoMn-N/S-C exhibits excellent half-wave potential(0.883 V)and turnover frequency(1.54 e·s^(−1)·site^(−1)),surpassing most of the reported state-of-the-art Pt-free ORR catalysts.The CoMn-N/S-C-based ZABs achieve extremely high specific capacity(959 mAh·g^(−1))and good stability(350 h@5 mA·cm^(−2)).Density functional theory(DFT)calculation shows that the introduction of Mn and S can break the electron configuration symmetry of the original Co 3d orbital,lower the dband center of the Co site,and optimize the desorption behavior of*OH intermediate,thereby increasing the ORR activity.展开更多
The development of industry is inseparable from the support of mining.However,mining processes consume a large amount of energy,and increased tailing emissions can have a significant impact on the environment.In the p...The development of industry is inseparable from the support of mining.However,mining processes consume a large amount of energy,and increased tailing emissions can have a significant impact on the environment.In the past few decades,the mining industry developed many technologies that are related to mineral energy management,of which cemented paste backfill(CPB)is one of the representative technologies.CPB has been successfully applied to mine ground control and tailings management.In CPB technology,the mixing process is the key to achieving materials with good final quality and controlled properties.However,in the preparation process,the mixed homogeneity of the CPB is difficult to achieve because of fine tailings,high solid volume fraction,and high viscosity.Most research focused on the effect of mixing ingredients on CPB properties rather than on the preparation process of the CPB.Therefore,improving the performance and reducing the production cost of CPB by optimizing the mixing process are important.This review summarizes the current studies on the mixing technology of CPB and its application status in China.Then,it compares the advantages and disadvantages of multiple mixing equipment and discusses the latest results and research hotspots in paste preparation.Finally,it concludes the challenges and development trends of mixing technology on the basis of the relevant application cases in China to promoting cement-based material mixing technology development.展开更多
Developing an efficient,interface-rich,and free-standing non-noble-metal electrocatalyst is vital for the flexible zinc-air batteries(ZABs).Herein,a three-dimensional(3D)heterogeneous carbon-based flexible membrane wa...Developing an efficient,interface-rich,and free-standing non-noble-metal electrocatalyst is vital for the flexible zinc-air batteries(ZABs).Herein,a three-dimensional(3D)heterogeneous carbon-based flexible membrane was assembled by Co@carbon nanosheets/carbon nanotubes and hollow carbon nanofiber(Co@NS/CNT-CNF)as an efficient oxygen reduction reaction(ORR)catalyst with a positive half-wave potential of 0.846 V and a small Tafel slope of 79 mV·dec^(-1).Meanwhile,the Co@NS/CNT-CNF electrode also exhibits excellent open-circuit voltage,peak power density,and long-time cycling stability in liquid-state ZABs(1.605 V,163 mW·cm^(-2),and 400 h)and flexible ZABs under flat/bending condition(1.47 V,102 mW·cm^(-2),and 80 h).Such heterogeneous flexible membrane architecture not only optimizes the electrolyte infiltration,but also provides capacious possibility for O_(2)and electrolyte transfer.Meanwhile,work-function analyses coupled with density functional theory(DFT)results demonstrate that the electron transfer capability and metal-support interaction can be well optimized in the obtained Co@NS/CNT-CNF catalyst.展开更多
To investigate the feasibility and effectiveness of establishing porcine ischemia-reperfusion models by ligating the left anterior descending(LAD)coronary artery,we first randomly divided 16 male Bama pigs into a sham...To investigate the feasibility and effectiveness of establishing porcine ischemia-reperfusion models by ligating the left anterior descending(LAD)coronary artery,we first randomly divided 16 male Bama pigs into a sham group and a model group.After anesthesia,we separated the arteries and veins.Subsequently,we rapidly located the LAD coronary artery at the beginning of its first diagonal branch through a mid-chest incision.Then,we loosened and released the ligation line after five minutes of pre-occlusion.Finally,we ligated the LAD coronary artery in situ two minutes later and loosened the ligature 60 min after ischemia.Compared with the sham group,electrocardiogram showed multiple continuous lead ST-segment elevations,and ultrasound cardiogram showed significantly lower ejection fraction and left ventricular fractional shortening at one hour and seven days post-operation in the model group.Twenty-four hours after the operation,cardiac troponin T and creatine kinase-MB isoenzyme levels significantly increased in the model group,compared with the sham group.Hematoxylin and eosin staining showed the presence of many inflammatory cells infiltrating the interstitium of the myocardium in the model group but not in the sham group.Masson staining revealed a significant increase in infarct size in the ischemia/reperfusion group.All eight pigs in the model group recovered with normal sinus heart rates,and the survival rate was 100%.In conclusion,the method can provide an accurate and stable large animal model for preclinical research on ischemia/reperfusion with a high success rate and homogeneity of the myocardial infarction area.展开更多
