Magnetic Investigation of Various NiFe<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>Bi<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>4</Subscript> Ferrite Nanostructures Synthesized by Ball Milling Technique

NiFe_2?x Bi _x O₄ (x = 0, 0.1, 0.2, 0.3) nanoparticles with various grain sizes were synthesized via annealing treatment followed by ball milling of its bulk component materials. Commercially available bismuth, nickel and iron oxide powders were first mixed and then annealed at 1200 °C in an oxygen environment furnace for 4 h. The samples were then milled for 2 h by high-energy ball milling. X-ray diffraction (XRD) pattern indicated that in this stage the samples are single phase. The microstructure investigation was carried out by a scanning electron microscope with maximum magnification of 30,000. The average grain size for different samples was estimated by XRD technique and transmission electron microscopy. Magnetic behavior of the samples at room temperature was studied using an alternating gradient force magnetometry. The Néel temperature of the powders was measured by a Faraday balance. Based on magnetic studies, increase in bismuth content leads to a decrease in the saturation magnetization, coercive field and Néel temperature. This can be attributed to the substitution of Bi³⁺ ion in the ferrite system as a nonmagnetic cation.     

Application of Heteropolyacids as Heterogeneous and Recyclable Catalysts for One-Pot Synthesis of 3-Cyanopyridine Derivatives

A simple, clean and environmentally benign route to the synthesis of 3-cyanopyridines is described via a one-pot multi-component reaction of 3,4-dimethoxyacetophenone, malonitrile or ethylcyanoacetate, aldehyde and ammonium acetate using heteropolyacids as heterogeneous and recyclable catalysts in very good yields.     

Longitudinal Proton Structure Function at LO and NLO Approximations

The purpose of this paper is to calculate the longitudinal structure function of proton through the well-known equation F _L =F ₂?2xF ₁. To determine this structure function, we need to identify parton distribution functions to find F ₂. In this case, the valon model and DGLAP equations are utilized to obtain the parton distributions. Our calculations are carried out in two approximations LO and NLO. The results at the NLO approximation are in better agreement with the experimental data.     

On character amenability of semigroup algebras

Let S be a foundation locally compact topological semigroup, and let M _a (S) be the space of all measures μ∈M(S) for which the maps x?|μ|?δ _x and x?|μ|?δ _x from S into M(S) are weakly continuous. The purpose of this article is to develop a notion of character amenability for semigroup algebras. The main results concern the χ-amenability of M _a (S). We give necessary and sufficient conditions for the existence of a left χ-mean on M _a (S)^?.     

Preparation,surface state and band structure studies of SrTi(1 − x)Fe(x)O(3 − δ) (x = 0–1) perovskite-type nano structure by X-ray and ultraviolet photoelectron spectroscopy

In this report, SrTi_(1 ? x)Fe_(x)O_(3 ? δ) photocatalyst powder was synthesized by a high temperature solid state reaction method. The morphology, crystalline structures of obtained samples, was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), respectively. The electronic properties and local structure of the perovskite STF_x (0 ≤ x ≤ 1) systems have been probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. The effects of iron doping level x (x = 0–1) on the crystal structure and chemical state of the STF_x have been investigated by X-ray photoelectron spectroscopy and the valence band edges for electronic band gaps were obtained for STF_x by ultraviolet photoelectron spectroscopy (UPS). A single cubic perovskite phase of STF_x oxide was successfully obtained at 1200 °C for 24 h by the solid state reaction method. The XPS results showed that the iron present in the STF_x perovskite structure is composed of a mixture of Fe³⁺ and Fe⁴⁺ (SrTi_(1 ? x)[Fe³⁺, Fe⁴⁺]_(x)O_(3 ? δ)). When the content x of iron doping was increased, the amount of Fe³⁺ and Fe⁴⁺ increased significantly and the oxygen lattice decreased on the surface of STF_x oxide. The UPS data has confirmed that with more substitution of iron, the position of the valence band decreased.     

