Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The w...Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The work begins by interpreting the experiment conducted by Collins and Jacobs(2002,J.Fluid Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium state.The thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock front.The kinetic effects are detected by two sets of TNE quantities.The first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of NOEF.All four TNE measures abruptly increase in the shock process.The second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,respectively.The mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.展开更多
Lead (Pb) inhibited the activities of Na+ -K+ ATPase (IC50= 2.0×10^(-6) M), K + -Para-Nitrophenyl phosphatase (PNPPase) (IC50= 3.5×10^(-6) M) and [3H]-ouabain binding (IC50 = 4.0×10^(-5) M) in rat brain...Lead (Pb) inhibited the activities of Na+ -K+ ATPase (IC50= 2.0×10^(-6) M), K + -Para-Nitrophenyl phosphatase (PNPPase) (IC50= 3.5×10^(-6) M) and [3H]-ouabain binding (IC50 = 4.0×10^(-5) M) in rat brain P2 fraction. A variable temperature or pH significantly elevated the inhibition of Na+-K+ ATPase by Pb in buffered acidic, neutral and alkaline pH ranges. Noncompetitive inhibition with respect to activation of Na+ -K+ ATPase by ATP was indicated by a variation in Vmax values with no significant changes in Km values at any temperature studied. In the presence of Pb, for Na+ -K+ ATPase at pH 6.5 and 8.5, Vmax was decreased with an increase in Km values suggesting a mixed type of inhibition. Sulfhydryl agents such as dithiothreitol (DTT) and cvsteine (Cyst), but not glutathione (GSH) offered varied levels of protection against Pb-inhibition of Na + -K+ ATPase at pH 7.5 and 8.5. The present data suggest that inhibition of Na+ -K+ ATPase by Pb is both temperature and pH-dependent. These results also indicate that Pb inhibited Na + -K + ATPase by interfering with phosphorylation of enzyme molecule and dephosphorylation of the enzyme-phosphoryl complex and exerted an effect similar to that of SH-blocking agents.展开更多
Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization proce...Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.展开更多
The co-gasification behavior and synergistic effect of petroleum coke, biomass, and their blends were studied by thermogravimetric analysis under CO2 atmosphere at different heating rates. The isoconversional method w...The co-gasification behavior and synergistic effect of petroleum coke, biomass, and their blends were studied by thermogravimetric analysis under CO2 atmosphere at different heating rates. The isoconversional method was used to calculate the activation energy. The results showed that the gasification process occurred in two stages: pyrolysis and char gasification. A synergistic effect was observed in the char gasification stage. This effect was caused by alkali and alkaline earth metals in the biomass ash. Kinetics analysis showed that the activation energy in the pyrolysis stage was less than that in the char gasification stage. In the char gasification stage, the activation energy was 129.1–177.8 k J/mol for petroleum coke, whereas it was 120.3–150.5 k J/mol for biomass. We also observed that the activation energy calculated by the Flynn–Wall–Ozawa(FWO) method were larger than those calculated by the Kissinger–Akahira–Sunosen(KAS) method. When the conversion was 1.0, the activation energy was 106.2 k J/mol when calculated by the KAS method, whereas it was 120.3 k J/mol when calculated by the FWO method.展开更多
The effects of the reaction temperature, the crosslinking degree of the matrix, the pore-forming agent and the initial concentration of PVA on the kinetic properties of the complex-resins were investigated. The ion-ex...The effects of the reaction temperature, the crosslinking degree of the matrix, the pore-forming agent and the initial concentration of PVA on the kinetic properties of the complex-resins were investigated. The ion-exchange rate of the complex-resin for L-lysine chlorate was three-fold that of 001×8 resin and two-fold that of D61 resin.展开更多
The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Re...The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Reactor(ITER)baseline scenario.The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron model and the fully drift-kinetic electron model in the NLT code,respectively.The linear simulations focus on the dependence of linear frequency on the plasma parameters,such as the ion and electron temperature gradientsκ_(Ti,e)≡R=L_(Ti,e),the density gradientκ_(n)≡R/L_(n)and the ion-electron temperature ratioτ=T_(e)=T_(i).Here,is the major radius,and T_(e)and T_(i)denote the electron and ion temperatures,respectively.L_(A)=-(δ_(r)lnA)^(-1)is the gradient scale length,with denoting the density,the ion and electron temperatures,respectively.In the kinetic electron model,the ion temperature gradient(ITG)instability and the trapped electron mode(TEM)dominate in the small and large k_(θ)region,respectively,wherek_(θ)is the