Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing ro...Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing road-surface dust. Analysis shows a single-peak distribution in the number size distribution and a double-peak mode for mass size distribution of the road surface dust. The median diameter of the mass concentration distribution of the road dust on a high-grade road was higher than that on a low-grade road. The ratio of PM2.5 to PM10 was consistent with that obtained in a similar study for Hong Kong. For the two selected road samples, the average relative deviation of the size distribution was 10.9% and 11.9%. All results indicate that the method introduced in this paper can effectively determine the size distribution of fugitive dust from traffic.展开更多
Cultivated rice (Oryza sativa L.) is structured into five genetic groups, indica, aus, tropical japonica, temperate japonica and aromatic. Genetic characterization of rice germplasm collections will enhance their util...Cultivated rice (Oryza sativa L.) is structured into five genetic groups, indica, aus, tropical japonica, temperate japonica and aromatic. Genetic characterization of rice germplasm collections will enhance their utilization by the global research community for improvement of rice. The USDA world collection of rice germ-plasm that was initiated in 1904 has resulted in over 18,000 accessions from 116 countries, but their ancestry information is not available. A core subset, including 1,763 accessions repre-senting the collection, was genotyped using 72 genome-wide SSR markers, and analyzed for genetic structure, genetic relationship, global distribution and genetic diversity. Ancestry analysis proportioned this collection to 35% indica, 27% temperate japonica, 24% tropical japonica, 10% aus and 4% aromatic. Graphing model-based ancestry coefficients demon-strated that tropical japonica showed up mainly in the American continents and part of the South Pacific and Oceania, and temperate japonica in Europe and the North Pacific far from the equator, which matched the responses to tem-perature. Indica is adapted to the warm areas of Southern Asia, South China, Southeast Asia, South Pacific and Central Africa and around the equator while aus and aromatic are special types of rice that concentrates in Bangladesh and India. Indica and aus were highly diversified while temperate and tropical japonicas had low diversity, indicated by average alleles and pri-vate alleles per locus. Aromatic has the most polymorphic information content. Indica and aromatic were genetically closer to tropical ja-ponica than temperate japonica. This study of global rice has found significant population stratification generally corresponding to major geographic regions of the world.展开更多
文摘Traffic-generated fugitive dust is a source of urban atmospheric particulate pollution in Beijing. This paper introduces the resuspension method, recommended by the US EPA in AP-42 documents, for collecting Beijing road-surface dust. Analysis shows a single-peak distribution in the number size distribution and a double-peak mode for mass size distribution of the road surface dust. The median diameter of the mass concentration distribution of the road dust on a high-grade road was higher than that on a low-grade road. The ratio of PM2.5 to PM10 was consistent with that obtained in a similar study for Hong Kong. For the two selected road samples, the average relative deviation of the size distribution was 10.9% and 11.9%. All results indicate that the method introduced in this paper can effectively determine the size distribution of fugitive dust from traffic.
文摘Cultivated rice (Oryza sativa L.) is structured into five genetic groups, indica, aus, tropical japonica, temperate japonica and aromatic. Genetic characterization of rice germplasm collections will enhance their utilization by the global research community for improvement of rice. The USDA world collection of rice germ-plasm that was initiated in 1904 has resulted in over 18,000 accessions from 116 countries, but their ancestry information is not available. A core subset, including 1,763 accessions repre-senting the collection, was genotyped using 72 genome-wide SSR markers, and analyzed for genetic structure, genetic relationship, global distribution and genetic diversity. Ancestry analysis proportioned this collection to 35% indica, 27% temperate japonica, 24% tropical japonica, 10% aus and 4% aromatic. Graphing model-based ancestry coefficients demon-strated that tropical japonica showed up mainly in the American continents and part of the South Pacific and Oceania, and temperate japonica in Europe and the North Pacific far from the equator, which matched the responses to tem-perature. Indica is adapted to the warm areas of Southern Asia, South China, Southeast Asia, South Pacific and Central Africa and around the equator while aus and aromatic are special types of rice that concentrates in Bangladesh and India. Indica and aus were highly diversified while temperate and tropical japonicas had low diversity, indicated by average alleles and pri-vate alleles per locus. Aromatic has the most polymorphic information content. Indica and aromatic were genetically closer to tropical ja-ponica than temperate japonica. This study of global rice has found significant population stratification generally corresponding to major geographic regions of the world.
