Interplay of Antiferromagnetic Coupling and Spin Crossover in Dinuclear Iron(II) Complexes

This article reports on the study of the interplay between magnetic coupling and spin transition in 2,2′-bipyrimidine (bpym)-bridged iron(II) dinuclear compounds. Coexistence of both phenomena has been observed in [Fe(bpym)(NCS)₂]₂bpym, [Fe(bpym)(NCSe)₂]₂bpym and [Fe(bt)(NCS)₂]₂bpym (bpym = 2,2′-bipyrimidine, bt = 2,2′-bithiazoline) by the action of external physical factors namely pressure or electromagnetic radiation. Competition between magnetic exchange and spin crossover has been studied in [Fe(bpym)(NCS)₂]₂bpym at 6.3 kbar. LIESST experiments carried out in [Fe(bpym)(NCSe)₂]₂bpym and [Fe(bt)(NCS)₂]₂bpym at 4.2 K have shown that is possible to achieve dinuclear molecules with different spin states in this class of compounds. This revised version was published online in August 2006 with corrections to the Cover Date.     

Radiation-induced synthesis of RuO2 nanoparticles by thermal decomposition of Ru-tris-acetylacetonate

Pure-phase RuO₂ nanoparticles were obtained by thermal decomposition of unirradiated and γ-irradiated Ru-tris-acetylacetonate precursors. Several influencing factors including absorbed dose, calcination times and temperatures and addition of surfactants were thoroughly investigated. The newly synthesized RuO₂ nanoparticles were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results showed that the best conditions for the preparation of mono-dispersed RuO₂ nanoparticles were achieved by calcinations of unirradiated Ru-tris-acetylacetonate for 6 h at 600°C. For γ-irradiated Ru-tris-acetylacetonate with 10² Gy total γ-ray doses, the optimal conditions for RuO₂ preparation were calcination for 2 h at 200°C. Thermal stability of RuO₂ nanoparticles was studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques, and the results were evaluated and discussed.     

钴络合物催化甲醇羰基化制甲酸甲酯反应的理论研究

本文运用密度泛函理论B3LYP方法,对C、O、H采用6-311+G(2d,p)基组,计算研究了钴络合物催化甲醇羰基化制甲酸甲酯反应的微观机理,优化了各反应物、中间体和过渡态的构型特征,用频率分析方法和内禀反应坐标方法对过渡态进行了验证,同时对各中间体进行电荷分析.对比了催化过程与非催化过程的能垒.结果表明,有催化剂参与后反应活化能明显降低.     

Reaction mechanism of ammonia oxidation over RuO2(1 1 0): A combined theory/experiment approach

Combining state-of-the-art density functional theory (DFT) calculations with high resolution core level shift spectroscopy experiments we explored the reaction mechanism of the ammonia oxidation reaction over RuO₂(1 1 0). The high catalytic activity of RuO₂(1 1 0) is traced to the low activation energies for the successive hydrogen abstractions of ammonia by on-top O (less than 73 kJ/mol) and the low activation barrier for the recombination of adsorbed O and N (77 kJ/mol) to form adsorbed NO. The NO desorption is activated by 121 kJ/mol and represents therefore the rate determining step in the ammonia oxidation reaction over RuO₂ (1 1 0).     

数字图像注入式红外目标捕获跟踪训练仿真

介绍一种利用数字图像注入构建目标环境来完成目标捕获跟踪仿真训练任务的新方法,该方法通过模拟目标的理论航迹,实时接收并解算编码器输出值,同时与目标的运动方程做综合处理,计算出目标的位置信息,最后在背景中合成目标后按照红外图像的格式将数字图像注入到数字图像处理系统中。该方法可以在不开启红外相机的情况下,方便地完成手动及自动跟踪的训练任务,节约了训练成本,并已成功运用到某光电跟瞄设备的仿真训练系统中。     

Beam-based calibrations of the BPM offset at C-ADS Injector Ⅱ

Beam-based BPM offset calibration was carried out for Injector II at the C-ADS demonstration facility at the Institute of Modern Physics(IMP), Chinese Academy of Science(CAS). By using the steering coils integrated in the quadrupoles, the beam orbit can be effectively adjusted and BPM positions recorded at the Medium Energy Beam Transport of the Injector II Linac. The studies were done with a 2 m A, 2.1 Me V proton beam in pulsed mode.During the studies, the "null comparison method" was applied for the calibration. This method is less sensitive to errors compared with the traditional transmission matrix method. In addition, the quadrupole magnet's center can also be calibrated with this method.     

基于FPGA的高速数据传输系统设计与实现

为了满足国家重点专项“量子科学实验卫星”中“量子存储板”高速串行数据传输的测试要求,提出了一种以Nios II嵌入式处理器为控制核心,TLK2711、RS422、USB2.0和千兆以太网为传输接口的高速数据传输解决方案;系统采用TLK2711完成高速数据的串并转换,采用RS422完成命令和控制信号的传输,实现与“量子存储板”的高速数据传输;利用Xilinx公司Zynq-7000芯片独有的ARM+FPGA架构实现千兆以太网完成数据的高速传输,利用EXAR公司XR21V1414 USB转串口芯片实现命令、遥测等数据的传输;采用Labview编写上位机控制整个系统的运行,实现命令发送、指令解析、运行状态显示、数据帧产生、高速数据传输、解析和存储等功能;实测结果表明,此系统数据传输速率高达600 Mbps,满足高速串行数据传输的要求,且具有稳定性高、可靠性好等优点。     

Constraining WIMP magnetic moment from CDMS II experiment

We consider a degenerate or a nearly degenerate dark matter sector where a sizable magnetic moment of a (almost) Dirac type neutral dark matter candidate N is anticipated. Then, due to soft photon exchange, the cross-section in direct detection of N   can be enhanced at low Q²$Q^2$ region. We discuss the implication of this type of models in view of the recent CDMS II report.     

Study of kinetics and mechanism of the acid dissociation of copper(II) complex of novel C-functionalized macrocyclic dioxotetraamines

The kinetics of the acid dissociation of copper(II) complexes of novel C-functionalized macrocyclic dioxotetraamines has been studied by means of a stopped-flow spectrophotometer. The acid dissociation rate follows the law V_d = C_comkK₁K₂H ²/(1+K₁H+K₁K₂H ²). From the experimental facts we have obtained, the dissociation kinetics are interpreted by a mechanism involving the negatively charged carbonyl oxygen of the complex being rapidly protonated in a pre-equilibrium step, the rate-determining step being intramolecular hydrogen (enolic tautomer) migration (to imine nitrogen). The dissociation rate reached a plateau in the strongly acidic solution. By means of temperature coefficient method, ΔH ^φ, ΔS ^φ of the pre-equilibrium step and ΔH ^≠, ΔS^≠ of the rate-determining step were obtained. The results of 13-membered macrocyclic dioxotetraamines have been discussed. The influence of the substituents to the acid dissociation rates has also been discussed. The Bronsted type linear free energy relationships do also exist in these C-functionalized dioxotetraamine copper(II) complexes.     

Aldehyde‐Assisted Ruthenium(II)‐Catalyzed CH Oxygenations

Versatile ruthenium(II) complexes allow for site‐selective C? H oxygenations with weakly‐coordinating aldehydes. The challenging C? H functionalizations proceed with high chemoselectivity by rate‐determining C? H metalation. The new method features an ample substrate scope, which sets the stage for the step‐economical preparation of various bioactive heterocycles.