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331.
332.
黄河经常改道,给中国带来肥沃的耕地,也带来灾难。历代黄河河道变迁反映在地图上,可以断定地图的成图年代。先秦至宋代,黄河基本在华北平原用不同河道进入渤海。自1194年开始,黄河夺淮,分两支,北入渤海,南注黄海。1580年治河后,黄河只有南支汇淮河入黄海,到1855年再恢复单支入渤海。黄河4次大改道的历史可以印证地图成图年代。《坤輿万国全图》上的黄河分两支,为1194—1580年状态,不是利玛窦与李之藻时代的黄河,他们应该目击而未更正,证明两者均没有参加《坤輿万国全图》的测绘,地图存在远较二人时代为早。卫匡国的《中国新地图集》,黄河只表示南支入黄海,是1580年以后的材料,比1541年的《广舆图》资料更新。地图制作有勘探、测绘、拼合、制版、印刷、翻译等步骤。严格来说,地图最重要的创作者是勘探测绘者,其他的任务是后勤,翻译重绘更是省事。《中国新地图集》主要制作人不是卫匡国,实为中国历代省、县、乡分工测绘,明代统其成,已用经纬线,球形投影绘制。《坤輿万国全图》则是郑和等率领大航海的经验总结。卫、利、李等人只参与翻译,添加地名和序言。这两份外国保存的中国地图重现中国历史,证明郑和时代的大航海是世界地理大发现的先驱,近代地图学为中国原创,中国地图学西传才更接近史实。  相似文献   
333.
采用考虑沉水植物影响的E-ε湍流动能闭合湖泊热力学过程模型,模拟2013年8月东太湖湖-气交换过程,并利用太湖的站点观测数据对模型进行了验证。太湖水温的模拟值与观测值吻合较好,模型计算的各层水温与观测值相比,均方根误差均未超过1℃。同时模型也较好地模拟出太湖表面感热通量和潜热通量,潜热通量的模拟值与观测值的标准差为54.7 W/m2。由于湖水较浅,太湖的水温层结会明显受到天气状况的影响。晴朗小风条件下的湖水呈现显著的热分层现象,当风速为0.8 m/s,高层和底层的温差达到7.9℃。大风天气条件驱动较强的水体湍流混合,水温的热分层消失,风速为12 m/s,湖泊上层与底层的水温差仅0.12℃。此外,模拟结果较好地呈现出了东太湖沉水植物的存在通过增大湖体消光系数,减小到达湖体内部的热量,并增加对湖水的阻力,影响湖体中湍流动能的分布,并进而影响湖水温度的分布。综上所述,该模型能够较好地模拟出浅水大湖湖-气交换的过程。  相似文献   
334.
Viral hemorrhagic septicemia virus (VHSV) and marine birnavirus (MABV) are the causative pathogens for some of the most explosive epidemics of emerging viral diseases in many Asian countries, leading to huge economic losses in aquaculture. Rapid molecular detection for surveillance or diagnosis has been a critical component in reducing the prevalence of pathogen infection. The loop-mediated isothermal amplification (LAMP) of DNA is currently one of the most commonly used molecular diagnostic tools, as it is simple, quick, and easy to amplify target DNA under isothermal conditions. In the present study, a novel and highly specific LAMP assay for the sensitive and rapid detection of VHSV and MABV infection in fish was developed. Using a set of synthesized primers matching a specific region of the genome, the efficiency and specificity of the LAMP assay were optimized in terms of the reaction temperature and DNA polymerase concentration, as they are the main determinants of the sensitivity and specificity of the LAMP assay. In particular, we demonstrated that our assay could be applied to efficient detection of VHSV and MABV infection in the wild fish, Paralichthys olivaceus. Our results demonstrate the simplicity and convenience of this method for the detection of viral infection in aquatic organisms.  相似文献   
335.
正Objective The uplift process and uplift mechanism of the Tibetan Plateau has been a research focus among geologists in recent years.This work put emphasis on the Cenozoic exhumation histories of the blocks bounded by the major faults at the central segment of the Longmenshan thrust belt,and the vertical faulting history,including the starting  相似文献   
336.