The green disposal of tailings solid waste is a problem to be solved in mine production.Cemented tailings filling stoping method can realize the dual goals of solid waste resource utilization and mined-out area reduct...The green disposal of tailings solid waste is a problem to be solved in mine production.Cemented tailings filling stoping method can realize the dual goals of solid waste resource utilization and mined-out area reduction.However,the volume of the mined-out area of the open-pit method is larger than the filling capacity,resulting in the complex stratification of the underground backfill,and the strength of the backfill cannot meet the requirements.In this paper,according to the delamination situation,the specimens of horizontal and inclination angle layered cemented tailings backfill(LCTB)is made for a uniaxial compression test,and the failure process of delamination backfill is reduced by PFC.The results show that the corresponding reduction factorφof horizontal LCTB is 0.560–0.932,and the correspondingφvalue of inclination angle LCTB is 0.338–0.772.The failure mode of backfill in different layers is mainly manifested as a tensile failure.The PFC numerical simulation results are consistent with laboratory test results,which verifies the correctness of backfill failure.The research results provide a reliable theoretical basis for the strength design of backfill in goaf,which is of great significance for solid waste utilization and environmental protection.展开更多
In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strengt...In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strength growth characteristics of HFS-BFRS were analyzed.And thefitting equation of compressive strength growth characteristics of HFS-BFRS under the synergistic effect of multiple factors was given.And based on the orthogonal experimental method,the effects on the compressive strength,splitting tensile strength andflex-ural strength of HFS-BFRS under the action of different levels of influencing factors were investigated.The effect of three factors on the mechanical properties of HFS-BFRS,3,and 28 d,respectively,was revealed by choosing the colloidal sand ratio(C/H),basaltfiber volume fraction(BF Vol)and naphthalene high-efficiency water reducing agent(FDN)as the design variables,combined with indoor tests and theoretical analysis.The results show that the sensitivity of the three factors on compressive strength andflexural strength is C/H>FDN>BF Vol,and split-ting tensile strength is BF Vol>FDN>C/H.Finally,thefitting ratio of HFS-BFRS was optimized by the factor index method,and the rationality was verified by thefield test.For thefluidity of HFS-BFRS,the slump can be improved by 139%under the action of 1.2%FDN,which guarantees the pump-ability of HFS-BFRS.展开更多
A study on the mathematical modeling of the two dimensional, time-dependentvariation of bottom topography caused by the spur dikes of the deep water navigation channel projectin the Yangtze estuary is reported. The hy...A study on the mathematical modeling of the two dimensional, time-dependentvariation of bottom topography caused by the spur dikes of the deep water navigation channel projectin the Yangtze estuary is reported. The hydro-dynamic flows are computed using the DELFT3D whichserves as the base of computation of sediment transport and bottom deformation. A model of finesediment transport is developed and implemented in an orthogonal curvilinear coordinate system bythe finite difference method. Using the observed water depth of the North Channel of Yangtze estuaryfrom 2001 to 2002, the model is calibrated and validated to determine the parameters in thesediment model. The computational results of the changes of the bed in the North Channel induced bythe spur dikes coincide with the measured data except the area near the structures.展开更多
Cobalt hydroxide nanosheet is among the most popular oxygen evolution reaction(OER)catalyst yet still suffers from sluggish catalytic kinetics,limited activity,and poor stability.Here,an efficient in situ electrochemi...Cobalt hydroxide nanosheet is among the most popular oxygen evolution reaction(OER)catalyst yet still suffers from sluggish catalytic kinetics,limited activity,and poor stability.Here,an efficient in situ electrochemical reconstructed CoFe-hydroxides derived OER electrocatalyst was reported.The introduction of Fe promoted the transformation of Co^(2+)into Co^(3+)in CoFehydroxides nanosheet,along with the formation of abundant amorphous/crystalline interfaces.Thanks for the retained nanosheet microstructure,high valence Co^(3+)and Fe^(3+)species,and the amorphous/crystalline heterostructure interfaces,the as-designed electrochemical reconstructed CoFeOOH nanosheet/Ni foam(CoFeOOHNS/NF)electrode delivers 100 mA·cm^(−2) in alkaline at an overpotential of 275 mV and can stably electrocatalyze water oxidation for at least 35 h at 100 mA·cm^(−2).Meanwhile,the alkaline full water splitting electrolyzer achieves a current density of 10 mA·cm^(−2) only at 1.522 V for CoFeOOHNS/NF‖Pt/C/NF,which is much lower than that of Ru/C/NF‖Pt/C/NF(1.655 V@10 mA·cm^(−2)).This work paves the way for in-situ synergetic modification engineering of electrochemical active components.展开更多
