阿尔法蒎烯臭氧分解反应的极紫外自山电子激光光电离质谱研究

阿尔法蒎烯是大气中含量最高的自然源萜类挥发性有机物,其臭氧化分解反应会产生大量的反应中间体和产物,精确表征这些物种被认为是大气化学最前沿、最具挑战性的课题之一.本文利用极紫外自由电子激光光电离质谱方法,研究了阿尔法蒎烯的臭氧分解反应机理.该反应是在2立方米的烟雾箱中进行,利用气动透镜把产生的气溶胶传输到质谱探测腔室,利用极紫外自山电子激光对气溶胶进行单光子软电离,测得了常规实验方法难以得到的飞行时间质谱,发现了一系列新物种.与量子化学理论计算相结合,揭示了这些新物种的反应机理.这些研究结果从分子水平上揭示了蒎烯的臭氧分解反应机制,有助于理解大气雾霾微观机理.

Development and application of knowledge-based subject group integration platforms:A case study of Shanghai Institute of Ceramics,CAS

Purpose:According to the different requirements of research group users,we established the knowledge-based subject group integration platforms of Shanghai Institute of Ceramics,the Chinese Academy of Sciences(abbreviated as SIC CAS hereinafter),which were designed and constructed to better meet the needs of CAS research groups for their development,collaboration and communication.Design/methodology/approach:We first identified the requirements of users via preliminary investigation,and then chose CASI1 P,iLibrary and XKE technology,respectively as the building tools compatible with the major demands of users.These steps helped us complete the layout design of SIC CAS integration platforms,as well as its knowledge organization and integration.Findings:According to the need of users,we applied three types of platform construction technologies to five SIC integration platforms,and formulated standard norms for the further construction process,which could provide useful reference for a sustainable development for the extensive construction in CAS institutes.Research limitations:In order to make the SIC integration platforms more intelligent and have more functions,we need to enlarge the scale of the Platforms and upgrade the building tools for the platform construction.Practical implications:The nature of SIC sub-project integration platforms is to construct a content-sensitive environment which can embed knowledge services and knowledge applications seamlessly into scientific activities,so the Platform is expected to be a useful tool to help researchers better understand the recent development of the research field and form collaborations with their peers.Originality/value:SIC integration platforms are the only pilot construction that used 3different platform technologies in the first batch of knowledge-based subject group integration platforms of the Chinese Academy of Sciences.The construction is user-centered throughout the whole process,namely,from the technology selection,content construction to the sustainable development of the platforms,which are all based on user requirements.During this process,we have not only established sustainable mechanisms for both the personalized feedback and security management of the institutional knowledge of SIC CAS,but also formed a service team for the sustainable development of SIC integration platforms.

Doubly Periodic Riemann Boundary Value Problem of Non-Normal Type for Analytic Functions on Two Parallel Curves

In this paper, we present and study a kind of Riemann boundary value problem of non-normal type for analytic functions on two parallel curves. Making use of the method of complex functions, we give the method for solving this kind of doubly periodic Riemann boundary value problem of non-normal type and obtain the explicit expressions of solutions and the solvable conditions for it.

Spectroscopic identification of water splitting by neutral group 3 metals

Spectroscopic study of water splitting by neutral metal clusters is crucial to understanding the microscopic mechanism of catalytic processes but has been proven to be a challenging experimental target due to the difficulty in size selection.Here,we report a size-specific infrared spectroscopic study of the reactions between neutral group 3 metals and water molecules based on threshold photoionization using a vacuum ultraviolet laser.Quantum chemical calculations were carried out to identify the structures and to assign the experimental spectra.All the M_(2)O_(4)H_(4)(M=Sc,Y,La)products are found to have the intriguing M_(2)(μ_(2)-O)(μ_(2)-H)(μ_(2)-OH)(η^(1)-OH)_(2) structures,indicating that the H-OH bond breaking,the M-O/M-H/M-OH bond formation,and hydrogen production proceed efficiently in the reactions between laser-vaporized metals and water molecules.The joint experimental and theoretical results on the atomic scale demonstrate that the water splitting by neutral group 3 metals is both thermodynamically exothermic and kinetically facile in the gas phase.These findings have important implications for unravelling the structure-reactivity relationship of catalysts with isolated metal atoms/clusters dispersed on supports.

