The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have bee...The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.展开更多
For a simple graph G,let A(G)and D(G)be the adjacency matrix and the diagonal degree matrix of G,respectively.[Appl.Anal.Discrete Math.,2017,11(1):81-107]defined the matrix A_(α)(G)of G as A_(α)(G)=αD(G)(1-α)A(G)...For a simple graph G,let A(G)and D(G)be the adjacency matrix and the diagonal degree matrix of G,respectively.[Appl.Anal.Discrete Math.,2017,11(1):81-107]defined the matrix A_(α)(G)of G as A_(α)(G)=αD(G)(1-α)A(G),α∈[0,1].The Aa-spectral radius is the largest eigenvalue of A_(α)(G).Let G_(n,β) be the set graphs with order n and dissociation numberβ.In this paper,we identify the b with maximal A_(α)-spectral radius among all graphs in G_(n,β).展开更多
Biology is governed by macromolecular interactions,perturbation of which often lies at the heart of disease.Most therapeutic drugs,whether they are small molecules or biologics,exert their effects through impeding suc...Biology is governed by macromolecular interactions,perturbation of which often lies at the heart of disease.Most therapeutic drugs,whether they are small molecules or biologics,exert their effects through impeding such interactions,whether they are of an enzyme with its substrate or a ligand with its receptor.Conversely,a handful of approved drugs and a larger number of candidates in development have the opposite effect:They either activate or inhibit a biological output by stabilizing a preexisting complex through reducing the rate at which its components dissociate(koff).展开更多
Extracting lithium from coal measures can alleviate the shortage of strategic metal resources.However,the lattice substitution characteristics of lithium in carrier minerals and its extremely fine intercalation and en...Extracting lithium from coal measures can alleviate the shortage of strategic metal resources.However,the lattice substitution characteristics of lithium in carrier minerals and its extremely fine intercalation and entrainment behavior are the challenges that constrain the extraction efficiency of lithium from coal series.This study focuses on improving the separation efficiency between lithium-contain-ing minerals and other minerals and the release behavior of lithium in the liquid phase.First,the feasibility of extracting lithium from car-rier minerals is confirmed based on the occurrence state and the process mineralogy characterized by Bgrimm process mineralogy analyz-ing system(BPMA)and time of flight secondary ion mass spectrometry(TOF-SIMS).The optimal selective grinding behavior is achieved within 15 min,allowing Li carrier minerals,including chlorite,kaolinite,and halloysite,to deliver the best dispersion effect with other minerals.Thus,the enriched lithium carrier minerals have been preenriched through screening.The leaching efficiency of Li has reached 97.43%under 1 mol/L hydrochloric acid,15 g/L pulp density,70℃,and 20 min.Leaching kinetics studies indicate that the de-crease in apparent energy validates the impact of grinding on metal leaching,aligning with the rate-controlling step of a chemical reaction.The process proposed in this study achieves the coordinated control of size and components in coal gangue and actualizes the effective se-lective enrichment of lithium through its low energy consumption and environmentally friendly nature.展开更多
Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear streng...Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear strength under varying dissociation conditions have not been thoroughly investigated. To this end,a series of triaxial compression tests were first carried out on sediments with varying initial hydratesaturations along dissociation pathways. Combining measured data with microscale analysis, the underlyingmechanism for the evolution of shear strength in hydrate-bearing sediment was studied undervarying partial dissociation pathways. Moreover, a shear strength model for hydrate-bearing sedimentwas proposed, taking into account the hydrate saturation and the unhydrated water content. Apart fromthe parameters derived from the hydrate characteristic curve, only one additional model parameter isrequired. The proposed model was validated using measured data on hydrate sediments. The resultsindicate that the proposed model can effectively capture the shear strength behavior of hydrate-bearingsediment under varying dissociation paths. Finally, a sensitivity analysis of the model parameters wasconducted to characterize the proposed model.展开更多
The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the t...The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the transported substance may undergo phase transitions between solid,liquid,or gas states during dissociation and hydration processes.To effectively predict hydrate dissociation performance influenced by multi-field coupling processes,this study proposes a novel bond-based peridynamic coupled finite difference model that accounts for gas-liquid two-phase seepage behavior.The developed peridynamic(PD)model simulates hydrate dissociation reactions accompanied by gas-liquid seepage,mass transfer,and heat transfer phenomena.The formulation demonstrates strong agreement with established analytical solutions for one-dimensional problems and finite element transient solutions for two-dimensional problems in the literature,validating the accuracy and reliability of the newly constructed model.This research presents an innovative approach to simulate heat transport and multiphase flow phenomena associated with hydrate dissociation.展开更多
Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and...Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and optimal adsorption sites,the hollow(H)sites were finally identified as favorable dissociation sites for N_(2).The dissociation barriers of N_(2)are 0.87eV on Ir(100)and 1.12eV on Ir(110),which can be overcome at around 348 and 448 K,respectively.Therefore,Ir(100)is screened as a promising catalyst for N_(2)dissociation compared to Ir(110).This can be attributed to the significantly higher adsorption energy of N_(2)on the H site of Ir(100)(−0.48 eV)compared to that on Ir(110)(−0.22 eV),leading to different dissociation mechanisms on Ir(100)and Ir(110).Ir(100)can dissociate N_(2)directly on H site and Ir(110)should firstly capture N_(2)via bridge site and further transfer the adsorbed N_(2)to the H site,which will dramatically deteriorate the reactivity of N_(2)dissociation.In addition,the following protonation processes of dissociated∗N atoms are all exothermal at 348 K on Ir(100),indicating that the ammonia synthesis can occur spontaneously as the temperature higher than 348 K.These results have provided a reasonable materials design scheme for subsequent ammonia synthesis.展开更多
Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,...Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,are critical for the reaction kinetics which involves multiple proton coupled electron transfer steps.Herein,we demonstrate that the two key steps(CO_(2)-^(*)COOH and^(*)CO-^(*)COH)efficiency can be precisely tuned by introducing proper amount of water dissociation center,i.e.,Fe single atoms,locally surrounding the Cu catalysts.In alkaline electrolyte,the Faradaic efficiency(FE)of multi-carbon(C^(2+))products exhibited a volcano type plot depending on the density of water dissociation center.A maximum FE for C^(2+)products of 73.2%could be reached on Cu nanoparticles supported on N-doped Carbon nanofibers with moderate Fe single atom sites,at a current density of 300 mA cm^(–2).Experimental and theoretical calculation results reveal that the Fe sites facilitate water dissociation kinetics,and the locally generated protons contribute significantly to the CO_(2)activation and^(*)CO protonation process.On the one hand,in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(in-situ ATR-SEIRAS)clearly shows that the^(*)COOH intermediate can be observed at a lower potential.This phenomenon fully demonstrates that the optimized local water dissociation kinetics has a unique advantage in guiding the hydrogenation reaction pathway of CO₂molecules and can effectively reduce the reaction energy barrier.On the other hand,abundant^(*)CO and^(*)COH intermediates create favorable conditions for the asymmetric^(*)CO-^(*)COH coupling,significantly increasing the selectivity of the reaction for C^(2+)products and providing strong support for the efficient conversion of related reactions to the target products.This work provides a promising strategy for the design of a dual sites catalyst to achieve high FE of C^(2+)products through the optimized local water dissociation kinetics.展开更多
The work considers the problem of gas hydrate dissociation in a porous medium using the two-term Forchheimer law,corresponding to high flow rates of reservoir fluids.Such rates can arise during the decomposition of ga...The work considers the problem of gas hydrate dissociation in a porous medium using the two-term Forchheimer law,corresponding to high flow rates of reservoir fluids.Such rates can arise during the decomposition of gas hydrates,since a large amount of gas is released.Intensive emissions of gases from the earth’s interior are observed on the ocean floor.They are also associated with a large number of subvertical geological structures under the ocean floor,coming to the surface in the formof local ring funnels(pockmarks).Many similar objects have also been found on land.Particular interest in this problemis caused by climate threats associated with the release of greenhouse gases.The movement of gas released fromthe hydrate to the breakthrough channel is similar to the gas inflow to the well(without hydrate),which is usually described by a two-term filtration law.In this work,a mathematical model of gas hydrate dissociation with a nonlinear Forchheimer-type law ofmotion is developed.The systemis split in two blocks by physical processes,taking into account the quadratic correction to the velocity in the filtration law.The first block is responsible for the convective transfer of saturation parameters in the model,water,gas and hydrate saturations are taken into account.The second block corresponds to the equation of dissipative piezoconductivity with a different number of thermodynamic degrees of freedom,taking into account heat and mass transfer in a porous medium.The performed splitting allows using explicit-implicit difference schemes when solving problems and avoiding strong refinement of the step in time and space.For numerical modeling,the support operator method is used,which makes it possible to discretize partial differential equations on irregular grids,which allows taking into account the complex geometry and lithology of the reservoir.A difference scheme based on the support operator method is developed,which,due to the mutually consistent approximation of vector analysis operations(divergence and gradient),allows to take into account the various flux laws between adjacent grid cells,including quadratic corrections to the velocity.Based on the developed numerical algorithms and their program implementations,calculations of gas hydrate dissociation are performed both in a reservoir of simple geometric structure and in a heterogeneous reservoir of complex configuration.The results obtained correspond to the physics of the processes under consideration.展开更多
Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-b...Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.展开更多
The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio ...The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio molecular dynamics(AIMD)with free energy perturbation is employed to calculate the dehydrogenation free energy of water chemisorbed at differently electrified Pt(111)/electrolyte interfaces.Our findings reveal that the onset potential for OH*formation shifts negatively as the pH increases at low pH condition(pH<4.3),aligning with the cyclic voltammetry curves observed in experimental studies.It indicates the dissociation of chemisorbed water is the primary route for OH*adsorption at low pH condition.Furthermore,it is also found that the variation in dehydrogenation energy across different pH is primarily due to the local hydrogen bonding network surrounding the chemisorbed water.In addition,it is proposed that at high pH conditions OH-oxidation emerges as the primary route for OH*adsorption on Pt(111)constrained by the water chemisorption process.This work provides crucial insights into the pH-dependent adsorption behavior of OH*on the Pt(111)surface and aims to guide the optimization of electrolytes to boost the efficiency of related reactions.展开更多
