Measurements of velocity distributions with a laser doppler imaging system

A laser Doppler imaging system with a TV camera has been constructed and velocity distributions of fluid flow in cross sections of a rectangular channel have been measured. Consequently, it has been found that the system has some advantages in comparison with usual laser Doppler velocimeters, for example, the visualization of flow can be easily achieved.     

Annealing behavior of a void network in amorphous silicon

A void network in a-Si films prepared by vacuum deposition was studied. A close relationship in annealing behavior has been observed between the changes in surface area of voids and in the ESR signal strength.     

Subpicosecond photon echoes by using nanosecond laser pulses

Subpicosecond time resolutions have been obtained in photon echoes when a sample was excited by two nanosecond dye laser pulses with a smooth and broad spectrum. The dye laser was pumped by second harmonics of a Q-switched Nd:YAG laser, and the pulse width was 10 ns. The sample was 3% Nd³⁺-doped silicate glass, and the center frequency of the dye laser was tuned at 5910 Å on resonance with the ⁴I_{$\text{9}\text{2}$} ? ²G_{$\text{7}\text{2}$}, ⁴G_{$\text{5}\text{2}$} transition of Nd³⁺. The homogeneous transverse relaxation time T₂ was measured to be 91 ps at 10 K in agreement with the previous measurements by picosecond pulses.     

Cycloaddition of oxetane and carbon dioxide catalyzed by tetraphenylstibonium iodide

Trimethylene carbonate was readily obtained in the reaction of oxetane and carbon dioxide in the presence of tetraphenylstibonium iodide.     

Synthesis in the diazasteroid group VI. A synthesis of 2,3-dimethoxy-15-methyl-8,15-diazaestra-1,3,5(10)triene

Homoveratrylamine (II) was condensed with 3-(2-carbomethoxyethyl)-1,3-dimethyl-2-pyrrol-idone (Ib) to furnish the corresponding amide (III), which was subjected to the Bischler-Napieralski reaction to afford the corresponding dihydroisoquinoline derivative (IV). Compound V was obtained by the reductive ring closure of Vila which was obtained by the hydrogena-tion of IV. The stereochemistry of V is proposed to have the anti-trans-trans quinolizidine conformation.     

A recyclable catalyst for asymmetric transfer hydrogenation with a formic acid-triethylamine mixture in ionic liquid

A novel task-specific ionic ligand with an imidazolium salt moiety was synthesized, and its catalytic ability and recyclability for asymmetric transfer hydrogenation of acetophenone derivatives with a formic acid-triethylamine azeotropic mixture in an ionic liquid [bmim][PF6] was examined.     

Polarization-maintaining photonic crystal fibers with near-zero flattened dispersion in 1.06 μm waveband for medical applications

In this paper we present the design of a modified hexagonal photonic crystal fiber (PCF) having high birefringence and a near-zero flattened dispersion. Using the finite-difference method (FDM), it is shown that the proposed multiple Gedoped core hexagonal PCF exhibits a high birefringence of order 10⁻³ and a nearly zero flattened dispersion in the optical coherence tomography (OCT) waveband. In addition, the proposed PCF has a confinement loss of less than 10⁻⁸ dB/m at 1.06 μm. PCFs with such properties are considered suitable for both endoscopic OCT and other experimental setups employing 1.06 μm lasers.     

Einstein-de Haas effect in dipolar Bose-Einstein condensates

The general properties of the order parameter for a dipolar spinor Bose-Einstein condensate are discussed based on symmetries of interactions. An initially spin-polarized dipolar condensate is shown to dynamically generate a nonsingular vortex via spin-orbit interactions--a phenomenon reminiscent of the Einstein-de Haas effect in ferromagnets.     

Identification and stereochemical assignment of the beta-hydroxytryptophan intermediate in the echinomycin biosynthetic pathway

[reaction: see text] Little is known about how quinoxaline-2-carboxylic acid (QC) is synthesized in nature. On the basis of analysis of echinomycin biosynthetic gene clusters as well as feeding experiments with labeled precursors, we have proposed a biosynthetic pathway to QC and identified the (2S,3S)-beta-hydroxytryptophan as a key intermediate.     

Current-induced domain wall motion in magnetic nanowires with spatial variation

We model current-induced domain wall motion in magnetic nanowires with the variable width. Employing the collective coordinate method we trace the wall dynamics. The effect of the width modulation is implemented by spatial dependence of an effective magnetic field. The wall destination in the potential energy landscape due to the magnetic anisotropy and the spatial nonuniformity is obtained as a function of the current density. For a nanowire of a periodically modulated width, we identify three (pinned, nonlinear, and linear) current density regimes for current-induced wall motion. The threshold current densities depend on the pulse duration as well as the magnitude of wire modulation. In the nonlinear regime, application of ns order current pulses results in wall displacement which opposes or exceeds the prediction of the spin transfer mechanism. The finding explains stochastic nature of the domain wall displacement observed in recent experiments.