Structure and Magnetic Properties of Nickel–Zinc Ferrite Nanoparticles Prepared by Glass Crystallization Method

Summary. The magnetic and microstructure properties of Fe₂O₃–0.4NiO–0.6ZnO–B₂O₃ glass system, which was subjected to heat treatment in order to induce a magnetic crystalline phase (Ni_0.4Zn_0.6-Fe₂O₄ crystals) within the glass matrix, were investigated. DSC measurement was performed to reveal the crystallization temperature of the prepared glass sample. The obtained samples, produced by heat treatment at 765°C for various times (1, 1.5, 2, and 3 h), were characterized by X-ray diffraction, IR spectra, transmission electron microscopy, and vibrating sample magnetometer. The results indicated the formation of spinel Ni–Zn ferrite in the glass matrix. Particles of the ferrite with sizes ranging from 28 to 120 nm depending on the sintering time were observed. The coercivity values for different heat-treatment samples were found to be in the range from 15.2 to 100 Oe. The combination of zinc content and sintering times leads to samples with saturation magnetization ranging from 12.25 to 17.82 emu/g.     

One-Pot,Three-Component Coupling Reaction: Catalyst-Free Green Synthesis of Novel N-Heteroaryl α-Naphthylglycines

A series of novel N-heteroaryl α-arylglycines containing naphthol rings has been prepared by one-pot, three-component condensation reaction of glyoxalic acid, heteroaryl amines and naphthols in water at ambient temperature and under reflux conditions in moderate to high yields. The promising advantages such as removal of organic solvent, no need to catalyst, simplicity of the reaction procedure and easy product separation will be discussed in this article.     

In Silico and Experimental Characterization of Chimeric Bacillus thermocatenulatus Lipase with the Complete Conserved Pentapeptide of Candida rugosa Lipase

Lipases are one of the highest value commercial enzymes as they have broad applications in detergent, food, pharmaceutical, and dairy industries. To provide chimeric Bacillus thermocatenulatus lipase (BTL2), the completely conserved pentapeptide (¹¹²Ala-His-Ser-Gln-Gly¹¹⁶) was replaced with similar sequences (²⁰⁷Gly-Glu-Ser-Ala-Gly²¹¹) of Candida rugosa lipase (CLR) at the nucleophilic elbow region. For this purpose, three mutations including A112G, H113E, and Q115A were inserted in the conserved pentapeptide sequence of btl2 gene. Based on the crystal structures of 2W22, the best structure of opened form of the chimeric lipases were garnered using the MODELLER v9.10 software. The native and chimeric lipases were docked to a set of ligands, and a trial version of Molegro Virtual Docker (MVD) software was used to obtain the energy values. Docking results confirmed chimeric lipase to be better than the native lipase. Following the in silico study, cloning experiments were conducted and expression of native and chimeric btl2 gene in Pichia pastoris was performed. The native and chimeric lipases were purified, and the effect of these mutations on characteristics of chimeric lipase studied and then compared with those of native lipase. Chimeric lipase exhibited 1.6-fold higher activity than the native lipase at 55 °C. The highest percentage of both lipases activity was observed at 60 °C and pH of 8.0. The ion Ca²⁺ slightly inhibited the activity of both lipases, whereas the organic solvent enhanced the lipase stability of chimeric lipase as compared with the native lipase. According to the results, the presence of two glycine residues at the conserved pentapeptide region of this chimeric lipase (¹¹² Gly-Glu-Ser-Ala-Gly ¹¹⁶) may increase the flexibility of the nucleophilic elbow region and affect the enzyme activity level.     

Ni(II), Co(II), and Cu(II) complexes incorporating 2-pyrazinecarboxylic acid：Synthesis,characterization, electrochemical evaluation,and catalytic activity for the synthesis of 2H-indazolo[2,1-b]phthalazine-triones

Three complexes containing 2-pyrazinecarboxylate (pzca–), including [Ni(pzca)2(H2O)2], [Co(pzca)2(H2O)2], and [Cu(pzca)2(H2O)2], have been synthesized and characterized using physico-chemical and spectroscopic methods. Furthermore, the structure of each complex was determined by single-crystal X-ray diffraction. All three complexes have an octahedral geometry, where the metal ion chelated by two carboxylate oxygens, two nitrogen atoms belonging to pyrazinic acid molecules, and two oxygen atoms of two water molecules. The catalytic activities of these complex-es were also investigated in the green synthesis of 2H-indazolo[2,1-b]phthalazine-triones by the reaction of hydrazine hydrate with an arylaldehyde, phthalic anhydride, and dimedone in acetic acid.     

