九孔鲍MSTN基因cSNP多态性及与生长性状关联分析   总被引：1，自引：0，他引：1  

艾加林  栗志民  刘建勇  申玉春 《热带海洋学报》2019,38(2):78-85

九孔鲍(Haliotis diversicolor supertexta)是中国南方具有较高经济价值的养殖贝类。肌肉生长抑制素(Myostatin, MSTN)是转化生长因子β超家族(TGF-β)中参与动物肌肉生长的重要调控因子, 因此MSTN基因是动物遗传改良的重要候选基因。为探究九孔鲍MSTN基因的多态性及其生长相关性, 实验采用PCR产物直接测序方法对九孔鲍MSTN基因进行单核苷酸多态性(SNP)筛选, 对MSTN基因SNP与体质量、壳长、壳宽进行关联性分析, 运用实时荧光定量PCR (qRT-PCR)技术检测九孔鲍MSTN基因不同基因型的表达水平。结果显示: 在九孔鲍MSTN基因中共筛选出9个SNP位点。SNP位点与生长性状关联分析发现, 九孔鲍MSTN基因编码区SNP位点g909C>T发生C/T同义突变与九孔鲍体质量、壳长、壳宽显著相关。TT基因型九孔鲍的体质量显著高于CC基因型和TC基因型个体; TT基因型的壳长、壳宽显著高于CC基因型(p<0.05)。通过qRT-PCR检测显示, 在九孔鲍MSTN基因SNP位点g909C>T的3种基因型中, TC和CC基因型的基因表达量显著高于TT基因型(p<0.05)。研究结果表明MSTN基因SNP位点g909C>T可作为九孔鲍标记辅助选择育种重要候选标记。  相似文献   

Formation of Carbon-Enhanced Metal-Poor RR Lyrae Stars     

《Chinese Astronomy and Astrophysics》2020,44(1):61-69

Carbon-enhanced metal-poor (CEMP) stars are considered to be related to the first generation of stars, and responsible for the chemical evolution of the early Galaxy. More than half of them are in binaries, and could be explained by the binary evolution, but the formation channel of them is still not fully understood. Among the hundreds of CEMP stars, there are nine CEMP RR Lyrae stars identified, and at least seven of which are very likely not binaries. The usual binary star evolution channel is difficult to produce such a single star, particularly that of carbon enrichment. One way in which such a single star might be produced is the merger of a helium white dwarf with a Hertzsprung gap (HG) star. We use a stellar evolution program to calculate the models of the merger remnants, and find that the models can reproduce the observed distribution of these CEMP single RR Lyrae stars in terms of surface temperature, gravity, and carbon abundance. Hence, it is extremely possible that the helium white dwarf and HG star merger model is one of the formation channels of the metal-poor carbon-rich RR Lyrae stars.  相似文献   

江苏海岸中部近岸冬季潮汐和潮流特征     

王逸涵  王韫玮  于谦  蔡辉  高抒 《海洋科学》2019,43(10):66-74

南黄海西侧的江苏海岸近岸区域,素以地形复杂、潮流强劲、悬沙输运剧烈著称,但是较长期的同步潮位和潮流观测数据仍然缺乏,尤其是在近岸(20 km)浅水(20 m)区域。2014年1月在大丰港附近开展了连续潮位和潮流观测,获得的数据揭示了一系列特征。此地潮汐潮流为正规半日潮,浅水分潮显著。平均潮差为3.05 m,最显著的两个分潮为M2和S2分潮,振幅分别为1.45 m和0.52 m。潮流最显著的半日分潮M2分潮和最显著的浅水分潮M4分潮在沿岸方向上振幅分别为0.84m/s和0.12m/s,在跨岸方向上振幅分别为0.24 m/s和0.01 m/s,沿岸方向占绝对优势。潮波的沿岸传播介于前进波和驻波之间,驻波的特征稍强。M2分潮潮流椭圆最大流(长轴)方向为南偏东7.4°。存在冬季沿岸向北的余流,垂向平均值的大小为2.2 cm/s。以上潮汐潮流特征为该区域海洋物质输运研究提供了基础资料。  相似文献   

