Dynamics for a Nonlocal Reaction-Diffusion Population Model with a Free Boundary

In this paper we focus on a nonlocal reaction-diffusion population model. Such a model can be used to describe a single species which is diffusing, aggregating, reproducing and competing for space and resources, with the free boundary representing the expanding front. The main objective is to understand the influence of the nonlocal term in the form of an integral convolution on the dynamics of the species. Precisely, when the species successfully spreads into infinity as \(t\rightarrow \infty \), it is proved that the species stabilizes at a positive equilibrium state under rather mild conditions. Furthermore, we obtain a upper bound for the spreading of the expanding front.

     

Determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples by cloud-point extraction and high-performance liquid chromatography

A highly sensitive method for the determination of manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples is proposed. The method is based on analytes reacted with ammonium pyrrolidinedithiocarbamate (APDC) to give hydrophobic chelates (M–APDC), which were separated and enriched by cloud-point extraction (CPE) with non-ionic surfactant Tergitol TMN-6 as extractant. The surfactant-rich phase containing the chelates is determined with a high-performance liquid chromatography system. To achieve the best CPE method, the Box–Behnken design was used to study the concentration of Tergitol TMN-6, equilibrium temperature, equilibrium time as well as their interaction. What followed was the individual research for the pH of the sample solutions and the concentration of APDC. What is more, in the given optimized experimental conditions, calibration plots were found to be linear in the range of 0.0200–0.500 mg/L for Mn (VII) and Cr (VI), meanwhile 0.0500–1.00 mg/L for Ni (II), the linear correlation coefficients were between 0.996 and 0.999, the recoveries ranged from 91.8 to 97.8 % and the relative standard deviations were between 1.09 and 2.30 % (n = 3). The limits of detection were 0.164 μg/L for Mn (VII), 0.562 μg/L for Cr (VI) and 5.12 μg/L for Ni (II), respectively. The proposed method was applied to determine manganese (VII), chromium (VI) and nickel (II) in medicinal herb samples with satisfactory results.     

Coumarin Sulfonamides and Amides Derivatives: Design,Synthesis, and Antitumor Activity In Vitro

Coumarins possesses immeasurable antitumor potential with minimum side effects depending on the substitutions on the basic nucleus, which exhibits great prospects for antitumor drug development. In an attempt to develop novel antitumor candidates, a series of coumarin sulfonamides and amides derivatives were designed and synthetized. The majority of these derivatives showed good cytotoxic activity against MDA-MB-231 and KB cell lines, among which compound 9c was the most potent against MDA-MB-231 cells, with IC₅₀ value of 9.33 μM, comparable to 5-fluorouracil. Further investigation revealed that compound 9c had versatile properties against tumors, including inhibition of cell migration and invasion as well as inducing apoptosis. Reactive oxygen species (ROS) assay and western blotting analysis suggested that compound 9c promoted cancer cell apoptosis by increasing ROS levels and upregulating the expression of caspase-3 in MDA-MB-231 cells. These results indicated that compound 9c could be promising lead compound for further antitumor drug research.     

二维导电金属有机骨架材料

金属有机骨架(MOFs)是由金属离子或簇与有机配体以配位键组装而成的晶态多孔材料,其高的孔隙率及功能可设计性使其广泛应用于各种领域.然而,传统MOFs多数电导率非常低,这严重制约了其在电学相关领域的发展.近年来,导电金属有机骨架尤其是二维导电金属有机骨架(2D ECMOFs)材料因其结构中独特的π-π堆积及π-d共轭作...     

有机单晶场效应晶体管

有机单晶场效应晶体管的研究对于探索电子的本质特性具有十分重要的意义。近几年来,不管是在制备技术还是在器件性能的研究方面,有机单晶场效应晶体管均取得了很大的进步,并由此引起了社会的广泛关注,成为场效应晶体管领域的一个重要研究方向。本文主要介绍了有机单晶的生长方法、有机场效应器件的各种制备技术、器件的迁移率及其影响因素,并对有机单晶场效应晶体管的发展前景和面临的一些问题作了简要的讨论。     

Shape reconstruction of an inverse boundary value problem of two‐dimensional Navier–Stokes equations

This paper is concerned with the problem of the shape reconstruction of two‐dimensional flows governed by the Navier–Stokes equations. Our objective is to derive a regularized Gauss–Newton method using the corresponding operator equation in which the unknown is the geometric domain. The theoretical foundation for the Gauss–Newton method is given by establishing the differentiability of the initial boundary value problem with respect to the boundary curve in the sense of a domain derivative. The numerical examples show that our theory is useful for practical purpose and the proposed algorithm is feasible. Copyright © 2009 John Wiley & Sons, Ltd.     

