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The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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The presence of heavy metals in environmental waters having an important place in the industrial waste is a major threat to viability. Heavy metals are transported to humans through the ecological cycle, damaging many tissues and organs. In recent years, agricultural and food waste can be used to remove heavy metals. At the present study, magnetically modified coffee grains which are alternative to conventional particle systems were prepared and heavy metal removal performances were investigated. The coffee grains used were magnetically modified by contact with water-based magnetic fluid. Magnetically modified coffee grains were characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis and electron spin resonance (ESR). Adsorption studies are made with four different heavy metal ions, namely Cu(II), Pb(II), Cd(II) and Zn(II). Adsorption isotherms were determined and heavy metal removal performance of magnetic coffee grains were investigated from synthetic waste water. 相似文献
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E.C. Ekuma 《Physica B: Condensed Matter》2011,406(20):3988-3989
Iron monosilicides (FeSi) is an important material with very interesting properties that can be harnessed for technological applications. Our attention has been drawn to the so-called first principle study of the electronic and thermodynamic properties of B2-FeSi by Zhao et al. (Physica B 406 (2011) 363-367) using pseudopotential plane wave method. They reported that FeSi in B2 phase is a narrow band gap material with a band gap of 0.05 eV using a generalized gradient approximation (GGA) potential implemented within the density functional theory (DFT) approximation. This comment comes to address an important oversight by these authors in the interpretation of their results. 相似文献
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