Determination of Elements of Groups Ⅲ A and ⅣA Using Microwave Plasma Torch Atomic Emission Spectrometry

The determination of the elements of groups ⅢA and ⅣA by means of microwave plasma torch atomic emission spectrometry(MPT AES) was studied systematically. Sample solutions were introduced into the plasma with a pneumatic nebulizer in continuous sampling mode and flow injection (FI) mode. The emission characteristics of these elements were investigated in details, and the basic data obtained are very important to the development of MPT AES. The analytical performances were examined. For most elements, the detection limits obtained by this method were principally the same as those obtained by inductively coupled plasma atomic emission spectrometry (ICP AES).

Decoupling Bang-Bang Group for Adiabatic Decoherence Control in a Three-Level Atom

In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of three-levelatom subjected to adiabatic decoherence. We also give the programs to design a sequence of periodic twinborn pulses to suppress the decoherence.

Single-Atom Protecting Group for on-Surface Synthesis of Graphdiyne Nanowires

On-surface synthesis of semiconducting graphdiyne nanowires usually suffer severe side reactions owing to the high reactivity of the butadiynylene units at noble metal surfaces,limiting the production of isolated nanowires. In this work, we report the high-yield synthesis of branchless graphdiyne nanowires [-C≡C-Ph2-C≡C-]nvia on-surface Ullmann coupling of 1,4-bis（4-bromophenyl）-1,3-butadiyne molecules with chemical vapor deposition method.Non-contact atomic force microscopy with single-bond resolution reveals that single gold adatoms act as effective protecting groups for butadiynylene units by forming Au-π ligand bonds, preventing unwanted branched coupling reactions and enabling the synthesis of ultralong isolated graphdiyne nanowires. This study will stimulate further investigation on the role of various surface adatoms in protecting on-surface reactions.

The breaking point between fast-and slow-light in a degenerate two-level atomic system

This paper investigates the breaking point between fast- and slow-light in a degenerate two-level atomic system, where fast-light can be converted to slow-light arbitrarily on a single transition line by adjusting the strength of the pumping field. An equivalent incoherent pumping rate is introduced in this simplified theoretical model which exploits the dependence of this feature. The experimental observation is presented as evidence of the breaking point where the injected power is about 0.08 mW.

Using Atomic Microstates and Atomic Number Parity in Support of Lutetium and Lawrencium Classification as Transition Metals

Unlike other groups of elements, Group 3 constituency remains unsettled. This article argues that ground level microstates and atomic number parity suggest Sc-Y-Lu-Lr Group 3 membership.

轻质中锰钢局部变形带的研究现状

轻质中锰钢是第三代先进高强钢的代表,在变形过程中由于C、Mn、Al等合金元素的存在其可动位错经历被固溶原子和C-Mn原子团钉扎和脱扎的过程,从而在应力-应变曲线上呈现出吕德斯(Lüders)带和Portrvin-Le Chatelier(PLC)带这两种最典型的局部变形带,导致材料表面质量降低,对后续加工使用不利。目前,消除Lüders带和PLC带引起的表面缺陷的常用方法是在成形前对材料施加小的预应变或者调控材料的组织。然而这种方法只适用于经历小Lüders带应变和PLC效应的材料,因此寻求一种更为有效的延迟或消除Lüders带与PLC带的方法显得极其重要。本文从发生机理入手,讨论预应变、退火温度、退火时间等工艺和合金元素对上述两种局部变形带的影响,进而从晶粒尺寸、组织形貌、位错密度等微观角度总结减弱或加剧二者的具体机制,并着重解释不同成分与热处理工艺对C-Mn原子团形成、移动速率和与位错交互时间的影响以及抑制局部变形带的形成与拓展的作用。随后根据已有研究提出的不同解决方案,结合上述宏观与微观影响因素,展望了未来该领域研究的发展。

Charge transfer and orbital reconstruction of non‐noble transition metal single‐atoms anchored on Ti_(2)CT_(x)‐MXenes for highly selective CO_(2) electrochemical reduction

