Sulfide oxidation by gene expressions of sulfide-quinone oxidoreductase and ubiquinone-8 biosynthase in Escherichia coli

Sulfides (S2),SH-) such as hydrogen sulfide belong to a class of sulfur compounds with unpleasant odors. In order to confer sulfide-oxidizing ability on the intestine-inhabiting bacteria, the sulfide-quinone oxidoreductase gene (sqr) in Rhodobacter capsulatus DSM-155 and genes for quinone biosynthesis (ubiC, ubiA and ispB) in Escherichia coli XL1 Blue-MRF' were transduced into E. coli BL21(DE3). Plasmids pT7-7 and pSTV were used as vectors of sqr, and ubiCA and ispB, respectively. The recombinants sqr-BL21(DE3) and ubiCA,ispB-sqr-BL21(DE3) were successfully constructed. The maximal sulfide-removing activities of the whole cells and membrane fractions of sqr-BL21(DE3) attained at pH 8.0 and 7.8, were 267 nmol/mg cells (dry weight)/min and 1250 nmol/mg membrane fraction (protein)/min, respectively. The molecular ratio of sulfide (S2-) oxidized and oxygen (O2) consumed was 2:1. SQR activity in the recombinant cells was positively restricted under anaerobic conditions and also by the addition of electron transfer inhibitors. Ubiquinone-8 (UQ-8) biosynthesis in the cells of ubiCA,ispB-sqr-BL21(DE3) increased as much as 2.2-fold compared with that of (pSTV)-sqr-BL21(DE3) during the 12-16 h incubation period. The maximal sulfide removal in the quinone-raised E. coli was attained slightly earlier, however, SQR activities thereafter were lower than those in (pSTV)-sqr-BL21(DE3).     

Surface improvement on water and oil affinities and absorption rate of PVA/Tung oil-coated paperboard and fiberboard

A novel coating material on paperboard and fiberboard from poly(vinyl alcohol) (PVA) modified with Tung oil was developed. The PVA/Tung oil coating was cured at several conditions: 25, 40, 50, and 60°C, in the presence of two types of catalysts, i.e., thermal catalyst using potassium persulfate (KPS) and redox catalyst using KPS and sodium thiosulfate. The chemical crosslinked structure of PVA/Tung oil-coating films was confirmed by FTIR. The result indicated the decrease in the double bonds of Tung oil by crosslinking reaction, especially at 60°C. In comparison with the same curing temperature, the films with redox catalyst showed more reduction in the number of double bonds of Tung oil. DMA results of the PVA/Tung oil-coating materials with redox catalyst showed the lowering of the heights of both β transition peak of Tung oil and α transition peak of PVA. FTIR and DMA results confirmed the more efficient crosslinking reaction of redox catalytic system than that of the thermal catalytic system. The water resistance and mechanical properties of these coating materials exhibited better values as projected to higher curing temperature and redox catalyst. SEM images showed the smooth surface of PVA/Tung oil covered on the paperboards with ~72 µm in thickness. The contact angle of water or oil drop and dynamic change in contact angle on the surfaces of PVA/Tung oil-coated paperboards and fiberboards were investigated. The results show the contact angles for both water and oil were lower than those of the uncoated ones, indicating the improvement of water and oil affinities of the PVA/Tung oil-coating materials. The dynamic changes in contact angle of the coated ones also decreased, suggesting the reduction in water and oil absorption rates of these coated substrates.     

Effects of growth temperature on the fatty acid composition of the free-living nematodeCaenorhabditis elegans

The effects of growth temperature on the fatty acid compositions of the phosphatidylcholine (PC), phosphatidylethanolamine (PE), and total lipid (TL) fractions of the free-living nematodeCaenorhabditis elegans were investigated. A reduction in growth temperature from 25 to 15°C caused the proportions of eicosapentaenoic acid (20∶5n-3) to increase from 23.6 to 32.5% in the PC, from 7.4 to 10.8% in the PE, and from 12.9 to 19.9% in the TL fractions. Conversely, the levels of dihomo-γ-linolenic acid (20∶3n-6) and arachidonic acid (20∶4n-6) in these phospholipid fractions and the TL fraction both decreased with decreasing growth temperature. Analysis of the positional distribution of fatty acids in the PC fraction revealed that the change in the composition of C₂₀ polyunsaturated fatty acid was obvious in positionsn-2. Lowering the growth temperature induced an increase in the level of the diacyl subclass of PE from 58% at 25°C to 71% at 15°C, with a concomitant decrease in the levels of the alkylacyl and alkenylacyl subclass of PE ofC. elegans. These changes observed in the phospholipids ofC. elegans might be one mechanism for adaptation to low temperature. Lipids 31, 1173–1178 (1996).     

Preparation of Cu(In,Ga)(S,Se)2 thin films by sequential evaporation and annealing in sulfur atmosphere

Cu(In,Ga)(S,Se)₂ thin films with high Ga/III ratio (around 0.8) were prepared by sequential evaporation from CuGaSe₂, CuInSe₂, In₂Se₃ and Ga₂Se₃ compounds and then annealing in H₂S gas atmosphere. The annealing temperature was varied from 400 to 500 °C. These samples were characterized by means of XRF, EPMA, XRD and SEM. The S/(S+Se) mole ratio in the thin films increased with increase in the annealing temperature, keeping the Cu, In and Ga contents nearly constant. The open circuit voltage increased and the short circuit current density decreased with increase in the annealing temperature. The best solar cell using Cu(In,Ga)(S,Se)₂ thin film with Ga/(In+Ga)=0.79 and S/(S+Se)=0.11 annealed at 400 °C demonstrated V_oc=535 mV, I_sc=13.3 mA/cm², FF=0.61 and efficiency=4.34% without AR-coating.     

