简介:定义了向量筐函数的C-Stieltjes近似可表示算子,并研究了它的性质。另外,我们定义了向量值函数的近似C-Stieltjes积分,并证明了它的收敛定理。
简介:IntroductionTherecentdiscoveryofaclassofcarboncontainingmoleculesknownasthefulereneshasproducedaseriesofmaterialswithawideran...
简介:Variousmesoporouschromiaaluminacatalystswerepreparedbyfivedifferentmethodsbasedonametal-organicframeworkMIL-101andtheircatalyticperformancesoverisobutanedehydrogenationwereinvestigated.ThehighlydispersedchromiumspecieswereproducedoncatalystKCrAl-I1withlargestspecificsurfaceareaof198m2g-1preparedwithaluminiumisopropoxide(Al(i-OC3H7)3)byultrasonicimpregnationmethod.However,thecatalystKCrAl-I2synthesizedbystirringimpregnationpossessedcrystallineα-Cr2O3phase,whichwaspoorlydispersed.TwotypesofCr-richandAl-richCrxAl2-xO3solidsolutions,designatedasCrAl-IandCrAl-IIphase,wereformedoverthecatalystsKCrAl-I3(preparedbyAl(i-OC3H7)3withnitricacidregulation),KCrAl-C4(preparedbyaluminiumchloridehexahydrate)andKCrAl-N5(preparedbyaluminiumnitratenonahydrate).CatalyticevaluationresultsrevealedthatKCrAl-I1exhibitedthehighisobutaneconversionduetoitshighlydispersedchromiumspecies.However,KCrAl-I3,KCrAl-C4andKCrAl-N5showedthehigherisobuteneselectivity(95.2%-96.4%)onaccountoftheformationofchromiaaluminasolidsolutionsinthecatalysts.Moreover,thesolidsolutionoverthechromiaaluminacatalystscouldgreatlysuppressthecokeformation.
简介:Inthiswork,aseriesofMIL-101-SO3H(x)polymericmaterialswerepreparedandfurtherusedforthefirsttimeasefficientheterogeneouscatalystsfortheconversionoffructose-basedcarbohydratesinto5-ethoxymethylfurfural(EMF)inarenewablemixedsolventsystemconsistingofethanolandtetrahydrofuran(THF).Theinfluenceof–SO3HcontentontheacidityaswellasonthecatalyticactivityoftheporouscoordinationpolymersinEMFproductionwasalsostudied.HighEMFyieldsof67.7%and54.2%couldbesuccessivelyobtainedfromfructoseandinulininthepresenceofMIL-101-SO3H(100)at130°Cfor15h.Thecatalystcouldbereusedforfivetimeswithoutsignificantlossofitsactivityandtherecoveryprocesswasfacileandsimple.Thisworkprovidesanewplatformbyapplicationofporouscoordinationpolymers(PCPs)fortheproductionofthepotentialliquidfuelmoleculeEMFfrombiomassinasustainablesolventsystem.
简介:Onenewsesquiterpenecompound,namely,illihenlactoneA(1),andonenewprenylatedC6–C3compound,illihenryioneH(2),alongwiththreeknownsesquiterpenes(3–5)wereisolatedfromthestemsofIlliciumhenryi.Thestructuresof1and2wereelucidatedbyspectroscopicevidenceincludingNMR,HRESIMSandcirculardichroism(CD).Compound2exhibitedaweakinhibitoryratioforbglucuronidasereleaseinducedbyplatelet-activatingfactor(PAF)inratpolymorphonuclearleukocytes(PMNs)invitro.
简介:Anenvironmentallyfriendlyprecursor,adenosine,hasbeenusedasadualsourceofCandNtosynthesizenitrogen-dopedcarboncatalystwith/withoutFe.Ahydrothermalcarbonizationmethodhasbeenusedandwateristhecarbonizationmedia.Themorphologyofsampleswith/withoutFecomponenthasbeencomparedbyHRTEM,andtheresultshowsthatFecanpromotethegraphitizationofcarbon.Furtherelectro-chemicaltestshowsthattheoxygenreductionreaction(ORR)catalyticactivityofFe-containingsample(C–FeN)ismuchhigherthanthatoftheFe-freesample(C–N).Additionally,theintermediatesofC–FeNformedduringeachsyntheticprocedurehavebeenthoroughlycharacterizedbymultiplemethods,andthefunctionofeachprocedurehasbeendiscussed.TheC–FeNsampleexhibitshighelectro-catalyticstabilityandsuperiorelectro-catalyticactivitytowardORRinalkalinemedia,withitshalf-wavepotential20mVlowerthanthatofcommercialPt/C(40wt%).Itisfurtherincorporatedintoalkalinepolymerelectrolytefuelcell(APEFC)asthecathodematerialandledtoapowerdensityof100mW/cm~2.
