学科分类
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108 个结果
  • 简介:Humanactivitiesmakestrongeffectsonsoilformation.AnthropogenicsoilsaremuchmoreintensiveandextensiveinChinafortheirhistoryofagriculturalproductioncanbedatedbacktomorethan7000yearsagoOwingtodifferentphysicalconditionsandlanduses,theanthropogenicsoil-formingprocessesarevariousAnthrosolsareproposed,andthecorrespondingsoilorderissetupinChineseSoilTaxonomy(CST),Mainlybasedon6Anthropogenicdiagnostichorizons,whichareanthraquicepipedon,hydragrichorizon,irragricepipedon,cumulicepipedon,fimicepipedonandagrichorzon,theAnthrosolsOrderissubividedinto2soilsubordersand4soilgroups.MeanwhiletheclassificationofAnthrosolsinCSThasbeenbasicallyacceptedastheclassificationofAnthrosolsinWorldReferenceBaseforSoilResources(WRB).

  • 标签: 土层 人为土 多样性 累积过程 中国 灌溉农业过程
  • 简介:ThenewChineseleadershipisfullyawareoftheimportanceofastableandpeacefulinternationalenvironmentforthecountry’sdevelopment.LastyearwasimportanttobothChinaandtheworldatlarge.Overshadowedbyalingeringglobaeconomicslump,thechillsoftheEuropeandebtcrisiswerestillbroadlyfelt,puttingadamperongrowthineconomiesaroundtheworld.Despite

  • 标签: 经济衰退 经济增长 阻尼器 世界
  • 简介:Background:ThiscontributionevaluatestheeffectofforeststructureandtreespeciesdiversityonplotproductivityandindividualtreegrowthintheuniqueKnysnaforestsinSouthernAfricausingmappedtreedatafromanobservationalstudythathasbeenre-measuredoveraperiodof40years.Methods:Theeffectsoftreespeciesdiversityandforeststructureontreegrowthandforestproductionareevaluatedonthreelevelsofresolution:a)theforestcommunity(canopy,sub-canopyspecies),b)thesubplots(numberoftreesperha,skewnessofthediameterdistribution,diametercoefficientofvariation)andc)theimmediateneighborhoodofselectedreferencetrees('Mingling','Dominance',Aggregation'and'SizeVariation').Results:Ananalysisofthecommunitylevelidentifiedtwodistinctclusters,oneincludingdominant/canopyspecieswiththehighestgrowthratesandagreatervariationofgrowth,andanotherclusterwhichincludestheremainingsubcanopyspecieswhichhaveasmallermaximumsizeandlowerratesofgrowth.Thearea-basedstructurevariablesonplotlevelhaveahighlysignificanteffectontotalbasalareagrowth.However,theeffectsofforestdensityandspeciesrichnessonproductivitywerenotstraightforward.Maximumbasalareaproductionofabout0.75m~2/ha/yearisachievedatmediumlevelsofrichness(around20speciesperha)andmediumlevelsofdensity(around30m~2/habasalarea)usingpercentileregressionestimates.Therelative'Dominance'ofaselectedreferencetreehadahighlysignificanteffectonindividualtreegrowthonallinvestigatedspecies.Otherneighbourhoodstructurevariableswereonlyoccasionallysignificantornotsignificantatall.Conclusion:Thiscontributionpresentsanewtheoreticalframeworkforanalysingnaturalforeststhatincludescommunity,plotandneighborhoodvariablesofforeststructureanddiversity,andafirstspecificanalysisofthestructureanddynamicsoftheKnysnaAfromontaneForest,basedonauniquesetoflongtermobservations.Thespecies-area(SAR

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  • 简介:TcellhomeostasiscommonlyreferstothemaintenanceofrelativelystableTcellnumbersintheperipherallymphoidorgans.AmongthelargenumbersofTcellsintheperiphery,Tcellsexhibitstructuraldiversity,I.e.,theexpressionofadiverserepertoireofTcellreceptors(TCRs),andfunctionaldiversity,I.e.,thepresenceofTcellsatna(I)ve,effector,andmemorydevelopmentalstages.AlthoughthehomeostasisofTcellnumbershasbeenextensivelystudied,investigationofthemechanismsunderlyingthemaintenanceofstructuralandfunctionaldiversityofTcellsisstillatanearlystage.ThefundamentalfeaturethroughoutTcelldevelopmentistheinteractionbetweentheTCRandeitherselforforeignpeptidesinassociationwithMHCmolecules.Inthisreview,wepresentevidenceshowingthathomeostasisofTcellnumberanddiversityismediatedthroughcompetitionforlimitingresources.ThenumberofTcellsismaintainedthroughcompetitionforlimitingcytokines,whereasthediversityofTcellsismaintainedbycompetitionforself-peptide-MHCcomplexes.Inotherwords,diversityoftheself-peptiderepertoirelimitsthestructural(TCR)diversityofaTcellpopulation.Wespeculatethatcognatelowaffinityself-peptides,actingasweakagonistsandantagonists,regulatethehomeostasisofTcelldiversitywhereasnon-cognateornullpeptideswhichareextremelyabundantforanygivenTCR,maycontributetothehomeostasisofTcellnumberbyprovidingsurvivalsignals.Moreover,self-peptidesandcytokinesmayformspecializednichesfortheregulationofTcellhomeostasis.

