The Evolution and Explosion of Massive Stars

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The Evolution and Explosion of Massive Stars S.E. Woosley∗ and A. Heger† Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 T.A. Weaver Lawrence Livermore National Laboratory, Livermore, CA 94551 (Dated: August 2, 2002) Like all true stars, massive stars are gravitationally confined thermonuclear reactors whose com- position evolves as energy is lost to radiation and neutrinos. Unlike lower mass stars (M <∼ 8 M¯) however, no point is ever reached where a massive star can be fully supported by electron degen- eracy.

• silicon burning
• convective core
• helium core
• mass loss
• massive stars
• evolution
• star
• ions
• hydrogen
• helium

Sujets

• Enrico Fermi Institute
• University of Chicago
• Compton
• University of California
• Hélium
• Hydrogen
• Convective
• Évolution
• Burning

Informations

• Publié par: ubbu0
• Nombre de lectures: 30
• Langue: English

Extrait

RationaleoftheTest

SAMPLEQUESTIONS FOR ENGLISHPROFICIENCYTESTFORCLASSX

Thetestistextindependenti.e.itisnotbasedonasettextorsyllabus.AsaProficiencyTest,ittests bothskillsandknowledge.Thereisabalancebetweenkeyaspectsoflanguage–as,forinstance, readingskills,involvinglanguageknowledgeaswellasabilitytoprocessmeaningsthrough inference,analysis,comparisonandevaluation;knowledgeofgrammarandvocabularytotheextent thatisrequiredforgeneralcommunicativetasks.Specificskillsinvolvedinwritingarealsoimportant e.g.awarenessofthestructureofsimplewrittentexts,howtheyareorganized,andthekindsof formatsthatareused‐inletters,forinstance.

Readingisgiven30marksasitisthebasisforgrammar&writingandbecauseitisimportantin furtherstudieswhichstudentshavetoundertakeintheirlateracademicwork.Onepassageof readingisofnarrativetype,(itmaybeanextractfromastory)andtestscandidates’understanding ofevents,characters,descriptionsandalsotheperceptionofmeaningswhichareimplicitinthe detailsofthestory.Onepassageisanon‐fictionaltextcontaininginformation,argument,opinion, factsandideas.Readingofthiskindisfocusedonabilitytoarriveatthegistofanidea/argument,to correctlyseparateopinionsfromfacts(whichimpliessomeabilitytoanalyse),tobeableto distinguishmainideasfromsubordinateones,tounderstandthetoneorviewpointe.g.humorous, ironic,seriousetc.Thethirdpassageisashortpoem,around20lines.Thisistotestifcandidatescan understandlanguagewhichiscomposeddifferently–itisnotlinear,hashiddenmeanings,unusual expressionsandusessoundeffects(e.g.rhyme),simileandmetaphorwhichconveysmeaning indirectlyratherthandirectly.

Vocabularyisgiven20marksas:

1.Vocabularyiscentralinreadingcomprehension,whereitisessentialinmeaning. 2.Itisalsotestedseparatelyinordertotestrangeofknowledgeofwords. Itistobekeptinmindthatthelevelofvocabularyissuchthatiscommonlyfoundintextsthat areprescribedintheschoolreadersatclass9and10. Grammar+Writing(30+20)TheMCQformatdoesnotallowtestingofwritingskillsaswritingis integrativeofotherskillsandneedstobetestedthroughproduction.However,itisfeltthatthe awarenessofthecomponentsofwritingcanbetestedhere ‐e.g.formatofletters,paragraph organization,linkagebetweensentencesetc.Thesearealsopartoflanguageknowledge. ClozeTesthasbeenincludedasitisatestwhichisthemostglobalandcomprehensivetestof language.Itconsistsofapassagewherethefirstsentencesetsthecontextofthepassageand subsequentlythereareblanksatregularintervals.Fillingtheseblanksrequiresanoverall understandingofmeaningandofthelanguageitemsthatwillfitintotheparticularcontextofthe sentences.Forexample,whentheuseofarticlesisexplainedinisolation,ausercannotunderstand whereacertainarticleneedstobeused/omitted.Itisonlyincontextthatadecisionregardingthe useofanarticleismade.Thereforeaclozetestisthebestwaytoknowifastudentcaninferfrom thecontextwhetherthatarticleistobeusedornot.Thesameappliestootheritemslike prepositions,conjunctionsetc.

