喀斯特自然土壤中AM真菌对先锋植物根系的影响

【目的】研究丛枝菌根(Arbuscular mycorrhiza，AM)真菌在喀斯特自然土壤条件下对喀斯特先锋草本植物根系的影响。【方法】通过自然土接种AM真菌(N)、灭菌土接种AM真菌(M)及灭菌土壤对照(S)共3种土壤处理，种植喀斯特先锋植物狗尾草(Setaria viridis)、荩草(Arthraxon hispidus)、鬼针草(Bidens pilosa)及狼杷草(Bidens tripartita)，并测定它们的根系生物量、根长、根表面积、根体积、根平均直径、根尖数及根分枝数。【结果】荩草、鬼针草及狼杷草在N处理及M处理下具有较高的菌根侵染率，狗尾草的菌根侵染率较低。与S处理相比，M处理下AM真菌明显提高了荩草、鬼针草及狼杷草的根系生物量、根长、根表面积、根体积、根尖数、根分枝数及组织密度，降低了根平均直径、比根长、比根面积及比根体积；与M处理相比，N处理明显降低了荩草、鬼针草及狼杷草的根系生物量、根长、根表面积、根体积、根尖数、根分枝数及组织密度，提高了比根长、比根面积及比根体积，但对根平均直径无明显影响。【结论】荩草、鬼针草及狼杷草具有较高菌根侵染率，能与AM真菌共生获得更加发达的根系，而自然土壤削弱了AM真菌对荩草、鬼针草及狼杷草根系生长的促进作用。     

Spectroscopic confirmation of a galaxy at redshift z = 8.6

Galaxies had their most significant impact on the Universe when they assembled their first generations of stars. Energetic photons emitted by young, massive stars in primeval galaxies ionized the intergalactic medium surrounding their host galaxies, cleared sightlines along which the light of the young galaxies could escape, and fundamentally altered the physical state of the intergalactic gas in the Universe continuously until the present day. Observations of the cosmic microwave background, and of galaxies and quasars at the highest redshifts, suggest that the Universe was reionized through a complex process that was completed about a billion years after the Big Bang, by redshift z?≈?6. Detecting ionizing Lyman-α photons from increasingly distant galaxies places important constraints on the timing, location and nature of the sources responsible for reionization. Here we report the detection of Lyα photons emitted less than 600?million years after the Big Bang. UDFy-38135539 (ref. 5) is at a redshift of z = 8.5549?±?0.0002, which is greater than those of the previously known most distant objects, at z = 8.2 (refs 6 and 7) and z = 6.96 (ref. 8). We find that this single source is unlikely to provide enough photons to ionize the volume necessary for the emission line to escape, requiring a significant contribution from other, probably fainter galaxies nearby.     

The formation and assembly of a typical star-forming galaxy at redshift z approximately 3

Recent studies of galaxies approximately 2-3 Gyr after the Big Bang have revealed large, rotating disks, similar to those of galaxies today. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation indicates that gas accretion is likely to be the dominant mode by which galaxies grow, because major mergers of galaxies would completely disrupt the observed velocity fields. But poor spatial resolution and sensitivity have hampered this interpretation; such studies have been limited to the largest and most luminous galaxies, which may have fundamentally different modes of assembly from those of more typical galaxies (which are thought to grow into the spheroidal components at the centres of galaxies similar to the Milky Way). Here we report observations of a typical star-forming galaxy at z = 3.07, with a linear resolution of approximately 100 parsecs. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to be assembling a spheroidal bulge similar to those seen in spiral galaxies at the present day. The presence of undisrupted rotation may indicate that galaxies such as the Milky Way gain much of their mass by accretion rather than major mergers.     

基于并行工程的产品开发过程管理的研究

并行工程采用集成化与并行化的思想来开发产品,强调在信息集成基础上的过程集成,运用工作流管理技术能够很好地达到此目的。在分析工作流管理技术的基础上,以冲压模具的开发过程为例来说明用工作流管理技术实现产品开发过程管理的     

GH220合金中碳化物相变规律

研究了合金中M_6C,M_(23)C_6及MC的晶体结构、化学组成、形态、分布及数量,它们的溶解析出规律及互相转化。