An electrochemical aptasensor for thrombin detection based on the recycling of exonuclease III and double-stranded DNA-templated copper nanoparticles assisted signal amplification

In this paper, we report an improved electrochemical aptasensor based on exonuclease III and double-stranded DNA (dsDNA)-templated copper nanoparticles (CuNPs) assisted signal amplification. In this sensor, duplex DNA from the hybridization of ligated thrombin-binding aptamer (TBA) subunits and probe DNA can act as an effective template for the formation of CuNPs on the electrode surface, so copper ions released from acid-dissolution of CuNPs may catalyze the oxidation of ο-phenylenediamine to produce an amplified electrochemical response. In the presence of thrombin, a short duplex domain with four complementary base pairs can be stabilized by the binding of TBA subunits with thrombin, in which TBA subunit 2 can be partially digested from 3′ terminal with the cycle of exonuclease III, so the ligation of TBA subunits and the subsequent formation of CuNPs can be inhibited. By electrochemical characterization of dsDNA-templated CuNPs on the electrode surface, our aptasensor can display excellent performances for the detection of thrombin in a broad linear range from 100 fM to 1 nM with a low detection limit of 20.3 fM, which can also specially distinguish thrombin in both PBS and serum samples. Therefore, our aptasensor might have great potential for clinical diagnosis of biomarkers in the future.     

电感耦合等离子体原子发射光谱（ICP-AES）法测定铁矿石中磷

采用盐酸-硝酸-高氯酸-氢氟酸前处理样品,电感耦合等离子体原子发射光谱法测定铁矿石中的磷。对磷元素的分析谱线、样品称样量等工作条件进行了优化,解决了非金属元素磷的分析谱线难选择、样品称样量影响测定准确度的技术难点;采用内标法,降低了样品基体效应及仪器波动产生的影响,提高了分析结果的精密度和准确度。利用所建立的方法快速分析了铁矿石中磷的含量,方法检出限为0.0036 mg/L,测定范围为0.012%~2%,测定结果与标准值和化学法测定结果相符,相对标准偏差(RSD,n=9)小于2%。拟定的方法和分光光度法进行比对实验,技术优势明显。     

关于单李超三系的分类(英文)

本文证明了特征零代数闭域上的单李超三系可分为两部分:一是将单李超代数视为李超三系;二是单李超代数的对合自同构的(-1)-特征子空间.这些推广了Lister和Meyberg给出的关于单李三系分类的相应结果.     

Band gaps and nonlinear defect modes in one-dimensional photonic crystals with anisotropic single-negative metamaterials

We propose a one-dimensional photonic crystal (1DPC) with multilayered periodic structures containing dispersive anisotropic single-negative (ASNG) (permittivity- or permeability-negative) metamaterials. The influences of the ratio of d_A/d_B and their scale on ASNG gaps are discussed. Moreover, the effect of a nonlinear defect layer introduced into the proposed structure is also analyzed, and the results show that the defect mode has two peaks of electrical fields in the defect layer and its bistability property is also different from a defect mode in PCs with isotropic SNG gaps.     

Photonic band gap and defect mode from a layered periodic structure with anisotropic nonmagnetic right-handed and left-handed metamaterials

We demonstrate a photonic band gap (PBG) from a layered periodic structure containing anisotropic nonmagnetic right-handed and left-handed metamaterials whose permittivity elements are partially negative. A set of criteria imposed on materials and structures to realize a PBG is derived, and the transmission spectra are also discussed. When a defect layer is introduced, some unusual properties are found in contrast to that of a defect mode in ordinary PBG structures.     

见血封喉乳汁中的化学成分研究

从海南产见血封喉[Antiaris toxicaria(Pers.)Lesch.]乳汁的乙醇提取物中分离得到6个化合物,经现代波谱技术,包括红外、一维、二维核磁共振谱和高分辨质谱,上述化合物的结构分别鉴定为:toxicarioside Ⅰ(1),毒毛旋花子苷元(2),杠柳苷元(3),(3β,5a,14P,17a)-3,14-二羟基孕甾-20-酮(4),α-生育酚(5)和3,4,5-三甲氧基苯酚(6),其中化合物1为新的强心苷,化合物4和5为首次从该植物中分离得到.经MTT法进行体外细胞毒活性测试,结果表明化合物1～3对慢性髓原白血病细胞(K562)、人胃癌细胞(SGC-7901)和人肝癌细胞(SMMC-7721)的增殖显示了抑制活性,其ICso值范围为0.001～12.3 μm01.L-1.     

简捷微波法制备麦穗状氧化锌微晶及其光学性能

以硝酸锌和三乙胺的水溶液为前驱体溶液,在回流条件下微波辐照5min,制得了麦穗状半导体ZnO微晶.采用XRD、SEM、EDS、UV-Vis和光致发光(PL)光谱对产品的晶体结构、形貌和光学性能进行表征.结果表明,ZnO微晶为六方纤锌矿结构,单个微晶呈麦穗状,是由大量麦粒样的纳米颗粒接种于微米棒表面构成的复合结构.UV-...     

The Estimation of Accelerated Failure Time Model with Right-Censored Data

The accelerated failure time model provides a natural formulation of the effects of covariates on the failure time variable. The presence of censoring poses major challenges in the semi-parametric analysis. The existing semi-parametric estimators are computationally intractable. In this article we propose an unbiased transformation for the potential censored response variable, thus least square estimators of regression parameters can be gotten easily. The resulting estimators are consistent and asymptotically normal. Based on these, we can get a strongly consistent K-M estimator for the distribution of random error. Extensive simulation studies show that the asymptotic approximations are accurate in practical situations.