《信息科学类专业英语》课件第25章

Lesson25About Nanotechnology)

(第二十五课关于纳米技术)

Vocabulary(词汇)ImportantSentences(重点句)QuestionsandAnswers(问答)Problems(问题)

Nanotechnologyisdefinedasfabricationofdeviceswithatomicormolecularscaleprecision.Deviceswithminimumfeaturesizeslessthan100nanometers(nm)areconsideredtobeproductsofnanotechnology.Ananometerisonebillionthofameter(10-9m)andistheunitoflengththatisgenerallymostappropriatefordescribingthesizeofsinglemolecules.Thenanoscalemarksthenebulousboundarybetweentheclassicalandquantummechanicalworlds;thus,realizationofnanotechnologypromisestobringrevolutionarycapabilities.Fabricationofnanomachines,nanoelectronicsandothernanodeviceswillundoubtedlysolveanenormousamountoftheproblemsfacedbymankindtoday.

Nanotechnologyiscurrentlyinaveryinfantilestage.However,wenowhavetheabilitytoorganizematterontheatomicscaleandtherearealreadynumerousproductsavailableasadirectresultofourrapidlyincreasingabilitytofabricateandcharacterizefeaturesizeslessthan100nm.Mirrorsthatdon’tfog,biomimeticpaintwithacontactanglenear180°,genechipsandfatsolublevitaminsinaqueousbeveragesaresomeofthefirstmanifestationsofnanotechnology.However,immenant

(imminent)breakthroughsincomputerscienceandmedicinewillbewheretherealpotentialofnanotechnologywillfirstbeachieved.[1]

Nanoscienceisaninterdisciplinaryfieldthatseekstobringaboutmaturenanotechnology.Focusingonthenanoscaleintersectionoffieldssuchasphysics,biology,engineering,chemistry,computerscienceandmore,nanoscienceisrapidlyexpanding.Nanotechnologycentersarepoppinguparoundtheworldasmorefundingisprovidedandnanotechnologymarketshareincreases.Therapidprogressisapparentbytheincreasingappearanceoftheprefix“nano”inscientificjournalsandthenews.Thus,asweincreaseourabilitytofabricatecomputerchipswithsmallerfeaturesandimproveourabilitytocurediseaseatthemolecularlevel,nanotechnologyishere.1ABriefHistoryofNanotechnology

Theamountofspaceavailabletousforinformationstorage(orotheruses)isenormous.Asfirstdescribedinalecturetitled,There’sPlentyofRoomattheBottomin1959byRichardP.Feynman,thereisnothingbesidesourclumsysizethatkeepsusfromusingthisspace.[2]Inhistime,itwasnotpossibleforustomanipulatesingleatomsormoleculesbecausetheywerefartoosmallforourtools.Thus,hisspeechwascompletelytheoreticalandseeminglyfantastic.Hedescribedhowthelawsofphysicsdonotlimitourabilitytomanipulatesingleatomsandmolecules.Instead,itwasourlackoftheappropriatemethodsfordoingso.However,hecorrectlypredictedthatthetimewouldcomeinwhichatomicallyprecisemanipulationofmatterwouldinevitablyarrive.

Prof.Feynmandescribedsuchatomicscalefabricationasabottom-upapproach,asopposedtothetop-downapproachthatweareaccustomedto.Thecurrenttop-downmethodformanufacturinginvolvestheconstructionofpartsthroughmethodssuchascutting,carvingandmolding.Usingthesemethods,wehavebeenabletofabricatearemarkablevarietyofmachineryandelectronicsdevices.However,thesizesatwhichwecanmakethesedevicesareseverelylimitedbyourabilitytocut,carveandmold.

Bottom-upmanufacturing,ontheotherhand,wouldprovidecomponentsmadeofsinglemolecules,whichareheldtogetherbycovalentforcesthatarefarstrongerthantheforcesthatholdtogethermacro-scalecomponents.Furthermore,theamountofinformationthatcouldbestoredindevicesbuildfromthebottom-upwouldbeenormous.

Sincethatinitialpreviewofnanotechnology,wehavedevelopedseveralmethodswhichprovethatProf.Feynmanwascorrectinhisprophesy.Themostnotablemethodsarescanningprobemicroscopyandthecorrespondingadvancementsinsupramolecularchemistry.Scanningprobemicroscopygivesustheabilitytopositionsingleatomsand/ormoleculesinthedesiredplaceexactlyasProf.Feynmanhadpredicted.AlthoughthelimitationsoftraditionalchemistrywerecriticizedinProf.Feynman’slectureduetoitsseeminglytediousandrandomnature,recentadvancementshaveimproveditspotentialusesfornanotechnology.2WhyMakeNanotechnology?

