3-D PTV measurement on turbulence modification due to an oil droplet in a plane Couette water flow

Three-dimensional particle tracking velocimetry (3-D PTV) measurements with a two-camera system have been conducted for a turbulent water plane Couette flow with an oil droplet in order to understand the modification of shear-dominant turbulence by the droplet. The parameters of the stereogrammetry, which are crucial for calculating the spatial coordinate of tracer particles from 2-D images of two cameras, have been determined with a careful calibration. The experimental results show that the axial and wall-normal turbulence intensities and the turbulent kinetic energy are enhanced locally in the confluence regions where axial main flow over the interface meets the secondary flow along the interface in the wall-normal direction. The secondary flows were observed only around the equator of the droplet. The wall-normal and transverse turbulence intensities are found to increase in the region above the droplet. This is due to the change in the direction of the primary flow over the top of the droplet. The turbulence in the other region is attenuated mainly because of the attenuation of the generation and evolution of the coherent structure in the neighbourhood of the droplet.     

Hexagonal Defect Array Formed under Steady Shear Flow in Water-in-Cholesteric Liquid Crystal Emulsions

The relation between the liquid crystalline textures and the steady shear viscosity has been investigated in cholesteric emulsions, composed of water, surfactants, and cholesteric liquid crystals. Both at the substrate surface and at the surfactant-coated droplet surface, a homeotropic anchoring is enforced to the adjacent liquid crystal. Under a steady shear flow with the shear rate below 100 s^–1, we observed that point defects spontaneously appear, and tend to adopt a regular hexagonal arrangement in the low shear-rate range of 1–20 s^–1. In viscosity measurements, the shear-thinning behavior was found, showing a clear correspondence to the texture change. We estimated the height of point defects in the hexagonal array from the viscosity increase in the shear-thinning, assuming that the shear-thinning behavior is caused by the reduction of the effective gap between cone and plate, owing to the presence of the hexagonal array anchored on the plate. The relation between the estimated height and the measured lateral size of point defects agreed with that of the quadrilateral array, which is formed after termination of the shear. This agreement informs that the shape of a point defect is preserved in both defect arrays, independently of shearing conditions.     

Selective monoiodination of aromatic compounds with electrochemically generated I+ using micromixing

Selective monoiodination of aromatic compounds such as dimethoxybenzene has been successfully achieved with I+, which is generated by anodic oxidation of I2 in acetonitrile, using micromixing.     

Raman lasing and cascaded coherent anti-Stokes Raman scattering of a two-phonon Raman band

Raman lasing of a two-phonon Raman band in the anti-Stokes side is demonstrated. Two femtosecond light pulses with identical wavelengths are irradiated onto a SrTiO3 crystal in a cross-beam configuration. Under low excitation power, several wave-mixing signals with identical wavelengths are emitted. When the power exceeds a critical value, cascaded coherent anti-Stokes Raman scattering (CARS) signals are emitted, the frequency step of which is coincident with that of the strongest two-phonon Raman band of 2TO2.     

A novel approach to confront electroweak data and theory

A novel approach to study electroweak physics at one-loop level in generic SU(2)_L×U(1)_Y theories is introduced. It separates the 1-loop corrections into two pieces: process specific ones from vertex and box contributions, and universal ones from contributions to the gauge boson propagators. The latter are parametrized in terms of four effective form factors $\bar e^2 (q^2 ), \bar s^2 (q^2 ), \bar g_Z^2 (q^2 )$ and $\bar g_W^2 (q^2 )$ corresponding to the γγ, γZ,ZZ andWW propagators. Under the assumption that only the Standard Model contributes to the process specific corrections, the magnitudes of the four form factors are determined atq ²=0 and atq ²=m _Z ² by fitting to all available precision experiments. These values are then compared systematically with predictions of SU(2)_L×U(1)_Y theories. In all fits α _s (m _Z ) and $\bar \alpha (m_Z^2 )$ are treated as external parameters in order to keep the interpretation as flexible as possible. The treatment of the electroweak data is presented in detail together with the relevant theoretical formulae used to interpret the data. No deviation from the Standard Model has been identified. Ranges of the top quark and Higgs boson masses are derived as functions of α _s (m _Z ) and $\bar \alpha (m_Z^2 )$ . Also discussed are consequences of the recent precision measurement of the left-right asymmetry at SLC as well as the impact of a top quark mass and an improvedW mass measurement.     

Iron-catalyzed cross-coupling of alkenyl sulfides with Grignard reagents

[reaction: see text] The iron-catalyzed cross-coupling reaction of alkenyl sulfides with Grignard reagents is described. While the cross-coupling proceeds efficiently at alkenyl-S bonds, almost no cross-coupling takes place at aryl-S bonds, attesting to a unique selectivity of iron catalysis. The beneficial effect of potentially coordinating 2-pyrimidyl group on sulfur is also described.