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HU Yushan BAI Dongren ZHANG Zhengpu WANG Yongmei HE Binglin 《Chinese Journal of Reactive Polymers》1999,(Z1)
1INTRODUCTIONSinceKulk~ietallllshowedthathighmolecularweightpolylactide(PLA)weredegradableinvivoandthusofinterestforbiomedicalapplications,PLAhasbeenstUdiedextensivelywithrespecttopotentialusesinsurgeryandinphannacology['l,suchasbonefractUrefixation,surgicalsut'Ureandcontrolledrelease.BecauseofitSbiocompatibility,itSdegradability,themetabolizationofdegradationbyproductsandthepossibilityofmodificationbytakingadvantageofcopolymerizationandblending,PLAispresentlyconsideredasthemostattra… 相似文献
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MECHANICAL ANALYSIS OF THE FORMATION AND PROPAGATION PROCESS OF FRACTURE SYSTEMS AND ITS APPLICATION
In this paper, the mechanical mechanism and propagation process of crustal fracture system are studied by using the principle and method of fracture mechanics. The trendings of two pairs of the X-shaped shearing fracture networks existing widely on the crust are calculated and the main causes to form them from the earth's rotation and thermal activity are considered. After the formation of X-shaped shearing fracture system, parts of them became a closed one but parts of them became more active and propagated further or interacted on each other since the stress field changed in the whole or regionally. Based on the propagating processes of single fracture and fracture systems, the formation process of the zigzag fractures of shear-tension and shear-compression are studied. Some examples showing that the propagating processes of fracture system can be applied to the research of earthquake prediction, are also indicated in this paper. 相似文献
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天然大分子木质素在超临界乙醇-甲酸介质中可以有效地降解为酚类化合物.超临界乙醇为木质素提供了理想的反应介质,甲酸热分解原位产生的氢作为木质素裂解自由基封端剂有效促进了降解向小分子转化;过渡金属盐可以催化降解反应.木质素超临界降解机理为自由基反应,在还原状态下氢可以对木质素自由基封端从而得到小分子化合物.木质素理想的超临... 相似文献
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介绍了测量不确定度的评定方法及其在基准试剂纯度、干涉滤光片波长标准物质、锌合金成分标准物质中的应用实例。 相似文献
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原位沉析法制备可吸收壳聚糖/羟基磷灰石棒材 总被引:19,自引:1,他引:19
利用原位沉析法制备出一种以壳聚糖 (Chitosan ,CS)为基体 ,羟基磷灰石 (Hydroxyapatite,HA)为填料的新颖的复合材料 ,系统研究了HA含量对复合材料的力学性能和吸水率的影响 .CS HA的弯曲强度为 6 7 8(MPa) ,弯曲模量为 3 3(GPa) ,剪切强度为 2 1 2 (MPa) ,压缩强度为 4 7 8(MPa) ,均比人的自然骨高 2~ 3倍 ,基本满足了作为骨折内固定材料的力学性能的要求 .HA加入到CS使CS HA复合材料的吸水率下降 ,有助于延缓其力学强度在湿态环境下的衰减 相似文献
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XIE Lanying ZHONG Kejun LIU Qi Technical Center of Changde Cigarette Factory Hunan China 《Chinese Journal of Reactive Polymers》2005,(Z1)
1. INTRODUCTION Tobacco smoking ranks as a major public health problem whose negative impacts have been well established since the report of “smoking and health” published by the royal medicine academy of English in 1954. Besides nicotine, the major inducer of tobacco dependence, cigarette smoke also contains various toxic compounds, notably N-nitrosamines. Nitrosamines are formed by the nitrosation(addition of an N=O group, from the nitroso ramifications NO2, N2O3,N2O4) of secondary… 相似文献
