Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections...Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections to the classical turbulent energy cascade and its mass cascade counterpart running in parallel.In particular,the formation and dynamics of sediment and larvae clusters are of interest to coral larvae settlement in coastal regions and particularly the resilience of green-gray coastal protection solutions.Analogous cluster behavior is relevant to cloud microphysics and precipitation initiation,radiation transport and light transmission through colloids and suspensions,heat and mass transfer in particle-laden flows,and viral and pollutant transmission.Following a comparison between various clustering techniques,we adopt a density-based cluster identification algorithm based on its simplicity and efficiency,where particles are clustered based on the number of neighboring particles in their individual spheres of influence.We establish parallels with lattice-based percolation theory,as evident in the power-law scaling of the cluster size distribution near the percolation threshold.The degree of discontinuity of the phase transition associated with this percolation threshold is observed to broaden with larger Stokes numbers and thereby large-scale clustering.The sensitivity of our findings to the employed clustering algorithm is discussed.A novel cluster tracking algorithm is deployed to determine the interscale transfer rate along the particle-number phase-space dimension via accounting of cluster breakup and merger events,extending previous work on the bubble breakup cascade beneath surface breaking waves.Our findings shed light on the interaction between particle clusters and their carrier turbulent flows,with an eye toward transport models incorporating cluster characteristics and dynamics.展开更多
Bottom-up and top-down endogenous automobile clusters exhibit distinct evolutionary traits and driving mechanisms,yet their comparative analysis remains understudied.Therefore,using Taizhou automobile industry cluster...Bottom-up and top-down endogenous automobile clusters exhibit distinct evolutionary traits and driving mechanisms,yet their comparative analysis remains understudied.Therefore,using Taizhou automobile industry cluster(TAIC)and Wuhu automobile industry cluster(WAIC)as cases,using historical statistical data and field interview data from the 1980s to 2023,combined with qualitative research methods of thematic and diachronic analysis,and quantitative research methods of social network analysis,we compare both endogenous automobile clusters’evolutionary traits and driving mechanisms.The results confirm both clusters undergo multi-scale spatial reconfiguration,organizational complexification,and intelligent networking technological transformation,yet diverge fundamentally:TAIC evolves through market-driven progressive expansion,transitioning from single to dual-core structures via private enterprise networking,with innovation following market-integrated logic and institutional thickness built on demand-driven evolution.Conversely,WAIC follows planned expansion,maintaining state-led hierarchical single-core stability through policy-driven breakthrough innovation and supply-dominated institutional construction-though both ultimately require formal-informal system synergy.Their coevolution is driven by dynamic interactions of path dependence(weakening influence),learning-innovation(strengthening influence),and relationship selection(inverted U-shaped trajectory),with divergent development paths rooted in TAIC’s grassroots self-organization genes versus WAIC’s top-level design genes,amplified by core enterprises’strategic disparities.The research findings can not only provide decision-making support for China’s industrial upgrading,but also contribute China’s insights to global economic governance.展开更多
Villager Pan Chunlin is witnessing a boom in his homestay business.More and more visitors are coming to his village,Yucun Village in Anji County,Huzhou City,Zhejiang Province.
In the Tianshan region,a complete textile industry chain has been established,covering the entire process from cotton cultivation and chemical fiber production,through spinning,weaving,dyeing,and finishing,and further...In the Tianshan region,a complete textile industry chain has been established,covering the entire process from cotton cultivation and chemical fiber production,through spinning,weaving,dyeing,and finishing,and further extending to apparel,home textiles,and industrial textiles.In November 2025,the first list of five characteristic textile and apparel industry clusters in Xinjiang was officially announced,marking a new stage in the clustering of Xinjiang's textile and apparel industry.Data shows that the total output value of Xinjiang's cotton and textile and apparel industry chain has exceeded 220 billion yuan.With the nation's largest cotton production,a complete industrial chain system,and strong synergistic effects,Xinjiang has become a leading and highly competitive textile industry hub in China.展开更多
Precise heterometal doping or substitution of specific metal sites in isostructural metal clusters remains a formidable synthetic challenge,despite its transformative potential for modulating excited-state characteris...Precise heterometal doping or substitution of specific metal sites in isostructural metal clusters remains a formidable synthetic challenge,despite its transformative potential for modulating excited-state characteristics and customizing optical properties.In this work,we achieved the precise synthesis of isostructural alloy clusters R/S-Ag_(3)Cu([Ag_(3)Cu(tppm)(R/S-IPTT)]ClO_(4),R/S-IPTT=R/S-4-isopropylthiazolidine-2-thiolate,tppm=tris(diphenylphosphino)methane)in high yield(89%-91%)through selective doping of a Cu(Ⅰ)atom into chiral homometallic cluster enantiomers R/S-Ag_(4)([Ag_(4)(tppm)(R/S-IPTT)]ClO_(4)).In stark contrast to R/S-Ag_(4)(Φ_(em)<0.5%)that displays weak circularly polarized luminescence(CPL)with phosphorescence characteristic,R/S-Ag_(3)Cu(Φ_(em)≈70%)demonstrates strong CPL properties featured with thermally activated delay fluorescence(TADF)at ambient temperature.The selective substitution of the apical Ag(Ⅰ)atom in Ag_(4)triangular pyramid with a Cu(Ⅰ)atom not only gives rise to beyond 100-fold boosting of photoluminescence quantum yield(PLQY),but also leads to more pronounced optically chiral activity of alloy clusters in excited states in view of the larger photoluminescence dissymmetry factors(g_(PL))of R/S-Ag_(3)Cu(-3.5×10^(-3)/3.4×10^(-3))than that of R/S-Ag_(4)(-2.7×10^(-3)/2.6×10^(-3)).Furthermore,compared with chiral homometallic clusters R/S-Cu_(4)([Cu_(4)(tppm)(R/S-IPTT)]ClO_(4))with the same TADF characteristic at ambient temperature,R/S-Ag_(3)Cu manifests 1.7-fold PLQY and 6-fold g_(PL)due to faster reverse intersystem crossing(RISC)and more effective coupling of electric and magnetic transition moments in alloy clusters.This work not only presents a typical example of selective heterometal doping to modulate excited-state properties of isostructural metal clusters,but also gets deeper insight into the doping chemistry of dissimilar metals at the molecular level.展开更多