The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just ...The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just add a constraint to the classic model by introducing a velocity-dependent randomization. Two typical randomization strategies are adopted in this paper. It is shown that the Matthew effect is a necessary condition to induce traffic meta-stable states, thus shedding a light on the prerequisites for the emergence of hysteresis loop in the fundamental diagrams.展开更多
Growing evidence has linked long-term fine particulate matter(PM_(2.5))exposure to neurological disorders.Less is known about the individual effects of PM_(2.5) components.A population-based cohort study investigated ...Growing evidence has linked long-term fine particulate matter(PM_(2.5))exposure to neurological disorders.Less is known about the individual effects of PM_(2.5) components.A population-based cohort study investigated the association between long-term(1-year average)exposure to PM_(2.5) components and dementia incidence among the elderly population(age,R65 years)in the United States.展开更多
Movement in response to mechanical perturbations in plants has long fascinated biologists and nature lovers.Rapid plant movements are of particular interest because they are highly recognizable and challenge the conve...Movement in response to mechanical perturbations in plants has long fascinated biologists and nature lovers.Rapid plant movements are of particular interest because they are highly recognizable and challenge the conventional perception that plants do not move as animals do.Good examples are predation strategies in carnivorous plants,such as sundew,Venus flytrap,and bladderwort[1].展开更多
Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate...Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate of spent lithiumion batteries. Conventional wisdom shows that Li^(+) with low valence states has a much weaker adsorption(and absorption energy) with graphene than multivalent ions such as Mg^(2+). Here, we show the selective adsorption of Li^(+) in thermally reduced graphene oxide(rGO) membranes over other metal ions such as Mg^(2+), Co^(2+), Mn^(2+),Ni^(2+), or Fe^(2+). Interestingly, the adsorption strength of Li^(+) reaches up to 5 times the adsorption strength of Mg^(2+),and the mass ratio of a mixed Mg^(2+)/Li^(+) solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg^(2+)/Li^(+) separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cation–π interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes.展开更多
The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensi...The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.展开更多
BACKGROUND The novel human coronavirus disease 2019(COVID-19)pandemic has claimed more than 600,000 lives worldwide,causing tremendous public health,social,and economic damages.Although the risk factors of COVID-19 ar...BACKGROUND The novel human coronavirus disease 2019(COVID-19)pandemic has claimed more than 600,000 lives worldwide,causing tremendous public health,social,and economic damages.Although the risk factors of COVID-19 are still under investigation,environmental factors,such as urban air pollution,may play an important role in increasing population susceptibility to COVID-19 pathogenesis.METHODS We conducted a cross-sectional nationwide study using zero-inflated negative binomial models to estimate the association between longterm(2010–2016)county-level exposures to NO2,PM2.5,and O3 and county-level COVID-19 case-fatality and mortality rates in the United States.We used both single-and multi-pollutant models and controlled for spatial trends and a comprehensive set of potential confounders,including state-level test positive rate,county-level health care capacity,phase of epidemic,population mobility,population density,sociodemographics,socioeconomic status,race and ethnicity,behavioral risk factors,and meteorology.RESULTS From January 22,2020,to July 17,2020,3,659,828 COVID-19 cases and 138,552 deaths were reported in 3,076 US counties,with an overall observed case-fatality rate of 3.8%.County-level average NO2 concentrations were positively associated with both COVID-19 case-fatality rate and mortality rate in single-,bi-,and tri-pollutant models.When adjusted for co-pollutants,per interquartile-range(IQR)increase in NO2(4.6 ppb),COVID-19 case-fatality rate and mortality rate were associated with an increase of 11.3%(95%CI 4.9%–18.2%)and 16.2%(95%CI 8.7%–24.0%),respectively.We did not observe significant associations between COVID-19 case-fatality rate and long-term exposure to PM2.5 or O3,although per IQR increase in PM2.5(2.6 mg/m3)was marginally associated,with a 14.9%(95%CI 0.0%–31.9%)increase in COVID-19 mortality rate when adjusted for co-pollutants.DISCUSSION Long-term exposure to NO2,which largely arises from urban combustion sources such as traffic,may enhance susceptibility to severe COVID-19 outc展开更多
