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41.
INTRODUCTIONBiogenicsulfideproducedbybacterialsulfatereductionisoneofthemostimportantindicatorsinanoxicmarineenvironments,particularlyinconfiningbays,pollutedestuariesandaquaculturear eas.Theincreaseofitsconcentrationusuallyindicatesworsenedconditions.… 相似文献
42.
A severe Cochlodinium geminatum red tide (>300 km2) was observed in the Zhujiang (Pearl) River estuary, South China Sea in autumn 2009. We evaluated the environmental conditions and phytoplankton community structure during the outbreak. The red tide water mass had significantly higher dissolved inorganic phosphate (DIP), ammonia, and temperature, but significantly lower nitrite, nitrate, dissolved inorganic nitrogen (DIN), and DIN/DIP relative to the non-red-tide zones. The phytoplankton assemblage was dominated by dinoflagellates and diatoms during the red tide. C. geminatum was the most abundant species, with a peak density of 4.13×107 cell/L, accounting for >65% of the total phytoplankton density. The DIN/DIP ratio was the most important predictor of species, accounting for 12.45% of the total variation in the phytoplankton community. Heavy phosphorus loading, low precipitation, and severe saline intrusion were likely responsible for the bloom of C. geminatum. 相似文献
43.
We established a line (screened) of Portunus trituberculatus by selectively breeding individuals that survived from challenge with Vibrio alginolyticus, and compared the response of screened and unscreened (control) P. trituberculatus challenged with V. alginolyticus. We measured superoxide dismutase, catalase, acid phosphatase, alkaline phosphatase, and peroxidase activity and the content of hemocyanin in the plasma and phenoloxidase activity in serum. The cumulative survival rate after 24-h challenge with V. alginolyticus was significantly higher in the screened crabs than in the unscreened crabs (P<0.05). T-SOD and PO activity were significantly lower in the screened stock than in the unscreened stock (P<0.05). POD, CAT, and ACP activity and hemocyanin content were significantly higher in the screened stock than in the unscreened stock. Our results suggest that the screened stock was more resistant to infection. Furthermore, the indices we measured may be used to evaluate the health state of P. trituberculatus. 相似文献
44.
基于弧段标记的交通网络时间最短路径算法 总被引:2,自引:0,他引:2
标号算法是经典的最短路径算法之一,在交通领域中具有广泛的应用。在交通领域中,时间最短路径比距离最短路径更有意义,而时间最短路径不仅与道路的时间权值有关,还与道路之间的转弯阻抗有关。在传统的交通路网抽象方式下,道路抽象为平面图中的弧段,道路间的交叉口抽象为节点。本文介绍了一种适用于传统交通路网模型的弧段标记时间最短路径算法,详细阐述了该算法的原理、数据基础与运行结构。通过分析和实例测试表明,该算法可以顾及城市路网在路口的交通限行与转弯延迟的影响,并且时间复杂度低,具有一定的实际应用价值。 相似文献
45.
鞍山市东部陈台沟村附近,有一套以斜长角闪岩类、石英岩类和长英质片麻岩类等组成的变质表壳岩(陈台沟表壳岩),它虽被划归为鞍山群但同该地区公认的鞍山群明显不同。它同白家坟花岗岩(3.8Ga)和陈台沟花岗岩(3.3Ga-3.1Ga)为断层接触。采用Kober提出的单颗粒锆石逐层蒸发-沉积方法,测定了侵入陈台沟表壳岩的两条花岗岩脉(A9212-3,Ch10)中锆石的年龄,A9212-3测定了8粒锆石,年龄为3357±4Ma-3315±4Ma(误差均为2d,Ch10测定了3粒锆石,结果为3337±12Ma,3228±37Ma和1813±7Ma。3357Ma和3337Ma是这两条花岗岩脉侵位时间。1813Ma是后期地质作用的时间。陈台沟表壳岩的年龄大于3.35Ga,建议将陈台沟表壳岩从鞍山群分离出来单独建群。 相似文献
46.
