Edge dispersion of supported MoS2 and WS2 catalysts as evaluated by using Co(CO)3NO as a probe molecule

SiO₂- and Al₂O₃-supported MoS₂ and WS₂ catalysts were prepared to exploit the evaluation technique of the edge dispersion of MoS₂ and WS₂ particles. A chemical vapor deposition (CVD) technique using Co(CO)₃NO as a probe molecule was used for the evaluation. Results were compared with those from conventional techniques such as NO adsorption and TEM. A proportional correlation was obtained between the amount of NO adsorption and the amount of Co atoms accommodated by the CVD technique on WS₂/SiO₂ and WS₂/Al₂O₃ catalysts, demonstrating a selective location of the Co atoms on the edges of WS₂ particles, as previously established for MoS₂ catalysts. A comparison of the amounts of NO adsorption and Co accommodation on MoS₂ and WS₂ catalysts suggested a 70% higher density of sulfur vacancy on MoS₂ particles than on WS₂ particles regardless of the support. The Co atoms on the edges of MoS₂ and WS₂ particles showed the identical NO adsorption property. We propose that Co(CO)₃NO can be used as a probe molecule to evaluate and directly compare the edge dispersions of MoS₂ and WS₂ catalysts. The dispersion of MoS₂ particles was about two times higher than that of WS₂ particles with the SiO₂-supported catalysts. With the Al₂O₃-supported catalysts, MoS₂ and WS₂ particles were dispersed to a similar extent but much more highly dispersed than the counterparts in the SiO₂-supported catalysts. The evaluation of the edge dispersion of MoS₂ and WS₂ particles by means of TEM may pose problems when SiO₂- and Al₂O₃-supported catalysts are compared. The edges of unpromoted MoS₂ particles exhibited a significantly higher intrinsic activity for the HDS of thiophene than those of WS₂ particles.     

Formation of formic acid,acetic acid and lactic acid from decomposition of citric acid by coal ash particles at room temperature

It was found for the first time that citric acid was decomposed to formic acid, acetic acid and lactic acid in the presence of coal ash particles at pH 3 at 20 °C, while it was not decomposed at more than pH 5. The yield of organic acid at stirring time of 60 min is in the order of formic acid > acetic acid > lactic acid. Since citric acid dissociates to citric anion at more than pH 5, it was suggested that citric anion and negatively charged coal ash particles repelled electrically each other at more than pH 5, resulting in that citric acid could not be adsorbed and not be decomposed on coal ash. Based on the obtained results, the decomposition of citric acid at pH 3 was suggested to be due to catalytic effects of coal ash. Since formic acid and acetic acid can be used as a material of hydrogen fermentation, coal ash could be used as a catalyst to synthesize the important material for hydrogen fermentation from wastewater of citric acid.     

Possible involvement of DNA methylation in 5-azacytidine-induced neuronal cell apoptosis

Firefly luciferase emits a burst of light when the substrates luciferin and ATP are mixed in the presence of oxygen. We (I. Ueda, A. Suzuki, Biophys. J. 75 (1998) 1052-1057) reported that long-chain fatty acids are specific inhibitors of firefly luciferase in competition with luciferin in microM ranges. They increased the thermal transition temperature. In contrast, 1-alkanols of the same carbon chain length inhibited the enzyme non-competitively in mM ranges and decreased the transition temperature. The present study showed that the action of fatty acids switched from specific to non-specific when the carbon chain length was reduced below C8 (octanoate). The fatty acids longer than C10 inhibited the enzyme in microM ranges whereas those shorter than C8 required mM ranges to inhibit it. The longer fatty acids increased whereas shorter fatty acids decreased the transition temperature. The Hill coefficients of longer chain bindings were less than one whereas those of shorter chain were more than one. The shorter fatty acids interacted with the enzyme cooperatively at multiple sites. Binding of the longer fatty acids is limited. Fatty acids longer than C10 are high-affinity specific binders and followed Koshland's induced-fit model. Those shorter than C8 are low-affinity non-specific denaturants and followed Eyring's rate process model. These results contradict the general consensus that the size of the receptor cavity discriminates specific binders.     

An experimental study of heat transfer in an open thermosyphon

An experimental study was performed on heat transfer of an open thermosyphon with constant wall heat flux. Water and aqueous glycerin were used as working fluids. The experimental range of modified Rayleigh number was 1 × 10³ < Ra_m < 3 × 10⁵. The average and local heat transfer coefficients, vertical temperature distributions of the tube wall and fluid at the centerline of the tube, and temperature fluctuations of the fluid were measured. Flow patterns were observed by adding tracer powder to the fluid. Fluid velocities were measured by laser Doppler velocimeter. Experimental results indicate that, for a water thermosyphon, there are three regimes where different heat transfer characteristics and flow patterns occur. For 1 × 10³ < Ra_m < 3 × 10³, the flow was laminar and the thermal boundary layer reached the center of the tube. Heat was exchanged between the wall and descending flow. Wall temperature increased in the downward direction. For 4 × 10³ < Ra_m < 3 × 10⁴, no turbulence was observed in the flow and the thermal boundary layer was localized in the vicinity of the wall. The wall temperature increased upward. For 3 × 10⁴ < Ra_m < 3 × 10⁵, flow was considerably disturbed by the mixing of upward and downward flow in the upper part of the tube. However, the flow was laminar in the lower part of the tube. Reduction of the flow rate induced by the flow mixing at high Ra_m can be one of the major causes of the deterioration of heat transfer from Lighthill's theory. © 2001 Scripta Technica, Heat Trans Asian Res, 30(4): 301–312, 2001     