poloidal wavenumber.The TEMdominant region becomes wider by increasing(decreasing)κ_(T_(e))(κ_(T_(i)))or by decreasingκ_(n).For the nominal parameters of the ITER baseline scenario,the maximum growth rate of dominant ITG instability in the kinetic electron model is about three times larger than that in the adiabatic electron model.The normalized linear frequency depends on the value ofτ,rather than the value of T_(e)or T_(i),in both the adiabatic and kinetic electron models.The nonlinear simulation results show that the ion heat diffusivity in the kinetic electron model is quite a lot larger than that in the adiabatic electron model,the radial structure is finer and the time oscillation is more rapid.In addition,the magnitude of the fluctuated potential at the saturated stage peaks in the ITGdominated region,and contributions from the TEM(dominating in the higher k_(θ)region)to the nonlinear transport can be neglected.In the adiabatic electron model,the zonal radial electric field is found to be mainly driven by the turbulent energy flux,and the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect.However,in the kinetic electron model,the turbulent energy flux is not strong enough to drive the zonal radial electric field in the nonlinear saturated stage.The kinetic electron effects on the mechanism of the turbulence-driven zonal radial electric field should be further investigated.展开更多
The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model,...The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), 6D = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of 6 and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the 6 and d, and vice versa. However, 6 and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Uriimqi is simulated. The simulated stable isotopic ratio vs temperature and the SD vs δ18O curves are very consistent with the actual regressions and MWL at Uriimqi, respectively.展开更多
With Venus Express magnetic field measurements at 32 Hz from 2006 to 2012, we investigate statistically the magnetic fluctuations in the near-Venusian space. The global spatial distribution of their spectral scaling f...With Venus Express magnetic field measurements at 32 Hz from 2006 to 2012, we investigate statistically the magnetic fluctuations in the near-Venusian space. The global spatial distribution of their spectral scaling features is presented in MHD and kinetic regimes. It can be observed that turbulence is a common phenomenon in the solar wind in both regimes. The solar wind MHD turbulence is modified at the Venusian bow shock;MHD turbulence is absent in the Venusian magnetosheath but present at the magnetosheath boundary layer. Pre-existing kinetic turbulence from the far upstream solar wind is modified in the near solar wind region, while kinetic turbulence can be extensively observed throughout the Venusian magnetosheath and in some regions of the induced magnetosphere. Our results reveal that, in the near-Venusian space, energy cascade can be developed at the boundary between magnetosheath and wake, and the turbulence-related dissipation of magnetic energy occurs extensively in the magnetosheath and the induced magnetosphere.展开更多
At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves(KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90° ...At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves(KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90° pitch angle is observed throughout the flux rope, where intense KAWs are identified. The KAWs can effectively trap electrons by the wave parallel electric field and the magnetic mirror force, allowing electrons to undergo Landau resonance and be transported into more field-aligned directions. The pitch angle range for the trapped electrons is estimated from the wave analysis, which is in good agreement with direct pitch angle measurements of the electron distributions. The newly formed beam-like electron distribution is unstable and excites whistler waves,as revealed in the observations. We suggest that KAWs could be responsible for the plasma depletion inside a flux rope by this transport process, and thus be responsible for the formation of a typical flux rope.展开更多
The ring-polymer molecular dynamics(RPMD)was used to calculate the thermal rate coefficients and kinetic isotope effects of the heavy-light-heavy abstract reaction Cl+XCl→XCl+Cl(X=H,D,Mu).For the Cl+HCl reaction,the ...The ring-polymer molecular dynamics(RPMD)was used to calculate the thermal rate coefficients and kinetic isotope effects of the heavy-light-heavy abstract reaction Cl+XCl→XCl+Cl(X=H,D,Mu).For the Cl+HCl reaction,the excellent agreement between the RPMD and experimental values provides a strong proof for the accuracy of the RPMD theory.And the RPMD results are also consistent with results from other theoretical methods including improved-canonical-variational-theory and quantum dynamics.The most novel finding is that there is a double peak in Cl+MuCl reaction near the transition state,leaving a free energy well.It comes from the mode softening of the reaction system at the peak of the potential energy surface.Such an explicit free energy well suggests strongly there is an observable resonance.And for the Cl+DCl reaction,the RPMD rate coefficient again gives very accurate results compared with experimental values.The only exception is at the temperature of 312.5 K,results from RPMD and all other theoretical methods are close to each other but slightly lower than the experimental value,which indicates experimental or potential energy surface deficiency.展开更多
