简介:摘要:MTBE/丁烯-1装置在化工生产中应用十分广泛,催化剂失活是装置生产过程中的重要问题。本文分析了催化剂寿命的影响因素,针对催化剂的失活原因简述了应对措施,最后探讨如何延长MTBE/丁烯-1装置催化剂寿命。
简介:着重探讨利用ARCGISVBA程序,快速、高效地对不同比例尺框架要素数据更新数据进行一致性、存在性质量检验,以及对框架要素数据库中重要要素进行重点检查的思路,以确保该数据库具有现势性、准确性与权成性。
简介:Anovelautomaticseamlessstitchingmethodispresented.Comparedtothetraditionalmethod,itcanspeedtheprocessingandminimizetheutilizationofhumanresourcestoproducegloballunarmap.Meanwhile,anewglobalimagemapoftheMoonwithspatialresolutionof~120mhasbeencompletedbytheproposedmethodfromChang’E-1CCDimagedata.
简介:Cytarabine(1-β-D-arabinofuranosylcytosine,Ara-C),isolatedfromaCaribbeanspongespeciesTethyacrypta,isthefirstantitumordrugfromamarineresource.In1980,theUSFoodandDrugAdministrationapprovedthisdrugforthetreatmentofdifferenttypesofleukemia.Thisdrughasashortplasmahalf-life,lowstability,limitedbioavailability,andseveresideeffects.Toimprovestabilityandbioavailability,wesynthesizedninenovelderivativesbyblockingthecytarabinemetabolicsitesandimprovinglipophilicity.ThecLogPvaluesofthenewlysynthesizedcompoundswerecalculated.Allthesynthesizedcompoundsweremorelipophilicthancytarabine,resultinginmembranepermeabilityandbioavailabilityimprovement.TheantitumoractivitiesagainstleukemiacelllineHL-60wereevaluatedbyusingtheMTTassay.ThebioassayresultsrevealedthattheIC50valuesofcompounds5,8and9were0.080,0.090and0.057μmolL-1,respectively,whichwassimilarwiththatofcytarabine(0.056μmolL-1).Incomparison,compound4withaphosphategroupatO5’wasinactive.Becausephosphoesterbondsareeasilyhydrolyzedbyalkalinephosphataseandarecommonlyusedinproducingprodrugstrategies,compound4mightalsobemetabolizedinvivoandgeneratecompound3orevencytarabinethroughamulti-stepreaction.Thus,compound4mightbeapromisingcompoundtobedevelopedasaprodrug.
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