  • 标签: 动态平衡 T细胞 细胞多样性 免疫器官
  • 简介:Healthcareconsumersnolongerwanttobepassivereceiversoftreatmentandcare,theywanttobetohealthinformation,thankslargelytotheInternet,andactivehealthconsumerorganizationshaveprovidedconsumerswithenablingindependenthealthinformation.Individualconsumersarealsomorewillingtoenterintoadialogue,participateandinfluencedecisionsconcerningtheirowncare.Atthesametimetheconsumerrolebecomesmorediverse.Populationsinmanycountriestodayareculturally,socially,anddemographicallydiverse.Understandingconsumerdiversityisoneofthegreatestchallengesfacinghealthcareproviders.Thereisariskthatthequalityofhealthcareprovidedtoconsumerscanvarydependingontheskillsoftheprofessionalstoruneintothevaluesandpreferencesoftheindividualconsumer.Healthcareprovidersneedtolistentoandincorporateconsumers'experiencesintotheirhealthserviceofferingsinnewandcreativeways.Theyneedtoengageinadialoguewithvariousconsumergroupsusingmultiplechannels.Thereisaneedforanewbusinesslogic,whichwouldstructurallyhelptheproviders,onanindividualbasistodealwithmoresophisticatedhealthcareconsumers.Thisisareviewpaperandprovidesaframeworkandasetofstrategiesfordealingwithhealthconsumerdiversity.Wedrawonthreeinterrelatedtheories-opensystemstheory,servicemanagementresearchandtheconceptofconsumersegmentationtounderstandhealthcareconsumers'attitudesandbehaviour,andtheirexpectations.

  • 标签: HEALTH consumers CONSUMER diversity culturally diverse
  • 简介:PlentyofworkhavebeendoneonSpace-Timeprocessinginwhichmultipletransmit/receiveantennasareusedinconjunctionwithcodingtoexploitbothspatialdiversityandtimediversity.ConstantModeAlgorithm(CMA)isanefficientblindadaptiveMulti-UserDetection(MUD)algorithmforCDMAsystems.Inthispaper,weputforwardanovelreceiver,whichcombinesCMAblindadaptiveMulti-userDetectionwithSTBCtechnique,andcomparetheperformancesofthesystemusingdifferentCMalgorithmsincludingSDCMA(Steepest-DescentCMA),StandardLinearityConfineCMA(SLCCMA)andLeastSquaresCMA(LSCMA).Simulationshavebeendonewithmulti-pathRayleighchannel.

  • 标签: CDMA 码分多址 传输多样性 块编码
  • 简介:通过对分布于欧洲的水青冈(Fagussylvatica和Fagusorentalis)和亚洲的水青冈(Fagusjaponica,Faguscrenata,Faguslucida,Fagusengleriana和Faguspashanica)的地理历史资料分析和凝胶电泳法等位酶的测定,探讨欧亚大陆水青冈地理变异和遗传多样性.所测定的酶系统包括:过氧化物酶(PX1和PX2)、磷酸葡萄糖脱氢酶(PGD)、酸性磷酸化酶(ACP1和ACP2)、超氧化物歧化酶(SOD)、谷氨酸草酰乙酸转氨酶(GOT1,GOT2和GOT3)、异柠檬酸脱氢酶(IDH)、磷酸果糖异构酶(PGI)、甲基萘醌还原酶(MNR)、葡萄糖磷酸变位酶(PGM1和PGM2)和苹果酸脱氢酶(MDH1和MDH2)10种酶系统.测定和分析了水青冈遗传相似性、固定指数及遗传多样性随经度、纬度和海拔高度的变化规律,讨论了水青冈起源和分布特点,为进一步研究水青冈的种间关系和地理历史进化过程提供了科学依据.

  • 标签: 欧亚大陆 遗传相似性 遗传多样性 固定指数