Ytterbium-decreasing Streptomyces sp. and its naphthoquinone-pigment production in the presence of rare-earth elements

We screened for oligotrophic microorganisms capable of decreasing the concentration of ytterbium (Yb), a representative of the heavy rare-earth elements, in a culture medium. From 476 strains of oligotrophic microorganisms (grown on 1/100 diluted nutrient agar) isolated from soil and river water samples, 5 strains capable of reducing the concentration of Yb in diluted nutrient broth containing 5 ppm Yb were selected. Among them, a strain capable of reducing the concentration of all rare-earth elements to a great extent was identified as Streptomyces sp. (strain YB-1). This strain produced redish-purple pigment(s) only in the presence of rare earths, but not in that of other metals. The pigment was extracted with ethyl acetate and purified by a series of column chromatography steps. From the results of structural analysis using ultraviolet or infrared absorption spectrometry and 13C-NMR, the pigment was determined to be a kind of naphthoquinone similar to nanaomycin produced by a Streptomyces sp. These results suggested that rare earths might affect the physiological activity of this strain.     

Proposal of new iterative scheme in GMRES

In the paper, GMRES is applied to various large matrices appearing in 3D field analyses. By changing the condition of the matrices, effective preconditioning of the matrix is sought. Also studied is a relationship between the residual norm and the precision evaluated during GMRES. The paper shows that the residual norm, which is indirectly computed in GMRES and has so far been used as a measure of precision, cannot be used as an indicator of the solution's accuracy. After discussing deterioration of precision, GMRES(m1), which solves matrices with a modified iterative scheme, is proposed. It is to be confirmed that GMRES(m1) is faster and more accurate than any of GMRES and its modified version, GMRES(m). © 1998 Scripta Technica, Electr Eng Jpn, 123(4): 15–24, 1998     

Development of an on‐line partial discharge monitoring system for gas insulated substations

This paper describes the results of tests and discussions carried out to develop a system for partial discharge monitoring in GIS. They include the propagation characteristics of partial discharge pulses in each GIS component, as well as the test results obtained using an actual 300‐kV GIS. We also report the results of verification test on the GIS partial discharge monitoring and location system developed by the authors. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 40–50, 1999     

Tribological properties of Si-containing diamond-like carbon film under ATF lubricated condition

Recent years have seen a rise in social needs regarding safety and the environment, and this has placed increasing importance on product development for automotive parts that leads to smaller sizes, higher capacity, and lower costs. Diamond-like carbon (DLC) coating technology is being focused on as an effective solution to such issues.This paper reports on the tribological properties of a Si-containing diamond-like carbon film under an automatic transmission fluid (ATF) lubricated condition, which dramatically improves the performance of an electromagnetic clutch used in electronically controlled All-wheel-drive (AWD) coupling. The Si-containing DLC film maintains its rough sliding surface while simultaneously exhibiting extremely low aggression against mating materials. Thus, the boundary lubrication state of the initial friction stage is maintained, while also displaying a positive μ–v slope with excellent anti-shudder performance and a satisfactory friction coefficient as demanded by the drive train.Based on time-of-flight secondary ion mass spectrometry (TOF-SIMS) of sliding surfaces, it was speculated that the mechanism behind the good tribological properties of a sliding material coated with Si-containing DLC film under fluid lubrication are in part connected to the material properties of the DLC-Si film and an adsorbate such as a succinimide-based dispersant.     

Production of high-purity medical radio isotope 64Cu with accelerator-based neutrons generated with 9 and 12 MeV deuterons

We conducted a feasibility study for producing a high-purity medical radioisotope ⁶⁴Cu from natural zinc with accelerator-based neutrons. ⁶⁴Cu isotopes were produced via the ⁶⁴Zn(n,p) reaction. The accelerator-based neutrons were generated via the C(d,n) reaction using low-energy deuterons of 9 and 12 MeV on a 1-mm-thick carbon target. First, the production purity was estimated using the evaluated nuclear data library JENDL-4.0 and our previously measured thick target neutron yield. We found that even when natural zinc was used as the starting material, significantly high-purity ⁶⁴Cu could be obtained. Next, irradiation experiments for producing ⁶⁴Cu using natural zinc were conducted at Kyushu University Tandem Laboratory, with the amounts of ⁶⁴Cu isotopes and other gamma-emission nuclides measured by a high-purity germanium detector. As a result, high-purity ⁶⁴Cu isotopes of 1.11(49) × 10⁰ and 3.70 (17) × 10⁰ Bq/g/μC were produced with incident deuteron energies of 9 and 12 MeV, respectively.     

