Speciation of Rare‐Earth Metal Complexes in Ionic Liquids: A Multiple‐Technique Approach

The dissolution process of metal complexes in ionic liquids was investigated by a multiple‐technique approach to reveal the solvate species of the metal in solution. The task‐specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf₂N]) is able to dissolve stoichiometric amounts of the oxides of the rare‐earth elements. The crystal structures of the compounds [Eu₂(bet)₈(H₂O)₄][Tf₂N]₆, [Eu₂(bet)₈(H₂O)₂][Tf₂N]₆?2H₂O, and [Y₂(bet)₆(H₂O)₄][Tf₂N]₆ were found to consist of dimers. These rare‐earth complexes are well soluble in the ionic liquids [Hbet][Tf₂N] and [C₄mim][Tf₂N] (C₄mim=1‐butyl‐3‐methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, ¹H, ¹³C, and ⁸⁹Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X‐ray absorption fine structure) and HEXS (high‐energy X‐ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry.     

Synthesis of Laurylchitosan and Its Use in the Separation of Flavonoids from Aleurites moluccana by Matrix Solid-Phase Dispersion

Chitosan was modified with lauroyl chloride to prepare a solid support for the application of matrix solid-phase dispersion (MSPD) for the extraction of flavonoids from the medicinal plant Aleurites moluccana. The laurylchitosan prepared by the homogenous and heterogeneous method, was characterized using analytical methods such as potentiometric titration and infrared spectroscopy. The hydrophobic properties were studied by naphthalene incorporation. The MSPD performance was evaluated by extraction of swertisin and 2″-O-rhamnosylswertisin from the leaves of A. moluccana.     

Sensitive and highly specific quantitative real-time PCR and ELISA for recording a potential transfer of novel DNA and Cry1Ab protein from feed into bovine milk

To address food safety concerns of the public regarding the potential transfer of recombinant DNA (cry1Ab) and protein (Cry1Ab) into the milk of cows fed genetically modified maize (MON810), a highly specific and sensitive quantitative real-time PCR (qPCR) and an ELISA were developed for monitoring suspicious presence of novel DNA and Cry1Ab protein in bovine milk. The developed assays were validated according to the assay validation criteria specified in the European Commission Decision 2002/657/EC. The detection limit and detection capability of the qPCR and ELISA were 100 copies of cry1Ab μL^?1 milk and 0.4 ng mL^?1 Cry1Ab, respectively. Recovery rates of 84.9% (DNA) and 97% (protein) and low (<15%) imprecision revealed the reliable and accurate estimations. A specific qPCR amplification and use of a specific antibody in ELISA ascertained the high specificity of the assays. Using these assays for 90 milk samples collected from cows fed either transgenic (n?=?8) or non-transgenic (n?=?7) rations for 6 months, neither cry1Ab nor Cry1Ab protein were detected in any analyzed sample at the assay detection limits.

Spectral inclusion for unbounded block operator matrices

In this paper we establish a new analytic enclosure for the spectrum of unbounded linear operators A admitting a block operator matrix representation. For diagonally dominant and off-diagonally dominant block operator matrices, we show that the recently introduced quadratic numerical range W²(A) contains the eigenvalues of A and that the approximate point spectrum of A is contained in the closure of W²(A). This provides a new method to enclose the spectrum of unbounded block operator matrices by means of the non-convex set W²(A). Several examples illustrate that this spectral inclusion may be considerably tighter than the one by the usual numerical range or by perturbation theorems, both in the non-self-adjoint case and in the self-adjoint case. Applications to Dirac operators and to two-channel Hamiltonians are given.     

Persilylated phosphoranyl radicals: the first persistent noncyclic phosphoranyl radicals

Persistent noncyclic phosphoranyl radicals have been prepared and observed by electron paramagnetic resonance (EPR) for the first time. They were obtained by UV-photolysis of a solution containing a bis(trialkylsilyl) peroxide (R = Me, Et) and a tris(trialkylsilyl) phosphite (R = Me, Et, iPr). EPR parameters (a(P) approximately 100 mT) are typical of phosphoranyl radicals exhibiting a trigonal-bipyramidal structure, with the odd electron in an equatorial site. Analysis of the pseudo-first-order decay shows that these phosphoranyl radicals decay by S(H)2 homolytic substitution on the bis(trialkylsilyl) peroxide and by loss of a trialkylsilyloxyl radical (alpha-scission reaction). Both the S(H)2 and alpha-scission reactions depend on the steric bulk of the alkyl groups, that is, the bulkier the alkyl group, the slower the S(H)2 and alpha-scission reactions.     

Fracture Mechanics of Rubber Material

This contribution presents an approach based on the material force method which allows to evaluate the fracture sensitivity of rubber material. In order to account for the rate–independent dissipation of filled elastomers subjected to low rates, an endochronic plasticity formulation is introduced. It is shown how configurational forces under consideration of material body forces correspond with the elastic and dissipative energy and how they can be related to energy release rates measured in test configurations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)