The newly discovered Paodaoling porphyry Au deposit from the Guichi region, Lower Yangtze River Metallogenic Belt(LYRB), contains 35 tons of Au at an average grade of ~1.7 g/t. It is a porphyry ‘Au-only' deposit, as revealed by current exploration in the depths, mostly above-400 m, which is quite uncommon among coeval porphyry mineralization along the LYRB. Additionally, there are also Cu-Au bearing porphyries and barren alkaline granitoids in the Paodaoling district. Zircon LA-ICP-MS U-Pb dating of the Cu-Au-bearing porphyries yield an age of 141–140 Ma, falling within the main magmatic stage of the LYRB, whereas the barren granites give an age of 125–120 Ma, coeval with the regional Atype granites. The Cu-Au-bearing porphyries are LILE-, LREE-enriched and HFSE-depleted, typical of arc magmatic affinities. The barren granites are HFSE-enriched, with lower LREE/HREE ratios and pronounced negative Eu anomalies. The Cu-Au-bearing porphyries in the Paodaoling district have high oxygen fugacities and high water content. Pyrite sulfur isotopes of the Paodaoling gold deposit indicate a magmatic-sedimentary mixed source for the ore-forming fluids. Based on the alteration and poly-metal zonation of the deepest exploration drill hole from the Paodaoling Au deposit, we propose that Cu ore bodies could lie at depth beneath the current Au ore bodies. The magmatism and associated Cu-Au mineralization of the Paodaoling district are likely to have formed in a subduction setting, during slab rollback of the paleo-Pacific plate.  相似文献   
337.
Hierarchical clustering analysis and principal component analysis (PCA) methods were used to assess the similarities and dissimilarities of the entire Excitation-emission matrix spectroscopy (EEMs) data sets of samples collected from Jiaozhou Bay, China. The results demonstrate that multivariate analysis facilitates the complex data treatment and spectral sorting processes, and also enhances the probability to reveal otherwise hidden information concerning the chemical characteristics of the dissolved organic matter (DOM). The distribution of di.erent water samples as revealed by multivariate results has been used to track the movement of DOM material in the study area, and the interpretation is supported by the results obtained from the numerical simulation model of substance tracing technique, which show that the substance discharged by Haibo River can be distributed in Jiaozhou Bay.  相似文献   
338.
The temporal and spatial variabilities of phytoplankton absorption coefficients (a ph (λ)) and their relationships with physical processes in the northern South China Sea were examined, based on in situ data collected from two cruise surveys during May 14 to 25, 2001 and November 2 to 21, 2002. Significant changes in the surface water in a ph values and B/R ratios (a ph (440)/a ph (675)) were observed in May, which were caused by a phytoplankton bloom on the inner shelf stimulated by a large river plume due...  相似文献   
339.
Identifying Indicator Species in Habitats Created by Coastal Structures   总被引:1,自引:1,他引:0  
In this paper,three approachs were developed to find indicator species from the habitat created by coastal structures.These approachs consist of a model of species co-occurrence probability,a model of k-environmental factor probability and a composite model.Simultaneously,a case study was conducted in Hsinchu Fishing Port of north-western Taiwan.Based on the aforementioned models,three primary producer species,Ahnfeltiopsis flabelliformis,Chondrus ocellatus and Sarcodia montagneana,were chosen as the indicator species which had the highest co-occurrence probabilities and showed greater tolerance to more critical environment.It is imperative to understand how the three species under particular co-occurring conditions and environmental factors influence the composition of sessile assemblages in coastal water.The results indicate that for the purpose of increasing biodiversity,these models are feasible to find indicator species of artificial structures,and to help make it possible to design coastal structures based on biological considerations.This study provides an innovative approach for further advanced application in the artificial habitat of coast management.  相似文献   
340.
彭艳  李心清  程建中  邢英  闫慧 《地球化学》2010,39(3):266-273
土壤微生物特性是土壤修复的指示因子,近年来西南喀斯特地区退化土壤的相关研究较多,但不同植被类型的土壤微生物特性的变化研究相对较少。对贵阳郊区耕作土壤、灌丛、女贞人工纯林和马尾松人工纯林表层土壤(0~10cm)微生物生物量碳(SMBC)、微生物呼吸(MR)和微生物代谢熵(qCO2)的研究结果表明,土壤SMBC和MR均表现为次生林高于耕作土壤,灌丛最高;与qCO2相反,马尾松林土壤微生物活动显著弱于其他样地,不同植被类型土壤微生物活动均表现为在秋季相对较强。与植被类型的显著影响相比,季节变化、植被与季节的交互作用对SM—BC和MR的影响不明显。SMBC与土壤温度不相关,与土壤含水量呈极显著相关而土壤含水量季节变化不明显。MR与土壤温度和含水量均无显著相关性可能是季节变化对两者影响不明显的主要原因,但需要大量区域样本进一步证实。认为演替初期的灌丛比人工阔叶或针叶纯林更有利于土壤微生物群落的生长,土壤有机质积累较快,植被自然恢复是喀斯特退化土壤恢复初期更适合的徐径.  相似文献   
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