Roche volume filling and the dissolution of open star clusters     

A. Ernst  P. Berczik  A. Just  T. Noel 《Astronomische Nachrichten》2015,336(6):577-589

From direct N‐body simulations we find that the dynamical evolution of star clusters is strongly influenced by the Roche volume filling factor. We present a parameter study of the dissolution of open star clusters with different Roche volume filling factors and different particle numbers. We study both Roche volume underfilling and overfilling models and compare with the Roche volume filling case. We find that in the Roche volume overfilling limit of our simulations two‐body relaxation is no longer the dominant dissolution mechanism but the changing cluster potential. We call this mechanism “mass‐loss driven dissolution” in contrast to “two‐body relaxation driven dissolution” which occurs in the Roche volume underfilling regime. We have measured scaling exponents of the dissolution time with the two‐body relaxation time. In this experimental study we find a decreasing scaling exponent with increasing Roche volume filling factor. The evolution of the escaper number in the Roche volume overfilling limit can be described by a log‐logistic differential equation. We report the finding of a resonance condition which may play a role for the evolution of star clusters and may be calibrated by the main periodic orbit in the large island of retrograde quasiperiodic orbits in the Poincaré surfaces of section. We also report on the existence of a stability curve which may be of relevance with respect to the structure of star clusters. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Comparison of chaos detection methods in the circular restricted three‐body problem     

O. Racoveanu 《Astronomische Nachrichten》2014,335(8):877-885

In this study, a sample of orbits is considered in the framework of the planar circular restricted three‐body problem. In order to separate ordered from chaotic orbits three numerical methods are compared: the Largest Lyapunov Characteristic Exponent (LLCE) and the Smaller Alignment Index (SALI) provide a fairly good characterization of the chaotic motions, while the computational time required is of the same order; the Correlation Dimension (CD) has the advantage of correctly classifying sticky orbits, but at the expense of a longer computational time. In order to classify a given orbit, any pair of the three methods can be considered, but LLCE and SALI are recommended due to their speed. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

A 16 ka climate record deduced from δ^13C and C/N ratio in Qinghai Lake sediments, northeastern Tibetan Plateau     

沈吉汪勇  刘兴起Ryo Matsumoto 《中国海洋湖沼学报》2006,24(2):103-110

1 INTRODUCTION δ13C in organic matters from lacustrine sedi- ments varies with several factors including aquatic plants, vegetation type in the catchment, atmos- pheric CO2 concentration, climate (temperature and precipitation), and properties of water, …  相似文献   

Bulk organic δ13C and C/N ratios as palaeosalinity indicators within a Scottish isolation basin     

Elizabeth A. V. Mackie  Melanie J. Leng  Jeremy M. Lloyd  Carol Arrowsmith 《第四纪科学杂志》2005,20(4):303-312

Microfossils in isolation basin sediments are frequently used to reconstruct sea‐level change, but preservation problems and non‐analogue situations can limit their usefulness. Here we investigate the potential of stable carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter, as an alternative proxy of salinity within isolation basin sediments from a basin in northwest Scotland. Within the Holocene sediment δ¹³C and C/N are determined largely by the mean weighted values of the predominant source of the organic material. Analysis of modern materials and comparison with the diatom record shows that the marine parts of the sequence are dominated by high δ¹³C and variable C/N. In the fresh water sequences the organic material is a mixture of both freshwater aquatic and terrestrial plant input that have relatively low δ¹³C and high C/N. The application of δ¹³C and C/N ratios in the studied basin in general follow the environmental change recorded by the diatoms and shows the potential of bulk organic matter in the investigation of salinity change in isolation basins. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

一株H_5N_1亚型禽流感病毒株NA基因的克隆与序列分析     

陈绍红  刘艳芬  张静  刘铀 《广东海洋大学学报》2007,27(4):85-88

用RT-PCR方法从1个H5N1亚型禽流感病毒分离株A/Chicken/Guangdong/DH/1997扩增NA基因cDNA片段,将其克隆至pMD18-T载体,获得重组质粒pMD-NA,并对其核苷酸序列进行测定和分析。结果表明,该毒株的NA基因长度为1350bp,编码449个氨基酸,与其它H5N1亚型AIV分离株的核苷酸序列同源性为97.0%～99.4%,氨基酸序列同源性为97.7%～99.1%,提示禽流感病毒NA基因保守性较高。NA基因氨基酸序列的聚类分析表明该毒株与来自香港的A/Pheasant/HK/FY155/01和A/Ch/HK/FY150/01两个分离株处于同一进化枝,亲缘关系较近。  相似文献   

Organic carbon and nitrogen stable isotopes in the intertidal sediments from the Yangtze Estuary, China   总被引：2，自引：0，他引：2  

Liu M  Hou LJ  Xu SY  Ou DN  Yang Y  Yu J  Wang Q 《Marine pollution bulletin》2006,52(12):1625-1633

