Optical properties of self-assembled ternary In(GA/Al)As quantum dots on (100) and (N 1 1)B InP substrates

In this paper, we investigated the self-assembled quantum dots formed on (100) and (N11)B (N = 2, 3, 4, 5) InP substrates by molecular beam epitaxy (MBE). Two kinds of ternary QDs (In0.9Ga0.1As and In0.9Al0.1As QDs) are grown on the above substrates; Transmission electron microscopy (TEM) and photoluminescence (PL) results confirm QDs formation for all samples. The PL spectra reveal obvious differences in integral luminescence, peak position, full-width at half-maximum and peak shape between different oriented surfaces. Highest PL integral intensity is observed from QDs on (411)B surfaces, which shows a potential for improving the optical properties of QDs by using high-index surface. (C) 2000 Elsevier Science B.V. All rights reserved.

吲哚生物碱Desbromoarborescidine A 的全合成及烯胺C-亚磺酰化反应研究

从新几内亚核桃木的树皮中分离得到的吲哚类喹诺里西定生物碱10-Desbromoarborescidine A，因发现其具有阻滞钙离子通道的活性而倍受关注。10-Desbromoarborescidine A由A、B、C、D���个环组成，只有一个手性中心，是吲哚生物碱中结构较简单的一种，常作为此类生物碱全合成方法的模型化合物。但迄今为止，能高效而简便的实现手性10-Desbromoarborescidine A不对称全合成方法线路不多，大多数以不对称诱导的方式建立其手性中心，手性催化的方式仅有一例金属催化。从逆合成分析可知，Desbromoarborescidine A的全合成可以通过亚胺不对称催化还原进行关键的手性中心构建，而本课题组在之前的研究中通过手性有机小分子催化剂的发展，已将三氯硅烷氢转移还原亚胺发展成了一类简便实用、高效、高对映选择性并具有优良底物适应范围的不对称催化反应，我们希望以这一反应作为关键手段，发展一条Desbromoarborescidine A及其类似物不对称合成新路线。 根据我们设计的新路线，首先成功合成了其关键中间体，然后我们进行了关键的不对称催化尝试。用本实验室已有的高性能有机小分子催化剂虽得到了较好的对应选择性，但是产率很低。同时，为了验证整条线路的可行性，我们也用消旋的中间体进行拉通线路的尝试。但不幸的是，在脱除保护基时遇到了很大困难。尝试换不同的保护基，或改变脱保护基的顺序，都未能成功合成目标产物。究其原因可能是由于吲哚的特殊性造成的，吲哚类亚胺与常规的芳香亚胺有较大的差异，其NH基团无论保护还是不保护，对与其2位相联接的C=N双键均有很大的影响，导致其不对称催化还原难以进行。另外，由于所设计的还原产物含有处在吲哚苄位的胺基，稳定性较差，造成保护基脱除困难。 烯胺C-亚磺酰化反应是本课题组最近发现的一个新反应，之前未见文献报道。本研究对该反应进行了反应条件优化和底物扩展，发现带Cbz，Ac，COt-Bu，CO2Et，Bz等保护基的一系列环状和非环状烯胺在亚磺酸钠、DMAc和MeSiCl3的共同作用下能高效高产率生成β-胺基烯基亚砜类新化合物，为合成多官能团化的烯基亚砜新化合物提供了一条简便实用的途径。 The main constituent of Dracontomelum mangiferum B1, indoloquinolizidine alkaloid 10-Desbromoarborescidine A, has drawn great attention due to its calcium channel blocking activity. Its molecular structure is relatively simple compared with the other alkaloids of the same type, which has only one chiral center, albeit with four cycles A, B, C, and D. This compound is often used as a model target for exploring different strategies for the total synthesis of indole alkaloids. Nevertheless, so far there still lack practical and highly efficient methods for the asymmetric total synthesis of 10-Desbromoarborescidine A. Most of the current available methods rely on stoichiometric asymmetric synthesis for the construction of the chiral center. There is only one example reporting utilization of asymmetric catalysis, but with transition metal complex as the catalyst. Our retrosynthetic analysis shows that catalytic asymmetric reduction of imine could be used as the key step for the construction of the chiral center of Desbromoarborescidine A. Since in the previous studies our group has developed the asymmetric reduction of imines by trichlorosilane into a practical and highly efficient and enantioselective method using newly designed chiral organocatalysts, we hope to apply this method to develop a novel synthetic route for the total synthesis of Desbromoarborescidine A and its analogues in this study. According to the newly designed synthetic route, we first accomplished the synthesis of the key intermediates which was then examined for the critical asymmetric catalysis. The asymmetric reduction using the highly efficient organocatalysts, developed in our lab afforded high ee but poor yield. We tried different reaction conditions to improve the yield, but failed to get any good results. Simultaneously, to vertify the feasibility of the synthetic route we designed, we also tired to go through the route toward the racemic synthesis of Desbromoarborescidine A. But unfortunately, protection and deprotection proved to be big hurdles. All the different protection groups and different sequences of protection and deprotection we tried failed to get us through the designed synthetic sequence and furnish the final product. Most likely, the indole part is the culprit behind the failures.The NH group of the indole, no matter protected or not, may impact the catalytic asymmetric reduction of C-N double bond connected with 2-C. Additionally, the reduction product we designed contains an amino group in the β-position of the indole, which may cause problems due to its instability. C-sulfenylation of enamines is a novel reaction discovered recently by our group, which has not been seen before in the literature. In this study, optimization of the reaction conditions and exploration of the substrate scope were further undertaken for this reaction, which reveal that a series of enamines with N-Cbz, Ac, COt-Bu, CO2Et protection groups could all undergo smooth C-sulfinylations with the comined use of sodium benzene sulphinate, DAMc and MeSiCl3, efficiently furnishing the β-amino vinylsulfoxide products in high yield, affording a practical and highly efficient methods for synthesis of functional vinylsulfoxides.