There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level,but it is of great challenge to cover the giant gap of biomagnetism betw...There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level,but it is of great challenge to cover the giant gap of biomagnetism between their experimental and theoretical results.Here we show that the diamagnetism of aromatic peptides is greatly enhanced for about 11 times by self-assembling,reaching two orders of magnitude higher than the mass susceptibility of pure water.The self-assembly of aromatic rings in the peptide molecules plays the key role in such a strong diamagnetism.展开更多
In this paper, the study was devoted to the traffic-grooming problem in a distributed-controlled WDM mesh network. We studied the optimization of the maximal number of ports configured at each node in the network. We ...In this paper, the study was devoted to the traffic-grooming problem in a distributed-controlled WDM mesh network. We studied the optimization of the maximal number of ports configured at each node in the network. We gave the maximumnumber simulation results in different network environment, which could be taken as a reference for network design.展开更多
文摘Dear Editor Targeted genome-editing tools are very important and efficient for plant functional genomics research, especially when proper mutants are not available. CRISPR/Cas9-based genome edit- ing is a recently developed powerful technology derived from the bacterial clustered regularly interspaced short palindromic repeats （CRISPR）/CRISPR-associated （Cas） defense system,
文摘Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted according to the local traffic density in its vision and its current velocity. The numerical simulation results show that the maximum traffic capacity of the improved model under the same parameters is greater than that of the Nagel-Schreckenberg model, and is closer to the measured data. In addition, the traffic flow and vehicle velocity under different meteorological conditions are simulated by using the improved model, and the synchronized flow phenomenon consistent with the actual traffic is reproduced. Meanwhile, the results show that under the same parameters, when the traffic density is equal to 0.3, the traffic flow of the improved model increases by about 11% compared with the original model, and when the traffic density increases to 0.6, the traffic flow increases by about 27%. .
基金financially supported by the National Natural Science Foundation of China(No.52104129)the Shandong Provincial Major Science and Technology Innovation Project,China(No.2019SDZY05)+2 种基金the key Laboratory of Mine Ecological Effects and Systematic Restoration,Ministry of Natural Resources(No.MEER-2022-09)the Double First-class Construction Project in Henan Province,China(No.AQ20230735)the Doctoral Fund of Henan Polytechnic University(No.B2021-59).
文摘The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste matrix.In this study,the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were studied.The size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring(FBRM)technique,and the influencing factors of aggregation and breakage kinetics of CPB were discussed.The results indicate that influenced by both internal and external factors,the paste kinetics evolution covers the dynamic phase and the stable phase.Increasing the mass content or the cement-tailings ratio can accelerate aggregation kinetics,which is advantageous for the rise of average floc size.Besides,the admixture and high shear can improve breaking kinetics,which is beneficial to reduce the average floc size.The chord length resembles a normal distribution somewhat,with a peak value of approximate 20μm.The particle disaggregation con-stant(k_(2))is positively correlated with the agitation rate,and k_(2) is five orders of magnitude greater than the particle aggregation constant(k1).The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.
基金supported by the National Key Research and Development Program of China(No.2020YFB1506300)the National Natural Science Foundation of China(Nos.21922502,22075018,and 22375017)+2 种基金Young Elite Scientists Sponsorship Program by BAST(No.BYESS2023163)CNPC Innovation Found(No.2022DQ02-0606)Institute of High Energy Physics,Chinese Academy of Sciences for synchrotron radiation(BSRF)testing,Beijing Institute of Technology Research Fund Program,and Analysis and Testing Center of Beijing Institute of Technology.
