Development of new analytical method based on beta-alpha coincidence method for selective measurement of 214Bi-214Po-application to dust filter used in radiation management

The radionuclide pair (214)Bi and (214)Po which belongs to the uranium series interferes with airborne radionuclide measurement needed for the radiation management of a nuclear facility. Time intervals between (214)Bi (β) and (214)Po (α) are much shorter than artificial radionuclides due to the short half-life of (214)Po (164 μs). The purpose of this study is to develop of a new analytical method (time interval analysis: TIA) based on the beta-alpha coincidence method for selective measurement of (214)Bi-(214)Po. The developed method was applied to an actual dust-filter measurement. The TIA system was highly effective in measuring of the filter with background subtraction.     

Effect of a vacuum-deposited metal film on the CV of the Li insertion/extraction reaction at a graphitized carbon fiber electrode

A metal film of silver, copper, or gold was vacuum-deposited on the surface of mesophase pitch-based carbon fiber prepared at 3100 °C, and the Li insertion/extraction behaviour was examined by measuring the cyclic voltammogram (CV) for various film thicknesses in a non-aqueous electrolyte containing 1 M LiClO₄. The peak height of the CV was examined in detail for the deposited silver film. The peak height increased at first with increasing film thickness up to 150 Å, but then began to decrease. At around 200 Å, a minimum peak height which was nearly the same as that of the pristine sample was observed. The peak height then increased again up to a film thickness of 400 Å, where it was two times higher than that of pristine sample, then decreased gradually. Such a complicated CV could not be observed with a gold or copper film where the enhancing effect was monotonous and more remarkable with a thinner film. X-ray diffraction patterns of the silver film deposited on the carbon fiber showed a strong crystal orientation to the carbon substrate like epitaxial growth, which was found to be dependent on both the thickness and the deposition rate. The CV peak height correlated well with the silver crystal orientation, implying that the electrochemical reaction rate differs on different crystal faces. Such could not be found in the case of gold or copper. The peak enhancing effect and the cycle behaviour were elucidated in view of the nature of solid electrolyte interphase (SEI), conductivity, and the effect of alloy formation.     

GaAs power m.e.s.f.e.t.s. with a graded recess structure

A new recess structure device was developed to improve the field distrubution and therfore the performance of GaAs power m.e.s.f.e.t.s. The linear gain and the output power were improved by 1?2 dB for this structure. The highest output powers obtained are 15 W with 4 dB associated gain at 6 GHz, and 4.3 W with 3 dB associated gain at 11 GHz.     

Growth of diamond particles from methane-hydrogen gas

Microcrystals of diamond were grown on non-diamond substrates including silicon, molybdenum and silica, as well as on diamond by chemical vapour deposition. Deposition was carried out by passing a mixture of hydrocarbon and hydrogen gases through a heated reaction chamber in which a hot tungsten filament was held near the substrates. The deposit was identified by reflection electron diffraction and Raman spectroscopy. The effects of experimental conditions on the growth features were studied.     

TEM observation of the giant carbon nanotube construction using Langmuir-Blodgett films

Langmuir-Blodgett (LB) films, which included Fe atoms as a catalytic metal material, were used for carbon nanotube (CNT) growth by chemical vapor deposition (CVD). A new form of localized nanotube growth was observed to result in a structure called a giant carbon nanotube construction (GNC). The GNC seems to be a self-assembled knitted structure formed by CNTs. The GNC is thin (∼5 µm in diameter) and long (∼100 µm) and is quite different from a CNT bundle. A growth mechanism for the GNC was developed from the results of TEM, SEM, and Raman spectral analysis. The GNC might find applications for CNT sensors, synthetic fibers, and so on. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Isolation and purification of nootkatone from the essential oil of fruits of Alpinia oxyphylla Miquel by high-speed counter-current chromatography

HSCCC technique in a semi-preparative scale was successfully applied in isolation and purification of nootkatone from the essential oil of fruits of Alpinia oxyphylla Miquel. Twelve kinds of two-phase solvent systems, consisting of seven non-aqueous and five organic-aqueous solvent systems, were selected with not only suitable partition coefficients of nootkatone but also suitable separation factors between nootkatone and valencene, the dominant impurity in the essential oil. Further on HSCCC, n-hexane–chloroform–acetonitrile (10:1:10, v/v) amongst the non-aqueous solvent systems and n-hexane–methanol–water (5:4:1, v/v) amongst the organic-aqueous solvent systems were separately screened out. However, n-hexane–methanol–water (5:4:1, v/v) was thought optimal due to quite shorter elution time and better HSCCC peak form. By eluting the lower phase of this solvent system in head–tail mode, 3.1 mg of nootkatone was obtained at a purity of 92.30% by GC–MS from 80 mg of crude essential oil in one step operation in less than 4 h. The chemical structure of nootkatone fraction was confirmed by EI-MS and ¹H NMR.     

Preparation of (vinylbenzylimino)oligo(dl-phenylalanine NCA) macromer with narrow molecular weight distribution

Summary Polymerization conditions of dl-phenylalanine N-carboxyanhydride (NCA) by m, p-vinylbenzylamine were examined for the preparation of (vinylbenzylimino)oligo(dl-phenylanaline NCA) macromer (VB-OPhe) with narrow molecular weight distribution. According to the results obtained, i.e., under the condition of short polymerization time (ca. 2 h) and in relatively high concentrations of the NCA in THF, the polymerizations of the NCA were carried out to give VB-OPhe macromers, which were found to have very narrow molecular weight distributions. Furthermore, their functionalities were proved to be approximately unity by the polymerization method.     

Numerical calculation of the bubbly two-phase flow around an airfoil

A model and the governing equations of two-phase bubbly flow are proposed; and the bubbly two-phase flow around an airfoil was calculated using a method based on the MacCormack method combined with the boundary-conforming curvilinear coordinates system. The compressibility and slip motion of the bubbles are considered in the calculation. The result revealed a wide ranging distribution of pressure and Mach number compared with single-phase flow. The effect of the slip velocity is also observed to be important in calculating the bubbly flow.