Multilevel augmentation methods for eigen-problems of compact integral operators

Numerical Algorithms - In this paper, we combine the ideas of multilevel augmentation methods for solving integral equations and the shifted-inverse power method to develop a new multilevel...     

发展高效的不对称Suzuki-Miyaura偶联反应及其合成应用

为解决不对称Suzuki-Miyaura交叉偶联反应中活性和选择性问题,我们设计并发展了一系列结构刚性的手性联芳基单膦配体.在发展高活性的大位阻交叉偶联反应方面,成功地实现了邻位四取代芳基芳基之间的Suzuki-Miyaura交叉偶联,并发展了官能团化的大位阻交叉偶联,在邻位二取代芳基溴苯与二级烷基硼酸之间的大位阻芳基烷基交叉偶联中也取得进展.在发展高立体选择性的交叉偶联反应方面,我们采用手性大位阻单膦配体和底物间次级作用相结合的设计理念,利用苯并噁唑啉酮辅基和芳基间的π-π作用,成功地发展了高立体选择性的邻位酰基化芳基芳基间不对称Suzuki-Miyaura偶联;利用极性基团双(2-氧代-3-噁唑烷基)次磷酰基(BOP)辅基和芳基间的极性π作用,成功地实现了应用性强的邻位氧基取代芳基芳基间高效不对称Suzuki-Miyaura偶联.最后我们首次将高效的不对称SuzukiMiyaura偶联方法学应用于天然产物合成,完成了手性联芳基天然产物Korupensamine A和Korupensamine B的高效不对称合成,并完成天然产物Michellamine B的立体选择性全合成.     

简化的溶胶凝胶法合成LiMn2-xLaxO4及电性能研究

采用以水溶液作为反应介质的简化的溶胶凝胶法制备了LiMn2O4和稀土La掺杂的LiMn1.98La0.02O4粉体材料, 此方法工艺简单, 容易控制, 制备周期短. 利用XRD, SEM对材料粉体进行结构形态表征, 并以合成的材料为正极活性材料测试其充放电性能、循环伏安性能、 电化学阻抗谱性能. 实验结果表明: 材料LiMn2O4和LiMn1.98La0.02O4具有较好的尖晶石结构, 且颗粒分布均匀, 掺杂La的材料循环性能有较大改善. 以LiMn2O4为正极活性物质的扣式电池首次放电比容量129.38 mAh · g-1, 循环20次后容量保持在94%, 以LiMn1.98La0.02O4为正极活性物质的扣式电池首次放电比容量106.77 mAh · g-1, 循环20此后容量保持在96.2%.     

Transport Coefficients of Two-temperature Lithium Plasma for Space Propulsion Applications

Lithium has been proposed as an attractive metal propellant for advanced electric propulsion. In our current work, transport coefficients including the viscosity, thermal conductivity, and electrical conductivity of lithium plasma under both the equilibrium and non-equilibrium conditions are calculated based on a two-temperature model. The collision integrals used in calculating the transport coefficients are significantly more accurate than values used in previous theoretical studies, resulting in more reliable values of the transport coefficients. Results are computed for different degrees of thermal non-equilibrium, i.e. the ratio of electron to heavy particle temperatures, from 1 to 15, with the electron temperature ranging from 300 to 60,000 K in a wide pressure range from 0.0001 to 100 atm. We compare our calculated results with existing published results and discrepancies are found and explained.     

