In the deduced amino acid sequence for the FeS protein, the domain including four cysteines and two histidines binding the 2Fe-2S cluster was conserved. Its N-terminal part more closely resembled the cyanobacteria-plastid type than the proteobacteria-mitochondria type when their sequences were compared. The amino acid sequence of cytochrome c 1 was not similar to either type; the thermophilic Bacillus cytochrome c 1 is composed of an N-terminal part corresponding to subunit IV with three membrane-spanning segments, and a C-terminal part of cytochrome c reminiscent of cytochrome c-551 of thermophilic Bacillus. The subunit IV in the enzyme of cyanobacteria and plastids is the counterpart of C-terminal part of cytochrome b of proteobacteria and mitochondria. These characteristics indicate that Bacillus cytochrome b 6 c 1 complex is unique.
The biogenic production of hydrogen sulfide is a serious problem associated with wastewater treatment. The aim of this study was to investigate the inhibitory effect of nitrate on the dynamics of sulfate-reducing bacteria (SRB) community in a laboratory-scale wastewater reactor, originating from a denitrifying plant using activated sludge. For this purpose, denaturing gradient gel electrophoresis (DGGE) analysis targeting the dsrB (dissimilatory sulfite reductase) gene was used in combination with chemical analyses and measurement of oxidation and reduction potential (ORP). The reactors were initially dosed with 1.0 and 4.0 g/L potassium nitrate and anaerobically incubated for 490 h. Addition of 4.0 g/L nitrate to the reactor was associated with a prolonged inhibition (over 300 h, i.e., 12.5 days) of sulfate reduction and this was consistent with a rapid decrease in ORP associated with nitrate depletion. The DGGE analysis revealed that nitrate addition remarkably attenuated a distinct group of dsrB related to Desulfovibrio, whereas other dsrB groups were not influenced. Furthermore, another sulfate reduction by Syntrophobacter in the later stages of the incubation period occurred in both reactors (regardless of the nitrate concentration), suggesting that different SRB groups are associated with sulfate reduction at different stages of the wastewater treatment process.
The shortest possible lasing wavelength and the lowest threshold current density of the GaInAsP visible injection laser diodes grown on (100) GaAs substrate by the liquid phase epitaxy using a two-phase solution growth technique are discussed. The lasing wavelength and threshold current density at room temperature under pulsed conditions are 705 nm and 9.4 kA/cm2, respectively. Light output power of 5–6 mW from one facet and maximum differential quantum efficiency of 38% are realized under the condition of fundamental lateral and transverse mode operation.
We investigated the thermoelectric properties of melt-grown Mg2Sn crystals doped with various impurities such as Al, Bi, Sb, P, In, Ag, Au, W, and Mo; a large difference in the carrier concentration was observed for each impurity. The Bi-and Sb-doped Mg2Sn crystals showed ntype conductivity and had enough electron concentrations in the order of 10 19 cm -3 by doping, and the maximum figure of merit (ZT) of 0.35 was observed in the crystal doped with 1.5 at% of Bi at 550 K. The Ag-, P-, In-, Au-, W-, and Mo-doped materials exhibited p-type conductivity. The Ag-doped samples had sufficient hole concentrations of more than 10 19 cm -3 , and the ZT reached 0.25 in the sample doped with 1.0 at% of Ag at 450 K. The P-and Sb-doped Mg2Sn crystals became dark gray powder within 1-2 weeks, but the crystals doped with the other impurities did not. This result suggested that the oxidation resistance of Mg2Sn crystals varied greatly depending on the type of dopant impurity.
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