A detailed abundance analysis of the hot post-AGB star ZNG-1 in M10     

C.J. Mooney  W.R.J. Rolleston  F.P. Keenan  P.L. Dufton  D.L. Pollacco  H.R. Magee 《Monthly notices of the Royal Astronomical Society》2001,326(3):1101-1109

We present a model-atmosphere analysis for the bright ( V ∼13) star ZNG-1, in the globular cluster M10. From high-resolution ( R ∼40 000) optical spectra we confirm ZNG-1 to be a post-asymptotic giant branch (post-AGB) star. The derived atmospheric parameters are T _eff=26 500±1000 K and log  g =3.6±0.2 dex . A differential abundance analysis reveals a chemical composition typical of hot post-AGB objects, with ZNG-1 being generally metal poor, although helium is approximately solar. The most interesting feature is the large carbon underabundance of more than 1.3 dex. This carbon deficiency, along with an observed nitrogen enhancement relative to other elements, may suggest that ZNG-1 evolved off the AGB before the third dredge-up occurred. Also, iron depletions observed in other similar stars suggest that gas–dust fractionation in the AGB progenitor could be responsible for the observed composition of these objects. However, we need not invoke either scenario since the chemical composition of ZNG-1 is in good agreement with abundances found for a Population II star of the same metallicity.  相似文献   

大伙房水库及浑河1∶2000水下地形测量项目的开展     

邰占宇 《测绘与空间地理信息》2017,40(5)

主要介绍了大伙房水库及浑河水下地形测量项目开展的工作要点与作业流程,着重对实际测绘过程中发现的问题及处理方法进行了系统的论述。  相似文献   

案例推理的制图综合应用背景与方法     

何海威  钱海忠  刘闯  谢丽敏 《测绘科学技术学报》2017,34(4)

从挖掘和利用经验数据的角度出发,提出了基于案例推理的智能化制图综合方法。首先探讨了基于算法和模型的自动综合实现方式所面临的瓶颈,并提出了采用制图综合案例推理辅助制图综合的思想;然后设计了制图综合专家案例的三元表示方法,以及获取、使用和管理流程;最后对实现该基于案例推理的智能化制图综合方法的五个关键性步骤进行了分析,并深入阐述该方法的原理和可行性,提出了基于案例推理的智能综合辅助系统架构。  相似文献   

A STUDY OF RAPID DECAY TYPHOONS IN OFFSHORE WATERS OF CHINA     

郑峰  曾智华  雷小途  陈联寿  杨涛  朱景 《热带气象学报(英文版)》2017,23(4):471-480

On the basis of NCEP/NCAR reanalysis data and yearbooks of CMA tropical cyclones, statistical analysis is performed for 1949—2013 offshore typhoons subjected to rapid decay(RD). This analysis indicates that RD typhoons are small-probability events, making up about 2.2% of the total offshore typhoons during this period. The RD events experience a decadal variation, mostly in the 1960 s and 1970 s(maximal in the 1970 s), rapidly decrease in the 1980 s and 1990 s and quickly increase from 2000. Also, RD typhoons show remarkable seasonal differences: they arise mainly in April and July-December, with the prime stage being in October-November. The offshore RD typhoons occur mostly in the South China Sea(SCS) and to a lesser extent in the East China Sea(ECS); however, none are observed over the Huang Sea and Bo Sea.Composite analysis and dynamic diagnosis of the RD typhoon-related large-scale circulations are performed.Physical quantities of the composite analysis consist of 500-h Pa height and temperature fields, vapor transfer, vertical wind shear(VWS), density of core convection(DCC), and high-level jet and upper-air outflow of the typhoon. The results suggest that(1) at the 500-h Pa height field, the typhoon is ahead of a westerly trough and under the effects of its passing trough;(2) at the temperature field, the typhoon is ahead of a temperature trough, with an invading cold tongue present;(3) at the vapor transfer field, water transfer into the RD typhoon is cut off; and(4) at higher levels, the related jet weakens and the outbreak of convection becomes attenuated in the typhoon core. In addition, VWS bears a relation to the RD typhoon; in particular, strong VWS favors RD occurrence.The differences in RD events between the SCS and ECS show that for the RD, the VWS of the ECS environmental winds is markedly stronger in comparison with its SCS counterpart. The cold advection invading into the typhoons is more intense in the SCS than in the ECS, and the low-level vapor transfer and high-level outflow are weaker in the SCS RD typhoons.Data analysis shows that sea surface temperature(SST), VWS, and DCC can be employed as efficient factors to predict RD occurrence. With appropriate SST, VWS, and DCC, a warning of RD occurrence can be given 36, 30-36,and 30 h, respectively, in advance. These values suggest that atmospheric SST responses lag. Owing to this time lag,the prediction of RD typhoons is possible.  相似文献   

