567 resultados para 1438


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A capillary array electrophoresis system with rotary corifocal fluorescence scanner was reported. High speed direct current rotary motor combined with a rotary encoder and the reflection mirror has been designed to direct exactly the excitation laser beam. to the array of capillaries, which are symmetrically distributed around the motor. The rotary encoder is introduced to accurately orient the position of each capillary and its output signal triggers the data acquiring system to record. the fluorescence signal corresponding to each capillary. Separations of several amino acids are demonstrated by eight-channel capillary array electrophoresis built by ourselves.

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采用原子对空间距离法表征化合物的三维结构信息.提出了计算端点的频数的方法,与段的频数相比,该方法能更好地描述原子对频数.以不同段的距离,分别采用上述两种频数计算得到化合物的相似度矩阵,然后把相似度衍生为新的变量.运用多元回归分析和人工神经网络分别构造了预测数学模型,并对所得到的预测结果进行了比较.这两种频数均较好地预测了HEPT类化合物的活性.

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Rotating minidisk-disk electrode (RMDDE) was developed by replacing ring electrode of rotating ring-disk electrode (RRDE) with a minidisk electrode. Its applications were demonstrated by studying electrochemical reactions of ferricyanide and divalent copper. The replacement of ring electrode by minidisk electrode results in following advantages. First, the fabrication of RMDDE is easier than that of RRDE with the same electrode material. Second, there is more freedom in choosing electrode materials and sizes, since it is difficult to make thin ring electrodes of RRDE with fragile materials. Third, the replacement of ring electrode by minidisk electrode saves electrode materials, especially rare materials. Finally, the substitution of minidisk electrode for ring electrode allows using multiple minidisks for simultaneous monitoring of multiple components. Therefore, RMDDE is a promising generator-collector system, especially when special generator-collector systems are not commercially available, such as corrosion study and electrocatalysis study of new electrode materials.

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构效关系研究中的分子拓扑指数 ( Am)通常仅代表一个化合物的拓扑特征 ,所以预测手性化合物活性的能力较差 .我们对 Am指数进行了扩展 ,得到 e Am指数 ,并将其应用于手性分子的结构 -活性相关研究 .结果表明 ,由手性拓扑指数得到的 QSAR模型比传统的拓扑指数有更好的统计和预测手性化合物活性的能力

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The dopant/host methodology, which enables efficient tuning of emission color and enhancement of the electroluminescence (EL) efficiency of organic light emitting diodes (OLEDs) based on small molecules, is applied to the design and synthesis of highly efficient green light emitting polymers. Highly efficient green light emitting polymers were obtained by covalently attaching just 0.3-1.0 mol% of a green dopant, 4-(N,N-diphenyl) amino-1,8-naphthaliniide (DPAN), to the pendant chain of polyfluorene (the host). The polymers emit green light and exhibit a high photoluminescence (PL) quantum yield of Lip to 0.96 in solid films, which is attributed to the energy transfer from the polyfluorene host to the DPAN dopant unit. Single layer devices (device configuration: ITO/PEDOT/Polymer/Ca/Al) of the polymers exhibit a turn on voltage of 4.8 V, luminance efficiency of 7.43 cd A(-1), power efficiency of 2.96 lm W-1 and CIE coordinates at (0.26, 0.58). The good device performance can be attributed to the energy transfer and charge trapping from the polyfluorene host to the DPAN dopant unit as well as the molecular dispersion of the dopant in the host.

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用一维1H NMR、13C NMR方法研究了对硝基偶氮苯衍生物的结构,并通过二维1H-1H同核相关(COSY)、13C-1H异核相关(HETCOR)及13C-1H异核远程相关谱进一步地确定了该衍生物的1H谱和13C谱中各谱峰的归属.为研究侧链液晶聚合物结构提供了结构数据。

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本文报道了6种新的丙烯酰胺衍生物的EI谱。在精确质量测量和B/E,B~2/E联动扫描亚稳离子测定的基础上,着重讨论了该类化合物的共同质谱特征:如分子离子失去H_2O的成环反应;产物离子的开环反应;分子内的氢重排反应等。同时,利用Hammett方程讨论了化合物中N-苯基端苯环上不同取代基对特定碎片离子强度的影响

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A transformation model for Laminaria japonica was established from 1993 to 1998, on the basis of which the transgenic kelp with heterologous gene encoding hepatitis B surface antigen (HBsAg) was obtained by using the micro-particle bombardment transformation method. Results of quantitative ELISA showed that HBsAg in transgenic kelp was 0.529 mug/mg soluble proteins on average and the highest value was 2.497 mug/mg, implying that recombinant HBsAg had natural epitope. Further support for the integration of HBsAg gene into kelp genome was obtained by PCR-Southern and total DNA hybridization. Prospect of kelp bio-reactor producing high value materials such as edible HBV vaccine was discussed as well.