Cloning and sequencing of the deacetylase gene from Vibrio alginolyticus H-8

A gene encoding deacetylase DA1 that is specific for N, N'-diacetylchitobiose was cloned using the shot-gun method with pUC118 and sequenced. The open reading frame encoded a protein of 427 amino acids including the signal peptide. The molecular mass of the mature enzyme estimated from the amino acid sequence data was 44.7 kDa, which is approximately similar to that, estimated by SDS-PAGE (48.0 kDa), of the purified enzyme reported previously. The N-terminal amino acid sequence deduced from the cloned deacetylase gene showed partial sequence homology with the Nod B protein from Rhizobium sp. (37% identity) and chitin deacetylase from Mucor rouxii (28%). It contained a domain, which showed homology with a chitin-binding domain of chitinase A from Bacillus circulans (39%).     

Development of a tube-type solar still equipped with heat accumulation for irrigation

A tube-type solar still is found to be suitable for use in desert irrigation. The effectiveness of a heat accumulator with regard to distillate productivity is experimentally and numerically verified. The heat accumulator consists of tube bundles immersed in wax in order to utilize the latent heat of wax. The dynamic response to stepwise variation of irradiative intensity verified the contribution of wax to an increase of productivity only when the phase change of wax occurred. The effective distillate productivity was found to be 294.3 g/m² during the cyclic stepwise change of irradiative intensity, from 200 to 600 W/m² and back. Velocity vectors driven by natural convection and temperature contours estimated by numerical simulation verified the effectiveness of the heat accumulator especially after peak solar intensity. The latent heat of wax effectively contributed to a 15% increase in total distillate productivity per day. The still can feasibly meet irrigation water supply demands above an irrigative threshold of 17 MJ/m² d.     

Fabrication method for IC-oriented Si single-electron transistors

A new fabrication method for Si single-electron transistors (SETs) is proposed. The method applies thermal oxidation to a Si wire with a fine trench across it on a silicon-on-insulator substrate. During the oxidation, the Si wire with the fine trench is converted, in a self-organized manner, into a twin SET structure with two single-electron islands, one along each edge of the trench, due to position-dependent oxidation-rate modulation caused by stress accumulation. Test devices demonstrated, at 40 K, that the twin SET structure can operate as two individual SET's. Since the present method produces two SET's at the same time in a tiny area, it is suitable for integrating logic circuits based on pass-transistor type logic and CMOS-type logic, which promises to lead to the fabrication of single-electron logic LSIs     

Evaporation and condensation heat transfer with a noncondensable gas present

To evaluate the system pressure of an external water wall type containment vessel, which is one of the passive systems for containment cooling, the evaporation and condensation behavior under a noncondensable gas presence has been experimentally examined. In the system, steam evaporated from the suppression pool surface into the wetwell, filled with noncondensable gas, and condensed on the containment vessel wall. The system pressure was the sum of the noncondensable gas pressure and saturated steam pressure in the wetwell. The wetwell temperature was, however, lower than the supression pool temperature and depended on the thermal resistance on the suppression pool surface. The evaporation and condensation heat transfer coefficients in the presence of air as noncondensable gas were measured and expressed by functions of steam/air mass ratio. The evaporation heat transfer coefficients were one order higher than the condensation heat transfer coefficients because the local noncondensable gas pressure was much lower on the evaporating pool surface than on the condensing liquid surface. Using logal properties of the heat transfer surfaces, there was a similar trend between evaporation and condensation even with a noncondensable gas present.