The natural isotopic compositions and C/N elemental ratios of sedimentary organic matter were determined in the intertidal flat of the Yangtze Estuary. The results showed that the ratios of carbon and nitrogen stable isotopes were respectively −29.8‰ to − 26.0‰ and 1.6‰–5.5‰ in the flood season (July), while they were −27.3‰ to − 25.6‰ and 1.7‰–7.8‰ in the dry season (February), respectively. The δ¹³C signatures were remarkably higher in July than in February, and gradually increased from the freshwater areas to the brackish areas. In contrast, there were relatively complex seasonal and spatial changes in stable nitrogen isotopes. It was also reflected that δ¹⁵N and C/N compositions had been obviously modified by organic matter diagenesis and biological processing, and could not be used to trace the sources of organic matter at the study area. In addition, it was considered that the mixing inputs of terrigenous and marine materials generally dominated sedimentary organic matter in the intertidal flat. The contribution of terrigenous inputs to sedimentary organic matter was roughly estimated according to the mixing balance model of stable carbon isotopes.  相似文献   

A New Carrier Gas Type for Accurate Measurement of N20 by GC-ECD     

《大气科学进展》2010,(6)

  相似文献   

种植不同作物对农田N2O和CH4排放的影响及其驱动因子   总被引：3，自引：0，他引：3  

陈书涛  黄耀  郑循华  陈玉泉 《气候与环境研究》2007,12(2):147-155

以种植玉米(Zea mays)、大豆(Glycine max)和水稻(Oryza sativa)的农田生态系统为研究对象,于2003年6~10月系统观测了N2O和CH4的排放、土壤温度和湿度以及相关的生物学因子。玉米和水稻分别施化肥氮300 kg.hm-2,大豆未施氮肥。研究结果表明,作物类型对农田N2O和CH4排放具有显著的影响。土壤-玉米系统、土壤-大豆系统和土壤-水稻系统的N2O季节性平均排放通量分别为620.5±57.6、338.0±7.5和238.8±13.6μg.m-2.h-1(N2O)。种植作物促进了农田生态系统的N2O排放,玉米地土壤和裸地土壤的N2O平均排放通量分别为364.2±11.7和163.7±10.5μg.m-2.h-1(N2O)。土壤-玉米系统、土壤-水稻系统、玉米地土壤和裸地土壤N2O排放受土壤温度的影响,与土壤湿度无显著统计相关,但受土壤温度和水分的综合影响。土壤-大豆系统N2O排放随作物绿叶干重的增加而指数增加,与土壤温度和水分条件无统计相关,由大豆作物自身氮代谢所产生的N2O-N季节总量约为6.2 kg.hm-2(N)。土壤-水稻系统CH4平均排放通量为1.7±0.1 mg.m-2.h-1(CH4),烤田抑制了稻田CH4的排放。烤田前影响稻田CH4排放的主要因素是水稻生物量,烤田后的浅水灌溉及湿润灌溉阶段的CH4排放与土壤温度和水稻生物量无关。本研究未观测到旱作农田有吸收CH4的现象。  相似文献   

华东稻麦轮作农田CH4、N2O和NO排放特征   总被引：2，自引：0，他引：2  

周再兴  郑循华  王明星  Klaus Butterbach-Bahl 《气候与环境研究》2007,12(6):751-760

利用同步自动观测系统对华东稻麦轮作农田的CH4、N2O和NO排放进行了长期连续观测,分析了这3种气体排放的季节特征及决定因素,结果表明,华东稻麦轮作农田的CH4、N2O和NO排放具有完全不同的季节变化形式。CH4的排放发生在水稻生长期,其他阶段排放不明显,土壤水分状况是决定整个轮作周期内CH4排放变化的主要因素。N2O排放具有"冬季无,水田少,旱地多"的季节变化特点,尤其以旱地阶段的排放为主,土壤水分状况和温度共同决定着N2O排放的季节变化形式。NO排放具有"冬季无,水田很少,春季旱地多于秋季旱地"的季节分布特点,轮作周期内97.3%±0.6%的NO排放都发生在除冬季以外的旱地阶段,NO排放的季节变化形式由土壤水分状况和温度共同决定。大多数情况下稻田CH4和N2O排放呈互为消长的关系,但在烤田期间,二者却有时甚至同时出现高排放。在N2O日平均排放通量小于5 mg.m-2.h-1时,稻麦轮作农田的N2O和NO排放呈明显的互为消长关系,但大于5 mg.m-2.h-1时,N2O排放很强,同时NO排放也很强。  相似文献   

江陵凹陷北部高速玄武岩下二维广角地震初探   总被引：2，自引：0，他引：2  

胡中平  顾连兴  王良书  胡文瑄  邬达理 《高校地质学报》2004,10(1):70-77

江汉油田江陵凹陷北部高速玄武岩发育,利用常规地震资料很难得到高速玄武岩下的地震反射。分析研究表明,广角地震有利于玄武岩下的地震成像。通过综合正演和实际地震数据完成了广角地震资料的处理,获得了江陵凹陷北部高速玄武岩下的反射地震信息。在开展广角地震波场的识别和利用研究过程中,从正演模型出发,探讨了在不同地质条件下高速层对地震波场的影响,并针对靶区资料讨论了如何识别广角地震信息。在上述基础上,通过对实际地震资料做精细的分析和处理,最终完成了高速玄武岩下地震资料的成像。  相似文献