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本论文对近10年凹顶藻中分离鉴定的146个结构新颖的次级代谢产物及其生物活性和结构鉴定技术进行了总结,并对采自中国沿海的马岛凹顶藻、俯仰凹顶藻、冈村凹顶藻、复生凹顶藻、齐腾凹顶藻、羽枝凹顶藻、三列凹顶藻和似瘤凹顶藻的次级代谢产物进行了提取分离,结构鉴定,生物活性筛选和化学分类学探讨。 干燥并粉碎的8种凹顶藻样品分别进行有机溶剂提取,粗提物进行硅胶柱、凝胶sephadex LH-20柱、制备薄层和高效液相等色谱方法分离纯化得单体化合物,利用核磁共振和质谱等现代谱学技术鉴定化合物的结构,共计分离鉴定139个化合物,其中新化合物33个,新天然产物6个,部分化合物由不同种中多次分离鉴定,结构类型涵盖倍半萜、二萜、三萜、C15-聚乙酰、吲哚和甾体类等,并且大多为卤代结构。 生物活性筛选和文献检索结果表明,8种凹顶藻的部分次级代谢产物,特别是大量存在的卤代化合物,具有抗菌、细胞毒和拒食杀虫等多种生物活性。 化学分类学分析表明,8种凹顶藻的次级代谢产物,特别是丰富的卤代结构,可为其分类学研究提供重要的分子证据。

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Based on 1997-1998 field investigations in the Changjiang river mouth, rain sampling from the river's upper reaches to the mouth, historical data, and relevant literature, the various sources of Total Nitrogen (TN) and Dissolved Inorganic Nitrogen (DIN) in the Changjiang river catchment and N transport in the Changjiang river mouth were estimated. The export fluxes of various form of were mainly controlled by the river runoff, and the export fluxes of NO3-N, DIN and TN in 1998 (an especially heavy flood year) were 1438 103 tonnes (t) yr(-1) or 795.1 kg km(-2) yr(-1) 1746 10(3) t yr(-1) or 965.4 kg km(-2) yr(-1) and 2849 10(3) t yr(-1) or 1575.3 kg km(-2) yr(-1), respectively. The TN and DIN in the Changjiang river came mainly from precipitation, agricultural nonpoint sources, N lost from fertilizer and soil, and point sources of industrial waste and residential sewage discharge, which were about 56.2% and 62.3%, 15.4% and 18.5%, 17.1% and 14.4%, respectively, of the N outflow at the Changjiang river mouth; maximum transport being in the middle reaches.

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Alpine meadow and shrub are the main pasture types on the Tibetan Plateau, and they cover about 35% of the total land area. In order to understand the structural and functional aspects of the alpine ecosystem and to promote a sustainable animal production system, the Haibei Alpine Meadow Research Station was established in 1976. A series of intensive studies on ecosystem structure and function, including the energy flow and nutrient cycling of the ecosystem, were the main tasks during the first 10 years. Meanwhile, studies with 5 different grazing intensities on both summer and winter pasture have been conducted. In the early years of the 1990s, the research station started to focus its research work on global warming, biodiversity and sustainable animal production systems in pastoral areas. Various methods for improving degraded pasturelands have been developed in the region.

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Along with the widespread and in-depth applications in petroleum prospecting and development, the seismic modeling and migration technologies are proposed with a higher requirement by oil industrial, and the related practical demand is getting more and more urgent. Based on theories of modeling and migration methods for wave equation, both related with velocity model, I thoroughly research and develop some methods for the goal of highly effective and practical in this dissertation. In the first part, this dissertation probes into the layout designing by wave equations modeling, focusing on the target-oriented layout designing method guided by wave equation modeling in complicated structure areas. It is implemented by using the fourth order staggered grid finite difference (FD) method in velocity-stress 2D acoustic wave equations plus perfectly matched layer (PML) absorbing boundary condition. To design target-oriented layout: (a) match the synthetic record on the surface with events of subsurface structures by analyzing the snapshots of theoretical model; (b) determine the shot-gather distance by tracking the events of target areas and measuring the receiving range when it reaches the surface; (c) restrict the range of valid shot-gather distance by drawing seismic windows in single shot records; (d) choose the best trace distance by comparing the resolution of prospecting targets from the simulated records with different trace distance. Eventually, we obtained the observation system parameters, which achieve the design requirements. In the second part, this dissertation presents the practical method to improve the 3D Fourier Finite Difference (FFD) migration, and carefully analyzes all the factors which influence 3D FFD migration’s efficiency. In which, one of the most important parameters of migration is the extrapolating step. This dissertation presents an efficient 3D FFD migration algorithm, which use FFD propagator to extrapolate wavefields over big layers, and use Born-Kirchhoff interpolator to image wavefields over small layers between the big ones. Finally, I show the effectiveness of this hybrid migration method by comparing migration results from 3D SEG/EAGE model with different methods.