超慢速扩张环境下超镁铁质岩系统的热液硫化物成矿机理以及启示

西南印度洋63.5°E热液区是在超慢速扩张洋脊发现的首个超镁铁质岩热液系统。对取自该区的热液硫化物样品进行了系统的矿物学和地球化学分析,矿物学分析结果表明:该热液区硫化物为富Fe型高温硫化物,且经历了较深程度的氧化蚀变,大量中间态的Fe氧化物充填在硫化物矿物间的孔隙及内部解理中;这些硫化物相以白铁矿为主,其次是等轴古巴矿和少量铜蓝,缺乏黄铁矿、闪锌矿。据推断,该区的热液成矿作用分为4个阶段:低温白铁矿阶段→高温等轴古巴矿阶段→自形白铁矿阶段→后期海底风化阶段（少量铜蓝以及大量的Fe的羟氧化物）。与之相对应,地球化学分析结果表明这些硫化物的Fe含量较高（31.57%~44.59%）,Cu含量次之（0.16%~7.24%）,而Zn含量普遍较低（0.01%~0.11%）;微量元素较为富集Co（328×10-6~2 400×10-6）和Mn（48.5×10-6~1 730×10-6）。该区硫化物中较高含量的Fe、Co与超镁铁质岩热液系统相似,明显高于镁铁质岩热液系统。独特的热液硫化物矿物学特征和元素组成可能与该区普遍出露的地幔岩、橄榄岩蛇纹石化作用以及拆离断层的广泛发育的环境有关。     

潮流界以下河段航道整治水位确定方法研究——以长江江阴以下河段为例

在总结分析现有整治水位确定方法的基础上,根据潮流界以下河段的水沙运动特性,本文提出一种基于输沙能力的航道整治水位确定方法。考虑上游来水、下游潮汐为独立事件,统计潮流界以下河段上游来水、下游潮汐不同等级组合出现的频率,采用数学模型计算相应组合下河段沿程的潮位、流速过程,以流速四次方代表水流的输沙能力,统计不同潮位等级对应的综合净输沙能力,确定最大综合净输沙能力对应的水位为(最优)航道整治水位。以长江下游白茆沙水道和福姜沙水道为例,计算了所在河段的航道整治水位,并探讨了起动流速对整治水位计算的影响和最高整治水位概念对工程的意义。     

Numerical study of sand scour with a modified Eulerian model based on incipient motion theory

Application of the standard Eulerian model to simulations of sand scour results in unrealistic phenomena. Therefore, the present work develops a modified Eulerian model based on sand incipient motion theory. The modified model is applied for simulating a two-dimensional single vertical jet and a moving planar jet. The simulation results generally demonstrate fairly good agreement with published results of scour profiles and the velocity contours of the water and sand phases. In addition, equations to describe self-similar scour profiles for the moving planar jet cases are given. The results demonstrate that the modified model efficiently and accurately simulates the two-dimensional sand scour produced by jets, particularly for the moving jet cases.     

An algorithm to resolve γ-rays from charged cosmic rays with DAMPE

The DArk Matter Particle Explorer(DAMPE),also known as Wukong in China,which was launched on 2015 December 17,is a new high energy cosmic ray and γ-ray satellite-borne observatory.One of the main scientific goals of DAMPE is to observe Ge V-Te V high energy γ-rays with accurate energy,angular and time resolution,to indirectly search for dark matter particles and for the study of high energy astrophysics. Due to the comparatively higher fluxes of charged cosmic rays with respect to γ-rays,it is challenging to identify γ-rays with sufficiently high efficiency,minimizing the amount of charged cosmic ray contamination. In this work we present a method to identify γ-rays in DAMPE data based on Monte Carlo simulations,using the powerful electromagnetic/hadronic shower discrimination provided by the calorimeter and the veto detection of charged particles provided by the plastic scintillation detector. Monte Carlo simulations show that after this selection the number of electrons and protons that contaminate the selected γ-ray events at～10 Ge V amounts to less than 1% of the selected sample.Finally,we use flight data to verify the effectiveness of the method by highlighting known γ-ray sources in the sky and by reconstructing preliminary light curves of the Geminga pulsar.     

LAMOST CCD camera-control system based on RTS2

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) is the largest existing spectroscopic survey telescope, having 32 scientific charge-coupled-device(CCD) cameras for acquiring spectra. Stability and automation of the camera-control software are essential, but cannot be provided by the existing system. The Remote Telescope System 2 nd Version(RTS2) is an open-source and automatic observatory-control system. However, all previous RTS2 applications were developed for small telescopes. This paper focuses on implementation of an RTS2-based camera-control system for the 32 CCDs of LAMOST. A virtual camera module inherited from the RTS2 camera module is built as a device component working on the RTS2 framework. To improve the controllability and robustness, a virtualized layer is designed using the master-slave software paradigm, and the virtual camera module is mapped to the 32 real cameras of LAMOST. The new system is deployed in the actual environment and experimentally tested. Finally, multiple observations are conducted using this new RTS2-frameworkbased control system. The new camera-control system is found to satisfy the requirements for automatic camera control in LAMOST. This is the first time that RTS2 has been applied to a large telescope, and provides a referential solution for full RTS2 introduction to the LAMOST observatory control system.     