Precisely identifying the atomic structure of reducible oxide-supported metal clusters remains challenging yet critical for understanding their catalytic behavior.Herein,we report the preparation of CeO_(2)-supported ...Precisely identifying the atomic structure of reducible oxide-supported metal clusters remains challenging yet critical for understanding their catalytic behavior.Herein,we report the preparation of CeO_(2)-supported bi-layer Pt clusters(Pt_(n)/CeO_(2))via a deposition-reduction strategy,with Pt cluster sizes ranging from 0.8 to 1.2 nm(9–30 atoms).Through combined aberration-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM)imaging,quantitative STEM simulations,and X-ray fine structure(XAFS)analysis,we reveal the bi-layer configuration featuring coordinatively unsaturated Pt^(0) sites on the top layer while maintaining Pt-CeO_(2)interfacial bonding at the bottom.When applied to anti-Markovnikov alkene hydrosilylation,Pt_(n)/CeO_(2)achieves 99.9%silane conversion with a mass-specific activity 2.0×and 8.8×higher than single-atom site(Pt_(1)/CeO_(2))and nanoparticle(Pt_(NP)/CeO_(2))counterparts,respectively.The bi-layer structure endows exceptional cycling stability and anti-leaching properties.This work establishes a multi-scale characterization paradigm to resolve atomic-precision structures of supported clusters,opening avenues for designing robust catalysts with tailored metal-oxide interfaces.展开更多
Objectives To identify core symptoms and symptom clusters in patients with neuromyelitis optica spectrum disorder(NMOSD)by network analysis.Methods From October 10 to 30,2023,140 patients with NMOSD were selected to p...Objectives To identify core symptoms and symptom clusters in patients with neuromyelitis optica spectrum disorder(NMOSD)by network analysis.Methods From October 10 to 30,2023,140 patients with NMOSD were selected to participate in this online questionnaire survey.The survey tools included a general information questionnaire and a self-made NMOSD symptoms scale,which included the prevalence,severity,and distress of 29 symptoms.Cluster analysis was used to identify symptom clusters,and network analysis was used to analyze the symptom network and node characteristics and central indicators including strength centrality(r_(s)),closeness centrality(r_(c))and betweeness centrality(r_(b))were used to identify core symptoms and symptom clusters.Results The most common symptom was pain(65.7%),followed by paraesthesia(65.0%),fatigue(65.0%),easy awakening(63.6%).Regarding the burden level of symptoms,pain was the most burdensome symptom,followed by paraesthesia,easy awakening,fatigue,and difficulty falling asleep.Six clusters were identified:somatosensory,motor,visual,and memory symptom clusters,bladder and rectum symptom clusters,sleep symptoms clusters,and neuropsychological symptom clusters.Fatigue(r_(s)=12.39,r_(b)=68.00,r_(c)=0.02)was the most central and prominent bridge symptom,and motor symptom cluster(r_(s)=2.68,r_(c)=0.10)was the most central symptom cluster among the six clusters.Conclusions Our study demonstrated the necessity of symptom management targeting fatigue,pain,and motor symptom cluster in patients with NMOSD.展开更多
An aluminoborate,Na_(2.5)Rb[Al{B_(5)O_(10)}{B_(3)O_(5)}]·0.5NO_(3)·H_(2)O(1),was synthesized under hydrothermal condition,which was built by mixed oxoboron clusters and AlO_(4)tetrahedra.In the structure,the...An aluminoborate,Na_(2.5)Rb[Al{B_(5)O_(10)}{B_(3)O_(5)}]·0.5NO_(3)·H_(2)O(1),was synthesized under hydrothermal condition,which was built by mixed oxoboron clusters and AlO_(4)tetrahedra.In the structure,the[B_(5)O_(10)]^(5-)and[B_(3)O_(7)]^(5-)clusters are alternately connected to form 1D[B_(8)O_(15)]_(n)^(6n-)chains,which are further linked by AlO_(4)units to form a 2D monolayer with 7‑membered ring and 10‑membered ring windows.Two adjacent monolayers with opposite orientations further form a porous‑layered structure with six channels through B—O—Al bonds.Compound 1 was characterized by single crystal X‑ray diffraction,powder X‑ray diffraction(PXRD),IR spectroscopy,UV‑Vis diffuse reflection spectroscopy,and thermogravimetric analysis(TGA),respectively.UV‑Vis diffuse reflectance analysis indicates that compound 1 shows a wide transparency range with a short cutoff edge of 201 nm,suggesting it may have potential application in UV regions.CCDC:2383923.展开更多
Ultrafine,highly dispersed Pt clusters were immobilized onto the Co nanoparticle surfaces by one-step pyrolysis of the precursor Pt(Ⅱ)-encapsulating Co-MOF-74.Owing to the small size effects of Pt clusters as well as...Ultrafine,highly dispersed Pt clusters were immobilized onto the Co nanoparticle surfaces by one-step pyrolysis of the precursor Pt(Ⅱ)-encapsulating Co-MOF-74.Owing to the small size effects of Pt clusters as well as the strongly enhanced synergistic interactions between Pt and Co atoms,the obtained Pt-on-Co/C400 catalysts exhib-ited excellent catalytic activity toward the hydrolysis of ammonia borane with an extremely high turnover frequency(TOF)value of 3022 min^(-1)at 303 K.Durability test indicated that the obtained Pt-on-Co/C400 catalysts possessed high catalytic stability,and there were no changes in the catalyst structures and catalytic activities after 10 cycles.展开更多
Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintill...Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintillation performance is challenging.Herein,we report an effective way to prepare high-quality scintillation films of two synthesized Cu(Ⅰ)clusters through vacuum evaporation deposition.The developed Cu(Ⅰ)clusters with rigid molecular structures show excellent scintillation performance with a high light yield of up to 19356.7 photons/MeV and a low detection limit of 158 nGy/s.The scintillation film based on the Cu(Ⅰ)clusters made by vacuum evaporation deposition is highly uniform with a small surface roughness value of 1.04 nm,which can be applied to X-ray imaging for various objects.These results not only provide important guidance to develop high-performance organic-inorganic hybrid scintillators,but also pave a straightforward way to prepare non-doped scintillation screens for remarkable X-ray imaging applications.展开更多
In modern distributed systems and cloud computing architectures,high availability and high scalability are core requirements to ensure the continuous and stable operation of services.As key technologies for achieving ...In modern distributed systems and cloud computing architectures,high availability and high scalability are core requirements to ensure the continuous and stable operation of services.As key technologies for achieving these two goals,high-availability clusters and load-balancing clusters have significant differences in their design concepts and application scenarios,while also maintaining close connections.This paper aims to conduct an in-depth analysis of the core objectives,working principles,technical advantages and disadvantages,and typical application cases of high-availability clusters and load-balancing clusters.By introducing an analogical model of a“restaurant kitchen,”the differences between the two are intuitively explained,and their technical characteristics are compared in detail.Additionally,a detailed practical case is included to specifically demonstrate the collaborative work of high-availability and load-balancing technologies through the construction process of Keepalived and HAProxy.Finally,taking the architecture of a typical e-commerce website as an example,this paper demonstrates the best practice of organically combining the two cluster technologies in a production environment to build a robust and high-performance distributed system.Research shows that understanding the differences between the two and implementing collaborative deployment is the cornerstone of designing modern IT infrastructure.展开更多
