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441.
Jørgen Houmøller Sydney H. Kaufman Dr. Kristian Støchkel Prof. Lokesh C. Tribedi Prof. Steen Brøndsted Nielsen Prof. J. Mathias Weber 《Chemphyschem》2013,14(6):1133-1137
We report electronic spectra of mass‐selected MnO4? and MnO4??H2O using electronic photodissociation spectroscopy. Bare MnO4? fragments by formation of MnO3? and MnO2?, while the hydrated complex predominantly decays by loss of the water molecule. The band in the visible spectral region shows a well‐resolved vibrational progression consistent with the excitation of a Mn? O stretching mode. The presence of a single water molecule does not significantly perturb the spectrum of MnO4?. Comparison with the UV/Vis absorption spectrum of permanganate in aqueous solution shows that complete hydration causes a small blueshift, while theoretical models including a dielectric medium have predicted a redshift. The experimental data can be used as benchmarks for electronic structure theory methods, which usually predict electronic spectra in the absence of a chemical environment. 相似文献
442.
Camacho CM Camsonne A Mazouz M Ferdi C Gavalian G Kuchina E Amarian M Aniol KA Beaumel M Benaoum H Bertin P Brossard M Chen JP Chudakov E Craver B Cusanno F de Jager CW Deur A Feuerbach R Fieschi JM Frullani S Garçon M Garibaldi F Gayou O Gilman R Gomez J Gueye P Guichon PA Guillon B Hansen O Hayes D Higinbotham D Holmstrom T Hyde-Wright CE Ibrahim H Igarashi R Jiang X Jo HS Kaufman LJ Kelleher A Kolarkar A Kumbartzki G Laveissière G Lerose JJ Lindgren R Liyanage N Lu HJ Margaziotis DJ 《Physical review letters》2006,97(26):262002
We present the first measurements of the e[over -->]p-->epgamma cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region. The Q(2) dependence (from 1.5 to 2.3 GeV(2)) of the helicity-dependent cross section indicates the twist-2 dominance of DVCS, proving that generalized parton distributions (GPDs) are accessible to experiment at moderate Q(2). The helicity-independent cross section is also measured at Q(2)=2.3 GeV(2). We present the first model-independent measurement of linear combinations of GPDs and GPD integrals up to the twist-3 approximation. 相似文献
443.
J M Levin B de B Frederick M H Ross J F Fox H L von Rosenberg M J Kaufman N Lange J H Mendelson B M Cohen P F Renshaw 《Magnetic resonance imaging》2001,19(8):1055-1062
Current understanding of blood oxygenation level dependent (BOLD) fMRI physiology predicts a close relationship between BOLD signal and blood hematocrit level. However, neither this relationship nor its effect on BOLD percent activation (BPA) has been empirically examined in man. To that end, BPA in primary visual cortex in response to photic stimulation was determined in a group of 24 normal subjects. A positive linear relationship between BPA and hematocrit was seen, particularly in men. To evaluate the effect of change in hematocrit on BPA, 9 men were studied before and following isotonic saline hemodilution, resulting in an average 6% reduction in hematocrit and an 8-31% reduction in BPA. No significant change in the number of activated pixels was seen. A model of predicted BPA as a function of hematocrit and vessel size was developed, and results from this model closely mirrored the empiric data. These results suggest that hematocrit significantly influences the magnitude of BPA and that such baseline factors should be accounted for when comparing BOLD data across groups of subjects, particularly in the many instances in which hematocrit may vary systematically. Such instances include several disease states as well as studies involving sex differences, drug administration, stress and other factors. Finally, the robust agreement between predicted and empiric data serves to validate a semiquantitative approach to the analysis of BOLD fMRI data. 相似文献