Two new sesquiterpenes from the leaves of Nicotiana tabacum and their anti-tobacco mosaic virus activities

Two new sesquiterpenes, nicotianasesterpenes A and B (1 and 2), together with five known sesquiterpenes (3–7) were isolated from the leaves of Nicotiana tabacum. Their structures were determined mainly by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. The anti-tobacco mosaic virus (anti-TMV) activities of compounds 1–7 were evaluated. The results revealed that compound 1 exhibited high anti-TMV activities with inhibition rates of 33.6%. This rate is high than that of positive control. The other compounds also showed potential activities with inhibition rates in the range of 18.8–28.4%, respectively.     

导热膨胀石墨/聚醚酰亚胺复合材料的制备与性能

利用膨胀石墨(EG)经高温处理后比表面积大的特点, 以膨胀石墨作为导热填料, 通过球磨和热模压方法制备了膨胀石墨/聚醚酰亚胺(PEI)导热复合材料, 并对其加工过程、 微观形貌、 热性能和导热性能进行了研究. 结果表明, 球磨处理可以打破膨胀石墨的“泡沫”状态并减少石墨纳米片间的间隙, 热压可以诱使和促进石墨纳米片沿着水平方向排列和取向, 从而显著提升了复合材料的平面内导热性能. 当膨胀石墨在复合材料中的质量分数为20%时, EG/PEI复合材料的面内导热系数为2.38 W?m^?1?K^?1. 与PEI相比, 复合材料导热系数的增幅约为12倍. 所制备的EG/PEI复合材料均具有良好的散热能力、 较好的热稳定性和较高的储能模量, 是一种综合性能优异的导热材料.     

Synthesis of new truxene based organic sensitizers for iodine-free dye-sensitized solar cells

Developing arylamine photosensitizers with high extinction coefficients, proper electronic structures, and steric properties is warranted for the dye-sensitized solar cells (DSCs) employing iodine-free redox shuttles. Two new organic sensitizers (M21 and M22) featuring unsymmetrical truxene-based triarylamine donor have been synthesized and compared to its reference sensitizer M4. The effects of unsymmetrical truxene-based triarylamine donors were investigated by their absorption spectra, electrochemical and photovoltaic properties. The incorporation of strong electron donor unit (i.e., dipropylfluorene and 4-methoxybiphenyl) has resulted in an improved light harvesting capacity, and thus photocurrent as well as efficiency of cells. M22 sensitized DSCs employing the Co(II/III)tris(1,10-phenanthroline)-based redox electrolyte affords a short circuit photocurrent of 13.1 mA cm⁻², an open circuit voltage of 861 mV, and a fill factor of 0.70, corresponding to an overall conversion efficiency of 7.89% under standard AM 1.5 sunlight.     

Raman study of pure,C‐coated and Co‐doped LiFePO4: thermal effect and phase stability upon laser heating

Pure, C‐coated and Co‐doped LiFePO₄ were prepared by the hydrothermal method. X‐ray diffraction patterns showed no impurity phase after carbon coating and Co doping. Thermal effect and phase stability of the three samples as a function of irradiation power density were systematically studied by means of Raman spectroscopy. The correlations between the power density of the excitation laser and the surface structure were accurately established and compared. Results show that the features of highest phase stability, excellent thermal stability and the most sensitive to power density were displayed in the samples of pure, C‐coated and Co‐doped LiFePO₄, which were mainly ascribed to the grain size, thermal conductivity and degree of order of the olivine structure, respectively. The results also indicate that particular attention should be paid in characterizing the structure and component of the material surface by Raman spectroscopy, where the thermal effect of laser irradiation will possibly alter material surface and thus induce wrong conclusions. Copyright © 2011 John Wiley & Sons, Ltd.     

