Surface and bulk modification of ethylene-propylene-diene terpolymer elastomer: Adhesion to polyurethane and mechanical properties

Effect of adding millable polyurethane as adhesion promoter to the ethylene-propylene-diene terpolymer as well as to the terpolymer modified by grafting of maleic anhydride on the adhesion between the terpolymer and polyurethane coating was studied. The results of peel test and water contact angle measurements showed that surface and bulk modification of terpolymer cause a significant improvement in its adhesion properties. The effect of the composition of the polymer blends on the loss tangent was studied to evaluate the extent of polymer compatibility and damping characteristics. Results demonstrated that modification of terpolymer with maleic anhydride can improve its compatibility with polyurethane, which was further confirmed by the results of the mechanical and morphological study.     

Chemical transduction with fluorescent lipid membranes using selective interactions of acetylcholine receptor with agonist/antagonist and acetylcholine with substrate

Alterations in the physical structure of vesicles and monolayers of phospholipids and soybean lecithin were monitored by measurement on the average fluorescence intensity changes from N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)dipalmitoyl-L-a-phosphatidyl ethanolamine (NBD-PE) located in the lipid matrices. This probe was intimately dispersed at a concentration of 1-2 mol-% in lipid membranes and had an emission sensitive to local environmental structure. Alterations in the structure of soybean lecithin vesicles were induced by the selective interaction of acetylcholine receptor with the agonist carbamylcholine and the antagonist alpha-bungarotoxin. Structural changes in vesicles with a 7:3 mole ratio of dipalmitoylphosphatidyl choline to dipalmitoylphosphatidic acid were observed for selective interactions between acetylcholinesterase and acetylcholine. Enhancement of fluorescence emission from the lipid membranes provided transduction of the selective binding events of the receptor and enzyme. A maximum sensitivity of about a 30% enhancement per micromole of carbamylcholine and a detection limit for the toxin of 10 nM were observed for the receptor. Fluorescence microscopy was used to establish that protein could be incorporated in monolayer lipid membranes and to provide information about potential mechanisms of fluorescence enhancement. These studies show that lipid membranes containing NBD-PE can be used as generic transducers of protein-ligand interactions.     

A novel, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines

A novel, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines is described. The reactive 1:1 zwitterionic intermediate, formed by the addition of isocyanides to dialkyl acetylenedicarboxylates, was trapped by N-(2-pyridyl)amides to produce the title compounds under mild reaction conditions in good yields.     

A new, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines

A new, one-pot and three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines is described. The reactive 1:1 zwitterionic intermediate, formed by the addition of isocyanides to dialkyl acetylenedicarboxylates, was trapped by N-(2-heteroaryl)amides to yield a ketenimine intermediate, which was cyclized and then rearranged under the reaction conditions to afford the title compounds under mild reaction conditions in good yields. Single-crystal X-ray analysis conclusively confirms the structure of the obtained bridgehead bicyclic 6-6 heterocyclic compounds.     

On the Energetics of Ions in Carbon and Gold Nanotubes

We investigate the insertion of halide and alkali atoms into narrow single‐walled carbon nanotubes with diameters <9 Å by density functional theory; both chiral and non‐chiral tubes are considered. The atoms are stored in the form of ions; the concomitant charge transfer affects the band structure and makes originally semiconducting tubes conducting. The electrostatic interaction between a charge and the walls of the tube is explicitly calculated. The insertion energies and the positions of the ions are determined by a competition between electrostatic energy and Pauli repulsion. For comparison, we consider ions in gold nanotubes. Alkali ions follow the same principles in gold as in carbon tubes, but chloride is specifically adsorbed inside gold tubes.     

Proposal of a New Hf(IV)/Zr(IV) Separation System by the Solvent Extraction Method

A liquid-liquid extraction study has been conducted to separate hafnium from zirconium, using Cyanex 301 in kerosene. Noticeably, it is the first time that Cyanex 301 is utilized to separate Hf(IV) from Zr(IV). In this series of experiments, several parameters influencing the separation have been investigated, such as the initial pH, the extractant concentration, the metal ion concentration, the temperature, the type of the diluents and the salt addition. Regarding the aging of the Zr(IV) and Hf(IV) solutions, the solutions with a maximum 3 d aging time could be used with no difficulties. It was observed that the initial pH increase caused an increase in the Zr(IV)/Hf(IV) separation factor. Moreover, the distribution decreased with the temperature increase, suggesting that the reaction is exothermic. In agreement with the resulting data, the optimum separation factor illustrates the value of 7 at a pH of 4.00 in the presence of NaCl as an added salt. The attractive characteristics of the presently designed method are the use of low acidic nitrate solutions, the lack of using thiocyanate and a higher extractability of hafnium-Cyanex 301 relative to zirconium-Cyanex 301 complexes.     

Novel potentiometric sensor for the trace-level determination of Zn2+ based on a new nanographene/ion imprinted polymer composite

In this research, a new strategy for construction of a development potentiometric carbon paste Zn²⁺-ion selective electrode based on a novel nano-sensing layer is suggested. The proposed nano-sensing layer was prepared with the addition of a synthesised Zn²⁺-ion imprinted polymer nanoparticles ‘as an efficient sensing agent’ into the carbon paste matrix consisting of graphite powder, nanographene-composite ‘graphene nanosheets decorated with silver nanoparticles’ and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ‘ an ionic liquid ’, as the conducting binder. Under the optimised experimental conditions, the suggested nanographene-composite potentiometric sensor presented a low detection limit of 1.93 × 10^?1 μg L^?1 and a linear analytical range from 2.62 × 10^?1 to 6.54 × 10⁵ μg L^?1 with an excellent Nernstian slope of 29.80 mV decade^?1. The proposed zinc selective sensor was successfully applied for the highly sensitive determination of trace amounts of Zn²⁺ in environmental and biological samples with satisfactory results.     

Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base

A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0 × 10⁻⁴ and 6.0 × 10⁻⁴ μmol L⁻¹ for Hg(II) and Pb(II) with a 90 s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.