The low-temperature performance of NOx storage and reduction catalyst

The catalytic performance and the behavior of NO_x storage and reduction (NSR) over a model catalyst for lean-burn gasoline engines have been mainly investigated and be discussed based on the temperature and reducing agents use in this study. The experimental results have shown that the NO_x storage amount in the lean atmosphere was the same as the NO_x reduction amount from the subsequent rich spike (RS) above the temperature of 400 °C, while the former was greater than the latter below the temperature of 400 °C. This indicated that when the temperature was below 400 °C compared with the NO_x storage stage, the reduction of the stored NO_x is somehow restricted. We found that the reduction efficiencies with the reducing agents decrease in the order H₂ > CO > C₃H₆ below 400 °C, thus not all of the NO_x storage sites could be fully regenerated even using an excessive reducing agent of CO or C₃H₆, which was supplied to the NSR catalyst, while all the NO_x storage sites could be fully regenerated if an adequate amount of H₂ was supplied. We also verified that the H₂ generation more favorably occurred through the water gas shift reaction than through the steam reforming reaction. This difference in the H₂ generation could reasonably explain why CO was more efficient for the reduction of the stored NO_x than C₃H₆, and hinted as a promising approach to enhance the low-temperature performance of the current NSR catalysts though promoting the H₂ generation reaction.     

Female Sex Pheromone of a Carpenter Moth, Cossus insularis (Lepidoptera: Cossidae)

This study describes the identification of a sex pheromone component of a cossid moth, Cossus insularis. Coupled gas chromatographic–electroantennographic detection (GC–EAD) analysis of solid-phase microextraction (SPME) collections of volatiles released by live female moths showed that two compounds elicited EAG responses from the antennae of male moths. These compounds were identified as (E)-3-tetradecenyl acetate (E3-14:Ac) and (Z)-3-tetradecenyl acetate (Z3-14:Ac) by mass spectral analysis and retention index comparisons with synthetic standards. The ratio of E3-14:Ac and Z3-14:Ac was 95:5 in the effluvia of a female. In field bioassays, sticky traps baited with blends of E3-14:Ac and Z3-14:Ac showed that E3-14:Ac is an essential component of the pheromone. However, the role of Z3-14:Ac is unclear, because E3-14:Ac as a single component was as attractive to male moths as blends of E3-14:Ac and Z3-14:Ac, including the 95:5 blend released by live female moths.     

Low-Temperature Synthesis of Aluminum Silicon Carbide Using Ultrafine Aluminum Carbide and Silicon Carbide Powders

The conditions for preparing α-aluminum silicon carbide (α-Al₄SiC₄) were examined by heating stoichiometric mixtures of ultrafine A1₄C₃ and SiC powders with sizes of <0.1 μm at and below 1600°C. The starting A1₄C₃ powder was obtained by the pyrolysis of trimiethylaluminum; the starting SiC powders were obtained by the pyrolyses of triethylsilane (3ES), tetraethylsilane (4ES), and hexamethyldisilane (6MDS). The reactivity of SiC with Al₄C₃ to form α-Al₄SiC₄ varies according to the kind of starting alkylsilane: 3ES > 4ES > 6MDS. The reaction of 3ES-derived SiC with A1₄C₃ produced α-Al₄SiC₄ at temperatures as low as 1400°C for 240 min, regardless of the presence of A1₄C₃ (trace). Only α-Al₄SiC₄ was formed at and above 1500°C for 60 min; the crystal growth was appreciable.     

Effect of dispersant on paste rheology in preparation of porous alumina with oriented pores by extrusion method

The effect of additives on paste rheology was investigated for preparation of porous ceramics with unidirectionally aligned cylindrical pores. Ammonium poly-carboxylic acid (APA) used as a dispersant and it was adsorbed on alumina powder surface. The adsorption isotherm of APA was fitted by Langmuir equation. The saturated monolayer adsorption was 5.9 mg/g. The apparent viscosity became a minimum at 0.8 mass % of APA corresponding to 71.2 mPa?s. This APA amount of 5.6 mg/g, is in good agreement with the observed APA amount. Since the nylon 66 fibers (0–35 vol. %) mixed with the alumina powder have a strong interaction with each other, they became twisted and agglomerated. This agglomeration increased with increasing fiber content but decreased by adding oleic acid. The pastes with added oleic acid were capable of being extruded at higher pressure. The obtained porous alumina ceramics showed highly oriented cylindrical pores parallel to the extrusion direction. The pore orientation was higher in the oleic acid added pastes than those without oleic acid. The added nylon 66 fibers are mostly converted to pores while maintaining the original shape after sintering. The pore size distribution of the obtained porous ceramics measured by mercury porosimetry method showed a peak at about 4 μm which is apparently smaller than that observed in the SEM photographs and the obtained result is considered to be corresponding to the necks formed by fiber contacts.     

Influence of superplasticizers on the hydration of cement and the pore structure of hardened cement

This paper describes the influence of various types of superplasticizers such as naphthalene type (β-NS), refined lignin sulfonate type (LS) and polycarboxylate types (P34, S34) on the hydration of cement and the pore structure of hardened cement. Other superplasticizers except β-NS delayed the initial hydration of cement. In any case, it hardly influences the hydration reaction at late stage of cement. The retardation by the addition of superplasticizers is not observed after 28 days of curing. Large pores of 0.1 μm or more for hardened cement with LS or β-NS are larger than those of hardened samples with P34 or S34 cured for 28, 56 and 91 days. This is related to the coagulated structures of fresh cement pastes with various types of superplasticizers. It was presumed that the size of the cluster of aggregated particles became small when S34 or P34 that has a high dispersing ability was added compared to LS or β-NS that has a lower dispersing ability.     