Mechanism and Cellular Kinetic Studies of the Enhancement of Antioxidant Activity by Using Surface‐Functionalized Gold Nanoparticles

The enhanced antioxidant activity of surface‐functionalized gold nanoparticles (AuNPs) synthesized by self‐assembly has attracted great attention, but little is known about the mechanism behind the enhanced activity. To address this challenge, the antioxidant activity of Au@PEG3SA (i.e., surface‐functionalization of spherical AuNPs with the antioxidant salvianic acid A) was used as an example to illustrate the mechanism of the enhanced activity. Evaluation of the antioxidant activity was performed in a radical‐scavenging reaction between Au@PEG3SA and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical. As expected, the rate constant for the reaction of Au@PEG3SA with DPPH was about nine times greater than that for the salvianic acid A monomer. A comparative analysis of the spectral characteristics of Au@PEG3SA and the salvianic acid A monomer further imply that the enhancement of the antioxidative reaction kinetics may be ascribed to the variation in the transition state for the DPPH‐radical scavenging reaction through π–π stacking interactions between and among adjacent groups on the surface of Au@PEG3SA. On the other hand, the kinetic enhancement of Au@PEG3SA on reactive‐oxygen‐species (ROS) scavenging can be observed in living cells and in vivo, which possibly provides new insight for the bioapplication of self‐assembly of surface‐functionalized AuNPs.     

微腔等离子体放电过程的数值研究

采用2维自洽完全流体模型,数值研究了阳极为通孔的高气压微腔放电结构中等离子体参数的变化过程。模拟结果获得了当氩气压强为13.3 kPa时,放电中的电势分布、等离子体密度分布、径向电场分布和电子温度分布等重要参数的演化过程。模拟结果表明在放电过程中,阴极附近的电场由轴向电场逐步转变为径向电场,等离子体密度最大值位于放电腔中间处,并随时间推移由阳极附近向阴极附近移动,电子温度的最大值出现在阴极环形鞘层区域。     

气相传输平衡技术制备LiGaO2薄膜

为获得与GaN薄膜晶格失配小的衬底材料,报道了利用气相传输平衡技术(VTE)在(100)-βGa2O3单晶衬底上制备高度[001]取向LiGaO2薄膜的方法。经过X射线衍射分析表明得到的薄膜是由单相LiGaO2组成。利用扫描电镜(SEM)观察表面形貌,发现经气相传输平衡技术处理得到的薄膜表面形貌主要受温度的影响,表面晶粒尺寸随温度上升而增大。而X射线衍射测试表明随着温度上升,所得到的薄膜也从多晶向单晶化转变。在经过退火处理后,通过观察吸收谱发现LiGaO2薄膜中产生色心,并且色心的种类与温度有关。表明可以通过气相传输平衡技术技术,在远低于LiGaO2熔点的温度制备外延GaN用(001)LiGaO2∥(100)β-Ga2O3复合衬底。     

缺锌对大鼠消化系癌发生的影响

在缺锌Ｗｉｓｔｅｒ大鼠模型中，用ＭＮＮＧ作为致癌剂，进行致消化系癌的实验研究。在３３例缺锌大鼠的实验组中发生９例胃癌，在４０例对照组中发生２例胃癌，差异非常显著。在实验组与对照组中均未发生其它消化系脏器癌变。     

Fluorescent-tagged block copolymer as an effective and green inhibitor for calcium sulfate scales

Allyloxy polyethoxy ether (APEG) and succinic anhydride were used to prepare allyloxy polyethoxy carboxylate (APEL). 8-Hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt (PY) was reacted with allyl chloride to produce fluorescent monomer 8-allyloxy-1,3,6-pyrene trisulfonic acid trisodium salt (PA). APEL and PA were copolymerized with maleic anhydride (MA) to synthesize PA tagged no phosphate and nitrogen free CaSO₄ inhibitor MA–APEL–PA. Structures of PA, APEG, APEL, and MA–APEL–PA were identified by ¹H NMR. The observation shows that the dosage of MA–APEL–PA plays an important role on CaSO₄ inhibition. The effect on formation of CaSO₄ was investigated with scanning electron microscope (SEM) analysis. Relationship between MA–APEL–PA’s fluorescent intensity and its dosage was studied. Correlation coefficient R ² of MA–APEL–PA fluorescent intensity and MA–APEL–PA dosage is 0.9991.