An effective modification of the homotopy perturbation method for stiff systems of ordinary differential equations

The present work deals with employing a new form of the homotopy perturbation method (NHPM) for solving stiff systems of linear and nonlinear ordinary differential equations (ODEs). In this scheme, the solution is considered as an infinite series that converges rapidly to the exact solution. Two problems are chosen as illustrative examples to show the effectiveness of the present method. In obtaining the exact solution for each case, the capability and the simplicity of the proposed technique is clarified.     

Synthesis of Core-Shell Magnetic Supramolecular Nanocatalysts based on Amino-Functionalized Calix[4]arenes for the Synthesis of 4H-Chromenes by Ultrasonic Waves

One of the most common phenol-formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features including being able to form host-guest complexes, having unique structural scaffolds and their relative ease of chemical modifications with a variety of functions on their upper rim and lower rim. Here, a functional magnetic nanocatalyst was designed and synthesized by using a synthetic amino-functionalized calix[4]arene. Its catalytic activity was evaluated in a one-pot synthesis of 2-amino-4H-chromene derivatives. Besides, this novel magnetic nanocatalyst was characterized by spectroscopic and analytical techniques such as FT-IR, EDX, FE-SEM, TEM VSM, XRD analysis.     

Synthesis of one-pot pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl) methanone derivatives via a multi-component using Fe3O4@TiO2-SO3H as a recoverable magnetic catalyst under microwave irradiation

ABSTRACT

A new one-pot method for the synthesis four-component of pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl)methanone derivatives has been developed in the presence of nano Fe₃O₄@TiO₂-SO₃H catalysts (heterogeneous acid) under microwave conditions and in a solvent-free environment at 180?W. One of the benefits of using this catalyst was its re-use in subsequent stages of its reaction without much loss in its activity, which was carried out by an external magnet and recovered. The catalyst was synthesized and characterized by XRD, EDX, TEM, FESEM, TGA-DTA, BET, VSM and AFM. The productivity of the products obtained from this protocol (MAOS) is significantly high and the shorter reaction time in the synthesis process over the reflux method. These results showed advantages for synthesis, such as mild reaction conditions, no use of toxic catalysts in the laboratory, solvent-free environment, low energy consumption and Economically Affordable.     

Electrochemical approach for monitoring the effect of anti tubulin drugs on breast cancer cells based on silicon nanograss electrodes

One of the most interested molecular research in the field of cancer detection is the mechanism of drug effect on cancer cells. Translating molecular evidence into electrochemical profiles would open new opportunities in cancer research. In this manner, applying nanostructures with anomalous physical and chemical properties as well as biocompatibility would be a suitable choice for the cell based electrochemical sensing. Silicon based nanostructure are the most interested nanomaterials used in electrochemical biosensors because of their compatibility with electronic fabrication process and well engineering in size and electrical properties. Here we apply silicon nanograss (SiNG) probing electrodes produced by reactive ion etching (RIE) on silicon wafer to electrochemically diagnose the effect of anticancer drugs on breast tumor cells. Paclitaxel (PTX) and mebendazole (MBZ) drugs have been used as polymerizing and depolymerizing agents of microtubules. PTX would perturb the anodic/cathodic responses of the cell-covered biosensor by binding phosphate groups to deformed proteins due to extracellular signal-regulated kinase (ERK^1/2) pathway. MBZ induces accumulation of Cytochrome C in cytoplasm. Reduction of the mentioned agents in cytosol would change the ionic state of the cells monitored by silicon nanograss working electrodes (SiNGWEs). By extending the contacts with cancer cells, SiNGWEs can detect minor signal transduction and bio recognition events, resulting in precise biosensing. Effects of MBZ and PTX drugs, (with the concentrations of 2 nM and 0.1 nM, respectively) on electrochemical activity of MCF-7 cells are successfully recorded which are corroborated by confocal and flow cytometry assays.     