Nucleotide binding domain,leucine-rich repeat,and pyrin domain-containing 3(NLRP3)is an NLR-protein family member that can be activated by diverse exogenous and endogenous stimuli but without direct binding of any of ...Nucleotide binding domain,leucine-rich repeat,and pyrin domain-containing 3(NLRP3)is an NLR-protein family member that can be activated by diverse exogenous and endogenous stimuli but without direct binding of any of these pathogen ligands.Biological studies show that inactive NLRP3 is usually in an as-sembly state and its activation requires a kinase protein,NEK7.However,our re-cent computational studies as well as other biological investigations have demonstrated that NEK7 does not play a significant role in the activation of NLRP3 assembly and activation.In-stead,biological studies suggest that NEK7 is essential in the dissociation of inactive NLRP3 assemblies.Despite extensive research,the dissociation mechanism of the inactive NLRP3 as-sembly remains largely elusive.In this work,an improved MM-PBSA method is applied to the protein-protein binding free energies in the inactive NLRP3 decamer.Combined with the po-tential mean force(PMF)computation for the 0°→5°conformational change,the standard free-energy change,ΔG^(0)is calculated for NEK7-driven association of the inactive NLRP3 de-camer.Our calculations show that in the absence of NEK7,the dissociation of the inactive NLRP3 decamer is an energetically unfavorable process(ΔG^(0)=99.69 kcal/mol),whereas upon NEK7 binding,the overall standard free energy differenceΔG^(0)=-24.21 kcal/mol is obtained for the inactive NLRP3 decamer dissociation.The free-energy difference calcula-tions in this work also disclose an energetically optimized dissociation pathway,along which the inactive NLRP3 decamer is disunited by a one-by-one dissociation mechanism.展开更多
Solar-driven hydrogen peroxide(H_(2)O_(2))production offers a sustainable and environmentally friendly alternative to the traditional anthraquinone oxidation method.Conjugated polymers(CPs)are emerging as promising ph...Solar-driven hydrogen peroxide(H_(2)O_(2))production offers a sustainable and environmentally friendly alternative to the traditional anthraquinone oxidation method.Conjugated polymers(CPs)are emerging as promising photocatalysts for H_(2)O_(2)production due to their unique electronic,optical properties,and tunable structures.However,the high exciton binding energy of CPs hinders efficient exciton dissociation and charge separation,limiting their photocatalytic performance.In this work,we synthesized scandium(Sc)atoms decorated CPs with enhanced ordered stacking and crystallinity by introducing benzaldehyde as an end-capping reagent.The strong interaction between charged Sc atoms and electrons facilitates exciton dissociation and improves charge transfer capability.Furthermore,the Lewis acidic nature of Sc atoms promotes oxygen adsorption and enhances the stabilization of superoxide anion intermediate(·O_(2)^(-)).As a result,the as-synthesized photocatalysts exhibit a high H_(2)O_(2)production rate of 18μmol h^(-1)in pure water,which is three times that of pristine CPs,This work provides valuable insights into the design of organic polymer photocatalysts for various photocatalytic reactions.展开更多
We investigated the ionization and dissociation processes of ammonia clusters ranging from dimer to pentamer induced by 800-nm femtosecond laser fields.Time-of-flight(TOF)mass spectra of the ammonia clusters were reco...We investigated the ionization and dissociation processes of ammonia clusters ranging from dimer to pentamer induced by 800-nm femtosecond laser fields.Time-of-flight(TOF)mass spectra of the ammonia clusters were recorded over a range of laser intensities from 2.1×10^(12)W/cm^(2) to 5.6×10^(12)W/cm^(2).The protonated ion signals dominate the spectra,which is consistent with the stability of the geometric structures.The ionization and dissociation channels of ammonia clusters are discussed.The competition and switching among observed dissociation channels are revealed by analyzing the variations in the relative ionic yields of specific protonated and unprotonated clusters under different laser intensities.These results indicate that the ionization of the neutral multiple-ammonia units,produced through the dissociation of cluster ions,may start to contribute,as well as the additional processes to consume protonated ions and/or produce unprotonated ions induced by the femtosecond laser fields when the laser intensity is above^4×10^(12)W/cm^(2).These findings provide deeper insights into the ionization and dissociation dynamics in multi-photon ionization experiments involving ammonia clusters.展开更多
In this study,six-dimensional(6D)time-dependent wave packet calcula-tions were employed to investigate the dissociation of HCl molecules on two bimetallic surfaces,Cu/Ag(111)and Cu/Au(111).These calculations were base...In this study,six-dimensional(6D)time-dependent wave packet calcula-tions were employed to investigate the dissociation of HCl molecules on two bimetallic surfaces,Cu/Ag(111)and Cu/Au(111).These calculations were based on two accurate potential energy surfaces(PESs)constructed using neu-ral network methodology.Density functional theory(DFT)calculations revealed that the static barrier heights for HCl on Cu/Ag(111)and Cu/Au(111)were 0.32 eV and 0.28 eV,respectively.These values are significantly lower than the barrier height on pure Cu(111)(0.52 eV),primarily due to surface strain effects.However,it was found that the 6D dissociation probability of HCl in(v=0,1,j=0)states on Cu/Au(111)was considerably lower,despite its barrier height being 0.04 eV lower than that for Cu/Ag(111).The underlying mechanism for this observation was attributed to the non-monotonic dependence of the minimum energy path(MEP)on the molecular orientation,which was induced by charge transfer effect for HCl+Cu/Au(111).In contrast,HCl+Cu/Ag(111)exhibited a monotonic dependence.These contrasting behaviors led to dis-tinct differences in rotational alignment and excitation effects for the two reactions.展开更多
