英语考研题源阅读二.docx
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英语考研题源阅读二.docx
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英语考研题源阅读二
Science&Technology
Headydiscoveries
TheyeastthatgaverisetolageristrackeddowntoSouthAmerica
INTHE15thcenturyaschismopenedintheworldofbeer.BrewersinBavariaalightedonanewversionofthatage-olddrink—onethatlikedtobefermentedinthecoldandcouldthusbebrewedinwinter.Thelagerrevolutionhadbegun.
Thedifferencebetweenlagersandmoretraditionalalesliesintheyeast.Alesaremadewithbaker’syeast,Saccharomycescerevisiae.Lagersuseahybrid,halfcerevisiaeandhalfsomethingelse.Theinterloper,though,hasneverbeenfound—untilnow.
Afteraworldwidesearch,ateamofgeneticistshaspinneditdowntoSouthAmerica.ChrisToddHittingeroftheUniversityofWisconsin-MadisonandDiegoLibkindoftheArgentineNationalCouncilforScientificandTechnicalResearch,foundtheirquarryover11,000km(7,000miles)fromBavaria,inthecoolalpineforestsofPatagonia.AstheyexplaininapaperintheProceedingsoftheNationalAcademyofSciences,thenewlydescribedspecies,namedSaccharomyceseubayanus,livesingallsthatinfectbeechtreesthere.Thesesugarygallsoftenfermentontheforestfloor,andlocalshavebeenknowntomakeanalcoholicbeveragefromthem.Geneticsequencingconfirmedthattheyeastinthegallsis99.5%identicalwiththenon-alehalfofthelager-yeastgenome.
Thatsolvesonemysterybutcreatesanother.HumantransportistheonlywaythefunguscouldhavetravelledfromPatagoniatoEurope,butexplorationoftheNewWorlddidnotbeginuntiltheendofthe15thcentury,andPatagoniawasnotreacheduntilthe16th.Yettherearerecordsofcold-fermentedbeerbeingmadeinMunichasearlyas1420.
DrHittingersuspectslageringinitsbasicform—lengthyandcoolfermentation—didprecedethearrivalofeubayanus,butthattheseearlylagerswerepoor.Then,inonebatch,eubayanusdriftedinandcouldthriveatthelowtemperatureswhichcerevisiaedisliked.Brewersfavouredthatbatch,andtheyeastspread.Indeed,thehistoricalrecordprovidesahintthatsomethingwasafootaroundthistime.In1553Bavariaoutlawedsummer-madebeerbecausewintertimebrewshadoutstrippedtheminquality.
Eventually,thetwoyeaststrainshybridisedtoformSaccharomycespastorianus,theyeastusedbylagerbrewerstoday.Thosebrewerswillcheerthediscoveryofeubayanus,asitopensatroveofgenesthatdidnotmakethetransitiontopastorianusbutwhichmighthelptheprocessofcoldbrewing.OneSouthAmericanbeercompanyisalreadydiscussingusingpureeubayanus,aswellaslab-createdhybrids,inatestbrew.Whetherthatwillimprovethelager’sflavourisanothermatter.AsDrHittingerpointsout,naturalselectionhasdoneaprettytastyjobalready.
Climatescience(I)
Seasonsofdiscontent
ElNiño,aworldwidefluctuationintheclimate,mayprovokecivilwaraswellasinclementweather
BELIEVERSextoltheinfantChrist,afterwhomtheglobalclimateoscillationElNiñoisnamed,asthePrinceofPeace.Notso,accordingtoanewanalysisbySolomonHsiangofColumbiaUniversityandhiscolleagues.Lookingatdataonweatherandwarfarefromaroundtheworldoverthepastsixdecades,Dr.HsiangfindsthatinthosecountrieswhereElNiñoexertsitseffectsitbringswithitasignificantextrariskofcivilconflict.Theresults,publishedinNature,cannotbetranslatedintoaprognosisfortheeffectsthatglobalwarmingmayhaveonancientgrudgesandnewmutinies.Buttheyprovideastrikinginsightintothewaysthatgeographycanshapehumanaffairs.
Theworkstartswithtwowell-establishedsetsofdata,oneonviolenceandtheotherontheweather.Fromthefirsttheteamcalculatedan“annualconflictrisk”forviolencewithincountries(asopposedtocross-borderwars).Fromtheseconditproducedamapoftheworlddividedinto82countrieswheretheweatherpayslittleheedtothepresenceorabsenceofNiñosand93wheretheweatherdoespaysuchheed—agroupthatcoversalmostallofthetropics.NiñosaresloshingsofwarmwateracrosstheequatorialPacificthattakeplaceonceortwiceadecade.Theymostlymakethemselvesfeltbyincreasingtropicaltemperaturesandloweringrainfallaroundthetropicalworld,thoughtheeffectsarenotthesameeverywhere.Suchsemi-regularinstabilityisnotexperiencedintemperateclimes,andithasdeeprepercussions.
InyearsofElNiño,theresearchersfound,theannualriskofconflictintheir93tropicalcountrieswas6%.Whentheoscillationreacheditsotherextreme,asituationknownasLaNiña,theriskwas3%.Inotherpartsoftheworlditstayedprettystablearound2%.Thisisnottosayclimateistheonlyormainfactorbehindconflict.Buttheresearchers’numberssuggestthatasmanyasafifthoftheinternalconflictsoftheperiodwereaffectedbyElNiño.
