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811.
杭州湾钱塘江两岸全新世以来的古植被及古气候研究   总被引:1,自引:0,他引:1  
根据杭州市三个钻孔的孢粉资料对杭州市地区全新世以来的植被和古气候演变进行讨论。这三个钻孔分别位于钱塘江两岸的三盈村(HZ1)、新街三星(HZ2)和下沙镇市场(HZ3),笔者对其进行了孢粉样分析和地层年代学研究。研究结果表明,该区自晚更新世晚期以来的植被演化可以划分为4个阶段:第一阶段为针叶林,气候温凉较湿,海平面低于现今海平面;第二阶段为针叶林或针阔叶混交林,气候温和较湿,海平面接近现今海平面;第三阶段为针阔叶混交林,枫香、榆花粉明显增多,气候温暖较湿,出现高海面;第四阶段为针叶林,气候暖和较湿,海平面接近现今位置。其中第一阶段为末次冰期,第二、三、四阶段为全新世。根据第三阶段的孢粉组合特征、岩性特征以及微体化石可知,全新世中期的气候比较适宜,气候温暖湿润。  相似文献   
812.
813.
1IN TR O D U C TIO NIntervening opportunity theory states thatthe num berofpeople traveling a given distance isdirectly proportionalto the num ber of opportunity at that distance, and in-versely proportional to the num ber of intervening op-portunity or t…  相似文献   
814.
The changes in heme (associated with hemoglobin), hemoglobin and hematin in the coelomic fluid of marine worm,Urechis unicinctus, exposed to different concentrations of sulfide, were investigated using biochemical techniques. When exposed to different sulfide concentrations for up to 96 h, the relative amounts of the three components changed in a regular pattern suggesting that the coelomocytes play an important role in the worm's tolerance to sulfide. The possible roles of heme compounds in sulfide tolerance of this species are discussed on the basis of our experimental data. This research was supported by the NSFC-KOSEF scientific cooperation program and NSFC (No. 30271039)  相似文献   
815.
The Longwangzhuang granite pluton occurs on the southern margin of the North China Craton and consists mainly of biotite syenogranite with aegirine granite being locally distributed.The granites are characterized by high silicon and alkaline contents(SiO2=72.17%-76.82%,K2O+Na2O=8.28%-10.22%,K2O/Na2O>>1),AI(agpaitic index) =0.84-0.95,DI=95-97,ASI(aluminum saturation index)=0.96-1.13,and very high Fe* number(FeO*/(FeO*+Mg)=0.90-0.99),thus the granites are assigned to the metaluminous to weakly peraluminous,alkalic to calc-alkalic ferroan A-type granites.The granites are rich in large ion lithophile elements(LILE),especially high in REE concentrations(REE+Y=854×10-6-1572×10-6);whereas the enrichment of high strength field elements(Nb,Ta,Zr,Hf) is obviously less than that of LILEs,exhibiting mild depletions on trace element spider plots;and the rocks are significantly depleted in Ba,Sr,Ti,and Pb.The low εNd(t) values(-4.5--7.2) and high model ages(2.3-2.5 Ga) of the granites as well as the low εHf(t) values(-1.11--5.26) and high Hf model ages(THf1= 2.1-2.3 Ga,THf2=2.4-2.6 Ga) of zircons from the biotite syenogranite suggest that the granites were probably derived from an enriched mantle source.The zircons from the biotite syenogranite are mainly colorless transparent crystals exhibiting well-developed oscillatory zoning on the cathodoluminescence images with a LA-ICPMS zircon U-Pb age of 1602.1±6.6 Ma(MSWD=0.48).Petrochemical,trace elements,as well as Nd and Hf isotopic compositions of the rocks demonstrate that the granites were formed in a within-plate extensional tectonic regime possibly related to the breakup of the Columbia supercontinent.The granites were most likely formed through extreme fractional crystallization of alkali basaltic magma resulted from partial melting of the mantle,which was fertilized by recycling crustal rocks triggered by the delamination of lithospheric mantle and lower crust following the ~1.8 Ga collision and amalgamation of the North China Craton which is part of the Columbia supercontinent.However,contamination of neo-Archean to Paleoproterozoic crustal rocks during the ascent and emplacement of the magma could not be excluded.Being the youngest known anorogenic magmatism on the southern margin of the North China Craton related to Columbia breakup,it might represent the break off of the North China Craton from Columbia supercontinent at the end of Paleoproterozoic.  相似文献   
816.