Kinetic Sunyaev-Zel'dovich (kSZ) stacking has great potential to become a powerful probe of missing baryons, due to advances in CMB experiments and galaxy surveys. In this paper, we study kSZ stacking in hydrodynam...Kinetic Sunyaev-Zel'dovich (kSZ) stacking has great potential to become a powerful probe of missing baryons, due to advances in CMB experiments and galaxy surveys. In this paper, we study kSZ stacking in hydrodynamic simulations with different gastrophysics. We quantify the kSZ stacking signal as a function of halo mass, redshift and projection depth. We compare between different simulations to estimate the impact of gastrophysics such as cooling and supernova feedback. Furthermore, we measure the contribution from warm-hot intergalactic medium (WHIM), which is believed to be the reservoir for most, if not all, missing baryons. We find that the WHIM contribution is significant, at the level of ~ 10%-70%, depending on the angular separation from the stacked halos and other factors. However, contribution from the intracluster medium along the line of sight is in general non-negligible. This complexity requires more detailed and comprehensive analysis on probing the missing baryons with kSZ stacking.展开更多
The migration of protons during the oxygen evolution reaction(OER)is a key factor that affects the performance of OER catalysts.To enhance proton transportation,we designed a catalyst based on nickel/iron-pyromellitic...The migration of protons during the oxygen evolution reaction(OER)is a key factor that affects the performance of OER catalysts.To enhance proton transportation,we designed a catalyst based on nickel/iron-pyromellitic acid(NiFe-PMA)prepared by the electrochemical deposition method.This catalyst exhibited a low overpotential of 188 mV at a current density of 10 mA·cm^(-2),a Tafel slope of 28.2 mV·dec^(-1),and long-term stability for 30 days with a current of 50 mA·cm^(-2).We characterized the NiFe-PMA catalyst using various techniques,including Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS),transmission electron microscopy(TEM),scanning electron microscopy(SEM),and inductively coupled plasma-optical emission spectrometry(ICP-OES).Our results showed that NiFe-PMA contains nickel,iron atoms,and both coordinated and uncoordinated carboxylate groups.Additionally,XPS data confirmed that carboxylate ligands could adjust the outer electronic structure of metal ions,resulting in the high valence state of Ni in NiFe-PMA.The result of XAS indicated that the nickel atoms present in the catalyst might be easier to maintain a higher chemical state.Further investigations using kinetic isotope effects(KIEs)and proton inventory revealed that the uncoordinated carboxylic protons played a crucial role in receiving protons during the OER,which promoted the proton transfer of the rate-determining step of the OER.Our novel electrocatalysts provide a new strategy for designing more active and cost-effective catalysts for the OER.展开更多
The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations ...The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations for a wide range of parameters extending and complementing previous findings. PIC simulations show that the scenario of reflectivity evolution and saturation is very sensitive to the temperatures, intensities, size of plasma and boundary conditions employed. The Langmuir decay instability is observed for rather small k_(epw)λ_D but has no influence on the saturation of Brillouin backscattering, although there is a clear correlation of Langmuir decay instability modes and ion-fractional decay for certain parameter ranges. Raman backscattering appears at any intensity and temperature but is only a transient phenomenon. In several configurations forward as well as backward Raman scattering is observed. For the intensities considered, I λ_o^2 above 10^(15) W μm^2/cm^2, Raman is always of bursty nature. A particular setup allows the simulation of multi-speckle aspects in which case it is found that Raman is self-limiting due to strong modifications of the distribution function. Kinetic effects are of prime importance for Raman backscattering at high temperatures. No unique scenario for the saturation of Raman scattering or Raman–Brillouin competition does exist. The main effect in the considered parameter range is pump depletion because of large Brillouin backscattering. However, in the low k_(epw)λ_D regime the presence of ion-acoustic waves due to the Langmuir decay instability from the Raman created electron plasma waves can seed the ion-fractional decay and affect the Brillouin saturation.展开更多
Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splittin...Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splitting,which is still challenging for developing efficient single-atom catalysts limited by their structural simplicity usually incompetent to handle this task.Incorporation of extra functional units should be viable.Herein,a proton deployment strategy is demonstrated via“atomic and nanostructured iron(A/N-Fe)pairs”,comprising atomically dispersed iron active centers spin-polarized by nanostructured iron carbide ferromagnets,to boost the critical protonation steps.The as-designed catalyst displays a broad window(300 mV)for CO selectivity>90%(98%maximum),even outperforming numerous cutting-edge M–N–C systems.The well-placed control of proton dynamics by A/N-Fe can promote*COOH/*CO formation and simultaneously suppress H2 evolution,benefiting from the magnetic-proximity-induced exchange splitting(spin polarization)that properly adjusts energy levels of the Fe sites’d-shells,and further those of the adsorbed intermediates’antibonding molecular orbitals.展开更多
An efficient and practical synthetic protocol to synthesize nonsymmetrical aryl thioethers by nucleophilic aromatic substitution(S_NAr)reaction of nitroarenes by thiols with potassium phosphate as the catalyst is desc...An efficient and practical synthetic protocol to synthesize nonsymmetrical aryl thioethers by nucleophilic aromatic substitution(S_NAr)reaction of nitroarenes by thiols with potassium phosphate as the catalyst is described.Various moderate to strong electron-withdrawing functional groups are tolerated by the system to provide thioethers in a good to excellent yields.We also showed that the present method allows access to 3 drug examples in a short reaction time.Finally,mechanistic studies suggest that the reaction may form the classic Meisenheimer complex through a two-step additionelimination mechanism.展开更多
基金supported by the National Natural Science Foundation of China(under Grant Nos.12172061,11875001,11575033,and 11975053)the opening project of the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)(under Grant No.KFJJ23-02M)+1 种基金Foundation of National Key Laboratory of Shock Wave and Detonation Physicsthe Foundation of National Key Laboratory of Computational Physics
文摘Kinetic effects in the inertial confinement fusion ignition process are far from clear.In this work,we study the Richtmyer-Meshkov instability and reshock processes by using a two-fluid discrete Boltzmann method.The work begins by interpreting the experiment conducted by Collins and Jacobs(2002,J.Fluid Mech.464,113-136).It shows that the shock wave causes substances in close proximity to the substance interface to deviate more significantly from their thermodynamic equilibrium state.The thermodynamic non-equilibrium(TNE)quantities exhibit complex but inspiring kinetic effects in the shock process and behind the shock front.The kinetic effects are detected by two sets of TNE quantities.The first set includes∣Δ_(2)^(*)∣,∣Δ_(3,1)^(*),∣Δ_(3)^(*)∣,and∣Δ_(4,2)^(*)∣,which correspond to the intensities of the non-organized momentum Flux(NOMF),Non-Organized Energy Flux(NOEF),the flux of NOMF and the flux of NOEF.All four TNE measures abruptly increase in the shock process.The second set of TNE quantities includes■_(NOMF),■_(NOEF)and■_(sum),which denote the entropy production rates due to NOMF,NOEF and their summation,respectively.The mixing zone is the primary contributor to■_(NOEF),while the flow field region outside of the mixing zone is the primary contributor to■_(NOMF).Additionally,each substance exhibits different behaviors in terms of entropy production rate,and the lighter fluid has a higher entropy production rate than the heavier fluid.
文摘Lead (Pb) inhibited the activities of Na+ -K+ ATPase (IC50= 2.0×10^(-6) M), K + -Para-Nitrophenyl phosphatase (PNPPase) (IC50= 3.5×10^(-6) M) and [3H]-ouabain binding (IC50 = 4.0×10^(-5) M) in rat brain P2 fraction. A variable temperature or pH significantly elevated the inhibition of Na+-K+ ATPase by Pb in buffered acidic, neutral and alkaline pH ranges. Noncompetitive inhibition with respect to activation of Na+ -K+ ATPase by ATP was indicated by a variation in Vmax values with no significant changes in Km values at any temperature studied. In the presence of Pb, for Na+ -K+ ATPase at pH 6.5 and 8.5, Vmax was decreased with an increase in Km values suggesting a mixed type of inhibition. Sulfhydryl agents such as dithiothreitol (DTT) and cvsteine (Cyst), but not glutathione (GSH) offered varied levels of protection against Pb-inhibition of Na + -K+ ATPase at pH 7.5 and 8.5. The present data suggest that inhibition of Na+ -K+ ATPase by Pb is both temperature and pH-dependent. These results also indicate that Pb inhibited Na + -K + ATPase by interfering with phosphorylation of enzyme molecule and dephosphorylation of the enzyme-phosphoryl complex and exerted an effect similar to that of SH-blocking agents.
