Global scale annual and semi-annual variations of daytime NmF2 in the high solar activity years

The annual and semi-annual variations of the ionosphere are investigated in the present paper by using the daytime F2 layer peak electron concentration (NmF2) observed at a global ionosonde network with 104 stations. The main features are outlined as follows. (1) The annual variations are most pronounced at magnetic latitudes of 40–60° in both hemispheres, and usually manifest as winter anomalies; Below magnetic latitude of 40° as well as in the tropical region they are much weaker and winter anomalies that are not obvious. (2) The semi-annual variations, which are usually peak in March or April in most regions, are generally weak in the near-pole regions and strong in the far-pole regions of both hemispheres. (3) Compared with their annual components, the semi-annual variations in the tropical region are more significant.In order to explain the above results, we particularly analyze the global atomic/molecular ratio of [O/N2] at the F2 layer peak height by the MSIS90 model. The results show that the annual variation of [O/N2] is closely related with that of NmF2 prevailing in mid-latitudes and [O/N2] annual variation usually may lead to the winter anomalies of NmF2 occurring in the near-pole region. Moreover, NmF2 semi-annual variations appearing in the tropical region also have a close relationship with the variation of [O/N2]. On the other hand, the semi-annual variations of NmF2 in the far-pole region cannot be simply explained by that of [O/N2], but the variation of the solar zenith angle may also have a significant contribution.     

Molecular modeling of the 10-Å phase at subduction zone conditions

Molecular dynamics (MD) modeling of the 10-Å phase, Mg₃Si₄O₁₀(OH)₂·xH₂O, with x=2/3, 1.0 and 2.0 shows complex structural changes with pressure, temperature and water content and provides new insight into the structures and stabilization of these phases under subduction zone conditions. The structure(s) of this phase and its role as a reservoir of water in the mantle have been controversial, and these calculations provide specific predictions that can be tested by in situ diffraction studies. At ambient conditions, the computed structures of talc (x=0) and the 10-Å phases with x=2/3 and 1.0 are stable over the 350-ps period of the MD simulations. Under these conditions, the 10-Å phases show phlogopite-like layer stacking in good agreement with previously published structures based on powder X-ray diffraction data for samples quenched from high-pressure and high-temperature experiments. The calculations show that the 10-Å phase with x=2.0 is unstable at ambient conditions. The computed structures at P=5.5 GPa and T=750 K, well within the known stability field of the 10-Å phase, change significantly with water content, reflecting changing H-bonding configurations. For x=2/3, the layer stacking is talc-like, and for x=1.0, it is phlogopite-like. The calculations show that transformation between these two stackings occurs readily, and that the talc-like stacking for the x=2/3 composition is unlikely to be quenchable to ambient conditions. For x=2.0, the layer stacking at P=5.5 GPa and T=750 K is different than any previously proposed structure for a 10-Å phase. In this structure, the neighboring basal oxygens of adjacent magnesium silicate layers are displaced by b/3 (about 3 Å) resulting in the Si atoms of one siloxane sheet being located above the center of the six-member ring across the interlayer. The water molecules are located 1.2 Å above the center of all six-member rings and accept H-bonds from the OH groups located below the rings. The b/3-displaced structure does not readily transform to either the talc-like or phlogopite-like structure, because neither of these stackings can accommodate two water molecules per formula unit. There is likely to be a compositional discontinuity and phase transition between the b/3-displaced phase and the phase with phlogopite-like stacking. The simulations reported here are the first to use the recently developed CLAYFF force field to calculate mineral structures at elevated pressures and temperatures.     

豫西济源谭庄组河流沉积中的Stipsellus遗迹组构

豫西济源盆地上三叠统谭庄组下段为曲流河沉积。本文通过描述和分析谭庄组河流沉积特征，划分了4种不同河流沉积组合类型，识别出Stipsellus遗迹组构，并发现该遗迹组构常与曲流河沉积物伴生，可作为此类沉积的典型生物遗迹标志。其中，Stipsellus sp．A代表发育在河漫滩较浅水体下或潮湿的软底细粒沉积物中的一种遗迹组构类型；Stipsellus sp．B则代表发育在曲流砂坝上部的男一种遗迹组构类型。     

Geochemical and isotopic characterization of trace fossil infillings: New insights on tracemaker activity after the K/Pg impact event

