质子射频场照射对~(13)C自旋晶格弛豫的影响

用扩展的Solomon方程描述1H受到射频 (RF)场照射时13 C的自旋晶格弛豫过程 .理论分析表明 ,在1H受到射频场照射时 ,13 C自旋晶格弛豫通常是一个三指数过程 ,但在特定实验条件下可以变为单指数过程 .数值模拟可显示出满足TC1TH1条件的13 C自旋晶格弛豫过程的明显差别以及不同射频场强度对13 C自旋晶格弛豫的影响 .通过实验观察固体L 缬氨酸的甲基13 C自旋晶格弛豫过程 ,测定相应的弛豫时间 .所得结果与理论分析和数值模拟完全吻合 .     

Combinatorial Design of Some Database Application Technologies Based on B/S

Evolving From principal-subordinate structure of C /S to flexible multileveled distributed structure, i.e. B/S architecture so as to form a wide, distributed and orderly Internet/Intranet integrated management inf ormation system, is the trend of development of application software of the whol e world. Advantages and disadvantages of the two modes: C/S and B/S are compared . It is pointed out that at present onefold B/S mode cannot yet fully fullfil th e demands of some complicated data processing, inform...     

Adsorption of Xe in zeolite MCM-22

Adsorption of xenon in zeolite MCM-22, a zeolite containing two separate pore systems，has been investigated in detail by variable temperature (VT) ¹²⁹Xe NMR spectroscopy. NMR results suggest that Xe atoms are preferentially adsorbed in the supercages of the zeolite at low Xe pressure (less than a few atmosphere), while Xe atoms can penetrate into the two-dimensional sinusoidal channels at high Xe pressure. Exchange of xenon at the different adsorption sites in the same supercage, i.e. xenon atoms in the two pockets and those in the central part of the supercage, was confirmed at 145 K by two-dimensional (2D) ¹²⁹Xe NMR exchange spectroscopy. The time scale for the exchange is about several milliseconds.     

Indicators of δ13C and δ18O of gas hydrate-associated sediments

The analyses of δ13C and δ18O of gas hydrate-associated sediments from two cores on Hydrate Ridge in Cascadia convergent margin offshore Oregon, eastern North Pacific show the values of d 13C from -29.81‰ to -48.28‰ (PDB) and d 18O from 2.56‰ to 4.28‰ (PDB), which could be plotted into a group called typical carbonate minerals influenced by the methane in cold venting. Moreover, the values of d 13C and d 18O show a consistent trend in both cores from top to bottom with increasing of d 13C and decreasing of d 18O. This trend could be explained as an effect caused by the anaerobic oxidation of methane (AOM) in depth and the oxygen fraction during the formation of gas hydrate in depth together. These characteristics of d 13C and d 18O indicate that the gas hydrate-associated sediments are significantly different from the normal marine carbonates, and they are deeply influenced by the formation and evolution of gas hydrate. So, the distinct characteristics of d 13C and d 18O of gas hydrate-associated sediments could be undoubtedly believed as one of parameters to determine the presence of gas hydrates in other unknown marine sediment cores.     

计算机分析离子注入芸豆种子的浓度与注入深度变化曲线

用C语言编制程序对钛离子注入芸豆子叶的离子浓度随注入深度变化的实验曲线进行数学拟合，找到描述该实验曲线的数学函数，并调试出函数的有关参数值，由该函数可以计算出注入到子叶某一深度层面上单位体积内的离子数平均值。     

Effects of H_2O_2 on Oxygen Supply in the Process of DCA Fermentation

IntroductionLong chainα,ω- dicarboxylic acids (DCA ) areversatile chemical intermediates used as rawmaterials for the preparation of perfumes,polymers,and adhesives[1] .Various strains of C.tropicalis are known to produce DCA whencultured with alkanes or fatty acids as the carbonsource[2 ,3] .　During aerobic and viscous fermentation,theoxygen supply is of crucial importance becauseinsufficient oxygen can lead to suboptimalproductivities[4 ] as well as products of low quality.Several meth…     

通用菜单程序的C语言函数指针实现方法

本文介绍了C语言函数指针的功能与用法 ,同时使用函数指针设计了一个通用菜单程序。采用该方法设计的菜单灵活 ,用户接口简捷、方便 ,用户界面清晰、美观     

国内维生素C仪器定量分析进展

综述了近十年来国内维生素C的仪器定量分析进展,包括光度分析法、电化学分析法和色谱分析法在食品、蔬菜、水果及药物中的维生素测定应用。引用文献94篇。     

PVP对十二烷基甜菜碱/正戊醇/正庚烷O/W型微乳液性质的影响

研究了聚乙烯吡咯烷酮（PVP）存在时，由两性表面活性剂十二烷基甜菜碱（C12BE）/正戊醇（C5OH）/正庚烷（C6H16）和NaCl组成的O/W型微乳液的黏度、Ph、界面张力及形成热效应的变化，结果表明，加入PVP后，微乳液的黏出现电站效应；PH值呈下降趋势，但PVP的分子量不同，PH值下降的幅度不同；PVP的存在，导致微乳液与油相的界面张力稍有升高；微量热测定结果表明，PVP的存在导致微乳液的热效应减少。     

自反Banach空间上C0半群的一些结果

设T（t）是自反Banach空间X上满足两个条件的一类C0半群。本文证明如果T（t）是弱L^p稳定的，则其生成元的谱界是负的。再由文献[1]得到的关于这一类C0半群在任何Banach空间上其增长界都与生成元谱界相等的结果得出，自反Banach空间上此类半群弱L^p稳定与指数稳定等价。