Long term competition between sulfate-reducing and methane-producing bacteria for acetate in anaerobic biofilm

A long term competition between sulfate-reducing bacteria (SRB) and methane-producing bacteria (MPB) for acetate was investigated using a laboratory scale anaerobic fluidized bed. When the synthetic wastewater composed of acetate and sulfate was fed at a low organic loading rate, averages of the remaining acetate and sulfate concentrations were 1.7 mg Cl⁻¹ and 78.5 mg l⁻¹, respectively. During several months of this acetate limited operation the methane production rate as well as the microbial mass of MPB declined gradually, whereas the amount of reduced sulfate along with the microbial mass of SRB increased, which apparently indicates that SRB out-compete MPB in the biofilm at lower acetate concentrations. On the other hand, MPB were able to form a biofilm faster than SRB at higher acetate concentrations presumably due to MPB's higher ability to adhere carrier surfaces compared with SRB. Kinetic constants for both species in the biofilm were determined and compared with those reported for pure MPB and SRB cultures. Based on the kinetic mechanism of this competition, operational conditions which would support methanogenesis by suppressing sulfate reduction were identified.     

In-service inspections and R&D of PCCVs in Japan

In Japan, the following five plants in operation use prestressed concrete containment vessels (PCCVs): Tsuruga #2 (in operation in 1987), Ohi #3 and #4 (in operation in 1991 and 1993, respectively), and Genkai #3 and #4 (in operation in 1994 and 1997, respectively). These plants have adopted the hemispherical dome type PCCV with two or three buttresses and unbonded prestressing system. For the above five PCCVs, lift-off tests in the in-service inspection have been carried out 1, 3 and 5 years after the beginning of operation. In addition, concrete strain and temperature have been measured periodically. This paper presents the in-service inspection methods and results of the lift-off tests and the measurement of concrete strain. The given results are as follows. Measured strain shows good agreement with calculated creep and shrinkage strain, so tendon tensile force can be predicted by the design method using calculated strain, and it also matches well the results of the lift-off tests.     

Stegobiol,a new sex pheromone component of drugstore beetle (Stegobium paniceum L.)

New sex pheromone component of femaleStegobium paniceum L. was isolated and identified as 2,3-dihydro-2,3,5-trimethyI-6-(1-methyl-2-hydroxybutyl)-4H-pyran-4-one, stegobiol, by spectral data and chemical conversion from stegobinone. Relative configuration at C-2, C-3, and C-1 was determined as 2S,3R,1S by the conversion from (2S,3R,1R)-stegobinone. This new sex pheromone elicits the pheromonal response from the species.     

Conjugate heat transfer with laminar flow in an annulus

The solution to the conjugate heat transfer problem in an annulus with a heated (cooled) core and an insulated outside tube is presented. Three kinds of boundary conditions are considered for a chosen radius ratio. From the results of parametric calculation over a wide range, it is concluded that wall heat conduction in a core can have substantial effects on the heat transfer characteristics in the areas surrounding the beginning and the end of the heat transfer section.     

Development status of high-efficiency HIT solar cells

This paper describes the development status of high-efficiency heterojunction with intrinsic thin-layer (HIT) solar cells at SANYO Electric. Presently, the conversion efficiency of our standard HIT solar cell has reached a level of 23.0% for a practical size of (100.4 cm²) substrate. On the other hand, we have developed special technologies for effectively using thinner substrates for HIT solar cells. Surprisingly, we have achieved a quite high open circuit voltage (V_oc) of 743 mV, and a high conversion efficiency of 22.8% using only a 98-μm-thick substrate. A 98-μm-thick cell also exhibits a good temperature coefficient, and allows the thickness of the substrate to be reduced by more than 50% while maintaining its efficiency. These results suggest that the HIT solar cell has the potential to further improve cost-performance.     

Physical properties and cutting performance of silicon nitride ceramic

Silicon nitride, a nitrogen compound of highly covalent bond character, has low density, high hardness, low thermal expansion and high thermal conductivity and excellent oxidation and corrosion resistance. Therefore it is considered to be a promising material for high temperature engineering components.However, it has very poor sinterability compared with the conventional oxide ceramics owing to its low self-diffusivity. By investigating starting materials, sintering additives and processing, a hot-pressed silicon nitride ceramic having grains enveloped by crystalline boundary phases can be produced.The silicon-nitride-based ceramic has high strength, high Weibull modulus, fracture toughness and thermal conductivity, and low thermal expansion compared with existing cutting tool ceramics such as Al₂O₃ + TiC, and it is expected to have superior thermal shock resistance.This new ceramic cutting tool shows superior performance in cutting cast irons at high speeds (10–16.75 m s^?1 (600–1000 m min^?1)) and rates (about 1.0 mm rev^?1), where conventional tools cannot be used.     

Hydrogenation of Yūbari coal coated with ZnCl2-MCln (CuCl,CrCl3 and MoCl5) catalyst melts

Hydrogenation of Yūbari coal coated with 5 wt% of ZnCl₂-MCl_n (CuCl, CrCl₃ and MoCl₅) was carried out at 400 °C for 3 h with an initial hydrogen pressure of 9.8 MPa. The binary melt catalysts showed relatively higher activity in increasing the yield of hexane-solubles than did ZnCl₂ alone. The ZnCl₂-MoCl₅ catalyst melt was best in view of its highest conversion (90.9 wt%), the highest yield of hexane-soluble material (50.5 wt%) and the smallest hydrogen consumption. In terms of yield of monoaromatics of the hexane-soluble material relative to polar materials, ZnCl₂-CrCl₃ catalyst was superior to ZnCl₂-MoCl₅ although its hydrogen consumption was high. The roles of CuCl, CrCl₃ and MoCl₅ in association with ZnCl₂ in coal-hydrogenation are discussed.