Onemightask,“whatexactlyarethepotentialusesofnanotechnology?”Inthelimitednumberofyearsthatnanotechnologyhasbeenconsideredpossible,aplethoraofanswerstothisquestionhavebeenpresented.Possibleanswersincludequantumcomputers,longtermlifepreservationandvirtuallyeverythinginbetween.Itseemsthatnanotechnologycouldpotentiallysolvejustaboutanyproblemthatwecouldthinkof;thus,amoreinterestingquestionis,“whatrealproblemswillnanotechnologysolvefirst?”Asofnow,itappearsthatthefirstrevolutionaryapplicationsofnanotechnologywillbeincomputerscienceandmedicine.Thesetwofieldswillmostlikelybeaffectedfirstsincetheybothcallformolecularscalemanipulationofmatterinthenearfuture.3SemiconductorFabrication

Moore’slaw,opticallithographyandthesearchforalternatives.

Computerchips(andthesiliconbasedtransistorswithinthem)arerapidlyshrinkingaccordingtoapredictableformula(byafactorof4every3years—Moore’sLaw).AccordingtotheSemiconductorIndustryAssociation’sextrapolationofformulassuchasthisone(SIAroadmap),itisexpectedthatthesizesofcircuitswithinourchipswillreachthesizeofonlyafewatomsinabout20years.

Sincealmostallofourmoderncomputersaremadefromsiliconsemiconductortransistorspatternedandcarvedbylight(photolithography),theshrinkingofcircuitspredictedbytheSIAmaynotbethemosteconomicalmethodforthefuture.Anenormousamountofmoneyhasbeeninvestedinthesemiconductorindustryinordertoconsistentlyshrinkandimproveoursemiconductorelectronics.Smallercircuitsrequirelessenergy,operatemorequicklyand,ofcourse,takeuplessspace.Thus,Moore’slawhasbeenadheredtosincecomputersfirstbecamecommerciallyavailable.However,thissimpleshrinkingofcomponentscannotcontinueformuchlonger.

AstransistorssuchastheMetal-OxideSemiconductorFieldEffectTransistor(MOSFET-oneoftheprimarycomponentsusedinintegratedcircuits)ismadesmaller,bothitspropertiesandmanufacturingexpensechangewiththescale.Currently,Ultravioletlightisusedtocreatethesiliconcircuitswithalateralresolutionaround200nm(thewavelengthofultravioletlight).Asthecircuitsshrinkbelow100nmnewfabricationmethodsmustbecreated,resultinginincreasingcosts.Furthermore,oncethecircuitsizereachesonlyafewnanometers,quantumeffectssuchastunnelingbegintobecomeimportant,whichdrasticallychangestheabilityforthecomputerstofunctionnormally.Thus,novelmethodsforcomputerchipfabricationhavebeenandarebeingintenselysoughtbymicrochipmanufactures.4MolecularandQuantumComputing

Alternativearchitecturesfornanocomputing

Inadditiontosingleelectrontransistors,twopromisingalternativestotraditionalcomputersaremolecularcomputingandquantumcomputing.Thesetwomethodsareintimatelyrelated,yetdealwithinformationontwodifferentlevels.Muchprogresshasbeenmadeintheseareasduringthelastyearsandbothhavebeenshowntobefeasiblereplacementsforsemiconductorchips.

Quantumcomputingseekstowriteprocessandreadinformationonthequantumlevel.Itisatthenanoscalethatquantummechanicaleffectssuchas(thewaveparticleduality)begintobecomeapparent.Numerousscientistsareseekingwaystostoreinformationwithinthequantummechanicalrealm.Thisisnotasimpletaskbecauseofthedelicatenatureofquantummechanicalsystems.However,sincethelawsofquantummechanicsinvolvesunintuitiveprinciplessuchassuperpositionandentanglement,aquantumcomputerwouldbeabletoviolatesomerulesthatlimitourclassicalcomputers.Forinstance,takingadvantageofsuperpositionwouldmeanthataquantumbitofinformation,termedaqubitwouldbeabletobeusedinseveralcomputationsatthesametime.Takingadvantageofentanglementwouldmeanthattheinformationcouldbeprocessedoverlongdistanceswithouttheclassicalrequirementofwires.[3]

Molecularcomputationisanothermethodcomplimentarytoquantumcomputingthatseekstowriteprocessandreadinformationwithinsinglemolecules.OnemoleculethathasprovedmostpromisingformolecularcomputationisDeoxyriboNucleicAcid(DNA).DNAisalongpolymermadeof4differentnucleotidesthatcanberepresentedbythelettersA,T,CandG.TheorderorsequenceofthesenucleotideswithinDNAprovidestheinformationformakingprotein,themaincomponentsofthemolecularscalemachineryusedbylivingorganismstocarryoutlifesustainingfunctions.