文摘Precisely designing atomic metal-nitrogen-carbon(M-N-C)catalysts with asymmetric diatomic configurations and studying their structure–activity relationships for oxygen reduction reaction(ORR)are important for zinc-air batteries(ZABs).Herein,a dualatomic-site catalyst(DASC)with CoN_(3)S-MnN_(2)S_(2) configuration was prepared for the cathodes of ZABs.Compared with Co-N-C(Mn-free)and CoMn-N-C(S-free doping),CoMn-N/S-C exhibits excellent half-wave potential(0.883 V)and turnover frequency(1.54 e·s^(−1)·site^(−1)),surpassing most of the reported state-of-the-art Pt-free ORR catalysts.The CoMn-N/S-C-based ZABs achieve extremely high specific capacity(959 mAh·g^(−1))and good stability(350 h@5 mA·cm^(−2)).Density functional theory(DFT)calculation shows that the introduction of Mn and S can break the electron configuration symmetry of the original Co 3d orbital,lower the dband center of the Co site,and optimize the desorption behavior of*OH intermediate,thereby increasing the ORR activity.
基金funded by the National Natural Science Foundation of China (No.52104129)the Key Laboratory of Mine Ecological Effects and Systematic Restoration,the Ministry of Natural Resources (No.MEER-2022-09)+2 种基金the China Postdoctoral Science Foundation (No.2022T150195)the Shandong Provincial Major Science and Technology Innovation Project (No.2019SDZY05)the Doctoral Fund of Henan Polytechnic University (No.B2021-59)
文摘The development of industry is inseparable from the support of mining.However,mining processes consume a large amount of energy,and increased tailing emissions can have a significant impact on the environment.In the past few decades,the mining industry developed many technologies that are related to mineral energy management,of which cemented paste backfill(CPB)is one of the representative technologies.CPB has been successfully applied to mine ground control and tailings management.In CPB technology,the mixing process is the key to achieving materials with good final quality and controlled properties.However,in the preparation process,the mixed homogeneity of the CPB is difficult to achieve because of fine tailings,high solid volume fraction,and high viscosity.Most research focused on the effect of mixing ingredients on CPB properties rather than on the preparation process of the CPB.Therefore,improving the performance and reducing the production cost of CPB by optimizing the mixing process are important.This review summarizes the current studies on the mixing technology of CPB and its application status in China.Then,it compares the advantages and disadvantages of multiple mixing equipment and discusses the latest results and research hotspots in paste preparation.Finally,it concludes the challenges and development trends of mixing technology on the basis of the relevant application cases in China to promoting cement-based material mixing technology development.
基金We acknowledge the support from the National Key Research and Development Program of China(No.2020YFB1506300)the National Natural Science Foundation of China(Nos.21625102,21971017,21922502,22075018,51991344,52025025,and 52072400)Beijing Institute of Technology Research Fund Program.
文摘Developing an efficient,interface-rich,and free-standing non-noble-metal electrocatalyst is vital for the flexible zinc-air batteries(ZABs).Herein,a three-dimensional(3D)heterogeneous carbon-based flexible membrane was assembled by Co@carbon nanosheets/carbon nanotubes and hollow carbon nanofiber(Co@NS/CNT-CNF)as an efficient oxygen reduction reaction(ORR)catalyst with a positive half-wave potential of 0.846 V and a small Tafel slope of 79 mV·dec^(-1).Meanwhile,the Co@NS/CNT-CNF electrode also exhibits excellent open-circuit voltage,peak power density,and long-time cycling stability in liquid-state ZABs(1.605 V,163 mW·cm^(-2),and 400 h)and flexible ZABs under flat/bending condition(1.47 V,102 mW·cm^(-2),and 80 h).Such heterogeneous flexible membrane architecture not only optimizes the electrolyte infiltration,but also provides capacious possibility for O_(2)and electrolyte transfer.Meanwhile,work-function analyses coupled with density functional theory(DFT)results demonstrate that the electron transfer capability and metal-support interaction can be well optimized in the obtained Co@NS/CNT-CNF catalyst.
基金supported by grants from the National Natural Science Foundation of China(Grant No.82070367).
