Behaviour of organoarsenic compounds in contact with natural zeolites

Batch experiments were conducted on aqueous solutions containing arsenite, arsenobetaine, methylarsonic acid or phenylarsonic acid in contact with natural zeolites to examine their interaction. The concentration of the arsenic species in the liquid phase at equilibrium before and after contact was measured by means of liquid chromatography coupled with inductively coupled plasma mass spectrometry detection. Clinoptilolites completely removed arsenobetaine from the solution and the resulting amounts of dimethylarsinic acid were detected. The methylarsonic acid maximum concentration diminution was reached at a mass—to volume V value of m/V = 0.2. Phenylarsonic acid solution decreased its concentration 75% after treatment with clinoptilolites. Untreated mordenites in contact with arsenite solutions led to the formation of arsenate, whereas acid‐washed mordenites practically removed arsenobetaine and were less effective for methylarsonic acid. To show the incompatibility of molecular dimensions with the zeolite windows, the molecular parameters of surface area, molecular volume, molecular length, and the width and depth of arsenite, arsenate and a series of ten organic arsenic compounds were calculated. Since sorption onto the external zeolite surface rather than a sieve process defined the interaction, an acid‐catalysed reaction mechanism is proposed to explain the transformation results. Copyright © 2001 John Wiley & Sons, Ltd.     

Zeta function for the Laplace operator acting on forms in a ball with gauge boundary conditions

The Laplace operator acting on antisymmetric tensor fields in a D-dimensional Euclidean ball is studied. Gauge-invariant local boundary conditions (absolute and relative ones, in the language of Gilkey) are considered. The eigenfuctions of the operator are found explicitly for all values of D. Using in a row a number of basic techniques, as Mellin transforms, deformation and shifting of the complex integration contour and pole compensation, the zeta function of the operator is obtained. From its expression, in particular, ζ(0) and ζ'(0) are evaluated exactly. A table is given in the paper for D=3,4,...,8. The functional determinants and Casimir energies are obtained for D=3,4,...,6. Received: 2 May 1996 / Accepted: 20 July 1996     

Determination of the degradation compounds formed by the oxidation of thiophosphinic acids and phosphine sulfides with nitric acid.

The degradation process that takes place at room temperature when bis(2,4,4-trimethylpentyl)monothiophosphinic acid (R2P(S)OH), bis(2,4,4-trimethylpentyl)dithiophosphinic acid (R2P(S)SH) and tris(2,4,4-trimethylpentyl)phosphine sulfide (R3PS) are in contact with 5 M HNO3 has been studied by FT-Infrared, FT-Raman spectroscopy and by gas chromatography with mass spectrometry detection (GC-MS). An exposure period of ten days of the rough reagents to 5 M HNO3 causes complete oxidation of the compounds. This process mainly leads to the formation of nitrogen dioxide, elemental sulfur and the oxo-analogues of the reagents. For dilute solutions of the reagents it was observed that after 15 min of contact with phase-shaking, R2P(S)OH and R3PS are completely oxidized to yield R2P(O)OH and R3PO, respectively, whereas for R2P(S)SH, the oxidation process is less severe, because the dithioacid is still present in the oxidized mixture, the oxidation products being R2P(S)OH and R2P(O)OH.     

Exact running coupling constants and approximate effective lagrangians

Relations between running coupling constants, which are exact to a number of loops fixed in advance, are derived. The corresponding effective lagrangians are studied, in particular their confining character. Contrary to Adler's conjecture, only the lagrangian corresponding to the one-loop-exact running coupling constant seems to have the desired properties leading to quark confinement.     

Synthesis of Styrene Monomers Hydroxyl Functionalized

Bifunctional monomers provide the possibility of preparing new polymeric and nano structures such as random or graft copolymers. These materials can potentially be used as surfactants or coupling agents in polymeric blends, especially where each functionality in the monomer has different chemical properties. This article describes the organic synthesis of bifunctional monomers derived from styrene through the Grignard reaction with aldehydes and ketones. The Grignard reagent was synthesized from 4-bromostyrene and magnesium in THF. At the end of the synthesis four different bifunctional monomers were obtained bearing two terminal substituents: a vinyl and a hydroxyl group. These monomers were obtained in high yield and purity. The reactivities of the monomers were probed via the random copolymerization of one of these monomers with styrene and acrylonitrile.     

Volumetric Properties of the Ternary System Dimethyl Carbonate + Butyl Methacrylate + Allyl Methacrylate and Its Binary Butyl Methacrylate + Allyl Methacrylate at 293.15 K and p=101.325 kPa

Densities of the ternary system dimethyl carbonate + butyl methacrylate + allyl methacrylate and its binary subsystem butyl methacrylate + allyl methacrylate have been measured in the whole composition range, at 293.15 K and atmospheric pressure, using an Anton Paar DMA 5000 oscillating U-tube densimeter. The calculated excess molar volumes of the binary system are positive and were correlated with the Redlich?CKister equation and with a series of Legendre polynomials. Several models were used to correlate ternary behavior from the excess molar volume data of their constituent binaries and found to fit the data equally well. The best fit was based on a direct approach, without information on the component binary systems.     

A Generating Tree Approach to <Emphasis Type="Italic">k</Emphasis>-Nonnesting Partitions and Permutations

We describe a generating tree approach to the enumeration and exhaustive generation of k-nonnesting set partitions and permutations. Unlike previous work in the literature which uses the connections of these objects to Young tableaux and restricted lattice walks, our approach deals directly with partition and permutation diagrams. We provide explicit functional equations for the generating functions, with k as a parameter. Key to the solution is a superset of diagrams that permit semi-arcs. Many of the resulting counting sequences also count other well-known objects, such as Baxter permutations, and Young tableaux of bounded height.     

Dilaton-Maxwell Gravity with Matter Near Two Dimensions

Unlike Einstein gravity, dilaton-Maxwell gravity with matter is renormalizable in 2 + e dimensions and has a smooth ϵ → 0 limit. By performing a renormalization-group study of this last theory we show that the gravitational coupling constant G has a non-trivial, ultraviolet stable fixed point (asymptotic freedom) and that the dilatonic coupling functions (including the dilatonic potential) exhibit also a real, non-trivial fixed point. At such point the theory represents a standard charged string-inspired model. Stability and gauge dependence of the fixed-point solution is discussed. It is shown that all these properties remain valid in a dilatonic-Yang-Mills theory with n scalars and m spinors, that has the UF stable fixed point G* = 3ϵ(48 + 12N – m – 2n)⁻¹. In addition, it is seen that by increasing N (number of gauge fields) the matter central charge C = n + m/2(0 < C < 24 + 6N) can be increased correspondingly (in pure dilatonic gravity 0 < C < 24).