<正>RSS改变了互联网内容的传递方式,它的成功与博客的兴起分不开。RSS是一个缩写的英文术语,在英文中被认为有几个不同的源头,并被不同的技术团体作不同的解释。它既可以是“Rich Site Summary”(丰富站点摘要),或“RDF Site Summary”(RDF站点摘要),也可以是“Really Simple Syndication”(真正简易联合)。通常RSS文档都标
Multivariate methods were successfully employed in a comprehensive scientometric analysis of geostatistics research, and the publications data for this research came from the Science Citation Index and spanned the period from 1967 to 2005. Hierarchical cluster analysis (CA) was used in publication patterns based on different types of variables. A backward discriminant analysis (DA) with appropriate statistical tests was then conducted to confirm CA results and evaluate the variations of various patterns. For authorship pattern, the 50 most productive authors were classified by CA into 4 groups representing different levels, and DA produced 92.0% correct assignment with high reliability. The discriminant parameters were mean impact factor (MIF), annual citations per publication (ACPP), and the number of publications by the first author; for country/region pattern, CA divided the top 50 most productive countries/regions into 4 groups with 95.9% correct assignments, and the discriminant parameters were MIF, ACCP, and independent publication (IP); for institute pattern, 3 groups were identified from the top 50 most productive institutes with nearly 88.0% correct assignment, and the discriminant parameters were MIF, ACCP, IP, and international collaborative publication; last, for journal pattern, the top 50 most productive journals were classified into 3 groups with nearly 98.0% correct assignment, and its discriminant parameters were total citations, impact factor and ACCP. Moreover, we also analyzed general patterns for publication document type, language, subject category, and publication growth.
Polycyclic aromatic hydrocarbons (PAHs) in two 210Pb dated sediment cores from the coastal East China Sea, strongly influenced by the discharge from the Yangtze River, were determined to help to reconstruct the economic development over the past century in East China. The variations in PAH concentrations and fluxes in the sediment cores were primarily due to energy structure change, severe floods and dam construction activities. The impact on PAHs by the river discharge overwhelmed the atmospheric depositions. The profiles of PAH fluxes and concentrations as well as compositions in the cores revealed the transformation from an agricultural economy to an industrial one especially after the 1990s' in the region. PAHs in the study area were dominated by pyrolytic sources.
The objective of this study was to detect the selenium level in the environment and the population of Zhoukoudian area, Beijing, and to discuss the influence of various factors on serum selenium level. The soil, drinking water, and foodstuff samples and venous blood samples of 401 individuals were obtained to determine the selenium level by gas chromatograph equipped with a (63)Ni electron capture detector (ECD). The selenium level was 0.210+/-0.013 microg/g in soil, 0.017 microg/L+/-0.002 in drinking water, 0.034+/-0.002 microg/g in rice, and 0.034+/-0.012 microg/g in wheat flour. This index showed that the Zhoukoudian area of Beijing was a moderate or marginal level selenium ecological landscape. The mean serum selenium level of the population was 75.01+/-28.35 microg/L, ranging between 35.2 and 160.4 microg/L. A total of 279 (69.6%) individuals exhibited serum selenium level below 80 microg/L, which is the lowest threshold for the activity of glutathione peroxidases (GPx) in vivo. A total of 35 (8.5%) individuals exhibited serum selenium level below 45 microg/L. It is widely recommended that below this value (45 microg/L) there is an increased risk of cardiovascular disease and cancer. Multiple linear regression analysis showed that serum selenium level was positively associated with body mass index (beta=0.137; P=0.011), serum total cholesterol TC (beta=0.785; P=0.000), however, negatively associated with systolic blood pressure (beta=-0.172; P=0.023), serum triglyceride (beta=-0.170; P=0.007), high density lipoprotein-cholesterol (beta=-0.121; P=0.027), and low high density lipoprotein-cholesterol (beta=-0.568; P=0.027).