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Pakorn Bovonsombat Rameez Ali Chiraphorn Khan Juthamard Leykajarakul Kawin Pla-on Suraj Aphimanchindakul Natchapon Pungcharoenpong Nisit Timsuea Anchalee Arunrat Napat Punpongjareorn 《Tetrahedron》2010,66(34):6928-181
para-Regioselective bromination of phenol and analogues, promoted by p-toluenesulfonic acid, is achieved in high to excellent yields at room temperature with N-bromosuccinimide. Chlorination with N-chlorosuccinimide and catalysed by p-toluenesulfonic acid also gives para-chlorinated phenol analogues in good yields at room temperature. 相似文献
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Setsompop K Alagappan V Zelinski AC Potthast A Fontius U Hebrank F Schmitt F Wald LL Adalsteinsson E 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2008,195(1):76-84
At high magnetic field, B(1)(+) non-uniformity causes undesired inhomogeneity in SNR and image contrast. Parallel RF transmission using tailored 3D k-space trajectory design has been shown to correct for this problem and produce highly uniform in-plane magnetization with good slice selection profile within a relatively short excitation duration. However, at large flip angles the excitation k-space based design method fails. Consequently, several large-flip-angle parallel transmission designs have recently been suggested. In this work, we propose and demonstrate a large-flip-angle parallel excitation design for 90 degrees and 180 degrees spin-echo slice-selective excitations that mitigate severe B(1)(+) inhomogeneity. The method was validated on an 8-channel transmit array at 7T using a water phantom with B(1)(+) inhomogeneity similar to that seen in human brain in vivo. Slice-selective excitations with parallel RF systems offer means to implement conventional high-flip excitation sequences without a severe pulse-duration penalty, even at very high B(0) field strengths where large B(1)(+) inhomogeneity is present. 相似文献
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