Thin-strip casting of steel with a twin-roll caster – discussion of product defects of ≍ 1 mm-Fe6%Si-strips

After a former detailed study of the thin strip casting process now defects of the strip and their avoidance are discussed. Hence it is deduced that the casting process should be carried out with small rolling forces. Thus the process of strip cooling has to be separated from the process of strip forming, and a cooling device has to be established close to the casting rolls.     

Effects of temperature and pressure on microcantilever resonance response

The variation in resonance response of microcantilevers was investigated as a function of pressure (10(-2)-10(6)Pa) and temperature (290-390K) in atmospheres of helium (He) and dry nitrogen (N(2)). Our results for a silicon cantilever under vacuum show that the frequency varies in direct proportion to the temperature. The linear response is explained by the decrease in Young's modulus with increasing the temperature. However, when the cantilever is bimaterial, the response is nonlinear due to differential thermal expansion. Resonance response as a function of pressure shows three different regions, which correspond to molecular flow regime, transition regime, and viscous regime. The deflection in flow transition regime resulting from thermal variation has minimal effect on frequency. The frequency variation of the cantilever is caused mainly by changes in the mean free path of gas molecules.     

Production of mycotoxins byFusarium species isolated in Germany 2. Time course of deoxynivalenol and 3-acetyldeoxynivalenol formation byFusarium graminearum in different liquid media

Summary Several semisynthetic liquid media were examined for the large-scale production of deoxynivalenol (DON) und 3-acetyldeoxynivalenol (AcDON) byFusarium graminearum 183. Only in three of the eight media used could high toxin yields of DON and AcDON be detected. The maximum levels of DON in a medium according to Miller were 3 mg/l and of AcDON 32 mg/1. In glucose-yeast extract-peptone (GYEP) medium containing 1 % glucose, the AcDON concentrations reached 33 mg/1 and the DON yields were 19 mg/1. In a rice flour liquid medium, however, the mean levels of AcDON and DON increased to 170 mg/l and 9 mg/l, respectively. The maximum amounts observed were 480 mg/1 for AcDON and 65 mg/1 for DON. The addition of trifluoracetic acid sodium salt or malonic acid, which are suggested to cause an accumulation of acetyl-CoA by inhibiting enzymes of the tricarboxylic acid cycle, did not stimulate the toxin formation.

---

Bildung von Mykotoxinen durch in Deutschland isolierteFusarium-Arten. 2. Zeitverlauf der Deoxynivalenol und 3-Acetyldeoxynivalenolbildung durchFusarium graminearum in verschiedenen Flüssigmedien

Zusammenfassung Zur Herstellung präparativer Mengen von Deoxynivalenol (DON) und 3-Acetyldeoxynivalenol (AcDON) durchFusarium graminearum 183 wurden verschiedene semisynthetische Flüssigme-dien untersucht. Nur in drei von acht eingesetzten Methen konnten hohe Toxingehalte an DON und AcDON nachgewiesen werden. Im Medium nach Miller betrugen die maximal erreichten Konzentrationen von DON 3 mg/1, von AcDON 32 mg/1. In GYEP-Medium mit einem Glucosegehalt von 1 % stieg die AcDON Konzentration bis 33 mg/1, die von DON bis 19 mg/1 an. Dagegen konnten in einem auf Reismehl basierenden Flüssigmedium durchschnittlich 170 mg/l AcDON und 9 mg/1 DON und maximal 480 mg/l AcDON und 65 mg/l DON erzielt werden. Der Zusatz von Natriumtrifluoracetat oder Malonsäure, die aufgrund einer Hemmung von Enzymen des Citratcyclus zu einer Anreicherung von Acetyl-CoA und damit zur vermehrten Bildung von Sekundärmetaboliten führen sollten, brachte keine Steigerung der Toxinbildung.