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51.
Jasmine Viger‐Gravel Claudia E. Avalos Dominik J. Kubicki David Gajan Moreno Lelli Olivier Ouari Anne Lesage Lyndon Emsley 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(22):7327-7331
The introduction of high‐frequency, high‐power microwave sources, tailored biradicals, and low‐temperature magic angle spinning (MAS) probes has led to a rapid development of hyperpolarization strategies for solids and frozen solutions, leading to large gains in NMR sensitivity. Here, we introduce a protocol for efficient hyperpolarization of 19F nuclei in MAS DNP enhanced NMR spectroscopy. We identified trifluoroethanol‐d3 as a versatile glassy matrix and show that 12 mm AMUPol (with microcrystalline KBr) provides direct 19F DNP enhancements of over 100 at 9.4 T. We applied this protocol to obtain DNP‐enhanced 19F and 19F–13C cross‐polarization (CP) spectra for an active pharmaceutical ingredient and a fluorinated mesostructured hybrid material, using incipient wetness impregnation, with enhancements of approximately 25 and 10 in the bulk solid, respectively. This strategy is a general and straightforward method for obtaining enhanced 19F MAS spectra from fluorinated materials. 相似文献
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Terashi K Tether S Theriot D Thurman-Keup R Tipton P Tkaczyk S Tollefson K Tollestrup A Toyoda H Trischuk W de Troconiz JF Tseng J Turini N Ukegawa F Vaiciulis T Valls J Vejcik S Velev G Vidal R Vilar R Volobouev I Vucinic D Wagner RG Wagner RL Wahl J Wallace NB 《Physical review letters》2000,85(22):4668-4673
An angular analysis of B0-->J/psiK(*0) and B(0)(s)-->J/psistraight phi has been used to determine the decay amplitudes with parity-even longitudinal ( A0) and transverse ( A( parallel)) polarization and parity-odd transverse ( A( perpendicular)) polarization. The measurements are based on 190 B0 and 40 B(0)(s) candidates obtained from 89 pb(-1) of &pmacr;p collisions at the Fermilab Tevatron. The longitudinal decay amplitude dominates with |A0|(2) = 0.59+/-0. 06+/-0.01 for B0 and |A0|(2) = 0.61+/-0.14+/-0.02 for B(0)(s) decays. The parity-odd amplitude is found to be small with |A( perpendicular)|(2) = 0.13(+0.12)(-0.09)+/-0.06 for B0 and |A( perpendicular)|(2) = 0.23+/-0.19+/-0.04 for B(0)(s) decays. 相似文献
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KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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We use the automorphism group Aut(H), of holes in the lattice L 8=A 2 ⊕ A 2 ⊕ D 4, as the starting point in the construction of sphere packings in 10 and 12 dimensions. A second lattice, L 4=A 2 ⊕ A 2, enters the construction because a subgroup of Aut(L 4) is isomorphic to Aut(H). The lattices L 8 and L 4, when glued together through this relationship, provide an alternative construction of the laminated lattice in twelve dimensions with kissing number 648. More interestingly, the action of Aut(H) on L 4 defines a pair of invariant planes through which dense, non-lattice packings in 10 dimensions can be constructed. The most symmetric of these is aperiodic with center density 1/32. These constructions were prompted by an unexpected arrangement of 378 kissing spheres discovered by a search algorithm. 相似文献
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[reaction: see text] A single biomimetic cascade sequence featuring intermolecular followed by intramolecular cyclizations allowed the biomimetic synthesis of nitraramine from simple C5-lysine-derived metabolites. In the course of the study, the structure of epinitraramine was also revisited. 相似文献