加拿大海盆夏季冰区细菌和原生生物群落特性分析          下载免费PDF全文

张灿  何剑锋黄涛林凌  曹叔楠张芳 《极地研究》2017,29(3):338-348

采用表面荧光显微分析方法对2014年夏季中国第6次北极科学考察期间采集于加拿大海盆7个海冰站位的融池、冰芯和冰下海水样品进行了细菌和原生生物群落分析。结果表明,上述3类生境中的第一优势类群均为细菌(不包括ICE07站位出现水华融池的统计),分别占总生物量的42.8%、37.8%和50.7%;第二优势类群均为鞭毛虫,分别占总生物量的40.2%、34.3%和37.5%。包含细菌、鞭毛虫和纤毛虫在内的异养生物在总生物量中占有优势,显示微食物环在其中起着重要作用。在北冰洋夏季快速融冰的背景下,3类生境总体上缺少快速生长的条件,总生物量偏低。其中ICE07站位出现融池水华和冰表自养鞭毛藻高值,推测合适的藻种和营养盐的额外补充共同促成了该站位冰表(融池)藻华的形成。  相似文献   

生态水文科学研究的现状与展望   总被引：35，自引：5，他引：35  

王根绪  钱鞠  程国栋 《地球科学进展》2001,16(3):314-323

生态水文科学研究是区域生态系统研究和区域水文科学研究的交叉领域 ,其核心内容是揭示不同环境条件下植物与水的相互关系机理 ,探索各种植被的生态水文作用过程。近年来 ,生态与水文相互作用过程的数学模拟和专门模型研制日益成为重要的发展领域 ,同时 ,生态水文学的研究十分注重尺度效应 ,把在一定尺度上获得的水文与生态原理或模型向其它不同尺度转换已成为最具挑战性的问题。山地生态系统成为全球变化研究最为重要的研究场所 ,开展与全球变化相关的生态系统物质与能量循环、生态过程的梯度效应及其与水文过程的耦合关系、生态系统结构与功能及其变化等方面的研究 ,是生态水文学研究最具活力的方向 ,其中建立包含区域气候变化因素的多元生态过程动态模拟模型 ,并使该模型具有不同时空尺度、不同地貌和生态带的广泛适应性是目前广泛关注的热点问题。  相似文献   

High-precision VLBI astrometric observations of radio-emitting stars for detection of extra-solar planets     

Jean-François Lestrade  Dayton L. Jones  Robert A. Preston  Robert B. Phillips 《Astrophysics and Space Science》1994,212(1-2):251-260

The displacement of a radio-emitting star around the barycenter of a possible planetary system can be measured by astrometric very long baseline interferometry (VLBI) observations. We have observed the radio-emitting star ² CrB at 8 epochs over 5 years by VLBI and fitted its 5 astrometric parameters to the observed coordinates. The post-fit coordinate residuals have an rms scatter of 0.22 milliarcseconds and show no systematic behavior. We use this result to set a limit on the presence of planets around ² CrB and conclude that our present VLBI astrometric precision corresponds to the threshold to detect a Jupiter-like planet around this star. We also discuss the astrometric monitoring program of 11 radio-emitting stars that we are conducting for the Hipparcos space mission and its possible contribution to a long-term planet search program.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

变参数赤潮藻类生长模型的非线性动力分析研究     

王洪礼  葛根  许佳  向建平 《海洋通报》2007,26(3):48-52

在对一个营养盐和赤潮藻类摄食模型进行非线性分析的基础上,提出了含有变参数的赤潮藻类生长模型。模型中用一个周期阶跃函数来近似模拟了藻类生长率参数,并对此模型做了数值模拟。结果表明,引入变参数后的模型更能体现藻类生长的季节性特点,和实际情况符合更好。  相似文献   

Mud Volcanoes and Dome-Like Structures at the Eastern Mediterranean Ridge   总被引：2，自引：0，他引：2  

Çifçi  G.  Limonov  A.  Dimitrov  L.  Gainanov  V. 《Marine Geophysical Researches》1997,19(5):421-438

Marine Geophysical Research - The Mediterranean Ridge is interpreted as a large accretionary complex, which originated due to the northern subduction of the African lithosphere below the Eurasian...  相似文献   

"人才争夺战"背景下人才流动的空间特征及影响因素——以中国"一流大学"毕业生为例   总被引：4，自引：2，他引：2  

王一凡  崔璨  王强  宁越敏  杨振山 《地理研究》2021,40(3):743-761

自2017年以来,“人才争夺战”如火如荼,城市步入以人才为核心要素的高维竞争阶段。作为人才争夺战的主要目标和人力资本的重要承载者,本文聚焦中国“一流大学”毕业生,基于2018年《毕业生就业质量报告》,运用Cartogram地图呈现了毕业生的空间流动特征,并梳理政府人才政策文件构建了人才政策评价指标体系,运用有向迁移模型剖析毕业生流动的影响因素。结果表明：① 就学地存在粘滞性,但区域差异显著,毕业生向一线城市集聚。② 城市吸引力水平分异明显,部分城市通过发布人才政策以补充地方经济、舒适性吸引力的不足。③ 经济维度要素与城市舒适性均能有效吸引毕业生流入,较高房价收入比会引发“挤出效应”。人才政策中,落户政策对毕业生流入起激励作用。  相似文献   