A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with ...A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence （Mo-CL） instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of ＋1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high.展开更多
Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3P...Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3PW91, B3P86） methods together with 6-31G^＊＊ and 6-311G^＊＊ basis sets. The results show that B3P86/6-311G^＊＊ method is the best method to compute the reliable BDEs for substituted chlorobenzene compounds which contain the C-C1 bond. It is found that the C-C1 BDE depends strongly on the computational method and the basis sets used. Substituent effect on the C-C1 BDE of substituted chlorobenzene compounds is further discussed. It is noted that the effects of substitution on the C-C1 BDE of substituted chlorobenzene compounds are very insignificant. The energy gaps between the HOMO and LUMO of studied compounds estimate the relative thermal stability ordering are also investigated and from this data we of substituted chlorobenzene compounds.展开更多
Shape resonances of electron-molecule system formed in the low-energy electron attachment to four low-lying conformers of serine （serine 1, serine 2, serine 3, and serine 4） in gas phase are investigated using the q...Shape resonances of electron-molecule system formed in the low-energy electron attachment to four low-lying conformers of serine （serine 1, serine 2, serine 3, and serine 4） in gas phase are investigated using the quantum scattering method with the non-empirical model potentials in single-center expansion. In the attachment energy range of 0-10 eV, three shape resonances for serine 1, serine 2, and serine 4 and four shape resonances for serine 3 are predicted. The one-dimensional potential energy curves of the temporary negative ions of electron-serine are calculated to explore the correlations between the shape resonance and the bond cleavage. The bond-cleavage selectivity of the different resonant states for a certain conformer is demonstrated, and the recent experimental results about the dissociative electron attachment to serine are interpreted on the basis of present calculations.展开更多
A home-made static NMR cell with pressure up to 10 MPa was employed to observe the formation and dissociation processes of methane hydrate by in situ ^1H and ^13C NMR spectroscopies. Methane hydrate can be formed or d...A home-made static NMR cell with pressure up to 10 MPa was employed to observe the formation and dissociation processes of methane hydrate by in situ ^1H and ^13C NMR spectroscopies. Methane hydrate can be formed or decomposed in the temperature range of -5 to -13℃ at pressures between 4.0 and 7.0 MPa. The higher methane pressure, the formation or dissociation temperature of methane hydrate was higher. In situ ^1H NMR experiments indicated that the critical size of the hydrate clusters is crucial for the formation of methane hydrate.展开更多
Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon ...Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12534013,12047561,and 12104507)the Science and Technology Innovation Program of Hunan Province(Grant Nos.2025ZYJ001 and 2021RC4026)the National University of Defense Technology Research Fund Project.
文摘The accumulation and circulation of carbon and hydrogen contribute to the chemical evolution of ice giant planets.Species separation and diamond precipitation have been reported in carbon-hydrogen systems and have been verified by static and shock compression experiments.Nevertheless,the dynamic formation processes underlying these phenomena remain insufficiently understood.In combination with a deep learning model,we demonstrate that diamonds form through a three-step process involving dissociation,species separation,and nucleation processes.Under shock conditions of 125 GPa and 4590 K,hydrocarbons decompose to give hydrogen and low-molecular-weight alkanes(CH_(4) and C_(2)H_(6)),which escape from the carbon chains,resulting in C/H species separation.The remaining carbon atoms without C-H bonds accumulate and nucleate to form diamond crystals.The process of diamond growth is associated with a critical nucleus size at which the dynamic energy barrier plays a key role.These dynamic processes of diamond formation provide insight into the establishment of a model for the evolution of ice giant planets.
基金Supported by NSFC (Nos.12171089,12271235)NSF of Jiangsu (No.BK20190919)NSF of Fujian (No.2021J02048)。
文摘For a simple graph G,let A(G)and D(G)be the adjacency matrix and the diagonal degree matrix of G,respectively.[Appl.Anal.Discrete Math.,2017,11(1):81-107]defined the matrix A_(α)(G)of G as A_(α)(G)=αD(G)(1-α)A(G),α∈[0,1].The Aa-spectral radius is the largest eigenvalue of A_(α)(G).Let G_(n,β) be the set graphs with order n and dissociation numberβ.In this paper,we identify the b with maximal A_(α)-spectral radius among all graphs in G_(n,β).
文摘Biology is governed by macromolecular interactions,perturbation of which often lies at the heart of disease.Most therapeutic drugs,whether they are small molecules or biologics,exert their effects through impeding such interactions,whether they are of an enzyme with its substrate or a ligand with its receptor.Conversely,a handful of approved drugs and a larger number of candidates in development have the opposite effect:They either activate or inhibit a biological output by stabilizing a preexisting complex through reducing the rate at which its components dissociate(koff).
基金supported by the National Key R&D Program of China(No.2023YFC2907701)This work was also supported by the Fundamental Research Program of Shanxi Province,China(No.202103021223045)+4 种基金the Shanxi Scholarship Council of China(No.2022-062)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(No.2021L064)This study was also funded by Open Foundation of State Key Laboratory of Mineral Processing(No.BGRIMM-KJSKL-2025-26)This work was supported by the National Natural Science Foundation of China(No.52104260)This work was supported by Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001).
