Construction of Various Bridged Polycyclic Skeletons by Palladium‐Catalyzed Dearomatization

A powerful palladium‐catalyzed dearomative cyclization was developed that provides facile access to eight types of bridged tetracyclic skeletons bearing various ring sizes and heterocycles. With this method, several skeletons or analogues of natural products, including tubingensin B and dracaenones, were synthesized. Asymmetric dearomative cyclization enables the construction of various enantiomerically enriched bridged polycyclic systems with up to 99 % ee by employing a chiral palladium catalyst.     

R~2上带奇异性的非线性多重调和方程的正整解

该文以 Schauder- Tychonoff不动点定理为工具 ,建立了一类平面上带奇异性的非线性多重调和方程的正的径向对称整体解的存在性定理 ,并给出了解的有关性质 ,所得的结果丰富和发展文 [1 - 4]的结果     

Reaction mechanism of oxidative desulfurization of heterocyclic organic sulfides: a computational study

The potential energy surfaces of the oxidation of two model heterocyclic organic sulfides thiophene and benzothiophene were examined using H₂O₂ and HCO₃H as oxidants adopting CCSD(T), ωB97X-D, M06-2X and B3LYP at the 6-311+G (d,p) level of theory. Stationary points on the potential energy surfaces for the first and second oxidation reaction were fully optimized and characterized. The natural orbital population analysis was also performed to understand the charge distribution. The results suggest that the oxidation of benzothiophene is faster than that of thiophene using both oxidants, and HCO₃H is more efficient than H₂O₂ in oxidation of both sulfides, which are in accordance with the experimental observation. Such results may assist in understanding the reaction mechanism of the oxidative desulfurization of sulfides.     

CPPI的优化策略及实证分析

CPPI策略作为一种重要的投资组合保险策略,在保本基金,保险等领域得到广泛应用,许多关于CPPI策略的研究都是假设市场在连续时间条件下.通过研究基于离散时间条件下的CPPI策略,并引入股指期货作为风险资产,对传统CPPI策略进行修正;同时讨论修正CPPI策略模型和传统CPPI策略模型在不同市场状况下的差异.采用Monte Carlo模拟方法对不同CPPI策略进行仿真,结果表明:在离散时间条件下,当放大乘数m较小时,不同CPPI策略都能实现保本,但不同CPPI策略期末价值差别明显.     

溶液蒸发冻结过程中冰体发展的分形模拟研究

根据溶液在蒸发冻结过程中的复杂性以及液面冰体分布的不规则,结合分形有限扩散聚集(DLA)理论,建立了湿度差作用下溶液蒸发冷冻过程中液面冰体生成、发展过程的数学模型,模拟分析了气流湿度差和气流流速对溶液表面冰体生成、发展的影响.结果表明,利用分形方法可以对溶液蒸发冻结过程中冰体的生成发展进行预测,同时也为研究溶液蒸发冻结和冰体生长提供了新的思路和方法.     

修正特征线有限元法的局部逐点误差估计

本文考虑抛物型对流占优的扩散问题的集中质量特征有限元方法，给出了与小粘性参数无关的局部逐点误差估计，即此格式在边界层外关于小粘性一致收敛．     

Exploring BH_2CN-based hydrophobic hypergolic fuels and effective fuel“additives”: Imidazolylidene cyanoborane complexes

Hydrophobic BH₂CN-based imidazolylidene cyanoborane complexes showed good fuel potential applications, such as water immiscibility, wide liquid range, short ignition delay time (13 ms), high density and good density impulse.     

Improved performance of comprehensive two-dimensional HPLC separation of traditional Chinese medicines by using a silica monolithic column and normalization of peak heights

Performance of comprehensive two-dimensional liquid chromatography system is greatly improved than we reported previously by using a silica monolithic column as for the second dimensional separation. Due to the increase of the elution speed on the second dimensional monolithic column, the first dimensional column efficiency and analysis rate can be greatly improved as comparing with conventionally second dimensional column. The developed system was applied to analysis of methanol extraction of two umbelliferae herbs Ligusticum chuanxiong Hort. and Angelica sinensis (Oliv.) Diels by using CN column as for the first dimensional separation and a silica monolithic ODS column for the second dimensional separation, and the obtained three-dimensional chromatograms were treated by normalization of peak heights with the value of the highest peak or setting a certain value using a software written in-house. It was observed that much more peaks for low-abundant components in TCM extract can clearly be detected here than we reported before, due to the large difference for the amount of components in TCMs' extract. With the above improvements in separation performance and data treatment, totally about 120 components in methanol extraction of Rhizoma chuanxiong and 100 in A. sinensis were separated with UV detection within 130 min. This result meant that both the number of peaks detected increase twice but the analysis time decrease twice if comparing with the previously reported result.     

Synthesis and Improved Properties of Hypergolic Boronium‐Based Ionic Liquids

A series of asymmetric monoimidazolium dihydroboronium‐based ionic liquids (ILs) were synthesized from amine‐boranes. All the resulting ILs were fully characterized by ¹H and ¹³C NMR, IR spectroscopy, elemental analysis or high resolution mass spectrum. Compared with the symmetric bisimidazolium dihydroboronium‐based ILs, these new ILs exhibited improved properties with shorter ignition delay times (IDs), higher densities, and lower phase transition temperature showing the promising application potential as green propellants.     

单分散性银纳米粒子的可控制备

以卤化银或氧化银作为前驱体,室温下以水为溶剂,在较高溶液浓度下,利用化学还原法制备了单分散性银纳米粒子,并通过改变前驱体的种类,实现了粒径可控制备。采取扫描电子显微镜（SEM）、紫外-可见光谱仪（UV-Vis）、X射线-粉末衍射仪（XRD）、X射线-光电子能谱仪（XPS）等对所制备的银纳米粒子的形貌及成分进行了表征。结果显示,所制备的银纳米粒子具有较高的单分散性,粒径在40~150 nm之间,具有面心立方多晶结构。该方法制备的银纳米粒子可用于喷墨打印RFID天线。