文摘Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.
基金supported by the Fundamental Research Fund for the Central Universities of China (FRF-TP-15063A1)the 111 Project (No.B13004)
文摘The co-gasification behavior and synergistic effect of petroleum coke, biomass, and their blends were studied by thermogravimetric analysis under CO2 atmosphere at different heating rates. The isoconversional method was used to calculate the activation energy. The results showed that the gasification process occurred in two stages: pyrolysis and char gasification. A synergistic effect was observed in the char gasification stage. This effect was caused by alkali and alkaline earth metals in the biomass ash. Kinetics analysis showed that the activation energy in the pyrolysis stage was less than that in the char gasification stage. In the char gasification stage, the activation energy was 129.1–177.8 k J/mol for petroleum coke, whereas it was 120.3–150.5 k J/mol for biomass. We also observed that the activation energy calculated by the Flynn–Wall–Ozawa(FWO) method were larger than those calculated by the Kissinger–Akahira–Sunosen(KAS) method. When the conversion was 1.0, the activation energy was 106.2 k J/mol when calculated by the KAS method, whereas it was 120.3 k J/mol when calculated by the FWO method.
基金Supported by the Tianjin scientific youth fund for 21th centrury
文摘The effects of the reaction temperature, the crosslinking degree of the matrix, the pore-forming agent and the initial concentration of PVA on the kinetic properties of the complex-resins were investigated. The ion-exchange rate of the complex-resin for L-lysine chlorate was three-fold that of 001×8 resin and two-fold that of D61 resin.
基金supported by the National MCF Energy R&D Program of China(No.2019YFE03060000)National Natural Science Foundation of China(Nos.12005063,12375215 and 12175034)the Collaborative Innovation Program of Hefei Science Center,CAS(No.2022HSC-CIP008).
文摘The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Reactor(ITER)baseline scenario.The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron model and the fully drift-kinetic electron model in the NLT code,respectively.The linear simulations focus on the dependence of linear frequency on the plasma parameters,such as the ion and electron temperature gradientsκ_(Ti,e)≡R=L_(Ti,e),the density gradientκ_(n)≡R/L_(n)and the ion-electron temperature ratioτ=T_(e)=T_(i).Here,is the major radius,and T_(e)and T_(i)denote the electron and ion temperatures,respectively.L_(A)=-(δ_(r)lnA)^(-1)is the gradient scale length,with denoting the density,the ion and electron temperatures,respectively.In the kinetic electron model,the ion temperature gradient(ITG)instability and the trapped electron mode(TEM)dominate in the small and large k_(θ)region,respectively,wherek_(θ)is the poloidal wavenumber.The TEMdominant region becomes wider by increasing(decreasing)κ_(T_(e))(κ_(T_(i)))or by decreasingκ_(n).For the nominal parameters of the ITER baseline scenario,the maximum growth rate of dominant ITG instability in the kinetic electron model is about three times larger than that in the adiabatic electron model.The normalized linear frequency depends on the value ofτ,rather than the value of T_(e)or T_(i),in both the adiabatic and kinetic electron models.The nonlinear simulation results show that the ion heat diffusivity in the kinetic electron model is quite a lot larger than that in the adiabatic electron model,the radial structure is finer and the time oscillation is more rapid.In addition,the magnitude of the fluctuated potential at the saturated stage peaks in the ITGdominated region,and contributions from the TEM(dominating in the higher k_(θ)region)to the nonlinear transport can be neglected.In the adiabatic electron model,the zonal radial electric field is found to be mainly driven by the turbulent energy flux,and the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect.However,in the kinetic electron model,the turbulent energy flux is not strong enough to drive the zonal radial electric field in the nonlinear saturated stage.The kinetic electron effects on the mechanism of the turbulence-driven zonal radial electric field should be further investigated.
