Highly Selective and Sensitive Electrochemical Determination of Ni(II) in Real Samples Based on Ion‐imprinted Polymer Technology

Nickel is one of the heavy metals which has been considered as a serious pollutant affecting the human health. Therefore, it is necessary to control its concentration in foods and drinks. Recently, ion‐imprinted polymer based electrochemical sensors have been attracted lots of attention due to their valuable selectivity and sensitivity toward target analytes. In this study, Ni(II)‐1,10‐phenanthroline complex was prepared in ethanol and added stepwise to the aqueous solution of dopamine, followed by pH adjustment for self‐polymerization of dopamine in alkaline conditions. During the polymerization process, Ni(II)‐imprinted polydopamine (Ni‐PDA) was formed due to effective interactions between polydopamine and 1,10‐phenanthroline ligands carrying Ni(II) ions. A thin film of Ni‐PDA was anchored on a glassy carbon electrode (GCE) through a simple casting procedure. After drying, the sensor was employed for the determination of Ni(II) ions by means of differential pulse voltammetry. Under optimum conditions, a linear calibration curve was obtained in the range 1–25 μM with the detection limit of 0.39 μM (S/N=3). Due to excellent selectivity to Ni(II) ions, the sensor was not suffered from the excess amount of interfering ions and used for Ni(II) determination in different water and tea samples.     

Comparison between Experimental and Theoretical Thermal Conductivity of Nanofluids Containing Multi-walled Carbon Nanotubes Decorated with TiO2 Nanoparticles

This article reports the thermal conductivity modeling of nanofluids containing decorated multi-walled carbon nanotubes with TiO₂ nanoparticles. TiO₂ nanoparticles and decorated multi-walled carbon nanotubes are synthesized with different amounts of TiO₂ nanoparticles. The experimental results show that the measured thermal conductivities of TiO₂ nanofluids and multi-walled carbon nanotube nanofluids are higher than the predicted values by theoretical models. The comparison results of multi-walled carbon nanotube nanofluids and multi-walled carbon nanotube–TiO₂ nanofluids reveal that the predicted values by the Xue model are closer to the measured values. In addition, the results show that the thermal conductivity of nanofluids containing multi-walled carbon nanotube–TiO₂ increases with respect to TiO₂ content of hybrid.     

Preparation of a novel sorptive stir bar based on vinylpyrrolidone‐ethylene glycol dimethacrylate monolithic polymer for the simultaneous extraction of diazepam and nordazepam from human plasma

A new monolithic coating based on vinylpyrrolidone‐ethylene glycol dimethacrylate polymer was introduced for stir bar sorptive extraction. The polymerization step was performed using different contents of monomer, cross‐linker and porogenic solvent, and the best formulation was selected. The quality of the prepared vinylpyrrolidone‐ethylene glycol dimethacrylate stir bars was satisfactory, demonstrating good repeatability within batch (relative standard deviation < 3.5%) and acceptable reproducibility between batches (relative standard deviation < 6.0%). The prepared stir bar was utilized in combination with ultrasound‐assisted liquid desorption, followed by high‐performance liquid chromatography with ultraviolet detection for the simultaneous determination of diazepam and nordazepam in human plasma samples. To optimize the extraction step, a three‐level, four‐factor, three‐block Box–Behnken design was applied. Under the optimum conditions, the analytical performance of the proposed method displayed excellent linear dynamic ranges for diazepam (36–1200 ng/mL) and nordazepam (25–1200 ng/mL), with correlation coefficients of 0.9986 and 0.9968 and detection limits of 12 and 10 ng/mL, respectively. The intra‐ and interday recovery ranged from 93 to 106%, and the relative standard deviations were less than 6%. Finally, the proposed method was successfully applied to the analysis of diazepam and nordazepam at their therapeutic levels in human plasma. The novelty of this study is the improved polarity of the stir bar coating and its application for the simultaneous extraction of diazepam and its active metabolite, nordazepam in human plasma sample. The method was more rapid than previously reported stir bar sorptive extraction techniques based on monolithic coatings, and exhibited lower detection limits in comparison with similar methods for the determination of diazepam and nordazepam in biological fluids.     

