The use of calcination in exposing the entrapped Fe particles from multi-walled carbon nanotubes grown by chemical vapour deposition

Multi-walled carbon nanotubes (MWCNTs) were synthesized a by chemical vapour deposition method. The effect of calcination at temperatures ranging from 300 to 550°C in exposing the metal nanoparticles within the nanotube bundles was studied. The degree of degradation of the structural integrity of the MWCNTs during the thermal process was studied by Raman spectroscopy, X-ray diffraction analysis, field-emission scanning electron microscopy, and transmission electron microscopy. The thermal behaviour of the as-prepared and calcined samples was investigated by thermogravimetric analysis. Calcination in air, at 400°C for 1 h, was found to be an efficient and simple method to extract metallic impurities from the amorphous carbon shells with minimal damage to the tube walls and lengths. The nanotubes were observed to be damaged at temperatures higher than 450°C.     

Catalytic oxidation and C–C coupling reactions of new ruthenium(III) Schiff base complexes containing PPh<Subscript>3</Subscript> or AsPh<Subscript>3</Subscript> co-ligands

New mononuclear ruthenium(III) Schiff base complexes of the type [RuX₂(EPh₃)(L)] (X = Cl or Br; E = P or As; L = monobasic tridentate Schiff base derived from o-aminophenol or o-aminothiophenol with ethylacetoacetate or ethylbenzoylacetate) have been synthesized. The Schiff base ligands chelate to ruthenium through O, N, and O/S by dissociation of the phenolic proton/thiophenolic proton forming chelate rings. These complexes have been characterized by physico-chemical and spectroscopic methods. Cyclic voltammetric data of all the complexes showed Ru(III)/Ru(IV) oxidation and Ru(III)/Ru(II) reduction within the range of 0–1.5 V and 0 to −1.5 V with respect to Ag/AgCl, respectively. The complexes were tested as catalysts in the oxidation of alcohols using molecular oxygen at ambient temperature, and also in C–C coupling reactions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Carbon nanotubes on unsteady MHD non-Darcy flow over porous wedge in presence of thermal radiation energy

The thermal radiation energy is the clean energy with a much lower environmental impact than the conventional energy. The objective of the present work is to investigate theoretically the effect of copper nanoparticles and carbon nanotubes (CNTs) in the presence of base fluid (water) with the variable stream condition due to the thermal radiation energy. Single-walled carbon nanotubes (SWCNTs) in the presence of base fluid flow over a porous wedge play a significant role compared to those of copper nanoparticles on absorbing the incident solar radiation and transiting it to the working fluid by convection.     

Lie group analysis for the effect of temperature-dependent fluid viscosity with thermophoresis on magnetohydrodynamic free convective heat and mass transfer over a porous stretching surface

This article concerns with a steady two-dimensional flow of an electrically conducting incompressible fluid over a vertical stretching sheet. A scaling group of transformations is applied to the governing equations. The system remains invariant due to some relations among the parameters of the transformations. Impact of thermophoresis particle deposition in the presence of temperature-dependent fluid viscosity plays an important role on the concentration boundary layer. The results thus obtained are presented graphically and discussed.     

One-pot synthesis of methyl piperazinyl–quinolinyl nicotinonitrile derivatives under microwave conditions and molecular docking studies with DNA

Derivatives of methyl piperazinyl–quinolinyl nicotinonitrile were synthesised by one-pot method under microwave conditions. This was achieved using the Knoevenagel condensation reaction. The novel derivatives described above were purified by column chromatography and characterised by FT-IR, ¹H, ¹³C, 2D-NMR and HRMS spectroscopic techniques. Furthermore, molecular docking was used to determine the binding sites of DNA with selected compounds. The synthetic method developed in this study showed several advantages including simplicity, high yield of products, coupled with safety and a short reaction time of 15 min.     

A convenient synthesis of 5-substituted-7-β-D-arabinofuranosylpyrrolo[2,3-d]pyrimidines structurally related to the antibiotics toyocamycin and sangivamycin

4-Amino-7-(2,3,5-tri-O-benzyl-β-D-arabinofuranosyl)pyrrolo[2,3-d]pyrimidine-5-carbonitrile ( 6a ), prepared from 2-ethoxymethyleneamino-5-bromopyrrole-3,4-dicarbonitrile ( 4 ), was debenzylated with boron trichloride to give ara-toyocamycin ( 6b ). Further functional group transformation of 6b provided a route to 4-amino-7-β-D-arabinofuranosylpyrrolo[2,3-d]pyrimidine-5-thiocarboxamide (ara-thiosangivamycin, 7a ), and the corresponding 5-carboxamidoxime 8a and 5-carboxamidine 8b derivatives. Phosphorylation of unprotected 7a with phosphorus oxychloride gave ara-thiosangivamycin 5′-monophosphate ( 7b ). 2′-O-Acetyl-ara-thiosangivamycin ( 10b ) was prepared as a prodrug by acetylation of 9a , followed by deprotection of the t-butyldimethylsilyl groups under acidic conditions without acyl migration.     

子半理想环

本文提出了环论中的一个新概念：子半理想，得到了群环为子半理想环的一个充要条件。     

论环{R×G×S}

本文定义了一个新的代数系｛Ｒ×Ｃ×Ｓ｝这是一个有环结构的自由Ｒ－模，并讨论了结构性质与Ｒ的性质．     

Development of new chiral building blocks for synthesis of bicyclo[3.3.0]octane compounds

Ti(II)-mediated tandem cyclization of (E)-5-(tert-butyldimethylsilyloxy)-8-trimethylsilyl-2-octen-7-ynoate (7) prepared from commercially available optically active epichlorohydrin (2) proceeded diastereoselectively to provide 7-(tert-butyldimethylsilyloxy)-2-trimethylsilylbicyclo[3.3.0]oct-1-en-3-one (1), which serves as a useful chiral building block or intermediate to prepare a variety of compounds having a bicyclo[3.3.0]octane framework.     

Reversed approach to S-farnesylation and S-palmitoylation: application to an efficient synthesis of the C-terminus of lipidated human N-ras hexapeptide

[reaction: see text] A general reversed approach is described to synthesize S-palmitoylated and S-farnesylated peptides via S(N)2 displacement of bromide by reaction of a thiol group containing lipid as nucleophile with bromoalanine-containing peptides as electrophile. By employing this approach, lipidated peptides, including characteristic partial structures of human Ras peptides, were synthesized in good yields. This method gives access to farnesylated, palmitoylated, and doubly lipidated peptides.