A Statistical Model for Predicting the Average Abundance Patterns of Heavier Elements in Metal-Poor Stars     

Bo Zhang  Yan-Xia Zhang  Ji Li  Qiu-He Peng Department of Physics  Hebei Normal University  Shijiazhuang Center of Theoretical Nuclear Physics  National Laboratory of Heavy Ion Accelerator  Lanzhou National Astronomical Observatories  Chinese Academy of Sciences  Beijing Department of Astronomy  Nanjing University  Nanjing 《中国天文和天体物理学报》2002,2(5):429-440

We have collected nearly all the available observed data of the elements from Ba to Dy in halo and disk stars in the metallicity range -4.0 <[Fe/H]< 0.5. Based on the observed data of Ba and Eu, we evaluated the least-squares regressions of [Ba/Fe] on [Fe/H], and [Eu/H] on [Ba/H]. Assuming that the heavy elements (heavier than Ba) are produced by a combination of the main components of s- and r-processes in metal-poor stars, and choosing Ba and Eu as respective representative elements of the main s- and the main r-processes, a statistical model for predicting the Galactic chemical evolution of the heavy elements is presented. With this model, we calculate the mean abundance trends of the heavy elements La, Ce, Pr, Nd, Sm, and Dy with the metallicity. We compare our results with the observed data at various metallicities, showing that the predicted trends are in good agreement with the observed trends, at least for the metallicity range [Fe/H]> -2.5. Finally, we discuss our results and deduce some importa  相似文献   

High-resolution Keck I spectroscopy of Galactic halo post-asymptotic giant branch stars     

C. J. Mooney  W. R. J. Rolleston  F. P. Keenan  P. L. Dufton  J. V. Smoker  R. S. I. Ryans  L. H. Aller 《Monthly notices of the Royal Astronomical Society》2002,337(3):851-860

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Rural household demographics, livelihoods and the environment   总被引：8，自引：0，他引：8  

Alex de Sherbinin  Leah K. VanWey  Kendra McSweeney  Rimjhim Aggarwal  Alisson Barbieri  Sabine Henry  Lori M. Hunter  Wayne Twine  Robert Walker 《Global Environmental Change》2008,18(1):38-53

This paper reviews and synthesizes findings from scholarly work on linkages among rural household demographics, livelihoods and the environment. Using the livelihood approach as an organizing framework, we examine evidence on the multiple pathways linking environmental variables and the following demographic variables: fertility, migration, morbidity and mortality, and lifecycles. Although the review draws on studies from the entire developing world, we find the majority of microlevel studies have been conducted in either marginal (mountainous or arid) or frontier environments, especially Amazonia. Though the linkages are mediated by many complex and often context-specific factors, there is strong evidence that dependence on natural resources intensifies when households lose human and social capital through adult morbidity and mortality, and qualified evidence for the influence of environmental factors on household decision-making regarding fertility and migration. Two decades of research on lifecycles and land cover change at the farm level have yielded a number of insights about how households make use of different land-use and natural resource management strategies at different stages. A thread running throughout the review is the importance of managing risk through livelihood diversification, ensuring future income security, and culture-specific norms regarding appropriate and desirable activities and demographic responses. Recommendations for future research are provided.  相似文献   

The depletion of carbon by extra mixing in metal-poor giants     

Richard J. Stancliffe  Ross P. Church  George C. Angelou  John C. Lattanzio 《Monthly notices of the Royal Astronomical Society》2009,396(4):2313-2318

There is an apparent dichotomy between the metal-poor  ([Fe/H]≤−2)  yet carbon-normal giants and their carbon-rich counterparts. The former undergo significant depletion of carbon on the red giant branch after they have undergone first dredge-up, whereas the latter do not appear to experience significant depletion. We investigate this in the context that the extra mixing occurs via the thermohaline instability that arises due to the burning of  ³He  . We present the evolution of [C/Fe], [N/Fe] and  ¹²C/¹³C  for three models: a carbon-normal metal-poor star, and two stars that have accreted material from a  1.5 M_⊙  AGB companion, one having received  0.01 M_⊙  of material and the other having received  0.1 M_⊙  . We find the behaviour of the carbon-normal metal-poor stars is well reproduced by this mechanism. In addition, our models also show that the efficiency of carbon-depletion is significantly reduced in carbon-rich stars. This extra-mixing mechanism is able to reproduce the observed properties of both carbon-normal and carbon-rich stars.  相似文献   

Distinguishing breeding populations of mallards (Anas platyrhynchos) using trace elements     

Bindu Kaimal  Ronald Johnson  Robyn Hannigan 《Journal of Geochemical Exploration》2009

