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71.
We report a label-free, aptamer-based chemiluminescent biosensor. The biosensor relies upon the catalytic activity of unmodified gold nanoparticles (AuNPs) on the luminol-H(2)O(2) chemiluminescence (CL) reaction, and the interaction of unmodified AuNPs with the aptamer. The unmodified AuNPs can effectively differentiate unstructured and folded aptamer. The binding of the aptamer with the target can induce the AuNP aggregation in the presence of 0.5 M NaCl, and after aggregation the catalytic activity of the AuNPs on the luminol-H(2)O(2) CL reaction is greatly enhanced. During the assay, no covalent functionalization of the AuNPs or aptamer is required. The detection limit of thrombin was estimated to be as low as 26 fM, and the sensitivity was more than 4 orders of magnitude better than that of known AuNP-based colorimetric methods for the detection of thrombin. This aptamer-based biosensor offers the advantages of being simple, cheap, rapid, and sensitive. 相似文献
72.
An applicable and easy-handling Ni-catalyst can be used to promote direct arylation of α-bromonitriles with various arylboronic acids to construct α-arylnitriles under mild conditions. The methodology tolerates β-hydrogens and functional groups in the substrates. 相似文献
73.
Cao X Wang G Zhang R Wei Y Wang W Sun H Chen L 《Organic & biomolecular chemistry》2011,9(19):6487-6490
A series of novel proline-based reduced dipeptides was developed and evaluated for a direct Michael addition of ketones and aldehydes to nitroalkenes. Excellent yields (up to 95%), diastereoselectivities (up to 98% dr) and enantioselectivities (up to 98% ee) were achieved in the presence of 5 mol% catalyst without any additional additives at room temperature. 相似文献
74.
In this article, we investigate the tail probability of the product of finitely many non-negative dependent random variables. They follow distributions from max-domains of attraction of extreme value distributions and their dependence is modeled via a multivariate Farlie–Gumbel–Morgenstern distribution. For each of the Fréchet, Gumbel and Weibull cases, we obtain an explicit asymptotic formula for the tail probability of the product. Our study extends a few known results in the literature. 相似文献
75.
Feng D Lv Y Wu Z Dou Y Han L Sun Z Xia Y Zheng G Zhao D 《Journal of the American Chemical Society》2011,133(38):15148-15156
We report for the first time the synthesis of free-standing mesoporous carbon films with highly ordered pore architecture by a simple coating-etching approach, which have an intact morphology with variable sizes as large as several square centimeters and a controllable thickness of 90 nm to ~3 μm. The mesoporous carbon films were first synthesized by coating a resol precursors/Pluronic copolymer solution on a preoxidized silicon wafer and forming highly ordered polymeric mesostructures based on organic-organic self-assembly, followed by carbonizing at 600 °C and finally etching of the native oxide layer between the carbon film and the silicon substrate. The mesostructure of this free-standing carbon film is confirmed to be an ordered face-centered orthorhombic Fmmm structure, distorted from the (110) oriented body-centered cubic Im3?m symmetry. The mesoporosity of the carbon films has been evaluated by nitrogen sorption, which shows a high specific BET surface area of 700 m(2)/g and large uniform mesopores of ~4.3 nm. Both mesostructures and pore sizes can be tuned by changing the block copolymer templates or the ratio of resol to template. These free-standing mesoporous carbon films with cracking-free uniform morphology can be transferred or bent on different surfaces, especially with the aid of the soft polymer layer transfer technique, thus allowing for a variety of potential applications in electrochemistry and biomolecule separation. As a proof of concept, an electrochemical supercapacitor device directly made by the mesoporous carbon thin films shows a capacitance of 136 F/g at 0.5 A/g. Moreover, a nanofilter based on the carbon films has shown an excellent size-selective filtration of cytochrome c and bovine serum albumin. 相似文献
76.
A novel, rapid, and efficient synthesis of bicyclic pyrimidine nucleosides and benzopyran-4-ones through oxidation of homopropargyl alcohols and subsequent isomerization, intramolecular addition of enol to allenic ketone has been developed. This methodology provides an efficient and promising approach to the structurally and pharmaceutically interesting pyrano[2,3-d]pyrimidine-2,5-dione nucleoside and benzopyran-4-one derivatives. 相似文献
77.
研究了偶氮基染料掺杂薄膜MO-PVA和EO-PVA的双光子存储特性。在对薄膜用Ar^+激光作预激发下实现了He-Ne激光的红光存储。获得了实时和短时存储照片。光电记录存储曲线,分析了双光四能级系统的存储机制。实现确定了最佳预激发功率约为0.28W/cm^2,最小He-Ne光可存储功率密度低于0.2W/cm^2。 相似文献
78.
We investigate the structure of a large precision matrix in Gaussian graphical models by decomposing it into a low rank component and a remainder part with sparse precision matrix.Based on the decomposition,we propose to estimate the large precision matrix by inverting a principal orthogonal decomposition(IPOD).The IPOD approach has appealing practical interpretations in conditional graphical models given the low rank component,and it connects to Gaussian graphical models with latent variables.Specifically,we show that the low rank component in the decomposition of the large precision matrix can be viewed as the contribution from the latent variables in a Gaussian graphical model.Compared with existing approaches for latent variable graphical models,the IPOD is conveniently feasible in practice where only inverting a low-dimensional matrix is required.To identify the number of latent variables,which is an objective of its own interest,we investigate and justify an approach by examining the ratios of adjacent eigenvalues of the sample covariance matrix?Theoretical properties,numerical examples,and a real data application demonstrate the merits of the IPOD approach in its convenience,performance,and interpretability. 相似文献
79.
Christine?BreinerEmail author Ailana?Fraser Lan-Hsuan?Huang Chikako?Mese Pam?Sargent Yingying?Zhang 《Calculus of Variations and Partial Differential Equations》2018,57(1):12
We determine regularity results for energy minimizing maps from an n-dimensional Riemannian polyhedral complex X into a CAT(1) space. Provided that the metric on X is Lipschitz regular, we prove Hölder regularity with Hölder constant and exponent dependent on the total energy of the map and the metric on the domain. Moreover, at points away from the \((n-2)\)-skeleton, we improve the regularity to locally Lipschitz. Finally, for points \(x \in X^{(k)}\) with \(k \le n-2\), we demonstrate that the Hölder exponent depends on geometric and combinatorial data of the link of \(x \in X\). 相似文献
80.
1,3,4,6-tetramethylpiperazine-2,5-dione was synthesized, and the crystal structure was characterized by single-crystal X-ray diffraction method, vibrational spectral measurements were obtained by Fourier transform infrared spectroscopy and Fourier transform Raman spectroscopy. The measurements agree well with the calculated geometrical structure and harmonic vibrational wavenumbers (usingab initio and density functional theory Becke’s three parameters hybrid method with the Lee, Yang, and Parr non-local functions methods with 6-311G and 6-311G** basis sets). 相似文献