Theformatandbreak‐upofpartsofthetestisasfollows: MaximumMarks:100 Time:2.30Hours

Thequestionpapercontains100questions.Allquestionsarecompulsory.

Thequestionsaredividedintothefollowingparts: (Reading3passages) AUnseenPassage(Narrativetype)Q.1‐10 BUnseenpassage(Informativetype)Q.11‐20 CPoemQ.21‐30 DVocabularyQ.31‐50 EGrammarQ.51‐65 FWritingQ.66‐85 GClozeQ.86‐100  EachMultipleChoiceQuestionhasfouroptionsoutofwhichonlyONEoptionis correct.Eachcorrectanswerearnsacreditof1mark.  Awronganswercarriesapenaltyof ‐¼mark.  Anunansweredquestionearnsnomark. Instructionforwritingontheanswersheet: ®UseonHBPenciltofilltheanswersheet.DONOTUSEAPen. ®Ifyouwanttochangeanentryafterfillingabubble,erasethefilledbubble. ThefollowingexampleillustratesthecorrectwayofansweringaMultipleChoiceQuestion: Example: They’vebothworkedhereovertenyears. a.in b.for c.since

d.during Answer:Theanswertothisquestionis(b).YouhavetomarkitontheAnswersheetasshown: abcd    DESCRIPTIONOFLEVELSOFPROFICIENCY: Thisisbeinggiveninordertodefinethelevelsofproficiencythatcorrelatewiththemarksobtained inthetest.Ithelpsthecandidatetoseewhichareasneedmoreattentionforthedevelopmentof higherlevelsofproficiency. 5.GoodUser‐Hasoperationalcommandofthelanguage.Generallyhandlescomplexlanguage wellandunderstandsdetailedreasoning,reflectiveofacertaindegreeofanalyticaland interpretativeskills.Hasarangeofvocabularyandcanunderstandcomplexstructures.Is awareofthestructureoforganizationandcoherenceintexts.Thisuserwillbeabletoscore verywellinallpartsofthetest,particularlyinreadingcomprehensionandclozeexercise. (80%andabove) 4.CompetentUser‐Hasgenerallyadequatecommandofthelanguagedespitesome inaccuraciesandmisunderstandings.Understandssomeconventionsinwriting,andcan interpretatext,knowsthestructures,butmaynothavearange.Thisuserwillbeableto scorefairlywell,mayscorebetterinsomepartsofthetest.Performanceinthecloze exercisemaymakeadifference–betterperformanceinthispartbringsthecandidate towardsthehigherendatthislevel.(60‐79%) 3.ModestUser‐Haspartialcommandofthelanguage,copingwithoverallmeaninginmost situations,thoughislikelytomakemanymistakesininterpretationandinunderstanding structuresandwritingconventions.Shouldbeabletohandlebasiccommunication reflectedinsomeknowledgeofgrammarandvocabulary.Thisuserwillmanageanaverage scoreinallpartsofthetest.(between40‐59%) 2.LimitedUser‐Basiccompetenceislimited.Hasfrequentproblemsin understandingnon‐ factualinformation(thiswillshowupinreadingcomprehension)andwillnotbeableto exerciseskillsneedinginferenceandinterpretation.Isnotabletouse&understand complexlanguage.Thisuserwillscorelowinreadingaswellasgrammarandcloze(willnot

understandtheoverallcoherenceofthepassage)andmaynotbeabletoanswerquestions

pertainingtotextorganization.(20‐39%)

1.ExtremelyLimitedUser‐Canunderstandonlyisolatedwords.Hasgreatdifficultyin

understandingstructures,butmaygivesomecorrectresponsestoquestionsofasimplerkind.

Maynotattempttoanswermanyofthequestions.Comprehensionlevelisverylowevenfor

simpletexts.(0‐19%)

