简介:Polyolefinsthatbearachiralsidechain(typicallyanisobutylgroup)experienceaso-calledmacromolecularamplificationofchirality:thechiralside-chaininducesaslightpreferenceforeithertgortg-mainchainconformation.Thisslightconformationalbiasisamplifiedcooperativelyalongthechain,andresultsinpreferredchiralityofthemainchainhelicalconformations.Asaresult,thesepolymersdisplayaliquid-crystal(LC)phasebothinsolutionand,inthemeltasatransientphaseonthewaytocrystallization.Theexistenceoftwoprocesses(melt-LCandLC-crystaltransitions)resultsinunconventionalbehaviorsthatwerefirstanalyzedbyPinoandcollaboratorsbackin1975.Thesepolymersalsoofferameanstotestthestructuralconsequencesofrecentlyintroducedcrystallizationschemes.Theseschemespostulatetheformationofatransientliquid-crystalphaseasageneralschemeforpolymercrystallization.
简介:Thesynthesisofanewtypeofhetero-macrocyclicpolyether2,3-henzo-1,4,7,13-tetraoxa-10-selenacyclopentadeca-2-eneisdeseribed.
简介:对[0,1]上的L—可积函数ф及α>0定义下列B—D—B算子;本文研究了Mna(ф,x)当α>0时,在LP(0,1](1≤p<+∞)的一致逼近;当α≥1时在LP[O,1]及L1P[0,1]逼近度的量化估计。作者在文[4]中定义了B—D—B算子:其中fnk(X)称为Bézeief基函数文[4]研究的是B—D—B称子在C[0,1]空间中的逼近性质,本文继续[4]的工作,专研究这个算子在LP[0,1](1≤P<+∞)的逼近性质,证明了Mna(фX)当α>0时在LP[0,1]中为一致逼近,并得到了当α≥1时在LP[0,1]及L1P[0,1]中逼近度的量化估计。
简介:Takingthe(2+1)-dimensionalBroer-Kaup-Kupershmidtsystemasasimpleexample,somefamiliesofrationalformsolitarywavesolutions,triangularperiodicwavesolutions,andrationalwavesolutionsareconstructedbyusingtheRiccatiequationrationalexpansionmethodpresentedbyus.Themethodcanalsobeappliedtosolvemorenonlinearpartialdifferentialequationorequations.
简介:<正>WestudythesolvabilityoftheCauchyproblem(1.1)-(1.2)forthelargestpossibleclassofinitialvalues,forwhich(1.1)-(1.2)hasalocalsolution.Moreover,wealsostudythecriticalcaserelatedtotheinitialvalueu0,for1
简介:Dithia-monoaza18-Crown-6anditsimmobilizationproduct,silica-bound1,7-dithia-4-aza-10,13,16-trioxa-cyclooctadecaneviaaspacerofthreecarbonatoms,anditsplatinumcomplexhavebeensynthesized.Itisfoundthattheplatinumcomplexisanefficienthydrosilylationcatalystforolefins.TheXPSdataoftheplatinumcomplexarereported.
简介:Basedonthestructure-activityrelationshipsofRGD-containingpeptides,aseriesof1,3-dihydro-l,3-dioxo-2H-isoindolederivativesweresynthesized.Allofthemwerefirstreported.Theirstructureswereconfirmedbyspectraldataandelementalanalysis.Theirabilitytoinhibitangiogenesiswereevaluatedinthechickembryochorioallantoicmembraneassayat-10^-5mol/L.Compounds5band5edisplayedobviouslyantiangiogenicactivity.
简介:运用电化学循环伏安和石英晶体微天平研究了1,4-丁二醇(1,4-BDL)在Pt电极及以Sb和S吸附原子修饰的Pt(Pt/Sbad和Pt/Sad)电极上的吸附和氧化过程.结果表明,1,4-丁二醇的氧化与电极表面氧物种有着极其密切的关系,表面质量变化提供了吸附原子电催化作用的新数据.Pt电极表面Sb吸附原子能在较低的电位下吸附氧,可显著提高1,4-丁二醇电催化氧化活性.与Pt电极相比,1,4-丁二醇在饱和吸附Sb原子的Pt电极上氧化的峰电位负移了0.20V,峰电流增加了1.5倍.相反,Pt电极表面S吸附原子的氧化会消耗表面氧物种,饱和吸附的S原子抑制了1,4-丁二醇的氧化.