基金This work was supported by the National High Technology Research and Development Program of China (863 Program, Grant No. 2002AA135360), the National Natural Science Foundation of China (Grant No. 40271025), the National Key Research Project (Grant No.
文摘The introduced mathematical model takes into account the role of the kinetic fractionation effect in a supersaturation environment at the ice surface as liquid and solid phases coexist in mixed cloud. Using the model, the temperature effect of stable isotopes in precipitation is simulated under different cooling conditions. The rate of change of δ18O against temperature in the process of wet adiabatic cooling is smaller than in the process of isobaric cooling under the same humidity. The increasing supersaturation ratio at the ice surface, Si, leads to the strengthening of the kinetic fractionation effect. The kinetic fractionation function makes the synthesis fractionation factor decreased and the change of δ18O with temperature flatted, compared with that in the equilibrium state. The simulated results show that the slope parameter b and the intercept d of the meteoric water line (MWL), 6D = bδ18O+d, in wet adiabatic cooling are both greater than those in isobaric cooling. The global MWL lies between the two MWLs simulated under wet adiabatic and isobaric cooling processes, respectively. The magnitudes of 6 and d are directly proportional to Si. The greater the Si, the stronger the kinetic fractionation effect, and thus the greater the 6 and d, and vice versa. However, 6 and d have low sensitivity to the liquid-water contents in the cloud. Using the kinetic fractionation model, the variation of stable isotopes in precipitation at Uriimqi is simulated. The simulated stable isotopic ratio vs temperature and the SD vs δ18O curves are very consistent with the actual regressions and MWL at Uriimqi, respectively.
基金supported by NSFC grants 41904156, 41974205, 41774171, 41574173, 41774167 and 41804157the Science and Technology Development Fund of Macao SAR (008/2016/A1 and 039/2013/A2)+3 种基金the China Postdoctoral Science Foundation (2019M651271)the financial support of the Shenzhen Science and Technology Research Program (JCYJ20170811154933612 and JCYJ20180306171918617)the 111 Project (B18017)supported by CAS Center for Excellence in Comparative Planetology
文摘With Venus Express magnetic field measurements at 32 Hz from 2006 to 2012, we investigate statistically the magnetic fluctuations in the near-Venusian space. The global spatial distribution of their spectral scaling features is presented in MHD and kinetic regimes. It can be observed that turbulence is a common phenomenon in the solar wind in both regimes. The solar wind MHD turbulence is modified at the Venusian bow shock;MHD turbulence is absent in the Venusian magnetosheath but present at the magnetosheath boundary layer. Pre-existing kinetic turbulence from the far upstream solar wind is modified in the near solar wind region, while kinetic turbulence can be extensively observed throughout the Venusian magnetosheath and in some regions of the induced magnetosphere. Our results reveal that, in the near-Venusian space, energy cascade can be developed at the boundary between magnetosheath and wake, and the turbulence-related dissipation of magnetic energy occurs extensively in the magnetosheath and the induced magnetosphere.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41474145,41574159,41731070 and 41504114the Frontier Science Foundation of the Chinese Academy of Sciences under Grant No QYZDJ-SSW-JSC028+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDA15052500the Specialized Research Fund for State Key Laboratories of China
文摘At the Earth's magnetopause, the electron transport due to kinetic Alfvén waves(KAWs) is investigated in an ion-scale flux rope by the Magnetospheric Multiscale mission. Clear electron dropout around 90° pitch angle is observed throughout the flux rope, where intense KAWs are identified. The KAWs can effectively trap electrons by the wave parallel electric field and the magnetic mirror force, allowing electrons to undergo Landau resonance and be transported into more field-aligned directions. The pitch angle range for the trapped electrons is estimated from the wave analysis, which is in good agreement with direct pitch angle measurements of the electron distributions. The newly formed beam-like electron distribution is unstable and excites whistler waves,as revealed in the observations. We suggest that KAWs could be responsible for the plasma depletion inside a flux rope by this transport process, and thus be responsible for the formation of a typical flux rope.