Attributed graph clustering plays a vital role in uncovering hidden network structures,but it presents significant challenges.In recent years,various models have been proposed to identify meaningful clusters by integr...Attributed graph clustering plays a vital role in uncovering hidden network structures,but it presents significant challenges.In recent years,various models have been proposed to identify meaningful clusters by integrating both structural and attribute-based information.However,these models often emphasize node proximities without adequately balancing the efficiency of clustering based on both structural and attribute data.Furthermore,they tend to neglect the critical fuzzy information inherent in attributed graph clusters.To address these issues,we introduce a new framework,Markov lumpability optimization,for efficient clustering of large-scale attributed graphs.Specifically,we define a lumped Markov chain on an attribute-augmented graph and introduce a new metric,Markov lumpability,to quantify the differences between the original and lumped Markov transition probability matrices.To minimize this measure,we propose a conjugate gradient projectionbased approach that ensures the partitioning closely aligns with the intrinsic structure of fuzzy clusters through conditional optimization.Extensive experiments on both synthetic and real-world datasets demonstrate the superior performance of the proposed framework compared to existing clustering algorithms.This framework has many potential applications,including dynamic community analysis of social networks,user profiling in recommendation systems,functional module identification in biological molecular networks,and financial risk control,offering a new paradigm for mining complex patterns in high-dimensional attributed graph data.展开更多
Chiral metal-organic clusters(MOCs)integrating lanthanide ions(Ln^(3+))and organic luminophores present a promising platform for modulating circularly polarized luminescence(CPL).However,achieving dual-wavelength CPL ...Chiral metal-organic clusters(MOCs)integrating lanthanide ions(Ln^(3+))and organic luminophores present a promising platform for modulating circularly polarized luminescence(CPL).However,achieving dual-wavelength CPL in discrete cluster systems constitutes a considerable challenge.Herein,two enantiomeric pairs of heterometallic EuSn oxo clusters,designated as Sn_(2)EuL_(2)-R/S and Sn_(2)EuL_(4)-R/S,were strategically synthesized using axially chiral binaphthol-phosphonate ligands.These hybrid clusters exhibit dual emission,characterized by a broad ligand-derived fluorescence band superimposed with sharp,characteristic Eu^(3+)f-f transitions,which enables excitation-dependent luminescence color tuning.Their emission profiles and quantum yields are found to be exquisitely adjusted by the distinct coordination environments of Sn^(4+)centers.Notably,Sn_(2)EuL_(2)-R/S demonstrates CPL activity in both near-UV(|g_(lum)|=1.7×10^(-3))and visible(|g_(lum)|=3.1×10^(-2))regions.This work not only reports the first instance of dual-wavelength CPL in a lanthanide/tin oxo complex but also establishes a robust design strategy for fabricating color-tunable chiral photonic materials.展开更多
Accurate description of noncova-lent interactions in large systems is challenging due to the require-ment of high-level electron corre-lation methods.The generalized energy-based fragmentation(GEBF)approach,in conjunc...Accurate description of noncova-lent interactions in large systems is challenging due to the require-ment of high-level electron corre-lation methods.The generalized energy-based fragmentation(GEBF)approach,in conjunc-tion with the domain-based local pair natural orbital(DLPNO)method,has been applied to assess the average binding energies(ABEs)of large benzene clus-ters,specifically(C6H6)13,at the coupled cluster singles and doubles with perturbative triples correction[CCSD(T)]level and the complete basis set(CBS)limit.Utilizing GEBF-DLPNO-CCSD(T)/CBS ABEs as benchmarks,various DFT functionals were evaluated.It was found that several functionals with empirical dispersion correction,including M06-2X-D3,B3LYP-D3(BJ),and PBE-D3(BJ),provide accurate descriptions of the ABEs for(C6H6)13 clusters.Additionally,the M06-2X-D3 functional was used to calculate the ABEs and relative stabili-ties of(C6H6)n clusters for n=11,12,13,14,and 15 revealing that the(C6H6)13 cluster ex-hibits the highest relative stability.These findings align with experimental evidence suggest-ing that n=13 is one of the magic numbers for benzene clusters(C6H6)n,with n≤30.展开更多
Objective This study aimed to investigate the prevalence of HIV pretreatment drug resistance(PDR)and the transmission clusters associated with PDR-related mutations in newly diagnosed,treatmentnaive patients between 2...Objective This study aimed to investigate the prevalence of HIV pretreatment drug resistance(PDR)and the transmission clusters associated with PDR-related mutations in newly diagnosed,treatmentnaive patients between 2020 and 2023 in Dehong prefecture,Yunnan province,China.Methods Demographic information and plasma samples were collected from study participants.PDR was assessed using the Stanford HIV Drug Resistance Database.The Tamura-Nei 93 model within HIVTRACE was employed to compute pairwise matches with a genetic distance of 0.015 substitutions per site.Results Among 948 treatment-naive individuals with eligible sequences,36 HIV subtypes were identified,with unique recombinant forms(URFs)being the most prevalent(18.8%,178/948).The overall prevalence of PDR was 12.4%(118/948),and resistance to non-nucleotide reverse transcriptase inhibitors(NNRTIs),nucleotide reverse transcriptase inhibitors(NRTIs),and protease inhibitors(PIs)was10.7%,1.3%,and 1.6%,respectively.A total of 91 clusters were identified,among which eight showed evidence of PDR strain transmission.The largest PDR-associated cluster consisted of six CRF01_AE drugresistant strains carrying K103N and V179T mutations;five of these individuals had initial CD4^(+)cell counts<200 cells/μL.Conclusion The distribution of HIV subtypes in Dehong is diverse and complex.PDR was moderately prevalent(12.4%)between 2020 and 2023.Evidence of transmission of CRF01_AE strains carrying K103N and V179T mutations was found.Routine surveillance of PDR and the strengthening of control measures are essential to limit the spread of drug-resistance HIV strains.展开更多
