经验基体校正方程系数选择的理论判据及其在赤泥分析中的应用

由于电子计算机在 X 射线荧光分析中的应用,用数学公式来校正元素的基体效应已越来越广泛,其中基本参数法由于一些物理参数尚不确定,且需要复杂的计算,一般计算机不能胜任;α系数法也需要大量的数据处理,一般实验室使用有一定困难。下面两个数学公式:c_i=sum from r=0 to 2 a_(ir)I_i~r+I_i ∑m _(ij)I_j+∑b_(ij)I_j (1)c_i=sum from r=0 to 2 a_(ir)I_i~r(1+∑f_(ij)c_j)+∑b_(ij)C_j (2)只要有一套合适的标准,用小型计算机多重回归法求     

DRASIN''''S PROBLEMS AND MUES'''' CONJECTURE

If f(z) is a transcendental meromorphic function, then we have(i) sum from a∈C to (δ(a,f)) + sum from b∈C to (δ(b,f~((k))))≤3 (k = 1,2,...);(ii) sum from b∈C to ( δ(b,f~((k))))≤1, k≥K,where K is a positive number depending only on f(z). The necessary and sufficient conditionto make the equality of (i) hold has also been obtained.     

丙烯和甲苯的超共轭效应的理论研究

用从头算对丙烯和甲苯2个超共轭体系进行计算,结果表明甲基上氢原子参与超共轭时,其碳氢键键长增大,氢上集居数减少,丙烯、甲苯的甲基旋转势垒为7.61及0.096 kJ/mol.超共轭基作用相当于一带有孤对电子参与共轭之杂原子,超共轭体系不同构型稳定性可用M=sum from i=1 to 3(sinθ_i[sin(θ_i-α)+sinα])来表征。     

叠氮根电负性的量子化学研究

用ab initio, MINDO/3, MNDO和DV-Xa等量子化学方法计算研究了一些分子型和离子型(碱金属)叠氮化物及相应氯化物的平衡构型和电子结构。结构表明: 在分子型叠氮化物中叠氮根的电负性较氯小、与氮相当; 而在离子型金属叠氮化物中,叠氮根的电负性和氯相当或较氯稍大。将计算所得正则离域分子轨道进行定域化处理, 发现产生这种电负性差异的主要原因是上述两类叠氮化物中N2的成键状况不同, 本文对此进行了较为细致的分析。     

含羟基镱单酞菁配合物的定域化分子轨道研究

用定域化INDO法讨论了含羟基镱单酞菁配合物(YbPcOH)分子的几何构型和电子结构。YbPcOH分子为金字塔形结构,Yb突出在酞菁平面外的中心轴上(h=1.8),Yb-O键长约为2.5,O-H也沿中心轴取向。正则波函数的前线轨道呈现π键性质。定域分子轨道分析表明,酞菁骨架中16轮烯型的共轭体系在配位后共轭程度降低,形成多个较小的共轭结构。金属和配体之间的化学键主要为共价性质,Yb的5d轨道对共价键有主要贡献,4f轨道则不参与成键。     

FEMO和HMO法间的关系

共轭分子的结构与性质除广泛使用HMO近似外，亦可由自由电子模型(以下简称FEMO)解释。如研究共轭分子的光谱、解释分子轨道对称守恒原理等。Simpson、Kuhm和Jaffe等探讨了FEMO和HMO法波函数间的关系，表明FEMO波函在原子i处的波函值Cp(i)恰能满足HMO系数方程，所以Cp(i)     

基团电负性的简易计算方法

本文建立了一种只利用pauling电负性数据直接计算各类非共轭共价基团的电负性的方法,并讨论了用电负性解释分子物理性质和化学性质的一些例子.     