Diversity of lactic acid bacteria in fermented brines used to make stinky tofu

Stinky tofu is a kind of fermented tofu with a strong odor. Although stinky tofu is a very popular snack in the Asian region, the community of microbes, and especially lactic acid bacteria (LAB), indigenous to the fermented brine from which it is made remains poorly described. We examined 168 isolates obtained from the original fermented brine (brine A) and two brines in which the hard tofu (brine B) and soft tofu (brine C) had been soaked. Through random amplified polymorphic DNA (RAPD) analysis for typing and 16S rDNA sequencing, 136 representative strains were identified as belonging to 7 genera and 32 species: Enterococcus (2 species), Lactobacillus (14 species), Lactococcus (3 species), Leuconostoc (6 species), Pediococcus (1 species), Streptococcus (2 species), and Weissella (4 species). The LAB composition of brine A was the most diverse: 19 different species were isolated, and 9 of them were classified as Lactobacillus species. The 16S rDNA sequences of 9 strains (6 from brine A and 3 from brine C) showed low values of similarity (below 98%) with currently known species by analysis using the FASTA software. Thus, a wide variety of LAB strains were associated with the fermentation of stinky tofu brines.     

Crosstalk Simulation for Parallel Microstrip Lines with a Nonlinear Capacitive Load Using the Dynamic C-V Characteristic

Crosstalk analysis is getting more important for avoiding malfunction of circuits. In this paper, crosstalk analysis of parallel microstrip lines with a nonlinear capacitive load is described. A characteristic of the nonlinear capacitive load is changed by a rapidly change of an applied voltage of the load. The change of the characteristic induces a complicated reflected wave that causes complicated crosstalk. To simulate such crosstalk precisely, the dynamic C-V characteristic can be used. However, if the dynamic C-V characteristic is complicated, it takes a long time to simulate the crosstalk by using a conventional method. Thus, a simulation method using a recurrence formula is introduced. The recurrence formula is derived from a function of the dynamic C-V characteristic simply. The calculated results computed by using the introduced method agree with the measured crosstalk and the introduced method is superior in computation time to the conventional method. It is confirmed that the introduced method is effective in crosstalk simulation. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Application of rice rhizosphere microflora for hydrogen production from apple pomace

The combination of substrate materials and bacteria is an important factor affecting conversion technology for biological hydrogen production. We performed anaerobic hydrogen fermentation of apple pomace wastes using rhizosphere bacterial microflora of rice as the parent inoculum. In the vial test, the optimal condition for hydrogen fermentation was initial pH 6.0, 35 °C, and 73.4 g pomace per liter of medium (equivalent to 10 g-hexose/L). In the batch experiment (pH 6.0, temperature 35 °C) the hydrogen yield reached 2.3 mol-H₂/mol-hexose. The time course of biogas production and PCR-DGGE analysis suggest that Clostridium spp. decomposed degradable carbohydrates rapidly and a part of the refractory carbohydrate (e.g. pectin) gradually in the apple pomace slurry. In addition to hydrogen, volatile fatty acids (VFAs) were produced in the anaerobic fermentation of apple pomace, which can be a substrate for methane fermentation. The rice rhizosphere can be a promising source of inoculum bacteria for hydrogen fermentation in combination with plant material waste like apple pomace.     

Growth of well-aligned carbon nanotubes by RF-DC plasma chemical vapor deposition

Highly aligned carbon nanotubes (CNTs) were grown under high sheath electric field and gas pressure conditions by the radio frequency (RF) plasma-enhanced direct current (DC) plasma chemical vapor deposition (CVD) method due to a stabilized DC discharge. The uniform growth of highly aligned multi-walled CNTs was achieved over the entire surface area of a 50 × 50 mm² iron foil. The growth of multi-walled CNTs on a 75 × 75 mm² iron foil was also confirmed.     

A study on heat affected zone softening in resistance spot welded dual phase steel by nanoindentation

The base metal (BM) and the heat affected zone (HAZ) of a resistance spot welded dual phase steel have been evaluated by nanoindentation hardness testing. Three different surface conditions have been explored on the BM for assessing the nanohardness response. Softening has been investigated along the sub-critical HAZ by making nanoindentations on individual phases such as ferrite and tempered martensite (TM) at various distances from the line of lower critical temperature Ac₁. A broken appearance accompanied with sub-micron particles were consistently found on TM at 100 μm from the Ac₁ line suggesting carbide precipitation along with partial recovery of martensite. The morphology of TM kept on changing while moving away from Ac₁ towards the BM as the fraction of broken appearance was reduced and the sub-micron particles became finer. SEM observations resulted in good agreement with the nanohardness of the TM phase along the sub-critical HAZ. In contrast, microhardness results suggested the termination of tempering at a shorter distance with respect to Ac₁ and hence a reduced extension of the softening region. The improved resolution for assessing softening through nanoindentation was due to the possibility of avoiding the contribution of the phase boundaries because of the smaller size of the indentation; this also permitted evaluation of TM at low peak temperatures far from Ac₁ where early stages of tempering took place.