Thermische Zersetzung von Pentacarbonyleisen in Zeolithen des Faujasit-Typs

Thermal Decomposition of Pentacarbonyl Iron in Faujasite-Type Zeolites The nature of the iron species resulting from the title reaction has been elucidated by thermogravimetry, X-ray diffraction, electron microscopy, Mössbauer spectrometry, and by normal analytical methods. The thermal decomposition of Fe(CO)₅ adsorbed in Y-type zeolite yields pure α-Fe. In X-type zeolite Fe(CO)₅ is converted into a highly dispersed form of iron, into iron-subcarbonyl, and into high-spin Fe^II, occupying different sites of the lattice. Dealuminized zeolites adsorb Fe(CO)₅ reversibly. The estimated size of the iron(III) oxide particles formed by air oxidation is in accordance with the assumption that Fe(CO)₅ decomposes in Y-type zeolite with iron migrating to the surface of the zeolite crystals, whereas in X-type zeolite the iron remains inside the zeolite cavities.     

On-target deuteration for peptide sequencing by laser mass spectrometry

Hydrogen–deuterium exchange was evaluated as a tool for sequence analysis of peptides by matrix-assisted laser desorption–ionization utilizing post-source decay (PSD-MALDI). The number of exchangeable hydrogens (EH) of precursor ions and product ions can be determined from the mass difference between ion signals originating from the deuterated and the non-deuterated form of a peptide, resulting in a second dimension of structural information. The reliability of sequence determination by combinatorial algorithms or pattern recognition techniques is considerably increased by employng this ‘EH spectroscopy.’ On-target deuteration is a simple preparatory step which can be performed reversibly with the already mass-analysed sample within a few minutes and without consumption of additional sample material. The efficiency of hydrogen–deuterium exchange with this technique is about 98.5%. In addition to supporting sequence analysis, deuteration can be used to investigate fundamental fragmentation mechanisms of peptides in PSD-MALDI. Inconsistencies with expected fragmentation pathways have been found for fragments a₁–a₃ of substance P.     

Structure analysis of branched oligosaccharides using post-source decay in matrix-assisted laser desorption ionization mass spectrometry

Post-source decay matrix-assisted laser desorption ionization (PSD-MALDI) of sodium ion-attached branched oligosaccharides derived from glycoproteins was demonstrated as a method of structure analysis by reflectron time-of-flight (TOF) mass spectrometry. Mono-, di- and triantennary structures were investigated. The fragmentation patterns of these (structurally related) substances as obtained in the positive-ion mode showed characteristic differences correlated with branching sites and linkage positions. Two-bond ring cleavages as known from fast atom bombardment/collision-induced dissociation and IR laser desorption mass spectrometry were also observed. Internal fragment ions formed by up to four consecutive cleavages were obtained with high intensity, allowing the branching structure of complex carbohydrates to be identified. PSD-MALDI of oligosaccharides is characterized by high sensitivity, very good signal-to-noise ratios and high reproducibility of fragmentation patterns and signal intensities.     

Polynomial viscosity methods for multispecies kinematic flow models

Multispecies kinematic flow models are defined by systems of strongly coupled, nonlinear first‐order conservation laws. They arise in various applications including sedimentation of polydisperse suspensions and multiclass vehicular traffic. Their numerical approximation is a challenge since the eigenvalues and eigenvectors of the corresponding flux Jacobian matrix have no closed algebraic form. It is demonstrated that a recently introduced class of fast first‐order finite volume solvers, called polynomial viscosity matrix (PVM) methods [M. J. Castro Díaz and E. Fernández‐Nieto, SIAM J Sci Comput 34 (2012), A2173–A2196], can be adapted to multispecies kinematic flows. PVM methods have the advantage that they only need some information about the eigenvalues of the flux Jacobian, and no spectral decomposition of a Roe matrix is needed. In fact, the so‐called interlacing property (of eigenvalues with known velocity functions), which holds for several important multispecies kinematic flow models, provides sufficient information for the implementation of PVM methods. Several variants of PVM methods (differing in polynomial degree and the underlying quadrature formula to approximate the Roe matrix) are compared by numerical experiments. It turns out that PVM methods are competitive in accuracy and efficiency with several existing methods, including the Harten, Lax, and van Leer method and a spectral weighted essentially non‐oscillatory scheme that is based on the same interlacing property. © 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 1265–1288, 2016     

Engineering of an all‐heteronuclear 5‐qubit NMR quantum computer

The realization of an all‐heteronuclear 5‐qubit nuclear magnetic resonance quantum computer is reported, from the design and synthesis of a suitable molecule through the engineering of a prototype 6‐channel probe head. Full control over the quantum computer is shown by a benchmark experiment. Copyright © 2015 John Wiley & Sons, Ltd.     

On entropy stable schemes for degenerate parabolic multispecies kinematic flow models

Entropy stable schemes for the numerical solution of initial value problems of nonlinear, possibly strongly degenerate systems of convection–diffusion equations were recently proposed in Jerez and Parés's study. These schemes extend the theoretical framework of Tadmor's study to convection–diffusion systems. They arise from entropy conservative schemes by adding a small amount of viscosity to avoid spurious oscillations. The main condition for feasibility of entropy conservative or stable schemes for a given model is that the corresponding first‐order system of conservation laws possesses a convex entropy function and corresponding entropy flux, and that the diffusion matrix multiplied by the inverse of the Hessian of the entropy is positive semidefinite. As a new contribution, it is demonstrated in the present work, first, that these schemes can naturally be extended to initial‐boundary value problems with zero‐flux boundary conditions in one space dimension, including an explicit bound on the growth of the total entropy. Second, it is shown that these assumptions are satisfied by certain diffusively corrected multiclass kinematic flow models of arbitrary size that describe traffic flow or the settling of dispersions and emulsions, where the latter application gives rise to zero‐flux boundary conditions. Numerical examples illustrate the behavior and accuracy of entropy stable schemes for these applications.     

Electricity swing option pricing by stochastic bilevel optimization: A survey and new approaches

We demonstrate how the problem of determining the ask price for electricity swing options can be considered as a stochastic bilevel program with asymmetric information. Unlike as for financial options, there is no way for basing the pricing method on no-arbitrage arguments. Two main situations are analyzed: if the seller has strong market power he/she might be able to maximize his/her utility, while in fully competitive situations he/she will just look for a price which makes profit and has acceptable risk. In both cases the seller has to consider the decision problem of a potential buyer – the valuation problem of determining a fair value for a specific option contract – and anticipate the buyer’s optimal reaction to any proposed strike price. We also discuss some methods for finding numerical solutions of stochastic bilevel problems with a special emphasis on using duality gap penalizations.