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完型Whentravelerspassfromonetimezonetoanother,theysufferfromdisruptedcircadianrhythms,anuncomfortablefeelingknownasjetlag.Forinstance,ifyoutravelfromCaliforniatoNewYork,youlose3hoursaccordingtoyourbody'sclock.Youwillfeeltiredwhenthealarmringsat8a.m.thenextmorningbecause,accordingtoyourbody'sclock,itisstill5a.m.Itusuallytakesseveraldaysforyourbody'scyclestoadjusttothenewtime.Toreducetheeffectsofjetlag,somedoctorstrytomanipulatethebiologicalclockwithatechniquecalledlighttherapy.Theyexposepeopletospeciallights,manytimesbrighterthanordinaryhouseholdlight,forseveralhoursnearthetimethesubjectswanttowakeup.Thishelpsthemresettheirbiologicalclocksandadjusttoanewtimezone.Symptomsmuchlikejetlagarecommoninpeoplewhoworknightsorwhoperformshiftwork.Becausethesepeople'sworkschedulesareatoddswithpowerfulsleep-regulatingcueslikesunlight,theyoftenbecomeuncontrollablydrowsyduringwork,andtheymaysufferinsomniaorotherproblemswhentheytrytosleep.Shiftworkershaveanincreasedriskofheartproblems,digestivedisturbances,andemotionalandmentalproblems,allofwhichmayberelatedtotheirsleepingproblems.Thenumberandseverityofworkplaceaccidentsalsotendtoincreaseduringthenightshift.Majorindustrialaccidentsattributedpartlytoerrorsmadebyfatiguednight-shiftworkersincludetheExxonValdezoilspillandtheThreeMileIslandandChernobylnuclearpowerplantaccidents.Onestudyalsofoundthatmedicalinternsworkingonthenightshiftaretwiceaslikelyasotherstomisinterprethospitaltestrecords,whichcouldendangertheirpatients.Itmaybepossibletoreduceshift-relatedfatiguebyusingbrightlightsintheworkplace,minimizingshiftchanges,andtakingschedulednaps.Manypeoplewithtotalblindnessexperiencelife-longsleepingproblemsbecausetheirretinasareunabletodetectlight.Thesepeoplehaveakindofpermanentjetlagandperiodicinsomniabecausetheircircadianrhythmsfollowtheirinnatecycleratherthana24-hourone.Dailysupplementsofmelatoninmayimprovenight-timesleepforsuchpatients.However,sincethehighdosesofmelatoninfoundinmostsupplementscanbuildupinthebody,long-termuseofthissubstancemaycreatenewproblems.Becausethepotentialsideeffectsofmelatoninsupplementsarestilllargelyunknown,mostexpertsdiscouragemelatoninusebythegeneralpublic.阅读AAsmallcardsitsaboveanemptyshelfintheWholeFoodsstoreinPetaluma,California.“Consumersareadvisednottoeatfreshbaggedspinachatthistime.Asaprecaution,WholeFoodsMarkethastemporarilyremovedallfreshspinachandfreshsaladmixescontainingspinachfromitsstores.”OnSeptember14ththeCentersforDiseaseControlandPreventioninAtlantaissuedthefirstofseveraldailyalertsconcerninganoutbreakofE.coli0157:H7,apotentiallylethalpathogentypicallyassociatedwithadulteratedbeef.Investigatorshadtracedittoconsumptionoffreshrawspinachsoldinbags.Afewdayslater,aninvestigationconductedbytheFoodandDrugAdministration(FDA)hadnarroweddowntheculpritstoaCalifornia-basedgrower,NaturalSelectionFoods,andatleastoneofitsdistributors.Sofar,a77-year-oldwomaninWisconsinhasdiedfromeatingspinachtracedbacktoNaturalSelection,and146peoplein23statesareill,someveryseriously.Halfofthevictimshavebeenhospitalized,ahighratethatmayindicateanespeciallyvirulentstrainofE.coli.Investigatorscontinuetosearchforthecauseoftheoutbreak.Theyhavescouredthecompany’sprocessingplantaswellasthefarmsthatgrowthespinach,lookingateverythingfromirrigationwatertotheproximityoflivestock,withnosureconnectionsmadesofar.ThefactthatNaturalSelectionisinCalifornia’sSalinasValleyhasraisedalarms,however.AccordingtotheFDA,freshproducefromthevalley,includingspinach,hasbeenthesourceofnineE.colioutbreakssince1995.MoreoverNaturalSelection,whichsuppliesseveralsupermarketchainsacrosstheUnitedStateswithconventionallyproducedfreshspinach,isalsothenation’slargestgrowerandshipperofcertifiedorganicproduce,underitsEarthboundFarmbrand.Iforganicspinachbecomesimplicated,thefinancialconsequencesfortheorganicsectorofthefreshproducemarket,whichpridesitselfonitspurity,couldbesevere.ButwiththeFDAadvisingconsumersnottoeatfreshspinachfromanysourceuntilfurthernotice,theoutbreakcouldruinCalifornia’swholespinachindustry.Thestategrowsaboutthree-quartersoftheAmericancrop.Inrecentyearsthemarketforfreshspinachhasbenefitedhugelyfromwhatoneproducers’spokesmancalls“agreathealthprofile”.In2005,percapitaconsumptioninAmericawasforecastat2.2pounds(onekilogram),upfromjust0.6poundstenyearsago.Thattotalisn’tlikelytoincreaseagainforawhile.阅读BAnotherroundhasjustbeenfoughtinthebattlebetweentobaccocompaniesandthosewhoregardthemasspawnofthedevil.InappearjustpublishedintheLancet,withtheprovocativetitle“Secretscience:tobaccoindustryresearchonsmokingbehaviorandcigarettetoxicity”,DavidHammond,ofWaterlooUniversityinCanadaandNeilCollishawandCynthiaCollard,twomembersofPhysiciansforaSmoke-FreeCanada,alobbygroup,criticizethebehaviorofBritishAmericanTobacco(BAT).Theysaythefirmconsideredmanipulatingsomeofitsproductsinordertomakethemlow-tarintheeyesofofficialdomwhiletheyactuallydeliveredhightarandnicotinelevelstosmokers.Itwasandisnosecret,asBATpointsout,thatpeoplesmokelow-tarcigarettesdifferentlyfromhigh-tarones.Thereasonisthattheywantadecentdoseofthen