排序方式: 共有16条查询结果,搜索用时 265 毫秒
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Rolf MP Hofman MB Kuijer JP Pai VM Greiser A van Rossum AC Heethaar RM 《Magnetic resonance imaging》2009,27(3):385-392
Multiecho phase-contrast steady-state free precession (PC-SSFP) is a recently introduced sequence for flow quantification. In this multiecho approach, a phase reference and a velocity-encoded readout were acquired at different echo times after a single excitation. In this study, the sequence is validated in vitro for stationary flow. Subsequently, the sequence was evaluated on cardiac output measurements in vivo for through-plane flow in comparison to regular single gradient echo velocity quantification [phase-contrast spoiled gradient echo (PC-GE)]. In vitro results agreed with regular flow meters (RMS 0.1 cm/s). Cardiac output measurements with multiecho PC-SSFP on 10 healthy subjects gave on average the same results as the standard PC-GE. However, the limits of repeatability of PC-SSFP were significantly larger than those of PC-GE (2 l/min and 0.5 l/min, respectively, P=.001). The multiecho approach introduced some specific problems in vivo. The difference in echo times made the velocity maps sensitive for water-fat shifts and B(0)-drifts, which in turn made velocity offset correction problematic. Also, the addition of a single bipolar gradient cancelled the flow compensated nature of the SSFP sequence. In combination with the prolonged TR, this resulted in flow artifacts caused by high and pulsatile through-plane flow, affecting repeatability. Given the significantly lower repeatability of PC-SSFP, cardiac output in turn is less reliable, thus impairing the use of multiecho PC-SSFP. 相似文献
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G. W. van Apeldoorn S. Barshay D. Harting D. J. Holthuizen P. G. Kuijer B. J. Pijlgroms V. Karimäki R. Kimumem M. Korkea-aho P. Johnson P. Michaelides Ch. Michaelidou D. G. Patel 《Zeitschrift fur Physik C Particles and Fields》1981,7(3):235-239
Using data of \(\bar pp\) annihilation at 12 GeV/c we have found that centrally-emitted pions follow a thermal energy spectrum with an inclusive temperature of 111±2 MeV, the same as has been found for pions produced in πp collisions at 16 GeV/c. An analysis of individual high-multiplicity events to search for fluctuations in the temperature parameter on an event-byevent basis has been made, using two different methods. We obtained the value 0.18±0.02 for the relative dispersion of the temperature fluctuations. 相似文献
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Van Baelen G Kuijer S Rýček L Sergeyev S Janssen E de Kanter FJ Maes BU Ruijter E Orru RV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(52):15039-15044
Compared with the widespread use of carbonylative Pd-catalyzed cross-coupling reactions, similar reactions involving isocyanide insertion are almost virgin territory. We investigated the intramolecular imidoylative cross-coupling of N-(2-bromoaryl)amidines, leading to 4-aminoquinazolines. After thorough optimization of the reaction with respect to palladium source and loading, ligand, base, temperature, and solvent, a small library of 4-aminoquinazolines was prepared to determine the scope of this method. Various substituents are tolerated on the amidine and the isocyanide, providing efficient access to a broad range of diversely substituted 4-aminoquinazolines of significant pharmaceutical interest. 相似文献
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Adeva B Becker U Becker-Szendy R Berdugo J Boehm A Branson JG Burger JD Capell M Cerrada M Chang CC Chang YH Chen HS Chen M Chen ML Chen MY Deffur E Demarteau M Dong BZ Duinker P Fesefeldt HS Fong D Fukushima M Garrido L Han RD Harting D Herten G Ho MC Hueser D Hussain M Ilyas MM Jiang DZ Krenz W Kuijer P Li QZ Linnhoefer D Luckey D Luit EJ Mana C Marquina MA Martinez M Massaro GG Mnich J Mount R Nadeem K Newman H Pohl M Poschmann FP Rau RR Rodriguez S Rohde M Rubio JA Rykaczewski H Salicio J 《Physical review letters》1985,54(16):1750-1753
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The structural and electronic transport properties of La1−x
Ce
x
MnO3 (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with
Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration
up to 50% doping. The system La0.5Ce0.5MnO3 also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition. 相似文献
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