Ultrafast Electron Diffraction with Spatiotemporal Resolution of Atomic Motion

Ultrafast electron diffraction （UED） is a rapidly advancing technique capable of recording the atomic-detail structural dynamics in real time. We report the establishment of the first UED system in China. Employing this UED apparatus, both the coherent and the concurrent thermal lattice motions in an aluminium thin-film, trigged by ultrafast laser heating, have been observed. These results demonstrate its ability to directly measure a sub-milli-angstrom lattice spacing change on a sub-picosecond time scale.     

Improved method for studying the propagation dynamics of ultrafast electron pulses based on mean-field models

We have studied the propagation dynamics of ultrafast electron pulses by using an improved mean-field model, in which the propagation of the electron pulses across the boundary of the acceleration region is explicitly considered. A large decrease in the speed spread of the electron pulses(we called "boundary kick") is observed and properly treated leading to a significant improvement in the simulation accuracy, particularly when the density of electrons is very large. We show that our method is consistent with the simulation by the N-particle method, while others can introduce factorial error.     

化学名词审定委员会在京成立

全国自然科学名词审定委员会和中国化学会,于1986年3月25日在北京召开了“化学名词审定委员会”成立会。梁树权任主任委员,梁晓天任副主任委员,王夔、张滂、周同惠、韩德刚、施良和、汪德熙分别担     

高反射效率高定向性的热解石墨晶体X射线谱仪

基于高定向热解石墨晶体(highly oriented pyrolitic graphite,HOPG)研制了一种新型反射式X射线谱仪.该谱仪具有高反射效率、较高能谱分辨率及相对较宽的能谱测量范围.根据计算,在相同的入射条件下,该谱仪的效率比一般X射线弯晶谱仪高3个量级;谱仪能谱分辨率理论值最高达350;理论探测范围是6.891keV至9.193 keV.我们将该谱仪应用在高功率密度激光与固体靶相互作用的实验中,发现在普通弯晶谱仪无法采到信号的实验条件下,HOPG谱仪依然采集到清晰的Cu K谱线.分析发现在8.048 keV(Cu的Kα光子能量)附近的能谱分辨能力最高达到40 eV,分辨率大于200.     

天津市医务工作者执业压力相关因素分析及对策研究

通过面向天津市全部公立医院进行的"天津市医务科技工作者现状调查"问卷调查,找到其中影响医务工作者执业压力的相关因素并分析其相关程度。结果表明,影响全市医务工作者职业压力的因素分别为职称、晋升机会、深造机会和医疗纠纷,据此建议通过员工帮助计划,与保险公司、专业的法律服务公司合作以及引入人工智能方法来提高工作效率,缓解执业压力。     

用超快电子衍射技术研究Al薄膜的超快动力学行为

超快电子衍射（UED）技术因其同时具有亚皮秒的时间分辨和亚毫埃的空间分辨能力,成为研究物质瞬态结构变化,特别是研究晶格材料超快动力学的有力工具.应用国内首台自行研制的UED系统,我们实时测量了超快激光脉冲激发下,20 nm金属Al多晶薄膜产生的相干声子和晶格热运动.实验结果显示,在晶格热运动加剧的同时,热应力的作用使晶格产生了相干振荡,并最终膨胀达到新的平衡位置.实验中测得的振荡周期以及晶格上升的温度与理论计算的结果符合较好,展示了UED技术在超快晶格动力学研究方面的广阔应用前景 关键词： 超快电子衍射 相干声子 晶格热运动     

天津市医务科技工作者从事医疗科研状况调查分析

面向天津市各级公立医院医务科技工作者进行问卷调查,并对结果进行统计分析.通过调查分析天津市医务科技工作者从事医疗科研工作现状,提出进一步优化我市医疗科研环境、全面提升我市医务科技人员科研能力的合理化建议.调查结果显示,天津市医务科技工作者从事医疗科研存在人数较少、科研成果形式单一等问题,还应该在综合管理、资金投入、搭建...     

探讨Dreamweaver中层的应用

层是Dreamweaver网页制作软件中非常重要的概念,可以大大增强网页设计的灵活性,可以不编写代码而实现网页中的动感效果。在实际教学中,学生对于层在运用过程中把握不够,本文通过四个实例来剖析具体用法,使学生掌握层的应用,达到良好的教学效果。     

Ultrafast electron diffraction

Ultrafast electron diffraction(UED) technique has proven to be an innovative tool for providing new insights in lattice dynamics with unprecedented temporal and spatial sensitivities. In this article, we give a brief introduction of this technique using the proposed UED station in the Synergetic Extreme Condition User Facility(SECUF) as a prototype. We briefly discussed UED's functionality, working principle, design consideration, and main components. We also briefly reviewed several pioneer works with UED to study structure-function correlations in several research areas. With these efforts,we endeavor to raise the awareness of this tool among those researchers, who may not yet have realized the emerging opportunities offered by this technique.     

稀土元素示踪坡面冲刷侵蚀过程的室内模拟试验研究

为确定坡面侵蚀产沙的时空演变规律,通过沿坡面垂直分段和分层结合布设不同稀土元素,采用室内放水冲刷试验系统,分析了各坡段侵蚀产沙量和侵蚀率变化过程. 结果表明:坡面侵蚀产沙可分为3个阶段:面蚀阶段、沟蚀阶段和沟蚀稳定阶段. 试验结束时,上坡段土壤总侵蚀量为17.527 kg,占坡面总侵蚀量的89.2%,其中La和Eu示踪区的侵蚀量各占坡面总侵蚀量的48.1%和23.8%. La,Eu,Yb,Tb,Ce,Nd和Sm 7个示踪区的累积侵蚀量之比为:1:0.495:0.184:0.177:0.146:0.030:0.074,坡面上段、中段和下段累积侵蚀量之比为:1:0 095:0.040. 试验过程中,上坡段细沟蚀剧烈,中坡段主要以面蚀为主,伴有轻微沟蚀,而下坡段始终以面蚀存在.