共轭分子的反应活性指标

现代量子化学对共轭分子反应活性的估价,在轨道对称守恒原理出现之前有两种以π电子近似为基础的理论——“静态”理论(孤立分子近似)和过渡状态理论(定域理论)。静态理论是从孤立的分子出发,不考虑反应的历程,仅考虑该分子被反应试剂进攻前和开始进攻瞬     

多个时间常数线性体系暂态响应方程参数的代数求解法

从线性条件出发, 推导了含n个时间常数体系恒电位阶跃时暂态响应方程, 并提出一套解析形为ΔI=ΔI_∞+sum from i=1 to n k_iexp(-t/τ_i)暂态方程各未知参数的代数解法。该方法可对未知体系时间常数个数进行判定, 比起一般曲线拟合更加快速简便, 且抗干扰能力较强。     

多个时间常数线性体系暂态响应方程参数的代数求解法

从线性条件出发,推导了含n个时间常数体系恒电位阶跃时暂态响应方程,并提出一套解析形为ΔI=ΔI_∞+sum from i=1 to n k_iexp(-t/τ_i)暂态方程各未知参数的代数解法。该方法可对未知体系时间常数个数进行判定,比起一般曲线拟合更加快速简便,且抗干扰能力较强。     

矿物质对煤显微组分热解的影响

用常压热天平考察了平朔气煤三种主要显微组分(镜质组、丝质组和稳定组)的热解特性及其原生矿物质和外加无机物对各显微组分热解的影响。用ST-03表面孔径测定仪测定了三种显微组分及焦样的比表面积。研究表明,各显微组分的热解反应性从强到弱的排列顺序为:稳定组>镜质组>丝质组;原生矿物质对各显微组分的热解具有抑制作用,对热解活化能也有影响,并使焦样的比表面积显著增加;外加CaO等无机物及其添加量对不同显微组分的热解有不同的影响,但都使焦样比表面积增加。用分段连续一级反应机理可以较好地描述各显微组分的热解过程,统一形式不同参数的动力学模型为dx_(ij)/dt_(ij)=k_(ij)(1-x_(ij))。     

Modification of the Wiener Index. 2

A novel topological index based on the Wiener Index is proposed as W = 1/2, summation(n/ij)=S*(ij) the element S*(ij) of the distance matrix is defined either as S*(ij)= square root (E(i)E(j)/R(ij) (atoms i and j are adjacent) or as S*(ij)=(j-i+1)square root (E(i)...xE /R(ij) (atoms i and j are not adjacent), where E(i) and E(j) represent the total energy of the valence electrons of vertexes i and j, respectively, R(ij) is the sum of the distance between the vertexes i and j in a molecular graph. The distance and the energy of the vertexes in a molecule are taken into account in this definition. Hence the application of the index W to multiple bond and heteroatom-containing organic systems and inorganic systems is possible. Good correlation coefficients are achieved not only in the standard formation enthalpy of methyl halides, halogen-silicon, but also in the retention index of gas chromatography of the hydrocarbons.     

含氮试剂对p-DCC/AlCl_3引发异丁烯正离子聚合的影响

以对-二枯基氯(DCC)/AlCl3体系引发异丁烯在二氯甲烷(CH2Cl2)正己烷(Hex)(40/60,V/V)混合溶剂中进行正离子聚合,探讨了DCC用量、含氮试剂2,6-二叔丁基吡啶(DtBP)和三苯胺(TPA)对异丁烯正离子聚合转化率、产物分子量及其分布的影响.结果表明,DCC和体系中微量水均可与AlCl3产生竞争络合,形成两种活性中心并引起相继的竞争引发,聚合产物的GPC谱图呈双峰分布,分子量分布宽;增加DCC用量有利于DCC与AlCl3的络合,致使链增长反应主要通过DCC与AlCl3络合形成的活性中心引发,但聚合产物分子量相对较低,分子量分布较宽;使用DtBP,可有效地抑制微量水引发及活性链向单体的转移反应,使分子量分布明显变窄,基本实现DCC的控制引发;采用DtBP与TPA共同调节聚合反应,可使聚合产物分子量分布变窄的同时,进一步提高分子量,从而得到相对较高分子量(Mw=103200)和单峰分子量分布(Mw/Mn=2.09)的聚异丁烯产物.     

