简介:-ThispaperdescribesaradioactivetracerexperimentcarriedoutatthelandwardspoilsiteoftheNorthPassageintheYangtzeEstuaryinJune,1991.Scandium-46wasselectedasthetracer,thetotalactivityreleasedwas179.45GBqandtheamountoftheSandium-46glasswas495g.Thepurposeoftheexperimentwastodeterminethesedimentmovementdirection,path,velocityandtransportrate,andtherefore,toprovidedirectevidenceforusingthelandwardspoilsiteinthefuture.Theexperimentalresultsshowedthatthesedimentmovementwasgovernedbytheebbtidecurrentduringtheperiodofmeanandneaptideswhentheradioactivetracerwasinjectedbothonthefloodandebbtides,andthesedimentmovedfromthereleasepointtothemiddleoftheNorthPassagenearnavigationbuoyNo.269.Thedirecitonofthesedimentmovementwas110°,theparticlevelocitywas758m/d,andthesedimenttransportrateperunitwidthwas47.8m3/md.
简介:BACKGROUND:Thecorticospinaltractisthecorestructureofcerebralcontrolofextremitymovementandplasticity,whichareprerequisitesformovementrehabilitationafterbraininjury.Themeasurementandassessmentofplasticitychangeswithinthecorticospinaltracthasbecomeoneofthekeygoalsinthisfield.OBJECTIVE:Toexploretheeffectsofbiotinylateddextranamine(BDA)asaneuraltracerintheratcorticospinaltractandthepossibilitiesofassessingplasticitywithinthecorticospinaltract.DESIGN:Anobservationalexperiment.SETTING:DepartmentofAcupunctureofChineseMedicalCollege,ChongqingMedicalUniversity,DepartmentofNeurology,theSecondAffiliatedHospital,ChongqingMedicalUniversity.MATERIALS:EighteenmaleadultSpragueDawley(SD)ratsofcleangrade,weighing200-250g,wereprovidedbytheexperimentalanimalcenterofChongqingMedicalUniversity.Theanimalproceduresinthisstudywereinaccordancewiththeanimalethicsstandards.BDAwasprovidedbyVectorLaboratoriesCompany(USA,catalogueSp-1140;serialnumberR0721).METHODS:ThisexperimentwasperformedintheLaboratoryofChongqingMedicalUniversitybetweenSeptemberandDecember2006.AdultSDratswereusedintheexperimentand15%BDAwasinjectedslowlywithamini-syringethroughtworound(3mmdiameter)holesintotheleftsensoryandmotorcortex.Thecenterofoneholewaslocated3mmanteriorfromtheanteriorfontaneland1.5mmleftofthemidline;thesecondholewaslocated1.5mmposteriorfromtheanteriorfontaneland4mmleftofthemidline.Threeinjectionsweremadeateachholeatthreedifferentlevels:1.4,1.2,and1mmventralfromthesurfaceoftheflatskull.After14days,thebrainsandspinalcordswereremovedandfrozen.SectionswerecutonacryostatandBDAtransportationabsorbedbyaxonswasobservedunderafluorescencemicroscope.MAINOUTCOMEMEASURES:AxonalabsorptionandtransportationofBDAwasobservedunderfluorescencemicroscope.RESULTS:EighteenS
简介:被动tracer的概率分布函数(PDF),由“一个吝啬的坡度”强迫了,被学习。首先,我们采取二条理论途径,Lagrangian和有条件的闭合形式体系,到学习如此的外部地强迫的被动示踪物的PDF。然后,我们在一个范围上并且为测试吝啬坡度的模型是否能被用于学习在中间的纬度混合的同温层的tracer的同温层的风遨游的中等范围的天气预报(ECMWF)的欧洲中心为理想化的随机的流动执行数字模拟地区,在哪个,并且是否一弱并且杆病房带平均数的坡度被示踪物漏通过极、热带的混合障碍维持在中间的纬度的示踪物变化的PDF与理论预言一致。数字模拟证明当散开的驱散被吝啬坡度的强迫平衡时,在随机的PDF流动,在ECMWF风中的南部半球的PDF显示出时间不变的指数的尾巴,与理论预言一致。在北半球,PDF展出non-Gaussian尾巴。然而,PDF尾巴不与理论期望一致。强迫的示踪物的PDF尾巴的长期的行为与腐烂的tracer的相比。腐烂的示踪物的PDF尾巴是时间依赖者,这被发现,并且演变向恭维比指数。
简介:DiffusionofAlinthinfilmnanocrystallineCu(18nm)hasbeeninvestigatedbymeansofsecondionmassspectroscopy(SIMS).Intheexperimentaltemperaturerangesfrom421to773K,thereseem-inglyexiststwodiffusionmechanisms.TheimpurityelementsOandCaresupposedtoaccumulatetothegrainboundariesandinhibitthefastgrainboundarydiffusion.
简介:摘要:PPP是一种数据链路层协议,遵循HDLC(高级数据链路控制协议)族的一般报文格式。在串行链路上封装IP数据报,涉及到添加帧头和帧尾,用于同步的特殊比特模式、地址、控制信息以及用于错误检测的校验和。
简介:在现实的网络环境中,交换机是使用最为广泛的网络设备之一,其原理与配置-直都是计算机网络课程的重要内容.为了深入学习交换机的原理,设计了一套由浅入深、可操作性强的实验,并采用PacketTracer进行模拟仿真.通过使用具体交换机的命令和利用PacketTracer的仿真模式查看数据帧传输,逐步理解交换机的原理和功能.同时,还对比了交换机和集线器的数据传输方式,以说明它们工作原理的差异.
简介:通过具体的实验对PacketTracer软件进行了仿真技术测试分析。并在真实网络互连上进行了对比实验验证。实现了Telnet、VLAN、STP、RIP、OSPF、PPP、FrameRelay、NAT、ACL、WAN、VPN、DHCP、HTTP、DNS、Emai等网络互连和仿真通信实验。基于PacketTracer的仿真技术,优化实践过程、改善实践教学环境、构建具有开放式的网络互连技术实验平台,能够较好地解决学生一旦离开实验室环境将变得束手无策的问题,学生将有更多的机会去参与实验学习和实践体验,激发了学生自主学习的积极性。同时,节约了实验设备成本、降低了实验室管理难度。
简介:ThedirectionofoilchargeswithinafieldintheNigerDelta,Nigeriawasdeterminedbythesumofdifferencesrankingmethodofcarbazoleconcentrationsafterascertainingotherpossiblegeologicalconstraintsontheircompositionalvariations.Theprincipleisthatthesmallerthesum,thecloserthewelltothesourcekitchen.Theapproachmakesuseofcarbazoles’interactionwiththematrix,whichleadstoareductionintheirconcentrationwithincreasingdistancefromthesourcekitchen,allowingpredictionofthechargingdirection.AwiderangeofcompositionalvariationswasobservedforC1(806.72–2152.90lg/g)andC2(767–2469.72lg/g)carbazoleswithinthefield.Basedontheseresults,weinferredafillingpathwayorientationfromwesttoeast.Thissuggeststhatthesourcekitchen-themostpromisingregionforoilexploration-islocatedinthewesternpartoftheoilfield.