The first three months after lung transplantation are the clinical“vulnerable period”.Complications during this period often appear in the form of symptom clusters.The core includes primary graft dysfunction(PGD),in...The first three months after lung transplantation are the clinical“vulnerable period”.Complications during this period often appear in the form of symptom clusters.The core includes primary graft dysfunction(PGD),infection,inflammatory response and multiple organ dysfunction,and are interconnected to form a complex network.The symptom cluster shows a clear dynamic trajectory:the risk of PGD peaks at 24 hours after surgery,and its evolution trajectory(recovery,delay,deterioration)directly affects long-term graft function;infections show a“double peak distribution”,with bacteria/fungi dominant in the early stage(<1 month)and viruses/opportunistic infections dominant in the middle stage(1-6 months),and promote each other with PGD.Influencing factors include four dimensions:donor(smoking history,infection),recipient(weakness,immune status),perioperative period(surgical method,support strategy)and postoperative management(balance of immunosuppression).In the future,dynamic prediction models and individualized management paths need to be built to improve patient outcomes.展开更多
LiNO_(3) is known to significantly enhance the reversibility of lithium metal batteries;however,the modification of solvation structures in various solvents and its further impact on the interface have not been fully ...LiNO_(3) is known to significantly enhance the reversibility of lithium metal batteries;however,the modification of solvation structures in various solvents and its further impact on the interface have not been fully revealed.Herein,we systematically studied the evolution of solvation structures with increasing LiNO_(3) concentration in both carbonate and ether electrolytes.The results from molecular dynamics simulations unveil that the Li^(+)solvation structure is less affected in carbonate electrolytes,while in ether electrolytes,there is a significant decrease of solvent molecules in Li^(+)coordination,and a larger average size of Li^(+)solvation structure emerges as LiNO_(3) concentration increases.Notably,the formation of large ion aggregates with size of several nanometers(nano-clusters),is observed in ether-based electrolytes at conventional Li^(+)concentration(1 M)with higher NO_(3)^(-) ratio,which is further proved by infrared spectroscopy and small-angle X-ray scattering experiments.The nano-clusters with abundant anions are endowed with a narrow energy gap of molecular orbitals,contributing to the formation of an inorganic rich electrode/electrolyte interphase that enhances the reversibility of lithium stripping/plating with Coulombic efficiency up to 99.71%.The discovery of nano-clusters elucidates the underlying mechanism linking ions/solvent aggregation states of electrolytes to interfacial stability in advanced battery systems.展开更多
Objective:This study aims to investigate the patterns of symptom occurrence in patients experiencing acute exacerbations of chronic obstructive pulmonary disease(AECOPD).It will explore the composition of symptom clus...Objective:This study aims to investigate the patterns of symptom occurrence in patients experiencing acute exacerbations of chronic obstructive pulmonary disease(AECOPD).It will explore the composition of symptom clusters and analyze the correlation between these clusters and health-related quality of life(HRQoL).Methods:A total of 207 patients with AE-COPD were surveyed from a tertiary grade A hospital.Data collection was conducted using three validated instruments:the Basic Information Questionnaire(BIQ),Disease Symptom Survey Questionnaire(MSAS),and Quality of Life Questionnaire(CAT).Statistical software SPSS 22.0 was used to analyze the correlation between symptom clusters and quality of life.Results:Exploratory factor analysis showed that five major symptom clusters existed in the patients,including the psycho-emotional symptom cluster,the sleep-related symptom cluster,the other side effects symptom cluster,the energy deficiency symptom cluster and the cough-loss of appetite symptom cluster,and the severity of the symptom clusters showed a significant negative correlation with the quality of life of the patients(P<0.05).Conclusion:Strengthening the comprehensive management of symptom clusters in patients with AE-COPD can help to effectively reduce the symptom burden of patients,and then significantly improve their quality of life.展开更多
Two-dimensional(2D)materials loaded with single atoms and clusters are being set at the forefront of catalysis due to their distinctive geometric and electronic features.However,the usually-complicated synthesis proce...Two-dimensional(2D)materials loaded with single atoms and clusters are being set at the forefront of catalysis due to their distinctive geometric and electronic features.However,the usually-complicated synthesis procedures impede in-depth clarification of their catalytic mechanisms.To this end,herein we developed an efficient one-step dimension-reduction carbonization strategy,with which we successfully architected a highly-efficient catalyst for oxygen reduction reaction(ORR),featured with symbiotic cobalt single atoms and clusters decorated in two-dimensional(2D)ultra-thin(3.5 nm thickness)nitrogen-carbon nanosheets.The synergistic effects of the two components afford excellent oxygen reduction activity in alkaline media(E_(1/2)=0.823 V vs.RHE)and thereof a high power density(146.61 mW cm^(-2))in an assembled Zn-air battery.As revealed by theoretical calculations,the cobalt clusters can regulate electrons surrounding those individual atoms and affect the adsorption of intermediate species.As a consequence,the derived active sites of single cobalt atoms lead to a significant improvement of the ORR performance.Thus,our work may fuel interests to delicate architectu re of single atoms and clusters coexisting 2D support toward optimal electrocatalytic performance.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
文摘Noncohesive particle clusters are identified and tracked in turbulent flows to determine the breakdown and time evolution of cluster statistics and their implications for interscale mass transfer,which has connections to the classical turbulent energy cascade and its mass cascade counterpart running in parallel.In particular,the formation and dynamics of sediment and larvae clusters are of interest to coral larvae settlement in coastal regions and particularly the resilience of green-gray coastal protection solutions.Analogous cluster behavior is relevant to cloud microphysics and precipitation initiation,radiation transport and light transmission through colloids and suspensions,heat and mass transfer in particle-laden flows,and viral and pollutant transmission.Following a comparison between various clustering techniques,we adopt a density-based cluster identification algorithm based on its simplicity and efficiency,where particles are clustered based on the number of neighboring particles in their individual spheres of influence.We establish parallels with lattice-based percolation theory,as evident in the power-law scaling of the cluster size distribution near the percolation threshold.The degree of discontinuity of the phase transition associated with this percolation threshold is observed to broaden with larger Stokes numbers and thereby large-scale clustering.The sensitivity of our findings to the employed clustering algorithm is discussed.A novel cluster tracking algorithm is deployed to determine the interscale transfer rate along the particle-number phase-space dimension via accounting of cluster breakup and merger events,extending previous work on the bubble breakup cascade beneath surface breaking waves.Our findings shed light on the interaction between particle clusters and their carrier turbulent flows,with an eye toward transport models incorporating cluster characteristics and dynamics.
