Fixed point results on metric-type spaces

In this paper we obtain fixed point and common fixed point theorems for self-mappings defined on a metric-type space, an ordered metric-type space or a normal cone metric space. Moreover, some examples and an application to integral equations are given to illustrate the usability of the obtained results.     

Magnetic field assisted μ-solid phase extraction of anti-inflammatory and loop diuretic drugs by modified polybutylene terephthalate nanofibers

A magnetic nanocomposite consisting of nanoparticles–polybutylene terephthalate (MNPs–PBT) was electrospun and used as an extracting medium for an on-line μ-solid phase extraction (μ–SPE)–high performance liquid chromatography (HPLC) set–up with an ultraviolet (UV) detection system. Due to the magnetic property of the prepared nanofibers, the whole extraction procedure was implemented under an external magnetic field to enhance the extraction efficiencies. The developed method along with the synthesized nanocomposite were found to be appropriate for the determination of trace levels of selected drugs including furosemide, naproxen, diclofenac and clobetasol propionate in the urine sample. The prepared MNPs-PBT electrospun nanocomposite was characterized using the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX) and Fourier transform infrared (FT–IR) spectroscopy. The prepared magnetic fibers showed high porosity, which was another driving force for the extraction efficiency enhancement. Major parameters affecting the extraction efficiency of the selected drugs were optimized. The limits of detections (LOD) of the studied drugs were in the range of 0.4–1.6 μg L⁻¹ and the limits of quantification (LOQ) were 1–4 μg L⁻¹ under the optimized conditions. Relative standard deviation (RSD%) for three replicates at three concentration levels of 6, 100 and 400 μg L⁻¹ were 5.9–8.0% while acceptable linear range with two orders of magnitude was obtained (R² = 0.99). The method was validated by the determination of the selected drugs in urine samples and the results indicated that this method has sufficient potential for enrichment and determination of the desired drugs in the urine sample. The relative recovery values were found to be in the range of 78–91%. Implementing the developed on–line μ–SPE method under the external magnetic field induction, led to higher extraction efficiencies for the selected drugs with various diamagnetic properties.     

Water-Accelerated Selective Synthesis of 1,2-Disubstituted Benzimidazoles at Room Temperature Catalyzed by Br⊘nsted Acidic Ionic Liquid

An environmentally benign method for the rapid and selective synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles by the reaction of o-phenylenediamines and aromatic aldehydes in the presence of 1-methylimidazolium triflouroacetate ([Hmim]TFA) at room temperature under aqueous conditions is described. The ionic liquid is reusable and could be recycled for several runs without any decrease in its efficiency.     

Synthesis of novel spiro-fused pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidines

New pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidines, with an associated spiro-3,3′-oxindole attachment, were prepared by three-component combinations of 5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinoline-1,2-dione with a pair of reactants chosen from a pyrazol-5-one, a pyrazole-5-amine, a barbituric acid, or a 6-aminouracil.     

Functionalized MgO,CeO<Subscript>2</Subscript> and ZnO nanoparticles with humic acid for the study of nitrate adsorption efficiency from water

In this study, the removal of nitrate using ZnO, MgO, and CeO₂ nanoparticles (NPs) modified by humic acid from water was tested. Nanoparticles were modified by humic acid using the microwave-assisted technique and then modified ZnO (Zn–H), modified MgO (Mg–H), and modified CeO₂ (Ce–H) were characterized through SEM, EDX, FTIR, and XRD analysis. Several important parameters influencing the removal of nitrate such as contact time, pH, adsorbent dosage and temperature were explored systematically by batch experiments. Isotherm studies were set up with the following optimum conditions: pH?=?5, adsorbent concentration of 1 g L^?1, 180 min and 25 °C. The results revealed that the adsorption were best fitted to pseudo-second order and simple Elovich kinetics models. Langmuir, Freundlich and linear adsorption models were fitted to describe adsorption isotherms and constants. The isotherm analysis indicated that the adsorption data can be represented by both Freundlich and linear isotherm models. The maximum adsorption capacity (q_m) was obtained at 55.1, 74.2 and 75.8 mg g^?1 for Zn–H, Ce–H, and Mg–H, respectively. The thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were obtained. From the thermodynamic parameters, it is suggested that the adsorption of nitrate on modified NPs (MNPs) followed the exothermic and spontaneous processes. The obtained results showed that the MNPs were efficient adsorbents for removing nitrate from aqueous media.     

A new analytical definition of the dead material zone for forward extrusion of shaped sections

This article aims to provide a new formulation for the analysis of the extrusion process for non-axisymmetric sections. The upper bound theorem has been used to obtain a generalized kinematically admissible velocity field. The geometry of the deforming region has been formulated considering variation of the dead zone size at different angular positions and three-dimensional curved surfaces have been employed to define the entry and exit surfaces of the deformation zone. Using this analytical method, extrusion of square, rectangular and L-shaped sections were analyzed and the effect of shape complexity on material flow and dead material zone (DMZ) formation under different conditions has been investigated. Physical modelling experiments and finite element analysis were carried out to reveal the capability of the proposed theoretical method.     

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.     

Bioactive compounds from <Emphasis Type="Italic">Smilax excelsa</Emphasis> L.

Phytochemical investigation of EtOAc extract of Smilax excelsa has led to isolation and structure elucidation of five compounds. The structures of these compounds are established by different spectroscopic techniques including 1D and 2D-NMR, HRMS and ECD spectroscopy. The compounds were: solanesol (1), violasterol A (2), trans-resveratrol (3), 5-O-caffeoylshikimic acid (4) and 6-O-caffeoyl-β-d-fructofuranosyl-(2-1)-α-d-glucopyranoside (5). The configuration of compound 2 was established by electronic circular dichroism (ECD) spectroscopy. Meanwhile the cytotoxicity and antibacterial activity of the compounds were evaluated by MTT and MIC assays. Compounds 1 and 2 showed promising inhibition on MCF-7 cell line with IC₅₀ of 161.6 and 190.0 µM, respectively. Also compounds 2 and 3 illustrated activity against Staphylococcus aureus with MIC values of 142.5 and 136.9 µM, respectively.