The properties of a GaAs-GaAlAs traveling-wave laser amplifier

The reflectivity of the cavity mirrors of a GaAs-GaAlAs DH semiconductor laser are reduced to 1*10^-4 by sputtering a film Si₃N₄. The gain of traveling-wave laser amplifiers is measured. The highest gain is about 25 dB. The dependence of gain on the injection current is measured. The measured frequency bandwidth shows the great advantage over other types of semiconductor laser amplifiers.     

Study on‘soft＇ and ‘hard＇ interactions in ^-pp （pp） collisions using HIJING and PYTHIA

This paper presents a study on ＇hard＇ and ＇soft＇ interactions in ^-pp （pp） collisions using a phenomenological model of HIJING, the jet-cone reconstruction method is employed to select the ＇hard＇ and ＇soft＇ event sub-samples from minimum bias events. It is found that the HIJING model can reproduce the energy scaling behaviour of mean transverse momentum （〈PT〉） distributions of charged hadrons versus multiplicity （Nch） in ＇soft＇ events. From the PYTHIA simulation comparing with the HIJING model, the enhancement of the kaon and proton yields from ＇hard＇ interactions comparing with ＇soft＇ interactions is observed to be due to the mini-jets effect. These mechanisms responsible for the increase of charged hadron＇s （PT） are different in ＇soft＇ and ＇hard＇ interactions.     

亚微米聚苯乙烯微球在气-液界面组装的机理研究

系统地研究了亚微米聚苯乙烯微球在气-液界面的组装机理.聚苯乙烯微球在介质对流的带动下会到达悬浮液的表面并在气-液界面组装，气-液界面处聚苯乙烯微球间由弯液面产生的毛细管力是组装的推动力.界面处聚苯乙烯微球在干燥过程中其润湿性发生了转变，由完全润湿到部分润湿并最终变成不润湿，相应的聚苯乙烯微球与分散介质间接触角也逐渐增大.研究表明，只有接触角达到或超过某数值θ′_critical时，才能够出现气-液界面组装现象.考虑到PS胶粒晶体的表面是“规则”粗糙的表面，由Wenzel公式知θ′_critical大于测量值θ＝22°.聚苯乙烯微球润湿性的转变是界面组装发生和持续进行的关键性因素. 关键词： 自组装 胶粒晶体 聚苯乙烯微球 润湿性     

300 eV—1GeV质子在硅中非电离能损的计算

非电离能损(NIEL)引起的位移损伤是导致空间辐射环境中新型光电器件失效的主要因素.引起质子在硅中NIEL的作用机理有库仑相互作用和核相互作用,质子能量范围从位移损伤阈能到1 GeV.当质子能量位于低能区时,库仑相互作用占主导地位,采用解析方法和TRIM程序计算NIEL;当质子能量位于高能区时,NIEL主要来自质子与靶原子核的弹性和非弹性相互作用,使用MCNPX/HTAPE3X进行模拟仿真计算由核反应引起的NIEL.实现了能量范围为300 eV—1 GeV的质子入射硅时NIEL的计算.计算结果表明,MCNPX/HTAPE3X可用于计算高能质子在材料中产生的反冲核所引起的NIEL,结合解析方法和TRIM程序可计算得到由于库仑相互作用引起的NIEL.     

拓扑绝缘体Bi_2Se_3中层堆垛效应的第一性原理研究

运用第一性原理方法,研究了拓扑绝缘体Bi_2Se_3块体和薄膜中的层堆垛对其结构、电子态、拓扑态和自旋劈裂的影响.发现不同的堆垛会引起Bi_2Se_3层间的相互作用,改变系统的中心对称性.块体的ABC和AAA堆垛都具有中心对称性和相似的能带结构.ABA堆垛破坏了体系的中心对称性,能带发生很大改变,并且产生了很大的能带自旋劈裂.用能带反转的方法判定体系的拓扑相,在不同堆垛的Bi_2Se_3块体中,考虑自旋轨道耦合时都发生了能带反转,因而具有不同堆垛的Bi2Se3仍是拓扑绝缘体.进一步研究了Bi_2Se_3薄膜中的堆垛效应,发现非中心对称的ABA堆垛在Bi_2Se_3薄膜中引起明显的自旋劈裂,并且提出和验证了用应变调控自旋劈裂的方法.     