基金Under the auspices of National Natural Science Foundation of China(No.42571219)Key Project of Zhejiang Province Soft Science Research Plan(No.2023C25014)。
文摘Bottom-up and top-down endogenous automobile clusters exhibit distinct evolutionary traits and driving mechanisms,yet their comparative analysis remains understudied.Therefore,using Taizhou automobile industry cluster(TAIC)and Wuhu automobile industry cluster(WAIC)as cases,using historical statistical data and field interview data from the 1980s to 2023,combined with qualitative research methods of thematic and diachronic analysis,and quantitative research methods of social network analysis,we compare both endogenous automobile clusters’evolutionary traits and driving mechanisms.The results confirm both clusters undergo multi-scale spatial reconfiguration,organizational complexification,and intelligent networking technological transformation,yet diverge fundamentally:TAIC evolves through market-driven progressive expansion,transitioning from single to dual-core structures via private enterprise networking,with innovation following market-integrated logic and institutional thickness built on demand-driven evolution.Conversely,WAIC follows planned expansion,maintaining state-led hierarchical single-core stability through policy-driven breakthrough innovation and supply-dominated institutional construction-though both ultimately require formal-informal system synergy.Their coevolution is driven by dynamic interactions of path dependence(weakening influence),learning-innovation(strengthening influence),and relationship selection(inverted U-shaped trajectory),with divergent development paths rooted in TAIC’s grassroots self-organization genes versus WAIC’s top-level design genes,amplified by core enterprises’strategic disparities.The research findings can not only provide decision-making support for China’s industrial upgrading,but also contribute China’s insights to global economic governance.
文摘Villager Pan Chunlin is witnessing a boom in his homestay business.More and more visitors are coming to his village,Yucun Village in Anji County,Huzhou City,Zhejiang Province.
文摘In the Tianshan region,a complete textile industry chain has been established,covering the entire process from cotton cultivation and chemical fiber production,through spinning,weaving,dyeing,and finishing,and further extending to apparel,home textiles,and industrial textiles.In November 2025,the first list of five characteristic textile and apparel industry clusters in Xinjiang was officially announced,marking a new stage in the clustering of Xinjiang's textile and apparel industry.Data shows that the total output value of Xinjiang's cotton and textile and apparel industry chain has exceeded 220 billion yuan.With the nation's largest cotton production,a complete industrial chain system,and strong synergistic effects,Xinjiang has become a leading and highly competitive textile industry hub in China.
基金supported by the National Natural Science Foundation of China(92061202,21531008,22175181)the Fujian Province Science and Technology Project Program(2022H0041)the Self-deployment Project Research Program of Haixi Institute,Chinese Academy of Sciences(CXZX-2022-GH11)。
文摘Precise heterometal doping or substitution of specific metal sites in isostructural metal clusters remains a formidable synthetic challenge,despite its transformative potential for modulating excited-state characteristics and customizing optical properties.In this work,we achieved the precise synthesis of isostructural alloy clusters R/S-Ag_(3)Cu([Ag_(3)Cu(tppm)(R/S-IPTT)]ClO_(4),R/S-IPTT=R/S-4-isopropylthiazolidine-2-thiolate,tppm=tris(diphenylphosphino)methane)in high yield(89%-91%)through selective doping of a Cu(Ⅰ)atom into chiral homometallic cluster enantiomers R/S-Ag_(4)([Ag_(4)(tppm)(R/S-IPTT)]ClO_(4)).In stark contrast to R/S-Ag_(4)(Φ_(em)<0.5%)that displays weak circularly polarized luminescence(CPL)with phosphorescence characteristic,R/S-Ag_(3)Cu(Φ_(em)≈70%)demonstrates strong CPL properties featured with thermally activated delay fluorescence(TADF)at ambient temperature.The selective substitution of the apical Ag(Ⅰ)atom in Ag_(4)triangular pyramid with a Cu(Ⅰ)atom not only gives rise to beyond 100-fold boosting of photoluminescence quantum yield(PLQY),but also leads to more pronounced optically chiral activity of alloy clusters in excited states in view of the larger photoluminescence dissymmetry factors(g_(PL))of R/S-Ag_(3)Cu(-3.5×10^(-3)/3.4×10^(-3))than that of R/S-Ag_(4)(-2.7×10^(-3)/2.6×10^(-3)).Furthermore,compared with chiral homometallic clusters R/S-Cu_(4)([Cu_(4)(tppm)(R/S-IPTT)]ClO_(4))with the same TADF characteristic at ambient temperature,R/S-Ag_(3)Cu manifests 1.7-fold PLQY and 6-fold g_(PL)due to faster reverse intersystem crossing(RISC)and more effective coupling of electric and magnetic transition moments in alloy clusters.This work not only presents a typical example of selective heterometal doping to modulate excited-state properties of isostructural metal clusters,but also gets deeper insight into the doping chemistry of dissimilar metals at the molecular level.
