Divergence time,historical biogeography and evolutionary rate estimation of the order Bangiales (Rhodophyta) inferred from multilocus data

Bangiales is the only order of the Bangiophyceae and has been suggested to be monophyletic. This order contains approximately 190 species and is distributed worldwide. Previous molecular studies have produced robust phylogenies among the red algae, but the divergence times, historical biogeography and evolutionary rates of Bangiales have rarely been studied. Phylogenetic relationships within the Bangiales were examined using the concatenated gene sets from all available organellar genomes. This analysis has revealed the topology((( Bangia, Porphyra) Pyropia) Wildemania). Molecular dating indicates that Bangiales diversifi ed approximately 246.40 million years ago(95% highest posterior density(HPD)= 194.78–318.24 Ma, posterior probability(PP)=0.99) in the Late Permian and Early Triassic, and that the ancestral species most likely originated from eastern Gondwanaland(currently New Zealand and Australia) and subsequently began to spread and evolve worldwide. Based on pairwise comparisons, we found a slower rate of nucleotide substitutions and lower rates of diversifi cation in Bangiales relative to Florideophyceae. Compared with Viridiplantae(green algae and land plants), the evolutionary rates of Bangiales and other Rhodophyte groups were found to be dramatically faster, by more than 3-fold for plastid genome(ptDNA) and 15-fold for mitochondrial genome(mtDNA). In addition, an average 2.5-fold lower dN/dS was found for the algae than for the land plants, which indicates purifying selection of the algae.     

The first complete organellar genomes of an Antarctic red alga,Pyropia endiviifolia:insights into its genome architecture and phylogenetic position within genus Pyropia(Bangiales,Rhodophyta)

Pyropia species grow in the intertidal zone and are cold-water adapted. To date, most of the information about the whole plastid and mitochondrial genomes(ptDNA and mtDNA) of this genus is limited to Northern Hemisphere species. Here, we report the sequencing of the ptDNA and mtDNA of the Antarctic red alga Pyropia endiviifolia using the Illumina platform. The plastid genome(195 784 bp, 33.28% GC content) contains 210 protein-coding genes, 37 tRNA genes and 6 rRNA genes. The mitochondrial genome(34 603 bp, 30.5% GC content) contains 26 protein-coding genes, 25 tRNA genes and 2 rRNA genes. Our results suggest that the organellar genomes of Py. endiviifolia have a compact organization. Although the collinearity of these genomes is conserved compared with other Pyropia species, the genome sizes show significant differences, mainly because of the different copy numbers of rDNA operons in the pt DNA and group II introns in the mtDNA. The other Pyropia species have 2–3 distinct intronic ORFs in their cox 1 genes, but Py. endiviifolia has no introns in its cox 1 gene. This has led to a smaller mtDNA than in other Pyropia species. The phylogenetic relationships within Pyropia were examined using concatenated gene sets from most of the available organellar genomes with both the maximum likelihood and Bayesian methods. The analysis revealed a sister taxa affiliation between the Antarctic species Py. endiviifolia and the North American species Py. kanakaensis.     

GM-ARMA-BP组合模型在建筑物沉降预测中的应用

针对建筑物变形监测中的沉降预测问题,本文结合灰色模型、时间序列模型和BP神经网络模型的优点,提出了GM-ARMA-BP组合模型进行沉降预测的方法,有效克服了单一模型稳定性差的缺点,并以某高层建筑沉降观测数据为样本,通过对这几种模型的沉降预测结果进行比较分析,结果表明:GMARMA-BP组合模型预测效果最好,精度较单一模型提高50%以上,并且具有一定的适用性。     

登陆中国东南沿海热带气旋气压变化的重现期分析

为正确考虑和衡量核电厂选址风暴潮灾害分析中热带气旋登陆过程时出现的气压填塞量的取值,利用1949-2014年在我国东南沿海登陆的台风气压资料,建立了登陆前TC中心气压与登陆后气压填塞量二维Copula联合分布函数,通过同现重现期表征出两种样本筛选条件下两种边缘分布的相关关系。结果表明:Frank Copula函数可以适应样本联合分布;考虑在台湾登陆的TC样本与不考虑时相比,相同同现重现期水平在登陆前气压边缘分布方向上要增加10 h Pa左右;气压填塞量在25 h Pa以内时,填塞量越小,同现重现期越大。     

1993—2016年喀喇昆仑山中部Shigar流域冰川物质平衡变化空间特征研究

基于Landsat系列卫星遥感影像、SRTM DEM和TanDEM-X DEM对喀喇昆仑山中部Shigar流域不同类型冰川的面积变化、物质平衡进行了分析.结果表明:1993—2016年间Shigar流域内有25条跃动冰川(面积增加1.30 km2),68条前进冰川(面积增加0.86 km2),50条退缩冰川(面积减少3...     

