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  • Author or Editor: Y. 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  

Power-time curves and metabolic properties of Tetrahymena thermophila BF5 exposed to different Yb3+ levels were studied by ampoule method of isothermal calorimetry at 28°C. Metabolic rate (r) decreased significantly while peak time (PT) increased with the increase of Yb3+. These results were mainly due to the inhibition of cell growth, which corresponded to the decrease of cell number obtained by cell counting. Compared with cell counting, calorimetry was sensible, easy to use and convenient for monitoring the toxic effects of Yb3+ on cells and freshwater ecosystem. It was also found that cell membrane fluidity decreased significantly under the effects of Yb3+, which indicated that Yb3+ could be membrane active molecules with its effect on cell membranes as fundamental aspect of its toxicity.

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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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Abstract  

The application of a microcalorimetric method to the study of extremophiles is described briefly. Using the LKB 2277 Bioactivity Monitor, the growth thermogenic curves of three strains of Halobacterium halobium were determined at 37C, and compared with the spectrophotometric curves. Then the suitable growth thermokinetic equation was established based on the characteristics of growth thermogenic curves. By using cycle-flow method, all of the growth thermogenic curves of H. halobium strains displayed a brief lag phase before the onset of exponential growth when they were cultured in Halo-2 medium.

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N,N,N',N'-Tetrabutyladipicamide (TBAA) was used for the extraction of nitric acid and uranyl(II) ion from nitric acid media into toluene. The effects of nitric acid, uranyl(II) ion, and extractant concentration, temperature and back extraction on the distribution coefficient of uranyl(II) ion have been studied. The main adduct of TBAA and HNO3 is TBAA·HNO3 in 1.0 mol/l nitric acid solution. The 1:2:2 complex of uranyl(II) ion, nitrate ion and TBAA as extracted species is further confirmed by IR spectra of the extraction of uranyl(II) ion with TBAA. The values of the thermodynamic parameters have also been calculated.

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Abstract  

Mn2O3/-Al2O3 catalysts were prepared by the impregnation method, and the maximum monolayer dispersion capacity or dispersion threshold value of Mn2O3 on the surface of -Al2O3 was determined to be 13.08% from the decomposition mass loss of supported Mn(NO3)2 in the monolayer state. This was compared with the values estimated from a close-packed monolayer model and an interaction model. It was confirmed that the high activities and selectivities of the catalysts for benzoic acid hydrogenation to benzaldehyde are due to the monolayer dispersion of the Mn2O3 on the surface of -Al2O3.

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Abstract  

The sorption behavior of technetium on pyrrhotine was studied with batch experiments and diluted sulfuric acid (less than 2.88 mol/l) was used to dissolve the technetium adsorbed on pyrrhotine. A significant sorption of technetium on pyrrhotine was observed under aerobic and anaerobic conditions, and the sorption on the mineral was supposed to be due to the reduction of TcO4 - to insoluble TcO2 .nH2O. Sorbed technetium on the mineral could be desorbed by diluted sulfuric acid. The maximum desorption ratio under aerobic conditions was much higher than that of under anaerobic conditions, meanwhile, the desorption rates under anaerobic conditions were higher than that of under aerobic conditions in the initial stage of the experiments.

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The thermogenic curves of the aerobic metabolism of the three strains of Bacillus thuringiensis B.t. A, B.t. B and B.t. C have been determined by using an LKB-2277 BioActivity Monitor. B.t. A was the host bacterium without foreign gene. B.t. B and B.t. C were constructed by transforming different foreign genes into the host B.t. A, respectively. B.t. B expressed erythromycin resistant gene, while B.t. C expressed both erythromycin resistant gene and tyrosinase gene. The heat flow rate of these strains is B.t. A> B.t. B >B.t. C. These results indicated that there is obvious interrelation between expression of foreign genes and heat flow rate of B.t. strains.

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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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