Spatial modulation of low-frequency spin fluctuations in hole-doped La2CuO4

Systematic neutron scattering measurements have been performed on the Sr-doped La_{2-x}Sr_xCuO₄ to study the doping dependence of spatially modulated dynamical spin correlations or so-called incommensurate spin fluctuations. The modulated spin correlations appear beyond x ≈ 0.05 which is close to the lower boundary of the superconducting phase. First evidence was observed for the linear relation between the degree of spatial modulation or the incommensurability Σ(x) and the maximumT _c atx. We present a universal curve for Σ(x) by adding data from other La₂CuO₂ systems such as oxygen-doped superconductors, oxygen-reduced or Zn-substituted nonsuperconductors, and La_1.6-xNd_0.4Sr_xCuO₄.     

Fluctuations of concentration overpotential generated at gas-evolving electrodes

The electrode overpotential is usually expressed in terms of partial components related to ohmic, activation and concentration effects. For a gas-evolving electrode, the overpotential fluctuates because of bubble evolution but only the global overpotential fluctuations and, more recently, their ohmic part are easily accessible by routine experiments. In the present paper, high-amplitude fluctuations of concentration overpotential have been experimentally revealed by an anomalous behaviour of the current fluctuations induced by hydrogen evolution on platinum electrodes under potential control in alkaline media with or without the presence of a second mass-transport-controlled reaction. Inverted current jumps, reproducibly observed owing to an artificial bubble-nucleation site created on the edge of the rotating electrode, which provoked periodic bubble eruption, were ascribed to local concentration changes drastically affecting the current-lines distribution. These experimental results validate the theoretical models that predicted those anomalies but remained unverified up to now. A quantitative estimation of each overpotential component at bubble eruption is addressed by means of a simplified analytical approach supported by the simultaneous measurement of the electrochemical current noise and electrolyte resistance fluctuations.     

信息熵理论在水力学中的应用

文中介绍了应用信息熵理论对脉动压力数据处理，对非宽浅河流断面流分布及断面泥沙浓度分布等问题所进行了探索，所得成果与实测资料吻合较好。     

Metallic stripes in high-temperature superconductors

A phenomenological approach is applied to explore signatures of disordered charge stripes and antiphase spin domains in single-particle properties of the high-temperature superconductors. Stripe phases are shown to explain many experimentally observed unusual features measured in angle-resolved photoemission and optical spectroscopy. It is argued that disordered and fluctuating stripe phases are a common feature of high-temperature superconductors, supported by the additional evidence from neutron scattering and NMR.     

Thermal Fluctuations in the Structure of Naturally Chiral Pt surfaces

The intrinsic chirality of metal surfaces with kinked steps (e.g., Pt(643)) endows them with enantiospecific adsorption properties. To understand these properties quantitatively the impact of thermally-driven step wandering must be assessed. We derive a lattice-gas model of step motion on Pt(111) surfaces using diffusion barriers from density functional theory. This model is used to examine thermal fluctuations of straight and kinked steps.     

Effective Mass Close to a Quantum Critical Point

The effective mass in heavy fermion materials is calculated, taking into consideration both the antiferromagnetic and ferromagnetic fluctuations. The temperature and the proximity of a quantum critical point effects are considered. The effective mass diverges at the quantum critical point and in the zero temperature limit.     

泵涨落对双模激光增益模型竞争效应的影响

研究了泵涨落对双模激光增益模型竞争效应的影响。通过线性稳定性分析得到一些很有意义的结论。     

Incommensurate fluctuations in Bi2Sr2CaCu2O8

A special neutron scattering technique has been used to discover an incommensurate fluctuation in Bi₂Sr₂CaCu₂O₈ that appears below T_c. The fluctuation is identified as a dynamic charge density wave since its scattering intensity appears to increase with increasing momentum transfer. The fluctuation is found at a wavevector near 2k_F and could be associated with a dynamic stripe phase.     

SEPARATOR FOR LIQUID-LIQUID DISPERSIONS

An apparatus for separation of fine liquid dispersions is described and its performance characteristics are studied. It provides high separational efficiency at high flowrates and small pressure drop. The emulsion enters axially in a cylindrical cartridge, then flows radially through a multi-layer packing where phase separation takes place. The coalesced phase forms a film, which is continuously lead to the interface. The main features of the unit are outlined and a comparison with other similar units is made.