Kinetic analysis of an extended single-path sequence of first-order reactions. The reaction of mesitonitrile in sulfuric acid

The system of a sequence of five first-order reactions, A → B → C → D → E → F, has been analyzed kinetically. An actual example is proposed in the reaction of mesitonitrile in 89.8% (w/w) sulfuric acid at 98.3°C. The analysis provides estimates of concentration ratios as functions of time, and the progress of the buildup and decay of the intermediate species can be monitored. The kinetics have been measured for the hydration of mesitonitrile, the hydrolysis of mesitamide, and the sulfonation of mesitylenesulfonic acid in 89.8% sulfuric acid. The calculated values of the concentration ratios of mesitylenedisulfonic acid as a function of time were satisfactorily close to those found in experiment.     

Spectrophotometric determination of rifampicin through chelate formation and charge transfer complexation in pharmaceutical preparation and biological fluids

Two simple and accurate spectrophotometric methods for determination of Rifampicin (RIF) are described. The first method is based on charge transfer (CT) complex formation of the drug with three pi-electron acceptors either 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 7,7,7,8-Tetracyanoquinodimethane (TCNQ) or 2,3,5,6-Tetrachloro-1,4-benzoquinone (p-chloranil) in acetonitrile. The method is followed spectrophotometrically by measuring the maximum absorbance at 584 nm, 761 nm (680 nm) or 560 nm for DDQ, TCNQ and p-chloranil, respectively. Under the optimized experimental conditions, the calibration curves showed a linear relationship over the concentration ranges of 5-140 microg/ml, 2-45 microg/ml (5-120 microg/ml) and 15-200 microg/ml, respectively. The second method is based on the reaction of RIF with iron(III) forming a water insoluble violet complex which is extracted into chloroform. The method determines RIF in concentration range of 10-240 microg/ml at 540 nm. The proposed methods applied to determination of RIF in capsule, human serum and urine samples with good accuracy and precision. The results were compared statistically with the official method and showed no significant different between the methods compared in terms of accuracy and precision.     

Characterization,thermal degradation kinetics,and morphological properties of a graphene oxide/poly (vinyl alcohol)/starch nanocomposite

Journal of Thermal Analysis and Calorimetry - In this study, we synthesized a biodegradable nanocomposite containing starch, polyvinyl alcohol (PVA), and graphene oxide (GO). The non-isothermal...     

Kinetics of cure for a coating system including DGEBA (n = 0)/1,8-NDA and barium carbonate

The increasing demand for low-cost and high performance coatings has promoted the development of chip epoxy-based coatings using inert fillers. Attention has been paid here on employing mixtures of DGEBA with barium carbonate as novel ceramic-based filler to produce a coating using 1,8-naphthalene diamine (1,8-NDA) as the crosslinking agent. A substantial increase in the T_g, from 85 to 100 °C, is observed for the optimum composition. The 1,8-NDA-cure of the epoxy composites showed an autocatalytic mechanism. At a specific conversion range the cure reaction of the composites will be controlled by a diffusion-control cure reaction rather than by Kamal autocatalytic model. Model-free isoconversional method is utilized to construct apparent activation energy dependence on conversion plot. The effect of diffusion control is described by an approach proposed by Chern and Poehlein. Greater diffusion control is observed as the cure temperature decreased.     

纳米多级孔分子筛：简短的综述

分子筛是一种三维微孔结构的硅铝酸盐晶体,具有灵活多变的骨架和组成、较高的物理和水热稳定性、无毒、高比表面积、离子可交换性以及很低的成本等特点,因而在油品精制、石油化学、农业、水和污水处理等众多领域中用作离子交换剂、催化剂和吸附剂。尽管分子筛的应用是基于其本身的微孔结构,但微孔也导致体积较大的反应物和产物分子的传质阻力高。通过制备纳米尺度和多级孔结构的分子筛等多种手段可克服常规分子筛所具有的传质限制。人们已经开发了多种方法制备了新型的分子筛材料,并考察了它们在各种催化反应和吸附反应中的性能。在反应体系中采用这种多级孔的纳米分子筛,有可能提高催化剂的使用寿命和催化性能,抑制积碳和失活。本综述概述了多级孔分子筛和纳米分子筛的高性能及其合成方法的最新进展,讨论了每个合成方法的优缺点,简述了纳米分子筛和二级孔结构分子筛的催化应用,并与常规分子筛进行了比较。