Zur natrium- und kaliumbestimmung mit ionensensitiven elektroden

Zusammenfassung Obwohl sie zu den häufigsten Elementen gehören, zählen die Bestimmungen des Natriums und Kaliums in der Lebensmittelchemie zu den Ausnahmen. Da zwischen der Kochsalzaufnahme und dem Bluthochdruck ein Zusammenhang zu bestehen scheint, nimmt das Interesse an der tatsächlichen Kochsalzaufnahme ständig zu.Vorgestellt wird die Natrium- und Kaliumbestimmung mit Hilfe von ionensensitiven Elektroden, die Vorteile gegenüber der AAS aufweisen. Hierbei ist besonders die minimale Probenvorbereitung zu nennen. Die Methode ist nicht auf Getreideprodukte oder Backwaren beschränkt, sondern läßt sich nach Änderung der Vorbereitung auf praktisch alle Lebensmittel anwenden. Die Richtigkeit und Genauigkeit der Bestimmung konnte durch Vergleiche und Zusatzversuche bestätigt werden.

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Determination of sodium and potassium by ion-sensitive electrodes

Summary Although sodium and potassium belong to the most common elements, their determination in foods is rarely carried out. Because there seems to be a relationship between the consumption of sodium chloride and hypertension there is a growing interest in the actual intake of sodium chloride.Ion-sensitive electrodes are utilized for the determination of sodium and potassium with obvious advantages over the AAS, particularly by requiring a minimum of sample preparation. The method is applicable for practically all types of foods. Recovery rates were 96–102% and the reliability was verified by comparison with other methodology.

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Nr. 5011 der Veröffentlichungen der Bundesforschungsanstalt für Getreide- und Kartoffelverarbeitung, Detmold     

Optische Methoden zur Charakterisierung von hochpolymeren Fasern. 1. Methodik der Interferenzmikroskopie

Density and orientation describe, besides other characteristics, the structure of high polymers. They can be obtained as a function of the radius by measurement of the refraction index of the fibre. The influence of refraction of light on the obtained index of refraction n(r) is demonstrated by an optical model of the fibre. For fibres having a radius R < 30 μm and changes in the refraction index < 0.02 the influence of refraction is less than ± 0.0002 and therefore of no significance for most textile fibres. Important is the exact adaption of the refraction index of the embeding medium to the margin of the fibre. The computed index at the margin of the fibre takes always the refraction index of the embeding medium. An incorrect adaption can be traced up to 0.2·R into the fibre. A spline function used for the approximation of the relative displacement of interference fringes gives the opportunity to calculate extreme variations in refractive index, this is demonstrated using hollow fibres filled with paraffin-oil. Using a HeNe-laser interference-holographie became possible.     

RNA helicases: versatile ATP-driven nanomotors

RNA helicases are a large family of molecular motors that utilize nucleoside triphosphates to unwind RNA duplexes and to remodel RNA protein complexes. In this review, we discuss the structure and function of RNA helicases with an emphasis on the potential application of these enzymes to control conformational changes in nanoassemblies that contain RNA.     

Aktuelle Probleme bei der Ultraschallprüfung von Freiformschmiedestücken

Die routinemäßige Ultraschallprüfung von Schmiedestücken und ihre Grenzen. Festlegungen in Regelwerken, Forderungen hinsichtlich Registrier- und Zulässigkeitsgrenzen. Prüfung austenitischer Bauteile, Einsatz spezieller Prüfköpfe und Geräte. Möglichkeiten der Automatisierung, Ausblick auf zukünftige Entwicklungen.     

Photoinitiated oxidation of geosmin and 2-methylisoborneol by irradiation with 254 nm and 185 nm UV light

The degradation of geosmin and 2-methylisoborneol (2-MIB) by UV irradiation at different wavelengths was investigated under varying boundary conditions. The results showed that conventional UV radiation (254 nm) is ineffective in removing these compounds from water. In contrast to the usual UV radiation UV/VUV radiation (254 + 185 nm) was more effective in the removal of the taste and odour compounds. The degradation could be described by a simple pseudo first-order rate law with rate constants of about 1.2 × 10⁻³ m² J⁻¹ for geosmin and 2-MIB in ultrapure water. In natural water used for drinking water abstraction the rate constants decreased to 2.7 × 10⁻⁴ m² J⁻¹ for geosmin and 2.5 × 10⁻⁴ m² J⁻¹ for 2-MIB due to the presence of NOM. Additionally, the formation of the by-product nitrite was studied. In the UV/VUV irradiation process up to 0.6 mg L⁻¹ nitrite was formed during the complete photoinitiated oxidation of the odour compounds. However, the addition of low ozone doses could prevent the formation of nitrite in the UV/VUV irradiation experiments.     

Ermittlung des Aufbaus und der Stoffkennwerte von Außenbauteilen mit Hilfe von In‐situ‐Messungen und FEM‐Berechnungen

Determination of the construction and the material identity values of outside building components with the help of in‐situ measuring procedures and FEM‐simulation calculations. The aims formulated nationwide and internationally to the climate protection can be achieved by combining of the energy‐efficient construction and rehabilitation of the existing buildings. Knowledge about the construction and the material identity values of the warmth‐transferring outside components is a condition for the energetic balance of buildings. The essential information to this can frequently be no more taken from the construction documents particularly for older buildings since they are no longer traceable or incomplete. At the example by univalve and bivalve out‐wall construction it is shown that the thermophysical qualities can be determined with the help of in‐situ measuring procedures and FE‐simulation calculations without destruction.     

Comparative Hydrodynamic Analysis of Narrow and Pilot‐Scale Bubble Columns with Internals

For a stable operation of exothermic processes in bubble column reactors, an appropriate heat control is required, e.g., through dense internal tube bundle heat exchangers. Their impact on hydrodynamic characteristics and scaling approaches is studied for columns of different scales. Two different column dimensions (DN100 and DN400) were equipped with two common tube patterns of triangular and square pitches to study local fluid dynamics. Based on geometrical tube bundle scaling quantities, hydrodynamic similarity as a scale‐up criterion with respect to average holdups, phase distributions, and local gas structures can be reached.     

Hardness and Fracture Toughness of Solid Solutions of Mg2Si and Mg2Sn

Semiconductors - Thermoelectric material development typically aims at maximizing produced electrical power and efficiency of energy conversion, even though sometimes, this means adding expensive...     

Morphology of Flashing Feeds at Critical Fluid Properties in Larger Pipes

Tailored conditioning and control of flashing feeds in industrial applications requires knowledge of the evolving flow morphology and phase fractions along the feed pipe. Design methods obtained from reference systems (e.g. water-air) are hardly applicable for commercial scales and critical fluid properties (e.g. high vapor densities, low surface tension). In this study, the flow morphology of flashing feeds in a novel refrigerant test rig at critical fluid properties was analyzed using wire-mesh sensors at two locations along the feed pipe and experimental data from the water-air system.