贡嘎山麦吊杉(Plcea brachytyly)群落的结构研究

群落结构的确定是群落研究的基础。本文立足于个体、种群、群落三级水平，从空间和时间两种概念出发，对贡嘎山麦吊杉(Picea brachytyla)群落的结构进行了研究。经初步统计，在麦吊杉林分布的主要地段共有维管束植物93科、263属、约560种，其中种子植物71科、220属、479种。通过种子植物区系地理成份的分析表明，麦吊杉群落的区系组成具有区系成分复杂、特有现象明显和成分古老的特点。在生活型组成上，麦吊杉群落的高位芽植物所占比例最大，其中小高位芽植物最多，而在叶级谱中小叶类型占有较明显的优势。通过种—面积曲线和重要值—面积曲线两种方法求得的麦吊杉群落的最小面积在800-900平方米之间，实际应用时可选用1000平方米的保守面积。在物种的综合特征分析中，群落表现出优势种明显的特征，而存在度II占有最大的比例。物种多样性的研究表明，贡嘎山麦吊杉群落的Shannon-Wiener指数在2.33-3.26之间，Simpson指数在0.43-0.70之间，种间相遇(PIE)在0.42-0.79之间，而以Shannon-Wiener指数为基础的均匀度在34.45%-62.90%之间。麦吊杉群落的垂直结构较为复杂，分层明显。一般可划分出乔木层、灌木层、草本层和活地被层四个基本层次，乔木层通常还可划分为2-3个亚层，由高海拔至低海拔成层现象有逐渐复杂的趋势。构成麦吊杉群落的层片类型较多，其中以常绿针叶大高位芽植物为其建群层片。麦吊杉林中的层外植物较丰富，种子植物、蕨类植物、以及苔藓植物和地衣植物皆可构成其空中层片，其中苔藓植物生长繁茂，反映出群落结构的完整性。麦吊杉群落结构的水平分化较明显，经研究，其密度值在0.32-0.41之间，平均距离在1.56-1.41之间。应用Raunkiaer的频度指数方法对整个麦吊杉群落的种群频度进行调查后表明，其频度分布情况与Raunkiaer的频度定律基本上是符合的，即A>B> C<D<E。通过应用负二项式K值、方差/均值比率、平均指数、聚块指数，以及Norisita格局指数等常用指标对麦吊杉群落优势种群的分布格局测定表明，除麦吊杉和铁杉(Tsuga chinensis)呈Poisson分布外，其余优势种多呈集群分布。在种间联结测定时，本文选用了联结系数方法对62种乔木和60种灌木的联结特征进行了测定，结果表明，该群落可以细划为四个结构组分，各组分都有其不同的种群生态组合。本文以立木级结构代替种群年龄结构，对麦吊杉种群的动态进行了分析，结合各种群存活曲线的分析，表明麦吊杉种群正界于相对稳定与衰退时期，由于补充率小于死亡率，衰退的趋势已明显表现出来。本文还从区系成分、生活型组成、生境特点、层片结构、结构分化等方面对麦吊杉群落的特点进行了分析和讨论，并对麦吊杉种群分布格局的成因进行了探讨。