基金This work was supported by the National Nature Science Foundation of China(No.21503130 and No.11674212 to Yong-le Li,and No.21603144 to Jia-ning Song)Yong-le Li is also supported by the Young Eastern Scholar Program of the Shanghai Municipal Education Commission(No.QD2016021)+1 种基金the Shanghai Key Laboratory of High Temperature Superconductors(No.14DZ2260700)Jia-ning Song is also supported by Shanghai Sailing Program(No.2016YF1408400).
文摘The ring-polymer molecular dynamics(RPMD)was used to calculate the thermal rate coefficients and kinetic isotope effects of the heavy-light-heavy abstract reaction Cl+XCl→XCl+Cl(X=H,D,Mu).For the Cl+HCl reaction,the excellent agreement between the RPMD and experimental values provides a strong proof for the accuracy of the RPMD theory.And the RPMD results are also consistent with results from other theoretical methods including improved-canonical-variational-theory and quantum dynamics.The most novel finding is that there is a double peak in Cl+MuCl reaction near the transition state,leaving a free energy well.It comes from the mode softening of the reaction system at the peak of the potential energy surface.Such an explicit free energy well suggests strongly there is an observable resonance.And for the Cl+DCl reaction,the RPMD rate coefficient again gives very accurate results compared with experimental values.The only exception is at the temperature of 312.5 K,results from RPMD and all other theoretical methods are close to each other but slightly lower than the experimental value,which indicates experimental or potential energy surface deficiency.
基金support by the National Natural Science Foundation of China (Grant Nos. 11473053, 11233005, U1331201 and 11121062)the National Key Basic Research Program of China (Grant No. 2015CB857001)the "Strategic Priority Research Program the Emergence of Cosmological Structures" of the Chinese Academy of Sciences (Grant Nos. XDB09000000 and XDB09010000)
文摘Kinetic Sunyaev-Zel'dovich (kSZ) stacking has great potential to become a powerful probe of missing baryons, due to advances in CMB experiments and galaxy surveys. In this paper, we study kSZ stacking in hydrodynamic simulations with different gastrophysics. We quantify the kSZ stacking signal as a function of halo mass, redshift and projection depth. We compare between different simulations to estimate the impact of gastrophysics such as cooling and supernova feedback. Furthermore, we measure the contribution from warm-hot intergalactic medium (WHIM), which is believed to be the reservoir for most, if not all, missing baryons. We find that the WHIM contribution is significant, at the level of ~ 10%-70%, depending on the angular separation from the stacked halos and other factors. However, contribution from the intracluster medium along the line of sight is in general non-negligible. This complexity requires more detailed and comprehensive analysis on probing the missing baryons with kSZ stacking.
基金supported by the National Key Research and Development Program of Ministry of Science and Technology of China(No.2021YFA1500604)ShanghaiTech University start-up funding.We would like to thank the Analytical Instrumentation Center(#SPST-AIC 10112914)at the School of Physical Science and Technology(SPST)+1 种基金ShanghaiTech University,for their generous support.We are grateful to Peihong Cheng at ShanghaiTech University for assisting with XPS measurements and Siyuan Du for assisting us in the XAS test at Shanghai Synchrotron Radiation Facility(SSRF)We appreciate the Centre for High-Resolution Electron Microscopy(CћEM),which is supported by SPST of ShanghaiTech University under contract No.EM02161943.
文摘The migration of protons during the oxygen evolution reaction(OER)is a key factor that affects the performance of OER catalysts.To enhance proton transportation,we designed a catalyst based on nickel/iron-pyromellitic acid(NiFe-PMA)prepared by the electrochemical deposition method.This catalyst exhibited a low overpotential of 188 mV at a current density of 10 mA·cm^(-2),a Tafel slope of 28.2 mV·dec^(-1),and long-term stability for 30 days with a current of 50 mA·cm^(-2).We characterized the NiFe-PMA catalyst using various techniques,including Fourier transform infrared(FTIR)spectroscopy,Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS),transmission electron microscopy(TEM),scanning electron microscopy(SEM),and inductively coupled plasma-optical emission spectrometry(ICP-OES).Our results showed that NiFe-PMA contains nickel,iron atoms,and both coordinated and uncoordinated carboxylate groups.Additionally,XPS data confirmed that carboxylate ligands could adjust the outer electronic structure of metal ions,resulting in the high valence state of Ni in NiFe-PMA.The result of XAS indicated that the nickel atoms present in the catalyst might be easier to maintain a higher chemical state.Further investigations using kinetic isotope effects(KIEs)and proton inventory revealed that the uncoordinated carboxylic protons played a crucial role in receiving protons during the OER,which promoted the proton transfer of the rate-determining step of the OER.Our novel electrocatalysts provide a new strategy for designing more active and cost-effective catalysts for the OER.
