《信息科學(xué)類專業(yè)英語(yǔ)》課件第25章

Lesson25About?Nanotechnology)

(第二十五課關(guān)于納米技術(shù))

Vocabulary(詞匯)ImportantSentences(重點(diǎn)句)QuestionsandAnswers(問(wèn)答)Problems(問(wèn)題)

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.云霧狀的，星云的，朦朧的,模糊的。

2.?infantileadj.嬰兒(期)的，<貶>幼稚的,孩子氣的;嬰兒的。

3.?biomimeticn.【醫(yī)】擬生態(tài)的，仿生的。

4.?aqueous水的，aqueoushumor水狀體。

5.?manifestationn.顯示,表明,表示;(幽靈的)顯現(xiàn)，顯靈。

6.?clumsyadj.笨拙的,笨重的；復(fù)雜難懂的，使用不便的；得罪人的，不得體的。Vocabulary

7.?covalentadj.共有原子價(jià)的,共價(jià)的。

8.?prophesyvt.預(yù)告;預(yù)言。

9.?plethoran.過(guò)多,過(guò)剩,過(guò)量。

10.?imminentadj.即將發(fā)生的,逼近的，臨近的。

11.?bringabout使(船)掉轉(zhuǎn)船頭，造成,引起〔導(dǎo)致〕(某事)。

12.fantasticadj.荒誕的,奇異的,古怪的;極大的,異乎尋常的;極出色的,了不起的。

13.?scanningprobemicroscopy掃描探針顯微鏡。

14.?entanglementn.瓜葛;牽連;糾纏;纏住。

15.?superpositionn.疊加。

16.?tunneln.地下通道,隧道,地道;(動(dòng)物棲息的)穴,洞穴通道vi.打通隧道。

17.?supramolecularchemistry超分子化學(xué)。

18.?photolithography光刻法，影印石版術(shù)。

19.?dogman.教義,教條;信條adj.教義的,教條的;信條的。

20.?transcriptionn.抄寫;標(biāo)音;抄本,副本,文字記錄,翻譯;按速記稿在打字機(jī)上打出文字;錄音,錄制。

21.?translationn.翻譯，譯本,譯文轉(zhuǎn)變；轉(zhuǎn)化。

22.?pharmaceuticaln.醫(yī)藥品。

23.?expendituren.花費(fèi),使用,((尤指金錢的)支出額、精力、時(shí)間、材料等的)耗費(fèi)，消耗。

24.?membranen.(動(dòng)物或植物體內(nèi)的)薄膜,隔膜,膜,(植物的)細(xì)胞膜;(可起防水、防風(fēng)等作用的)膜狀物。

25.?biomimeticsn.仿生學(xué)。

[1]However,immenant(imminent)breakthroughsincomputerscienceandmedicinewillbewheretherealpotentialofnanotechnologywillfirstbeachieved.

然而，納米技術(shù)首先發(fā)揮其真正的潛力的地方是即將發(fā)生的在計(jì)算科學(xué)和醫(yī)藥領(lǐng)域的突破。ImportantSentences

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

我們可以利用的信息存儲(chǔ)(或者用做其他)空間是巨大的。正如RichardP.Feynman在1959年的名為“There’sPlentyofRoomattheBottom(在底層有大量的空間)”的講演中描述的，除了我們的體積笨重之外，沒(méi)有什么能阻止我們使用這些空間。

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

但是，由于量子力學(xué)包括一些不直觀的原理，比如疊加和糾纏，量子計(jì)算機(jī)可能違背某些限制經(jīng)典計(jì)算機(jī)的規(guī)則。例如，利用疊加原理，一個(gè)叫做qubit的量子比特信息可能同時(shí)用于幾個(gè)計(jì)算。利