Research on the Methods of Performance Monitoring and Evaluation for Active Hydrogen Maserstwo     

《Chinese Astronomy and Astrophysics》2019,43(2):292-304

Active hydrogen maser is the main frequency standard for establishing and maintaining the time scale. It has the characteristics of high short-term stability and low phase noise. At present, it plays an increasingly important role in the international atomic time (TAI) and various local time scales. Firstly, in combination with the internal state parameters of an active hydrogen maser, the correlation between the internal state parameters and the comparison data of a hydrogen maser is analyzed, and a method for the performance monitoring of a hydrogen maser is proposed. Secondly, according to the characteristics of hydrogen maser performance, a method for evaluating the performance of a hydrogen maser is given. The hydrogen maser performance includes mainly two aspects, namely the frequency stability and predictability. The performances of two types of active hydrogen masers (CH1-75 and MHM-2010) are evaluated by this method. The correlation analysis of the atomic clock state parameters and comparison data shows that the state parameter monitoring can effectively predict the variation of the hydrogen maser performance. The evaluation results of atomic clock frequency stability and predictability show that the atomic clock with a higher medium-and-long term frequency stability has a better predictability. There are two methods for the predictability evaluation, one is based on the data published by BIPM (Bureau International des Poids et Measures), and another one is based on the quadratic model. Both methods are consistent with the weights published by BIPM. Therefore, the two methods can be used as a quantitative method to evaluate the predictability of a hydrogen maser.  相似文献   

基于历史TLE的空间目标轨道预报误差演化规律研究     

许晓丽  熊永清 《天文学报》2019,60(4):26-38

北美防空司令部(North American Aerospace Defense Command, NORAD)发布的双行根数(Two Line Element, TLE)是广大航天工作者最常用的轨道根数,与其对应的轨道模型是SGP4/SDP4 (Simplified General Perturbation Version 4/Simplified Deep-space Perturbation Version 4)解析模型.由于TLE中并没有包含相应的轨道精度信息,编目轨道的应用范围受到很大的限制.基于Space-Track网站发布的历史TLE数据和配套的SGP4/SDP4动力学模型,采用定轨标预报的方法统计并生成了大量目标轨道的预报误差,通过对预报轨道的时间区间划分给出了每个目标的预报误差随预报时间变化的拟合系数,并进一步对不同类型轨道预报误差的演化规律和特征进行了分类讨论,给出了4种轨道类型目标的轨道预报误差随时间演化的平均解析模型,为拓展双行根数的应用提供有价值的参考.  相似文献   

Study of Star/Galaxy Classification Based on the XGBoost Algorithm     

《Chinese Astronomy and Astrophysics》2019,43(4):539-548

Machine learning has achieved great success in many areas today. The lifting algorithm has a strong ability to adapt to various scenarios with a high accuracy, and has played a great role in many fields. But in astronomy, the application of lifting algorithms is still rare. In response to the low classification accuracy of the dark star/galaxy source set in the Sloan Digital Sky Survey (SDSS), a new research result of machine learning, eXtreme Gradient Boosting (XGBoost), has been introduced. The complete photometric data set is obtained from the SDSS-DR7, and divided into a bright source set and a dark source set according to the star magnitude. Firstly, the ten-fold cross-validation method is used for the bright source set and the dark source set respectively, and the XGBoost algorithm is used to establish the star/galaxy classification model. Then, the grid search and other methods are used to adjust the XGBoost parameters. Finally, based on the galaxy classification accuracy and other indicators, the classification results are analyzed, by comparing with the models of function tree (FT), Adaptive boosting (Adaboost), Random Forest (RF), Gradient Boosting Decision Tree (GBDT), Stacked Denoising AutoEncoders (SDAE), and Deep Belief Nets (DBN). The experimental results show that, the XGBoost improves the classification accuracy of galaxies in the dark source classification by nearly 10% as compared to the function tree algorithm, and improves the classification accuracy of sources with the darkest magnitudes in the dark source set by nearly 5% as compared to the function tree algorithm. Compared with other traditional machine learning algorithms and deep neural networks, the XGBoost also has different degrees of improvement.  相似文献   