Inclusive pi(0), eta, and direct photon production at high transverse momentum in p plus p and d plus Au collisions at root s(NN)=200 GeV

We report a measurement of high-p(T) inclusive pi(0), eta, and direct photon production in p + p and d + Au collisions at root s(NN) = 200 GeV at midrapidity (0 < eta < 1). Photons from the decay pi(0) -> gamma gamma were detected in the barrel electromagnetic calorimeter of the STAR experiment at the Relativistic Heavy Ion Collider. The eta -> gamma gamma decay was also observed and constituted the first eta measurement by STAR. The first direct photon cross-section measurement by STAR is also presented; the signal was extracted statistically by subtracting the pi(0), eta, and omega(782) decay background from the inclusive photon distribution observed in the calorimeter. The analysis is described in detail, and the results are found to be in good agreement with earlier measurements and with next-to-leading-order perturbative QCD calculations.

Instability of anthocyanin accumulation in Vitis vinifera L. var. Gamay Freaux suspension cultures

The inherent instability of metabolite production in plant cell culture-based bioprocessing is a major problem hindering its commercialization. To understand the extent and causes of this instability, this study was aimed at understanding the variability of anthocyanin accumulation during long-term subcultures, as well as within subculture batches, in Vitis vinifera cell cultures. Therefore, four cell line suspensions of Vitis vinitera L. var. Gamay Freaux, A, B, C and D, originated from the same callus by cell-aggregate cloning, were established with starting anthocyanin contents of 2.73 +/- 0.15, 1.45 +/- 0.04, 0.77 +/- 0.024 and 0.27 +/- 0.04 CV (Color Value)/g-FCW (fresh cell weight), respectively. During weekly subculturing of 33 batches over 8 months, the anthocyanin biosynthetic capacity was gradually lost at various rates, for all four cell lines, regardless of the significant difference in the starting anthocyanin content. Contrary to this general trend, a significant fluctuation in the anthocyanin content was observed, but with an irregular cyclic pattern. The variabilities in the anthocyanin content between the subcultures for the 33 batches, as represented by the variation coefficient (VC), were 58, 57, 54, and 84% for V vinifera cell lines A, B, C and D, respectively. Within one subculture, the VCs from 12 replicate flasks for each of 12 independent subcultures were averaged, and found to be 9.7%, ranging from 4 to 17%. High- and low-producing cell lines, VV05 and VV06, with 1.8-fold differences in their basal anthocyanin contents, exhibited different inducibilities to L-phenylalanine feeding, methyl jasmonate and light irradiation. The low-producing cell line, showed greater potential in enhanced the anthocyanin production.