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1.
INTRODUCTIONAnAdeno associatedvirus(AAV)particleiscomposedofthreestructuralproteinsandalin ear ,single strandedDNA (ssDNA)genomeofapproximately 4 .7kb .AAVisadefectivehu manparvovirusthatnormallyreplicatesproduc tivelyonlyinthepresenceofhelperfunctionsprovide…  相似文献   

2.
INTRODUCTIONRibozymewasfirstdescribedbyCechandAltmanin 1 981 .ThisformofRNAhadhighlyspecificendonucleaseactivitiestoRNA (Krugeretal.,1 982 ) .Ribozymeshavethreestructures:hammerhead ,hairpinandaxeribozymes.Amongthem ,thehammerheadribozymehasasimplersecondarystruc…  相似文献   

3.
浅议计算机辅助教学   总被引:1,自引:0,他引:1  
ComputerAssistedlnstruction (CAI)isthetermusedtodescribecomputerprogramsdesignedforteaching .ItisimportantnottoconfusethistermwithCALL(ComputerAssistedLanguageLearning)———thecatchalltermfordiffer entformsofL2instructionaccomplishedwiththeuseofcomputers.Fo…  相似文献   

4.
OBSTACLE DETECTION BY ALV USING TWO 2D LASER RANGE FINDERS   总被引:6,自引:0,他引:6  
INTRODUCTIONObstacleavoidanceisanessentialtaskoftheALV .Toachievethis,aquickandreliablede tectionofobstaclesisveryimportant.Severalclassesofactivesensorscanbeusedforthispur pose .Alaserrangefinder (LRF)cansuitablybeusedtodetectobstaclesaheadoftheALV .3DLRFs…  相似文献   

5.
ThevarietyofEnglishspokenintheUSAiscalledAmericanEnglish .AmericanEnglishgrewoutofBritishEnglishofthe 17thcentury.WiththefurthergrowthoftheUnitedStates,AmericanEnglishhasevolvedfroma“colonialbranch”toavariantorna tionalstandardofEnglish .Thecharacteristic…  相似文献   

6.
TomwasfollowingUncleSamtotherainforestinBrazil’sAmazonregion①.AshewalkeddeepinsidetherainforestwithUncleSam ,hesawthetreetopstoucheachother,creatingashaded②forestinside .Allofasudden ,Tomheardtheraindropspatting③onthetreeleaves.Tomputonhisraincoatassoona…  相似文献   

7.
1 Introduction LetX ,YbetwoHilbertspacesandletAbeaboundedlinearoperator,i.e .,A∈B(X ,Y) .Consid ertheoperatorequationAx=y . (1)IfR(A) ,therangeofA ,isnonclosedinY ,Eq .(1)isill posed[1] .Manyimportantproblemsinappliedsci encesresultinthiskindofequations[2 ,3] .Inthispaperwec…  相似文献   

8.
从一个例子谈起 已知△ABC的三个内角A、B、C满足 :A C =2B ,secA secC =- 2secB ,求cos A -C2 的值 .解 由A C =2B ,得A C =12 0° ,B =6 0° .∵ secA secC =- 2secB ,∴ cosA cosC =- 2 2cosAcosC ,2cos A C2 cos A -C2=- 2〔2cos2 A -C2 - 1 cos(A C)〕 ,即  4 2cos2 A -C2 2cos A -C2 - 32 =0 .因 - 324 <- 1,故解得cos A -C2 =22 .1 关于解题思维表现的分析上例中 ,条件是三角形三内角的一个关系式和有关这些角的一…  相似文献   

9.
NTRODUCTIONAftermuchresearchandsomesuccessfulap plicationsofArtificialNeuralNetwork (ANN)tocontrolsystems,ANNhasbecomeoneoftheim portanttoolstoshowtheintelligenceofthehu manbrain .SinceANNcanbeusedtodescribeanynonlinearcontinuousfunction ,ithasdrawnmuchat…  相似文献   