MathematicianshavefiguredoutnumerouswaystouseDNAandthevariousproteinsthatcomewithittocarryoutnumericalcomputationsthatarenotoriouslydifficultforsiliconcomputers,namelyNP-completeproblems.TheadvantagethatmolecularcomputingusingDNAhasoverconventionalcomputingisthatitismassivelyparallel.ThismeansthateachDNAmoleculecanfunctionasasingleprocessor,whichgreatlyimprovesthespeedofcomputationforcomplexproblems.5MedicalApplications

Molecularmedicine,bioinformaticsandbiomolecularnanotechnologyarerapidlyincreasingourabilitytohealandstayhealthy.

Theotherfieldinwhichmolecularscalemanipulationofmatterisreceivingabundantattentionismedicine.Sincealllivingorganismsarecomposedofmolecules,molecularbiologyhasbecometheprimaryfocusofbiotechnology.Countlessdiseaseshavebeencuredbyourabilitytosynthesizesmallmoleculescommonlyknowas‘drugs’thatinteractwiththeproteinmoleculesthatmakeupthemolecularmachinerythatkeepsusalive.OurunderstandingofhowproteinsinteractwithDNA,phospholipidsandotherbiologicalmoleculesiswhatallowssuchprogress.

Livingsystemsareabletolivebecauseofthevastamountofhighlyorderedmolecularmachineryfromwhichtheyarebuilt.ThecentraldogmaofmolecularbiologystatesthattheinformationrequiredtobuildalivingcellororganismisstoredintheDNA(whichwasdescribedaboveforitsuseinmolecularcomputation).ThisinformationistransferredfromtheDNAtotheproteinsbytheprocessescalledtranscriptionandtranslation.Theseprocessesareallexecutedbyvariousbiomolecularcomponents,mostlyproteinandnucleicacids.

Molecularbiologyisafieldinwhichthestudyoftheseinteractionshasledtothediscoveryofnumerouspharmaceuticalsthathavebeenenormouslyeffectiveincuringdisease.Understandingofmolecularmechanismsincludingsubstraterecognition,energyexpenditure,electrontransport,membraneactivityandmuchmorehavegreatlyimprovedourmedicaltechnology.

So,whatdoesthishavetodowithnanotechnology?Firstofallitshowstheabilitiesofmolecularscalemachinery.Sincethegoalofnanotechnologyismolecularandatomicprecision,nanotechnologyhasmuch(ifnoteverything)tolearnfromnature.Copying,borrowingandlearningtricksfromnatureisoneoftheprimarytechniquesusedbynanotechnologyandhasbeentermedbiomimetics.Secondly,ourabilitytodesignsynthetic,semi-syntheticandnaturalmolecularmachinerygivesusanenormouspotentialforcuringdiseaseandpreservinglife.AnextensivetextbooktitledNanomedicinehasbeenwrittenanddoesanexcellentjobofsummarizinghownanotechnologyischangingmedicine.6MolecularSimulation

Computermodelsofatoms,moleculesandnanostructuresprovidethetheorybehindnanoscience.

Finally,abranchofcomputersciencethatisallowingrapidprogresstobemadeinnanotechnologyisthecomputersimulationofmolecularscaleevents.Molecularsimulationisabletoprovideandpredictdataaboutmolecularsystemsthatwouldnormallyrequireenormousefforttoobtainphysically.Byorganizingvirtualatomsinamolecularsimulationenvironment,onecaneffectivelymodelnanoscalesystems.DeepakSrivastava,oneoftheworldsleadingexpertsinmolecularsimulationandcomputationalnanotechnology,hasdescribedthesituationwiththefollowingquote,

Currentlimitationsofmolecularsimulationtechniquesarethemolecularsimulationalgorithmandcomputationtimeforcomplexsystems.Forcefieldalgorithmsarecurrentlyquiteefficientandareoftenusedtoday.However,suchmodelsneglectelectronicpropertiesofthesystem.Inordertocalculateelectrondensity,quantummechanicalmodelsarerequired.However,asthenumberofatomsandelectronsisincreased,thecomputationalcomplexityofthemodelquicklyreachesthelimitsofourmostmodernsupercomputers.Thus,asthecomputationalabilitiesofourcomputersareimproved(oftenwithhelpfromnanoscience),increasinglycomplexsystemswillbewithinthereachofmolecularsimulation.7TheFuture

Nanotechnologyhasarrived,butithasyettorealizeitsfullpotential.

