Carbon isotopic characteristics and their genetic relationships for individual lipids in plants and sediments from a marsh sedimentary environment   总被引：2，自引：0，他引：2  

DUAN Yi  ZHANG Hui  ZHENG Chaoyang  WU Baoxiang & ZHENG Guodong . Lanzhou Institute of Geology  Chinese Academy of Sciences  Lanzhou  China  . Department of Earth & Planetary System Science  Graduate School of Science  Hiroshima University  Higashi-Hiroshima -Japan 《中国科学D辑(英文版)》2005,48(8):1203-1210

The carbon isotopic compositions of individual lip-ids can provide the genetic information about sedi-mentary lipids so that it has extensively applied pros-pects in geochemically studied field[1―8]. However, this applied research relies heavily on the accumula-tion of studied data in the genetic relationships between carbon isotopic compositions of individual lipids and their biological precursors in different sedi-mentary environments. Recently, the useful δ 13C data of individual lipids f…  相似文献   

Choosing the level of detail for depicting two-variable spatial relationships     

Jonathan D. Phillips 《Mathematical Geology》1987,19(6):539-547

A method for determining the most appropriate scale for presentation of spatial relationships between two variables combines the principle of entropy decomposition with Phipps' entropy-based method for determining mutual information of landscape patterns. The method enables determination of the optimal level of detail for maps, data matrices, or other depictions of two spatially associated phenomena. An example from wetland mapping is given.  相似文献   

Site-specific effects on productivity of an upper trophic-level marine predator: Bottom-up, top-down, and mismatch effects on reproduction in a colonial seabird     

Robert M. Suryan  David B. Irons  Evelyn D. Brown  Patrick G.R. Jodice  Daniel D. Roby 《Progress in Oceanography》2006,68(2-4):303

We investigated the relative roles of bottom-up and top-down factors in limiting productivity of an upper trophic level marine predator. Our primary working hypothesis was that the reproductive success of black-legged kittiwakes (Rissa tridactyla) a piscivorous, colonial-nesting seabird, was most limited by the abundance, distribution, and species composition of surface-schooling forage fishes. A secondary working hypothesis was that reproductive loss to kittiwake nest predators was greatest during years of reduced prey availability. We report on a broad-scale, integrated study of kittiwakes and their prey in Prince William Sound, Alaska. Our study spanned five breeding seasons (1995–1999) and focused on three colonies that differed in size (ranging from ca. 220 to ca. 7000 breeding pairs) and proximity to each other (50–135 km apart). Kittiwakes in PWS encountered a variety of aquatic habitats, creating a complex foraging environment for breeding birds. We measured kittiwake reproductive success and foraging activities, while simultaneously measuring the abundance of surface schooling forage fishes throughout the foraging range of breeding kittiwakes. The abundance of primary prey species for kittiwakes (Pacific herring Clupea pallasi, Pacific sand lance Ammodytes hexapterus, and capelin Mallotus villosus) varied both annually and regionally, with no one region consistently having the greatest abundance of prey. Likewise, kittiwake reproductive success varied considerably among colonies and years.We found that bottom-up, top-down, timing mismatch, and colony-specific effects were all important to kittiwake productivity. Although bottom-up effects appeared to be strongest, they were not evident in some cases until other effects, such as geographic location (proximity of colony to prey concentrations) and top-down predation, were considered. Important bottom-up effects on kittiwake reproductive success were not only total prey abundance and distribution, but also species, age composition, and chronology of prey occurrence (match/mismatch of timing with critical brood-rearing periods); these effects varied by colony.Top-down effects of predation on kittiwake nest contents (independent of prey abundance) confounded seabird-forage fish relationships. Ultimately, when confounding factors were minimized, non-linear asymptotic relationships were identified between kittiwakes and their prey, with an asymptotic threshold of fish school surface area density of ca. 5 m²/km², beyond which top-down, physiological, or phylogenetic constraints likely restrict further reproductive output. The integrated approach of our investigations provided a more thorough understanding of the mechanisms underlying predator–prey relationships in the complex marine environment. However, such mechanistic theories can only be tested and refined through long-term research and monitoring of much greater duration than the 5-year study reported herein.  相似文献   

3维GIS中位置关系的定性描述与推理   总被引：2，自引：0，他引：2  

刘新  刘文宝  李成名  崔先国 《测绘学报》2008,37(4):0-520

3维空间中位置关系的定性描述和推理是当前城市和矿山GIS界的重要理论课题之一,主要涉及如何用定性距离和方向关系来综合描述目标对象及相对于其参照物的空间位置关系的方法。本文基于投影系统划分空间方向区域,利用解析几何工具表达距离关系和方向关系,建立组合距离和方向关系来描述位置关系的概念框架,导出位置关系组合推理的一般表达式,并通过例子说明一些典型的位置关系定性推理过程和结果。  相似文献   

基于Oracle Spatial的空间线／面拓扑关系判断的实现     

乔柱  岳国森 《东北测绘》2008,31(1):130-134

利用OracleSpatial提供的简单的空间关系查询操作算子,对九交模型所描述的任意两个2维空间不自相交的线目标与面目标（不合空洞）的拓扑关系判断设计了算法,最终进行了试验验证,实现了线目标与面目标间的19种空间拓扑关系的判断。  相似文献   

