Mechanism insights of ethane C-H bond activations by bare [Fe(III)═O]+: explicit electronic structure analysis

Alkane C-H bond activation by various catalysts and enzymes has attracted considerable attention recently, but many issues are still unanswered. The conversion of ethane to ethanol and ethene by bare [Fe(III)═O](+) has been explored using density functional theory and coupled-cluster method comprehensively. Two possible reaction mechanisms are available for the entire reaction, the direct H-abstraction mechanism and the concerted mechanism. First, in the direct H-abstraction mechanism, a direct H-abstraction is encountered in the initial step, going through a collinear transition state C···H···O-Fe and then leading to the generation of an intermediate Fe-OH bound to the alkyl radical weakly. The final product of the direct H-abstraction mechanism is ethanol, which is produced by the hydroxyl group back transfer to the carbon radical. Second, in the concerted reaction mechanism, the H-abstraction process is characterized via overcoming four/five-centered transition states (6/4)TSH_c5 or (4)TSH_c4. The second step of the concerted mechanism can lead to either product ethanol or ethene. Moreover, the major product ethene can be obtained through two different pathways, the one-step pathway and the stepwise pathway. It is the first report that the former pathway starting from (6/4)IM_c to the product can be better described as a proton-coupled electron transfer (PCET). It plays an important role in the product ethene generation according to the CCSD(T) results. The spin-orbital coupling (SOC) calculations demonstrate that the title reaction should proceed via a two-state reactivity (TSR) pattern and that the spin-forbidden transition could slightly lower the rate-determining energy barrier height. This thorough theoretical study, especially the explicit electronic structure analysis, may provide important clues for understanding and studying the C-H bond activation promoted by iron-based artificial catalysts.     

小型化可调光镊设计

光镊利用强会聚激光对微粒产生的梯度力来捕获微粒,可以进行无损、远程操控,同时具有皮牛精度的测力特性,已经成为物理学、生命科学和胶体化学等研究领域中不可缺少的研究工具。光镊效应可以表现微小的光子动量和角动量,是物理学的重要教学工具。本文根据高斯光束传播和变换规律,设计具有稳定捕获性能的最小化光镊,并给出了典型参数。光镊系统由捕获激光、光束耦合系统、倒置生物显微镜和大数值孔径物镜组成,成像系统由物镜、摄影目镜和CCD相机组成。本光镊系统具有紧凑特性,同时通过保持物镜后瞳充满度来实现稳定捕获。在该最小光镊系统上,可以根据用户需求增加光镊阱位操控系统、刚度调节系统和其他辅助设备以满足不同操控要求,可以很好地满足科研和教学需求。     

关于素数阶循环群中短序列的等价类

考虑了素数阶循环群中的短序列的等价序列,并在某些情况下给出序列的Index值的上界．     

Generalizations of the nonstationary multisplitting iterative method for symmetric positive definite linear systems

In this paper, we generalize the nonstationary parallel multisplitting iterative method for solving the symmetric positive definite linear systems. With several choices of variable weighting matrices, the convergence properties of these generalized methods can be improved. Finally, the numerical comparison of several nonstationary parallel multisplitting methods are shown.     

Cu/ZrO_2催化剂的结构及其CO_2加氢合成甲醇催化反应性能

采用低温氮气吸脱附、XRD、TPR、In-situ IR和XPS等表征手段,对分步沉淀法、浸渍沉淀法和固态反应法制备的CuO/ZrO2催化剂进行表征,同时考察了其CO2加氢合成甲醇反应性能。结果表明,制备方法对CuO/ZrO2的物理结构和还原性能影响很大,其中浸渍沉淀法制备的催化剂Cu与ZrO2相互作用最强,并显示了较高的CO2转化率和甲醇收率。Cu与ZrO相互作用的强弱直接影响CO加氢合成甲醇反应性能的优劣,而催化剂的比表面积不是影响反应性能的主导因素。     

流动注射化学发光法检测水相中溶解臭氧浓度

基于碱性水溶液中臭氧氧化鲁米诺产生化学发光的现象,建立了利用流动注射化学发光技术检测水体溶解臭氧(DO3)的方法。检测了较高和较低两部分的DO3浓度范围,低浓度DO3从20μg/L到65μg/L,工作曲线为y=27．658In(X)-192．75;检出限为8．5μg/L(7次空白信号检测);高浓度D03从0．089mg／L到0．890mg／L,线性关系为y=0．0018x-23．711。溶液中的。DO3由靛蓝二磺酸钠法确定。随后利用化学发光系统检测鼓人臭氧气体的自来水,由工作曲线可以确定自来水中DO3的量。方法简便,结果准确。     

分子模拟在高性能聚合物纤维力学性能研究中应用

聚合物力学性能取决于单个分子链的力学性质和分子链聚集形态。综述了通过分子模拟研究高度取向的液晶高分子纤维的微观力学行为,从微观角度揭示聚合物力学性能的本质,解释其力学破坏的结构因素。     

[Ni(H2O)4(phen)]SO4(C3H8N2O)材料的合成、热学和光谱性质

使用六水合硫酸镍、邻二氮菲、二甲基脲为原料合成一种配合物[Ni(H2O)4(phen)]SO4(C3H8N2O).通过元素分析仪测定碳、氢、氮元素所占百分比.利用X射线单晶衍射测定晶体结构.利用热分析法测定该晶体材料的脱水温度为75 ℃、二甲基脲和phen的分解温度分别为150℃和500℃.测量晶体的紫外-可见光谱特性发现,该配合物紫外全部吸收,phen与Ni2配位后Ni2的3A2g光谱项发生移动,在610 nm处具有很强的吸收,在450 ～550 nm范围内可见光区域具有较好的透过性能.     

KTX反场箍缩装置中等离子体小破裂现象研究

在科大反场箍缩磁约束实验装置(KTX)实验中，观测并研究等离子体的显著位移及其带来的小破裂现象。通过分析H_α 谱线、软X 射线辐射以及磁探针数据，发现其主要特征是破裂前等离子体电流重心的缓慢外移，在小破裂后等离子体电流重心在百微秒时间迅速反向移动，重新达到稳定位形。同时，等离子体小破裂伴随着m=1 的边界磁场扰动、稳定壳上显著变化的涡流、以及H_α 谱线和软X 射线辐射的增强。通过对KTX 小破裂实验数据的分析与统计，得出回弹位移与等离子体位移成线性关系。对等离子体电流分布及稳定壳涡流，建立了唯象电路模型，得出了和实验相一致的结论，确定了稳定壳上快速变化的涡流是等离子体小破裂后回复平衡的重要因素。     

正交实验法优化氟硅丙乳液的制备工艺

利用L25(56)正交实验设计方法,研究了引发剂,乳化剂,有机硅、氟的用量以及聚合温度,单体配比等因素对乳液单体转化率的影响.在本实验条件下,得出制备氟硅丙乳液的最佳工艺条件为:乳化剂用量为4%,引发剂用量为ω=0.6%,单体配比为n(BA):n(MMA)=44:54,有机硅用量ω=10%,有机氟用量ω=4%,聚合温度...