The response of microstructure to processing in a series of poly(siloxaneimide) copolymers

Poly(siloxaneimide) (PSI) segmented copolymers exhibit organized microdomains if the blocks are sufficiently incompatible. As with neat diblock and triblock copolymers, the processing route employed to prepare films of PSI materials is expected to influence the dimensions and/or morphology of the resultant microstructure. In this work, small-angle neutron scattering (SANS) is utilized to characterize the disordered microstructure found in films of a series of PSI copolymers which are subjected to solvent casting and various thermal treatments. Microstructural dimensions such as the periodicity and correlation length are deduced from the Teubner-Strey (TS) model for disordered microemulsions. The scattering intensity of each copolymer up to q = 5.0 nm^?1, where q is the scattering vector, is found to scale as q^?2.8+?0.1. Results indicate that processing the materials as cast films or as melt-pressed films allowed to cool slowly has a small, but discernible, effect on microstructural characteristics. SANS profiles of films quenched from elevated temperatures reveal a clear transition in microdomain periodicity, which correlates well with the glass transition temperature of the imide microphase in these and other materials of similar chemical structure. © 1993 John Wiley & Sons, Inc.     

Interval parameter perturbation method for evaluating the bounds on natural frequencies of structures with interval parameters

For structural parameters with uncertainties, interval mathematics can, in the case where the probabilistic distribution density of uncertain variables is unavailable, deal with the influence of uncertainties in structural parameters on the response of structures. In order to evaluate the region containing natural frequencies of structures with interval parameters, the interval parameter perturbation method is presented in this paper. The advantage of the present method is its computational efficiency in evaluating the region containing natural frequencies. A numerical example is used to illustrate the efficiency of the method proposed. The project is supported by National Youth Natural Science Foundation of China and National Outstanding Youth Science Foundation of China.     

A method for selection and use of numerical integration points for molecules with cylindrical symmetry

Boys and Handy [1] have discussed the solution of the bivariational equations with restricted numerical integration. One of the weaknesses of the method was that in the numerical summations over points, some points arose with r _ij= 0 and non-zero weights. This makes the method quite impractical for the Schrodinger Hamiltonian (because of the singularity at r _ij= 0), and it cannot be advantageous for the transcorrelated Hamiltonian C^–1HC because there will be some discontinuous higher derivatives at r _ij=0. Here it is shown how the symmetry of cylindrically symmetric molecules can be used to eliminate such points, without losing any of the advantages of the overall method, such as the convergence of the eigensolutions. It is also shown how the primary numerical integration points (z _i, r_i) may be chosen in any calculation such that each is associated with an equal amount of one-electron density. The choice of the angular coordinates are governed by the removal of the r _ij=0 points and maintaining the natural orthogonality between orbitals of different symmetry types. The method has been programmed and found to be practical, although no new molecular calculations have yet been performed. It is to be hoped that these points will give a basis for new transcorrelated calculations on diatomic molecules.This paper was presented during the session on numerical integration methods for molecules of the 1970 Quantum Theory Conference in Nottingham. It has been revised in the light of the interesting discussion which followed.     

On the average length of lexicographic paths

A bound is given for the average length of a lexicographic path, a definition that is motivated by degeneracies encountered when using the randomized simplex method.     

涂敷法制作质谱场电离发射丝的方法及性能研究

本文介绍一种新的质谱场电离发射丝的制备方法——涂敷法,并研究了其制备机理及影响发射丝灵敏度的因素。此外,还对涂敷法制作的发射丝及高温活化法制作的发射丝进行了各项性能对比试验。最后,介绍了涂敷发射丝的应用效果。     

A statistical thermodynamic supermolecule-continuum study of ion hydration: Cell and shell methods

A theoretical study of ion hydration using the statistical thermodynamic supermolecule-continuum method is described. The cell and shell methods are used for configurational averaging. Enthalpies, free energies and entropies are calculated for Li⁺, Na⁺, K⁺, F^– and Cl^– each four coordinated with water. The results are in reasonable accord with experiment. A comparison of the site method, cell method and shell method results is presented. The supermolecule-continuum approach to solvent effects seems to be capable of accommodating essential features for the calculation of solvation energy and solvent effects on structure and properties.     

Bimetallic Alkoxides of Barium and Zirconium: Preparation of BaZrO3 Powder

Complex formation in solutions of barium and zirconium alkoxides in ROH (R=i-Pr, Et) was studied. A number of bimetallic complexes were isolated, and their structure and properties were studied. The sol-gel method yields a single-phase BaZrO₃ powder only wheni-PrOH solutions of the alkoxides are used. In this case, the oxocomplex, BaZrO(OPr-i)₄.(1–2)i-PrOH, is the precursor of the mixed oxide.     

Synthesis and Structure of the New Ammonium Indium Phosphate (NH4)In(OH)PO4

A new ammonium indium phosphate (NH₄)In(OH)PO₄ was prepared by hydrothermal reaction in the In₂O₃-NH₄H₂PO₄-NH₃/OH system (T=200°C, autogenous pressure, 7 days). The formula (NH₄)In(OH)PO₄ was determined on the basis of chemical and thermal analysis (TG/DSC), X-ray powder diffraction and IR-spectroscopy. (NH₄)In(OH)PO₄ crystallizes in the tetragonal system with space group P4₃2₁2 (No. 96); a=9.4232(1) Å, c=11.1766(1) Å, V=992.45(2) ų; Z=8. The crystal structure was refined by the Rietveld method (R_w=6.35%, R_p=5.10%). The second-harmonic generation study confirmed that structure of (NH₄)In(OH)PO₄ does not have a center of symmetry. The cis-InO₄(OH)₂ octahedra form helical chains, parallel to the c-axis. The In-O-In bonds are nearly equidistant. The chains are interconnected by phosphate tetrahedra and create tunnels containing the NH₄⁺ ions along the c-axis. (NH₄)In(OH)PO₄ is isostructural with RbIn(OH)PO₄.     

Modern Analysis

The important advances being made in modern analytical methods are indicative of the fundamental changes that are occuring in the theory and practice of “analytical chemistry”. “Information optimization” demands a new approach in teaching and research, and calls for the intergration of chemistry with other scientific and technical disciplines.     

苯胺气相N－烷基化反应研究Ⅱ．苯胺和乙醇常压催化合成N－乙基苯胺的工业应用

苯胺气相Ｎ－烷基化反应研究Ⅱ．苯胺和乙醇常压催化合成Ｎ－乙基苯胺的工业应用陈骏如，李瑞祥，韩银仙，李贤均（四川大学化学系成都６１００６４）Ｎ－乙基苯胺是制造染料、塑料、炸药和医药等许多化工产品的重要中间体，其合成方法过去多采用无机酸催化剂，如Ｈ＿２Ｓ...