Three unusual 22-beta-O-23-hydroxy-(5 alpha)-spirostanol glycosides from the fruits of Solanum torvum

Three novel 22-beta-O-spirostanol oligoglycosides, torvosides J (1), K (2) and L (3) have been isolated from the fruits of Solanum torvum SWARTZ and their chemical structures have been characterized based on the spectroscopic means. They are worth of note as rare 22-beta-O-spirostanol glycosides.     

Effects of surface roughness of a moving test body on laser-interferometric displacement measurements

Displacement measurements by laser-homodyne or laser-heterodyne methods are dicussed analytically with respect to the relevant surface roughness. Expressions of the output signal and its signal-to-noise ratio are derived on the basis of gaussian statistics of the roughness. The roughness does not impose restrictions on the measurable minimum displacement but degrades the signal-to-noise ratio of the output signal.     

Modulation effects of a sound wave on the mutual coherence function of light

A theoretical investigation is described on coherence effects in a light-sound interaction. The mutual coherence function can be modulated in time and space by electronic means using a simple travelling sound wave. The modulation factor is expressed in terms of the zeroth-order Bessel function whose argument is a function of the two-point separation of interest and the time delay between the two light waves to be correlated. The spectral characteristics obtained from the space-time Fourier transform of the mutual coherence function coincides with an earlier statement in the Raman-Nath theory.     

Speckle-pattern contrast of semiconductor laser propagating in a multimode optical fiber

Speckle patterns produced by coherent light from a GaA1As double-hetero-structure laser diode that has been transmitted through a multi-mode optical fiber are experimentally studied by analyzing the average contrast. It has been found that the speckle contrast observed in the far-field region is significantly lowered when the spectral width of a laser diode is as broad as a few tens of Angstroms.     

Simulation of stochastic differential equations

A lot of discrete approximation schemes for stochastic differential equations with regard to mean-square sense were proposed. Numerical experiments for these schemes can be seen in some papers, but the efficiency of scheme with respect to its order has not been revealed. We will propose another type of error analysis. Also we will show results of simulation studies carried out for these schemes under our notion.     

Effects of substrate microstructure on the magnetic anisotropy of sputtered cobalt alloy film

The magnetic properties and crystalline structure of Co alloy film deposited on a regularly corrugated substrate have been studied. Microscopic grooves are lithographically fabricated on InP substrates. In-plane anisotropy energy is 4–5×10⁴J/m³. The magnetic anisotropy is affected by the crystallographic orientation and the microscopic shape of the corrugated Co alloy film.