排序方式: 共有82条查询结果,搜索用时 15 毫秒
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Stephan Berner Andreas B. Schmidt Mirko Zimmermann Dr. Andrey N. Pravdivtsev Dr. Stefan Glöggler Prof. Dr. Dr. h.c. Jürgen Hennig PD Dr. Dominik von Elverfeldt Prof. Dr. Jan-Bernd Hövener 《ChemistryOpen》2019,8(6):728-736
The signal enhancement provided by the hyperpolarization of nuclear spins of biological molecules is a highly promising technique for diagnostic imaging. To date, most 13C-contrast agents had to be polarized in an extra, complex or cost intensive polarizer. Recently, the in situ hyperpolarization of a 13C contrast agent to >20 % was demonstrated without a polarizer but within the bore of an MRI system. This approach addresses some of the challenges of MRI with hyperpolarized tracers, i. e. elevated cost, long production times, and loss of polarization during transfer to the detection site. Here, we demonstrate the first hyperpolarization of a biomolecule in aqueous solution in the bore of an MRI at field strength of 7 T within seconds. The 13C nucleus of 1-13C, 2,3-2H2-succinate was polarized to 11 % corresponding to a signal enhancement of approximately 18.000. Interesting effects during the process of the hydrogenation reaction which lead to a significant loss of polarization have been observed. 相似文献
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PD Dr. Holger Kohlmann 《无机化学与普通化学杂志》2010,636(11):2046-2046
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Daunne Christa PD Dr. 《ZDM》2003,35(3):102-109
It is reported about a longitudinal study run at the Institute of Cognitive Mathematics of the University of Osnabrueck, in which pupils’ verbal and text productions from mathematics lessons at a grammar school are analysed by means of cognitive theoretical methods. First of all, a teaching scene from an instruction to probability calculus and further text productions from an introductory lesson about exponential functions are analysed, in which five pupils take part whose cognitive structures have been assessed and classified in individual examinations. The characteristics brought out according to these teaching scenes indicate different ideas and thinking processes of the pupils. The second part shows that the pupils’ behaviour described is not only to be regarded in isolation but it can also be found in longitudinal examinations and can therefore be considered as a stable, typical characteristic. These results lead to consequences for the planning and design of mathematics lessons based on a well-founded theory of cognition. 相似文献
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The crystal structure of K[BF3(CN)] (Pbcn (Nr. 60) with a = 13.3486(15) b = 6.5239(7) c = 10.0085(11) Å, and eight formula units per unit cell) has been determined and the one of K[BF2(CN)2] was confirmed and improved. The different networks in the complete series of borates K[BFx(CN)4–x], x = 0–4 are compared and discussed. 相似文献
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Dawes A Mukerji RJ Davis MP Holtom PD Webb SM Sivaraman B Hoffmann SV Shaw DA Mason NJ 《The Journal of chemical physics》2007,126(24):244711
The authors present the results of a morphological study of solid ammonia using both Fourier-transform infrared and vacuum ultraviolet (VUV) spectroscopy. Dramatic changes in the VUV and infrared spectra at temperatures between 65 and 85 K provide a deeper insight into the structure of ammonia ice particularly with the observation of an exciton transition at 194 nm (6.39 eV) in the VUV spectrum, revealing a structure that is composed of crystallites. A complementary structure is observed in the IR spectrum at 1100 cm(-1) which is assigned to the symmetric deformation of ammonia molecules at the surfaces of the crystallites. Such spectral signatures may be used to identify the environment within which the ammonia ice is formed and provide a new route for obtaining information on the physical and chemical conditions occurring within the interstellar medium, on the surfaces of planetary bodies, and in Kuiper belt objects. 相似文献
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