简介：利用Gaussian-94计算程序中的B3LYP方法,在6-311+G(2d)6d基组下,对Si5,Si5H3,Si5H6,Si5Li3和Si5Na3原子簇的几何结构进行优化和频率计算.结果表明,Si5原子簇中最稳定的具有D3h对称性的结构中,位于同一平面上的3个Si原子确实具有剩余的成键能力,可以与3个H,Li,Na原子和6个H原子形成稳定的化合物.研究还发现,虽然H,Li和Na都属同一主族,但它们与Si5原子簇中Si原子的键连方式却不同,而且它们的加入,对Si5原子簇的'三角双锥'结构也有不同的影响.

简介：Temperature-dependentphotoluminescencecharacteristicsoforganic-inorganichalideperovskiteCH3NH3PbI3-xClxfilmspreparedusingatwo-stepmethodonZnO/FTOsubstrateswereinvestigated.Surfacemorphologyandabsorptioncharacteristicsofthefilmswerealsostudied.Scanningelectronmicroscopyrevealedlargecrystalsandsubstratecoverage.Theorthorhombic-to-tetragonalphasetransitiontemperaturewas140K.Thefilms’excitonbindingenergywas77.6±10.9meVandtheenergyofopticalphononswas38.8±2.5meV.TheseresultssuggestthatperovskiteCH3NH3PbI3-xClxfilmshaveexcellentoptoelectroniccharacteristicswhichfurthersuggeststheirpotentialusageinperovskitebasedoptoelectronicdevices.

简介：AlphaGo以悬殊的比分战胜围棋世界冠军李世石迅速成为近期的新闻热点。这里我们暂不关心其中的技术细节(其中的数学知识无疑有待于你今后深入学习),而只关注它的决策生成原则。首先,AlphaGo为自己设定了一个全局的目标'WIN',局中每一步落子的决策并不一定是'当前局面下最好

简介：让M是紧缩的orientable无法缩减的3-manifold，和F是在把M切成二manifoldsM1和M2的M的必要连接关上的表面。如果Mi有最小的Heegaard切开Mi=$V_i\cup_{H_i}$V_i\cup_{H_i}有d(H1)的Wi+d(H2)2(g(M1)+g(M2)？g(F))+1，然后g(M)=g(M1)+g(M2)？g(F)。

简介：TwopossiblereactionmechanismsofVS~+(~3∑~-,~1Γ)withCOinthegasphasehavebeenstudiedbyusingB3LYP/TZVPandCCSD(T)/6-311+G(3dr,3pd)methods:theO/Sexchangereaction(VS~++CO→VO~++CS)andtheS-transferreaction(VS~++CO→V~++COS).Thetworeactionsproceedviatwo-stepandone-stepmechanism,respectively.ThebarriersofthetripletandsingletPESsare30.6and50.9kcal/mol,respectively,forO/Sexchangereactionand7.3and50.2kcal/mol,respectively,fortheS-transferreaction.Theresultsindicatethatthetripletgroundstatereactionismorefavorable,andtheS-transferreactionismorefavorablethantheO/Sexchangereaction,whichisingoodagreementwiththeexperimentalobservation.

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简介：Inthisnotesomerecurrencerelationsforthedimensionsofthesplinespacesonsocalled0-starsarepresented.

简介：Generally,ROSareregardedashostdefensemoleculesthatarereleasedbyneutrophilstodestroyexogenouspathogenssuchasbacteriaandtoactassecondarymessengersinsignaltransduction.However,increasedproductionofROSisalsoinvolvedininducingpathophysiologicalchangessuchasapoptosis,cellcycledisruption,andnecrosis.Forthisreason,inductionofROS-mediateddamageincancercellsbypharmacologicalagentsthateitherpromoteROSgenerationordisablethecellularantioxidantsystemisconsideredapotentialtherapeuticstrategyforpreferentiallykillingcancercells[1].

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简介：P1(G)是指这样的图：G中的所有k路作为P1(G)的顶点集，两个不同的顶点在Pk(G)中邻接当且仅当它们所对应的两条k路的并为G中的(k+1)路或k圈，那么，完美图猜想对于路图P3（G)是成立的。

简介：TheinhomogeneityinacongrunetLiTaO3crystalhasbeenobservedbytransmissionsynchrotrontopography.ManyextraordinaryregionsexistincongruentLiTaO3crystalandtheyoftenshowdiffractionintensitydifferentfromthatofordinaryregionsinsynchrotrontopographs.DifferentialthermalanalysisindiatesthattheCurietemperatureoftheextraordinaryregionislowerthanthatofordinaryregion,andtheextraordinaryregionisreallyahighdefectdensityregion.Thediffractioncontrastoftheextraordinaryregioninsynchrotrontopographsisexplainedqualitativelybyacalculationattheselectedwavelength.2001PublishedbyElsevierScienceB.V.