PS Vir:a short-period solar-like contact binary

We present multi-color photometric observations and a one-dimensional spectrum, acquired from March 2016 to May 2017, for the short-period eclipsing binary PS Vir, by using the 2.16-m,85-cm and 60-cm telescopes at Xinglong station, which is administered by National Astronomical Observatories, Chinese Academy of Sciences. The spectral type was determined as G2V from the onedimensional spectrum. The photometric solution was reduced from BV Rc light curves. The results imply that PS Vir is a W-subtype contact binary with a mass ratio of q = 0.305(±0.008) and a fill-out factor of f = 14.4(±1.8)%. The orbital period may be undergoing a cyclic oscillation with an amplitude of A = 0.0027(±0.0001) d and a modulated period of 11.7(±0.2) yr, which may result from the light-time effect due to a third body. The lower limit on mass for the assumed component is 0.12 M⊙.Moreover, the more massive component of PS Vir may be a bit more evolved star as determined from the mass-luminosity diagram.     

Binary Star Fractions from the LAMOST DR4

Stellar systems composed of single, double, triple or higher-order systems are rightfully regarded as the fundamental building blocks of the Milky Way. Binary stars play an important role in formation and evolution of the Galaxy. Through comparing the radial velocity variations from multiepoch observations, we analyze the binary fraction of dwarf stars observed with LAMOST. Effects of different model assumptions, such as orbital period distributions on the estimate of binary fractions,are investigated. The results based on log-normal distribution of orbital periods reproduce the previous complete analyses better than the power-law distribution. We find that the binary fraction increases with Teff and decreases with [Fe/H]. We first investigate the relation between α-elements and binary fraction in such a large sample as provided by LAMOST. The old stars with high [α/Fe] dominate with a higher binary fraction than young stars with low [α/Fe]. At the same mass, earlier forming stars possess a higher binary fraction than newly forming ones, which may be related with evolution of the Galaxy.     

A Population Genetic Analysis of Continuously Selected Chlamys farreri Populations

This study applied an optimized one-step 2b-RAD library construction strategy and performed simplified genome sequencing of 539 individuals from three continuously selected Chlamys farreri populations. SNP screening was performed using RAD typing software and population genetic parameters for the continuously selected populations from three generations(G1, G2, G3) were determined. The results showed that the optimized one-step 2b-RAD library construction strategy greatly simplified the experimental process, making it suitable for efficiently constructing a large number of libraries. A total of 18450 SNP markers were identified, which evenly distributed throughout the genome. Population genetic analysis of these three generations showed that the mean value of observed heterozygosity was 0.275 ± 0.177, 0.272 ± 0.181 and 0.275 ± 0.166, respectively. Meanwhile, the mean value of expected heterozygosity was 0.275 ± 0.141, 0.274 ± 0.145 and 0.280 ± 0.133, respectively. The Wright's fixation index(F) was 0.04291, 0.04976 and 0.06685, respectively. Markers deviated from Hardy–Weinberg equilibrium accounted for 10.34%, 12.64%, and 23.11%, and the Shannon diversity index was 0.0999 ± 0.0404, 0.0921 ± 0.0388 and 0.0733 ± 0.0308. FIS(also known as the inbreeding coefficient) of the three populations was 0.0256, 0.0323 and 0.0468, respectively. We suggested that the 2b-RAD method is well suited to population genetic studies of aquacultured organisms. Moreover, our results indicated that the continuous selection affected the population genetic structure of the cultured Penglai-Red scallop, but the change was not significant; therefore, population selection should continue.     

Effects of feeding time on complement component C7 expression in Pelteobagrus vachellii subject to bacterial challenge

Journal of Oceanology and Limnology - Shifting the feeding time for fish from daytime to nighttime could alter their digestive behavior, disturb their metabolism, and may affect immune-related...     

Detrital apatite fission track constraints on Cenozoic tectonic evolution of the northeastern Qinghai-Tibet Plateau,China: Evidence from Cenozoic strata in Lulehe section,Northern Qaidam Basin

The Northern Qaidam Basin is located at the northeastern part of the Qinghai-Tibetan Plateau. It contains very thick Cenozoic terrestrial clastic sediments, which records the formation of the northern Qaidam Basin due to compressional deformation during the Indo-Asian collision. In this paper, we used detrital apatite fission-track thermochronology, including 4 sandstones and 2 conglomerates samples from the Lulehe section, to reveal the Cenozoic evolution of the northern Qaidam Basin. Fission-track dating indicated the source region of the Lulehe section has experienced important cooling and uplifting in the Late Cretaceous (at ~85.1 Ma and ~65 Ma) and the Eocene (~52 Ma), respectively. The AFT age distribution on the section suggested that the provenance of Lulehe section sediments were mainly derived from the south Qilian Shan (Qilian Mountains) and Altun Shan (Altun Mountains), and two significantly provenance changes may occur at 43.4-46.1 Ma and ~37.8 Ma, respectively. The results may have strong constrains on the Cenozoic deformation and tectonic evolution of the northern Qaidam Basin and Qinghai-Tibet Plateau.