An aqueous suspension system for phospholipase D-mediated synthesis of PS without toxic organic solvent

Enzymatic synthesis of PS by phospholipase D (PLD)-mediated transphosphatidylation in an aqueous media was investigated. The purpose of this study was to establish a novel synthetic method where no toxic organic solvents were used. An attempt to react soybean lecithin (simply dispersed in an aqueous buffer) with an aqueous solution of l-serine and PLD was unsuccessful, giving only 20% of PS. By contrast, a suspension of lecithin adsorbed on fine powders such as silica was effectively converted into PS in an aqueous solution of l-serine and PLD. After screening various powders for use as the lecithin adsorbent, calcium sulfate was found to be the best with respect to lecithin conversion. In addition, calcium sulfate did not require prior adsorption of lecithin (i.e., the reaction proceeded effectively simply by adding the powder to an aqueous mixture of lecithin, l-serine, and PLD). With this “aqueous suspension system” of calcium sulfate, up to 180 mg/mL lecithin was completely converted, resulting in more than 80% PS in 24 h. The synthesized PS could easily be recovered from the powder by extracting with a mixture of n-hexane, ethanol, and diluted HCl.     

Scanning electron microscopy of food-poisoning bacterium Bacillus cereus using a variable-pressure SEM

A variable-pressure scanning electron microscopy (VP-SEM) with a cooling stage permits long hours of observation of water-containing specimens in their natural or close to natural state, without the conventional specimen preparations of fixation, dehydration, drying and metal coating. It reduces water vaporization and beam damage by keeping the specimens at a low temperature. We observed Bacillus cereus colonies on nutrient agar, which would shrink significantly if any conventional specimen preparation technique were used. We also studied the growing process of the bacteria on raw and steamed rice using the VP-SEM without conventional preparation techniques. Original specimens were directly mounted onto specimen holders and their backscattered electron images observed under the following conditions: specimen stage temperature, -10 degrees C; specimen chamber vacuum level, 30-70 Pa; and accelerating voltage, 15-20 kV. We recognized that the VP-SEM minimized deformation of the colonies due to shrinkage of the nutrient agar, and successfully imaged the morphology of the colonies and bacteria without a decline in bacteria number, which is apt to occur during fixation and dehydration. Also, the growth process of the bacteria on raw or steamed rice could be observed promptly, since there is no specimen preparation step.     

A fluorogenic reagent, 4-mercapto-7-methylthio-2,1,3-benzoxadiazole for carboxylic acids, designed by prediction of the fluorescence intensity

During the course of our studies of the development of fluorogenic reagents having a 4,7-disubstituted benzofurazan structure, we previously proposed 7-acetylamino-4-mercapto-2,1,3-benzoxadiazole (AABD-SH) as a fluorogenic reagent for carboxylic acids. Since then, progress has made it possible to estimate the fluorescence quantum yields of the 4,7-disubstituted benzofurazan compounds on the basis of the PM3 calculation of their S1-T2 energies. Subsequently, a new fluorogenic reagent, 4-mercapto-7-methylthio-2,1,3-benzoxadiazole (MTBDSH) was designed and synthesized. In the presence of condensation reagents, triphenylphosphine (TPP) and 2,2'-dipyridyl disulfide (DPDS), MTBD-SH readily reacted with n-caprylic acid within 1 min at room temperature. The derivatives of five carboxylic acids (n-caprylic acid, n-capric acid, lauric acid, myristic acid, and palmitic acid) were well-separated on a reversed-phase column and were fluorimetrically detected at 519 nm with excitation at 391 nm. The detection limits (S/N = 3) were 2.4-5.0 fmol. Thus, MTBD-SH had properties that were considered to be superior. For carboxylic acids, itwas superior not only to AABD-SH, but also to many other conventional reagents. The superiority was examined in terms of its reactivity and sensitivity and the avoidance of interfering peaks that were derived from the reagent itself or degradation products in the chromatogram.     

Submicron dry-etching behavior of β-FeSi2 thin films towards fabrication of photonic crystals

We have investigated dry-etching properties of polycrystalline β-FeSi₂ films formed by ion-beam sputter-deposition (IBSD) and the films epitaxially grown on Si by metal organic chemical vapor deposition (MOCVD) in order to realize fabrication of photonic crystals with several hundreds nanometers in dimension. Using reactive ion etching with magnetic neutral loop discharge (NLD) plasma, we succeeded in realizing a comparatively higher etching rate than that obtained by inductively coupled plasma (ICP). Both reactive ion etching and impact ion etching modes may contribute to etching of β-FeSi₂. We have fabricated a two-dimensional photonic crystal of β-FeSi₂ on Si substrates and confirmed its predicted photonic properties in a reflectance spectrum of polarized light.     

