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  • Author or Editor: J. Shen x
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Abstract  

A series of Zn–Al hydrotalcites with Zn/Al molar ratios of 1, 2, 3 and 6 were prepared by co-precipitation method. TG-DTG results showed that the hydrotalcites decompose in two stages, corresponding to the two endothermic peaks around 180 and 220°C. After calcination at 400°C, the samples were converted into Zn–Al mixed oxides with the only XRD pattern of ZnO, except for the sample with the ratio of 6. The Zn–Al mixed oxides possess similar surface acidity revealed by microcalorimetric adsorption of NH3. The basicity of the samples increases with the order: ZnO>6Zn/Al>1Zn/Al>Al2O3.

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Abstract  

Substoichiometric extraction in conjunction with a double tracer technique is employed to simultaneous determination of extraction constants of simple metal pyrrolidinedithiocarbamates and chloride-mixed metal pyrrolidinedithiocarbamates. The metals involved include Hg(II), Bi(III), In(III), As(III), Cd(II) and Fe(II). The extraction constants for Bi(III) and Cd(II) obtained are compared with the values available in the literature. The extraction constants for all the other metals are reported for the first time.

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Abstract  

The gold content of placer gold flakes and gold bearing ores has been determined by instrumental neutron activation analysis /INAA/ and radiochemical neutron activation analysis /RNAA/. It was discovered that significant errors result in the instrumental method for gold flakes as small as 10 mg due to sample self-absorption of neutrons during irradiation. Reliable results were obtained, for both ore samples and gold flakes, by dissolving the samples in aqua regia prior to irradiation.

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Abstract  

Carburization and coke deposition of unsupported and carbon-supported Fe, Mo and Fe−Mo catalysts in syngas have been studied using thermogravimetry. Compositions of the carbides formed are evaluated on the basis of the amount of metals in the catalysts and amount of carbon deposited during carburization. It is shown that carburization temperature and the nature of the carbides formed (Fe5C2 and Fe2C for iron and Mo2C for molybdenum) depend on the metals but are influenced by the support and metal loading. Coke deposition on these catalysts takes place as soon as carburization is complete.

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Abstract  

The catalytic performance of unsupported and carbon-supported Fe, Mo and Fe−Mo catalysts for Fischer-Tropsch synthesis is greatly influenced by the final reduction states of the catalysts. In this investigation, the reduction process of the catalysts by H2 was studied by using TG-DTG. The reduction process depends not only on the reducibility of metals but also on the nature of the support. Methanation of the support occurred as soon as the supported metals were completely reduced for the carbon-supported catalysts. For these, the reduction temperature should by carefully selected so that the metal oxides are reduced as completely as possible, whilst the methanation of the support must be avoided to obtain optimum reduced catalysts.

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Rice straw represents a significant energy source for ruminant animals, and fibers and lignin contents of rice straw are negatively related to intake potential of forages. For improvement of the digestibility of rice straw, it is necessary to understand the genetic basis of the related traits. In present study, mapping of quantitative trait loci (QTL) for acid detergent fiber (ADF), neutral detergent fiber (NDF), and acid detergent lignin (ADL) was carried out using a doubled haploid (DH) population derived from a cross between indica variety Zai-Ye-Qing 8 (ZYQ8) and japonica variety Jing-Xi 17 (JX17). The results indicated that all three parameters were continuously distributed among the DH lines, but many DH lines showed transgressive segregation for all the three traits. A total of three main-effect QTLs were identified for ADF and ADL, two of which, qADF-9 and qADL-9, shared the same region on chromosome 9. These two main-effect QTLs explained more than 20% of the total phenotypic variations, whereas the other QTL, qADF-5, explained 12.8% of the total phenotypic variation for ADF. In addition, another two epistatic QTLs, qADF-2 and qADF-3 could explain 17.6% of the total variations. Thus, we concluded that both main-effects and epistatic QTLs were important in controlling the genetic basis of ADF.

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Abstract  

We report the optical absorption characteristics of highly porous, polycrystalline TiO2electrodes and the influence of hydrolysis period for the preparation processes by photoacoustic (PA) spectroscopy together with photoelectrochemical (PEC) current ones. The PA spectra show peaks which are attributed to the lowest transition energy due to the quantum confinement effect. The peak intensity decreases with the increase of hydrolysis periods, indicating the possibilities of the changes in the thermal properties and the densities due to hydrolysis processes. The PEC spectra indicate that the photocurrent intensity also show peak and that of the longer hydrolysis periods is somewhat smaller than others, indicating the increase of interface states due to the formation of grain boundaries with the increase of hydrolysis processes.

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Abstract  

The microcalorimetric method and DNA site-directed mutagenesis technique were used together to study the effect of transcription start site mutagenesis on RM07 promoter activity and gene transcription efficiency in Escherichia coli. The results revealed that once the putative transcription start site G was mutated to T, the promoter activity of RM07 promoter fragment was decreased and the transcription strength of cat reporter gene was weakened. Our work suggests that the nucleotide component of transcription start site is very critical for the promoter strength and the gene transcription efficiency. Our research also provides a new and useful technique for determining the transcription start site using both chemical and biological method.

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