多通道带乘性噪声系统观测噪声的最优估计

研究在多通道观测时观测噪声的最优估计问题。就多通道的乘性噪声为对角阵且动态噪声一步相关并与观测噪声在同时刻和过去相邻时刻也相关的复杂情况下给出了在线性最小方差意义下的观测噪声最优滤波估计算法和固定区间平滑估计算法。针对这些算法进行了仿真研究 ,仿真结果表明了算法的有效性。     

基于时频稀疏性分析法的低信噪比微震事件识别与恢复

微震监测是直观评价压裂过程和压裂效果的有效手段.微震事件识别是微震监测的首要步骤.然而对于低信噪比微震监测数据,常规识别方法很难取得满意效果.基于微震事件在时频域中的稀疏性,本文提出利用Renyi熵值表示微震监测数据的时频稀疏程度,并以时频距离为约束条件,建立以低熵值的道数为判别阈值的目标函数.本文方法能在识别出微震事件的同时,恢复出较为清晰的微震事件.通过数值计算和对实际监测数据的测试,表明该方法对低信噪比的微震监测数据有较好的处理效果.     

Spatiotemporal distribution of protozooplankton and copepod nauplii in relation to the occurrence of giant jellyfish in the Yellow Sea

The occurrence of the giant jellyfish, Nemopilema nomurai, has been a frequent phenomenon in the Yellow Sea. However, the relationship between the giant jellyfish and protozoa, in particular ciliates, remains largely unknown. We investigated the distribution of nanoflagellates, ciliates, Noctiluca scintillans, and copepod nauplii along the transect 33~N in the Yellow Sea in June and August, 2012, during an occurrence of the giant jellyfish, and in October of that year when the jellyfish was absent. The organisms studied were mainly concentrated in the surface waters in summer, while in autumn they were evenly distributed in the water column. Nanoflagellate, ciliate, and copepod nauplii biomasses increased from early June to August along with jellyfish growth, the first two decreased in October, while N. scintillans biomass peaked in early June to 3 571 pg C/L and decreased in August and October. In summer, ciliate biomass greatly exceeded that of copepod nauplii （4.61-15.04 ~tg C/L vs. 0.34-0.89 pg C/L）. Ciliate production was even more important than biomass, ranging from 6.59 to 34.19 ~tg C/（L.d） in summer. Our data suggest a tight and positive association among the nano-, micro-, and meso-zooplankton in the study area. Statistical analysis revealed that the abundance and total production of ciliate as well as loricate ciliate biomass were positively correlated with giant jellyfish biomass, indicating a possible predator-prey relationship between ciliates and giant jellyfish. This is in contrast to a previous study, which reported a significant reduction in ciliate standing crops due to the mass occurrence ofN. nomurai in summer. Our study indicates that, with its high biomass and, in particular, high production ciliates might support the mass occurrence of giant jellyfish.     

页岩气的资本迷局

第二轮页岩气招标的落幕,并没有令各路资本押宝页岩气止步. 近日,没有直接参与招标的四川民企宏华集团以与神华地质勘探有限责任公司(以下简称神华地勘)合作的方式,曲线进入页岩气开发领域.与此同时,美国页岩气"巨鳄"Carrizo公司也跃跃欲试,想通过技术合作从中国页岩气市场分得杯羹. 不过,值得警惕的是,当前页岩气勘探开发中存在"虚火"成分.据了解,一些企业跨界进军页岩气有着更多"画大饼"式的炒作成分,一些地方也出现一哄而上、跑马圈地、炒作矿权的苗头,而拿出"真金白银"付诸勘探开发的则很少.     

基于区块特征的元胞自动机土地利用演化模型研究

针对传统元胞自动机模型中栅格式规则空间模拟复杂地理元素精度不高的问题,提出一种基于土地区块特征的非规则空间元胞自动机模型,以地理单元实质不规则实体形状作为元胞空间单元,进行土地利用变化的仿真模拟,运用MapInfo建立非规则空间元胞自动机模型的应用软件.对头灶镇土地利用演化的实证研究表明,非规则空间元胞自动机模型可以更真实地描述元胞地理信息、局部空间关系和演化规则,可为城市规划提供决策支持.