Starting method of a superconducting generator in a combined‐cycle power plant

In the combined‐cycle power plant generators are started by using the igniting arrangement up to the ignition rotational speed of the gas turbine. On the other hand, in the case of using the superconducting generator, it is difficult to apply the igniting arrangement used to generate electricity on the combined cycle for the structure as is. We examined the induction motor starting method for the superconducting generator by using the 70‐MW‐class quick‐response excitation superconducting model generator and the VVVF power supply. From the examination, we confirmed the ability to raise the rotational speed from 6 to 360 rpm. Moreover, it was found to be able to start 200‐MW‐class superconducting generators by the induction motor starting method with the analysis. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 30– 38, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20283     

Development and evaluation of a diamond electron source for electron beam instruments

Since diamonds indicated low or negative electron affinity, they have been expected to be high performance electron emitters. New diamond electron sources have been developed, which are configured for electron beam instruments such as electron beam lithography systems and electron microscopes. As a result of thermionic emission evaluations, an electron emission current of practical level (116 µA at 600 °C) was obtained. The energy spread of an electron beam generated by thermionic emission was measured as 0.23 eV (FWHM), the value of which was lower than those of a lanthanum hexaborate (LaB₆) cathode and a zirconium oxide/tungsten (ZrO/W) cathode measured together. The result of field emission evaluations, a practical beam current (459 pA) and stability (6% rms for 10 h) for scanning electron microscope (SEM) was achieved. The energy spread of a high-current electron beam of over 200 pA generated by field emission from a diamond emitter reached about the same as that of a cold field emission cathode made of tungsten. A scanning electron micrograph (SEM) with a diamond electron source having a tip of submicron order allowed measurement a resolution of 5 nm. It was found that unprecedentedly high-current and high-convergence electron sources could be generated by using diamonds.     

Beat Noise Mitigation of Spectral Amplitude Coding OCDMA Using Heterodyne Detection

In order to relax the limitation of the number of multiplexed signal lights caused by beat noise between signal lights, we investigate the applicability of a heterodyne detection technique to a spectral amplitude coding optical code division multiple access scheme. In this investigation, for the first time, we found analytically that the optical frequency chips that form parts of the signal and local lights require uniform phase differences even for envelope detection. We also confirm this requirement and our theoretical analysis experimentally.     

A Microcomputer System for Spatiotemporal Visual Receptive Field Analysis

A microcomputer system was developed to measure visual spatiotemporal receptive fields. The system performs three functions: 1) generation of a binary spatiotemporal white-noise stimulus, 2) acquisition of spike discharges from retinal ganglion cells, and 3) extraction of the linear part of the spatiotemporal receptive flelds by cross correlating the input against the output. We have applied this system to the measurement of the spatiotemporal receptive fields of cat and catfish retinal ganglion cells.     

Optical polarisation control utilising an optical heterodyne detection scheme

An optical polarisation control scheme utilising optical heterodyne detection for coherent transmission is proposed and demonstrated at a wavelength of 1.5 ?m. It converts an arbitrary polarisation state to a linear state at a received optical power level of less than ?70 dBm.     

Epitaxial growth of titanium oxide thin films on MgO(100) single-crystal substrates by reactive deposition methods

We synthesized titanium oxide thin films on MgO(100) single-crystal substrates by two reactive deposition methods and compared the structures of the thin films formed by these methods. In one method (pulsed-molecular-beam deposition method), molecular oxygen is supplied to the substrates by using a pulsed-molecular-oxygen beam source and deposition of one unit layer of titanium and subsequent supply of molecular oxygen are repeatedly performed. In the other method (radical beam deposition method), atomic oxygen is irradiated to the substrates by using an atomic oxygen beam generated by the radical beam source and irradiation of the atomic oxygen and deposition of titanium are simultaneously performed. In the case of the pulsed-molecular-beam deposition method, the crystal structure was changed by increasing the number of oxygen pulses supplied from the beam source. We found that the crystal structure of titanium oxide depended on the composition ratio of O:Ti in the film. The maximum ratio of O:Ti attainable by this method was 1.85, and at this ratio, (100)-oriented pseudorutile was formed. In the case of the radical beam deposition method, (100)-oriented anatase was formed below the titanium deposition rate of 0.10 nm/s and pseudorutile (TiO_2−δ) was formed above 0.15 nm/s. The pseudorutile structure synthesized on this experiment was very stable in air. We concluded that the crystal structure of the pseudorutile is a new crystal structure of titanium oxide.