Correlation between the chromatographic poperties of silica phenyl packing materials and the retention behaviour of methylated β-cyclodextrins

Summary The chromatographic properties of five columns packed with phenyl-bonded phases were characterized by an approach based on Tanaka's method for column to column comparisons in order to develop an LC analysis of partially methylated β-cyclodextrins. The retention behaviour of β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin was examined in order to evaluate the different interactions between phenyl stationary phase and this family of compound. Chromatograms show that the residual silanol activity of the packing materials plays a beneficial role in the partially methylated β-cyclodextrins separation process. It is concluded that knowledge of the interactions involved allows one to make a reasoned choice of the stationary phase in order to obtain the best possible analysis of three different commercial samples of partially methylated β-cyclodextrins.     

Volatility and crystal lattice energy of palladium(II) chelates

Temperature dependence of saturated vapor pressure has been measured by gas saturation technique for volatile bis-chelates of palladium(II) with such ligands as acetylacetone, hexafluoroacetylacetone, diethyldithiocarbamate, diisopropyldithiophosphate, and also mixed ligand complex with acetylacetone and cyclooctadiene-2,4. Standard thermodynamic parameters of vaporization ΔH _T ⁰ and ΔS _T ⁰ were calculated. Crystal molecular packings and intermolecular interactions were analyzed basing on structural data. Atomatom potential calculation of van der Waals energy E_cryst in crystal lattice was performed and compared to the experimentally obtained values of sublimation enthalpy for the complexes under study.     

An investigation of 3μm reverse-phase octadecylsilane packing materials for high-performance liquid chromatography

Summary The efficiency of high-performance liquid chromatography columns packed with 5 m and 3 m reverse-phase octadecylsilane packing materials has been evaluated using four test mixtures. Both stopped flow and valve injection have been used and typical efficiencies are given.     

激光大气闪烁的分形分析

 采用分形理论分析了激光大气闪烁的统计特征。研究结果表明：在弱起伏条件下，激光大气闪烁的分形维和奇异性随光强起伏的增强而增大，而其长期相关性则减小；不同Fresnel尺度下具有相同闪烁指数的激光大气闪烁的分形特征存在着明显的差别；在强起伏条件下，有限的数据中尚未发现分形维有饱和现象，因此可以用来描述激光大气闪烁的强度。     

1,3,5-trichlorotricyanobenzene complexes with mesitylene (1/1) and benzene (1/3)

Trichlorotricyanobenzene-mesitylene (1/1) is monoclinic, space group P2₁/n; at −88°Ca=10.509(3),b=14.863(7),c=11.518(3) ?, β=99.38(2)⁰,V=1775(2) ?³,D _x =1.409(2) g cm⁻³,Z=4. Trichlorotricyanobenzene-benzene (1/3) is hexagonal, space group ; at −99°Ca=17.3914(3),c=7.2673(1) ?,V=1903.6(1) ?³,D _x =1.2844(1) g cm⁻³,Z=3. In both complexes there are stacks of alternating trichlorotricyanobenzene and hydrocarbon molecules. In both complexes there are sheets of molecules perpendicular to the stacks. In the mesitylene complex these sheets contain equal numbers of both kinds of molecules with the trichlorotricyanobenzene molecules arranged in tapes. In the benzene complex the sheets contain only one kind of molecule or the other. The sheets containing the trichlorotricyanobenzene molecules have approximately linear C−N...Cl−C intermolecular interactions with N...Cl distances about 3.02 ?.     

Crystal structure of Al(tBu)3(NH2CH2CH2Ph): A molecular “slinky”

The molecular structure of Al(^tBu)₃(NH₂CH₂CH₂Ph) is determined by the crystal packing of the phenyl rings and the pseudo spherical Al(^tBu)₃ units, and may be viewed as a layered structure consisting of double sheets of the phenyl rings and the Al(^tBu)₃ units. The Al–N–C–C linkage shows severe disorder as a result of its flexibility. The structure of Al(^tBu)₃ (NH₂CH₂CH₂Ph) can be likened to a molecular slinky, in which the rigid ends are fixed in space by molecular packing forces, leaving the interior link to adopt multiple orientations. Crystal data: orthorhombic, Cmca,a=13.282(9),b=25.01(1),c=13.210(9), Å,V=4388(10) ų,Z=4,R=0.0957,R _w=0.0957.     

煤焦分形维数及其对比热容的影响研究

比热容是煤炭热物理性质之一,在煤矿的矿井防火、防止煤与瓦斯突出、井下降温设计及煤炭加工利用(如煤炭的燃烧、气化、焦化、液化等)等方面是关键参数之一,对提高煤炭热能利用率、提高经济效益、减少环境污染等,具有非常重要的意义。比热容的影响因素很多,如煤化程度、水分质量分数、热解温度等,煤焦微观结构的影响也是其中很重要的一方面。分形几何由Mandelbrot 1982年创立,是定量描述自相似或自相关等不规则形体的工具。研究表明,煤焦微观结构具有分形特征。在煤焦分形的研究中,常用的实验技术方法为吸附法、小角度X射线散射法和孔度法,采用扫描电子显微镜和数字图象处理方法研究煤焦的分形结构,能更加深入地理解其分形维数与性能的关系。     

增维精细积分法的适用范围研究

对线性定常结构动力系统提出的增维精细积分法,能够将非齐次动力方程转化为齐次动力方程,不用对状态矩阵求逆就能方便高效地求解出结构的动力响应。本文在仔细分析增维精细积分法性质的基础上,提出了其适用条件,进一步拓宽了其应用范围,并给出了将荷载项展开成傅里叶级数时,相应增维精细积分法的表达式。同时,在一个时间步长内,通过对非齐次项作线性化假设,成功地将增维精细积分法应用到了非线性动力分析领域。本文方法计算格式统一,易于编程,具有很高的计算效率。数值算例证明了本文方法的有效性。     

Attactors of dissipative soliton equation

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一维周期耗散媒质中的电磁波模及其数值分析

文中推导了一维周期耗散媒质中电磁波模式特征值方程,证明其解分类为一系列的"导带"和"禁带";用实数Re(K_z²)代替复特征值K_z标识模式,可清晰地显示出带结构,便于模式的分类和比较。文中用数值方法给出了几组参数下横电波、横磁波模最低两个带的图示,并与周期势场中的电子能带作了对比。