Reaction of perfluoroalkylethylens with nucleophiles

Perfluoroalkylethylenes react with some carbon-, oxygen-, sulfur-, selenium-, nitrogen-, and phosphorus-based nucleophiles by formal S_N2′ displacement of fluoride ion.     

Surface-enhanced raman scattering as a function of molecule-surface separation

The dependence of Raman enhancement on molecule-surface separation is measured for pyridine on roughened Ag surfaces in UHV. Results follow predictions for local field enhancement by small Ag spheroid resonances by McCall, Platzman and Wolff, showing multi-layer enhancement. Isotopic studies confirm that several layers contribute to the enhanced Raman signal.     

Some Problems for Cubic Nonlinear Equations on a Half-Line

The paper deals with a problem of developing an inverse-scattering based formalism for solving problems for the cubic nonlinear (or the modified Korteweg–de Vries (KdV)) equations: q _t +q _xxx +6q ² q _x =0, 0x<, –<t<,q _t +q _xxx –6q ² q _x =0, with the given initial and boundary conditions: q(x,0)=q(x),q(0,t)=p(t), p(t)L ₁(–,). The relation between the solution of the initial-boundary value problem (1), (3), (4) and that of the KdV equation on the half-line is shown. The Cauchy problem for the cubic nonlinear equation: q _t +q _xxx –6|q|² q _x =0, 0x<, –<t<, with the given initial condition (3) is considered also. Here we solve the above problems on the half-line 0x< but with –<t<.     

Large time behavior of solutions for critical and subcritical complex Ginzburg-Landau equations in H<Superscript>1</Superscript>

Considering the Cauchy problem for the critical complex Ginzburg-Landau equation in H¹(Rⁿ), we shall show the asymptotic behavior for its solutions in C(0, ∖;H¹(Rⁿ)) ∩ L²(0, ∖;H^1,2n/(n-2)(R²)), n≥3. Analogous results also hold in the case that the nonlinearity has the subcritical power in H¹(Rⁿ), n≥1. Dedicated to Professor Zhou Yulin for his 80th birthday.     

Synchronization of underdamped Josephson-junction arrays

Our recent experiments show that arrays of underdamped Josephson junctions radiate coherently only above a threshold number of junctions switched onto the radiating state. For each junction, the radiating state is a resonant step in the current-voltage characteristics due to the interaction between the junctions in the array and an electromagnetic cavity. Here we show that a model of a one-dimensional array of Josephson junctions coupled to a resonator can produce many features of the coherent be havior above threshold, including coherent radiation of power and the shape of the array current-voltage characteristic. The model also makes quantitative predictions about the degree of coherence of the junctions in the array. However, in this model there is no threshold; the experimental below-threshold region behavior could not be reproduced.Received: 11 April 2003, Published online: 23 July 2003PACS: 74.50.+r Tunneling phenomena; point contacts, weak links, Josephson effects - 85.25.-j Superconducting devices     

Unique Continuation at the Boundary for Elliptic Operators in Dini Domains

Let u be the solutions to some elliptic equations of the form

Magnetic characterization of ZnO doped with vanadium

The magnetic properties of vanadium doped ZnO nanorods formed by different growth methods were examined. The samples under investigation were either grown by metallorganic vapour-phase epitaxy (MOVPE) with in situ incorporation of the V atoms or by aqueous chemical growth (ACG) in combination with an ion-implantation process. The V concentration for all samples was less than 2 at.%.Field-cooled SQUID measurements only reveal a weak ferromagnetic signal still in a very sensitive measuring range. However, the MFM micrographs obtained at room temperature show a clear magnetic contrast and complex structures, the images are in good agreement with the phase images expected for vertically aligned magnetic dipoles. This is a strong indication for a ferromagnetic behaviour at room temperature.     

空气比热容比的标准值与测量的误差

在绝热膨胀过程中,用电磁阀、大口径管((φ)≥4mm)迅速放气和关闭.对空气的比热容比γ的标准值进行了详细的论证计算1.3990＜γ＜1.4025,并对实测值的误差进行了分析讨论.     

用双粒子模型研究微量元素与Ni在Ni3Al晶界共富集现象

双粒子模型的基础是描述原子之间相互作用势为EAM(embedded atom method)势的Monte Carlo模拟. 模型建议：在Ni₃Al晶界弛豫时，微量元素原子既被看作为偏析子又被看作为诱发子. 作为偏析子它在晶界偏析(或富集)，作为诱发子它诱发Ni原子在晶界偏析(或富集). 可见本模型能解析共偏析(或共富集)现象. 根据正(或诱发子)效应与负(或偏析子)效应的联合影响，模型解释了Ni在Ni₃Al晶界最明显富集现象. 关键词： 偏析子与诱发子 基体效应 在晶界共富集 晶界内聚性