一种新型地面开关过分相技术的系统方案研究

首先阐述了电气化铁路过分相的来由,简要介绍了地面开关过分相技术优势。在满足安全性、可靠性、可用性、可维护性等设计原则的基础上,分析并阐述了一种新型地面开关过分相技术的列车位置检测(计轴信号)、逻辑控制、开关执行、继电保护等4个核心子系统的技术设计方案,以及中性段长度的计算过程和方法。该新型地面开关过分相技术完全适应中国电气化铁路,解决了接触网中性区快速带电,列车持续保持动力的难题,有效提高列车运行速度,提升运营效率、节约旅行时间;同时也解决了在长大坡道或重载线路上采用传统过分相方案可能造成列车非正常停车或滑坡问题,具备推广使用条件。

Genetic Variation and Differentiation in Wide Ranging Populations of Razor Clam(Sinonovacula constricta) Inferred from AFLP Markers

The genetic variation and differentiation of the razor clam Sinonovacula constricta distributed along the coast of China were studied through amplified fragment length polymorphism(AFLP) analysis.Six primer combinations generated 193 fragments.The He values varied from 0.322 to 0.463 and the percentage of polymorphic loci ranged from 74.1% to 98.4%,which indicates a high level of genetic diversity.Cluster analysis by Nei's pairwise distance grouped all specimens by geographical origins.AMOVA consistently showed that genetic variation among populations was 8.71%,and most of the variation came from the genetic variation within populations(91.29%).Genetic differentiation among the six populations was moderate;pairwise FST ranged from 0.0282 to 0.1480,which indicated that S.constricta populations along the coast of China are genetically connected.Among all the six populations,the Beihai population is the mostly differentiated from the others,suggesting that Hainan Island and Leizhou Peninsula act as barriers to gene flow.All populations abide isolation by distance model as indicated by Mantel test,except for ZS(Zhoushan) and YQ(Yueqing) populations.Information obtained in this study will provide guidelines for conservation and fishery management of this species in the future.

Genetics and phylogeny of genus Coilia in China based on AFLP markers

The taxonomy of Coilia has been extensively studied in China,and yet phylogenetic relationships among component taxa remain controversial.We used a PCR-based fingerprinting technique,amplified fragment length polymorphism(AFLP) to characterize and identify all four species of Coilia in China.We examined the genetic relationships of the four species of Coilia and a subspecies of Coilia nasus with AFLP.A total of 180 AFLP loci were generated from six primer combinations,of which 76.11% were polymorphic.The mean genetic distance between pairs of taxa ranged from 0.047 to 0.596.The neighbor-joining tree and UPGMA dendrogram resolved the investigated species into three separate lineages:(1) C.mystus,(2) C.grayii and(3) C.brachygnathus,C.nasus,and C.nasus taihuensis.Phylogenetic analysis of the AFLP data is inconsistent with current morphological taxonomic systems.The AFLP data indicated a close relationship among C.brachygnathus,C.nasus taihuensis,and C.nasus.Therefore,the two species described under Coilia(C.brachygnathus and C.nasus taihuensis) are treated as synonyms of C.nasus.

Genetic diversity of populations and clones of Rhopilema esculentum in China based on AFLP analysis

Amplified fragment length polymorphisms(AFLP) markers were developed to assess the genetic variation of populations and clones of Rhopilema esculentum Kishinouye(Scyphozoa,Rhizostomatidae).One hundred and seventy-nine loci from 56 individuals of two hatchery populations and two wild populations were genotyped with five primer combinations.The polymorphic ratio,Shannon's diversity index and average heterozygosity were 70.3%,0.346 and 0.228 for the white hatchery population,74.3%,0.313,and 0.201 for the red hatchery population,79.3%,0.349,and 0.224 for the Jiangsu wild population,and 74.9%,0.328 and 0.210 for the Penglai wild population,respectively.Thus,all populations had a relatively high level of genetic diversity.A specific band was identified that could separate the white from the red hatchery population.There was 84.85% genetic differentiation within populations.Individual cluster analysis using unweighted pair-group method with arithmetic mean(UPGMA) suggested that hatchery populations and wild populations could be divided.For the hatchery populations,the white and red populations clustered separately;however,for the wild populations,Penglai and Jiangsu populations clustered together.The genetic diversity at the clone level was also determined.Our data suggest that there are relatively high genetic diversities within populations but low genetic differentiation between populations,which may be related to the long-term use of germplasm resources from Jiangsu Province for artificial seeding and releasing.These findings will benefit the artificial seeding and conservation of the germplasm resources.

Temporal stability of Symbiodinium phylotype in scleractinian coral Galaxea fascicularis from a tropical fringing reef in the South China Sea

Symbiodinium sp. occurs in a symbiotic association with various marine invertebrates, including the seleractinian corals. Understanding the flexibility and specificity in coral-algal symbiosis can have important implications for predicting the future of coral reefs in the era of global climate change. In the present study, we conducted Symbiodinium phylotype analysis, based on polymerase chain reaction and restriction fragment length polymorphism （PCR-RFLP）, in the scleractinian coral, Galaxeafascicularis, from a tropical fringing reef in Hainan Island, over a 1-yr period. Our results showed that Galaxea fascicularis could associate with Symbiodinium clade C and D either individually or simultaneously. However, during the sampling period, the Symbiodinium phylotype did not change significantly in the scleractinian coral Galaxeafascicularis, although the seawater temperature decreased sharply in the winter season. This study further suggests that the shift in Symbiodinium communities in response to seasonally fluctuating environments might not be a universal feature of coral-algal associations.