Optical properties of C60/a-C superlattice structures for solar cell applications

C₆₀/amorphous carbon superlattice structures were fabricated by shutter-controlled molecular beam deposition. The periodic structure of resulted films was confirmed by X-ray diffraction measurements. From the UV–vis reflectance/transmittance measurements, the energy shift of absorption edge was observed in the superlattice structures as a function of their well width. The carbon-based superlattice structure is the useful technique to control the band gap energy of carbon materials.     

Crystalline properties of multiple BP-Si layers grown on silicon substrate

In BP (100) epitaxially grown on Si (100), a high density of defects existed in the early growth layer of the BP less than 100 nm from the Si interface. The BP layer then had a uniform distribution of defects over the high density defect layer. The Si (100) grown on the BP (100) had a uniform distribution of defects. As multiple BP-Si layers were grown, the crystalline quality gradually degraded. The crystalline quality of the underlying BP layer strongly influenced the Si epitaxial layer.     

Barosensitivity in Saccharomyces cerevisiae is Closely Associated with a Deletion of the COX1 Gene

High hydrostatic pressure causes physical stress to microorganisms; therefore, this technology may be applied to food pasteurization without introducing the unfavorable effects of thermal denaturation. However, its application is limited to high‐value foods because the treatment requires a robust steel vessel and expensive pressurization equipment. To reduce these costs, we studied the pasteurization of Saccharomyces cerevisiae using relatively moderate high‐pressure levels. A mutant strain isolated by ultraviolet mutagenesis showed significant loss of viability under high‐pressure conditions. Gene expression analysis of the mutant strain revealed that it incurred a deletion of the COX1 gene. Our results suggest that the pressure‐sensitivity can readily be introduced into industrial/food microorganisms by complementing a COX1 deleted mitochondria.     

Mycotoxicological quality evaluation of corn samples used by processing industries in the Northern region of Paraná State,Brazil

Based on fungal and fumonisin contamination of 870 freshly harvested samples, the quality of corn used by processing industries in the Northern region of Paraná State, Brazil (2003 and 2004 crop-year) was evaluated. Sampling was carried out for each crop at two points in the production chain, i.e. at reception by the processors and at the pre-drying step. Corn samples were more frequently contaminated with Fusarium sp. (100%) and Penicillium sp. (84.1–95.3%) than Aspergillus sp. (5.6–19.8%). Fumonisin B₁ (FB₁) was detected in all samples from the two points in both crop-years. FB₁ levels ranged 0.02–11.83 µg g^?1 in the reception and 0.02–10.98 µg g^?1 in the pre-drying samples of the 2003 crop. Samples from the 2004 crop showed FB₁ levels ranging 0.03–12.04 µg g^?1 in the reception and 0.06–7.74 µg g^?1 in the pre-drying samples. FB₂ levels ranged 0.02–5.25 µg g^?1 in the reception and 0.01–7.89 µg g^?1 in the pre-drying samples (2003 crop-year). In samples from the 2004 crop, FB₂ levels ranged 0.02–6.12 µg g^?1 in the reception and 0.05–3.47 µg g^?1 in the pre-drying samples. Low fumonisin levels were detected in most corn samples used by processors in the Northern region of Paraná State, showing a decreasing trend in fumonisin contamination over the years.     

Roles of sulfuric acid in elemental mercury removal by activated carbon and sulfur-impregnated activated carbon

This work addresses the discrepancy in the literature regarding the effects of sulfuric acid (H(2)SO(4)) on elemental Hg uptake by activated carbon (AC). H(2)SO(4) in AC substantially increased Hg uptake by absorption particularly in the presence of oxygen. Hg uptake increased with acid amount and temperature exceeding 500 mg-Hg/g-AC after 3 days at 200 °C with AC treated with 20% H(2)SO(4). In the absence of other strong oxidizers, oxygen was able to oxidize Hg. Upon oxidation, Hg was more readily soluble in the acid, greatly enhancing its uptake by acid-treated AC. Without O(2), S(VI) in H(2)SO(4) was able to oxidize Hg, thus making it soluble in H(2)SO(4). Consequently, the presence of a bulk H(2)SO(4) phase within AC pores resulted in an orders of magnitude increase in Hg uptake capacity. However, the bulk H(2)SO(4) phase lowered the AC pore volume and could block the access to the active surface sites and potentially hinder Hg uptake kinetics. AC treated with SO(2) at 700 °C exhibited a much faster rate of Hg uptake attributed to sulfur functional groups enhancing adsorption kinetics. SO(2)-treated carbon maintained its fast uptake kinetics even after impregnation by 20% H(2)SO(4).     

