Synthesis and properties of poly(ethylene oxide)‐grafted polyethylene copolymer and terpolymer

A series of graft copolymers were synthesized based on ethylene‐co‐m,p‐methylstyrene (EMS) (backbone copolymer), ethylene‐1‐hexene‐m,p‐methylstyrene (EHMS) (backbone terpolymer), and polyethylene glycol monomethyl ethers (PEGM) (grafts) in this study. The PEGMs with molecular weights of 750 and 2000 were used. The chemical composition of the graft copolymers was analyzed by NMR and DSC measurements. The graft copolymers exhibited a phase‐separated morphology with the backbone and the methoxy polyethylene glycol (MPEG) grafts forming separate crystalline phases. The MPEG phase had a melting temperature lower than the corresponding MPEG homopolymer, as determined by DSC. The melting point of the crystalline phase formed by the EMS and EHMS main chains was lower than that of pure polymer backbone. Copyright © 2009 John Wiley & Sons, Ltd.     

Diels-Alder cycloaddition of o-quinonedimethides and alkylidene-5H-furan-2-ones: new and rapid access to lambertellol cores and arthrinone derivatives

An efficient synthesis of deoxy-lambertellols was reported through a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disiloxybenzocyclobutenes and 2-methylprotoanemonine. Such transformation with δ-substituted γ-alkylidenebutenolides, to prepare new analogues of these tricyclic spirolactones, which would be very difficult to prepare by other ways, was also studied.     

Far- and mid-infrared of crystalline 2,2'-bithiophene: ab initio analysis and comparison with infrared response

Infrared intramolecular vibrations and lattice modes in the crystalline phase of 2,2'-bithiophene (2T) are investigated using the direct method combined with density functional theory (DFT)-based total energy calculations. For the first time, the far- and mid-infrared responses have been calculated from the Gamma-point modes and the Born effective charge tensors of the 2T crystalline phase. The relative good agreement between the calculated and experimental infrared spectra allows us to assign the origin of the main features of the experimental spectra, which is of particular interest in the far-infrared domain. These assignments are useful for understanding all the properties of the 2T crystalline phase in which phonon-phonon and electron-phonon interactions play an important role.     

Preparation of a fast-flow agarose-based chelating adsorbent with a novel dioxime derivative for selective column preconcentration of copper.

Fast-flow spherical homogeneous agarose beads were prepared by an emulsification method, and were cross-linked and activated by repeated treatment with allylbromide and bromine/water, followed by alkali. Bis(2-aminopyridyl)dioxime (APD) was synthesized by the reaction of 2-aminopyridine, and dichloroglyoxime and characterized by melting-point as well as IR, 1HNMR, 13CNMR and MS spectroscopies. APD was chemically linked to activated agarose beads to be employed for the column preconcentration of metal ions. Capacity measurements for eight metal ions indicated a high selectivity of the adsorbent towards Cu2+ with a capacity of 25.7 micromol per ml packed adsorbent. A factorial design was used for optimization of the effects of 5 different variables on the recovery of Cu2+. Under the optimized conditions, Cu2+ was quantitatively accumulated on a 0.25 ml packed column of the adsorbent in the pH range of 4 to 6, and simply eluted with 2 ml of a 1 mol 1(-1) hydrochloric acid solution. The column could tolerate salt concentrations up to 0.5 mol 1(-1), sample flow rates up to 15 ml min(-1), and sample volumes beyond 1000 ml. Matrix ions of Na+, Mg2+ and Ca2+ and potentially interfering ions of Ni2+, Cd2+, Zn2+, Fe3+ and Co2+ with relatively high concentrations did not show any significant effect on the analyte's signal. Preconcentration factors up to 500 and a detection limit of 0.16 microg 1(-1) were obtained for the determination of the analyte by flame AAS. Application of the method to the determination of natural and spiked copper in river water and seawater samples resulted in quantitative recoveries.     

Predictive QSAR models for the anti-cancer activity of topoisomerase IIα catalytic inhibitors against breast cancer cell line HCT15: GA-MLR and LS-SVM modeling

Structural Chemistry - Structural analysis of topoisomerase IIα catalytic inhibitors exhibited anti-tumor properties to use them in cancer therapeutic procedures. In this study, a quantitative...     

Analytical and visual modeling of InGaN/GaN single quantum well laser based on rate equations

An analytical, visual and open source model based on solving the rate equations for InGaN/GaN single quantum well (QW) lasers has been carried out. In the numerical computations, the fourth-order Runge–Kutta method has been used for solving the differential rate equations. The rate equations which have been considered in this simulation include the two level rate equations for the well and separate confinement heterostructure (SCH) layers. We present a new and inexpensive modeling method with analytical, visual and open source capabilities to investigate and comprehend the QW laser characteristics such as time behavior of carriers in SCHs and QW, photon density, output power and gain, and also the output power versus current which presents the threshold current of the laser. The characteristics of the QW lasers, which include laser time response (P–t), turn-on delay time of lasing and output power–current (P–I) characteristic and related features such as threshold current and slope efficiency have been investigated. Our model accurately computes the P–t and P–I characteristics such as turn-on delay time, threshold current and slope efficiency, and also illustrates the effects of parameters such as the injection current and geometry.     

Josephson current versus potential strength of the interface in ferromagnetic superconductors

Based on the scattering theory, we calculate the Josephson current in a junction between two ferromagnetic superconductors as a function of the interface potential z. We consider the ferromagnetic superconductor(FS) in three different Cooper pairing states: spin singlet s-wave pairing(SWP) state, spin triplet opposite spin pairing(OSP) state, and spin triplet equal spin pairing(ESP) state. We find that the critical Josephson current as a function of z shows clear differences among the SWP, OSP, and ESP states. The obtained results can be used as a useful tool for determining the pair symmetry of the ferromagnetic superconductors.     

Adsorption isotherms and ideal selectivities of hydrogen sulfide and carbon dioxide over methane for the Si-CHA zeolite: comparison of carbon dioxide and methane adsorption with the all-silica DD3R zeolite

Adsorption isotherms of H₂S, CO₂, and CH₄ on the Si-CHA zeolite were measured over pressure range of 0–190 kPa and temperatures of 298, 323, and 348 K. Acid gases adsorption isotherms on this type of zeolite are reported for the first time. The isotherms follow a typical Type-I shape according to the Brunauer classification. Both Langmuir and Toth isotherms describe well the adsorption isotherms of methane and acid gases over the experimental conditions tested. At room temperature and pressure of 100 kPa, the amount of CO₂ adsorption for Si-CHA zeolite is 29 % greater than that reported elsewhere (van den Bergh et al. J Mem Sci 316:35–45 (2008); Surf Sci Catal 170:1021–1027 (2007)) for the pure silica DD3R zeolite while the amounts of CH₄ adsorption are reasonably the same. Si-CHA zeolite showed high ideal selectivities for acid gases over methane at 100 kPa (6.15 for H₂S and 4.06 for CO₂ at 298 K). Furthermore, H₂S adsorption mechanism was found to be physical, and hence, Si-CHA can be utilized in pressure swing adsorption processes. Due to higher amount of carbon dioxide adsorbed and lower heats of adsorption as well as three dimensional channels of Si-CHA pore structure, this zeolite can remove acid gases from methane in a kinetic based process such as zeolite membrane.