The main aim of this work is to understand the distribution of minerals by obtaining a shallow velocity structure around the Karatungk(喀拉通克) region.Data were acquired in 2009 by a denser array in deploying a transportable seismometer with 4.5 Hz vertical geophone.All the P-wave arrival times are picked automatically with Akaike information criterion,and then checked man-machine interactively by short-receiver geometry.The database for local active-source tomographic in-version involves 4 241 P-wave arrival ...  相似文献   
817.
浙江煤炭地质局勘探一队主要从事地质勘查及延伸业、机械制造业二大产业,按目前设备分类方法,二大产业占有设备净值分别为40%和60%,但二者创造的经营收入及利润却相差悬殊,设利比(设备余值与利润比值)高达190倍,可见地质勘查及延伸业仍是浙江煤炭地质局勘探一队目前的主要经营方向,而未取得理想效果的机械制造业仍有巨大的潜力。通过对生产设备的综合分析,提出了根据设备构成、设备新度系数、设备完好率等诸多因素分析其对地勘单位发展潜力影响的新方法。  相似文献   
818.
The influence of the asymmetric structure of hurricane wind field on storm surge is studied with five types of numerical experiments using a three-dimensional storm surge model. The results from the case of Hurricane Floyd (1999) show that Floyd-induced peak surge would have been much higher had the region of maximum wind rotated 30–90° counterclockwise. The idealized cases (the hypothetical hurricanes) with a wind speed asymmetry of 20 m s?1 show that the peak (negative) surge varied from 4.7 to 6.0 m (?5 to ?5.7 m) or equivalent to ?8.8% and 16.3% (2.8% and ?10.4%) differences as compared to the control experiment. The area of flooding varied from 3552 to 3660 km2. The results from two other idealized cases of varying degree of wind speed asymmetry further show that with decreasing (increasing) asymmetry of wind fields, the variations of peak surge and peak negative surge caused by the rotation of wind fields decrease (increase) accordingly. The results suggest that in storm surge simulations forced by winds derived from balanced models, considerable uncertainty in storm surge and inundation can result from wind asymmetries. This is true even if all other storm parameters, including maximum wind speed, the radius of maximum winds (storm size), minimum central pressure, storm translation speed, drag coefficient, and model settings (domain size and resolution) are identical. Thus, when constructing ensemble and probabilistic storm surge forecasts, uncertainty in wind asymmetry should be considered in conjunction with variations in storm track, storm intensity and size.  相似文献   
819.
采用RT-PCR方法,研究了促性腺激素受体(FSHR和LHR)基因在雄性半滑舌鳎繁殖周期中的季节表达规律。结果表明,FSHR mRNA在雄鱼精巢、脑和脾中及LHR mRNA在雄鱼的精巢和脾中均呈季节规律性变化。3月份样品中,FSHR mRNA在精巢表达量最低,12月份,表达量最高;FSHR mRNA在脑中表达模式与精巢...  相似文献   
820.
Evaporation loss from the saturated soil beneath drip irrigation emitters highly influences the irrigation efficiency of drip irrigation (DI). Subsurface drip irrigation (SDI) is one good approach to curb this inefficiency, but in a new irrigation method, straight tube irrigation (STI), the irrigation tubes do not need to be buried and thus STI is recommended to increase the irrigation efficiency under normal surface-applied DI. STI consists of only connectors and water-transference tubes that can directly transfer irrigation water from the lateral emitters in the drip line to the root zone of plants. Five-month field experiments were carried out in Aeolian sand soil in the forest-belts of the Taklimakan Desert, which have poor water storage capacity, to compare the potential water saving between STI and DI. The preliminary results showed that, compared with DI, STI (1) improved the soil water content in soil depths from 40 to 100 cm under the soil surface; (2) achieved the same irrigation effects in relatively shorter irrigation durations; (3) had very little water loss due to deep seepage; and (4) formed a layer of dry sand about 10 to 30 cm thick immediately below the soil surface, which lessened evaporation loss of soil water beneath the emitters on the soil surface. This demonstrates that STI can maximize the water-saving potential of DI through the reduction of wetted soil perimeters on the soil surface. This is valuable information for water-saving engineering applications and projects with STI in arid and semiarid regions.  相似文献   
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