基金support from grant ANR-11-IDEX-0004-02 Plas@Parsupport from the project ELI:Extreme Light Infrastructure (CZ.02.1.01/0.0/ 0.0/15-008/0000162) from European Regional Development
文摘The co-existence of the Raman and Brillouin backscattering instability is an important issue for inertial confinement fusion. The present paper presents extensive one-dimensional(1D) particle-in-cell(PIC) simulations for a wide range of parameters extending and complementing previous findings. PIC simulations show that the scenario of reflectivity evolution and saturation is very sensitive to the temperatures, intensities, size of plasma and boundary conditions employed. The Langmuir decay instability is observed for rather small k_(epw)λ_D but has no influence on the saturation of Brillouin backscattering, although there is a clear correlation of Langmuir decay instability modes and ion-fractional decay for certain parameter ranges. Raman backscattering appears at any intensity and temperature but is only a transient phenomenon. In several configurations forward as well as backward Raman scattering is observed. For the intensities considered, I λ_o^2 above 10^(15) W μm^2/cm^2, Raman is always of bursty nature. A particular setup allows the simulation of multi-speckle aspects in which case it is found that Raman is self-limiting due to strong modifications of the distribution function. Kinetic effects are of prime importance for Raman backscattering at high temperatures. No unique scenario for the saturation of Raman scattering or Raman–Brillouin competition does exist. The main effect in the considered parameter range is pump depletion because of large Brillouin backscattering. However, in the low k_(epw)λ_D regime the presence of ion-acoustic waves due to the Langmuir decay instability from the Raman created electron plasma waves can seed the ion-fractional decay and affect the Brillouin saturation.
基金This work was financially supported by National Natural Science Foundation of China(Grant Nos.22075245,21922811,21878270,and 21961160742)Zhejiang Provincial Natural Science Foundation of China(Grant No.LR19B060002)+2 种基金Fundamental Research Funds for the Central Universities(Grant No.2020XZZX002-09)Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang(Grant No.2019R01006)Startup Foundation for Hundred-Talent Program of Zhejiang University,Key Laboratory of Marine Materials and Related Technologies,Chinese Academy of Science,and Zhejiang Key Laboratory of Marine Materials and Protective Technologies(2020K10).
文摘Unlocking of the extremely inert C=O bond during electrochemical CO_(2) reduction demands subtle regulation on a key“resource”,protons,necessary for intermediate conversion but also readily trapped in water splitting,which is still challenging for developing efficient single-atom catalysts limited by their structural simplicity usually incompetent to handle this task.Incorporation of extra functional units should be viable.Herein,a proton deployment strategy is demonstrated via“atomic and nanostructured iron(A/N-Fe)pairs”,comprising atomically dispersed iron active centers spin-polarized by nanostructured iron carbide ferromagnets,to boost the critical protonation steps.The as-designed catalyst displays a broad window(300 mV)for CO selectivity>90%(98%maximum),even outperforming numerous cutting-edge M–N–C systems.The well-placed control of proton dynamics by A/N-Fe can promote*COOH/*CO formation and simultaneously suppress H2 evolution,benefiting from the magnetic-proximity-induced exchange splitting(spin polarization)that properly adjusts energy levels of the Fe sites’d-shells,and further those of the adsorbed intermediates’antibonding molecular orbitals.
基金financial support by the National Natural Science Foundation of China (No.U1532135)
文摘An efficient and practical synthetic protocol to synthesize nonsymmetrical aryl thioethers by nucleophilic aromatic substitution(S_NAr)reaction of nitroarenes by thiols with potassium phosphate as the catalyst is described.Various moderate to strong electron-withdrawing functional groups are tolerated by the system to provide thioethers in a good to excellent yields.We also showed that the present method allows access to 3 drug examples in a short reaction time.Finally,mechanistic studies suggest that the reaction may form the classic Meisenheimer complex through a two-step additionelimination mechanism.