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991.
Ke-Shun Liu 《Journal of the American Oil Chemists' Society》1994,71(11):1179-1187
Theoretically, preparation of fatty acid methyl esters (FAMEs) deals with reversible chemical reactions in a complex system.
Methodologically, there are numerous ways, generally characterized by the type of catalysts used and steps involved. Although
there are more than a half dozen common catalysts, the majority fall into either acidic (HCl, H2SO4 and BF3) or alkaline types (NaOCH3, KOH and NaOH), with each having its own catalytic capability and application limitations. In terms of steps, many conventional
methods, including those officially recognized, consist of drying, digestion, extraction, purification, alkaline hydrolysis,
transmethylation/methylation and postreaction work-up. Although these methods are capable of providing reliable estimates
if some precautions are taken, they are cumbersome, time-consuming and cost-inefficient. A new approach has been to transmethylate
lipidsin situ. Due to its simplicity, high sensitivity, comparable reliability and capability to determine total fatty acids, the method
of direct transmethylation is finding a unique place in lipid determination. Regardless of which method is used, quantitative
methylation requires chemists to take precautions at every step involved, particularly during FAME formation and subsequent
recovery steps. Evidently, there is an urgent need for more systematic studies, guided by the chemical principle of reactions
involved and physicochemical properties of regents and end products, into factors affecting these steps. Hopefully, this will
lead to an improved method, which measures lipid composition in biological materials not only with high accuracy but also
with high efficiency and minimum costs. 相似文献
992.
脉冲功率器件直流和动态热特性探测 总被引:1,自引:0,他引:1
介绍了针对影响微波脉冲功率器件可靠性的热性能问题,应用红外热分析技术。对比探测微波脉冲功率器件在动态和直流状态下的温度分布,峰值结温,热阻及其变化规律。 相似文献
993.
A.Varada Rajulu G. Babu Rao B. Ravi Prasad Rao A. Madhu Sudana Reddy Jiasong He Jun Zhang 《应用聚合物科学杂志》2002,84(12):2216-2221
Studies on some properties such as the density, the degradation temperatures, the morphology and the spectral features of the ligno‐cellulose fiber Hildegardia were carried out in both untreated and alkali treated form. The fibers are found to have good morphology and moderate initial and final degradation temperatures. On alkali treatment, the lignin was found to be eliminated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2216–2221, 2002 相似文献
994.
TRT入口方管道爆裂原因剖析 总被引:1,自引:0,他引:1
介绍了鞍钢7#高炉TRT装置入口方管道爆裂事故经过,进行了原因分析,并提出了解决措施。 相似文献
995.
高分辨率层序地层学克服了岩性地层对比穿时的缺点.高分辨率层序地层对比是等时的高精度的地层对比,它满足了勘探开发中地层对比等时性和高分辨率的要求.测井资料的纵向分辨率较高,是高分辨率层序地层研究的重要资料.提出了利用测井相分析技术,从测井资料上识别出单井岩性和沉积微相剖面,结合测井曲线特征,划分单井基准面旋回,并进行连井地层等时对比,这为定量地进行高分辨率层序地层分析提供了一种方法.通过研究区实际资料的处理,验证了该方法的有效性. 相似文献
996.
997.
二次型时频分析技术的开发与应用 总被引:1,自引:1,他引:0
基于二次型的时频分析是高分辨率时频分析技术的有效方法之一,该项技术能够有效反映时变信号的频谱特性,具有分辨率高、能量集中和跟踪瞬时频率的特点。从时变信号的特点出发,阐述了二次型时频分析技术的基本方法原理,采用正演模型分析验证了该方法的有效性,并在实际地震资料中应用于识别物源方向、划分沉积相带、预测储层结构以及相对厚度等诸多方面,均取得了较好的效果。 相似文献
998.
Economic ideas and processes are becoming increasingly integrated with more traditional engineering and hydrologic models
of water management problems. Combining economic management concepts and performance indicators with an engineering-level
of understanding of a hydrologic system can provide results and insights more directly relevant for water management decisions
and policies. When such models are developed and used with involvement of stakeholders, they can become a basis for shared
understanding of water problems as a foundation for negotiated management and policy solutions. When implemented with optimization
software, integrated hydro-economic models also can suggest promising innovative solutions for policy-makers to consider.
Their applications to river basin management problems are reviewed. Economic and integrated economic-engineering-hydrologic
modeling is then discussed in the context of the evolving European Water Framework Directive. Relevant items are cost recovery
and water pricing, cost-effectiveness of water management measures, and public participation in decision processes. 相似文献
999.
Frédéric Debode Eric Janssen Gilbert Berben 《European Food Research and Technology》2007,226(1-2):273-280
In this paper, four different physical treatments (microwaves, heating by conduction, sonication and pressure autoclaving)
were performed to degrade a pure DNA extract, and their influence on GMO quantification was studied. The aim was to check
the hypothesis that processing of agrofood products results in a similar degradation rate for both the transgenic target and
the specific target. Indeed we could observe that even if the used physical treatments could lead to a significant increase
of C
t values for both transgenic and specific targets, the resulting ΔC
t remained stable. So, the main conclusion of the study is that the aforementioned hypothesis seems valid and thus a physical
degradation of DNA will not affect the relative quantitation of the GMO content, provided that both the specific and transgenic
targets have very similar size. A second important issue of the experiments performed was that DNA is a very robust molecule
as it is extremely difficult to reach a mean size below 100 bp. The study also gives evidence of the importance of using small
targets. 相似文献
1000.
利用River2D软件模拟了大连市大沙河多孔栖息单元式生态护岸修建后的水流状况和鱼类栖息地条件。为了选定护岸铺设的位置,以便达到最佳的河流恢复效果,把护岸铺设分为4种方案:方案一维持原貌,不铺设护岸;方案二在整个河段沿岸修建护岸;方案三在需要保护的地方修建河流护底;方案四护岸与护底同时修筑。对比了4种方案下鲤鱼流速适宜指数和河段权重可利用面积,指出了在不同流量下的护岸最佳铺设方式。结果表明利用软件进行数值模拟的方法可以弥补室内实验方法和实地观测方法的不足。 相似文献