简介:采用密度泛函B3LYP/6-311G(d,p)方法对CH3F与C2H3的反应体系进行了理论研究,获得了反应的势能面信息及可能的微观机理.在QCISD(T)/6-311++G(d,p)水平上精确计算了各反应物种的单点能.结果表明,除抽提氢反应外,标题反应还存在抽提氟(R1)、消氟化氢(R2)、消氢(R3)和自由基形成(R4)四类反应.在QCISD(T)/6-311++G(d,p)//B3LYP/6-311G(d,p)水平上,R1,R2,R3和R4反应的能垒分别是163.9,152.2,209.8和224.2kJ·mol-1,相应反应能为-56.6,-164.3,-2.7和-156.0kJ·mol-1,所有反应均放热,为热力学允许的反应.
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: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:Inthispaper,weintroduceaconditionweakerthantheLpdifferentiability,whichwecallCpcondition.Weprovethatifafunctionsatisfiesthisconditionatapoint,thenthereexiststhebestlocalapproximationatthatpoint.WealsogiveanecessaryandsufficientconditionforthatafunctionbeLpdifferentiable.Inaddition,westudytheconvexityofthesetofclusterpointsofthenetofbestappoximationsoff,{Pe(f)}ase→0.