Radiation hybrid mapping: a somatic cell genetic method for constructing high-resolution maps of mammalian chromosomes

Radiation hybrid (RH) mapping, a somatic cell genetic technique, was developed as a general approach for constructing long-range maps of mammalian chromosomes. This statistical method depends on x-ray breakage of chromosomes to determine the distances between DNA markers, as well as their order on the chromosome. In addition, the method allows the relative likelihoods of alternative marker orders to be determined. The RH procedure was used to map 14 DNA probes from a region of human chromosome 21 spanning 20 megabase pairs. The map was confirmed by pulsed-field gel electrophoretic analysis. The results demonstrate the effectiveness of RH mapping for constructing high-resolution, contiguous maps of mammalian chromosomes.     

Synchrotron X-ray Diffraction Measurements of Single-Crystal Hydrogen to 26.5 Gigapascals

The crystal structure and equation of state of solid hydrogen have been determined directly to 26.5 gigapascals at room temperature by new synchrotron x-ray diffraction techniques. Solid hydrogen remains in the hexagonal close-packed structure under these pressure-temperature conditions and exhibits increasing structural anisotropy with pressure. The pressure-volume curve determined from the x-ray data represents the most accurate experimental measurement of the equation of state to date in this pressure range. The results remove the discrepancy between earlier indirect determinations and provide a new experimental constraint on the molecular-to-atomic transition predicted at higher pressures.     

不同年代大豆品种(系)根系生长动态的比较研究

不同年代大豆品种根干重积累动态可以用Logistic曲线方程进行模拟。在不同施肥水平下,根干重最大增长速率及出现的时间和平均增长速率有所不同。根干重最大增长速率出现的时间,中国当代品种、美国当代品种及中国20世纪20年代的品种间差异不显著,各品种间差异及施肥处理间差异也不显著。根干重最大增长速率,中国当代、美国当代及中国20世纪20年代的品种间差异不显著,各品种间差异也不显著,施肥处理间差异显著。平均增长速率,中国当代、美国当代及中国20年代的品种间差异显著,各品种间及施肥处理间差异也显著。不同施肥水平、不同生育时期,中国当代品种与美国当代品种根干重都比中国20年代品种大。     

The global circulation of seasonal influenza A (H3N2) viruses

Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection.