Carbene‐Catalyzed Desymmetrization and Direct Construction of Arenes with All‐Carbon Quaternary Chiral Center

Multisubstituted arenes such as indanes with attached all‐carbon quaternary centers are unique scaffolds in synthetic functional molecules and sophisticated natural products. A key challenge in preparing such molecules lies in the enantioselective installation of the quaternary carbon centers. Conventional methods in this direction include asymmetric substitution reactions and substrate‐controlled cyclization reactions. These reactions lead to poor stereoselectivities and/or require long and tedious synthetic steps. Disclosed here is a one‐step organic catalytic strategy for enantioselective access to this class of molecules. The reaction involves an N‐heterocyclic carbene catalyzed process for direct benzene construction, indane formation, remote‐carbon desymmetrization, and excellent chirality control. This approach will enable the concise synthesis of arene‐containing molecules, including those with complex structures and challenging chiral centers.     

Hydrodehalogenation of Aryl Halides through Direct Electrolysis

A catalyst- and metal-free electrochemical hydrodehalogenation of aryl halides is disclosed. Our reaction by a flexible protocol is operated in an undivided cell equipped with an inexpensive graphite rod anode and cathode. Trialkylamines nBu₃N/Et₃N behave as effective reductants and hydrogen atom donors for this electrochemical reductive reaction. Various aryl and heteroaryl bromides worked effectively. The typically less reactive aryl chlorides and fluorides can also be smoothly converted. The utility of our method is demonstrated by detoxification of harmful pesticides and hydrodebromination of a dibrominated biphenyl (analogues of flame-retardants) in gram scale.     

O-Alkyldithiophosphate Nickel Complexes with dcpf Ligand as Efficient Electrocatalysts for Hydrogen Evolution

Six new O-alkyldithiophosphate nickel complexes with dcpf ligand, [(dcpf)Ni(S₂P{O}OR)] (dcpf = 1,1′-bis (dicyclohexylphosphino)ferrocene, R = CH₃ ( 1 ), CH₃CH₂ ( 2 ), Ph ( 3 ), 4-MeC₆H₄ ( 4 ), PhCH₂ ( 5 ) and PhCH₂CH₂ ( 6 )), have been synthesized by the treatment of dcpf with ((RO)₂PS₂)₂Ni in satisfactory yields. These complexes were characterized by elemental analysis, spectroscopy (FTIR, UV–vis, ¹H, ¹³C, and ³¹P NMR), thermogravimetric analysis and single crystal X-ray diffraction. The nickel atom in 1 , 2 ·CH₂Cl₂, 3 ·CH₂Cl₂, 4 ·2CH₂Cl₂·THF, and 2( 5 )·hexane adopts a slightly distorted square-planar coordination environment finished by two phosphorus atoms of dcpf ligand and two sulfur atoms of O-alkyldithiophosphate ligand. Furthermore, the electrochemical properties for complexes 1 – 6 were also investigated by cyclic voltammetry. With the addition of 120 mM trifluoroacetic acid (TFA), the turnover frequency (TOF) values for 1 – 6 are estimated to be 1243.83, 1046.54, 1331.71, 2545.29, 1899.03, and 1191.37 s⁻¹, with the overpotential (η) values of 0.62, 0.58, 0.71, 0.67, 0.60, and 0.56 V, respectively. The result of electrochemical studies indicates that all complexes can be used as efficient molecular eletrocatalysts for the reduction of protons to hydrogen in the presence of TFA in MeCN.     

A Crosslinked Nucleic Acid Nanogel for Effective siRNA Delivery and Antitumor Therapy

Functional siRNAs are employed as cross‐linkers to direct the self‐assembly of DNA‐grafted polycaprolactone (DNA‐g‐PCL) brushes to form spherical and nanosized hydrogels via nucleic acid hybridization in which small interfering RNAs (siRNAs) are fully embedded and protected for systemic delivery. Owing to the existence of multivalent mutual crosslinking events inside, the crosslinked nanogels with tunable size exhibit not only good thermostability, but also remarkable physiological stability that can resist the enzymatic degradation. As a novel siRNA delivery system with spherical nucleic acid (SNA) architecture, the crosslinked nanogels can assist the delivery of siRNAs into different cells without any transfection agents and achieve the gene silencing effectively both in vitro and in vivo, through which a significant inhibition of tumor growth is realized in the anticancer treatment.     

