极地维管植物研究进展

极地维管植物因其所处环境的特殊性而备受关注。本文综述了极地维管植物在结构、生理、遗传和起源方面的研究进展,从而了解其对环境的适应机制,以及遗传多样性的特点、拓殖和起源方式。由叶片超微结构显示出叶绿体突起、叶绿体与线粒体的紧密相连等结构特点与植物适应极地环境有关。低温和长日照下糖类和蛋白质积累、酶活性的保持或提高、与胁迫相关基因的表达保证了植物在严酷环境下的生存。次生代谢物质含量随紫外线和光强度而变化,从而保护植物免受强辐射的伤害。极地地理和气候环境影响了植物遗传多样性和拓殖方式。南极植物(发草)群体的遗传多样性低,基因流动主要发生在邻近群体之间,其拓殖方式符合步石模型。北极植物则存在着长距离拓殖。多领域的研究观点表明,维管植物最有可能通过鸟类的帮助而迁入南极。     

香鱼(Plecoglossus altivelis)脾脏酪氨酸激酶SYK的鉴定及其介导的MAPK信号通路研究

脾脏酪氨酸激酶(SYK)是一种非受体型酪氨酸激酶(non-receptor tyrosine kinase, NRTK)。在哺乳动物中,SYK是重要的细胞信号通路接头分子,其在免疫细胞活化,胞外刺激的信号转导和病原体识别等多种生命过程中扮演重要角色,然而在鱼类中却鲜有报道。本研究以香鱼(Plecoglossus altivelis)为研究对象,探讨了其SYK(PaSYK)在应对病原微生物感染及在活化免疫信号通路中的作用。我们克隆获得了香鱼SYK的cDNA序列,并利用多重序列比对、构建进化树等生物信息学方法分析PaSYK的进化地位;采用实时荧光定量PCR(RT-qPCR)方法分析PaSYK在健康组织及鳗弧菌(Vibrio anguillarum)感染后的表达变化;亚细胞定位检测PaSYK在HEK293T细胞的分布情况;在香鱼头肾单核/巨噬细胞(Monocyte/macrophage,MO/MΦ)中过表达PaSYK,研究其对炎症细胞因子表达的调控作用并在HEK293T细胞及香鱼头肾MO/MΦ中研究PaSYK对MAPK信号通路的活化作用。多重序列比对结果显示,SYK的蛋白质序列和结构域在进化...     

柴达木盆地一里坪盐湖富锂卤水特征、储层物性及富水区分析

一里坪盐湖是柴达木盆地中一个典型的富锂卤水矿床,具有重大的经济价值。本文以查明盐湖深部卤水分布为目的,从卤水储层的空间分布特征和储层物性的角度对富水区进行预测,为卤水开发提供依据。研究区位于一里坪成盐盆地沉积中心区域,晚更新世末期以来,以沉积浅湖相的含淤泥和黏土粉砂岩,盐湖相的含粉砂和黏土的石盐岩为特征。在垂向上,由上下两套石盐岩夹中部粉砂岩组成一里坪富锂卤水的储层;平面上,研究区北部主要为浅湖相,往南过渡为盐湖相,石盐岩厚度在东南部最大。对储层厚度、孔隙度和给水度的分析表明,第Ⅱ矿层孔隙型和晶间型卤水优质储层均位于研究区东部,可作为卤水资源勘查开采的重点区域。     