文摘To investigate the feasibility and effectiveness of establishing porcine ischemia-reperfusion models by ligating the left anterior descending(LAD)coronary artery,we first randomly divided 16 male Bama pigs into a sham group and a model group.After anesthesia,we separated the arteries and veins.Subsequently,we rapidly located the LAD coronary artery at the beginning of its first diagonal branch through a mid-chest incision.Then,we loosened and released the ligation line after five minutes of pre-occlusion.Finally,we ligated the LAD coronary artery in situ two minutes later and loosened the ligature 60 min after ischemia.Compared with the sham group,electrocardiogram showed multiple continuous lead ST-segment elevations,and ultrasound cardiogram showed significantly lower ejection fraction and left ventricular fractional shortening at one hour and seven days post-operation in the model group.Twenty-four hours after the operation,cardiac troponin T and creatine kinase-MB isoenzyme levels significantly increased in the model group,compared with the sham group.Hematoxylin and eosin staining showed the presence of many inflammatory cells infiltrating the interstitium of the myocardium in the model group but not in the sham group.Masson staining revealed a significant increase in infarct size in the ischemia/reperfusion group.All eight pigs in the model group recovered with normal sinus heart rates,and the survival rate was 100%.In conclusion,the method can provide an accurate and stable large animal model for preclinical research on ischemia/reperfusion with a high success rate and homogeneity of the myocardial infarction area.
基金supported by the National Natural Science Foundation of China(No.51834001).
文摘The green disposal of tailings solid waste is a problem to be solved in mine production.Cemented tailings filling stoping method can realize the dual goals of solid waste resource utilization and mined-out area reduction.However,the volume of the mined-out area of the open-pit method is larger than the filling capacity,resulting in the complex stratification of the underground backfill,and the strength of the backfill cannot meet the requirements.In this paper,according to the delamination situation,the specimens of horizontal and inclination angle layered cemented tailings backfill(LCTB)is made for a uniaxial compression test,and the failure process of delamination backfill is reduced by PFC.The results show that the corresponding reduction factorφof horizontal LCTB is 0.560–0.932,and the correspondingφvalue of inclination angle LCTB is 0.338–0.772.The failure mode of backfill in different layers is mainly manifested as a tensile failure.The PFC numerical simulation results are consistent with laboratory test results,which verifies the correctness of backfill failure.The research results provide a reliable theoretical basis for the strength design of backfill in goaf,which is of great significance for solid waste utilization and environmental protection.
基金This work was supported by the National Natural Science Foundation of China(51834001,52104129)a project supported by the China Postdoctoral Science Foundation(2020M672226,2022T150195)Key Laboratory of Mine Ecological Effects and Systematic Restoration,Ministry of Natural Resources,Open Fund(MEER-2022-09).
文摘In order to improve the comprehensive utilization rate of highfines sand(HFS)produced by the mine,full solid waste shotcrete(HFS-BFRS)was prepared with HFS asfine aggregate in cooperation with basaltfiber(BF).The strength growth characteristics of HFS-BFRS were analyzed.And thefitting equation of compressive strength growth characteristics of HFS-BFRS under the synergistic effect of multiple factors was given.And based on the orthogonal experimental method,the effects on the compressive strength,splitting tensile strength andflex-ural strength of HFS-BFRS under the action of different levels of influencing factors were investigated.The effect of three factors on the mechanical properties of HFS-BFRS,3,and 28 d,respectively,was revealed by choosing the colloidal sand ratio(C/H),basaltfiber volume fraction(BF Vol)and naphthalene high-efficiency water reducing agent(FDN)as the design variables,combined with indoor tests and theoretical analysis.The results show that the sensitivity of the three factors on compressive strength andflexural strength is C/H>FDN>BF Vol,and split-ting tensile strength is BF Vol>FDN>C/H.Finally,thefitting ratio of HFS-BFRS was optimized by the factor index method,and the rationality was verified by thefield test.For thefluidity of HFS-BFRS,the slump can be improved by 139%under the action of 1.2%FDN,which guarantees the pump-ability of HFS-BFRS.