基金supported by the National Key Research and Development Program of China(2021YFA1500500)the CAS Project for Young Scientists in Basic Research(YSBR-051)+9 种基金the National Science Fund for Distinguished Young Scholars(21925204)the National Natural Science Foundation of China(NSFC)(22302185,22221003,22250007,22361162655)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(2022QNRC001)the Fundamental Research Funds for the Central Universities(WK9990000167)the Collaborative Innovation Program of Hefei Science Center,CAS(2022HSC-CIP004)the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(YLU-DNL Fund 2022012)the Natural Science Foundation of Anhui Province(2308085QB53)the State Key Laboratory of Catalysis(2024SKL-A-01)the International Partnership Program of Chinese Academy of Sciences(123GJHZ2022101GC)support from the Tencent Foundation through the XPLORER PRIZE。
文摘Precisely identifying the atomic structure of reducible oxide-supported metal clusters remains challenging yet critical for understanding their catalytic behavior.Herein,we report the preparation of CeO_(2)-supported bi-layer Pt clusters(Pt_(n)/CeO_(2))via a deposition-reduction strategy,with Pt cluster sizes ranging from 0.8 to 1.2 nm(9–30 atoms).Through combined aberration-corrected high-angle annular dark field scanning transmission electron microscope(HAADF-STEM)imaging,quantitative STEM simulations,and X-ray fine structure(XAFS)analysis,we reveal the bi-layer configuration featuring coordinatively unsaturated Pt^(0) sites on the top layer while maintaining Pt-CeO_(2)interfacial bonding at the bottom.When applied to anti-Markovnikov alkene hydrosilylation,Pt_(n)/CeO_(2)achieves 99.9%silane conversion with a mass-specific activity 2.0×and 8.8×higher than single-atom site(Pt_(1)/CeO_(2))and nanoparticle(Pt_(NP)/CeO_(2))counterparts,respectively.The bi-layer structure endows exceptional cycling stability and anti-leaching properties.This work establishes a multi-scale characterization paradigm to resolve atomic-precision structures of supported clusters,opening avenues for designing robust catalysts with tailored metal-oxide interfaces.
基金supported by the Specific Research Fund for Top-notch Talents of Guangdong Provincial Hospital of Chinese Medicine(No.2022KT1188).
文摘Objectives To identify core symptoms and symptom clusters in patients with neuromyelitis optica spectrum disorder(NMOSD)by network analysis.Methods From October 10 to 30,2023,140 patients with NMOSD were selected to participate in this online questionnaire survey.The survey tools included a general information questionnaire and a self-made NMOSD symptoms scale,which included the prevalence,severity,and distress of 29 symptoms.Cluster analysis was used to identify symptom clusters,and network analysis was used to analyze the symptom network and node characteristics and central indicators including strength centrality(r_(s)),closeness centrality(r_(c))and betweeness centrality(r_(b))were used to identify core symptoms and symptom clusters.Results The most common symptom was pain(65.7%),followed by paraesthesia(65.0%),fatigue(65.0%),easy awakening(63.6%).Regarding the burden level of symptoms,pain was the most burdensome symptom,followed by paraesthesia,easy awakening,fatigue,and difficulty falling asleep.Six clusters were identified:somatosensory,motor,visual,and memory symptom clusters,bladder and rectum symptom clusters,sleep symptoms clusters,and neuropsychological symptom clusters.Fatigue(r_(s)=12.39,r_(b)=68.00,r_(c)=0.02)was the most central and prominent bridge symptom,and motor symptom cluster(r_(s)=2.68,r_(c)=0.10)was the most central symptom cluster among the six clusters.Conclusions Our study demonstrated the necessity of symptom management targeting fatigue,pain,and motor symptom cluster in patients with NMOSD.
文摘An aluminoborate,Na_(2.5)Rb[Al{B_(5)O_(10)}{B_(3)O_(5)}]·0.5NO_(3)·H_(2)O(1),was synthesized under hydrothermal condition,which was built by mixed oxoboron clusters and AlO_(4)tetrahedra.In the structure,the[B_(5)O_(10)]^(5-)and[B_(3)O_(7)]^(5-)clusters are alternately connected to form 1D[B_(8)O_(15)]_(n)^(6n-)chains,which are further linked by AlO_(4)units to form a 2D monolayer with 7‑membered ring and 10‑membered ring windows.Two adjacent monolayers with opposite orientations further form a porous‑layered structure with six channels through B—O—Al bonds.Compound 1 was characterized by single crystal X‑ray diffraction,powder X‑ray diffraction(PXRD),IR spectroscopy,UV‑Vis diffuse reflection spectroscopy,and thermogravimetric analysis(TGA),respectively.UV‑Vis diffuse reflectance analysis indicates that compound 1 shows a wide transparency range with a short cutoff edge of 201 nm,suggesting it may have potential application in UV regions.CCDC:2383923.
文摘Ultrafine,highly dispersed Pt clusters were immobilized onto the Co nanoparticle surfaces by one-step pyrolysis of the precursor Pt(Ⅱ)-encapsulating Co-MOF-74.Owing to the small size effects of Pt clusters as well as the strongly enhanced synergistic interactions between Pt and Co atoms,the obtained Pt-on-Co/C400 catalysts exhib-ited excellent catalytic activity toward the hydrolysis of ammonia borane with an extremely high turnover frequency(TOF)value of 3022 min^(-1)at 303 K.Durability test indicated that the obtained Pt-on-Co/C400 catalysts possessed high catalytic stability,and there were no changes in the catalyst structures and catalytic activities after 10 cycles.
