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The clinical efficacy of nonsteroidal anti-inflammatory drugs has been related to ionization energies [Mehler and Gerhards, Int. J. Quantum Chem. 1989, 25, 205]. In this paper we employ modern quantum-chemical calculations to re-examine the statistical correlation between clinical efficacy and ionization energies. Ionization energies are computed by density functional theory, with and without Koopman's theorem, for a series of salicylic acids and phenols whose activities, or efficacy, are known. Using a regression analysis, we show that improving the treatment of electron correlation beyond previous studies enhances the statistical correlation between clinical activities and ionization energies. 相似文献
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KB McTiernan SC Jarvis D Allen R Bol D Scholefield 《Rapid communications in mass spectrometry : RCM》1999,13(18):1803-1807
The composition of dissolved organic matter (DOM) in a soil is the product of a variety of soil processes. Changes in the composition of DOM in water discharged from soil should, therefore, give an important insight into modifications in these soil processes. We hypothesise that these processes in soils, under different grassland management regimes, would be affected to different extents by the short-term disturbance of a storm event and that evidence of this could be detected in delta(13)C and delta(15)N signatures in drainage and surface runoff waters. During a storm event we collected discharge waters from 1 ha grassland lysimeters, with or without artificial drainage, which received contrasting fertiliser inputs, and delta(13)C and delta(15)N signatures were determined. Changes in (13)C enrichment during the storm event were clearly identifiable, as were differences between plots for (13)C and (15)N, illustrating that this technique has potential to be a useful tool for identifying and investigating short- and long-term changes in soil organic matter dynamics. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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In order to study the effect of substitution of Fe3+ by Al3+ and Cr3+ in Li0.5Fe2.5O4 on its structural and magnetic properties, the spinel system Li0.5Al x Cr x Fe2.5?2x O4 (x=0.0, 0.2, 0.4, 0.5, 0.6 and 0.8) has been characterized by X-ray diffraction, high field magnetization, low field ac susceptibility and 57Fe Mossbauer spectroscopy. Contrary to the earlier reports, about 50% of Al3+ is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on magnetic sextet in the Mössbauer spectra (x>0.5). 相似文献
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