柴达木盆地一里坪盐湖成盐卤水成分变化及其意义——来自LA-ICP-MS分析石盐流体包裹体组成的证据

一里坪盐湖是柴达木盆地一个以富锂卤水为主的干盐湖,蕴藏有丰富的卤水钾锂资源,目前对成矿过程中卤水的成分及其演变规律方面的研究较少。论文选取一里坪盐湖中部钻孔HC2105岩芯的石盐为主要对象,利用激光剥蚀-电感耦合等离子质谱法开展了单个石盐原生流体包裹体成分分析,探讨恢复了一里坪盐湖地区晚更新世以来成盐期的古卤水成分。结果表明,一里坪盐湖下层石盐古卤水Li、B、K等离子浓度均高于上层石盐,这说明晚更新世成矿条件更好。古卤水中Li、B、K和Mg等离子具有正相关性,再结合对Ca离子浓度变化的研究,说明一里坪盐湖的主要物质来源为那棱郭勒河,深部卤水对其物质来源贡献较小;石盐流体包裹体中各离子浓度的演变规律与钻孔沉积韵律以及古气候变化三者基本可以拟合,从而证实盐湖卤水成分变化受到古气候变化的影响,干冷期可能更有利于富锂卤水矿的形成。     

Highly efficient iterative methods for solving linear equations of three-dimensional sphere discontinuous deformation analysis

The efficiency of solving equations plays an important role in implicit-scheme discontinuous deformation analysis (DDA). A systematic investigation of six iterative methods, namely, symmetric successive over relaxation (SSOR), Jacobi (J), conjugate gradient (CG), and three preconditioned CG methods (ie, J-PCG, block J-PCG [BJ-PCG], and SSOR-PCG), for solving equations in three-dimensional sphere DDA (SDDA) is conducted in this paper. Firstly, simultaneous equations of the SDDA and iterative formats of the six solvers are presented. Secondly, serial and OpenMP-based parallel computing numerical tests are done on a 16-core PC, the result of which shows that (a) for serial computing, the efficiency of the solvers is in this order: SSOR-PCG > BJ-PCG > J-PCG > SSOR>J > CG, while for parallel computing, BJ-PCG is the best solver; and (b) CG is not only the most sensitive to the ill-condition of the equations but also the most time consuming under both serial and parallel computing. Thirdly, to estimate the effects of equation solvers acting on SDDA computations, an application example with 10 000 spheres and 200 000 calculation steps is simulated on this 16-core PC using serial and parallel computing. The result shows that SSOR-PCG is about six times faster than CG for serial computing, while BJ-PCG is about four times faster than CG for parallel computing. On the other hand, the whole computation time using BJ-PCG for parallel computing is 3.37 hours (ie, 0.061 s per step), which is about 36 times faster than CG for serial computing. Finally, some suggestions are given based on this investigation result.     

三种统计预报模型在江苏省道路低温预警中的应用

为了更好地开展道路交通低温灾害的预警,减轻道路结冰给车辆行驶造成的危害,本文利用2012—2016年江苏省高速公路网AWMS系统交通气象观测数据,在对路面低温发生规律进行分析的基础上,结合多元线性回归、朴素贝叶斯以及支持向量机3种统计预报方法,开展了路面低温预警的统计建模与预报试验。结果表明:(1)江苏全省高速公路网路面温度出现0℃以下、-2℃以下、-5℃以下的低温频率均呈"北高南低"分布。(2)全省高速公路网路面温度出现0℃以下的低温时次大多在15:00到次日06:00之间。(3)在对京沪高速M9308站的单站建模与预报试验中发现,路面低温预报因子组合中以13:00气温、13:00—18:00气温变温、13:00路面温度、13:00—18:00路面变温、13:00路基温度、13:00—18:00路基变温、18:00相对湿度和18:00风速U分量为自变量组合的预报方程效果最好,3种方法中以朴素贝叶斯模型的预报准确率最高;(4)就全省高速公路网而言,3种统计预报模型的路面低温预报准确率均超过75%,通过对全路网路面低温预报的试验结果对比发现,多元线性回归方法对江苏省北部路网的预报效果最好,预报准确率大多在85%以上;而支持向量机模型对江苏省南部路网的预报效果最好,大部分站点的低温预报准确率达95%以上。     