文摘Extracting lithium from coal measures can alleviate the shortage of strategic metal resources.However,the lattice substitution characteristics of lithium in carrier minerals and its extremely fine intercalation and entrainment behavior are the challenges that constrain the extraction efficiency of lithium from coal series.This study focuses on improving the separation efficiency between lithium-contain-ing minerals and other minerals and the release behavior of lithium in the liquid phase.First,the feasibility of extracting lithium from car-rier minerals is confirmed based on the occurrence state and the process mineralogy characterized by Bgrimm process mineralogy analyz-ing system(BPMA)and time of flight secondary ion mass spectrometry(TOF-SIMS).The optimal selective grinding behavior is achieved within 15 min,allowing Li carrier minerals,including chlorite,kaolinite,and halloysite,to deliver the best dispersion effect with other minerals.Thus,the enriched lithium carrier minerals have been preenriched through screening.The leaching efficiency of Li has reached 97.43%under 1 mol/L hydrochloric acid,15 g/L pulp density,70℃,and 20 min.Leaching kinetics studies indicate that the de-crease in apparent energy validates the impact of grinding on metal leaching,aligning with the rate-controlling step of a chemical reaction.The process proposed in this study achieves the coordinated control of size and components in coal gangue and actualizes the effective se-lective enrichment of lithium through its low energy consumption and environmentally friendly nature.
基金supported by the National Natural Science Foundation of China(Grant No.51939011)the Science and Technology Program of CNOOC Research Institute(Grant No.2023OTKK03)supported by the program of the Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2020326).
文摘Shear strength of hydrate-bearing sediment is an essential parameter for assessing landslide potential ofhydrate reservoirs under exploration conditions. However, the characteristics and simulation of thisshear strength under varying dissociation conditions have not been thoroughly investigated. To this end,a series of triaxial compression tests were first carried out on sediments with varying initial hydratesaturations along dissociation pathways. Combining measured data with microscale analysis, the underlyingmechanism for the evolution of shear strength in hydrate-bearing sediment was studied undervarying partial dissociation pathways. Moreover, a shear strength model for hydrate-bearing sedimentwas proposed, taking into account the hydrate saturation and the unhydrated water content. Apart fromthe parameters derived from the hydrate characteristic curve, only one additional model parameter isrequired. The proposed model was validated using measured data on hydrate sediments. The resultsindicate that the proposed model can effectively capture the shear strength behavior of hydrate-bearingsediment under varying dissociation paths. Finally, a sensitivity analysis of the model parameters wasconducted to characterize the proposed model.
基金financially supported by the National Natural Science Foundation of China(General Program,Grant No.52374011)the Research and Innovation Fund for Graduate Students of Southwest Petroleum University(Grant No.2021CXYB04)the Sichuan Province Science and Technology Support Program(Grant No.2023NSFSC1980)。
文摘The numerical simulation and analysis of natural gas hydrates with heat and mass transfer are essential for identifying and predicting reservoir states during dissociation and seepage processes.In specific cases,the transported substance may undergo phase transitions between solid,liquid,or gas states during dissociation and hydration processes.To effectively predict hydrate dissociation performance influenced by multi-field coupling processes,this study proposes a novel bond-based peridynamic coupled finite difference model that accounts for gas-liquid two-phase seepage behavior.The developed peridynamic(PD)model simulates hydrate dissociation reactions accompanied by gas-liquid seepage,mass transfer,and heat transfer phenomena.The formulation demonstrates strong agreement with established analytical solutions for one-dimensional problems and finite element transient solutions for two-dimensional problems in the literature,validating the accuracy and reliability of the newly constructed model.This research presents an innovative approach to simulate heat transport and multiphase flow phenomena associated with hydrate dissociation.
基金funded by the Natural Science Foundation of China(No.21603109)the Henan Joint Fund of the National Natural Science Foundation of China(No.U1404216)+1 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.20JK0676)supported by Natural Science Basic Research Program of Shanxi(Nos.2022JQ-108,2022JQ096)。
文摘Density functional theory(DFT)was performed to systematically study the adsorption and dissociation of N_(2)on Ir(100)and Ir(110)surfaces.By analyzing the properties,including adsorption energies,reaction barriers,and optimal adsorption sites,the hollow(H)sites were finally identified as favorable dissociation sites for N_(2).The dissociation barriers of N_(2)are 0.87eV on Ir(100)and 1.12eV on Ir(110),which can be overcome at around 348 and 448 K,respectively.Therefore,Ir(100)is screened as a promising catalyst for N_(2)dissociation compared to Ir(110).This can be attributed to the significantly higher adsorption energy of N_(2)on the H site of Ir(100)(−0.48 eV)compared to that on Ir(110)(−0.22 eV),leading to different dissociation mechanisms on Ir(100)and Ir(110).Ir(100)can dissociate N_(2)directly on H site and Ir(110)should firstly capture N_(2)via bridge site and further transfer the adsorbed N_(2)to the H site,which will dramatically deteriorate the reactivity of N_(2)dissociation.In addition,the following protonation processes of dissociated∗N atoms are all exothermal at 348 K on Ir(100),indicating that the ammonia synthesis can occur spontaneously as the temperature higher than 348 K.These results have provided a reasonable materials design scheme for subsequent ammonia synthesis.
