Magnetocrystalline anisotropy and dynamic spin reorientation of half-doped Nd_(0.5)Pr_(0.5)FeO_(3)single crystal

The single crystals of Nd_(0.5)Pr_(0.5)FeO_(3)were successfully grown by optical floating zone method.Room temperature x-ray diffraction and Laue photograph declared the homogeneity and high quality of the crystal.The significant magnetic anisotropy and multiple magnetic transitions illustrate the complex magnetic structure.At high temperatures(T>66 K),it shows the typical characteristics ofΓ_(4)(G_(x),A_(y),F_(z))state.With the decrease of the temperature,it undergoes a first-order spin reorientation transition fromΓ_(4)(G_(x),A_(y),F_(z))toΓ_(2)(F_(x),C_(y),G_(z))state in the temperature window of 45-66 K under an applied magnetic field of 0.01 T.As the temperature drops to~17 K,a new magnetic interaction mechanism works,which results in a further enhancement of magnetization.The T-H phase diagram of Nd_(0.5)Pr_(0.5)FeO_(3)single crystal was finally constructed.

体内连续进化技术的研究进展

实验室进化是遗传育种、提高微生物性能的重要方式。近几十年来,实验室进化的方法快速发展,应用也越来越广泛,但是常见的菌株进化策略以及针对特定蛋白的进化存在突变过程不连续,需要多轮操作、工作量大等缺点。微生物突变和筛选技术的进步促进了体内连续进化的发展,大大提高了实验室进化的效率。体内连续进化技术实现了体内突变,完美地把突变与筛选相结合,以最少的人工干预进化出特定表型。文中总结了近年来在微生物底盘中开发的基因组范围的体内连续进化技术,以及独立于基因组的针对特定蛋白的体内连续进化技术,主要对这些技术实现体内连续突变的原理及其相关应用进行了介绍。在此基础上,分析了现有技术的优缺点,并对体内连续进化技术的发展进行了展望。