Mixed finite element methods for incompressible flow: Stationary Stokes equations

In this article, we develop and analyze a mixed finite element method for the Stokes equations. Our mixed method is based on the pseudostress‐velocity formulation. The pseudostress is approximated by the Raviart‐Thomas (RT) element of index k ≥ 0 and the velocity by piecewise discontinuous polynomials of degree k. It is shown that this pair of finite elements is stable and yields quasi‐optimal accuracy. The indefinite system of linear equations resulting from the discretization is decoupled by the penalty method. The penalized pseudostress system is solved by the H(div) type of multigrid method and the velocity is then calculated explicitly. Alternative preconditioning approaches that do not involve penalizing the system are also discussed. Finally, numerical experiments are presented. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2010     

Thermochemical hole burning on a triethylammonium bis-7,7,8,8-tetracyanoquinodimethane charge-transfer complex using single-walled carbon nanotube scanning tunneling microscopy tips

The present article describes a thermochemical hole burning (THB) effect on a charge-transfer complex triethylammonium bis-7,7,8,8-tetracyanoquinodimethane (TEA(TCNQ)(2)) using single-walled carbon nanotube (SWNT) scanning tunneling microscopy (STM) tips, which demonstrates the possibility of optimizing the THB storage materials and the writing tips for ultrahigh-density data storage. TEA(TCNQ)(2) is proven to be a high-performance THB storage material, which gives deeper holes and larger hole depth-to-diameter ratio as compared to the previous materials dipropylammonium bis-7,7,8,8-tetracyanoquinodimethane and N-methyl-N-ethylmorpholinium bis-7,7,8,8-tetracyanoquinodimethane. Instead of conventional Pt/Ir STM tips, SWNT tips made by a unique chemical assembly technique we developed have been shown to be excellent writing tips for greatly decreasing the hole sizes and increasing the storage density. Possible reasons for the improvements on the storage performance were discussed.     

稀土离子及其配合物对二棕榈酰磷脂酰乙醇胺酯双层结构的影响

随着稀土在工农业和医疗保健上的广泛应用，稀土的生物无机化学研究受到了普遍的关注．以往的研究多集中在稀土离子的宏观毒理学[1]，而研究稀土离子与生物膜的作用较少[2]．稀土的生物小分子配体的配合物与生物膜作用的研究则未见报道．本文介绍了用拉曼光谱研究稀土离子及其柠檬酸、二乙三胺五乙酸（DTPA）配合物对二栋相酸乙醇胺（DPPE）脂双层的流动性以及碳氢链的构象转变和晶格有序性排列的影响．1实验部分DPPE系Sigma公司产品。La2O3（99．9％）为跃龙化工厂产品，柠檬酸、DTPA为北京化工厂产品．L3Cl3溶液由L32O3溶于盐酸…     

Molecular positional order in a dipalmitoylphosphatidic acid Langmuir–Blodgett monolayer by atomic force microscopy

Langmuir–Blodgett monolayers of dipalmitoylphosphatidic acid were studied by using atomic force microscopy on the large- and nano-scale. A molecularly resolved image was achieved at high surface pressure. The monolayer shows a dramatic long-range orientational and positional ordering of molecular organization of aliphatic tails. The ordered molecular arrangement of aliphatic tails may result from the strong intermolecular hydrogen bonding interactions between adjacent phosphate groups in the polar region.     

含有未建模动态的多输入非线性串级系统的自适应控制

本文对一大类含有未知参数和未建模动态的多输入非线性串级系统,基于backstepping递推设计方法,进行了自适应控制设计,得到的参数自适应律的阶次等于未知参数的个数,故该设计是非过参数化的.当自适应控制律作用于该系统时,闭环系统的所有信号是有界的.并且给出了第一子系统的状态界的一个估计.     

基于兴趣点检测的目标识别算法

为了有效地确定目标位置,提出了一种基于兴趣点检测的目标识别方法.根据像素点的灰度和边缘强度信息,确定兴趣点的分布位置.以兴趣点为中心,利用位势函数构建目标函数,目标函数取最大值的位置确定为目标位置.提出了一种改进的概率混沌优化算法求解目标函数的最大值.概率混沌优化算法将搜索空间分为原始搜索空间和精搜索空间,分别以不同的概率同时对两个空间进行搜索,并逐渐增大精搜索空间的搜索概率,从而可在确保算法具有全局寻优能力的前提下加快寻优速度.研究结果表明,该方法可有效地确定目标位置,且结果不受目标平移、旋转、缩放、甚至变形等影响,仿真结果验证了该方法的有效性.