Succinimide sulfonic acid (SuSA): an efficient and recyclable catalyst for the chemoselective <Emphasis Type="Italic">N</Emphasis>-Boc protection of amines

Abstract  

Succinimide sulfonic acid (SuSA) as a stable reagent is easily prepared by the reaction of succinimide with neat chlorosulfonic acid. This compound is able to catalyze the chemoselective conversion of amines to their corresponding N-Boc protected derivatives with (Boc)₂O. All reactions were performed under mild conditions, giving the desired products in good to high yields.     

The stability of limit cycles in nonlinear systems

In this paper, a necessary condition is first presented for the existence of limit cycles in nonlinear systems, then four theorems are presented for the stability, instability, and semistabilities of limit cycles in second order nonlinear systems. Necessary and sufficient conditions are given in terms of the signs of first and second derivatives of a continuously differentiable positive function at the vicinity of the limit cycle. Two examples considering nonlinear systems with familiar limit cycles are presented to illustrate the theorems.     

4,4′-Trimethylenedipiperidine,a safe and greener alternative for piperidine,catalyzed the synthesis of N-methyl imines

A practical and facile synthesis of various N-methyl imines, versatile scaffolds, was conducted at 85 °C using 4,4′-trimethylenedipiperidine as a safe and green catalyst. This reagent is a commercially available solid and can be handled easily. It has high thermal stability, low toxicity, and good solubility in green solvents such as water and ethanol. The regenerated catalyst demonstrated stable activity after several recycle runs, and any changes were detected in its chemical structure by ¹H NMR monitoring. The novelty of the current work is that the 4,4′-trimethylenedipiperidine can act as a promising alternative for piperidine in organic reaction at higher temperatures due to its broad liquid range temperature, thermal stability, acceptor/donor hydrogen bond property, and other unique merits. Furthermore, the current protocol avoids waste generation in the workup process, which is a drawback in most previous reported procedures.

     

A promising green method in cyclization reaction.Oxidation of 3-methylcatechol in the presence of 1,10-phenanthroline

Electrochemical oxidation of 3-methylcatechol as a model compound has been studied in the presence of 1,10-phenanthroline as a bi-dentate nucleophile in water/acetonitrile(70/30,v/v) solution using cyclic voltammetry and controlled-potential coulometry. The results revealed that anodically generated 3-methylcyclohexa-3,5-diene-1,2-dione participates in inter and intramolecular Michael addition reactions with 1,10-phenanthroline and via an ECEC pathway converts to the corresponding heterocyclic compound.The present work has led to the development of a facile and one-pot method with high atom economy under ambient conditions and in an undivided cell using a carbon electrode.     

Comparison of the Morphological,Mechanical, and UV Protection Properties of TiO2/Polyamide 6 (PA6), and ZnO/PA6 Nanocomposite Multifilament Yarns

The properties of TiO₂/polyamide 6 (PA6) and ZnO/PA6 nanocomposite filament yarns produced on a pilot-plant melt spinning machine were compared. Concentrated masterbatches were prepared using a twin screw extruder. Then continuous multifilament yarns were produced by blending nylon 6 chips and various amounts of the prepared masterbatches. Melt spinning was carried out at the spinning temperature of 265°C and take-up speed of 4000 m/min. As-spun multifilament yarns were then drawn and textured. Morphological properties of the produced yarns were studied. Thermal behavior and physical properties, including shrinkage and tensile properties, were measured. Weft-knitted fabrics were evaluated for their ultraviolet protection properties. Although both kinds of the nanoparticles had a positive effect on the ultraviolet protection properties of their nanocomposite fabrics as compared to pure PA6 fabric, the efficiency of the TiO₂ nanoparticles was more than that of the ZnO ones for the same concentrations. The differences between the different properties of the two kinds of nanocomposites are discussed based on their interaction with the polymeric matrix, specific surface area, steric hindrance effect, and band gap energies.