文摘A study on the mathematical modeling of the two dimensional, time-dependentvariation of bottom topography caused by the spur dikes of the deep water navigation channel projectin the Yangtze estuary is reported. The hydro-dynamic flows are computed using the DELFT3D whichserves as the base of computation of sediment transport and bottom deformation. A model of finesediment transport is developed and implemented in an orthogonal curvilinear coordinate system bythe finite difference method. Using the observed water depth of the North Channel of Yangtze estuaryfrom 2001 to 2002, the model is calibrated and validated to determine the parameters in thesediment model. The computational results of the changes of the bed in the North Channel induced bythe spur dikes coincide with the measured data except the area near the structures.
基金support from the National Key Research and Development Program of China(No.2020YFB1506300)the National Natural Science Foundation of China(Nos.21625102,21971017,21922502,22075018,51991344,52025025,and 52072400)+1 种基金Beijing Institute of Technology Research Fund Program,The Natural Science Foundation of Hainan Province(No.2019RC166)Beijing Natural Science Foundation(No.Z190010).
文摘Cobalt hydroxide nanosheet is among the most popular oxygen evolution reaction(OER)catalyst yet still suffers from sluggish catalytic kinetics,limited activity,and poor stability.Here,an efficient in situ electrochemical reconstructed CoFe-hydroxides derived OER electrocatalyst was reported.The introduction of Fe promoted the transformation of Co^(2+)into Co^(3+)in CoFehydroxides nanosheet,along with the formation of abundant amorphous/crystalline interfaces.Thanks for the retained nanosheet microstructure,high valence Co^(3+)and Fe^(3+)species,and the amorphous/crystalline heterostructure interfaces,the as-designed electrochemical reconstructed CoFeOOH nanosheet/Ni foam(CoFeOOHNS/NF)electrode delivers 100 mA·cm^(−2) in alkaline at an overpotential of 275 mV and can stably electrocatalyze water oxidation for at least 35 h at 100 mA·cm^(−2).Meanwhile,the alkaline full water splitting electrolyzer achieves a current density of 10 mA·cm^(−2) only at 1.522 V for CoFeOOHNS/NF‖Pt/C/NF,which is much lower than that of Ru/C/NF‖Pt/C/NF(1.655 V@10 mA·cm^(−2)).This work paves the way for in-situ synergetic modification engineering of electrochemical active components.
文摘The measurements on actual traffic have revealed the existence of meta-stable states with high flow. Such nonlinear phenomena have not been observed in the classic Nagel-Schreckenberg traffic flow model. Here we just add a constraint to the classic model by introducing a velocity-dependent randomization. Two typical randomization strategies are adopted in this paper. It is shown that the Matthew effect is a necessary condition to induce traffic meta-stable states, thus shedding a light on the prerequisites for the emergence of hysteresis loop in the fundamental diagrams.
基金This studywas supported by theNational Institute onAging(NIA/NIHR01 AG074357)the HERCULES Center(P30 ES019776)and the Goizueta Alzheimer’s Disease Research Center(ADRC)of Emory University(P50 AG025688)the U.S.Environmental Protection Agency(RD-835872),and NASA(80NSSC21K0508).
文摘Growing evidence has linked long-term fine particulate matter(PM_(2.5))exposure to neurological disorders.Less is known about the individual effects of PM_(2.5) components.A population-based cohort study investigated the association between long-term(1-year average)exposure to PM_(2.5) components and dementia incidence among the elderly population(age,R65 years)in the United States.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0502)the Natural Science Foundation of Hubei Province(2019CFA066)the Plateau Ecology Youth Innovative Fund of Wuhan University(413100105)。
文摘Movement in response to mechanical perturbations in plants has long fascinated biologists and nature lovers.Rapid plant movements are of particular interest because they are highly recognizable and challenge the conventional perception that plants do not move as animals do.Good examples are predation strategies in carnivorous plants,such as sundew,Venus flytrap,and bladderwort[1].
