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The Lyudahuofang section located in the east of Songnen Plain is a typical natural section for the study of selenium (Se) source in the Se-rich soil belt of Songnen Plain. A total of 33 samples are collected from two vertical sections of Cretaceous Nenjiang Formation (K2n) to analyze Se and its seven occurrence forms, and physicochemical indexes such as TOC and pH. The results show that the Se content is 0.01x10-6-3.05x10-6, averagely 0.56 x10-6, with great variance in samples from different layers. Residual selenium is the main form in section samples with the average content of 0.092x10-6, accounting for 51.98%. The Se content is mainly affected by parent material (oil shale). The correlation analysis results show that TOC and pH have certain effects on the distribution of Se content. That is, TOC is positively correlated with Se of strong organic bound, humic acid bound, ion-exchangeable and water soluble forms; while pH is negatively correlated with Se of all forms. [ABSTRACT FROM AUTHOR]

Based on the 7 701 high-precision soil data obtained from 1 :50 000 special survey of the Se-rich land in Heilongjiang Province, the paper analyzes the physiochemical indexes such as Se, TOC and pH, and uses statistical analysis and correlation analysis to study the spatial distribution characteristics of Se in farmland soil of Suiling County and discuss the relation between soil property and Se. The results show that the soil Se content is 0.05x10-6-0.87x10-6, averagely 0.27x10-6. The farmland soil is Se-sufficient dominated, accounting for 88.00%, with Se-rich soil 3.90%, potential Se-deficiency soil 7.24% and Se-deficient soil 0.86%. The average Se content in different soil types from high to low is as follows: black soil, meadow soil, dark brown soil, albic soil and aeolian sandy soil. The correlation analysis results indicate that TOC is the major factor affecting soil Se content, while the influence of pH is not so obvious. [ABSTRACT FROM AUTHOR]

Homologous recombination is one of important sources in shaping the bacterial population diversity, which disrupts the clonal relationship among different lineages through horizontal transferring of DNA-segments. As consequence of blurring the vertical inheritance signals, the homologous recombination raises difficulties in phylogenetic analysis and reconstruction of population structure. Here we discuss the impacts of homologous recombination in inferring phylogenetic relationship among bacterial isolates, and summarize the tools and models separately used in recombination measurement and identification. We also highlight the merits and drawbacks of various approaches, aiming to assist in the practical application for the analysis of homologous recombination in bacterial evolution research.

Since plague is an important natural focus zoonosis, the typing of natural plague foci becomes one of the elements in understanding the nature and developing related prevention program of the disease. Natural foci of plague are composed by four fundamental parts which include Eco-geographical landscape (natural plague foci), hosts, vectors and pathogens (Yersinia pestis) that comprehensively interact through the large temporal scale of evolution. Human activities have had great impact on the foci of natural plague. Based on the published serial research papers, we tried to integrate the knowledge of each factor in natural plague foci and focusing on theoretical aspects, so as to strengthen the prevention and surveillance programs of plague to be extrapolated to other zoonosis.

Objective: To group and characterize natural plague foci in China., Methods: A novel two-class typing method as well as a three-indication nomenclature method were established to group and characterize the natural plague foci, on the basis of eco-geographical landscapes of plague foci, genetics of Yersinia pestis, zoology of rodent reservoirs and the entomology of flea vectors., Results: A total of 12 distinct natural plague foci (including 19 subtypes) as well as their biological features were characterized., Conclusion: Natural plague foci in China were grouped and characterized in this study.

Objective: To summarize the clinical feature of splenic artery aneurysms (SAA) in OLT recipient, and review the experience in diagnosis and management., Methods: The clinical data, results of four-phase CT scanning and CT angiography of 450 recipients, who underwent OLT from December 2001 to December 2003 were analyzed statistically., Results: Twenty of 450 recipients were diagnosed as SAA, the incidence was about 4.4%. Nineteen of them were diagnosed by four-phase CT scanning. Fifteen patients did not receive any treatment for SAA during OLT, but two of them suffered SAA rupture after OLT, among which one died of hemorrhagic shock although emergency operations were performed. The five patients, who were performed splenectomy with SAA resection during transplantation, recovered successfully after OLT, and their grafts' function was satisfactory., Conclusions: Morbidity of SAA is higher in patients of liver cirrhosis. Four-phase CT scanning can diagnose SAA exactly. In the early period post-OLT, SAA rupture happens frequently, so SAA resection should be performed during transplantation.