反铁磁拓扑绝缘体MnBi_(2)Te_(4)/Bi_(2)Te_(3)超晶格具有不变近零能隙的表面态研究

磁性拓扑材料蕴含拓扑磁电效应等丰富拓扑物理现象,成为近年来拓扑量子材料研究热点.最近,在本征反铁磁拓扑绝缘体MnBi_(2)Te_(4)中发现了量子反常霍尔效应及轴子绝缘体态,使得此体系引发了广泛的关注.由MnBi_(2)Te_(4)及Bi_(2)Te_(3)插层得到的超晶格结构材料(MnBi_(2)Te_(4))m(Bi_(2)Te_(3))n,同样具有本征反磁序及非平庸拓扑相,为研究磁性与拓扑电子结构相互关系提供了重要的可调控材料平台.本文利用具有空间分辨能力的激光和同步辐射角分辨光电子能谱系统(ARPES),全面且系统地测量了此材料体系中Mn Bi4Te7的电子结构,发现在MnBi2Te4及Bi2Te3解理面均存在近零能隙的拓扑表面态;文章通过变温测量,发现其体态电子受到反铁磁序的强烈影响,但其拓扑表面态在反铁磁相变时保持近零能隙不变.这些结果印证了MnBi2Te4体系的不变近零能隙的普遍性,为理解中磁性与拓扑物态之间相互作用以及其调控提供了重要的谱学信息.

Atmospheric particle-bound polycyclic aromatic compounds over two distinct sites in Pakistan:Characteristics,sources and health risk assessment

Much attention is drawn to polycyclic aromatic hydrocarbons(PAHs)as an air pollutant due to their toxic,mutagenic and carcinogenic properties.Therefore,to understand the levels,seasonality,sources and potential health risk of PAHs in two distinct geographical locations at Karachi and Mardan in Pakistan,total suspended particle(TSP)samples were collected for over one year period.The average total PAH concentrations were 31.5±24.4 and 199±229 ng/m^(3) in Karachi and Mardan,respectively.The significantly lower concentration in Karachi was attributed to diffusion and dilution of the PAHs by the influence of clean air mass from the Arabian sea and high temperature,enhancing the volatilization of the particle phase PAHs to the gas phase.Conversely,the higher concentration(^(-)6 times)in Mardan was due to large influence from local and regional emission sources.A clear seasonality was observed at both the sites,with the higher values in winter and post-monsoon due to higher emissions and less scavenging,and lower values during monsoon season due to the dilution effect.Diagnostic ratios and principal component analysis indicated that PAHs in both sites originated from traffic and mixed combustion sources(fossil fuels and biomass).The average total Ba P equivalent concentrations(Ba P eq)in Karachi and Mardan were 3.26 and 34 ng/m^(3),respectively,which were much higher than the WHO guideline of 1 ng/m^(3).The average estimates of incremental lifetime cancer risk from exposure to airborne Ba P eq via inhalation indicated a risk to human health from atmospheric PAHs at both sites.

CO oxidation on the heterodinuclear tantalum-nickel monoxide carbonyl complex anions

The series of heterodinuclear metal oxide carbonyls in the form of TaNiO(CO)_(n)(n=5-8) are generated in the pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy.During the consecutive CO adsorption,the μ^(2)-O-bent structure initially is the most favorable for TaNiO(CO)_(5),and subsequently both μ^(2)-O-bent and μ^(2)-O-linear structures are degenerate for TaNiO(CO)_(6),then the μ^(2)-O-linear structure is most preferential for TaNiO(CO)_(7),and finally the η^(2)-CO_(2)-tagged structure is the most ene rgetically competitive one for TaNiO(CO)_(8),i.e., the CO oxidation occurs at n=8.ln contrast to the literature reported CO oxidation on heteronuclear metal oxide complexes generally proceeding via Langmuir-Hinshelwood-like mechanism,complementary theo retical calculations suggest that both Langmuir-Hinshelwood-like and Eley-Rideal-like mechanisms prevail for the CO oxidation reaction on TaNiO(CO)_(8) complex.Our findings provide new insight into the composition-selective mechanism of CO oxidation on heteronuclear metal complexes,of which the composition be tailored to fulfill the desired chemical behaviors.