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31.
利用X-射线衍射(XRD)和3D图像处理软件(Image-pro)研究了四种不同火灾类型金属熔痕的显微组织、平均晶粒度、物相组成及其分布规律。结果表明:金属火灾熔痕主要由立方晶系的Cu2O和胞、枝状的Cu组成。在四种不同的起火方式下,金属熔痕的显微组织和成分有显著的差别:(1)一次短路的火灾熔痕平均晶粒度为3~5 μm,其Cu2O含量最低;过载熔痕的平均晶粒度与一次短路的类似,但其Cu2O含量为30%左右;(2)二次短路熔痕中含有一定数量直径较大的微观空洞,平均晶粒度约为30 μm;其Cu和Cu2O衍射峰出现展宽和辟裂,烧蚀程度最深;(3)火灾熔痕中粗大的Cu2O等轴晶衍射峰强度最大,且显微组织中几乎没有微观空洞存在。 相似文献
32.
DING Jian DING Xue-jia XU Ri-wei YU Ding-sheng * Materials College Beijing University of Chemical Technology Beijing P. R. China Received May 《高等学校化学研究》2005,21(2):227-231
The viscoelastic behavior of isotactic polypropylene with ultra-high molecular weight (UHPPH) and broad molecular weight distribution(MWD), produced in the presence of Ziegler-Natta catalyst, was investigated by means of oscillatory rheometry at 180 and 200 ℃, whose loss modulus(G") plots at 180 and 200 ℃versus the natural logarithm of angular frequency(ω) present a pronounced maximum at 34.35 and 69.21 rad/s, respectively, and do not show a maximum peak at 0. 01-100 rad/s for Ziegler-Natta catalyzing ethylenepropylene random copolymerization (PPR) with a conventional molecular weight and broad MWD. The fact indicates that the high molecular weight is responsible for a maximum peak of G"(ω) vs. lnω curves for UHPPH. This makes it possible to determine the plateau modulus (G0N) of UHPPH from a certain experimental temperature G"(ω) curve directly. For UHPPH, the G0N determined to be 4. 28×105 and 3. 62×105 Pa at 180and 200 ℃, respectively, decreases with the increase of temperature and is independent of the molecular weight, which directly confirms reputation theoretical prediction that the G0N has no relation to the molecular weight. 相似文献
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YANG Hong-li * VAULTIER MichelSynthèse et Electrosynthèse Organiques UMR CNRS Université de Rennes Campus de Beaulieu Avenue du Général Leclerc RENNES CEDEX France 《高等学校化学研究》2002,18(4):414-418
IntroductionGrubbs catalyst bis(tricyclohexylphosphine)benzylidene ruthenium( ) dichloride1 can be usedin a variety of ring- closing metathesis (RCM )reactions,cross metathesis(CM) reactions andring- opening metathesis polymerization(ROMP) [1— 4 ] .It remains metathetically active inthe presence of a variety of functional groups,suchas carbonyls,alcohols,and amides[1] .The use ofcatalyst1 in the synthesis has drawn more andmore attention[5— 13] . However,this catalyst is veryexpensive,an… 相似文献
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Cigang Xu Emmanuel Flahaut Sam R. Bailey Gareth Brown Jeremy Sloan Karl S. Coleman V. Clifford Williams Malcolm L. H. Green * . Inorganic Chemistry Laboratory University of Oxford Oxford OX QR UK 《高等学校化学研究》2002,18(2):130-132
IntroductionSingle walledcarbonnanotubes(SWNTs)havebeensynthesisedbyusingvariousmethods[1— 3] andthechemicalvapourdeposition (CVD )methodhasbeenconsideredasa promisingmethodto produceSWNTsonanindustrialscale[3— 5] .However ,alltheSWNT productssynthesisedtodateco… 相似文献
35.
溶液中分子的快速弛豫过程直接反映了溶液中溶质和周围溶剂分子间的相互作用[1-3].在液相体系中分子取向通常是随机分布的.当溶质分子被线偏振光激发至激发态时,其分子取向将由原来各向同性的球形分布瞬间变成各向异性的椭球分布.由于溶质分子周围大量溶剂分子的存在,通过二者之间相互作用,激发态溶质分子在一定方向上的取向优势将很快弛豫掉.这种溶液中的取向弛豫过程通常是几个到几百皮秒[1-3]. 相似文献
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Hong Ping LI Hai Fei ZHANG Jun LIU Bu Xing HAN* Center for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 《中国化学快报》2001,(4)
There are some unique advantages for chemical reactions in SCFs. For example, reaction rates, yields, and selectivity can be tuned by pressure or small amount of cosolvent. SCFs can be used to replace environmentally undesirable solvents. It is not surprised that in recent years the use of SCFs as solvents for chemical reaction media has received much attention. However, mechanism for the effect of pressure and cosolvents on chemical reactions is not very clear. Tautomeric reactions are id… 相似文献
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1 INTRODUCTIONItwaswellknown thatelementsofthesecondary and higherrow are in generaldifficulty to form multiplebondsin which apπ hybridized stateisinvolved〔1〕.Thus,simple compounds containing multiple phosphorus carbon bonds,such as methyl dynephosphine( HC≡P) 〔2 - 3〕 and methylenephosphine( H2 C=PH〔4〕,are notstableat room temperature.Three methods to stabilize compounds containing double ormultiple bond involving phosphorusatom in the pπ hybridized state are often used.The f… 相似文献
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Our group have explored the reaction of allylsamarium bromide with a variety of substrates, such as N-(2-aminoalkyl)benzotriazoles1, imines2, nitriles3, diorgano diselenides4, disulfides5, isocyanates6 and nitroalkenes7. Here we wish to report the monoallylation of gem-diacetates with allylsamarium bromide. Gem-diacetates are stable in neutral and basic media, thus they are frequently used to protect aldehydes8. However, the presence of two leaving groups at the same carbon may make carbon … 相似文献
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Xue Mei LUO Wei Jiang HE Yu ZHANG Zi Jian GUO Long Gen ZHU* State Key Laboratory of Coordination Chemistry Nanjing University Nanjing 《中国化学快报》2000,11(11)
Selectively chemical cleavage of peptides and proteins is one of the most important reactions in both chemical and biochemical processes. Over the past decade, the interaction of palladium(II) complexes with methionine, cysteine and histidine-containing peptides and proteins and the hydrolytic cleavage of the corresponding amide bond by Pd(II) complexes have been extensively studied1-13. However, reports concerning the directly selective hydrolysis of peptides and proteins with other simple … 相似文献
40.
运用分子动力学模拟,研究了腺苷酸(激动剂)与A2AAR腺苷受体蛋白的相互作用和配体结合诱导的蛋白动力学变化.识别了与腺苷酸结合力强于0.5kcal/mol的关键基团:A63^2.61,I66^2.64,V84^3.32,L85^3.33,T88^3.36,F168^5.29,M177^5.38,L249^6.51,H250^6.52和N253^6.55,观察到腺苷酸没有与L167^5.28相互作用,这一结果支持了L167^5.28是抑制剂特异性结合位点,不与激动剂结合.未结合配体(激动剂或抑制剂)的单体A2AAR和腺苷酸结合后的A2AAR在构象上有三个不同功能性开关.腺苷酸结合可以诱导A2AAR腺苷受体蛋白的构象调整,使得三个功能性开关器件的构象与单体A2AAR不同. 相似文献