Geochemical and isotopic analyses of the Cretaceous–Paleogene (K/Pg) boundary deposits were conducted at the Caravaca section (External Subbetic, southeast of Spain) in order to evaluate the recovery of the macrobenthic tracemaker community and the bioturbational disturbance. Samples from the infilling material of several lower Danian dark-colored trace fossils (Chondrites, Planolites, Thalassinoides and Zoophycos) located in the uppermost 8-cm of the light upper Maastrichtian strata, as well as samples from the host sedimentary rock of these trace fossils, were analyzed and compared with data from the lower Danian deposits. The values of element ratios indicative of extraterrestrial contamination (Cr/Al, Co/Al and Ni/Al) are higher in the infilling trace fossil material than in the upper Maastrichtian and lower Danian deposits, which suggests a contribution of the ejecta layer. Regarding the isotope composition, the δ¹³C values are lower in the infilling material than in the Maastrichtian host sedimentary rocks surrounding the traces, while the δ¹⁸O are higher in the infilling material. The geochemical and isotopic compositions of the infilling material evidence the unconsolidated character of the sediment, including the red boundary layer. Softground conditions confirm a relatively rapid recovery by the macrobenthic tracemaker community, starting a few millimeters above the K/Pg boundary layer. The mixture of the infilling material of the trace fossils moreover reveals a significant macrobenthic tracemaker activity affecting K–Pg boundary transition sediments that may have significantly altered original signatures.     

Taenidium at the lower Barremian El Hoyo dinosaur tracksite (Teruel,Spain): Assessing palaeoenvironmental conditions for the invertebrate community

An analysis of lower Barremian invertebrate trace fossils at the El Hoyo dinosaur tracksite (Teruel, Spain) was conducted in order to interpret the macrobenthic tracemaker community and the palaeoenvironmental conditions during bioturbation. Abundant bioturbation structures are characterized by meniscate, cylindrical, straight to sinuous, unbranched epichnia, showing the absence of lining, mantle and longitudinal striations. These structures are included in the ichnogenus Taenidium. Burrow width, distance between menisci, type of their fill, and general shape, allow for identification of the ichnospecies Taenidium serpentinum and T. barretti. Dominance to near exclusiveness of Taenidium in the invertebrate trace fossil assemblage suggests assignation to the Scoyenia ichnofacies. This agrees with the presence of vertebrate tracks. Accordingly, a transitional zone between terrestrial and nonmarine aquatic environments, i.e., floodplain areas adjacent to rivers and affected by low energy conditions, could correspond to the El Hoyo site. The pervasive ichnofabric of Taenidium reveals an opportunistic behaviour of the tracemaker, bioturbating rapidly after deposition; bioturbation took place in moist to wet substrates—softgrounds—in shallow tiers, during favourable yet episodic conditions. The opportunistic strategy might owe to a rapid accumulation of nutrients buried within the sediment during alluvial discharges. After bioturbation, minor erosions during fluvial discharges or subaerial exposure may have caused differences in the preservation of the Taenidium.     

从平衡-封闭-静态转向非平衡-开放-动力学研究-热液矿床成因的若干新概念概述

热液金属矿床成因研究过程中,观测与实验始终是密切结合的。上世纪70年代,平衡热力学的实验数据的快速积累,使人们用热力学理论计算可以预测和反演矿石和岩石的成因。但是,没有矿物-水溶液的反应速率数据,又没有与流体力学的结合,搞清楚矿石成因是困难的。七、八十年代,开始研究矿物与水溶液的反应动力学实验。科学家们开始瞄准了从平衡-封闭-静态转向非平衡-开放-动力学研究的这个大方向。1992年我们建立地球化学动力学开放研究实验室。研究高温高压矿物与水反应速率,发现固液的开放体系的自组织现象。实验发现温度影响矿物的各个元素反应速率改变,发现在跨越水临界态时矿物与水反应速率涨落、在近临界的气-液两相不混溶区一些金属进入气相、超临界流体的氧化作用及特别的溶剂性能影响矿物溶解性质。实验证实:临界态区流体与矿石成因有关。水岩相互作用的反应动力学实验温度从低温到550度,揭示矿石的金属来源、迁移、金属与蚀变分带机制。一大批大于300度的矿物与水反应动力学实验在国际界是少有报道的。九十年代,超高压的科学发展,与同步辐射光源的技术进步的结合,使固体地球科学又迈向了地球深内部。我们发展了高温高压流体性质的原位直测(测量850℃水溶液)红外谱,发现深部流体的新性质:气液两相流体的新结构,在临界温度区(300~400℃),水分子氢键网络的破坏受压力影响不大(23MPa~3GPa),同时,出现水的高电导率。研发新仪器为开放-流动-非平衡的反应动力学实验与极端条件下物质性质的直接观测结合,在科学前沿领域开辟了创新道路。     