Microstructural Characterization of Porous Silicon Carbide Membrane Support With and Without Alumina Additive

Porous silicon carbide (SiC) membrane supports sintered at 1500°–1800°C were prepared by cold isostatic pressing (CIP) under different pressures and using different amounts of alumina additive (0%–4%). The relationship between processing factors and pore size and microstructure was examined. Varying the sintering temperature, the CIP pressure and the amount of additive used were found to be effective for controlling pore size and microstructure. The pore size and particle size of the membrane support prepared without alumina were found to increase with increasing sintering temperature. This was attributed to surface diffusion. Densification of the undoped support did not occur, however, because of concurrent pore development. In the SiC membrane support containing 4% alumina, small particles and a pore size of around 100 nm were retained. This was because of the formation of a limited amount of SiO₂–Al₂O₃ liquid phase during sintering.     

Particle Redistribution During Dendritic Solidification of Particle Suspensions

Solidification of the liquid medium in ceramic suspensions containing less than a critical volume fraction powder leads to the formation of particle-free dendrites of the frozen medium. These particle-free dendrites create, after sublimation of the frozen vehicle, large dendrite pores. We define the conditions under which particle-free dendrites form, and relate the size and volume fraction of the dendrites to the volume fraction powder and the solidification rate.     

Investigation of characterization method for nanoparticles in roadside atmosphere by thermal desorption-gas chromatography/mass spectrometry using a pyrolyzer

Atmospheric nanoparticles (<0.050 microm) have caused great concern recently due to their potential to affect human health. However, little is known about the chemical composition, sources, and atmospheric behavior of atmospheric nanoparticles. Although gas chromatography/mass spectrometry (GC/MS) after solvent extraction is a commonly used and powerful method for the identification of nonpolar organic compounds in particles, solvent-extraction methods are difficult to apply to nanoparticles because nanoparticles are present in small masses in spite of their high number concentrations. Therefore, we made an attempt to apply thermal desorption-GC/MS (TD-GC/MS), which was expected to be more sensitive than solvent-extraction methods, to atmospheric nanoparticles. A commercial pyrolyzer was used for TD. Prior to the application, the optimum TD-GC/MS conditions for atmospheric particles and diesel exhaust particles (DEP) collected on filters were investigated. Various TD parameters, including desorption time and temperature, were investigated using these test samples and a n-alkanes standard solution. The optimum TD conditions were as follows: ramped desorption from 50 degrees C to 450 degrees C at 50 degrees C min(-1) and then hold for 2 min. Desorption was incomplete at temperatures of 250 degrees C or lower, and considerable pyrolysis occurred at temperatures of 550 degrees C or higher. The TD-GC/MS performance, including the linearity of the calibration curves, repeatability, detection and quantification limits, and sample recovery, under the optimized conditions was evaluated for n-alkanes. It was found that the TD-GC/MS could be applied to extremely small amount of particles (e.g., 5 microg for DEP). The TD-GC/MS was applied to the size-resolved particles, including the nanoparticle fraction (0.0290-0.0580 microm), from roadside atmosphere, and the concentrations of C18-C33 n-alkanes in the particles were determined. The chromatogram pattern of the roadside 0.102-0.163 microm (major size range for DEP) particles was similar to that of the DEP sample. The chromatogram pattern of the roadside nanoparticles was similar to that of diesel lubricating oil, although the proportion of less volatile compounds was slightly larger in the nanoparticles. It is suggested that lubricating oil strongly contributed to the nonpolar organic composition of the roadside nanoparticles, and that more volatile organic compounds in the nanoparticles evaporated in the atmosphere. It was shown that the TD-GC/MS is effective for characterization of atmospheric nanoparticles.     

Scenario Violation in Nursing Activities: Nursing Risk Management from the Viewpoint of Chance Discovery

This paper introduces scenarios that from a time series of events under a coherent context of performing nursing risk management. First, we describe general nursing risk management procedures. Then we review our previous nursing accident or incident protection model based on abduction. This paper extends the nursing accident or incident protection model by using the concept of scenario. That is, the model introduces chronological information in knowledge presentation. Then this paper regards a set of nursing activities as a scenario and characterizes a (nursing) accident or incident as a scenario violation. The main purpose of this paper is to present nursing risk management from the viewpoint of scenario violation in the context of chance discovery.     

Excellent heat resistance of Si-Zr-C-O fibre

In order to obtain the high heat-resistant fibre, Si-Zr-C-O fibre has been developed. Si-Zr-C-O fibre was produced by the use of polyzirconocarbosilane as the precursor polymer. In this paper, the difference in heat-resistance between Si-Ti-C-O and Si-Zr-C-O fibres was clarified. Si-Zr-C-O fibre showed excellent heat resistance (up to 1773 K) compared with Si-Ti-C-O fibre (up to 1573 K). Generally speaking, decomposition reaction of this type of fibre proceeds accompained by the release of CO gas which was formed by the reaction between excess carbon and oxygen included in the fibre. In the case of Si-Zr-C-O fibre, Zr can strongly capture the oxygen atoms, so that the aforementioned decomposition hardly proceeds up to 1873 K (ZrO2 + 3C = ZrC + 2CO; G<0 at over 1906 K).