Theory and experiment of spatially and temporally partially coherent speckle shearing interferometry

The theory and experiment of spatially and temporally partially coherent speckle shearing interferometry is reported in this rapid communication for the first time. The general requirements for the surface roughness and coherence area of a diffuse object surface in spatially and temporally partially coherent speckle shearing interferometry are discussed. An experimental verification is presented and the results of theory and experiment are in good agreement.     

TDDFT study of one- and two-photon absorption properties: donor-pi-acceptor chromophores

We report a comprehensive time-dependent density functional theory (TDDFT) study of one-photon and two-photon absorption (OPA and TPA, respectively) spectra for donor-pi-acceptor molecules. The calculated excitation energies were generally shown to be in good agreement with experiment, particularly when compared to results from measurements carried out in a nonpolar solvent, although the oscillator strengths were overestimated in some cases. Calculated TPA cross sections applying the two-state approximation were shown to be highly dependent on the form of the line-shape function used. Although a good agreement with experimental TPA spectra was generally observed, the wide range in the experimentally measured values and lack of systematic experimental data on solvent effects limited a detailed comparison as yet.     

Measurements of velocity distributions in the deformation zone in cold rolling by a scanning LDV

Experimental determination of the velocity distribution in the deformation zone is of significant importance to investigate the metal flow in both conventional and asymmetrical rolling processes. In this paper, a scanning laser Doppler velocimetry (LDV) system, designed for measuring the velocity distributions in the deformation zone in plate rolling is reported. The LDV used for the rolling process is briefly described and then the scanning mechanism based on beam displacement by a rotating transparent plate is introduced. The relationship among the scanning distance, the beam-cross angle of the LDV system and the rotating angle of the plate is established. The scanning LDV was first tested with a rotating disk and then applied in the rolling process. The test results have demonstrated the feasibility of the scanning LDV.     

Interference Patterns of Two Focused Gaussian Beams in an LDA Measuring Volume

Based on a model of spherical Gaussian beam interference, the fringe spacing variations in the measuring volume of a differential LDA system are analysed and the fringe patterns are obtained for different locations of beam waists. It is found that when the incident beams are sharply focused and a large beam cross-angle is used to obtain high spatial resolution, fringe gradients occur along both the x- and z-directions, even though the incident beams intersect at their waists. When the measuring volume is very small, the measurement accuracy of an LDA is limited by inherent fringe gradients mainly along the z-direction. © 1997 Elsevier Science Ltd. All rights reserved.     

Extrudate swell for a round jet with large surface tension

The problem of extrudate swell of a viscoelastic fluid from a round pipe is studied by the method of domain perturbations. The perturbation problems are solved by a finite-element method through second-order in the flow rate parameter ∈ for small flow rates. The analysis extends the work of Sturges on swelling in two-dimensional channels to round capillary tubes. In perturbation studies for small ∈, the rheology of the fluid may be expressed by three parameters, the viscosity and the two constants α₁ and α₂ appearing at order two in the expansion of the extra stress around zero shear. Surface tension has an important influence on the shape of the jet at low speeds. The shape of the surface on a round jet depends on α₁ and α₂, in the plane jet only on α₁. The analysis predicts that no matter what the constitutive equation may be, the jet will first contract if the radius of the pipe is sufficiently small. The contraction takes place in a length less than $\text{1}\text{10}$ the diameter of the jet and is followed by a swell. The contraction is usually small and may be hard to observe. There are five different contributions to the jet shape at second-order but only the viscoelastic ones persist as the pipe radius goes to zero.     

Inotilone and related phenylpropanoid polyketides from Inonotus sp. and their identification as potent COX and XO inhibitors

By bioassay-guided isolation, phenylpropanoid-derived polyketides, including an unusual 5-methyl-3(2H)-furanone derivative (inotilone) with potent cyclooxygenase (COX) and xanthone oxidase (XO) inhibitory activities were obtained from the fruiting body of the mushroom Inonotus sp.     

Effective magnetic monopoles and universal conductance fluctuations

The observation of isolated positive and negative charges, but not isolated magnetic north and south poles, is an old puzzle. Instead, evidence of effective magnetic monopoles has been found in the abstract momentum space. Apart from Hall-related effects, few observable consequences of these abstract monopoles are known. Here, we show that it is possible to manipulate the monopoles by external magnetic fields and probe them by universal conductance fluctuation measurements in ferromagnets with strong spin-orbit coupling. The observed fluctuations are not noise, but reproducible quasiperiodic oscillations as a function of magnetization direction, a novel Berry phase fingerprint of the magnetic monopoles.     

External control of a metal-insulator transition in GaMnAs wires

Quantum transport in disordered ferromagnetic (III,Mn)V semiconductors is studied theoretically. Mesoscopic wires exhibit an Anderson disorder-induced metal-insulator transition that can be controlled by a weak external magnetic field. This metal-insulator transition should also occur in other materials with large anisotropic magnetoresistance effects. The transition can be useful for studies of zero-temperature quantum critical phase transitions and fundamental material properties.