模拟混凝土孔溶液中钢筋钝化膜生长动力学及孔蚀过程的研究

用恒电位电流衰减法及激光扫描光电化学显微技术研究了在于ＰＨ＝１２．５及１３．８的模拟混凝土孔溶液中钢筋钝化化膜的生长动力学及相应的破坏过程，实验结果表明，钢筋钝化膜的生长过程存在两个主要阶段，各阶段膜厚均与生长时间存在正比对数关系，但当ｔ＜３０秒和ｔ＞３０秒时，膜的生长表出出不同的动力学特征，在钝化发生点蚀前，钝化膜的微区光电流一定的预兆，腐蚀抑制剂ＮａＮＯ２影响膜的生长过程及膜厚，能提高钢筋的抗     

Sensitive Voltammetric Sensing of the 2,3‐Dimethyl‐2,3‐dinitrobutane (Dmnb) Explosive Taggant

The highly sensitive voltammetric detection of the 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB), a required additive to commercial plastic explosives, is described. The protocol relies on a fast square‐wave voltammetric measurement of the DMNB explosive taggant at an unmodified carbon fiber electrode using a phosphate buffer (pH 7.0) solution. Different solutions and working electrodes were evaluated. Under the optimal conditions, a linear response is observed over the 300–3000 μg/L DMNB concentration range examined, with a detection limit of 60 μg/L. A highly stable response, with a relative standard deviation (RSD) of 2.6%, is observed for 30 repetitive measurements. Such electrochemical approach offers great promise for a simple, rapid, sensitive and inexpensive field screening of plastic explosives. Preliminary data illustrate the utility of electrochemical detection for electrophoretic microchips for the simultaneous measurements of DMNB, cyclotrimethylenetrinitramine (RDX) and pentaerythritoltetranitrate (PETN).     

Protein identification by peptide mass fingerprinting and peptide sequence tagging with alternating scans of nano-liquid chromatography/infrared multiphoton dissociation Fourier transform ion cyclotron resonance mass spectrometry

We have developed a method for protein identification with peptide mass fingerprinting and sequence tagging using nano liquid chromatography (LC)/Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). To achieve greater sensitivity, a nanoelectrospray (nano-ES) needle packed with reversed-phase medium was used and connected to the nano-ES ion source of the FTICR mass spectrometer. To obtain peptide sequence tag information, infrared multiphoton dissociation (IRMPD) was carried out in nano-LC/FTICR-MS analysis. The analysis involves alternating nano-ES/FTICR-MS and nano-ES/IRMPD-FTICR-MS scans during a single LC run, which provides sets of parent and fragment ion masses of the proteolytic digest. The utility of this alternating-scan nano-LC/IRMPD-FTICR-MS approach was evaluated by using bovine serum albumin as a standard protein. We applied this approach to the protein identification of rat liver diacetyl-reducing enzyme. It was demonstrated that this enzyme was correctly identified as 3-alpha-hydroxysteroid dehydrogenase by the alternating-scan nano-LC/IRMPD-FTICR-MS approach with accurate peptide mass fingerprinting and peptide sequence tagging.     

Preparation of core–shell structure Fe3O4@SiO2 superparamagnetic microspheres immoblized with iminodiacetic acid as immobilized metal ion affinity adsorbents for His‐tag protein purification

The core–shell structure Fe₃O₄/SiO₂ magnetic microspheres were prepared by a sol–gel method, and immobiled with iminodiacetic acid (IDA) as metal ion affinity ligands for protein adsorption. The size, morphology, magnetic properties and surface modification of magnetic silica nanospheres were characterized by various modern analytical instruments. It was shown that the magnetic silica nanospheres exhibited superparamagnetism with saturation magnetization values of up to 58.1 emu/g. Three divalent metal ions, Cu²⁺, Ni²⁺ and Zn²⁺, were chelated on the Fe₃O₄@SiO₂–IDA magnetic microspheres to adsorb lysozyme. The results indicated that Ni²⁺‐chelating magnetic microspheres had the maximum adsorption capacity for lysozyme of 51.0 mg/g, adsorption equilibrium could be achieved within 60 min and the adsorbed protein could be easily eluted. Furthermore, the synthesized Fe₃O₄@SiO₂–IDA–Ni²⁺ magnetic microspheres were successfully applied for selective enrichment lysozyme from egg white and His‐tag recombinant Homer 1a from the inclusion extraction expressed in Escherichia coli. The result indicated that the magnetic microspheres showed unique characteristics of high selective separation behavior of protein mixture, low nonspecific adsorption, and easy handling. This demonstrates that the magnetic silica microspheres can be used efficiently in protein separation or purification and show great potential in the pretreatment of the biological sample. Copyright © 2015 John Wiley & Sons, Ltd.     