Furtheranalysisbacksuptheidea.ThoughthenamecomesfromeffectsfeltinSouthAmericaaroundChristmastime,NiñosstarttohittheirstrideinAprilandMay.Thismakesitreasonabletoexpecttheirimpacttoshowupmoreinthesecondpartoftheyearthanthefirst.AndinyearsofElNiñotheonsetofconflictsinthesusceptible93wasindeedskewedlate,withabulgefromSeptembertoNovember.ThereisnosuchbulgeinyearsofLaNiña,norinplacesthatdonotrespondmuchtoNiños.Aninterestingfurtherpatternisthatthepoorerthecountry,themorestronglyitschancesofinternalconflictseemtobetiedtoElNiño.
Thecorrelationsseemrobust,asdoesthedirectionofcausation.Thoughhumanscanaffecttheclimate,theintentionoffightingacivilwarisunlikelytochangethetemperatureofthetropicalPacific.Themechanisms,asalwaysinsuchmatters,presentmoreofaproblem.
Poorharvests—whichNiñosoftencause—mightmakerecruitingrebelscheaper,asthereisaslackerlabourmarket.Theymightheightentensionsbetweenpeopleincitiesandthoseinthecountryside.Theymightreducetheabilityofgovernmentstobuyofftrouble.Andhotterweathermaymakesomesortsoffightingmorelikely.Inbaseballithasbeenfoundthatifoneteam’spitcherhitsabatterwiththeball,thelikelihoodoftheotherteam’spitcherretaliatinginkindgoesupwiththetemperature.Rampingupretaliationlikethisisagoodwayofincreasingthechancesofstrife.
Sire,sire,thepeasantsarerevolting
Atleastonepreviousstudy,publishedin2009,hasclaimedarelationbetweenunusuallyhotyearsandtheriskofcivilstrife.ItdetectedsuchalinkinAfrica(thoughtherehavebeenargumentsaboutitsmethods,andastringofrelativelyconflict-freeyearsaftertheperiodexaminedweakenstheeffect).Dr.Hsiangisnotsure,however,thatthatconnectionhasanythingtodowithElNiño.TheNiñoeffecthefoundseemstoholdupevenwhenstatisticsareusedtoremovethedirectinfluenceonlocalrainfallandtemperature,whichwaswhattheAfricanstudydealtwith.Ifthatisright,somethingsubtlerintheweather,orsomesystematiceconomicfactors,mustbeinvolved.HistorianshavealsopointedtolinksbetweenparticularlysevereNiñosandepisodesofseriousstrife.TheBoxeruprisinginChinain1900,forexample,wasspurredbyaNiño-relatedfamine.AndtheFrenchrevolution—nottropical,tobesure—beganwithcropfailuresthatsomehavelinkedtoawhopperofaNiñothengettingunderway.
Whatwillhappenastheplanetwarmsfurther?
IfNiñoswereexpectedtogetmorecommontheremightbeaclearimplication.ButclimatemodellersdonotagreeonwhatwillbecomeofElNiñointhefuture.Theypointonlytoageneralwarmingwithanaverageyear-on-yearincreasemuchsmallerthanthedifferencebetweenanormalyearandaNiñoyear.Howpeoplerespondtoyear-on-yearchanges,whichiswhattheNiñoworkandearlierstudiesontemperaturespickout,mayhavelittletodowithhowtheyrespondtochangesthattakeplaceoverdecades.
YetDr.HsiangthinkstheNiñoanalysisshowsanexampleofaclearlinkbetweenclimateandconflict,andthatthisputsanewonusofproofonanyonesayingthatnosuchlinkwillbeatworkastheclimatechangesinthefuture,evenifitdoesnotshowwhatthatfuturelinkmightbe.
Itdoes,though,bringupapairofsomewhatgloomyinsights.Oneisonthelimitsofadaptation.Inaworldthatisnotdoingmuchtomitigateclimatechange,anincreasingemphasisisputonthecapacitytoadapttoit.ThatElNiño,whichhasbeenaroundforallofhistory,exertsstrongeffectsonagricultureandonviolencehighlightsthedifficultiesthatpoorcountrieshaveinadaptingtofamiliarclimaticchallenges,andthuscallsintoquestionanyhopethattheymighteasilyrespondtonewones.Gettingricherhelps,buttheworst-hitcountriesarethosewheredevelopmenthasprovedhardesttocomeby.
Andthenthereisthepessimist’sreading.Peopledoadapttoclimatechallenges—byfightingeachother.
Climatescience(II)
Cloudsinajar
Anewexperimentwitholdapparatusrevealsaflawinmodelsoftheclimate
CLOUDchambershaveanhonouredplaceinthehistoryofphysics.Thesedevices,whichgeneratevapourtrailsthatmarkthepassageofhigh-energysubatomicparticles,werethefirstapparatusthatallowedsuchpassagetobetracked.Thatwasinthe1920sandled,amongotherthings,tothediscoveryofcosmicrays.Sciencehasmovedonsincethen,ofcourse,andcloudchambersarenowlargelymuseumpieces.Buttheworld’sleadinghigh-energyphysicslaboratory,CERN,outsideGeneva,isdustingtheideaoffandputtingitintoreverse.Insteadofusingcloudstostudycosmicrays,itisusingcosmicraystostudyclouds.Indoingso,itmayhavethrownaspannerintotheworksoftheworld’scomputermodelsoftheclimate.
Cloudsareformedbythecondensationofwatervapo
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