基于18S和ITS-5.8S rDNA基因序列的白色霞水母(Cyanea nozakii)的分子鉴定与检测

采用通用引物PCR扩增法,测定了辽东湾海域的白色霞水母(Cyanea nozakii)螅状体、碟状体及水母体的18S以及ITS-5.8S r DNA序列,同时利用Gene Bank数据库中已有同源序列对其进行序列分析及系统分析。结果显示,白色霞水母3个个体的18S和ITS-5.8S r DNA序列完全一致。白色霞水母样品的ITS-5.8S r DNA序列与Gen Bank中未知真核生物的序列高度相似(≥99%),推测该物种可能是早期发育阶段(卵、浮浪幼虫或碟状体)的白色霞水母样品。霞水母属不同种间18S r DNA序列经比对后同源序列长度为1709bp,多态位点数33个;比对后ITS1同源序列长度为368bp,其中变异位点203个,简约信息位点数178个,单变异位点21个。基于18S r DNA基因序列的霞水母属种内和种间平均遗传距离分别为0、0.008,而基于ITS1序列的霞水母属种内和种间平均遗传距离分别为0.019、0.284。基于ITS1的种间遗传距离是种内遗传距离的15倍,适合于进行物种鉴定。NJ系统树的结果也表明同种的不同个体各自聚枝,其聚类结果大致与形态分类吻合。研究表明,ITS基因片段在霞水母不同种间变异较大,更适于大型水母种类鉴定、检测及属内种间水平的系统进化研究。     

利用父母本微卫星标记估计大菱鲆(Scophthalmus maximus L.)幼鱼生长性状的遗传参数

The estimation of genetic parameters has played an important role in animal selective breeding for growth traits.Recently studies show that molecular markers can be incorporated into genetic evaluations. In order to improve the performance of an incomplete pedigree(i.e, only parents are known) in the genetic evaluations, 12 microsatellite markers have been applied in the estimation of the genetic parameters for body weight in a farmed population(n=1 890) of juvenile turbot(Scophthalmus maximus L.). A new relatedness called parental molecular relatedness(PMR) is estimated based on results of genotyping of 48 parents(31 males, 17 females) with microsatellites markers. The feasibility of PMR in estimation of genetic parameters is verified by comparison with pedigree related(PR) which is obtained from a complete pedigree. The results demonstrate that a high correlation(0.872) between them is found. Heritabilities are estimated using the PMR(0.52±0.13) and PR(0.55±0.22) with the same animal model. A cross-validation shows that the predictive abilities of models using the PMR and the PR are identical(0.81). From that, a conclusion can be made that PMR and PR predicted genetic values equally well in a population of juvenile turbot. Therefore PMR can be applied as an alternative of the PR when only parents are known. However, for a better performance, more markers and more families should be included in a further study.     

西藏塔惹增地区下白垩统捷嘎组的厘定及其地质意义

笔者于西藏仲巴县塔惹增地区一带前人划分的一套早白垩世早期则弄群中发现了具有典型意义的、代表早白垩世晚期的Ampullina xainzaensis Yu,Ampullina cf. larteli Landerer,Tylostoma cf. brasilianus Maury,Pseudamaura cf. subfournaeti (Pcelincev),Gyrodes gaultiana Orbigny,Leviathania cf. gerassimovi(Pcelincev),Gymnentome cf. pizcuetana(Vilanova)等腹足类化石,以及较为丰富的中圆笠虫Mesorbitolina sp.和达克斯虫Daxia sp。表明在该区则弄群中至少有一部分以前没有被识别出的早白垩世晚期地层。通过岩石组合特征、基本层序、生物化石时代对比,将该套地层归属于捷嘎组。这一地层的确定为冈底斯带白垩系地层划分对比、地层格架建立提供了重要的依据,并丰富了该地层的古生物资料,且为中生代盆地的演化历史、古地理轮廓的确定提供了新的基础资料。