Metallic Particles from Complexing Microcapsules Dispersed in a Silica Gel

A new process to control the distribution of metal nanoparticles is proposed. It involves the use of complexing microcapsules obtained by interfacial polycondensation. The latter are hollow spheres constituted of a polymer membrane, containing an insoluble active ingredient, such as a polyacrylic acid, which can complex Co²⁺ ions. These capsules are dispersed in a silica sol followed by thermal treatments and reduction under H₂ which results in metallic Co nanoparticles confined in the capsules domains. The particles do not diffuse in the matrix.     

Separating Ag, B, Cd, Dy, Eu, and Sm in a Gd matrix using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester extraction chromatography for ICP-AES analysis

The separation procedure for Ag, B, Cd, Dy, Eu and Sm as impurities in Gd matrix using ICP-AES technique with an extraction chromatographic column has been developed. The spectral interference of the Gd matrix on the elements was eliminated using a chromatography technique with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as the mobile phase and XAD-16 resin as the stationary phase. Ag⁺, B₄O₇²⁻, and Cd²⁺ were eluted with 0.1 M HNO₃, while rare earth ions were not. The best eluent for separating Eu and Sm in the Gd matrix was 0.3 M HNO₃. The limit of quantitation for these elements was 0.6-3.0 ng mL⁻¹. The recovery of Ag, B, and Cd was 90-104% using 0.1 M HNO₃ as the eluent, while that of Eu, Gd, and Sm ranged from 100 to 102% with 0.3 M HNO₃. Dy was recovered quantitatively with 4 M HNO₃. The relative standard deviation of the methods for a set of three replicates was between 1.0 and 15.4% for the synthetic and standard Gd solutions. The proposed separation procedure was used to measure Ag, B, Cd, Dy, Eu, and Sm in a standard Gd solution.     

Photo-initiated base-formation in a polymer matrix

It was found that amines were formed efficiently by the photolysis of O-acyloximes followed by hydrolysis in polystyrene films and the relationship between structures of O-acyloximes and yields of amines were investigated. O-phenylacetyl acetophenone oxime (PaApO), O-pivaloyl acetophenone oxime (PApO), and O-benzoyl acetophenone oxime (BApO) as monofunctional O-acyloximes and O,O′-succinyl diacetophenone oxime (SDApO) and O,O′-glutaryl diacetophenone oxime (GDApO) as bifunctional O-acyloximes were examined. The yields of amines for PaApO and SDApO under N₂ were ca. 70%, which was the highest among O-acyloximes examined in this experiment. On the other hand, the yields for PApO, BApO, and GDApO were less than 15% and it was verified that the hydrogen abstraction by imino radicals via 6-membered cyclic intermediates resulted in the lowering of yields. Although the effect of oxygen under photolysis on the yields of amine for PaApO was negligible under 50% conversion of PaApO, the yield decreased with further increase in the conversion and was 50% at 90% conversion. © 1994 John Wiley & Sons, Inc.     

PREPARATION OF POLY（METHYL METHACRYLATE）/LAYERED DOUBLE HYDROXIDES NANOCOMPOSITES via in situ SOLUTION POLYMERIZATION

An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased.     

Ce(IV) ion initiated graft polymerization of glycidylmethacrylate onto a demineralized bone matrix: effect of reaction parameters

Studies on chemical modification of demineralized bone matrix (DBM) have opened new arenas in the field of clinical orthopedics owing to its potential osteoinductivity with desired chemical functionality. To widen its usage to biomolecular delivery, graft polymerization of glycidylmethacrylate onto DBM was carried out by a free-radical initiating process using ceric ammonium nitrate as an initiator. The evidence of the grafting reaction was examined by chemical analysis using Fourier transform IR spectroscopy. The grafting condition was standardized by regulating the reaction parameters such as the concentrations of the backbone, the monomer and the initiator, the polymerization temperature and time. The optimum polymerization temperature and time to have the maximum grafting yield were 40 °C and 3 h, respectively. The percentage of grafting and the percentage of grafting efficiency were determined as a function of the reaction parameters, and both were found to increasing initially and thereafter decrease in most of the cases. The grafting results are discussed in a detailed fashion and a reaction mechanism is proposed.     

