Experimental Discussion on Eye-Safe 1.54 μm Photon Counting Lidar Using Avalanche Photodiode

A Mie hdar system with an eye-safe wavelength of 1.54 m was developed and its performance characteristics were experimentally discussed. The wavelength was generated by a Nd:YAG based methane-shifted Raman laser. The collected backscattering light was detected by an InGaAs avalanche photodiode working in photon counting mode at that wavelength. Results of atmospheric observation showed clearly the dynamics of multi-layered cluds up to an altitude of 7 km. The systems performance was confirmed on the point of signal to noise ratio in both the observation and the simulation. Advantages of the eye-safe 1.54 m wavelength in lidar atmospheric research and system limitations were discussed. © 2004 The Optical Society of Japan     

Enzymatic polymerization behavior using cellulose-binding domain deficient endoglucanase II

A mutant enzyme, EGII(core), in which the cellulose-binding domain was deleted from endoglucanase II from Trichoderma viride, was expressed in yeast, and the secreted enzyme was examined for the enzymatic polymerization to obtain artificial cellulose. EGII(core) polymerized beta-cellobiosyl fluoride to afford crystalline cellulose of type II. Comparison of the polymerization behavior of EGII(core) with that of EGII revealed the following: i) the crystalline product obtained with EGII(core) was stable in the polymerization solution, although the product was readily hydrolyzed in the presence of EGII; ii) the turnover number of EGII(core) was as high as that of EGII; iii) EGII(core) produced highly crystalline cellulose. EGII(core) is therefore advantageous for enzymatic polymerization.     

The revised structure of an oxidation product from the reaction of an α-tocopherol model compound, 2,2,5,7,8-pentamethylchroman-6-ol,with potassium superoxide; 6 -hydroxy -2,2,6,7,8- pentamethylchroman- 5 (6H) -one1

The previously reported structure of an oxidation product obtained from the reaction of an (α-tocopherol model compound(1) with KO₂ is revised to 6-hydroxy-2,2,6,7,8-pentamethylchroman-5(6H)-one(3) on the basis of the X-ray crystallographic and ¹⁸O-labeling studies.     

Chiral vector determination of carbon nanotubes by observation of interference patterns near the end cap

We have observed clear interference images near the end caps of semiconducting carbon nanotubes with quasiarmchair and zigzag chiral vectors, using a scanning tunneling microscope. We performed a simple tight-binding calculation to simulate the interference patterns, in which Bloch states with k and -k wave vectors were superimposed. The calculations were able to reproduce the observed interference patterns. In addition, we demonstrated that the interference patterns can be categorized by the positions of k_{min} in the Brillouin zone that yield minimum energy in the conduction band, and can give information on the chiral vector of a carbon nanotube.     

Structural analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes

Structure of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) fibers prepared by drawing and annealing processes has been analyzed through wide-angle X-ray diffraction (WAXD), density, infrared dichroism, and birefringence measurements. There are three different types of crystalline structure in these fibers: two of these are the two types of orthorhombic with different orientation modes (the ordinary c-axis orientation (c//Z), and the preferential orientation of c-axis to the direction perpendicular to the fiber axis (c⟂Z)); and the third is pseudohexagonal. The weight fractions of the three types of crystals and amorphous phase were analyzed combining the WAXD integrated intensity and density data. The relation between crystalline orientation factors obtained separately from the WAXD measurement and the infrared dichroic ratio is also discussed. The birefringence of these fibers shows negative and positive values, depending on drawing and annealing temperatures. Considering the intrinsic birefringence and weight fraction of the c//Z, c⟂Z, and pseudohexagonal crystals, birefringence of the amorphous phase was evaluated. The amorphous birefringence shows positive values and decreases with an increase in the annealing temperature. From the analyzed fiber structure, it was speculated that the c⟂Z and pseudohexagonal crystals are preferentially formed in the drawing process irrespective of the drawing temperature.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2471–2482, 1998     

A Per-O-Isoprofylidene Derivative of (1→4)-β-D-Mannan

Abstract

Isopropylidene acetals of carbohydrates are important as intermediates for the synthesis of other sugar derivatives. The isopropylidenation reaction is generally applied to only low molecular weight carbohydrates. However in 1982, we applied the reaction to a polysaccharide² and demonstrated that (1→3)-β-D-glucan was isopropylidenated at the 4- and 6-hydroxyl groups of the D-glucose units. These results suggested that some chemical modification at the unprotected 2-hydroxyl groups might be possible. Consequently, (1→3)-β-D-glucomannan^3,4 was derived from (1→3)-β-D-glucan through inversion of the 2-hydroxyl groups.     

X‐Ray and Electron Diffraction Study of Poly(p‐dioxanone)

Summary: Solution‐grown lamellar crystals of poly(p‐dioxanone) (PPDX) have been crystallized isothermally from butane‐1,4‐diol at 100 °C. The crystal structure of PPDX has been determined by interpretation of X‐ray fiber diagrams of PPDX fibers and electron diffraction diagrams of lozenge‐shaped chain‐folder lamellar crystals. The unit cell of PPDX is orthorhombic with space group P2₁2₁2₁ and parameters: a = 0.970 nm, b = 0.742 nm, and c (chain axis) = 0.682 nm. There are two chains per unit cell, which exist in an antiparallel arrangement.

Transmission electron micrograph of PPDX chain‐folded lamellar crystals obtained by isothermal crystallization and its electron diffraction diagram.     

Layered scalable coding of multispectral images based on visible component separation

This paper presents multispectral image coding methods based on visible component separation techniques. By coding the visible components separately from other spectral components, the color information can be used without decoding the whole multispectral image. Two types of separation techniques are introduced: one is a direct separation of visible and invisible layers, while the other is a scalable separation. In the scalable separation, visible components are first compressed to produce the base layer bitstream. The enhancement layer data include not only invisible components but also the information on the distortion of the coded visible components. Such a separation technique improves the accuracy of decoded multispectral images especially when visible components are highly compressed. The performance of the proposed methods was evaluated for different bit allocations to visible components. In general, the coding performance reduces when data are divided and coded separately to incorporate scalabilities. Nonetheless, it is found that the proposed scalable approach realizes a peak signal-to-noise ratio PSNR value comparable to that achieved by employing JPEG2000, which incorporates no scalability.     

Synthesis of polyamides by a new direct polycondensation reaction using triphenyl phosphite and lithium chloride

Metal salts such as lithium chloride were found to facilitate significantly the reaction of carboxylic acids and amines promoted by triphenyl phosphite, and the reaction was applied successfully to the direct polycondensation reaction of dicarboxylic acids and diamines and of p-aminobenzoic acid. Among metal salts tested, lithium chloride was most effective to the reaction; the chloride was involved catalytically in the reaction, its addition of about twice equivalent to triphenyl phosphite giving the most favorable results. Triphenyl phosphite was most effective, whereas diphenyl phosphite was less effective, and alkyl esters gave no polymers. The reaction was also markedly affected by solvents, the most favorable results being given in N-methylpyrrolidone (NMP). Various polyamides of high molecular weight were obtained in quantitative yield.