Beitr?ge zur Analytik von als Lebensmittelzusatzstoffe verwendeten Polysacchariden

Zusammenfassung Ein Gemisch von polysaccharidhaltigen Dickungsmitteln, die sich in ihrer Bausteinzusammensetzung nicht unterscheiden, kann durch eine Methylierungsanalyse sicher identifiziert werden, wenn Unterschiede in der Verknüpfungsart bei den einzelnen Komponenten bestehen. Die freien Hydroxylgruppen im Polysaccharid werden mit Natriumhydrid und Methyljodid in wasserfreiem Dimethylsulfoxid methyliert, das methylierte Produkt durch Säure hydrolysiert und die entstandenen Methylzucker dünnschichtchromatographisch oder gaschromatographisch getrennt und identifiziert.

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Analysis of polysaccharides used as food additivesVI. Identification of Mixtures of Polysaccharides by Methylation Analysis

Summary Polysaccharide mixtures used as stabilizers having identical sugar units, but differing in their linkages can be identified with confidence by means of methylation analysis. Such mixtures are methylated with sodium hydride and methyl iodide in anhydrous dimethylsulfoxide. The methylated products are acid hydrolyzed and the resulting methyl sugars are separated and identified by thinlayer- or gaschromatography.

     

Reflections in anechoic chambers in 100-200 GHz range

Three anechoic chambers have been tested at 110 and 183 GHz. Typical sidewall reflectivity levels are about -60 dB at 110 GHz and -50 dB at 183 GHz measured with pyramidal horns which have a gain of 20 dB. Backwall reflectivity levels are about -35 dB at 110 GHz and -25 dB at 183 GHz.<>     

Electromagnetic Gaussian beam beyond the paraxial regime

A modified electromagnetic beam technique is derived analytically from the asymptotic field expressions for the quasi-optical, millimeter-wave, plane polarized Laguerre-Gaussian modes of arbitrary order. The method makes use of the paraxial-wave formulas only, yet it accurately gives the full electric field vector at any point far beyond the conventional Gaussian beam regime. The technique is assessed numerically against the exact Green's function results     

A new method for correcting phase errors caused by flexing ofcables in antenna measurements

A simple method for correcting phase errors due to flexing of cables in an antenna measurement setup is introduced. The method that makes it possible to measure the phase error in the cable is described, and the error is removed numerically from the antenna measurement results. The method has been verified with experimental measurements at 10 GHz. The measurements show that the accuracy of the phase correction is limited by the accuracy of the phase measurement device in the system     

Beitr?ge zur analytik der als Lebensmittelzusatzstoffe verwendeten polysaccharide

Zusammenfassung Die dünnschichtelektrophoretische Trennung von polysaccharidhaltigen Dickungsmitteln erfolgt auf Schichten aus silanisiertem Kieselgel, dessen Oberfläche durch einen dünnen Film von Octanol-1 bedeckt ist. Als Puffer dient wäßrige Boratlösung (0,3 mol/1) bei pH 10. Die Visualisierung erfolgt durch ein spezielles Naphthoresorcin-Schwefelsäurereagens. Mit dieser Methode ist es möglich, komplizierte Mischungen von Dickungsmitteln aufzutrennen und zu identifizieren.

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Separation of polysaccharide containing thickeners by thin layer electrophoresis

Summary The thinlayer electrophoretic separation of polysaccharide containing thickening agents is carried out on layers of silanized silicagel whose surface is covered with a thin film of octanol-1. 0.3 mol/1 Borate solutions at pH 10 as buffer serves. A special naphthoresorcinol-sulfuric acid reagent is used for visualisation. This method makes a good separation and identification of complex mixtures of thickening agents possible.

     

Industrielle aspekte der suspensionspolymerisation

Suspension polymerization is one of the most important processes for the production of high polymers. Great demands are made on the technical applicability of the polymers. In order to meet these requirements the distribution of the particle sizes and the morphology of the particles are of great importance. The size and the structure of the particles depend in a complicated interaction on factors such as the chemical structure of the suspending agent, the concentration of the suspending agent and on the agitation conditions. The interdependence of these factors have been and still are explained differently. Important mechanistic and process engineering aspects of the suspension polymerization are demonstrated by the polymerization of vinylchloride and styrene.     

Surface characteristics of tubercle mass and graphitic residue in cast iron water pipelines

Graphitic residues from cast iron water mains were characterized by surface area measurements. The surface areas were about 4–5 times higher than those determined for reference graphite Samples. Their capacity to retain water equalled that of activated charcoal. Adsorption properties were examined by using methylene blue and rhodamine B. Under the conditions employed, methylene blue behaved as a cationic species whereas rhodamine B seemed to have little charge effects. Ferric iron was found to adsorb on graphitic residues in a pH-dependent manner. Surface characteristics of tubercle material that overlyes graphitized areas in cast iron pipes were examined by scanning electron microscopy. A high degree of particle aggregation was observed and the size distribution varied with the crystallinity of the tubercle components.     

Effect of pH,iron concentration,and pulp density on the solubilization of uranium from ore material in chemical and microbiological acid leach solutions: Regression equation and confidence band analysis

The solubilization of uranium from a finely ground ore material was investigated in leaching tests each lasting for about 24 h. Ferric iron, added as Fe₂(SO₄)₃ or produced by prior microbiological oxidation of FeSO₄, accelerated the rates of uranium leaching, as compared with those obtained with sulfuric acid or acidic ferrous sulfate. Pulp density and initial pH were also test variables. Yields of up to 100% uranium extraction were obtained within 24 h. Quadratic response surfaces were fitted to the experimental leach curves and confidence bands were calculated to assess the significance of the effects of pH, iron concentration, and pulp density on uranium solubilization. The general separation of the confidence bands indicated that each factor had a significant effect.     

RF MEMS impedance tuners for 6–24 GHz applications

RF MEMS tuners with wide impedance coverage have been developed for 6–24 GHz noise parameter and load‐pull measurement systems. The tuners are based on triple‐, double‐, and single‐stub topologies loaded with switched MEMS capacitors. Several designs are presented, and they use 10–13 switched MEMS capacitors to produce 1024–8192 (2¹⁰–2¹³) different impedances. The measured impedance coverage agrees well with simulations and it is the widest ever measured impedance coverage from any planar tuner to‐date. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.