Structure and mass function of three young open clusters     

《New Astronomy》2014

Using UBVRI CCD data taken from 104-cm Sampurnanand Telescope, ARIES, Nainital, we present the structure, initial mass function and mass segregation of three young age (∼10 Myr) open star clusters: NGC 2129, NGC 1502 and King 12. Based on photometric as well as astrometric criteria, the cluster member stars as well as field stars have been identified. We construct luminosity function which is further used to estimate the mass functions by employing theoretical stellar evolutionary isochrones. The entire cluster region mass function (MF) slopes for NGC 2129, NGC 1502 and King 12 are obtained as −2.55 ± 0.14, −2.73 ± 0.36 and −1.94 ± 0.12 respectively. It is found that changes in the MF slope of King 12 are significantly different compared to NGC 2129 and NGC 1502 from inner region to outer region. The MF slope for King 12 is steeper at larger radii. The dynamical relaxation times for all three clusters are found to be less than age of the clusters. This indicates that all these clusters are dynamically relaxed. We show that for NGC 1502 and King 12, passing off of low mass stars from the inner region of the clusters to the halo occurs during the course of evolution.  相似文献   

DMSP and DMS dynamics and microzooplankton grazing in the Labrador Sea: application of the dilution technique     

Gordon V. Wolfe  Maurice Levasseur  Guy Cantin  Sonia Michaud 《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(12):687

We adapted the dilution technique to study microzooplankton grazing of algal dimethylsulfoniopropionate (DMSP) vs. Chl a, and to estimate the impact of microzooplankton grazing on dimethyl sulfide (DMS) production in the Labrador Sea. Phytoplankton numbers were dominated by autotrophic nanoflagellates in the Labrador basin, but diatoms and colonial Phaeocystis pouchetii contributed significantly to phytomass at several high chlorophyll stations and on the Newfoundland and Greenland shelfs. Throughout the region, growth of algal Chl a and DMSP was generally high (0.2–1 d⁻¹), but grazing rates were lower and more variable, characteristic of the early spring bloom period. Production and consumption of Chl a vs. DMSP followed no clear pattern, and sometimes diverged greatly, likely because of their differing distributions among algal prey taxa and size class. In several experiments where Phaeocystis was abundant, we observed DMS production proportional to grazing rate, and we found clear evidence of DMS production by this haptophyte following physical stress such as sparging or filtration. It is possible that grazing-activated DMSP cleavage by Phaeocystis contributes to grazer deterrence: protozoa and copepods apparently avoided healthy colonies (as judged by relative growth and grazing rates of Chl a and DMSP), and grazing of Phaeocystis was significant only at one station where cells were in poor condition. Although we hoped to examine selective grazing on or against DMSP-containing algal prey, the dilution technique cannot differentiate selective ingestion and varying digestion rates of Chl a and DMSP. We also found that the dilution method alone was poorly suited for assessing the impact of grazing on dissolved sulfur pools, because of rapid microbial consumption and the artifactual release of DMSP and DMS during filtration. Measuring and understanding the many processes affecting organosulfur cycling by the microbial food web in natural populations remain a technical challenge that will likely require a combination of techniques to address.  相似文献   

冰后期最大海侵以来长江口潮波特性的变化   总被引：1，自引：0，他引：1  

朱玉荣 《海洋科学》2000,24(5):34-36

冰后期最大海侵时,现今长江三角洲地区为一巨大河口湾,研究古长江河口湾及其周围海域的潮波特性,并与现今长江口的进行对比,有助于深入了解长江三角洲形成发育的动力过程。根据冰后期最大海侵时古长江河口湾及其周围海域３５个计算站一个半日潮周期的潮位、潮流过程曲线得知,冰后期最大海侵时古长江河口 及其周围海域的潮波为驻波以及驻波－前进波混合型。此后,丰古长江河口被充填、长江口东进南移,长江口的潮波也逐渐转 变  相似文献   