代际传递视角下中国城市家庭住房产权获得——基于上海的实证研究     

崔璨  崔军茹  李佳怡 《世界地理研究》2021,30(1):167-178

随着中国城市住房价格大幅上涨,住房可支付性成为青年面临的严峻挑战。尽管越来越多的研究开始关注中国城市住房不平等问题,但大多侧重住房资源分配由国家向市场的转移,相对而言,家庭在住房资源获取中的作用被忽视。本文选取上海市作为研究区域,使用2013年长三角社会变迁调查数据,以上海“80后”青年家庭为研究对象,重点关注夫妻双方父母的住房状况和社会经济属性对青年家庭住房产权获得的影响及性别差异。研究发现,父母户口很大程度上影响着青年家庭的住房结果;不同户口状况的父母住房财富存在较大分化,其影响着年轻家庭可获得的家庭购房资助的数额。与妻子父母相比,丈夫父母的户口状况对青年家庭住房结果的影响更大;而妻子父母在本地且拥有住房产权的双重优势与青年家庭住房产权获得有更强的正向联系。家庭背景对子代住房的影响结合婚姻匹配机制使住房优势或劣势在青年家庭内部累积,或会加剧住房分化现象。  相似文献   

青海省多彩地玛地区铅多金属矿地质特征及找矿标志          下载免费PDF全文

陈根  赵利  李钧  李力生  叶娇珑 《地质找矿论丛》2016,31(1):55-62

青海省多彩地玛地区位于"三江"北段著名的有色金属及贵金属成矿带,近年来的地质矿产研究与预测取得了显著的成果。文章通过大量的野外地质调查,结合前人的研究成果,对多彩地玛铅锌、铜多金属矿床产出地质特征及找矿方向进行了总结,系统阐述了多彩地玛矿区的岩石、构造地质特征和矿体特征,分析了铅多金属矿成矿条件、矿化成因和找矿标志,为区内进一步找矿工作提供了思路。  相似文献   

The Bekten Fault: the palaeoseismic behaviour and kinematic characteristics of an intervening segment of the North Anatolian Fault Zone,Southern Marmara Region,Turkey     

Selim Özalp  Akın Kürçer  Ersin Özdemir  Tamer Y. Duman 《Geodinamica Acta》2016,28(4):347-362

The Bekten Fault is 20-km long N55°E trending and oblique-slip fault in the dextral strike-slip fault zone. The fault is extending sub-parallel between Yenice-Gönen and Sar?köy faults, which forms the southern branch of North Anatolian Fault Zone in Southern Marmara Region. Tectonomorphological structures indicative of the recent fault displacements such as elongated ridges and offset creeks observed along the fault. In this study, we investigated palaeoseismic activities of the Bekten Fault by trenching surveys, which were carried out over a topographic saddle. The trench exposed the fault and the trench stratigraphy revealed repeated earthquake surface rupture events which resulted in displacements of late Pleistocene and Holocene deposits. According to radiocarbon ages obtained from samples taken from the event horizons in the stratigraphy, it was determined that at least three earthquakes resulting in surface rupture generated from the Bekten Fault within last ~1300 years. Based on the palaeoseismological data, the Bekten Fault displays non-characteristic earthquake behaviour and has not produced any earthquake associated with surface rupture for about the last 400 years. Additionally, the data will provide information for the role of small fault segments play except for the major structures in strike-slip fault systems.  相似文献   

Surface modes in the infrared spectrum of hydrous minerals: the OH stretching modes of bayerite     

Etienne Balan  Marc Blanchard  Jean-François Hochepied  Michele Lazzeri 《Physics and Chemistry of Minerals》2008,35(5):279-285

The theoretical infrared (IR) and Raman spectra of bayerite (β-Al(OH)₃) are computed in the density functional theory framework, using the linear response theory. The results are consistent with the occurrence of six non-equivalent OH groups in a bayerite structure with space group P2₁/n. Similar to gibbsite, the transmission powder IR spectrum of bayerite in the region of the OH stretching bands is found to depend on the shape of particles. In particular, the broadening of the strong band observed at about 3,460 cm⁻¹ in the spectrum of Al hydroxides is related to the electrostatic charges occurring at the surface of the polarized dielectric particles. The experimental correlation observed between the shape of this band and morphological parameters has therefore a physical, instead of chemical, origin.  相似文献