The knowledge of connectivity among breeding and overwintering populations of migratory bird species is critical for the conservation of their habitats. Conventional field work for the tracking of migratory birds involving bird banding often yields poor results due to low recovery rates, or is expensive when satellite tracking methods are used. Intrinsic tools such as genetic markers, stable isotopes, strontium isotopes and trace elements have been successfully used for tracing origins and/or migratory pathways of bird populations. We studied elemental signatures in the tail feathers to group breeding populations and an overwintering population of Mallards (Anas platyrhynchos). Tail feathers from five locations in Canada and the U.S. were analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We used 18 elements to discriminate between Mallard populations. Linear discriminant analysis on a selected set of elements demonstrated that 93% of the Mallards could be accurately located back to their predicted locations. Mallard feathers from Arkansas (an important overwintering area), grouped together with any combination of elements as predictors. We predicted the breeding locations of overwintering Mallards from Arkansas. Our results confirm that the LA-ICP-MS technique shows high potential to estimate the origin of migratory animals.  相似文献   

代表性人口空间分布数据集的精度评价——以2010年广东省为例   总被引：1，自引：0，他引：1  

林丹淳  谭敏  刘凯  柳林  朱远辉 《热带地理》2020,40(2):346-356

以人口密度差异显著的广东省为研究区,比较Worldpop、GPW v4和2种中国公里网格人口分布数据集的空间分布一致性,并以第六次全国人口普查数据为真值,按人口密度分为高、中、低3组,从误差的数值分布和空间分布两方面定量评价4种数据集的精度,最后讨论估算误差的可能来源及数据适用性。结果表明,4种网格人口数据集中Worldpop整体精度最高,且在人口密集区的精度也是最高;GPW v4在低人口密度和中人口密度区域精度略高于Worldpop,但对镇街内人口分布细节刻画不够详细;2种中国公里网格人口分布数据集精度较前两者低,主要受空间化方法和模型变量的选择所限制。Worldpop适合用于人口密度中等及人口密度高区域的精细化研究,GPW v4适合用于长时序、最小研究单元大于镇街的研究,第一种中国公里网格人口分布数据集适合用于需要考虑镇街内人口分布和空间异质性的研究,第二种中国公里网格人口分布数据集适用于需要考虑人口分布细节和空间格局变化的长时序研究。  相似文献   

Integration of nighttime light remote sensing images and taxi GPS tracking data for population surface enhancement     

Bailang Yu  Ting Lian  Yixiu Huang  Xinyue Ye  Zuoqi Chen 《International journal of geographical information science》2019,33(4):687-706

The population distribution grid at fine scales better reflects the distribution of residents and plays an important role in investigating urban systems. The recent years have witnessed a growing trend of applying the nighttime light data to the estimation of population at micro levels. However, using the nighttime light data alone to estimate population may cause the overestimation problem due to excessively high light radiance in specific types of areas such as commercial zones and transportation hubs. In dealing with this issue, this study used taxi trajectory data that delineate people’s movements, and explored the utility of integrating the nighttime light and taxi trajectory data in the estimation of population in Shanghai at the spatial resolution of 500 m. First, the initial population distribution grid was generated based on the NPP-VIIRS nighttime light data. Then, a calibration grid was created with taxi trajectory data, whereby the initial population grid was optimized. The accuracy of the resultant population grid was assessed by comparing it with the refined survey data. The result indicates that the final population distribution grid performed better than the initial population grid, which reflects the effectiveness of the proposed calibration process.  相似文献   

城市可持续发展的问题与对策   总被引：2，自引：0，他引：2  

谢理  邓毛颖 《热带地理》1999,19(1):71-75

城市的发展基于对环境资源的利用,但这一利用的同时又造成了对环境资源不可避免的破坏,如何维持保护人类的生存环境,实现城市的可持续发展,就成为当今城市研究的主题。本文就当今城市发展中所出现的一系列问题做了较深入的探讨,并相应提出了促进城市可持续发展的种种对策。  相似文献   

日本对虾野生种群和养殖种群遗传结构的RAPD标记研究   总被引：46，自引：5，他引：41  

宋林生  相建海  李晨曦  周岭华  刘保忠  刘瑞玉 《海洋与湖沼》1999,30(3):261-266

于１９９７年４月在福建和山东青岛分别采集地虾野生种群和养殖群体的样品,采用ＲＡＰＤ标记技术对其遗传结构进行初步研究。用２０个随机引物在野生种群和养殖群体中分别扩增出１５７和１５３条ＤＮＡ片段,其中多态性段数分别为８５和５８条,多态性片段的比例分别为５４．１４％和３７．９１％,平均杂合度分别为０．２５１７和０．１３４３。  相似文献   

基于手机位置数据的四川九寨沟7.0级地震人流分析     

李东平  黄乐  陈海鹏  刘倩倩 《中国地震》2017,33(4):602-612

2017年8月8日四川九寨沟7.0级震后,浙江省地震局利用大数据采集了1031.99万条手机位置记录和4.46万个空间格网位置。本文结合24hr连续定位的手机数据,使用手机位置数据分别对九寨沟灾区人口从时间和地理维度上进行了量化分析,估计了多维人口分布的偏差,同时,探讨了剔除微观误差数据用户来估算灾区通讯基站退服分布的方法。该项工作为震后快速获取灾区人口实时动态分布提供了有效途径,同时也为地震灾害评估提供了较准确的依据。  相似文献