Direct preparation of oximes and Schiff bases by oxidation of primary benzylic or allylic alcohols in the presence of primary amines using Mn(III) complex of polysalicylaldehyde as an efficient and selective heterogeneous catalyst by molecular oxygen

The present work introduced the new strategy for direct preparation of Schiff base as well as oxime compounds through oxidation of primary benzylic or allylic alcohols in the presence of amines by complexation of Mn(III) to a polymeric Schiff base ligand based on polysalicylaldehyde (PSA-Schiff base-Mn(III) complex). As a new environmentally benign protocol, manganese heterogeneous polymeric catalytic system demonstrated promising oxidation of alcohols in ethanol using molecular oxygen. PSA was synthesized through polycondensation reaction of 2-hydroxy-5-chloromethyl-benzaldehyde and then treated with 2-aminophenol to form polymeric ligand. Average molecular weight of PSA was studied by an analytical method as well as GPC analysis. Formation of the catalyst was characterized step by step by FTIR, UV–Vis, ¹H NMR, TGA, CHN and EDX analyses. Loading amounts of metal ions as well as leaching amount of the catalysis were studied by ICP-OES instrument. The catalyst shows up to high yields for oxidation of primary and secondary primary benzylic or allylic alcohols to carbonyl compounds, especially direct imine formation in a mild, inexpensive and efficient method which can be successfully recovered from the reaction mixture and reused for several times without any remarkable reactivity loss. Effect of solvent, temperature, catalyst amount and oxygen donors along with some blank experiments to elucidation of catalyst activity was evaluated in this work. Also chemoselectivity behavior of the catalyst was investigated with some combinations.     

Direct Analysis of Triterpenes from High-Salt Fermented Cucumbers Using Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI)

High-salt samples present a challenge to mass spectrometry (MS) analysis, particularly when electrospray ionization (ESI) is used, requiring extensive sample preparation steps such as desalting, extraction, and purification. In this study, infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) coupled to a Q Exactive Plus mass spectrometer was used to directly analyze 50-μm thick slices of cucumber fermented and stored in 1 M sodium chloride brine. From the several hundred unique substances observed, three triterpenoid lipids produced by cucumbers, β-sitosterol, stigmasterol, and lupeol, were putatively identified based on exact mass and selected for structural analysis. The spatial distribution of the lipids were imaged, and the putative assignments were confirmed by tandem mass spectrometry performed directly on the same cucumber, demonstrating the capacity of the technique to deliver confident identifications from highly complex samples in molar concentrations of salt without the need for sample preparation.

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Ionic Liquid-Assisted Fabrication of Bioactive Heterogeneous Magnetic Nanocatalyst with Antioxidant and Antibacterial Activities for the Synthesis of Polyhydroquinoline Derivatives

Antibacterial materials have obtained much attention in recent years due to the presence of hazardous agents causing oxidative stress and observation of pathogens. However, materials with antioxidant and antibacterial activities can cause toxicity due to their low biocompatibility and safety profile, urging scientists to follow new ways in the synthesis of such materials. Ionic liquids have been employed as a green and environmentally solvent for the fabrication of electrically conductive polymers. In the present study, an antibacterial poly(p-phenylenediamine)@Fe₃O₄ (PpPDA@Fe₃O₄) nanocomposite was fabricated using [HPy][HSO₄] ionic liquid. The chemical preparation of PpPDA@Fe₃O₄ nanocomposite was initiated through the oxidative polymerization of p-phenylenediamine by ammonium persulfate in the presence of [HPy][HSO₄]. The PpPDA@Fe₃O₄ nanocomposite exhibited antibacterial properties against Gram-negative (Escherichia coli) and Gram-positive (Bacillus subtilis) bacteria. The PpPDA@Fe₃O₄ nanocomposite was employed as a heterogeneous nanocatalysis for one-pot synthesis of polyhydroquinoline derivatives using aromatic aldehyde, dimedone, benzyl acetoacetate, and ammonium acetate. Polyhydroquinoline derivatives were synthesized in significant yields (90–97%) without a difficult work-up procedure in short reaction times. Additionally, PpPDA@Fe₃O₄ nanocatalyst was recycled for at least five consecutive catalytic runs with a minor decrease in the catalytic activity. In this case, 11 derivatives of polyhydroquinoline showed in vitro antioxidant activity between 70–98%.