2-cyanoprop-2-yl dithiobenzoate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile targeting a polymer with a higher molecular weight

The reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylonitrile (AN) mediated by 2-cyanoprop-2-yl dithiobenzoate was first applied to synthesize polyacrylonitrile (PAN) with a high molecular weight up to 32,800 and a polydispersity index as low as 1.29. The key to success was ascribed to the optimization of the experimental conditions to increase the fragmentation reaction efficiency of the intermediate radical. In accordance with the atom transfer radical polymerization of AN, ethylene carbonate was also a better solvent candidate for providing higher controlled/living RAFT polymerization behaviors than dimethylformamide and dimethyl sulfoxide. The various experimental parameters, including the temperature, the molar ratio of dithiobenzoate to the initiator, the molar ratio of the monomer to dithiobenzoate, the monomer concentration, and the addition of the comonomer, were varied to improve the control of the molecular weight and polydispersity index. The molecular weights of PANS were validated by gel permeation chromatography along with a universal calibration procedure and intrinsic viscosity measurements. H-1 NMR analysis confirmed the high chain-end functionality of the resultant polymers.

Syntheses and reactions of heterometallic complexes of nickel and copper with tetrathiotungstates. The molecular structures of [Ph(4)P](2)[S2W(mu-S)(2)Ni(S-2)] and W(mu-S)(4)Cu-2(PPh(3))(4)center dot py

Reaction of [Ph(4)P]2WS4 With NiCl2 in methanol solution in the presence of NaOCH3 leads to the formation of [Ph(4)P](2) [S2W(mu-S)(2)Ni(S-2)] (I) A Similar reaction between (NH4)(2)WS4 and NiCl2 under O-2 atmosphere in the presence of Ph(4)PCl or (n)Bu(4)NCl affords [Ph(4)P](2)([(S-2)W(O)(mu-S)(2)]Ni-2] (IIa) and [(n)Bu(4)N](2)([(S-2)W(O)(mu-S)(2)]Ni-2} (IIb) Under argon the same reaction gives [Ph(4)P](2)[Ni(WS4)(2)] (IIIa) and [(n)Bu(4)N](2)[Ni(WS4)(2)] (IIIb). [Ph(4)P](2)[Ni(WOS3)(2)] (IV) and [Ph(4)P](2)[Ni(WO2S2)(2)] (V) can be prepared from the reaction of [Ph(4)P]2WOS3 and [Ph(4)P]2WO2S2 with NiCl2. Treatment of (NH4)(2)WS4 with CuCl in the presence of PPh(3) in boiling pyridine produces W(mu-S)(4)Cu-2(PPh(3))(3) (VI), which can further react with excess PPh(3) to give W(mu-S)(4)Cu-2(PPh(3))(4) . py (VII). Complex I crystallizes in the space group P2(1)/n with the cell parameters: a = 20.049(4), b = 17.010(4), c = 14.311(7) Angstrom; beta = 110.24(3)degrees and Z = 4; R = 0.058 for 4267 independent reflections. The structural study confirms that complex I contains two terminal sulfide ligands, two bridging sulfide ligands, a side-on disulfide ligand, and a planar central W(mu-S)(2)Ni four membered ring. Complex VII crystallizes in the space group C2/c with the cell parameters: a = 26.436(8), b = 20.542(6), c = 19.095(8) Angstrom; beta = 125.00(3)degrees and Z = 4; R = 0.080 for 3802 independent reflections. The structural study reveals a perfect linear arrangement of the three metal atoms Cu-W-Cu.

细胞色素C的电化学行为研究

本文评述了细胞色素C电化学研究的发展概况,重点介绍了细胞色素C在促进剂作用下的电化学行为、促进荆种类、影响促进作用的因素及促进机理。

[(C_9H_7)_2PrClTHF]_2的合成及晶体结构

三茚基或取代三茚基稀土有机配合物的合成和X光晶体结构已有报道,但至今未见到有关二茚基稀土氯化物的分子结构的报道。我们采用无水PrCl_3和2mol茚基钠在THF中于较高温度下,长时间充分反应的方法成功地分离得到了二茚基镨氯化物

高聚物状态方程的研究

在高分子状态方程的研究中,多数理论工作集中在高分子液态体系上,而对高分子固体状态方程的理论研究并不多,在对其压强(p),体积(V)及温度(T)之间关系的描述上,多采用经验或半经验的状态方程。 当一高分子体系处于平衡状态时,其压

极化SAR图像海面船只监测方法研究

船只监测不论是在民用还是军用方面都有广阔的应用前景。极化合成孔径雷达（PolSAR）可以测量目标的极化散射特性，能够提高舰船检测的准确度和分类精度。论文以工程应用为背景，以深刻理解PolSAR图像成像原理及理论为基础，重点围绕PolSAR图像船海对比度增强和海上目标识别等方面开展了研究。 本文在文献综述的基础上，全面分析了单极化和PolSAR图像舰船目标检测的研究现状。在现有的PolSAR图像目标检测方法基础上，针对双极化数据首次提出二维卷积方法提高船海对比度；针对全极化数据改进广义最优化方法，构造极化特征向量，将回波强度和极化散射特征有机结合，提高船海对比度。上述两种方法能解决船只回波强度和海面回波强度相近或高海况下船目标检测问题。将聚类方法应用到海上目标识别中，采用非监督分类-模糊聚类可以将船只、海上人造目标、船尾迹等识别开来，在海上目标识别方面将有广阔的应用前景。 应用极化电磁波基本理论，将极化熵概念应用到船只监测。首次采用Bragg模式和双尺度模式分析两种不同极化熵随着入射角、波数和风场的变化情况，从而确定在低风速下Cloude熵相对Touzi熵更适合船只监测。

