987 resultados para 404
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综述了近年来聚(β 羟基丁酸酯)和β 羟基丁酸酯 β 羟基戊酸酯共聚物经共混改性所得到的共混物的相容性、结晶性、热性能、加工性能、力学性能和生物降解性能。
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中国科学院山西煤炭化学研究所
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It is found that Ply adsorbed roughed silver electrode, it is easy to immobilize MP-11 with the electrostatic interaction and to prepare the MP-11/Ply/Ag modified electrode. The preparation method of the modified electrode is simple. In addition, the modified electrode obtained shows the high and stable electrocatalytic activity for O-2 reduction. It is also found that when the sixth coordination of heme in MP-11 is replaced with other coordination species with stronger coordination ability, such as imidazole, its formal redox potential shifts to the negative direction and the electrocatalytic activity for O-2 reduction is reduced.
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发现利用吸附在粗糙Ag电极上的聚赖氨酸(Ply),以静电作用方式固定微过氧化酶-11(MP-11)来制备MP-11/Ply/Ag修饰电极,不但方法简单,而且制得的修饰电极对O2的还原有高的电催化活性和好的稳定性.另外还发现MP-11分子中血红素的第六配体被配位能力较强的配体,如咪唑取代时,其本身的氧化还原电位负移,对O2还原的电催化活性降低.
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应用一氯二乙基铝和苄基氯催化剂体系进行了丁苯橡胶的阳离子环化反应。研究了反应温度、苄基氯/ 一氯二乙基铝比例、溶剂、原胶浓度对环化的影响。发现通过控制苄基氯/ 一氯二乙基铝比,可在高温(120℃) 、高原胶浓度(2~4%w/v)下进行丁苯橡胶的环化,制得特性粘度较原胶有大幅度降低,可溶性无凝胶的环化丁苯胶。通过对红外光谱、1H-NMR谱的初步解析,证实了环化反应的发生。
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在Al2 O3_B2 O3_Ce2 O3体系中 ,于 12 0 0~ 140 0℃的温度范围内 ,合成了一系列不同配比 (Al/B比从 4 5~ 2变化 )磷光体 .研究了它们的结构和光谱特性之间的相关性 .发现随着基质配比Al/B从 4 5~ 2的变化 ,基质结构发生明显的变化 .这种变化导致光谱特性的巨大变化 ,表明铈离子晶场环境的变化 ,随着配比的变化 ,激发与发射峰向短波方向移动 .在合适的配比下 ,可以获得新型的稀土发光材料
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人工核酸酶是一类具有限制性内切酶的功能、能高效高选择性地催化水解DNA或RNA的断裂工具。它们一般由核酸结构识别系统及催化断裂系统组成,将两种功能有效地结合起来,可模拟核酸的酶切反应。本文综述了稀土及其配合物对核酸的断裂作用,并对其断裂机制进行了探讨
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用同步法合成了聚环氧氯丙烷聚氨酯/聚甲基丙烯酸甲酯互穿网络聚合物[PU(PECH)/PMMAIPN],调节IPN中两组分组成比制备出由完全弹性体、增强弹性体、增韧塑料到脆性塑料多种高聚物合金材料.用DSC、动态力学谱、TEM对IPN的研究结果表明,PU(PECH)/PMMAIPN的两组分是完全相容的;同时对各种组成比的IPN材料进行力学性能测试,用相容性IPN中互穿、缠结结构解释其力学行为,并用SEM对断面形貌进行了观察解释.
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用锥权流变仪及DSC的方法研究了5种不同分子量的酞侧基聚芳醚酮(PEK—C)在低剪切速率区(10-2-10s-1)的流变行为及其分子量与玻璃化转变温度(Tg)的关系.结果表明,样品的粘流活化能随分子量的增加而增大,Tg随分子量的变化是二个线性区,其交点值与所求的样品的临界分子量(Mc)值相对应.利用测得的零剪切粘度值(η0)首次求得了PEK—C的临界分子量(Mc)值.同时也讨论了Mc与温度及η0和Tg与分子量的关系.
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合成了化合物YCa_2Cu_3Oy,这个化合物结构属正交晶系a=6.528A, b=5.421(?),c=10.404(?)。氧含量y=6.55。Yca_2Cu_3Oy是黑色n型半导体材料,室温电阻率1.2×10~5Ω·cm。测量了该化合物的R—T关系,并把它的组成、结构和性质与超导化合物YBa_2Cu_3Oy进行了对比和分析。
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In this work, the photosynthetic performances of Enteromorpha prolifera thalli collected from the surface and bottom of the sea of Qingdao sea area were studied with chlorophyll fluorescence and oxygraph technology. The samples with the highest photosynthetic activity among their kinds, the floating thalli from the sea surface of the south of the Qingdao Olympic Sailing Center and the sedimentary thalli from the mud surface of the bottom Tuandao bay, were chosen as representatives of surface thalli and bottom thalli, respectively. The results showed that the maximal PSII quantum yield of the floating thalli was significantly lower than the normal level although their photosynthetic activities were relatively high; the photosynthetic potential of the thalli form the mud surface was extremely low. Thus, it is indicated that the floating thalli are seriously stressed by their environment and the thalli from the mud surface are already dead or are dying. On the other hand, the results of the laboratory cultivation showed that the sedimentary thalli cannot regain normal photosynthetic activity even under normal illumination conditions. Thus, the thalli from the mud surface cannot become reproductive source of the alga even if they can reach sea surface again. Therefore, a preliminary conclusion can be reached that, up to mid-July 2008, the environmental conditions of the Qingdao sea area are not suitable for the growth of the alga E. prolifera and for this reason the biomass of E. prolifera, in the area, could be declining.