Granite is an Effective Helium Source Rock: Insights from the Helium Generation and Release Characteristics in Granites from the North Qinling Orogen, China     

ZHANG Wen  LI Yuhong  ZHAO Fenghu  ZHOU Zheng  HAN Wei  ZHOU Junlin  ZHANG Qiao 《《地质学报》英文版》2020,94(1):114-125

Global helium(He) shortage is a challenging problem; however, the types of helium source rock and the mechanisms of He generation and release therein remain still poorly understood. In this study, in order to evaluate the potential of granite as an effective helium source rock, we collected granitic samples from the North Qinling Orogen, Central China, in the south of the helium-rich Weihe Basin. The helium generation and release behaviors in granite were studied through analysis of U and Th concentrations, EMPA images, and He and Ar concentrations and isotopic ratios extracted by crushing and stepwise heating. The results indicate that Ar has a better retention and a lower mobility than He. 3 He/4 He ratios released by crushing and stepwise heating are 0.016–0.056 RA and 0.003–0.572 RA, respectively, where RA is the atmospheric 3 He/4 He of 1.4×10-6, reflecting a crustal and radiogenic source. Helium concentrations extracted by the two ways are 0.13–0.95 ucm3 STP/g and 7.82–115.62 ucm3 STP/g, respectively, suggesting that matrix-sited He accounts for more than 98% of total helium preserved in granite. In addition, the total generated He amounts in granites are calculated based on the measured U and Th concentrations in granitic samples. Dividing the preserved He quantities by the generated He amounts, it turned out that less than 10% of He produced since the formation of the granite is preserved in the rock over geological time, suggesting that more than 90% generated He can be transferred to the Weihe Basin. Temperature and fracture are the two critical factors controlling He release. Based on the relationship between He diffusivity of granites and temperature and the He closure temperatures of a variety of U-and Th-rich minerals(27–250°C), we estimate that He can be partially released out of granite at the depths 400 m and totally released at the depths 7800 m. Fractures provide effective transfer of free He from deep source rocks to shallow reservoirs. Finally, a model on granite as an effective helium source rock is established. We suggest exploring He resources in hydrocarbon basins with granitic basement(or adjacent to granite bodies), high geothermal field, and young active fractures.  相似文献   

滇东南南秧田钨矿床白钨矿原位Sr同位素对成矿的指示     

王忠强  李超  张定才  江小均  周利敏  严清高 《岩矿测试》2020,39(2):285-299

南秧田钨矿床位于滇东南老君山W-Sn矿集区,地处扬子地块和印支地块的结合部位,地质背景复杂并遭受了多期岩浆活动和区域变质事件,其成矿时代和成因一直存在争议。本文对矽卡岩型和长石-石英脉型白钨矿开展了年代学、原位微量元素、Sr同位素研究,分析了两类白钨矿年龄、成因以及物质来源的差异。结果表明,长石-石英脉内与白钨矿共生辉钼矿的Re-Os同位素等时线年龄为151.0±1.3Ma,明显晚于矽卡岩矿体年龄,属于后期成矿事件。矽卡岩型白钨矿的轻稀土富集、重稀土强烈亏损,Eu呈明显负异常(δEu=0.46),∑REE平均含量为65.60μg/g,Mo平均含量为240.16μg/g,Sr平均含量为883.43μg/g;长石-石英脉型白钨矿稀土呈Eu正异常(δEu=2.8)的平坦型,∑REE平均含量为194.40μg/g,Mo平均含量为16.01μg/g,Sr平均含量为129.26μg/g。以上两者微量、稀土元素含量的差别显示它们具有性质明显不同的流体来源,Eu异常指示矽卡岩型白钨矿形成于氧逸度较高的环境,长石-石英脉型白钨矿形成于还原性环境。矽卡岩白钨矿~(87)Sr/~(86)Sr值相对较低,并且比较均一,介于0.71319～0.71491之间,表明成矿流体主要来自岩浆热液;长石-石英脉型白钨矿~(87)Sr/~(86)Sr值较高且变化范围大,介于0.71537～0.72803之间,平均0.72079,呈现出变质流体特征。两种不同类型白钨矿Sr同位素都具有二元混合的特征,显示长石-石英脉型白钨矿对矽卡岩型白钨矿有叠加改造作用,成矿流体与围岩的强烈交代作用是白钨矿形成的关键。  相似文献   

