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21.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(11):885-888
As part of an exploration of new coordination polymers, a cadmium‐dicyanamide complex, namely poly[benzyltriethylammonium [tri‐μ‐dicyanamido‐κ6N 1:N5‐cadmium(II)]], {(C13H22N)[Cd(C2N3)3]}n , has been synthesized by the reaction of benzyltriethylammonium bromide, cadmium nitrate tetrahydrate and sodium dicyanamide in aqueous solution, and characterized by single‐crystal X‐ray diffraction at room temperature. In the crystal structure, each CdII cation is coordinated by six nitrile N atoms from six anionic dicyanamide (dca) ligands to furnish a slightly distorted octahedral geometry. Neighbouring CdII cations are linked by dicyanamide bridges to construct a two‐dimensional anionic layer coordination polymer. One amide N atom in the bridging dca ligand is disordered over two sites. The cations lie between the anionic frameworks and there are no hydrogen‐bond interactions between the cations and anions. The organic cations are not involved in the formation of the supramolecular network. 相似文献
22.
《Journal of separation science》2017,40(13):2688-2693
Radix Sophorae flavescentis is generally used for the treatment of different stages of prostate cancer in China. It has ideal effects when combined with surgical treatment and chemotherapy. However, its active components are still ambiguous. We devised a comprehensive two‐dimensional PC‐3 prostate cancer cell membrane chromatography system for screening anti‐prostate cancer components in Radix Sophorae flavescentis . Gefitinib and dexamethasone were chosen as positive and negative drugs respectively for validation and optimization the selectivity and suitability of the comprehensive two‐dimensional chromatographic system. Five compounds, sophocarpine, matrine, oxymatrine, oxysophocarpine, and xanthohumol were found to have significant retention behaviors on the PC‐3 cell membrane chromatography and were unambiguously identified by time‐of‐flight mass spectrometry. Cell proliferation and apoptosis assays confirmed that all five compounds had anti‐prostate cancer effects. Matrine and xanthohumol had good inhibitory effects, with half maximal inhibitory concentration values of 0.893 and 0.137 mg/mL, respectively. Our comprehensive two‐dimensional PC‐3 prostate cancer cell membrane chromatographic system promotes the efficient recognition and rapid analysis of drug candidates, and it will be practical for the discovery of prostate cancer drugs from complex traditional Chinese medicines. 相似文献
23.
《Journal of separation science》2017,40(18):3612-3620
The linear solvent strength model was used to predict coverage in online comprehensive two‐dimensional reversed‐phase liquid chromatography. The prediction model uses a parallelogram to describe the separation space covered with peaks in a system with limited orthogonality. The corners of the parallelogram are assumed to behave like chromatographic peaks and the position of these pseudo‐compounds was predicted. A mix of 25 polycyclic aromatic compounds were used as a test. The precision of the prediction, span 0–25, was tested by varying input parameters, and was found to be acceptable with root mean square errors of 3. The accuracy of the prediction was assessed by comparing with the experimental coverages. Less than half of experimental coverages were outside prediction ± 1 × root mean square error and none outside prediction ± 2 × root mean square error. Accuracy was lower when retention factors were low, or when gradient conditions affected parameters not included in the model, e.g. second dimension gradient time affects the second dimension equilibration time. The concept shows promise as a tool for gradient optimization in online comprehensive two‐dimensional liquid chromatography, as it mitigates the tedious registration and modeling of all sample constituents, a circumstance that is particularly appealing when dealing with complex samples. 相似文献
24.
《Journal of separation science》2017,40(14):2895-2905
Bioactive equivalent combinatorial components play a critical role in herbal medicines. However, how to discover and enrich them efficiently is a question for herbal pharmaceuticals researchers. In our work, a novel two‐dimensional reversed‐phase/hydrophilic interaction high‐performance liquid chromatography method was established to perform real‐time components trapping and combining for preparation and isolation of coeluting components. Arenaria kansuensis was taken as an example, and solid‐phase extraction coupled with liquid–liquid extraction as a simple and efficient method for enriching trace components, reversed phase column coupled with hydrophilic interaction liquid chromatography XAmide column as two‐dimensional chromatography technology for isolation and preparation of coeluting constituents, enzyme‐linked immune‐sorbent assay as bio‐guided assay, and anti‐inflammatory bioactivity evaluation for bioactive constituents. A combination of 12 β‐carboline alkaloids was identified as anti‐inflammatory bioactive equivalent combinatorial components from A. kansuensis , which accounts for 1.9% w/w of original A. kansuensis . This work answers the key question of which are real anti‐inflammatory components from A. kansuensis and provides a fast and efficient approach for discovering and enriching trace β‐carboline alkaloids from herbal medicines for the first time. More importantly, the discovery of bioactive equivalent combinatorial components could improve the quality control of herbal products and inspire a herbal medicine based on combinatorial therapeutics. 相似文献
25.
