Synthesis of 2,20'-arylmethylene bis (3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) in aqueous medium at room temperature

The reaction of dimedone with various aromatic aldehydes produces 2,2'-arylmethylene bis (3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) in excellent yields. The reactions occur in water as solvent at room temperature and avoiding the addition of any catalyst. The workup procedure is very simple and the products do not required further purification.     

Determining the effect of centrifugal and electrical forces on the jet behaviors,the nanofiber structure,and morphology

The increasing demand for nanofibers production has led to the rapid growth of the usage of electro‐centrifugal spinning (ECS) systems especially in recent years. Besides the rapid developments, fabrication of novel fibrous materials with novel techniques is still under investigation. Polyvinylepyrrolidone (PVP) is one of the multifunctional materials, which has attracted scientific interests to be employed in a variety of advanced applications. The main objective of the present study was therefore to explore the effects of essential parameters involved in fabrication of PVP nanofibers via an ECS system. The effects of rotational speed (197‐4051 r/min) and applied voltage (0‐14 kV) on the structural and morphological properties of nanofibers were also investigated. Analyses of the scanning electron microscope (SEM) images were performed with Digimizer and SPSS16.0 software to characterize the diameter distribution of the nanofibers. The degree of crystallinity was evaluated by the X‐ray diffraction method. In order to explain the unexpected results, further investigations were performed on the motion of the jet and flow rate. The results showed that instead of nanofibers, microparticles were formed at lower voltages and rotational speeds. The increase in the applied voltage resulted in a decrease in the minimum rotational speed that is required to form continuous fluid jet. The bending instabilities were changed from whipping to spiraling at the voltages above 10 kV. This resulted in the minimum fiber diameter at a voltage between 6 and 10 kV. Moreover, the applied voltage slightly affected the degree of crystallinity. No significant change was observed in the degree of crystallinity by varying the rotational speed.     

Electrochemical deposition of Ni on F-doped SnO<Subscript>2</Subscript> substrate and its post-annealing for use as current collector of dye-sensitized solar cell

Current collector is an important part of nanostructured dye-sensitized solar cells (DSSCs), which reduces ohmic loss. In the present work, Ni current collector was electrochemically deposited on fluorine-doped tin oxide (FTO) for use as current collector of DSSC. The adhesion of Ni to FTO was improved by post-annealing in ambient atmosphere. A new method was proposed to prevent Ni coating from oxidation during annealing. According to this method, a carbon over-layer was applied on Ni coating, which protected Ni from oxidation. Visual inspection and X-ray diffraction (XRD) results showed the effectiveness of this method in protection of Ni coating from oxidation. Furthermore, the effect of current collector on photovoltaic performance of DSSCs was investigated using current density-voltage curve measurement and electrochemical impedance spectroscopy methods. It was observed that post-annealing in ambient atmosphere, under protection of carbon over-layer, improves both the adhesion of Ni current collector to FTO and the photovoltaic performance of DSSC. However, Ni oxidation during post-annealing of Ni current collector, without carbon over-layer, significantly decreased the photovoltaic parameters of DSSC. The above observations were explained by considering the series resistance of DSSC.     

Existence of positive solution for nonlocal singular fourth order Kirchhoff equation with Hardy potential

This paper is concerned with the existence of positive solution to a class of singular fourth order elliptic equation of Kirchhoff type

$$\begin{aligned} \triangle ^2 u-\lambda M(\Vert \nabla u\Vert ^2)\triangle u-\frac{\mu }{\vert x\vert ^4}u=\frac{h(x)}{u^\gamma }+k(x)u^\alpha , \end{aligned}$$

under Navier boundary conditions, \(u=\triangle u=0\). Here \(\varOmega \subset {\mathbf {R}}^N\), \(N\ge 1\) is a bounded \(C^4\)-domain, \(0\in \varOmega \), h(x) and k(x) are positive continuous functions, \(\gamma \in (0,1)\), \(\alpha \in (0,1)\) and \(M:{\mathbf {R}}^+\rightarrow {\mathbf {R}}^+\) is a continuous function. By using Galerkin method and sharp angle lemma, we will show that this problem has a positive solution for \(\lambda > \frac{\mu }{\mu ^*m_0}\) and \(0<\mu <\mu ^*\). Here \(\mu ^*=\Big (\frac{N(N-4)}{4}\Big )^2\) is the best constant in the Hardy inequality. Besides, if \(\mu =0\), \(\lambda >0\) and h, k are Lipschitz functions, we show that this problem has a positive smooth solution. If \(h,k\in C^{2,\,\theta _0}(\overline{\varOmega })\) for some \(\theta _0\in (0,1)\), then this problem has a positive classical solution.

