Isolation and characterization of acidophilic heterotrophic iron-oxidizing bacterium from enrichment culture obtained from acid mine drainage treatment plant

An acidophilic heterotrophic bacterium, designated as HIB4, having the ability to oxidize ferrous ion was newly isolated from a sample of an enrichment culture for iron-oxidizing bacteria, using the modified washed agarose/yeast extract (WAYE) medium with ferrous sulphate. The isolate HIB4 was an acidophilic, heterotrophic, mesophilic and gram-positive bacterium. Phylogenetically, it was classified under the genus Alicyclobacillus and was the closest to Alicyclobacillus disulfidooxidans SD-11 with 99.7% 16S rDNA homology. It grew and oxidized ferrous ion in the medium containing 0.02% (w/v) yeast extract. Yeast extract was an essential substrate for this bacterium because it could not grow or oxidize ferrous ion without yeast extract. However, a higher concentration of yeast extract inhibited the growth of HIB4, so that the optimum concentration of yeast extract for this bacterium to grow was 0.02% (w/v) at 0.08 mol/l of ferrous ion. On the other hand, ferrous ion oxidation occurred almost at the end of the bacterium's logarithmic growth phase and the isolate was able to grow without ferrous ion. These results denote that HIB4 did not obtain any energy from the ferrous ion oxidation and that HIB4 is an obligate heterotrophic and aerobic bacterium even though it oxidized ferrous ion. Also, HIB4 could not utilize any organic compounds, among the several organic chemicals used in this study, as a carbon source except yeast extract. These characteristics were completely different from these of A. disulfidooxidans SD-11 so that HIB4 might be a different species.     

Quantitative hydrogen analysis of zircaloy-4 using low-pressure laser plasma technique

It is found in this work that variation of laser power density in low-pressure plasma spectrochemical analysis of hydrogen affects sensitively the hydrogen emission intensity from the unwanted and yet ubiquitous presence of ambient water. A special experimental setup has been devised to allow the simple condition of focusing/defocusing the laser beam on the sample surface. When applied to zircaloy-4 samples prepared with various hydrogen impurity concentrations using low-pressure helium surrounding gas, good-quality hydrogen emission lines of very high signal to background ratios were obtained with high reproducibility under weakly focused or largely defocused laser irradiation. These measurements resulted in a linear calibration line with nonzero intercept representing the residual contribution from the recalcitrant water molecules. It was further shown that this can be evaluated and taken into account by means of the measured intensity ratio between the oxygen and zirconium emission lines. We have demonstrated the applicability of this experimental approach for quantitative determination of hydrogen impurity concentrations in the samples considered.     

Two-step Design of Critical Control Systems Using Disturbance Cancellation Integral Controllers

An efficient critical control system design is proposed in this paper.The key idea is to decompose the design problem into two simpler design steps by the technique used in the classical loop transfer recovery method (LTR).The disturbance cancellation integral controllcr is uscd as a basic controller.Since the standard loop transfer recovery method cannot bc applied to the disturbance cancellation controller, the nonstandard version recently found is used for the decomposition.Exogenous inputs with constraints both on the amplitude and rate of change are considered. The majorant approach is taken to obtain the analytical sufficient matching conditions.A numerical design example is presented to illustrate the effectiveness of the proposed design.     

Kinetics of Reverse Transformation from Pearlite to Austenite in an Fe-0.6 Mass pct C Alloy and the Effects of Alloying Elements

Substitutional alloying effects on reversion kinetics from pearlite structure at 1073 K (800 °C) in an Fe-0.6 mass pct C binary alloy and Fe-0.6C-1 or 2 mass pct M (M = Mn, Si, Cr) ternary alloys were studied. Reverse transformation in the Fe-0.6C binary alloy at 1073 K (800 °C) was finished after holding for approximately 5.5 seconds. The reversion kinetics was accelerated slightly by the addition of Mn but retarded by the addition of Si or Cr. The difference of acceleration effects by the addition of the 1 and 2 mass pct Mn is small, whereas the retardation effect becomes more significant by increasing the amount of addition of Si or Cr. It is clarified from the thermodynamic viewpoint of carbon diffusion that austenite can grow without partitioning of Mn or Si in the Mn- or Si-added alloys. On the one hand, austenite growth is controlled by the carbon diffusion, whereas the addition of them affects carbon activity gradient, resulting in changes in reversion kinetics. On the other hand, thermodynamic calculation implies that the long-range diffusion of Cr is necessary for austenite growth in the Cr-added alloys. It is proposed that austenite growth from pearlite in the Cr-added alloys is controlled by the diffusion of Cr along austenite/pearlite interface.     

Combinatorial synthesis of phosphors using arc-imaging furnace

We have applied a novel ‘melt synthesis technique’ rather than a conventional solid-state reaction to rapidly synthesize phosphor materials. During a synthesis, the mixture of oxides or their precursors is melted by light pulses (10–60 s) in an arc-imaging furnace on a water-cooled copper hearth to form a globule of 1–5 mm diameter, which is then rapidly cooled by turning off the light. Using this method, we synthesized several phosphor compounds including Y₃Al₅O₁₂:Ce(YAG) and SrAl₂O₄:Eu,Dy. Complex phosphor oxides are difficult to produce by conventional solid-state reaction techniques because of the slow reaction rates among solid oxides; as a result, the oxides form homogeneous compounds or solid solutions. On the other hand, melt reactions are very fast (10–60 s) and result in homogeneous compounds owing to rapid diffusion and mixing in the liquid phase. Therefore, melt synthesis techniques are suitable for preparing multi component homogeneous compounds and solid solutions.     

Estimation of magneto-crystalline uniaxial anisotropy constant of β-FeOOH by Mössbauer spectroscopy

The magneto-crystalline uniaxial anisotropy constant, K_u, of β-FeOOH was estimated by analyzing temperature dependence of Mössbauer absorption spectra taking into account the thermal relaxation of the internal magnetic fields. It was deduced to be 2.1 × 10³ J/m³, using a typical volume (9 × 10^?24 m³) of synthesized β-FeOOH particles observed by TEM. The value, K_u of β-FeOOH is in the same order but twice as large as that of α-FeOOH, 1 × 10³ J/m³.     

Effect of HCl concentrations on apatite-forming ability of NaOH–HCl- and heat-treated titanium metal

Titanium (Ti) metal was treated with water or HCl solutions after 5 M NaOH solution treatment and then subjected to heat treatment at 600°C. The apatite-forming abilities of the treated Ti metals were examined in simulated body fluid. The apatite-forming ability of the Ti metal subjected to NaOH, water and heat treatment was lower than that of just NaOH and heat treatments. Ti metals subjected to NaOH, HCl and heat treatment showed apatite-forming abilities, which increased with increasing HCl concentrations up to the same level as that of NaOH- and heat-treated Ti metal. The former did not show a decrease in its apatite-forming ability, even in a humid environment for a long period, whereas the latter decreased its ability. The increase in the apatite-forming ability with increasing HCl concentrations suggests a different mechanism of apatite formation from that previously proposed.