基金Supported by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China(Grant Nos. 11974366, 11675246, 12074341, U1832170, and U1832150)+2 种基金the Key Research Program of Chinese Academy of Sciences(Grant No. QYZDJ-SSW-SLH053)the Computer Network Information Center of the Chinese Academy of Sciencesthe Shanghai Supercomputer Center of China。
文摘Lithium plays an increasingly important role in scientific and industrial processes, and it is extremely important to extract lithium from a high Mg^(2+)/Li^(+) mass ratio brine or to recover lithium from the leachate of spent lithiumion batteries. Conventional wisdom shows that Li^(+) with low valence states has a much weaker adsorption(and absorption energy) with graphene than multivalent ions such as Mg^(2+). Here, we show the selective adsorption of Li^(+) in thermally reduced graphene oxide(rGO) membranes over other metal ions such as Mg^(2+), Co^(2+), Mn^(2+),Ni^(2+), or Fe^(2+). Interestingly, the adsorption strength of Li^(+) reaches up to 5 times the adsorption strength of Mg^(2+),and the mass ratio of a mixed Mg^(2+)/Li^(+) solution at a very high value of 500 : 1 can be effectively reduced to 0.7 : 1 within only six experimental treatment cycles, demonstrating the excellent applicability of the rGO membranes in the Mg^(2+)/Li^(+) separation. A theoretical analysis indicates that this unexpected selectivity is attributed to the competition between cation–π interaction and steric exclusion when hydrated cations enter the confined space of the rGO membranes.
基金supported by the National Natural Science Foundation of China(Grant Nos.22176181,11874306,and 12174320)the Foundation of Science and Technology on Surface Physics and Chemistry Laboratory(Grant No.WDZC202101)the Natural Science Foundation of Chongqing,China(Grant No.cstc2021jcyj-msxmX0209)。
文摘The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.
基金supported by the Emory HERCULES Exposome Research Center through the National Institute of Environmental Health Sciences(grant P30ES019776)support provided by the National Science Foundation(award BCS-2027375)。
文摘BACKGROUND The novel human coronavirus disease 2019(COVID-19)pandemic has claimed more than 600,000 lives worldwide,causing tremendous public health,social,and economic damages.Although the risk factors of COVID-19 are still under investigation,environmental factors,such as urban air pollution,may play an important role in increasing population susceptibility to COVID-19 pathogenesis.METHODS We conducted a cross-sectional nationwide study using zero-inflated negative binomial models to estimate the association between longterm(2010–2016)county-level exposures to NO2,PM2.5,and O3 and county-level COVID-19 case-fatality and mortality rates in the United States.We used both single-and multi-pollutant models and controlled for spatial trends and a comprehensive set of potential confounders,including state-level test positive rate,county-level health care capacity,phase of epidemic,population mobility,population density,sociodemographics,socioeconomic status,race and ethnicity,behavioral risk factors,and meteorology.RESULTS From January 22,2020,to July 17,2020,3,659,828 COVID-19 cases and 138,552 deaths were reported in 3,076 US counties,with an overall observed case-fatality rate of 3.8%.County-level average NO2 concentrations were positively associated with both COVID-19 case-fatality rate and mortality rate in single-,bi-,and tri-pollutant models.When adjusted for co-pollutants,per interquartile-range(IQR)increase in NO2(4.6 ppb),COVID-19 case-fatality rate and mortality rate were associated with an increase of 11.3%(95%CI 4.9%–18.2%)and 16.2%(95%CI 8.7%–24.0%),respectively.We did not observe significant associations between COVID-19 case-fatality rate and long-term exposure to PM2.5 or O3,although per IQR increase in PM2.5(2.6 mg/m3)was marginally associated,with a 14.9%(95%CI 0.0%–31.9%)increase in COVID-19 mortality rate when adjusted for co-pollutants.DISCUSSION Long-term exposure to NO2,which largely arises from urban combustion sources such as traffic,may enhance susceptibility to severe COVID-19 outc
基金Supported by the National Natural Science Foundation of China(Grant Nos.U1632135,11974366,U1932123,51763019 and U1832125)the Key Research Program of Chinese Academy of Sciences(Grant No.QYZDJ-SSW-SLH053)the Fundamental Research Funds for the Central Universities.
文摘There is a considerable amount of work that shows the biomagnetism of organic components without ferromagnetic components at the molecular level,but it is of great challenge to cover the giant gap of biomagnetism between their experimental and theoretical results.Here we show that the diamagnetism of aromatic peptides is greatly enhanced for about 11 times by self-assembling,reaching two orders of magnitude higher than the mass susceptibility of pure water.The self-assembly of aromatic rings in the peptide molecules plays the key role in such a strong diamagnetism.
文摘In this paper, the study was devoted to the traffic-grooming problem in a distributed-controlled WDM mesh network. We studied the optimization of the maximal number of ports configured at each node in the network. We gave the maximumnumber simulation results in different network environment, which could be taken as a reference for network design.