Numerical analysis of coupled transport and reaction phenomena in an anode-supported flat-tube solid oxide fuel cell

Heat and mass transfer with electrochemical reaction in an anode-supported flat-tube solid oxide fuel cell (FT-SOFC) is studied by means of three-dimensional numerical simulation. The distributions of the reaction fields in the anode-supported FT-SOFC are found to be similar to those in the planar SOFC with co-flow arrangement. However, in comparison with the latter, the concentration and activation overpotentials of the former can be reduced by additional reactant diffusion through the porous rib of the fuel channel. Parametric survey reveals that, for a fixed activation overpotential model, the output voltage can be improved by increasing the pore size of anode, while the cross-sectional geometry has smaller effect on the cell performance. Based on the results of three-dimensional simulation, we also develop a simplified numerical model of anode-supported FT-SOFC, which takes into account the concentration gradients in the thick anode of complex cross-sectional geometry. The simplified model can sufficiently predict the output voltage as well as the distributions of temperature and current density with very low computational cost. Thus, it can be used as a powerful tool for surveying wide range of anode-supported FT-SOFC design parameters.     

Rh/γ-Al2O3 Catalytic Layer Integrated with Sol–Gel Synthesized Microporous Silica Membrane for Compact Membrane Reactor Applications

An efficient and compact catalytic membrane reactor for reforming of CH₄ was developed by integrating a hydrogen perm-selective silica membrane with an Rh/-Al₂O₃ catalyst layer. The catalytic layer was sandwiched between the outer surface of the -Al₂O₃ support tube and the silica membrane with an aim of improving the heat and mass transfer rates through the system and to simplify the reactor geometry. The system showed improved efficiency for reforming of CH₄ at comparatively lower operating temperatures and steam to C molar ratios than the conventional fixed-bed steam reforming systems. Under optimized conditions, a nearly 25-30% improvement from the equilibrium conversion level was achieved as a result of abstraction of hydrogen from the product stream by the silica membrane integrated with the catalyst layer. The performance of the system was evaluated as a function of various process parameters. Because of the compactness and efficiency, the present system emerges as a promising alternative to the conventional membrane reactors, which possess separate catalytic and membrane units.     

Imaging of optical disc using reflection-mode scattering-type scanning near-field optical microscopy

A phase-change optical disc was observed using a reflection-mode scattering-type scanning near-field optical microscope (RS-SNOM). In an a.c.-mode SNOM image, the 1.2 microm x 0.6 microm recording marks were successfully observed although the data were recorded on the groove. In contrast, no recording marks could be resolved in a d.c.-mode SNOM image. These results are in good agreement with those from a numerical simulation using the finite difference time domain method. The resolution was better than 100 nm with a.c.-mode SNOM operation and the results indicate that recording marks in phase-change optical media can be directly observed with the RS-SNOM.     

Corrosion characteristics of reduced activation ferritic steel, JLF-1 (8.92Cr–2W) in molten salts Flibe and Flinak

Static corrosion tests were performed in molten salts, LiF–BeF₂ (Flibe) and LiF–NaF–KF (Flinak), at 500 °C and 600 °C for 1000 h. The purpose is to investigate the corrosion characteristics of reduced activation ferritic steels, JLF-1 (8.92Cr–2W) in the fluids. The concentration of hydrogen fluoride (HF) in the fluids was measured by slurry pH titration method before and after the exposure. The HF concentration determined the fluoridation potential. The corrosion was mainly caused by dissolution of Fe and Cr into the fluids due to fluoridation and/or electrochemical corrosion. Carbon on the surface might be dissolved into the fluids due to the corrosion, and this resulted to the decrease of carbide on the surface. The corrosion depth of the JLF-1 specimen, which was obtained from the weight losses, was 0.637 μm in Flibe at 600 °C and 6.73 μm in Flinak at 600 °C.     

The Association of Cholesterol Uptake and Synthesis with Histology and Genotype in Cortisol-Producing Adenoma (CPA)

Cortisol-producing adenoma (CPA) is composed of clear and compact cells. Clear cells are lipid abundant, and compact ones lipid poor but associated with higher production of steroid hormones. PRKACA mutation (PRKACA mt) in CPA patients was reported to be associated with more pronounced clinical manifestation of Cushing’s syndrome. In this study, we examined the association of histological features and genotypes with cholesterol uptake receptors and synthetic enzymes in 40 CPA cases, and with the quantitative results obtained by gas chromatography-mass spectrometry (GC-MS) analysis in 33 cases to explore their biological and clinical significance. Both cholesterol uptake receptors and synthetic enzymes were more abundant in compact cells. GC-MS analysis demonstrated that the percentage of compact cells was inversely correlated with the concentrations of cholesterol and cholesterol esters, and positively with the activity of cholesterol biosynthesis from cholesterol esters. In addition, hormone-sensitive lipase (HSL), which catalyzes cholesterol biosynthesis from cholesterol esters, tended to be more abundant in compact cells of PRKACA mt CPAs. These results demonstrated that both cholesterol uptake and biosynthesis were more pronounced in compact cells in CPA. In addition, more pronounced HSL expression in compact cells of PRKACA mt CPA could contribute to their more pronounced clinical manifestation.