基于条件平差的卫星双向时间传递链路性能优化方法          下载免费PDF全文

王翔  宋会杰  王威雄  高喆  张继海  武文俊  董绍武 《天文学报》2020,61(3):25

卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)是目前精度最高的时间传递方法之一,同时也是参与国际原子时计算的守时实验室之间比较原子时尺度的一种主要方法.提高TWSTFT链路的短期稳定度,降低周日效应对链路时间传递结果的影响,对优化TAI (International Atomic Time)的性能具有现实意义.提出了一种基于条件平差的TWSTFT链路性能优化方法,先依据TWSTFT链路测量噪声水平与谱分析结果建立TWSTFT链路性能优化网络(简称优化网络),再根据优化网络中各链路测量噪声分析结果设置权系数阵,建立条件平差模型.选取亚太地区的中国计量科学研究院(National Institute of Metrology, NIM)-中国科学院国家授时中心(National Time Service Center, NTSC)卫星双向时间传递链路作为待优化链路,以NTSC、NIM以及德国联邦物理技术研究所(Physikalisch-Technische Bundesanstalt,PTB)之间的TWSTFT链路组成优化网络,对优化网络的组网方法和条件平差模型进行实验验证.结果表明,平差后待优化链路短期稳定度得到了改善,同时其受周日效应的影响降低了约24.6%.使用该方法,能够有效提高待优化链路的时间传递性能.  相似文献   

山东半岛南北两侧海域真核浮游生物群落特征及与环境因子的相关性分析   总被引：1，自引：0，他引：1  

刘朋超  王卫军  骆启豪  李彬  孙国华  赵强  张金浩  杨建敏 《海洋与湖沼》2019,50(4):876-885

为了解山东半岛南北两侧的烟台崆峒岛(KTD)海域和日照东港(DG)海域真核浮游生物群落特征,采用高通量测序技术,以18S rDNA V4区为目标基因,对2017年10月至2018年7月两海域的真核浮游生物多样性进行了检测;同期测定两海域的环境因子(溶解氧、氨氮含量等10个理化指标),并与真核浮游生物丰富度做相关性分析。实验结果表明:通过高通量测序技术共鉴定出浮游生物455种,其中,KTD海域共检测出真核浮游生物36个门类424种;DG海域共检测出真核浮游生物34个门类365种。绿藻门(Chlorophyta)、硅藻门(Diatomea)是两海域浮游植物中整体丰度最高的门类。KTD海域,绿藻门各月丰度在3.0%—21.3%之间,其中2018年7月(K1807)最高,达到了21.3%;硅藻门各月丰度在2.0%—16.59%之间,其中2018年2月(K1802)最高,达到了16.59%。DG海域,绿藻门各月丰度在2.0%—12.3%之间,其中2017年11月份(D1711)最高,达到了12.3%;硅藻门各月丰度在2.0%—47.0%之间,其中1月(D1801)最高,达到了47.0%。占优势地位的浮游动物主要是节肢动物门类的物种,其每月丰度分别在6.0%—38.9%和7.6%—48.6%之间。环境因子相关性分析表明水温、DO、pH、硅酸盐、硝酸盐氮等环境因子为影响该海域浮游生物群落结构的主要因子。研究结果对了解双壳经济贝类养殖区饵料组成及其在时空的变化,对海岸带食物网、生态基础管理和海洋经济贝类养殖生产等方面提供数据支撑。  相似文献