Modification of Wiener Index and its application

A novel topological index based on the Wiener Index is proposed as W* = 1/2 sigma (n)(i,j=1) S(*)(ij), the element S(*)(ij) of the distance matrix is defined either as S(*)(ij) = alpha x square root of I(i)I(j)/R(ij) (atoms i and j are adjacent) or as S(*)(ij) = = alpha x (j-i+1)square root of I(i) x x x x x I(j)/R(ij) (atoms i and j are not adjacent), where I(i) and I(j) represent the electronegativity of vertices i or j, respectively, R(ij)() is the sum of the bond length between the vertices i and j in a molecular graph, and alpha = (Z(i)/Z(j))(0.5), where Z(i) and Z(j) are the atomic numbers of the positive valence atom i and the negative valence atom j, respectively. The properties and the interaction of the vertices in a molecule are taken into account in this definition. That is why the application of the index W to heteroatom-containing and multiple bond organic systems and inorganic systems is possible. Correlation coefficients above 0.97 are achieved in the prediction of the retention index of gas chromatography of the hydrocarbons, the standard formation enthalpy of methyl halides, halogen-silicon, and inorganic compounds containing transition metals.     

EFFECT OF POLYMERIZATION CONDITIONS ON THE MOLECULAR WEIGHT OF POLYPHENYLSILSISQUIOXANE

Samples of polyphenylsilsisquioxane (PPSQ)using CaF_2 or MgF_2 as the main catalysts hadbeen prepared under different polymerization conditions. The results were treated on anorthogonal design L_9 (3~4). All weight-average molecular weights (M_W ) of PPSQ had beenmeasured by gel permeation chromatography (GPC). Effects of polymerization conditionsincluding reaction temperature, composition of the dual catalysts (CaF_2 or MgF_2 and DCC),mixture of solvents and reaction time on M_W of PPSQ have been discussed. The quantity of thecatalysts is the most important factor that affects M_W of PPSQ. Reaction temperature is thesecond important factor. Appropriate polymerization condition has been established to get PPSQwith high M_W.     

DCC/AlCl_3体系引发异丁烯正离子聚合

研究以对-二枯基氯(DCC)/AlCl3体系引发异丁烯在CH2Cl2/Hex(40/60,V/V)混合溶剂中进行正离子聚合,探讨了DCC用量、给电子试剂,如三苯胺(TPA)、2,6-二甲基吡啶(DMPy)对异丁烯正离子聚合转化率、产物分子量及其分布的影响.结果表明,在无给电子试剂存在时,DCC和体系中微量水均可与AlCl3产生络合竞争引起相继的引发竞争,聚合产物GPC谱图呈双峰分布,分子量分布宽,需要大量的引发剂DCC(DCC/H2O=5.3)来减少体系中微量水的不可控引发;在少量上述给电子试剂存在下,可提高DCC的引发效率,减少向单体链转移反应,提高聚合产物的分子量和使分子量分布呈较窄的单峰分布,即使在较低DCC用量下也可基本抑制体系中微量水的不可控引发,达到DCC定量引发,并得到分子量分布相对较窄(Mw/Mn≈2.3)的聚异丁烯产物.     

EFFECT OF POLYMERIZATION CONDITIONS ON THE LADDERLIKE STRUCTURE OF POLYPHENYLSILSESQUIOXANE

The ladderlike structure of PPSQ synthesized by using four kinds of catalysts (MgF_2,LiF, KOH and DCC) at different polymerization conditions has been investigated by IRand NMR. In the system using MgF_2 as the main catalyst, the most important factorwhich affects the ladderlike structure of PPSQ is the composition of the dual catalysts,MgF_2 and DCC. PPSQ prepared by using KOH as the catalyst has the highest regularityof ladderlike structure among all samples. PPSQ with different degree of ladder regularitycan be obtained by choice of polymerization conditions.     

Extract of Lillium candidum L. can modulate the genotoxicity of the antibiotic zeocin

