Mechanical strength of acrylic bone cements impregnated with antibiotics

Admixing of several antibiotic powders which were insoluble in methyl methacrylate did not decrease the compressive and diametral tensile strengths of two acrylic bone cements when tested after setting for 1 day and after leaching 40 days in water at 37 degrees C. When antibiotics were added as water solutions, the included water resulted in a significant decrease in these bulk mechanical properties. Storage in water for 40 days caused surface irregularities only on specimens of the set antibiotic admixtures. Approximately 0.5% of the admixed dosage of these water-soluble antibiotics could be leached from the set cements. The observed surface channels, presumably left by the loss of antibiotic, suggest further study of surface-sensitive mechanical properties may be needed. The bulk mechanical strengths presented here are conclusive only for the particular combinations of antibiotics and cements investigated, and should not be generalized at this time to any or all antibiotic admixtures or other mechanical properties.     

Die Wirkung anorganischer Phosphat-Zus?tze auf tierisches Eiwei? IV. Mitteilung Das Verhalten des pH-Wertes bei der Hitzecoagulation von Fleischeiwei?

Zusammenfassung Durch die Hitzecoagulation von Fleischbrei bzw. -brät wird der p_H-Wert bis zu 0,3 p_H-Einheiten nach der alkalischen Seite verschoben. Die p_H-Änderung ist um so geringer, je höher der p_H-Wert des Ausgangsmaterials ist. Auch bei Phosphat-Zusatz macht sich der Einfluß der Hitzecoagulation in gleicher Weise bemerkbar. Durch Räucherung bzw. durch geringe Formaldehyd-Mengen verringern sich die nach der Coagulation eingetretenen p_H-Differenzen.     

Nachweis und Bestimmung von Nitrosaminen in Lebensmitteln

Zusammenfassung Die Prüfung auf das Vorkommen von Dimethyl- und Diäthy1nitrosamin in Fleischerzeugnissen, Tilsiter Käse und Mehl mit Hilfe colorimetrischer, spektroskopischer und gaschromatographischer Methoden ergab bisher keinen einwandfreien positiven Beweis, da ein eventueller Gehalt bei 1 mg/kg und darunter liegt. Zur exakten Bestimmung von Nitrosaminen in dieser Größenordnung warden geeignete Methoden erarbeitet, die nunmehr zur Untersuchung von Lebensmitteln herangezogen warden.Der Deutschen Forschungsgemeinschaft danken wir für die gewährte Unterstiitzung.     

Operations on fuzzy sets—an axiomatic approach

We introduce intersection and union of fuzzy sets, constructed by means of operations on the unit interval which may depend on the considered element of the universe of discourse. A similar approach for complementation was given by Lowen [7]. The main result is that element-dependent operations are not compatible with the preservation of the intersection and union under the inverse image of a function. Finally we consider fuzzy σ-algebras built with these set-theoretic operations.     

An approach to long-range electron transfer mechanisms in metalloproteins: in situ scanning tunneling microscopy with submolecular resolution

In situ scanning tunneling microscopy (STM) of redox molecules, in aqueous solution, shows interesting analogies and differences compared with interfacial electrochemical electron transfer (ET) and ET in homogeneous solution. This is because the redox level represents a deep indentation in the tunnel barrier, with possible temporary electronic population. Particular perspectives are that both the bias voltage and the overvoltage relative to a reference electrode can be controlled, reflected in spectroscopic features when the potential variation brings the redox level to cross the Fermi levels of the substrate and tip. The blue copper protein azurin adsorbs on gold(111) via a surface disulfide group. Well resolved in situ STM images show arrays of molecules on the triangular gold(111) terraces. This points to the feasibility of in situ STM of redox metalloproteins directly in their natural aqueous medium. Each structure also shows a central brighter contrast in the constant current mode, indicative of 2- to 4-fold current enhancement compared with the peripheral parts. This supports the notion of tunneling via the redox level of the copper atom and of in situ STM as a new approach to long-range electron tunneling in metalloproteins.     

Ignitability test for building materials: influence of fuel gases and the design of the Burner's flame stabilizer on test results

In the harmonization of the European test codes in the context of preventive fire‐protection techniques for buildings, the single flame source test is to be adopted as a European test method. This method is used to evaluate the fire behaviour of a building material subjected to an impingement by a small flame, e.g. the flame of a match. The technique is used to provide evidence in the determination of whether a building material may be assigned the Euroclass E. Building materials that do not meet the requirements of this building material class are designated as Euroclass F. The Federal Institute of Material Research and Testing (BAM) has looked into the question of whether the design of the flame stabilizer of the burner and the use of three different fuel gases (propane, butane and methane) affect the assignation of building materials to a Euroclass, particularly the area between Euroclass E and F. The evaluation showed that the minimum thickness timber boards required to meet Euroclass E requirements would be reduced by approximately 10% when butane and an output stabilizer equipped with a punch disc was used. This means that under modified test conditions, certain timber materials previously assigned to Euroclass F would now be designated Euroclass E. Consequently the safety standard regarding fire protection in buildings may be compromised. Copyright © 1999 John Wiley & Sons, Ltd.