文摘Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,are critical for the reaction kinetics which involves multiple proton coupled electron transfer steps.Herein,we demonstrate that the two key steps(CO_(2)-^(*)COOH and^(*)CO-^(*)COH)efficiency can be precisely tuned by introducing proper amount of water dissociation center,i.e.,Fe single atoms,locally surrounding the Cu catalysts.In alkaline electrolyte,the Faradaic efficiency(FE)of multi-carbon(C^(2+))products exhibited a volcano type plot depending on the density of water dissociation center.A maximum FE for C^(2+)products of 73.2%could be reached on Cu nanoparticles supported on N-doped Carbon nanofibers with moderate Fe single atom sites,at a current density of 300 mA cm^(–2).Experimental and theoretical calculation results reveal that the Fe sites facilitate water dissociation kinetics,and the locally generated protons contribute significantly to the CO_(2)activation and^(*)CO protonation process.On the one hand,in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(in-situ ATR-SEIRAS)clearly shows that the^(*)COOH intermediate can be observed at a lower potential.This phenomenon fully demonstrates that the optimized local water dissociation kinetics has a unique advantage in guiding the hydrogenation reaction pathway of CO₂molecules and can effectively reduce the reaction energy barrier.On the other hand,abundant^(*)CO and^(*)COH intermediates create favorable conditions for the asymmetric^(*)CO-^(*)COH coupling,significantly increasing the selectivity of the reaction for C^(2+)products and providing strong support for the efficient conversion of related reactions to the target products.This work provides a promising strategy for the design of a dual sites catalyst to achieve high FE of C^(2+)products through the optimized local water dissociation kinetics.
基金the framework of the state assignment of Keldysh Institute of Applied Mathematics of RAS(Project No.125020701776-0)the Ministry of Education and Science of Russia for IO RAS(Project No.FMWE-2024-0018).
文摘The work considers the problem of gas hydrate dissociation in a porous medium using the two-term Forchheimer law,corresponding to high flow rates of reservoir fluids.Such rates can arise during the decomposition of gas hydrates,since a large amount of gas is released.Intensive emissions of gases from the earth’s interior are observed on the ocean floor.They are also associated with a large number of subvertical geological structures under the ocean floor,coming to the surface in the formof local ring funnels(pockmarks).Many similar objects have also been found on land.Particular interest in this problemis caused by climate threats associated with the release of greenhouse gases.The movement of gas released fromthe hydrate to the breakthrough channel is similar to the gas inflow to the well(without hydrate),which is usually described by a two-term filtration law.In this work,a mathematical model of gas hydrate dissociation with a nonlinear Forchheimer-type law ofmotion is developed.The systemis split in two blocks by physical processes,taking into account the quadratic correction to the velocity in the filtration law.The first block is responsible for the convective transfer of saturation parameters in the model,water,gas and hydrate saturations are taken into account.The second block corresponds to the equation of dissipative piezoconductivity with a different number of thermodynamic degrees of freedom,taking into account heat and mass transfer in a porous medium.The performed splitting allows using explicit-implicit difference schemes when solving problems and avoiding strong refinement of the step in time and space.For numerical modeling,the support operator method is used,which makes it possible to discretize partial differential equations on irregular grids,which allows taking into account the complex geometry and lithology of the reservoir.A difference scheme based on the support operator method is developed,which,due to the mutually consistent approximation of vector analysis operations(divergence and gradient),allows to take into account the various flux laws between adjacent grid cells,including quadratic corrections to the velocity.Based on the developed numerical algorithms and their program implementations,calculations of gas hydrate dissociation are performed both in a reservoir of simple geometric structure and in a heterogeneous reservoir of complex configuration.The results obtained correspond to the physics of the processes under consideration.
基金supported by the National Key R&D Program of China(No.2023YFA1406801)the National Natural Science Foundation of China(Nos.12174011,12434013).
文摘Ionization and dissociation are fundamental processes that molecules undergo in intense femtosecond laser fields.Professor Fanao Kong is a pioneering researcher in this field within China.He has developed an orbital-based molecular ionization model and a laser field-assisted molecular dissociation model to elucidate experimental observations and predict potential applications.The predictions of these models have been corroborated by subsequent theoretical and experimental studies.This review highlights Professor Kong’s significant contributions to the study of molecular ionization and dissociation in intense femtosecond laser fields,emphasizing key advancements and outlining future directions in the field of strong-field laser chemistry.
基金support from the National Natural Science Foundation of China(Nos.22272193,22225302,21991151,and 21991150)the Ningbo Natural Science Foundation(No.2022J294)+1 种基金the Yongjiang Talent Introduction Program(No.2021A-115-G)Key Laboratory of Advanced Marine Materials,Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences,Ningbo.(No.2021A-115-G).