简介：Thenew-typetractionboundaryintegralequationsdevelopedbyHuandwithnohypersingularintegralareappliedtoanalysisof3Dfinitecrackedbodies.Anumericalalgorithmforgeneral3Dproblemsandasemi-analyticaloneforaxisymmetricproblemsarepresented.Someexamplesofthickplatesandcylindricalcolumnsincludingpenny-shapedcrack(s),andrectangularplatesincludinganellipticalcracknormaltothesurfaceareanalyzed.Thecomparisonbetweenpresentresultsandthoseinliteratureshowsthehighaccuracyandeffectivenessofthepresentmethod.

简介：Wegiveadetaileddescriptionofnonconstantharmonicfunctionsonthelevel3SierpinskigasketThenweextendthemethodonβ-setwith1/3<β<1/2.

简介：FurfuralinaqueoussolutionwastreatedbyUV/O3method.Theresultsshowthattheremovalrateoffurfuralisseverelyenhancedandthesynergismphenomenonappearswhenultravioletandozonearepresenttogether.TheinfluencesofexperimentalparameterssuchaspH,theintensityoflightandthenegative-positiveionsonfurfuraldegradationwereinvestigated.Theresultsindicatethatfurfural(300mg/L)isalmostcompletelydegradedafter3hundertheoptimumconditions.TheintermediateinthefurfuraldegradationwascharacterizedbyGC-MSandIRspectrumandthedegradationmechanismoffurfuralbyUV/O3technologywasproposed.

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简介：Thetitlecompounds5a-5cwerepreparedviathereactionofmethyl2-perfluoroal-kynoates(4)withmethyl5-oxo-4-(triphenylphosphoranylidene)hex-2-enoate(3),whichwasobtainedfromthereactionofmethylpropynate(2)withacetylmethylenetriphenylphosphorane(1)at-5-0℃.IntramoleculareliminationofPh3POtookplacewhencompound5washeatedinaqueousmethanolat115-120℃insealedtube,yieldingdimethyl2-trifluoromethyl-4-methylisophthalate(6a)from5aandmethyl5-acetyl-4-hydroxy-2-heptafluoropropanylbenzoate(6b)from5b,respectively.Thestructuresofcompounds5,6aand6bwereconfirmedbyIR,MS,1HNMR,19FNMRand13CNMRspectroscopyandelementalanalyses.Rectionmechanismsfortheformationofcompounds5,6aand6bwereproposed.

简介：Pt/WO3/CnanocompositeswithparallelWO3nanorodsweresynthesizedandappliedasthecathodecatalystforprotonexchangemembranefuelcells(PEMFCs).Electrochemicalresultsandsinglecelltestsshowthatanenhancedactivityfortheoxygenreductionreaction(ORR)isobtainedforthePt/WO3/CcatalystcomparedwithPt/C.ThehighercatalyticactivitymightbeascribedtotheimprovedPtdispersionwithsmallerparticlesizes.ThePt/WO3/Ccatalystalsoexhibitsagoodelectrochemicalstabilityunderpotentialcycling.Thus,thePt/WO3/CcatalystcanbeusedasapotentialPEMFCcathodecatalyst.

简介：Erbium,Ytterbium-codopedZrO2nanoparticles(ZrO2∶Er3+,Yb3+)werepreparedbythesol-emulsion-geltechnique.Thepurposeofthepresentstudyistheapplicationofupconversionphosphorinthebiologicallabel.Inordertomakeoutthemechanismofupconversionunder980nmexcitationthe488nmpumpwasused.Theinfluenceoftemperatureonthecrystallitephasewasstudied.TheresultsconfirmtheupconvertedmechanisminZrO2∶Er3+,Yb3+nanocrystalsisduetoanenergytransferupconversion(ETU).

简介：CaF2:Ho3+/Yb3+nano-particleswithintensegreenup-conversion(UC)luminescencearesuccessfullysynthesizedviaafacilehydrothermalapproachbyusingNH4FasthefluoridesourceandNa2EDTAasachelatingreagent.PowderXraydiffraction(XRD),transmissionelectronmicroscopy(TEM),fieldemissionscanningelectronmicroscopy(FE-SEM),andUCemissionspectraareusedtocharacterizethestructures,shapes,andluminescentpropertiesofthesamples.TheeffectsfromfluoridesourcesandchelatingreagentsontheformationsofCaF2nano-particlesareinvestigated,andtheformationprocessisalsodeduced.Undertheexcitationofa980-nmlaserdiode,thesampleseachshowagreenup-conversionemissioncenteredat540nmcorrespondingtothe5S2/5F4→5I8transitionsofHo3+.Moreover,theUCmechanismsofHo3+/Yb3+co-dopedCaF2nano-particlesarealsodiscussed.

简介：(-)-cis-1,3-Dibenzyl-hexahydrofuro[3,4-d]imidazole-2,4-dionewaspreparedbyanewsynthesismethodfrommesodicarboxylicacidanddehydroabietylaminebyasymmetricreductioningoodyieldwithupto91.6%e.e.value.