氰基羧酸二茂铁配体及其有机锡配合物的合成与光电性质

设计合成了一种D-π-A型(Donor-π-Accept)氰基羧酸二茂铁配体,它与有机锡化合物二丁基氧化锡(n-Bu₂SnO)反应,得到了一种新型二茂铁有机锡羧酸酯配合物。通过¹H NMR、¹¹⁹SnNMR、IR、FT-IR、UV-Vis和元素分析等对配体及其配合物进行了全面的表征,利用X-射线单晶衍射测定了配合物的晶体结构,运用CV和Z-scan测试方法系统地研究了它们的电化学和双光子吸收性质。结果表明：与配体相比较,配合物更难被氧化,且具有更大的双光子吸收截面。     

Metathesis of butene to propene on WO<Subscript>3</Subscript> supported on MTS-9 titanium-silica: effect of loading on selectivity of product and yield of propene

An advanced heterogeneous catalyst for olefin disproportion was prepared by supporting WO₃ on titanium-silica sieve (MTS-9). The nature of the surface tungsten oxide species present in these catalysts was determined as a function of tungsten oxide loading by X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectra (UV–DRS) and ultraviolet–visible Raman (UV-Raman). The catalyst showed high activity for the metathesis of butene to propene. The active centers are not crystallites of WO₃ but rather surface tungsten oxide species. The conversion of butene varies with the degree of catalyst loading.     

A Strong-Acid-Resistant [Th6] Cluster-Based Framework for Effectively and Size-Selectively Catalyzing Reductive Amination of Aldehydes with N,N-Dimethylformamide

Utilization of N,N-dimethylformamide (DMF) as an amine source and reductant for synthesizing tertiary amines is a promising way to replace the substrates formaldehyde and dimethylamine, and it is desirable to seek porous acid-resistant catalysts for heterogeneous catalysis of this reaction. Herein, a robust metal–organic framework (MOF) {[Th₆O₄(OH)₄(H₂O)₆(BCP)₃]⋅10 DMF}_n ( 1 ) containing stacked nanocages with a diameter of 1.55 nm was constructed. Compound 1 can maintain its single-crystal structure even kept in air at 400 °C for 3 h, and in DMF or water at 200 °C for 7 days. Density functional theory (DFT) calculations suggested that the high interaction energy between the [Th₆O₄(OH)₄(H₂O)₆]¹²⁺ clusters and ligands was responsible for the excellent stability of 1 . Catalytic investigations revealed that 1 can effectively and size-selectively catalyze the reductive amination of aldehydes with DMF, and it can be reused at least five times without obvious loss in catalytic activity.     

Thermocatalytic Conversion of CO2 to Valuable Products Activated by Noble-Metal-Free Metal-Organic Frameworks

Thermocatalysis of CO₂ into high valuable products is an efficient and green method for mitigating global warming and other environmental problems, of which Noble-metal-free metal–organic frameworks (MOFs) are one of the most promising heterogeneous catalysts for CO₂ thermocatalysis, and many excellent researches have been published. Hence, this review focuses on the valuable products obtained from various CO₂ conversion reactions catalyzed by noble-metal-free MOFs, such as cyclic carbonates, oxazolidinones, carboxylic acids, N-phenylformamide, methanol, ethanol, and methane. We classified these published references according to the types of products, and analyzed the methods for improving the catalytic efficiency of MOFs in CO₂ reaction. The advantages of using noble-metal-free MOF catalysts for CO₂ conversion were also discussed along the text. This review concludes with future perspectives on the challenges to be addressed and potential research directions. We believe that this review will be helpful to readers and attract more scientists to join the topic of CO₂ conversion.