简介:LetT=(T(t))t≥0beaboundedC-regularizedsemigroupgeneratedbyAonaBanachspaceXandR(C)bedenseinX.WeshowthatifthereisadensesubspaceYofXsuchthatforeveryx∈Y,σu(A,Cx),thesetofallpointsλ∈iRtowhich(λ-A)^-1Cxcannotbeextendedholomorphically,isatmostcountableandσr(A)NiR=Ф,thenTisstable.AstabilityresultforthecaseofR(C)beingnon-denseisalsogiven.Ourresultsgeneralizetheworkonthestabilityofstronglycontinuoussenfigroups.
简介:Variousagriculturalcropresiduesincludingcornstover,corncob,andsorghumstalkwithamoisturecontentof75wt%weresubjectedtoalongpretreatment(12-60h)withsupercriticalCO2(scCO2),atlowtemperature(50-80℃)andapressureof17.5-25.0Mpa.Thesugaryieldsfromtheenzymatichydrolysis(EH)ofthepretreatedsampleswereasmuchasthree-tofourfoldgreaterthanthoseaffordedbytherawmaterials.However,whenpretreatmentwasconductedwithinashorttime(e.g.0.5h),aspreviouslyreportedintheliterature,onlyaslightincreaseintheEHsugaryieldswasobserved.TheproposedscCO2pretreatmentmechanismdemonstratedtheroleofmoistureinthesystem.Wetting,softening,andswellingwereobservedtomainlyaffectthelignocellulosewhenasuitableamountofwaterwasadded.Finally,thesampleswereanalysedbyX-raydiffractionandscanningelectronmicroscopy,beforeandafterpretreatment,toinvestigatethechangesinthemicroscopicstructureofthebiomass.
简介:Thispaperreportstwolanthanidecomplexesofformula(C9H7)Ln(C8H8)·(THF)2whereLnisProrNd,C9H7isindenyl,andC8H8iscyclooctatetraene(COT).ThecomplexeswerepreparedbythereactionofLnCl3withK(C9H7)andK2(C8H8)inTHF.(C9H7)Pr(C8H8)·(THF)2crystallizesinTHFat-15℃inthemonoclinicspacegroupP21:withunitcelldimensionsa=8.446(0),b=10.083(2),c=13.407(3),β=105.48(1)°,V=1100.43(35)3,Dc=1.52g/cm3andZ=2.ThefinalRvalueis0.033,Rwvalueis0.030,respectively.In(C9H7)Pr(C8H8)·(THF)2afive-memberedringcentroidofC9H7,theC8H8ringcentroidandthetwooxygenatomsfromthetwoTHFmoleculesformadistortedtetrahedralgeometryaroundthemetal.
简介:Adoubleactivecentersystem,namelySalen-Cu(Ⅱ)@MIL-101(Cr),wassuccessfullysynthesizedviathe“shipinabottle”approach,whichactedasabifunctionalmaterialforbothcaptureandconversionofCO2inasingleprocess.Forthefirsttime,Salen-Cu(Ⅱ)@MIL-101(Cr)catalystwasdevelopedforthesynthesisofpropylenecarbonatefromCO2andpropyleneoxideunderroomtemperatureandambientpressurewithayieldof87.8%over60h.Furthermore,thereactionmechanismwasalsodiscussed.
简介:Inthispaper,weintroduceaconditionweakerthantheLpdifferentiability,whichwecallCpcondition.Weprovethatifafunctionsatisfiesthisconditionatapoint,thenthereexiststhebestlocalapproximationatthatpoint.WealsogiveanecessaryandsufficientconditionforthatafunctionbeLpdifferentiable.Inaddition,westudytheconvexityofthesetofclusterpointsofthenetofbestappoximationsoff,{Pe(f)}ase→0.