     

Ligandless C‐C bond formation via Suzuki–Miyaura reaction in micelles or water–ethanol solution using PdPtZn and PdZn nanoparticle thin films

PdPtZn and PdZn nanoparticle (NP) thin films were synthesized by the reduction of [PdCl₂(cod)], [PtCl₂(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Zn(acac)₂] (acac = acetylacetonate) complexes at an oil–water interface. The structure and morphology of the as‐prepared NPs were characterized with X‐ray diffraction, transmission electron microscopy and energy dispersive analysis of X‐rays. Catalytic activity of the prepared NPs was investigated in the Suzuki–Miyaura cross‐coupling reaction in H₂O–EtOH and various micellar media systems such as cetyltrimethylammonium bromide (cationic surfactant), sodium dodecylsulfate (anionic surfactant) and Pluronic P123 (non‐ionic surfactant). PdPtZn and PdZn thin films exhibited higher catalytic activity compared to Pd thin film in the Suzuki–Miyaura coupling reaction due to the appropriate interaction between palladium, platinum and zinc metals. Copyright © 2015 John Wiley & Sons, Ltd.     

Multi-solutions with specific geometrical wave structures to a nonlinear evolution equation in the presence of the linear superposition principle

Lump solutions are one of the most common solutions for nonlinear evolution equations.This study aspires to investigate the generalized Hietarintatype equation.We auspiciously provide multiple M-lump waves.On the other hand,collision phenomena to multiple M-lump waves with soliton wave solutions are also provided.During the collision,the amplitude of the lump will change significantly over the processes,whereas the amplitude of the soliton will just minimally alter.As it is of paramount importan...     

Elucidation of Antioxidant Compounds in Moroccan Chamaerops humilis L. Fruits by GC–MS and HPLC–MS Techniques

The aim of this study was to characterize the phytochemical content as well as the antioxidant ability of the Moroccan species Chamaerops humilis L. Besides crude ethanolic extract, two extracts obtained by sonication using two solvents with increased polarity, namely ethyl acetate (EtOAc) and methanol-water (MeOH-H₂O) 80:20 (v/v), were investigated by both spectroscopy and chromatography methods. Between the two extracts, the MeOH-H₂O one showed the highest total polyphenolic content equal to 32.7 ± 0.1 mg GAE/g DM with respect to the EtOAc extract (3.6 ± 0.5 mg GAE/g DM). Concerning the antioxidant activity of the two extracts, the EtOAc one yielded the highest value (1.9 ± 0.1 mg/mL) with respect to MeOH-H2O (0.4 ± 0.1 mg/mL). The C. humilis n-hexane fraction, analyzed by GC–MS, exhibited 69 compounds belonging to different chemical classes, with n-Hexadecanoic acid as a major compound (21.75%), whereas the polyphenolic profile, elucidated by HPLC–PDA/MS, led to the identification of a total of sixteen and thirteen different compounds in both EtOAc (major component: ferulic acid: 104.7 ± 2.52 µg/g) and MeOH-H₂O extracts (major component: chlorogenic acid: 45.4 ± 1.59 µg/g), respectively. The attained results clearly highlight the potential of C. humilis as an important source of bioactive components, making it a valuable candidate to be advantageously added to the daily diet. Furthermore, this study provides the scientific basis for the exploitation of the Doum in the food, pharmaceutical and nutraceutical industries.     

Highly efficient one-pot synthesis of tetrahydropyridines

The combination of aromatic aldehydes, and 1,3-dicarbonyl compounds in the presence of a catalytic amount of poly(N,N′-dibromo-N-ethyl-benzene-1,3-disulfonamide) [PBBS] and N,N,N′,N′-tetrabromobenzene-1,3-disulfonamide [TBBDA] leads to the formation of highly substituted tetrahydropyridines. In this way, a series of pharmacologically interesting substituted piperidine derivatives were obtained in moderate to high yields at room temperature.