Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in(Fe₅₀Co₂₅B₁₅Si₁₀)₈₀Cu₂₀ melt-spun ribbons

(Fe50Co25B15Si10)80Cu20 ribbons are prepared by using the single-roller melt-spinning method.A dual-layer structure consisting of a(Fe,Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification.The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature.It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state.The crystallization leads to the increase of coercivity and decrease of saturation magnetization.     

准连续性动脉自旋标记技术在磁共振系统上的序列实现和参数优化

准连续性动脉自旋标记技术(pCASL)是一种新兴的动脉自旋标记脑灌注成像技术(ASL)：一方面,它克服了连续性动脉自旋标记技术(CASL)需要独立发射线圈的硬件限制;另一方面,也避免了脉冲式动脉自旋标记技术(PASL)带来的标记效率低的影响．为了在 1.5 T 磁共振系统上开发一款可稳定应用于临床扫描的 pCASL 序列;并使用该序列准确获得反
应灌注功能的局部脑血流量值(Regional Cerebral Blood Flow, rCBF)．该文利用水模测试pCASL 序列,验证了标记部分的标记性能并通过人体实验,优化了协议中标记位置中心到成像层面中心的距离和标记部分结束点到成像脉冲开始前的等待时间这两项参数．基于优化了参数的 pCASL 协议,扫描 12 组正常志愿者,观测灌注信号分布情况,并对特定灰质区域定量计算,对比不同个体该区域的 rCBF 值．通过人体实验,经验性地确定了延迟时间为 1 200 ms、标记距离为 70 mm 时灌注图像的信噪比达到最优．将两项优化后的参数存入协议中,并使用协议扫描,共获取 12 组结果,其中的 10 组都表明灌注信号稳定均匀,并且灰质区域的 CBF 值同经验结果一致．该工作在1.5 T 的磁共振系统上成功实现了 pCASL序列,经优化参数后的协议扫描,可以获得准确稳定的脑部灌注信号．
     

Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in （Fe50Co25B15Si10）80Cu20 melt-spun ribbons

（Fe50Co25B15Si10）80Cu20 ribbons are prepared by using the single-roller melt-spinning method. A dual-layer structure consisting of a （Fe, Co）-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification. The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature. It is indicated that the coercivity of the ribbon is almost zero in the as-quenched state. The crystallization leads to the increase of coercivity and decrease of saturation magnetization.     

Structures and physical properties of R_2TX_3 compounds

Rare-earth compounds have been an attractive subject based on the unique electronic structures of the rare-earth elements. Novel ternary intermetallic compounds R2TX3 (R = rare-earth element or U, T = transition-metal element, X = Si, Ge, Ga, In) are a significant branch of this research field due to their complex and intriguing physical properties, such as magnetic order at low temperature, spin-glass behavior, Kondo effect, heavy fermion behavior, and so on. The unique physical properties of R2TX3 compounds are related to distinctive electronic structures, crystal structures, micro-interaction, and external environment. Most R2TX3 compounds crystallize in AlB2-type or derived AlB2-type structures and exhibit many similar properties. This paper gives a concise review of the structures and physical properties of these compounds. Spin glass, magnetic susceptibility, resistivity, and specific heat of R2TX3 compounds are discussed.