Decarboxylative Cyclization of Allylic Cyclic Carbamates: Mechanism Studies and Applications to the Synthesis of Natural Products

The mechanism of decarboxylative cyclization of allylic cyclic carbamates 1 leading to 2-substituted △~3-piperidines and-pyrrolidines, as well as its applications to the total synthesis of (--)codonopsine, are described.     

藏药"西藏猫乳"的色谱指纹谱研究

用75%乙醇回流法提取出藏药"西藏猫乳(生等)"的有效成分并浓缩精制后,采用HPLC梯度洗脱法,在选定的色谱条件{DuPont ZORBAX ODS C18色谱柱(4.6 mm×25 cm),用甲醇(A)-甲酸铵水溶液(pH=3.5,1.0 mL·min-1,B)进行梯度洗脱(甲醇浓度0～10 min,20%～25%;10～20 min,25%～40%;20～55 min,40%～55%;55～75 min,55%～75%;75～85 min,75%～90%),检测波长为290 am}下,对藏药"生等"的提取液进行了有效的分离与检测,并建立了"生等"药材的数字化色谱指纹谱(DFPS).所建立的方法能对藏药的产地归属进行有效的分辨.     

钒氧酞菁薄膜瞬态光电压性能的研究

本文分别用1064nm, 532nm和 355nm激发波长的YAG脉冲激光对所制备的phase Ⅱ结构钒氧酞菁膜Al\phase ⅡVOPc\ITO夹心电池进行瞬态光电压响应研究.随着3种波长激发光脉冲强度的增加, 瞬态光电压信号均增强. 激发光波长1064nm、532nm处于酞菁膜Q-带吸收区肩部, 光电压的极性与激发光入射方向无关, 均为负信号; 而激发光波长 355nm处于酞菁膜B-带, 光电压的极性与激发光入射方向有关, 从ITO极方向激发产生正电压信号, 从A1极激发产生负电压信号. 激发光波长对夹心电池的光电压产生有明显的作用, 光电压产生过程中应存在不同的机理. 这与前文^[1]对同一夹心电池稳态光电压响应研究所推断的结论一致.     

Sequential Power-Dependence Theory

Existing methods for predicting resource divisions in laboratory exchange networks do not take into account the sequential nature of the experimental setting. We extend network exchange theory by considering sequential exchange. We prove that Sequential Power-Dependence Theory—unlike Power-Dependence Theory and most other exchange theories—has a unique point prediction for resource divisions in every network, and we show that these point predictions fare well in comparison to those from established theories.     

Yb3+/Er3+共掺(MLaFn)x(M=0,K;n=3,4;x=1,1.5)纳米材料的控制合成及其上转换发光性质

采用水热与溶剂热结合的方法,在乙二醇-正己醇体系中,通过调节KF与RE(RE=La,Yb,Er)的量比、反应温度和反应时间实现了由LaF_3(六角相)到KLaF_4(立方相、六角相)晶型的控制合成。借助透射电子显微镜(TEM)和X射线粉末衍射(XRD)对样品的结构和微观形貌进行表征。结果表明,当KF/RE比例为2. 25时,制备的样品为片状的六角相LaF_3纳米颗粒;当KF/RE比例为3. 00时,得到具有近似球形的立方相KLaF_4纳米颗粒;当KF/RE比例为4. 25时,得到了六角相(KLaF_4)_(1. 5)纳米颗粒。上转换发射光谱显示:所有的样品在近红外光(980 nm)激发下,均有3个明显的发射峰,在522 nm、544 nm处分别对应于Er~(3+)的~4S_(3/2),~2H_(11/2)→~4I_(15/2)能级跃迁,655 nm处属于Er~(3+)的~4F_(9/2)→~4I_(15/2)能级跃迁。     

The Numerical Solution of Laplace's Equation on a Wedge

Laplace's equation is considered on regions in the plane, withthe boundary having corners; and the double-layer potentialis used to derive a solution. The essential difficulties, boththeoretically and numerically, are reduced to the case in whichthe boundary is a simple open wedge. The theoretical behaviourof the double layer integral equation is studied explicitly,and then piecewise linear and piecewise quadratic collocationmethods are applied to the numerical solution of the equation.The major question of interest is the stability of the inversesof the approximating equations. The behaviour of the numericalmethods is somewhat surprising, and it is much better than pastanalyses would have led one to expect.     

拟桶式空间的强对偶空间值的向量测度

证明了在某种紧性条件下拟桶式空间的强对偶空间值的向量测度的唯一存在性。     

对四-2,3-吡啶并紫菜嗪铬的薄膜电极的光电化学研究

Photocurrent spectra and photoluminescence measurements of the electrode covered by a thin film of chromium tetra-2,3-pyridinoporphyrazine by conventional 3-electrode system method have been performed. The cathodic photocurrent has been measured. The shape of the photocurrent spectrum is similar to that of photoluminescence spectrum. Their intensities change as a function of the applied potential. Two photoluminescence peaks are located at about 470 nm and 520 nm. The results indicate that the thin film behaves like a p-type semiconductor with a band gap width of about 2 eV.     

EXCITATION OF CHLOROPLASTS IN Euglena gracilis IN THE ABSENCE OF LIGHT

Abstract— Challenging Euglena gracilis —a unicellular microorganism that contains chloroplasts—with phenylacetaldehyde induces malondialdehyde formation, sustained red emission and Hill activity. In chloroplasts, phenylacetaldehyde appears to undergo peroxidase catalyzed oxidation to formic acid and triplet benzaldehyde; the latter or, less likely, a precursor thereof promotes lipid peroxidation. Triplet benzaldehyde and/or the excited species formed in lipid peroxidation transfer energy to the chlorophylls. This explanation also applies to spinach chloroplasts preparations, thus accounting for the previous unexplained observation that phenylacetaldehyde induced sustained red emission and Hill activity. A homogeneous picture is now available regarding the intracellular generation of excited states and concomitant excitation of built-in structures.