文摘Organic-inorganic hybrid clusters with strong X-ray radioluminescence have exhibited great potential in scintillator field.However,fabricating the X-ray imaging screens of the clusters without sacrificing the scintillation performance is challenging.Herein,we report an effective way to prepare high-quality scintillation films of two synthesized Cu(Ⅰ)clusters through vacuum evaporation deposition.The developed Cu(Ⅰ)clusters with rigid molecular structures show excellent scintillation performance with a high light yield of up to 19356.7 photons/MeV and a low detection limit of 158 nGy/s.The scintillation film based on the Cu(Ⅰ)clusters made by vacuum evaporation deposition is highly uniform with a small surface roughness value of 1.04 nm,which can be applied to X-ray imaging for various objects.These results not only provide important guidance to develop high-performance organic-inorganic hybrid scintillators,but also pave a straightforward way to prepare non-doped scintillation screens for remarkable X-ray imaging applications.
文摘In modern distributed systems and cloud computing architectures,high availability and high scalability are core requirements to ensure the continuous and stable operation of services.As key technologies for achieving these two goals,high-availability clusters and load-balancing clusters have significant differences in their design concepts and application scenarios,while also maintaining close connections.This paper aims to conduct an in-depth analysis of the core objectives,working principles,technical advantages and disadvantages,and typical application cases of high-availability clusters and load-balancing clusters.By introducing an analogical model of a“restaurant kitchen,”the differences between the two are intuitively explained,and their technical characteristics are compared in detail.Additionally,a detailed practical case is included to specifically demonstrate the collaborative work of high-availability and load-balancing technologies through the construction process of Keepalived and HAProxy.Finally,taking the architecture of a typical e-commerce website as an example,this paper demonstrates the best practice of organically combining the two cluster technologies in a production environment to build a robust and high-performance distributed system.Research shows that understanding the differences between the two and implementing collaborative deployment is the cornerstone of designing modern IT infrastructure.
基金supported by the National Natural Science Foundation of China(Grant No.72571150)Beijing Natural Science Foundation(Grant No.9182015)。
文摘Attributed graph clustering plays a vital role in uncovering hidden network structures,but it presents significant challenges.In recent years,various models have been proposed to identify meaningful clusters by integrating both structural and attribute-based information.However,these models often emphasize node proximities without adequately balancing the efficiency of clustering based on both structural and attribute data.Furthermore,they tend to neglect the critical fuzzy information inherent in attributed graph clusters.To address these issues,we introduce a new framework,Markov lumpability optimization,for efficient clustering of large-scale attributed graphs.Specifically,we define a lumped Markov chain on an attribute-augmented graph and introduce a new metric,Markov lumpability,to quantify the differences between the original and lumped Markov transition probability matrices.To minimize this measure,we propose a conjugate gradient projectionbased approach that ensures the partitioning closely aligns with the intrinsic structure of fuzzy clusters through conditional optimization.Extensive experiments on both synthetic and real-world datasets demonstrate the superior performance of the proposed framework compared to existing clustering algorithms.This framework has many potential applications,including dynamic community analysis of social networks,user profiling in recommendation systems,functional module identification in biological molecular networks,and financial risk control,offering a new paradigm for mining complex patterns in high-dimensional attributed graph data.
基金financially supported by the National Natural Science Foundation of China(22471268)the National Key Research and Development Project(2022YFA1503900)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB1170000)the Natural Science Foundation of Fujian Province(2022J05090,2024T3003)the Self-deployment Project Research Program of Haixi Institutes,Chinese Academy of Sciences(CXZX-2022-GH03,CXZX-2024-JQ08).
文摘Chiral metal-organic clusters(MOCs)integrating lanthanide ions(Ln^(3+))and organic luminophores present a promising platform for modulating circularly polarized luminescence(CPL).However,achieving dual-wavelength CPL in discrete cluster systems constitutes a considerable challenge.Herein,two enantiomeric pairs of heterometallic EuSn oxo clusters,designated as Sn_(2)EuL_(2)-R/S and Sn_(2)EuL_(4)-R/S,were strategically synthesized using axially chiral binaphthol-phosphonate ligands.These hybrid clusters exhibit dual emission,characterized by a broad ligand-derived fluorescence band superimposed with sharp,characteristic Eu^(3+)f-f transitions,which enables excitation-dependent luminescence color tuning.Their emission profiles and quantum yields are found to be exquisitely adjusted by the distinct coordination environments of Sn^(4+)centers.Notably,Sn_(2)EuL_(2)-R/S demonstrates CPL activity in both near-UV(|g_(lum)|=1.7×10^(-3))and visible(|g_(lum)|=3.1×10^(-2))regions.This work not only reports the first instance of dual-wavelength CPL in a lanthanide/tin oxo complex but also establishes a robust design strategy for fabricating color-tunable chiral photonic materials.
基金supported by the National Key R&D Program of China(No.2023YFB3712504)the National Natural Science Foundation of China(Nos.22273038,22073043,and 22033004)。
文摘Accurate description of noncova-lent interactions in large systems is challenging due to the require-ment of high-level electron corre-lation methods.The generalized energy-based fragmentation(GEBF)approach,in conjunc-tion with the domain-based local pair natural orbital(DLPNO)method,has been applied to assess the average binding energies(ABEs)of large benzene clus-ters,specifically(C6H6)13,at the coupled cluster singles and doubles with perturbative triples correction[CCSD(T)]level and the complete basis set(CBS)limit.Utilizing GEBF-DLPNO-CCSD(T)/CBS ABEs as benchmarks,various DFT functionals were evaluated.It was found that several functionals with empirical dispersion correction,including M06-2X-D3,B3LYP-D3(BJ),and PBE-D3(BJ),provide accurate descriptions of the ABEs for(C6H6)13 clusters.Additionally,the M06-2X-D3 functional was used to calculate the ABEs and relative stabili-ties of(C6H6)n clusters for n=11,12,13,14,and 15 revealing that the(C6H6)13 cluster ex-hibits the highest relative stability.These findings align with experimental evidence suggest-ing that n=13 is one of the magic numbers for benzene clusters(C6H6)n,with n≤30.