Inspired by MXene nanosheets and their regulation of surface functional groups,a series of Ti_(2)C‐based single‐atom electrocatalysts(TM@Ti_(2)CT_(x),TM=V,Cr,Mn,Fe,Co,and Ni)with two dif‐ferent functional groups(T=–O and–S)was designed.The CO_(2)RR catalytic performance was stud‐ied using well‐defined ab initio calculations.Our results show that the CO_(2) molecule can be more readily activated on TM@Ti_(2)CO_(2) than the TM@Ti_(2)CS_(2) surface.Bader charge analysis reveals that the Ti_(2)CO_(2) substrate is involved in the adsorption reaction,and enough electrons are injected into the 2π*u orbital of CO_(2),leading to a V‐shaped CO_(2) molecular configuration and partial negative charge distribution.The V‐shaped CO_(2) further reduces the difficulty of the first hydrogenation reac‐tion step.The calculatedΔG of the first hydrogenation reaction on TM@Ti_(2)CO_(2) was significantly lower than that of the TM@Ti_(2)CS_(2) counterpart.However,the subsequent CO_(2) reduction pathways show that the UL of the potential determining step on TM@Ti_(2)CS_(2) is smaller than that of TM@Ti_(2)CO_(2).Combining the advantages of both TM@Ti_(2)CS_(2) and TM@Ti_(2)CO_(2),we designed a mixed functional group surface with–O and–S to anchor TM atoms.The results show that Cr atoms an‐chored on the surface of mixed functional groups exhibit high catalytic activity for the selective production of CH4.This study opens an exciting new avenue for the rational design of highly selec‐tive MXene‐based single‐atom CO_(2)RR electrocatalysts.

Variable Hardy Spaces on the Heisenberg Group

We consider Hardy spaces with variable exponents defined by grand maximal function on the Heisenberg group. Then we introduce some equivalent characterizations of variable Hardy spaces. By using atomic decomposition and molecular decomposition we get the boundedness of singular integral operators on variable Hardy spaces. We investigate the Littlewood-Paley characterization by virtue of the boundedness of singular integral operators.

Mapping HⅠ in the NGC 4636 Galaxy Group with FAST

This paper presents data from a 21 cm H I emission drift scan observation of a field partially covering the NGC 4636 galaxy group with the Five-hundred meter Aperture Radio Telescope(FAST). We construct a pipeline to reduce the data, and use So Fi A for source finding. When not contaminated by Radio Frequency Interference(RFI), the FAST observations are capable of detecting all of the galaxies previously detected by the Arecibo Legacy Fast ALFA(ALFALFA) survey in the same region. Comparing to ALFALFA for the detections in common, the FAST data show consistent integrated spectra when the H I disks are spatially unresolved, and capture more flux when the H I disks are resolved. The FAST data further reveal 10 new detections in the region mutually covered with ALFALFA, and 18 new detections beyond the footprint of ALFALFA. All of the new detections have the matching optical counterparts. For the member galaxies of the NGC 4636 group, the detection limit of FAST is deeper by 0.4 dex in H I mass than that of the ALFALFA data. After correcting for the incompleteness caused by RFI contamination, we show that the H I detection rate of galaxies rises steeply with radius out to the virial radius of the group, and flattens beyond that. We also examine four spatially resolved galaxy systems with potential tidal interaction features in detail. Considering that the data have been taken during the“shared-risk” period before a major source of local RFI was eliminated, the results highlight the power of FAST in detecting extragalactic H I.

保留取代基团的苯环选择加氢反应催化剂研究进展

具有复杂取代基团苯基衍生物的苯环选择加氢属于原子经济反应,不仅可以消除苯环对人体健康的潜在危害,而且能够赋予所合成材料以特殊功能。该文综述了保留取代基团苯环选择加氢反应的催化剂、操作条件及反应性能的研究进展,主要包括芳香二胺、芳香酯类、芳香族氨基甲酸甲酯、聚苯乙烯、联苯及双酚A等的苯环催化加氢反应。为了使苯环上取代基团不发生反应,多采用Rh、Ru、Pd和Pt等贵金属催化剂。Ni等非贵金属催化剂的活性和选择性有待进一步提高。因此,今后研究重点应是开发减量或替代贵金属的高性能催化剂。