Ourcomputersarequitefastandsmall,butnorevolutionarybreakthroughincomputinghashappenedsincethetransistorwasinvented.Thehumangenomeprojecthasreachedcompletion,yetlimitsinourabilitytocurediseaseonamolecularbasisremain.Whileitisoftendifficulttopredictthefuture,somethingsseeminevitable.Justasaballthrownintotheaircanbeexpectedtofalltotheground,socanweexpectourtechnologytoreachthemolecularscale?

1. nebulousadj.云雾状的，星云的，朦胧的,模糊的。

2. infantileadj.婴儿(期)的，<贬>幼稚的,孩子气的;婴儿的。

3. biomimeticn.【医】拟生态的，仿生的。

4. aqueous水的，aqueoushumor水状体。

5. manifestationn.显示,表明,表示;(幽灵的)显现，显灵。

6. clumsyadj.笨拙的,笨重的；复杂难懂的，使用不便的；得罪人的，不得体的。Vocabulary

7. covalentadj.共有原子价的,共价的。

8. prophesyvt.预告;预言。

9. plethoran.过多,过剩,过量。

10. imminentadj.即将发生的,逼近的，临近的。

11. bringabout使(船)掉转船头，造成,引起〔导致〕(某事)。

12.fantasticadj.荒诞的,奇异的,古怪的;极大的,异乎寻常的;极出色的,了不起的。

13. scanningprobemicroscopy扫描探针显微镜。

14. entanglementn.瓜葛;牵连;纠缠;缠住。

15. superpositionn.叠加。

16. tunneln.地下通道,隧道,地道;(动物栖息的)穴,洞穴通道vi.打通隧道。

17. supramolecularchemistry超分子化学。

18. photolithography光刻法，影印石版术。

19. dogman.教义,教条;信条adj.教义的,教条的;信条的。

20. transcriptionn.抄写;标音;抄本,副本,文字记录,翻译;按速记稿在打字机上打出文字;录音,录制。

21. translationn.翻译，译本,译文转变；转化。

22. pharmaceuticaln.医药品。

23. expendituren.花费,使用,((尤指金钱的)支出额、精力、时间、材料等的)耗费，消耗。

24. membranen.(动物或植物体内的)薄膜,隔膜,膜,(植物的)细胞膜;(可起防水、防风等作用的)膜状物。

25. biomimeticsn.仿生学。

[1]However,immenant(imminent)breakthroughsincomputerscienceandmedicinewillbewheretherealpotentialofnanotechnologywillfirstbeachieved.

然而，纳米技术首先发挥其真正的潜力的地方是即将发生的在计算科学和医药领域的突破。ImportantSentences

[2]Theamountofspaceavailabletousforinformationstorage(orotheruses)isenormous.Asfirstdescribedinalecturetitled,‘There’sPlentyofRoomattheBottom’in1959byRichardP.Feynman,thereisnothingbesidesourclumsysizethatkeepsusfromusingthisspace.

我们可以利用的信息存储(或者用做其他)空间是巨大的。正如RichardP.Feynman在1959年的名为“There’sPlentyofRoomattheBottom(在底层有大量的空间)”的讲演中描述的，除了我们的体积笨重之外，没有什么能阻止我们使用这些空间。

[3]However,sincethelawsofquantummechanicsinvolvesunintuitiveprinciplessuchassuperpositionandentanglement,aquantumcomputerwouldbeabletoviolatesomerulesthatlimitourclassicalcomputers.Forinstance,takingadvantageofsuperpositionwouldmeanthataquantumbitofinformation,termedaqubitwouldbeabletobeusedinseveralcomputationsatthesametime.Takingadvantageofentanglementwouldmeanthattheinformationcouldbeprocessedoverlongdistanceswithouttheclassicalrequirementofwires.

但是，由于量子力学包括一些不直观的原理，比如叠加和纠缠，量子计算机可能违背某些限制经典计算机的规则。例如，利用叠加原理，一个叫做qubit的量子比特信息可能同时用于几个计算。利