Density measurement of 1-d confined water by small angle neutron scattering method: pore size and hydration level dependences

Small angle neutron scattering (SANS) is used to measure the absolute density of water contained in 1-D cylindrical pores of a silica material MCM-41-S with pore diameters of 19 and 15 A. By being able to suppress the homogeneous nucleation process inside the narrow pore, one can keep water in the liquid state down to at least 160 K. From a combined analysis of SANS data from both H(2)O and D(2)O hydrated samples, we determined the absolute value of the density of 1-D confined water. We found that the average density of water inside the fully hydrated 19 A pore is 8% higher than that of the bulk water at room temperature. The temperature derivative of the density shows a pronounced peak at T(L) = 235 K signaling the crossing of the Widom line at ambient pressure and confirming the existence of a liquid-liquid phase transition at an elevated pressure. Pore size and hydration level dependences of the density are also studied.     

Improved Electrocatalytic Activity and Stability by Single Iridium Atoms on Iron-based Layered Double Hydroxides for Oxygen Evolution

Full understanding to the origin of the catalytic performance of a supported nanocatalyst from the points of view of both the active component and support is significant for the achievement of high performance. Herein, based on a model electrocatalyst of single-iridium-atom-doped iron (Fe)-based layered double hydroxides (LDH) for oxygen evolution reaction (OER), we reveal the first completed origin of the catalytic performance of such supported nanocatalysts. Specially, besides the activity enhancement of Ir sites by LDH support, the stability of surface Fe sites is enhanced by doped Ir sites: DFT calculation shows that the Ir sites can reduce the activity and enhance the stability of the nearby Fe sites; while further finite element simulations indicate, the stability enhancement of distant Fe sites could be attributed to the much low concentration of OER reactant (hydroxyl ions, OH⁻) around them induced by the much fast consumption of OH⁻ on highly active Ir sites. These new findings about the interaction between the main active components and supports are applicable in principle to other heterogeneous nanocatalysts and provide a completed understanding to the catalytic performance of heterogeneous nanocatalysts.     

基于RFM的机载余度计算机软件快速测试平台

现代飞机普遍采用电传飞行控制系统,飞行控制计算机是该系统的核心。为了提升飞控计算机的可靠性,普遍采用余度技术构建余度飞控计算机,该计算机由多个通道构成,每个通道有一个CPU,互相构成备份。但是,这给飞控计算机的软件调试和测试带来的巨大的困难,因为各个通道的机载软件之间相互同步、通信和交叉监控,必须并行调试和测试,这就造成了机载软件调试和测试的滞后,必须等待真实的飞控计算机开发出来之后才能开展工作。本文提出了一种基于RFM(反射内存)的余度计算机快速原型测试平台设计方法。该平台使用商用货架产品构成余度计算机的多个冗余通道,使用RFM模拟多通道间的通信、同步过程,通过对底层驱动封装实现硬件故障模拟和余度功能模拟,方便实现软件调试和从性能、功能测试,大大提高了开发效率,减少了研制周期。     

纳米(Y0.95Eu0.05)2O3及其SiO2气凝胶介孔组装体的制备与光致发光

采用尿素溶胶法合成（Ｙ０．９５Ｅｕ０．０５）２Ｏ３纳米粉,用超临界干燥技术制备了ｎ－（Ｙ０．９５Ｅｕ０．０５）２Ｏ３／ＳｉＯ２气凝胶介孔组装体。结果表明,当Ｙ＾３＋：Ｅｕ＾３＋＝２０：１,均相反应时间为４ｈ,且经６８０℃、４ｈ灼烧热处理后得到的ｎ－（Ｙ０．９５Ｅｕ０．０５）２Ｏ３中,光致发光强度最大（发光峰位于６１２ｎｍ）,以Ｓｉ与２Ｙ摩尔比为１：７的ｎ－（Ｙ０．９５Ｅｕ０．０５）２Ｏ３／ＳｉＯ２气凝胶介孔组装体,经同样条件热６１６ｎｍ）。对产生上述发光强度减弱和峰位红移现象进行讨论。     

消偏光纤陀螺的理论和实验研究

本文首次在理论上导出消偏型光纤陀螺的零漂和标度因子表达式,并得出以下两个结论:1)在使用约 40 dB偏振器时,导致陀螺漂移的主要因素是强度误差而并不是振幅误差;2)由光学标度因子与各种器件参量关系表明开环解调时陀螺的线性误差较大.试验样机证明了以上结果,并找出减小漂移的方法.     

离子色谱法快速连续测定锗和锡的研究

介绍了一种快速测定锗和锡的新方法──离子色谱法。锗和锡在双功能的分离柱上被分离后进行柱后显色反应,然后经可见检测器于５２０ｎｍ处检测。此法具有较高的灵敏度和选择性,整个分析过程仅需５ｍｉｎ,样品分析结果令人满意。