Concise Synthesis of Photocleavable Molecular Tag for Laser Desorption Ionization Mass Spectrometry via Fries Reaction

Abstract

A new synthetic route for the photocleavable molecular tag for laser desorption ionization mass spectrometry (LDI-MS) was achieved using the Fries reaction of 2,6-dimethylphenyl ester as its key reaction. Zirconium chloride was used as uniquely efficient adjuvant to promote the reaction. The molecular tag was obtained in five steps without chromatographic purification.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Why indexing works

We develop a simple stock selection model to explain why active equity managers tend to underperform a benchmark index. We motivate our model with the empirical observation that the best performing stocks in a broad market index often perform much better than the other stocks in the index. Randomly selecting a subset of securities from the index may dramatically increase the chance of underperforming the index. The relative likelihood of underperformance by investors choosing active management likely is much more important than the loss those same investors take due to the higher fees of active management relative to passive index investing. Thus, active management may be even more challenging than previously believed, and the stakes for finding the best active managers may be larger than previously assumed.     

一类非线性时滞网络控制系统的无源性分析

本文研究了一类非线性时滞网络控制系统的无源性问题.利用Lyapunov稳定性理论,结合线性矩阵不等式(LMI)技术,通过构造Lyapunov-Krasovskii泛函,在考虑两种不同时滞的情况下,获得了系统满足无源性的充分条件,最后通过仿真算例验证了结论的正确性和方法的有效性.     

The effect of the change in the microscopic structures of the iron on corrosion resistance and passivated properties

The passive film of iron showed n‐type semiconductor characteristic in borate buffer solution, and its donor concentration increased slightly after tensile strain in the present study. However, comparing with solution‐annealed sample, the anodic passive film formed on tensile‐strained one was highly protective. The more dislocations on tensile‐strained sample promoted the diffusion of iron and oxygen vacancy. Moreover, more donor density (mainly oxygen vacancies) promoted the diffusion of oxygen. They all facilitated tensile‐strained sample to form Fe₂O₃ and thicker passive film on the surface. More Fe₂O₃ and thicker passive film on the surface of tensile‐strained iron could improve corrosion resistance. Copyright © 2014 John Wiley & Sons, Ltd.     

Improved Dermal and Transdermal Delivery of Curcumin with SmartFilms and Nanocrystals

Poor aqueous solubility of active compounds is a major issue in today’s drug delivery. In this study the smartFilm-technology was exploited to improve the dermal penetration efficacy of a poorly soluble active compound (curcumin). Results were compared to the dermal penetration efficacy of curcumin from curcumin bulk suspensions and nanocrystals, respectively. The smartFilms enabled an effective dermal and transdermal penetration of curcumin, whereas curcumin bulk- and nanosuspensions were less efficient when the curcumin content was similar to the curcumin content in the smartFilms. Interestingly, it was found that increasing numbers of curcumin particles within the suspensions increased the passive dermal penetration of curcumin. The effect is caused by an aqueous meniscus that is created between particle and skin if the dispersion medium evaporates. The connecting liquid meniscus causes a local swelling of the stratum corneum and maintains a high local concentration gradient between drug particles and skin. Thus, leading to a high local passive dermal penetration of curcumin. The findings suggest a new dermal penetration mechanism for active compounds from nano-particulate drug delivery systems, which can be the base for the development of topical drug products with improved penetration efficacy in the future.