State-of-the-Art of Gas Hydrates and Relative Permeability of Hydrate Bearing Sediments     

J. Joseph  P. Kumar  S. K. Dewri  C. Tandi  J. Singh 《Marine Georesources & Geotechnology》2016,34(5):450-464

The methane gas production potential from its hydrates, which are solid clathrates, with methane gas entrapped inside the water molecules, is primarily dependent on permeability characteristics of their bearing sediments. Moreover, the dissociation of gas hydrates, which results in a multi-phase fluid migration through these sediments, becomes mandatory to determine the relative permeability of both gaseous and aqueous fluids corresponding to different hydrate saturations. However, in this context, the major challenges are: (1) obtaining undisturbed in-situ samples bearing gas hydrates; and (2) maintenance of the thermodynamic conditions to counter hydrate dissociation. One of the ways to overcome this situation is synthesis of gas hydrates in laboratory conditions, followed by conducting permeability tests on them. In addition, empirical relationships that relate permeability of the gas hydrate bearing sediments to pore-structure characteristics (viz., pore size distribution and interconnectivity) can also be conceived. With this in view, a comprehensive review of the literature dealing with different techniques adopted by researchers for synthesis of gas hydrates, permeability tests conducted on the sediments bearing them, and analytical and empirical correlations employed for determination of permeability of these sediments was conducted and a brief account of the same is presented in this article.  相似文献   

地理系统模拟的CA模型理论探讨   总被引：4，自引：1，他引：3  

周成虎  欧阳  马廷  覃彪 《地理科学进展》2009,28(6):833-838

在系统认识和理解地理元胞自动机（CA）模型的基本性质基础上,重点从自然与人文综合的复杂地理系统模拟研究角度,对地理元胞模型所涉及的基本理论与方法问题进行了进一步的探讨。研究表明：从地理系统的模拟看,CA模型的研究和应用提供了一种从地理系统的微观出发、将自然与人文统一的地理系统模拟的新视角与新途径。在此基础上,提出了地理系统模拟的CA模型需要解决的三队基本关系和三个基本科学方法问题。  相似文献   

内蒙古乌梁素海叶绿素a浓度时空分布及其与氮、磷浓度关系   总被引：6，自引：1，他引：6  

杨志岩  李畅游  张生  孙标 《湖泊科学》2009,21(3):429-433

采用2005-2007年乌梁素海监测数据,对乌梁素海水体中叶绿素a浓度的时空分布进行分析,并对叶绿素a浓度与总氮、总磷浓度相关关系进行研究,结果表明:乌梁素海叶绿素a浓度具有明显的时空分布特征,在时间上,5月份>7、8月份>10月份>9月份>6月份,可以看出5月份、10月份叶绿素a浓度偏高,其原因是乌梁素海特殊的地域性,补水来源主要为河套灌区的农田退水,5月份、10月份正处于春浇秋灌时期,农田退水携带充足的氮磷元素进入乌梁素海,使藻类迅速增长繁殖;在空间上,北部区>南部区.通过分析得出,2006年叶绿素a与氮、磷浓度的相关关系在5月、10月存在明显的相关性,8月份相关性较小,其他月份无明显相关性.  相似文献   

Magnitude Formulae and Intensity–Magnitude Relations for Early Instrumental Earthquakes in the Iberian Region     

Elena Samardjieva  Gonzalo Payo  Jose Badal 《Natural Hazards》1999,19(2-3):189-204

The magnitudes of early instrumentally recorded earthquakes in the Iberian region (1912–1962) have been studied through processing of digitized seismograms of Wiechert seismograph and analysis of macroseismic information. A magnitude system based on instrumental registrations and macroseismic observations has been proposed. It consists of two compatible magnitude formulae depending on the total duration of seismic oscillations and on the maximum ground amplitude/period ratio of surface waves and includes correspondent intensity–magnitude relationships.  相似文献   

Broadband (0.05 to 20 s) prediction of displacement response spectra based on worldwide digital records   总被引：6，自引：0，他引：6  

Carlo Cauzzi  Ezio Faccioli 《Journal of Seismology》2008,12(4):453-475

A new set of empirical equations for prediction of displacement response spectral ordinates from 20 Hz to T = 20 s is illustrated. The coefficients of the equations were obtained by regressing a dataset based on 1,155 tri-axial digital and 9 analog accelerometer records from 60 earthquakes worldwide. Long period disturbances in the accelerograms were evaluated and removed using a very recent method, aimed at preserving the long-period spectral content of the records. Analysis of variance has disclosed only little evidence for regional dependence of ground motions, while a carefully conducted evaluation of site effects resulted in clearly differentiated spectral amplification bands associated to the main ground types B, C, and D of Eurocode 8. Spectral ordinates for vibration periods >5 s were found to scale with magnitude quite consistently with theoretical scaling from Brune’s model. On the other hand, comparison of results with those yielded by recent prediction models in Europe and the United States (NGA), indicated that the latter may not be uniformly reliable at long periods. The proposed empirical equations are easily implemented in computer programs for seismic hazard assessment, being characterized by a simple functional form and a restricted number of predictor variables. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献