Capillary electrophoresis with contactless conductivity detection for uric acid determination in biological fluids

The suitability of capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C⁴D) for the direct determination of uric acid in human plasma and urine was investigated. It was found that a careful optimization of the buffer composition and pH was necessary to achieve selective determination in the complex sample matrices. An electrolyte solution consisting of 10 mM 2-morpholinoethanesulfonic acid (MES), 10 mM histidine and 0.1 mM hexadecyltrimethylammonium bromide (CTAB), pH 6.0, was finally found suitable for use as running buffer for both sample matrices. The limit of detection (3 S/N) was determined as 3.3 μM. The linearity of the response was tested for the range between 10 and 500 μM and a correlation coefficient of 0.9996 was obtained. Intra- and inter-day variabilities were <10%. Quantitative analysis of urine and plasma samples showed a good correlation with the routine enzymatic method currently used at the University Hospital of Basel.     

Analysis of phenolic choline esters from seeds of Arabidopsis thaliana and Brassica napus by capillary liquid chromatography/electrospray‐ tandem mass spectrometry

Total phenolic choline ester fractions prepared from seeds of Arabidopsis thaliana and Brassica napus were analyzed by capillary LC/ESI‐QTOF‐MS and direct infusion ESI‐FTICR‐MS. In addition to the dominating sinapoylcholine, 30 phenolic choline esters could be identified based on accurate mass measurements, interpretation of collision‐induced dissociation (CID) mass spectra, and synthesis of selected representatives. The compounds identified so far include substituted hydroxycinnamoyl‐ and hydroxybenzoylcholines, respective monohexosides as well as oxidative coupling products of phenolic choline esters and monolignols. Phenolic choline esters are well separable by reversed‐phase liquid chromatography and sensitively detectable using electrospray ionization mass spectrometry in positive ion mode. CID mass spectra obtained from molecular ions facilitate the characterization of both the type and substitution pattern of such compounds. Therefore, LC/ESI‐MS/MS represents a valuable tool for comprehensive qualitative and quantitative analysis of this compound class. Copyright © 2008 John Wiley & Sons, Ltd.     

Micelle and Vesicle Formation of Amphiphilic Nanoparticles

Nanoparticle brushes : Complex nanostructures can be formed by self assembly of amphiphilic CdSe/CdS core–shell nanoparticles that bear a brushlike layer of poly(ethylene oxide) chains. This route is based on controlling the volume fractions of hydrophilic and hydrophobic moieties within the particles and allows the formation of micellar, cylindrical, or vesicular nanoobjects (see picture).

     

On Tries, Contention Trees and Their Analysis

In this paper a survey on tries, a contention resolution algorithm, their similarities, dissimilarities, and their mathematical treatment, will be given. It has already been mentioned in some papers that tries and contention trees follow one common stochastic model, but still they are frequently treated as separate objects in the literature. Hence the aim of the current work is to contribute to the unification of the various results in that area and to exhibit the employed methods, which involve, among others, analytic poissonization/depoissonization and the Mellin transform. For the sake of the example, a new parameter in contention trees, the number of terminal frames, will be studied.      

Nonlinear and adaptive frame approximation schemes for elliptic PDEs: Theory and numerical experiments

This article is concerned with adaptive numerical frame methods for elliptic operator equations. We show how specific noncanonical frame expansions on domains can be constructed. Moreover, we study the approximation order of best n‐term frame approximation, which serves as the benchmark for the performance of adaptive schemes. We also discuss numerical experiments for second order elliptic boundary value problems in polygonal domains where the discretization is based on recent constructions of boundary adapted wavelet bases on the interval. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009     

Modelling of interfacial damage and delamination of sprayed coatings with cohesive elements

Delamination of thermally sprayed corrosion protection coatings as a consequence of thermo-mechanical fatigue is investigated. This study focusses on the modelling of interfacial damage initiation and evolution under cyclic loading with the help of a cohesive zone model. The presented model features a slight non-linearity at unloading from the exponential “damage locus” as well as cyclic damage accumulation restricted to (re)loading conditions. Additionally, an endurance limit is introduced indicating the maximum sustainable traction for an infinite number of load cycles. The capability of the model is demonstrated. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fast solvers with block‐diagonal preconditioners for linear FEM–BEM coupling

The purpose of this paper is to present optimal preconditioned iterative methods to solve indefinite linear systems of equations arising from symmetric coupling of finite elements and boundary elements. This is a block‐diagonal preconditioner together with a conjugate residual method and a preconditioned inner–outer iteration. We prove the efficiency of these methods by showing that the number of iterations to preserve a given accuracy is bounded independent of the number of unknowns. Numerical examples underline the efficiency of these methods. Copyright © 2008 John Wiley & Sons, Ltd.     

Proof of the local REM conjecture for number partitioning. II. Growing energy scales

We continue our analysis of the number partitioning problem with n weights chosen i.i.d. from some fixed probability distribution with density ρ. In Part I of this work, we established the so‐called local REM conjecture of Bauke, Franz and Mertens. Namely, we showed that, as n → ∞, the suitably rescaled energy spectrum above some fixed scale α tends to a Poisson process with density one, and the partitions corresponding to these energies become asymptotically uncorrelated. In this part, we analyze the number partitioning problem for energy scales α_n that grow with n, and show that the local REM conjecture holds as long as n^‐1/4α_n → 0, and fails if α_n grows like κn^1/4 with κ > 0. We also consider the SK‐spin glass model, and show that it has an analogous threshold: the local REM conjecture holds for energies of order o(n), and fails if the energies grow like κn with κ > 0. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009