Electroplating silver tetracyanoquinodimethane between gold micro-gap electrodes for the fabrication of coplanar devices, a new way to integrate material synthesis and devices fabrication within one step

In this paper we propose a method for the integration of the synthesis of silver-tetracyanoquinodimethane (AgTCNQ) and the fabrication of its devices within one step. The method was performed by electroplating Ag between gold coplanar micro-gap electrodes in tetracyanoquinodimethane (TCNQ) solution. As soon as silver was electrochemically dissolved in the TCNQ solution, it immediately reacted with TCNQ to form AgTCNQ and then deposited between Au gap electrodes. With the continuing of the reaction, the Au micro-gap electrodes were connected by AgTCNQ to form Au/AgTCNQ/Au coplanar gap devices. With this electroplating technique, series gap devices of AgTCNQ were fabricated, and the devices exhibited switching phenomena with good reproducibility. This method integrated the synthesis of AgTCNQ and the fabrication of its devices within a single step, and should be also inspirable for other charge transfer complexes. PACS 81.05.Hd; 81.20.Ka; 82.45.Aa; 82.45.Qr     

A Sodium-Ion-Conducting Direct Formate Fuel Cell: Generating Electricity and Producing Base

A barrier that limits the development of the conventional cation-exchange membrane direct liquid fuel cells (CEM-DLFCs) is that the CEM-DLFCs need additional base to offer both alkaline environment and charge carriers. Herein, we propose a Na⁺-conducting direct formate fuel cell (Na-DFFC) that is operated in the absence of added base. A proof-of-concept Na-DFFC yields a peak power density of 33 mW cm⁻² at 60 °C, mainly because the hydrolysis of sodium formate provides enough OH⁻ and Na⁺ ions, proving the conceptual feasibility. Moreover, contrary to the conventional chlor-alkali process, this Na-DFFC enables to generate electricity and produce NaOH simultaneously without polluting the environment. The Na-DFFC runs stably during 13 hours of continuous operation at a constant current of 10 mA, along with a theoretical production of 195 mg NaOH. This work presents a new type of electrochemical conversion device that possesses a wide range of potential applications.     

Magnetic Solid-Phase Extraction and Ionic Liquid Dispersive Liquid–Liquid Microextraction Coupled with High-Performance Liquid Chromatography for the Determination of Hexachlorophene in Cosmetics

An efficient, simple, and fast method based on ionic liquid dispersive liquid–liquid microextraction (IL-DLLME) followed by magnetic solid-phase extraction (MSPE) was developed as a new technique for extracting and purifying hexachlorophene (HCP) in cosmetics prior to high-performance liquid chromatography (HPLC) determination. In this method based on IL-DLLME and MSPE, 1-hexyl-3-methylimidazolium hexafluorophosphate ([C₆MIM][PF₆]) is used as the extraction solvent and Fe₃O₄ nanoparticles are used to remove hydrophobic additives in the cosmetics by physical adsorption. The main parameters affecting the efficiency of the IL-DLLME and MSPE of HCP were investigated and optimized. Under the optimum conditions, the method was linear in the range 0.5–40 µg mL^?1 with a correlation coefficient (R ²) of 0.9976 and had a detection limit of 0.14 µg mL^?1 at a signal-to-noise ratio (S/N) of 3. The recoveries of HCP in three cosmetic samples using the proposed method were in the range 74.5–97.7%, and the relative standard deviations (RSD, n = 5) were in the range 3.8–6.7%. The developed method was successfully applied to the determination of HCP in cosmetics.     

化学法快速测定铁基非晶合金中硼含量的试样分解方法研究

用化学法测定铁基非晶合金中硼元素时,因合金试样难溶性及硼的某些特性,存在试样分解难的问题。利用H2O2强氧化性及硼既溶于酸又溶于碱的性质,通过试验确定了用H2O2(30%)与HCl(密度约1.19g/mL)分解试样,试样溶解完全。将该方法用于测定硼质量分数大于0.5%的铁基非晶合金中的硼,测定结果与ICP-AES法测定结果相符,测定结果的相对标准偏差小于1.5%(n=10)。