Peroxodicarbonate as a Green Oxidizer for the Selective Degradation of Kraft Lignin into Vanillin

Lignin, the world's largest resource of renewable aromatics, with annually roughly 50 million tons of accruing technical lignin, mainly Kraft lignin, is highly underdeveloped regarding the production of monoaromatics. We demonstrate the oxidative depolymerization of Kraft lignin at 180 °C to produce vanillin 1 in yields up to 6.2 wt % and 92 % referred to the maximum yield gained from the quantification reaction utilizing nitrobenzene. Using peroxodicarbonate (C₂O₆²⁻) as “green” oxidizer for the degradation, toxic and/or harmful reagents are prevented. Also, the formed waste can serve as makeup chemical in the pulping process. Na₂C₂O₆ is synthesized in an ex-cell electrolysis of aqueous Na₂CO₃ at BDD anodes, achieving a yield of Na₂C₂O₆ with 41 %. At least, the oxidation and degradation of Kraft lignin is analysis via UV/Vis and NMR spectroscopy.     

High-performance size-exclusion chromatography with crosslinked polystyrene. Separation of polymers and oligomers using LiChrogel PS

Summary A new series of polystyrene-divinyl benzene PS/DVB-based microparticulate packings for size-exclusion chromatography [SEC] is presented. These gel-based packings are characterized by mechanical stability, minimal interaction with solutes and ability to handle a wide variety and size range of polymers and low relative molecular mass samples. Combinations of different pore sizes are discussed and separations of standard polymers and commercial products are shown.     

Validation and Limits of Finite Inflatable Beam Elements

Although nowadays inflatable tubular beams are often used in the field of civil engineering, by now there are only few publications dealing with finite deformation inflatable beam elements, see e.g. [1], [2] and [3]. All formulations of inflatable beams have several assumptions in common, as constant cross sections throughout the deformation, a constant internal gas pressure and the negligence of circumferential stresses. These assumptions have to be validated either by experiments or numerical analysis. In the current contribution beam–like structures are investigated using a finite element shell or membrane formulation and featuring a volume dependent gas loading, see e.g. [5] and [4]. In general the formulation substitutes the internal gas pressure by an energetically equivalent volume dependent loading and thus enables to check for potential gas pressure changes during the deformation process of the inflated beam as a consequence of volume changes. Further local deformations as occurring in the vicinity of supports or almost single loads can be considered. In this paper the focus will be only on the initial assumption of the beam theory that the biaxial stress state is neglected. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controlling jumps in correlated processes of Poisson counts

Processes of autocorrelated Poisson counts can often be modelled by a Poisson INAR(1) model, which proved to apply well to typical tasks of SPC. Statistical properties of this model are briefly reviewed. Based on these properties, we propose a new control chart: the combined jumps chart. It monitors the counts and jumps of a Poisson INAR(1) process simultaneously. As the bivariate process of counts and jumps is a homogeneous Markov chain, average run lengths (ARLs) can be computed exactly with the well‐known Markov chain approach. Based on an investigation of such ARLs, we derive design recommendations and show that a properly designed chart can be applied nearly universally. This is also demonstrated by a real‐data example from the insurance field. Copyright © 2008 John Wiley & Sons, Ltd.     

An Approach to Shape Optimization with State Constraints

We introduce a new approach to solve shape optimization problems with state constraints. The problem is reformulated on a fixed reference domain using conformal pull-back. The shape dependence is then hidden in the conformal parameter. The problem is discretized using FEM and solved as an NLP. Finally the optimal shape can be reconstructed from the optimal conformal parameter. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Conservation properties of higher order time stepping schemes based on variational integrators

This paper deals with higher order accurate variational integrators for finite element systems. The variational integrator (VI) is based on higher order LAGRANGE polynomials as shape functions and a higher order GAUSSIAN quadrature rule. The goals of this paper are to implement a discrete gradient to preserve the balance of total energy and fulfill the constraints with the LAGRANGE multiplier method and a NEWTON-COTÊS quadrature rule. We show the calculation of bearing forces from the LAGRANGE multipliers, which are essential for the balance of total linear momentum and the balance of total angular momentum. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Embedded constant mean curvature surfaces with special symmetry

We give sharp, necessary conditions on complete embedded CMC surfaces with three ends and an extra reflection symmetry. The respective submoduli space is a two-dimensional variety in the moduli space of general CMC surfaces. Fundamental domains of our CMC surfaces are characterized by associated great circle polygons in the three-sphere. Received: 23 January 1998 / Revised version: 23 October 1998