北京自由电子激光最近进展──实现饱和振荡

北京自由电子激光(BFEL)装置于1993年底在10.68μm处实现了饱和振荡.输出激光能量为3mJ,饱和平顶宽度2μs.对应饱和振荡平均功率为210kW(宏脉冲),峰值功率约为20MW,比自发辐射高8个量级,单程小讯号净增益为24%,转换效率为0.45%,与理论预期结果相符.光束质量接近衍射极限.目前装置可工作于9-11μm.     

UV-light irradiation preparation of soybean residue-based hydrogel composite from inorganic/organic hybrids for degradable slow-release N-fertilizer

Research on Chemical Intermediates - Biomass waste, which was the by-product generated along with the production of food, was transformed into high-value constituent in slow-release fertilizers....     

The measurements of coexistence curves and critical behavior of a binary mixture with a high molecular weight polymer

The critical behavior of solutions of poly (diallydimethylammonium chloride) (PDDAC, M_w = 3.2 × 10⁵) in the critical binary mixture of isobutyric acid (I) + water (W) was studied by the refractive index measurements. The measurements were performed at three different PDDAC concentrations near and far away from the critical point. We observed that the critical temperatures increase linearly with increasing the concentration of PDDAC. As the distance from the critical point increases, the system exhibits a crossover from the renormalized Ising critical behavior to the mean-field one. For the solutions with the highest PDDAC concentration, experiments suggest a crossover to tricritical behavior.     

脑部磁共振结合静息态fMRI方法在卒中患者认知障碍中的应用

本研究主要探讨脑部磁共振结合静息态fMRI方法在卒中患者认知障碍中的应用。本研究将符合卒中认知障碍患者25例设为患者组,将25例健康者设为对照组。采用脑部静息态核磁共振对实验者进行扫描,以脑部双侧海马为种子点进行功能连接分析,并通过软件分析两组实验者静息态双侧海马差异。结果发现,与对照组相比,患者组右侧海马与左右侧额中回、左侧额下回等的连接减少;右侧海马与左侧颞上中回、双侧丘脑的连接增加;左侧海马与左侧颞额中回、右侧颞额上回、右侧额下回的连接减少;左侧海马与右侧顶下回连接增加。总之,本研究发现卒中患者海马脑区与颞叶皮层、额叶皮层之间的连接减少,可能是由卒中患者脑损害导致。     

Recent Progress of the Beijing FEL──Realized Saturated Oscillation

Beijing FEL facility has been built in IHEP,the saturated oscillation has been obtained at a wavelength of 10.68μm,on Dec.28,1993.The average output energy and the pulse width were measured respectively to be 3mJ,2μs.The corresponding osillation power is greater than 210kW,peak power is about 20MW, which is about 10⁸ times higher than that of spontaneous emission. The FWHM of the FEL spectracal bandwidth is less than 2%.The small signal net gain is 24% per pass.The extraction efficiency is 0.45%.In the present experimental resules,BFEL can be saturated by changing electron energy at the wavelength range from 9-10μm,the maxmium average output energy and extraction efficiency are 10mJ,0.52% respectively,the minimum spectral bandwidth of 0.3% has achieved by shorting cavity length.