Metal powder bed fusion in high gravity

Many studies have focused on the stabilization of additive manufacturing (AM) in microgravity for its use in various space projects. Nevertheless, this paper presents a vital clue for innovating metal AM technologies from the perspective of high gravity. High-gravitational powder bed fusion has an excellent potential to address various challenges in AM, such as density enhancement, spatter suppression, and precise fabrication. This study summarizes an analogy among phenomena in different gravitational fields and establishes a combined machine for centrifuge and powder bed fusion. The results confirm the spatter suppression and fine-powder availability in high gravity, both theoretically and experimentally.     

Water permeation properties of SiO2-RSiO3/2 (R = methyl,vinyl, phenyl) thin films prepared by the sol-gel method on nylon-6 substrate

Nylon-6 substrates were coated with SiO₂-RSiO_3/2 (R = methyl, vinyl, phenyl) thin films by the sol-gel method, and their water permeability was evaluated Tetraethoxysilane (TEOS) and trifunctional alkoxides such as methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), and phenyltriethoxysilane (PhTES) were used as starting materials. Water permeability coefficients of the nylon-6 substrates coated with these SiO₂-RSiO_3/2 thin films were increased with an increase in the content of these trialkoxysilanes in the films. The water permeability coefficients of these coated nylon-6 substrates were smaller in the order of the systems TEOS-PhTES < TEOS-VTES < TEOS-MTES in the relatively low content of the trialkoxysilanes. © 1996 John Wiley & Sons, Inc.     

Fabrication of octacalcium phosphate block through a dissolution-precipitation reaction using a calcium sulphate hemihydrate block as a precursor

Although octacalcium phosphate (OCP) powder and a collagen/gelatin composite demonstrate good potential as bone substitutes, an OCP block has not been fabricated to date. In this study, the feasibility of fabricating an OCP block was evaluated through a dissolution-precipitation reaction using a calcium sulfate hemihydrate (CSH) block as a precursor. When the block was immersed in a phosphate salt solution, its composition changed to that of OCP, while its structure was maintained. The diametral tensile strength (DTS) of the OCP block was 1.0?±?0.2?MPa. The macroporosity and microporosity of the OCP block were 33.4?±?4.5% and, 69.0?±?1.6%, respectively. New bone attached well to the OCP block, and this block was partially replaced by bone 2 weeks after implantation. Four weeks after implantation, the surface of the OCP block was nearly covered with new bone and ~30% of the block was replaced by new bone, while no replacement by bone was observed in the case of a hydroxyapatite (HAp) block used as a control. It is concluded that OCP blocks are potentially suitable for their use as artificial bone substitutes.     

Dielectric response and polarization mechanism of alkali silicate glasses in gigahertz to terahertz frequency range

Oxide glasses are dielectric materials with potential applications in high-frequency communications; hence, their dielectric properties in the gigahertz to terahertz frequency range should be investigated. In this study, the dielectric properties of silica glass and five single alkali silicate glasses were measured at 0.5–10 THz using terahertz time-domain spectroscopy and far-infrared spectroscopic ellipsometry. At 0.5–10 THz, the silica glass exhibited low dielectric dispersion with a low dielectric constant and loss. By contrast, the alkali silicate glasses exhibited high dielectric dispersion, and the dielectric constant and loss were higher than those of the silica glass. The shape of the dielectric dispersion profile depended on the alkali-metal ions; it was broader for lighter ions such as Li ions and sharper for heavier ions such as Cs ions. The peak dielectric loss shifted toward a lower frequency as the weight of the alkali-metal ions in the alkali-silicate glass increased. To understand the dielectric dispersion, the complex permittivity was calculated using molecular dynamics simulations. The theoretical results qualitatively agreed with the experimental data. Ion dynamics analysis revealed that alkali-metal ions vibrate and migrate under an applied electric field, which affects the dielectric constant and loss of alkali-silicate glasses at gigahertz to terahertz frequencies. To fabricate filter devices at low temperatures, alkali metals should be added to silicate glass; therefore, a minimum amount of light alkali metals should be used to minimize the dielectric loss of the glass materials while maintaining productivity.     

A rotating disk electrode study on the ammonia oxidation

The anodic oxidation of ammonia in alkaline solutions was investigated by using rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. The ammonia oxidation current on the rotating platinum disk was confirmed not to increase but to decrease with increasing the rotation rate at 25-60 °C. The in situ ring electrode detector gave two kinds of signals for the electroactive species transported from the disk electrode engaged in ammonia oxidation; one can be again reduced and another can further be oxidized on Pt or Ni ring. These results suggested that at least some of the intermediates involved in ammonia oxidation on Pt may not be strongly adsorbed but be detached from the surface regions.