红外非线性晶体材料AgGa1-xInxSe2的生长和性能表征

AgGa1-xInxSe2是近几年来研制的新型红外非线性光学晶体材料,其主要特点是借着Ga和In含量,即x值的变化,改变材料的折射率、双折射,实现三波共线非线性作用的非临界(90°)相位匹配.我们用垂直布里奇曼法生长单晶,获得了φ35mm×50mm的AgGa1-xInxSe2单晶棒.对生长出晶体棒In的浓度分布进行了测试.晶体元件用红外观察镜和分光光度计分别进行了观察和测试,晶体透光率良好.用一台TEA CO2激光泵浦一块5×6×16mm3的AgGa1-xInxSe2(x=0.3234)晶体元件,成功地实现了10.6μm非临界相位匹配倍频,输出5.3μm的中红外激光.     

NMR研究甲烷水合物在中孔SBA-15内的生成

利用自行研制的高压釜和原位高压核磁共振研究了甲烷水合物在具有孔径均一的中孔SBA-15中的形成过程. 结果发现在静止的状态下,甲烷在中孔SBA-15内与水也能生成甲烷水合物,但其形成所需要的诱导时间比在纯水的条件下要短,SBA-15可促进甲烷水合物的形成;原位高压¹H和¹³C NMR研究表明即使甲烷过量,在一定压力下,SBA-15孔道内的水也不能完全形成甲烷水合物.     

Stimulated Brillouin scattering by the interaction between different-order optical and acoustical modes in an As2Se3 photonic crystal fiber

Brillouin gain spectra(BGS)in an As2Se3 photonic crystal fiber(PCF)are investigated numerically.The profiles of the BGS are simulated by calculating the characteristics of different-order optical and acoustic waves in the PCFs with different core diameters.For the small-core PCF,there are two peaks in BGS,but there is only one peak for the large-core PCF.We also reveal that in the small-core PCF,the difference of Brillouin frequency shift between the LP01 and LP11 modes is obvious,while it is not obvious in the large-core PCF.The Brillouin threshold increases with the core diameter increasing.     

Rh基催化剂上氢甲酰化反应过程的原位高压NMR研究

制备了用于丙烯氢甲酰化反应的Rh/SBA-15 和PPh₃修饰的PPh₃-Rh/SBA-15催化剂. 应用原位变温高压核磁共振技术,对比研究了丙烯在Rh/SBA-15 和PPh₃修饰的多相催化剂PPh₃ Rh/SBA-15上的氢甲酰化反应,实现了高压条件下催化反应的原位固体核磁共振表征. ¹³C MAS NMR研究结果表明：在1.0 MPa的反应压力下,随着反应温度升高丙烯与合成气在Rh/SBA-15催化剂上可转化生成丁醛,而PPh₃配体修饰的PPh₃-Rh/SBA-15催化剂上丁醛产物的正异比显著提高.     

20~#钢不同晶粒度试件拉伸损伤试验的声发射特性研究

采用声发射技术,对四种不同晶粒度20~#钢试件的单轴拉伸过程进行监测,探究不同晶粒度对于金属材料损伤过程中声发射特性的影响。试验结果表明:声发射信号的幅值、能量和撞击计数等特征参数能够很好地描述材料不同晶粒度大小对材料拉伸过程中声发射特性的影响。细晶粒试件声发射信号数较少,强度较低,随着试件晶粒度的增大,声发射信号的强度和活性呈现明显增加的趋势。说明粗晶粒试件力学性能劣化严重,拉伸过程极易损伤,因此,试验结果也反映了金属材料微观损伤过程中声发射与材料内部的损伤演化密切相关。     

末端功能化的树枝状聚合物载体与质粒组装的热力学和动力学

通过二代和四代聚酰胺-胺树枝状聚合物(G2和G4表示)末端分别修饰苯丙氨酸和色氨酸合成了多种新型聚合物载体,进而考察了其与质粒的组装行为.研究结果显示,Phe-G4和Trp-G4与质粒组装为结构致密的纳米粒子,其中Phe-G4与质粒形成的纳米粒子更加紧密.这一过程是由聚合物载体与质粒间的静电相互作用和结构重排共同驱动的.此外,末端修饰方法显著降低了载体的细胞毒性.细胞转染结果表明,Phe-G4和Trp-G4成功介导质粒pEGFP-CL在COS-7细胞中表达,Phe-G4/pEGFP-CL的转染效率提高到作为阳性对照的脂质体组的4倍以上.因此,Phe-G4载体是一种有应用潜力的新型基因传递系统.     

用原位变温19F NMR研究三氟甲磺酸根在苯乙烯不对称环丙烷化反应中的作用

The role of trifluoromethanesulfonate ion (OTf -) in asymmetric cyclopropanation of styrene catalyzed by ruthenium complex of chiral N, P ligand is investigated by in situ variable temperature 19 F NMR. The temperature of NMR experiment varies from 243 K to 283 K. After ethyl diazoacetate and styrene are added into the catalytic system, the process that the OTf - leaves from the central metal is observed from the change of the 19 F NMR spectra. Owing to the weakly coordinating behavior, trifluoromethanesulfonate ion can be easily removed from the central metal and replaced by substrates to form the reactive intermediate during the reaction. So that the catalytic reactivity can be improved greatly when the silver trifluoromethanesulfonate is added to the catalytic system.     

Asymmetric exchange bias training effect in spin glass(FeAu)/FeNi bilayers

A significant exchange bias(EB) training effect has been observed in sputter deposited FeAu/FeNi bilayers, wherein the exchange field(HE) exhibits a special sign-changeable temperature dependence. Very interestingly, despite the absence of multiple easy axes in the FeAu spin glass(SG) layer, HEdrops abruptly between the first and second magnetic cycles,which is followed by a more gradual continuous change in the subsequent cycles. This training behavior cannot be described by the empirical n-1/2law because of the asymmetric magnetization reversal processes. We propose modifying Binek’s model to include the asymmetric changes of the pinning SG spins at the descending and ascending branches. This new model successfully describes the EB training effect in FeAu/FeNi bilayers.     

热驱动微光学

通过实例研究和近期报道的文献,论述了热驱动微光学的研究进展。驱动器主要通过应用在液体和液气界面的压力来调控光学微流体,包括微镜片和薄膜微透镜,热驱动器利用芯片上的温度变化产生所需要的压力差,从而对微透镜进行调控。同时还讨论了用于微光学结构的各种设备、结构、液体和膜材料,并提供了典型操作特性。     

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本文是对近十年来科学前沿热点问题之一的 全基因组关联研究(genome-wide association study, GWAS)的一个综述, 侧重于介绍其中所用到的统计分析方法, 讨论当前GWAS中存在的一些问题及挑战, 并就其发展前景作一个展望.