文摘The adsorption/desorption of OH*on electrode surfaces is pivotal in numerous electrocatalytic reactions.To understand the effect of electrolyte pH on that process,in this work,an advanced approach combining ab initio molecular dynamics(AIMD)with free energy perturbation is employed to calculate the dehydrogenation free energy of water chemisorbed at differently electrified Pt(111)/electrolyte interfaces.Our findings reveal that the onset potential for OH*formation shifts negatively as the pH increases at low pH condition(pH<4.3),aligning with the cyclic voltammetry curves observed in experimental studies.It indicates the dissociation of chemisorbed water is the primary route for OH*adsorption at low pH condition.Furthermore,it is also found that the variation in dehydrogenation energy across different pH is primarily due to the local hydrogen bonding network surrounding the chemisorbed water.In addition,it is proposed that at high pH conditions OH-oxidation emerges as the primary route for OH*adsorption on Pt(111)constrained by the water chemisorption process.This work provides crucial insights into the pH-dependent adsorption behavior of OH*on the Pt(111)surface and aims to guide the optimization of electrolytes to boost the efficiency of related reactions.
基金supported by Ministry of Science and Technology of China(2022YFA1303100)the National Natural Science Foundation of China(No.32090040)。
文摘Nucleotide binding domain,leucine-rich repeat,and pyrin domain-containing 3(NLRP3)is an NLR-protein family member that can be activated by diverse exogenous and endogenous stimuli but without direct binding of any of these pathogen ligands.Biological studies show that inactive NLRP3 is usually in an as-sembly state and its activation requires a kinase protein,NEK7.However,our re-cent computational studies as well as other biological investigations have demonstrated that NEK7 does not play a significant role in the activation of NLRP3 assembly and activation.In-stead,biological studies suggest that NEK7 is essential in the dissociation of inactive NLRP3 assemblies.Despite extensive research,the dissociation mechanism of the inactive NLRP3 as-sembly remains largely elusive.In this work,an improved MM-PBSA method is applied to the protein-protein binding free energies in the inactive NLRP3 decamer.Combined with the po-tential mean force(PMF)computation for the 0°→5°conformational change,the standard free-energy change,ΔG^(0)is calculated for NEK7-driven association of the inactive NLRP3 de-camer.Our calculations show that in the absence of NEK7,the dissociation of the inactive NLRP3 decamer is an energetically unfavorable process(ΔG^(0)=99.69 kcal/mol),whereas upon NEK7 binding,the overall standard free energy differenceΔG^(0)=-24.21 kcal/mol is obtained for the inactive NLRP3 decamer dissociation.The free-energy difference calcula-tions in this work also disclose an energetically optimized dissociation pathway,along which the inactive NLRP3 decamer is disunited by a one-by-one dissociation mechanism.
基金supported by the Natural Science Foundation of China(22408278,22275139,21971190,U21A2077)the Key Project of Natural Science Foundation of Tianjin City(Contract No.22JCZDJC00510)Key Laboratory of Functional Inorganic Material Chemistry(Heilongjiang University),Ministry of Education。
文摘Solar-driven hydrogen peroxide(H_(2)O_(2))production offers a sustainable and environmentally friendly alternative to the traditional anthraquinone oxidation method.Conjugated polymers(CPs)are emerging as promising photocatalysts for H_(2)O_(2)production due to their unique electronic,optical properties,and tunable structures.However,the high exciton binding energy of CPs hinders efficient exciton dissociation and charge separation,limiting their photocatalytic performance.In this work,we synthesized scandium(Sc)atoms decorated CPs with enhanced ordered stacking and crystallinity by introducing benzaldehyde as an end-capping reagent.The strong interaction between charged Sc atoms and electrons facilitates exciton dissociation and improves charge transfer capability.Furthermore,the Lewis acidic nature of Sc atoms promotes oxygen adsorption and enhances the stabilization of superoxide anion intermediate(·O_(2)^(-)).As a result,the as-synthesized photocatalysts exhibit a high H_(2)O_(2)production rate of 18μmol h^(-1)in pure water,which is three times that of pristine CPs,This work provides valuable insights into the design of organic polymer photocatalysts for various photocatalytic reactions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.92261201,12134005,12334011)。
文摘We investigated the ionization and dissociation processes of ammonia clusters ranging from dimer to pentamer induced by 800-nm femtosecond laser fields.Time-of-flight(TOF)mass spectra of the ammonia clusters were recorded over a range of laser intensities from 2.1×10^(12)W/cm^(2) to 5.6×10^(12)W/cm^(2).The protonated ion signals dominate the spectra,which is consistent with the stability of the geometric structures.The ionization and dissociation channels of ammonia clusters are discussed.The competition and switching among observed dissociation channels are revealed by analyzing the variations in the relative ionic yields of specific protonated and unprotonated clusters under different laser intensities.These results indicate that the ionization of the neutral multiple-ammonia units,produced through the dissociation of cluster ions,may start to contribute,as well as the additional processes to consume protonated ions and/or produce unprotonated ions induced by the femtosecond laser fields when the laser intensity is above^4×10^(12)W/cm^(2).These findings provide deeper insights into the ionization and dissociation dynamics in multi-photon ionization experiments involving ammonia clusters.
基金supported by the National Key R&D Program of China(No.2018YFE0203003)the National Natural Science Foundation of China(Nos.22173101,22173099,22288201,21703242)+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0970203)the Innovation Program for Quantum Science and Technology(No.2021ZD0303305)Dalian Talents Innovation Support Program(No.2021RD05)the Open Fund(SKLMRD-K202508)of the State Key Laboratory of Molecular Reaction Dynamics in Dalian Institute of Chemical Physics,Chinese Academy of Sciences.The computational resources are supported by SongShan Lake HPC Center(SSL-HPC)in Great Bay University.
