35 resultados para 366.28


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系统地研究了2-乙基己氧基甲基膦酸二(2-乙基己基)酯(代号PT28)对硫酸、磷酸、硝酸、高氯酸、盐酸和醋酸六种酸的萃取行为,发现PT-28对硫酸、磷酸、高氯酸和盐酸均不萃取,只对硝酸和醋酸萃取,这与中性磷氧萃取剂甲基膦酸二甲庚酯(P350)和磷酸三正丁酯(TBP)对强酸的萃取有显著的不同,并对其萃取机理进行了讨论。

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对 Ni6 9.5Al2 8Y2 .5粉末进行球磨 ,获得 Ni Al金属间化合物 .研究粉末结构与球磨时间的关系 ,探索以中间合金的形式加入稀土元素的机械合金化方法 .结果表明 ,加入稀土元素后 ,用机械合金化的方法可以生成新的金属间化合物.

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系统研究了2-乙基已氧基甲基膦酸工(2-乙基已基)酯(代号PT-28)在硝酸介质中萃取三价镧系元素的行为,讨论了萃取剂浓度的变化、硝酸钠的浓度及温度变化对萃取率的影响,并对PT-28. 萃取HNO_3的机理进行了探讨。

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The extracts obtained from 28 species of marine algae were evaluated for their antioxidant activity (AA) versus the positive controls butylated hydroxytoluene (BHT), gallic acid (GA), and ascorbic acid (AscA). Most of the tested samples displayed antioxidant activity to various degrees. Among them, the extract of Symphyocladia latiuscula exhibited the strongest AA, which was comparable to BHT, GA, and AscA in radical scavenging activity, as shown in the DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) assay, and higher than those of the positive controls in beta-carotene-linoleate assay system. In addition, the ethyl acetate-soluble fraction isolated from the crude extract of S. latiuscula exhibited the highest antioxidant activity in both assay systems. This fraction was further fractionated into seven subfractions (F1-F7) by vacuum liquid chromatography (VLC). F1 and F4 were found to be the most effective subfractions in scavenging DPPH radical assay and in the beta-carotene-linoleate assay, respectively. The total phenolic content (TPC) and reducing power (RP) for all of the extracts, fractions, and subfractions (F1-F7) were also determined. The TPC of the 28 extracts ranged from 0.10 to 8.00 gallic acid equivalents (mg/g seaweed dry weight) while the RP ranged from 0.07 to 11.60 ascorbic acid equivalents (mg center dot g(-1) seaweed dry weight). Highly positive relationships between AA and TPC as well as between AA and RP were found for the extracts and fractions, while for the subfractions F1-F7 only weak or no such relations were found. The results obtained from this study indicate that further analysis is needed of those marine algal species that contain the most antioxidant activity in order to identify the active principles.

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在进行褐牙鲆(Paralichthys olivaceus)和夏牙鲆(P. dentatus)的杂交及回交的基础上,利用染色体计数、AFLP、线粒体DNA和核基因部分序列等分析方法对褐牙鲆和夏牙鲆正反交和回交子代进行遗传学研究,探讨了褐牙鲆和夏牙鲆正反交不对称的遗传学基础及其生殖隔离现象,主要结果如下: 1. 褐牙鲆和夏牙鲆正反交的活力是不对称的,褐牙鲆♀×夏牙鲆♂的正交杂种活力正常,能够正常存活、生长和发育,而反交夏牙鲆♀×褐牙鲆♂的杂种体态畸形,孵出后不久死亡。染色体计数发现正交个体的染色体核型与父母本一致,均为48条端部着丝粒染色体;而反交杂种比亲本缺失了两条染色体,仅为46条端部着丝粒染色体,这表明反交杂种为非整倍体。进一步利用AFLP方法对遗传物质从亲本到子代的传递进行了分析,结果显示正反交遗传物质的传承方式存在很大差异。几乎所有亲本的AFLP位点(97.71%)均传递到正交子代。然而,仅有86.64%的AFLP位点从亲本传递到反交子代,反交子代中亲本位点的丢失比例显著高于正交子代和亲本种内交配子代的比例 ( P < 0.05),这可能与反交杂种染色体丢失有关。进一步分析发现,杂交组中的偏分离标记高于对照组,尽管经2检验发现其差异并不显著 (P > 0.05)。 2. 对于可以成活的正交杂种进行培育达到性成熟后,利用褐牙鲆和夏牙鲆的精液分别与雌性杂交鲆的卵子进行母本回交实验。通过统计受精率、孵化率及杂交适合度值(CFM,受精率和孵化率相乘获得的结果)评估褐牙鲆和夏牙鲆的杂交可适度,结果表明正交及各回交组中的CFM值均显著低于褐牙鲆自交(P < 0.05)。同时,利用AFLP对回交子代基因组的变化进行了分析,发现回交中不仅存在亲本位点的丢失(褐牙鲆回交子代-回交1, 3.96%; 夏牙鲆回交子代-回交2, 6.03%)的现象,也存在非亲位点(回交1, 5.63%; 回交2, 3.28%)的现象。而且,两回交组合分别有27.40%和31.18%的AFLP标记偏离孟德尔遗传。 3. 利用线粒体DNA 16S rDNA、COⅠ基因及核基因rag1的部分序列对正反交及回交子代的线粒体及核DNA的传承进行分析,发现正反交子代的16S rDNA和线粒体DNA片段的同源性和母本一致,各回交组中16S rDNA和COⅠ基因片段与褐牙鲆的同源性较高 (98%),这表明褐牙鲆和夏牙鲆杂交及回交遵循母性遗传规律。但在回交子代中发现16S rDNA和COⅠ基因具有多种单倍型。褐牙鲆和夏牙鲆的rag1基因具有高度的保守性,但在正交子代中发现rag1多种单倍型。 4. 进一步利用线粒体DNA的16S rDNA、COⅠ基因的部分序列对8种重要海水养殖鱼类的系统进化分析,计算了其种间的遗传距离。根据这几种鲆鲽鱼的杂交是否可行的试验结果,评价种间遗传距离与杂交可适度的关系,结果表明,这8种鲆鲽鱼类的种间遗传距离与杂交可适度呈显著的负相关 (r2 = 0.805,P < 0.01),即种间遗传分化越大,杂交成功的可能性越小,这表明鲆鲽鱼类中可能存在物种进化的不亲和钟 (Incompatibility clock)。