短脉冲激光尾流场中的前向Raman散射

用212维粒子模拟分析了前向Raman散射对激光尾流场加速电子的影响.前向Raman散射使脉冲长度在传播方向上被拉长，脉冲后沿变陡，产生的尾流场相速度明显减小，而且超热电子的最大动能明显小于理论估计值.此外激光频率整体向低频移动.     

聚砜-尼龙6嵌段共聚物结构的研究

<正> 以金属钠作催化剂合成的聚砜-尼龙6嵌段共聚物对尼龙6的吸水性有一定的改善,而且可以作为聚砜与尼龙共混物的相容剂,但共聚物中聚砜组分的含量都不超过25％。这可能与共聚物的结构有关。近年来的工作表明:反相气相色谱法(IGC)是高聚物结构分析的有用的工具之一。我们试图用反相气相色谱法,通过观察嵌段共聚物     

不同孔径的介孔碳分子筛对VB12的吸附性质研究

摘要利用SBA-15为模板, 在不同温度下合成了孔径大小在3.7(CMK-3-100)和6-3 nm(CMK-3-150)之间的介孔碳， 以其作为吸附剂, 研究了它们在水溶液中对VB12的吸附作用. 结果表明, CMK-3-130与CMK-3-100和CMK-3-150相比， 表现出对VB12最大的吸附能力(吸附能力为412.5 mg/g), 这是因为它有比较高的有序结构和比较大的孔容.     

物理老化对聚苯基单醚喹啉薄膜银纹化的影响

物理老化实质上是聚合物材料在 Tg 以下存放过程中 ,其凝聚态结构通过链段或更小运动单元的运动 ,从热力学非平衡态向平衡态过渡的一个结构弛豫过程[1] .在这一过程中 ,聚合物的密度、自由体积、焓、熵和力学性质随温度和时间产生变化 .因为银纹化是聚合物的特性 ,所以银纹化也将随结构回复过程而产生变化 .有关物理老化对聚合物银纹化的影响尚未得出一致的结论 [2～ 4 ] .聚苯基单醚喹啉 (结构见 Scheme1 )是一种高性能的芳杂环聚合物 [5] ,它可以在比较苛刻的条件下作为绝缘材料和膜材料使用 .有关这类高性能的芳杂环聚合物的物理老化…     

铜在HOPG上电沉积过程的现场ECSTM研究

用自制的电化学扫描隧道显微镜（ＥＣＳＴＭ）现场研究Ｃｕ在ＨＯＰＧ上的电沉积过程．结果表明Ｃｕ在ＨＯＰＧ上的电沉积为三维成核的过程．当电位较低或Ｃｕ２＋离子浓度较低时，铜在本体金属生长主要沿着台阶方向．过电位较高时，铜的成核数目增加，沉积层的晶粒有所细化．同时，非现场ＥＣＳＴＭ比较研究表明，ＳＴＭ针尖对针尖局部区域的电沉积起屏蔽作用，针尖所在区域Ｃｕ的沉积速度比其它区域明显减小     

NMR of Terminal Oxygen. Part 14. Kinetically stabilized simple enols containing methylated uracil groups: Application of a 17O-NMR test of H-bonding

In the crystalline N,N′-dimethylated uracil derivatives 2a , b , the kinetically stabilized enol group forms an H-bond with O? C(4), as demonstrated by increased shielding of specifically labelled 2a and 2b in the ¹⁷O-NMR spectra (Δδ(¹⁷O)(C(4)—O) ? ?30 ppm); absence of dilution and solvent effects show that the H-bridge is intra-molecular, forming an eight-membered chelate ring. The (apparent) shielding effect Δδ(¹⁷O) in 2a, b is larger than that in salicylamide. The strong H-bond explains why the enols 2 , in spite of the absence of steric hindrance, are kinetically stabilized.     

含二茂铁和吡啶单元的手性席夫碱配体在钌催化的不对称氢转移反应中的应用

Chiral Schiff base complexes are very efficient for a wide range of reactions, including expoxidation[1], epoxide ring opening[2], Diels-Alder reaction[3], aldol reaction[4], etc. However, there are only few examples of P-N chelate Schiff bases being used as the chiral ligands in the asymmetric transfer hydrogenation of ketones. Recently, Gao et al[5] reported a series of P,N,N,P Schiff base ligands that have relatively low enantioselectivity in the asymmetric transfer hydrogenation of ketones.     

Highly enantioselective 1,4-conjugate addition of diethylzinc to acyclic enones with chiral phosphite–pyridine ligands derived from H8-NOBIN

A series of new phosphite–pyridine ligands, based on the H₈-binaphthyl backbone, were synthesized and employed in the copper-catalyzed enantioselective 1,4-conjugate addition of diethylzinc to acyclic enones. Ligands derived from (S)-H₈-NOBIN provided better results than their parent ligands in the reaction. Ligand L1 provided excellent ees for trans-4-aryl-3-buten-2-ones (up to 97.8% ee) as substrates. Ligand L2 was very efficient for various para-chalcones, and up to 97.2% ee was achieved.