Synthetische Umwandlung des Abietinsäuregerüstes. Abbau der Carboxylfunktion

Summary Aluminiumoxide-induced rearrangement of the tosylate7 (derived from abietic acid methyl ester byLAH reduction and Tosylation), leads under migration of CH₃-4 to a mixture of exocyclic and endocyclic olefines8 – 11. Photochemical isomerisation of these olefines yields the endocyclic isomer10 as single product.

     

[1+2]-cycloadditionen von isocyaniden an indiamine

Arylisocyanides and aroylisocyanides add to ynediamines in [1+2]- cycloaddition reactions to yield the corresponding cyclopropenonimines; electron withdrawing substituents in the arylisocyanides accelerate the rate of addition.     

Funktionelle Lebensmittel: Mehr als ein Trend?

Food is considered to be functional if it shows a beneficial health effect beyond the supply of nutrients with proven functions. Regarding the prevention of a variety of chronic diseases carotinoides, polyphenoles and phytosterols seem to be of particular interest. However, it has not been sufficiently investigated to what extent single substances, for example given as a food supplement, can effectively be used for this purpose. More importance should be assigned to natural food which guarantees the uptake even of those nutrients of which biological functions are currently still unknown.     

Experimental investigation and modelling of compressibility induced by damage in carbon black-reinforced natural rubber

While natural rubber is commonly considered as an incompressible material, this study shows how carbon black-reinforced natural rubber (NR-CB), when subjected to various mechanical loading conditions (uniaxial, hydrostatic, monotonic, cyclic), is affected by volume change. Experiments show a volume variation even for low straining values and a significant volume change for large elongations. Moreover, volume change can be either reversible or not, depending on the loading conditions. It is related to a competition between void growth, chain orientation, and stress softening. At a microscopic scale, in situ Scanning Electron Microscopy (SEM) examinations and image analysis allow one to record damage and microscopic volume change as a function of elongation. Therefore the volume change measured at the microscopic scale is equal to the macroscopic one. Based on the experimental results, this paper shows that the hypothesis of incompressibility is worth being revisited. Thus, a nearly compressible approach was considered, where the strain energy is assumed to be the sum of spherical and deviatoric parts that are both affected by damage. The model was then implemented in a finite-element code. Good agreement was obtained between experimental results and model predictions for low triaxiality test conditions.