REBO_3中Ce^(3+)和Bi^(3+)对Sm^(3+)光致发光的影响

在紫外光(UV)激发下,系统地研究了REBO_3(RE=La,Gd,Y)中Sm^(3+),Ce^(3+)和Bi^(3+)的发射光谱、激发光谱及其发光强度与组成、结构的关系.结果表明:Ce^(3+)、Bi^(3+)均可敏化LaBO_3中Sm^(3+)的发光;而在GdBO_3和YBO_3中,只有Bi^(3+)能敏化Sm^(3+)的发光,Ce^(3+)猝灭Sm^(3+)的发光.本文还探讨了三种基质中Sm^(3+)发光浓度猝灭的机理.

REBO_3基质中Sm^（3＋）的阴极射线发光特性

ＲＥＢＯ＿３基质中Ｓｍ￣（３＋）的阴极射线发光特性郭凤瑜彭夷安（北京大学１００８７１）（湖南医学专科学校）ＲＥＢＯ＿３（ＲＢ＝Ｌａ、Ｇｄ、Ｙ）是一类优良的发光材料的基质。对于ＲＥＢＯ＿３中稀土离子（如Ｃｅ￣（３＋）、Ｐｒ￣（３＋）、Ｓｍ￣（３＋）、Ｅ...

REBO模型的平衡态分子动力学模拟

为了得到合适的"计算机实验"的"试样"进行固体炸药冲击起爆现象的分子动力学研究,对REBO模型进行了NVE,NVT两种平衡态分子动力学模拟;作为对比,同时还进行了不施加任何人工干预,系统的演化完全由运动方程驱动的分子动力学模拟,讨论了根据对"试样"的不同要求选择适当模拟方法的原则。

Overexpression of the bacterial tryptophan oxidase RebO affects auxin biosynthesis and Arabidopsis development

Both tryptophan （Trp） and auxin are essential for plant growth and Trp is a precursor for auxin biosynthesis. Concentrations of Trp and auxin need to be tightly con- trolled to ensure optimal growth and development. It has been very difficult to study the homeostasis of these two essential and inter-dependent compounds. Auxin is mainly synthesized from Trp via a two-step pathway using indole- 3-pyruvate （IPA） as the intermediate. Here we used a bacterial Trp oxidase RebO, which does not exist in Ara- bidopsis and which converts Trp to the imine form of IPA, to modulate IPA levels in Arabidopsis. Our results demonstrate that Arabidopsis plants use two strategies to ensure that no excess IPA is made from Trp. IPA is made from Trp by the TAA family of aminotransferases, which we show catalyzes the reverse reaction when IPA level is high. Moreover, excess IPA is converted back to Trp by the YAS1 aminotransferase. We show that the VASl-cat- alyzed reaction is very important for Trp homeostasis. This work not only elucidates the intricate biochemical mech- anisms that control the homeostasis of Trp, IPA, and auxin, but also provides novel tools for further biochemical studies on Tip metabolism and auxin biosynthesis in plants.

Molecular mechanics-based finite element analysis of graphene sheet and carbon nanotubes using the rebo potential

Molecular mechanics-based finite element(FE)models of graphene sheet and singlewalled zigzag and armchair carbon nanotubes(CNTs)are developed on the basis of the assumption that the carbon nanostructures,when loaded,behave like frame structures.The behavior of carbon–carbon bonds,which are represented by beam elements,is simulated using the many-body second generation reactive empirical bond order(REBO)potential.By means of the FE models,the tensile behavior of carbon nanostructures is simulated.The FE models are verified against molecular dynamics simulations.The computed results in terms of tensile stress–strain curves and fracture patterns are compared with results obtained using the pairwise modified-Morse potential.Different tensile properties and fracture patterns are predicted using the two potentials.This is mainly attributed to the deviations in the force–bond length curves and to the contribution of bond angle variation which is present in REBO.The present work is the first attempt to implement the REBO potential into a continuum model of carbon nanostructures and paves the way for a more systematic incorporation of atomistic simulation methods into continuum models.

Short Rebound or Beginning of Recovery?

After the Chinese New Year (January 26th),China’s economy started to showobvious signs of a rebound-the total value of new loans from banks to enterprisescontinued to grow;consumer spending is still high and excessive inventories havebeen sold down in some industries.In the chemical industry,the December im-ports of polyethylene,polypropylene and polyvinyl chloride-the three

氢原子在金刚石(001)表面沉积的分子动力学模拟

利用分子动力学模拟方法,研究了氢原子在金刚石表面的沉积机理.调查了氢原子的入射能量、入射点位置、入射姿势及衬底温度对其在金刚石(001)表面沉积的影响.研究发现氢原子的入射能量、入射姿势及碰撞点位置对其沉积的影响很大;而在常温和低温下,衬底温度对其沉积的影响较小.这对进一步探索实验条件对薄膜质量的影响具有重要的意义.