《Journal of separation science》2017,40(8):1674-1685
It is difficult to identify unknown impurities in nucleotide analogues by mass spectrometry because mass‐spectrometry‐incompatible mobile phases need to be used to separate the major ingredient from impurities. In this study, vidarabine monophosphate was selected, and unknown impurities were identified by online heart‐cutting two‐dimensional high‐performance liquid chromatography and linear ion trap mass spectrometry. The one‐dimensional reversed‐phase column was filled with a mobile phase containing nonvolatile salt. In two‐dimensional high‐performance liquid chromatography, we used an Acclaim Q1 column with volatile salt, and the detection wavelength was 260 nm. The mass spectrum was scanned in positive‐ and negative‐ion mode. The online heart‐cutting and online demineralization technique ensured that the mobile phase was compatible with mass spectrometry; seven impurities were identified by MS2 and MS3 fragments. The mass fragmentation patterns of these impurities were investigated. The two isomers were semiprepared and complemented by nuclear magnetic resonance. The results were further compared with those of normal‐phase high‐performance liquid chromatography with mass spectrometry. The online heart‐cutting two‐dimensional high‐performance liquid chromatography with mass spectrometry was superior in identifying more impurities. The method solves the problem of incompatibility between the mobile phase and mass spectrometry, so it is suitable for identifying unknown impurities. This method may also be used for investigating impurities in other nucleotide analogues. 相似文献
26.
Local and parallel finite element algorithm for stationary incompressible magnetohydrodynamics 下载免费PDF全文
Yuhong Zhang Yanren Hou Li Shan Xiaojing Dong 《Numerical Methods for Partial Differential Equations》2017,33(5):1513-1539
This article presents a local and parallel finite element method for the stationary incompressible magnetohydrodynamics problem. The key idea of this algorithm comes from the two‐grid discretization technique. Specifically, we solve the nonlinear system on a global coarse mesh, and then solve a series of linear problems on several subdomains in parallel. Furthermore, local a priori estimates are obtained on a general shape regular grid. The efficiency of the algorithm is also illustrated by some numerical experiments.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 1513–1539, 2017 相似文献
27.
Global dynamics of a Vector‐Borne disease model with two delays and nonlinear transmission rate 下载免费PDF全文
In this paper, we investigate a Vector‐Borne disease model with nonlinear incidence rate and 2 delays: One is the incubation period in the vectors and the other is the incubation period in the host. Under the biologically motivated assumptions, we show that the global dynamics are completely determined by the basic reproduction number R0. The disease‐free equilibrium is globally asymptotically stable if R0≤1; when R0>1, the system is uniformly persistent, and there exists a unique endemic equilibrium that is globally asymptotically. Numerical simulations are conducted to illustrate the theoretical results. 相似文献
28.
当前对股利政策的研究主要集中在产权对股利政策的影响、自由现金流对股利政策的影响、公司过渡投资行为对股利政策的影响以及宏观经济波动对股利政策的影响等,而缺乏控股股东对股利政策的影响研究.现实中,控股股东对股利政策具有较大的影响,围绕控股股东对上市公司股利分配倾向的影响进行深入分析.具体而言,以2013-2014年度上证A股数据,建立Log斌ic模型和多元线性回归模型分析控股股东的几方面特征对股利分配倾向产生的多种影响.研究从理论上客观地评价了控股股东对股利分配倾向的影响,现实中对维护中小股东权益有重要意义. 相似文献
29.
分析循环取货模式和协同运输问题的关联性,提出了供需节点分离下的多车场一体化协同运输路线优化问题,考虑运输价值和运输成本,引入节点-弧流量的概念,通过比较流量大小确定节点集合,构建了问题的多供应点、多需求点运输模型.考虑取货的单向性和送货的闭合性,构造了求解模型的两阶段算法,运用动态规划的递推解法确定取货最优路线,然后基于余弦定理的几何法求解出发点和返回点不相同的送货路径优化问题,最后通过算例分析,说明了模型的合理性和算法的有效性. 相似文献
30.
采用格子自洽场理论计算研究了受限于2个平行板间的对称星形共聚物AmBm(m=1,2,3,4,5)熔体形成的层状相结构.在给定的相互作用下(χNAB不变,χ为Flory-Huggins相互作用参数,NAB=(N?1)/m为单个聚合物分子中一对AB臂的总链节数目),针对平行板间距为体相周期的情况,系统考察了共聚物链长N和单个聚合物分子中A(或B)臂数目m对受限层结构细节及层取向的影响.由计算结果,当N或NAB不变时,受限层的归一化界面宽度随m的增大而减小.受限板为中性时,垂直层结构的单链自由能比平行层结构的低.随着板对共聚物中一种嵌段的选择作用Λ的增大,体系发生垂直层到平行层的转变,该转变为一阶相变.当m不变时,N越小,上述转变出现在越大的Λ值处,体系越容易保持垂直层结构.并且N越小,层状结构周期越小.当N或NAB不变时,m越大体系越容易保持垂直层结构.总之,星形共聚物的链长越短、臂数越多时,垂直层稳定的Λ区间越大、层状结构的界面宽度越小.这些结论可以指导刻蚀应用中对体系参数的选择. 相似文献