Rhein induces apoptosis and cell cycle arrest in human hepatocellular carcinoma BEL-7402 cells

Rhein, an anthraquinone derivative of rhubarb, inhibits the proliferation of various human cancer cells. In this paper, we focused on studying the effects of rhein on human hepatocelluar carcinoma BEL-7402 cells and further understanding the underlying molecular mechanism in an effort to make the potential development of rhein in the treatment of cancers. Using MTT assay and flow cytometry, we demonstrate a critical role of rhein in the suppression of BEL-7402 cell proliferation in a concentration- and time-dependent manner. The increase of apoptosis rate was observed after incubation of BEL-7402 cells with rhein at 50-200 mu M for 48 hours, and the cells exhibit typical apoptotic features including cellular morphological change and chromatin condensation. Moreover, rhein-induced cell cycle S-phase arrest. Additionally, after rhein treatment, expression levels of c-Myc gene were decreased, while those of caspase-3 gene were increased in a dose-dependent manner by using real-time PCR assay. The results demonstrate for the first time that cell cycle S-phase arrest is one of the mechanisms of rhein in inhibition of BEL-7402 cells. Rhein plays its role by inducing cell cycle arrest via downregulation of oncogene c-Myc and apoptosis through the caspase-dependent pathway. It is expected that rhein will be effective and useful as a new agent in hepatocelluar carcinoma treatment in the future.

Separation and determination of the major active components in Tibetan folk medicinal species Swertia franchetiana by HPLC with DAD

A sensitive and specific reversed-phase high performance liquid chromatography (RP-HPLC) method with diode array detection (DAD) was established for the quantitative determination of the nine active components, namely, swertiamarin (SWM, 1), mangiferin (MA, 2), gentipicroside (GE, 3), sweroside (SWO, 4), isoorientin (IS, 5), swertisin (SWS, 6), swertianolin (SWN, 7), 7-O-[alpha-L-rhamnopyranosyl-1 -> 2)-beta-D-xylopyranosyl]-1,8-dihydroxy-3-methoxyxanthone (RX, 8), and bellidifolin (BE, 9) used as the external standard, in Tibetan folk medicinal species Swertia franchetiana. Based on the baseline chromatographic separation of most components from the methanolic extract of Swertia franchetiana on a reversed-phase Eclipse XDB-C8 column with water-acetonitrile-formic acid as mobile phase, the nine components were identified by comparison with standard samples and qualified by using the external standard method with DAD at 254 nm. The correlation coefficients of all the calibration curves were found to be higher than 0.9980. The relative standard deviations (RSDs) of the peak areas and retention times for the nine standards were less than 2.07% and 2.86%, respectively.

气压伺服及气液连动控制发展概况综述

本文综述了气压伺服应用情况、发展概况、存在的问题、气液连动的重要性及发展概况。

最近130ka来黄土物质化学风化强度的空间格局

Chemical weathering intensity of loess deposits is largely determined by three factors: chemical weathering in source regions, grain size and post-depositional weathering. The third factor is influenced by climatic conditions such as precipitation and temperature, and the dust sedimentation rate in the area of deposition. Previous studies have shown that the (CaO+MgO+Na2O)/TiO2 ratio of decarbonated residue from loess is independent of grain size changes and thus is a reliable proxy for chemical weathering. However, the validity of (CaO+MgO+Na2O)/TiO2 to describe changes in monsoon intensity requires further study. In this study, 48 sections over the last glacial-interglacial cycle on the Chinese Loess Plateau were sampled, and the major elemental concentrations of 248 decarbonated residue samples were measured to investigate the utility of the (CaO+MgO+Na2O)/TiO2 ratio as a proxy for changes in monsoon intensity. Results show that the (CaO+MgO+Na2O)/TiO2 ratio, is relatively more sensitive to climate change than other indexes independent of grain size, and is not affected substantially by sedimentation rate. Assuming the weathering regime is relatively stable in the loess source regions, the (CaO+MgO+Na2O)/TiO2 ratio is a reliable proxy for the intensity of summer monsoon. A decreasing (CaO+MgO+Na2O)/TiO2 ratio from northwest to southeast both in loess and paleosols indicates that the Chinese Loess Plateau is in the control of the East Asian summer monsoon during both interglacial and glacial times. In addition, the spatial distributions of (CaO+MgO+Na2O)/TiO2 ratios show a greater north-south gradient during interglacial periods than during glacial periods. This may suggest that the spatial precipitation gradient, controlled by the summer monsoon, is steeper during interglacials than in glacials.

Understanding student information behavior in relation to electronic information services: lessons from longitudinal monitoring and evaluation Part 2

Urquhart, C. & Rowley, J. (2007). Understanding student information behavior in relation to electronic information services: lessons from longitudinal monitoring and evaluation Part 2. Journal of the American Society for Information Science and Technology, 58(8), 1188-1197. Sponsorship: JISC

Credit and Debt in medieval England, c.1180-c.1350

Schofield, Phillipp, and N. J. Mayhew, eds., Credit and Debt in medieval England, c.1180-c.1350 (Oxford: Oxbow Books, 2002), pp.x+164 RAE2008

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