Enhancement origin of SERS from pyridine adsorbed on AgCl colloids

SERS of pyridine molecules adsorbed on AgCl colloids are recorded. The enhancement origins are discussed by studying the effects of illumination, thiosulfate, hydrogen peroxide and ferricyanide on SERS of pyridine on AgCl colloids. In addition to an important contribution of local field enhancement on photolytic Ag particles in AgCl colloid, the surface Ag⁺ complexes on AgCl colloids as the SERS-active sites also make an important contribution to SERS of pyridine on AgCl colloid.     

Rearrangements of 6-methoxycarbonyl 7-oxabicyclo[2.2.1]hept-2-enes under prévost's reaction conditions

The rearrangement of 7-oxabicyclo[2.2.1]hept-2-enes to 2-oxabicyclo[2.2.1]heptane derivatives, when reacted with iodine and silver acetate, provides further insight into the migratory preferences of alkyl groups involved in Wagner-Meerwein 1,2-bond shifts in unbiased situations.     

Manganese (III) based oxidative free-radical cyclizations. 2. Polycyclization reactions proceeding through tertiary cations.

Oxidative cyclization of 5 with Mn(OAc)₃ ·2H₂O gives mainly the bicyclic products 7 and 8. On the other hand, oxidative cyclization of 16 and 17 gives mainly the lactones 18 and 20. These data suggest that oxidation of a monocyclic radical to a cation precedes cyclization to form 3, 4, 7, and 8.     

Conformational energies of trans-1,4-difluoro- and trans-1-chloro-4-fluorocyclohexane. The role of electrostatic interactions.

The conformational energies of the title compounds were extrapolated from solution ¹⁹F NMR measurements to vapour phase dielectric medium. Vapour phase values were satisfactorily reproduced by MM2 computations including electrostatic interactions between charges obtained by the PEOE method.     

L波段高功率线极化径向线阵列天线理论分析与数值模拟

 探索了L波段的高功率线极化径向线阵列天线。基于三角形栅格形式实现了径向线圆形平面阵列天线,分析并给出了径向线并联馈电网络,并以同轴馈电的水平单圆环线极化天线为基础,利用径向线并联馈电网络设计出了间距小于一个波长下L波段高功率线极化径向线阵列天线。研究结果表明：这种结构实现径向线阵列天线的线极化辐射是可行的,该天线在中心频率1.57 GHz下,增益为19.97 dBi,轴比为-52.06 dB,反射系数为0.105 2;在1.37～1.77 GHz的频率范围内增益大于18.64 dBi,轴向轴比值小于-46.45 dB。     

基于孔口出流模型的实验研究及理论分析

基于孔口出流模型对底部有小孔的圆柱体容器中液体液面高度随时间的变化规律进行了实验研究,并通过计入液体表面张力引起的孔口收缩和流体黏滞力导致的能量损失对实验结果进行了理论分析,与实验结果一致.     

A relativistic density functional study of gaseous uranium tetrahalides

The molecular structures and vibrational frequencies of gaseous UX₄ (X = F, Cl, Br and I) molecules have been investigated using generalized gradient approximation (GGA) functions (BP, BLYP, PBE and RPBE) with triple-zeta polarized (TZP) basis set. Scalar relativistic effects are introduced via the zeroth-order regular approximation (ZORA) approach to the Dirac equation in the present study. Of the methods examined here the RPBE has the best performance in terms of the errors compared with experiment and reference for the vibrational frequencies. The bond dissociation energies (BDE) for U–X bonds in the UX₄ were obtained using the RPBE method, and are in good agreement with experimental values. In addition, satisfactory calculated entropies of UX₄ have also been obtained at temperatures ranging from 600 to 1200 K in 50 steps using the same method.     

无穷积分余项与其被积函数比值的收敛阶

对一类函数的无穷积分余项与该函数的比值得到当x趋于无穷大时的收敛阶,这类函数是幂函数与指数函数的乘积函数,并将其应用到Mittag-Leffler函数.同时考虑了对应的级数情形.