胶南造山带西段显示了以韧性剪切带为主,穹隆构造、弧形构造及复杂的叠加褶皱共存的构造格局。主要的剪切系统有近水平拆离型、平行造山带走向的高角度走滑型、呈弧形展布的推覆型和造山带边缘隆-滑型韧性剪切带。走滑型剪切带是该区变形最明显的一组强剪切应变带,其运动性质以右行平移为主;弧形韧性剪切带由垂直造山带走向的近南北向转为平行造山带走向的近东西向,呈向NW凸出的弧形,自SEE向NWW方向推覆;造山带边缘韧性剪切带具明显的纵向分段性,反映了其在隆升的同时形成了垂直造山带和平行造山带的运动分量。主要的穹隆构造有尚庄穹隆、丝山穹隆、甲子山穹隆和官山穹隆。尚庄穹隆由片麻理围斜外倾、环形韧性剪切带及环状分布的包体群所显示,是岩浆强力定位造成的真正的片麻岩穹隆。弧形构造主要有龙古弧、诗雒弧和临沐弧,它们显示了胶南造山带三维空间上的“立交桥”式结构特征。 相似文献
47.
Zhigao Sun Xiaojie Mou Xinhua Li Lingling Wang Hongli Song Huanhuan Jiang 《中国地理科学(英文版)》2011,21(2):129-148
Stable isotope techniques have been proved useful as tools for studying the carbon (C) and nitrogen (N) biogeochemical cycles of ecosystem. This paper firstly introduced the basic principles and the distribution characteristics of stable isotope, then reviewed the recent advances and applications of stable isotope in the C and N biogeochemical cycles of ecosystem. By applying the 13 C natural abundance technique, ecologists are able to understand the photosynthetic path and CO 2 fixation of plants, the CO 2 exchange and C balance status of ecosystem, the composition, distribution and turnover of soil organic C and the sources of organic matter in food webs, while by using the 13 C labeled technique, the effects of elevated CO 2 on the C processes of ecosystem and the sources and fate of organic matter in ecosystem can be revealed in detail. Differently, by applying the 15 N natural abundance technique, ecologists are able to analyze the biological N 2 -fixation, the N sources of ecosystem, the N transformation processes of ecosystem and the N trophic status in food webs, while by using the 15 N labeled technique, the sources, transformation and fate of N in ecosystem and the effects of N input on the ecosystem can be investigated in depth. The applications of both C and N isotope natural abundance and labeled techniques, combined with the elemental, other isotope ( 34 S) and molecular biomarker information, will be more propitious to the investigation of C and N cycle mechanisms. Finally, this paper concluded the problems existed in current researches, and put forward the perspective of stable isotope techniques in the studies on C and N biogeochemical cycles of ecosystem in the future. 相似文献
48.
49.
CARBON DYNAMICS OF WETLAND IN THE SANJIANG PLAIN 总被引:2,自引:0,他引:2
SONG Chang-chun WANG Yi-yong WANG Yue-si YAN Bai-xing WANG De-xuan ZHAO Zhi-chun LOU Yan-jing 《中国地理科学(英文版)》2003,13(3):228-231
1INTRODUCTIONWetlandsplayanimportant roleintheprocessofcar-bonstorage.Thetotalcarbonstoredindifferentkindsofwetlandsisabout15%-35%ofthetotalcarboninthegloballandsoils(POSTetal.,1982;GORHAM,1991).Inaddition,wetlandsaresignificantnaturalsources fortheatmospheric CH4 (MOORE,1994).It isestimatedthatabout110×1012gCH4 originates fromanaerobicdecompositioninthenaturalwetlands,CH4 emission fromthenaturalwetlandsis15%-30%oftheglobalCH4 emission andtheCH4 emission from thepeat land at hi… 相似文献
50.
2000国家GPS大地控制网数据处理方法与结果 总被引:7,自引:2,他引:7
介绍了我国GPS大地控制网的基本情况,阐述了结合地壳运动观测网络工程建立全国统一的“2000国家GPS大地控制网”的意义,并介绍了整网平差中采用的技术方法和最后平差结果及精度。 相似文献