A Review on Bioengineering Approaches to Insulin Delivery: A Pharmaceutical and Engineering Perspective

Diabetes mellitus (DM) is the most prevalent non‐contagious disease, which has affected a large number of people all over the world. Among all treatments known to have a positive influence in the control of DM, insulin therapy is the most common and effective one. Nowadays, various methods of insulin delivery are under investigation, which are able to reach a plausible bioavailability with ignorable side effects instead of insulin injection. This article presents a comprehensive review of the insulin therapy approach with a focus on modified methods in insulin delivery strategies and current advances in engineered insulin delivery systems.     

An efficient and green synthesis of phthalide-fused pyrazole and pyrimidine derivatives

An efficient and green method for the synthesis of phthalide [isobenzofuran-1(3H)-one] fused pyrazoles via the catalyst-free condensation reaction of 2-formylbenzoic acid, hydrazine hydrate, and acetylenic esters in water is reported. Reaction of 2-formylbenzoic acid with 6-amino-uracils or cyclic 1,3-diketones resulted in the formation of phthalide-fused pyrimidine or cyclic 1,3-diketone derivatives.     

5-乙氧羰基-4-取代-6-甲基-3,4-二氢嘧啶-2（1H）-酮的电子轰击飞行时间质谱表征

研究了一系列5-乙氧羰基-4-取代-6-甲基-3,4-二氢嘧啶-2(1H)-酮的电子轰击飞行时间质谱,建立了此类化合物的裂解方式和分子离子峰的强度规律.利用飞行时间质谱的中分辨能力,测得了各碎片离子的精确质量,这些数据经OpenLynx软件导出所有分子离子和碎片离子的元素组成.根据质谱裂解规律,主要质谱离子得到了归属.两类主要裂解途径为:对所有标题化合物,通过失去4位上的R1,酯基上的C2H4(麦氏重排)和H2O(通过环状六员过渡态)形成三种阳离子;对4-芳基化合物,通过失去EtCO2形成另一类阳离子.此外,还提出了个别化合物的一些重要裂解行为.     

An efficient method for catalytic enantioselective addition of diethylzinc to aryl aldehydes by a C2-symmetric chiral imino alcohol

The enantioselective alkylation of aryl aldehydes with diethylzinc in the presence of a C₂-symmetric chiral ligand derived from 2-hydroxy-3-pinanone was achieved at room temperature with high enantiomeric excesses.     

Congruence preserving functions of Wilke’s tree algebras

As a framework for characterizing families of regular languages of binary trees, Wilke introduced a formalism for defining binary trees that uses six many-sorted operations involving letters, trees and contexts. In this paper a completeness property of these operations is studied. It is shown that all functions involving letters, binary trees and binary contexts which preserve congruence relations of the free tree algebra over an alphabet, are generated by Wilke’s functions, if the alphabet contains at least seven letters. That is to say, the free tree algebra over an alphabet with at least seven letters is affine-complete. The proof yields also a version of the theorem for ordinary one-sorted term algebras: congruence preserving functions on contexts and members of a term algebra are substitution functions, provided that the signature consists of constant and binary function symbols only, and contains at least seven symbols of each rank. Moreover, term algebras over signatures with at least seven constant symbols are affine-complete.Received March 18, 2004; accepted in final form October 8, 2004.     

THE THEORETICAL INVESTIGATION OF THz ELECTROMAGNETIC WAVES IN A ROD DEGENERATE PLASMA-WAVEGUIDE

By using the Fourier components of dielectric tensor elements of cold collisionless degenerate plasmas, the dispersion relation of electromagnetic waves in a cylindrical metallic waveguide with a degenerate plasma column protected by an annular dielectric layer are obtained. The permissible frequency regions for slow and fast waves in E-mode (TM) are presented. Furthermore, the graph of cutoff frequency versus the radius of plasma column for the fast waves is investigated. In addition, the time growth rate for excitation of symmetric slow E-modes (TM) by a thin annular relativistic electron beam (TAREB) is studied. The graph of time growth rate respect to radius of dielectric layer and accelerating voltage are presented. PACS No. 52.25.