On the Permanental Polynomials of Some Graphs

Let G be a simple graph with adjacency matrix A(G) and (G,x) the permanental polynomial of G. Let G × H denotes the Cartesian product of graphs G and H. Inspired by Kleins idea to compute the permanent of some matrices (Mol. Phy. 31 (3) (1976) 811–823), in this paper in terms of some orientation of graphs we study the permanental polynomial of a type of graphs. Here are some of our main results.1.If G is a bipartite graph containing no subgraph which is an even subdivision of K _2,3, then G has an orientation G ^e such that (G,x) = det (xI-A(G ^e )), where A(G ^e ) denotes the skew adjacency matrix of G ^e.2.Let G be a 2-connected outerplanar bipartite graph with n vertices. Then there exists a 2-connected outerplanar bipartite graph with 2n+2 vertices such that (G,x) is a factor of .3.Let T be an arbitrary tree with n vertices. Then , where ₁ , ₂ , ..., _n are the eigenvalues of T.     

Influence of the preparation procedure on the properties of polyaniline based magnetic composites

A versatile process for the preparation of composite films consisting of magnetite (Fe₃O₄) nanoparticles embedded in a polyaniline (PANI) matrix is reported. Spectroscopic properties of polyaniline matrix (PANI-EB), polyaniline protonated with camphor sulfonic acid (PANI-CSA_0.5) PANI-ES and PANI/Fe₃O₄-CSA_0.5 composites were studied, both in the state of the solutions of m-cresol and in thin films processed from the same solvents. The results of these studies indicate that m-cresol can be used for PANI/Fe₃O₄ composite preparation. Such films show both reasonably high electrical conductivity and magnetic permeability. A controlled application of a magnetic field during the casting process resulted in the formation of the materials with an unusual combination of magnetic and transport properties. The obtained films show the behavior that can be explained by the presence of both ferromagnetic and paramagnetic phases. The superparamagnetic contribution, if any, is very small. Application of the external magnetic field during fabrication of the composites stimulates creation of the aggregates of magnetic particles which, although keeps conductivity at a relatively high level, leads to a small decrease of the conductivity value.     

Molecular conformation search by distance matrix perturbations

Three-dimensional molecular structure is fundamental in chemical function identification and computer-aided drug design. The enumeration of a small number of feasible conformations provides a rigorous way to determine the optimal or a few acceptable conformations. Our contribution concerns a heuristic enhancement of a method based on distance geometry, typically in relation with experiments of the NMR type. Distance geometry has been approached by different viewpoints; ours is expected to help in several subtasks arising in the process that determines 3D structure from distance information. More precisely, the input to our algorithm consists of a set of approximate distances of varying precision; some are specified by the covalent structure and others by Nuclear Magnetic Resonance (NMR) experiments (or X-ray crystallography which, however, requires crystallization). The output is a valid tertiary structure in a specified neighborhood of the input. Our approach should help in detecting outliers of the NMR experiments, and handles inputs with partial information. Moreover, our technique is able to bound the number of degrees of freedom of the conformation manifold. We have used numerical linear algebra algorithms for reasons of speed, and because they are well-implemented, fully documented and widely available. Our main tools include, besides distance matrices, structure-preserving matrix perturbations for minimizing singular values. Our MATLAB (or SCILAB) implementation is described and illustrated.AMS subject Classification: 92E10 Molecular structure, 92C40 Biochemistry, molecular biology, 65F15 Eigenvalues, eigenvectors, 15A18 Eigenvalues, singular values, and eigenvectors     

X-射线荧光分析散射幂函数法原理及其应用I·RhKα相干散射平方法

本文发现6~40号元素对能量为20keV的X_射线的质量吸收系数和质量相干散射系数之间呈二次幂函数关系,并据此提出了X_射线荧光定量分析校正基体效应的新方法——RhKa相干散射平方法.用国家标准物质GBW对该原理进行了验证.本法用于硅酸盐地质样品中微量元素的测定取得令人满意的结果.