Choice of Steel Material to Avoid Brittle Fracture for Hollow Section Structures

European cold-formed hollow sections in general exhibit better toughness properties than required by EN 10219. However, limits in applying the toughness related rules for the choice of steel material in EN 1993 1 10 to cold-formed hollow sections still constitute barriers to free marketing. By requests from European producers a conservative assessment procedure has been developed which is based on toughness measurements and a concept using effective strains. Due to the cold-forming process such plastic strains may occur in the bent areas of the profiles associated with a noticeable reduction in material toughness. For the degradation of these toughness properties an appropriate temperature shift Delta Tcf has been derived for both circular and rectangular hollow sections. In order to guarantee the proper application of this temperature shift Table 2.1 in EN 1993 1 10 had to be extended to lower temperatures down to -120 °C.JRC.G.5-European laboratory for structural assessmen

Yarrowia lipolytica growth under increased air pressure: influence on enzymes production

Improvement of microbial cell cultures oxygenation can be achieved by the increase of total air pressure, which increases oxygen solubility in the medium. In this work, a pressurized bioreactor was used for Yarrowia lipolytica batch cultivation under increased air pressure from 1 to 6 bar. Cell growth was strongly enhanced by the pressure rise. Fivefold and 3.4-fold increases in the biomass production and in specific growth rate, respectively, were observed under 6 bar. The increase of oxygen availability caused the induction of the antioxidant enzyme superoxide dismutase, which indicates that the defensive mechanisms of the cells against oxidative stress were effective and cells could cope with increased pressure. The pregrowth of Y. lipolytica under increased pressure conditions did not affect the lipase production ability of the cells. Moreover, the extracellular lipase activity increased 96% using a 5-bar air pressure instead of air at 1- bar pressure during the enzyme production phase. Thus, air pressure increase in bioreactors is an effective mean of cell mass and enzyme productivity enhancement in bioprocess based in Y. lipolytica cultures