向被攻击对象网络服务器或工作站发送3vN-无用的且要求回复的信息,以消耗其网络 带宽或系统资源,从而使被攻击对象的网络或系统无法负荷以致瘫痪的攻击方式叫做()
A、端口扫描探测攻击C
暂无解析
Anincreasingnumberofmuseumstendtochargeadmissionfeesfromtouristsratherthanprovidingservicefreeofcharge.Doyouthinktheadvantagesoutweighthedisadvantages?
温室气体的增多加剧了温室效应。
Welookforwardtoyourearlyreplyandtrustthatthroughourmutuallycooperationweshallbeabletoconcludethistransactionwithyouinthenearfurther.
Whattypesofpeoplewereincludedintheresearch?
Roguetheoryofsmellgetsaboost
1.Acontroversialtheoryofhowwesmell,whichclaimsthatourfinesenseofodourdependsonquantummechanics,hasbeengiventhethumbsupbyateamofphysicists.
2.CalculationsbyresearchersatUniversityCollegeLondon(UCL)showthattheideathatwesmellodourmoleculesbysensingtheirmolecularvibrationsmakessenseintermsofthephysicsinvolved.
3.That'sstillsomewayfromprovingthatthetheory,proposedinthemid-1990sbybiophysicistLucaTurin,iscorrect.Butitshouldmakeotherscientiststaketheideamoreseriously.
4."Thisisabigstepforward,"saysTurin,whohasnowsetuphisownperfumecompanyFlexitralinVirginia.Hesaysthatsincehepublishedhistheory,"ithasbeenignoredratherthancriticized."
5.Mostscientistshaveassumedthatoursenseofsmelldependsonreceptorsinthenosedetectingtheshapeofincomingmolecules,whichtriggersasignaltothebrain.Thismolecular'lockandkey'processisthoughttoliebehindawiderangeofthebody'sdetectionsystems:itishowsomepartsoftheimmunesystemrecogniseinvaders,forexample,andhowthetonguerecognizessometastes.
6.ButTurinarguedthatsmelldoesn'tseemtofitthispictureverywell.Moleculesthatlookalmostidenticalcansmellverydifferent—suchasalcohols,whichsmelllikespirits,andthiols,whichsmelllikerotteneggs.Andmoleculeswithverydifferentstructurescansmellsimilar.Moststrikingly,somemoleculescansmelldifferent—toanimals,ifnotnecessarilytohumans—simplybecausetheycontaindifferentisotopes(atomsthatarechemicallyidenticalbuthaveadifferentmass).
7.Turin'sexplanationforthesesmellyfactsinvokestheideathatthesmellsignalinolfactoryreceptorproteinsistriggerednotbyanodourmolecule'sshape,butbyitsvibrations,whichcanenourageanelectrontojumpbetweentwopartsofthereceptorinaquantum-mechanicalprocesscalledtunnelling.Thiselectronmovementcouldinitiatethesmellsignalbeingsenttothebrain.
8.Thiswouldexplainwhyisotopescansmelldifferent:theirvibrationfrequenciesarechangediftheatomsareheavier.Turin'smechanism,saysMarshallStonehamoftheUCLteam,ismorelikeswipe-cardidentificationthanakeyfittingalock.
9.Vibration-assistedelectrontunnellingcanundoubtedlyoccur—itisusedinanexperimentaltechniqueformeasuringmolecularvibrations."Thequestioniswhetherthisispossibleinthenose,"saysStoneham'scolleague,AndrewHorsfield.
10.StonehamsaysthatwhenhefirstheardaboutTurin'sidea,whileTurinwashimselfbasedatUCL,"Ididn'tbelieveit".But,headds,"becauseitwasaninterestingidea,IthoughtIshouldproveitcouldn'twork.Ididsomesimplecalculations,andonlythenbegantofeelLucacouldberight."NowStonehamandhisco-workershavedonethejobmorethoroughly,inapapersoontobepublishedinPhysicalReviewLetters.
11.TheUCLteamcalculatedtheratesofelectronhoppinginanosereceptorthathasanodorantmoleculeboundtoit.Thisratedependsonvariouspropertiesofthebiomolecularsystemthatarenotknown,buttheresearcherscouldestimatetheseparametersbasedontypicalvaluesformoleculesofthissort.
12.Thekeyissueiswhetherthehoppingratewiththeodorantinplaceissignificantlygreaterthanthatwithoutit.Thecalculationsshowthatitis—whichmeansthatodouridentificationinthiswayseemstheoreticallypossible.
13.ButHorsfieldstressesthatthat'sdifferentfromaproofofTurin'sidea."Sofarthingslookplausible,butweneedproperexperimentalverification.We'rebeginningtothinkaboutwhatexperimentscouldbeperformed."
14.Meanwhile,Turinispressingaheadwithhishypothesis."AtFlexitralwehavebeendesigningodorantsexclusivelyonthebasisoftheircomputedvibrations,"hesays."Oursuccessrateatodorantdiscoveryistwoordersofmagnitudebetterthanthecompetition."Attheveryleast,heisputtinghismoneywherehisnoseis.
Questions5-9
Completethesentencesbelowwithwordsfromthepassage.UseNOMORETHANTHREEWORDSforeachanswer.
5.Thehypothesisthatwesmellbysensingthemolecularvibrationwasmadeby______.
6.Turin'scompanyisbasedin______.
7.Mostscientistsbelievedthatournoseworksinthesamewayasour______.
8.Differentisotopescansmelldifferentwhen______weighdifferently.
9.AccordingtoAudrewHorsfield,itisstilltobeprovedthat______couldreallyoccurinhumannose.