原子氧辐照对含苯并咪唑结构聚酰亚胺摩擦学性能影响研究

聚合物及其复合材料的抗原子氧辐照性是影响其在空间装备应用过程中可靠性和安全性的重要因素。研究表明含硫、氮等杂原子的芳杂环聚合物具有一定的抗原子氧辐照性能。因此,从聚合物分子链角度出发设计并制备具有抗辐照性能的聚合物是一种有效的途径。目前,关于聚醚砜、聚砜及聚酰亚胺等聚合物抗辐照性能的研究表明,引入具有良好耐热性能的化学基团能有效提高聚合物的抗原子氧辐照性能。聚苯并咪唑因结构中特殊的苯并咪唑结构赋予了其良好的耐热性能,使其表现出良好的抗原子氧辐照的潜质。但聚苯并咪唑的合成条件较为苛刻,因此将苯并咪唑结构引入聚酰亚胺的主链中成为了一种改善其抗辐照性能的良好解决方案。本工作采用传统的两步法合成了一种含苯并咪唑结构的聚酰亚胺(PMI),研究了聚合物薄膜在原子氧辐照(AO)前后的力学性能和摩擦学性能,并与不含苯并咪唑基团的聚酰亚胺(YS-20)薄膜进行了比较。结果表明,含苯并咪唑结构聚酰亚胺的抗氧化性能和力学性能均优于不含苯并咪唑基团的聚酰亚胺(YS-20)。通过对比辐照时间对薄膜的影响,发现不同辐照时间后,PMI系列表现出较低的粗糙度。这一结果通过表面三维形貌图也得到了证明。通过对辐照后表面C和O元素价态和组成分析结果表明,与YS-20相比,PMI表现出较低的碳化程度。同时主链中芳杂环结构也提高了聚合物的耐温性能和机械强度,其中PMI的玻璃化转变温度高达365℃。通过球盘摩擦实验考察了辐照前后摩擦性能的演变。结果表明,由于抗AO性能的不同,聚合物薄膜的显微硬度和模量呈现出不同的变化趋势,导致AO辐照后的摩擦学性能不同。

挑流水舌入水喷溅的水滴生成数值模型研究

挑流泄洪雾化与水滴的生成及运动特性密切相关,其中水滴的生成问题是一个关键。本研究使用欧拉方法和拉格朗日方法相结合,提出了一种新的数值模型,用于模拟挑流水舌入水喷溅的水滴生成。首先,采用流体体积法获取挑流水舌的形态、速度和湍流动能等背景场信息。然后,利用液滴破碎的能量平衡理论构建特征参数,计算喷溅水滴的生成位置和数量。最后,使用拉格朗日方法追踪水滴的运动轨迹,并将模拟结果与水工模型试验数据进行对比。结果表明,模拟获得的水舌挑距、水滴生成位置、水滴群分布和降雨强度分布与水工模型试验的观测情况和数据高度一致,验证了模型的准确性,为挑流泄洪雾化研究提供了新思路。

Molecular electronegativity in density functional theory (II) --Direct calculation of group electronegativity and the atomic charges in a group

On the basis of a more precise expression of the atomic effective electronegativity deduced from the density functional theory and electronegativity equalization principle, a new scheme for calculating the group electronegativity and the atomic charges in a group is proposed and programed, and various parameters of electronegativity and hardness are given for some common atoms. Through calculation, analysis and comparison of more than one hundred groups, it is shown that the results from this scheme are reasonable and may be extended.

Mg_(12)O_(12)纳米线掺杂3d过渡金属元素的第一性原理计算研究

基于密度泛函第一性原理计算,系统研究了Mg_(12)O_(12)笼状团簇组装一维纳米线及其掺杂3d族元素体系的几何结构与电子结构.结果表明:Mg_(12)O_(12)团簇组装一维纳米线为非磁性半导体,带隙值为3.16 eV;掺杂Sc和V后,体系由半导体转变为金属;掺杂Ti、Cr、Mn、Fe、Co、Ni、Cu后体系仍然保持半导体特性、但带隙值明显减小,而掺杂Zn时带隙值变化不大;掺杂V、Cr、Mn、Fe、Co、Ni、Cu后纳米线具有磁性.

浮选药剂性能判据应用进展

随着药剂性质研究理论和方法的不断进步,浮选药剂构效关系也从定性分析逐步转变至定量研究阶段。定量研究的关键是确定一些可预先判断药剂分选性能的原理或准则,即浮选药剂性能判据。介绍了目前常见的浮选药剂性能判据及其优缺点,以期为高效浮选药剂的研发提供依据。性能判据按大类可分为药剂性质判据、基团或键合原子性质判据以及结合能判据等。这些判据多关注药剂与矿物表面的作用过程,导致其在使用过程中多起到筛选作用。为开发新型高效的浮选药剂,需要依托浮选药剂与矿物作用强弱的表征理论和方法,有针对性地选取浮选药剂性质参数,建立性质参数与作用强弱的相关关系,从而形成新的、更高效的药剂性能判据。

Atomically Dispersed Main Group Magnesium on Cadmium Sulfide as the Active Site for Promoting Photocatalytic Hydrogen Evolution Catalysis