Lilium candidum L. extract (LE) is well known in folk medicine for the treatment of burns, ulcers, inflammations and for healing wounds. This work aims to clarify whether the genotoxic potential of the radiomimetic antibiotic zeocin (Zeo) could be modulated by LE. Our results indicate that LE exerts no cytotoxic, DNA-damaging and clastogenic activity in in Chlamydomonas reinhardtii, Pisum sativum L. and Hordeum vulgare L. test systems over a broad concentration range. Weak but statistically significant clastogenic effects due to the induction of micronuclei and chromosome aberrations have been observed in H. vulgare L. after treatment with 200 and 300 μg/mL LE. To discriminate protective from adverse action of LE different experimental designs have been used. Our results demonstrate that the treatment with mixtures of LE and Zeo causes an increase in the level of DNA damage, micronuclei and "metaphases with chromatid aberrations" (MwA). Clear evidence has been also obtained indicating that pretreatment with LE given 4 h before the treatment with Zeo accelerates the rejoining kinetics of Zeo-induced DNA damage in P. sativum L. and C. reinhardtii, and can decrease clastogenic effect of Zeo measured as frequencies of micronuclei and MwA in H. vulgare L. Here, we show for the first time that LE can modulate the genotoxic effects of zeocin. The molecular mode of action strongly depends on the experimental design and varies from synergistic to protective effect (adaptive response-AR). Our results also revealed that LE-induced AR to zeocin involves up-regulation of DSB rejoining in C. reinhardtii and P. sativum L. cells.     

Thermochemical excess properties of multicomponent systems: Representation and estimation from binary mixing data

A general equation for the estimation of thermodynamic excess properties of multicomponent systems from observed excess properties of the various binary combinations of the components has been developed, based on a simple model of the multicomponent system. This estimation takes the form $$\Delta \bar Z_{12...N}^{ex} = \sum\limits_{i = 1}^N {\sum\limits_{j > i}^N {(X_i + X_j )(f_i + f_j )(\Delta \bar Z_{ij}^{ex} )^* } } $$ in which \((\Delta \bar Z_{ij}^{ex} )^* \) is the molar excess property (enthalpy, entropy, volume, free energy, etc.), of the binary system with components at the same molar ratio as in the multicomponent system, and f_i, f_j are weighted mole fractions using weighting factors based on the excess properties of the binary systems. The important features of this equation are: it is applicable to a broad range of thermodynamic properties, its application to both integral and differential mixing properties is independent of the manner in which the binary mixing data is represented (Redlich-Kister equation, Wilson equation, etc.), and it provides reasonably accurate predictions ranging from quite good for simple systems of nonspecific interactions to only fair for associated solutions. This equation is recommended as a point-of-departure for mathematical representation of experimental data for multicomponent systems.     

Diffusion of alkane mixtures in zeolites: validating the maxwell-stefan formulation using MD simulations

Molecular dynamics (MD) simulations have been carried out for pure components, binary, ternary, and quaternary mixtures containing methane, ethane, propane, and n-butane in FAU zeolite at 300 K for a range of molecular loadings Theta, approaching saturation limits. The n-dimensional matrix of Maxwell-Stefan (M-S) diffusivities [Delta], defined by (N) = -rho[Delta][Gamma](nabla Theta), was determined along with the self-diffusivities, D(i)(,self). Additionally, configurational-bias Monte Carlo (CBMC) simulations were carried out to obtain the pure component sorption isotherms and the saturation capacities Theta(i)(,sat). From the information on Delta(ij), D(i)(,self), and Theta(i)(,sat), the various M-S diffusivities were determined: (1) component D(i), reflecting the interactions of the species i with the zeolite, self-exchange D(ii), and (2) binary exchange D(ij). The obtained data underline the major advantage of the M-S formulation that at a given occupancy, theta = Sigma(N)(n)(i=l)Theta(j)/Theta(j)(,sat) within the zeolite, the D(i) has nearly the same value for species i whether this species is present on its own or in a mixture with other species. The same advantage holds, too, for the self-exchange D(ii); the value at a given occupancy, theta, is the same whether determined from pure component, binary, or ternary mixture data. For all binary and ternary mixtures studied, it was verified that the binary exchange coefficient D(ij) can be interpolated from the corresponding values of the self-exchange parameters D(ii) and D(jj) using a generalization of the interpolation formula developed earlier (Skoulidas et al., Langmuir, 2003, 19, 7977). We also demonstrate that if the occupancy dependence of the pure component parameters D(i) and D(ii) are modeled properly, this information is sufficient to provide very good estimates of the matrix [Delta] for mixtures with 2, 3, or 4 components over the entire range of loadings. Simulations of mixture diffusion of alkanes in MFI and LTA confirm that the above-mentioned advantages of the M-S formulation also hold for these zeolite topologies.