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β放射源主要用作β活度测量和β能量响应刻度时的参考源和工作源,还可用作()。

A、放射性测厚仪
B、皮科敷贴器
C、气相色谱仪的电子捕集器
D、放射性密度计
E、射线荧光分析仪
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正确答案:

ABC

答案解析:

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InItaly,whenpeopletouchtheireyes,itrepresents:

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1.Thefailureofahigh-profilecholesteroldrughasthrownaspotlightonthecomplicatedmachinerythatregulatescholesterollevels.Butmanyresearchersremainconfidentthatdrugstoboostlevelsof'good'cholesterolarestilloneofthemostpromisingmeanstocombatspirallingheartdisease.

2.DrugcompanyPfizerannouncedon2Decemberthatitwascancellingallclinicaltrialsoftorcetrapib,adrugdesignedtoraiseheart-protectivehigh-densitylipoproteins(HDLs).Inatrialof15000patients,asafetyboardfoundthatmorepeoplediedorsufferedcardiovascularproblemsaftertakingthedrugplusacholesterol-loweringstatinthanthoseinacontrolgroupwhotookthestatinalone.

3.Thenewscameasakickintheteethtomanycardiologistsbecauseearliertestsinanimalsandpeoplesuggesteditwouldlowerratesofcardiovasculardisease."Therehavebeennoredflagstomyknowledge,"saysJohnChapman,aspecialistinlipoproteinsandatherosclerosisattheNationalInstituteforHealthandMedicalResearch(INSERM)inPariswhohasalsostudiedtorcetrapib."Thiscancellationcameasacompleteshock."

4.TorcetrapibisoneofthemostadvancedofanewbreedofdrugsdesignedtoraiselevelsofHDLs,whichferrycholesteroloutofartery-cloggingplaquestotheliverforremovalfromthebody.Specifically,torcetrapibblocksaproteincalledcholesterolestertransferprotein(CETP),whichnormallytransfersthecholesterolfromhigh-densitylipoproteinstolowdensity,plaque-promotingones.Statins,incontrast,mainlyworkbyloweringthe'bad'low-densitylipoproteins.

Underpressure

5.Researchersarenowtryingtoworkoutwhyandhowthedrugbackfired,somethingthatwillnotbecomeclearuntiltheclinicaldetailsarereleasedbyPfizer.Onehintliesinevidencefromearliertrialsthatitslightlyraisesbloodpressureinsomepatients.Itwasthoughtthatthismildproblemwouldbeoffsetbytheheartbenefitsofthedrug.Butitispossiblethatitactuallyprovedfatalinsomepatientswhoalreadysufferedhighbloodpressure.Ifbloodpressureistheexplanation,itwouldactuallybegoodnewsfordrugdevelopersbecauseitsuggeststhattheproblemsarespecifictothiscompound.OtherprototypedrugsthatarebeingdevelopedtoblockCETPworkinaslightlydifferentwayandmightnotsufferthesamedownfall.

6.ButitisalsopossiblethatthewholeideaofblockingCETPisflawed,saysMotiKashyap,whodirectsatherosclerosisresearchattheVAMedicalCenterinLongBeach,California.WhenHDLsexcretecholesterolintheliver,theyactuallyrelyonLDLsforpartofthisprocess.SoinhibitingCETP,whichpreventsthetransferofcholesterolfromHDLtoLDL,mightactuallycauseanabnormalandirreversibleaccumulationofcholesterolinthebody."You'reblockingaphysiologicmechanismtoeliminatecholesterolandeffectivelyconstipatingthepathway,"saysKashyap.Goingup

7.Mostresearchersremainconfidentthatelevatinghighdensitylipoproteinslevelsbyonemeansoranotherisoneofthebestroutesforhelpingheartdiseasepatients.ButHDLsarecomplexandnotentirelyunderstood.Oneapproveddrug,calledniacin,isknowntobothraiseHDLandreducecardiovascularriskbutalsocausesanunpleasantsensationofheatandtingling.Researchersareexploringwhethertheycanbypassthissideeffectandwhetherniacincanlowerdiseaseriskmorethanstatinsalone.Scientistsarealsoworkingonseveralothermeanstobumpuphigh-densitylipoproteinsby,forexample,introducingsyntheticHDLs."Theonlythingweknowisdeadinthewateristorcetrapib,notthewholeideaofraisingHDL,"saysMichaelMiller,directorofpreventivecardiologyattheUniversityofMarylandMedicalCenter,Baltimore.

Questions7-13

Matchtorcetrapib,HDLs,statinandCETPwiththeirfunctions(Questions8-13)..WritethecorrectletterA,B,CorDinboxes8-13onyouranswersheet.NBYoumayuseanylettermorethanonce.

7.Ithasbeenadministeredtoover10,000subjectsinaclinicaltrial.

8.Itcouldhelpridhumanbodyofcholesterol.

9.Researchersareyettofindmoreaboutit.

10.Itwasusedtoreducethelevelofcholesterol.

11.AccordingtoKashyap,itmightleadtounwantedresultifit'sblocked.

12.Itproducedcontradictoryresultsindifferenttrials.

13.ItcouldinhibitLDLs.Listofchoices

A.TorcetrapicB.HDLSC.StatinD.CETP

Peoplethrowthingsawayandbuynewonesinsteadofrepairingthemandusingagain.Whatdoyouthinkmaybethereasonsforthis?Whatproblemsmightthiscauseinsociety?

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