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Effective elastic properties of piezoelectric composites containing an infinitely long, radially polarized cylinder embedded in an isotropic non-piezoelectric matrix are theoretically investigated under an external strain field. Analytical solutions of elastic displacement and electric potentials are exactly derived, and the effective elastic responses are formulated in the dilute limit. Meanwhile, a vanishing piezoelectric response mechanism is revealed in the piezoelectric composite containing radially polarized cylinders. Furthermore, it is shown that the effective elastic properties can be enhanced (or reduced) due to the increase of the piezoelectric (or dielectric) constants of the cylinders. (C) 2009 Elsevier B.V. All rights reserved.
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采用活体注射秋水仙碱制备鱼类肾细胞染色体、PHA肌肉注射制备肾细胞染色体和鱼类早期胚胎制备染色体等多种方法。以空气干燥法制片Giemsa染色,对鲻鱼Mugil cephalus Linnaeus、真鲷Pagrosomus major(Temminck et Schlegel)、黑鲷Sparus macrocephalus(Basilewsky)、黑鮶Sebastes schlegeli (Hilgendorf)、石鲽Kareius bicoloratus (Basilewsky)、牙鲆Paralichthys olivaceus (Temminck et Schlegel)等分属四目、五科的六种海产鱼的染色体组型进行了考察和分析。研究结果表明:1、一般活体注射秋水仙碱制备海产鱼肾细胞染色体方法的有丝分裂指数虽然略低于PHA制备肾细胞染色体方法的有丝分裂指数。但它是最快最简便且很有效的方法,利用鱼类早期胚胎制备海产鱼染色体标本的方法也很有效,但要受到生物季节的限制。2、通过对六种海产鱼染色体组型分析得到,鲻鱼为48条端部着丝点染色体;真鲷的二倍体2n=48,有1对亚端部着丝点染色体。其余全部为端部着丝点染色体;黑鲷的二倍体2n=48。有3对中部着丝点染色体。2对亚中部着丝点染色体,其余全部为端部着丝点染色体。黑鮶的二倍体2n=48,有1对中部着丝点染色体,其余全部为端部着丝点染色体,石鲽的二倍体2n=48。全部为端部着丝点染色体;牙鲆的二倍体2n=48,全部为端部着丝点染色体。本文还对鱼类染色体的多态现象以及染色与进化的关系进行了讨论。
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目的 探讨唐古特大黄中五种蒽醌衍生物的含量与生长年限的关系.方法 用高效液相色谱法测定不同生长年限唐古特大黄中大黄素、大黄酚、大黄酸、芦荟大黄素、大黄素甲醚的含量.色谱柱为C_(18)柱,流动相为甲醇-0.1%磷酸(85∶15),流速为1.0 mL•min~(-1),检测波长为254 nm,柱温为室温,按外标法定量.结果 与结论 唐古特大黄中五种蒽醌衍生物的含量随生长年限的增加而增加,第4年增长趋势变缓,且两年生唐古特大黄已符合药典要求.
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黄河上游谷地位于青海省的东部,约处北纬35°20′-36°25′,东经100°55′-102°50′。属青藏高原和黄土高原的过渡地带,海拔1780—4969m,面积约13480km^2,属于大陆性气候或高原大陆性气候类型。本区共有野生种子植物86科、404属、1027种。分别占青海省总科数的95.56%、总属数的79.53%、总种数的44.95%。区系特征如下:(1)种类相对较丰富,木本丰富。(2)植物种的中国特有性高,地区特有性小高。(3)就属的层面而言,中国种子植物区系15个分布区类型,特别是6个热带类型在青海境内唯一于本区都有出现。(4)属和种的分析表明,本区属于以北温带成分,特别是欧亚大陆温、寒地带典型成分为优势的,兼具温性、寒温和高寒类型的温带区系性质。(5)许多种、属和多数热带类型均以本区为边缘分布区,因而区系的边缘性质明显。(6)在植物区系地理方面,本区(特别是孟达林区)为华北区系、横断山区系、青藏高原的高山区系和柴达木高寒荒漠区系的交汇过渡地带,过渡区系性质明显。所以,本区作为远离青藏高原腹地的边缘地带和过渡区系,保持了其高原、高山类型的区系性质,应属距我国北方区系最为接近而高寒区系性质最弱的唐古特地区植物区系。