The characterisation of alkali metal phosphites,arsenites and antimonites

Infrared spectra have been obtained for the molecular species MPO₂, MAsO₂ and MSbO₂ (M = alkali metal) isolated in nitrogen matrices and three of these are characterised in detail. In NaPO₂ fundamentals are observed at 1151.6 (ν PO), 1062.1 (ν PO) and 523.0 (δ PO₂) cm^?1 whilst in CsAsO₂ and KSbO₂ corresponding modes are observed at 863.0, 851.5 and 393.0 cm^?1 and at 764.6, 744.9 and 339.0 cm^?1. ¹⁸O enrichment experiments indicate C_2v ring structures for all three MXO₂ species and bond angles were estimated as OPO = 114°, OAsO = 115° and OSbO = 106°.     

The interaction of EDTA with barium sulfate

Ethylenediaminetetraacetic acid (EDTA) is a known complexing agent that interacts with a host of cations. In this paper, various techniques are used to elucidate the mechanism of interaction between EDTA and barium sulfate surfaces. It is shown that complexation with metal ions is not sufficient to explain the inhibition of barite crystallization but that other processes such as chemisorption must also occur. EDTA is shown to always adsorb as the mono-protonated species - suggesting that the molecule is able to lose a proton when it adsorbs at lower pH. Molecular modelling shows that the interaction of the surface barium ions with the carboxylate group is an important one. Finally, in situ turbidity measurements provide information about the mechanism of nucleation/growth modification. It is found that the EDTA molecule inhibits barium sulfate nucleation and that this could be its primary means of inhibiting precipitation of barium sulfate.     

Bootstrapping sums of independent but not identically distributed continuous processes with applications to functional data

In many areas of application, the data are of functional nature, such as (one-dimensional) spectral data and two- or three-dimensional imaging data. It is often of interest to test for the significance of some set of factors in the functional observations (e.g., test for the mean differences between two groups). Testing hypotheses point-by-point (voxel-by-voxel in neuroimaging studies) results in a severe multiple-comparisons problem as the number of measurements made per observation is typically much larger than the number of observations (“large p, small n”). Thus solutions to this problem should take into account the spatial correlation structure inherent in the data. Popular approaches in such a setting include the general Statistical Parametric Mapping (SPM) approach and the permutation test, but these rely on strong parametric and exchangeability assumptions. In situations in which these assumptions are not satisfied, a nonparametric multiplier bootstrap approach may be used. Motivated by this problem, we present general results for multiplier bootstraps for sums of independent but not identically distributed processes. We also consider the application of these results to an imaging setting and provide sufficient conditions that will ensure asymptotic control of the familywise error rate.     

Finite elastic deformations of transversely isotropic circular cylindrical tubes

We consider the finite radially symmetric deformation of a circular cylindrical tube of a homogeneous transversely isotropic elastic material subject to axial stretch, radial deformation and torsion, supported by axial load, internal pressure and end moment. Two different directions of transverse isotropy are considered: the radial direction and an arbitrary direction in planes normal locally to the radial direction, the only directions for which the considered deformation is admissible in general. In the absence of body forces, formulas are obtained for the internal pressure, and the resultant axial load and torsional moment on the ends of the tube in respect of a general strain-energy function. For a specific material model of transversely isotropic elasticity, and material and geometrical parameters, numerical results are used to illustrate the dependence of the pressure, (reduced) axial load and moment on the radial stretch and a measure of the torsional deformation for a fixed value of the axial stretch.     

Affinity of An(VI) for N4-Tetradentate Donor Ligands: Complexation of the Actinyl(VI) Ions with N4-Tetradentate Ligands

In this report the affinity of four N₄-tetradentate ligands that incorporate the 2-methylpyridyl functionality with hexavalent actinides $(\mathrm{AnO}_{2}^{2+})$ has been investigated in methanol solution. The ligands studied include N,N??-bis(2-methylpyridyl)diaminoethane (BPMDAE), N,N??-bis(2-methylpyridyl)-1,3-diaminopropane (BPMDAP), N,N??-bis(2-pyridylmethyl)piperazine (BPMPIP), and trans-N,N-bis(2-pyridylmethyl)-1,2-diaminocyclohexane (BPMDAC). Conditional stability constants describing the strength of the interaction were determined by UV?Cvisible spectrophotometry. The log₁₀ K ₁₀₁ values for both U(VI) and Pu(VI) are comparable and show the same trend of stability with ligand structure. Dinuclear complexes are also indicated as being important. The log₁₀ K ₂₀₁ values for Pu(VI) complexation with the N₄-ligands are identical for the four ligands (within experimental error), indicating that the structure of the ligand backbone has little effect on the stability of the (PuO₂)₂L²⁺ complex. The exception to this trend is the behavior of N,N??-bis(2-pyridylmethyl)piperazine (BPMPIP) with Pu(VI). This ligand displays a tendency to reduce Pu(VI) within the experimental time frame of 45 minutes. BPMPIP is the only ligand tested that contains tertiary amines in the ligand backbone. The decomposition of BPMPIP by Pu(VI) suggests a susceptibility of tertiary amines to oxidative degradation.     

Nonlinear axisymmetric deformations of an elastic tube under external pressure

The problem of the finite axisymmetric deformation of a thick-walled circular cylindrical elastic tube subject to pressure on its external lateral boundaries and zero displacement on its ends is formulated for an incompressible isotropic neo-Hookean material. The formulation is fully nonlinear and can accommodate large strains and large displacements. The governing system of nonlinear partial differential equations is derived and then solved numerically using the C++ based object-oriented finite element library Libmesh. The weighted residual-Galerkin method and the Newton-Krylov nonlinear solver are adopted for solving the governing equations. Since the nonlinear problem is highly sensitive to small changes in the numerical scheme, convergence was obtained only when the analytical Jacobian matrix was used. A Lagrangian mesh is used to discretize the governing partial differential equations. Results are presented for different parameters, such as wall thickness and aspect ratio, and comparison is made with the corresponding linear elasticity formulation of the problem, the results of which agree with those of the nonlinear formulation only for small external pressure. Not surprisingly, the nonlinear results depart significantly from the linear ones for larger values of the pressure and when the strains in the tube wall become large. Typical nonlinear characteristics exhibited are the “corner bulging” of short tubes, and multiple modes of deformation for longer tubes.     

Photolysis of (Me2Si)6 in argon matrices doped with high concentrations (ca. 20%) of N2O or C2H4O: formation of (Me2SiO)6

Irradiation using a low pressure mercury lamp (λ=ca. 250 nm) of argon matrices containing ca. 1% (Me₂Si)₆ and ca. 20% ethylene oxide (C₂H₄O) or nitrous oxide (N₂O) for a period of ca. 20 h leads to the formation of the cyclic compound (Me₂SiO)₆. This has a 12-membered ring with alternating Si and O atoms. It is identified by comparison of its infrared spectrum with a spectrum of an authentic sample. The reaction appears to proceed by stepwise insertion of O atoms into Si---Si bonds.     

A variational formulation for magneto-active elastomers based on a total energy function

This paper focuses on a variational formulation for a magneto-active elastomer completely surrounded by free space. The free space is considered infinite, with an applied magnetic field or magnetic induction vector as the far field boundary conditions. In addition to the effect of the Maxwell stress exterior to the body on its surface, a mechanical load is applied over a portion of the surface, but no displacement constraints are considered. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)