基于义务教育校际分异的学校类型及其空间分布模式——以大连市初中为例     

刘天宝  陈子叶  陈爽 《地理科学》2022,42(8):1402-1412

利用2015年大连市初中学校多维数据,在分析社会群体间分异状况及其空间表现的基础上,概括了学校的基本类型及其空间分布特征,总结了义务教育校际分异的空间模式。在市域范围内存在4类学校,即成绩较好的城市综合社会群体子女学校;成绩一般的产业工人及一般技术人员子女学校;成绩优异的教师、政府和企事业单位管理者及专业技术人员子女学校;成绩落后但生均教育资源充沛的农村地区学校。4类学校在市域范围内分异明显,形成了从内向外的5个教育圈,即城市中心教育圈、城市郊区教育圈、城市新区教育圈、外围城镇教育圈和外围乡村教育圈。教育资源在教育圈之间呈高低相间分布的特点,教学成绩和学生家庭社会经济地位呈现出从中心向外围逐步降低的特征。  相似文献   

川东北飞仙关组鲕滩天然气地球化学特征与成因   总被引：29，自引：3，他引：26  

谢增业  田世澄  李剑  胡国艺  李志生  马成华 《地球化学》2004,33(6):567-573

四川盆地东北部下三叠统飞仙关组鲕滩气藏天然气烃类气体以甲烷为主,含量主要分布在75%～90%之间,C2 含量很少,为0%～0.15%,干燥系数为0.997 0～0.999 8,是典型的干气;非烃气体以H2S和CO2为主,含量分别为4.21%～16.24%和0.97%～10.41%.天然气δ13C1值为-29.0‰～-31.5‰,δ13C2值为-29.4‰～-32.4‰.多参数表明鲕滩气藏天然气是以腐泥型为主的高过成熟天然气.高含H2S的天然气分布区域与含石膏地层分布基本一致,这些H2S为飞仙关组气藏附近的石膏经热化学硫酸盐还原作用(TSR)而生成,CO2是其主要的副产物.在TSR过程中,C2 重烃气体比甲烷更容易与硫酸盐发生反应,也就是C2 重烃气体的消耗速率大于甲烷,从而导致发生TSR反应的天然气C2 含量低、H2S和CO2含量高.天然气δ13C1值与甲烷含量之间具有很好的负相关关系,而与天然气酸性系数[H2S/(H2S CnH2n 2)]具有正相关关系.根据同位素动力学的分馏效应,随着TSR的进行,烃类分子中的12C损耗速率大于13C,残留下来的烃类分子中则更加富集13C,也就是TSR反应使天然气碳同位素变重.  相似文献   

沉积物中酸可挥发性硫化物的分析方法研究   总被引：1，自引：0，他引：1  

李力  王小静  刘季花 《海洋与湖沼》2015,46(1):96-101

酸可挥发性硫化物(AVS)是评价沉积物中重金属生物毒性的一个重要参数,但AVS易随氧化还原环境变化,所以对分析测试要求较高。以往AVS的测定方法较为费时费力,无法用于常规监测,或不适用于测定AVS含量偏低的沉积物样品。本研究在现有分析方法的基础上进行了改进,建立了一个扩散法和亚甲基蓝比色法联用的分析方法,使其适用于测定AVS含量偏低的海洋和湖泊沉积物样品。通过对回收率、空白、重复性的实验显示,该方法能够快速、准确的进行大批量样品的测试。应用该方法对渤海湾和莱州湾上百个沉积物样品的分析发现,AVS含量低于0.6μmol/g(DW)的样品量达到75%。因我国近岸海域有机碳含量偏低,AVS的含量也可能偏低,所以该方法对我国近岸海洋沉积物中AVS的分析测试有普适性。该分析方法的建立为我国应用AVS对沉积物中重金属生物毒性的研究提供了便利。  相似文献   

电感耦合等离子体发射光谱法测定硫化物矿中的高含量铅   总被引：3，自引：2，他引：1  

王蕾  温宏利  马新荣  张保科  马生凤  许俊玉  巩爱华 《岩矿测试》2011,30(3):305-309

铅含量高的硫化物矿在氧化性酸的存在下极易形成硫酸铅沉淀而影响样品中铅的准确测定。文章通过王水-双氧水分解和高温灼烧后王水分解两种不同的样品处理方法,有效地去除样品中的硫,配合使用高盐雾化器采用电感耦合等离子体发射光谱法对硫化物矿石中的高含量铅进行测定。王水-双氧水分解可以测定硫化物矿中的铅、银和锑,高温灼烧后王水分解只能测定铅;两种样品处理方法均操作简便,具有准确度好、精密度高、分析速度快等优点。用这两种样品处理方法10次测定铅精矿(GBW 07167)中的铅,精密度(RSD)分别为0.38%和0.56%,相对误差分别为-0.41%和0.14%;测定方铅矿(GBW 07269)中铅精密度分别为0.76%和0.66%,相对误差分别为0.82%和0.45%。  相似文献   

