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To improve the reproducibility, stability, and sensitivity of bismuth film electrode (BiFE), we studied the performances of a mixed coating of two cation‐exchange polymers, Nafion (NA) and poly(sodium 4‐styrenesulfonate) (PSS), modified glassy carbon BiFE (GC/NA‐PSS/BiFE). The characteristics of GC/NA‐PSS/BiFE were investigated by scanning electron microscopy and cyclic voltammetry. Various parameters were studied in terms of their effect on the anodic stripping voltammetry (ASV) signals. Under optimized conditions, the limits of detection were 71 ng L?1 for Cd(II) and 93 ng L?1 for Pb(II) with a 10 min preconcentration. The results exhibited that GC/NA‐PSS/BiFE can be a reproducible and robust tool for monitor of trace metals by ASV rapidly and environmentally friendly, even in the presence of surface‐active compounds. 相似文献
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Many graphs arising in various information networks exhibit the "power law" behavior -the number of vertices of degree k is proportional to k-# for some positive #. We show that if # > 2.5, the largest eigenvalue of a random power law graph is almost surely(1+ o(1))?m (1+ o(1))\sqrt{m} where m is the maximum degree. Moreover, the klargest eigenvalues of a random power law graph with exponent # have power law distribution with exponent 2# if the maximum degree is sufficiently large, where k is a function depending on #, mand d, the average degree. When 2<#< 2.5, the largest eigenvalue is heavily concentrated at cm3-# for some constant c depending on # and the average degree. This result follows from a more general theorem which shows that the largest eigenvalue of a random graph with a given expected degree sequence is determined by m, the maximum degree, and [(d)\tilde] \tilde{d} , the weighted average of the squares of the expected degrees. We show that the k-th largest eigenvalue is almost surely (1+ o(1))?{mk} (1+ o(1))\sqrt{m_k} where mk is the k-th largest expected degree provided mk is large enough. These results have implications on the usage of spectral techniques in many areas related to pattern detection and information retrieval. 相似文献
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Let ${\mathbb{Q}^3}$ be the moduli space of oriented circles in the three dimensional unit sphere ${\mathbb{S}^3}$ . Given a natural complex structure such space becomes a three dimensional complex manifold, with a M?bius invariant Hermitian metric h of type (2, 1). Up to M?bius transformations, all geodesics with respect to the Lorentz metric g = Re(h) on ${\mathbb{Q}^3}$ are determined to form a one-parameter family of circles on a helicoid in a space form ${\mathbb{R}^3, \mathbb{H}^3}$ or ${\mathbb{S}^{3}}$ , resp. We show also that any two oriented circles in ${\mathbb{S}^3}$ are connected by countably infinitely many geodesics in ${\mathbb{Q}^3}$ . 相似文献
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在本文,我们研究谱半径至多为$\sqrt[r]{2+\sqrt{5}}$的超图.我们得到此种超图必须具有一个基普结构,这与Woo-Neumaier在2007年对谱半径至多为$\frac{3}{2}\sqrt{2}$的图的分类结果类似. 相似文献
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重组家蚕核多角体病毒(rBmNPV)的复制及所载HuIFN-α基因的表达 总被引:3,自引:0,他引:3
报道了重组家蚕核多角体病毒(BombyxmorinuclearPolyhedrosisVirusBmNPV)在家蚕细胞BmN中复制的细胞病理学变化,除了不形成多角体以外,与野生型病毒相同.研究了病毒感染复数、细胞接种密度和细胞生长阶段对重组病毒复制和α-干扰素(IFN-α)表达量的影响.在一定低感染复数时,α-干扰素的产量较高.对于重组病毒的复制,最适的细胞接种密度为3.6~7.0×105细胞/瓶.在细胞指数生长前期(48~60h)接种重组病毒,对于获得较高的重组病毒复制效价和α-干扰素的产量都是有利的. 相似文献
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§1.IntroductionConsidera11tensorfieldIonasmoothmanifoldM.Thenaturalgeneralizationofthecomplexstructureandparacomplexstructu... 相似文献
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A new kind of bismuth film modified electrode to sensitively detect trace metal ions based on incorporating highly conductive ionic liquids 1‐butyl‐3‐methyl‐imidazolium hexafluorophosphate (BMIMPF6) in solid matrices at glassy carbon (GC) was investigated. Poly(sodium 4‐styrenesulfonate) (PSS), silica, and Nafion were selected as the solid matrices. The electrochemical properties of the mixed films modified GC were evaluated. The electron transfer rate of Fe(CN)64?/Fe(CN)63? can be effectively improved at the PSS‐BMIMPF6 modified GC. The bismuth modified PSS‐BMIMPF6 composite film electrodes (GC/PSS‐BMIMPF6/BiFEs) displayed high mechanical stability and sensitive stripping voltammetric performances for the determination of trace metal cations. The GC/PSS‐BMIMPF6/BiFE exhibited well linear response to both Cd(II) and Pb(II) over a concentration range from 1.0 to 50 μg L?1. And the detection limits were 0.07 μg L?1 for Cd(II) and 0.09 μg L?1 for Pb(II) based on three times the standard deviation of the baseline with a preconcentration time of 120 s, respectively. Finally, the GC/PSS‐BMIMPF6/BiFEs were successfully applied to the determination of Cd(II) and Pb(II) in real sample, and the results of present method agreed well with those of atomic absorption spectroscopy. 相似文献
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Predicting missing links via local information 总被引:6,自引:0,他引:6
Tao Zhou Linyuan Lü Yi-Cheng Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,71(4):623-630
Missing link prediction in networks is of both theoretical
interest and practical significance in modern science. In this
paper, we empirically investigate a simple framework of link
prediction on the basis of node similarity. We compare nine
well-known local similarity measures on six real networks. The
results indicate that the simplest measure, namely Common
Neighbours, has the best overall performance, and the Adamic-Adar
index performs second best. A new similarity measure, motivated by
the resource allocation process taking place on networks, is
proposed and shown to have higher prediction accuracy than common
neighbours. It is found that many links are assigned the same scores
if only the information of the nearest neighbours is used. We
therefore design another new measure exploiting information on the
next nearest neighbours, which can remarkably enhance the prediction
accuracy. 相似文献
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