Samplequestions ReadingComprehension Thisisasamplepassage(200words),shorterthantheonewhichwillappearinthetest(whichwill beof300‐350words),butofthesamelevelofdifficulty.Inthesample,5MCQsaregiven.Inthe actualpaper,therewillbe10MCQsoneachpassage(seeabove). Readthefollowingpassageandchoosethecorrectanswerforthequestions: Inthisworlditisnotonlyfutileforthesmalltoappealtoauthority,itisdangerousaswell. Fortunately,thetinyvoiceseldomreachesbigearsorwhoknowswhatmighthappen?WhenGafur returnedhomefromthelandlord’sandquietlylaydown,hisfaceandeyeswereswollen.Thechief causeofsomuchsufferingwasMahesh.WhenGafurlefthomethatmorning,Maheshbrokeloose fromhistether,andenteringthegroundsofthelandlord,hadeatenupflowersandupsetthecorn dryinginthesun.Whenfinallytheytriedtocatchhim,hehadhurtthelandlord’syoungestdaughter andhadescaped.Thiswasnotthefirsttimethishadhappened,butGafurwasforgivenbecausehe waspoor.Ifhehadcomearound,andasonotheroccasions,beggedforthelandlord’sforgiveness, hewouldprobablyhavebeenforgivenbutinsteadhehadclaimedthathepaidrent,andthathewas nobody’sslave.ThiswastoomuchforShibubabu,thelandlord,toswallow.Gafurhadbornethe beatingsandtortureswithoutprotest.Athome,too,helayinacornerwithoutaword.Hisheart burntwithinhimlikethesunoutside.Hekeptnocountofhowtimehadpassed. Q.1Inthepassage,whosevoiceisdescribedas`tiny’? a.Thevoiceofthebigpeople b.Thevoiceofthesmallpeople c.Thewrongpeople d.Thepeoplewhoarestrong Q.2WhywereGafur’seyesandfaceswollen? a.Hehadbeenbeatenbythelandlord. b.Hewasill.

c.Hewaslyingdown

d.HehadbeenhurtphysicallybyMahesh

Q.3WhydidGafurnotaskthelandlord’sforgiveness?

a.Hewaspoor.

b.Hedidn’tbotheraboutthelandlord.

c.Hewashappythatthelandlord’spropertyhadbeendamaged.

d.Hewantedtosavehisdignity

Q5.`Tokeepcountoftime’means: a.Tobeabletocount b.Tobeawareofthepassageoftime c.Tobeunconscious d.Tolookataclock Vocabulary: 1.Choosetheoptionclosestinmeaningtothewordinbold: Ancestora.oldb.forefatherc.pastd.dead 2.Choosetheoptionoppositeinmeaningtothewordinbold: Exteriora.internalb.inferiorc.superiord.interior Grammar: Choosetherightoptiontofillintheblank: 1.What____________youliketodrink? a.willb.mightc.wouldd.shall 2.Thereareotherpeopleinthepark_________ourselves. besidesb.besidec.befored.around 3.Hehadaheartattack.Thedoctorwasimmediately___________. a.Sentoffb.sentforc.sentind.sentthrough Writing Q.1Thefollowingsentences(A‐E)canbeputtogether toformawell‐connectedpassagebutarenot inthecorrectorder.Choosetheoptionthatgivesthebestorderofthesentences. A.Thentheywentbackintothecabin. B.Hisfatherwalkedintothelargebedroomtotherightofthekitchen.

C.Michaelwentintothelittleroomontheleft.

D.Theystoodinsilenceforafullfiveminutes.

E.Eachhungeredtoembracetheother,tocry,toscreamwithexcessofsorrow.

a.DACBEb.DEACBc.CBDEAd.CBEDA Q.2Readthefollowingandchoosetherightwordtoconnectthesentences: Theweatherofficehadpredictedthatitwouldrain_____1______.Theirpredictionsareusually accurate.____2_____,itdidnotrainforseveraldays.When____3_____theraindidcome,itwas insufficient___4______thecropsweredamaged. 1.a.frequentlyb.muchc.soond.well 2.a.howeverb.butc.thoughd.instead 3.a.definitelyb.intheendc.atlastd.lastly 4.a.andb.alsoc.evend.that Cloze Clozetestisatestofgrammar,sentenceconnection,vocabularyetc.,withinacontext,and thereforeteststheoverallproficiencylevel.Thereisapassagewithblanksatregularintervalsand thecorrectchoicehastobeindicated.ThetestforclassXwillhaveoneclozetestof15questions, worth15marks.Thesamplegivenbelowisashortpassagewith5questions. MybrotherandIusedtofightagreatdealaschildren.Wedid__________ofthingstogether,not alwaysincomplete_______.Infact,ononeoccasion,heactually________myarm.Isupposehe reallydidmea________,asImissedtheschoolexams______thatyear. Q.1a.manyb.somec.alotd.adeal

Q.2a.harmonyb.friendshipc.unisond.liking

Q.3a.damagedb.brokec.rippedd.tore

Q.4a.courtesyb.benefitc.favourd.privilege

Q.5a.forb.aroundc.atd.during