氧化锰矿物的生物成因及其性质的研究进展   总被引：5，自引：0，他引：5  

刘凡  冯雄汉  陈秀华  邱国红  谭文峰  贺纪正 《地学前缘》2008,15(6):66

土壤中的氧化锰矿物是原生矿物风化和成土过程的产物,是最具反应活性的一类矿物,决定着环境中许多物质的形态、迁移和转化,在元素生物地球化学循环中起着重要的作用,其形成机制和环境效应备受关注。已有的研究表明,环境中氧化锰的形成与微生物作用紧密相关,微生物作用可使自然环境中的Mn(Ⅱ)氧化速率提高105倍。参与Mn(Ⅱ)氧化的微生物在环境中广泛存在,已知的典型锰氧化细菌分布在变形菌门、放线菌门或厚壁菌门,它们均通过胞外聚合物中的多铜氧化酶来催化氧化Mn(Ⅱ)。细菌氧化Mn(II)成Mn(Ⅳ)是酶催化的两个连续的快速单电子传递过程,Mn(Ⅲ)在溶液中以与酶结合的瞬时中间态出现。生物形成氧化锰的最初形态为层状锰矿物,与δ-MnO2或酸性水钠锰矿很类似,且结晶弱,粒径小,锰氧化度高,结构中的八面体空穴多,因而比化学形成的氧化锰具有更强的吸附、氧化等表面活性。环境中Mn(Ⅱ)微生物氧化及形成的Mn(Ⅲ)中间体与碳、氮、硫等生命元素的地球化学循环的关系令人关注。  相似文献   

Iodine budget in surface waters from Atacama: Natural and anthropogenic iodine sources revealed by halogen geochemistry and iodine-129 isotopes     

《Applied Geochemistry》2016

Iodine enrichment in the Atacama Desert of northern Chile is widespread and varies significantly between reservoirs, including nitrate-rich “caliche” soils, supergene Cu deposits and marine sedimentary rocks. Recent studies have suggested that groundwater has played a key role in the remobilization, transport and deposition of iodine in Atacama over scales of millions-of-years. However, and considering that natural waters are also anomalously enriched in iodine in the region, the relative source contributions of iodine in the waters and its extent of mixing remain unconstrained. In this study we provide new halogen data and isotopic ratios of iodine (¹²⁹I/I) in shallow seawater, rivers, salt lakes, cold and thermal spring water, rainwater and groundwater that help to constrain the relative influence of meteoric, marine and crustal sources in the Atacama waters. Iodine concentrations in surface and ground waters range between 0.35 μM and 26 μM in the Tarapacá region and between 0.25 μM and 48 μM in the Antofagasta region, and show strong enrichment when compared with seawater concentrations (I = ∼0.4 μM). In contrast, no bromine enrichment is detected (1.3–45.7 μM for Tarapacá and 1.7–87.4 μM for Antofagasta) relative to seawater (Br = ∼600 μM). These data, coupled to the high I/Cl and low Br/Cl ratios are indicative of an organic-rich sedimentary source (related with an “initial” fluid) that interacted with meteoric water to produce a mixed fluid, and preclude an exclusively seawater origin for iodine in Atacama natural waters. Iodine isotopic ratios (¹²⁹I/I) are consistent with halogen chemistry and confirm that most of the iodine present in natural waters derives from a deep initial fluid source (i.e., groundwater which has interacted with Jurassic marine basement), with variable influence of at least one atmospheric or meteoric source. Samples with the lowest isotopic ratios (¹²⁹I/I from ∼215 to ∼1000 × 10⁻¹⁵) strongly suggest mixing between the groundwater and iodine storage in organic-rich rocks (with variable influence of volcanic fluids) and pre-anthropogenic meteoric water, while samples with higher values (∼2000–93,700 × 10⁻¹⁵) indicate the input of anthropogenic meteoric fluid. Taking into account the geological, hydrologic and climatic features of the Atacama region, we propose that the mean contribution of anthropogenic ¹²⁹I is associated with ¹²⁹I releases during nuclear weapon tests carried out in the central Pacific Ocean until the mid 1990's (¹²⁹I/I = ∼12,000 × 10⁻¹⁵). This source reflects rapid redistribution of this radioisotope on a global scale. Our results support the notion of a long-lived continental iodine cycle in the hyperarid margin of western South America, which is driven by local hydrological and climate conditions, and confirm that groundwater was a key agent for iodine remobilization and formation of the extensive iodine-rich soils of Atacama.  相似文献   

Re-parameterization of a quasi-analytical algorithm for colored dissolved organic matter dominant inland waters     