Photoabsorption charge separation/transfer and surface reaction are the three main factors influencing the efficiency of photocatalysis.Band structure engineering has been extensively applied to improve the light absorption of photocatalysts,however,most of the developed photocatalysts still suffer from low photocatalytic performance due to the limited active site(s)and fast recombination of photogenerated charge carriers.In this work,atomically dispersed main group magnesium(Mg)is introduced onto CdS monodispersed nanospheres,which greatly enhances the photocatalytic hydrogen evolution reaction.The photocatalytic hydrogen evolution reaction rate reaches 30.6 mmol·gcatalyst^(-1)·h^(-1),which is about 11.8 and 2.5 times that of pure CdS and Pt(2 wt.%)-CdS.The atomically dispersed Mg on CdS acts as an electron sink to trap photogenerated electrons,and at the same time,greatly reduces the Gibbs free energy of hydrogen evolution reaction(HER)and accelerates HER.

非线性光学原子响应理论及最新进展

二阶非线性光学晶体材料通过倍频效应转换激光频率,并且调制激光的振幅和位相,在现代制造、激光医疗、光通信,以及基础科学研究领域都有重要用途。本文简要介绍了近年来在部分响应泛函方法的基础上发展起来的非线性光学原子响应理论。该理论使人们能够在第一性原理计算的基础上定量评估单个组成原子及轨道对非线性光学晶体材料倍频效应的贡献。在此基础上,本团队还发展了一套普适的以物理性能为标准的基团划分方案,为确定倍频效应的功能基元提供了概念基础。本工作对该理论方法的最新进展及其带来的一些新观点,如导带的作用、原子负贡献、静态偶极矩的作用、非共价基团的压倒性贡献、线性规律等进行解释和阐述,并给出了在新材料设计中的应用实例。

s-g原子轨道角度分布函数在MATLAB中的可视化

以功能强大的MATLAB计算软件为作图工具,在没有M文件的情况下,通过设置球极坐标参数θ∈[0,π]以及Φ∈[0,2π],直接使用内置的曲面绘制函数mesh(X,Y,Z)以及坐标变换原理实现了原子轨道角度分布函数Y_(l,m)(θ,Φ)的可视化。同时,详细给出了s-g系列Y_(l,m)(θ,Φ)的数学表达式以及MATLAB代码表示;包括程序设计以及所有的运行结果。而目前有关原子轨道的可视化工作方面,国内外的一些报道中,最高也只是做到了f轨道;并且没有介绍“立方组”。

Atomic defects,functional groups and properties in MXenes

MXenes,a new family of functional two-dimensional(2 D) materials,have shown great potential for an extensive variety of applications within the last decade.Atomic defects and functional groups in MXenes are known to have a tremendous influence on the functional properties.In this review,we focus on recent progress in the characterization of atomic defects and functional group chemistry in MXenes,and how to control them to directly influence various properties(e.g.,electron transport,Li^(+) adsorption,hydrogen evolution reaction(HER) activity,and magnetism) of 2 D MXenes materials.Dynamic structural transformations such as oxidation and growth induced by atomic defects in MXenes are also discussed.The review thus provides perspectives on property optimization through atomic defect engineering,and bottom-up synthesis methods based on defect-assisted homoepitaxial growth of MXenes.

配位聚合物｛[Zn(CF_3COO)_2(C_5H_5ON)·]H_2O｝_n的合成、晶体结构及表征

new coordination polymer {[Zn(CF3COO)2(C5H5ON)]·H2O}n was synthesized based on the reaction of zinc(Ⅱ) trifluoroacetate and 3-hydroxypyridine(C5H5ON) in methanol medium for the first time. The structure of the coordination polymer was confirmed by IR, 1H NMR, elemental analysis and thermal analysis. The crystal structure of the coordination polymer was also determined by X-ray single crystal diffraction. The crystal belongs to monoclinic system with space group P21/m, and crystallographic data of the coordination polymer are: a= 0.863 1(4) nm, b=0.717 7(3) nm, c=1.116 4(5) nm, α=γ=90°, β=107.542(6)°, V=0.659 4(5) nm3; Dc=2.037 g·cm-3; Z=2; F(000)=400; μ=1.969 mm-1. Zinc(Ⅱ) atom lies at the center of an octahedron formed by the coordination of zinc atom and six O atoms which come from four different trifluoroacetate ions and two different 3-hydroxypyridine molecules where each trifluoroacetate ion and 3-hydroxypyridine are coordinated to two different zinc ions to form coordination polymer. CCDC: 253909.