Mitigation of Diffraction Fringe in Quasi-Far Field Pattern Using an Edge-Shaped Plate

A new concept is developed for improving the laser intensity distribution in quasi-far field using geometrical optics of a continuous phase (so-called edge-shaped plate). The diffraction fringe on a quasi-far field beam pattern of a well collimated He-Ne laser beam 5 cm in diameter is mitigated by the insertion of an edge-shaped plate with a super-Gaussian (n=40) surface profile. A diffraction code using Fresnel-Kirchhoff diffraction integration was developed to calculate diffraction patterns of aspherical optical elements. The measured beam profile is in good agreement with the calculated beam pattern.     

Composition Triple Systems and Realization of Triple Products in Terms of Bilinear Algebras

We give a definition of new triple systems and study the correspondence between triple and bilinear products for many triple systems.     

Mode-selective excitation of coherent surface phonons on alkali-covered metal surfaces

We demonstrate the mode-selective excitation of coherent phonons at Pt(111) surfaces covered with submonolayer caesium atoms. A burst of 150 fs laser pulses with the repetition rate of 2.0-2.9 THz was synthesized by using a spatial-light modulator, and used for the coherent surface phonon excitation. The coherent nuclear motion was monitored by time-resolved second harmonic generation. By tuning the repetition rate, we succeeded in controlling the relative amplitude of the vibrational coherence of the Cs-Pt stretching mode (2.3-2.4 THz) to that of the Pt surface Rayleigh phonon mode (2.6 or 2.9 THz, depending on the Cs coverage).     

Tremorgenic indole alkaloids. The total synthesis of (-)-penitrem D

A convergent, stereocontrolled total synthesis of the architecturally complex tremorgenic indole alkaloid (-)-penitrem D (4) has been achieved. Highlights of the synthesis include an efficient, asymmetric synthesis of the western hemisphere; the stereocontrolled assembly of the I-ring; discovery of a novel autoxidation to introduce the C(22) tertiary hydroxyl group, required for tremorgenic activity; union of fully elaborated eastern and western hemispheres, exploiting an indole synthetic protocol developed expressly for this purpose; and a late-stage, stereoselective construction of the A and F rings exploiting a Sc(OTf)(3-)promoted reaction cascade. The longest linear sequence leading to (-)-penitrem D (4) was 43 steps.     

Reaction of prostacyclin methyl ester with benzenesulfenyl chloride preparation of stable prostacyclin analogs

Several phenyl sulfides including stable 5- and 7-phenylthioprostacyclins were obtained by the reaction of the vinyl ether ($\text{1}$) and prostacyclin methyl ester ($\text{5}$) with PhSCl.     

Analysis of guest—host and intra-guest transitions for hydronaphthyl radicals in naphthalene crystals

High resolution spectroscopic studies of optical absorption and emission around 539 nm and 636 nm for 1- and 2-hydronaphthyl radicals in naphthalene crystals have been made. For each radical several lines with the same polarization as the intra-guest OO vibrational lines were assigned as the vibrational progression, the separation being explained in terms of the intramolecular vibrations of naphthalene. About 20 other lines for each radical, including completely a- or b-polarized lines, were ascribed to the guest—host charge transfer transitions. Each line was assigned to the transition to specific molecules around the radical taking the polarization into consideration. The energy of the transition to a molecule at a distance r can be described by a coulombic relation with the dielectric constant ?: E = E_∞ ?e²/?r, where E_∞ is a constant. The phonon sidebands of the absorption and emission lines of the most intense charge transfer transition in the 1-hydronaphthyl radical was also analyzed and compared with phonon singularities in naphthalene crystals.     

Comments on miscibility in monolayers

The pressure-area curve in the liquidigas transition region can be used to confirm whether the equilibrium in the monolayer is attained. Three criteria for detecting the partial miscibility in monolayers are proposed. Collapse pressure data also are useful for detecting miscibility if appropriate attention is paid to the establishment of equilibrium. The general tendency of the changes of not consistent with that of most bulk liquid mixtures but with that of exceptional bulk alkane mixtures. For mixed monolayers of cholesterol with lecithins and trilaurin, Gershfeld's regular solution treatment yields positive G_ex values, whereas Goodrich's theory yields negative ones. The former theory seems to be better referenced.     

Effect of pulse width and fluence of femtosecond laser on the size of nanobump array

Conical nanobump arrays were generated on gold thin film processed by interfering femtosecond laser. The transition of the height and diameter as functions of fluence and pulse width was investigated. When the fluence was 87 mJ/cm², the height and diameter were not so different at 350 fs or shorter pulse width. They decreased at longer pulse width, and no bump could be generated over 1.6 ps. The results suggest the decrease of size is due to the diffusion of electron to not-excited region, and due to heat conduction to not heated region or substrate, or change of absorbance of laser. At long pulse width of 2.4 ps and relatively higher fluence of 190 mJ/cm², nanobump had liquid-like structure as a stop motion of a water drop.     

Look-up table and Gaussian filter-based inverse halftoning method excellent in gray-scale reproducibility of details and flat regions

Halftoning is a technique in which gray-scale images are converted into binary ones, and has been used widely in many practical image processing applications. On the other hand, inverse halftoning is a technique of reproducing a grayscale image from a binary one. One of the sophisticated inverse halftoning methods which can yield a high quality grayscale image is that based on a look-up table (LUT). In this paper, a new inverse halftoning method based on a combination of this LUT method and a Gaussian filter is discussed. Here, the output gray-scale image is reproduced by blending the output of the LUT-based inverse halftoning and that of the Gaussian filtering appropriately in accordance with local statistics of the image. The effectiveness and the validity of the described method are verified through experiments.