《International Journal of Applied Earth Observation and Geoinformation》2016

Quasi-Analytical Algorithms (QAAs) are based on radiative transfer equations and have been used to derive inherent optical properties (IOPs) from the above surface remote sensing reflectance (R_rs) in aquatic systems in which phytoplankton is the dominant optically active constituents (OACs). However, Colored Dissolved Organic Matter (CDOM) and Non Algal Particles (NAP) can also be dominant OACs in water bodies and till now a QAA has not been parametrized for these aquatic systems. In this study, we compared the performance of three widely used QAAs in two CDOM dominated aquatic systems which were unsuccessful in retrieving the spectral shape of IOPS and produced minimum errors of 350% for the total absorption coefficient (a), 39% for colored dissolved matter absorption coefficient (a_CDM) and 7566.33% for phytoplankton absorption coefficient (a_phy). We re-parameterized a QAA for CDOM dominated (hereafter QAA_CDOM) waters which was able to not only achieve the spectral shape of the OACs absorption coefficients but also brought the error magnitude to a reasonable level. The average errors found for the 400–750 nm range were 30.71 and 14.51 for a, 14.89 and 8.95 for a_CDM and 25.90 and 29.76 for a_phy in Funil and Itumbiara Reservoirs, Brazil respectively. Although QAA_CDOM showed significant promise for retrieving IOPs in CDOM dominated waters, results indicated further tuning is needed in the estimation of a(λ) and a_phy(λ). Successful retrieval of the absorption coefficients by QAA_CDOM would be very useful in monitoring the spatio-temporal variability of IOPS in CDOM dominated waters.  相似文献   

夏季辽东湾西部海域大型底栖动物群落结构与多样性   总被引：1，自引：0，他引：1       下载免费PDF全文

王智  曲方圆  隋吉星  王振钟  季相星  赵宁  于子山 《海洋科学》2016,40(1):40-47

为了解夏季辽东湾西部海域大型底栖动物群落结构与多样性,作者于2009年8月对六股河口外海域15个站位进行了大型底栖动物调查。整个研究海域共采到大型底栖动物124种,其总平均丰度为(2824±1537)个/m2,总平均生物量为(22.01±38.58)g/m2。利用相对重要性指数和优势度指数所确定的前三位优势种一致,分别为二齿半尖额涟虫(Hemileucon bidentatus)、深钩毛虫(Sigambra bassi)和独指虫(Aricidea fragilis),其余优势种存在细微差异。各站位香农-维纳多样性指数、Pielou均匀度指数和Margalef丰富度指数均呈现河口和中部海域低,近岸和外围海域高的分布规律。在50%相似度水平上,可将研究海域划分为4个群落。研究结果表明:研究海域底栖环境整体清洁,底层水环境因子对大型底栖动物群落的影响较弱。  相似文献   

北大西洋大青鲨渔业生物学初步研究     

高春霞  戴小杰  田思泉  吴峰 《海洋科学》2016,40(10):55-62

大青鲨(Prionace glauca)是金枪鱼延绳钓渔业中最主要的兼捕鱼种之一,作为海洋生物链的顶端物种对海洋生态系统的稳定性和多样性起到了重要作用。作者根据中国金枪鱼渔业科学观察员在北大西洋海域(3°~55°N,15°~40°W)采集的2 112尾大青鲨数据,按不同性别对其渔业生物学特征进行初步研究。结果表明:雌、雄大青鲨的优势叉长组分别为180~220 cm、190~230 cm,雄性叉长均值显著大于雌性,雌、雄性比符合1︰1;大青鲨叉长-全长、尾凹长-全长的线性关系分别为L_F=0.8008L_T+7.3361,L_P=0.7576L_T–1.8479;北大西洋热带海域(3°~13°N)兼捕的大青鲨群体组成以大个体为主(180~240 cm),冰岛附近海域(48°~51°N)兼捕的大青鲨群体组成以小个体为主(100~210 cm);大青鲨叉长和质量关系式为W_R=7×10~(–6)L_F~(2.9994);大青鲨肝脏为性腺的发育提供能量,成熟个体的肝质量指数显著小于未成熟个体;热带海域兼捕的大青鲨以性成熟个体为主(96.9%),冰岛海域兼捕的大青鲨以未成熟个体居多(77.1%);50%雌性性成熟个体对应的叉长为178.7 cm,50%雄性性成熟个体对应叉长为173.6 cm;雌性怀仔大青鲨的叉长与其怀仔数量线性关系为L_S=0.419×L_F–49.7(R~2=0.3905),幼仔雌雄性比符合1︰1;胃含物中以沙丁鱼和鱿鱼出现频率最高。作者的研究有助于更好地了解北大西洋大青鲨的生物学特征,为区域性渔业管理组织评估大青鲨种群资源状态提供数据参考。  相似文献   

数字地形分析应用适配性知识的案例表达与推理方法     

吴雪薇  秦承志  朱阿兴 《地理科学进展》2016,35(1):89-97

数字地形分析(Digital Terrain Analysis, DTA)在应用时依赖于建模知识,尤其是关于所建的应用模型是否与研究区特点、数据等条件相适配的知识(称为“应用适配性知识”);由于这类知识难以形式化表达,现有的数字地形分析工具对此类知识缺乏利用,从而导致普通用户在应用数字地形分析时建模困难。针对该问题,设计了一套数字地形分析领域应用适配性知识的案例表达与相应的推理方法。以美国32个河网提取案例为例,通过交叉验证,初步表明案例及其推理应用方法适合于数字地形分析领域应用适配性知识的形式化表达与应用,该方法通过与建模环境的集成,可大幅降低数字地形分析应用建模难度。  相似文献