文摘In this study,six-dimensional(6D)time-dependent wave packet calcula-tions were employed to investigate the dissociation of HCl molecules on two bimetallic surfaces,Cu/Ag(111)and Cu/Au(111).These calculations were based on two accurate potential energy surfaces(PESs)constructed using neu-ral network methodology.Density functional theory(DFT)calculations revealed that the static barrier heights for HCl on Cu/Ag(111)and Cu/Au(111)were 0.32 eV and 0.28 eV,respectively.These values are significantly lower than the barrier height on pure Cu(111)(0.52 eV),primarily due to surface strain effects.However,it was found that the 6D dissociation probability of HCl in(v=0,1,j=0)states on Cu/Au(111)was considerably lower,despite its barrier height being 0.04 eV lower than that for Cu/Ag(111).The underlying mechanism for this observation was attributed to the non-monotonic dependence of the minimum energy path(MEP)on the molecular orientation,which was induced by charge transfer effect for HCl+Cu/Au(111).In contrast,HCl+Cu/Ag(111)exhibited a monotonic dependence.These contrasting behaviors led to dis-tinct differences in rotational alignment and excitation effects for the two reactions.
文摘A two-channel thermal dissociation cavity ring down spectroscopy （CRDS） instrument has been built for in situ, real-time measurement of NO2 and total RNO2 （peroxy nitrates and alkyl nitrates） in ambient air, with a NO2 detection limit of 0.10 ppbv at 1 s. A 6-day long measurement was conducted at urban site of Hefei by using the CRDS instrument with a time resolution of 3 s. A commercial molybdenum converted chemiluminescence （Mo-CL） instrument was also used for comparison. The average RNO2 concentration in the 6 days was measured to be 1.94 ppbv. The Mo-CL instrument overestimated the NO2 concentration by a bias of ＋1.69 ppbv in average, for the reason that it cannot distinguish RNO2 from NO2. The relative bias could be over 100% during the afternoon hours when NO2 was low but RNO2 was high.
基金This work was supported by the National Natural Science Foundation of China （No.10774039）.
文摘Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3PW91, B3P86） methods together with 6-31G^＊＊ and 6-311G^＊＊ basis sets. The results show that B3P86/6-311G^＊＊ method is the best method to compute the reliable BDEs for substituted chlorobenzene compounds which contain the C-C1 bond. It is found that the C-C1 BDE depends strongly on the computational method and the basis sets used. Substituent effect on the C-C1 BDE of substituted chlorobenzene compounds is further discussed. It is noted that the effects of substitution on the C-C1 BDE of substituted chlorobenzene compounds are very insignificant. The energy gaps between the HOMO and LUMO of studied compounds estimate the relative thermal stability ordering are also investigated and from this data we of substituted chlorobenzene compounds.
基金This work is supported by the National Natural Science Foundation of China （No.21303212 and No.21573209）, the Ministry of Science and Technology of China （No.2013CB834602）.
文摘Shape resonances of electron-molecule system formed in the low-energy electron attachment to four low-lying conformers of serine （serine 1, serine 2, serine 3, and serine 4） in gas phase are investigated using the quantum scattering method with the non-empirical model potentials in single-center expansion. In the attachment energy range of 0-10 eV, three shape resonances for serine 1, serine 2, and serine 4 and four shape resonances for serine 3 are predicted. The one-dimensional potential energy curves of the temporary negative ions of electron-serine are calculated to explore the correlations between the shape resonance and the bond cleavage. The bond-cleavage selectivity of the different resonant states for a certain conformer is demonstrated, and the recent experimental results about the dissociative electron attachment to serine are interpreted on the basis of present calculations.
基金We gratefully acknowledge the National Natural Science Foundation of China for the financial support （No.90210024）.
文摘A home-made static NMR cell with pressure up to 10 MPa was employed to observe the formation and dissociation processes of methane hydrate by in situ ^1H and ^13C NMR spectroscopies. Methane hydrate can be formed or decomposed in the temperature range of -5 to -13℃ at pressures between 4.0 and 7.0 MPa. The higher methane pressure, the formation or dissociation temperature of methane hydrate was higher. In situ ^1H NMR experiments indicated that the critical size of the hydrate clusters is crucial for the formation of methane hydrate.
基金This work was supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China （No.10805047）. Authors appreciate the kind help from Dr. Yang Pan in experiments.
文摘Photon-induced dissociation pathways of thymine are investigated with vacuum ultraviolet photoionization mass spectrometry and theoretical calculations. The photoionization mass spectra of thymine at different photon energy are measured and presented. By selecting suitable photon energy, exclusively molecular ion m/z=126 is obtained. At photon energy of 12.0 eV, the major ionic fragments at m/z=98, 97, 84, 83, 70, and 55 are obtained, which are assigned to C4H6N2O＋, C4H5N2O＋, C3H4N2O＋ （or C4H6NO＋）, C4H5NO＋, C2NO2＋, and C3H5N＋, respectively. With help of theoretical calculations, the detailed dissociation pathways of thymine at low energy are well established.