基金supported by the National Key Research and Development Program of China(2022YFC2305201)National Natural Science Foundation of China(71874168)。
文摘Objective This study aimed to investigate the prevalence of HIV pretreatment drug resistance(PDR)and the transmission clusters associated with PDR-related mutations in newly diagnosed,treatmentnaive patients between 2020 and 2023 in Dehong prefecture,Yunnan province,China.Methods Demographic information and plasma samples were collected from study participants.PDR was assessed using the Stanford HIV Drug Resistance Database.The Tamura-Nei 93 model within HIVTRACE was employed to compute pairwise matches with a genetic distance of 0.015 substitutions per site.Results Among 948 treatment-naive individuals with eligible sequences,36 HIV subtypes were identified,with unique recombinant forms(URFs)being the most prevalent(18.8%,178/948).The overall prevalence of PDR was 12.4%(118/948),and resistance to non-nucleotide reverse transcriptase inhibitors(NNRTIs),nucleotide reverse transcriptase inhibitors(NRTIs),and protease inhibitors(PIs)was10.7%,1.3%,and 1.6%,respectively.A total of 91 clusters were identified,among which eight showed evidence of PDR strain transmission.The largest PDR-associated cluster consisted of six CRF01_AE drugresistant strains carrying K103N and V179T mutations;five of these individuals had initial CD4^(+)cell counts<200 cells/μL.Conclusion The distribution of HIV subtypes in Dehong is diverse and complex.PDR was moderately prevalent(12.4%)between 2020 and 2023.Evidence of transmission of CRF01_AE strains carrying K103N and V179T mutations was found.Routine surveillance of PDR and the strengthening of control measures are essential to limit the spread of drug-resistance HIV strains.
文摘The first three months after lung transplantation are the clinical“vulnerable period”.Complications during this period often appear in the form of symptom clusters.The core includes primary graft dysfunction(PGD),infection,inflammatory response and multiple organ dysfunction,and are interconnected to form a complex network.The symptom cluster shows a clear dynamic trajectory:the risk of PGD peaks at 24 hours after surgery,and its evolution trajectory(recovery,delay,deterioration)directly affects long-term graft function;infections show a“double peak distribution”,with bacteria/fungi dominant in the early stage(<1 month)and viruses/opportunistic infections dominant in the middle stage(1-6 months),and promote each other with PGD.Influencing factors include four dimensions:donor(smoking history,infection),recipient(weakness,immune status),perioperative period(surgical method,support strategy)and postoperative management(balance of immunosuppression).In the future,dynamic prediction models and individualized management paths need to be built to improve patient outcomes.
基金supported by the National Natural Science Foundation of China(No.22372083,52201259)the National Key R&D Program of China(2021YFB2500300)+2 种基金the Fundamental Research Funds for the Central Universities:Nankai University(63241607)the Natural Science Foundation of Tianjin(No.22JCZDJC00380)the Young Elite Scientist Sponsorship Program by CAST.
文摘LiNO_(3) is known to significantly enhance the reversibility of lithium metal batteries;however,the modification of solvation structures in various solvents and its further impact on the interface have not been fully revealed.Herein,we systematically studied the evolution of solvation structures with increasing LiNO_(3) concentration in both carbonate and ether electrolytes.The results from molecular dynamics simulations unveil that the Li^(+)solvation structure is less affected in carbonate electrolytes,while in ether electrolytes,there is a significant decrease of solvent molecules in Li^(+)coordination,and a larger average size of Li^(+)solvation structure emerges as LiNO_(3) concentration increases.Notably,the formation of large ion aggregates with size of several nanometers(nano-clusters),is observed in ether-based electrolytes at conventional Li^(+)concentration(1 M)with higher NO_(3)^(-) ratio,which is further proved by infrared spectroscopy and small-angle X-ray scattering experiments.The nano-clusters with abundant anions are endowed with a narrow energy gap of molecular orbitals,contributing to the formation of an inorganic rich electrode/electrolyte interphase that enhances the reversibility of lithium stripping/plating with Coulombic efficiency up to 99.71%.The discovery of nano-clusters elucidates the underlying mechanism linking ions/solvent aggregation states of electrolytes to interfacial stability in advanced battery systems.
文摘Objective:This study aims to investigate the patterns of symptom occurrence in patients experiencing acute exacerbations of chronic obstructive pulmonary disease(AECOPD).It will explore the composition of symptom clusters and analyze the correlation between these clusters and health-related quality of life(HRQoL).Methods:A total of 207 patients with AE-COPD were surveyed from a tertiary grade A hospital.Data collection was conducted using three validated instruments:the Basic Information Questionnaire(BIQ),Disease Symptom Survey Questionnaire(MSAS),and Quality of Life Questionnaire(CAT).Statistical software SPSS 22.0 was used to analyze the correlation between symptom clusters and quality of life.Results:Exploratory factor analysis showed that five major symptom clusters existed in the patients,including the psycho-emotional symptom cluster,the sleep-related symptom cluster,the other side effects symptom cluster,the energy deficiency symptom cluster and the cough-loss of appetite symptom cluster,and the severity of the symptom clusters showed a significant negative correlation with the quality of life of the patients(P<0.05).Conclusion:Strengthening the comprehensive management of symptom clusters in patients with AE-COPD can help to effectively reduce the symptom burden of patients,and then significantly improve their quality of life.
基金supported by the National Natural Science Foundation of China(51872115 and 12234018)Beijing Synchrotron Radiation Facility(BSRF)4B9A.
文摘Two-dimensional(2D)materials loaded with single atoms and clusters are being set at the forefront of catalysis due to their distinctive geometric and electronic features.However,the usually-complicated synthesis procedures impede in-depth clarification of their catalytic mechanisms.To this end,herein we developed an efficient one-step dimension-reduction carbonization strategy,with which we successfully architected a highly-efficient catalyst for oxygen reduction reaction(ORR),featured with symbiotic cobalt single atoms and clusters decorated in two-dimensional(2D)ultra-thin(3.5 nm thickness)nitrogen-carbon nanosheets.The synergistic effects of the two components afford excellent oxygen reduction activity in alkaline media(E_(1/2)=0.823 V vs.RHE)and thereof a high power density(146.61 mW cm^(-2))in an assembled Zn-air battery.As revealed by theoretical calculations,the cobalt clusters can regulate electrons surrounding those individual atoms and affect the adsorption of intermediate species.As a consequence,the derived active sites of single cobalt atoms lead to a significant improvement of the ORR performance.Thus,our work may fuel interests to delicate architectu re of single atoms and clusters coexisting 2D support toward optimal electrocatalytic performance.
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.
