Structure and magnetism of bcc(1 1 0)-like Fe films grown on Cu(0 0 1) via ion beam triangulation and spin-polarized electron capture

The structure and magnetism of thin epitaxial Fe layers grown on Cu(0 0 1) is investigated by grazing scattering of fast H and He atoms. Information on the atomic structure of the film and substrate surfaces is obtained by making use of ion beam triangulation with protons. The magnetic behavior is studied via the polarization of light emitted after capture of spin-polarized electrons into excited atomic terms during scattering of He atoms. For the formation of bcc(1 1 0)-like Fe films at higher coverages, we detect differences in structural and magnetic properties for room and low temperature growth. We suggest that the crystalline structure depends on the film morphology and that Cu impurities affect the magnetic properties.     

双奇核188Au的准粒子带结构研究

利用在束γ谱学实验技术, 通过¹⁷³Yb(¹⁹F,4nγ)反应 布居了¹⁸⁸Au的高自旋态, 并对其准粒子带结构进行了研究. 基于实验测量结果, 对原有的双奇核¹⁸⁸Au能级纲图做了较大的修改. 通过系统性比较, 对15⁺以上的能级结构进行了讨论.     

Threshold electrical switching in As45Te55-xInx and As50Te50-xInx glasses

The electrical switching behaviour of As₄₅Te_55-xIn_x (5≤x≤15) and As₅₀Te_50-xIn_x (2.5≤x≤11.5) has been studied over a wide range of compositions. These glasses are found to exhibit threshold switching. The composition dependence of switching voltage (V_t) has been found to exhibit a change in slope and a local minimum at compositions x=10 and 12.5 for As₄₅Te_55-xIn_x and x=7.5 and 10.8 for As₅₀Te_50-xIn_x, respectively. The slope change in V_t verses x and the local minimum have been identified using two network topological effects, namely the rigidity percolation threshold and the chemical threshold. Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 11 February 2002     

CP violation and extra dimensions

It is shown that new sources of CP violation can be generated in models with more than one extra dimension. In the supersymmetric models on the space-time , where the radius moduli have auxiliary vacuum expectation values and the supersymmetry breaking is mediated by the Kaluza–Klein states of the gauge supermultiplets, we analyze the gaugino masses and trilinear couplings for two scenarios and obtain the result that there exist relative CP violating phases among the gaugino masses and trilinear couplings. Received: 10 October 2001 / Published online: 20 December 2001     

Single chain force spectroscopy - Reading the sequence of HP protein models

We study the elastic properties of single A/B random copolymer chains, with a specific sequence and use them as theoretical model for so called HP proteins. HP proteins carry hydrophilic (P) and hydrophobic (H) monomers. We predict a rich structure in the force-extension relations which can be attributed to the information in the sequence. The variational method is used to probe local minima on the path of stretching and releasing for the chain molecules. At a given force, we find multiple configurations which are separated by energy barriers. A collapsed globular configuration consists of several domains which unravel cooperatively. Upon stretching, the unfolding path shows a stepwise pattern corresponding to the unfolding of each domain. While releasing, several cores can be created simultaneously in the middle of the chain, resulting in a different path of collapse. The long-range interactions and stiffness of the chain simplify the potential landscape given by the disorder in sequence. Received 5 March 2002 / Received in final form 16 May 2002 Published online 13 August 2002     

Controlling global stochasticity of Hamiltonian systems by nonlinear perturbation

A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust against small external noise. The mechanism underlying this high control efficiency is intuitively explained. Received 15 January 2002 Published online 6 June 2002     

Constraint Molecular Dynamics and results on isotopic distributions produced in heavy ion collision — The Sn + Ni systems

The Constraint Molecular Dynamics approach is illustrated together with calculation on different heavy ion collisions. In particular the charge-mass distribution produced in the collision ¹²⁴Sn + ⁶⁴Ni and ¹¹²Sn + ⁵⁸Ni at 35 MeV/nucleon is discussed. By comparing the Y = (N ? Z)/A distributions for fragments produced in central collisions it results that this observable can be sensitive to the dynamic effects induced on the two systems by the different charge/mass ratio.     

Effect of hardness and composition gradients on Barkhausen emission in case hardened steel

The effect of gradients in hardness, structure and composition in the surface layers on magnetic Barkhausen noise (MBN) was investigated in two widely used low alloy steels. One material was case hardened by induction hardening. The other was case carburised. Similar hardness profiles were produced by the two treatments. It was found that the variation in structure and hardness through the case in the induction-hardened steel had a minor effect on the MBN profile. In contrast, the inhomogeneity in the case-carburised material showed up clearly. This took the form of a broadened or two-peak MBN profile. When the surface layer containing the case was removed by etching, the broadened profile was replaced by a profile with a single peak. It is concluded that the shape and position of the MBN profile is significantly affected when a gradient in microstructure is induced by a gradient in carbon content. On the other hand, a gradient in microstructure induced by heat treatment with a constant carbon level has much less affect on the MBN profile for the induction-hardened steel.     

A critical review of the chemical kinetics of SF4, SF5, and S2F10 in the gas phase

The gas phase chemical kinetics of SF₄, SF₅, and S₂F₁₀ are reviewed with particular emphasis on relevance to the general problem of the dielectric breakdown of SF₆. Specific reaction systems treated are SF₄ + F₂, SF₅ + SF₅, and the pyrolysis of S₂F₁₀. Computer modeling calculations were carried out to arrive at the best estimates of rate parameters. Based on the results of these calculations, sets of recommended rate parameters are provided. The major discrepancies and problems in establishing the kinetic data base are described. Thermochemical consequences of different model calculations are given.