中国枢纽机场网络体系演变格局

枢纽机场是机场网络体系的核心要素。文章首次提出利用网络模型k-核概念定义枢纽机场网络体系,并对中国1990―2015年的枢纽机场网络体系的演变过程进行量化分析。研究表明：中国航空网络k-核极大值呈增大趋势,尽管加入枢纽机场的阈值增大,但其数量仍呈稳步增加趋势,由1990年的26个增加到2015年的36个。枢纽机场网络连接率由1990年的7.1增长到2015年15.4,网络演变具有异速增长特征,同时较低的平均路径长度值显示网络具有十分高的组织效率。枢纽机场体系的客货吞吐量集中程度较高,近10年来市场集中度呈下降趋势,但2015年枢纽机场的客货吞吐量市场占比仍分别高达86.7%和95.1%。文章甄别的枢纽机场体系在较大程度上揭示了“规模优先”与“区域均衡”规划模式,能为枢纽机场的发展规划提供决策支撑。     

An organizational model and border port hinterlands for the China-Europe Railway Express

Facilities connectivity is a priority area for implementing the Belt and Road Initiative (BRI). The “China-Europe Railway Express” (CER Express) mode of transport organization links China with Europe by fast-track cargo rail. A major instance of facilities connectivity related to this project is an important practical and symbolic instance of BRI transport cooperation. The strategic significance of the CER Express and a number of operational issues are outlined, as are the implications of limited market potential for costs and competitiveness. A “hub-and-spoke” organizational model that can generate scale economies and reduce costs is proposed. To examine the establishment of an organizational model of this kind, the economic hinterlands of Alashankou, Erenhot, and Manzhouli are identified under high-, mediumand low-cost scenarios using an analytical methodology that determines distance and economic costs, and a number of transport hubs (that include Harbin, Zhengzhou, and Lanzhou) are identified. The results found that the cost of the routes from 314 Chinese cities to Moscow is the lowest via Manzhouli in the high- and medium-cost scenarios, but the routes change via Erenhot in the low-cost scenario. A number of policy recommendations should follow up.     

Complete mitochondrial genomes of two deep-sea pandalid shrimps,Heterocarpus ensifer and Bitias brevis: insights into the phylogenetic position of Pandalidae (Decapoda: Caridea)

Journal of Oceanology and Limnology - The mitochondrial genome (mitogenome) analysis is a significant tool for investigating the evolutionary history of metazoan animals. The family Pandalidae is a...     

Distribution of aliphatic des-A-triterpenoids in the Dajiuhu peat deposit, southern China

Aliphatic des-A-triterpenoids have been tentatively assigned in samples taken from a 260 cm thick peat sequence from the Dajiuhu Basin of southern China using gas chromatography–mass spectrometry (GC–MS). The compounds, possessing the carbon skeletons of oleanane, ursane or lupane, are generally considered as the microbial degradation products of plant triterpenoids under anoxic conditions. Abundant aliphatic des-A-triterpenoids were observed only in peat samples during the transitional period from the last glaciation to the early Holocene (9.5–11.6 cal ¹⁴C ka BP). Among these, des-A-lupane is the only saturated ring A-degraded compound, whilst mono- and di-unsaturated des-A-triterpenes are dominated by oleanane and ursane derivatives. The mono- and di-unsaturated des-A-triterpenes show a strong correlation (R² 0.94) in abundance, indicating that they may be derived from the same source or process. Des-A-lupane shows no correlation in abundance with the mono- or di-unsaturated des-A-triterpenes (R² < 0.25) and may be derived from a different source or process in the catchment. The period with abundant aliphatic des-A-triterpenoids corresponds to the interval with relatively high sedimentation rate (> 0.3 mm per year). These data indicate that the abundance of aliphatic des-A-triterpenoids in the Dajiuhu peat deposit in the early Holocene may result from the prevailing reducing conditions in the water table or surficial sediment and/or rapid preservation of the early diagenetic products. Our study highlights the potential application of des-A-triterpenes in the reconstruction of palaeoenvironments based on peat sequences.