10.
1 —Whichofthetwotieswillyoutake ?—I’lltake ,forachangesome times.A .either B .both C .neither D .all2 .Thepolicecouldn’tseewhichthecarwent.A .path B .way C .street D .road3.Thebusdriverwasbadlyinbothlegsinthetrafficaccident.A .damaged    B .woundedC .injuredD .destroye…  相似文献   

11.
INTRODUCTIONItiswellknownthatinfreeradicalpolymerization,thediffusioncontrolledprocessesstronglyinfluencetherateofpolymerizationandthepropertiesoftheproducedpolymer.Anumberofmodelsweredevelopedtodescribethisphenomenaquantitatively(Achiliasetal.,1988;Achil…  相似文献   

12.
《河北自学考试》2000,(9):33-37
Ⅰ .VocabularyandStucture (1 0 points,1 pointforeach)1 .Almosteverythingamanagerdoes  deci sions;indeed ,somesuggestthatthemanagementpro cessisdecisionmaking .[A]imposes[B]improvises[C]involves[D]indi cates2 .Astronomersandscientiststhinkthatablackholeisaregionofspace…  相似文献   

13.
INTRODUCTIONAntisenseoligodeoxynucleotides (ASODN )caninhibittranscriptionandinterferewithspe cialgeneexpression .AfixedpointontheK rasgenewithhighmutationrateinpancreaticcarci nomaoffersanintracellulartargetforpancreaticcarcinomagenetherapywithASODN (Cai…  相似文献   

14.
AlthoughmydearbrotherFrankisalreadyeight 1 .yearsold ,hetriestobehaveasifheisolder.Heis 2 .rathershort,andhasblackhair.Ibringhimtoschool 3.everymorning .Anditiseasytopickouthimfromthe 4.crowdwhileIgoandfetchhimafterschool.Hewears 5 .hishairwildlyandoftenhashisbut…  相似文献   

15.
1 Introduction LetX ,YbetwoHilbertspacesandletA∈B(X ,Y) ,i .e .,aboundedlinearoperator .ConsidertheoperatorequationAx =y (1.1)IfR(A) ,i .e .,therangeofA ,isnon closedinY ,Eq .(1.1)isill posed[1] .Manyimportantproblemsinappliedsciences ,especiallyinverseproblems ,resultinthiski…  相似文献   

16.
INTRODUCTIONTocopewiththemoreandmoreserioushar monicproblemsmainlycausedbypowerelec tronicequipmentapplication ,variouskindsofactivefiltershavebeenproposedandputintofieldapplicationsrecently.Amongthem ,aSeri alHybridActivePowerFilter (SHAPF)asshowninFig.1 (…  相似文献   

17.
IntroductionMostofustakeitfor grantedthatunderstandinganutterancemeansthecomprehensionofthetotalmeaningconveyedbythespeaker.Asamatteroffact,itusuallyturnsoutthatitisfarfromenoughforustounderstandandinterpretthemeaningfullyandcorrectly .AnEnglishwordusu…  相似文献   

18.
1 Introduction Withthedevelopmentofthe powerelectronicstechnology ,stationarypowerconvertingdevicessuchasAC DCconvertersandDC ACinvertersareappliedinvariousindustrialareas .However ,thishasledtosomeproblems ,e .g .theincreaseofharmonicsinpowersupply ,andtheEM…  相似文献   

19.
1 Introduction Itiswellknownthatmetalhydridesareanidealmediumforhydrogenstorageduetotheirhighdensityandhigh purityofhydrogen .However ,allknownconventionalmetalhydrides ,includingintermetalliccompoundsAB5,AB2 ,andAB ,havereversiblegravi metricH densitiesnomo…  相似文献   

20.
ISTHENOVELDEAD ?Therehasbeennolackofpropheciesofthedeathofthenovelsincethebeginningofthe2 0thcentury .Manyprestigiouscritics,suchasT .S .Eliot,OrtegaY .Gasset,AlbertoMoraviaandCyrilConnolly ,haverelentlesslypronounceddeathsentenceonthenovel.Althoughthousandso…  相似文献   

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