Spatial transformations in a “loosening state”: South Africa in a comparative perspective     

《Geoforum》2015

This study explores the spatial transformation of urban South Africa since the ending of Apartheid rule two decades ago. It places this experience within the context of countries which have also gone through a “loosening” of political control and of related controls over spatial arrangements. The paper provides a discussion of South Africa’s spatial trends between 1996 and 2011, focusing on urbanisation; urban form; and socio-spatial segregation, and exploring the extent to which changes identified are shaped by the state, private sector investment, and the everyday actions of households and individuals. It shows that South Africa’s urban spatial transformation, post-Apartheid, is both idiosyncratic and comparable. The consequences of spatial controls, and of their loosening, have been diverse across countries, but also within countries. Loosening has led to differing relationships between state, citizenry and private enterprise, and to complex new crossing points between these groupings, affecting spatial change. In South Africa, significant trends have been: movement to the major cities where employment growth is stronger; levels of racial desegregation; and densification of parts of cities and towns, along with peripheral growth and employment decentralisation. Many of the changes however are differentiated across space and between settlements. While proactive state policies have had some impact (not necessarily in the direction of desired spatial transformation), and there are complex interrelationships, our empirical studies suggest that the major weight of evidence is towards the roles of private enterprise and people in shaping spatial change, enabled in part by forms of state loosening.  相似文献   

新疆喀拉通克铜镍硫化物矿床Y9岩体年代学与成岩成矿机制探讨   总被引：6，自引：1，他引：5  

焦建刚  王勇  钱壮志  王斌  鲁浩  刘欢  郑鹏鹏 《矿床地质》2014,33(4):675-688

新疆喀拉通克是中国大型铜镍硫化物矿床中基性程度最低的,显示出罕见的Cu平均品位大于Ni平均品位。矿区划分为南、北2个岩带,南岩带主要为原生矿,北岩带主要为氧化矿。文章研究对象为北岩带中的Y9岩体,近年发现其下部存在原生矿石。通过单颗粒锆石SHRIMP测年,获得Y9岩体中辉长岩的结晶年龄为(287±4)Ma,与Y1岩体的成岩年龄〔(287±5)Ma〕一致,结合岩石地球化学和同位素地球化学特征,证明喀拉通克矿区南、北岩带具有同期同源岩浆演化的特征,岩浆源自亏损型地幔部分熔融与不含沉积物消减板片脱水物质的混合。研究认为喀拉通克铜镍矿床形成于亏损地幔在相对较高的氧逸度条件下低程度部分熔融,产生硫化物不饱和的岩浆,岩浆源区相对富水和较高的氧逸度,原始岩浆具有较高的钛含量,具有富碱亲合性。  相似文献   

金川铜镍矿床龙首矿区半金属元素与铂族元素地球化学特征及成因意义     

江金进  宋谢炎  陈列锰  王亮  符志强 《矿物岩石地球化学通报》2014,33(6)

岩浆硫化物矿床中的铂族元素矿物主要是与半金属元素的化合物,但有关这些半金属元素在岩浆系统中的行为的研究却甚少。对金川龙首矿区不同类型矿石的Cu、Ni、铂族元素和半金属元素的分析研究发现,在熔离过程中这些半金属元素会与铂族元素一起进入硫化物熔浆中,在硫化物熔浆分离结晶过程中倾向于在残余熔体中富集,在单硫化物固溶体分离过程中部分半金属元素趋于进入镍黄铁矿中。由于半金属元素与铂族元素(PGE),特别是Pt和Pd,具有很强的亲和力,所以在半金属元素达到铂族矿物结晶所需要的饱和浓度前,其存在会阻碍PGE进入金属硫化物(BMS)中。此外,金川矿床S/Se值的变化不仅受同化混染作用及硫化物熔离强度的影响,还受后期热液蚀变作用的影响。  相似文献