Diaminobisbenzothiazole chain extended polyurethanes as a novel class of thermoplastic polyurethane elastomers with improved thermal stability and electrical insulation properties

This work was devoted to the development of a new class of modified polyurethane as an electrical insulating material. For this purpose, NCO‐terminated urethane prepolymers at different NCO contents were prepared and chain extended by 6,6′‐oxybis(2‐aminobenzothiazole) (ABT) to produce thermoplastic polyurethane elastomers. All of the polymers were characterized by FTIR and ¹HNMR spectroscopies and examined for their thermal, mechanical, and electrical properties. The dynamic mechanical measurements results showed two glass transitions indicating phase separation. A considerable improvement in the thermal and electrical properties in comparison to common polyurethanes was detected for these polymers. The level of enhancement in the measured properties was related to the polyol molecular weight, hard segment content, and consequently the amount of the introduced urea and benzothiazole moieties. These findings indicated the improved high service temperature performance of these materials as electrical insulator for metallic surfaces. Copyright © 2008 John Wiley & Sons, Ltd.     

Dowex as Reusable Acidic Polymeric Catalyst in the Efficient and Regioselective Conversion of Epoxides into β‐Hydroxy Thiocyanates under Solvent Free Conditions

A convenient and efficient procedure for the regioselective ring opening of epoxides in the presence of Dowex (strongly acidic cationic exchange resin), as reusable eco‐friendly catalyst under solvent free conditions is described. Thus, several β‐hydroxy thiocyanates, useful intermediates toward pharmaceutical and biologically active molecules, are easily obtained in high isolated yields.     

The numerical solution of problems in calculus of variation using Chebyshev finite difference method

The Chebyshev finite difference method is used for finding the solution of the ordinary differential equations which arise from problems of calculus of variations. Our approach consists of reducing the problem to a set of algebraic equations. This method can be regarded as a non-uniform finite difference scheme. Some numerical results are also given to demonstrate the validity and applicability of the presented technique. The method is easy to implement and yields very accurate results.     

Testing catalytic activity of ruthenium(III) acetylacetonate in the presence of trialkylphosphite or trialkylphosphine in hydrogen generation from the hydrolysis of sodium borohydride

Catalytic activity of Ru(acac)₃ in the presence of different phosphorus compounds (P(OMe)₃, P(OPh)₃, PPh₃ and dppe) was investigated for the first time in the hydrolysis of NaBH₄. Phosphorus compound, usually known as poison in catalysis, is involved in the formation of a species which has higher catalytic activity in comparison with Ru(acac)₃ alone. Varying the phosphorus compound affects the catalytic activity and lifetime of the catalyst as well as the kinetics and the activation parameters of the hydrolysis of NaBH₄. For all of the phosphorus compounds, the hydrogen generation was found to be zero-order with respect to the substrate concentration and first-order regarding the catalyst concentration. The catalyst system with P(OMe)₃ shows the highest catalytic activity and provides the largest total turnover number (TTON = 20,700 over 72 h) in the hydrolysis of NaBH₄. The highest activation energy and enthalpy values were obtained for the catalyst with dppe (E_a = 59 ± 2, ΔH^# = 60 ± 2 kJ/mol) while the lowest values were found for the catalyst system with PPh₃ (E_a = 46 ± 2, ΔH^# = 43 ± 1 kJ/mol).     

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones is described. A mixture of N-isocyaniminotriphenylphosphorane, an aldehyde, and Meldrum's acid undergo a 1:2:1 addition reaction under mild conditions to afford the title compounds in good to excellent yields.     

Alternative supply chain production-sales policies for new product diffusion: An agent-based modeling and simulation approach

Applying agent-based modeling and simulation (ABMS) methodology, this paper analyzes the impact of alternative production-sales policies on the diffusion of a new generic product and the generated NPV of profit. The key features of the ABMS model, that captures the marketplace as a complex adaptive system, are: (i) supply chain capacity is constrained; (ii) consumers’ new product adoption decisions are influenced by marketing activities as well as positive and negative word-of-mouth (WOM) between consumers; (iii) interactions among consumers taking place in the context of their social network are captured at the individual level; and (iv) the new product adoption process is adaptive. Conducting over 1 million simulation experiments, we determined the “best” production-sales policies under various parameter combinations based on the NPV of profit generated over the diffusion process. The key findings are as follows: (1) on average, the build-up policy with delayed marketing is the preferred policy in the case of only positive WOM as well as the case of positive and negative WOM. This policy provides the highest expected NPV of profit on average and it also performs very smoothly with respect to changes in build-up periods. (2) It is critical to consider the significant impact of negative word-of-mouth in choosing production-sales policies. Neglecting the effect of negative word-of-mouth can lead to poor policy recommendations, incorrect conclusions concerning the impact of operational parameters on the policy choice, and suboptimal choice of build-up periods.     

Chemical composition of the essential oil of aerial parts of Haussknechtia elymaitica Boiss. from Iran: a good natural source for trans-asaron

The chemical composition of the essential oil of Haussknechtia elymaitica Boiss. was investigated by capillary GC and GC/MS for the first time. Twelve components were identified which accounting for 99.7% of the oil composition. The major compounds were trans-asarone (59.9%), trans-methyl isoeugenol (22.4%), α-zingiberene (7.96%), β-sesquiphellandrene (4.7%) and β-bisabolene (4.3%). The first three compounds considered as the main components of the essential oil were isolated and characterised by spectroscopic techniques.     

A new flavonoid and other constituents from Centaurea nicaeensis All. var. walliana M

A new flavone glucoside, apigenin 4'-(6″-methylglucuronide) (1), together with six known compounds, cirsilineol, jaceosidin, melitensin, apigenin, apigenin 7-(6″-methylglucuronide) and prunasin, were isolated from the ethanolic extract of the aerial parts of Centaurea nicaeensis All. var. walliana M. (Asteraceae) collected from Souk-Ahras, eastern Algeria. The structures were established by spectral analysis, mainly HRESI-MS, UV and 2D-NMR experiments (COSY, HSQC and HMBC).     

Organic-Assisted Nano-Sized Antimony Telluride Prepared by Co-Precipitation Reductive Route

Nano-sized antimony telluride is of much interest for improving the thermoelectric figure of merit. In the present work, organic-assisted antimony telluride nanorods were successfully fabricated by a simple hydrothermal method. The products were characterized by means of X-ray diffraction, scanning electron microscope, and transmission electron microscope. The results show that the typical antimony telluride synthesized by co-precipitation reductive route is rodlike in shape with about 35 nm in thickness and 300 nm in edge length.