Untersuchungen an oxidischen Katalysatoren. XXXIV. Redoxverhalten des Nickels in NiNaY-Zeolithen 1. Reduzierbarkeit und Reoxydierbarkeit von Nickel in NiNaY-Zeolithen

Studies on Oxide Catalysts. XXXIV. Redoxbehaviour of Nickel in Zeolite NiNaY. 1. Reducibility and Reoxidizability of Nickel in Zeolites NiNaY The properties of metallic nickel in reduced (470–870 K) and reoxidized (470, 670 K) samples were studied by chemical analysis (reaction with K₂Cr₂O₇) and spectroscopic methods (FMR, IR after CO adsorption, UV/VIS). The reduction of Ni²⁺ cations from oxidic clusters proceeds in an onestep reaction. Contrary to this, isolated Ni²⁺ cations are reduced stepwise to Ni⁺ cations and subsequently to metallic nickel. The reduction degree depends in characteristic manner on the reduction temperature. Metallic nickel which was reduced at temperatures < 620 K, can be completely reoxidized at 470 K. Higher temperatures result in metallic aggregations which are not completely reoxidized even at 670 K.     

Development of surface plasmon resonance-based sensor for detection of silver nanoparticles in food and the environment

Silver nanoparticles are recognized as effective antimicrobial agents and have been implemented in various consumer products including washing machines, refrigerators, clothing, medical devices, and food packaging. Alongside the silver nanoparticles benefits, their novel properties have raised concerns about possible adverse effects on biological systems. To protect consumer's health and the environment, efficient monitoring of silver nanoparticles needs to be established. Here, we present the development of human metallothionein (MT) based surface plasmon resonance (SPR) sensor for rapid detection of nanosilver. Incorporation of human metallothionein 1A to the sensor surface enables screening for potentially biologically active silver nanoparticles at parts per billion sensitivity. Other protein ligands were also tested for binding capacity of the nanosilver and were found to be inferior to the metallothionein. The biosensor has been characterized in terms of selectivity and sensitivity towards different types of silver nanoparticles and applied in measurements of real-life samples-such as fresh vegetables and river water. Our findings suggest that human MT1-based SPR sensor has the potential to be utilized as a routine screening method for silver nanoparticles, that can provide rapid and automated analysis dedicated to environmental and food safety monitoring.     

Comparative study on control concepts of a robot manipulator with multiple-link/joint flexibilities

If one is dealing with active vibration suppression on a highly nonlinear flexible system, various techniques are needed. On the one hand a suitable dynamic model of the system is required. And on the other hand intelligent model based control concepts are necessary for active vibration damping. We deal with a basic model, where the flexibilities are approximated with linear springs and dampers, a so called lumped element model (LEM). For the control design we propose a control structure with two degrees of freedom (2DoF) for solving the tracking problem, based on the LEM. Such an approach allows designing the feedforward part independently of the feedback part. Hereby the feedforward control is based on the flatness approach, while for the feedback control several strategies are studied using acceleration- and gyrosensor-measurements. The contribution is completed with a validation by measurements from a very fast trajectory on an articulated robot with two flexible links and three elastic joints. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Universal quadratures for boundary integral equations on two-dimensional domains with corners

We describe the construction of a collection of quadrature formulae suitable for the efficient discretization of certain boundary integral equations on a very general class of two-dimensional domains with corner points. The resulting quadrature rules allow for the rapid high-accuracy solution of Dirichlet boundary value problems for Laplace’s equation and the Helmholtz equation on such domains under a mild assumption on the boundary data. Our approach can be adapted to other boundary value problems and certain aspects of our scheme generalize to the case of surfaces with singularities in three dimensions. The performance of the quadrature rules is illustrated with several numerical examples.     

lin-Benzo-ATP and-ADP: Versatile fluorescent probes for spectroscopic and biochemical studies

lin-Benzo-adenine nucleotides can act not only as probes for fluorescence studies but also as structural active site probes for enzymes. To understand the basic properties oflin-benzo-ATP and-ADP, protolysis and Mg²⁺ and Ca²⁺, binding are investigated between pH 6.2 and pH 8.5 by spectrophotometric and spectrofluorometric titrations. Based on a reaction model, a set of equilibrium constants is determined which is consistent with all available experimental results. The pK values of the Mg²⁺ and Ca²⁺ complex oflin-benzo-ATP in the chosen medium are 4.6 and 4.1, respectively, and those for the corresponding diphosphate are 3.1 and 2.8, respectively. Fluorescence and absorption spectra are reported.This is a peer-reviewed conference proceeding article from the Third Conference on Methods and Applications of Fluorescence Spectroscopy, Prague, Czech Republic, October 18–21, 1993.     

SIMS investigations of titanium profiles in LiNbO3 produced by ion beam mixing and diffusion

Summary In order to increase the refractive indices of LiNbO₃ just beneath the surface, i.e. to produce waveguides, titanium was incorporated into y-cut substrates by two different methods: Evaporated Ti layers were either diffused at 1000°C or mixed into the substrate with a 3 MeV Ti⁺ beam. Radiation damage caused by ion beam mixing was removed by epitaxial regrowth. The resulting Ti concentration profiles were investigated by means of secondary ion mass spectrometry. The diffused profiles could be fitted by half Gaussians with a diffusion constant ofD = 5.25 × 10^–17 m²/s at 1000°C. The ion beam mixed and annealed profiles show a non-zero slope at the surface and differ significantly from Gaussians.

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SIMS-Untersuchung von Titanprofilen in LiNbO₃ hergestellt durch Ionenstrahl-Mischung und Diffusion

     

A study of photographic paper by secondary-ion-mass-spectrometry

Summary Constant quality of photographic paper is significantly depending on constant composition of the pulp. While this can be supervised by chemical investigations, secondary ion mass spectrometry (SIMS) is the method of choice for detection of composition changes in the final product. Several samples of photographic paper were analyzed using 6 keV Ar⁺.

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Untersuchung von photographischem Papier durch Sekundärionen-Massenspektrometrie

     

Untersuchungen an oxidischen Katalysatoren. XXXVI. Struktur und thermisches Verhalten röntgenamorpher Al2O3–SiO2-Festkörper

Studies on Oxide Catalysts. XXXVI. Structure and Thermal Behaviour of Silica–Alumina The effect of thermal treatment up to 500°C on silica-alumina was studied by i.r. investigation in the lattice vibration region and the condensation degree of the silicate fragments in the silica-alumina was characterized using the molybdato method. The results of both methods demonstrate the proton form of the amorphous alumosilicates to be thermal instable and to undergo extraction of the aluminium from the alumosilicate lattice. The consequences resulting from this process on the catalytic efficiency of silica-alumina in the cracking reaction of cumene are discussed.