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Niklas Ottosson Emad F. Aziz Ioana L. Bradeanu Sbastien Legendre Gunnar
hrwall Svante Svensson Olle Bjrneholm Wolfgang Eberhardt 《Chemical physics letters》2008,460(4-6):540-542
Formaldehyde in aqueous solution is hydrolysed and forms methanediol. Using X-ray absorption spectroscopy we show that the hydrolysation product can be identified by a distinct electronic signature in the spectra. This is manifested by the disappearance of the oxygen 1s → π* absorption line. The X-ray absorption spectrum of aqueous formaldehyde is compared with those of the structurally similar formamide and urea, which are in contrast not hydrolysed in aqueous solution. We thereby demonstrate the exceptional sensitivity and simplicity of the technique to monitor this fundamental process in the aqueous phase. 相似文献
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Marie‐Fran?oise Incardona Gleb P. Bourenkov Karl Levik Romeu A. Pieritz Alexander N. Popov Olof Svensson 《Journal of synchrotron radiation》2009,16(6):872-879
EDNA is a framework for developing plugin‐based applications especially for online data analysis in the X‐ray experiments field. This article describes the features provided by the EDNA framework to ease the development of extensible scientific applications. This framework includes a plugins class hierarchy, configuration and application facilities, a mechanism to generate data classes and a testing framework. These utilities allow rapid development and integration in which robustness and quality play a fundamental role. A first prototype, designed for macromolecular crystallography experiments and tested at several synchrotrons, is presented. 相似文献
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Laevorotatory crystals of isomorphous Bi12SiO20 and Bi12GeO20 are shown, by use of the anomalous X-ray scattering component in the structure amplitudes, to have identical chirality (handedness of atomic arrangement) in contrast with the case of NaC103 and NaBrO3, in which crystals of the same chirality rotate plane polarized light in opposite senses. 相似文献
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Aminoacridines have a long history in the drug and dye industries and display a wide range of biological and physical properties. Despite the historical relevance of 9-aminoacridines, there have been few studies investigating their stability. 9-Aminoacridines are known to hydrolyze at the C9-N15 bond, yielding acridones. In this study, the pH-dependent hydrolysis rates of a series of 9-substituted aminoacridines are investigated. In addition, ground-state physical properties of the compounds are determined using ab initio quantum mechanics calculations to gain insight into the forces that drive hydrolysis. An analysis of the bond orders, bond dissociation energies, and conformational energies show that the rate of hydrolysis depends on two main factors: delocalization across the C9-N15 bond and steric effects. The computational results are applied to explain the change in experimental rates of hydrolysis going from primary to secondary and to tertiary substituted 9-aminoacridines. In the case of tertiary substituted amines, the calculations indicate the C9-N15 bond is forced into a more gauche-like conformation, greatly diminishing delocalization (as shown by reductions in bond orders and bond energy), which leads to rapid hydrolysis. A model of intramolecular hydrogen bonding is also presented, which explains the increased rate of hydrolysis observed for highly substituted compounds under acidic conditions. 相似文献
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