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介绍测量不确定度的产生及其评定和表述的一般原则。讨论了离子色谱法测量中影响测量不确定的因素并进行了分析和评定,给出了测量结果的表述方法。 相似文献
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N-nitrosamines are strong carcinogens for humans. This paper gives an overview of the nitrosmaines in cigarette smoke including the formation, the harmfulness, the analytical methods of the nitrosmaines and the adsorptions and degradations of N -nitrosamines. 相似文献
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热分析方法用于研究聚对次苯基硫醚的相转变及热裂解反应的动力学 总被引:4,自引:0,他引:4
利用DTA和TBA观察了聚对次苯基硫醚(PPS)的T_(gg)、T_g、T_c、T_m和相对刚度的变化,并用TG、DTG和DSC研究了它们在空气中热裂解反应的动力学过程,得出PPS起始裂解温度在400℃附近(β=1℃/分)。裂解分两个阶段进行:第一阶段属于线型链段部份的裂解;第二阶段,由于结构中出现芳稠环和含硫的稠杂环,提高了热稳定性,裂解活化能达到100—105(千卡/克分子),反应级数为1.7,频率因子为10~(26)(秒~(-1))。 相似文献
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催化荧光分析法研究进展及应用 总被引:1,自引:0,他引:1
评述催化荧光分析法的发展及其应用。催化荧光分析法的主要研究进展包括:新体系的发现与新试剂的合成,增效试剂的应用,流动注射技术与催化荧光分析法的结合,活化剂与抑制剂的应用。介绍了催化荧光分析法在测定无机物、有机物和酶等方面的实际应用。 相似文献
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1.INTRODUCTIONPolylactide(PLA)isabsorbablepolyester,whichhasbeenprovedtobewelltoleratedbytissuesandcanbemanufacturedforinternalfixationdevicesforexample,rods,pins,wires,tacks,platesandscrews.ItwasverydifficultytousethePLAinthecourseofmanufacturingtheinternalfixationscrewsofbonefracture,becauseofitsstrengthisnotstrongenoughtomeettheneedofthepracticaluse.Infact,poly-L-lactide(PLLA)hasbeenfoundamoresuitablepolymericmaterialforthistarget.II-7]Inrecentyears,L-lacticacidhasbeenindustrializ… 相似文献
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用不同分子量的聚苯乙烯在乳液体系中进行过氧化氢基化反应,然后测定这些产品的特性粘数,HPO值(每1,000个苯乙烯结构单元中所合的过氧化氢基平均数目)等。在过氧化氢基聚苯乙烯的红外光谱里,可以在3,200—3,600厘米~(-1)吸收区里观察到过氧化氢基的吸收带,其吸收强度随着HPO值的增大而加强。最后用这些大分子过氧化物引发甲基丙烯酸甲酯及苯乙烯聚合,得到接枝聚合物。经过分离提纯后,用下列的方法: (1)浊度滴定; (2)热机械性能的测试; (3)水解后测定交换量; (4)红外吸收光谱;证明它们是接枝共聚物。 相似文献
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反式氢化茚酮是全合成甾体的合成子。本文综述了五种合成方法:即分子内 Diels-Alder 反应,分子内 Michael 反应;联合 Cope-Claisen 重排;Lewis 酸催化环合γ,δ-不饱和羰基化合物以及二环庚烷的裂解。 相似文献
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综述了壳聚糖、甲壳素在污水处理、电化学、原子吸收光谱、高效液相色谱、吸光光度法中的应用。引用文献28篇。 相似文献
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New concepts such as intramolecular orientational order parameter and corresponding model as well as theory were proposed to describe the intramolecular orientation of mesogenic units in the liquid crystalline polymer chains. The relationship between the intramolecular orientational order parameter and the molecular geometrical parameters such as the bond angle, the bond rotational angle and the rotational potential energy of chemical bonds was deduced. A significant even-odd oscillation of the intramolecular orientational order parameter of LCPs with different length of flexible spacer was found and rationally related to even-odd zig-zag manner of transition properties The verification and application of the theory are also discussed. The isotropic transition temperature predicted by the theory is shown to be in favourable agreement with the experiments. 相似文献